On the inner dome we find a small daughterboard held in by a T6 Torx screw. It's labeled as E2230JG along with a barcode.

Mounted on the daughterboard is the OMRON EE-SX1131 Photomicrosensor (manufactured in either Santa Clara, CA or Schaumburg, IL.)

Photomicrosensors are small photoelectric sensors that provide reliable position sensing in a space-saving and cost-efficient package.