Patent ID: 6114682
Filing Date: 2000-09-05
Classification: G02B,G06K,H01S,H04N

Abstract:
A light intensity control apparatus comprising:an optical beam splitter which splits light emitted from a light source device having at least one light source into monitor light and principal light;a polarization beam splitter which splits said monitor light into first and second linearly polarized light components having orthogonal oscillation directions;a monitor light detector for separately detecting the light intensities of said first and second linearly polarized light components of said monitor light;an object surface on which said principal light being scanned;a polarization correction device for correcting the output of said monitor light detector so that the intensity of the output signal of said monitor light detector and the light intensity of the principal light on said object surface have a predetermined correlation, regardless of the polarization state of the light incident upon said optical beam splitter;a humidity dependency correction device which corrects the output of said monitor light detector via said polarization correction device by detecting a variation in polarization dependency characteristics of said optical beam splitter, caused by a change in humidity, and feeding the variation back to said polarization correction device, so that the output signal intensity of said monitor light detector and the light intensity of the principal light on said object surface have a predetermined correlation, regardless of a change in humidity; anda light emission controller for controlling the emission of the light of said light source device in accordance with the output signal of said monitor light detector which have been corrected by said polarization correction device and said humidity dependency correction device.