Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Its difficult finding a UV photodiode under AU$100.
There are blue enhanced photodiodes go down to about 350nm with
%10 sensitivity relative to peak sensitivity.
Farnell have the BPW21R for AU$20 which I can live with.
http://www.vishay.com/document/81519/81519.pdf

Its the 365nm peak emitted from mercury vapor that is most
important for photoresists. This is just within the passband
range for standard glass, and the BPW21R photodiode. The inkjet
transparency film with mylar base and its ink receptive coating
no doubt has its own influence on the UV.

NEC blacklight tubes (BL-B type) are widely available so thats
not a problem, http://www.nelt.co.jp/nhe_hp/special/special.htm


I might not be hugely important to get the camera taking images
from a UV backlighted photomask. More important is knowing the
average UV absorption from a solid black area of print. This
absorption figure can be measured with a standard BL-B tube and a
photodiode like the BPW21R. I'm guessing the relative absorption
will be measured by taking intensity reading with solid black and
another reading without print.

A = log(Io/Ii)

where Io= photodiode current without ink
Ii= photodiode current with ink
A = relative absorption

I can measure and tabulate values of A for various inkjet
transparencies / inkjet printers.




Russell Shaw wrote:

> Adam Seychell wrote:
>
>>Hello,
>>I was interested in testing performance of various inkjet
>>printers and transparency print media...
>
> ...
>
>>Now there is the question can a simple back-light images show how
>>well it can work as a photomask in UV photoresist exposure?
>
>
> Maybe you could print a black area a few cm square then
> detect how much uv gets thru with a uv photodiode.
>
> http://www.google.com.au/search?q=uv+photodiode&ie=UTF-8&oe=UTF-8&hl=en&btnG=Google+Search&meta=
>
> Some washing powder has a phosphor in it that converts
> uv to visible, making white look "whiter".
>
> A photomultiplier tube would be sensitive and has a sharp
> cut-off for longer wavelengths.
>
>
>
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