If you check around you might be able to find an old offset press camera
for very little, they were used to make the plates. It seems a
computers, scanners and laser printers have replaced them. I saw one in
thrift store for #10.00 about a year ago, it included the lense. I
didn't buy it as I had no room to store it.
Bill Higdon
Ron Amundson wrote:
> It would be a lot easier to by a used process camera than to try and build
> your own system for reduction. There are lots of business' closing doors in
> this economy, and used equipement is really cheap.
>
> If you did try to build your own, there are a multitude of things that can
> go wrong. You are trying to accurately create a 2:1 reduction in image size
> over a large area. Now, if you don't need fine resoultion over a large pcb,
> eg 15//15 across a 4 x 6 pcb, a home brew unit may work fine, and its a
> matter of experimentation to see what will work.
>
> A single simple lens will not work mainly due to the fact that sin(x)=x for
> only small angles which is the basis of the thin lense equation. Once you
> start having running ray traces with angles greater than 10 degrees, you
> need to start using series expansion techniques and the matrix of design
> starts getting a little crazy. You also find out that in short order, you
> either need to go with multiple lenses, and hope that you can build the
> assembly to the tolerances needed, or you need to have an aspheric lense
> made. Sorry to be a bit negative, but optical designs for high accuracy
> reduction/enlargement are quite tricky.
>
> If you do seriously want to get into optical design, Warren Smiths book on
> Modern Optical Design is extremely valuable. I took a class from him when I
> first started. There are a lot of very practical hints in his book that are
> lacking in a lot of the other more academic texts.
>
> Steve Greenfield mentioned chromatic aberation, as most of the films used in
> reproduction are monochromatic, it won't be an issue, but the other 4 common
> aberations will be.
>
> I consider myself at novice at optical desing too. I've taken probably 10
> classes, designed hundreds of units, taken a number of designs through
> production, and I still feel like I'm just beginning to understand the
> concepts.
> Thanks
> Ron