| 摘要 |
For a projection lens apparatus having a six-group structure that enlarges and projects an image displayed on a projection tube, an appropriate distance is maintained between a power lens and an aspherical lens group that is located near a power lens on the image generation source side, and physical interference with the power lens is eliminated, so that productivity is increased while a cost reduction is achieved. A meniscus lens that has a concave face directed toward a screen and has a refracting power is employed as an aberration correction lens (fourth group lens 4 ) that is located near the power lens (third group lens 3 ) on the image generation source side. Further, the lens surface of the meniscus lens on the screen side has an aspherical shape, so that a curvature is increased from the light axis to a predetermined point located between the light axis and the outer edge, and is reduced from the predetermined point to the outer edge. Furthermore, an inexpensive low refractive index material that has an Abbe number (nud) of 57 or higher and a refractive index (nd) of 1.500 or lower and that has superior flowability is employed as the base material for the fourth group lens that is located nearest the glass power lens on the image generation source side.
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