| 摘要 |
PURPOSE:To accomplish autofocusing to the average height of entire visual field without being influenced by ruggedness on a document. CONSTITUTION:As for a lens for matching 5, the flux of rays for focusing 3 is made incident on an objective lens 2 at a spread angle with a specified diameter, and a focusing position is deviated from the focusing position of objective lens 2 so that the beam diameter of the bundle of rays for focusing on the document 1 may be nearly the same as the diameter of the visual field of a microscope. The flux of rays for focusing 3 reflected on the document 1 passes through the objective lens 2, and is converged on a PSD 7 by a light receiving lens 6. At such a time, the flux of rays for focusing 3 is eccentrically made incident on the lens 2 and irradiates the document 1 by forming an angle, and the change of a distance between the document 1 and the objective lens 2 is detected as the displacement of a position on a light receiving surface on the PSD 7. Since the beam diameter on the document 1 is nearly the same as the diameter of the visual field of the microscope, the detected change corresponds to the change of the average height of the entire visual field, so that autofocusing to the average height of the entire visual field of the microscope is performed based on a light receiving position signal (a) from the PSD 7. |
