CN102789045B - Zoom projection lens - Google Patents

Abstract

The invention relates to a zoom projection lens, which comprises a first lens group and a second lens group in sequence from an object end to an image end, and has negative and positive refractive powers in sequence. The first lens group is a first lens, and the second lens group is composed of a second lens, a third lens, a fourth lens, and an aperture stop located between the second lens and the third lens. The first lens is an aspherical plastic lens, and one of the third lens and the fourth lens is an aspherical glass lens. The zoom projection lens satisfies 1.463＜|tt/lt|＜1.505, tt is the total length of the zoom projection lens, and lt is the length of the zoom projection lens. The zoom projection lens is composed of only four lenses, which reduces the number of lenses to save costs, and can meet the requirements of being light, thin, and short. The aberration of the projected image can be effectively corrected through the aspherical lens.

Description

zoom projection lens

technical field

The invention relates to an optical lens, in particular to a zoom projection lens for a projector.

Background technique

In recent years, Cathode Ray Tube (CRT) projection devices have been gradually replaced by thinner and smaller projection devices such as Liquid Crystal Display (Liquid Crystal Display) and Digital Light Processing (DLP) projection devices.

Wherein, the chief ray (chief ray) of the non-telecentric system (Non-telecentric) of the digital light source processing projection device is not parallel to the optical axis, and the zoom projection lens of the non-telecentric system can be compared with the zoom projection lens of the telecentric system. A total internal reflection prism is omitted to save the cost of the zoom projection lens. In addition, since the chief ray of the non-telecentric system is not parallel to the optical axis, it enters the zoom projection lens at an angle, causing the projected image to shift upwards on the projection screen, which meets the requirements of a front projection projector.

In the past, a non-telecentric system front projection projector, such as disclosed in Taiwan Patent No. I288290, included two sets of lens groups, and these lens groups were composed of four and seven lenses, not only because of the large number of lenses However, the cost cannot be effectively saved, and the length of the zoom projection lens cannot be reduced, which cannot meet the requirements of lightness, thinness and shortness.

Contents of the invention

The technical problem to be solved by the present invention is to provide a zoom projection lens that can save costs and meet the requirements of thinness and shortness in view of the defect that the zoom projection lens in the prior art cannot meet the requirements of thinness and shortness.

The technical solution adopted by the present invention to solve the technical problem is to provide a zoom projection lens, which sequentially includes a first lens group and a second lens group from the object end to the image end, and sequentially has negative and positive refractive powers, The first lens group is a first lens, the second lens group is composed of a second lens, a third lens, a fourth lens and an aperture stop between the second lens and the third lens, and the first lens is a non- A spherical plastic lens, one of the third lens and the fourth lens is an aspheric glass lens, and the zoom projection lens satisfies:

1.463<|tt/lt|<1.505,

tt is the total length of the zoom projection lens, and lt is the length of the zoom projection lens.

The effect of the present invention is that the zoom projection lens is only composed of four lenses, reducing the number of lenses to save cost, and can meet the requirements of thinness and shortness, and the aberration of the projected image is effectively corrected through the aspheric plastic lens or glass lens.

Description of drawings

Fig. 1 is a configuration diagram illustrating a first specific embodiment of the zoom projection lens of the present invention;

Fig. 2 is a spherical aberration diagram at the wide-angle end of the first specific embodiment;

Fig. 3 is a diagram of chromatic aberration of magnification at the wide-angle end of the first specific embodiment;

Fig. 4 is the image field curvature diagram of the meridian ray at the wide-angle end of the first specific embodiment;

Fig. 5 is the curvature of field diagram of the sagittal ray at the wide-angle end of the first specific embodiment;

Fig. 6 is a distortion diagram at the wide-angle end of the first specific embodiment;

Fig. 7 is the optical transfer function diagram of the wide-angle end of the first specific embodiment;

Fig. 8 is a spherical aberration diagram of the telescopic view of the first specific embodiment;

Fig. 9 is a diagram of chromatic aberration of magnification at the telephoto range of the first specific embodiment;

Fig. 10 is the image field curvature diagram of the long-distance meridian rays in the first specific embodiment;

Fig. 11 is the image field curvature diagram of the sagittal ray looking at the remote end of the first specific embodiment;

Fig. 12 is a distortion diagram of the telephoto of the first specific embodiment;

Fig. 13 is the optical transfer function diagram of the telescopic view in the first specific embodiment; and

FIG. 14 is a configuration diagram illustrating a second specific embodiment of the zoom projection lens of the present invention.

Detailed ways

The aforementioned and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of two preferred embodiments with accompanying drawings.

Before the present invention is described in detail, it should be noted that in the following description, similar components are denoted by the same numerals.

Referring to FIG. 1 , a preferred embodiment of the zoom projection lens of the present invention includes a first lens group 1 and a second lens group 2 sequentially from the object end to the image end, with negative and positive refractive powers in sequence.

The first lens group 1 is a first lens 11, and the first lens 11 is an aspheric plastic lens to effectively reduce the total length of the zoom projection lens and correct the aberration of the projected image, and the first lens 11 is convex toward the object end negative meniscus.

The second lens group 2 is composed of a second lens 21, a third lens 22, a fourth lens 23, and an aperture stop 24 (aperture stop) positioned between the second lens 21 and the third lens 22. The second lens The second lens 21, the third lens 22, and the fourth lens 23 of group 2 have positive, negative, and positive refractive powers in sequence. The second lens 21 is a spherical glass lens, and the second lens 21 is convex toward the object end. plano-convex lens or moon convex lens (postive meniscus), the third lens 22 is a biconcave lens (biconcave), the fourth lens 23 is a biconvex lens (biconvex), and one of the third lens 22 and the fourth lens 23 is a non- Spherical glass lens, through the use of aspheric glass lens, to correct the aberration of the projected image and to lengthen the back focal length of the zoom projection lens.

The zoom projection lens is only composed of four lenses, reducing the number of lenses to save cost, and can meet the requirements of thinness and shortness. For the change of ambient temperature, the length of the distance between the first lens group 1 and the second lens group 2, or zoom The back focal length of the projection lens is used to compensate and adjust the aberration of the projected image caused by the change of the ambient temperature.

Wherein, the zoom projection lens satisfies the following conditional formula:

|f1/f2|≤1.59 (1)

0.696＜|(f1+f2)/fw|＜0.732 (2)

2.985＜|tt/bf|＜3.161  (3)

1.463＜|tt/lt|＜1.505  (4)

1.311＜|ex/bf|＜1.383  (5)

f1 is the focal length of the first lens group 1, f2 is the focal length of the second lens group 2, fw is the focal length of the zoom projection lens at the wide-angle end, tt is the total length of the zoom projection lens, and bf is the zoom projection lens at the wide-angle end The length of the back focus, lt is the length of the zoom projection lens, and ex is the exit pupil position of the system.

By satisfying conditional formulas (1) and (2), the total length tt of the zoom projection lens can be effectively reduced, and the aberration of the projected image can be corrected; by satisfying conditional formula (3), the back focal length bf of the zoom projection lens can be effectively lengthened; by If conditions (4) and (5) are satisfied, the total length tt of the zoom projection lens can be further reduced, and the back focus length bf of the zoom projection lens can be further lengthened. The elongation of the length bf can increase the zoom magnification ratio from the wide-angle end (Wild-Angle) to the telephoto (Telephoto).

<First specific embodiment>

Table 1-1 shows various parameters of the first specific embodiment of the zoom projection lens, S1 to S8 from the object end to the image end are the object end surface S1 of the first lens 11, the image end surface S2 of the first lens 111, and And so on to the image end surface S8 of the fourth lens 23 .

In this first specific example, the second lens 21 is a plano-convex lens, the third lens 22 is a spherical glass lens, the fourth lens 23 is an aspheric glass lens, and the focal length f1 of the first lens group 1 is -41.6498 mm. The focal length f2 of the second lens group 2 is 26.1888 mm. The focal length fw of the zoom projection lens at the wide-angle end is 21.1343 mm. The total length tt of the zoom projection lens is 82 mm. is 56.0554 mm, and the exit pupil position ex of the system is -34.0751 mm, satisfying the aforementioned conditional formulas (1) to (5).

In addition, the numerical aperture (F-number) is 2.64, 2.70, and 2.75 in sequence from the wide-angle end, the intermediate state, and the telephoto lens. The focal length of the zoom projection lens is 21.1343 mm, 22.1594 mm, and 23.0025mm.

An aspheric surface can be expressed by the following conditional expression:

$\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}{<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; C</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 16</span>}}$

, taking the surface vertex as a reference point, D is the displacement value from the optical axis at the height H along the optical axis direction, K is the conic coefficient (conic coefficient), C is the reciprocal of the radius of curvature, E ₄ to E ₁₆ are high-order non- Spherical coefficients, the aspheric coefficients of the first lens 11 and the fourth lens 23 are shown in the following table 1-2:

The spherical aberration (longitudinal aberration) diagram of the first specific embodiment at the wide-angle end is shown in FIG. 2, wherein the pupil radius (pupil radius) is 4.0576 millimeters. Figure 3 is a chromatic aberration diagram of magnification (lateral color), and the highest half-height of the vertical axis is 10.2 mm. Figure 4 and Figure 5 are field curvature diagrams showing astigmatism, the imaging positions at different heights on the surface, Figure 4 represents meridian rays, and Figure 5 represents sagittal rays, and the abscissa is from the imaging point to the ideal image plane , the ordinate is the ideal image height. FIG. 6 is a distortion diagram showing distortion aberration, showing lateral magnification, the abscissa is the percentage difference from the imaging point to the ideal image point, and the ordinate is the ideal image height. FIG. 7 is a diagram of an optical transfer function (MTF, modulation transfer function), showing the modulus of the OTF (optical transfer function) corresponding to the change of the spatial frequency (spatial frequency).

The spherical aberration diagram, chromatic aberration diagram of magnification, field curvature diagram of meridional ray, field curvature diagram of sagittal ray, distortion diagram, and optical transfer function diagram of the first specific embodiment are shown in sequence as Fig. 8 to Figure 13.

<Second specific embodiment>

Table 2-1 is various parameters of the second specific embodiment of the zoom projection lens, the second lens 21 is a biconvex lens, the third lens 22 is an aspheric glass lens, the fourth lens 23 is a spherical glass lens, the The focal length f1 of the first lens group 1 is -41.4927 mm, the focal length f2 of the second lens group 2 is 26.7895 mm, the focal length fw of the zoom projection lens at the wide-angle end is 21.1367 mm, the total length tt of the zoom projection lens is 77.4095 mm, and the zoom projection lens The back focus length bf of the lens is 25.9365 mm, the length lt of the zoom projection lens is 51.4730 mm, and the exit pupil position ex of the system is -35.8658 mm, which satisfy the aforementioned conditional formulas (1) to (5).

In addition, the numerical aperture (F-number) is 2.64, 2.70, and 2.76 in sequence from wide-angle end, intermediate state, and telephoto. The focal length of the zoom projection lens is 21.1367 mm, 22.1754 mm, and 23.1736mm.

The aspheric coefficients of the first lens 11 and the third lens 22 are shown in Table 2-2 below:

In summary, the effects of the present invention are organized as follows:

1. The first lens 11 is an aspheric plastic lens to effectively reduce the total length of the zoom projection lens and correct the aberration of the projected image.

2. One of the third lens 22 and the fourth lens 23 is an aspheric glass lens. By using the aspheric glass lens, the aberration of the projected image is corrected and the back focal length of the zoom projection lens is lengthened.

3. The zoom projection lens is only composed of four lenses, reducing the number of lenses to save costs, and can meet the needs of thinness and shortness.

4. By satisfying conditional formulas (1) to (5), the total length tt of the zoom projection lens is reduced, and the back focal length bf of the zoom projection lens is reduced to meet the requirements of lightness, thinness and shortness, and increase the ratio of zoom ratio from wide-angle end to telephoto.

The above descriptions are only preferred embodiments of the present invention, and cannot limit the scope of the present invention with this. All simple equivalent changes and modifications made according to the claims of the present invention and the content of the description of the invention still belong to the present invention. covered by the patent.

Claims (8)

1. a Zooming-projection camera lens, is sequentially comprised to picture end by thing end:

First lens combination and the second lens combination, be sequentially negative, positive refractive index, this first lens combination is the first lens, it is characterized in that, this second lens combination is made up of the second lens, the 3rd lens, the 4th lens and the aperture diaphragm be positioned between these second lens and the 3rd lens, these first lens are aspherical plastic lens, and the 3rd lens, the 4th lens wherein one are aspherical glass lens, and this Zooming-projection camera lens meets:

1.463<|tt/lt|<1.505，

Tt is Zooming-projection camera lens overall length, and lt is Zooming-projection camera lens length.

2. Zooming-projection camera lens according to claim 1, is characterized in that, this Zooming-projection camera lens meets:

1.311<|ex/bf|<1.383，

Ex is system exit pupil position, and bf is Zooming-projection camera lens back focal length degree.

3. Zooming-projection camera lens according to claim 2, is characterized in that, this Zooming-projection camera lens meets: 2.985<|tt/bf|<3.161.

4. Zooming-projection camera lens according to claim 3, is characterized in that, this Zooming-projection camera lens meets: 0.696<| (f1+f2)/fw|<0.732,

F1 is the focal length of this first lens combination, and f2 is this is the focal length of this second lens combination, and fw is the focal length of this Zooming-projection camera lens in wide-angle side.

5. Zooming-projection camera lens according to claim 4, is characterized in that, this Zooming-projection camera lens meets:

|f1/f2|≤1.59。

6. Zooming-projection camera lens according to claim 5, is characterized in that, the second lens of this second lens combination, the 3rd lens, the 4th lens are sequentially positive and negative, positive refractive index.

7. Zooming-projection camera lens according to claim 6, is characterized in that, the 4th lens are aspherical glass lens.

8. Zooming-projection camera lens according to claim 6, is characterized in that, the 3rd lens are aspherical glass lens.