JPH09288240A - Visual field direction changing optical system for endoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a visual field direction changing optical system with which a good object image is obtainable by removing the harmful rays to be the cause for ghosts and flares and production at a low cost is possible. SOLUTION: This optical system is constituted by arranging, successively from the object side in a diagonal viewing direction, cover glass 4, a concave lens unit 5, a visual field direction changing prism 1 and a stabilizing optical element 2. The concave lens unit 5, the visual field direction changing prism 1 and the stabilizing optical element 2 are housed in an inside frame 6. The cover glass 4 is constituted integrally with the outside frame 7. The exit surface 1d of the visual field direction changing prism 1 and the incident surface 2a of the stabilizing optical element 2 are joined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a visual field direction changing optical system used in an endoscope for observing an object in a perspective direction.

[0002]

2. Description of the Related Art As a conventional visual field direction changing optical system for an endoscope, there is one disclosed in, for example, Japanese Patent Laid-Open No. 5-11196. In this visual field direction changing optical system, as shown in FIG. 8, harmful rays other than the effective luminous flux of the rays forming the object image are blocked by the light blocking section of the diaphragm 10 after passing through the cover glass 4. Therefore, it does not enter the visual field direction conversion prism 1. Therefore, it is possible to obtain a good image by preventing the occurrence of ghost and flare when observing the object.

Another conventional visual field direction changing optical system for an endoscope is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-108013. As shown in FIG. 9, this viewing direction changing optical system has an object side in the perspective direction (left side in the drawing).
In this order, the viewing direction conversion prism 1 and the stabilizing optical element 2
And are arranged. Here, since the field-of-view direction conversion prism 1 and the stabilizing optical element 2 are both formed in a shape like a circular cylinder, the relative positioning of both can be accurately performed. In addition, since both of them are joined together, the length in the optical axis direction with respect to the outer diameter direction is longer than when each is used alone, and rattling of the prism occurs when mounted on the endoscope. hard. Therefore, it is possible to suppress the deterioration of the optical performance due to the deviation of the visual field direction and the generation of astigmatism due to the decentering occurring in the optical system.

[0004]

As described above, in the endoscope visual field direction changing optical system shown in FIG. 8, the diaphragm 10 is provided on the object side of the visual field direction converting prism 1 to block harmful rays. Although provided, when the diaphragm 10 is configured as a mechanical diaphragm, the number of parts is increased by one. Furthermore, when aligning the diaphragm 10 and the field-of-view direction conversion prism 1, a process of joining the diaphragm 10 when the diaphragm 10 is a mechanical diaphragm and vapor deposition when the diaphragm 10 is a vapor deposition diaphragm are required. As described above, in the visual field direction conversion optical system shown in FIG. 8, since the number of parts and the number of assembling steps are increased in order to block harmful rays, there is a problem that the manufacturing cost is increased.

Further, in the endoscope visual field direction changing optical system shown in FIG. 9, a ray other than an effective light beam for forming an object image reaches an image forming plane as shown by x in the figure. Possible harmful rays are present. This harmful ray x passes through the field-of-view direction conversion prism 1 without being reflected, and further passes through the stabilizing optical element 2 to enter the objective lens system of the endoscope. Here, since the harmful ray x passing through the stabilizing optical element 2 overlaps with the effective luminous flux, ghost and flare may occur. Ghosts and flares are not preferable because they cause a great obstacle to the observation of the object image. As described above, since the visual field direction changing optical system shown in FIG. 9 does not have a configuration for blocking harmful rays, ghosts and flares occur when observing an object image, and a good image is always obtained. It has the drawback that it cannot

In view of the above-mentioned problems of the prior art, the present invention eliminates harmful rays that may cause ghosts and flares to obtain a good object image, and enables low-cost manufacturing. It is an object of the present invention to provide a visual field direction changing optical system for an endoscope.

[0007]

In order to achieve the above-mentioned object, a visual field direction changing optical system for an endoscope according to the present invention, in an endoscope capable of observing an object in a perspective direction, allows a light beam from the object side to pass through. An incident surface that transmits light, a first reflecting surface that is coated with a metal for reflecting the light flux that has passed through the incident surface, and the light flux reflected by the first reflecting surface are reflected to the image side. A field-of-view direction conversion prism including a second reflecting surface formed by selectively applying a metal coating to the entrance surface and an exit surface that transmits the light flux reflected by the second reflecting surface to the image side. And a stabilizing optical element bonded to the exit surface of the visual field direction conversion prism, and the shapes of the visual field direction converting prism and the stabilizing optical element satisfy the following conditional expressions. . 0.1 ≦ a / φ ≦ 0.3 where φ is the outer diameter of the stabilizing optical element, and a is the stabilizing optical element on the exit surface of the view direction changing prism joined to the stabilizing optical element. The effective radius on the side of the first reflection surface of the visual field direction conversion prism around the optical axis is shown.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the basic principle of an endoscope visual field direction changing optical system according to the present invention will be described with reference to FIGS.

6 and 7 are sectional views taken along the optical axis showing the structure of a visual field direction changing optical system arranged at the tip of an endoscope for observing an object in a perspective direction. FIG. FIG. 7 shows the configuration of an endoscope visual field direction changing optical system according to the present invention, and FIG. 7 shows the configuration of a conventional endoscope visual field direction changing optical system. Each of the endoscope field-of-view direction conversion optical systems shown here has a field-direction conversion prism 1 and an exit surface 1 thereof.
and the stabilizing optical element 2 bonded to d. The visual field direction conversion prism 1 includes an incident surface 1a that transmits a light beam from the object side, a first reflecting surface 1b provided with a metal coat 1e for reflecting the light beam that has passed through the incident surface 1a, and a first reflecting surface. A second reflection surface 1c formed by selectively applying a metal coat 1f to the incident surface 1a for reflecting the light flux reflected by 1b toward the image side, and the light flux reflected by the second reflection surface 1c toward the image side. It is composed of a transparent exit surface 1d.

Further, in the endoscope visual field direction changing optical system according to the present invention shown in FIG. 6, the visual field direction changing prism 1 and the stabilizing optical element 2 satisfy the following conditional expressions. I am trying. 0.1 ≦ a / φ ≦ 0.3 (1) where φ is the outer diameter of the stabilizing optical element 2 and a is the exit surface of the view direction changing prism 1 joined to the stabilizing optical element 2. 1d
Shows the effective radius of the field-of-view direction conversion prism 1 on the side of the first reflection surface 1b with the optical axis of the stabilizing optical element 2 as the center.

Further, in the endoscope visual field direction changing optical system shown in FIGS. 6 and 7, the outer diameters of the visual field direction converting prism 1 and the stabilizing optical element 2 and the visual field direction converting prism 1 are used.
The angles of the respective surfaces with respect to the optical axis are all equal. The only difference between the two shapes is that the exit surface 1d of the view direction changing prism 1 in the view direction changing optical system for an endoscope of the present invention shown in FIG. 6 differs from the conventional one shown in FIG. In comparison, only the point that the lens is moved in parallel to the image side so as to satisfy the conditional expression (1).

In the conventional endoscope field-of-view direction changing optical system shown in FIG. 7, among harmful rays, the harmful ray x having a bright point below the optical axis from the oblique direction is a view-direction changing prism. The light passes through the inside of 1 without being reflected, and also through the stabilizing optical element 2, and enters the objective lens system of the endoscope. Here, the harmful ray x that has entered the objective lens system
May overlap with an effective light flux forming an object image, resulting in a ghost or flare. These ghosts and flares are
This can be a great obstacle to observing a good object image. On the other hand, in the endoscope visual field direction changing optical system shown in FIG. 6, the position of the exit surface 1d of the visual field direction converting prism 1 is parallel to the image side so as to satisfy the conditional expression (1). By moving the harmful ray x, the harmful ray x is totally reflected by the first reflection surface 1b of the visual field direction conversion prism 1, and then absorbed by the edge of the stabilizing optical system 2. Therefore, the harmful ray x does not reach the image plane, and it becomes possible to remove the harmful ray which causes ghost and flare when observing the object, and a good observation image can be obtained. .

Here, regarding the value of a / φ, a /
When the value of φ is increased, harmful rays are transmitted through the field-of-view direction conversion prism 1 without being reflected, and ghost and flare are likely to occur. On the other hand, when the value of a / φ is reduced, the effective light beam is eclipsed by the exit surface 1d of the visual field direction conversion prism 1, and the peripheral portion of the image becomes dark in particular. Therefore, the shapes of the visual field direction conversion prism 1 and the stabilizing optical element 2 need to be formed so as to suppress the generation of ghosts and flares and minimize the amount of effective light beam shed.
The condition provided to enable this is conditional expression (1).
It is.

Of the harmful rays, those having a bright spot above the optical axis from the perspective direction are the view direction conversion prisms 1.
Since the second reflecting surface 1c formed by applying the metal coat 1f to the entrance surface 1a is shielded from light, the image surface cannot be reached, and ghost and flare do not occur. That is, the second reflecting surface 1c of the visual field direction conversion prism 1 also has a function of blocking harmful rays having a bright spot above the optical axis in the oblique direction. The range of the metal coat 1e applied to the first reflection surface 1b of the visual field direction conversion prism 1 is the first reflection surface 1
It is a necessary condition to be able to reflect all the effective light beams incident on b. When the metal coating is applied to the other area, the effective light flux is 3 in the view direction conversion prism 1.
There is a possibility that harmful rays will be generated after being reflected more than once and passing through the stabilizing optical element 2, which is not preferable. On the other hand, metal coat 1
Even if the range in which e is applied is limited to be substantially equal to the incident range of the effective light flux, positioning of the metal coat 1e becomes difficult, and a highly difficult manufacturing process is required, which is not preferable. Therefore, it is preferable that the range in which the metal coat 1e is applied is a range in which the metal coat 1e can be easily applied, including the range of the effective light flux incident on the first reflecting surface 1b.

Furthermore, regardless of the angle of the first reflecting surface 1b of the field-of-view direction converting prism 1 with respect to the optical axis and the refractive index of the material forming the field-of-view direction converting prism 1, the harmful rays reaching the first reflecting surface 1b are In order to prevent the light from passing through the first reflecting surface 1b and entering the stabilizing optical element 2, the first reflecting surface 1b may be provided with a metal coat 1e and then a light-shielding means such as black treatment.

The present invention will be described in detail below with reference to the illustrated embodiments.

First Embodiment FIG. 1 is a sectional view taken along the optical axis showing the construction of a visual field direction changing optical system for an endoscope according to this embodiment. This visual field direction changing optical system is arranged and used at the tip portion of the endoscope. The visual field direction conversion optical system of the present embodiment is configured by disposing a cover glass 4, a concave lens unit 5, a visual field direction conversion prism 1 and a stabilizing optical element 2 in this order from the object side in the perspective direction. The concave lens unit 5, the visual field direction changing prism 1 and the stabilizing optical element 2 are housed in the inner frame 6, and the cover glass 4 is formed integrally with the outer frame 7. In addition, the exit surface 1 of the visual field direction conversion prism 1
d and the stabilizing optical element 2 are joined. The visual field direction conversion prism 1 and the stabilizing optical element 2 both have a shape like a cylinder cut into rings, and both have an outer diameter φ of 5.7 m.
m. Further, the inner frame 6 has a cross section 6a on the incident surface 1a side, the direction of which coincides with the incident surface 1a of the view direction converting prism 1, and is integrally joined to the view direction converting prism 1.

The effective luminous flux centered in the oblique direction of 45 ° which enters through the cover glass 4 passes through the entrance surface 1a of the field-of-view direction conversion prism 1 and is reflected by the metal coat 1e formed on the first reflecting surface 1b. After being reflected and subsequently reflected to the image side by the second reflecting surface 1c formed by applying the metal coat 1f to the entrance surface 1a, the exit surface 1d and the entrance surface 2 of the stabilizing optical element 2 are reflected.
After passing through a, it enters the objective lens system of the endoscope (not shown) from the exit surface 2b and forms an image. In order to have the above-mentioned effect on the effective luminous flux from the oblique direction of 45 °,
In the endoscope visual field direction changing optical system of the present embodiment, the incident surface 1a (the second reflecting surface 1c) of the visual field direction converting prism 1 and the first
Angles θ ₁ , θ ₂ , and θ ₃ of the reflecting surface 1b and the exit surface 1d with respect to the optical axis of the stabilizing optical element 2 are 45 °, 22.5 °, and
It is set to 90 °. Further, the first reflecting surface 1b and the second
The metal coats 1e and 1f of the reflecting surface 1c are provided in a range sufficient to reflect all the effective luminous flux.

On the other hand, among the harmful rays incident through the cover glass 4, those having a bright spot above the optical axis in the oblique direction are those of the second reflecting surface 1c of the view direction changing prism 1. The coat 1f does not reach the image plane because it acts as a light shielding means. The range of the metal coat 1f is set so as to be able to reflect all the effective luminous flux, and thereby all harmful rays can be blocked. Here, if the range to which the metal coat 1f is applied is set to be larger than necessary, all the effective light beams will be blocked or the amount of the effective light beams will be blocked on the entrance surface 1a of the view direction conversion prism 1. The range in which the metal coat 1f is applied is limited to the minimum necessary range for reflecting all harmful rays. In the present embodiment, the range to which the metal coat 1f is applied is the distance t ₁ (= 0.42 mm) from the intersection of the second reflection surface 1c of the view direction changing prism 1 and the optical axis to the optical axis side in the perspective direction. The range is from the moved position to the ridgeline between the second reflecting surface 1c and the exit surface 1d. Also, among harmful rays that enter through the cover glass 4, those that have a bright point below the optical axis from the perspective direction and that have passed through the entrance surface 1a of the view direction changing prism 1 will be described with reference to FIG. As described above, after being reflected by the first reflecting surface 1b of the field-of-view direction conversion prism 1, it is absorbed by the edge of the stabilizing optical element 2 and does not reach the image plane.

In order to have such an action, in the visual field direction changing optical system of the present embodiment, the optical axis of the stabilizing optical element 2 at the exit surface 1d of the visual field direction changing prism 1 joined to the stabilizing optical element 2. The effective radius a of the field-of-view direction conversion prism 1 on the side of the first reflection surface 1b is 0.78 mm. Further, in the visual field direction changing optical system of this embodiment,
The relationship between the value of a and the outer diameter φ of the stabilizing optical element 2 is a / φ = 0.14.

As described above, according to the visual field direction changing optical system of the present embodiment, only the effective light flux necessary for forming the object image in the oblique direction is guided to the image plane, and the harmful ray is prevented from entering the image plane. Since this can be prevented, a good observation image can be obtained without causing ghosts and flares when an object observation image is observed.

Further, in the visual field direction changing optical system of this embodiment, the visual field direction changing prism 1 and the stabilizing optical element 2 both have a shape like a cylinder cut into a circular slice, and therefore the relative direction between the two. The positioning can be easily performed. Further, by joining the two, the length of the stabilizing optical element 2 in the optical axis direction with respect to the outer diameter direction is made longer as compared with the case where each of them is used alone. It is possible to suppress backlash and prevent decentering of the optical system. Therefore, it is possible to suppress the deviation of the visual field direction and the occurrence of the relative point aberration, and prevent the deterioration of the optical performance. At this time, the shape of the stabilizing optical element 2 is such that the thickness d of the stabilizing optical element 2 in the optical axis direction is 3.22 mm, and the relationship between the value of this d and the outer diameter φ of the stabilizing optical element 2. , D / φ = 0.56 is satisfied.

Further, in the visual field direction changing optical system of this embodiment,
No aperture is used to block harmful rays and prevent them from reaching the image plane. Therefore, the number of parts can be reduced as compared with the case of using the mechanical diaphragm. Further, since the step of positioning the diaphragm with respect to the optical axis and performing the bonding in the case of the mechanical diaphragm and the vapor deposition in the case of the vapor deposition diaphragm are not necessary, the manufacturing cost can be further reduced. Furthermore, since the entrance pupil position can be arranged in the visual field direction conversion prism 1, the size of the effective luminous flux diameter on each surface of the visual field direction conversion prism 1 is reduced, and the vignetting of the effective luminous flux on each surface is suppressed. For this purpose, it is preferable to select a material having a large refractive index as the material forming the visual field direction conversion prism 1 and set the optical path length as long as possible. Therefore, in the visual field direction changing optical system of the present embodiment, the refractive index is 1.
The visual field direction conversion prism 1 is configured by using the material 81. Further, in the visual field direction changing optical system of the present embodiment, the inner frame 6 having the cross section 6a on the incident surface 1a side, the cross section 6a having the same direction as the incident plane 1a of the visual field direction changing prism 1, and the receiving portion for receiving the cross section 6a. And an outer frame 7 having a portion 7a. Therefore, the cross section 6 a of the inner frame 6 and the receiving portion 7 of the outer frame 7
By aligning with a, it is possible to easily align the position in the rotational direction of the visual field direction conversion prism 1.

Second Embodiment FIG. 2 is a sectional view taken along the optical axis showing the configuration of the endoscope visual field direction changing optical system according to the present embodiment. This endoscope field-of-view direction changing optical system is arranged and used at the tip portion of the endoscope. In the visual field direction changing optical system of this embodiment,
Of the harmful rays incident through the cover glass 4, those having a bright spot below the optical axis from the perspective direction and transmitted through the incident surface 1a of the view direction changing prism 1 are the view directions of the first embodiment. Similar to the conversion optical system, the light is reflected by the first reflection surface 1b of the view direction conversion prism 1 and then absorbed by the edge of the stabilizing optical element 2, or the view direction conversion prism 1
It is configured to be absorbed by the chamfered portion for shading provided on the ridge line portion of the first reflection surface 1b and the exit surface 1d. Further, the shape of the stabilizing optical element 2 used in the visual field direction changing optical system of the present embodiment is such that the stabilizing optical element 2 has a thickness d in the optical axis direction of 4.43 mm and an outer diameter of the stabilizing optical element 2. The relationship with φ is configured to satisfy d / φ = 0.78. The other configurations are the same as those of the visual field direction changing optical system of the first example.

Third Embodiment FIG. 3 is a sectional view taken along the optical axis showing the configuration of the endoscope field-of-view direction changing optical system according to the present embodiment. This view direction changing optical system is configured by arranging a cover glass 4, a concave lens 5, a correction prism 3, a view direction changing prism 1 and a stabilizing optical element 2 in this order from the object side in the perspective direction. Further, the concave lens 5, the correction prism 3, the visual field direction changing prism 1 and the stabilizing optical element 2 are housed in the inner frame 6, and the cover glass 4 is formed integrally with the outer frame 7. The exit surface 3b of the correction prism 3 and the entrance surface 1a of the view direction changing prism 1 are joined together, and the exit surface 1d of the view direction changing prism 1 is joined to the entrance surface 2a of the stabilizing optical element 2. . The correction prism 3, the field-of-view direction conversion prism 1, and the stabilizing optical element 2 all have a shape like a cylinder cut into a circle, and their outer diameter φ is 5.
It is 7 mm.

The field-of-view direction converting optical system of this embodiment is different from the first and second examples in that the correction prism 3 is joined to the object side of the field-of-view direction converting prism 1 and the perspective direction is set to 30 °. It differs from what is shown. The incident surface 3a of the correction prism 3 is disposed perpendicular to the incident optical axis from the perspective direction of 30 degrees, and the incident surface 3a of the correction prism 3 and the incident surface 1a of the view direction changing prism 1 (second reflection). Surface 1
c), stabilizing optical element 2 having first reflecting surface 1b and exit surface 1d
The angles θ, θ ₁ , θ ₂ , and θ _{3 with} respect to the optical axis are 60
It is set to °, 45 °, 30 ° and 90 °. Furthermore,
In the visual field direction changing optical system of the present embodiment, of the harmful rays incident through the cover glass 4, the incident surface 1 of the visual field direction changing prism 1 has a bright point below the optical axis from the perspective direction.
The light that has passed through a is not reflected by the first reflection surface 1b of the visual field direction conversion prism 1 and then absorbed by the edge of the stabilizing optical element 2 and so does not reach the image plane.

In order to have such an action, in the present embodiment, the viewing direction about the optical axis of the stabilizing optical element 2 at the exit surface 1d of the viewing direction changing prism 1 joined to the stabilizing optical element 2 is used. First reflection surface 1b of conversion prism 1
The effective radius a on the side is 1.42. Further, in the visual field direction changing optical system of the present embodiment, the relationship between the value of a and the outer diameter φ of the stabilizing optical element 2 is defined as a / φ = 0.25.

Further, in the present embodiment, of the harmful rays incident through the cover glass 4, as the light shielding means for the rays having a bright point above the optical axis from the perspective direction, the incident surface of the view direction changing prism 1 is used. A second reflecting surface 1c formed by applying a metal coat 1f to 1d is used. Metal coat 1
f is a distance t ₂ (= 1.35) from the intersection of the second reflection surface 1c of the visual field direction conversion prism 1 and the optical axis toward the optical axis in the perspective direction.
mm) to a ridgeline between the second reflection surface 1c and the exit surface 1d.

Further, in the visual field direction changing optical system of this embodiment,
In order to suppress the deterioration of the optical performance due to the deviation of the visual field direction and the astigmatism caused by the backlash that occurs when incorporated in the endoscope, the stabilizing optical element 2 is used, and this is used as the visual field direction conversion prism 1. It is joined. In the present embodiment, regarding the shape of the stabilizing optical element 2, the thickness d of the stabilizing optical element 2 in the optical axis direction is 3.34 mm, and the relationship between the value of this d and the outer diameter φ of the stabilizing optical element 2. Is configured to satisfy d / φ = 0.59. Further, in the visual field direction changing optical system of the present embodiment, the correction prism 3 is arranged so that the incident optical axis from the oblique direction is made incident perpendicularly to the incident surface 3a of the correction prism 3. This suppresses the generation of astigmatism.

By the way, in this type of field-of-view direction changing optical system, an astigmatism is likely to occur because an incident light ray from the oblique direction does not enter perpendicularly to the incident surface 1a of the field-of-view direction converting prism 1. However, in this embodiment, since the incident surface 1a of the visual field direction conversion prism 1 is joined to the exit surface 3b of the correction prism 3, the medium is the correction prism 3 near the incident surface 1a of the visual field direction conversion prism 1.
The material, the adhesive, and the material of the visual field direction conversion prism 1 are changed. Therefore, in this embodiment, the correction prism 3 is not arranged (in this case, the medium changes from the air to the material of the visual field direction conversion prism 1).
Compared with, the change in refractive index is small and the occurrence of astigmatism is also small.

Further, in the visual field direction changing optical system of this embodiment,
The exit surface 3b of the correction prism 3 and the visual field direction conversion prism 1
Since the light-incident surface 1a of the correction prism 3 is joined to the light-incident surface 1a of the field-of-view direction conversion prism 1, the light-incident surface 1a of the field-of-view direction conversion prism 1 is coated with a metal coat 1f instead of the second reflective surface 1c. May be given. Therefore, even if only one reflecting surface is provided on the view direction changing prism 1 for some reason, the view direction changing optical system of the present embodiment can sufficiently exert the effect. Also, the viewing direction conversion prism 1
In order to reduce the vignetting of the effective light flux on each surface, it is preferable to select a material having a large refractive index as the material of the field-of-view direction conversion prism 1 and configure the optical path length as long as possible. Therefore, in the optical system of the present embodiment, the visual field direction conversion prism 1 is made of a material having a refractive index of 1.88.

Further, in the visual field direction changing optical system of this embodiment,
An inner frame 6 having a cross section 6a on the side of the incident surface 3a, the cross section 6a of which is aligned with the direction of the incident surface 3a of the correction prism 3,
An outer frame 7 having a receiving portion 7a for receiving is provided. Therefore, by aligning the cross-section 6a of the inner frame 6 with the receiving portion 7a of the outer frame 7, it is possible to easily align the visual field direction conversion prism 1 in the rotational direction.

Further, by making the refractive index of the correction prism 3 and the refractive index of the material of the field-of-view direction conversion prism 1 the same, the light ray passing through the correction prism 3 and the first reflection surface 1b of the field-direction conversion prism 1 are made. The reaching light beam is parallel and suppresses the generation of astigmatism. At this time, the adhesive formed between the correction prism 3 and the field-of-view direction conversion prism 1 also has the same refractive index as that of the correction prism 3 and the field-of-view direction conversion prism 1 or is formed as close as possible. The thickness of the agent layer is also preferably as thin as possible.

Fourth Embodiment FIG. 4 is a sectional view taken along the optical axis showing the structure of the endoscope visual field direction changing optical system according to the present embodiment. In this embodiment, the frame structure is omitted and only the optical system portion is shown. This view direction changing optical system is provided with a cover glass 4, in order from the object side.
Concave lens 5, correction prism 3, view direction changing prism 1
And the stabilizing optical element 2 are arranged.
The exit surface 3b of the correction prism 3 and the visual field direction conversion prism 1
Is joined to the entrance surface 1a of the stabilizing optical element 2 and the exit surface 1d of the view direction changing prism 1 and the entrance surface 2a of the stabilizing optical element 2.
And are joined. The correction prism 3, the field-of-view direction conversion prism 1 and the stabilizing optical element 2 are all shaped like a circular cylinder, and their outer diameter φ is 1.65.
mm.

In the visual field direction changing optical system of this embodiment, the perspective direction is set to 30 ° as in the case of the third embodiment. Further, the incident surface 3a of the correction prism 3 is also arranged perpendicularly to the incident optical axis from the perspective direction of 30 degrees, and the incident surface 3a of the correction prism 3 and the incident surface 1a of the view direction changing prism 1 (first 2 reflective surfaces 1c), first reflective surface 1
b, the angles θ, θ ₁ , θ ₂ , and θ ₃ of the exit surface 1d with respect to the optical axis of the stabilizing optical element 2 are 60 °, 45 °, 30 °,
It is set to 90 °. Further, in the visual field direction changing optical system of the present embodiment, of the harmful rays incident through the cover glass 4, there is a bright point below the optical axis from the perspective direction, and the incident surface 1a of the visual field direction changing prism 1 is present. The one that is transmitted through
Since it is reflected by the first reflecting surface 1b of the visual field direction conversion prism 1 and then absorbed by the edge of the stabilizing optical element 2, it does not reach the image plane.

In order to have such a function, in the visual field direction changing optical system of this embodiment, the visual field direction changing prism 1 is used.
The effective radius a on the first reflecting surface 1b side of the field-of-view direction conversion prism 1 centered on the optical axis of the stabilizing optical element 2 on the exit surface 1d is set to 0.35, and the value of this a and the stabilizing optical element 2 are set.
The outer diameter φ of is defined as a / φ = 0.21.

Further, of the harmful rays incident through the cover glass 4, as a means for blocking a ray having a bright spot above the optical axis from the perspective direction, the view direction conversion prism 1 is used.
The second reflecting surface 1c formed by applying the metal coat 1f to the incident surface 1a of is used. Here, the metal coat 1f
The range to be applied is a distance t ₃ from the intersection of the second reflection surface 1c of the visual field direction conversion prism 1 and the optical axis to the optical axis side in the perspective direction.
It extends from the position moved by (= 0.27 mm) to the ridgeline of the second reflecting surface 1c and the exit surface 1d.

Further, in the visual field direction changing optical system of this embodiment,
In order to suppress the deterioration of the optical performance due to the deviation of the visual field direction and the astigmatism caused by the backlash that occurs when incorporated in the endoscope, the stabilizing optical element 2 is used, and this is used as the visual field direction conversion prism 1. It is joined. In this embodiment, the shape of the stabilizing optical element 2 is such that the thickness d of the stabilizing optical element 2 in the optical axis direction is 1.73 mm, and the relationship between the value of this d and the outer diameter φ of the stabilizing optical element 2. Is configured to satisfy d / φ = 1.05.

Further, in the visual field direction changing optical system of the present embodiment, the first reflecting surface 1b and the second visual plane of the visual field direction changing prism 1 are arranged.
A reflection enhancing film is added to the metal coatings 1e and 1f of the reflecting surface 1c on the side of the view direction changing prism 1. By adding this reflection-enhancing film, the reflectance of one reflecting surface can be improved by 7% or more as compared with the case where only the metal coat is used.
The field of view can be brightened by 4% or more. in this way,
By adding the reflection film enhancing film to the metal coat, it is possible to provide an endoscope visual field direction changing optical system having a brighter visual field than conventional. Incidentally, the reflection enhancing film, if necessary,
It will be added to one or both of the two sided metal coats.

Fifth Embodiment FIG. 5 is a sectional view taken along the optical axis showing the configuration of the endoscope visual field direction changing optical system according to the present embodiment. The configuration of the visual field direction changing optical system of this embodiment is basically the same as that shown in the fourth embodiment. That is, the visual field direction changing optical system of the present embodiment is configured by disposing the cover glass 4, the concave lens 5, the correction prism 3, the visual field direction changing prism 1 and the stabilizing optical element 2 in this order from the object side. The exit surface 3b of the correction prism 3 and the entrance surface 1a of the visual field direction conversion prism 1 are joined together, and the visual field direction conversion prism 1 is also provided.
The exit surface 1d of the above is joined to the entrance surface 2a of the stabilizing optical element 2. Correction prism 3, viewing direction conversion prism 1
The stabilizing optical element 2 and the stabilizing optical element 2 all have a shape like a cylinder cut into a circle, and their outer diameter φ is 5.7 mm.

Of the harmful rays incident through the cover glass 4, in order to shield the rays having a bright point below the optical axis from the oblique direction, the view direction changing optical system of the present embodiment uses the view direction. The effective radius a on the first reflection surface 1b side of the field-of-view direction conversion prism 1 centered on the optical axis of the stabilization optical element 2 on the exit surface 1d of the conversion prism 1 is 1.22, and the value of this a and the stabilization optics The relationship with the outer diameter φ of the element 2 is defined as a / φ = 0.21.

Of the harmful rays incident through the cover glass 4, the view direction conversion prism 1 serves as a means for blocking the rays having a bright spot above the optical axis from the oblique direction.
The second reflecting surface 1c formed by applying the metal coat 1f to the incident surface 1d of is used. The range where the metal coat 1f is applied is a distance t ₄ (= 1.2) from the intersection of the second reflection surface 1c of the visual field direction conversion prism 1 and the optical axis toward the optical axis in the perspective direction.
1 mm) to the ridgeline of the second reflecting surface 1c and the exit surface 1d.

Further, in the visual field direction changing optical system of this embodiment,
In order to suppress the deterioration of the optical performance due to the deviation of the visual field direction and the astigmatism caused by the backlash that occurs when incorporated in the endoscope, the stabilizing optical element 2 is used, and this is used as the visual field direction conversion prism 1. It is joined. In the present embodiment, the shape of the stabilizing optical element 2 is such that the relationship between the thickness d of the stabilizing optical element 2 in the optical axis direction and the outer diameter φ of the stabilizing optical element 2 is d / φ = 0.46. It is structured to satisfy.

As described above, the endoscope visual field direction changing prism according to the present invention has the following features (1) to (9) in addition to the features described in the claims. .

(1) The field of view for an endoscope according to claim 1, wherein the ridge line between the first reflecting surface and the exit surface of the field-of-view direction changing prism is chamfered for light shielding. Direction changing optics.

(2) An incident surface, which is arranged on the object side of the visual field direction conversion prism, is arranged perpendicular to the incident optical axis from the perspective direction and transmits the light beam from the object side, and transmits the incident surface. 2. A correction prism comprising an exit surface for transmitting a light beam to the side of the view direction changing prism, wherein the exit surface of the correction prism is joined to the entrance surface of the view direction changing prism. A visual field direction changing optical system for an endoscope according to.

(3) The endoscope according to the above (2), wherein a metal coat is applied to the exit surface of the correction prism instead of the metal coat of the second reflecting surface of the view direction changing prism. Viewing direction changing optical system.

(4) In all or either of the metal coatings on the first and second reflecting surfaces of the view direction changing prism, a reflectance enhancing film is added to the view direction changing prism side of the metal coat. The visual field direction changing optical system for an endoscope according to claim 1 or (3).

(5) The view direction changing optical system for an endoscope according to claim 1, wherein the view direction changing prism is made of a material having a refractive index of 1.8 or more.

(6) The endoscope visual field according to (2), wherein the refractive index of the material forming the correction prism is the same as the refractive index of the material of the visual field direction changing prism. Direction changing optics.

(7) The shape of the stabilizing optical element satisfies the following conditional expression:
A visual field direction changing optical system for an endoscope according to. 0.3 ≦ d / φ ≦ 1.2 where φ is the outer diameter of the stabilizing optical element, and d is the thickness of the stabilizing optical element in the optical axis direction.

(8) A frame having a cross section whose direction coincides with the incident surface of the visual field direction changing prism on the incident surface side of the visual field direction converting prism is integrally joined to the visual field direction converting prism. The visual field direction changing optical system for an endoscope according to claim 1.

(9) A frame having a cross section whose direction coincides with the direction of the incident surface of the correction prism on the incident surface side of the correction prism is integrally joined to the correction prism. The visual field direction changing optical system for an endoscope according to (2).

[0054]

As described above, according to the endoscope field-of-view direction changing optical system of the present invention, harmful rays that may cause ghosts and flares can be removed, so that a better endoscopic image can be obtained. Obtainable. Further, the manufacturing cost can be reduced by reducing the number of parts.

[Brief description of drawings]

FIG. 1 is a sectional view taken along the optical axis showing the configuration of a visual field direction changing optical system for an endoscope according to a first example.

FIG. 2 is a sectional view taken along the optical axis showing the configuration of the endoscope visual field direction changing optical system according to the second example.

FIG. 3 is a sectional view taken along the optical axis showing the configuration of a field-of-view direction changing optical system for an endoscope according to a third example.

FIG. 4 is a sectional view taken along the optical axis showing the configuration of a visual field direction changing optical system for an endoscope according to a fourth example.

FIG. 5 is a sectional view taken along the optical axis showing the configuration of a field-of-view direction changing optical system for an endoscope according to a fifth example.

FIG. 6 is a diagram for explaining a basic configuration of a visual field direction changing optical system for an endoscope of the present invention.

FIG. 7 is a diagram for explaining the basic configuration of a conventional endoscope field-of-view direction changing optical system.

FIG. 8 is a sectional view taken along the optical axis showing the configuration of a conventional endoscope field-of-view direction changing optical system.

FIG. 9 is a sectional view taken along the optical axis showing the configuration of a conventional endoscope field-of-view direction changing optical system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Field-of-view direction conversion prism 1a Incident surface 1b 1st reflective surface 1c 2nd reflective surface 1d Exit surface 1e, 1f Metal coat 2 Stabilizing optical element 2a Incident surface 3 Correction prism 3a Incident surface 3b Exit surface 4 Cover glass 5 Concave lens (unit ) 6 inner frame 6a cross section 7 outer frame 7a receiving part 10 diaphragm

Claims (1)

[Claims] 1. An endoscope capable of observing an object in a perspective direction, wherein a first surface is provided with an incident surface for transmitting a light beam from the object side and a metal coat for reflecting the light beam transmitted through the incident surface. Second reflecting surface and the second reflecting surface formed by selectively applying a metal coat to the incident surface in order to reflect the light flux reflected by the reflecting surface and the first reflecting surface to the image side. A field-of-view direction conversion prism composed of an exit surface that transmits the light beam reflected by the surface to the image side, and a stabilizing optical element bonded to the exit surface of the field-of-view direction conversion prism. A field-of-view direction conversion optical system for an endoscope, wherein the shape of the conversion prism and the stabilizing optical element satisfy the following conditional expressions. 0.1 ≦ a / φ ≦ 0.3 where φ is the outer diameter of the stabilizing optical element, and a is the effective radius at the exit surface of the view direction changing prism joined to the stabilizing optical element.