This sensor works basically the same way as an optical mouse, helping your iNAV quad to maintain position without GPS! This module also integrates a laser time-of-flight range sensor. Check out Paweł Spychalski's video below.
For a comprehensive guide check out Setting up Optic Flow in INAV by digitalentity Also check out the Lidar options in Betaflight !
Specifications
Optical Flow: PMW3901
Lidar: VL53L0X
Interface UART
Protocol: INAV MSP
Working Range: 8cm~200cm
Field of view: 42 degree(PMW3901), 27 degree(VL53L0X)
Minimum Illumination >60Lux
Input voltage: 4.5~5.5V
Power Consumption: 40mA
Size: 36*12mm, 2g
Tips
Be sure Optical Flow lens to ground >2cm for opflow initialization while FC starting up.
Maximum range of VL53L0X is 2m,  Altitude hold 0~2m @ throttle 0~100% if VL53L0X is enabled.
Any unused UART of FC supports it
Sonar connection (Trig & Echo) has not been implemented