| 摘要 |
PURPOSE:To attain efficiently and accurately focusing at image reading by providing a lamp at a position deviated from the center position of the curvature of a spherical lens. CONSTITUTION:A part of luminous flux is reflected in a spherical mirror by a lamp 2 arranged at a position deviated from the center position of the curvature of the spherical mirror 1 and a lamp image 3 is formed. The luminous flux made incident on a microfilm 5 is diffused through a film image pickup and converged by a projection lens 6. The image forming luminous flux converged by the lens 6 consists of two luminous fluxes; that from the lamp 2 and that the lamp image 3, as shown in solid and broken lines, and the position where the two luminous fluxes are crossed as one luminous flux by the lens 6 is sensor photodetection plane 7 of a position B. When the plane 7 is at a position A or C, since two peak values are obtained from a line sensor output, the moving direction of the lens 6 is discriminated by comparing the level of two peak values P2, P3. |
