My cat likes to chase a laser pointer. While I was playing with him the other day I ran the laser point across a poster that I made hanging in my living room. I noticed that as the spot passed over black areas of the poster the light reflected back dimmed and over a lighter area the reflectivity increased. I discovered something that people had discovered thousands of years ago. That different materials absorb light differently. Not a big thing, I know.

But this gave me an idea. What if I were to do a long exposure on a camera as I swept the pointer back and forth. It should make a series of lines of varying widths. That might look neat. I decided to give it a try. 

I guessed the best way would be to build something to hold the laser and sweep it past the object while moving it up and down. A screw seemed like the perfect way to do this. As it sweeps past the object it lowers automatically. I never did come up with a way to make the pointer sweep left to right while moving down. Gravity kept interfering. What I did come up with was mounting the screw horizontally so that the pointer sweeps top to bottom and moves left to right.

At the hardware store I picked up a threaded rod and some washers. This one is 5/8" diameter.  I built my light kit (which I will explain later in another post) into a simple cube with a place to hold two ends of the screw. On one end of the screw I put a mounting to hold the laser pointer and on the other a place to attach a hand drill.

For my first test I used a alien skull I had sitting on a shelf.  The skull doesn't really have areas that bring out the absorbing light that originally attracted me to this project but it does have a nice 3d shape.

The photos of the first pass and the second one came out a little dark so I had to enhance them. The results are good.

Next I want to try mounting a laser pointer on a computer controlled thingy. My friend Vern says he can build a device that can position the laser pointer given an X and Y position. He will build it using two servo motors and a basic stamp processor. This will allow me to do things like sweep a grid pattern over an object while doing the long exposure.

I hope the photos from the next one come out looking as groovy as these did.

The first test image:

The second test image: