Flare light compensator in a flying spot scanner

Claim 2

In an electro-optical image scanning system wherein a flying spot scanner generates a light raster having predetermined dimensions and wherein a light detector generates a video signal representative of the image illuminated by said raster, an apparatus for compensating for the effects of flare light in said scanning system, comprising: a flying spot scanner having a faceplate which a thickness at least as great as H/4 Tan theta where H is the shortest dimension of said raster and theta is the critical angle for internal reflection of light for the faceplate material, thereby causing said flying spot scanner to emit a substantially uniform flare light from said raster; means, responsive to said video signal, for developing a pedestal signal having an amplitude representative of the uniform flare light in said scanning system; and means for combining said pedestal signal with said video signal to compensate for the portion of said video signal caused by the uniform flare light in said scanning system, thereby providing a compensated output video signal.

Claim 3

Apparatus in accordance with claim 1 wherein said pedestal signal developing means comprises means for averaging said video signal over an image scan period to develop a signal having an amplitude proportional to the average amplitude of said video signal; and means for establishing said average amplitude signal at a fixed reference level during each blanking interval of said raster to provide said pedestal signal.

Claim 4

Apparatus in accordance with claim 2 wherein said averaging means develops a signal having a polarity opposite to that of said video signal and wherein said combining means comprises means for adding said pedestal signal and said video signal.

Claim 5

Apparatus in accordance with claim 1 wherein said faceplate consists of a continuous body of transparent glass.

Claim 6

Apparatus in accordance with claim 1 wherein said faceplate consists of a glass portion having interior and exterior surfaces and a transparent plastic portion substantially thicker than said glass and arranged to be contiguous to the exterior surface of said glass portion.

Claim 7

In an electro-optical image scanning system wherein a flying spot scanner generates a light raster having predetermined dimensions and wherein a light detector generates a video signal representative of the image illuminated by said raster, an apparatus for compensating for the effects of flare light in said scanning system, comprising: a flying spot scanner having a face plate with a thickness at least as great as H/4 Tan theta where H is the shortest dimension of said raster and theta is the critical angle for internal reflection of light for the faCeplate material, thereby causing said flying spot scanner to emit a substantially uniform flare light from said raster; means for averaging said video signal over an image scan period to develop a signal having an amplitude proportional to the average amplitude of said video signal; means for clamping said average amplitude signal to a fixed reference level during each blanking interval of said raster, to develop an intermediate pedestal signal; means, for adjusting the amplitude of said intermediate pedestal signal to provide a pedestal signal with an amplitude proportional to the uniform flare light in said scanning system; means for adjusting the amplitude of said intermediate pedestal signal to provide a pedestal signal with an amplitude proportional to the uniform flare light in said scanning system; and means for combining said pedestal signal with said video signal to compensate for the portion of said image representative signal caused by uniform flare light in said scanning system thereby providing a compensated output video signal.

Claim 8

In an electro-optical image scanning system wherein a flying spot scanner generates a light raster having predetermined dimensions and wherein a light detector generates a video signal representative of the image illuminated by said raster, an apparatus for compensating for the effects of flare light in said scanning system, comprising: a flying spot scanner having a face plate with a thickness at least as great as H/4 Tan theta where H is the shortest dimension of said raster and theta is the critical angle for internal reflection of light for the faCeplate material, thereby causing said flying spot scanner to emit a substantially uniform flare light from said raster; means for averaging said video signal over an image scan period to develop a signal having an amplitude proportional to the average amplitude of said video signal; means for clamping said average amplitude signal to a fixed reference level during each blanking interval of said raster, to develop an intermediate pedestal signal; means, for adjusting the amplitude of said intermediate pedestal signal to provide a pedestal signal with an amplitude proportional to the uniform flare light in said scanning system; means for adjusting the amplitude of said intermediate pedestal signal to provide a pedestal signal with an amplitude proportional to the uniform flare light in said scanning system; and means for combining said pedestal signal with said video signal to compensate for the portion of said image representative signal caused by uniform flare light in said scanning system thereby providing a compensated output video signal.

Claim 9

Apparatus in accordance with claim 6 wherein said averaging means develops a signal having an opposite polarity to that of said video signal and said combining means compresses means for adding said pedestal signal to said video signal.

Claim 10

Apparatus in accordance with claim 6 wherein said faceplate consists of a continuous body of transparent glass.

Claim 11

Apparatus in accordance with claim 6 wherein said faceplate consists of a glass portion having interior and exterior surfaces and a transparent plastic portion substantially thicker than said glass and arranged to be contiguous to the exterior surface of said glass portion.

Claim 12

Apparatus in accordance with claim 6 wherein said adjusting means comprises a transistor amplifier cooperating with a variable resistor to adjust the amplitude of said intermediate pedestal signal.