| 摘要 |
PURPOSE:To execute quickly a readjustment against a change of a focus caused by a temperature change, by adjusting automatically a focus, in an optical device such as a microfilm reader, etc. CONSTITUTION:A real image of a microfilm 1 illuminated by a lamp is formed on a CCD image sensor 12. This real image is converted photoelectrically, amplified by a video amplifier 20, and thereafter, A/D-converted by an A/D converter 21, and applied as a digital signal to a line memory 22. The line memory 22 is provided with an all bit (picture element) portion of the CCD sensor with respect to a video data of at least one scanning line. With regard to the data accumulated in the line memory 22, a difference of the data of adjacent picture elements is calculated by a calculating circuit 23, and the largest one is compared by an operating circuit 24 and selected from among the data of a difference of the adjacent picture elements obtained by moving an optical system. By a command from the operating circuit 24, a servo-motor controlling circuit 25 is operated, and an optical system moving mechanism 26 is moved. |
