JPH08262340A - Optical system for endoscope - Google Patents

Abstract

PURPOSE: To provide an optical system for an endoscope in which the direction of the optical axis of crystal forming a low-pass filter is easily and surely confirmed, and the low-pass filter is assembled in a correct direction. CONSTITUTION: In the optical system for an endoscope, the low-pass filter 13c made of crystal is arranged in an optical path cut the light of high spatial frequency component in a specified direction included in observing light, and a light shielding mask 26 for intercepting the unnecessary light at the peripheral part of the optical path is provided on the end face of the low-pass filter 13c. An index 27 is provided in a specified direction with respect to the optical axis of the crystal forming the low-pass filter 13c on the light shielding mask 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endoscope optical system including a low pass filter made of quartz.

[0002]

2. Description of the Related Art In an electronic endoscope in which an observation image of an endoscope is picked up by a solid-state image pickup device and transmitted as an electronic signal, a so-called color false signal is generated as in a general color television camera. In order to prevent this, it is desirable to provide a low-pass filter for cutting high spatial frequency components in the horizontal direction included in the observation light in the imaging optical system. For that purpose, a uniaxial crystal made of quartz is used. A low pass filter is used.

Further, in an optical fiberscope using an image guide fiber bundle for transmitting an observation image, a low pass filter made of quartz is provided in the eyepiece optical system so that the mesh of the fiber fiber is not conspicuous. can do.

[0004]

In order to cut the high spatial frequency component in the horizontal direction contained in the observation light, the optical axis of the crystal, which is a uniaxial crystal, has a predetermined correct value with respect to the scanning direction of the solid-state image sensor. It is necessary to set it in the direction. However, since the optical axis of the crystal cannot be easily seen, there is a risk that the optical axis may be assembled in the wrong direction.

Further, when the eyeglass optical system is provided with a low-pass filter made of quartz, the direction of the optical axis of the quartz is changed even when the mesh of fiber fibers is made inconspicuous.
It is necessary to set in a predetermined correct direction with respect to the arrangement direction of the fiber fibers.

Therefore, the present invention provides an optical system for an endoscope in which the direction of the optical axis of the crystal forming the low-pass filter can be easily and surely confirmed and the low-pass filter can be assembled in the correct direction. The purpose is to

[0007]

In order to achieve the above object, the optical system for an endoscope of the present invention has an optical path in an optical path for cutting light of a high spatial frequency component in a specific direction contained in observation light. In a endoscope optical system in which a low-pass filter made of crystal is arranged and a light-shielding mask for blocking unnecessary light in the peripheral portion of the optical path is provided on the end face of the low-pass filter, the low-pass filter is formed on the light-shielding mask. The index is provided in a predetermined direction with respect to the optical axis of the quartz crystal.

The index may be formed on the edge of the light-shielding mask, or the light-shielding mask may be formed on the end face of the low-pass filter by vapor deposition or printing. In this case, the low-pass filter may be formed by arranging a large number of the light-shielding masks and the indexes on a quartz material at the same time and forming them simultaneously, and then dividing them into individual low-pass filter sizes.

[0009]

Embodiments will be described with reference to the drawings. 2 is a side cross-sectional view of the tip of the electronic endoscope, and FIG. 3 is a III-III cross-sectional view thereof.

In FIG. 2, reference numeral 1 is a curved portion formed at the tip of an elongated flexible tube forming an insertion portion, and a plurality of node rings 2 are rotatably connected by rivets. The outer circumference thereof is covered with a mesh tube 4 made of thin metal wires and a jacket tube 5 made of rubber.

A bending operation wire 7 which is remotely pulled.
Is inserted into the wire guide 8 projecting inwardly from each node ring 2 so as to be able to move back and forth. The tip of each bending operation wire 7 is fixed to the most advanced wire guide 8 by silver brazing. Reference numeral 9 denotes a stopper pipe that is fixed to the end portion of the most advanced wire guide 8 by silver brazing or the like to prevent it from coming off.

Reference numeral 11 denotes a tip portion main body connected to the tip of the bending portion 1 through a connecting tube 12, and a metal body portion 11b.
And a head portion 11a made of an electrically insulating plastic and joined to the tip portion thereof.

The tip body 11 is on the tip side (left side in FIG. 2).
It has a circular cross-sectional shape when viewed from the inside, and an objective optical system (imaging optical system) 13 is built therein. The objective optical system 13 includes an objective lens group 13a including a plurality of lenses, a right-angle prism 13d, and the like.

The axial direction of the objective lens group 13a coincides with the axial direction of the tip end main body 11, and the object in front is the subject. The observation window 14 is formed by the most advanced lens of the objective optical system 13. Reference numerals 15 and 16 are lens frames to which the objective lens group 13a is fitted and adhered. 17 is an aperture stop.
Reference numeral 18 is an O-ring for sealing.

A solid-state image pickup device 31 using, for example, a CCD (charge coupled device) is arranged in the body portion 11b of the tip end main body 11. The image receiving surface 31a of the solid-state image sensor 31 is formed in a square or a rectangle, and the objective lens group 13a
Are arranged parallel to the optical axis of. Reference numeral 31b is a cover glass which is arranged in close contact with the image receiving surface 31a.

The optical axis of the objective optical system 13 is perpendicularly intersected with the center of the image receiving surface 31a of the solid-state image sensor 31 by the right-angle prism 13d arranged between the objective lens group 13a and the solid-state image sensor 31. It is reflected at a right angle.

Right angle prism 13d and objective lens group 13a
Between the connection tube 19 and the rear half of the lens frame 16.
A color correction filter 13b and a low pass filter 13c made of quartz are bonded and interposed in the inside, and a right-angle prism 13d and a low pass filter 13c are also bonded to each other.

With such an arrangement, the image of the subject on the left side of FIG.
An image is formed on the image receiving surface 31 a of the solid-state image pickup device 31 and is picked up by the solid-state image pickup device 31.

On the front side of the color correction filter 13b, a first light blocking mask 25 for blocking unnecessary light in the peripheral portion of the optical path is attached. A second light-shielding mask 26 is also formed on the rear end surface of the low pass filter 13c made of quartz by vapor deposition so as to shield unnecessary light around the optical path.

The first and second light-shielding masks 25 and 26 provided in this way significantly reduce the incidence of unnecessary light on the prism 13d and prevent the generation of ghosts.

The low-pass filter 13c is for cutting high spatial frequency components in the horizontal direction contained in the observation light. For that purpose, the optical axis of the uniaxial crystal, quartz, is set in the scanning direction of the solid-state image pickup device 31. It is necessary to set in a predetermined correct direction with respect to.

Therefore, the three views of FIG. 1 (front view, side view,
As shown in the bottom view), an index 27 is formed on the edge portion of the second light-shielding mask 26 formed on the end surface of the low-pass filter 13c in alignment with the X-axis direction of the optical axis of the crystal.

In this embodiment, the index 27 is formed by protruding the edge portion of the second light-shielding mask 26 in a semicircular shape to the outside. Note that, in order to facilitate understanding, in the front view of FIG. 1, the light shielding mask 26 portion is shaded. This diagonal line does not represent the cross section.

By providing such an index 27,
At the time of assembly, as shown in FIG.
If the low-pass filter 13c is incorporated so that 7 faces upward, the low-pass filter 13c is set so that the optical axis of the crystal is always in a predetermined correct direction with respect to the image pickup surface of the solid-state image pickup device 31.

For manufacturing the low-pass filter 13c having the index 27, as shown in FIG. 4, for example, a large number of second light-shielding masks 26 having the index 27 are regularly arranged on a large crystal plate material 130. Then, they may be vapor-deposited at the same time, and thereafter, they may be cut into individual low-pass filters 13c.

By doing so, the direction of the optical axis of the low-pass filter for endoscope 13c in which the size of one piece is extremely small and the direction of the optical axis is not easily discriminated, and the state of the large quartz plate material 130 before cutting is set. Since it can be easily discriminated by, it is possible to surely form the index 27 in the correct direction. The second light-shielding mask may be formed by printing light-shielding paint instead of vapor deposition.

The index 27 need not always be in the X-axis direction, but may be formed in a constant direction with respect to the optical axis direction of the crystal of the low-pass filter 13c. Also, indicator 2
7 may be formed outside the edge portion of the second light-shielding mask 26 and outside the edge portion.

Returning to FIG. 2, 42 is a solid-state image pickup device 31.
Is a flexible circuit board 42 to which electronic components (not shown) for performing signal processing of
It is fixedly connected to the tip portion of 3 by soldering. The solid-state image sensor 31 is fixed to the tip side thereof, and the image-receiving surface 31a side of the solid-state image sensor 31 is joined to the right-angle prism 13d.

The circuit board 42 is bent into a U-shaped cross section, and the periphery thereof is covered with a shield tape 44 and an insulating tape 45. The internal space is filled with an epoxy adhesive 60 so that it is not deformed. Has been hardened.

In this way, the objective optical system 13, the solid-state image pickup device 31, the circuit board 42 and the signal cable 43 are integrally formed as one unit as a whole, and the connecting cylinder 12 is provided with a pair of upper and lower pressing plates 46. Through the fixing screw 5
2 fixed.

In FIG. 3, 51 is a light guide fiber bundle for illumination, 52 and 53 are air supply tubes and water supply tubes, and 54 is a forceps channel. The present invention is not limited to the above embodiment, and the present invention may be applied to, for example, an eyepiece optical system of a fiberscope.

[0032]

According to the present invention, the light-shielding mask provided on the end face of the low-pass filter is provided with an index in a predetermined direction with respect to the optical axis of the crystal forming the low-pass filter. Moreover, the direction of the optical axis of the crystal can be easily and surely confirmed from the direction of the index, and the low-pass filter can be always installed in the correct direction.

By forming an index on the edge portion of the light-shielding mask by vapor deposition or printing, it is easy to form the index and visually confirm it.

[Brief description of drawings]

FIG. 1 is a trihedral view showing directions of indices for a low pass filter according to an embodiment.

FIG. 2 is a side sectional view of a distal end portion of the endoscope of the embodiment.

FIG. 3 is a front (III-III) sectional view of the embodiment.

FIG. 4 is a front view of the low-pass filter illustrating the manufacturing process of the index of the embodiment.

[Explanation of symbols]

 13c low-pass filter 26 light-shielding mask 27 index

Claims (4)

[Claims] 1. A light-shielding mask for blocking unnecessary light in a peripheral portion of an optical path by disposing a low-pass filter made of quartz in the optical path for cutting light of a high spatial frequency component in a specific direction included in observation light. In the endoscope optical system provided on the end face of the low-pass filter, the light-shielding mask is provided with an index in a predetermined direction with respect to the optical axis of the crystal forming the low-pass filter. Optical system for mirrors. 2. The optical system for an endoscope according to claim 1, wherein the index is formed on an edge portion of the light shielding mask. 3. The endoscope optical system according to claim 1, wherein the light-shielding mask is formed on the end surface of the low-pass filter by vapor deposition or printing. 4. The low-pass filter is formed by arranging a large number of the light-shielding masks and indexes regularly on a quartz material, forming them simultaneously, and then dividing them into individual low-pass filter sizes. 2. The optical system for an endoscope according to 2 or 3.