Interpreting garage door sensor signal using a microcontroller/opamp
After a quick read of the patent, my first thoughts were confirmed: the sensor expects to receive a periodic train of pulses that cease when the beam is interrupted.  The receiver can be as simple as a retriggerable monostable timer.  This would be straightforward to implement in a microcontroller, particularly one with a built-in comparator.


Run a tick timer in the background that fires an interrupt every 1ms.
Use the comparator to trigger an interrupt every time a pulse is detected from the receiver.
Tick timer interrupts increment a counter; comparator interrupts reset the same counter.
If the counter reaches a reasonable value, say 100, then the beam has been interrupted; take action appropriately (set an output high, for example).