Position control system for objects in space vehicle - uses holographic plate with holes on axes to form point sources for laser to generate interference fringes

摘要

A cylindrical support tube (1) forms a reference element for a position indicator. One end of the tube is blanked by two circular base plates (2) spaced by a spring (3) and through the centre of which passes a laser (4) in which the head protrudes into the tube. The other end of the tube is closed by a cover (5) of transparent material with a low coefficient of expansion. Its external surface is coated with a metallic layer (6) in which four holes (S) are located on the perpendicular axes. A lens (7) and holographic recording plate (8) are located between the layer and the laser. The laser beam (10) is directed precisely by the holographic plate to the four holes to form point sources of coherent light. Interference fringes formed by these sources enable positions of instruments to be determined in the perpendicular axes.