Method and apparatus for exposing a latent watermark on film

An apparatus for exposing a latent watermark as a series of lengthwise stripes along a length of photosensitive medium comprising:

• (a) an illumination source comprising an LED for providing an exposure illumination and a drive circuit for providing pulses to the LED in excess of the continuous current rating of the LED;
• (b) a first spatial light modulator for modulating said exposure illumination to form a first exposure pattern according to image data;
• (c) a second spatial light modulator for modulating said exposure illumination to form a second exposure pattern according image data;
• (d) combining optics providing a single output path for directing said first and second exposure patterns onto the photosensitive medium;
• (e) transport means for providing, during exposure, continuous lengthwise displacement of the photosensitive medium with respect to said single output path;
• wherein said first and second spatial light modulators cyclically alternate in providing respective said first and second exposure patterns to said combining optics, such that during a cycle wherein said first spatial light modulator forms said first exposure pattern, said second spatial light modulator loads the image data for providing said second exposure pattern;
• and
• said first and second exposure patterns thereby forming the latent watermark, wherein each of the lengthwise stripes has a predetermined intensity corresponding to said first and second exposure patterns.

An apparatus for exposing a latent watermark as a series of lengthwise stripes along a length of photosensitive medium, the apparatus comprising:

• (a) an illumination source for providing an exposure illumination;
• (b) a spatial light modulator for modulating said exposure illumination to form an exposure pattern according to image data;
• (c) a lens for directing said exposure pattern toward the photosensitive medium;
• (d) transport means for providing, during exposure, continuous lengthwise displacement of the photosensitive medium with respect to said lens;
• and
• said exposure pattern thereby forming the latent watermark, wherein each of the lengthwise stripes has a predetermined intensity corresponding to said exposure pattern.

A method for exposing a latent watermark along a length of photosensitive medium, the method comprising:

• (a) energizing an illumination source for providing an exposure illumination;
• (b) forming a first exposure pattern according to image data by modulating said exposure illumination at a first spatial light modulator;
• (c) forming a second exposure pattern according to image data by modulating said exposure illumination at a second spatial light modulator;
• (d) directing said first and second exposure patterns onto the photosensitive medium over a single output path;
• (e) providing, during exposure, a continuous lengthwise displacement of the photosensitive medium with respect to said single output path, exposing a set of lengthwise stripes thereby;
• and
• wherein said first and second spatial light modulators cyclically alternate in forming respective first and second exposure patterns, such that during a cycle wherein said first spatial light modulator forms said first exposure pattern, said second spatial light modulator loads the image data for forming said second exposure pattern.

A method for exposing a latent watermark along a length of photosensitive medium, the method comprising:

• (a) energizing an illumination source for providing an exposure illumination;
• (b) forming an exposure pattern according to image data by modulating said exposure illumination at a spatial light modulator;
• (c) directing said exposure pattern onto the photosensitive medium over an output path;
• and
• (d) providing, during exposure, a continuous lengthwise displacement of the photosensitive medium with respect to said output path, exposing a set of lengthwise stripes thereby.

A method for encoding a watermark on a photosensitive motion picture medium comprising:

• a) transporting the un-imaged motion picture medium continuously past a spatial light modulator;
• b) forming at least one spot by modulating a plurality of adjacent pixels on the spatial light modulator;
• and
• c) modulating light at the at least one spot to expose a corresponding stripe on the motion picture medium.

A method for exposing and detecting a latent watermark along a length of photosensitive medium, the method comprising:

• (a) energizing an illumination source for providing an exposure illumination;
• (b) forming a first exposure pattern according to image data by modulating said exposure illumination at a first spatial light modulator;
• (c) forming a second exposure pattern according to image data by modulating said exposure illumination at a second spatial light modulator;
• (d) directing said first and second exposure patterns onto the photosensitive medium over a single output path;
• (e) providing, during exposure, a continuous lengthwise displacement of the photosensitive medium with respect to said single output path, exposing a set of lengthwise stripes to produce said latent watermark;
• wherein said first and second spatial light modulators cyclically alternate in forming respective first and second exposure patterns, such that during a cycle wherein said first spatial light modulator forms said first exposure pattern, said second spatial light modulator loads the image data for forming said second exposure pattern;
• (f) developing said photosensitive medium to produce a detectable watermark;
• and
• (g) detecting said watermark.