Digitising collections of microfiche - Re: Looking for opinions...

[Jon Elson]

On 03/29/2018 06:25 AM, Pete Turnbull via cctalk wrote:
> On 29/03/2018 05:26, Shaun Halstead via cctalk wrote:
>
>> Using the wrong filament orientation can cause some weird 
>> artifacts
>> to appear on scanned images, because of the high 
>> magnification. I
>> strongly suspect that an attempt using an LED source 
>> would face
>> similar (and possibly worse) issues.
>
>> Light source.  Due to lensing requirements, LED's are 
>> probably out, unless a way can be found to suitably 
>> diffuse or blend the source without losing significant 
>> light.  This requires a very strong light source.
>
> Yet there are plenty of LED light sources used in 
> photomicroscopy so I
> don't believe it's that hard to do,which is why I 
> suggested it. I've seen it done with a high-brightness 5mm 
> LED, but if a bit more "oomph" or a larger emitting area 
> is required, there are inexpensive 1W and 3W LEDs that 
> look like they'd work.  I'm no expert, but the biggest 
> problem in photomicroscopy seems to be the spectrum, which 
> isn't really an issue for monochrome microfiche.
>
I built a laser photoplotter (see 
http://pico-systems.com/photoplot.html ) to make PC board 
master artwork.
it does very accurate plotting at 1000 x 1000 DPI.  The 
writing head uses a 5 mW red laser, and can focus to a spot 
smaller than .001". I actually defocus it slightly so the 
raster lines blend together.
It uses a microfiche objective lens plus a double-meniscus 
lens and a 2mm sphere lens right against the laser.  Similar 
optics could be used for a read head.  It would not be real 
hard to make a version like this to scan microfiche, 
scanning the entire card at once.

Not sure that LEDs would work, but red lasers are just a 
couple $ now.

Jon