JPS6296923A - Optical system of endoscope - Google Patents

Abstract

PURPOSE:To reduce the diameter of the front end part of an endoscope as much as possible by arranging a solid-state image pickup element along the axis of the front end part of the endoscope or its nearby part and inclining reflecting faces facing the image pickup face of the solid-state image pickup element. CONSTITUTION:An observation light incident on an endoscope front end part 11 in the direction of an arrow X passes an objective lens 12 and is reflected upward by a prism 15 and is made incident on a roof prism 14. This light is reflected on the second reflecting face 14b and is totally reflected on the bottom and is reflected on the first reflecting face 14a and is emitted from the prism 14 and is focused on an image pickup face 13a of a solid-state image pickup element 13. Since the solid-state image pickup element 13 is arranged along the axis of the endoscope front end part, the part having the smallest dimensions of the solid-state image pickup element 13 is placed in the part having the longest width of the endoscope front end part 11, and the prism 14 is stored in the space in the side of the image pickup face 13a of the solid-state image pickup element 13. Thus, the diameter of the endoscope front end part 11 is not increased by arrangement of the prism 14, and the diameter of the endoscope front end part 11 is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical system for an endoscope that captures images using a solid-state image sensor.

[Conventional technology]

In general, a solid-state imaging device has the shape of a dual in-line IC package, and an imaging surface is disposed on a part of the top surface of the puff cage, and peripheral circuits are built into the inside of the imaging surface. The entire solid-state image sensor is several times larger than its imaging surface. Therefore, when configuring an endoscope that performs imaging using such a solid-state image sensor, the tip end 1 of the endoscope is configured as shown in FIG. 2(A).
When a solid-state image sensor 3 is disposed perpendicularly to the longitudinal axis of the endoscope behind the objective lens 2, the diameter of the endoscope tip 1 increases as shown in Fig. 2 ( As shown in B), it became large, which was not desirable. Therefore, for example, according to Japanese Patent Application Laid-Open No. 58-46922, FIG.
), a reflective member 4 such as a prism is disposed behind the objective lens 2 within the endoscope tip 1, and the optical axis from the objective lens 2 is bent perpendicularly to the longitudinal axis of the endoscope. A configuration is known in which observation light is received by a solid-state image sensor 3 disposed along the longitudinal axis of an endoscope. However, in this case, as is clear from FIG. 3(B), the solid-state image sensor 3' is disposed offset from the optical axis of the objective lens 2, so the solid-state image sensor 3' is located at the tip l of the endoscope. The diameter of the endoscope tip l, which can be disposed near the central axis, still has to be large.

[Problem that the invention seeks to solve]

The present invention relates to an endoscope that uses a solid-state image sensor to perform imaging, and the endoscope has a diameter as small as possible at the tip of the endoscope that houses an objective lens and a solid-state image sensor. The purpose is to provide optical systems.

[Means and actions for solving the problem] This purpose is to
In an endoscope that has an objective lens and a solid-state image sensor built into the distal end of the endoscope, the solid-state image sensor captures an observation image formed by the objective lens on the solid-state image sensor. An image sensor is disposed along the central axis of the endoscope tip or its vicinity, and a reflective surface obliquely arranged opposite to the imaging surface of the solid-state image sensor and an objective lens provide an image observed on the solid-state. It is characterized by including a deflection means disposed in front of the objective lens and/or in the objective lens and/or between the objective lens and the reflective surface so that the image is formed on the imaging surface of the imaging element. This problem is solved by the optical system of the endoscope.

〔Example〕

The present invention will be explained below based on the embodiments shown in the drawings.
In FIG. 1, 10 is a direct-viewing endoscope according to the present invention, 11 is an endoscope tip, and 12 is approximately aligned with the central axis of the endoscope tip 11, as is clear from FIG. 1(B). The objective lens 13 is arranged concentrically along the central axis (or near the central axis) of the endoscope tip 11, that is, at the substantially widest part of the cross section of the endoscope tip 11. The positioned solid-state image sensor 14 is the imaging surface 13 of the solid-state image sensor 13
The prism is a chevron-shaped prism including a first reflective surface 14a and a second reflective surface 14b that are obliquely arranged opposite to the angle A, and the first and second reflective surfaces 14a and 14b are formed of mirror surfaces such as aluminum coating. ing. 15 is objective lens 1
The observation light incident on the endoscope tip 11 in the direction of the arrow X passes through the objective lens 12 and is then reflected upward by the prism 15 in FIG. 1(A). It enters the chevron prism 14, is reflected by its second reflective surface 14b, is totally reflected from its bottom surface, is reflected by the first reflective surface 14a, and then exits from the chevron prism 14 to form a solid-state image sensor 13. The image is formed on the imaging surface 13a of the.

Since the embodiment of the present invention is configured as described above, the solid-state image sensor 13 is disposed along the central axis (or the vicinity thereof) of the distal end of the endoscope, so that the minimum dimension of the solid-state image sensor 13 is The chevron prism 14 is located at the widest part of the endoscope distal end 11, and the chevron prism 14 is accommodated in the space on the imaging surface 13a side of the solid-state image sensor 13. There is no need to increase the diameter of the endoscope tip 11, and thus the diameter of the endoscope tip 11 can be minimized.

Note that FIG. 4 is a detailed diagram of the chevron prism 14 and the reflecting prism 15 in FIG. The inclination angles of the first reflective surface 14a, the second reflective surface 14b of the prism 14, and the reflective surface of the reflective prism 15 are α and β, respectively, as shown in FIG.
and T, then ψ α−β+r=90” −− is established. Also, the angle prism 14 and the reflecting prism 15
The chevron prism 14 may be connected to the solid-state image sensor 1 or may be spaced apart from the solid-state image sensor 1 with a narrow air gap.
It may also serve as a cover glass for the imaging surface 13a of No. 3.

5 to 12 show variations of the embodiment shown in FIG. 1. First, FIG. 5 shows the chevron prism 14 in FIG.
The bottom part of the prism 14' is formed of a material with a smaller refractive index as a separate plate-shaped prism 14', so that the light reflected on the second reflective surface 14b of the chevron-shaped prism 14 is totally reflected at the interface with the prism 14'. Its operation is the same as that of the embodiment shown in FIG.
5 is also joined, total reflection at the bottom surface of the chevron prism 14 can be ensured. 61st! I is a solid-state image sensor 13 in place of the chevron prism 14 in the embodiment shown in FIG.
A prism 16 is provided obliquely to face the imaging surface 13a of the prism 16, and a roof prism 17 is provided to allow the light from the reflecting prism 15 to enter the prism 16. In this case, the prism 15 and 16 may be constructed as a roof prism, and in either case, the same effect as in the embodiment shown in FIG. 1 is performed. FIG. 7 shows an example in which two prisms 18 and 19 are arranged as shown in place of the chevron prism 14 and reflective prism 15 in the embodiment shown in FIG. 1, and FIG. 8 shows the prism 18 in FIG. In either case, the operation is the same as in the embodiment shown in FIG. 1, and the longer solid-state image sensor 13
may be used. FIG. 9 shows two prisms 21 and 22 that have fewer reflections than the example shown in FIG.
In this configuration example, either one of the prisms 21 or 2
2 may be used as a roof prism. Figure 10 shows an example using three prisms 23, 24 and 25.
may be a roof prism.

FIG. 11 shows an example in which two prisms 26 and 27 are used.d The embodiments shown in FIGS. 9 to 11 all operate in the same manner as the embodiment shown in FIG.

FIG. 12 shows an embodiment in which a side-viewing objective lens 28 including a prism in the middle is provided in place of the direct-viewing objective lens 12 in the embodiment shown in FIG.

FIG. 13 shows a second embodiment of the endoscope according to the present invention, in which 30 is a side-viewing endoscope, 3! endoscope tip, 32
33 is an objective lens disposed perpendicularly to the central axis of the endoscope tip 31; 33 is a solid-state image sensor disposed along the central axis (or near) of the endoscope tip 31; 34
is a chevron prism including a first reflective surface 34a and a second reflective surface 34b which are obliquely arranged opposite to the image plane 33a of the solid-state image sensor 33, and the light beam passing through the objective lens 32 is reflected by the chevron prism 34. and its second and first reflecting surfaces 34b.
, 34a, the light is emitted from the radial chevron prism 34, and is imaged on the imaging surface 33a of the solid-state imaging device 33. FIG. 14 shows that in the embodiment shown in FIG. 13, when the overall length of the objective lens 32 is relatively long, the components of the objective lens 32 are arranged in a portion 32a disposed on the front side of the second angle-shaped prism 35 and on the rear side. In both the embodiments shown in FIGS. 13 and 14, the optical axis of the objective lens 32 is set laterally on the imaging plane side from the central axis of the endoscope. The solid-state image sensor 33 can be disposed near the central axis of the endoscope distal end 31 because the solid-state image sensor 33 is reflected by the solid-state image sensor 33 and guided to the reflective surface diagonally provided opposite the imaging surface 33a.

FIG. 15 shows a third embodiment of an endoscope according to the present invention, which includes a prism 36 inserted in the middle of a perspective-viewing objective lens and a prism 37 disposed above an imaging surface 33a. FIG. 16 shows a modification of the embodiment of FIG. 15, which includes prisms 38 and 39. The examples shown in FIGS. 15 and 16 are both applied to a perspective-viewing endoscope, so that the solid-state image sensor 33 can be disposed near the central axis of the distal end of the endoscope.

FIG. 17 shows a modified example of FIG. 6 in which the constituent elements of the objective lens are prisms 16 and 17 when the total length of the objective lens is long.
A modified example is shown in which it is arranged between the two.

In each of the above-mentioned sides, if the distance from the objective lens to the imaging surface is too long and the light from the objective lens cannot form an image on the imaging surface, the distance between the objective lens and the imaging surface of the solid-state image sensor The image may be formed on the imaging plane by inserting a relay lens at an appropriate position.

Furthermore, imaging using a solid-state image sensor is likely to cause moire, so to prevent moire, at least one of the prisms inserted in the optical path should be made of a birefringent material such as quartz. .

In addition, in order to prevent moiré, a phase film with a wavelength of one wavelength where the retardation beam is formed is formed on at least one surface of the prism by vapor deposition as minute dots occupying half of the area of the line surface at random as shown in FIG. You may.

In order to remove unnecessary infrared rays, at least one of the prisms inserted in the optical path may be made of infrared absorbing glass, or at least one surface of the prism may be coated with an infrared reflective coating.

In the above explanation, a prism is used to reflect the light beam from the objective lens, but it goes without saying that a mirror may be used instead of this prism.

〔Effect of the invention〕

As described above, according to the present invention, the solid-state image sensor is arranged along the central axis of the endoscope tip or its vicinity, and the reflective surface is tilted opposite to the first most image plane of the solid-state image sensor. Further, a deflection means is provided in front of the objective lens and/or in the objective lens and/or between the objective lens and the reflective surface so that the image observed by the objective lens is formed on the image plane of the solid-state image sensor. Because of this arrangement, the smallest dimension part of the solid-state image sensor is located at the largest width part of the tip of the endoscope.
Since the reflective surface facing the image plane is housed in the space between the solid-state image sensor and the endoscope tip, the arrangement of the reflective surface does not increase the diameter of the endoscope tip. Not,
Therefore, the diameter of the endoscope tip can be minimized relative to the solid-state imaging device, which is extremely effective.

[Brief explanation of drawings]

FIG. 1 shows a first embodiment of the endoscope according to the present invention (A
>Schematic side view and (B) front view, Figures 2 and 3 are (A) schematic side view, (B) front view, and Figure 4 of a conventional endoscope.
The figure is a detailed view of the prism of the embodiment shown in FIG. 1, FIGS. 5 to 12 are views showing modifications of the embodiment shown in FIG. 1, FIG. 14 is a diagram showing a modification of the embodiment shown in FIG. 13, FIG. 15 is a diagram showing a third embodiment, FIG. 16 is a diagram showing a modification of the embodiment shown in FIG.
FIG. 7 is a diagram showing another configuration example, and FIG. 18 is a diagram showing the shape of a phase film for moire prevention. 10.30... Endoscope, 11.31... Endoscope tip, 12.32... Objective lens, 13.33...
... Solid-state image sensor, 14,34.35... Chevron prism, 15,16.17.1B, 19.20°21.
22, 23.24.25, 26, 27.36.37.3
8.39. ,...prism, 28...objective lens. Figure 1 Z-Haku Figure 2 Figure 3 Fang Figure 4 Figure 16 Figure 8 Figure O9 Figure Fang 15 Figure 16 Figure 17

Claims (1)

[Scope of Claims] An objective lens and a solid-state image sensor are built into the distal end of the endoscope, and an observation image formed on the solid-state image sensor by the objective lens is imaged by the solid-state image sensor. In an endoscope, a solid-state image sensor is disposed along or near a central axis of a distal end of the endoscope, and further includes a reflective surface obliquely arranged opposite to an imaging surface of the solid-state image sensor, and an objective. a deflecting means disposed in front of the objective lens and/or in the objective lens and/or between the objective lens and the reflective surface so that the image observed by the lens is formed on the imaging surface of the solid-state image sensor; The optical system of an endoscope is characterized by: