WO2017073292A1

WO2017073292A1 - Endoscopic imaging unit

Info

Publication number: WO2017073292A1
Application number: PCT/JP2016/079916
Authority: WO
Inventors: 片倉正弘
Original assignee: オリンパス株式会社
Priority date: 2015-10-29
Filing date: 2016-10-07
Publication date: 2017-05-04
Also published as: JPWO2017073292A1

Abstract

Provided is an endoscopic imaging unit for synthesizing images by causing two optical images to focus on a single imaging element, with which good image quality with little flare can be achieved. The endoscopic imaging unit 100, 120 causes two optical images, separately formed by an optical system having two optical paths, to focus onto a single imaging element 22. An objective optical system LNS having two optical paths includes a first negative lens L1 disposed closest to an object, a first non-circular anti-flare diaphragm FS1 disposed on the image side of the first lens L1, and a second non-circular anti-flare diaphragm FS2 disposed closer to the image than the first non-circular anti-flare diaphragm FS1. The objective optical system satisfies the following conditional expression (1). 0.3 < S01_v / S02_v < 5.0 ... (1) Where, when v represents a direction along which the two optical images are adjacent, S01_v represents a radius of the first non-circular anti-flare diaphragm FS1 in the v direction, and S02_v represents a radius of the second non-circular anti-flare diaphragm FS2 in the v direction.

Description

Endoscopic imaging unit

The present invention relates to an endoscope imaging unit.

In a conventional endoscope system, in order to expand the depth of field, a configuration is known in which a self-portrait is divided into two to form an image, and the two acquired images are combined by image processing. A configuration is also known in which two images, a left eye image and a right eye image, are combined by image processing to obtain a stereoscopic image. In this way, it may be necessary to combine two optical images.

When one image sensor is provided for each optical path to capture an image, two image sensors are required to acquire two images. For this reason, since a cost will rise, it is not preferable. If two image sensors are used, two image capturing devices are required, which increases the cost and increases the possibility of failure, which is not preferable.

Therefore, in order to expand the depth of field or obtain a stereoscopic image, a configuration in which two images are acquired by one image sensor is desirable. In such an optical system, for example, there is a configuration disclosed in Patent Document 1 in order to reduce flare.

In the configuration of Patent Document 1, in order to reduce flare, one flare stop is provided in the optical path. The flare stop has a non-circular opening such as a rectangle.

Japanese Patent No. 5509400

When obtaining an image with one image sensor per conventional optical path, a flare having an extremely high image height is incident on the outside of the effective image pickup area, and this is not a problem. However, in the case of a configuration in which two images IA and IB are formed on one image sensor, a flare generated in one optical path for the image IA occurs in an adjacent effective imaging region for the other image IB. This causes the problem of being reflected. This is a problem because flare occurs between the two effective imaging areas.

The present invention has been made in view of such problems, and an object thereof is an endoscope imaging unit for forming two optical images on one imaging element and performing image synthesis. An object of the present invention is to provide an endoscope imaging unit capable of obtaining a good image quality with little flare.

In order to solve the above-described problems and achieve the object, the present invention provides the following means.
One aspect of the endoscope imaging unit according to the present invention is:
In an endoscope imaging unit that forms two optical images formed separately by an optical system having two optical paths on one imaging element,
The optical system having two optical paths includes a negative first lens disposed closest to the object side, a first flare-preventing non-circular stop disposed on the image side of the first lens, and a first anti-flare non-circular stop. And a second anti-flare noncircular stop disposed on the image side, and satisfying the following conditional expression (1).
0.3 <S01_v / S02_v <5.0 (1)
here,
When the V direction is a direction in which two optical images are adjacent to each other,
S01_v is the radius in the V direction of the first anti-flare noncircular stop,
S02_v is the radius in the V direction of the second anti-flare non-circular diaphragm,
It is.

One embodiment of the present invention is an endoscope imaging unit for forming two optical images on one imaging element and performing image synthesis, and endoscope imaging capable of obtaining a good image quality with little flare There is an effect that a unit can be provided.

It is a figure which shows the cross-sectional structure of the endoscope imaging unit which concerns on 1st Embodiment of this invention. It is a figure which shows the cross-sectional structure of the endoscope imaging unit which concerns on 2nd Embodiment of this invention. It is a figure which shows the cross-sectional structure of the endoscope imaging unit which concerns on 3rd Embodiment of this invention. It is a front view of the 1st flare prevention non-circular stop. It is a front view of the 2nd flare prevention non-circular stop. It is sectional drawing of a 1st flare prevention non-circular stop. It is another front view of the 1st flare prevention non-circular stop. It is a figure which shows the image in an effective imaging area. It is another figure which shows the image in an effective imaging area. It is a functional block diagram which shows the structure of the endoscope imaging unit which concerns on embodiment of this invention. It is a schematic block diagram of the optical path division part and imaging device which the endoscope imaging unit which concerns on embodiment of this invention has. It is a schematic block diagram of the image pick-up element which the endoscope imaging unit which concerns on embodiment of this invention has. It is a figure which shows the cross-sectional structure in the normal observation state of the objective optical system which the endoscope imaging unit which concerns on Example 1 of this invention has, an optical path division part, and an image pick-up element. It is a figure which shows the cross-sectional structure in the close observation state of the objective optical system which the endoscope imaging unit which concerns on Example 1 of this invention has, an optical path division | segmentation means, and an image pick-up element. It is a figure which shows the cross-sectional structure of the objective optical system which the endoscope imaging unit which concerns on Example 2 of this invention has, an optical path division part, and an image pick-up element. It is a figure which shows the cross-sectional structure in the normal observation state of the objective optical system which the endoscope imaging unit which concerns on Example 3 of this invention has, an optical path division part, and an image pick-up element. It is a figure which shows the cross-sectional structure in the close observation state of the objective optical system which the endoscope imaging unit which concerns on Example 3 of this invention has, an optical path division part, and an image pick-up element. It is a figure which shows the generation | occurrence | production reason of the conventional flare. It is another figure which shows the generation | occurrence | production reason of the conventional flare. It is another figure which shows the conventional flare.

Hereinafter, the reason and operation of the endoscope imaging unit according to this embodiment will be described with reference to the drawings. In addition, this invention is not limited by the following embodiment.

(First embodiment)
In the first embodiment, as shown in FIGS. 1A and 1C, an endoscope imaging unit 100 that forms two optical images separately formed by an optical system having two optical paths on one imaging element 22, In 120, an objective optical system LNS having two optical paths includes a negative first lens L1 disposed closest to the object side, a first anti-flare noncircular stop FS1 disposed on the image side of the first lens L1, and A second flare-preventing non-circular stop FS2 disposed on the image side of the first flare-preventing non-circular stop FS1, and satisfying the following conditional expression (1).
0.3 <S01_v / S02_v <5.0 (1)
here,
When the V direction is a direction in which two optical images are adjacent to each other,
S01_v is the radius in the V direction of the first anti-flare noncircular stop,
S02_v is the radius in the V direction of the second anti-flare non-circular diaphragm,
It is.

As shown in FIGS. 1A and 1C, the

endoscope imaging units

100 and 120 according to the present embodiment each receive two optical images separately formed by two optical paths by the optical path splitting unit 20 in one imaging element 22. It is used for the endoscope 1 that forms an image and obtains one endoscope image by performing image synthesis. That is, the optical system having two optical paths includes an objective optical system LNS having one optical axis AX and an optical path dividing unit 20 that divides the optical path into two. The

endoscope imaging units

100 and 120 according to the present embodiment are suitable for increasing the depth of field.

(Second Embodiment)
Further, in the second embodiment, as shown in FIG. 1B, an endoscope imaging in which two optical images separately formed by objective optical systems LNSa and LNSb having two optical paths are formed on one imaging element 22. In the unit 110, the objective optical systems LNSa and LNSb having two optical paths are a negative first lens L1 disposed closest to the object side and a first flare-preventing noncircular diaphragm disposed on the image side of the first lens L1. FS1 and a second flare-preventing non-circular stop FS2 disposed on the image side of the first flare-preventing non-circular stop FS1, and satisfying the above-described conditional expression (1).

As shown in FIG. 1B, the endoscope imaging unit 110 according to the present embodiment forms two optical images separately formed by the objective optical systems LNSa and LNSb having two optical paths on one imaging element 22. The endoscope 2 is used for the endoscope 2 that obtains one endoscopic image by performing image synthesis. The endoscope imaging unit 110 according to the present embodiment is suitable for obtaining a stereoscopic image based on a right eye image and a left eye image.

In the first embodiment and the second embodiment, the “non-circular diaphragm” is a diaphragm having openings having different shapes in two orthogonal directions. Parameters S01_v and S02_v are shown in FIGS. 2A and 2B, respectively. The shapes of the first flare-preventing non-circular stop FS1 and the second flare-preventing non-circular stop FS2 will be described later.

Furthermore, FIG. 3A shows two optical images in the two

effective imaging regions

22a and 22b of the

endoscope imaging units

100 and 120 according to the first embodiment. FIG. 3B shows two optical images in the two

effective imaging regions

22a and 22b of the endoscope imaging unit 110 according to the second embodiment. 3A and 3B, a direction in which images are adjacent to each other is a V direction, and a direction perpendicular to the V direction is an H direction.

First, the reason why flare occurs in the conventional configuration will be described. FIG. 10A shows a configuration of an optical path splitting unit 20 that splits an optical path from one objective optical system LNS into two. Details of the optical path splitting unit 20 will be described later.

The configuration of the optical path dividing unit 20 will be briefly described. The optical path dividing unit 20 includes a polarization beam splitter 21 that divides a subject image into two optical images with different focus points, and an imaging element 22 that captures two optical images and acquires two images. The imaging element 22 has an effective imaging area A and an effective imaging area B adjacent to the effective imaging area A.

The optical path dividing unit 20 divides the light from one objective optical system LNS into an optical path having the optical axis AXa and an optical path having the optical axis AXb using polarized light. The two optical images are formed on the effective imaging area A and the effective imaging area B, respectively.

In the conventional configuration, like the flare FL indicated by a broken line in FIG. 10A, the light generated in one optical path may be reflected in the adjacent effective imaging area A for the other image. FIG. 11 is a diagram showing the flare FL generated in this way.

Further, for example, in order to obtain a stereoscopic image, an objective optical system LNSa having an optical axis AXa and an objective optical system LNSb having an optical axis AXb are arranged as shown in FIG. A configuration for obtaining two optical images can be employed.

In the conventional configuration shown in FIG. 10B, the flare FL indicated by the broken line generated in the optical path having the optical axis AXb may be reflected in the effective imaging area A for the other image. Also in this case, a flare FL as shown in FIG. 11 occurs.

In contrast to such a conventional configuration, the

endoscope imaging units

100, 110, and 120 according to the first embodiment and the second embodiment have the objective optical systems LNS, LNSa, and LNSb having two optical paths as the most object. The first negative lens L1 disposed on the side, the first flare-preventing non-circular stop FS1 disposed on the image side of the first lens L1, and the first flare-preventing non-circular stop FS1 are disposed on the image side. A second anti-flare non-circular diaphragm FS2.

The flare FL as described above can be efficiently shielded by the two stops, the first flare prevention non-circular stop FS1 and the second flare prevention non-circular stop FS2.

The reason for using a diaphragm having a non-circular opening instead of a circular opening will be described. FIG. 2A is a diagram illustrating the shape of the non-circular opening AP1 of the first flare-preventing non-circular stop FS1. FIG. 2B is a diagram illustrating the shape of the non-circular opening AP2 of the second flare-preventing non-circular stop FS2. The openings of the first flare-preventing non-circular stop FS1 and the second flare-preventing non-circular stop FS2 include shapes such as an oval, quadrangular (rectangular), and octagonal shape.

When two optical images are formed on one image sensor 22, the configuration in which two images are arranged in the longitudinal opposite side direction with the lowest image height can minimize the outer diameter of the endoscope. preferable.

In this case, since the image height in the longitudinal opposite side direction is smaller than the image height in the diagonal direction, the ray height is also reduced. For this reason, for example, a non-circular diaphragm having a rectangular opening is used. This makes it possible to create a large opening in the diagonal direction where the image height is large and a small opening in the longitudinal opposite side direction where the image height is small. As a result, flare, which is an unnecessary light beam, can be shielded efficiently.

Further, depending on the relationship between the size of the image sensor 22 and the image height, arranging the two images in the lateral opposite direction may make the outer diameter of the endoscope the smallest. In the present embodiment, it is assumed that optical images are arranged in the vertical opposite side direction and the horizontal opposite side direction. For this reason, the direction in which the two optical images are adjacent to each other is referred to as the V direction.

Conditional expression (1) prescribes the ratio of the opening diameters in the V direction of the first flare prevention non-circular diaphragm FS1 and the second flare prevention non-circular diaphragm FS2.

When the conditional expression (1) is satisfied, an appropriate aperture diameter ratio can be obtained. The upper and lower rays of the flare can be effectively shielded by the two non-circular stops. Thereby, flare can be reduced while securing the peripheral light quantity.

If the lower limit of conditional expression (1) is not reached, the diameter of the first flare-preventing non-circular stop FS1 in the V direction becomes too small, and the amount of peripheral light is increased, which makes it difficult to observe the periphery.

If the upper limit value of conditional expression (1) is exceeded, the diameter in the V direction of the first flare-preventing non-circular stop FS1 becomes too large, and flare cannot be cut. When the opening diameter in the V direction of the non-circular diaphragm is different in the vertical direction, a small opening diameter value is used.

Thus, according to the

endoscope imaging units

100, 110, and 120 according to the first embodiment and the second embodiment, at least two first and second flare-preventing non-circular shapes in the objective optical systems LNS, LNSa, and LNSb. By arranging the stops FS1 and FS2 and selecting an appropriate opening shape that satisfies the conditional expression (1), the occurrence of the flare FL as described above can be suppressed.

Note that it is desirable to satisfy the following conditional expression (1) ′ instead of conditional expression (1).
1.0 <S01_v / S02_v <3.0 (1) ′
Furthermore, it is desirable to satisfy the following conditional expression (1) ″ instead of conditional expression (1).
1.4 <S01_v / S02_v <1.8 (1) "

Moreover, according to a preferable aspect of the present embodiment, it is desirable that the following conditional expression (2) is satisfied.
0.2 <ih_v / S02_v <5.0 (2)
here,
ih_v is the image height in the V direction,
S02_v is a radius in the V direction of the second anti-flare non-circular diaphragm,
It is.

Conditional expression (2) defines the ratio between the image height in the longitudinal opposite side direction and the aperture diameter of the second flare-preventing non-circular stop FS2.

If the upper limit value of conditional expression (2) is exceeded, the opening diameter of the second flare prevention non-circular stop FS2 becomes too small. For this reason, the peripheral light amount is increased, which makes it difficult to observe the peripheral region, which is not preferable.

If the lower limit value of conditional expression (2) is not reached, the opening diameter of the second flare-preventing non-circular stop FS2 becomes too large, and flare occurs, which is not preferable.

Note that it is desirable to satisfy the following conditional expression (2) ′ instead of conditional expression (2).
0.8 <ih_v / S02_v <3.0 (2) ′
Further, it is desirable to satisfy the following conditional expression (2) ″ instead of conditional expression (2).
1.0 <ih_v / S02_v <2.0 (2) "

Moreover, according to a preferable aspect of this embodiment, it is desirable that the following conditional expression (3) is satisfied.
1.0 <ih_AB / S02_v <10.0 (3)
here,
ih_AB is the distance between the optical axes on the image sensor,
S02_v is a radius in the V direction of the second anti-flare non-circular diaphragm,
It is.

Conditional expression (3) prescribes the ratio of the distance between the optical axes AXa and AXb on the image sensor 22 and the aperture diameter of the second flare prevention non-circular stop FS2. 3A and 3B show the parameter ih_AB.

If the upper limit value of conditional expression (3) is exceeded, the image formation positions of the two images are far apart, so that the flare does not enter the adjacent effective imaging region.

If the lower limit value of conditional expression (3) is not reached, the opening diameter of the second flare-preventing non-circular stop FS2 becomes too large, and flare occurs, which is not preferable.

In addition, it is preferable to satisfy the following conditional expression (3) ′ instead of conditional expression (3).
2.0 <ih_AB / S02_v <8.0 (3) ′
Furthermore, it is desirable to satisfy the following conditional expression (3) ″ instead of conditional expression (3).
2.5 <ih_AB / S02_v <6.0 (3) "

According to a preferred aspect of the present embodiment, the optical system having two optical paths includes an objective optical system LNS having one optical axis AX, an optical path splitting unit 20 (optical path splitting optical system) that splits the optical path into two, and The second flare prevention non-circular stop FS2 is preferably disposed between the objective optical system LNS and the optical path dividing unit 20.

Two images without parallax (convergence angle) can be obtained by comprising one objective optical system LNS and the optical path splitting unit 20 that splits the optical path into two.

Further, according to a preferred aspect of the present embodiment, it is desirable that the optical system having two optical paths is composed of objective optical systems LNSa and LNSb having two optical axes AXa and AXb.

By configuring the two optical paths with the objective optical systems LNSa and LNSb having the two optical axes AXa and AXb, it becomes possible to obtain parallax (convergence angle) during stereoscopic observation.

Further, according to a preferred aspect of the present embodiment, as shown in FIG. 1A, the objective optical system LNS includes, in order from the object side, a negative first lens group G1, a movable positive second lens group G2, A positive third lens group G3 is desirable.

In order from the object side, the negative first lens group G1, the movable positive second lens group G2, and the positive third lens group G3 are configured to reduce the number of lenses in each group. Can do. Thereby, shortening of the total lens length and cost reduction can be achieved. In addition, a long back focus can be secured while suppressing the size of the lens in the radial direction. Furthermore, it becomes possible to change the focus position by moving the positive second lens group G2, and it is possible to suppress aberration fluctuations and field angle fluctuations when the focus changes.

Further, according to a preferred aspect of the present embodiment, as shown in FIGS. 1A and 1C, the objective optical system LNS includes, in order from the object side, the first lens group G1, the aperture stop S, and the positive rear group. It is desirable to be composed of

An endoscope objective optical system having a long back focus is configured with a small number of lenses by including a negative or positive first lens group G1, an aperture stop S, and a positive rear group in order from the object side. be able to.

Further, according to a preferred aspect of the present embodiment, as shown in FIG. 1C, the objective optical system LNS includes, in order from the object side, a positive first lens group G1, a movable negative second lens group G2, A positive third lens group G3 is desirable.

In order from the object side, the positive first lens group G1, the movable negative second lens group G2, and the positive third lens group G3 are configured to reduce the number of lenses in each lens group. Can do. Thereby, shortening of the total lens length and cost reduction can be achieved. It is possible to change the angle of view by moving the negative second lens group G2, and it is possible to suppress aberration fluctuations when the angle of view changes.

Further, according to a preferable aspect of the present embodiment, in the objective optical systems LNSa and LNSb having the two optical axes AXa and AXb, at least one of the first flare prevention non-circular diaphragm FS1 and the second flare prevention non-circular diaphragm FS2 is used. The diaphragm preferably has two non-circular openings APa and APb.

As shown in FIG. 2D, by forming two non-circular openings AP1 and AP2 in one first flare-preventing non-circular stop FS1, the alignment of the non-circular openings APa and APb in the rotational direction is adjusted. A process becomes unnecessary.

Moreover, according to a preferable aspect of the present embodiment, it is desirable that the following conditional expression (4) is satisfied.
0.1 <S01_v / emp_wide <5.0 (4)
here,
enp_wide is the entrance pupil position of the objective optical system LNS, LNSa, LNSb in the widest angle state,
S01_v is a radius in the V direction of the first non-circular diaphragm for preventing flare,
It is.

Conditional expression (4) defines the ratio between the entrance pupil position and the opening diameter of the first flare-preventing non-circular stop FS1.

If the upper limit of conditional expression (4) is exceeded, the first flare-preventing non-circular stop FS1 is too large for the light ray height on the image plane side of the first lens L1, and flare is preferably generated. Absent.

If the lower limit of conditional expression (4) is not reached, the opening diameter of the first flare-preventing non-circular stop FS1 is too small, and the peripheral light amount becomes too small.

Further, according to a preferred aspect of the present embodiment, the non-circular openings AP1 and AP2 included in at least one of the first flare-preventing non-circular stop FS1 and the second flare-preventing non-circular stop FS2 have the optical axes AX and AXa. In addition, it is desirable to have a tapered shape 32 inclined in one direction in the cross section along AXb, and further, the diaphragm has

notches

30 and 31 at predetermined positions with respect to the non-circular openings AP1 and AP2.

As shown in FIG. 2C, the non-circular opening AP1 has a tapered shape 32 inclined in one direction in a cross section along the optical axes AX, AXa, and AXb. Processing the taper shape from both sides (object side and image surface side) is not preferable because the processed surface is tilted and flare occurs. Further, as shown in FIGS. 2A and 2B, by having the

cutout portions

30 and 31, the direction of the tapered shape 32 of the first and second non-circular diaphragms FS1 and FS2 can be easily recognized.

Also, according to a preferred aspect of the present embodiment, it is desirable to have a cover glass on the most object side.

This makes it possible to easily incorporate the endoscope imaging unit into the endoscope. Further, the object-side surface of the first lens L1 can be formed into a planar shape so that the first lens L1 can also function as a cover glass.

Example 1
Next, the endoscope imaging unit 100 according to the first embodiment will be described. 7A and 7B are diagrams illustrating a cross-sectional configuration of the objective optical system LNS of the endoscope imaging unit 100. FIG. Here, FIG. 7A is a diagram illustrating a cross-sectional configuration of the objective optical system LNS in a normal observation state (a long distance object point). FIG. 7B is a diagram illustrating a cross-sectional configuration of the objective optical system LNS in the close-up observation state (short-distance object point).

The objective optical system LNS according to the present example includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a positive refractive power. The third lens group G3. The second lens group G2 moves on the optical axis AX to the image side, and corrects the change in the focal position accompanying the change from the normal observation state to the close observation state.

The first lens group G1 includes a planoconcave negative lens L1, a parallel plate L2, a biconcave negative lens L3, and a positive meniscus lens L4 having a convex surface facing the object side. Here, the negative lens L3 and the positive meniscus lens L4 are cemented.

The second lens group G2 is composed of a positive meniscus lens L5 having a convex surface directed toward the object side.

The third lens group G3 includes a biconvex positive lens L6, a negative meniscus lens L7 having a convex surface facing the image side, a planoconvex positive lens L8, a biconvex positive lens L9, and a negative meniscus having a convex surface facing the image side. It consists of a lens L10. Here, the positive lens L6 and the negative meniscus lens L7 are cemented. The positive lens L9 and the negative meniscus lens L10 are cemented.

The first anti-flare non-circular stop FS1 is disposed on the image side of the plano-concave negative lens L1 and between the plano-concave negative lens L1 and the parallel plate L2. The second flare prevention non-circular stop FS2 is disposed on the image side of the negative meniscus lens L10.

The optical path dividing unit 20 is disposed on the image side of the third lens group G3. In the prism in the optical system, the optical path is bent. The optical path splitting unit 20 will be described later. The parallel flat plate L2 is a filter provided with a coating for cutting a specific wavelength, for example, 1060 nm of a YAG laser, 810 nm of a semiconductor laser, or an infrared region.

(Example 2)
Next, the endoscope imaging unit 110 according to the second embodiment will be described. FIG. 8 is a diagram illustrating a cross-sectional configuration of the objective optical systems LNSa and LNSb of the endoscope imaging unit 110.

The objective optical systems LNSa and LNSb according to the present embodiment have a configuration in which two lens systems having the same configuration are arranged in parallel. For this reason, one objective optical system LNSa will be described as an example.

In order from the object side, the first lens unit G1 having a positive refractive power, an aperture stop S, and a second lens unit G2 having a positive refractive power are configured.

The first lens group G1 includes a planoconcave negative lens L1 and a biconvex positive lens L2.

The second lens group G2 includes a parallel plate L3, a biconvex positive lens L4, a negative meniscus lens L5 having a convex surface directed toward the image side, a parallel plate F1, and a parallel plate CG.

The first flare prevention non-circular diaphragm FS1 is disposed on the image side of the plano-concave negative lens L1. The second flare-preventing non-circular stop FS2 is located on the image side of the first flare-preventing non-circular stop FS1, and is disposed between the negative meniscus lens L5 and the parallel plate F1.

The parallel plate L3 is a filter provided with a coating for cutting a specific wavelength, for example, 1060 nm of a YAG laser, 810 nm of a semiconductor laser, or an infrared region.

(Example 3)
Next, the endoscope imaging unit 120 according to the third embodiment will be described. 9A and 9B are diagrams showing a cross-sectional configuration of the objective optical system LNS of the endoscope imaging unit 120. FIG. Here, FIG. 9A is a diagram illustrating a cross-sectional configuration of the objective optical system LNS in a normal observation state (a long distance object point). FIG. 9B is a diagram showing a cross-sectional configuration of the objective optical system LNS in the close-up observation state (short-distance object point).

The objective optical system LNS according to this example includes, in order from the object side, a first lens group G1 having a positive refractive power, an aperture stop S, a second lens group G2 having a negative refractive power, and a positive refractive power. The third lens group G3. The second lens group G2 moves on the optical axis AX to the image side, and corrects the change in the focal position accompanying the change from the normal observation state to the close observation state.

The first lens group G1 includes a plano-concave negative lens L1, a parallel plate L2, a positive meniscus lens L3 having a convex surface facing the image side, a plano-convex positive lens L4, and a negative meniscus lens L5 having a convex surface facing the image side. Consists of. Here, the positive lens L4 and the negative meniscus lens L5 are cemented.

The second lens group G2 includes a plano-concave negative lens L6 and a positive meniscus lens L7 having a convex surface directed toward the object side. The negative lens L6 and the positive meniscus lens L7 are cemented.

The third lens group G3 includes a biconvex positive lens L8, a biconvex positive lens L9, and a biconcave negative lens L10. Here, the positive lens L9 and the negative lens L10 are cemented.

The first anti-flare non-circular stop FS1 is disposed on the image side of the plano-concave negative lens L1 and between the plano-concave negative lens L1 and the parallel plate L2. The second flare prevention non-circular diaphragm FS2 is disposed on the image side of the negative lens L10.

(Description of the optical path splitting unit)
Next, the optical path splitting unit 20 in the above embodiment and examples will be described.
FIG. 4 is a functional block diagram of the

endoscope imaging units

100 and 120. FIG. 5 is a diagram illustrating a schematic configuration of the optical path splitting unit 20.

The light emitted from the objective optical system LNS of each embodiment described above enters the optical path dividing unit 20.

The optical path dividing unit 20 includes a polarization beam splitter 21 that divides a subject image into two optical images with different focus points, and an imaging element 22 that captures two optical images and acquires two images.

As shown in FIG. 5, the polarization beam splitter 21 includes a first prism 21b, a second prism 21e, a mirror 21c, and a λ / 4 plate 21d. Both the first prism 21b and the second prism 21e have beam split surfaces having an inclination of 45 degrees with respect to the optical axis.

A polarization splitting film 21f is formed on the beam splitting surface of the first prism 21b. The first prism 21b and the second prism 21e constitute the polarization beam splitter 21 by bringing the beam split surfaces into contact with each other via the polarization separation film 21f.

The mirror 21c is provided near the end face of the first prism 21b via a λ / 4 plate 21d. The image sensor 22 is attached to the end face of the second prism 21e via a parallel plate (cover glass) CG.

The subject image from the objective optical system LNS is separated into a P-polarized component (transmitted light) and an S-polarized component (reflected light) by the polarization separation film 21f provided on the beam splitting surface in the first prism 21b, and reflected light. The optical image is separated into two optical images, ie, an optical image on the side and an optical image on the transmitted light side.

The optical image of the S-polarized component is reflected to the imaging element 22 by the polarization separation film 21f, passes through the A ′ optical path, passes through the λ / 4 plate 21d, is reflected by the mirror 21c, and is reflected to the imaging element 22 side. Wrapped. The folded optical image is transmitted through the λ / 4 plate 21d again to rotate the polarization direction by 90 °, passes through the polarization separation film 21f, and forms an image on the imaging device 22.

The optical image of the P-polarized component is reflected by a mirror surface provided on the side opposite to the beam splitting surface of the second prism 21e that passes through the polarization separation film 21f, passes through the B ′ optical path, and is folded vertically toward the image sensor 22. Then, an image is formed on the image sensor 22. At this time, the prism glass path is set so that a predetermined optical path difference of, for example, about several tens of μm is generated between the A ′ optical path and the B ′ optical path, and two optical images with different focus are obtained from the image sensor 22. An image is formed on the light receiving surface.

That is, the first prism 21b and the second prism 21e can be separated into two optical images having different focus positions so that the optical path length (glass path length) on the transmitted light side to the imaging element 22 in the first prism 21b can be separated. The optical path length on the reflected light side is short (small).

As shown in FIG. 6, the image sensor 22 receives two optical images with different focus positions by individually receiving and picking up two optical images. Regions) 22a and 22b are provided.

The light receiving areas (effective imaging areas) 22a and 22b are arranged so as to coincide with the image planes of these optical images in order to capture two optical images. In the image sensor 22, the light receiving area (effective imaging area) 22a is shifted (shifted) toward the near point relative to the light receiving area (effective imaging area) 22b. The focus position of the area (effective imaging area) 22b is relatively shifted to the far point side with respect to the light receiving area (effective imaging area) 22a. Thereby, two optical images with different focus are formed on the light receiving surface of the image sensor 22.

In addition, by changing the refractive indexes of the glass materials of the first prism 21b and the second prism 21e, the optical path length to the image sensor 22 is changed, and the focus positions relative to the light receiving areas (effective imaging areas) 22a and 22b are relatively set. You may make it move to.

Further, around the light receiving areas (effective imaging areas) 22a and 22b, a correction pixel area 22c for correcting a geometric shift of the optical image divided into two is provided. In the correction pixel region 22c, manufacturing errors are suppressed, and correction by image processing is performed by an image correction processing unit 23b (FIG. 4), which will be described later, so as to eliminate the above-described geometrical deviation of the optical image. It has become.

The second lens group G2 of Examples 1 and 3 described above is a focusing lens and can be selectively moved to two positions in the direction of the optical axis. The second lens group G2 is driven by an actuator (not shown) so as to move from one position to the other position and from the other position to one position between two positions.

In the state where the second lens group G2 is set to the front side (object side) position, the second lens group G2 is set so as to focus on the subject in the observation area when performing far-field observation (normal observation). Further, in the state where the second lens group G2 is set to the rear side position, it is set to focus on the subject in the observation region when performing close-up observation (magnification observation).

Note that, as in the present embodiment, when the polarization beam splitter 21 is used for the polarization separation, the brightness of the separated image is different unless the polarization state of the light to be separated is a circular polarization. Regular brightness differences are relatively easy to correct in image processing. However, if brightness differences occur locally and under viewing conditions, they cannot be corrected completely, resulting in uneven brightness in the composite image. May end up.

The subject observed with the endoscope may have uneven brightness in the relatively peripheral part of the visual field of the composite image. It should be noted that the unevenness in brightness with the polarization state broken is conspicuous when the subject has a relatively saturated brightness distribution.

In the peripheral part of the visual field, the endoscope often sees the blood vessel running and the mucous membrane structure of the subject image relatively close to each other, and there is a high possibility that the image will be very troublesome for the user.
Therefore, for example, as shown in FIG. 5, it is preferable to arrange the λ / 4 plate 21d closer to the object side than the polarization separation film 21f of the optical path splitting unit 20 so as to return the polarization state to the circularly polarized state. .

It should be noted that a half mirror that splits the intensity of incident light can be used instead of the polarizing beam splitter as described above.

Next, with reference to FIG. 4, the synthesis of the two acquired images will be described.

The image processor 23 reads an image related to two optical images captured by the image sensor 22 and has different focus positions, and an image for performing image correction on the two images read by the image read unit 23a. The image processing apparatus includes a correction processing unit 23b and an image composition processing unit 23c that performs image composition processing for combining the two corrected images.

The image correction processing unit 23b is configured so that the differences other than the focus are substantially the same with respect to the images related to the two optical images formed on the light receiving areas (effective imaging areas) 22a and 22b of the imaging element 22, respectively. to correct. That is, the two images are corrected so that the relative positions, angles, and magnifications in the optical images of the two images are substantially the same.

When the subject image is separated into two and formed on the image sensor 22, geometrical differences may occur. That is, each optical image formed on the light receiving regions (effective imaging regions) 22a and 22b of the image sensor 22 may have a relative displacement of magnification, displacement of position, angle, that is, displacement in the rotation direction, and the like. .

Although it is difficult to completely eliminate these differences at the time of manufacturing or the like, if the amount of misalignment increases, the composite image becomes a double image or unnatural brightness unevenness occurs. Therefore, the above-described geometric difference and brightness difference are corrected by the image correction processing unit 23b.

When correcting the difference in brightness between two images, the lower one of the two images or images or the image or image having the lower luminance at the relatively same position of the two images or images is used as a reference. It is desirable to make corrections.

The image composition processing unit 23c selects a relatively high contrast image in a corresponding region between the two images corrected by the image correction processing unit 23b, and generates a composite image. That is, by comparing the contrast in each spatially identical pixel area in two images and selecting a pixel area having a relatively higher contrast, a composite image as one image synthesized from the two images Is generated.

When the contrast difference in the same pixel area of the two images is small or substantially the same, a composite image is generated by a composite image process in which the pixel area is added with a predetermined weight.

Further, the image processor 23 performs subsequent image processing such as color matrix processing, contour enhancement, and gamma correction on one image synthesized by the image synthesis processing unit 23c. The image output unit 23d outputs an image that has been subjected to subsequent image processing. The image output from the image output unit 23d is output to the image display unit 24.

Further, the first prism 21b and the second prism 21e are made of different glass materials according to the near point optical path and the far point optical path leading to the image sensor 22, and the refractive index is made different so that the relative focus position is relatively increased. It may be shifted.

Thereby, it is possible to obtain images related to two optical images with different focus and to synthesize these images by the image composition processing unit 23c to obtain a combined depth of field. Far-field observation is suitable for screening a wide range by endoscopy, and close-up observation is suitable for observing or diagnosing the details of a lesion.

By adopting such a configuration, it becomes possible to expand the depth of field without reducing the resolving power even when an image sensor having a larger number of pixels is used. Furthermore, since there is a focusing mechanism, it is possible to freely switch the observation range and perform high-quality endoscope observation and diagnosis.

The numerical data of each of the above examples is shown below. Symbols r are the radius of curvature of each lens surface, d is the distance between the lens surfaces, nd is the refractive index of the d-line of each lens, νd is the Abbe number of each lens, FNO is the F number, and ω is the half field angle It is.

Numerical example 1
Unit mm

Surface data Surface number r d nd νd
1 ∞ 0.48 1.88300 40.76
2 1.673 0.83
3 (FS1) ∞ 0.21
4 ∞ 0.83 1.52100 65.12
5 ∞ 0.34
6 -11.775 0.76 1.88300 40.76
7 1.866 2.10 1.84666 23.78
8 17.956 Variable 9 1.976 0.79 1.48749 70.23
10 2.106 0.41
11 (Brightness stop) ∞ Variable 12 4.016 0.91 1.64769 33.79
13 -1.601 0.32 2.00330 28.27
14 -5.954 0.06
15 ∞ 0.88 1.69895 30.13
16 -3.128 0.14
17 40.949 0.93 1.48749 70.23
18 -2.174 0.39 1.92286 18.90
19 -4.393 1.00
20 (FS2) ∞ 3.52
21 ∞

Zoom data Normal Expanded focal length 1.00 1.00
FNO. 3.58 3.54
Angle of view 2ω 145.02 139.22
fb (in air) 4.47 4.39
Total length (in air) 16.52 16.44

d7 0.46 1.18
d11 41.23 0.51

Each group focal length
f1 = -1.15 f2 = 21.90 f3 = 3.20

Numerical example 2
Unit mm

Surface data Surface number r d nd νd
1 ∞ 0.30 1.88300 40.76
2 0.689 0.42
3 (FS1) ∞ 0.08
4 4.817 1.57 1.80610 40.92
5 -1.521 0.10
6 (Brightness stop) ∞ 0.04
7 ∞ 0.89 1.52100 65.12
8 ∞ 0.15
9 3.167 1.27 1.75500 52.32
10 -1.199 0.45 1.92286 18.90
11 -3.669 0.50
12 (FS2) ∞ 0.07
13 ∞ 0.75 1.51633 64.14
14 ∞ 0.01 1.00000 64.00
15 ∞ 0.75 1.00000 50.49
16 ∞

Various data
fb (in air) 1.46
Total length (in air) 6.73

Focal length for each group Front group = 3.03 Rear group = 3.11

Numerical Example 3
Unit mm

Surface data Surface number r d nd νd
1 ∞ 0.30 1.88300 40.76
2 0.909 0.45
3 (FS1) ∞ 0.27
4 ∞ 0.34 1.52100 65.12
5 ∞ 0.17
6 -7.718 1.62 1.58144 40.75
7 -1.795 0.26
8 ∞ 0.68 1.53172 48.84
9 -1.125 0.26 1.92286 18.90
10 -1.774 0.04
11 (Brightness stop) ∞ Variable 12 ∞ 0.21 1.77250 49.60
13 1.321 0.47 1.69895 30.13
14 3.510 Variable 15 3.621 1.02 1.81600 46.62
16 -5.962 0.04
17 4.016 1.40 1.58913 61.14
18 -2.042 0.30 1.92286 18.90
19 9.007 0.50
20 (FS2) ∞ 1.26
21 ∞

Zoom data Normal Expanded focal length 1.00 1.25
FNO. 6.13 7.68
Angle of view 2ω 140.39 78.40
fb (in air) 1.67 1.01
Full length (in air) 11.73 11.07

d11 0.29 1.86
d14 1.94 0.38

Each group focal length
f1 = 1.74 f2 = -3.88 f3 = 2.78

The numerical values of conditional expressions (1) to (4) in the objective optical systems according to Example 1, Example 2, and Example 3 are shown below.

Conditional Example 1 Example 2 Example 3
(1) S01_v / S02_v 1.447 1.500 1.800
(2) ih_v / S02_v 1.030 1.655 1.800
(3) ih_AB / S02_v 2.809 5.500 4.000
(4) S01_v / enp_wide 0.576 0.651 0.831

Parameter Example 1 Example 2 Example 3
S01_v 0.94 0.71 0.77
S02_v 0.65 0.47 0.43
ih_v 0.67 0.78 0.77
ih_AB 1.82 2.59 1.70
enp_wide 1.63 1.08 0.92

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.

As described above, the present invention is an endoscope imaging unit for forming two optical images on one imaging device and performing image synthesis, and an endoscope capable of obtaining good image quality with less flare. Useful for imaging units.

1, 2

Endoscopes

100, 110, 120 Endoscope imaging unit 20 Optical path dividing unit 21 Polarizing beam splitter 21a λ / 4 plate 21b First prism 21c Mirror 21d λ / 4 plate 21e Second prism 21f Polarization separation film 22

Imaging Element

22a, 22b Light receiving area (effective imaging area)
22c correction pixel area 23 image processor 23a image reading unit 23b image correction processing unit 23c image composition processing unit 23d image output unit 24

image display unit

30, 31 notch 32 taper shape CG parallel flat plate (cover glass)
LNS, LNSa, LNSb Objective optical system (optical system)
G1 First lens group G2 Second lens group G3 Third lens group S Brightness stop FS1 First flare prevention non-circular stop FS2 Second flare prevention non-circular stop AP1, AP2, APa, APb Non-circular opening (opening)
A, B Effective imaging area FL Flare AX, AXa, AXb Optical axis

Claims

In an endoscope imaging unit that forms two optical images formed separately by an optical system having two optical paths on one imaging element,
The optical system having the two optical paths includes a negative first lens disposed closest to the object side, a first anti-flare noncircular stop disposed on the image side of the first lens, and the first anti-flare non-circular stop. An endoscope imaging unit comprising: a second flare-preventing non-circular aperture disposed on the image side of the circular aperture, and satisfying the following conditional expression (1):
0.3 <S01_v / S02_v <5.0 (1)
here,
When the V direction is the direction in which the two optical images are adjacent,
S01_v is a radius in the V direction of the first non-circular diaphragm for preventing flare,
S02_v is a radius in the V direction of the second anti-flare non-circular diaphragm,
It is.
The endoscope imaging unit according to claim 1, wherein the following conditional expression (2) is satisfied.
0.2 <ih_v / S02_v <5.0 (2)
here,
ih_v is the image height in the V direction,
S02_v is a radius in the V direction of the second anti-flare non-circular diaphragm,
It is.
The endoscope imaging unit according to claim 1, wherein the following conditional expression (3) is satisfied.
1.0 <ih_AB / S02_v <10.0 (3)
here,
ih_AB is the distance between the optical axes on the image sensor,
S02_v is a radius in the V direction of the second anti-flare non-circular diaphragm,
It is.
The optical system having the two optical paths is composed of an objective optical system having one optical axis and an optical path dividing optical system that divides the optical path into two parts,
The endoscope imaging according to any one of claims 1 to 3, wherein the second flare-preventing non-circular stop is disposed between the objective optical system and the optical path dividing optical system. unit.
The endoscope imaging unit according to any one of claims 1 to 3, wherein the optical system having the two optical paths includes an objective optical system having two optical axes.
The objective optical system is configured by a negative first lens group, a movable positive second lens group, and a positive third lens group in order from the object side. The endoscope imaging unit according to 5.
The endoscope imaging unit according to claim 4 or 5, wherein the objective optical system includes, in order from the object side, a first lens group, an aperture stop, and a positive rear group. .
The objective optical system is configured by a positive first lens group, a movable negative second lens group, and a positive third lens group in order from the object side. The endoscope imaging unit according to 5.
In the objective optical system having the two optical axes, at least one of the first flare-preventing non-circular stop and the second flare-preventing non-circular stop has two non-circular openings. The endoscope imaging unit according to any one of Items 5 to 8.
The endoscope imaging unit according to claim 6, wherein the following conditional expression (4) is satisfied.
0.1 <S01_v / emp_wide <5.0 (4)
here,
emp_wide is the entrance pupil position of the objective optical system in the widest angle state,
S01_v is a radius in the V direction of the first non-circular diaphragm for preventing flare,
It is.
The opening of at least one of the first flare-preventing non-circular stop and the second flare-preventing non-circular stop has a tapered shape that is inclined in one direction in a cross section along the optical axis,
The endoscope imaging unit according to any one of claims 1 to 3, wherein the diaphragm has a notch at a predetermined position with respect to the opening.
The endoscope imaging unit according to claim 1, further comprising a cover glass on the most object side.