Cover glass

AN4545

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DocID026571 Rev 1

Figure 9. Graph of range output vs. target distance with cross talk calibration. The

test was performed in the dark and with cover glass

5.1.1

Cross ross talk calibration procedure

This section describes a procedure for calibrating system cross talk.

1.

Perform the offset calibration (recommended)

a)

See Section 4.1.1.

Note:

If the offset is incorrectly calibrated, cross talk calibration will be inaccurate.

2.

Place a dark target at 100mm away from VL6180X.

a)

Low reflectance target recommended, e.g. 3% target.

3.

Ensure SYSRANGE__CROSSTALK_COMPENSATION_RATE {0x1e} is set to 0.

4.

Collect a number of range measurements with the target in place and calculate mean

of the range results and Return signal rate.

a)

For a reliable measurement, take at least 10 measurements.

5.

Calculate the cross talk:

6.

Apply offset:

a)

Write the calculated cross talk value to

SYSRANGE__CROSSTALK_COMPENSATION_RATE {0x1e}.

Note:

{0x1e} is a 316-bit register in 9.7 format:

For cross talk value of 0.4 Mcps = 0.4 x 128 =51.2, register value to be written = 0x33.

cross-talk [Mcps]

Average Rtn Rate [Mcps]

1

Average range

Target Distance

------------------------------------------

–





×

=

cross-talk [Mcps]

Rtn Rate [Mcps]

1

Average range 100

⁄

–

()

×

=