IC1 astable gives a fixed square wave at pin 3, C1 and R1 derive uS trigger pulses from IC1 and this will trigger IC2 monostable or single shot, the voltage at pin 5 of IC2 will change the pulse width output of IC2, to get it working all the three RC combinations have to be figured out.
Optical Obstacle Switch.
Pulse width modulation using 555
The 555 was the first SmartChip of the early days, in those days we had Opamp and Logic Chips, this was a Mixed Signal Design chip that was Field Programmable, with presets of course. Innovation Par-Excellence.