| 摘要 |
PURPOSE:To make it possible to vary the contraction scale ratio of the projection optical image without steps and make the device small-size, by providing the second mirror form control mechanism which changes the angle of the second mirror, which projects the light from the first mirror, for the optical axis. CONSTITUTION:A projection lens displacement mechanism is provided which displaces projection lens 5 along optical axis L2 of lens 5 without steps, and the second mirror form control mechanism which displaces the second mirror 6 along optical axis L2 of lens 5 and changes the angle of the second mirror 6 for optical axis L2 is so provided that displacement of the focus position generated by displacement of projection lens 5 dependent upon the projection lens displacement mechanism may be compensated. A helicoid mechanism or the like is most suitable as the projection lens displacement mechanism, and this displacement mechanism and the second mirror form control mechanism are interlocked with each other, as a result, the construction scale ratio can be varied without steps, and the occupation space can be small to make the device small-size. |
