Data Sheet

DocID031478 Rev 1 21/28
UM2356 Calibration functions
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3.3 Crosstalk calibration
Crosstalk (xtalk) is defined as the amount of the return signal received on the sensing array
which is due to VCSEL light reflection inside the protective window (cover glass) added on
top of the module for aesthetic and protective reasons.
Depending on the cover glass quality, the amount of the return signal can be significant and
can affect the sensor performance. The VL53L1X has a built-in correction that allows for this
crosstalk phenomenon to be compensated.
Crosstalk calibration is used to estimate the amount of correction needed to compensate
the effect of a cover glass added on top of the module.
3.3.1 Cross talk calibration function
A dedicated function is available for this operation:
VL53L1_PerformSingleTargetXTalkCalibration(&VL53L1Dev,
XtalkCalDistance);
One argument of the function is the crosstalk calibration distance in millimeters.
Note: This function must be called in third place in the calibration flow, after the offset
compensation is done (calibration done or offset parameters loaded).
3.3.2 Cross talk calibration procedure
The cross talk calibration should be conducted in a dark environment, with no IR
contribution.
When the calibration function is called, the crosstalk calibration is performed and the
crosstalk correction is applied at the end.
3.3.3 Crosstalk calibration distance characterization
The crosstalk calibration distance needs to be characterized by the user, as it depends on
the system environment, mainly the cover glass material and optical properties, and the air
gap value (distance between the sensor and the cover glass).
Figure 8: VL53L1X crosstalk calibration distance definition shows the crosstalk effect on the
ranging curve. From a given distance, the effect of the crosstalk is predominant, and the
sensor starts to under-range.
Table 6. Crosstalk calibration set up
Chart
Chart distance
(
XtalkCalDistance)
Ambient conditions
Gray target
(17 % reflectance at 940 nm)
As defined in Section 3.3.3: Crosstalk
calibration distance characterization
Dark
(no IR contribution)