JPS6198316A - Optical system for strabismus - Google Patents

Abstract

PURPOSE:To reflect normal light rays to guide it to an eyepiece system and to transmit light rays to be ghost to suppress the generation of the ghost by forming a low refractive index layer on the outside of the 1st reflecting surface of a visual field converting prism. CONSTITUTION:Normal light (a) to be observed is made incident upon the 2nd prism 11 through an inclined concave lens 1 and the 1st prism 9, totally reflected by the 1st reflecting surface 10, reflected by the 2nd reflecting surface, and then guided into the eyepiece system through an iris. On the other hand, light (b) to be superposed to the course of the normal light (a) as a ghost is similarly made upon the 2nd prism 11 through the lens 1 and the prism 9 and transmitted without reflection because a MgFe layer 14 exists in the 1st reflecting surface 10 and a critical angle on the 1st reflecting surface 10 is increased. The transmitted light is absorbed by an absorbing layer, so that ghost light is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a strabismus optical system for a rigid endoscope.

[Conventional technology]

As a conventional optical system for strabismus, there is one example, JP-A-50-91.
There is one disclosed in No. 333.

Figure 3 shows the objective lens part of this optical system.
The objective lens Lu is composed of a front lens group L1, which is a combination of an inclined concave lens 1, a first prism 2, a second prism 3, and a convex lens 4, and a rear lens group L2.
The source that is incident obliquely with respect to the longitudinal direction of the hard internal record passes once through the boundary between the first prism 2 and the second nibism 3, and then is reflected by the first reflection surface 5 and the second reflection surface 6 of the second nibism 3. It is designed to be ejected in a direction that coincides with the longitudinal direction of the rigid endoscope. However, in the case of this optical system for strabismus, the first reflective surface 5 of the first nibism 3 is at a fairly large angle with the longitudinal direction of the rigid endoscope. As a result, the outer diameter of the first nibism 3 is small, and considering that it is placed inside the tip of an endoscope with a small diameter, processing the second nibism 3 and roughening the objective lens Lo is extremely troublesome. There was a problem with becoming. In addition, since the length of the nibrism 3 is shortened, it tilts and the deviation in the viewing direction increases (this is likely to occur).
There was a problem. Furthermore, since the function of the rear end surface 7 of the second nib lens 3 has to be reduced, in the case of a wide (bright) optical system with a single beam, there is a problem that the beam is distorted and the loss of light amount is large. Furthermore, in the case of this optical system for strabismus,
Air f;' at the boundary between the first prism 2 and the second prism 3
3B is provided, and transmission and reflection are performed at this boundary by utilizing the refractive straw between this air layer 8 and each prism 2.3, but the objective lens L is extremely small.

It is difficult to provide an air layer in the front lens group L1 of
As a result, there was a problem that assembling the objective lens Lo became even more troublesome.

As a solution to these drawbacks, the applicant has disclosed the following in Japanese Patent Application No. 58-245549. As shown in Fig. 4, the front group LI of the objective lens spring is replaced by the inclined concave lens 1
and the first set perpendicular to the direction of the incident ff11kl field, g −jUib9 and 8−reflection “1°
'Hard internal sharpening 0 1st nibism parallel to the longitudinal direction
It is constructed from a visual field conversion prism system and a convex lens 4. Here, the image of the brightness diaphragm of the rigid mirror optical system as a whole determined by the optical system behind this (relay lens system, eyepiece, etc.) can be considered as the virtual diaphragm 12. The interface between the prism 9 and the second prism 11 is made to form an acute angle with the longitudinal direction of the rigid endoscope. As the second reflective surface 13 of the second nibism 11,
This interface is bonded with adhesive, and at the same time the following condition 3 α Icos (-α) l <−< l cos (1)
l.

2 nG (α is the viewing direction angle, nc is the refractive index of the adhesive, and flG is the refractive index of both prisms), and the incident light ray is reflected by the first reflective surface 10 and then reflected by the second reflective surface 13. The structure is simple and easy to assemble by increasing the length of the first nibism 11 and adhering the first prism 9 and the second nibism 11, as described above. This solution solves the conventional drawbacks of .

[Problem that the invention seeks to solve]

However, in this optical system for perspective viewing, as shown in FIG. After being totally reflected at point b of the IO, it is reflected at point C at the interface between the second nib lism 11 and the adhesive, and overlaps the path of the normal ray a, which has the disadvantage that good image quality cannot be obtained.

The present BA was created by focusing on these problems, and aims to provide an optical system for strabismus that is small in diameter, easy to process and assemble in one part, and has no ghost and excellent image quality. purpose.

Measures to Solve Problem C] In this optical system for oblique viewing, as shown in FIG. There is a prism 11 that directs the reflection from a first reflective surface 10 and a second reflective surface 13 toward the longitudinal direction of the endoscope, and the first reflective surface 10 of this prism 11
A layer 14 having a refractive index lower than that of the prism 11 is provided on the outside of the prism 11 .

Furthermore, an absorption layer 15 is provided outside the low refractive index layer 14.

[Effect]

According to this configuration, by providing the low refractive index layer 14 on the outside of the first reflective surface 10 of the visual field conversion prism 11, the rear view that is totally reflected on the first reflective surface 10, which is the normal ray to be observed, is reflected. The light beam is reflected by the second reflective surface 13 and guided to the eyepiece system (not shown), and becomes a ghost.

In addition, by further providing absorption 1→15 on the outside of the four low refractive index layers 14, the light beam aperture transmitted by the first reflective surface 10, which becomes a ghost, is absorbed, and this transmitted light beam aperture has a low refractive index. This prevents ghost rays from being reflected off the outer surface of layer 14. This absorption layer 15 also plays the role of blocking light rays entering from the outside.

〔Example〕

FIG. 1 and FIG. 2 are diagrams showing one embodiment of the present invention,
This is an enlarged view of only the outside of the field conversion prism system at the tip of the objective lens.
It is similar to the one shown in the figure. The visual field conversion prism system of this embodiment is as shown in FIG. The second prism 11 is configured to form an acute angle with the longitudinal direction of the rigid endoscope, which is the interface between the first prism 9 and the second nibism 11. 13, and this interface is joined with adhesive, and at the same time, the following conditions (α is the viewing direction angle, n (is the refractive index of the adhesive, and n (H is the refractive index of both prisms) A transmission layer 14 of MgFz having a refractive index lower than that of the first niblism 11 is provided on the outside of the first reflective surface 10, and a layer of carbon, etc. An absorbent layer 15 made of black paint is provided.

In addition, the viewing direction angle α and the refraction of the first niblism 11 *nG
It is preferable that the following relationship be satisfied between the refraction i nu of the transmission N14 and the refraction i nu of the transmission N14.

From this relationship ′L2f′I4, the viewing direction angle α
The light that is incident parallel to , that is, the light that is incident on the reflection surface 10 of the second prism 11 at an incident angle of 90''-α, is totally reflected, and the incident light that overlaps as a ghost on the path of this light, that is, the second prism 11 Light incident on the first reflecting surface 1° at an incident angle of 90°-2α is transmitted.

Furthermore, the thickness of the transmission layer 14 (transmission/?!14 thickness) x (transmission layer 14 thickness FT''4
nM) should be at least 1.2 times the wavelength used (in this case, since it is visible light, the maximum wavelength is 700 nm). By setting the film thickness in this way, it is possible to almost prevent light leakage, and to prevent the image from becoming dark due to light loss.

Next, the action based on 6 above? This will be explained using FIG.

The normal ray A to be observed enters the second nib prism 11 via the inclined concave lens l and the first prism 9, is totally reflected by the fringe-reflecting surface lO, and then is reflected by the second reflective surface 13.
It passes through an aperture (not shown) and is guided to the eyepiece system. On the other hand, the ray aperture that overlaps the path of the normal ray A and becomes a ghost is
Similarly, the light is incident on the second nibism 11 via the inclined concave lens l and the first prism 9.

Since there is MgF2R14 on the first reflective surface 10, the critical angle of this surface is large, so the light is transmitted without being reflected.The light then reaches the absorption layer 15 and is absorbed, so that it does not become a ghost light.

The relationship between the refractive index and the specific shape of the prism will be described below. - As an example, 30jMiJ2 is shown. The specific data is as follows.

Refractive index of first prism 9 nG: 1.7859 Refractive index of second prism 11 nQ = 1.7859 Refractive index of adhesive nC
= 1.56 Refractive index nB4 of transmission layer 14 = 1.38 transmission/! 14
The film thickness d = 0.7 μm during the maximum flame λ of the used wavelength 700
nm Included angle θ1 between the inclined concave lens 1 of the first prism 9 and the second nibism 11 = 45° Included angle θz between the first prism 9 of the first nibism 11 and the transparent layer 14 = 15' From the above data, the adhesive and the nibism What is the total reflection angle with 11? , 8'', and the total reflection angle between the transmission layer 14 and the second niblism 11 is 50.6°.

With this configuration, after light approximately parallel to the viewing direction passes through the lens 1, it is transmitted because the incident angle θ3 = 45° at the interface point C between the layer agent and each prism 9, 11, and the MgFz vapor deposited film is transmitted. At point d on the interface between No. 14 and No. 11, θ4=
Since the angle is 60°, there is total reflection, and the adhesive and Nibrism 1
At point e on the interface with 1, total reflection occurs at θ5=75°, and 4
Pass through the current 1''!J white eyepiece and observe.

On the other hand, the ghost and 7L rays, which are reflected four times within the real nibism 11 that overlaps with the above-mentioned rays, are incident at point a on the interface between the reverse sludge and each prism 9° 11 after passing through the inclined concave/space 2. Since the angle θ6=15°, &L passes, and IVigF2
At the interface between the vapor deposited film 14 and the meni prism 11, the incident angle θy=30'. Therefore, -IJ! permeates inside the MgFz vapor deposited film. It is absorbed at i yield no' + 15 and does not become a ghost.

Also, in this example, The optical 'FIk loss can also be sufficiently suppressed.

Here, in this example, the state in which the vapor deposited film 14 of RIgFz and the absorption layer 15y are not applied, that is, the nibrism 11O
) Considering the case where the second reflective rice cake 10 is in contact with air, the critical angle between the air and the second niblism 11 is θ=34'
Therefore, the above-mentioned light rays that become ghosts do not become ghost rays because they are transmitted out of the first nib 11 at the first reflective surface 10 where the ni brism 11 is in contact with the air. , since the actual observation light has an opening width of about 8 degrees on both sides of the viewing direction in the glass, this light ray is totally reflected at the first reflecting surface 10 and becomes a ghost. There is. Also, Nibrism 1111)! - There is a possibility that 7 rare light rays may enter from outside the reflective surface 10.

Furthermore, during assembly, adhesive easily sticks to this surface, and if it is left at a temperature that exceeds 30 degrees Fahrenheit, normal light rays will pass through without being totally reflected on this surface.

Therefore, in order to prevent the Nibrism 11 from coming into contact with air, it is possible to apply aluminum vapor deposition only to the areas through which normal light rays pass, and to apply paint to serve as an absorbing layer to the other areas, but this method is not applicable. is not suitable for this embodiment because it is limited to cases where the positions on the reflecting surface through which the normal ray and the ghost ray pass are completely different. Also, even if it can be used, is aluminum steaming fft? Applying it to a certain limited area is difficult because the prism is minute.

Next, preferred conditions for the refractive index of the vapor-deposited material in the embodiment having the above-mentioned characteristics will be described.

11f) The angle of incidence of the normal ray on the first reflecting surface lO? Considering this, an element that is incident parallel to the viewing direction is incident at an incident angle θc=60°. Considering the spread width 8@ of the observation light, the angle of incidence has a range of 52° to 68''.On the other hand, the original light that becomes a ghost that overlaps the normal ray, which is reflected 4 times within the nibrism 11, The initial angle of incidence on the first reflecting surface lO is θ4 = 30', so it has a width of 226 to 38 degrees.From the above, the critical angle should be between 38 and 52. It is particularly advantageous to set the refractive index of the deposited material to .

Since the refractive index of the prism is tlG=1.7859.

The refractive index of the deposited material is HM=1. It can be seen that a value between 1 and 1.407 is particularly good.

[Effects of the Invention] As described above, the optical system for strabismus according to the present invention provides a low refractive index layer on the outside of the first reflective surface of the field conversion prism, so that normal light rays are reflected and the optical system for strabismus is reflected. This is an optical system with excellent image quality that guides the image to the image and transmits the rays that cause ghosts, thereby preventing the generation of ghosts.It is a simple four-component optical system that is easy to assemble and has high precision.

Furthermore, an absorbing layer is placed on the outside of this low refractive NA scrap! This makes it possible to more completely remove ghost light and prevent the incidence of 7-rare light from the outside.

FIGS. 3 and 4 are diagrams showing a conventional perspective view optical system for endoscopy, and FIG. 5 is an enlarged view of the main part of FIG. 4.

Claims (2)

[Claims] (1) In an optical system for strabismus equipped with a visual field conversion prism that reflects light incident from a diagonal direction on a first reflective surface and a second reflective surface and directs it in the longitudinal direction of an endoscope, the first An optical system for strabismus, characterized in that a layer having a refractive index lower than that of the prism is provided outside the reflective surface. (2) The optical system for strabismus according to claim 1, characterized in that an absorption layer is provided outside the low refractive index layer.