JPWO2017187814A1 - Endoscope objective optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an endoscope objective optical system that can be easily manufactured and that can reduce flare generated between two optical systems for acquiring two images having different parallaxes for stereoscopic viewing. Yes. The endoscope objective optical system according to the present invention is an endoscope objective optical system used for imaging for an endoscope for stereoscopic observation, and the lens L1 closest to the object side is one optical member having two concave portions. It is characterized in that reflected light reducing means is provided in the intermediate region between the two concave surface portions L11 and L12.

Description

  The present invention relates to an endoscope objective optical system.

  Conventionally, a stereoscopic observation system is known. The stereoscopic observation system uses a method of imaging two stereoscopic images with different parallaxes formed on an imaging surface of an imaging device on substantially the same plane (see, for example, Patent Documents 1 and 2). And in the structure of a prior art, in order to obtain two images with different parallax, it has two different optical systems.

International Publication No. 2013-108500 Japanese Patent Laid-Open No. 11-6967

  In the technology configuration, flare may occur in the region between the two optical systems. Such flare is undesirable because it degrades the quality of the observed image.

  The present invention has been made in view of the above, and an object thereof is to provide an endoscope objective optical system that is easy to manufacture and that can reduce flare generated between two optical systems. To do.

  In order to solve the above-described problems and achieve the object, at least some embodiments of the present invention are endoscope objective optical systems used for endoscopic imaging for stereoscopic observation, and are the most object side. The lens is one optical member having two concave surface portions, and is characterized in that reflected light reducing means is provided in an intermediate region between the two concave surface portions (L11, L12).

  INDUSTRIAL APPLICABILITY The present invention has a configuration that can be easily manufactured and can provide an endoscope objective optical system that can reduce flare generated between two optical systems.

It is a figure which shows the lens cross-section structure of the endoscope objective optical system which concerns on 1st Embodiment. It is a figure which shows the front structure of the lens of the most object side of the endoscope objective optical system which concerns on 1st Embodiment. It is a figure which shows the lens cross-section structure of the most object side of the endoscope objective optical system which concerns on 1st Embodiment. It is another figure which shows the lens cross-sectional structure of the most object side of the endoscope objective optical system which concerns on 1st Embodiment. (A), (b) is a figure which shows the flare which generate | occur | produces with the lens of the most object side of an endoscope objective optical system. It is a figure which shows the lens cross-section structure of the endoscope objective optical system which concerns on 2nd Embodiment. It is a figure which shows the front structure of the flare stop of the endoscope objective optical system which concerns on 2nd Embodiment. (A), (b) is a figure which shows the brightness distribution of the right-eye image of the endoscope objective optical system which concerns on 2nd Embodiment, and a left-eye image, respectively. It is a figure which shows schematic structure of the endoscope system which has an endoscope objective optical system which concerns on 2nd Embodiment. It is a figure which shows the lens cross-section structure of the endoscope objective optical system which concerns on Example 1. FIG. FIG. 10 is a diagram illustrating a lens cross-sectional configuration of an endoscope objective optical system according to Example 2.

  Hereinafter, an endoscope objective optical system according to an embodiment will be described in detail based on the drawings. In addition, this invention is not limited by this embodiment.

(First embodiment)
FIG. 1 is a diagram illustrating a lens cross-sectional configuration of the endoscope objective optical system according to the first embodiment. This embodiment is an endoscope objective optical system used for imaging for an endoscope for stereoscopic observation, and the lens L1 on the most object side is one optical member having two concave portions, and two concave portions. The present invention is characterized in that reflected light reducing means is provided in an intermediate area A between L11 and L12.

  The optical system for stereoscopic observation is a first optical system LNS1 and a second optical system LNS2 that generate two optical images having parallax with each other. For example, the first optical system LNS1 forms an image for the right eye, and the second optical system LNS2 forms an image for the left eye.

  The lens on the most object side is a lens L1 of one optical member having two concave surface portions L11 and L12. Reflected light reducing means is provided in an intermediate region A between the two concave portions L11 and L12.

  FIG. 2 is a diagram illustrating a front configuration of the lens L1 closest to the object side of the endoscope objective optical system according to the first embodiment.

  Further, according to a preferred aspect of the present embodiment, it is desirable that the reflected light reducing means is an intermediate region A in which two concave surface portions L11 and L12 are connected by a gently convex surface.

  FIG. 3 is a diagram illustrating a cross-sectional configuration of the lens L1 closest to the object side in the present embodiment. For comparison with the present embodiment, FIG. 5A shows a cross-sectional configuration of the most object side lens L1 of the conventional configuration.

  In the configuration shown in FIG. 5A, the shape between the two concave surface portions L11 and L12 has a sharp and sharp shape portion B. The light ray RAY1 incident on the sharp and sharp shaped part B is totally reflected by the concave part L12, totally reflected by the concave part L11, and further reflected by a plane. As a result, flare occurs.

  In the configuration shown in FIG. 5B, the shape between the two concave surface portions L11 and L12 has a sharp and sharp shape portion B. The light ray RAY1 'incident on the sharp pointed portion B is reflected by the sharp pointed portion B and further reflected by a plane. As a result, flare occurs.

  In the sharp and sharp shape portion B, even if an antireflection film is coated, total reflected light cannot be reduced. Further, the sharp and sharp shape portion B has a problem that it is easily broken during the manufacture of the lens L1.

  Here, according to a preferred aspect of the present embodiment, the reflected light reducing means is preferably an antireflection coat applied to the intermediate region A. Even in the gently convex intermediate region A, the light ray RAY2 shown in FIG. 3 may be emitted to the image side by being reflected twice in the lens L1, and may cause flare. Such flare can be reduced by the antireflection coating.

  Thereby, since the light quantity reflected in the intermediate | middle area | region A and reflected in a plane can be reduced, flare can be reduced.

  The antireflection coat is preferably applied not only to the intermediate region A but also to the effective range of the two concave portions L11 and L12. Accordingly, the antireflection coat may be coated on the two concave portions L11 and L12 and the intermediate region A at a time. For this reason, the cost at the time of manufacture can be reduced by man-hour reduction.

  Moreover, according to the preferable aspect of this embodiment, it is desirable that the sphere notch depth of the intermediate region A provided with the reflected light reducing means is shallower than the sphere notch depth of the concave surface part.

  FIG. 4 is a diagram illustrating a lens cross-sectional configuration of the lens L1 closest to the object side of the endoscope objective optical system. The sphere missing depth will be described.

  The notch depth of the concave surface portion means a length dp1 between the intersection P2 between the edge portion P1 and the optical axis AX1 and the top surface position P3 of the concave surface of the concave surface portion L11. Further, the sphere notch depth of the intermediate region A refers to a length dp2 between the vertex position P4 of the intermediate region A and the position P5 corresponding to the top surface position P3 of the concave surface of the concave surface portion L11.

  It is desirable that dp1> dp2. As a result, the sphere notch depth of the intermediate region A becomes shallower than the sphere notch depths of the concave surface portions L11 and L12. For this reason, flare as shown in FIG. 5A can be reduced.

(Second Embodiment)
FIG. 6 is a diagram illustrating a lens cross-sectional configuration of the endoscope objective optical system according to the second embodiment. The present embodiment is an endoscope objective optical system used for endoscope imaging for stereoscopic observation, and the lens L1 closest to the object side is one optical member having two concave portions L11 and L12.

  The optical system for stereoscopic observation is a first optical system LNS1 and a second optical system LNS2 that generate two optical images having parallax with each other. For example, the first optical system LNS1 forms an image for the right eye, and the second optical system LNS2 forms an image for the left eye.

  The middle of the two concave surface portions L11 and L12 has a sharp pointed shape.

  And according to the preferable aspect of this embodiment, the reflected light reducing means is a flare that is disposed on the image side of the lens L1 that is an optical member and has two openings FS1 and FS2 corresponding to the two concave surface portions L11 and L12. The aperture FS, and the two openings FS1 and FS2, the length a from the edge near the intermediate region to the optical axis is preferably shorter than the length b from the other edge to the optical axis.

  FIG. 7 is a diagram showing a front configuration of the flare stop FS. The light-shielding portion is indicated by hatching. Each of the two openings FS1 and FS2 has an octagonal irregular shape. As described above, the length a <length b is satisfied.

  In other words, the two openings FS1 and FS2 are configured such that the opening diameters on the opposite sides are small. In the present embodiment, the flare as shown in FIGS. 5A and 5B occurs in the region between the concave portions L11 and L12. According to the flare stop FS of this embodiment, only such flare can be effectively reduced.

  Further, the flare stop FS is preferably composed of a single metal plate. Thereby, compared with the case where the flare stop is manufactured using two metal plates having one opening, in the present embodiment, no gap is generated between the openings FS1 and FS2, and therefore, more effective. Flare can be reduced. In addition, since the flare stop FS is composed of a single metal plate, assembly during manufacture is easy.

  In the present embodiment, the opening diameter in the parallax direction of the flare stop FS is small. For this reason, the brightness distribution of the obtained image is as shown in FIGS. FIG. 8A is a diagram showing the right-eye image brightness distribution. FIG. 8B is a diagram showing the left-eye image brightness distribution. Thus, only one side in the parallax direction becomes dark. The direction of darkness is reversed between the right eye image (LNS1) and the left eye image (LNS2). This causes a problem that the brightness differs between the left and right images.

  FIG. 9 is a diagram showing a schematic configuration of an endoscope system having an endoscope objective optical system according to the present embodiment. In this embodiment, as shown in FIG. 9, a shading correction unit 103 is provided in the image processing apparatus 102. A signal from the image sensor IMG is input to the image processing apparatus 102 via the A / D conversion unit 101.

  The shading correction unit 103 corrects the brightness distribution with an odd or higher order function in the parallax direction. Accordingly, the screen can be observed with uniform brightness on the display unit 104. Further, since shading correction is performed only in a specific direction, image quality deterioration (noise increase due to gain) accompanying correction can be minimized.

  If the opening shape of the flare stop FS is rotationally symmetric, it is necessary to reduce the opening diameter in all directions from the viewpoint of flare countermeasures. In this case, it is necessary to increase the image gain in the peripheral part in all directions for both the left eye image and the right eye image. Therefore, the image has a poor S / N compared to the present embodiment.

  In the configuration of the first embodiment, the flare can be further effectively reduced by using the flare stop FS described in the second embodiment.

Example 1
An endoscope optical system according to Example 1 will be described. FIG. 10 is a diagram illustrating a lens cross-sectional configuration of the endoscope optical system according to the present embodiment.

  The present embodiment includes a first optical system LNS1 and a second optical system LNS2 that generate two optical images having parallax with each other. Each optical system includes, in order from the object side, a plano-concave negative lens L1 having a concave surface on the image side, a negative meniscus lens L2 having a convex surface on the image side, a parallel plate F1, an aperture stop S, The lens includes a convex positive lens L3, a biconvex positive lens L4, a negative meniscus lens L5 having a convex surface on the image side, a plano-convex positive lens L6 having a convex surface on the object side, and a parallel plate CG.

  The planoconvex positive lens L6 is a field lens. Thereby, focus adjustment accuracy can be relaxed.

(Example 2)
An endoscope optical system according to Example 2 will be described. FIG. 11 is a diagram illustrating a lens cross-sectional configuration of the endoscope optical system according to the present embodiment. The lens data is the same as in Example 1 except that a flare stop FS is provided on the image side surface of the lens L1.

  Below, the numerical data of each said Example are shown. Symbols r are the radii of curvature of the lens surfaces, d is the spacing between the lens surfaces, nd is the refractive index of the d-line of each lens, and νd is the Abbe number of each lens. Further, S is an aperture stop, and FS is a flare stop.

Numerical example 1
Unit mm

Surface data Surface number rd nd νd
1 ∞ 0.2500 1.88815 40.76
2 0.5920 0.5400
3 -2.6449 0.8360 1.85504 23.78
4 -2.8388 0.1900
5 ∞ 0.4000 1.49557 75.00
6 ∞ 0.0807
7 (S) ∞ 0.1338
8 3.6829 0.6446 1.83932 37.16
9 -2.2104 0.3395
10 1.5521 0.7800 1.69979 55.53
11 -0.8302 0.3523 1.93429 18.90
12 -35.2793 0.3040
13 1.5026 0.5000 1.51825 64.14
14 ∞ 0.3500 1.50700 63.26
Imaging surface ∞

Total focal length f1 0.41769
Parallax 1.1mm

Sphere missing depth dp1 = 0.37
dp2 = 0.26

Numerical example 2
Unit mm

Surface data Surface number rd nd νd
1 ∞ 0.2500 1.88815 40.76
2 0.5920 0.3700
3 (FS) ∞ 0.1700
4 -2.6449 0.8360 1.85504 23.78
5 -2.8388 0.1900
6 ∞ 0.4000 1.49557 75.00
7 ∞ 0.0807
8 (S) ∞ 0.1338
9 3.6829 0.6446 1.83932 37.16
10 -2.2104 0.3395
11 1.5521 0.7800 1.69979 55.53
12 -0.8302 0.3523 1.93429 18.90
13 -35.2793 0.3040
14 1.5026 0.5000 1.51825 64.14
15 ∞ 0.3500 1.50700 63.26
Imaging surface ∞

Total focal length f1 0.41769
Parallax 1.1mm

Parameters of flare stop FS Length a = 0.40mm
Length b = 0.45mm

  Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and may be implemented by appropriately combining the configurations of these embodiments without departing from the spirit of the present invention. The form is also within the scope of the present invention. For example, the optical system is not limited to the single focus optical system of the present embodiment, and can also be applied to a zoom optical system. In addition, the present embodiment has two optical systems, but the present invention is not limited to this. There are three or more optical systems, and images of any two of these optical systems are selected for stereoscopic observation. It may be configured to. In that case, the optical member and reflected light reducing means of this embodiment may be applied to the two optical systems with the shortest parallax. In this embodiment, the two optical systems have individual lenses, but the lens on the image side of L1 is used as a common lens (one concave or convex lens) for the two optical systems. It may be deformed. Further, an anti-reflection coating may be added to the flat portion on the object side of L1 (surface number 1 in the numerical example) to further reduce flare.

  As described above, the present invention has a configuration that can be easily manufactured, and is useful for an endoscope objective optical system that can reduce flare generated between two optical systems.

LNS1 First optical system LNS2 Second optical system AX1, AX2 Optical axis IMG Imaging element I Image plane (imaging plane)
L11, L12 Concave surface portion L1-L6 Lens F1, F2, CG Parallel plate S Brightness stop FS Flare stop A Middle region B Sharp pointed shape

In order to solve the above-described problems and achieve the object, at least some embodiments of the present invention are endoscope objective optical systems used for endoscopic imaging for stereoscopic observation, and are the most object side. The lens is one optical member having two concave surface portions, and is characterized in that reflected light reducing means is provided in an intermediate region in which the two concave surface portions (L11, L12) are connected by gently convex curved surfaces .

To solve the above problems and achieve the object, at least some embodiments of the present invention is an endoscope objective optical system for use in endoscopic imaging for stereoscopic viewing, the parallax First and second optical systems that generate two optical images, and lenses closest to the object side of the first and second optical systems, the two corresponding to the first and second optical systems, respectively . One optical member having a concave surface portion on the image side, and a reflected light reducing member provided in an intermediate region in which two concave surface portions (L11, L12) are connected by a gently convex curved surface, To do.

Claims (5)

An endoscope objective optical system used for imaging for an endoscope for stereoscopic observation,
The most object side lens is one optical member having two concave portions,
An endoscope objective optical system, characterized in that reflected light reducing means is provided in an intermediate region between the two concave surface portions.   The endoscope objective optical system according to claim 1, wherein the reflected light reducing unit is the intermediate region in which the two concave surface portions are connected by a gently convex surface.   The endoscope objective optical system according to claim 1 or 2, wherein the reflected light reducing means is an antireflection coating applied to the intermediate region.   The endoscope objective according to any one of claims 1 to 3, wherein a sphere notch depth of the intermediate region provided with the reflected light reducing means is shallower than a sphere notch depth of the concave surface part. Optical system. The reflected light reducing means is a flare stop disposed on the image side of the optical member and having two openings corresponding to the two concave surface portions,
2. The endoscope objective optical according to claim 1, wherein the length of the two openings from the edge near the intermediate region to the optical axis is shorter than the length from the edge of the other part to the optical axis. system.

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