Method and apparatus for watermarking film

Details Method and apparatus for watermarking film Method and apparatus for watermarking film

2005-04-19

2005-04-19

Tran, Huan (Department: 2861)

Incremental printing of symbolic information

Light or beam marking apparatus or processes

Reexamination Certificate

active

06882356

ABSTRACT:
A printing method and apparatus (100) for pre-exposing a digital watermark image onto a photosensitive medium (140) at the time of manufacture is disclosed. For exposure energy, the apparatus employs a single color light source (60) consisting of an array of LEDs. The LEDs are spatially modulated in intensity by means of a reflective LCD array (91). The photosensitive medium (140) may be compensated to allow such single color pre-exposure while avoiding hue shift and contrast loss. The exposure at the film may be increased by: employing partial frame illumination, pulsing the LEDs with high currents with short pulse durations and low duty cycles, employing two LCD devices (91, 92) to utilize both polarizations, and dichroically combining two LED (60, 61) arrays of slightly different wavelengths.

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Roy Berns; Billmeyer and Saltzman's Principles of Color Technology, Third Edition; 2000, pp. 14-16.

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