VL53L0X: How to narrow the FOV

[JOsbo.1]

Greetings Team,

Have a question (that may not be so quick). Currently working on a project where I need to detect a tube's length, using the VL53L0X, from ~30 to 200mm. The problem is that the inside dimensions of the tube are 20x11mm, quite tight.

I've been experimenting with various 3D-printed "caps" to limit the FOV, but with limited success. So far, I've only been able to get up to 150mm.

Any suggestions?

Thanks!

[John E KVAM · Accepted solution]

the only way to do this is switch to the VL53L1X. The lens over the L1X receiver, means we can ignore all the photons coming from the outside of the Field of View.

The L1X is a bit more expensive due to that lens, but it's probably a similar cost to the cap you were trying to invent.

• john

[daan]

Hi,
I have the same kind of issue, I would need to narrow down the FoV to about 1 degree. Have you any experience with some kind of lenses. Do we need to narrow the FoV of the transmitter or the receiver or both?

[John E KVAM]

Please do NOT put any sort of magnifying lens in front of the device. It's DANGEROUS.
In theory it would work, but you would need a Laser expert insure you didn't hurt someone.
The 940nm light will enter your eye, and in concentrations it can damage the eye. And being invisible, the user will not know to turn away.
We work extremely hard and calibrate every sensor to not exceed the accepted safe levels - called Class1. 
If you concentrate that light to get your 1 degree, you will create a hazard.
You can put a blinder over the sensor to block all the light that doesn't go straight out, but blocking that much light will severely limit your range.
I don't have a good solution for you in an inexpensive part. The carpenter range finders work because they use a visible light. Still dangerous, but you know to look away.

[daan]

Thank you for the warning. We are currently trying with the carpenter ranger finders but they are looking through the fluid. I read that the ST sensors can be used for water level sensing so you must have solved the translucency problem which the laser ranger finder has not. 

[John E KVAM]

940nm light and water have an interesting relationship. We chose that frequency because 9409nm is absorbed by water. So the moisture in the upper atmosphere absorbs 940 meaning there is less 940 than other near-by frequencies. This means that if your water is deeper than about 15cm, you won't see refections off the bottom.

Notice, only the light that hits at perpendicular is reflected. So if you look, you don't need a 1 degree FoV. The 18 degree FoV only returns the center spot when looking at water. 

If the bottom of your container is not smooth glass or a mirror finish, you should be able to use the VL53L4CD for smaller containers or the VL53L8CX for larger ones.

There is a bit of software from ST's Imaging group, STSW-IMG039. It contains the code for these 2 sensors. Look  at the documentation. They may just fix your issue.