Reflecting type optical system

An optical system of reflecting type comprising:

• an optical element composed of a transparent body having an entrance surface, an exit surface, and at least three curved reflecting surfaces of internal reflection, a first curved reflecting surface, when counted from an object side, having a converging action, and being formed to an ellipsoid of revolution;
• and
• a stop located adjacent to the entrance surface of said optical element,
• wherein a light beam coming from an object and entering at the entrance surface is reflected from at least one of the reflecting surfaces to form a primary image within said optical element and is, then, made to exit from the exit surface through the remaining reflecting surfaces to form an object image on a predetermined plane, and wherein 70% or more of the length of a reference axis in said optical element lies in one plane, and
• wherein the shape of said first curved reflecting surface is expressed by using a local coordinate system (x,y,z) for said first curved reflecting surface and making coefficients representing the shape of a base zone of said first curved reflecting surface be denoted by a, b, and t, and wherein, putting
• A=(a+b) (y.sup.2 cos.sup.2 t+x.sup.2)
• B=2ab cos t[1+{(b-a) y sin t/(2ab)}+{1+{(b-a)y sin t/(ab)-}y.sup.2 /(ab)}-{4ab cos.sup.2 t+(a+b).sup.2 sin.sup.2 t}x.sup.2 /(4a.sup.2 b.sup.2 cos.sup.2 t)}.sup.1/2 ]
• and defining
• z=A/B+C.sub.02 y.sup.2 +C.sub.20 x.sup.2 +C.sub.03 y.sup.3 +C.sub.21 x.sup.2 y+C.sub.04 y.sup.4 +C.sub.22 x.sup.2 y.sup.2 +C.sub.40 x.sup.4
• the following conditions are satisfied:
• ab>0
• 0.9<t/.vertline..theta..vertline.<1.5
• 0.9<a/d<2.0
• 0.9<b/d<2.0
• where .theta. is an angle of inclination of said first curved reflecting surface with respect to the reference axis and d is the distance between the center of said stop and said first curved reflecting surface as measured along the reference axis.

An optical system of reflecting type comprising:

• an optical element having at least three curved reflecting surfaces of surface reflection whose reference axis lies on one plane and which are formed in unison so as to be opposed to each other, wherein a light beam coming from an object is reflected from at least one of the three curved reflecting surfaces to form an object image, and the object image is then re-formed in a contracted fashion on a predetermined plane by the remaining reflecting surfaces, and wherein a first curved reflecting surface, when counted from the object side of the optical element, has a converging action, the first curved reflecting surface being formed to an ellipsoid of revolution;
• and
• a stop located on an object side of said optical element,
• wherein the shape of said first curved reflecting surface is expressed by using a local coordinate system (x,y,z) for said first curved reflecting surface and making coefficients representing the shape of a base zone of said first curved reflecting surface be denoted by a, b, and t, and wherein, putting
• A=(a+b) (y.sup.2 cos.sup.2 t+x.sup.2)
• B=(2ab cos t [1+{(b-a) y sin t/(2ab)}+{1+{(b-a)y sin t/(ab)}-{y.sup.2 /(ab)}-{4ab cos.sup.2 t+(a+b).sup.2 sin.sup.2 t}x.sup.2 /(4a.sup.2 b.sup.2 cos.sup.2 t)}.sup.1/2 ]
• and defining
• z=A/B+C.sub.02 y.sup.2 +C.sub.20 x.sup.2 +C.sub.03 y.sup.3 +C.sub.21 x.sup.2 y+C.sub.04 y.sup.4 +C.sub.22 x.sup.2 y.sup.2 +C.sub.40 x.sup.4
• the following conditions are satisfied:
• ab>0
• 0.9<t/.vertline..theta..vertline.<1.5
• 0.9<a/d<2.0
• 0.9<b/d<2.0
• where .theta. is an angle of inclination of said first curved reflecting surface with respect to the reference axis and d is the distance between the center of said stop and said first curved reflecting surface as measured along the reference axis.

An optical system of reflecting type comprising:

• an optical element having formed therein in unison at least three curved reflecting surfaces composed of surface reflecting mirrors and a reflecting surface whose normal line at a point of intersection with a reference axis is inclined with respect to a plane in which the reference axis among the at least three reflecting surfaces lie, wherein, as a light beam coming from an object repeats reflection from the at least three reflecting surfaces and then exits to form an image of the object, the object beam coming from the object is once focused to form an object image in at least one of spaces among the plurality of reflecting surfaces and is then focused to re-form the object image, a first curved reflecting surface, when counted from the object side, of said optical element having a converging action and being formed to an ellipsoid of revolution;
• and
• a stop located on an object side of said optical element,
• wherein the shape of said first curved reflecting surface is expressed by using a local coordinate system (x,y,z) for said first curved reflecting surface and making coefficients representing the shape of a base zone of said first curved reflecting surface be denoted by a, b, and t, and wherein, putting
• A=(a+b) (y.sup.2 cos.sup.2 t+x.sup.2)
• B=(2ab cos t [1+{(b-a) y sin t/(2ab)}+{1+{(b-a)y sin t/(ab)}-{y.sup.2 /(ab)}-{4ab cos.sup.2 t+(a+b).sup.2 sin.sup.2 t}x.sup.2 /(4a.sup.2 b.sup.2 cos.sup.2 t)}.sup.1/2 ]
• and defining
• z=A/B+C.sub.02 y.sup.2 +C.sub.20 x.sup.2 +C.sub.03 y.sup.3 +C.sub.21 x.sup.2 y+C.sub.04 y.sup.4 +C.sub.22 x.sup.2 y.sup.2 +C.sub.40 x.sup.4
• the following conditions are satisfied:
• ab>0
• 0.9<t/.vertline..theta..vertline.<1.5
• 0.9<a/d<2.0
• 0.9<b/d<2.0
• where .theta. is an angle of inclination of said first curved reflecting surface with respect to the reference axis and d is the distance between the center of said stop and said first curved reflecting surface as measured along the reference axis.

An optical device, comprising:

• an aperture stop;
• and
• an optical unit forming an image of an object based on a light flux emitted from said aperture stop in an optical medium, said optical unit having a reflective curved surface of rotationary non-symmetry and a refractive surface,
• wherein said reflective curved surface is decentered relative to a reference axis, and
• wherein said reflective curved surface includes not more than one plane of symmetry which defines a pair of symmetric surfaces.