| 摘要 |
PURPOSE:To compensate an error present without an IR region and to perform exact detection of a focus by detecting a defocusing quantity with prescribed two wavelengths in the IR region and calculating the defocusing rate relative to the reference wavelength in a visible region from the detected defocusing quantity. CONSTITUTION:If lambdad is designated as a standard wavelength and lambda1, lambda2 are designated as reference wavelengths, a straight line L1 deviates upward by DELTAd at the wavelength lambdad and is therefore imaged backward of an intended focal plane. Since a straight line LII deviates downward by DELTAd' at the wavelength lambdad, said light is imaged forward of the intended focal plane. The deviation quantity DELTAd or DELTAd' from the standard light is consequently calculated by the equation from the deviation quantities (DELTA1, DELTA2) detected with the respective wavelengths and the photographing lens is adjusted until the deviation is made zero, by which the focusing is accomplished. |
