Good OPTICAL Sensors for Meters?

[seoguy]

What are the best optical sensor devices to use for a power meter?

Is it best to use...

• Solar Cell? (Monocrystal? Polycrystal? Non-Silicon?)
• PhotoDiode?
• PhotoTransistor?
• PhotoCell? (CdS? Other?)
• IC Sensor?
• CCD Sensor?
• Something Else?

Now, I know that optical sensors will typically not have a flat spectral response curve (although a sensor that has at least some response over the entire visible spectrum is obviously preferred!), nor be suitable for high power levels without filtering.

And this does not mean that I have abandoned a DIY thermal approach - far from it, I've got a slew of ideas I am putting together for Benm's diode design, along with some new stuff I am waiting to arrive in the mail shortly!

But upon further reflection, I think I may have allowed a commercial vendor to talk me out of pursuing the optical approach prematurely. Optical designs also have their own benefits. Even Coherent makes optical models! So I am exploring both approaches.

So what say you all - what is the best type of optical sensor for power measurements?

Thanks!

 

[lasersbee]

Have you seen this....

http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&rd=1&item=150330135224&ssPageName=STRK:MESE:IT&ih=005

I don't want to sound negative.... (and I am not against your project)...

But... you will still need a Calibrated LPM to be able to calibrate your Optical LPM...
and as we have already seen here... the the optical LPMs don't seem to like the
405nm Wavelengths...

For a DIY LPM... I still think that Benm's thermal Power Guage would be a better
approach... since it will cover most wavelengths of lasers... IMHO  


Jerry

 

[Benm]

All these sensors have their problems when it comes to spectral response and power handling. The latter could be mitigated by inserting a suitable ND filter in the optical path, but fixing the spectral response is tricky.

If you manage to get a photodiode or LDR with a good spectral response curve it its datasheet it might be possible to compensate as long as you know the wavelength. CdS LDR's are sensitive all the way to 400 nm, but feature a big sensitivity peak in the middle of the visible spectrum and require huge compensation factors at either end - not unlike the perceptual brightness the human eye renders.