interpreting photosensor specs
 

http://datasheet.octopart.com/QS18VN...heet-30942.pdf

Does anyone know for sure what the "Output Response" and "Repeatability" spec numbers mean?

Re: interpreting photosensor specs
 

I don't "know" but can guess with confidence:

Response time is latency: How long in time between the sensor sensing the condition to turn it on (or off) and when the signal actually turns on (or off). Propagation delay might be another word, depends on your field.

Repeatability is jitter: The time difference you might see from one 'event' to the next.

An engineer might write this as "750 uS +/- 50 uS for ON in Opposed Mode". For example. Maybe they mean +100, or -100, or even +/-100, can't say for sure. But I'm guessing +/- 50 is what they were trying to say.

Re: interpreting photosensor specs
 

I don't know if this makes any difference, but the spec doesn't say "response time", it says "output response".

In any event, your guess is the same as mine, but then that leads to the following problem: nowhere in the datasheet does it give a spec for the minimum required pulse width in order to be detected reliably.