JP2006251412A - Lens for observation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens optical system achieving the miniaturization of a pen type microscope or the like. <P>SOLUTION: A first lens 421 being a biconvex lens having positive refractive power, an aperture stop 430 forming a predetermined aperture, a second lens 422 being a biconcave lens having negative refractive power, and a third lens 423 being a biconvex lens having positive refractive power are arrayed in order from an object side to an image surface side in a lens barrel 410. Since the aperture stop is arranged between the first lens and the second lens in three-lens constitution, the outside diameters of the first lens and the second lens are made small, and the lens for observation whose diameter is small as a whole and which is held in a compact lens barrel is obtained. Therefore, when the lens is mounted in the pen type microscopic unit, the miniaturization of the unit is realized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an observation lens applied to a small microscope unit for magnifying and observing an object, and more particularly to an observation lens applied to a low-magnification pen-type microscope unit or the like having a built-in light source that irradiates an object. .

  A small pen-type microscope unit with a built-in light source that illuminates an object is known to be applicable when observing magnified insects outdoors and inspecting the finish of the fabric surface at a fabric production plant. Yes. This type of microscope unit employs, as a light source, a combination of a halogen lamp and glass fiber, or a light emitting diode arranged in a ring shape.

  Since this microscope unit is assumed to be used by being grasped by hand, it is required to be as light and compact as possible. On the other hand, since it is necessary to secure a space for incorporating illumination components including a light source such as a light emitting diode, it is conceivable to reduce the size and weight of the observation lens excluding these illumination components.

As an observation lens applied to a microscope unit, a triplet lens composed of a first lens, a second lens, and a third lens is known because it is small and used at a relatively low magnification. (For example, refer to Patent Document 1, Patent Document 2, and Patent Document 3).
The lens disclosed in Patent Document 1 is a standard lens in which an aperture stop is disposed between the second lens and the third lens. However, in a lens adopting this arrangement, the distance from the first lens to the aperture stop becomes long, so that the outer diameter (diameter) of the first lens is set to the other two in order to secure the necessary field of view and peripheral light quantity. It needs to be larger than the lens. As a result, the diameter of the tip of the lens barrel is increased, which is against size reduction.

  The lens disclosed in Patent Document 2 has an aperture stop arranged behind the third lens (closer to the image plane side), and is applied to an inexpensive camera. However, in a lens employing this arrangement configuration, the distance from the first lens to the aperture stop is further increased, and thus the outer diameter of the first lens is further increased, which is inappropriate.

  The lens disclosed in Patent Document 3 has an aperture stop disposed in front of the first lens (closer to the object side), and improves telecentricity by separating the exit pupil from the image plane. However, in a lens employing this arrangement, the distance from the aperture stop to the first lens or the second lens is shortened, so that the outer diameter of these lenses can be reduced, but the outer diameter of the third lens is increased. There is a problem that a gap is generated between the aperture stop and the first lens, and dust or the like accumulates in the gap.

JP 7-325251 A Japanese Patent Laid-Open No. 7-168095 Japanese Patent Laid-Open No. 5-188284

  The present invention has been made in view of the above-mentioned problems of the prior art, and the object of the present invention is to reduce the outer diameter of the lens as much as possible with a three-lens configuration and to facilitate assembly. Providing a lightweight and compact observation lens suitable for pen-type microscope units, which can prevent misassembly, etc., and obtain high-quality captured images by controlling stray light due to reflection in the lens barrel There is to do.

The observation lens of the present invention includes a biconvex first lens having a positive refractive power, an aperture stop having a predetermined aperture, and a negative refractive power, which are arranged in order from the object side to the image plane side. And a biconvex second lens having positive refractive power and a biconvex third lens having positive refractive power.
According to this configuration, in the three-lens configuration including the first lens, the second lens, and the third lens, the aperture stop is disposed between the first lens and the second lens. The outer diameter (diameter) of the second lens can be reduced, and an observation lens that has a small diameter and can be accommodated in a small lens barrel as a whole can be obtained. Therefore, when mounted on a pen-type microscope unit, miniaturization of the unit is achieved. In addition, since the aperture stop is disposed on the image plane side with respect to the first lens, no gap is formed in front of the first lens, and dust and the like can be prevented from accumulating.

In the above configuration, when the outer diameter of the first lens is φ1, the outer diameter of the second lens is φ2, and the outer diameter of the third lens is φ3,
φ1 = φ2 <φ3
A configuration that satisfies the above can be adopted.
According to this configuration, the first lens and the second lens have the same outer diameter that is smaller than the outer diameter of the third lens, so that the lens barrel can adopt a two-stage cylindrical shape. Therefore, when this observation lens is mounted on a microscope unit in which a light source such as a light emitting diode is arranged in the vicinity of the front end side (object side) of the lens barrel, the parts can be integrated and the whole size can be further reduced. be able to. In addition, since the lens barrel has a two-stage cylindrical shape with a thin object side and a thick image surface side, the first lens, the second lens, and the third lens are sequentially assembled from the image surface side when assembling the lens barrel. Can be assembled smoothly.

In the above configuration, when the radius of curvature of the object side surface of the second lens is R4 and the radius of curvature of the image side surface is R5,
R4 = -R5
A configuration that satisfies the above can be adopted.
According to this configuration, since the second lens is formed as a symmetric lens with no front and back, the front and back are not mistaken during the assembly, the assembly work can be performed efficiently, and stable quality is obtained. be able to.

In the above configuration, a configuration can be adopted in which a stray light restricting plate that restricts the stray light reflected in the lens barrel from reaching the image plane side is disposed on the image plane side of the third lens. .
According to this configuration, in a state where the first lens, the second lens, and the third lens are incorporated and held in the barrel, the light beam enters from the first lens side, and the aperture stop, the second lens, and the third lens. Then, when entering the image sensor (light receiving element) such as a CCD, the light beam (stray light) reflected on the inner peripheral surface of the lens barrel is regulated by the stray light regulating plate, and the stray light reaches the image sensor. Is prevented. Thereby, in the image of the image sensor, it is possible to prevent a decrease in contrast and a decrease in image quality, and a high-quality captured image can be obtained.

  According to the observation lens having the above-described configuration, the outer diameter of the lens can be reduced as much as possible in the three-lens configuration, and it is easy to assemble and prevent erroneous assembly. By limiting the stray light due to reflection, a high-quality captured image can be obtained, and a light and small observation lens suitable for a pen-type microscope unit can be obtained.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the accompanying drawings.
1 to 3 show an embodiment of an observation lens according to the present invention. FIG. 1 is a schematic configuration diagram showing a microscope unit on which the observation lens is mounted. FIG. FIG. 3 is a structural view of an observation lens.

As shown in FIG. 1, the microscope unit is provided with a case 10 bent in a substantially L shape, a plurality of light sources 20 arranged in the case 10, and an inclined area in a region passing through the centers of the plurality of light sources 20. The reflecting mirror 30, the lens barrel 40 disposed behind the reflecting mirror 30, the imaging device 50 having an imaging surface P such as a CCD disposed behind the lens barrel 40, and the LCD monitor 60 provided in the case 10 Etc. In this microscope unit, an image photographed by the image sensor 50 is appropriately processed by an image processing circuit (not shown) or the like, and an enlarged photographed image is displayed on the LCD monitor 60.
That is, when the microscope unit is observed close to an object, the illumination light emitted from the light source 20 is reflected by the object and enters the reflecting mirror 30 as subject light. Then, the reflected light that is bent and reflected by the reflecting mirror 30 passes through the lens barrel 40 and reaches the image sensor 50 to be imaged. The captured image is displayed on the LCD monitor 60.

As shown in FIG. 1, the case 10 has an observation window 10 a at a bent distal end portion, and is formed so that an operator can grasp an intermediate portion extending in the horizontal direction with a hand.
The light source 20 irradiates an object when observing the object in a close-up state, and a plurality of light sources 20 are arranged in an annular shape around the optical axis L1 in the vicinity of the inside of the observation window 10a. As the light source 20, for example, a light emitting diode, a halogen lamp, or the like can be applied.
The reflecting mirror 30 refracts a light beam centered on the optical axis L1 entering from the observation window 10a at a right angle and guides it to the lens barrel 40 as a reflected light beam centered on the optical axis L2. Therefore, a prism may be adopted instead of the reflecting mirror 30.

2, the lens barrel 40 includes a lens barrel 410, a first lens 421, a second lens 422, a third lens 423, an aperture stop 430 having a predetermined aperture, spacers 441 and 442, a lens presser 443, A stray light restricting plate 450 is provided.
In the lens barrel 410, a first lens 421, an aperture stop 430, a second lens 422, and a third lens 423 are arranged in order from the object side to the image plane side, and behind the third lens 423 (image plane). A stray light restricting plate 450 is arranged on the side.

  As shown in FIG. 2, the lens barrel 410 is formed in a cylindrical shape having a two-stage configuration of a small diameter portion 411 and a large diameter portion 412. The small-diameter portion 411 is formed with an abutting portion 413 that abuts the outer peripheral portion of the front surface of the first lens 421 and an inner peripheral surface 414 that fits and holds the first lens 421 and the second lens 422. An inner peripheral surface 415 that has a larger diameter than the inner peripheral surface 414 and fits and holds the third lens 423 is formed at the transition portion from the small diameter portion 411 to the large diameter portion 412. The large-diameter portion 412 is formed with a female screw portion 416, an inner peripheral surface 417, and an inner peripheral surface 418 so that the inner diameter increases sequentially.

The first lens 421 is a biconvex lens having a positive refractive power having a convex surface (spherical surface) on the object side and a convex surface (spherical surface) on the image surface side.
The second lens 422 is a biconcave lens having negative refractive power having a concave surface (spherical surface) on the object side and a concave surface (spherical surface) on the image surface side.
The third lens 423 is a biconvex lens having a positive refractive power having a convex surface (spherical surface) on the object side and a convex surface (spherical surface) on the image surface side.

  Here, in the configuration in which the first lens 421, the aperture stop plate 430, the second lens 422, the third lens 423, and the image plane P are sequentially arranged along the optical axis L2 from the object side to the image plane side. 3, each surface is Si (i = 1 to 7), the radius of curvature of each surface Si is Ri (i = 1 to 7), the refractive index with respect to the d-line is Ni, and the Abbe number is νi (i = 1 to 3), and the distance (thickness, air distance) on each optical axis L2 from the first lens 421 to the image plane P is represented by Di (i = 1 to 7), and the outer diameter of the first lens 421 (Diameter) is represented by φ1, the outer diameter (diameter) of the second lens 422 is represented by φ2, and the outer diameter (diameter) of the third lens 423 is represented by φ3.

  As described above, in the three-lens configuration including the first lens 421, the second lens 422, and the third lens 423, the aperture stop 430 is disposed between the first lens 421 and the second lens 422. The outer diameter φ1 of the first lens 421 and the outer diameter φ2 of the second lens 422 can be reduced, and an observation lens that has a small diameter and can fit in a small lens barrel as a whole can be obtained. Therefore, when mounted on a pen-type microscope unit, miniaturization of the unit is achieved.

Further, since the aperture stop 430 is disposed on the image plane side with respect to the first lens 421, a gap is not formed in front of the first lens 421, and accumulation of dust or the like can be prevented.
Here, the outer diameter φ1 of the first lens 421, the outer diameter φ2 of the second lens 422, and the outer diameter φ3 of the third lens 423 are:
φ1 = φ2 <φ3
It may be formed so as to satisfy
According to this, by making the first lens 421 and the second lens 422 have the same outer diameter smaller than the outer diameter of the third lens 423, the lens barrel 410 can also adopt a two-stage cylindrical shape. . Therefore, as shown in FIG. 1, in the microscope unit in which the light source 20 such as a light emitting diode is disposed in the vicinity of the front end side (object side) of the lens barrel 410, it is possible to achieve the integration of parts and further reduce the overall size. Can be

Further, the curvature radius R4 of the object-side surface S4 and the curvature radius R5 of the image-side surface S5 of the second lens 422 are:
R4 = -R5
It may be formed so as to satisfy
According to this, since the second lens 422 is formed as a symmetric biconcave lens with no front and back, the front and back are not mistaken during assembly, the assembly work can be performed efficiently, and stable quality is achieved. Obtainable.

Further, as shown in FIG. 2, a stray light restricting plate 450 is disposed on the inner peripheral surface 418 of the large diameter portion 412 positioned on the image plane side with respect to the third lens 423. The stray light restricting plate 450 is formed in an annular shape from an inexpensive thin metal plate.
Therefore, the light beam that has entered from the first lens 421 side passes through the aperture stop 430, the second lens 422, and the third lens 423, and enters the image pickup device (light receiving device) 50 such as a CCD. At this time, as shown in FIG. 2, the light beam that has traveled through the lens barrel 410 is reflected by the inner peripheral surface 417 and is reflected by the stray light regulating plate 450 even if it travels to the image surface side as stray light. Reaching to the surface side, that is, the image sensor 50 is restricted. Thereby, in the image of the image sensor 50, it is possible to prevent a decrease in contrast and a decrease in image quality, and a high-quality captured image can be obtained.

Next, assembling of the lens barrel 40 will be described. First, the first lens 421 is inserted in order from the image plane side (rear side) of the lens barrel 410 and positioned in contact with the contact portion 413. Subsequently, the spacer 441, the aperture stop 430, and the second lens 422 are inserted. Then, after the spacer 442 is inserted and the third lens 423 is inserted, the lens presser 443 is screwed into the female screw portion 416 to fix all the lenses. Thereafter, the stray light restricting plate 450 is inserted and fixed with an adhesive or the like.
In this assembling operation, the lens barrel 410 has a two-stage cylindrical shape in which the object side is thin and the image surface side is thick. Therefore, when the first lens 421, the second lens 422, and the third lens 423 are assembled to the lens barrel 410, In addition, it can be assembled smoothly while being easily centered.

  Next, specific numerical examples of the observation lens are shown below as Example 1 and Example 2.

The main specification specifications and various numerical data (setting values) of the first lens 421 to the third lens 423 in Example 1 are as follows.
<Specification specifications>
Main wavelength = 587 nm, focal length (λd) = 13.39 mm, field size = φ10 mm,
The outer diameter of the first lens φ1 = 5.4 mm, the outer diameter of the second lens φ2 = 5.4 mm,
Third lens outer diameter φ3 = 6.2 mm, aperture stop diameter φ = 3.0 mm, F value = 3.1,
Conjugate length (object to image plane) = 60 mm, photographing magnification = 0.48
<Curvature radius>
R1 = 4.7678 mm, R2 = −12.6980 mm, R3 = ∞,
R4 = −5.2456 mm, R5 = 4.6640 mm, R6 = 13.210 mm,
R7 = −6.2504mm
<Surface spacing>
D1 = 2.43 mm, D2 = 0.70 mm, D3 = 0.27 mm, D4 = 1.04 mm,
D5 = 1.53 mm, D6 = 2.00 mm, D7 = 15.06 mm (including 0.4 mm of protective glass)
<Refractive index (Nd)>
N1 = 1.56883, N2 = 1.67270, N3 = 1.62041
<Abbe number (νd)>
ν1 = 56.3, ν2 = 32.1, ν3 = 60.3

The aberration diagrams regarding the spherical aberration, astigmatism and distortion in Example 1 are as shown in FIG. In FIG. 4, S represents the aberration on the sagittal plane, and M represents the aberration on the meridional plane.
According to the lens specifications according to Example 1, it is possible to obtain an imaging lens with high optical performance in which spherical aberration, astigmatism, and distortion are favorably corrected.

The main specification specifications and various numerical data (setting values) of the first lens 421 to the third lens 423 in Example 2 are as follows.
<Specification specifications>
Main wavelength = 587 nm, focal length (λd) = 13.37 mm, field size = φ10 mm,
The outer diameter of the first lens φ1 = 5.4 mm, the outer diameter of the second lens φ2 = 5.4 mm,
Third lens outer diameter φ3 = 6.2 mm, aperture stop aperture φ = 3.2 mm, F value = 3.1,
Conjugate length (object to image plane) = 60 mm, photographing magnification = 0.48
<Curvature radius>
R1 = 5.00034mm, R2 = -12.138mm, R3 = ∞,
R4 = −5.1710 mm, R5 = 5.1710 mm, R6 = 16.573 mm,
R7 = −5.9774 mm
<Surface spacing>
D1 = 2.10 mm, D2 = 0.65 mm, D3 = 0.45 mm, D4 = 1.00 mm,
D5 = 1.38mm, D6 = 2.20mm, D7 = 15.34mm (including protective glass 0.4mm)
<Refractive index (Nd)>
N1 = 1.56883, N2 = 1.67270, N3 = 1.62041
<Abbe number (νd)>
ν1 = 56.3, ν2 = 32.1, ν3 = 60.3

The aberration diagrams regarding the spherical aberration, astigmatism and distortion in Example 2 are as shown in FIG. In FIG. 5, S represents the aberration on the sagittal plane, and M represents the aberration on the meridional plane.
According to the lens specifications according to Example 2, it is possible to obtain an imaging lens with high optical performance in which spherical aberration, astigmatism, and distortion are favorably corrected.

  As described above, the observation lens of the present invention has a three-lens configuration, and can reduce the outer diameter of the lens as much as possible, can be easily assembled, can prevent erroneous assembly, and the like. Since it is possible to obtain high-quality captured images by controlling stray light due to reflection in the interior, it can be applied as an observation lens for a pen-type microscope unit with a built-in illumination light source. If it is an application having a magnification and a conjugate length, it is useful as a lens optical system for other observation or monitoring.

It is sectional drawing which shows the microscope unit provided with the lens for observation which concerns on this invention. It is sectional drawing of the lens barrel which shows one Embodiment of the lens for observation which concerns on this invention. It is a block diagram which shows the lens structure of the lens for observation which concerns on this invention. FIG. 3 is an aberration diagram showing spherical aberration, astigmatism, and distortion in Example 1. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion in Example 2.

Explanation of symbols

L1, L2 Optical axis P Image plane 10 Case 10a Observation window 20 Light source 30 Reflective mirror 40 Lens barrel 50 Imaging device 60 LCD monitor 410 Lens barrel 411 Small diameter portion 412 Large diameter portions 414, 415, 416, 417, 418 Inner peripheral surface 421 First lens 422 Second lens 423 Third lens 430 Aperture stop 441, 442 Spacer 443 Lens retainer φ1 Outer diameter of first lens φ2 Outer diameter of second lens φ3 Outer diameter of third lens R4 Object side of second lens Radius of curvature R5 radius of curvature of the image side surface of the second lens

Claims (4)

A biconvex first lens having a positive refractive power, an aperture stop having a predetermined aperture, and a biconcave second having a negative refractive power, which are arranged in order from the object side to the image plane side. A lens, and a biconvex third lens having a positive refractive power,
An observation lens characterized by that. When the outer diameter of the first lens is φ1, the outer diameter of the second lens is φ2, and the outer diameter of the third lens is φ3,
φ1 = φ2 <φ3
The observation lens according to claim 1, wherein: When the radius of curvature of the object side surface of the second lens is R4 and the radius of curvature of the image side surface is R5,
R4 = -R5
The observation lens according to claim 1, wherein the observation lens is satisfied. A stray light restricting plate that restricts stray light reflected in the lens barrel from reaching the image surface side is disposed on the image surface side of the third lens.
The observation lens according to claim 4.

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