US 4,852,956 AGranted

Hologan scanner system

AssigneeHolotek Ltd.

InventorCharles J. Kramer

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Abstract

A hologon scanning system which generates an essentially bow-free scan line or lines across a surface using a planar, and preferably a holographic, grating disposed in a holding assembly which is rotated about an axis. The surface of the grating is at a constant angle of incidence with respect to a collimated beam of laser light propagating along the axis of rotation. The grating period for the wavelength of the laser beam and for the coordinate system associated with the rotating grating provides a diffraction angle from the grating which is constant with rotation angle; the diffracted beam being perpendicular to the rotation axis. An essentially bow-free, straight scan line is obtained across the receptor surface which may be a flat image plane or a cylindrical image plane having its axis along the axis of rotation of the grating. The beam scan angle across the receptor surface is equal to the angle of rotation of the grating, rather than being related to the angle of rotation by a factor approximately equal to the ratio of wavelength of the laser light to the grating period.

Claims37

Dependent claims

A hologon scanner system which comprises a planar light transmissive member having a difference grating formed thereon, means providing a beam of light incident upon an area of said member with an angle of incidence .theta..sub.i, which is essentially equal to the diffraction angle .theta..sub.d, at every point across the entire area, means for rotating said member about an axis with said grating inclined at a predetermined angle to said axis so that a beam of light propagating with a principal direction component in the direction of said axis is diffracted by said grating to produce a diffracted beam transverse to said axis which scans an essentially bow free line across an image surface over a scan angle .theta..sub.S =.theta..sub.R, where .theta..sub.R is the angle of rotation of said grating, said predetermined angle being such that the angle of incidence of said beam to said grating .theta..sub.i and the diffraction angle .theta..sub.d of said diffracted beam exciting said grating are essentially equal and remain constant over all angles of rotation .theta..sub.R ;

and
sin .theta.=.lambda./2D
where .theta. is approximately equal to .theta..sub.i which is essentially equal to .theta..sub.d for all values of .theta..sub.R, and where .lambda. is the wavelength of light and D is the grating period.

Dependencies are inferred from the claim text.