摘要 |
A dichroic mirror is a wedge-shaped quadrangular prism whose cross-section is a trapezoid having an upper base d and a lower base d+&Dgr;d. The dichroic mirror receives on its top surface parallel light emitted from a collimating lens and reflects, off the top surface, most of the parallel light towards a wavelength plate. Moreover, the dichroic mirror transmits, through the top surface, part of the parallel light to output the part of the parallel light from a bottom surface facing the top surface toward a front monitor. The dichroic mirror has, on the bottom surface thereof, an inclination of an angle &phgr; with respect to the top surface in a direction where a normal vector N of the bottom surface intersects with an xy-plane formed of: an optical axis x of incident light from the collimating lens; and an optical axis y of light emitted towards the wavelength plate.
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