| 摘要 |
PURPOSE:To realize high-accuracy automatic focusing without generating any false focus error signal by the pattern of an object surface by setting an index projection surface where an index image is formed at a position which is not conjugate to an object projection surface about an object lens. CONSTITUTION:The cause of the influence of the pattern of the object surface 3 on the index image 5 on a photodetecting means is that the object surface 3 and index light projection surface 6 are set conjugate to each other about the objective 2, so this is utilized to set the optical arrangement between the object surface 3 and index projection surface 6 not to satisfy the conjugation relation about the objective 2. Consequently, even if the index light incident on the index projection surface 6 is under the influence of the object surface pattern, the pattern lighted by the index light is not image-formed sharply on the index projection surface 6, but formed in an out-of-focus state, so the light quantity distribution of the index image on the index projection surface 6 is averaged and the superposition of an error signal on the output of the photodetecting means is suppressed. |
