Patent ID: 8067894

Claim:
A light source system comprising: a light source having a LIT state wherein the light source emits light and an UNLIT state wherein the light source does not emit light; a light-sensing device operative for detecting light from the light source, the light-sensing device having an ON state wherein the light-sensing device detects light and an OFF state wherein the light-sensing device does not detect light; a calculation means for calculating a net light amount by subtracting a measurement environment component from a light amount detected by the light-sensing device, the measurement environment component being independent of a lighting state in the light source; and a light source control means for controlling the light source on the basis of the net light amount obtained by the calculation means, wherein the measurement environment component is composed of an electrical offset component of a circuit section including the light-sensing device and a background component which is a component other than the electrical offset component and the calculation means operates in conjunction with the light source and the light-sensing device in a first light detection mode, a second light detection mode and a third light detection mode such that, in the first light detection mode, the light source is in the LIT state and the light-sensing device is in the ON state to determine a first detection light amount including an original light amount component, the background component and the electrical offset component, in the second light detection mode, the light source is in the UNLIT state and the light-sensing device is in the ON state to determine a second detection light amount including the background component and the electrical offset component, and, in the third light detection mode, the light source is in the UNLIT state and the light-sensing device is in the OFF state to determine a third detection light amount that equals the electrical offset component so that the calculation means calculates the background component by subtracting the third detection light amount from the second detection light amount and calculates the original light amount component by subtracting the background component and the electrical offset component from the first light sensor value.