| 摘要 |
PURPOSE:To perform a high-precision focusing, by moving a focusing optical system along the optical axis on a basis of the output from a photoelectric converting device so that the focusing state of one chart is equal to that of the other. CONSTITUTION:An index 5 is illuminated with a light source 7, and charts 5a and 5b of the index 5 are focused onto a light receiving face of a photodetector 10 through a lens 8 to be examined and a focusing lens 9. On a basis of the output from the photodetector 10, the lens 8 to be examined is moved along the optical axis through a processing circuit 11 by a lens driving circuit 12 so that focusing states of both charts 5a and 5b are equal to each other; and when focusing states of both charts 5a and 5b are equal to each other, the image of the middle position between both charts 5a and 5b, namely, an object face 6 is focused distinctly onto the light receiving face of the photodetector 10 through the lens 8 to be examined and the focusing lens 9. |
