JP3579488B2 - Optical system for endoscope - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an optical system for an endoscope including a low-pass filter made of quartz.
[0002]
[Prior art]
In an electronic endoscope in which an observation image of an endoscope is captured by a solid-state imaging device and transmitted as an electronic signal, in order to prevent the occurrence of a so-called false color signal, like a general color television camera or the like. It is desirable to provide a low-pass filter for cutting a high spatial frequency component in the horizontal direction included in the observation light in the imaging optical system, and for that purpose, a low-pass filter made of quartz, which is a uniaxial crystal, is used. .
[0003]
In the case of an optical fiberscope using an image guide fiber bundle for transmitting observation images, a low-pass filter made of quartz is provided in the eyepiece optical system, so that the mesh of the fiber fibers can be made inconspicuous. it can.
[0004]
[Problems to be solved by the invention]
In order to cut a high spatial frequency component in the horizontal direction contained in the observation light, it is necessary to set the optical axis of the crystal, which is a uniaxial crystal, in a predetermined correct direction with respect to the scanning direction of the solid-state imaging device. However, since the optical axis of quartz cannot be easily viewed, there is a risk that the optical axis may be assembled in the wrong direction.
[0005]
Also, in the case where the mesh of the fiber fiber is made inconspicuous by providing a low-pass filter made of crystal in the eyepiece optical system, the direction of the optical axis of the crystal is set to a predetermined direction with respect to the arrangement direction of the fiber fiber. It must be set in the correct direction.
[0006]
Therefore, an object of the present invention is to provide an optical system for an endoscope that can easily and surely confirm the direction of the optical axis of a quartz crystal forming a low-pass filter and can assemble the low-pass filter in a correct direction. And
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the optical system for an endoscope of the present invention arranges a low-pass filter made of quartz in an optical path to cut light of a high spatial frequency component in a specific direction included in observation light. In an endoscope optical system in which a light-shielding mask for blocking unnecessary light in a peripheral portion of an optical path is provided on an end surface of the low-pass filter, the light-shielding mask has a predetermined position with respect to an optical axis of a crystal forming the low-pass filter. An index is provided in the direction of.
[0008]
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 regularly arranging a large number of the light-shielding masks and indices on a quartz material, forming them at the same time, and then cutting the low-pass filter into individual low-pass filter sizes.
[0009]
【Example】
Embodiments will be described with reference to the drawings.
FIG. 2 is a side sectional view of a distal end portion of the electronic endoscope, and FIG. 3 is a sectional view taken along line III-III of FIG.
[0010]
In FIG. 2, reference numeral 1 denotes a curved portion formed at the distal end of an elongated flexible tube forming an insertion portion, and a plurality of node rings 2 are rotatably connected by rivets. The outer periphery is covered with a mesh tube 4 made of a thin metal wire and a jacket tube 5 made of rubber.
[0011]
The bending operation wire 7 that is remotely towed is inserted in a wire guide 8 protruding inward from each node ring 2 so as to be able to move forward and backward. The distal end 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 for securing the wire guide 8, which is fixed to the end of the wire guide 8 by soldering silver or the like.
[0012]
Reference numeral 11 denotes a distal end main body connected to the distal end of the curved portion 1 via a connecting tube 12, and includes a metal trunk 11b and an electrically insulating plastic head 11a joined to the distal end. Is formed.
[0013]
The distal end body 11 has a circular cross-sectional shape when viewed from the distal end side (left side in FIG. 2), and has an objective optical system (imaging optical system) 13 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.
[0014]
The axial direction of the objective lens group 13a coincides with the axial direction of the distal end body 11, and an object ahead 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 denote lens frames into which the objective lens group 13a is fitted and adhered. 17 is an aperture stop. Reference numeral 18 denotes an O-ring for sealing.
[0015]
A solid-state imaging device 31 using, for example, a CCD (charge-coupled device) is arranged in the body 11b of the tip body 11. The image receiving surface 31a of the solid-state imaging device 31 is formed in a square or a rectangle, and is arranged parallel to the optical axis of the objective lens group 13a. Reference numeral 31b is a cover glass disposed in close contact with the image receiving surface 31a.
[0016]
The right-angle prism 13d disposed between the objective lens group 13a and the solid-state imaging device 31 forms a right-angle prism so that the optical axis of the objective optical system 13 intersects perpendicularly with the center of the image receiving surface 31a of the solid-state imaging device 31. Is reflected in.
[0017]
Between the right-angle prism 13d and the objective lens group 13a, a color correction filter 13b and a low-pass filter 13c made of quartz are inserted and connected to each other in a connection tube 19 connected to the rear half of the lens frame 16. The right-angle prism 13d and the low-pass filter 13c are also joined to each other.
[0018]
With such an arrangement, the image of the subject on the left in FIG. 2 is formed on the image receiving surface 31 a of the solid-state imaging device 31 by the objective optical system 13, and is captured by the solid-state imaging device 31.
[0019]
On the front side of the color correction filter 13b, a first light-shielding mask 25 for blocking unnecessary light around the optical path is attached. Further, a second light-shielding mask 26 for blocking unnecessary light around the optical path is formed on the rear end face of the low-pass filter 13c made of quartz by vapor deposition.
[0020]
The first and second light-shielding masks 25 and 26 provided in this way greatly reduce the incidence of unnecessary light on the prism 13d and prevent ghosts and the like.
[0021]
The low-pass filter 13 c is for cutting a high spatial frequency component in the horizontal direction included in the observation light. It must be set in a predetermined correct orientation.
[0022]
Therefore, as shown in three views (a front view, a side view, and a bottom view) of FIG. 1, the edge of the second light-shielding mask 26 formed on the end face of the low-pass filter 13c is provided with the X axis of the quartz optical axis. An index 27 is formed in accordance with the direction of the axis.
[0023]
In this embodiment, the index 27 is formed by projecting the edge of the second light-shielding mask 26 outward in a semicircular shape. Note that, in order to facilitate understanding, in the front view of FIG. 1, the light shielding mask 26 is hatched. This oblique line does not indicate a cross section.
[0024]
By providing such an index 27, at the time of assembling, as shown in FIG. 3, if the low-pass filter 13c is incorporated so that the index 27 is directed upward, for example, the optical axis of the quartz crystal can be adjusted to the imaging surface of the solid-state imaging device 31. , The low-pass filter 13c is set so as to always be in a predetermined correct direction.
[0025]
As shown in FIG. 4, for example, as shown in FIG. 4, a large number of second light-shielding masks 26 with indexes 27 are regularly arranged on a large crystal plate material 130 to manufacture the low-pass filter 13c with the indexes 27. May be simultaneously vapor-deposited, and then cut into individual low-pass filters 13c.
[0026]
In this way, the direction of the optical axis of the low-pass filter 13c for an endoscope, in which one dimension is extremely small and it is not easy to determine the direction of the optical axis, can be easily changed in the state of the large quartz plate material 130 before cutting. Since the determination can be made, the index 27 can be reliably formed in the correct direction. Note that the second light-shielding mask may be formed by printing a light-shielding paint or the like instead of vapor deposition.
[0027]
The index 27 need not always be formed in the X-axis direction, but may be formed always in a fixed direction with respect to the optical axis direction of the crystal of the low-pass filter 13c. In addition, the index 27 may be formed on the outer side of the second light-shielding mask 26 away from the edge thereof.
[0028]
Returning to FIG. 2, reference numeral 42 denotes a flexible circuit board 42 to which electronic components (not shown) for performing signal processing of the solid-state imaging device 31 are attached. Are fixedly connected. A solid-state image sensor 31 is fixed to the tip side, and the image receiving surface 31a side of the solid-state image sensor 31 is joined to the right-angle prism 13d.
[0029]
The circuit board 42 is bent into a U-shaped cross-section, and its periphery is covered with a shield tape 44 and an insulating tape 45. The interior space is filled with an epoxy-based adhesive 60 and hardened to prevent deformation. Have been.
[0030]
In this way, the objective optical system 13, the solid-state imaging device 31, the circuit board 42, and the signal cable 43 are integrally formed as a single unit as a whole, and are connected to the connecting cylinder 12 via a pair of upper and lower pressing plates 46. , Are fixed by fixing screws 52.
[0031]
3, 51 is a light guide fiber bundle for illumination, 52 and 53 are an air supply tube and a water supply tube, and 54 is a forceps channel.
Note that the present invention is not limited to the above-described embodiment, and the present invention may be applied to, for example, an eyepiece optical system of a fiberscope.
[0032]
【The invention's effect】
According to the present invention, the index is provided in the light-shielding mask provided on the end face of the low-pass filter in a predetermined direction with respect to the optical axis of the crystal forming the low-pass filter. Thus, the direction of the optical axis of the quartz crystal can be easily and reliably confirmed, and the low-pass filter can always be assembled in the correct direction.
[0033]
If an index is formed on the edge of the light-shielding mask by vapor deposition or printing, formation of the index and confirmation by visual inspection are easy.
[Brief description of the drawings]
FIG. 1 is a three-view drawing 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 according to the embodiment.
FIG. 3 is a front (III-III) sectional view of the embodiment.
FIG. 4 is a front view of a low-pass filter illustrating a manufacturing process of the index according to the embodiment.
[Explanation of symbols]
13c Low-pass filter 26 Light-shielding mask 27 Index

Claims (2)

A low-pass filter made of quartz is arranged in the optical path to cut off light of a high spatial frequency component in a specific direction included in the observation light, and a light-shielding mask for blocking unnecessary light around the optical path is provided by the low-pass filter. In the endoscope optical system provided on the end face,
The light-shielding mask is formed by vapor deposition or printing on a peripheral portion of an end face in a direction perpendicular to the optical axis of the low-pass filter, and at the same time, the light-shielding mask positioned in a predetermined direction with respect to an optical axis of crystal forming the low-pass filter. An optical system for an endoscope, wherein an index is formed by partially protruding an edge portion of the optical element outward . The low-pass filter, after forming them simultaneously to the shielding mask and indicators regularly arrayed in a crystal material, an endoscope according to claim 1, wherein the formed cut to the size of the individual low-pass filter Optical system.

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