Measuring the power of scanning lasers such as barcode scanners presents a problem. A bar code laser beam scans back and forth at a very high frequency so an ordinary photodiode power meter will not measure the power in the beam but rather the average power impinging on it, i.e. the power times the fraction of time the beam is on the detector. Therefore, when exposed to a scanned beam, the reading will be much lower than the actual power in the beam. For example, if a scanning laser delivers 2mW to a photodiode sensor and the beam is on the sensor only 1% of the time, the instrument will read only 0.02 mW.
There are a few different ways to measures laser power, but the most common is the photodiode. Photodiodes translate light energy into electricity (current), which can be measured by a current sensor.
Ophir uses a few types of photodiodes in its PD300 series.
Going to Munich for LASER World of PHOTONICS 2015?
We’ll be showing several new products in Munich, not to mention quite a few of our classics.
You’re going to be busy. You can’t (and shouldn’t) go to every booth. So I’m going to very clear. Our booth is not for everyone. However,
With high power lasers, there’s always a safety concern for equipment and people nearby.
(Of course, I’m not qualified to give a detailed analysis of what needs to be taken into account for laser safety. For that, you should consult a laser safety officer.)
I want to specifically ask whether there’s an issue of laser light reflecting off power measuring equipment.
In applications where a human observer is involved (for example illumination applications), it is often important to measure using the eye-response-matched Photometric system of units. Ophir’s PD300-CIE is a photometric sensor, and is designed to measure illuminance (in units of Lux or Foot-Candles).
A clear benefit of knowing the M2 of your laser is getting a lot of information about beam quality all in one number.
As simple as the output is, it is harder than you may imagine to measure and calculate M-Squared.
Let’s take a quick look at the theory behind M2 to see how it can be measured.