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ArcticMyst Security by Avery
latency for laser measuring devices
- Thread starter tomhale
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Are you just trying to measure power? If so, yes, there is a definite rise time.
Most all the hobbyist power meters on here are thermal, and have significant rise times, like >1s, but that's ok because most all hobbyists on here are interested in measuring CW, so a 1s rise time is fine. If you need shorter, you'll have to go optical, like a photodiode. Start at Newport and Thor Labs, looking at their calibrated photodiode laser power meters, the rise time will be listed in their specs. But be careful, because most of the characteristics listed in their specs may be wavelength-dependent, so you might not get that spec'd performance at your wavelength of interest unless you investigate more deeply.
How fast does the response time need to be? Power requirements? Size requirements?
Higher power and higher size are both inversely proportional to rise time, so for fastest times you need lower-power and smaller photodiodes. You can then *possibly* use ND filters to knock the power down if you need, or lenses for a smaller photodiode, but these are all things to think about, plus a lot more.
Most all the hobbyist power meters on here are thermal, and have significant rise times, like >1s, but that's ok because most all hobbyists on here are interested in measuring CW, so a 1s rise time is fine. If you need shorter, you'll have to go optical, like a photodiode. Start at Newport and Thor Labs, looking at their calibrated photodiode laser power meters, the rise time will be listed in their specs. But be careful, because most of the characteristics listed in their specs may be wavelength-dependent, so you might not get that spec'd performance at your wavelength of interest unless you investigate more deeply.
How fast does the response time need to be? Power requirements? Size requirements?
Higher power and higher size are both inversely proportional to rise time, so for fastest times you need lower-power and smaller photodiodes. You can then *possibly* use ND filters to knock the power down if you need, or lenses for a smaller photodiode, but these are all things to think about, plus a lot more.
You're forgetting about silicon detectors, which have waaay faster response than thermal detectors but are wavelength dependent. You'll find a cheap one if you watch for it. Photodiodes are for super fast response. You can make a real cheap power meter if you have a stable reference laser to use to keep it calibrated, and you're only interested in ballpark numbers.
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Last edited:
You know what I mean. Besides, I didn't realize they made detectors out of the same substance they use to augment women's breasts!:thinking::crackup:
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Good one... fixed...
I still can't get my head around your new name...:beer:
Jerry
I still can't get my head around your new name...:beer:
Jerry
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I just did....
That doesn't sound good...:crackup:
J/K
Jerry
That doesn't sound good...
:crackup:J/K
Jerry
Benm
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There is always some latency, and its much larger for any type of thermal detector compared based on photodiodes. There should be 6 to 10 orders of magnitude between the systems in terms of response time, but the accuracy may be well worth that.
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Thanks for the assist. :beer:
Besides silicon, many other materials are used depending on the wavelengths you're interested in.
Also, if you're truly interesting in the fastest responses times, you'll need to look at biasing the detector as well, and all the other effects of the biasing on noise, etc. You can sacrifice some noise-to-signal for the speed with biasing, for instance.
Thanks for all the feedback. I am by no means an expert on lasers. What I am after a little more specifically is a laser measuring device that can measure the distance from it to where ever it is pointed at in real time. The laser does not need to charge up with no lag time but when fully on would be able to give a precise stream of data regarding this distance with no lag time as the laser was moved around. I realize it may not be possible using current technology but was wondering if I was wrong and that it may in fact be possible.
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If you are talking about Laser Data transmission then it is not a Laser
Power Meter you want...
A photo diode circuit is what you are looking for... There was a recent
Thread about just that...
You will need to do a little research using the search button...:beer:
The second part of your Post suggests that you want a Laser Range finder..
Two different circuits....IMO
Jerry
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Here's a neat little system I recently found you might be interested in seeing. It's a Heathkit/Zenith He-Ne Laser Trainer with matching Laser Receiver from 1985. I have all the books and schematics for it. There's an input for a microphone on the laser, and a photocell and speaker in the receiver. Add an off-the-shelf laser rangefinder and appropriate computer stuff and you're there!
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If you're measuring solid objects indoors (within a large room) or in sheltered outdoors conditions, you would probably be better off with a handheld sonar range-finder instead. If you aren't working in suitable conditions, either a standard laser rangefinder could be used, or two lasers could be used, which rapidly change angle until the spots overlap. The angle needed to achieve overlap can be used to get a distance output. This way would be quite complex and need quite fast visual feedback, and a high-precision scanning mechanism though.
