Patent ID: 6534756
Filing Date: 2003-03-18
Classification: G02B

Abstract:
A light source having a substantially constant output level, for use with a power supply that controls vapor lamp current according to a control signal, the light source comprising:a light guide having an end; a vapor lamp positioned near the end of the light guide; a beam splitter positioned along a first optical path extending between the vapor lamp and the end of the light guide; and a reference detector to receive a portion of the light output by the vapor lamp and generate a feedback signal for use as the control signal, the reference detector being positioned along a second optical path extending from the beam splitter angled away from the first optical path; wherein the end of the light guide has a predetermined numerical aperture, and wherein the second optical path is configured such that the reference detector receives light produced by the light source according to a numerical aperture that substantially coincides with the numerical aperture of the end of the light guide.