Patent ID: 8767783

Claim:
A light source device for illuminating an illumination object with coherent light, comprising: a single coherent light source for emitting single coherent light; and a pattern changer configured to change an interference pattern of the single coherent light on a surface of the illumination object and reduce speckle noise of the single coherent light, wherein the pattern changer includes: a thermal lens crystal which is arranged between the single coherent light source and the illumination object and on an optical path of the single coherent light and exhibits a thermal lens effect for the single coherent light emitted from the single coherent light source, and a changer configured to change at least one of a light intensity distribution, a polarization direction, a wavelength and an intensity of the single coherent light incident on the thermal lens crystal in a time period shorter than a period required for the temperature distribution of the thermal lens crystal to stabilize, and wherein a side surface of the thermal lens crystal totally reflects the single coherent light.