| 摘要 |
503,673. Optical sound recording and reproducing. KODAK, Ltd. Oct. 7, 1937, No. 27212. Convention date, Oct. 7, 1936. [Class 40 (ii)] [Also in Group XX] An optical system for producing a uniform flat image 26 of a linear light source 22, more particularly for sound recording or sound reproduction, comprises an objective 25 having an inwardly curved image field and a toric lens 21 positioned to receive light from source 22 and to focus it to form two astigmatic images, one of which is a curved line 23 in the curved image field of the objective and has a width which is reduced relatively to the source, and the other of which, 24, is substantially in the entrance pupil of the objective and has an area greater than said entrance pupil. Various forms of toric lenses are described including one having a non-circular minor curvature on the principle mentioned in Specification 461,259, and one in which the minor radius of curvature varies along the meridian of the major curvature as claimed in Specification 503,751
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