Photodiodes?
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Posts: 46,084
Is there anyway to filter a photodiode to react to a certain wavelength
only? (red or green laser) Perhaps a way to strobe the laser and have the
stamp only react to photo sources of that frequency? Thanks.
Jeff
only? (red or green laser) Perhaps a way to strobe the laser and have the
stamp only react to photo sources of that frequency? Thanks.
Jeff
Comments
>Good narrow bandpass filters can be pricey,
>though.
>What are you trying to do?
>--Stu Wrenn
Stu,
I am trying to use a laser and a photodiode array as a navigation tool for
a robot. I would like to be able to shine a laser pointer at a particular
object and have the robot home in on the dot. The maximum range of detection
will be about 4 feet. I have had some successful experiments but things go
awry under different lighting conditions. I will like to filter out as much
"ambient" light as possible. Another Basicstamp subscriber emailed me off
list about filters that were available through Edmunds scientific, but it
looks like the laser pass filters have a pretty large spectral range.
(around 900nm) I would assume that these filters have a peak efficiency at
the target range and decrease from there. Do you think these filters are
what I need? Thank you for your reply.
Jeff
DESIGNED AND/OR BUILT?
Try this site:
http://www.omegafilters.com/prod/laser_line.html
Cheers,
Doug
On Mon, 19 Feb 2001, Jeff Mitchell wrote:
> >Absolutely! It's done all the time.
> >Good narrow bandpass filters can be pricey,
> >though.
> >What are you trying to do?
> >--Stu Wrenn
>
>
>
> Stu,
> I am trying to use a laser and a photodiode array as a navigation tool for
> a robot. I would like to be able to shine a laser pointer at a particular
> object and have the robot home in on the dot. The maximum range of detection
> will be about 4 feet. I have had some successful experiments but things go
> awry under different lighting conditions. I will like to filter out as much
> "ambient" light as possible. Another Basicstamp subscriber emailed me off
> list about filters that were available through Edmunds scientific, but it
> looks like the laser pass filters have a pretty large spectral range.
> (around 900nm) I would assume that these filters have a peak efficiency at
> the target range and decrease from there. Do you think these filters are
> what I need? Thank you for your reply.
>
> Jeff
>
>
>
>
Good narrow bandpass filters can be pricey,
though.
What are you trying to do?
--Stu Wrenn
Original Message
From: Jeff Mitchell <EL-JEFE@P...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, February 18, 2001 9:23 PM
Subject: [noparse][[/noparse]basicstamps] Photodiodes?
> Is there anyway to filter a photodiode to react
to a certain wavelength
> only? (red or green laser) Perhaps a way to
strobe the laser and have the
> stamp only react to photo sources of that
frequency? Thanks.
>
> Jeff
>
>
>
>
>
> Is there anyway to filter a photodiode to react to a certain wavelength
>only? (red or green laser) Perhaps a way to strobe the laser and have the
>stamp only react to photo sources of that frequency? Thanks.
>
>Jeff
Another approach is to use a prism or a grating in a housing, and put
the photodiode behind a mask to pick up the desired spectral line.
-- Tracy
electronically monitored ecosystems
http://www.emesystems.com
center wavelength, bandpass, size, mounting,
environmental requirements, etc.
The best place to start is Edmund Industrial
Optics www.edmundoptics.com
They also offer very good phone support for us
non-optical engineers.
Original Message
From: Production Technology, L.L.C.
<fixemerd@a...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, February 19, 2001 7:55 AM
Subject: RE: [noparse][[/noparse]basicstamps] Photodiodes?
> wHAT IS PRICY FOR A "GOOD" BAND PASS FILTER AND
WHERE MIGHT I HAVE ONE
> DESIGNED AND/OR BUILT?
>
>
>
you use this idea and replace the IR led with a laser pulsed at 40 khz for
detection rather than avoiding the object go to it. there are
phototransistor's that are set for 38, 37 and 40 khz detection maybe other
freq. also
Jeff Mitchell wrote:
>
> Is there anyway to filter a photodiode to react to a certain wavelength
> only? (red or green laser) Perhaps a way to strobe the laser and have the
> stamp only react to photo sources of that frequency? Thanks.
>
> Jeff
>Not much point in an invisible pointer is there?
>I'd go for a narrow (say 20-30 nm or less) at
>whatever
>your laser's center wavelength is.
>Are you using one of the linear diode array chips?
>How wide is the acceptance angle of the system?
>--Stu
The laser I'm using right now is 670nm but they are cheaper than the
filters so I guess my priority would be the narrowest filter I can find in a
diode laser wavelength.
I am not using one of the linear diode array chips. In fact, I have no
earthly idea of what they are.[noparse]:)[/noparse] What are they? If they are as their name
implies, I would assume they can differentiate between light sources falling
on different sections of the array?
The minimum acceptance angle of the entire system needs to be 45 degrees
x,y . anything beyond that is gravy. Resolution is not critical, just the
ability to keep the dot between the sensors.
Another option concerns an earlier post by B.D. Hornback, that I read
recently about a Mitsubishi camera and edge detection.
http://members.home.net/daniel.herrington/gbcam.html This sounds great but
I would like to avoid the use of a PC to interpret the data.
What wavelength is your laser? If it's IR, then a
visible blocking filter should do the job. These
are not very expensive. If you are using a
visible laser, then a narrow bandpass filter would
reduce but not eliminate the effects of ambient
(visible) light. Modulating the laser might be
the answer.
--Stu
Original Message
From: Jeff Mitchell <EL-JEFE@P...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, February 19, 2001 7:30 AM
Subject: Re: [noparse][[/noparse]basicstamps] Photodiodes?
> >Absolutely! It's done all the time.
> >Good narrow bandpass filters can be pricey,
> >though.
> >What are you trying to do?
> >--Stu Wrenn
>
>
>
> Stu,
> I am trying to use a laser and a photodiode
array as a navigation tool for
> a robot. I would like to be able to shine a
laser pointer at a particular
> object and have the robot home in on the dot.
The maximum range of detection
> will be about 4 feet. I have had some successful
experiments but things go
> awry under different lighting conditions. I will
like to filter out as much
> "ambient" light as possible. Another Basicstamp
subscriber emailed me off
> list about filters that were available through
Edmunds scientific, but it
> looks like the laser pass filters have a pretty
large spectral range.
> (around 900nm) I would assume that these filters
have a peak efficiency at
> the target range and decrease from there. Do you
think these filters are
> what I need? Thank you for your reply.
>
> Jeff
>
>
>
>
>
OOPs, sorry! You did say laser POINTER.
Not much point in an invisible pointer is there?
I'd go for a narrow (say 20-30 nm or less) at
whatever
your laser's center wavelength is.
Are you using one of the linear diode array chips?
How wide is the acceptance angle of the system?
--Stu
http://www.edmundoptics.com/IOD/DisplayProduct.cfm?productid=1936
At 09:55 AM 2/19/2001 -0600, you wrote:
>wHAT IS PRICY FOR A "GOOD" BAND PASS FILTER AND WHERE MIGHT I HAVE ONE
>DESIGNED AND/OR BUILT?
>
>
>Reply-To: <basicstamps@yahoogroups.com>
>From: "Stu Wrenn" <swrenn@z...>
>To: <basicstamps@yahoogroups.com>
>References: <001e01c09a34$1a6cf8e0$4730c440@frank>
>Subject: Re: [noparse][[/noparse]basicstamps] Photodiodes?
>Date: Mon, 19 Feb 2001 12:55:38 -0600
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_________________________________
Mike Walsh
walsh@i...
California Institute of Technology
Biology Electronics Shop
MS 216-76
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