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US4548480A Projection lens apparatus 失效
投影镜头装置

Projection lens apparatus
摘要:
A projection lens apparatus for projecting an image from a CRT onto a remote screen. The lens apparatus is basically a Petzval type for a large aperture ratio and comprises three lenses. The first lens is a plastic lens having at least one aspherical surface and the third lens has a bi-aspherical surface. To reduce the thermal drift of the focal position, the second lens is a glass lens, having relatively largely positive optical power.
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