ToF on 3mm cover glass?

[MHarr.9]

Hi,

we have a project which must be equiped with 3mm thick cover glass. However, all notes and recommendations we found are about 1mm and max. 2mm.

Would it be possible with a good calibration to run a ToF on 3mm glass?

Which sensor would be best for our appliance? We should reach a distance for up to 1m.

Thank you in advance for any feedback here.

Br,

Markus

[Julien NGUYEN]

Hi Markus,

3mm is a bit challenging but it should work if you can keep the air gap (distance between the cover and the ToF) as small as possible.

What is the dimension and the material of the object to detect at 1m?

Please check out the VL53L8CX ToF for your application.

Thanks

Julien

[MHarr.9]

Hi Julien,

thank you for your quick response!

Seems to be VL53L8CX is quiet new and not available on any distributor yet.

Is there some "older" one which is optimized for our critical cover glass environment?

>What is the dimension and the material of the object to detect at 1m?

Basically it is a human presence proximity detection. So the device will be placed in about 1.6m high and should detect a person within 1m. Multiple detection fields would not be required.

br,

Markus

[John E KVAM]

If you read the article:

https://community.st.com/s/article/Time-of-Flight-Cover-glass

it will explain the problem.

If your 'glass' is thick then all the other parameters have to be spot on.

Because all those issues are additive.

But say you make a coverglass out of:

AC400 Acrylic Oleophobic VIS A/R Coated UV-Block Protective Window from MidOpt.

(Not assocated with ST at all. They just sell optial plastics)

Thats got good optical qualities and is 3mm thick.

Find a way to put the sensor up against the window.

So of the 7 qualities, you are only really only violating one of them.

Then test it.

Before getting a range, the system must subract all the photons that hit the glass and return. So if that's a large number the number coming from the target must be large.

But if you are looking for large things - like people - you should be fine.

[MHarr.9]

Hi John,

thank you for your feedback. Actually I found this article already and it is really useful.

Unfortunately we could not change to PMMA due to rigidity requirements. This is also the reason because we have to go with 3mm cover glass.

If I assume right, the crosstalk calibration will detect the traveling distance within the glass and define some kind of blind spot for this distance.

However, as I do not know the specific optical behavior / performance of the sensors ST is offering, it would really be helpful if you could advice which sensor we should go with?

The VL53L8CX seems not to be available yet.

br,

Markus