digital tachometer schematic
Yes, I would say you were on a good path, except it may be simpler if you used a microcontroller. I'm going to use the PIC as an example as that is all I know. The current from the IR receiver is fed into the PIC's RA4/T0CKI. The PIC waits an exact and programmed time, while the TIMER0 increases with every pass of the reflective tape. When times up, the value is in TIMER0 is calculated and displayed on whatever display you choose.
Regards,
Sputnik :idea: