Other Parts Discussed in Thread: DLP4500
I have a laser at 1.37um illuminating a DLP4500NIR from 10cm away with 24 degree AOI. The input beam is collimated and expanded to cover the entire active area of the DMD. I am using the DMD as an external monitor and I have the DMD displaying a white circle with a black background for the image. I measured the reflections using a Thorlabs infrared detector card at 10cm from the DMD.
As expected, the OFF state displays 1 image and there is a reflection off the DMD surface. But I have a problem with the ON state as it is reflecting 4 diffracted images instead of 1. The ON state should only produce 1 diffracted image. And as I move the infrared card away, the same 4 images continue to diverge.
Has anyone seen something similar, perhaps with the visible DLP4500 using a monochromatic source? Could this be from the geometry of the diamond pixel array?
The attached image is the result. From left to right: 4 circles in ON state, 0th order diffracted reflection off DMD surface, Conjugate image in OFF state.
Cheers,
Vincent