Hey!
Deactivate screensaver if not done yet.
That may be a cause.
How do you controll the display? Are you using a command like /opt/vc/nin/tvservice -o and /opt/vc/nin/tvservice -p or just tvservice -o?
And is the display connected via hdmi?
If that’s the case you could try the following:
In /boot/config.txt add hdmi_blanking=1 and reboot. Now try HDMI Output OFF with vcgencmd display_power 0 and HDMI Output ON with vcgencmd display_power 1 instead of the command above.
Descript here. :)