Patent ID: 7926956
Filing Date: 2011-04-19
Classification: G03B

Abstract:
1. An image forming apparatus that emits a beam corresponding to an image onto an image-projected object to allow the image to be formed on the image-projected object, the apparatus comprising: a lamp configured to serve as a light source for the beam emitted onto the image-projected object; a lamp power supply configured to drive said lamp; a lens configured to focus the beam emitted from said lamp upon the image-projected object; a brightness sensor configured to measure brightness of direct or indirect light in a light path from said lamp to said lens, as a lamp brightness; a memory configured to store, as a reference brightness value, said lamp brightness measured by said brightness sensor at a first time when brightness of the beam on the image-projected object has reached a target value; and a control circuit configured to control the image forming apparatus, wherein at a second time later than the first time, said control circuit performs first control of a) varying an output power of said lamp power supply and obtaining said lamp brightness measured by said brightness sensor for respective levels of the output power, b) generating or updating correspondence information that indicates a correspondence between a change in the output power of said lamp power supply and a change in said lamp brightness at the second time, based on the values obtained, and c) storing the generated or updated correspondence information in said memory, and at a third time later than the second time, said control circuit performs second control of loading the reference brightness value and the correspondence information from said memory, identifying a level of the output power of said lamp power supply corresponding to the reference brightness value based on the correspondence information, and driving said lamp power supply with the identified level of the output power.