Patent ID: 7777893

Claim:
An optical image measurement device comprising: a light source configured to emit a low-coherence light; an interference-light generator configured to generate an interference light by splitting the emitted low-coherence light into a signal light heading toward a measurement subject and a reference light heading toward a reference object, and superimposing the signal light passed through the measurement subject and the reference light passed through the reference object; a changer configured to change a difference in optical path length between the signal light and the reference light; a detector configured to detect the generated interference light; an image forming part configured to form an image based on the result of the detection by the detector; an analyzer configured to analyze the formed image to calculate either a signal level of the image or a ratio of a signal level of the image to a noise level of the same image, and determine whether the signal level or the ratio of the signal level and the noise level exceeds a threshold value; and a controller configured to control the changer to change the difference in optical path length so that the analyzer determines the signal level or the ratio to exceed the threshold value.