OPT3002: How to decompose optical power through the different wavelengths

Hi Carlos,

Equation 4 only works for a single wavelength input. If you take a look at "Figure 2. Spectral Response vs Wavelength" you'll see that the sensor responds differently at different wavelengths. If you are trying to measure the intensity of a single wavelength and you can ensure that no other wavelengths are exposed to the sensor then you can compensate for the sensor's normalized response at that wavelength using equation 4. However, if multiple wavelengths are present then there is no way to determine how much a specific wavelength contributes to the overall sensor reading.

Best,

Alex

Hello Alex,

Thanks for the rapid response.
Just one more doubt:
To get the optical power from the OPT3002 I need to use equation 2 (Optical_Power = (2 E[3:0] ) × R[11:0] × 1.2 [nW/cm 2 ]), where E is characterized in table 8: "Result Register: Full-Scale Range (FSR) and LSB Size as a Function of Exponent Level" for wavelength 505nm. When I expose the sensor to the sun light, which is composed by multiple wavelength, and calculate the output power with equation 2 what will be the meaning of that result?
What I really want to know is, if the sensor is exposed to multiple wave lengths will the optical power outputted by it have any useful meaning, or the sensor will be useless in such situations?

Thanks,
Carlos

Hi Carlos,

The sensor still gives you an intensity reading. This reading is equivalent to taking the sum (integral across wavelength) of the sensor's nominal response (from figure 2) multiplied by the intensity of the input light at each wavelength. Please let me know if this explanation does not make sense and I will try to expand on it more.

In an application with many wavelengths, such as sunlight, the sensor can be used to measure relative light levels and detect changes in lighting conditions. Does your application require

1) measuring the power at multiple wavelengths for sunlight (e.g. 300, 400, 500nm)
2) obtaining a single overall power reading for with all the wavelengths combined
3) detecting relative changes in lighting?

And what type of precision are you looking for? As I noted above, 1) will be tough with this sensor. 2) is possible depending on how precise you need the reading.

Best,

Alex

Hello Alex,

There is no need to expand more your explanation, I think I understood it.

What I need to know is the overall amount of lumen to which the user is exposed to in the visible spectrum.

However, the sensor output is mw/cm2, and to convert it to lumen (according to this site: www.dfisica.ubi.pt/.../ch07.html), I need the light wavelength. This means that I cannot perform the conversion, because the sensor output in mw/cm2 is the integration of all the lights received on its wide optical spectrum range, right?

Is it possible to convert the sensor output to lumen?

Thanks,

Carlos

 

Hello Alex,

Thanks for the prompt reply.

In fact OPT3001 is the ideal sensor for our application. 

Thanks for the help.

Carlos