JPH10151105A - Endoscope optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system for an endoscope, allowing the reduction of the diameter of an endoscope insertion part as well as the reduction of the length of a hard part at the front end thereof and having the capability of forming an erect object image in the case of the horizontal arrangement of a CCD along the lengthwise direction of the endoscope insertion part. SOLUTION: This endoscope optical system is formed out of an objective optical system A consisting of a front group F having negative refracting power and a rear group R having positive refracting power, a filter FL, an optical path converting prism P1 , a correcting prism P2 , and an image pickup unit U consisting of a cover glass G and a CCD 1. In particular,. the optical path converting prism P1 and the correcting prism P2 are jointed to each other with an adhesive 2 having a smaller refractive index nC than the refractive index nP thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system disposed at a distal end of an endoscope.

[0002]

2. Description of the Related Art In recent years, endoscopes for observing organs by inserting an elongated insertion portion into a narrow lumen or body cavity have been widely used. In particular, a solid-state imaging device (video signal circuit) equipped with a solid-state imaging device (hereinafter referred to as a CCD) is provided at the end of the endoscope or the eyepiece so that inspection with the endoscope can be easily performed. Also, electronic endoscope apparatuses for observing through a monitor have come to be used frequently.

By the way, not only electronic endoscopes but also all endoscopes have to insert the elongated insertion portion into a narrow lumen or body cavity, and therefore, it is desired to reduce the diameter of the insertion portion. .
It is also desired to reduce the length of the rigid portion at the distal end of the insertion portion in order to improve the insertability of the bent portion and to reduce the pain given to the patient in the case of a medical endoscope. In order to meet these demands, in particular, in the case of an electronic endoscope, it is necessary to further reduce the size of the solid-state imaging device provided at the distal end or the eyepiece, and furthermore, to reduce the size of the CCD. However, when the size of the CCD is reduced, the pixel size becomes smaller, and C
The area of the photosensitive portion of the CD is also reduced, and the amount of light for forming a subject image that can be incident on the CCD image area is reduced, thereby causing a problem that the output level of the signal is gradually reduced. In this respect, there is a limit to the miniaturization of the CCD.

In view of such circumstances, existing large CCs
For example, Japanese Utility Model Publication No. 4-42816, Japanese Patent Application Laid-Open No.
As disclosed in 149620 and the like, there is a method of arranging the CCD horizontally or obliquely with respect to the longitudinal direction of the endoscope insertion portion. Further, as disclosed in Japanese Patent Application Laid-Open No. Hei 5-288895, there is an optical system in which the entire length of the objective optical system is shortened so as to shorten the hard distal end portion of the endoscope insertion portion.

[0005]

However, in the method disclosed in Japanese Utility Model Publication No. 4-42816, although the diameter of the endoscope insertion portion can be reduced, the CCD package can be mounted in the longitudinal direction of the endoscope insertion portion. Therefore, there is a problem that the hard end portion becomes long. Further, in the method disclosed in the above-mentioned JP-A-63-149620,
By arranging the CD obliquely with respect to the longitudinal direction of the endoscope insertion portion, it is possible to reduce the length of the distal end hard portion as compared with the method disclosed in Japanese Utility Model Publication No. 4-42816.
This is disadvantageous in reducing the diameter of the endoscope insertion section as compared with the case where D is arranged horizontally. Further, Japanese Unexamined Patent Application Publication No. 5-288
In the method disclosed in Japanese Patent No. 985, since the CCD is arranged perpendicular to the longitudinal direction of the endoscope insertion section, it is not possible to reduce the diameter of the endoscope insertion section. As described above, each of the above-mentioned methods has advantages and disadvantages, and further miniaturization of the CCD cannot be realized, and it is not possible to satisfy both the reduction in the diameter of the endoscope insertion portion and the reduction in the length of the rigid end portion. It is possible.

[0006] At present, there are mainly two types of electronic endoscopes: a small-diameter scope in which a CCD is arranged horizontally with respect to the longitudinal direction of the endoscope insertion section, and a scope with a shortened distal end rigid portion arranged vertically. There is. In addition, depending on the difference in the observation site, the case where the length of the distal end hard portion is required to be shorter than the diameter of the endoscope insertion portion is required, and the case where the diameter of the insertion portion is required to be smaller than that of the distal end hard portion is required. Divided into cases. Therefore, by using a common CCD and solid-state imaging device and changing the configuration of the optical system disposed at the distal end hard portion of the endoscope insertion portion so as to be able to use them properly according to the needs of the user, Tried to solve the problem.

However, when a solid-state image pickup device is constructed so that an erect image of a subject can be obtained on a monitor in a small-diameter scope, for example, in Japanese Utility Model Publication No. 4-42816, the optical axis is Since a once-reflected triangular prism is used to bend perpendicularly to the longitudinal direction of the endoscope insertion portion, a problem occurs in which a back image in which the left-right direction of the subject image is reversed is displayed on the monitor. . As means for solving this, Japanese Patent Application Laid-Open No. 61-504 discloses a method.
As disclosed in Japanese Unexamined Patent Publication No. 6 (1994), image information from a CCD is temporarily stored in a memory provided in a solid-state imaging device, and when the image information is read from this memory, a direction opposite to a writing direction is used. There is a method of performing horizontal scanning on a monitor based on the read information and electrically inverting the image.

However, in this case, a memory circuit, a reverse reading circuit, a switch for switching between an erect image and a back image, or a scope detection (determination) mechanism for determining whether or not the endoscope image is an erect image is provided on the solid-state imaging device side. And so on.
Such a mechanism is unnecessary for a user who uses only a scope provided with a CCD perpendicular to the longitudinal direction of the endoscope insertion section, and rather than sharing the solid-state imaging device, the size of the imaging device is large. This leads to problems such as cost increase and cost increase. Therefore, it is preferable to form an erect image using an optical system provided in the scope, rather than providing an electric image inversion mechanism. In order to optically form an erect image, the optical member must be configured such that the number of times of reflection of the subject image by the optical member until reaching the CCD light receiving surface is an even number.

In this respect, the rear group of prisms described in Japanese Patent Application Laid-Open No. 63-149620 can reflect an object image twice, which is convenient for forming an erect image. However, the CCD must be arranged obliquely with respect to the longitudinal direction of the endoscope insertion section, which is disadvantageous in reducing the diameter of the insertion section as compared with the case where the CCD is arranged horizontally. still,
In this case, there is a problem that the assemblability deteriorates as the distal end hard portion of the insertion portion becomes shorter.

When a roof prism is used in place of the triangular prism, the exit surface of the prism in contact with the CCD light receiving surface is far away from the optical axis in the longitudinal direction of the endoscope insertion section in the side direction of the endoscope insertion section. Becomes Since it is preferable that the CCD is disposed on the center axis of the scope as much as possible, when using the roof prism, the lens portion of the objective optical system disposed on the distal end hard portion of the endoscope insertion portion is inserted more than the center axis of the scope. As a result, the outer diameter of the lens is restricted. In this case, it is impossible to form a bright subject image.

Further, in the case of employing a prism configuration having a reflection action of four or more times, the back focus tends to be extremely long and the focal length of the objective optical system tends to be long.
The viewing angle becomes narrow. Therefore, this configuration is contrary to the recent demand for a wide-angle endoscope to observe a wide range at a time with an endoscope, and is not suitable.

In view of the above, the present invention has been made in view of the above-mentioned problems of the prior art. In particular, when the CCD is arranged horizontally with respect to the longitudinal direction of the endoscope insertion portion, the insertion of the endoscope is performed. It is an object of the present invention to provide an optical system of an endoscope in which the diameter of a portion is reduced and the length of a rigid portion at the tip thereof is reduced, and an upright subject image is obtained.

[0013]

In order to achieve the above object, an endoscope optical system according to the present invention has an endoscope having a solid-state imaging device arranged horizontally with respect to the longitudinal direction of an endoscope insertion portion. In the optical system, the optical path between the objective optical system and the solid-state imaging device has an incident surface perpendicular to the optical axis of the objective optical system and an emission surface oblique to the light-receiving surface of the solid-state imaging device. A correction prism having an optical path conversion prism, an entrance surface joined to an exit surface of the optical path conversion prism by an adhesive having a refractive index lower than that of the prism, and an exit surface parallel to a light receiving surface of the solid-state imaging device. And are provided. In addition, a vapor deposition film having a refractive index lower than the refractive index of the adhesive may be formed on a joint surface between the optical path conversion prism and the correction prism.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments.

First Embodiment FIG. 1 is a view showing a state in which an optical system according to the present embodiment is arranged at a distal end hard portion of an endoscope insertion portion, and shows a cross section along an optical axis. The optical system according to the present embodiment is used for a direct-viewing type endoscope, and includes an objective optical system A and an imaging unit U arranged on the exit side thereof.

The objective optical system A is a so-called retrofocus type optical system comprising a front unit F having a negative refractive power and a rear unit R having a positive refractive power. Therefore, since the back focus of the objective optical system A is formed to be long, by arranging the imaging unit U in this portion, the length of the distal end hard portion of the endoscope in which the optical system of the present embodiment is arranged can be reduced. . The optical axis of the objective optical system A is parallel to the longitudinal direction of the endoscope insertion section.

On the other hand, the imaging unit U includes a filter FL, an optical path conversion prism P ₁ and a correction prism P _2, which are arranged in order from the objective optical system A side,
₂ comprises a cover glass G and a CCD 1 arranged on the emission side. The optical path conversion prism P ₁ and the correction prism P ₂ are made of a material having the same refractive index n _P. The optical path conversion prism P ₁ and the correction prism P ₂ are joined by an adhesive 2 having a refractive index n _C lower than n _P.

As the filter FL, a so-called optical low-pass filter, an infrared cut filter for removing unnecessary spectral components, a color temperature conversion filter, and the like are used. This filter FL is a cylinder or a part of a cylinder (CCD1).
Is cut off on the side where
1 of positioning is joined to the incident surface a of the optical path changing prism P ₁ which is disposed after being made. Further, by fixing the imaging unit U by fitting the lens barrel 10 to the outer periphery of the filter FL, the optical axis of the objective optical system A and the optical axis of the imaging unit U can be easily matched with each other. Can also be improved.

Next, the prism configuration of the imaging unit U will be described in detail with reference to FIG. The optical path conversion prism P ₁ constituting the imaging unit U has an incident surface a whose objective optical system A
Are arranged so as to be perpendicular to the optical axis. The optical path changing prism P ₁ is a light beam incident perpendicularly to the incident surface a, is totally reflected by the inclined surface b, and a direction perpendicular to the further longitudinal of the endoscope insertion portion is reflected by the top surface c The inclined surface b is transmitted through. Imaging unit U
Forming from it has an optical path deflecting prism P ₁ that is configured as described above, the light flux from the object incident on the light path changing prism P ₁ on the light receiving surface of the CCD1 is reflected twice by the inclined surface b and the top surface c And an erect image can be obtained. Further, since the optical path changing prism P ₁ with respect to the longitudinal direction of the endoscope insertion portion an optical path can be converted to a vertical direction, the distal end rigid head of the endoscope insertion portion in which the optical system of the present embodiment is arranged It can also be shortened.

Here, each surface a of the optical path conversion prism P ₁ ,
When the angle between the incident surface a and the inclined surface b is θ ₁ and the angle between the inclined surface b and the upper surface c is θ ₂ in b and c, the following relational expression is given by Snell's formula. Holds. θ ₁ ≧ sin ⁻¹ (n _C / n _P ), where n _C <n _P (1) θ ₂ = 45 ° (2)

[0021] Condition (1) shows the condition for the light incident on the incident surface a parallel to the optical path conversion and the optical axis of the objective optical system A prism P ₁ is totally reflected at the slope b, condition ( 2)
Is C arranged horizontally with respect to the longitudinal direction of the endoscope insertion portion.
The conditions for vertically entering a light beam on the light receiving surface of the CD 1 are shown. Also, the luminous flux reflected by the upper surface c again becomes the slope b
When the light beam passes through the light source,
Since the incident light is inclined at −θ ₁ ) °, aberration occurs on the inclined surface b. However, the incident surface d of the correcting prism P ₂ which is joined to the inclined surface b of the optical path changing prism P ₁ is set to be parallel to the inclined surface b, the aberration generated in the slope b at the incident surface d is The opposite sign aberration can be generated. As a result, in the luminous flux reaching the CCD 1, the two aberrations generated on the inclined surface b and the incident surface d cancel each other out and become very small, so that there is no practical problem. Incidentally, the exit surface e of the correcting prism P ₂ is a perpendicular to the optical axis, by passing through the cover glass G represents a parallel flat plate, the exit surface e and CCD
1 is kept parallel to the light receiving surface.

[0022] Also, as shown by dotted lines in FIG. 2, by cutting the effective outer portion of the side surface side of the endoscope insertion portion of the optical path changing prism P _1, the insertion portion side direction of the optical path changing prism P ₁ High Can be kept low.

FIG. 3 is a sectional view taken along the incident surface a of the optical path conversion prism P ₁ as viewed from the objective optical system A side. Effective outer portion of the optical path changing prism P ₁ described above is chamfered D is decorated on the surface was cut. Thus, cut portion is outside a use region of the optical path changing prism P _1, by chamfering D thereto, diameter of the endoscope insertion portion can be reduced.
In addition, it becomes possible to layout the insertion portion side surface from the optical axis of the endoscope insertion portion to the entire optical system of the present embodiment having the optical path changing prism P _1. For this reason, a large space can be taken for the light guide L disposed on the opposite side, and a light guide having a large diameter can be provided, so that a bright observation image can be obtained.

[0024]Second embodiment This embodiment is a modification of the first embodiment. FIG.
Example of an imaging unit U used for an endoscope optical system
It is a figure for explaining a prism composition. Light of this embodiment
In the imaging unit U used for academic systems, the optical path conversion prism
Mu P₁Of the adhesive 2 used in the first embodiment on the slope b of the first embodiment.
Folding ratio n_CVapor deposition film 3 having a smaller refractive index than
Then, the deposited film 3 and the correction prism P_TwoAnd the adhesive 2
Are joined. Also, this optical path conversion prism P₁of
Relationship between the incident surface a with respect to the optical axis, the inclined surface b and the correction prism
P_TwoIs the same as that of the optical system of the first embodiment.
It is kept in. Therefore, the optical path conversion prism P₁Entering
Angle θ between launch surface a and slope b ₁Is the optical system of the first embodiment.
Can be further reduced. Therefore, this implementation
In the optical system of the example, the optical path is further changed than that of the first embodiment.
Prism P₁The reflection angle of light on each reflective surface
To shorten the length of the rigid end of the endoscope.
Can be.

By the way, it is originally used for optical members.
The refractive index of the adhesive is around 1.5 to 1.6, for example
For example, each prism P₁, P_TwoRefractive index n_PIs 1.8,
Refractive index n of adhesive 2_CIs 1.56, the θ₁of
The size must be set to 60 ° or more. to this
On the other hand, in the present embodiment, the optical path conversion prism P₁Slope
b, for example, on an anti-reflection coating, etc.
Magnesium fluoride used (MgF _Two) Metal film
If used, MgF_TwoRefractive index of coat n_C’Is 1.38
So that the θ₁Should be at least 50 °
No. Therefore, this optical path conversion prism P₁Mounted on endoscope
In this case, the luminous flux reflected by the slope b is large and in front of the endoscope.
Side (right side of the figure), and consequently the endoscope
The length of the hard end portion can be reduced.

In this embodiment, each prism P₁, P_Two
Refractive index n_PIs set to 1.8 and the above θ ₁For the size of
But n_PIf the value of is further increased, θ₁Less than
You can set it up. Also, select the material of the deposited film 3
The refractive index n of the deposited film 3_C’
Thereby θ₁Can be further reduced.
However, it should be noted here that the thickness of the deposited film 3 is 1 μm.
m or more. Because the film
When the thickness is less than 1 μm, the luminous flux is not totally reflected on the slope b.
This is because the light is transmitted to the light source, leading to a loss of light quantity.

[0027]Third embodiment FIG. 5 shows that the optical system according to the present embodiment has a distal end of an endoscope insertion portion.
FIG. 5 is a diagram showing a state where the light emitting device is disposed in
Is shown. An imaging unit used in the optical system according to the present embodiment.
In U, the upper surface G of the cover glass G ₁Is an optical path conversion prism
Mu P₁Inward than the position g where the entrance surface a and the slope b intersect
It is configured to be located on the optical axis side along the longitudinal direction of the mirror
I have. Other configurations are the same as those of the optical system of the first embodiment.
You. Thus, in the optical system of the present embodiment, the cover glass
Top surface G of G₁To the optical path conversion prism P₁Incident surface a and oblique
From the position g where the surface b intersects, along the longitudinal direction of the endoscope insertion portion.
The optical axis and the CCD 1
The distance to the light surface can be further shortened, further endoscope
The diameter of the insertion portion can be reduced.

Furthermore, when joining the exit surface e of the correcting prism P ₂ directly on the light receiving surface of CCD1, you can move the light-receiving surface of the thickness of only further CCD1 cover glass G in the optical axis side, and further The diameter of the endoscope insertion section can be reduced. However, in the case where a microlens array for improving sensitivity is provided on the light receiving surface of CCD1, when pasted on a light receiving surface of the exit surface e of the correcting prism P ₂ directly CCD1, adhesive flows into a lens surface Care must be taken because the light-collecting effect of the microlens array cannot be obtained.

[0029] In order to avoid such problems, as shown in FIG. 6, the deposition film 4 outside the scope of the exit surface e of the correcting prism P ₂ may be formed thicker than the microlens array . The deposited film 4 plays a role of a spacer for providing the air layer between the correcting prism P ₂ and CCD 1. Further, as a material of the vapor deposition film 4, SiO ₂ , SiO, Al ₂ O _3, etc. are several μm to several tens μm.
It is suitable because it is easy to vapor-deposit with a thickness of, but is not limited thereto. Further, the paint may be allowed to adhere to the compensating prism P ₂ in place of deposition. However, a thin metal plate such as a phosphor bronze plate may be used as the spacer,
In this case, it is necessary to adhere and fix both to the correction prism P ₂ and the CCD 1. In particular, when adhering to the correction prism P ₂ side, there is a possibility that the adhesive may flow into an effective range, and the workability is significantly deteriorated. Therefore, it is not appropriate.

Fourth Embodiment This embodiment is a modification of the second embodiment. FIG. 7 is a diagram for explaining the prism configuration of the imaging unit U used in the endoscope optical system according to the present embodiment. In the imaging unit U used in an optical system of the present embodiment, the optical path changing prism P ₁ slope b to the formed vapor deposition film 3 sandwiched manner further deposited film 3a shown in the second embodiment, 3b is formed I have. In particular, in this embodiment, the refractive index of the material of the deposited films 3a and 3b, the refractive index n _C ′ of the deposited film 3 and the prism P
It is preferable that the relationship between ₁ and P _{2 with} the refractive index n _P satisfies the following conditional expression. n _C ′ <refractive index of material of deposited films 3a and 3b <n _P (3)

When the exit pupil position of the objective optical system A is close to the image plane, that is, the light receiving surface of the CCD 1, the angle of incidence of the incident light beam on the periphery of the CCD 1 becomes large. Further, when the light beam parallel to the optical axis of the objective optical system A is incident on the correction prism P ₂ transmitted through the optical path changing prism P _1, that the light beam that is oblique to the inclined surface b (or incident surface d) Therefore, the angle of incidence of each light beam on the inclined surface b greatly differs depending on the incident position. In Therefore, different spectral characteristics of Fresnel reflection between the slope b of the optical path changing prism P ₁ and the incident surface d of the correcting prism P _2, a direction along its optical axis to light rays transmitted through the correcting prism P ₂ Color unevenness occurs. In particular, when a fluorescent lamp or a metal halide lamp is used as the light source connected to the light guide of the endoscope, the light emitted from this light source has a bright line spectrum and is highly coherent (coherent). When the light is reflected by the subject and enters the optical system of the endoscope, the occurrence of color unevenness becomes conspicuous.

Therefore, in this embodiment, the vapor deposition films 3a and 3b having a refractive index satisfying the conditional expression (3) are formed, and Fresnel reflection generated at the boundary between the prisms P ₁ and P ₂ and the vapor deposition film 3 is formed. And the level of occurrence of color unevenness is suppressed. Furthermore, since the refractive index n _C of the adhesive 2 applied to the entrance surface d of the correction prism P ₂ also affects the Fresnel reflection, the materials of the vapor deposition films 3a and 3b do not necessarily have to be the same. . If the refractive index n _C of the adhesive 2 is n _C ′ <n _C <1.5 (4), Fresnel reflection occurring at the interface between the adhesive 2 and the deposited film 3 is small. Therefore, there is no practical problem even if the vapor deposition film 3b is omitted.

As described above, in the endoscope optical system according to the present invention, in an endoscope in which the CCD is horizontally arranged in the longitudinal direction of the endoscope, the diameter of the endoscope insertion portion is reduced and the length of the distal end hard portion is increased. Can be shortened.

Further, as shown in FIG. 8, the endoscope 11a incorporating the endoscope optical system of the present invention can form an erect subject image by itself without using an image erecting mechanism. The CCD can be used only with the conventional endoscope 11b in which the CCD is arranged perpendicular to the longitudinal direction of the endoscope insertion portion, and can be used with the imaging device 12 having no image erecting mechanism. . The imaging device 12 is connected to a monitor 13 for displaying an image of a signal output from the imaging device 12 and a light source device 14 for sending illumination light to the imaging device 12. Here, the imaging device 12, the monitor 13, and the light source device 14 are shown individually, but they may be integrated. Other optional devices (air supply, water supply, etc.) used arbitrarily are omitted.

As described above, the endoscope optical system according to the present invention has the following features (1) to (8) in addition to the features described in the claims.

(1) The surface of the CCD cover glass on the correction prism side is located closer to the optical axis of the objective optical system than the lower end of the exit surface of the optical path conversion prism. 3. The endoscope optical system according to 2.

(2) The exit surface of the correction prism is C
3. The endoscope optical system according to claim 1, wherein the endoscope optical system is directly bonded to a light receiving surface of a CD.

(3) The method according to (2), wherein a vapor-deposited film is formed outside the effective area of the emission surface of the correction prism, and an air layer is provided between the correction film and the light receiving surface of the CCD. Endoscope optics.

(4) The multi-layered film is formed on the joint surface between the optical path conversion prism and the correction prism on which the vapor-deposited film having a refractive index lower than the refractive index of the adhesive is formed. The endoscope optical system according to any one of claims 1 to 2 or (1) to (3).

(5) A part of the optical path conversion prism or the correction prism is chamfered according to the inner diameter of the endoscope insertion portion, or the above (1). The endoscope optical system according to any one of (1) to (4).

(6) A substantially cylindrical optical member is disposed in an optical path between the objective optical system and the optical path conversion prism. The endoscope optical system according to any one of 5).

(7) The substantially cylindrical optical member is joined to the entrance surface of the optical path conversion prism, and the outer periphery of the optical member is fitted to the lens barrel of the objective optical system. The endoscope optical system according to (6).

(8) The substantially cylindrical optical member is a color temperature conversion filter, an optical low-pass filter, or a filter having both of them, as described in (6) or (7) above. Endoscope optics.

[0044]

As described above, according to the endoscope optical system of the present invention, when the CCD is arranged horizontally with respect to the longitudinal direction of the endoscope insertion section, the diameter of the endoscope insertion section is small. And the length of the hard portion at the tip thereof can be shortened. Further, in the optical system of the present invention, an erect subject image can be obtained without using any other image adjustment mechanism, so that the optical system can be used together with a conventional imaging apparatus having no image erecting function.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view along an optical axis showing a configuration of an endoscope optical system according to a first example.

FIG. 2 is a diagram for explaining a prism configuration of an imaging unit used in the optical system according to the first embodiment.

FIG. 3 shows an optical path conversion prism P ₁ viewed from the objective optical system A side.
FIG. 3 is a cross-sectional view taken along an incident surface a of FIG.

FIG. 4 is a diagram for explaining a prism configuration of an imaging unit used in the optical system according to the second embodiment.

FIG. 5 is a sectional view along an optical axis showing a configuration of an endoscope optical system according to a third example.

FIG. 6 is a diagram for explaining a prism configuration of an image pickup unit used in an optical system according to a third embodiment.

FIG. 7 is a diagram for explaining a prism configuration of an imaging unit used in an optical system according to a fourth embodiment.

FIG. 8 is a diagram for explaining a usage mode of an endoscope in which the endoscope optical system according to the present invention is incorporated.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 CCD (solid-state image sensor) 2 Adhesive 3,3a, 3b, 4 Evaporated film 10 Lens barrel 11a Endoscope in which the endoscope optical system of the present invention was incorporated 11b Conventional endoscope 12 Imaging device 13 Monitor 14 light source device A objective optical system F front group FL filter G coverslip L light guide P ₁ optical path changing prism P ₂ correcting prism R RLG U imaging unit a, d incident surface b slope c top e exit surface

Claims (2)

[Claims] 1. An endoscope optical system having a solid-state imaging device disposed horizontally with respect to a longitudinal direction of an endoscope insertion portion, wherein an optical path between an objective optical system and the solid-state imaging device is provided in the optical path. An optical path conversion prism having an entrance surface perpendicular to the optical axis of the objective optical system and an exit surface oblique to the light receiving surface of the solid-state imaging device; and an exit surface of the optical path conversion prism having a refractive index of the optical path conversion prism. An endoscope optical system, comprising: a correction prism having an incident surface joined by an adhesive having a low refractive index and an exit surface parallel to a light receiving surface of the solid-state imaging device. 2. A vapor deposition film having a refractive index lower than the refractive index of the adhesive is formed on a joint surface between the optical path changing prism and the correction prism.
3. The endoscope optical system according to claim 1.