Patent ID: 7768651

Claim:
An apparatus for obtaining depth information on an object of measurement using optical coherence tomography based on spectral interference, the apparatus comprising: an interference optical system arranged to split a light with a short coherence length in order to use a part of the light as a measurement light of a measurement light projecting optical system and another part of the light as a reference light of a reference optical system, to make the measurement light converge at respective measurement points of the object by using an objective lens, and to synthesize the measurement light reflected from the object and the reference light to be an interference light; and a spectrometer unit including: a dispersing element arranged to disperse the interference light into frequency components; an array of light receiving elements arranged to photo-receive a dispersed light, the array of light receiving elements being disposed in a position conjugate with the object; and means arranged to vary a spectral characteristic of a light to be photo-received by changing a frequency range stepwise or continuously, wherein the spectral characteristic varying means comprises a variable power optical system disposed between the dispersing element and the array of light receiving elements.