Datum beam projecting apparatus for use with surveying equipment
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United States of America Patent
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Jul 16, 1991
Grant Date -
N/A
app pub date -
Oct 27, 1989
filing date -
Oct 27, 1988
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A datum beam projecting apparatus for use with surveying equipment projects light rays emitted from a light source as the datum beam through a projecting lens system, wherein the apparatus uses a plane-parallel glass serving to compensate for tilt of the datum beam, thereby maintaining a direction of the projected datum beam constant with respect to a tilt of the apparatus. The plane-parallel glass is tiltably located in an optical path defined between the light source and the projecting lens system so that the following relationship may be satisfied: tan .beta.=K tan .alpha. where .alpha. represents a tilt of the apparatus, .beta. represents a tilt of the plane-parallel glass and K is a constant. With the apparatus, a tilt of the data beam can be effectively compensated merely by tilting the plane-parallel glass by the angle .beta. corresponding to a predetermined times the tilt .alpha. of the apparatus, so that the complicated arrangement comprising concave lenses, prisms etc. usually required for compensation can be eliminated. Thereby, not only can the structure be simplified but also reliable precision can be obtained at a reasonable cost.
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