| 摘要 |
PROBLEM TO BE SOLVED: To realize a projection lens unit realizing a short focal distance (wide angle), high focus and high contrast at low cost as a projection lens unit used for a back projection type picture display device. SOLUTION: A lens positioned on the screen side of a power lens 3 is formed in such a shape that its central part has positive refractive power and its circumferential part has negative refractive power, and a lens of the power lens positioned on the video generating source side is formed in meniscus shape that its central part is biconvex and its circumferential part turns its concave surface to the video generating source side, whereby excellent focusing performance is realized in a short projection distance (wide angle) even in the case of using an inexpensive low refractive index glass lens.
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