Debouncing a TTL Photodiode Detector
You need to transition on the screen going white within 0.5ms, transition on the screen going black within 10ms, but ignore periods of black lasting less than 4ms. This is more constraining than simple R/C circuits can provide: you need a timer.

The venerable 555 timer will do what you need. Set it up in monostable mode, with a duration of 6ms (make it adjustable), and drive the reset line from the output of your OPA141. Then, any glow from the screen will reset the timer, but if there's no light for 6ms then the output will go active. (You may have to play with the various polarities.)

An alternative would be using one of the simplest microcontrollers (e.g. an 8-pin PIC12) with an analog input. Less than $2, but incredibly versatile.