PURPOSE: To provide an IR wide angle single lens which has an excellent imaging characteristic and is simultaneously approximately uniform in a peripheral light quantity ratio.
CONSTITUTION: This IR wide angle single lens 1 is a biconvex lens having a diaphragm on an object side and has constitution satisfying the conditions (1), (2), (3), (4), (5) of Dist=(y-y0)/y0. (1)-3.6<r1/r2<-0.9. (2) 0.3<d0/f<0.6. (3) 0.6<(d0+d1/n)/f<0.9 (4)-0.19<Dist<-0.16. (5) 0.7<bf/f<1 where d0 is defined as the interface distance from the diaphragm to the first face of the lens, d1 as the central thickness of the lens, r1 as the radius of curvature of the first face, r2 as the radius of curvature of the second face, n is the refractive index of the glass material at a wavelength 10μm, (f) a focal length, bf a back focus, the ideal height at the max. image height of a half angle of view of 35deg as y0, the main ray image height of an actual ray as (y) and the distortion aberrations at the max. image height as Dist.
YOSHIKAWA TOMONOBU
BOKU KAZUTAKE
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