TOF Sensor Lens Fogging and Icing Problems

[qiangtech]

Hi all.

I'm using a TOF sensor VL53L0X to make a small short range probe. the TOF sensor is not suitable for direct exposure, so there will be a piece of lens to cover the TOF sensor. Now the problem is, in the low-temperature environment, the lens surface will appear fogging and icing, and once there is fogging and icing, the detected distance will be a big error, basically can not be used.

I would like to ask the users, have you encountered similar problems and solutions?

[John E KVAM · Accepted solution]

When running the VL53L0 runs kind of hot. Unless it were really cold, I'd expect the sensor to warm the glass enough that it wouldn't fog up. But lots of people run the sensor occasionally - rather than full time.

I did an experiment where I used a particular type of coverglass, and covering that glass with a rather large amount of coffee creamer (to simulate dust) produced no false readings - but it did limit the distance at which the sensor could range. 

Have a look at 閎喬光學 – Hornix Optical Technology 

www.hornix.com.tw/en/home

Click on Product and search almost all the way down. 

That coverglass on the right (IR079C0-IC09-A066-2) has a raised barrier of opaque plastic between the transmit glass and the receive glass. And it fits tightly over the sensor preventing any photons from short-circuiting the system.

With a glass such as this I'm hopeful the chip will warm the glass enough to keep you out of trouble. 

With a glass dust and dirt might prevent you from getting an answer, but you will not get a wrong answer. 

Note: Hornix is not sponsored by ST. But we did jointly design that coverglass.

[qiangtech]

Thank you very much for your reply.
Your approach has been very helpful and enlightening to my problem. I checked the HORNIX catalog and it is also temperature resistant above 0 degree Celsius. However, this is a probe that I need to work continuously and stably in a low temperature environment, and I'm not sure if it will meet the requirement even if I use the HORNIX cover. Anyway, I will run some tests and hopefully get good results.
TKS!

[John E KVAM]

If the Hornix coverglass does not fit your temperature profile, you have 2 options.

You can make one yourself that does meet your temperature needs. The trick is to use to separate bit of glass (acrylic or polycarbonate work too) and place an opaque barrier between them. 

Or you could ask Hornix to help you design one. They do optical quality molding. (It's one of the reasons we picked them to make that mold.)

-john