JPH11109257A - Image pickup optical system of endoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup optical system of endoscope capable of simultaneously obtaining plural observation images without causing the fluctuation of a focal position and defects of image even when an objective optical system at the tip is exchanged according to an observation purpose. SOLUTION: A tip adaptor 5 of an endoscope is attachable/detachable to an endoscope main body. Objective optical systems 6, 7 are arranged on the object side of the tip adaptor 5 and form the images of object on a visual field mask 9, respectively. An image transmission optical system 10 transmits once the image to CCD 11 while the position of the visual field mask 9 is made to be an object plane. The image transmission optical system 10 is separated by a brightness diaphragm 12 located on a pupil, a front group lens 10a and the rear group lens 10b are arranged on the side of the tip adaptor 5 and on the side of the endoscope main body 4, respectively. A color temp. converting filter 14 and an optical low pass filter 15 are joined in this order to the cover glass 13 of CCD 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endoscope apparatus, and more particularly, to an endoscope apparatus including a plurality of objective optical systems and one solid-state image sensor.
The present invention relates to an imaging optical system suitable for use in an electronic endoscope apparatus in which images of an object obtained through respective objective optical systems are formed on different portions of the solid-state imaging device for observation.

[0002]

2. Description of the Related Art In recent years, with the development of various industries, practically, for example, water supply pipes for cooling water in nuclear power plants, turbine blades of steam generators of various power generation plants, and engines of aircraft, etc. As instruments that cannot be disassembled or are not easy to disassemble have increased, endoscopes have been used to observe and inspect the inside of such instruments. . As an endoscope used in that case, a solid-state imaging device represented by a CCD is arranged at the tip of the insertion section, and an object image formed on the solid-state imaging device is displayed on a screen of a television monitor. An electronic endoscope apparatus for displaying and observing is generally used.

In the case of an endoscope used in the industrial field, it is effective if the objective optical system has a variable power function. For example, a cooling water pipe is arranged inside a steam generator of a power plant, but when observing the inner wall of such a pipe using an endoscope, the endoscope is initially inserted. In this case, since it is necessary to check the inspection location quickly and quickly access a predetermined location, it is advantageous to use an optical system having a wide-angle field of view. However, once it has reached a predetermined location, it is more advantageous to use a high-magnification, or narrow-angle, field of view optical system to observe very small cracks or defects. Therefore, in such a case, it is extremely effective to have a zooming function.

[0004] However, if the endoscope is provided with a zooming function, there is a disadvantage in that the configuration is mechanically complicated and the diameter of the insertion portion is increased. In addition, when inspecting the inner wall of a small-diameter pipe, the inner wall is positioned parallel to the insertion direction of the endoscope, so that merely having a zooming function can be applied only to the front of the pipe. There is a problem that it is not possible to observe and it is impossible to observe the inner wall in detail. Therefore, in order to enable such observation, it is necessary to provide a direct-view objective system for observing the front of the endoscope and a side-view objective system for observing the lateral direction, and switch between them for observation. But
If an endoscope having such a configuration is to be provided with a zooming function, the structure becomes more complicated mechanically, and the configuration becomes unsuitable for an endoscope.

In Japanese Patent Application Laid-Open No. 1-197716, a plurality of solid-state imaging devices are arranged at the end of an endoscope, and a plurality of objective optical systems corresponding to each are arranged, so that a plurality of observations can be made simultaneously. An endoscope apparatus for obtaining an image has been proposed. However, since the occupation ratio of the solid-state imaging device in the distal end portion of the endoscope increases, the diameter of the distal end portion of the endoscope cannot be avoided.

Conventionally, an objective optical system has been fixed to a solid-state image sensor. However, in the current industrial field,
The objective optical system at the end of the endoscope is detachable, and it is common to select and use various types of objective optical systems such as direct view, side view, wide angle, and narrow angle according to the observation purpose. Therefore, in the endoscope used in this way, if each objective optical system is fixed to each solid-state imaging device, it cannot be said that it is advantageous in terms of handling and cost. ,
This is extremely inconvenient as a method for dealing with a wider range of observation objects.

For this reason, an endoscope optical system for solving such inconvenience is disclosed in Japanese Patent Application Laid-Open No. 9-122068, and FIG. 10 shows a conventional example thereof.
As shown in FIG. 10A, this conventional endoscope includes a single solid-state imaging device (CC) provided in an endoscope main body 31.
D) 37 is an endoscope in which two observation images are obtained at the same time by arranging two objective optical systems 33 and 34 having different specifications provided on the distal end adapter 32. Further, in this endoscope, as shown in FIG. 10B, a distal end adapter 32 is detachable from the endoscope main body 31 at a stage subsequent to the final lens of the two objective optical systems 33 and 34, and For example, it is possible to replace one objective optical system with an adapter for a simultaneous direct-viewing / side-viewing optical system in which a side-viewing optical system is used.

[0008]

However, FIG.
In the configuration of the prior art as shown in FIG. 1, the rattling of the attachment / detachment mechanism causes the objective optical systems 33 and 34 to vibrate.
It is not possible to keep the distance between the camera and the solid-state image sensor 37 constant, and the focal position may be shifted. For example, when the distance between the endoscope main body 31 and the distal end adapter 32 is larger than a predetermined distance, the focus position is shifted to the near side, so that a distant image is blurred and cannot be observed. The problem arises. Further, the division position of the optical system between the endoscope main body 31 and the distal end adapter 32 is
Since the position of the light flux near the image plane is narrow, if dust or scratches are formed on the surface of the cover glass 38 on the endoscope main body 31 side, the dust or the like is likely to be captured as an image, resulting in a defective image. There is a point.

The present invention has been made in order to solve such a problem, and an object thereof is as follows.
Even when the tip objective optical system is replaced according to the observation purpose, multiple observation images can be obtained at the same time without fluctuation of the focus position or image defect due to rattling of the attachment / detachment mechanism or adhesion of dust. An object of the present invention is to provide an endoscope imaging optical system.

[0010]

In order to achieve the above object, the present invention provides, in order from an object side, a plurality of objective optical systems and a plurality of images formed by the objective optical systems once. In an endoscope imaging optical system including an image transmission optical system for transmitting and a solid-state imaging device, the objective optical system side and the solid-state imaging device side are detachable at a substantially pupil position of the image transmission optical system. To be there. Further, in the endoscope imaging optical system of the present invention, preferably, the entrance pupils of the plurality of objective optical systems are formed at different positions. In the endoscope imaging optical system of the present invention,
Preferably, the plurality of objective optical systems have different viewing directions. Further, in the endoscope imaging optical system according to the present invention, preferably, the plurality of objective optical systems include two optical systems having the same configuration.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, an endoscope imaging optical system according to the present invention includes a plurality of objective optical systems arranged in parallel from the tip on the object side and each objective optical system. It is composed of one image transmission optical system for transmitting a plurality of formed images once, and one solid-state imaging device, and is provided at a substantially pupil position of the image transmission optical system with the objective optical system. The solid-state imaging device side is made detachable. As described above, when a plurality of objective optical systems are arranged in parallel so that the image forming positions are on the same plane, the plurality of images formed on the same plane are:
From the point of view of the image transmission optical system, it can be considered as one object image, and these images can be simultaneously formed on the imaging surface of the solid-state imaging device by one image transmission optical system.

Further, by dividing the objective optical system side (tip adapter side) and the solid-state image pickup device side (endoscope main body side) substantially at the pupil position of the image transmission optical system, the separation at the thick portion of the image forming light beam is performed. This makes it possible to prevent image defects due to dust, scratches and the like, which have been problems in the prior art. Further, in the image transmission optical system, an imaging plane (so-called image plane) on the solid-state imaging device side is set at a position near the focal point on the rear side of the rear lens unit disposed on the solid-state imaging device side, thereby achieving an internal The focus position of the optical system of the endoscope body alone becomes almost infinity, and the focus position does not change due to variations between the end adapter body side and the endoscope body side due to rattling or dust of the attachment / detachment mechanism. Has become.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Four embodiments will be described below with reference to the drawings. FIGS. 1 to 5 are diagrams for explaining the first embodiment, FIG. 6 is for explaining the second embodiment, FIGS. 7 and 8 are for explaining the third embodiment, and FIG. 9 is for explaining the fourth embodiment. In addition, members that are considered to be substantially the same between the embodiments are denoted by the same reference numerals for convenience.

[Embodiment 1] In general, an endoscope apparatus comprises an endoscope 1 shown in FIG. 1 and a light source (not shown), a video signal processing device, a television monitor, and the like. The electric signal of the object image output by the endoscope 1 is converted into a television signal by a video signal processing device, and the television signal is displayed on a television monitor so as to be observed. Endoscope 1
As shown in FIG. 2, the distal end portion 3 is configured such that the endoscope main body 4 and the distal end adapter 5 can be attached and detached.
The endoscope main body 4 is provided with a CCD, which will be described later, which is a solid-state image sensor. The adapter 5 has two objective optical systems 6 and 7 having different specifications depending on the observation purpose, and a light (not shown). An illumination optical system 8 for irradiating the object surface with light from a light source via a guide is arranged.

Next, a detailed configuration of the above-mentioned distal end portion 3 will be described with reference to FIG. FIG. 3 is a cross-sectional view as viewed from above in FIG. The two objective optical systems 6 and 7 described above are arranged side by side at the object-side tip of the tip adapter 5, and form an object image at the field mask 9 respectively. The entrance pupils of the objective optical systems 6 and 7 are indicated by 6p and 7p, respectively. Image transmission optical system 1
0 indicates the CCD 11 with the position of the field mask 9 as the object plane.
Image is transmitted once. The image transmission optical system 10
Denotes a brightness stop 12 at the pupil position, which is divided into the endoscope main body 4 side and the distal end adapter 5 side.
a is disposed on the distal end adapter 5 side, and the rear lens group 10b is disposed on the endoscope main body 4 side. Further, the CCD 11 has a rectangular shape, and its longitudinal direction is arranged in the vertical direction in FIG. 3. A color temperature conversion filter 14 and an optical low-pass filter 15 are sequentially joined to a cover glass 13 of the CCD 11. Have been.

In this configuration, the imaging surface 11a of the CCD 11 is disposed at the rear focal position of the rear lens group 10b. Therefore, the best object observation position of the optical system on the endoscope main body 4 side (hereinafter referred to as a best distance) is infinity. Therefore, even if the attachment position of the distal end adapter 5 is slightly moved back and forth with respect to the endoscope main body 4 in the optical axis direction, the entire focal position does not change. . Further, since the pupil diameter is sufficiently large, there is also an effect that it is less susceptible to dust, scratches, and the like than in the past.

Further, according to the configuration of this embodiment, the front lens group 10a of the image transmission optical system 10 adjusts the front focal position to the position of the field mask 9 and the rear focal position to the pupil position. Thereby, the position of the entrance pupil of the image transmission optical system 10 is set at infinity. The optical axes 6 'of the objective optical systems 6 and 7,
7 'is parallel to the optical axis 10' of the image transmission optical system 10.
Therefore, in order to make the image transmission optical system 10 coincide with the optical axis direction of the objective optical systems 6 and 7, it is necessary to set the entrance pupil position to infinity. On the other hand, in order to prevent the peripheral light quantity from being lost, it is desirable that the objective optical systems 6 and 7 have the exit pupil position at almost infinity (a so-called telecentric optical system). In the case of the present embodiment, the shape of the field mask 9 (see FIG. 4) is directly projected on the CCD 11, so that the observation image projected on the television monitor can be obtained clearly up to the peripheral portion.

FIG. 5A shows a case where the monocular adapter 16 is attached to the endoscope main body 4, and FIG.
Shows a state in which the monocular adapter is being removed. According to the present embodiment, since the field mask 9 is disposed on the distal end adapter 5, the optical system of the endoscope body 4 does not require a field mask, and the normal CCD imaging area is fully used. Such a monocular adapter 16 can be attached. In the case of this embodiment, the viewing angle is 80
Although the optical system of ° is shown, it is clear that an optical system of other specifications can be mounted. In this case, it is effective to arrange the aperture stop 12 on the distal end adapter side in order to be able to cope with various uses.

Embodiment 2 Next, Embodiment 2 will be described with reference to FIG.
Will be described. FIG. 6 is a diagram viewed from above in FIG. 2 in the same manner as FIG. 3, but shows only the configuration of the optical system unlike the case of FIG. The configuration of the present embodiment is intended to widen the observation field of view. The two objective optical systems 17 and 18 are configured such that one objective optical system 17 is a direct-view optical system while the other objective optical system 17 is a direct-view optical system. The system 18 is a side viewing optical system. With this configuration, as already described, for example, a cooling water pipe inside the steam generator,
It becomes possible to efficiently observe the inner wall of a very small diameter pipe. In addition, although the reflecting prism 18p is used for the objective optical system 18 for side view, it is preferable to use a two-time reflecting prism as the reflecting prism in that case.
This is because if the reflection prism is used an odd number of times, the observation image becomes a back image, and it is difficult to associate the observation image with a direct-view image.

In this embodiment, the brightness stop 1
2 is provided with a cover glass 19 to prevent dust from entering the distal end adapter 5. that time,
Regardless of which surface of the cover glass 19 is disposed, there is no optical difference, but the diaphragm 12 is disposed on the outside (right side) of the distal end adapter 5, contrary to the state shown in FIG. In this case, the observer may erroneously break the aperture 12 when removing dust and the like. Therefore, as shown in FIG. 6, it is preferable to dispose the diaphragm 12 inside the tip adapter 5 (left side). . In this embodiment, a side-viewing optical system in which the side-viewing visual field direction is 90 ° is used for one of the objective optical systems. It is needless to say that various combinations such as a combination of a direct view and a perspective and a combination of a perspective and a perspective may be used.

Third Embodiment Next, a third embodiment will be described with reference to FIGS. FIG. 7 is shown in the same manner as FIG. The configuration of the present embodiment aims at further expanding the observation visual field range than the case of the above-described second embodiment. That is, in the case of the present embodiment, three objective optical systems 20, 21, and 22 are provided, and among these, the objective optical system 20 is a direct optical system, and the other objective optical systems 2 are used.
By using the side-view optical systems 1 and 22, it is possible to observe a wider range at a time.

Thus, the three objective optical systems 20,
When the lenses 21 and 22 are provided, the required area of the objective lens at the image forming position becomes longer in the lens arrangement direction (vertical direction in FIG. 7, that is, the longitudinal direction of the CCD) in order to prevent interference between adjacent lenses. . Therefore, as shown in FIG. 8 (FIG. 8A is a front view, FIG. 8B is a side view), the front group lens 10c of the image transmission optical system 10 in the present embodiment cuts unnecessary portions. In addition, the planar shape centered on the optical axis is formed in an oval shape, thereby preventing the outer diameter from increasing. In addition, such a cut makes it possible to efficiently arrange an optical fiber for illumination in an empty space created thereby.

[Embodiment 4] Finally, Embodiment 4 will be described with reference to FIG. 9. In this embodiment, the length measurement function is realized by disposing two objective optical systems 23 and 24 having the same specifications. It is what you have. In recent endoscopy, there is an increasing need not only for observation but also for obtaining the length and depth of a wound at the same time. The conventional measuring method is
The length measurement by the projection method is mainstream, and the measurement is performed by a method such as projecting a lattice chart on an object surface and comparing and measuring the size. However, this method has a disadvantage that a mechanism for projecting the grid chart is considerably large, and
When the object surface is close to the mirror surface, the reflected light of the grating chart cannot be observed by the objective optical system, and there is a disadvantage that measurement cannot be performed.

Therefore, in order to eliminate such inconveniences, images obtained by two objective optical systems having the same specifications are converted into one C image.
A method of taking a CD and measuring the length of the object by triangulation has been proposed and implemented in the above-mentioned Japanese Patent Application Laid-Open No. 9-122068. However, in order to increase the accuracy of such triangulation, it is necessary to dispose the objective optical systems apart from each other, but the objective optical systems cannot be separated from each other beyond the width of the CCD. Had difficulty measuring However, in this embodiment, the image transmission optical system 10
By changing the focal length of the front lens group 10d, it is possible to adjust the image interval between the objective optical systems 23 and 24. Therefore, for example, when it is desired to increase the image interval between the objective optical systems 23 and 24 in order to increase the measurement accuracy, the focal length of the front group lens 10a may be increased. It should be noted that all of the above embodiments have been described on the premise that the flexible mirror shown in FIG. 1 is used. However, as can be understood from the description so far, the present invention relates to such a flexible mirror. It is needless to say that the present invention is not limited to this case, and can be applied to the case of a rigid endoscope having a hard insertion portion.

As is clear from the above description,
In addition to the configuration described in each claim, the following configuration is a feature of the present invention. (1) In the image transmission optical system, a rear group optical system is arranged behind the pupil position, and an imaging surface of the solid-state imaging device is arranged at a rear focal position of the rear group optical system thereafter. The endoscope imaging optical system according to any one of claims 1 to 4, wherein: (2) In the image transmission optical system, a front group optical system is disposed in front of the pupil position, and a front focus position of the front group optical system and a field mask located on an image plane of the objective optical system. 5. The endoscope according to claim 1, wherein a position of the pupil is substantially the same, and a rear focal position of the front group optical system and the pupil position are substantially the same. 6. Mirror imaging optical system. (3) The endoscope imaging optical system according to any one of claims 1 to 4, wherein the objective optical system is a telecentric optical system. (4) A brightness stop is arranged at a pupil position of the image transmission optical system, and the stop is detachable together with the objective optical system. An endoscope imaging optical system according to any one of the above. (5) One or more of the objective optical systems is a side-view or perspective optical system, and the reflecting prism that converts the optical axis by the side-view or perspective optical system is a prism that performs a plurality of reflections. The endoscope imaging optical system according to any one of claims 1 to 4, wherein: (6) In the image transmission optical system, a front group optical system is disposed on the front side of the pupil position, and the plane shape of the front group optical system about the optical axis is in the longitudinal direction of the solid-state imaging device. The endoscope imaging optical system according to any one of claims 1 to 4, wherein the endoscope imaging optical system has an oval shape correspondingly cut in the vertical direction.

[0026]

As described above, according to the present invention, even if the tip objective optical system is replaced in accordance with the observation purpose, the focus position may be changed due to rattling or dust of the attachment / detachment mechanism of the tip optical system. Image defects do not occur, and a plurality of observation images can be obtained at the same time.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an overall configuration of an endoscope to which a first embodiment is applied;

FIG. 2 is a perspective view showing a distal end portion of the endoscope shown in FIG. 1 in detail.

FIG. 3 is a cross-sectional view of a distal end portion of the endoscope according to the first embodiment.

FIG. 4 is a diagram illustrating an opening shape portion of a field mask in the first embodiment.

FIG. 5 is a cross-sectional view of a case where a monocular adapter is used as the distal end adapter of Example 1, and FIG.
FIG. 4B illustrates a state in which the monocular adapter is attached to the endoscope main body, and FIG. 4B illustrates a state in which the monocular adapter is being removed.

FIG. 6 is a configuration diagram illustrating an objective optical system according to a second embodiment.

FIG. 7 is a configuration diagram illustrating an objective optical system according to a third embodiment.

8A and 8B are diagrams illustrating a shape of a front lens group of an image transmission optical system according to a third embodiment, where FIG. 8A is a front view and FIG.
(B) is a side view.

FIG. 9 is a configuration diagram illustrating an objective optical system according to a fourth embodiment.

FIG. 10 is a sectional view showing a conventional example, and FIG.
10A shows a state where the distal end adapter is attached to the endoscope main body, and FIG. 10B shows a state where the distal end adapter is being removed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Endoscope 2 Insertion part 3 Tip part 4 Endoscope main body 5 Tip adapter 6,7,17,18,20,21,22,23,24
Objective optical system 6p, 7p Entrance pupil 6 ', 7', 10 'Optical axis 8 Illumination optical system 9 Field mask 10 Image transmission optical system 10a, 10c, 10d Front group lens 10b Rear group lens 11 CCD 11a Imaging surface 12 Brightness Aperture 13, 19 Cover glass 14 Color temperature conversion filter 15 Optical low-pass filter 16 Monocular adapter

Claims (4)

[Claims] 1. A plurality of objective optical systems in order from an object side,
In an endoscope imaging optical system including an image transmission optical system that transmits a plurality of images formed by the objective optical systems once and a solid-state imaging device, the objective transmission optical system is located at a substantially pupil position of the image transmission optical system. An endoscope imaging optical system, wherein an optical system side and the solid-state imaging device side are detachable. 2. An entrance pupil of each of the plurality of objective optical systems is formed at a different position.
4. The endoscope imaging optical system according to claim 1. 3. The endoscope imaging optical system according to claim 1, wherein the plurality of objective optical systems have different viewing directions. 4. The endoscope imaging optical system according to claim 1, wherein the plurality of objective optical systems are composed of two optical systems having the same configuration.