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WHITE LIGHT EMITTING APPARATUS AND LINE ILLUMINATOR USING THE SAME IN IMAGE READING APPARATUS

  • US 20100320928A1
  • Filed: 08/10/2010
  • Published: 12/23/2010
  • Est. Priority Date: 02/13/2008
  • Status: Active Grant
First Claim
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1. A white light emitting apparatus for an image reading apparatus, that uses a white LED having a blue LED chip and a phosphor, comprising:

  • a light source section in which a first white LED that emits white light whose chromaticity deviates to a blue side from a predetermined white region of a CIE chromaticity diagram and a second white LED that emits white light whose chromaticity deviates to a yellow side from the predetermined white region are adjacently disposed such that optical axes thereof are in substantially the same direction; and

    a current regulator that independently drives the blue LED chip of the first and second white LEDs, respectively;

    wherein the current regulator performs PWM control for a drive current of at least one of the first and second white LEDs, and by setting respective pulse widths for driving the first and second white LEDs that are inversely proportional to a distance from a target chromaticity point to a chromaticity point of emitted light of the first white LED and a distance from the target chromaticity point to a chromaticity point of emitted light of the second white LED on a CIE chromaticity diagram,adjusts a color mixture of lights emitted from the first and second white LEDs to a chromaticity of the predetermined white region.

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