# How to measure laser class of LIDAR

I just bought a LIDAR with the intention of building an indoors robot that uses it to navigate rooms in my apartment.

The manufacturer website states:

Low power infrared transmitter conforms to the Class 1 laser safety standard and reaches the human eye safety level.

So, I went to the FDA site about laser classes to inform myself about it (https://www.fda.gov/radiation-emitting-products/home-business-and-entertainment-products/laser-products-and-instruments), and in fact they say Class I is considered non-hazardous (with hazard increasing if viewed with any optical aid such as a magnifier).

It seems this is a Chinese product, I don't know if the FDA is actually regulating this product, or the manufacturer is including this just as a reference.

I'm concerned about the safety of pets and people in the household, so I thought it could be a good idea not to trust this Class I rating at face value, but to double-check the emission intensity with some equipment.

Can this measuring be done and if so with what equipment? Does it make sense to do it?

(I tried posting this question in the robotics site, no answer after a week there, so I'm trying here as well).

Thanks!

• The equipment is expensive. Even a IR laser detection card is a few hundred dollars. – DKNguyen Jul 25 '19 at 3:10
• @DKNguyen, I could build a reasonably (1%?) accurate laser power meter for somewhere in the neighborhood of $200-300. Of course I'd still need a few$1000's worth of test gear to calibrate my power meter. – The Photon Jul 25 '19 at 4:22
• @DKNguyen Thanks. I'm not concerned about costs at this stage, but more about knowledge, so suppose a few hundred dollars could be invested in these tests. How would you do that? With what equipment exactly? Remember I just want to double-check an existing product under normal operating conditions, not make a real complete class 1 certification or anything. – jotadepicas Jul 26 '19 at 13:12
• A photodiode and transimpedance amplifier is the place to start. – DKNguyen Jul 26 '19 at 13:46

You can't simply measure whether a device is in a particular laser class.

Because to be class 1, you have to not only operate the laser below a specified level (around 1 mW for visible and near IR wavelengths), you also have to design the laser so that under any foreseeable single-fault condition the power will remain below that level.

Demonstrating this requirement isn't done with a measurement, but either by destructive testing of several laser samples, or a complete knowledge of the laser and power supply design so that the likely failure modes and their consequences can be analyzed.

I thought it could be a good idea not to trust this Class I rating at face value, but to double-check the emission intensity with some equipment. ... Can this measuring be done and if so with what equipment? Does it make sense to do it?

You can measure the laser power with an appropriate optical power meter. These are available from several companies. The exact model you should get depends on the wavelength of your laser and the diameter of the beam.

Expect the cost for an off-the-shelf instrument to be in the range of $500 -$5000.

• Thank you for your answer. If understand you right, you're saying I cannot measure it because it's class 1, and it's non-detectable by definition? In reality I just want to double-check this existing product it's not emitting anything harmful under normal conditions (not interested in actually re-certifying it as class 1, with all the failure tests involved, etc). Can't I measure that? I mean, that is not emitting any harmful signals when operating under normal conditions? – jotadepicas Jul 26 '19 at 13:10
• You can measure the power output under normal operating conditions. But power output under normal operating conditions is not the only thing you need to know to determine if the device is class 1. – The Photon Jul 26 '19 at 14:36