Mysterious covered sensor

[AKLZ]

Washing my new-to-me 2019 Corolla TS Excel 2.0 today for the first time today.

I lifted up the windscreen wiper arms and noticed a spot of white on the very lower part of the windscreen glass, exactly where the tip of the drivers side* wiper blade rests when inactive. I presumed this to be bird poo, and scratched it off with my thumb nail, but realised it was actually a dot of ‘paint’ and underneath it was a little tiny circular sensor (perhaps like a lens) under the glass. The paint was there to cover it up. Very odd! 

What is this sensor and why would it be ‘painted over’ like this?

 

* actually as I sit here typing this, I now can’t remember if it was the drivers or passenger side wiper blade, but it was precisely underneath the very tip of the blade when in the resting ‘off’ position.

[flash22]

If it has climate it's possibly the sunload sensor

[AKLZ]

Thanks! I’ll google that... can you think why Toyota (it was an ex demo) would have put a dot of paint to cover it over?