| 摘要 |
PROBLEM TO BE SOLVED: To provide a rear projection optical system which is advantageous in the mass productivity and cost while maintaining good optical performance and which is made thin and includes compact optical parts. SOLUTION: The optical system is equipped with a projection optical system to project an image of a panel display screen (I1) onto a screen plane (I2), and the projection optical system contains four curved reflection mirrors. When a beam propagating from the screen center of the panel display screen (I1) through the center of a diaphragm (ST) to the screen center of the screen plane (I2) is defined as the screen center beam, the optical system satisfies the relation of 0.5<D/H<3.5 and 100 deg.<θ<70 deg., wherein D is the optical distance of the screen center beam from the last face of the projection optical system to the screen plane (I2), H is the size of the screen plane (I2) in the parallel direction to the plane made by the normal line of the screen (I2) and the screen center beam, andθis the incident angle of the screen center beam to the screen plane (I2).
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