US 6,185,046 B2Granted

Multiple prism image forming optical system

AssigneeOlympus Optical Co., Ltd.

InventorTakayoshi Togino

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Abstract

A high-performance image-forming optical system made compact and thin by folding an optical path using reflecting surfaces arranged to minimize the number of reflections. The image-forming optical system has a first prism placed on the object side and a second prism placed on the image side and does not form an intermediate image. The first and second prisms each have a first surface through which a light beam enters the prism, a second surface reflecting the incident light beam in the prism, a third surface reflecting the reflected light beam in the prism, and a fourth surface through which the light beam exits from the prism. At least one of the second and third surfaces has a rotationally asymmetric curved surface configuration that gives a power to a light beam and corrects aberrations due to decentration. Any optical element that gives a refracting power contributing to the image-forming action of a light beam is not placed between the second prism and an image formed by the image-forming optical system.

Claims34

Dependent claims

An image-forming optical system having a positive refracting power as a whole for forming an object image, said image-forming optical system comprising:

a first prism and a second prism, each of said first prism and second prism being formed from a medium having a refractive index (n) larger than 1 (n>1), said second prism being placed at a position on an image side of said first prism in an optical path exiting said first prism and leading to a plane where said object image is formed,
wherein no intermediate image is formed,
said first prism having, in order from an object side thereof;
a first surface through which a light beam enters said first prism;
a second surface that reflects said light beam in said first prism;
a third surface that reflects said light beam reflected by said second surface in said first prism;
and
a fourth surface through which said light beam exits from said first prism;
wherein at least one of said second surface and said third surface of said first prism has a curved surface configuration providing a refractive power acting on said light beam, said curved surface configuration having a rotationally asymmetric surface configuration that corrects aberrations due to decentration;
said second prism having, in order from an object side thereof;
a first surface through which said light beam enters said second prism;
a second surface that reflects said light beam in said second prism;
a third surface that reflects said light beam reflected by said second surface in said second prism;
and
a fourth surface through which said light beam exits from said second prism;
wherein at least one of said second surface and third surface of said second prism has a curved surface configuration providing a refractive power acting on said light beam, said curved surface configuration having a rotationally asymmetric surface configuration that corrects aberrations due to decentration;
and
wherein any optical element that gives a refracting power contributing to an image-forming action of said light beam is placed other than between said second prism and an image formed by said image-forming optical system.

15 more elements

An image-forming optical system having a positive refracting power as a whole for forming an object image, said image-forming optical system comprising:

a first prism and a second prism, each of said first prism and second prism being formed from a medium having a refractive index (n) larger than 1 (n>1), said second prism being placed on an image side of said first prism,
wherein no intermediate image is formed,
said first prism having, in order from an object side thereof:
a first surface through which a light beam enters said first prism;
a second surface that reflects said light beam in said first prism;
a third surface that reflects said light beam reflected by said second surface in said first prism;
and
a fourth surface through which said light beam exits from said first prism;
wherein at least one of said second surface and said third surface of said first prism has a curved surface configuration providing a refractive power acting on said light beam, said curved surface configuration having a rotationally asymmetric surface configuration that corrects aberration due to decentration;
said second prism having, in order from an object side thereof:
a first surface through which said light beam enters said second prism;
a second surface that reflects said light beam in said second prism;
a third surface that reflects said light beam reflected by said second surface in said second prism;
and
a fourth surface through which said light beam exits from said second prism;
and
wherein at least one of said second surface and said third surface of said second prism has a curved surface configuration providing a refractive power acting on said, said curved surface configuration having a rotationally asymmetric surface configuration that corrects aberrations due to decentration;
and
wherein said second prism is arranged such that a first axial principal ray that is led from said third surface of said second prism to said fourth surface of said second prism is closer to a second axial principal ray that is led from said third surface of said first prism to said fourth surface of said first prism than a third axial principal ray of said light beam incident on said first prism that is led from said first surface of said first prism to said second surface of said first prism and an extension of said third axial principal ray.

16 more elements

An image-forming optical system having a positive refracting power as a whole for forming an object image, said image-forming optical system comprising:

a first prism and a second prism, each of said first prism and second prism being formed from a medium having a refractive index (n) larger than 1 (n>1), said second prism being placed on an image side of said first prism,
wherein no intermediate image is
said first prism having, in order from an object side thereof:
a first surface through which a light beam enters said first prism;
a second surface that reflects said light beam in said first prism;
a third surface that reflects said light beam reflected by said second surface in said first prism;
and
a fourth surface through which said light beam exits from said first prism;
wherein at least one of said second surface and said third surface of said first prism has a curved surface configuration providing a refractive power acting on said light beam, said curved surface configuration having a rotationally asymmetric surface configuration that corrects aberrations due to decentration;
said second prism having, in order from an object side thereof:
a first surface through which said light beam enters said second prism;
a second surface that reflects said light beam in said second prism;
a third surface that reflects said light beam reflected by said second surface in said second prism;
and
a fourth surface through which said light beam exits from said second prism;
wherein at least one of said second surface and third surface of said second prism has a curved surface configuration providing a refractive power acting on said light beam, said curved surface configuration having a rotationally asymmetric surface configuration that corrects aberrations due to decentration;
and
wherein the fourth surface of said first prism and said first surface of said second prism face each other, and said third surface of said second prism faces a direction other than said second surface of said first prism and lies closer to said fourth surface of said first prism than said second surface of said first prism so that said first surface and second surface of said first prism and said third surface and said fourth surface of said second prism and further an image plane do not lie in parallel on a line extending straight from an axial principal ray entering said first prism, said third surface and fourth surface of said second prism and said image plane being off said line extending straight from said axial principal ray entering said first prism.

15 more elements

Dependencies are inferred from the claim text.