JPH1123983A - Television camera apparatus for endoscope and its focusing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily, smoothly and rapidly perform focusing without substantially changing image-formation magnification in the state that an image guide, an image pickup optical system and a solid-state image pickup means are assembled by integrally holding the image pickup optical system and the solid-state image pickup means and moving them in the optical axis direction to perform the focusing. SOLUTION: An image pickup unit 13 is constituted by coupling a camera holder 17 provided by fixing a solid-state image pickup means 12 with a lens holder 18 to which an image pickup optical system 11 is attached and is coupled with the emitting end 5a of an image guide 5 inserted in an adjusting barrel 16 capable of adjusting an optical axis in a mount barrel 15 and capable of focusing. A fixed barrel 20 in which the lens holder 18 is inserted is coupled and fixed in the barrel 15 and a cam ring 22 is fit to barrel 20. When the ring 22 is turned, the optical system 11 and the means 12 are moved in the optical axis direction without changing an interval between the optical system 11 and the means 12 to perform the focusing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television camera apparatus for an endoscope for capturing an image transmitted by a light guide member provided in an insertion portion of the endoscope and displaying the image on a monitor screen. More particularly, the present invention relates to a focus adjustment mechanism in the television camera device and a focusing method using the focus adjustment mechanism.

[0002]

2. Description of the Related Art An endoscope is used for observing the inside of a body cavity and the like. This observation method is roughly divided into two methods. First, there is an optical endoscope in which an image in a body cavity is transmitted by an image guide formed of an optical fiber bundle. In addition, information about the image in the body cavity is converted into an electric signal using a television camera, extracted, transmitted to an image signal processing device, subjected to predetermined signal processing, and then displayed on the monitor screen. There is an electronic endoscope which displays the image of the electronic endoscope.

In an electronic endoscope, an objective lens is made to face an observation window provided at a distal end of an insertion portion to be inserted into a body cavity or the like, and an image of a subject is formed at a predetermined position. A solid-state imaging means is disposed in the device, and the solid-state imaging means converts the signal into an electric signal. However, in an endoscope that is inserted along a thin insertion path, such as a urethroscope, the solid-state imaging means cannot be arranged at the distal end of the insertion section in order to form the insertion section in an extremely fine shape. . For this purpose, at least in the insertion section, the subject image must be transmitted by the light guide member. For this purpose, an image guide is used in a flexible mirror, and an incident end of the image guide is made to face an image forming position of an objective lens, and an optical image of a subject is transmitted through the image guide in the insertion section. In this manner, the image guide is guided at least to the main body operation unit located outside the body cavity. However, it is necessary to convert an optical image into a video signal so that a plurality of persons can observe the image at the same time. An imaging optical system and a solid-state imaging means are arranged in the optical pickup, and the solid-state imaging means converts an optical image of an image guide into an electric signal. by this,
A video signal to be displayed on the monitor screen is obtained.

Here, as described above, in an electronic endoscope of a type in which a subject image is transmitted using an image guide in an insertion portion, focus adjustment for displaying a focused and clear image on a monitor screen is performed. The operation is performed between the emission end of the image guide, the imaging optical system, and the solid-state imaging means.
However, it is not necessary to simply have a focus, but the imaging magnification must be constant. The image of the endoscope is not displayed on the entire monitor screen, but a circular display area is set at almost the center position of the screen, and the image is displayed only in this display area. Since the endoscope uses a wide-angle lens, if the imaging magnification varies depending on the individual TV camera devices, it is not possible to accurately recognize the image displayed particularly on the periphery of the display area on the monitor screen. As a result, the accuracy of inspection and diagnosis may be affected.

[0005] In view of the above, when incorporating an imaging optical system and solid-state imaging means into an endoscope, focus adjustment and magnification adjustment must be performed. Normally, when incorporating the image guide, first, the emission end position of the image guide is determined as a reference, and the imaging optical system and the solid-state imaging means are respectively set to predetermined positions so that the emission end of the image guide and the optical axis coincide with each other. After being incorporated in the position, the imaging optical system and the solid-state imaging means are moved in the optical axis direction so that the imaging magnification is set to be constant, and at the same time, the focus adjustment is performed.

As a method of adjusting the magnification and the focus, first, the position of the imaging optical system and the solid-state imaging means is adjusted so as to have a preset imaging magnification in relation to the exit end position of the image guide. . To perform focus adjustment in this state, for example, the imaging optical system is moved. However, if the imaging optical system is moved to a position where focus is achieved, the imaging magnification changes. For this reason, the imaging magnification is adjusted again. However, since the adjustment of the imaging magnification causes a focus shift, the focus must be adjusted again. Therefore, unless the focus adjustment and the correction of the imaging magnification are repeated a plurality of times, it is not possible to adjust the positions of the respective components so that a clear image with the optimum imaging magnification and in focus is displayed on the monitor screen. . As described above, strictly adjusting the two factors of the focus and the imaging magnification to the extent that they can be simultaneously satisfied requires extremely high skill and requires a long time.

Here, since the focal length of the imaging optical system is known, if the exit end position of the image guide is determined,
The positions of the imaging optical system and the solid-state imaging means are theoretically determined based on calculations, and the imaging optical system and the solid-state imaging means may be arranged so as to have a predetermined positional relationship with the image guide. Needless to say, the position of the imaging optical system and the solid-state imaging means must be adjusted because of an assembly error and the like. Therefore, if the assembling accuracy is improved, the correction based on the assembling error can be corrected with a very small movement. Therefore, it is only necessary to substantially adjust the focus, and there is no problem in practical use even if the imaging magnification is not particularly corrected. As a result, the adjustment is completed only by moving the imaging means or the solid-state imaging means alone in the optical axis direction and performing focus adjustment.

[0008]

By the way, an imaging optical system usually has a focal length error due to a processing error or the like at the time of manufacturing a lens. Therefore, even if the imaging optical system and the solid-state imaging means are accurately arranged at the theoretical positions described above, there is a possibility that the image will be out of focus by the focal length error range in the imaging optical system. The allowable focal length error range of a general lens is about ± 5%, and it is impossible to prevent an error of ± 3% from occurring even if lens processing is performed with high accuracy. If there is a focal length error in such a range, no matter how the assembly accuracy is improved,
When the focus adjustment is performed, the imaging magnification may greatly change beyond an allowable limit.

In FIG. 4, the emission end of the image guide is G, the imaging optical system is L, the light receiving surface of the solid-state imaging device is D, and the distance between the emission end surface G and the imaging optical system L is a.
When the distance between the imaging optical system L and the light receiving surface D is b, and the distance between the emission end face G and the light receiving surface D, that is, the conjugate length is c, the focus adjustment for arranging the imaging optical system at the best focus position is performed. ,
This can be done in several ways. First, it is conceivable to move only the imaging optical system in the optical axis direction while keeping the conjugation length c constant. Also, with the distance a fixed,
The focus can also be adjusted by changing the distance b. In this case, only the solid-state imaging means needs to be moved in the optical axis direction. Further, even if the distance b is fixed and the distance a is variable, the focus can be adjusted. Focus adjustment can be performed using any of the above methods. However, when the imaging optical system is moved, the distance a and the distance b are changed, and when the image guide or the solid-state imaging device is moved, the conjugate length c is increased. As a result, the imaging magnification naturally changes. Therefore, the position adjustment of any one of the emission end of the image guide, the imaging optical system, and the solid-state imaging device may not be simply performed.

The present invention has been made in view of the above points, and an object of the present invention is to substantially change an imaging magnification while incorporating an image guide, an imaging optical system, and solid-state imaging means. An object of the present invention is to enable smooth and easy focus adjustment without causing the focus adjustment.

[0011]

First, FIG. 5 shows the correlation between the focal length and the imaging magnification in the image pickup optical system. In this figure, the dotted line shows the change in the imaging magnification when the focal length of the imaging optical system L is changed while the conjugation length c is kept constant. Now, when an imaging optical system having a focal length of 3.8 mm is used, when a ± 3% focal length error is considered, the actual focal length of the imaging optical system varies within a range of 3.69 mm to 3.91 mm. That is, this range is the actual focal length range. For this reason, the imaging magnification is 3.15 for the lens having the shortest focal length in the range of the error, whereas the imaging magnification is 4.15 for the longest focal length of 3.91 mm. 16 and the imaging magnification is 3.15 to 4.1.
6 will be changed. Therefore, when the adjustment is made to the best focus position, the imaging magnification changes extremely depending on the imaging optical system.

In the case where the distance b is fixed and the distance a is made variable, the result is as shown by a dashed line in FIG. 1. Further, the focal position and the imaging magnification when only the distance a is made variable. Is shown by a solid line in FIG. As described above, when an imaging optical system having a focal length of 3.8 mm is used and the focus adjustment is performed by changing the distance b, the error of the imaging magnification in the actual focal length range is reduced. When the focus adjustment is performed by changing the distance a, the error of the imaging magnification in the actual focal length range is 3.47 to 3.74. Therefore, focusing by changing only the distance a minimizes the change in the imaging magnification.

In consideration of the above points, the television camera apparatus of the present invention extends the light-emitting member's light-emitting member, whose light-emitting member faces the image-forming position of the objective lens provided at the distal end of the insertion portion, toward the main-body operating portion. The imaging optical system and the solid-state imaging means are arranged on an extension of the optical axis of the emission end to form a subject image on the solid-state imaging means. It is characterized by comprising a holding means for integrally holding and a focusing means capable of adjusting the focus by moving the holding means in the optical axis direction.

The holding means comprises a lens holder for holding the imaging optical system and a camera holder for holding the solid-state imaging means. The lens holder and the camera holder are connected to the imaging optical system and the solid-state imaging means. It is preferable to be able to connect and fix it while adjusting the position in the optical axis direction between them. The focusing means can be constituted by, for example, a cylindrical cam mechanism.

According to the focusing method of the present invention, the emission end of the light guide member whose entrance end faces the image forming position of the objective lens provided at the distal end of the insertion section is extended toward the main body operation section. The imaging optical system and the solid-state imaging means are arranged on the extension of the optical axis at the emission end, and when the subject image is formed on the solid-state imaging means, an interval between the imaging optical system and the solid-state imaging means is imaged. In a state adjusted according to the focal length of the optical system, the positional relationship is fixed, and the imaging optical system and the solid-state imaging means are simultaneously moved in the optical axis direction, so that the imaging optical system and the solid-state imaging device are close to and away from the emission end face of the light guide member. The focus adjustment is performed by moving in the direction in which the focus adjustment is performed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a cross section of a connection portion of the television camera device in the endoscope.
FIG. 2 shows a schematic configuration of the entire endoscope. Further, FIG.
FIG. 4 is a development view of a cylindrical cam mechanism.

First, in FIG. 2, reference numeral 1 denotes an endoscope. The endoscope 1 includes a main body operation section 2 and a main body operation section 2.
And a universal cord 4 removably connected to a light source device (not shown). Although not shown, an illumination window and an observation window are formed at the distal end of the insertion portion 3, and the observation window is irradiated with illumination light from the illumination window in a state where the insertion portion is inserted into a body cavity. Observation inside the body cavity can be performed through.

A light guide comprising an optical fiber bundle is provided for transmitting illumination light. The light guide is guided into the universal cord 4 from the distal end of the insertion section 3 via the main body operation section 2, and the universal cord 4 is connected to the light source device, whereby illumination light from a light source lamp built in the light source device is emitted. Irradiated. On the other hand, an objective lens faces the observation window, and the incident end of the image guide 5 (see FIG. 1) is located at an image forming position of the objective lens. This image guide 5 is, like the light guide,
The optical fiber bundle is formed of an optical fiber bundle, and is guided into the main body operation unit 2 from the distal end of the insertion unit 3, and its emission end 5 a faces the rear end of the main body operation unit 2. Here, the image guide 5 is a light guide member, and the image guide 5 is used because the insertion portion 3 has a flexible structure and the insertion portion is formed of a hard pipe. In this case, the light guide member can be formed using a relay lens or the like.

As described above, by providing only the light guide and the image guide in the insertion section 3, the diameter can be reduced. In addition, by arranging the image guide at the center and arranging the light guide so as to surround the periphery thereof, the insertion portion 3 can be formed to have a smaller diameter, and the illumination light irradiated through the light guide can be formed. Are also illuminated evenly throughout.

A television camera device 10 is mounted on the main body operation unit 2 at an end opposite to a side connected to the insertion unit 3. As is clear from FIG. 1, the television camera device 10 includes an imaging unit 13 integrally provided with an imaging optical system 11 and a solid-state imaging unit 12;
And a housing 14 surrounding the housing. And
From the end surface of the casing of the main body operation unit 2 to the mounting cylinder 15
In the mounting tube 15, an adjusting tube 16 that can be adjusted in the axial direction and the tilt direction with respect to the mounting tube 15 for enabling the optical axis adjustment is inserted. The image guide 5 is inserted into the adjustment barrel 16, and the emission end 5 a faces the end face position of the adjustment barrel 16.

The image pickup unit 13 has a camera holder 17 provided with a solid-state image pickup device 12a and a substrate 12b constituting the solid-state image pickup means 12, and is connected to the camera holder 17 to mount the image pickup optical system 11. The camera holder 1.
The lens holder 7 and the lens holder 18 are assembled in a state where their positions are adjusted to each other, and are fixedly connected by screws 19. Therefore, the camera holder 17 and the lens holder 18 constitute a holding unit that integrally holds the imaging optical system 11 and the solid-state imaging unit 12. A fixed cylinder 20 is fitted to the mounting cylinder 15, and the mounting cylinder 15 and the fixed cylinder 20 are connected and fixed using fixing screws 21.

The lens holder 18 constituting the imaging unit 13 is inserted into a fixed barrel 20 fixed to the mounting barrel 15, and the lens holder 18 is movable in the axial direction. Therefore, this lens holder 18
Is moved in the axial direction in the fixed cylinder 20,
Focus adjustment can be performed by moving the imaging unit 13 holding the imaging optical system 11 and the solid-state imaging means 12 in a fixed positional relationship in the optical axis direction with the optical axis aligned with the image guide 5. it can. Various mechanisms are used as a focusing unit for performing the focus adjustment. For example, the focusing unit may be configured using an eccentric pin. It is shown.

That is, a cam ring 22 is fitted to the fixed cylinder 20 so as to be relatively rotatable, and a cam groove 23 is provided in a peripheral body of the fixed cylinder 20 so as to penetrate in the thickness direction thereof. . The cam groove 23 extends obliquely with respect to the axis of the cam ring 22 as shown in FIG. The fixed cylinder 20 in which the cam ring 22 is fitted is provided with an elongated hole 24 having a predetermined length in the axial direction. Further, the lens holder 1
A cam pin 25 is provided upright by screw insertion in 8, and this cam pin 25 is inserted into the cam groove 23 of the cam ring 22 through the long hole 24 of the fixed cylinder 20. The diameter of the cam pin 25 substantially matches the width of the elongated hole 24 and the cam groove 23.

Therefore, when the cam ring 22 is rotated,
The cam pin 25 relatively moves along the cam groove 23. Since the cam pin 25 passes through the long hole 24 of the fixed cylinder 20, the position of the lens holder 18 is restricted in the rotation direction, and the lens holder 18 is in the axial direction, It will only move in the axial direction. As a result, depending on the rotation direction of the cam ring 22, the image guide 5 moves in a direction approaching or away from the emission end 5a of the image guide 5. Thereby, the imaging unit 13
Moves in the optical axis direction, and focus adjustment is performed. In order to fix the cam ring 22 at the in-focus position, set screws 26 and 27 engageable between the cam ring 22 and the fixed barrel 20 and between the fixed barrel 20 and the lens holder 18, respectively. Is provided.

Further, the housing 14 constituting the outer body of the television camera device 10 is inserted and fitted into an annular screw ring portion 28 formed so as to surround the protruding portion of the mounting tube 15 in the main body operation portion 3, and a nut is provided. 29. Thus, the components of the television camera device 10 are always protected, and if the housing 14 is detached from the main body operation unit 3, focus adjustment by the cam ring 22 and other operations can be performed. In the figure, reference numeral 30 denotes a signal cable connected to the solid-state imaging means 12, and the signal cable 30 is guided into the universal cord 4. Therefore, a connector which is detachably connected to a signal processing device for processing a video signal is provided at the end of the universal cord 4, and the signal cable 30 is connected to the electrode of this connector. Also, 31
Is a VTR switch provided on the housing 14. An operator or the like operates the VTR switch 31 while holding the main body operation unit 2 so that a VTR (video tape recorder) can be turned on and off. ing.

The present embodiment is configured as described above. The focus adjustment is performed by fixing the relative position between the imaging optical system 11 and the solid-state imaging means 12 and adjusting the position between the imaging optical system 11 and the emission end of the image guide 5. The adjustment is made by adjusting the interval between them. Thereby, as explained in FIG.
Even when the focus adjustment is performed, the degree of change in the imaging magnification is minimized. Therefore, when performing focus adjustment based on the focal length error in the imaging optical system 11, a change in the imaging magnification can be suppressed to a level that does not hinder practical use,
Focus adjustment based on the focal length error can be performed without considering the change in the imaging magnification. As a result, focus adjustment can be performed easily, smoothly, and quickly.

The focus adjustment is actually performed as follows. Since the imaging optical system 11 and the solid-state imaging means 12 are individually mounted on the camera holder 17 and the lens holder 18, respectively, when connecting the camera holder 17 and the lens holder 18, The camera holder 17 and the lens holder 18 are connected and fixed by the screw 19 in a state where the imaging optical system 11 and the solid-state imaging means 12 are arranged so as to have a predetermined positional relationship based on the designed focal length of the camera. . Thereby, the imaging unit 13 is formed. On the other hand, the housing 14 is detached and the adjusting cylinder 16 is attached to the mounting cylinder 15.
Is fixed with its position adjusted in the axial direction and the tilt direction with respect to. The inclination of the adjusting cylinder 16 is adjusted by a driving screw 32.
The fixing is performed by the set screw 33. by this,
The position of the exit end 5a of the image guide 5 is determined and fixed at a predetermined position.

After the imaging unit 13 is inserted into the fixed barrel 20 and the cam ring 22 is fitted into the fixed barrel 20, the cam pins 25 are passed through the long holes 24 of the fixed barrel 20 from the cam grooves 23 of the cam ring 22. Then, it is fixed by screwing it into the lens holder 18. In the assembly assembled in this manner, the fixing cylinder 20 is connected to the mounting cylinder 15 and fixed with screws 21. Here, since the position of the image guide 5 can be adjusted in the inclination direction with respect to the mounting cylinder 15, when the fixed cylinder 20 is fitted to the mounting cylinder 15,
Image guide 5, imaging optical system 11, and solid-state imaging means 1
2 can be exactly aligned.

When the cam ring 22 is rotated in the above state, the distance between the light emitting end 5a of the image guide 5 and the distance between the light emitting end 5a of the image guide 5 is adjusted while the distance between the image pickup optical system 11 and the solid state image pickup means 12 is fixed. , Focus adjustment is performed. When the best focus position is reached, the set screw 26,
27 is screwed in to fix the cam ring 22. Further, by connecting the housing 14 to the screw ring portion 28 using a nut 29, the main body operation portion 2 of the endoscope 1 is provided.
Is mounted with the television camera device 10.

Since the imaging optical system 11 has a predetermined focal length and the positional relationship between the imaging optical system 11 and the solid-state imaging means 12 is fixed, if focus adjustment is performed, The set imaging magnification is reached. However,
As described above, the imaging optical system 11 has a focal length error of at least ± 3% with respect to the designed focal length. The position is a position separated from the position by a predetermined distance in a direction close to or away from the image guide 5. As a result, the conjugation length changes, so that the imaging magnification is naturally affected. However, since the change in the imaging magnification is the smallest and is practically acceptable, it is necessary to correct the imaging magnification again. No need to do. That is, when the imaging optical system 11 having the focal length of 3.8 mm is used, the imaging magnification is 3.47 at the minimum and 3.74 at the maximum in the focal length error range.
It is within the range.

An image pickup optical system 11 and an image guide 5 are fixedly held between the image pickup optical system 11 and the solid-state image pickup means 12.
It is conceivable to move the image guide 5 to change the relative positional relationship between the image guide 5 and the light emitting end 5a. However, since the image guide 5 has a certain amount of rigidity and is a long member, Exit end 5a of guide 5
It is relatively difficult to fine-tune the position of. However, since the imaging optical system 11 and the solid-state imaging unit 12 are integrated as the imaging unit 13 and the imaging unit 13 is movable, more accurate focusing can be performed. Also, since the imaging optical system 11 and the solid-state imaging means 12 are not fixedly incorporated in the imaging unit 13 but are configured as separate lens holders 18 and camera holders 17, respectively, fine adjustment of the relative positional relationship after assembly is performed. Therefore, the imaging optical system 11 and the solid-state imaging means 12
Can be minimized.

[0032]

As described above, according to the present invention, the imaging optical system and the solid-state imaging means are integrally held, and the focus is adjusted by moving the imaging optical system in the optical axis direction.
With the image guide, imaging optical system and solid-state imaging means incorporated, without substantially changing the imaging magnification,
There are effects such as easy, smooth and quick focus adjustment.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a television camera device of an endoscope according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an endoscope equipped with a television camera device.

FIG. 3 is a development view of a cylindrical cam mechanism constituting the focus adjustment mechanism.

FIG. 4 is an operation explanatory view showing a focus adjustment method.

FIG. 5 is a diagram illustrating a correlation between a focal length and an imaging magnification according to each focus adjustment method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Endoscope 2 Main body operation part 3 Insertion part 5 Image guide 5a Emission end 10 Television camera device 11 Imaging optical system 12 Solid-state imaging means 13 Imaging unit 15 Mounting tube 16 Adjustment tube 17 Camera holder 18 Lens holder 20 Fixed cylinder 22 Cam ring 25 Cam pin

Claims (4)

[Claims] 1. An emission end of a light guide member having an incidence end facing an image forming position of an objective lens provided at a tip of an insertion portion is extended toward a main body operation portion, and imaging is performed on an optical axis extension line of the emission end. An optical system and a solid-state imaging unit arranged to form a subject image on the solid-state imaging unit; and a holding unit that integrally holds the imaging optical system and the solid-state imaging unit; And a focusing means for adjusting a focus by moving the television camera to a television camera apparatus for an endoscope. 2. The image forming apparatus according to claim 1, wherein the holding unit includes a lens holder that holds the imaging optical system, and a camera holder that holds the solid-state imaging unit. 2. The television camera apparatus for an endoscope according to claim 1, wherein the television camera apparatus is configured to be connected and fixed in a state where a position in a direction of an optical axis with respect to the means is adjusted. 3. An endoscope television camera apparatus according to claim 1, wherein said focusing means is constituted by a cylindrical cam mechanism. 4. An emission end of a light guide member having an incident end facing an image forming position of an objective lens provided at a tip of an insertion portion is extended toward a main body operation unit, and imaging is performed on an optical axis extension line of the emission end. An optical system and a solid-state imaging unit are arranged to form a subject image on the solid-state imaging unit. In the apparatus, the distance between the imaging optical system and the solid-state imaging unit is adjusted according to the focal length of the imaging optical system. In this state, the positional relationship is fixed, the imaging optical system and the solid-state imaging means are simultaneously moved in the optical axis direction, and the focus adjustment is performed by moving the imaging optical system and the solid-state imaging means in a direction approaching / separating from the emission end face of the light guide member. A focusing method for a television camera device of an endoscope, which is performed.