Re: UV-densitometer
Has anyone ever made an exposure unit with these LEDs?
----- Original Message -----
From: "etienne garbaux" <photographeur@nerdshack.com>
To: <alt-photo-process-l@usask.ca>
Sent: Thursday, December 03, 2009 1:50 PM
Subject: Re: UV-densitometer
Erich wrote:
Years ago I built my own visible light transmission densitometer.Now I
need to build an UV-densitometer. * * * Can anyone tell me what
UV-sensor and what UV- light source is used in your UV-densitometer ?
These days, a UV LED is the preferred source. Most emit between 350 and
395 nm, which matches most UV-sensitive photo systems well.
Here is a review of several products:
http://home.att.net/~ledmuseum/leduv.htm
They are available down to 200 nm or so:
http://www.s-et.com/?gclid=CL6P_vGau54CFclD5godQjlqUQ
You can buy individual UV LEDs from most electronics suppliers (Digi-Key,
Newark, Allied, Mouser in the US), or UV flashlights containing UV LEDs
from lots of sources (check Amazon or do a Google search, but make sure
you get an LED flashlight -- some UV flashlights use filtered xenon
bulbs). The flashlights are sold for detecting blood and urine stains,
verifying bank notes, viewing flourescent materials, etc.
Silicon photodiodes ("SPDs"), often fitted with blue filters to block
infrared sensitivity and then known as "silicon blue photodiodes," have
useful sensitivity in the 400 nm region. You will need to filter an SPD
to block visible wavelengths if there is any ambient light.
Best regards,
etienne
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