Optical diffraction grating scanning device

Claim 1

An optical scanning device for exploring a line on a surface by means of a light-spot, comprising: means producing a number of monochromatic light-spots, each having the same wave-length ( lambda ) and Being between 0.1 and 100 microns in diameter; and means rotating the spots simultaneously about a common axis so as to describe a single circle intersecting the surface along the line; said light-spot producing means comprising a member having a concave surface, said surface lying on a portion of the surface of an imaginary sphere centered on said axis; diffraction grating means formed on said concave surface, the number of said diffraction grating means being equal to the number of light-spots produced; and a source of nonochromatic light of the said wavelength ( lambda ) located at the center of said imaginary sphere, whereby each diffraction grating means receiving light from said source diffracts a light-spot lying in a common imaginary circle; and wherein said diffraction grating means is a holographic grating produced by recording a system of interference fringes, obtained on said member from two sources of coherent light of wave length lambda o positioned respectively at the center of said imaginary sphere and at a point such that said point and the spot it is desired to obtain divide harmonically, in the ratio lambda / lambda o, a diameter of the said imaginary sphere, which diameter passes through said point and the spot.