Intensity of laser light measured through a photodiode

Hey everyone,

This is my first post, so I hope it is in the right section. I have a problem with measuring the intensity of a laser. Baically what I have is: 632.8 nm laser with 10mW; a SFH 203 P photodiode; and in the setup I use 10M resistor.

In the serial plotter I can observe that intensity changes when I shine some light on the photodiode. But I have no idea what the scale is. The data ranges from 0 to 1024. Could you tell me what the unit of this data is, or how to calculate the actual brightness.

Hugs, K

karolsuchy: Hey everyone,

This is my first post, so I hope it is in the right section. I have a problem with measuring the intensity of a laser. Baically what I have is: 632.8 nm laser with 10mW; a SFH 203 P photodiode; and in the setup I use 10M resistor.

In the serial plotter I can observe that intensity changes when I shine some light on the photodiode. But I have no idea what the scale is. The data ranges from 0 to 1024. Could you tell me what the unit of this data is, or how to calculate the actual brightness.

Hugs, K

Welcome to the Arduino forum. In order to determine anything about your laser, you must have be able to calibrate your entire light detecting system. This is not an easy undertaking.

Part of the calibration process is to relate the 0-1023 values of the analog read to standard light intensities. Then you can measure the laser light.

Brightness is a subjective human perception and varies from person to person.

Paul

I put a different resistor. Right now at a room light it shows an almost stable value of 20 (the range is 0-1024)

How can I proceed with that?

When I measure the laser light the value gets up to 56.

Is it appropriate to measure the brightness as lumens or mW or something else?

What does Wikipedia tell you about light measurement?

Paul

to use the lumens if I understand correctly, but I still don't know how to relate the data obtained to the lumens

Unfortunately you have a difficult task, and it is difficult to impossible to accomplish it with just a photodiode/resistor and an Arduino.

Because a laser beam is so narrow, to measure the intensity in any useful units (like milliWatts per square centimeter) requires specialized instruments.

You could make a light meter to measure room lighting, and in that case there are cheap light meters than can be used to calibrate your circuit. You might also find this article on making a solar pyranometer helpful.

jremington: Unfortunately you have a difficult task, and it is difficult to impossible to accomplish it with just a photodiode/resistor and an Arduino.

Because a laser beam is so narrow, to measure the intensity in any useful units (like milliWatts per square centimeter) requires specialized instruments.

You could make a light meter to measure room lighting, and in that case there are cheap light meters than can be used to calibrate your circuit. You might also find this article on making a solar pyranometer helpful.

how if i have voltage output data from laser beam using photodiode. can i convert it into lux or any photonic unit? how can i convert it?

Calibrate it against a known light source.