Abstract: A surveying instrument includes a sighting telescope having an objective lens and an eyepiece; an erecting optical system functioning so that an image formed by said objective lens is viewed as an erect image through the eyepiece; and a light shield device, positioned in an optical path extending from an incident surface of the erecting optical system to an exit surface of the erecting optical system, for preventing an off-field light bundle which is incident on the erecting optical system from reaching the eyepiece.

Abstract: A surveying instrument includes a sighting telescope having an objective lens and an eyepiece; an erecting optical system functioning so that an image formed by said objective lens is viewed as an erect image through the eyepiece; and a light shield device, positioned in an optical path extending from an incident surface of the erecting optical system to an exit surface of the erecting optical system, for preventing an off-field light bundle which is incident on the erecting optical system from reaching the eyepiece.

Abstract: An integral transmitter-receiver optical communication apparatus, including: a transmitter-receiver device including: a transmitter having a laser source for emitting a laser beam modulated in accordance with a transmission information signal, a receiver having a position detecting sensor and a light receiving element each of which receives a complementing modulated laser beam transmitted from a complementing transmitter, and a beam splitting device for splitting the modulated laser beam and the complementing modulated laser beam into two separate laser beams; a telescopic optical system for transmitting the modulated laser beam emitted by the laser source, and for receiving the complementing modulated laser beam transmitted from the complementing transmitter, the telescopic optical system including a first afocal optical system; a light beam deflecting device positioned between the telescopic optical system and the transmitter-receiver device, wherein the light beam deflecting device is controlled in accorda

Abstract: A surveying instrument includes a sighting telescope for sighting an object; an optical distance meter which includes a light-transmitting optical system for transmitting a measuring light toward the object via the sighting telescope, a light-receiving optical system for receiving light reflected by the object, and a light-receiving element which receives the measuring light reflected by the object and received by the light-receiving optical system; and a light shield mask positioned on an optical axis between the eyepiece and the light-receiving element to cut off incoming rays from the eyepiece.

Abstract: Disclosed is an integral transmitter-receiver optical communication apparatus, including: a transmitter-receiver device which includes: a transmitter having a laser source for emitting a laser beam modulated in accordance with a transmission information signal, a receiver having a position detecting sensor and a light receiving element which receive a complementing modulated laser beam transmitted from a complementing transmitter, and a beam splitting device for splitting the modulated laser beam and the complementing modulated laser beam which are incident thereon as two separate laser beams; a telescopic optical system for transmitting the modulated laser beam emitted by the laser source and for receiving the complementing modulated laser beam transmitted from the complementing transmitter; and a light beam deflecting device positioned between the telescopic optical system and the transmitter-receiver device, wherein the light beam deflecting device is controlled in accordance with a signal output from the

Abstract: A surveying instrument includes a sighting telescope having an objective lens and an eyepiece; an erecting optical system functioning so that an image formed by said objective lens is viewed as an erect image through the eyepiece; and a light shield device, positioned in an optical path extending from an incident surface of the erecting optical system to an exit surface of the erecting optical system, for preventing an off-field light bundle which is incident on the erecting optical system from reaching the eyepiece.

Abstract: A surveying instrument includes a sighting telescope for sighting an object; an optical distance meter which includes a light-transmitting optical system for transmitting a measuring light toward the object via the sighting telescope, a light-receiving optical system for receiving light reflected by the object, and a light-receiving element which receives the measuring light reflected by the object and received by the light-receiving optical system; and a light shield mask positioned on an optical axis between the eyepiece and the light-receiving element to cut off incoming rays from the eyepiece.

Abstract: An optical axis correcting system includes a first afocal optical system, an optical deflector which corrects the deviation of an optical axis of light incident upon the first optical system, a second afocal optical system, and a light convergent optical system. The optical axis correcting system satisfies (1) 3.60<.vertline.fp(I)/fN(I).vertline.<5.30, (2) 1.00<.vertline.fp(II)/fN(II).vertline.<2.41, and (3) 0.12 <r1 (II)/f<0.

Abstract: In a concentric ND filter in which multi-layered circular ND filter elements whose diameter is decreased stepwise toward the uppermost layer from the lowermost layer are concentrically provided on a first transparent substrate, a surrounding space of the concentrically multi-layered ND filter elements defined by and between the surface of the transparent substrate and the surface of the central ND filter layer of the smallest diameter is filled with a transparent adhesive.

Abstract: An apparatus for reading information from an optical recording medium includes a laser beam source, a beam splitter, and a fixed mirror which is disposed in an optical path of a laser beam for reflecting the laser beam from the laser beam source to the beam splitter. The laser beam source is arranged so that a linearly polarized, light oscillating plane, which includes an optical axis as well as an oscillating direction of the laser beam, is perpendicular to a plane which includes a normal of the fixed mirror and the optical axis of the laser beam. In addition, the beam splitter is arranged so that a plane which includes a normal of a reflection plane of the beam splitter and the optical axis of the laser beam is parallel to the linearly polarized, light oscillating plane. According to this construction, attenuation of the laser beam is reduced.