Not 100%.
If one pulse is interrupted, then the output will go high for one pulse.
If the object passes so fast that it doesn't block at least one pulse, then obviously it can't be detected.
A block of one pulse is shown in the simulation below for an R1C1 of 31ms.
The output goes high about 33ms after the loss of one input pulse and stays high until the next pulse is received.
Not 100%.
If one pulse is interrupted, then the output will go high for one pulse.
If the object passes so fast that it doesn't block at least one pulse, then obviously it can't be detected.
A block of one pulse is shown in the simulation below for an R1C1 of 31ms.
The output goes high about 33ms after the loss of one input pulse and stays high until the next pulse is received.
Yes, I had your duty-cycle reversed in my simulation.
The problem was due to feedback from the input to the Ref voltage.
To cure the problem add a 1uF or larger capacitor from Ref to ground.
Simulation below with added C3:
Yes, I had your duty-cycle reversed in my simulation.
The problem was due to feedback from the input to the Ref voltage.
To cure the problem add a 1uF or larger capacitor from Ref to ground.
Simulation below with added C3: