| 摘要 |
PURPOSE:To compensate distortion due to a field lens excellently and to perform high-precision focus detection by setting two lens surfaces of the field lens and two lens surfaces of a compensating lens on specific refracting power condition. CONSTITUTION:The pupil of an image forming lens 1 is divided into two pupil areas 8-1 and 8-2 by an image re-formation system. Luminous flux passed through the pupil area 8-1 forms the primary object image near a visual field mask 2 and is then passed through the field lens 6 and prisms 4-1 and 4-2 to form the secondary object image near photoelectric converting element arrays 7- 1 and 7-2 through an image re-forming lens 5. Their relative positions are detected to detect the focus state of the image forming lens 1, and the compensating lens 10 composes of a single lens for compensating distortion due to the field lens 6 is arranged in front of the photoelectric converting means 7. Then, inequalities hold, provided that psi1 and psi2 are refracting power values of the object-side and image-side lens surfaces of the field lens and psi3 and psi4 are those of the object-side and image-side lens surfaces of the compensating lens. |
