(EN) 544,694. Photographic objectives. BRITISH THOMSON-HOUSTON CO., Ltd., and GABOR, D. Jan. 28, 1941, No. 1105. [Class 97 (i)] An objective of large aperture comprises a concave spherical mirror 1, a meniscus lens 2 with two sperical curvatures directed like that of the mirror, and a shield 3 obscuring the central part of the aperture, the meniscus lens being so dimensioned and positioned that spherical aberration and coma for the effective annular zone are substantially smaller than for the mirror above. A plans-convex or biconvex lens 4 may be provided having its surface of smaller curvature near the image field i to reduce astigmatism and field curvature, and a plane mirror 5, Fig. 3, may be placed between the spherical mirror 1 and meniscus lens 2 to serve as the shield and to direct the rays through an aperture in the mirror 1 and produce an image field i in or behind it. The lenses may be formed from a single kind of glass or other material such as quartz or rocksalt. Optical data are included in the Specification.