I have a circuit to demodulate 2KHz Infrared pulsed light which is generated by 555 timer IC and its output drives an IR transmitter circuit, which is received by IR receiver located 10 cm apart which amplify the signal with a transistor and then the output signal from it goes to missing pulse detector circuit based on 555 IC. Because I need a high pulse when an object block the IR light path between transmitter and receiver, I have used Schmitt trigger Hex inverter to invert the signal after the missing pulse detector circuit. Please see the attached schematic.
This circuit works well except on the power on and power off conditions, where there are unwanted pulses on both the instances without any object blocking the iR light path. I am trying to find a way to avoid or remove those pulses without losing out the circuit above-mentioned ability. I have tried LM393 based comparator but it didn't help. I also tried RC filter to replace 555 missing pulse circuit but it only detect bigger object and does not solve the problem.
The unwanted pulses on power on and power off looks like as in screenshot below.
What modification can I do to avoid these unwanted pulses? Or should I try a different circuit altogether?