Control and optimization of the stray light in laser projectors

Laser projectors are more and more widely used because of their large screen, and high brightness. However, the stray light outside the screen affects the user's viewing effect dramatically. In some cases, it looks like there's a halo on the top, or loos like some light outside the picture in the black. Since the stray light comes from the reflection of mechanical structural parts in the lens, and some stray light is launched by the light on digital micromirror device (DMD) off state in the illumination system, how to carry out theoretical analysis effectively is a difficult problem. On the other hand, how to trace stray light back to the source after it hits the screen and reduce it is also a challenge. Herein, some effective theoretic analysis methods and practical analysis methods are put forward, and effective countermeasures are given. Through experiments, the stray light situation is effectively improved.