发明名称 |
Variable focal length projection lens for use on overhead projectors |
摘要 |
A variable focal length overhead projector lens having four elements positioned in a projection head with two elements on either side of a folding mirror and having a single movable negative lens element closest to the screen being movable to vary the focal length and magnification at a fixed object-to-image distance to fill the screen.
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申请公布号 |
US4380374(A) |
申请公布日期 |
1983.04.19 |
申请号 |
US19810254947 |
申请日期 |
1981.04.16 |
申请人 |
MINNESOTA MINING & MANUFACTURING COMPANY |
发明人 |
VANDERWERF, DENNIS F. |
分类号 |
B42D15/00;G02B9/34;G02B11/22;G02B15/177;G03B21/00;G03B21/132;(IPC1-7):G02B9/58;G02B15/14 |
主分类号 |
B42D15/00 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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