VL53L4CD Performance at Short Range (10 cm)

[Jort]

Dear Sir/Madam,

I am currently using a Nucleo development board to perform trials with the VL53L4CD ToF sensor.

I have a question regarding the sensor’s performance in the near field range of approximately 1 to 15 cm. During testing, I positioned a matte white reference object at around 10 cm. In the data log files, I frequently observe NaN values in the measurements. However, in the GUI, a distance value is always displayed, which may possibly be interpolated.

I have attached a figure from my data log showing the measurements with the reference object at approximately 10 cm.

- Is this a known issue? Additionally, are there recommended methods or configuration settings to improve data quality at short distances?

- What would be considered a proper or expected signal rate for this sensor? Is there a recommended range to strive for in order to ensure reliable measurements?

Thank you in advance for your support.

Kind regards,
Jort 

[Zhiyuan.Han]

Hi 

Normally L4CD can working perfect between 1 to 15cm, your ranging log shows not only the ranging data is jumping, but also the return signal rate is jumping, a bit wired.  I attached my test result with one piece of A4 print paper at 10cm, the ranging distance is 10cm and return signal rate is around 6mcps.

May I know the exact type and size of your matte white reference object?

and please share your GUI settings, any offset/xtalk compensation applied?

This could help us to identify the issue.

Br

Zhiyuan.Han

[John_Kvam · Accepted solution]

Whenever you get the signal strength jumping around, it's that the sensor is adjusting the number of SPAD (Single Photon Avalanche Diodes) it's using. Normally with a stationary target the number settles down after a couple of ranges, and you get a nice clean result. 

In your experiment, check the number of SPADs. And ALWAYS check the ReturnStatus. 

There have been reports that a given target at a given distance just never seems to converge. But any movement at all makes the experiment impossible to repeat. 

Try your experiment again and if you get the same result, send the log file and a description of your test. But I'm guessing it will be very difficult to reproduce. 

- john