I had on hand a rotating polygon with 6 facets, a 5mw red laser diode and a few first surface mirrors.

I thought build a small laser system and see if it works and if it does scale it up.

First problem. How fast does the polygon have to rotate to display a raster. We have a 625 line system here using interlace. The line rate is 15625 Hz. There is one full frame (625 lines) every 1/25 of a second so the lines per second is 625 times 25 equeals 15625 times 60 to get lines per minute equeals 937500.

This means if I had a polygon with one mirror it would have to rotate at 937500 revs per minute.

My polygon has 6 mirrors so speed drops way down to only 156250 revs per minute.

My polygon ex a laser printer said it could do 7701 revs per minute. Big difference between 156250 and 7701 rpm.

This problem seemed insurmountable however if I had a polygon with 625 mirrors each rotation of the polygon would be drawing a full frame of 625 lines therefor its speed would only need to be 25 frames per second times 60 equeals 1500 revs per minute. Well within my polygon speed range. There are no polygons available with 625 mirrors but what if I used stationary mirrors instead of rotating mirrors.

I did not fancy the idea of cutting and mounting such a large number of mirrors so how about using the 6 mirrors on the polygon to assist the stationary mirrors. That way I only need 600mirrors approximately divided by 6 equeals only 100 mirrors at 1500 revs per minute. Still too many mirrors. 50 mirrors speed goes to 3000 rpm and 25 mirrors speed of the polygon becomes 6000 rpm.

I tested this out with 5 mirrors arranged in a radius around the polygon in a special way which I will describe later and obtained 5 raster lines on top of each other. A slight tilt of each mirror gave me a 5 line raster.

That showed the idea was feasible and would work. The mirrors only have to be small about 1/2 an inch square.

I will be fitting a frame polygon so the mirrors dont have to be tilted but that one operates at a reasonably low speed so I am not worried about that.

Part 2 tommorow enough light. I have not solved this problem yet but will post how far I have got.

Richard