Patent ID: 8054555

Claim:
A sighting device comprising, in order from a target object side: a meniscus lens having positive refractive power with a convex surface facing toward the target object; and a meniscus lens having negative refractive power with a convex surface facing toward the target object, wherein each meniscus lens is only a segment of a corresponding whole round lens, and the whole round lenses have a common optical axis which is offset from a line of sight of the sighting device, said segments being located at a same side of said common optical axis with respect to a perpendicular direction thereto, away from said common optical axis and on the line of sight of the sighting device to be viewed by an observer's eye; wherein a surface of said meniscus lens having positive refractive power that faces away from said target object or the surface of said meniscus lens having negative refractive power that faces toward said target object is adapted to constitute a semi-transparent reflection surface or a wavelength selective reflection surface, wherein said semi-transparent reflection surface or said wavelength selective reflection surface and a refracting surface of said meniscus lens having negative refractive power, which refracting surface faces away from said target object side, form a catadioptric optical system, wherein said meniscus lens having positive refractive power and said meniscus lens having negative refractive power have substantially zero refractive power for light rays transmitting therethrough, wherein a point source is provided at a side of said semi-transparent reflection surface or said wavelength selective reflection surface where said negative meniscus lens is located and at a focal point of said catadioptric optical system on said common optical axis, to be disposed outside the field of view of the sighting device, and wherein light beams from the target object passing through the sighting device are substantially parallel and the degree of parallelism of the light beams is within ±2 minutes in the distance range of ±12 mm from the line of sight of the sighting device.