Broad considerations:
- lens -- most sensors have 30 degree+ lens installed. For narrow FOV, either read just central pixels or use a lens.
- sensor -- fast readout, low power, few pixels so the arduino can handle the data
- otf data preparation -- need to do flat-fielding, hot/cold pixel rejection on the microcontroller
- algorithm -- threshold or something simple to find white spots on black background
- data stream -- send just locations of first n detected white pixels. Make sure it works with screen edges, etc.
Pre-positioned point lights.
- Many small lights
- small FOV sensor (pencil beam)