Patent ID: 7623308
Filing Date: 2009-11-24
Classification: G02B

Abstract:
1. A rear projection device for projecting image light to a screen from behind said screen, said rear projection device comprising: (a) a front lens group; (b) a rear lens group disposed behind said front lens group; (c) a first lens barrel for retaining said front lens group; (d) a second lens barrel for retaining said rear lens group; (e) a third lens barrel for rotatably accommodating said second lens barrel, said third lens barrel not being rotated; (f) a first moving mechanism for moving said front lens group in an optical axial direction when said first lens barrel being rotated, said first moving mechanism including a first female helicoid disposed on an inner circumference of said third lens barrel and a first male helicoid disposed on an outer circumference of said first lens barrel to engage with said first female helicoid; (g) a second moving mechanism for moving said rear lens group in said optical axial direction when said first lens barrel being rotated, said second moving mechanism including a second female helicoid disposed on an inner circumference of said first lens barrel and a second male helicoid disposed on an outer circumference of said second lens barrel to engage with said second female helicoid; and (h) a rotation stopper mechanism for linearly moving said second lens barrel in said optical axial direction without rotating said second lens barrel when said first lens barrel being rotated.