Optical system with tilted concave mirror and astigmatism compensator

Claim 2

In an image-forming optical system for a magnifying instrument, a concave mirror tilted about a first tilt axis so that its axis is at a predetermined small angle of a few degrees with the path of the central light ray through the system to transmit an image out of the light path of an object to be observed, whereby astigmatism is introduced, a single, refracting member having plane, optically parallel, entrance and exit surfaces, the member being positioned in a nonparallel portion of the light path and tilted about a second tilt axis parallel to the first tilt axis to an extent such that the entrance and exit surfaces are disposed off of normal with the path of the central light ray incident on the surfaces of the refracting member by such an angle of tilt and the member having such a predetermined thickness and such a predetermined index of refraction, all correlated to the tilt angle of the concave mirror, to compensate substantially fully for the astigmatism introduced by the tilt of the mirror, and observing means receiving light from the mirror.

Claim 3

In an optical instrument for providing magnified observation of objects within its field of view, a concave mirror for producing a real image of an object located within the field of view, the mirror being tilted about a first tilt axis so that its axis is at a small angle of a few degrees with the path of the central light ray through the instrument to transmit the image out of the path of the object, whereby astigmatism is introduced, a single refracting member having a plane entrance surface and a plane exit surface disposed optically parallel with each other, the member being positioned in a nonparallel portion of the light path and tilted about a second tilt axis parallel to the first axis at such a predetermined angle off of normal with the path of the central light ray incident on the surfaces of the member and having such a predetermined thickness and such a predetermined index of refraction relative to the light path of the system, all correlated to the tilt angle of the concave mirror, to compensate substantially fully for the astigmatism introduced by the tilt of the concave mirror, an eyepiece, and means defining a flat mirror for receiving the light from the concave mirror and rEflecting it toward the eyepiece.

Claim 4

In an optical instrument for providing magnified observation of objects within its field of view, a concave mirror for producing a real image of an object located within the field of view, the mirror being tilted about a first tilt axis so that its axis is at a small angle of a few degrees with the path of the central light ray through the instrument to transmit the image out of the path of the object, whereby astigmatism is introduced, a single refracting member having a plane entrance surface and a plane exit surface disposed optically parallel with each other, the member being positioned in a nonparallel portion of the light path and tilted about a second tilt axis parallel to the first axis at such a predetermined angle off of normal with the path of the central light ray incident on the surfaces of the member and having such a predetermined thickness and such a predetermined index of refraction relative to the light path of the system, all correlated to the tilt angle of the concave mirror, to compensate substantially fully for the astigmatism introduced by the tilt of the concave mirror, an eyepiece, and means defining a flat mirror for receiving the light from the concave mirror and rEflecting it toward the eyepiece.

Claim 5

The optical instrument of claim 2 wherein the refracting means is a plane parallel plate.

Claim 6

The optical instrument of claim 3 wherein the plane parallel plate has an index of refraction of about 1.519, a thickness of 6.13 mm. and a tilt angle of about 17*30'' and a tilt angle of the mirror is about 2*30''.

Claim 7

The optical instrument of claim 2 wherein the means defining the flat mirror is a reflective portion of the exit surface of the refracting member.

Claim 8

The optical instrument of claim 2 wherein the compensating means is a 45* right prism, with the legs forming the entrance and exit plane surfaces and with the hypotenuse forming the flat mirror.

Claim 9

In a reflecting microscope for providing magnified observation of objects within its field of view, an optical housing having an entrance aperture for receiving light rays and a plurality of optical elements mounted in the housing and disposed along the optical axis of the microscope as defined by the central light ray path, the optical elements including a concave spherical mirror facing the entrance aperture and tilted about a first tilt axis so that its axis is at a small, predetermined angle with the central light ray path to deflect an image out of the path of the rays from an object, an inclined eyepiece, a transparent refracting plate of a predetermined thickness and a predetermined index of refraction disposed between the concave mirror and the entrance aperture in a nonparallel portion of the light path so that the light rays pass through the plate prior to reaching the concave mirror, the plate being tilted about a second tilt axis parallel to the first axis at such an angle that plane parallel entrance and exit surfaces of the plate are inclined off of normal with the central light ray path incident on the surfaces of the refracting plate, the thickness, index of refraction and tilt of said plate being correlated to the tilt angle of said concave mirror to compensate substantially fully for astigmatism introduced by the tilt of the concave mirror, and a flat-mirror covering part of the exit surface of the plate for receiving light rays from the concave mirror and reflecting them toward the inclined eyepiece.

Claim 10

In a reflecting microscope for providing magnified observation of objects within its field of view, an optical housing having an entrance aperture for receiving light rays and a plurality of optical elements mounted in the housing and disposed along the optical axis of the microscope as defined by the central light ray path, the optical elements including a concave spherical mirror facing the entrance aperture and tilted about a first tilt axis so that its axis is at a small, predetermined angle with the central light ray path to deflect an image out of the path of the rays from an object, an inclined eyepiece, a transparent refracting plate of a predetermined thickness and a predetermined index of refraction disposed between the concave mirror and the entrance aperture in a nonparallel portion of the light path so that the light rays pass through the plate prior to reaching the concave mirror, the plate being tilted about a second tilt axis parallel to the first axis at such an angle that plane parallel entrance and exit surfaces of the plate are inclined off of normal with the central light ray path incident on the surfaces of the refracting plate, the thickness, index of refraction and tilt of said plate being correlated to the tilt angle of said concave mirror to compensate substantially fully for astigmatism introduced by the tilt of the concave mirror, and a flat-mirror covering part of the exit surface of the plate for receiving light rays from the concave mirror and reflecting them toward the inclined eyepiece.

Claim 11

The microscope of claim 7, wherein the axis of the spherical mirror intersects the exit surface of the plate approximately at the point where the flat mirror terminates.