There are alternative ways to unlock the screen other than writing the password?
Anthentication in Ubuntu is handled using PAM. Looking for PAM modules, you'll find alternative ways to authenticate, and playing with PAM configuration, you'll be able to enable / disable thoses modules depending on the context.
For example, you can have a look at pam-face-authentication.
Another alternative is using Fingerprint readers with libpam-fprintd (see here)
Each pam module provides integration guide, but beware, it's quite easy to lock you out of your system when playing with PAM configuration!