Laser Wood Burning

I usually complete my projects about 85-90% before moving on to the next one. As I mentioned before, I wanted to do a laser wood burner. The idea is you would take a gray scale image with has the data stored in a particular way. Regardless of how your program would interpret the data, there is a scale from light to dark.

Gray Scale Range

I want to use this stored data in an image file to control a laser. It would ride on a X-Y carriage as the laser is controlled maybe by pulse width modulation. This would effect how long the laser burns and at what intensity to get contrast on the image.

Pulse Width Modulation

I think this would be a cool project to do where you can have 

1. An image processed
2. Converted to data for the laser to interpret X,Y and power
3. Have a microcontroller or computer control the burning process

The end result would hopefully be something along the lines of

Hopefully final result for the laser wood burning project

If this can be done by hand why not have a computer do it :-) I think it would be a pretty cool challenge . Any suggestions are appreciated.