Projector and method for controlling light source for projector

A method of controlling a light source that is carried out in a projector that has:

• an image input unit that receives as input a first image signal that is synchronized with a vertical synchronizing signal;
• a resolution conversion output unit that converts said first image signal to a second image signal that indicates an image of a predetermined resolution and supplies the result as output;
• a light source unit that is provided with a light source and an image-forming element that uses illumination light from the light source to generate image light;
• a light source control unit that controls the light quantity of said light source;
• and
• an image-forming element drive unit that drives said image-forming element on the basis of said second image signal,
• said method of controlling a light source comprising steps of:
• calculating, by said image input unit, a ratio of a resolution of the image indicated by said first image signal and a resolution of the image indicated by said second image signal, an average luminance level of said first image signal, first histogram data that are a luminance distribution of said first image signal and second histogram data that are obtained by multiplying said ratio by said first histogram data;
• sending, by said image input unit, to said light source control unit image input information that contains said average luminance level and said second histogram data;
• using, by said light source control unit, said image input information to control said light source;
• sending, by said image input unit, to said light source control unit said image input information for said first image signal that is synchronized with a first vertical synchronizing signal in synchronization with a second vertical synchronizing signal that follows said first vertical synchronizing signal;
• and
• carrying out, by said resolution conversion output unit, conversion such that said second image signal is supplied between said second vertical synchronizing signal and a third vertical synchronizing signal that follows said second vertical synchronizing signal.