This reflectometer application example can be used to approximate the reflectance of various materials (e.g. clothes, paint, objects, walls etc.).
To calibrate the VL53L0X sensor, a target of known reflectance is required (calibrated paper is available on the market).
The plastic enclosure is used to remove any ambient light.
For any more information, you can refer to the video “Building a Reflectometer Using an ST Time-of-Flight VL53L0X” available on st.com.