JPS5856848B2 - Shashiyoukogakkei - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a strabismus optical system in which the observation direction is at a constant angle with respect to the image transmission direction (length direction), which is used in a long and narrow image transmission optical system such as an endoscope. It is related to the system.

Generally, the end objective system of a long and narrow image transmission optical system is required to be small, and in particular, it is required to be smaller in the outer diameter direction than in the length direction.

For example, if the outer diameter of an endoscope is the same as that of a dog,
This is due to the fact that the insertion is painful for the patient.

Furthermore, depending on the location to be observed, the outer diameter may be physically limited, and depending on the size of the outer diameter, insertion may become impossible.

For example, in a cystoscope or the like, the outer diameter is limited to a very small diameter of 2 to 3 mm.

Optical systems placed within such a limited outer diameter are intended for purposes other than direct viewing, and include side viewing where the viewing direction is 90° to the length direction and strabismus where the viewing direction is 60°. Ma,
This can be achieved by using a 45° right-angle prism or a 300° right-angle prism, but in the case of strabismus at other angles, for example, when observing in a direction 30° to the direct viewing direction, the strabismus shown in Figure 1 A and B can be achieved. Therefore, the length shown by a in the drawings is long, and the above-mentioned requirement to reduce the outer diameter cannot be satisfied.

Further, if the outer diameter is made small as required above, it becomes impossible to obtain a sufficient effective diameter at the entrance/exit surface with an optical system arranged as shown in FIG.

The present invention has been made in view of the above-mentioned circumstances, and it overcomes the above-mentioned defects by giving a viewing direction converting prism used for changing the viewing direction for strabismus a refractive effect. The object of the present invention is to provide an optical system for strabismus in which astigmatism caused by a viewing direction conversion prism having a refractive effect is removed by a correction prism provided separately from the prism.

The details of the optical system of the present invention will be explained below based on the drawings. FIG. 2 shows an embodiment of the present invention.

In this figure, the part indicated by reference numeral 1 is the tip of an endoscope, etc., and 2 is an objective lens system.

A correction prism 3 and a visual field direction conversion prism 4 are arranged at the tip of the objective lens system 2.

Further, a concave lens 5 is arranged in front of the correction prism 3,
Together with the objective lens system 2, it forms a retrofocus type super wide-angle lens system.

The correction prism 3 and the visual field direction conversion prism 4 have the shapes shown in the figure, and the correction prism 3 has an entrance surface 3a located almost perpendicular to the incident optical axis from the oblique direction, and an incident surface 3a located almost perpendicular to the incident optical axis from the oblique direction. and a refractive surface 3b arranged so as to emit light.

The visual field direction conversion prism 4 also includes a refractive surface 4a that is close to the refractive surface 3b of the correction prism 3 and that refracts the optical axis emitted from the refractive surface 3b, and a refractive surface 4a that refracts the optical axis refracted by the refractive surface 4a. It has a reflecting surface 4b that reflects the light back toward the refractive surface 4a, and an exit surface 4C that is located substantially perpendicular to the direct viewing direction from which the optical axis reflected by the refractive surface 4a and directed toward the direct viewing direction exits.

Each prism is constructed and arranged so that the magnitude of refraction of the refraction surface 3b of the correction prism 3 and the magnitude of refraction of the refraction surface 4a of the viewing direction conversion prism 4 are approximately equal.

Here, the magnitude of refraction of the refraction surface 3b of the correction prism 3 and the magnitude of refraction of the refraction surface 4a of the viewing direction conversion prism 4 are equal, which means that the incident optical axis is refracted by the refraction surface 3b and exits from the correction prism 3. Then, when it is refracted by the refracting surface 4a and enters the field of view, the optical axis before being refracted by the Δ-refractive surface 3b and the optical axis after being refracted by the refractive surface 4a are parallel to each other. It means that it will become.

The optical system of the present invention has the above-described configuration, and the prism 4 converts the viewing direction, and the prism 4 has a refractive effect so that the outer diameter can be small. .

However, such a refractive effect is not preferable because astigmatism occurs and the image quality is extremely degraded.

Particularly in the case of having an ultra-wide-angle lens system as in the present invention, astigmatism occurs significantly and the effect on image quality is extremely severe, making it practically impossible to use.

The correction prism 3 is arranged with the main purpose of correcting this astigmatism.

An optical system comprising the correction prism 3 and the viewing direction changing prism 4 of the present invention can be schematically represented as shown in FIG.

In this optical system, the refractive index is set to 01 along the direction of light propagation.
to n51 plane spacing is d.

The angle of incidence of the optical axis with respect to the first surface is determined as
Assuming that the refraction angles are θi and θi1, the astigmatism ΔP generated in this optical system is expressed as follows.

However, PMl is the distance from the first surface, that is, the incident surface of the correction prism 3, to the object point.

In the optical system of the present invention, the incident optical axis, the incident surface (first surface) 3a of the correction prism 3, the exit surface (fourth surface) 4C of the visual field direction conversion prism 4, and the exit optical axis are almost perpendicular to each other. be.

Further, since the magnitude of refraction of the refraction surface 3b (second surface) of the correction prism 3 and the magnitude of refraction of the refraction surface 4a (third surface) of the viewing direction conversion prism 4 are almost equal, the angle formed by the two surfaces There is a relationship when β is

Using the above relational expression and the relational expression obtained by applying Snell's law to the refraction of light at the second and third surfaces, further assuming that the front and back of both prisms are air, n1=n5
=1, equation (1) is simplified as follows.

In the present invention, since the refractive surface 3b of the correction prism 3 and the refractive surface 4a of the viewing direction conversion prism 4 are arranged close to each other, d2 is extremely small.

Further, the difference in refractive index of materials used as prisms is not so large except for special ones, so it is n2/n421.

Therefore, both the first term and the second term of the equation (po) have small values.

That is, according to the present invention, the occurrence of astigmatism can be suppressed to a small level.

Incidentally, in the present invention, the entrance surface 3a of the correction prism 3 and the exit surface 4C of the visual field direction conversion prism 4 are made so that the optical axis is substantially perpendicular to each other.
This is also preferable because the viewing angle does not differ between when used in the air and when used underwater.

In the present invention, it is preferable that the distance between the main bone direction converting prism 4 and the correction prism 3, that is, the distance between 4a and 3b, be smaller because astigmatism will be less likely to occur.

In particular, if this distance becomes more than 1/2 of the sum of the lens paths of the correction prism 3 and the visual field direction conversion prism 4, it is not preferable because astigmatism will occur significantly and the outer diameter cannot be made sufficiently small.

In practice, even if the above-mentioned interval is on the order of a wavelength, the surface 4a can be used as a total reflection surface.

When the distance is made small to this extent, the occurrence of astigmatism can be made very small.

Further, in the embodiment, a portion of the refractive surface 4a of the viewing direction conversion prism 4 that is necessary for reflecting the light reflected by the reflection mj4b may be plated.

In this case, if the pond is filled with adhesive, no astigmatism will occur at all.

As explained above, the optical system of the present invention has problems such as side view and 6
Even in the case of θ other than 0° strabismus, for example, 30° strabismus, the outer diameter of the strabismus optical system can be kept extremely small.
Moreover, it has effects such as enabling observation with good image quality.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventionally used optical system for perspective viewing, FIG. 2 is a sectional view showing an embodiment of the present invention, and FIG. 3 is a diagram for explaining astigmatism correction. 3...Correction prism, 4...Viewing direction conversion prism, 5...Concave lens.

Claims (1)

[Claims] 1. A correction prism having a surface located substantially perpendicular to the incident optical axis from the perspective direction and a refracting surface arranged so that the incident optical axis is refracted and exits, and a correction prism that is close to the refractive surface of the correction prism. The correction prism has a refracting surface for refracting the optical axis emitted from the correction prism, a reflecting surface for reflecting the light refracted by the refracting surface, and an exit surface located substantially perpendicular to the direct viewing direction, a viewing direction conversion prism configured such that the reflected optical axis is reflected on the refraction surface and then exits from the exit surface; and a concave lens disposed in front of the correction prism, the refraction surface of the correction prism. An optical system for strabismus, characterized in that the magnitude of refraction of the prism is approximately equal to the magnitude of refraction of the refraction surface of the viewing direction conversion prism.