I wanted to try a laser engraving on the back of a mirror with our 6W LD. I added a frame to the border so the engraving would blend into the mirrors reflection on the edges. Laser engraving on mirrors gives similar results as spindle engraving Lithophanes, except the image is visible when backlit or not.
I Dithered the image to 1bit Black & White in the PEP5 image editor so the laser would just pulse on/off. I then Flipped the image so it will view on the front properly. I used the Negative selection so the white areas will burn with the highest power which comes out white on the front. The mirror's reflection gives you the black shading effect.
I set the feedrate at 150IPM with a FRC of 20%. Black areas ran at 150IPM at zero laser power (off), then it slows to 120IPM to burn the white areas at full laser power. There are 1,642,528 lines of gcode in the file and the size is 10" X 8". It took 2:07:02 in time to engrave. The hardest part is trying to take pictures of the finished mirror engraving because everything in front of it comes out in the photo.
Here it is backlit.
Here it is without being backlit.