| 摘要 |
PURPOSE:To offer the auto focus device which can execute satisfactory plotting by adjusting a focus of a luminous flux to a scanning object, even if a laser photoplotter, etc., having a scanning optical system of high resolution. CONSTITUTION:The auto focus device is provided with a moving table 2 on which a scanning object of a scanning optical system for scanning a luminous flux in one direction is placed, a carrying means 3 for moving relatively the moving table 2 in the sub-scanning direction being roughly orthogonal to the scanning direction of the luminous flux of the scanning optical system 4, a focusing detection sensor 7 for detecting a focused state of the scanning optical system with respect to an unscanned position which precedes in the sub-scanning direction against a scanning position of the luminous flux on the scanning object, a memory part 10 for storing the focused state of the scanning optical system, and a focusing adjusting part 11 for adjusting a converging position of the luminous flux in accordance with this focused state. |
