Patent ID: 7268885

Claim:
An optical image measuring apparatus for forming an image of an object to be measured based on interference light, comprising: a light source for emitting a light beam; an optical interference system that divides the light beam emitted from the light source into signal light propagating through the object to be measured and reference light propagating through a predetermined reference object, shifts a frequency of the signal light and a frequency of the reference light relative to each other, and then superimposes the signal light propagating through the object to be measured and the reference light propagating through the predetermined reference object on each other to produce the interference light; intensity modulator operable to modulate an intensity of the interference light at a predetermined frequency; a photo detector for receiving the interference light whose intensity is modulated and converting the received interference light into an electrical signal to be outputted; and calculator operable to calculate an intensity of a direct current component composed of background light of the interference light based on the electrical signal outputted from the photo detectors, wherein the intensity modulator modulates the intensity of the interference light beam at a frequency which is not synchronized with a beat frequency of the interference light beam, and the calculator time-averages the electrical signal outputted from the photo destector based on the interference light beam whose intensity is modulated at the frequency to calculate the intensity of the direct current component.