There is no minimum value given for the distance as it depends on your cover glass. There is also a limit called VL53L0X_CHECKENABLE_RANGE_IGNORE_THRESHOLD, where UM2039 mentiones on page 17:
Measurements with signal rates below this value are ignored. This ensures that false measurements are not made due to reflection from the housing.
Please also read the AN4907 carefully, which contains some guidelines for cover windows.
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/Peter
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