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OPTICAL DENSITY DETERMINATION METHODS AND APPARATUS

  • US 20110149284A1
  • Filed: 12/18/2009
  • Published: 06/23/2011
  • Est. Priority Date: 12/18/2009
  • Status: Active Grant
First Claim
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1. An optical density determination apparatus comprising:

  • a first light source configured to emit a first light beam in a first direction towards a substrate;

    a second light source configured to emit a second light beam in a second direction towards the substrate, the second direction being different than the first direction;

    a first sensor configured to sense light of the first light beam reflected from the substrate;

    a second sensor configured to sense light of the second light beam reflected from the substrate; and

    wherein the first and second sensors are configured to provide signals indicative of the light sensed by the first and second sensors and which are useable to determine optical density of the substrate.

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