Off topic Laser question
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Posts: 46,084
Shorter wavelength lasers seem brighter to the human eye. Does a photodiode
or photoresistor perform better with the lower wavelengths as well?
Inquiring minds want to know.
Jeff
or photoresistor perform better with the lower wavelengths as well?
Inquiring minds want to know.
Jeff
Comments
Human eye's peak response is in the Green region (500nm). It falls on either
side of that wavelength region.
Simple photodiodes and semiconductor devices have peak response in the near
Infrared (~800nm) side of the spectrum - I don't know much about the latest
blue sensitive photodiodes. Photmultiplier's response depend on the
photochathode, and they inexpensive photomultiplers (like the IP28s) usually
respond well in the shorter wavelength range -usually blue (their resposnse
is limited by the glass envelop at shorter wavelengths (UV). But as you can
guess, there are PMTs that are optimized
for both IR as well as UV)
Vetrivel
UCSF [/font]
as I was experimenting with narrow bandpass filters and a laser pointer in
an attempt to make a laser navigation system. My filter is supposed to be
80% efficient at 670nm but my results are less than stellar. I now believe
that the wavelength of my laser is not as advertised. If I point the laser
and my photodiode at a reflective material, (White melamine) I get clear and
measurable results. If I install the +-10nm filter over the photodiode my
measurements are barely perceptible. The reason I want the filter in place
is for reliability in less than laboratory conditions. Thanks again.
Jeff
Original Message
From: <Lvetri@a...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, March 13, 2001 1:23 AM
Subject: Re: [noparse][[/noparse]basicstamps] Off topic Laser question
> Jefff,
> Human eye's peak response is in the Green region (500nm). It falls on
either
> side of that wavelength region.
> Simple photodiodes and semiconductor devices have peak response in the
near
> Infrared (~800nm) side of the spectrum - I don't know much about the
latest
> blue sensitive photodiodes. Photmultiplier's response depend on the
> photochathode, and they inexpensive photomultiplers (like the IP28s)
usually
> respond well in the shorter wavelength range -usually blue (their
resposnse
> is limited by the glass envelop at shorter wavelengths (UV). But as you
can
> guess, there are PMTs that are optimized
> for both IR as well as UV)
> Vetrivel
> UCSF
>