SMALL-SIZED PROJECTION OBJECTIVE Russian patent published in 1995 - IPC

FIELD: optical instrument engineering. SUBSTANCE: in four-lens objective the first lens is positive meniscus, turned with its convexity to subject, the second lens is biconcave, the third one is biconvex, the fourth one is negative meniscus, turned with its convexity to image plane. Refractivity n_e and dispersion coefficients ν_e satisfy the following conditions: n_e≥ 1,746 and ν_e≅ 50 for positive lenses, and n_e≅ 1,58 and ν_e≅ 37,7 for negative lenses. EFFECT: improved precision. 9 dwg, 1 tbl