Introduction
A projector using DMDs (Digital Micromirror Devices) can be damaged by external laser sources that enters the projector via the projection lens.
A projector lens acts like a converging optic, focusing incoming laser light onto the DMD. Even a relatively low-power laser pointer can exceed safe irradiance at the focal plane. This results in very localized excessive power load onto the mirror surface of the DMD, leading to (thermal) damage.
Shows or environments with laser effects (concerts, industrial settings) have documented cases of camera sensors and projectors being permanently damaged when beams enter the lens directly. Also laser pointers or lasers used in construction equipment can damage the DMD.
Phenomenon
There are several cases reported with image defects similar as in the pictures below:
Typically, one or more clusters of failed pixels are seen, which can be in combination with either horizontal, vertical or both horizontal and vertical lines of defect pixels. As the driving circuitry of a DMD runs along the vertical and horizontal direction damage below the mirror surface, due to incident laser light, can result in vertical or horizontal lines in the image.
Root cause investigation
DMD’s with that type of damage were sent back to TI for further investigation.
TI found melted mirrors at the cluster defect location with no additional damage to other parts of the DMD that could have explained the cause of the defect.
Pictures show the mirrors were melted with no damage to other parts of the DMD.
This confirms the damage to the DMD is caused by an external laser light hitting the DMD.
Conclusion
It should absolutely be avoided to have external lasers entering the projection lens of a projector, as this can cause DMD damage. There are no means inside the projector to protect the DMD’s from this failure mode.
