Continuous tone recording system incorporating feedback control circuit

Claim 1

An image recording system comprising: a. means including a solid state laser diode for generating an analog signal-controlled, intensity-modulated beam of light, b. a feedback circuit means for responding to the instantaneous intensity of said light beam for continuously providing a feedback control signal coupled to said generating means for adjusting said laser diode to modulate the laser beam by changing the current applied to the laser diode and to stabilize its light output, allowing virtually instantaneous changes in output intensity in response to an input signal while maintaining the output constant regardless of changes in the characteristics of said laser diode, c. means for at least one of collimating, focusing, and controlling the path of said beam of light, d. means for scanning said light beam across the width of an image plane at which a photosensitive recording medium having a sensitivity and exposure range matched to the intensity-modulated light beam may be positioned, said means providing scan lines on said recording medium, e. means for positioning said scan lines consecutively and accurately along the length of said image plane, by at least one of transporting the medium perpendicular to the scan line direction and by optical deflection of the scan line, whereby the combination of the recited elements enables the formation at the image plane of a continuous tone image at a rate of at least 80 lines/sec., said elements being capable of creating at least 64 gray levels when imaged onto a transparent medium or at least 32 gray levels when imaged onto an opaque medium.