JP4105785B2 - Endoscopic imaging optical system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes an endoscope apparatus, particularly, a plurality of objective optical systems and a single solid-state imaging device, and images of objects obtained through the respective objective optical systems are connected to different portions of the solid-state imaging device. The present invention relates to an imaging optical system that is suitable for use in an electronic endoscope apparatus that is to be imaged and observed.
[0002]
[Prior art]
In recent years, with the development of various industries, it can be practically disassembled, such as cooling water supply pipes at nuclear power plants, steam generator turbine blades of various power plants, aircraft engines, etc. Since there are many devices that are not easy to disassemble or disassemble, endoscopes have come to be used when observing or inspecting the inside of such devices. As an endoscope used in that case, a solid-state image sensor represented by a CCD is arranged at the tip of the insertion portion, and an object image formed on the solid-state image sensor is displayed on the screen of a television monitor. The case of an electronic endoscope apparatus that is displayed and observed is common.
[0003]
Further, in the case of an endoscope used in the industrial field, it is effective that the objective optical system has a zooming 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 quickly check the inspection location and to access a predetermined location quickly, it is advantageous to use an optical system with a wide-angle field of view. However, after reaching a predetermined location, it is advantageous to use an optical system with a high magnification, that is, a narrow-angle field of view, in order to observe very small cracks and 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, the structure is mechanically complicated, and there is a disadvantage that the diameter of the insertion portion is increased. In addition, when inspecting the inner wall of a small-diameter pipe, the inner wall is located in parallel with the insertion direction of the endoscope. There is a problem that the inner wall cannot be observed 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. However, if an endoscope with such a configuration is provided with a zooming function, it becomes mechanically more complicated and unsuitable for an endoscope.
[0005]
Therefore, in JP-A-1-197716 and the like, a plurality of observation images are obtained simultaneously by disposing a plurality of solid-state imaging elements at the distal end portion of the endoscope and disposing a plurality of objective optical systems corresponding to each. An endoscopic apparatus configured as described above has been proposed. However, in those cases, since the occupation ratio of the solid-state imaging device at the endoscope distal end portion is increased, it is still inevitable to increase the diameter of the endoscope distal end portion.
[0006]
Conventionally, the objective optical system is fixed to the solid-state image sensor. However, in the current industrial field, the objective optical system at the distal end of the endoscope is detachable, and various objective optical systems such as direct view, side view, wide angle, and narrow angle are selected according to the observation application. Therefore, in an endoscope used in such a manner, if each objective optical system is fixed to each solid-state image sensor, handling is also difficult. However, it is not advantageous in terms of cost, and it is extremely inconvenient for dealing with a wider range of observation objects.
[0007]
For this reason, an endoscope optical system for solving such an inconvenience is disclosed in Japanese Patent Laid-Open No. 9-122068, and a conventional example thereof is shown in FIG. As shown in FIG. 10A, the endoscope of this conventional example has a specification provided on the distal end adapter 32 with respect to one solid-state imaging device (CCD) 37 provided on the endoscope main body 31. The endoscope is configured such that two observation images can be obtained simultaneously by arranging two different objective optical systems 33 and 34. In addition, as shown in FIG. 10B, the endoscope has a distal adapter 32 that can be attached to and detached from the endoscope body 31 at the rear stage of the last lens of the two objective optical systems 33 and 34. For example, it is possible to replace one objective optical system with an adapter for a direct-view / side-view simultaneous observation optical system in which a side-view optical system is used.
[0008]
[Problems to be solved by the invention]
However, in the configuration of the conventional example as shown in FIG. 10, the gap between the objective optical systems 33 and 34 and the solid-state imaging device 37 cannot be kept constant due to rattling of the attachment / detachment mechanism. 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 in-focus position moves closer to the near side. The problem that it ends up occurs. In addition, since the optical system dividing position of the endoscope main body 31 and the tip adapter 32 is a thin position of the light beam near the image plane, dust or scratches are formed on the surface of the cover glass 38 on the endoscope main body 31 side. If it is attached, there is a problem that they are easily captured as an image and an image defect occurs.
[0009]
The present invention has been made to solve such problems, and the object of the present invention is to provide a backlash of the attachment / detachment mechanism even when the tip objective optical system is replaced depending on the observation application. Another object of the present invention is to provide an endoscope imaging optical system capable of simultaneously obtaining a plurality of observation images without causing focus position fluctuations or image defects due to adhesion of dust or the like.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention comprises, in order from the object side, a plurality of objective optical systems, an image transmission optical system that transmits a plurality of images formed by these objective optical systems, and a solid state. In an endoscope imaging optical system including an imaging element, the objective optical system side and the solid-state imaging element side are detachable at a substantially pupil position of the image transmission optical system.
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, it is preferable that the plurality of objective optical systems have different visual field directions.
In the endoscope imaging optical system of the present invention, it is preferable that the plurality of objective optical systems include two optical systems having the same configuration.
In the endoscope imaging optical system of the present invention, a front group optical system is disposed in front of the pupil position in the image transmission optical system, and a front focal position of the front group optical system and the objective The position of the field mask located on the imaging plane of the optical system is substantially the same, and the rear focal position of the front group optical system and the pupil position are substantially the same.
In the endoscope imaging optical system of the present invention, the objective optical system is a telecentric optical system.
Furthermore, in the endoscope imaging optical system of the present invention, the image transmission optical system has a front group optical system disposed on the front side of the pupil position, and the plane of the front group optical system centered on the optical axis. The shape is an oval shape in which the vertical direction is cut in correspondence with the longitudinal direction of the solid-state imaging device.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
As described above, the endoscope imaging optical system of the present invention includes a plurality of objective optical systems arranged in parallel in order from the tip on the object side, and a plurality of images formed by the respective objective optical systems. The image transmission optical system for transmitting the image once and a solid-state image sensor, and the objective optical system side and the solid-state image sensor side are detachable at a substantially pupil position of the image transmission optical system. It is trying to become. As described above, when a plurality of objective optical systems are arranged in parallel so that the imaging positions are on the same plane, a plurality of images formed on the same plane can be seen as one object image when viewed from the image transmission optical system. Therefore, these images can be simultaneously formed on the imaging surface of the solid-state imaging device by one image transmission optical system.
[0012]
Also, by dividing the objective optical system side (tip adapter side) and the solid-state image sensor side (endoscope body side) at the approximate pupil position of the image transmission optical system, it becomes possible to separate the imaged light beam at a thick place. Thus, it is possible to prevent image defects due to dust, scratches and the like as described above, which has been a problem in the prior art. Further, by setting an imaging surface (so-called image plane) on the solid-state imaging device side at a position near the focal point on the rear side of the rear group lens system arranged on the solid-state imaging device side in the image transmission optical system, The focus position of the optical system in the endoscope body alone is almost infinite, and the focus position does not change due to variations in the surface between the tip adapter side and the endoscope body side due to rattling or dust of the attachment / detachment mechanism. It has become.
[0013]
【Example】
Hereinafter, four embodiments will be described with reference to the drawings. 1 to 5 illustrate the first embodiment, FIG. 6 illustrates the second embodiment, FIGS. 7 and 8 illustrate the third embodiment, and FIG. 9 illustrates the fourth embodiment. Moreover, the same code | symbol is used for the member etc. which may be considered substantially the same between each Example for convenience.
[0014]
[Example 1]
In general, the endoscope apparatus includes an endoscope 1 shown in FIG. 1, a light source, a video signal processing device, a television monitor, and the like (not shown), and an object output by the endoscope 1. An electric signal of the image is converted into a television signal by a video signal processing device, and the image is displayed on a television monitor so that it can be observed. The endoscope 1 is composed of a flexible insertion portion 2 and a hard distal end portion 3, and the distal end portion 3 is configured such that an endoscope body 4 and a distal end adapter 5 can be attached and detached as shown in FIG. It has become. The endoscope body 4 is provided with a CCD, which will be described later, which is a solid-state imaging device. The adapter 5 has two objective optical systems 6 and 7 having different specifications depending on the observation application, 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 disposed.
[0015]
Then, next, the detailed structure of the above-mentioned front-end | tip part 3 is demonstrated using FIG. FIG. 3 is a cross-sectional view seen from above in FIG. The above-mentioned two objective optical systems 6 and 7 are arranged side by side at the object-side tip of the tip adapter 5, and an object image is formed at the field mask 9. The entrance pupils of the objective optical systems 6 and 7 are indicated by 6p and 7p, respectively. The image transmission optical system 10 transmits the image once to the CCD 11 with the position of the field mask 9 as the object plane. In addition, the image transmission optical system 10 is divided into an endoscope main body 4 side and a tip adapter 5 side by an aperture stop 12 at the pupil position, and the front group lens 10a is arranged on the tip adapter 5 side. The lens 10b is disposed on the endoscope body 4 side. Further, the CCD 11 has a rectangular shape, and its longitudinal direction is arranged in the vertical direction in FIG. 3, and the color temperature conversion filter 14 and the optical low-pass filter 15 are sequentially joined to the cover glass 13 of the CCD 11. Has been.
[0016]
In this configuration, the imaging surface 11a of the CCD 11 is disposed at the rear focal position of the rear group lens 10b. Therefore, the best object observation position (hereinafter referred to as the best distance) of the optical system on the endoscope body 4 side is infinity. Therefore, even if the attachment position of the distal end adapter 5 is slightly back and forth with respect to the endoscope body 4 in the optical axis direction, the overall focal position does not change, so that there is no variation in focus during observation. . In addition, since the pupil diameter is sufficiently large, there is an effect that it is less susceptible to dust and scratches than in the past.
[0017]
Further, according to the configuration of the present 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 entrance pupil position of the transmission optical system 10 is set to infinity. The optical axes 6 ′ and 7 ′ of the objective optical systems 6 and 7 are parallel to the optical axis 10 ′ of the image transmission optical system 10. For this reason, in order to make the image transmission optical system 10 coincide with the optical axis direction of the objective optical systems 6 and 7, the entrance pupil position needs to be infinite. On the other hand, in order not to lose the peripheral light amount, it is desirable that the objective optical systems 6 and 7 have the exit pupil position at approximately infinity (so-called telecentric optical system). In the case of the present embodiment, since the shape of the field mask 9 (see FIG. 4) is projected onto the CCD 11 as it is, there is an effect that the observation image projected on the television monitor can be clearly obtained up to the peripheral portion.
[0018]
5A shows a case where the monocular adapter 16 is attached to the endoscope body 4, and FIG. 5B shows a state in the middle of removing the monocular adapter. According to the present embodiment, since the field mask 9 is arranged on the tip adapter 5, the field mask is not necessary for the optical system of the endoscope body 4, and the normal CCD imaging area is fully used. Such a monocular adapter 16 can be attached. In this embodiment, an optical system with a viewing angle of 80 ° is shown, but it is obvious that an optical system with other specifications can be mounted. In this case, it is effective to arrange the brightness diaphragm 12 on the tip adapter side in order to be able to cope with various uses.
[0019]
[Example 2]
Next, Example 2 will be described with reference to FIG. 6 is a view seen from above in FIG. 2 in the same manner as FIG. 3, but only the configuration of the optical system is shown unlike the case of FIG. The configuration of the present embodiment is intended to widen the observation visual field range. The two objective optical systems 17 and 18 have one objective optical system 17 which is a direct-view optical system, but the other objective optical system. The system 18 is a side view optical system. With this configuration, as already described, the inner wall of a very small diameter pipe such as a cooling water pipe inside the steam generator can be efficiently observed. Further, although the reflecting prism 18p is used in the side-view objective optical system 18, it is preferable to use a twice reflecting prism as the reflecting prism in that case. This is because, when an odd number of times of reflection prisms are used, the observation image becomes a back image, which makes it difficult to associate with the direct view image.
[0020]
In this embodiment, a cover glass 19 is provided on the aperture stop 12 so as to prevent dust from entering the tip adapter 5. At that time, there is no optical difference between the surface of the cover glass 19 and the diaphragm 12 is arranged. However, contrary to the state shown in FIG. ), The observer 12 may accidentally break the diaphragm 12 when removing dust or the like, so that it is disposed inside (on the left side) of the tip adapter 5 as shown in FIG. Is preferred.
In this embodiment, a side-view optical system with a 90 ° side-view visual field direction is used for one objective optical system, but a perspective optical system with a visual field direction of 45 ° or the like is used, and a combination of objective optical systems is used. It goes without saying that various combinations such as a combination of direct view and strabismus and a combination of strabismus and strabismus may be used.
[0021]
Example 3
Next, Example 3 will be described with reference to FIGS. FIG. 7 is the same as FIG. The configuration of this example is intended to further widen the observation visual field range as compared with the case of Example 2 described above. That is, in the present embodiment, three objective optical systems 20, 21, 22 are provided. Among these, the objective optical system 20 is a direct-light optical system, and the other objective optical systems 21, 22 are side-view optical. By making it a system, it is possible to observe over a wider range at once.
[0022]
Thus, when the three objective optical systems 20, 21, and 22 are provided, in order to prevent interference between adjacent lenses, the required area at the imaging position of the objective lens is the lens alignment direction (FIG. 7). It becomes longer in the vertical direction (that is, the longitudinal direction of the CCD). Therefore, the front group lens 10c of the image transmission optical system 10 in this embodiment is cut unnecessary portions as shown in FIG. 8 (FIG. 8A is a front view and FIG. 8B is a side view). In addition, the planar shape centered on the optical axis is an oval shape to prevent the outer diameter from being increased. Moreover, if it cuts in this way, it will become possible to arrange | position the optical fiber for illumination efficiently in the empty space formed by it.
[0023]
Example 4
Finally, Example 4 will be described with reference to FIG. 9. In this example, two objective optical systems 23 and 24 having the same specifications are arranged to provide a length measuring function. In recent endoscopy, there is a growing need for not only observing but also determining the length and depth of the wound at the same time. In the conventional length measurement method, the measurement by the projection method is the mainstream, and the measurement is performed by a method of projecting a grid chart on the object surface and comparing the size. However, this method has the disadvantage that the mechanism for projecting the grid chart is considerably large, and when the object plane is close to a mirror surface, the reflected light of the grid chart cannot be observed with the objective optical system. However, there is a disadvantage that the measurement cannot be performed, and the environment in which the measurement can be used is very limited.
[0024]
Therefore, in order to eliminate such inconvenience, a method of taking an image obtained by two objective optical systems having the same specification into one CCD and measuring the object by triangulation is disclosed in the above-mentioned Japanese Patent Laid-Open No. 9-12068. Proposed and implemented in the Gazette. However, in order to increase the accuracy of such triangulation, it is necessary to place the objective optical systems apart from each other, but the objective optical systems cannot be separated beyond the width of the CCD, especially at a far point. There was difficulty in measuring. In the present embodiment, however, the focal distance of the front lens group 10d of the image transmission optical system 10 can be changed, so that the image interval between the objective optical systems 23 and 24 can be adjusted. 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 lens group 10a may be increased.
Each of the above embodiments has been described on the premise of the case of the flexible mirror shown in FIG. 1, but as can be understood from the above description, the present invention is not limited to such a flexible mirror. Needless to say, the present invention is not limited to the case and can be applied to a rigid endoscope having a hard insertion portion.
[0025]
As is clear from the above description, in addition to the configuration described in each claim, the following configuration is also a feature of the present invention.
(1) In the image transmission optical system, a rear group optical system is disposed behind the pupil position, and an imaging surface of the solid-state image sensor is disposed at the rear focal position of the rear group optical system. The endoscope imaging optical system according to any one of claims 1 to 4, wherein the endoscope imaging optical system is configured as described above.
(2) A front group optical system is disposed in front of the pupil position in the image transmission optical system, and a front focal position of the front group optical system and a field mask positioned on the imaging plane of the objective optical system 5. The internal vision according to claim 1, wherein the position of the first lens system is substantially the same, and the rear focal position of the front group optical system is substantially the same as the pupil position. 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) An aperture stop is disposed at a pupil position of the image transmission optical system, and the stop is attached and detached together with the objective optical system. An endoscope imaging optical system according to claim 1.
(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.
(6) A front group optical system is disposed in front of the pupil position in the image transmission optical system, and a planar shape of the front group optical system with the optical axis as a center is in a longitudinal direction of the solid-state image sensor. The endoscope imaging optical system according to any one of claims 1 to 4, wherein the endoscope imaging optical system has an oval shape in which the vertical direction is cut correspondingly.
[0026]
【The invention's effect】
As described above, according to the present invention, even if the tip objective optical system is exchanged according to the observation application, the focus position change or image defect does not occur due to backlash or dust of the attachment / detachment mechanism of the tip optical system. A plurality of observation images can be obtained simultaneously.
[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.
2 is a perspective view showing in detail a distal end portion of the endoscope shown in FIG. 1. FIG.
FIG. 3 is a cross-sectional view of the distal end portion of the endoscope according to the first embodiment.
4 is a view showing an opening shape portion of a field mask in Example 1. FIG.
5 is a cross-sectional view when a monocular adapter is used as the tip adapter of Example 1, and FIG. 4 (a) shows a state in which the monocular adapter is attached to the endoscope body, and FIG. (B) has shown the state in the middle of removing a monocular adapter.
6 is a configuration diagram showing an objective optical system of Example 2. FIG.
7 is a configuration diagram showing an objective optical system of Example 3. FIG.
FIGS. 8A and 8B are diagrams illustrating the shape of a front lens group of the image transmission optical system in Example 3, in which FIG. 8A is a front view and FIG. 8B is a side view.
FIG. 9 is a configuration diagram showing an objective optical system of Example 4.
10A and 10B are cross-sectional views showing a conventional example, in which FIG. 10A shows a state in which a tip adapter is attached to an endoscope body, and FIG. 10B shows a state in the middle of removing the tip adapter. Indicates the state.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Endoscope 2 Insertion part 3 End part 4 Endoscope body 5 End adapter 6, 7, 17, 18, 20, 21, 22, 23, 24 Objective optical system 6p, 7p Entrance pupils 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 diaphragm 13, 19 Cover glass 14 Color temperature conversion filter 15 Optical low-pass filter 16 Monocular adapter

Claims (7)

  In order from the object side, an endoscope imaging optical system including a plurality of objective optical systems, an image transmission optical system that transmits a plurality of images formed by these objective optical systems once, and a solid-state imaging device, An endoscope imaging optical system, wherein the objective optical system side and the solid-state imaging element side are detachable at a substantially pupil position of the image transmission optical system.   The endoscope imaging optical system according to claim 1, wherein entrance pupils of the plurality of objective optical systems are formed at different positions, respectively.   The endoscope imaging optical system according to claim 1, wherein the plurality of objective optical systems have different visual field directions.   The endoscope imaging optical system according to claim 1 or 2, wherein the plurality of objective optical systems includes two optical systems having the same configuration. In the image transmission optical system, a front group optical system is disposed in front of the pupil position, a front focal position of the front group optical system, and a position of a field mask positioned on the imaging plane of the objective optical system, The endoscope imaging optical according to any one of claims 1 to 4, wherein the rear focal position of the front group optical system and the pupil position are substantially the same. system. The endoscope imaging optical system according to any one of claims 1 to 4, wherein the objective optical system is a telecentric optical system. In the image transmission optical system, a front group optical system is disposed in front of the pupil position, and the planar shape of the front group optical system with the optical axis as the center corresponds to the longitudinal direction of the solid-state image sensor. The endoscope imaging optical system according to any one of claims 1 to 4, wherein the endoscope imaging optical system has an oval shape in which a vertical direction is cut.

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