Optoma HT31 Manual page 26

Adjusting the position using the vertical lens shift
function
If the projector is not positioned right in front of the center of the screen, you
can adjust the vertical position of projected image by moving the vertical lens
ring within the shift range of the lens.
The display position can be shifted upward up to 17% elevation of the dis-
play. (When turn the vertical lens shift ring to the right (left), the display
moves up (down)).
Attention
Please note the following s when using the projector.
Do not touch the lens while it is moving as this could cause injury to the fingers.
Never allow children to touch the lens.
EN-26
Shift to top
0.17V
1V
0.15V
Lens shift adjustable range
17%
Lens shift center position
Vertical lens shift ring
Shift range