Auto focus mechanism in image input apparatus

摘要

An auto focus mechanism mounts a target of reading on a manuscript board and moves an optical read unit which is long in a main scanning direction along a sub scanning direction to read an image of the target of reading. The auto focus mechanism is provided to an image input apparatus for inputting image data. The read unit includes: an optical source for irradiating the target of reading with a read light ray; a lens which accepts a reflected light ray from the target of reading and is long in the main scanning direction; a lens thickness change portion which is provided on both sides of the lens in the longitudinal direction and mechanically operates so as to change a thickness of the lens in the longitudinal direction by an electric lens; a SELFOC lens for focalizing a reflected light ray at a central portion in the sub scanning direction; and a photoelectric transfer portion for photoelectric-transferring a focalized reflected light ray to generate image data. The read portion performs focusing adjustment of the lens by using a control portion which controls the drive of the lens thickness change portion based on an electric signal photoelectric-transferred by the photoelectric transfer portion and a drive portion which generates a drive signal for driving the lens thickness change portion based on a control signal from the control portion and outputs the drive signal to the lens thickness change portion to partially change the thickness of the lens in the main scanning direction.