JP2003241089A - Electronic image pickup unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a zoom system which is made small-sized and simple and has stable high image forming performance from an infinite distance to a short distance and the depth of which is reduced when the lens system is stored by making the total thickness of individual lens groups small. <P>SOLUTION: A zoom lens of an electronic image pickup unit having the zoom lens and an electronic imaging element comprises a negative 1st group G1, a positive 2nd group G2, and a positive 3rd group G3. The 2nd group G2 comprises two lens elements, the image-side lens element of which is in a meniscus shape which is concave to the image plane side. The 3rd group G comprises one positive lens element. The 2nd group G2 moves only to the object side during power variation from a wide-angle end to a telephoto end when focused or an object at infinity, and the 3rd group G3 moves by a quantity different from that of the 2nd group G2 when the power is varied. In the focusing operation, the 3rd group G3 moves and all refracting surfaces of the 3rd group G3 meets a condition (1) concerning an aspherical surface deviation quantity. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic image pickup device, and more particularly to an electronic image pickup device such as a video camera or a digital camera which has been made thinner in the depth direction by devising an optical system portion such as a zoom lens. is there. Also, the zoom lens is related to one that enables rear focus.

[0002]

2. Description of the Related Art In recent years, a digital camera (electronic camera) has been attracting attention as a next-generation camera to replace a silver salt 35 mm film (commonly called Leica version) camera. Furthermore, it has come to have several categories in a wide range from high-performance type for business use to portable popular type.

In the present invention, attention is paid particularly to the portable popular type category, and it is aimed to provide a technique for realizing a video camera and a digital camera having a small depth while ensuring high image quality. The biggest bottleneck in reducing the depth direction of the camera is the thickness from the most object side surface of the optical system, particularly the zoom lens system, to the image pickup surface. Recently, it has become mainstream to employ a so-called collapsible lens barrel in which the optical system is pushed out of the camera body at the time of photographing and is housed in the camera body when carrying.

However, the thickness of the optical system when it is collapsed varies greatly depending on the lens type and filter used.
In particular, in order to set specifications such as zoom ratio and F value to be high, a so-called positive-leading type zoom lens in which the lens unit closest to the object side has a positive refractive power has a large thickness and dead space of each lens element, Even if it is retracted, the thickness does not become so thin (Japanese Patent Laid-Open No. 11-258507). The negative-leading type zoom lens having a two- or three-group structure is particularly advantageous in that respect, but it is collapsed even when the number of constituent elements in the group is large, the element thickness is large, and the lens closest to the object side is a positive lens. Does not become thin (Japanese Patent Laid-Open No. 11-52246)
issue). As an example of a currently known one suitable for an electronic image pickup device, having a good imaging performance including a zoom ratio, an angle of view, an F value, etc. and having a possibility of making the collapsed thickness the thinnest, Japanese Patent Laid-Open No. 11- 287953, JP-A-2000-26700
9, JP-A 2000-275520 and the like.

To make the first lens unit thin, it is preferable to make the entrance pupil position shallow, but for that purpose, the magnification of the second lens unit must be increased. On the other hand, for this reason, not only is the load on the second lens group increased, making it difficult to make itself thin, but also the difficulty of aberration correction and the effectiveness of manufacturing errors increasing, which is not preferable. In order to make the device thinner and smaller, it is sufficient to make the image pickup device smaller, but in order to make the number of pixels the same, it is necessary to make the pixel pitch small, and it is necessary to cover the lack of sensitivity with an optical system. The effect of diffraction is no different.

In order to obtain a camera body with a small depth, it is effective in the layout of the drive system to move the lens at the time of focusing by the so-called rear focus rather than by the front group. Then, it becomes necessary to select an optical system in which the aberration variation is small when the rear focus is performed.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation of the prior art, and an object thereof is to reduce the number of constituents, to make the layout of a mechanism such as a rear focus type small and easy to simplify, Select a zoom method or zoom configuration that has stable and high imaging performance from infinity to short distances, and further reduce the lens element of the zoom lens to reduce the total thickness of each group and select filters. Considering this, it is essential to make video cameras and digital cameras thinner.

[0008]

In order to achieve the above object, the electronic image pickup device of the present invention is an electronic image pickup device having a zoom lens and an electronic image pickup element arranged on the image side thereof, wherein the zoom lens is In order from the object side, a first lens group having a negative refracting power as a whole, a second lens group having a positive refracting power as a whole, and a third lens group having a positive refracting power as a whole, The second lens group is 2
The third lens unit is composed of one positive lens component, and at least the second lens unit is at infinity. Upon zooming from the wide-angle end to the telephoto end when focusing on an object point, only the object side moves during zooming, and the third lens group moves by a different amount than the second lens group during zooming, The third lens group moves,
All the refracting surfaces of the lens group are characterized by satisfying the following conditions.

(1) 0 ≦ | Asp3 | <3.0 × 10 ⁻³ · L where L is the diagonal length of the effective image pickup area in the electronic image pickup device, and Asp3 is the refracting surface of each of the third lens groups. Is the amount of aspherical surface deviation, and is the amount of aspherical surface deviation when the height from the optical axis to the reference spherical surface having the radius of curvature on the optical axis is 0.4 L, and if the refracting surface is a spherical surface, the aspherical surface deviation amount Asp3 is Set to 0.

In the following, the reason why the above structure is adopted and the operation thereof will be described.

In order to achieve the above-mentioned object, the electronic image pickup device of the present invention is an electronic image pickup device having a zoom lens and an electronic image pickup device arranged on the image side thereof. Is composed of a first lens group having a negative refracting power, a second lens group having a positive refracting power as a whole, and a third lens group having a positive refracting power as a whole, and the second lens group has two The lens component on the image side has a meniscus shape with a concave surface facing the image side, the third lens unit includes one positive lens component, and at least the second lens unit includes an object point at infinity. It moves only to the object side during zooming from the wide-angle end to the telephoto end during focusing, the third lens group moves a different amount than the second lens group during zooming, and the third lens group moves during focusing operation. Is adopted .

Particularly, when the amount of movement of the lens when the lens is retracted and stored is as small as possible, the lens barrel can be simplified and the volume can be made small. Therefore, it is preferable to design the total length in the photographing state as short as possible. Therefore, the second lens group is configured by two lens components, and the lens component on the image side has a meniscus shape with a concave surface facing the image side.

In the present invention, the lens means a lens made of a single medium as one unit, and the cemented lens is made up of a plurality of lenses. Further, the lens component means a lens group having no air gap between them, and means a single lens or a cemented lens.

In a negative-positive two-group zoom lens which has been often used as a zoom lens for silver halide film cameras for a long time, the magnification of the positive rear group (second lens group) at each focal length is reduced in order to reduce the size of the zoom lens. It is better to make it higher, but for that reason, a positive lens component is added to the image side of the second lens unit as a third lens unit, and the distance between the second lens unit and the second lens unit is changed when zooming from the wide angle end to the telephoto end. The method of letting it is well known. Further, this third lens group has a possibility that it can also be used for focusing.

When the object of the present invention is achieved, that is, when the total thickness of the lens portion is reduced when the lens barrel is retracted and the focusing is performed by the third lens group, fluctuations in off-axis aberration such as astigmatism are suppressed. In order to suppress, the aberration correction capability of the second lens group is particularly important.

When focusing with the third lens group,
Aberration fluctuation becomes a problem, but when an unnecessary amount of aspherical surface enters the third lens group, the astigmatism remaining in the first lens group and the second lens group is generated in order to exert its effect. However, if the third lens group moves for focusing, the balance is lost, which is not preferable. Therefore, when focusing with the third lens group, the third lens group needs to be configured with a spherical system or a small amount of aspherical surface. That is, (1) It is important to satisfy 0 ≦ | Asp3 | <3.0 × 10 ⁻³ · L. Here, L is the diagonal length (mm) of the effective image pickup area in the electronic image pickup device, Asp3 is the amount of aspherical surface deviation of each refracting surface of the third lens group, and a reference spherical surface having a radius of curvature on the optical axis. Is set to an aspherical surface deviation amount when the height from the optical axis is 0.4 L, and the aspherical surface deviation amount Asp3 is set to 0 when the refracting surface is a spherical surface.

That is, the aspherical surface deviation amount in the present invention is
As shown in FIG. 14, when the diagonal length of the effective image pickup area of the electronic image pickup element is L with respect to the spherical surface (reference spherical surface) having the radius of curvature r on the optical axis of the target aspherical surface, Is the deviation amount of the aspherical surface at a height of 0.4 L. Note that it is premised that the electronic image sensor is used so that the wide-angle end angle of view includes 55 ° or more.

When the upper limit of 3.0 × 10 ⁻³ · L of the condition (1) is exceeded, the off-axis aberration due to focusing is significantly deteriorated.
Not preferable.

It is better to do the following.

(1) ′ 0 ≦ | Asp3 | <2.0 × 10 ⁻³ · L Furthermore, the following is most preferable.

(1) ″ 0 ≦ | Asp3 | <1.0 × 10 ⁻³ · L Further, when the shape of the lens component of the third lens unit is set as follows, the aberration on the far distance side is in the entire zoom range. Good and can reduce aberration fluctuation due to focus.

(2) −1.0 <(R _3F + R _3R ) / (R _3F −R _3R ) <0.7 where R _3F and R _3R are the most object side surfaces of the third lens group, and It is the radius of curvature of the image side surface on the optical axis.

When the upper limit of 0.7 of the condition (2) is exceeded,
Even if the astigmatism variation due to rear focus becomes too large and the astigmatism can be satisfactorily corrected at the infinite object point, the astigmatism easily deteriorates at the near object point. Of the lower limit
When it exceeds 1.0, astigmatism variation due to rear focus is small, but it becomes difficult to correct aberration for an infinite object point.

It is better to do the following.

(2) ′ − 0.8 <(R _3F + R _3R ) / (R _3F −R _3R ) <0.3 Further, the following is most preferable.

(2) ″ − 0.6 <(R _3F + R _3R ) / (R _3F −R _3R ) <0 For the second lens group, the lens component on the image side is moved from the object side to the positive lens, If a negative lens is cemented in this order and the shape is a meniscus shape with the concave surface facing the image side, it contributes to shortening the overall length in the shooting state, but the following condition is further satisfied: The relative decentering sensitivity between the two lens components of the group may be low, and the radius of curvature of the cemented surface has a great influence on the chromatic aberration of spherical aberration in addition to the axial chromatic aberration of magnification. 2 of the second lens group
When trying to shorten the total length by making the component on the medium object side of the two components a stronger positive refracting power, the Petzval sum tends to be negative, so some ingenuity is required.

(3) 0.45 <R _22R / R _22F <0.9 (4) 0 <L / R _22C <1.0 (5) 0 <n _22R −n _22F <0.3 where R _22F , R _22R , and R _22C are the radii of curvature on the optical axis of the most object-side surface, the most image-side surface, and the cemented surface of the second lens group image-side lens component, respectively. L is the diagonal length (mm) of the electronic image sensor used. Note that it is premised that the electronic image sensor is used so that the wide-angle end angle of view includes 55 ° or more. n _22F and n _22R are d of the medium of the object side lens and the image side lens of the second lens group image side lens component, respectively.
The refractive index of the line.

When the upper limit of 0.9 of the condition (3) is exceeded, it is advantageous for correcting spherical aberration, coma aberration, and astigmatism of all system aberrations, but the effect of mitigating decentration sensitivity due to cementing is small. When the lower limit of 0.45 is exceeded, it becomes difficult to correct spherical aberration, coma aberration, and astigmatism of all system aberrations.

If the lower limit of 0 to condition (4) is not reached, it is advantageous for correction of axial chromatic aberration and lateral chromatic aberration, but spherical aberration chromatic aberration tends to occur, and even if spherical aberration at the reference wavelength can be corrected well. However, short-wavelength spherical aberration is not preferable, because it causes a remarkably overcorrected state and causes color bleeding in an image. If the upper limit of 1.0 is exceeded, axial chromatic aberration and lateral chromatic aberration tend to be undercorrected.

If the lower limit of 0 of the condition (5) is exceeded, the Petzval sum of the entire system tends to have a large negative value, which is likely to cause deterioration of off-axis aberrations. On the other hand, there are only a few combinations of media that exceed the upper limit of 0.3,
Abbe number, spectral characteristics, price, physicochemical properties are not satisfied.

It is more preferable to set one or more or all of the conditions (3) to (5) as follows.

(3) ′ 0.5 <R _22R / R _22F <0.85 (4) ′ 0.2 <L / R _22C <0.9 (5) ′ 0 <n _22R −n _22F <0. 25 Furthermore, it is more preferable to set any one or more of the conditions (3) to (5) as follows. In particular, it is best to do all of the following.

(3) ″ 0.55 <R _22R / R _22F <0.8 (4) ″ 0.4 <L / R _22C <0.8 (5) ″ 0 <n _22R −n _22F <0. 2 Since the image-side lens component of the second lens unit is a cemented lens component, a single lens is sufficient for the object-side lens component, and the first lens unit has a negative refractive power in terms of aberration correction. Since the divergent light beam is incident on the second lens group,
The shape factor of the object-side positive lens component near the optical axis may be set as in condition (6).

(6) 0.1 <(R _21F + R _21R ) / (R _21F −R _21R ) <5 where R _21F and R _21R are the object-side surfaces of the lens components on the object side of the second lens group, respectively. , The radius of curvature of the image side surface on the optical axis.

Whether the upper limit of 5 or the lower limit of 0.1 of condition (6) is exceeded, spherical aberration becomes difficult to correct even if a plurality of aspherical surfaces are introduced on the object side of the second lens group.

It is better to do the following.

(6) ′ 0.3 <(R _21F + R _21R ) / (R _21F −R _21R ) <4 Furthermore, the following is most preferable.

(6) ″ 0.5 <(R _21F + R _21R ) / (R _21F −R _21R ) <3 Furthermore, the object-side lens component of the second lens unit is formed of an aspherical surface on both air contact surfaces. Then, in terms of spherical aberration correction, the relative decentering sensitivity in the group is mitigated, and the manufacturing cost is large.These aspherical surfaces are both biased toward the object side with respect to the reference spherical surface having the radius of curvature on the optical axis. With the shape
In terms of spherical aberration correction, it is excellent in that the relative decentering sensitivity within the group is relaxed.

Then, these aspherical surfaces should satisfy the following conditions.

(7) 5.0 × 10 ^-4 · L <| Asp21R | <| Asp21F | <3.0 × 10 ⁻² · L However, Asp21F and Asp21R are the lens components on the object side of the second lens group. The amount of aspherical surface displacement on the air contact surface on the object side and the air contact surface on the image side, respectively, and the height from the optical axis with respect to the reference spherical surface having a radius of curvature on the optical axis are 0.3L.
Is the amount of aspherical deviation at. This aspherical surface displacement amount is shown in FIG.
Similar to the aspherical surface displacement amount described in, the diagonal length of the effective image pickup area of the electronic image pickup element is L with respect to the spherical surface (reference spherical surface) having the radius of curvature r on the optical axis of the target aspherical surface. In this case, the deviation amount of the aspherical surface at the position where the height from the optical axis is 0.3L is described.

The lower limit of condition (7) is 5.0 × 10 ⁻⁴
When L is exceeded or when the central inequality sign is reversed, spherical aberration is insufficiently corrected. When the upper limit of 3.0 × 10 ^-2 L is exceeded, the relative eccentricity with each component in the group increases.

It is better to do the following.

(7) ′ 8.0 × 10 ⁻⁴ · L <| Asp21R | <| Asp21F | <2.0 × 10 ⁻² · L Further, the following is best.

(7) ″ 1.0 × 10 ⁻³ · L <| Asp21R | <| Asp21F | <1.0 × 10 ⁻² · L The zoom lens configuration of the present invention is the second for the sake of size reduction. The magnification of the subsequent compound system, including the lens group, is set to -1 at approximately the center of the variable power range, that is, the magnification of the second lens group is set higher than that of a normal negative group type zoom lens. Therefore, it is advisable to set the magnification at the telephoto end of the second lens unit in the 3 × class to the following condition.

(8) 1.45 <-β _2T <2.1 where β _2T is the magnification of the entire second lens group at the telephoto end when focusing on an object point at infinity.

When the lower limit of 1.45 to condition (8) is exceeded,
The distance between the first lens group and the second lens group at the wide-angle end is too large, and the effective diameter of the first lens group must be increased, which increases the thickness. When the upper limit of 2.1 is exceeded, it becomes more difficult to correct aberrations in both the first lens group and the second lens group.

It is better to do the following.

(8) '1.5 <-β _2T <2.05 Further, the following is best.

(8) ″ 1.55 <−β _2T <2.0 Then, if the two lens components of the second lens unit are a positive lens component and a negative lens component in order from the object side, then the second lens Even if the lens group has a high magnification, the back focus in the shooting state does not become long.

Next, if the first lens group is composed of only two lenses, a negative lens including an aspherical surface and a positive lens, while satisfying the following conditions, chromatic aberration and each Seidel off-axis aberration can be corrected well. Therefore, it contributes to the reduction in thickness.

(9) 10 <ν ₁₁ −ν ₁₂ <24 (10) −4 <(R ₁₃ + R ₁₄ ) / (R ₁₃ −R ₁₄ ) <− 1.1 where ν ₁₁ is the first lens group. Abbe number of the medium based on the d-line of the negative lens, ν ₁₂ is the Abbe number of the medium based on the d-line of the positive lens of the first lens group, and R ₁₃ is the optical axis of the object side surface of the positive lens of the first lens group R ₁₄ is the radius of curvature on the optical axis of the image side surface of the positive lens in the first lens group.

The condition (9) defines the fluctuations of the axial and lateral chromatic aberrations during zooming. Lower limit of 10
When it exceeds, the axial chromatic aberration is likely to be overcorrected and the lateral chromatic aberration is likely to be undercorrected. If the upper limit of 24 is exceeded, the opposite tends to occur.

The condition (10) defines the shape factor of the positive lens in the first lens group. If the lower limit of -4 is exceeded, it will be disadvantageous in correction of astigmatism and also disadvantageous in that an extra distance from the second lens group is required to avoid mechanical interference during zooming. If the upper limit of -1.1 is exceeded, the distortion correction tends to be disadvantageous.

It is better to set either or both of the conditions (9) and (10) as follows.

(9) ′ 12 <ν ₁₁ −ν ₁₂ <22 (10) ′ −3.5 <(R ₁₃ + R ₁₄ ) / (R ₁₃ −R ₁₄ ) <− 1.3 Further, the condition (9) More preferably, either or both of (10) and (10) are set as follows. In particular, it is best to do both as follows.

(9) ″ 14 <ν ₁₁ −ν ₁₂ <20 (10) ”−3 <(R ₁₃ + R ₁₄ ) / (R ₁₃ −R ₁₄ ) <− 1.5 When the following conditions are satisfied: Good.

(11) 0.2 <d ₁₁ /L<0.65 where d ₁₁ is the air distance between the negative lens and the positive lens of the first lens group on the optical axis.

If the upper limit of 0.65 to condition (11) is exceeded, it is advantageous for correction of coma, astigmatism, and distortion, but the optical system becomes thicker, and the lower limit of 0.2 is exceeded. Then, it becomes difficult to correct these aberrations despite the introduction of the aspherical surface, and at the same time, the relative decentration sensitivity in the first lens group tends to increase.

It is better to do the following.

(11) ′ 0.25 <d ₁₁ /L<0.6 Further, the following is best.

(11) ″ 0.3 <d ₁₁ /L<0.55 The third lens group may be composed of one positive lens. Practical aberration level correction is possible. Contribute to slimming down.

Since the zoom lens of the present invention can emit the off-axis chief ray in a state of being almost perpendicular to the image plane, it is desirable to construct it as an electronic image pickup apparatus having an image pickup element on the image plane side. .

At that time, it is more preferable that the diagonal length L of the effective image pickup area of the image pickup device is 3.0 mm to 12.0 mm in order to achieve both good image quality and miniaturization.

If the lower limit of 3.0 mm is exceeded and the size of the image pickup device becomes small, it becomes difficult to cover the lack of sensitivity. On the other hand, when the image pickup device becomes larger than the upper limit value of 12.0 mm, the size of the zoom lens tends to increase accordingly, and the effect of thinning is diminished.

The present invention is also advantageous in constructing an electronic image pickup device including a wide angle range. In particular, it is preferable that the half angle of view ω _W in the diagonal direction at the wide angle end be used in an electronic image pickup device satisfying the following condition (the half angle of view at the wide angle end described in each embodiment described later corresponds to ω _W ). ).

27.5 ° <ω _W When the lower limit value of 27.5 ° is exceeded and the wide angle end half angle of view becomes narrow, it is advantageous for aberration correction, but it is not a practical angle of view at the wide angle end.

Further, an upper limit may be set to set 27.5 ° <ω _W <42 °.

If the upper limit of 42 ° is exceeded, distortion and chromatic aberration of magnification are likely to occur, and the number of lenses increases.

Further, according to the present invention, it is preferable that the electronic image pickup apparatus is provided with a zoom lens having a variable power ratio which satisfies the following conditions, since it is possible to balance downsizing and a required variable power ratio.

2.4 <Z <4.0 where Z is the zoom ratio of the zoom lens and is the telephoto end focal length / wide-angle end focal length.

If the lower limit of 2.4 of this condition is exceeded, it is advantageous for downsizing, but high zooming will not be achieved. When the upper limit of 4.0 is exceeded, it becomes difficult to reduce the size with a small number of lenses.

Further, it is more preferable that the lower limit value is 2.7 or 2.8. On the other hand, the upper limit value is 3.5 or 3.
It is more preferable to set it to 0.

As described above, the means for improving the image forming performance while reducing the collapsible thickness of the zoom lens portion is provided.

Next, the matter of thinning the filters will be described. In an electronic image pickup device, an infrared absorption filter having a certain thickness is usually inserted on the object side of the image pickup device so that infrared light does not enter the image pickup surface. Consider replacing this with a thin coating. Naturally, it will be thinned by that amount, but there is a secondary effect. A near-infrared sharp cut coat with a transmittance (τ ₆₀₀ ) at a wavelength of 600 nm of 80% or more and a transmittance (τ ₇₀₀ ) of ₇₀₀ nm of 8% or less is provided on the object side of the image pickup device behind the zoom lens system. When introduced, the transmittance in the near-infrared region of 700 nm or more is lower than that of the absorption type, and the transmittance on the red side is relatively high, which is a drawback of solid-state imaging devices such as CCDs having complementary color mosaic filters. The CC having a primary color filter in which the magenta tendency on the side is alleviated by gain adjustment
Color reproduction similar to that of a solid-state image sensor such as D can be obtained.

That is, it is desirable to satisfy (12) τ ₆₀₀ / τ ₅₅₀ ≧ 0.8 (13) τ ₇₀₀ / τ ₅₅₀ ≦ 0.08. However, τ ₅₅₀ is the wavelength 550
It is the transmittance in nm.

It is better to set either or both of the conditions (12) and (13) as follows.

(12) ′ τ ₆₀₀ / τ ₅₅₀ ≧ 0.85 (13) ′ τ ₇₀₀ / τ ₅₅₀ ≦ 0.05 Furthermore, if either or both of the conditions (12) and (13) are set as follows: Even better. In particular, it is best to do both as follows.

(12) ”τ ₆₀₀ / τ ₅₅₀ ≧ 0.9 (13)” τ ₇₀₀ / τ ₅₅₀ ≦ 0.03 Another drawback of the solid-state image sensor such as CCD is the sensitivity to the wavelength of 550 nm in the near ultraviolet region. Is much higher than that of the human eye. This also highlights the color fringing at the edge portion of the image due to the chromatic aberration in the near-ultraviolet region. In particular, it is fatal to downsize the optical system. Therefore, wavelength 4
The ratio of transmittance (τ ₄₀₀ ) at 00 nm to that (τ ₅₅₀ ) at ₅₅₀ nm is less than 0.08, 440 nm
Of transmittance (τ ₄₄₀ ) at 550 nm (τ ₅₅₀ )
If an absorber or reflector with a ratio of more than 0.4 is inserted in the optical path, the wavelength range necessary for color reproduction will not be lost (while maintaining good color reproduction) and noise such as color bleeding will occur. It is considerably reduced.

That is, it is desirable that (14) τ ₄₀₀ / τ ₅₅₀ ≦ 0.08 (15) τ ₄₄₀ / τ ₅₅₀ ≧ 0.4.

It is better to set either or both of the conditions (14) and (15) as follows.

(14) ′ τ ₄₀₀ / τ ₅₅₀ ≦ 0.06 (15) ′ τ ₄₄₀ / τ ₅₅₀ ≧ 0.5 Furthermore, if either or both of the conditions (14) and (15) are set as follows: Even better. In particular, it is best to do both as follows.

(14) ″ τ ₄₀₀ / τ ₅₅₀ ≦ 0.04 (15) ″ τ ₄₄₀ / τ ₅₅₀ ≧ 0.6 It is preferable that these filters are installed between the image forming optical system and the image pickup device.

On the other hand, in the case of the complementary color filter, since the transmitted light energy is high, the sensitivity is substantially higher than that of the CCD with the primary color filter, and the resolution is advantageous. The merit is great.
Also for the optical low-pass filter which is the other filter, it is preferable that the total thickness t _LPF (mm) thereof satisfies the following condition.

(16) 0.15 <t _LPF /a<0.45 where a is the horizontal pixel pitch (unit: μm) of the image sensor, which is 5 μm or less.

To make the collapsible thickness thin, it is effective to make the optical low-pass filter thin, but in general, the moire suppressing effect is reduced, which is not preferable. On the other hand, as the pixel pitch becomes smaller, the contrast of frequency components above the Nyquist limit decreases due to the influence of diffraction of the imaging lens system, and the phenomenon of the moire suppressing effect is allowed to some extent. For example, when the azimuth angle at the time of projection on the image plane is horizontal (= 0 °) and has crystal axes in ± 45 ° directions, 3
It is known that there is a considerable moire suppressing effect when using different kinds of filters in the direction of the optical axis. The specifications for the thinnest filter in this case are horizontal a
It is known that SQRT (1/2) * aμm is shifted in the μm and ± 45 ° directions, respectively. The filter thickness at this time is approximately [1 + 2 * SQRT (1/2)] * a / 5.88 (m
m). Here, SQRT is a square root and means a square root. This is a specification that makes the contrast zero at a frequency just corresponding to the Nyquist limit. If the thickness is reduced by about several percent to several tens of percent, the contrast of the frequency corresponding to the Nyquist limit will be slightly generated, but it can be suppressed by the influence of the above diffraction.

Condition (16) including filter specifications other than the above, including the case of stacking two or one filter
Should be satisfied. When the upper limit value of 0.45 is exceeded, the optical low-pass filter is too thick, which hinders reduction in thickness. If the lower limit of 0.15 is exceeded, moire removal will be insufficient. However, the condition of a when implementing this is 5
μm or less.

If a is 4 μm or less, it is more susceptible to the influence of diffraction, and therefore (16) ′ 0.13 <t _LPF /a<0.42 may be set.

Further, depending on the horizontal pixel pitch and the number of low-pass filters to be overlapped, the following may be performed.

(16) ″ 0.3 <t _LPF /a<0.4 However, when three sheets are stacked and 4 ≦ a <5 (μm), 0.2 <t _LPF /a<0.28 When two sheets are stacked and 4 ≦ a <5 (μm), 0.1 <t _LPF /a<0.16 However, when only one sheet and 4 ≦ a <5 (μm), 0.25 <t _LPF /A<0.37 However, when three sheets are stacked and a <4 (μm), 0.16 <t _LPF /a<0.25 However, when two sheets are stacked and a <4 (μm), 0. 08 <t _LPF /a<0.14 However, when only one sheet and a <4 (μm).

When an electronic image pickup device having a small pixel pitch is used, the image quality is deteriorated due to the diffraction effect due to the narrowing down. Therefore, there is a plurality of apertures having a fixed aperture size, and one of them is used as an optical path between the most image side lens surface of the first lens group and the most object side lens surface of the third lens group. The electronic image pickup device can be inserted into the inside of the electronic device and can be exchanged with other apertures to adjust the image plane illuminance.
It is preferable to adjust the light amount by using media having different transmittances for m and less than 80%. Alternatively, a (μm) / F number <0.4
When the adjustment is performed so that the amount of light corresponds to such an F value, it is preferable to use an electronic image pickup apparatus having media having different transmittances for 550 nm and less than 80% in the aperture. For example, when the open value is out of the range of the above conditions, the medium is not used, or a dummy medium having a transmittance of 91% or more for 550 nm is set, and when the range is within the range, the aperture stop diameter may be made small enough to be affected by diffraction. Instead, it is better to adjust the light quantity with something like an ND filter.

In addition, the plurality of apertures are made to have diameters which are inversely proportional to the F value and made uniform, and optical low-pass filters having different frequency characteristics are inserted in the apertures instead of the ND filter. But it's okay.
Since the diffraction deterioration increases as the aperture is narrowed down, the frequency characteristic of the optical low pass filter is set higher as the aperture diameter becomes smaller.

In the above, for each conditional expression,
Even if each is individually limited to the configurations described in [1] to [13] below, it is effective in either miniaturization or higher performance.

Further, regarding each conditional expression limitation, naturally, the same effect can be obtained by limiting only the lower limit value or the upper limit value of the limited conditional expression, and further, the value corresponding to each conditional expression of the embodiment described later is obtained. Can be changed to near the boundary value of each conditional expression.

[0094]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments 1 to 5 of the zoom lens used in the electronic image pickup apparatus of the present invention will be described below. Wide-angle end (a) at the time of focusing on an object point at infinity in Examples 1 and 2,
The lens cross-sectional views at the intermediate state (b) and at the telephoto end (c) are shown in FIGS. 1 and 2, respectively. For Examples 3 to 5, FIG.
Since it is almost the same as, the illustration is omitted. 1 in FIG. 1 and FIG.
The lens group is G1, the diaphragm is S, the second lens group is G2, and the third.
The lens group is denoted by G3, the infrared cut absorption filter is denoted by IF, the low-pass filter is denoted by LF, the CCD cover glass which is an electronic image pickup element is denoted by CG, and the image plane of the CCD is denoted by I.
Instead of the infrared cut absorption filter IF, a transparent flat plate may be provided with a near infrared sharp cut coat on the incident surface, or the low pass filter LF may be directly subjected to the near infrared sharp cut coat. .

As shown in FIG. 1, the zoom lens of Example 1 includes a first lens unit G1 having a negative refractive power, which includes a negative meniscus lens having a convex surface on the object side and a positive meniscus lens having a convex surface on the object side. A stop S, a biconvex positive lens, a second lens group G2 having a positive refractive power, which is composed of a positive meniscus lens convex on the object side and a cemented lens of a negative meniscus lens convex on the object side, and a biconvex positive lens. The third lens group G3 has a positive refractive power, and when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves in a concave locus on the object side, and at the telephoto end, the image plane is wider than the wide-angle end. The second lens group G2 moves toward the object side together with the aperture stop S, the third lens group G3 moves along a convex locus toward the object side, and slightly moves from the wide-angle end to the object side at the telephoto end. It becomes the side position. In order to focus on a short-distance subject, the third lens group G3 is extended to the object side.

There are three aspherical surfaces, namely the image side surface of the negative meniscus lens of the first lens group G1, the object side surface of the biconvex positive lens of the second lens group G2, and the object side surface of the cemented lens. It is used.

In the zoom lenses of Examples 2 to 5, as shown in FIG. 2, the first lens unit G1 having a negative refractive power, which is composed of a negative meniscus lens convex on the object side and a positive meniscus lens convex on the object side. , An aperture stop S, a positive meniscus lens having a convex surface on the image side, and a second lens group G2 having a positive refractive power composed of a cemented lens of a positive meniscus lens having a convex surface on the object side and a negative meniscus lens having a convex surface on the object side. It consists of a third lens group G3 having a positive refracting power consisting of one convex positive lens, and when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves in a concave locus toward the object side, At the end, the position is closer to the image side than the wide-angle end, the second lens group G2 moves toward the object side together with the aperture stop S, and the third lens group G3 moves along a convex locus toward the object side, and the telephoto end. At the end, the position is slightly closer to the object side than the wide-angle end.
In order to focus on a short-distance subject, the third lens group G3 is extended to the object side.

Regarding aspherical surfaces, Examples 2 to 4 are
An image side surface of the negative meniscus lens of the lens group G1, a second surface
The third lens group G2 is used for three surfaces on both sides of a single positive meniscus lens, and in the fifth embodiment, the first lens group G1 is used.
Of the negative meniscus lens on the image side, the second lens group G2
Are used for the four surfaces of the both sides of the single positive meniscus lens and the object side surface of the biconvex positive lens of the third lens group G3.

Numerical data of each of the above-mentioned embodiments will be shown below. Symbols are other than the above, f is the focal length of the entire system, ω is a half angle of view,
F _NO is the F number, WE is the wide-angle end, ST is the intermediate state, T
E is the telephoto end, r ₁ , r ₂ ... Is the radius of curvature of each lens surface, d
₁ , d ₂ ... Intervals between lens surfaces, n _d1 , n _d2 ..., Refractive index of d line of each lens, ν _d1 , ν _d2, ... Abbe number of each lens. The aspherical shape is represented by the following formula, where x is an optical axis with the traveling direction of light being positive and y is a direction orthogonal to the optical axis.

X = (y ² / r) / [1+ {1- (K +
1) (y / r) ² } ^1/2 ] + A ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁸ +
A ₁₀ y ¹⁰ However, r is a paraxial radius of curvature, K is a conic coefficient, A ₄ , A ₆ ,
A ₈ and A ₁₀ are aspherical coefficients of the 4th, 6th, 8th and 10th orders, respectively.

Example 1 r ₁ = 146.0335 d ₁ = 0.7000 n _d1 = 1.80610 ν _d1 = 40.92 r ₂ = 4.8376 (aspherical surface) d ₂ = 2.0000 r ₃ = 9.4028 d ₃ = 1.8000 n _d2 = 1.84666 ν _d2 = 23.78 r ₄ = 31.3558 d ₄ = (variable) r ₅ = ∞ (aperture) d ₅ = 1.2000 r ₆ = 39.1621 (aspherical surface) d ₆ = 1.8000 n _d3 = 1.69350 ν _d3 = 53.21 r ₇ = -7.6492 d ₇ = 0.1500 r ₈ = 4.3803 (aspherical surface) d ₈ = 1.7000 n _d4 = 1.74320 ν _d4 = 49.34 r ₉ = 10.0000 d ₉ = 0.7000 n _d5 = 1.84666 ν _d5 = 23.78 r ₁₀ = 2.8121 d ₁₀ = (variable) r ₁₁ = 14.5109 _{d 11 = 1.8000 n d6 = 1.58913} ν d6 = 61.14 r 12 = -26.9622 d 12 = ( _{variable) r 13 = ∞ d 13 =} 0.8000 n d7 = 1.51633 ν d7 = 64.14 r 14 = ∞ d 14 = 1.5000 n d8 = 1.54771 ν _d8 = 62.84 r ₁₅ = ∞ d ₁₅ = 0.8000 r ₁₆ = ∞ d ₁₆ = 0.7500 n _d9 = 1.51633 ν _d9 = 64.14 r ₁₇ = ∞ d ₁₇ = 1.2062 r ₁₈ = ∞ (image plane) aspheric coefficient second surface _{K = 0 A 4 = -1.0695 ×} 10 -3 A 6 = 2.8824 × 10 -5 A 8 = -3.3729 ₁₀ ^-6 A 10 = 0.0000 Sixth Surface _{K = 0 A 4 = -2.7692 ×} 10 -3 A 6 = 8.8573 × 10 -5 A 8 = 1.4733 × 10 -6 A 10 = 0.0000 eighth surface K = 0 A ₄ = 1.9841 × 10 ^-3 A ₆ = 1.8697 × 10 ^-5 A ₈ = -8.7311 × 10 ^-7 A ₁₀ = 0.0000 Zoom data (∞) WE ST TE f (mm) 4.52432 8.70520 12.89629 F _NO 2.5943 3.4614 4.5554 ω (° ) 33.1 17.9 12.3 d ₄ 13.65335 4.56398 1.50000 d ₁₀ 2.53628 7.47701 12.76228 d ₁₂ 0.92173 1.04621 1.00069.

Example 2 r ₁ = 138.0405 d ₁ = 0.7000 n _d1 = 1.80610 ν _d1 = 40.92 r ₂ = 4.9091 (aspherical surface) d ₂ = 2.0000 r ₃ = 9.3688 d ₃ = 1.8000 n _d2 = 1.84666 ν _d2 = 23.78 r ₄ = 28.4607 d ₄ = (variable) r ₅ = ∞ (aperture) d ₅ = 1.2000 r ₆ = -71.0164 (aspherical surface) d ₆ = 1.8000 n _d3 = 1.74320 ν _d3 = 49.34 r ₇ = -8.0688 (aspherical surface) ) D ₇ = 0.1500 r ₈ = 3.5770 d ₈ = 1.7000 n _d4 = 1.74320 ν _d4 = 49.34 r ₉ = 10.0000 d ₉ = 0.7000 n _d5 = 1.84666 ν _d5 = 23.78 r ₁₀ = 2.5761 d ₁₀ = (variable) r ₁₁ = 15.4548 d ₁₁ = 1.8000 n _d6 = 1.58913 ν _d6 = 61.14 r ₁₂ = -25.3502 d ₁₂ = (variable) r ₁₃ = ∞ d ₁₃ = 0.8000 n _d7 = 1.51633 ν _d7 = 64.14 r ₁₄ = ∞ d ₁₄ = 1.5000 n _d8 = 1.54771 ν _d8 = 62.84 r ₁₅ = ∞ d ₁₅ = 0.8000 r ₁₆ = ∞ d ₁₆ = 0.7500 n _d9 = 1.51633 ν _d9 = 64.14 r ₁₇ = ∞ d ₁₇ = 1.2096 r ₁₈ = ∞ (image plane) aspheric coefficient 2 sides K = 0 A ₄ = -1.0115 × 10 ^-3 A ₆ = 2.7045 × 10 ^-5 A ₈ = -3.0432 × 10 ^-6 A ₁₀ = 0.0000 6th surface K = 0 A ₄ = -1.5275 × 10 ^-3 A ₆ = -7.7582 × 10 ^-5 A ₈ = 1.0811 × 10 ^-5 A ₁₀ = 0.0000 7th surface K = 0 A ₄ = -7.6607 × 10 ^-4 A ₆ = -3.9147 × 10 ^-5 A ₈ = 6.0006 × 10 ^-6 A ₁₀ = 0.0000 Zoom data (∞) WE ST TE f (mm) 4.49828 8.69102 12.89987 F _NO 2.5943 3.4614 4.5554 ω (°) 33.3 18.0 12.3 d ₄ 13.63493 4.17454 1.50000 d ₁₀ 2.53628 6.81122 12.65699 d ₁₂ 0.92173 1.49607 0.99778.

Example 3 r ₁ = 79.4132 d ₁ = 0.7000 n _d1 = 1.80610 ν _d1 = 40.92 r ₂ = 4.8327 (aspherical surface) d ₂ = 2.0000 r ₃ = 8.8447 d ₃ = 1.8000 n _d2 = 1.84666 ν _d2 = 23.78 r ₄ = 22.3225 d ₄ = (variable) r ₅ = ∞ (aperture) d ₅ = 1.2000 r ₆ = -16.0062 (aspherical surface) d ₆ = 1.9000 n _d3 = 1.74320 ν _d3 = 49.34 r ₇ = -6.1582 (aspherical surface) ) D ₇ = 0.1500 r ₈ = 3.8024 d ₈ = 2.0000 n _d4 = 1.72916 ν _d4 = 54.68 r ₉ = 9.0000 d ₉ = 0.7000 n _d5 = 1.84666 ν _d5 = 23.78 r ₁₀ = 2.7164 d ₁₀ = (variable) r ₁₁ = 13.3500 d ₁₁ = 1.8000 n _d6 = 1.48749 ν _d6 = 70.23 r ₁₂ = -19.5882 d ₁₂ = (variable) r ₁₃ = ∞ d ₁₃ = 0.8000 n _d7 = 1.51633 ν _d7 = 64.14 r ₁₄ = ∞ d ₁₄ = 1.5000 n _d8 = 1.54771 ν _d8 = 62.84 r ₁₅ = ∞ d ₁₅ = 0.8000 r ₁₆ = ∞ d ₁₆ = 0.7500 n _d9 = 1.51633 ν _d9 = 64.14 r ₁₇ = ∞ d ₁₇ = 1.2102 r ₁₈ = ∞ (image plane) aspheric coefficient 2 sides K = 0 A ₄ = -1.0103 × 10 ^-3 A ₆ = 3.1536 × 10 ^-5 A ₈ = -3.4456 × 10 ^-6 A ₁₀ = 0.0000 6th surface K = 0 A ₄ = -2.4614 × 10 ^-3 A ₆ = -8.7697 × 10 ^-5 A ₈ = 4.2836 × 10 ^-6 A ₁₀ = 0.0000 7th surface K = 0 A ₄ = -1.0556 × 10 ^-3 A ₆ = -2.8401 × 10 ^-5 A ₈ = 1.2812 × 10 ^-6 A ₁₀ = 0.0000 Zoom data (∞) WE ST TE f (mm) 4.49965 8.69150 12.89970 F _NO 2.5981 3.4381 4.5399 ω (°) 33.3 18.0 12.3 d ₄ 13.23405 3.88655 1.50000 d ₁₀ 2.53628 6.56595 12.86016 d ₁₂ 0.92173 1.73176 0.99795.

Example 4 r ₁ = 101.9664 d ₁ = 0.7000 n _d1 = 1.80610 ν _d1 = 40.92 r ₂ = 4.8139 (aspherical surface) d ₂ = 2.000 r ₃ = 9.0081 d ₃ = 1.8000 n _d2 = 1.84666 ν _d2 = 23.78 r ₄ = 24.6570 d ₄ = (variable) r ₅ = ∞ (aperture) d ₅ = 1.2000 r ₆ = -18.0167 (aspherical surface) d ₆ = 1.9000 n _d3 = 1.69350 ν _d3 = 53.21 r ₇ = -5.9692 (aspherical surface) ) D ₇ = 0.1500 r ₈ = 3.7700 d ₈ = 2.0000 n _d4 = 1.69680 ν _d4 = 55.53 r ₉ = 8.5000 d ₉ = 0.7000 n _d5 = 1.84666 ν _d5 = 23.78 r ₁₀ = 2.7329 d ₁₀ = (variable) r ₁₁ = 13.2790 d ₁₁ = 1.8000 n _d6 = 1.48749 ν _d6 = 70.23 r ₁₂ = -19.7163 d ₁₂ = (variable) r ₁₃ = ∞ d ₁₃ = 0.8000 n _d7 = 1.51633 ν _d7 = 64.14 r ₁₄ = ∞ d ₁₄ = 1.5000 n _d8 = 1.54771 ν _d8 = 62.84 r ₁₅ = ∞ d ₁₅ = 0.8000 r ₁₆ = ∞ d ₁₆ = 0.7500 n _d9 = 1.51633 ν _d9 = 64.14 r ₁₇ = ∞ d ₁₇ = 1.2101 r ₁₈ = ∞ (image plane) aspherical coefficient No. dihedral _{K = 0 A 4 = -1.0438 ×} 10 -3 A 6 = 2.9959 × 10 -5 A 8 = -3.4809 ₁₀ ^-6 A 10 = 0.0000 Sixth Surface _{K = 0 A 4 = -2.6839 ×} 10 -3 A 6 = -9.7649 × 10 -5 A 8 = 1.2873 × 10 -6 A 10 = 0.0000 seventh surface K = 0 A ₄ = -1.1651 × 10 ^-3 A ₆ = -3.3214 × 10 ^-5 A ₈ = 5.2387 × 10 ^-8 A ₁₀ = 0.0000 Zoom data (∞) WE ST TE f (mm) 4.49922 8.69156 12.89987 F _NO 2.5981 3.4381 4.5399 ω (°) 33.3 18.0 12.3 d ₄ 13.23405 3.98202 1.50000 d ₁₀ 2.53628 6.78005 12.93567 d ₁₂ 0.92173 1.61825 0.99804.

Example 5 r ₁ = 89.5504 d ₁ = 0.7000 n _d1 = 1.80610 ν _d1 = 40.92 r ₂ = 4.8314 (aspherical surface) d ₂ = 2.0000 r ₃ = 8.9067 d ₃ = 1.8000 n _d2 = 1.84666 ν _d2 = 23.78 r ₄ = 23.2563 d ₄ = (variable) r ₅ = ∞ (aperture) d ₅ = 1.2000 r ₆ = -14.4264 (aspherical surface) d ₆ = 1.9000 n _d3 = 1.69350 ν _d3 = 53.21 r ₇ = -5.5904 (aspherical surface) ) D ₇ = 0.1500 r ₈ = 3.7334 d ₈ = 2.0000 n _d4 = 1.69680 ν _d4 = 55.53 r ₉ = 8.5000 d ₉ = 0.7000 nd _d = 1.84666 ν _d5 = 23.78 r ₁₀ = 2.6938 d ₁₀ = (variable) r ₁₁ = 11.9542 (aspherical surface) d ₁₁ = 1.8000 n _d6 = 1.48749 ν _d6 = 70.23 r ₁₂ = -24.0704 d ₁₂ = (variable) r ₁₃ = ∞ d ₁₃ = 0.8000 n _d7 = 1.51633 ν _d7 = 64.14 r ₁₄ = ∞ d ₁₄ = 1.5000 n _d8 = 1.54771 ν _d8 = 62.84 r ₁₅ = ∞ d ₁₅ = 0.8000 r ₁₆ = ∞ d ₁₆ = 0.7500 n _d9 = 1.51633 ν _d9 = 64.14 r ₁₇ = ∞ d ₁₇ = 1.2099 r ₁₈ = ∞ (image plane) Aspheric coefficient 2nd surface K = 0 A ₄ = -1.0038 × 10 ^-3 A ₆ = 2.8728 × 10 ^-5 A ₈ = -3.3852 × 10 ^-6 A ₁₀ = 0.0000 6th surface K = 0 A ₄ = -3.1665 × 10 ^-3 A ₆ = -9.3446 × 10 ^-5 A ₈ = -4.0244 × 10 ^-6 A ₁₀ = 0.0000 7th surface K = 0 A ₄ = -1.3270 × 10 ^-3 A ₆ = -2.5438 × 10 ^-5 A ₈ = -1.8415 × 10 ^-6 A ₁₀ = 0.0000 11th surface K = 0 A ₄ = -4.7969 × 10 ^-6 A ₆ = 1.2960 × 10 ^-5 A ₈ = -4.9951 × 10 ^-7 A ₁₀ = 0.0000 Zoom data (∞) WEST TE f (mm) 4.50008 8.69135 12.89964 F _NO 2.5950 3.4438 4.5331 ω (°) 33.2 18.1 12.4 d ₄ 13.23383 3.85945 1.50000 d ₁₀ 2.53628 6.56374 12.97929 d ₁₂ 0.92173 1.76341 0.99823.

FIG. 3 is an aberration diagram in the case of focusing to infinity in the first embodiment, and FIG. 4 is an aberration diagram in the case of focusing to a shooting distance of 10 cm by moving the third lens group G3 to the object side. Show. 5 and 6 are similar aberration diagrams of the second embodiment, and FIG. 7 is a similar aberration diagram of the third embodiment.
8 and FIGS. 8A and 8B, similar aberration diagrams of Example 4 are shown in FIGS.
Similar aberration diagrams for Example 5 are shown in FIGS. 11 and 12, respectively. In these aberration charts, (a) is the wide-angle end, (b) is the intermediate state, (c) is the telephoto end, "SA" is spherical aberration, "AS" is astigmatism, and "DT" is distortion. Aberration, "C
C "indicates lateral chromatic aberration. Also, in each aberration diagram," FI "
Y "indicates the image height.

Next, the conditions (1)-
As for (6), (8) to (16) values, and condition (7)
The values of p21F, Asp21R, and L, Z are shown. Example 1 2 3 4 5 (1) 0 0 0 0 0.00120 (2) -0.30023 -0.24250 -0.18939 -0.19510 -0.33633 (3) 0.64200 0.72019 0.71440 0.72491 0.72155 (4) 0.56000 0.56000 0.62222 0.65882 0.65882 (5) 0.10346 0.10346 0.11750 0.14986 0.14986 (6) 0.67319 1.25636 2.25065 1.99094 2.26535 (8) 1.56862 1.56518 1.60728 1.61320 1.61656 (9) 17.14000 17.14000 17.14000 17.14000 17.14000 (10) -1.85663 -1.98145 -2.31248 -2.15127 -2.24139 (11) 0.35714 0.35714 0.35714 0.35714 0.35714 0.314 1.0 1.0 1.0 1.0 1.0 (13) 0.04 0.04 0.04 0.04 0.04 (14) 0.0 0.0 0.0 0.0 0.0 (15) 1.06 1.06 1.06 1.06 1.06 (16) 0.333 0.333 0.333 0.333 0.333 (a = 3.0) (a = 3.0) (a = 3.0) (a = 3.0) (a = 3.0) Asp21F -0.01997 -0.01323 -0.02131 -0.02349 -0.02758 Asp21R 0 -0.00660 -0.00897 -0.01002 -0.01126 L 5.6 5.6 5.6 5.6 5.6 Z 2.85 2.87 2.87 2.87 2.87.

The total thickness t _LPF of the low-pass filters of Examples 1 to 5 is 1.500 (mm), and three sheets are stacked. Of course, the above-described embodiment can be variously modified within the range of the above-described configuration, for example, the low-pass filter F is configured by one sheet.

Here, the diagonal length L of the effective image pickup surface and the pixel spacing a will be described. FIG. 13 is a diagram showing an example of a pixel array of the image sensor, in which R (red) and G are arranged at a pixel interval a.
Pixels of (green) and B (blue) or pixels of four colors of cyan, magenta, yellow and green (green) (FIG. 17) are arranged in a mosaic pattern. The effective image pickup surface means an area in the photoelectric conversion surface on the image pickup element used for reproducing a captured image (display on a personal computer, printing by a printer, etc.). The effective image pickup surface shown in the drawing is set in a region narrower than the entire photoelectric conversion surface of the image pickup element in accordance with the performance of the optical system (image circle which can ensure the performance of the optical system).
The diagonal length L of the effective image pickup surface is the diagonal length of this effective image pickup surface. It should be noted that the image pickup range used for reproducing the image may be variously changed, but when the zoom lens of the present invention is used in an image pickup apparatus having such a function, the diagonal length L of the effective image pickup surface changes. In such a case, the diagonal length L of the effective image pickup surface in the present invention is the maximum value in the range of L.

The infrared cut means includes an infrared cut absorption filter and an infrared sharp cut coat, and the infrared cut absorption filter is used when the glass contains an infrared absorber. The cut coat is cut by reflection, not absorption. Therefore, as described above, the infrared cut absorption filter may be removed and the low pass filter may be directly subjected to the infrared sharp cut coat, or may be applied onto the dummy transparent flat plate.

The near infrared sharp cut coat in this case has a transmittance of 80% or more at a wavelength of 600 nm and a wavelength of 70% or more.
It is desirable that the transmittance at 0 nm be 10% or less. Specifically, for example, it is a multilayer film having the following 27-layer structure. However, the design wavelength is 78
It is 0 nm.

Base plate material Physical film thickness (nm) λ / 4 ─────────────────────────────── 1st layer Al ₂ O ₃ 58.96 0.50 Second layer TiO ₂ 84.19 1.00 Third layer SiO ₂ 134.14 1.00 Fourth layer TiO ₂ 84.19 1.00 Fifth layer SiO ₂ 134. 14 1.00 6th layer TiO ₂ 84.19 1.00 7th layer SiO ₂ 134.14 1.00 8th layer TiO ₂ 84.19 1.00 9th layer SiO ₂ 134.14 1.00 10th layer Layer TiO ₂ 84.19 1.00 11th layer SiO ₂ 134.14 1.00 12th layer TiO ₂ 84.19 1.00 13th layer SiO ₂ 134.14 1.00 14th layer TiO ₂ 84.19 1.00 15th layer SiO ₂ 178.41 1.33 16th layer TiO ₂ 101.03 1.21 17th layer SiO ₂ 167.67 1.25 18th layer TiO ₂ 96.82 1.15 19th layer SiO ₂ 147.55 1.05 20th layer TiO ₂ 84.19 1.00 21st layer SiO ₂ 160 .97 1.20 22nd layer TiO ₂ 84.19 1.00 23rd layer SiO ₂ 154.26 1.15 24th layer TiO ₂ 95.13 1.13 25th layer SiO ₂ 160.97 1.20 26th layer TiO ₂ 99.34 1.18 27th layer SiO ₂ 87.19 0.65 ────────────────────────────── ──

The transmittance characteristics of the above-mentioned near-infrared sharp cut coat are as shown in FIG.

Further, by providing or coating on the exit surface side of the low-pass filter a color filter that reduces the transmission of colors in the short wavelength region as shown in FIG. 16, the color reproducibility of the electronic image is further improved. Is increasing.

Specifically, this filter or coating has a ratio of the transmittance of the wavelength of 420 nm to the transmittance of the wavelength of 400 nm to 700 nm which is the highest, and the ratio of the transmittance of the wavelength of 420 nm is 15% or more. The ratio of the transmittance at the wavelength of 400 nm to the transmittance is preferably 6% or less.

As a result, it is possible to reduce the difference between the color recognition of the human eye and the color of the image picked up and reproduced. In other words, it is possible to prevent the deterioration of the image due to the color on the short wavelength side, which is difficult to be recognized by human eyes, to be easily recognized by human eyes.

The transmittance ratio at the wavelength of 400 nm is 6
If it exceeds%, a single wavelength castle that is difficult for the human eye to recognize will be reproduced at a wavelength that can be recognized.
If the transmittance ratio of the wavelength of nm is less than 15%, the reproduction of the wavelength castle that can be recognized by humans becomes low, and the color balance becomes poor.

Such means for limiting the wavelength is more effective in the image pickup system using the complementary color mosaic filter.

In each of the above embodiments, as shown in FIG.
The transmittance at a wavelength of 400 nm is 0%, the transmittance at 420 nm is 90%, and the transmittance peak 1 is at 440 nm.
The coating is 00%.

By the above-mentioned action with the near-infrared sharp cut coat, a transmittance of 99 at a wavelength of 450 nm is obtained.
% As a peak, and the transmittance at 400 nm is 0%,
The transmittance at 420 nm is 80%, the transmittance at 600 nm is 82%, and the transmittance at 700 nm is 2%. Thereby, more faithful color reproduction is performed.

Further, the low-pass filter uses three kinds of filters having crystal axes in the horizontal (= 0 °) and ± 45 ° azimuth angles when projected on the image plane, which are superposed in the optical axis direction. , For each, horizontally aμm, ±
Moire suppression is performed by shifting by SQRT (1/2) × a in the 45 ° direction. Here, SQRT is a square root as described above and means a square root.

Further, as shown in FIG. 17, cyan, on the image pickup surface of the CCD arranged on the image plane I of the above-mentioned Examples 1 to 5,
A complementary color mosaic filter is provided in which four color filters of magenta, yellow, and green (green) are provided in a mosaic pattern corresponding to the image pickup pixels. These four types of color filters are arranged in a mosaic pattern so that the numbers of the filters are substantially the same and adjacent pixels do not correspond to the same type of color filters. This allows more faithful color reproduction.

The complementary color mosaic filter is specifically,
As shown in FIG. 17, at least four types of color filters are used, and the four types of color filters preferably have the following characteristics.

The green color filter G has a spectral intensity peak at a wavelength G _P , the yellow color filter Y _e has a spectral intensity peak at a wavelength Y _P , and the cyan color filter C has a wavelength C _P. The magenta color filter M has a peak of the spectral intensity and the peaks of the wavelengths M _P1 and M _P2 , which satisfy the following conditions.

[0125] _{510nm <G P <540nm 5nm <} Y P -G P <35nm -100nm <C P -G P <-5nm 430nm <M P1 <480nm 580nm <M P2 <640nm Furthermore, green, yellow, cyan The filter has an intensity of 80% or more at a wavelength of 530 nm with respect to each spectral intensity peak, and the magenta color filter has an intensity of 10% at a wavelength of 530 nm with respect to the spectral intensity peak.
% To 50% is more preferable in order to improve color reproducibility.

FIG. 18 shows an example of each wavelength characteristic in each of the above embodiments. Green color filter G is 5
It has a spectral intensity beak at 25 nm. The yellow color filter Y _e has a spectral intensity peak at 555 nm. Cyan color filter C has a peak of spectral intensity at 510 nm. Magenta color filter M
Has peaks at 445 nm and 620 nm. In addition, in each color filter at 530 nm, G is 99% and Y _e is 95% with respect to each spectral intensity peak.
%, C is 97%, and M is 38%.

In the case of such a complementary color filter, a controller (or a controller used in a digital camera) (not shown) electrically performs the following signal processing to obtain a luminance signal Y = | G + M + Y _e + C | × 1 / Four color signals R-Y = | (M + Y _e )-(G + C) | B-Y = | (M + C)-(G + Y _e ) | signal processing, and R (red), G (green), B (blue) Is converted to a signal.

By the way, the arrangement position of the above-mentioned near infrared sharp cut coat may be any position on the optical path. Also, the number of low-pass filters is 2 as described above.
Either one or one may be used.

The image pickup apparatus of the present invention as described above is
A photographing device that forms an image of an object with a zoom lens and receives the image by an electronic image pickup device such as a CCD for photographing, especially a digital camera, a video camera, a personal computer which is an example of an information processing device, a telephone, and is particularly convenient to carry. It can be used for mobile phones. The embodiment will be exemplified below.

19 to 21 are conceptual diagrams showing a configuration in which the zoom lens according to the present invention is incorporated in the photographing optical system 41 of a digital camera. 19 is a front perspective view showing the external appearance of the digital camera 40, FIG. 20 is a rear perspective view of the same, and FIG. 21 is a sectional view showing the configuration of the digital camera 40. In this example, the digital camera 40 includes a photographing optical system 41 having a photographing optical path 42, a finder optical system 43 having a finder optical path 44, a shutter 45, and a flash 4.
6. When the shutter 45, which includes the liquid crystal display monitor 47 and the like and is arranged above the camera 40, is pressed, the photographing is performed through the photographing optical system 41, for example, the zoom lens of the first embodiment in conjunction with the shutter 45. An object image formed by the photographing optical system 41 is formed on the image pickup surface of the CCD 49 via an infrared cut absorption filter IF formed by applying a near infrared cut coat on a dummy transparent flat plate and an optical low pass filter LF. . The object image received by the CCD 49 is displayed as an electronic image on the liquid crystal display monitor 47 provided on the rear surface of the camera via the processing means 51. Further, the recording means 52 is connected to the processing means 51, and the captured electronic image can be recorded. Incidentally, this recording means 5
The unit 2 may be provided separately from the processing unit 51, or may be configured to record and write electronically by a floppy (registered trademark) disk, memory card, MO, or the like. Also,
A silver salt camera in which a silver salt film is arranged instead of the CCD 49 may be configured.

Further, a finder objective optical system 53 is arranged on the finder optical path 44. The object image formed by the finder objective optical system 53 is formed on the field frame 57 of the Porro prism 55 which is an image erecting member. Behind the poly prism 55, an eyepiece optical system 59 for guiding an erect image to the observer's eye E is arranged. A cover member 50 is arranged on each of the incident side of the photographing optical system 41 and the objective optical system 53 for the finder, and the exit side of the eyepiece optical system 59.

The digital camera 40 configured as described above
Since the photographic optical system 41 is a zoom lens having a wide angle of view, a high zoom ratio, good aberrations, a high brightness, and a large back focus in which filters and the like can be arranged, high performance and low cost can be realized.

In the example of FIG. 21, a plane parallel plate is arranged as the cover member 50, but a lens having power may be used.

The electronic image pickup apparatus of the present invention described above can be configured, for example, as follows.

[1] In an electronic image pickup apparatus having a zoom lens and an electronic image pickup element arranged on the image side thereof, the zoom lens has, in order from the object side, a first lens group having a negative refracting power as a whole, A second lens group having a positive refracting power as a whole and a third lens group having a positive refracting power as a whole
The second lens group is composed of two lens components, the middle image side lens component has a meniscus shape with a concave surface facing the image plane side, and the third lens group is
At least the second lens unit moves toward the object side only at the time of zooming from the wide-angle end to the telephoto end at the time of focusing on an object point at infinity, and the third lens unit moves at the third side during zooming. An electronic image pickup apparatus characterized in that the third lens group moves in a different amount from that of the two lens groups, the third lens group moves during a focusing operation, and all the refracting surfaces of the third lens group satisfy the following conditions.

(1) 0 ≦ | Asp3 | <3.0 × 10 ⁻³ · L where L is the diagonal length of the effective image pickup area in the electronic image pickup device, and Asp3 is the refracting surface of each of the third lens groups. Is the amount of aspherical surface deviation, and is the amount of aspherical surface deviation when the height from the optical axis to the reference spherical surface having the radius of curvature on the optical axis is 0.4 L, and if the refracting surface is a spherical surface, the aspherical surface deviation amount Asp3 is Set to 0.

[2] The electronic image pickup device according to the above item 1, wherein the following condition is satisfied.

(2) −1.0 <(R _3F + R _3R ) / (R _3F −R _3R ) <0.7 where R _3F and R _3R are the most object side surfaces of the third lens group, It is the radius of curvature of the image side surface on the optical axis.

[3] The image-side lens component of the second lens group is composed of a cemented lens component in which a positive lens and a negative lens are cemented in this order from the object side, and the following condition is satisfied: The electronic imaging device according to 1 or 2 above.

(3) 0.45 <R _22R / R _22F <0.9 (4) 0 <L / R _22C <1.0 (5) 0 <n _22R −n _22F <0.3 However, R _22F , R _22R and R _22C are the radius of curvature on the optical axis of the most object side surface, the most image side surface and the cemented surface of the second lens group image side lens component, n _22F and n _22R are the second lens group image side lens, respectively. It is the refractive index of the d-line of the medium of the object side lens and the image side lens, respectively.

[4] The electron element according to any one of the above items 1 to 3, wherein the object-side lens component of the second lens group is composed of one single lens and satisfies the following condition: Imaging device.

(6) 0.1 <(R _21F + R _21R ) / (R _21F −R _21R ) <5 where R _21F and R _21R are the object-side surfaces of the lens components on the object side of the second lens group, respectively. , The radius of curvature of the image side surface on the optical axis.

[5] The object-side lens component of the second lens group is a reference spherical surface having an aspherical surface on both the object-side air contact surface and the image-side air contact surface and having a radius of curvature on the optical axis. On the other hand, both air contact surfaces are aspherical surfaces that are biased toward the object side.
The electronic imaging device according to the item.

[6] The electronic image pickup device according to the above item 5, wherein the following conditions are satisfied.

(7) 5.0 × 10 ⁻⁴ · L <| Asp21R | <| Asp21F | <3.0 × 10 ⁻² · L However, Asp21F and Asp21R are the lens components on the object side of the second lens group. The amount of aspherical surface displacement on the air contact surface on the object side and the air contact surface on the image side, respectively, and the height from the optical axis with respect to the reference spherical surface having a radius of curvature on the optical axis are 0.3L.
Is the amount of aspherical deviation at.

[7] The electronic image pickup device as described in any one of the above items 1 to 6, which satisfies the following condition.

(8) 1.45 <−β _2T <2.1 where β _2T is the magnification of the entire second lens group at the telephoto end when focusing on an object point at infinity.

[8] The electronic image pickup according to any one of 1 to 7, wherein the two lens components of the second lens group are, in order from the object side, a positive lens component and a negative lens component. apparatus.

[0149]

[9] The first lens group is composed of two lenses, a negative lens including an aspherical surface and a positive lens, and satisfies the following condition, any one of the above 1 to 8 The electronic imaging device described.

(9) 10 <ν ₁₁ −ν ₁₂ <24 (10) −4 <(R ₁₃ + R ₁₄ ) / (R ₁₃ −R ₁₄ ) <− 1.1 where ν ₁₁ is in the first lens group. Abbe number of the medium based on the d-line of the negative lens, ν ₁₂ is the Abbe number of the medium based on the d-line of the positive lens of the first lens group, and R ₁₃ is the optical axis of the object side surface of the positive lens of the first lens group R ₁₄ is the radius of curvature on the optical axis of the image side surface of the positive lens in the first lens group.

[10] The electronic image pickup device according to the above item 9, wherein the following condition is satisfied.

(11) 0.2 <d ₁₁ /L<0.65 where d ₁₁ is the air distance between the negative lens and the positive lens of the first lens group on the optical axis.

[11] The above-mentioned items 1 to 10, wherein the third lens group is composed of one positive lens.
The electronic imaging device according to claim 1.

[12] The electronic image pickup apparatus described in any one of the above items 1 to 11, wherein the diagonal length L of the effective image pickup area of the electronic image pickup element satisfies the following condition.

3.0 mm <L <12.0 mm [13] The half angle of view ω _{W in the} diagonal direction at the wide-angle end satisfies the following condition: (1)-(12) Electronic imaging device.

27.5 ° <ω _W

[0157]

As described above, according to the present invention, it is possible to obtain a zoom lens having a thin collapsible thickness, excellent storability, high magnification, and excellent image forming performance even in rear focus. It is possible to achieve a thorough reduction in thickness.

[Brief description of drawings]

FIG. 1 is a lens cross-sectional view of Example 1 of a zoom lens used in an electronic image pickup apparatus of the present invention at a wide-angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity. Is.

FIG. 2 is a lens cross-sectional view similar to FIG. 1 of the zoom lens of Embodiment 2.

FIG. 3 is an aberration diagram for Example 1 upon focusing on an object point at infinity.

FIG. 4 is an aberration diagram for Example 1 when a subject distance is 10 cm.

FIG. 5 is an aberration diagram for Example 2 upon focusing on an object point at infinity.

FIG. 6 is an aberration diagram for Example 2 when a subject distance is 10 cm.

FIG. 7 is an aberration diagram for Example 3 upon focusing on an object point at infinity.

FIG. 8 is an aberration diagram for Example 3 when focused on a subject at a distance of 10 cm.

FIG. 9 is an aberration diagram of Example 4 upon focusing on an object point at infinity.

FIG. 10 is an aberration diagram for Example 4 when focused on a subject at a distance of 10 cm.

FIG. 11 is an aberration diagram for Example 5 upon focusing on an object point at infinity.

FIG. 12 is an aberration diagram for Example 5 when focused on a subject at a distance of 10 cm.

FIG. 13 is a diagram for explaining a diagonal length of an effective image pickup surface when an image is taken by an electronic image pickup device.

FIG. 14 is a diagram for explaining the definition of the amount of aspherical surface deviation in the present invention.

FIG. 15 is a diagram showing transmittance characteristics of an example of a near infrared sharp cut coat.

FIG. 16 is a diagram showing transmittance characteristics of an example of a color filter provided on the exit surface side of a low-pass filter.

FIG. 17 is a diagram showing a color filter arrangement of complementary color mosaic filters.

FIG. 18 is a diagram showing an example of wavelength characteristics of a complementary color mosaic filter.

FIG. 19 is a front perspective view showing the outer appearance of a digital camera incorporating the zoom lens according to the present invention.

20 is a rear perspective view of the digital camera shown in FIG.

21 is a cross-sectional view of the digital camera shown in FIG.

[Explanation of symbols]

G1 ... First lens group G2 ... Second lens group G3 ... Third lens group S ... Aperture stop F ... Combination of infrared cut absorption filter and low-pass filter CG ... Cover glass I ... Image plane IF ... Infrared cut absorption filter LF ... optical low-pass filter E ... observer eye 40 ... digital camera 41 ... shooting optical system 42 ... shooting optical path 43 ... finder optical system 44 ... finder optical path 45 ... shutter 46 ... flash 47 ... liquid crystal display monitor 49 ... CCD 50 ... Cover member 51 ... Processing means 52 ... Recording means 53 ... Finder objective optical system 55 ... Porro prism 57 ... Field of view frame 59 ... Eyepiece optical system

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H087 KA01 MA14 PA05 PB06 QA02                       QA07 QA17 QA21 QA25 QA31                       QA42 QA45 RA01 RA43 SA06                       SA13 SA62 SA63 SA64 SB03                       SB14 SB22                 2H101 BB07 DD62                 5C022 AA00 AB44 AB66 AC54 CA00

Claims (3)

[Claims] 1. An electronic image pickup apparatus having a zoom lens and an electronic image pickup device arranged on an image side thereof, wherein the zoom lens has a first lens group having a negative refracting power as a whole in order from an object side, and Is composed of a second lens group having a positive refractive power and a third lens group having a positive refractive power as a whole, the second lens group is composed of two lens components, and the lens component on the middle image side is It has a meniscus shape with a concave surface facing the image plane side, the third lens group consists of one positive lens component, and at least the second lens group changes from the wide-angle end to the telephoto end when focusing on an object point at infinity. Moves only to the object side when doubling,
The third lens group moves by a different amount from that of the second lens group during zooming, the third lens group moves during focusing operation, and all the refracting surfaces of the third lens group satisfy the following conditions. An electronic imaging device characterized by satisfying. (1) 0 ≦ | Asp3 | <3.0 × 10 ⁻³ · L where L is the diagonal length of the effective image pickup area in the electronic image pickup device, and Asp3 is the aspherical surface of each refracting surface of the third lens group. The amount of deviation is the amount of deviation of the aspherical surface at a height of 0.4 L from the optical axis with respect to a reference spherical surface having a radius of curvature on the optical axis, and if the refracting surface is a spherical surface, the amount of aspherical surface deviation Asp3 is set to 0. . 2. The electronic image pickup device according to claim 1, wherein the following condition is satisfied. (2) −1.0 <(R _3F + R _3R ) / (R _3F −R _3R ) <0.7 where R _3F and R _3R are the most object-side surface and the most image-side surface of the third lens group, respectively. It is the radius of curvature of the surface on the optical axis. 3. The image-side lens component of the second lens group is composed of a cemented lens component in which a positive lens and a negative lens are cemented in this order from the object side, and the following condition is satisfied: The electronic image pickup device according to claim 1 or 2. (3) 0.45 <R _22R / R _22F <0.9 (4) 0 <L / R _22C <1.0 (5) 0 <n _22R -n _22F <0.3 where R _22F and R _22R , R _22C is the radius of curvature on the optical axis of the most object side surface, the most image side surface, and the cemented surface of the second lens group image side lens component, and n _22F and n _22R are the second lens group image side lens component, respectively. It is the d-line refractive index of the medium of the object side lens and the image side lens.