Apart from the aperture size and distance of sensor from glass, a major factor for optimal performance is the type of plastic or glass. The material selected should transmit enough visible light but should be aesthetically appealing as well -e.g It should not be transparent to electronics underneath the ALS opening. Thus, a trade-off is needed between the opacity/darkness of the glass vs the amount of visible light it lets through. Common material used for optical glass is acrylic or poly-carbonate. The material chosen should allow sufficient visible light for light sensing. Typically around 7-10% transmission in visible should be OK.
Vendors of these plastic material are “Covestro plastics” and “Sabic Innovative plastics”.
https://www.plastics.covestro.com/
https://www.sabic-ip.com/gep/en/Home/Home/home.html