| 摘要 |
PROBLEM TO BE SOLVED: To obtain a lens device for projection excellently satisfying various aberrations while realizing miniaturization and a wider angle in order to miniaturize a projection type picture display device. SOLUTION: In this lens device for projection, a 1st group lens having negative refractive power, a 2nd group lens having positive refractive power and a 3rd group lens having positive refractive power are successively arranged from a screen side to a picture display element side. When it is assumed that the focal distance of an entire system is (f), the focal distance of the 1st group lens is f1, the focal distance of the 3rd group lens is f3, the synthetic focal distance of the 2nd and the 3rd group lenses is f23, and the back focus of the entire system is fb, the lens device satisfies a condition decided by following expressions (1) to (4), (1) 1.4<|f1|/f, (2) 2.8<f3/f, (3) 3.6<fb/f and (4) 0. 1<|f1/f23|<0.3. |
