| 摘要 |
PURPOSE:To detect a focus position promptly and at a high accuracy by obtaining different signals between image signals and smoothed or average processed image signals and by controlling a lens system to maximuze the different signals. CONSTITUTION:A projected screen of a television receiver 1 to be inspected is image picked up by a photoelectric conversion element 3 through the lens system of a drive device 2 for focus adjustment. An image signal V0 from an element 3 is supplied to a smoothing device 4, and the device 4 performs transfer average processing of the signal V0 and supply an output signal V0 to a comparator 5. The comparator 5 performes a subtraction processing using the signals V0 and V0' to obtain difference signals V0-V0', where the device performs variance for the whole picture screen and designated area. As a result, even when a point at which the dispersion is maximum is a video signal containing much noise at a mating focus, the device can obtain the mating focus position at a high accuracy. |
