| 摘要 |
<p>1,260,245. Photo-electric control of focusing. COMMISSARIAT A L'ENERGIE ATOMIQUE. May 23, 1969 [June 7, 1968], No.26382/69. Heading G1A. [Also in Division G2-3] Automatic focusing of an optical instrument is obtained by moving the objective lens rectilinearly parallel to its optical axis in accordance with the increase or decrease in the light received in a light sensitive system after passing through an element which produces substantial spherical aberration of the image. The objective lens 1 is mounted in the centre of thin annular plate 5 which forms the armature of electromagnet 6. The image from lens 1 passes through binocular 11 one part going to an eyepiece and the other part to a spherical aberration variator 12 which converts the variations in contrast due to focusing into variations in luminous flux. This flux passes through a further binocular to lenses 18, 17, to photo-resistive cell 15 and photo-emissive cell 14. The lenses 18, 17 are adjusted so that cell 15 receives the flux from the field of view in the focusing plane and cell 14 receives flux from the same field of view but outside the focusing plane. By this arrangement changes in overall illumination produce opposite effects in the detectors 14, 15 which cancel and have no effect on the energization of the electromagnet. Variation in focus will however only affect the illumination of photoresistor 15 and will cause a change in the energization of electromagnet 6 to restore the focus.</p> |
