VL53L5CX Emitter: 940nm light?

DWang.7 · ‎2022-09-08

Hi, I would like to know if VL53L5CX emits only signals at this wavelength 940nm or from 900nm to 940 nm, because when I put the sensor in front of a lidar using 905nm, it is clear that the lidar picks up the interference signal from VL53L5CX.

If so, how can I remove/reduce the Interference to Lidar when I use VL53L5CX?

Thanks,

Wayne

Peter BENSCH · ‎2022-09-08

VL53L5CX emits mainly at the peak wavelength 940nm. The width of the peak in the spectrum is not specified in the data sheet, but typically VCSEL lasers emit over a bandwidth of 10...15nm. However, the LIDAR may still be disturbed by the ToF signal due to broadband sensitivity. In that case, only an appropriate IR filter in front of the LIDAR can help to block the 940nm from the ToF.

Does it answer your question?

Regards

/Peter

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John E KVAM · ‎2022-09-08

Peter is right. 940 +/- 10nm is what we are shooting for. But the filter is not absolute. If you point enough energy at the sensor, you will blow through the filter. And that is basically what you are doing. I had a guy with a green laser do the same thing. One would like to believe that an optical filter was absolute, but life does not work like that.

I'm sure it will work if only some indirect light hits the sensor, but not a full-on assualt.

john

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DWang.7 · ‎2022-09-08

@John E KVAM @Peter BENSCH

Thanks for the Answer. Is it possible to add a lens in front of the L5 Sensor to filter only the 940nm light to output, which will affect the sensor's performance? Because as John said, there is already a lens on Lidar, but it seems to be not strong enough. And the fantastic thing is, that the Lidar doesn't affect the measurement of L5.

And the Lidar uses 905 nm light in the datasheet, I didn't think it will be interferenced by 940 nm light...😂

Regards,

Wayne

John E KVAM · ‎2022-09-08

One does not use the word lens when dealing with the ToF sensors. If you add a lens that changes the optics on the sensor, you might make violate the eye-safety. Use the word filter. That implies a flat piece of glass,

And yes a better filter or even just the fact that there are now two of them will cut out more unwanted light.

Worth a try.

We were constrained by the cost, and the size. but you might be able to put that filter into your coverglass and solve the issue that way.

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DWang.7 · ‎2022-09-08

Hi John,

thanks! I will try the filter😀. It means the L5 receiver just absorbs 940 nm light for measurement, but it emits 940 nm +/- 10nm. So blocking the light (>940 nm and >940 nm) should not be a performance problem for L5. Am I right?

Regards,

Wayne

Peter BENSCH · ‎2022-09-08

Right.

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