Projection lens apparatus and projection type image display apparatus

#1. Field of the Invention

#The present invention relates to a projection lens apparatus for allowing a source light to be made incident in an image display apparatus so that an overhead projection of the reflected light or the transmitted light is performed on a projection screen, and also relates to a projection type image display apparatus equipped with the projection lens apparatus.

#2. Description of the Prior Art

#FIG. 1 is a schematic view of a projection lens apparatus according to a first embodiment of the present invention;

#FIG. 2 is an illustration of spherical aberration of the projection lens apparatus according to the first embodiment;

#FIG. 3 is an illustration of astigmatism of the projection lens apparatus according to the first embodiment;

#Referring now to the attached drawings, preferred embodiments of the present invention will be described. FIGS. 1, 5, 9, 13, and 17 are illustrations of projection lens apparatuses according to the embodiments of the present invention. The following description will be focused mainly on FIG. 1, and descriptions on FIGS. 5, 9, 13, and 17 will be omitted since these figures are considered to be understood from data in Tables 2 to 5 and on the analogy of the description on FIG. 1.

#FIG. 1 is a schematic view of a first embodiment of the projection lens apparatus and its associated optical components showing, from a projection screen (not shown) or the left side of the plane of the figure, a first lens group 1, a second lens group 2, a third lens group 3, a total reflection prism (hereinafter, referred to as a TIR prism) 5, and a DMD element 6 in this order. The above three lens groups 1 to 3 constitute a projection lens apparatus 4. A ray emitted from a light source is made incident on an incidence plane 51 of the TIR prism 5, and is totally reflected at a total reflection plane 52 of the TIR prism 5, and then is made incident on the DMD element 6. After reflected on an active plane of the DMD element 6, the incident ray transmits the TIR prism 5, and is made incident on the projection lens apparatus 4, and then is projected on the screen.

#The projection lens apparatus 4 is provided with the first lens group 1 having a negative refracting power, the second lens groups 2 having a positive refracting power, and third lens groups 3 having a positive refracting power. The first lens group 1 includes a first lens 11 as well as a second lens 12 of negative meniscus lenses facing their convex surfaces toward the screen, and a third lens 13 of a biconcave lens, in addition to a fourth lens 14 of a biconvex lens. The second lens group 2 includes a fifth lens 21 of a biconvex lens, an aperture 22, and a sixth lens 23 of a biconvex lens. The third lens group 3 includes a seventh lens 31 and an eighth lens 32 having a mating face therebetween, a ninth lens 33 facing its concave surface toward the screen, and a tenth lens 34 of a biconvex lens.