| 摘要 |
PROBLEM TO BE SOLVED: To provide a lens capable of suppressing an influence of back focus variation even if an environment changes although being inexpensive, and a projection image display device using the same.SOLUTION: Since a leg part LG of a collimator lens COL has its length T determined so that an expression (1) is satisfied, the leg part LG extends and contracts ((T±ΔT) as an ambient temperature varies, so that variation in back focus can be suppressed. Additionally, the collimator lens COL has a pair of cuts CT, so even after an end face of the leg part LG is bonded to a stem part ST, a laser chip CP is not sealed in the collimator lens COL and cooled with outside air via the cuts CT, so that the collimator lens COL can be suppressed from rising in temperature, thereby effectively suppressing variation in back focus. Here, BF≤T≤φ (1), where BF is a distance (mm) from a light source-side optical surface to a condensing point, and φ is a lens outer diameter (mm).SELECTED DRAWING: Figure 6 |
