JPH09159930A - Structure of objective part of endoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the structure of the objective part which can obtain a formed image of good quality by fixing a light shield mask to a concave lens surface in precise position relation. SOLUTION: When the thin plate type light shield mask 29 for cutting off unnecessary light is arranged adjacently to the concave lens surface A of an objective 16b put in a lens frame 17, a plane part which is perpendicular to the optical axis is formed annularly nearby the outer edge part of the concave lens surface A. Then the light shield mask 29 is fixed to the objective 16b while made to abut against the plane part C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an objective lens portion of an endoscope in which a thin plate-shaped light shielding mask for shielding unnecessary light is arranged.

[0002]

2. Description of the Related Art In an objective lens of an endoscope, an unnecessary light ray which often hits a lens frame or an edge portion of the lens and is reflected is often incident on an image receiving portion to deteriorate a formed image. Therefore, in order to block such unnecessary light, a thin plate-shaped light blocking mask is arranged adjacent to the lens surface located at the rearmost end.

[0003]

In the objective lens of the endoscope, the lens surface at the rearmost end is often a concave surface. In that case, since the concave surface portion cannot have a bonding area of the light shielding mask, the light shielding mask is It is bonded and fixed to the lens frame.

FIG. 5 shows the structure of the objective lens portion of such a conventional endoscope, and the light-shielding mask 91 is at the rearmost end on a flat portion formed on the lens frame 92 perpendicularly to the optical axis. It is joined and fixed so as not to collide with the lens 93.

However, the position of the rearmost concave lens surface A is
Variation in the thickness of each lens that makes up the objective lens group,
The dimensional error of the lens frame 92 and other metal parts is accumulated, so that the variation occurs as shown by the broken line in FIG.

As a result, unnecessary light is not blocked by the light-shielding mask 91 and enters the image receiving portion (light-receiving surface of the solid-state image sensor) B to deteriorate the formed image, or conversely, necessary light is shielded by the light-shielding mask 91. There was an inconvenience that it was blocked by and the surrounding area became dark.

Therefore, an object of the present invention is to provide a structure of an objective lens section of an endoscope which can fix a light shielding mask in an accurate positional relationship with respect to a concave lens surface to obtain a high quality image. To do.

[0008]

In order to achieve the above object, the structure of the objective lens portion of the endoscope of the present invention is such that unnecessary light is provided adjacent to the concave lens surface of the objective lens housed in the lens frame. In the structure of the objective lens portion of the endoscope in which a thin plate-shaped light-shielding mask for light-shielding is arranged, a flat surface portion perpendicular to the optical axis is formed annularly near the outer edge portion of the concave lens surface, and the light-shielding mask is formed. , Is fixed to the objective lens while being in contact with the flat surface portion.

The concave lens surface may be the lens surface located at the rearmost end of the objective lens group, and the mask shape of the light shielding mask is arranged at a position where a subject image is formed by the objective lens group. It may be formed in a shape corresponding to the shape of the image receiving portion.

[0010]

Embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows the distal end portion of the insertion portion of the endoscope, in which the distal end portion main body 1 is provided at the distal end of the insertion portion formed of a slender flexible tube so as to be bendable by remote control. It is connected to the tip.

The curved portion 2 has a large number of node rings 3 rotatably connected by rivets 4, a mesh tube 5 is covered on the outer periphery thereof, and an outer surface thereof is covered with a rubber tube 6 or the like, and an end portion thereof is formed. Is bound and bonded to the outer peripheral surface of the tip portion main body 1. Reference numeral 7 is a bending operation wire.

The tip body 1 is made of stainless steel metal block 1a which is connected to the tip of the curved portion 2 and is not exposed to the outside, and a plastic block which is fixed to the front side of the metal block 1a and is exposed to the outside. And 1b.

The endoscope of the present embodiment is a so-called front-viewing type endoscope for observing the front of the tube axis, and an observation window 11, an illumination window 12, and an illumination window 12 are provided on the tip surface of the tip body 1. An unillustrated forceps channel outlet hole, an air / water supply nozzle, and the like are provided.

An objective lens group 16 is provided inside the observation window 11.
Is fixedly arranged in the metal lens frame 17. The first lens 16a on the surface is mechanically fixed to the lens frame 17 by caulking at a step portion formed midway on the outer peripheral surface thereof. Reference numeral 18 is an aperture stop, and 19 is a spacer.

An insulating ring 21 made of an electrically insulating plastic material is joined to the outer peripheral portion of the front half of the lens frame 17, and is inserted into a recess formed so that the front end portion of the lens frame 17 is not exposed. It is filled with the foamed epoxy adhesive 22.

The outer peripheral surface of the insulating ring 21 is fitted in a hole formed in the plastic block portion 1b of the tip end body 1, and an O-ring 23 for sealing is attached to the fitting portion. .

A shield pipe 25 made of metal is fitted and joined to the outer peripheral surface of the rear portion of the lens frame 17, and a solid-state image pickup device 26 made of, for example, a charge coupled device (CCD) is provided in the shield pipe 25 as an image receiving portion B. It is fixed facing forward.

A transparent cover glass 27 is arranged in close contact with the front side of the cover glass, and a YAG laser light cut filter 28 is attached to the front surface thereof. An observation light image is formed on the image receiving surface of the solid-state imaging device 26 by the objective lens group 16 through the transparent members 27 and 28.
Reference numeral 29 is a light-shielding mask for shielding unnecessary light.

Inside the shield pipe 25, an electronic component 31 for processing a signal input / output to / from the solid-state image pickup device 26 is mounted behind a solid-state image pickup device 26 and attached to a wiring board 32, and a signal cable 33 is provided. Has been pulled backwards from there.

Insulating tapes 34 and 35 are respectively wound around the outer peripheral surface of the component arranged inside the shield pipe 25 and the outer peripheral surface of the shield pipe 25 to electrically insulate the shield pipe 25 from the inside and outside thereof. ing. The rear end of the insulating tape 35 on the outer surface side of the shield pipe 25 continuously covers the outer peripheral surface of the front end of the signal cable 33.

The illumination window 12 is used to widen the light distribution angle of the illumination light.
The light guide fiber bundle 3 for illumination which is passed through the endoscope insertion portion is provided inside the concave lens 37 attached to the
Eight injection ends are arranged.

Reference numeral 50 denotes a tip cap made of an elastic member that is detachably attached to the tip body 1, and the tip cap of the tip body 1 is provided on the outer peripheral surface of the plastic block portion 1b of the tip body 1. It is attached from the tip side.

As described above, in the objective lens group 16, the first lens 16a at the tip is fixed to the lens frame 17 by crimping, and the lens and the spacer 19 behind it are arranged in the lens frame 1.
It is fitted into the inside of the lens 7 from the rear side and fixed to the lens frame 17 by joining.

The rear end surface of the rearmost lens 16b is a concave lens surface A. As shown in the enlarged view of FIG. 1, a flat surface portion C perpendicular to the optical axis is ground by grinding in the vicinity of the outer edge portion of the concave lens surface A. Has been formed.

This plane portion C is, as shown in FIG.
The concave lens surface A is formed in a ring shape in the vicinity of the outer edge of the concave lens surface A, and the surface thereof is roughened in a so-called grain shape.

The light-shielding mask 29 is formed by subjecting a thin metal plate to a black surface treatment, and as shown in FIG.
The shape of the mask 29a is a shape in which a rectangle corresponding to the shape of the image receiving portion B of the solid-state image sensor 26 is slightly expanded into a barrel shape.

The outer edge shape of the light-shielding mask 29 is formed in a slender shape corresponding to the outer edge shape of the solid-state image pickup element 26, and the outer edge portion shows the direction of assembly and the distinction from other similar parts. An index 29b for is formed.

As shown in FIG. 2 and FIG. 1 which is a partially enlarged view of the same, the portion of the lens frame 17 in which the light-shielding mask 29 is housed is formed in such a shape that the inner wall surface 17a is substantially in contact with the outer peripheral surface of the light-shielding mask 29. However, the wall surface 17b facing the plate surface of the light-shielding mask 29 is formed so as to escape from the plate surface of the light-shielding mask 29 toward the front with a gap.

The plate surface of the light-shielding mask 29 is brought into contact with the above-mentioned flat surface portion C formed in the vicinity of the outer edge portion of the concave lens surface A at the rearmost end of the objective lens group 16, and in that state, the lens 16b and the lens frame. It is joined and fixed to 17.

Therefore, the position of the light shielding mask 29 does not vary at all with respect to the concave lens surface A at the rearmost end of the objective lens group 16 and is always arranged and fixed at an accurate position. Therefore, the unnecessary light passing through the objective lens group 16 is appropriately cut by the light-shielding mask 29 without excess or deficiency, and a good-quality subject is imaged on the image receiving section B of the solid-state image sensor 26.

The present invention is not limited to the above-described embodiment, but may be applied to, for example, the structure of the objective lens portion of a side-view endoscope, and an image guide is used instead of the solid-state image sensor. It may be applied to an endoscope using a fiber bundle, a rigid endoscope, or the like.

[0032]

According to the present invention, the light-shielding mask is fixed to the objective lens while being in contact with the flat portion formed near the outer edge of the concave lens surface of the objective lens. However, since the unnecessary light is properly cut without excess and deficiency, it is possible to always obtain a good quality image.

[Brief description of the drawings]

FIG. 1 is a partially enlarged cross-sectional view of an objective lens section of an endoscope according to an embodiment of the present invention.

FIG. 2 is a side sectional view of the distal end portion of the endoscope according to the embodiment of the present invention.

FIG. 3 is a perspective view of the rearmost lens according to the embodiment of the present invention.

FIG. 4 is a front view of the light-shielding mask according to the embodiment of the present invention.

FIG. 5 is a side sectional view of an objective lens section of a conventional endoscope.

[Explanation of symbols]

 16 Objective Lens Group 16b Objective Lens at Last End 17 Lens Frame 29 Light-shielding Mask A Concave Lens Surface B Image Receiving Area C Flat Surface Area

Claims (3)

[Claims] 1. A structure of an objective lens portion of an endoscope, wherein a thin plate-shaped light-shielding mask for shielding unnecessary light is arranged adjacent to a concave lens surface of an objective lens housed in a lens frame. A flat portion perpendicular to the optical axis is formed in an annular shape near the outer edge of the surface, and the light shielding mask is fixed to the objective lens in a state of being in contact with the flat portion. Structure of the objective lens part of the mirror. 2. The structure of an objective lens portion of an endoscope according to claim 1, wherein the concave lens surface is a lens surface located at the rearmost end of the objective lens group. 3. A mask shape of the light-shielding mask is formed in a shape corresponding to a shape of an image receiving portion arranged at a position where a subject image is formed by the objective lens group.
The structure of the objective lens part of the described endoscope.