| 摘要 |
PURPOSE:To adjust a focus accurately and to read an image stably by providing an arithmetic means which detects focal lengths at least two points on the image of an information recording medium and estimates each focal length on a line connecting the two points, and a means which adjusts the focus of an optical system. CONSTITUTION:A microfilm F as the information recording medium is guided to a linear sensor 10. This linear sensor 10 consists of a CCD (charged coupled element) and a wire 17 is moved through pulleys 15 and 16 through the driving of a motor 18 to make a read in a subscanning direction on shafts 12 and 13, reading a projection image (f). Further, the image is recorded on the microfilm F as shown in a figure. Further, a focus adjusting lens 7 is fitted to a lever 22, on which an eccentric cam 23 provided to the shaft 21a of a stepping motor 21 abuts to move up and down according to the quantity of rotation of the stepping motor 21, so that a shift is focus position is made possible. |
