MrYou 

An OCR (optical character recognition) process is used to process graphical text or book pages into digital text. CAPTCHAs are a challenge-response test to ensure the response is coming from a human vs machine. OCR is sometimes used to circumvent CAPTCHAs.

I'm aware. Captchas are also used for the purpose I described above, according to a TED video.

Ah I see that seems to be related to the "reCAPTCHA" service.

Sorry for getting off topic.