| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical system for a projection type display apparatus which adjusts focus by moving an image forming element on an optical axis, the optical system being designed such that uniform brightness and satisfactory display image quality are retained for any projection screen size corresponding to focus adjustment; and to provide a projection type display apparatus. SOLUTION: A light guide member includes a first light guide member 21 in the form of a hollow prism and a second light guide member 22 that is an element in the form of a hollow prism with a reflecting film formed on an internal face thereof, the first and second light guide members 21 and 22 being slid against each other. The emission end face of the second light guide member 22 and the incident face of the image forming element 30 are held in a predetermined positional relation. The second light guide member 22 is moved in the direction of the optical axis 29 together with the image forming element 30. In such a structure, even when the image forming element 30 is moved on the optical axis for focus adjustment, a relation between an illuminating luminous flux and the effective pixel area of the image forming element is prevented from being changed. Accordingly, uniform brightness and satisfactory display image quality can be retained for any projection screen size. COPYRIGHT: (C)2007,JPO&INPIT
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