| 摘要 |
A symmetric relay system for endoscopes includes an optically-aligned pair of elongated concavo-convex rod-type lenses formed from crown glass, to the convex end surface of each of which a meniscus-shaped flint lens is cemented. The concave ends of the rod lenses are disposed to face the intermediate images of the relay system, and the convex ends to face the aperture of the relay system. A pair of achromatic lenses, each formed of a pair of lens elements x, y, are disposed adjacent and in optical alignment with the respective concave ends of the rod lenses between the concave rod ends and the intermediate images. Each achromatic lens fulfills the condition n x/ny=vx/vy. Apochromatic glass combinations may be used in the rod lenses to significantly reduce the secondary spectrum.
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