| 摘要 |
PURPOSE:To improve the accuracy of focus detection by disposing a filter having such a density distribution as to negate the nonuniformity in the light quantity distribution in the diametral direction centering at the optical axis, which nonuniformity is generated in an optical system of a pupil splitting system, on the optical axis forward of the intersected point excluding a conjugate position. CONSTITUTION:The filter 7 which has the density changing gradually in accordance with the distances from the optical axis X and in which the change of the density changes symmetrically with the optical axis is disposed on the optical axis X except the conjugate position R of the apertures of imaging lens 4a, 4b nearer on a subject side than the point S where the split luminous fluxes 6a, 6b respectively split from the luminous flux from the subject in the different parts of the pupil of a photographing lens 1 and passed through said parts intersect with the optical axis X. The nonuniform light quantity distribution generated by the optical system is thereby approximately uniformly corrected. The light quantity of the image on a photodetecting element array is, therefore, uniformized with inexpensive and simple constitution. The accuracy of the focus detection is thereby improved. |
