User manual
Functional description VL6180X
28/79 DocID026171 Rev 6
1. Position a white target (88% reflectance
(g)
) at a distance of 50 mm from the top of the
cover glass.
2. Perform a minimum of 10 range measurements and compute the average range (from
RESULT__RANGE_VAL{0x62}).
3. If the average range is within the 50 ± 3 mm, offset calibration is not required.
Otherwise, complete this calibration procedure.
4. Set SYSRANGE__PART_TO_PART_RANGE_OFFSET{0x24} = 0.
5. Perform a minimum of 10 range measurements and compute the average range (from
RESULT__RANGE_VAL{0x62}).
6. Calculate the part-to-part offset as follows:
7. Write the part-to-part offset result (in two’s complement notation) to
SYSRANGE__PART_TO_PART_RANGE_OFFSET.
2.12.4 Cross-talk calibration procedure
This section describes a procedure for calibrating system cross-talk.
1. Perform offset calibration if required (see Section 2.12.3).
Note: If the offset is incorrectly calibrated, cross-talk calibration will be inaccurate.
2. Position a black target (3% reflectance
(h)
) at a distance of 100 mm from the top of the
cover glass.
3. Ensure SYSRANGE__CROSSTALK_COMPENSATION_RATE{0x1E} = 0.
4. Perform a minimum of 10 range measurements and compute the average return rate
(from
RESULT__RANGE_RETURN_RATE{0x66}) and the average range (from
RESULT__RANGE_VAL{0x62}).
5. Calculate the cross-talk factor as follows:
6. Write the cross-talk result in 9.7 format to
SYSRANGE__CROSSTALK_COMPENSATION_RATE.
For example, cross-talk = 0.4 Mcps => 0.4 x 128 = 51.2. Write 51 to
SYSRANGE__CROSSTALK_COMPENSATION_RATE.
Note: Cross-talk compensation is only applied to targets above 20 mm. This is to ensure that
cross-talk correction is not applied to near targets where the signal rate is decreasing. The
cross-talk height qualifier is defined in register
SYSRANGE__CROSSTALK_VALID_HEIGHT{0x21}. The default is 20 mm.
g. Target reflectance should be high but absolute value is not critical.
part-to-part offset 50 mm average range–=
h. Target reflectance should be low but absolute value is not critical.
cross-talk (in Mcps) average return rate 1
average range
100 mm
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×=