Because the convex lens of the lens deviates. If you make sure that the light emitted by the projector is perpendicular to the angle between the curtains, you can only adjust the direction of the lens.

There is a principle that must be followed in the installation and debugging of the projector, that is, the middle line of the light beam emitted by the projector must be perpendicular to the projection screen, or the plane where the curtain is located must be parallel to the plane where the projector lens is located, so as to ensure that the projected picture is trapezoidal. The reason is simple: the farther the light is from the curtain, the bigger the image, and the closer it is to the curtain, the smaller the image.

Generally speaking, when designing a projector, the projection angle will be considered, so that the light of the projector can still present a regular rectangle after it is obliquely incident on the curtain. So the divergence relationship between the lens and the light is slightly adjusted.

First, turn on the projector and enter the settings; Click "Trapezoidal Correction Function" for correction to ensure that the picture is a standard rectangle; If it is a problem with the projection screen, it needs to be replaced.

All projector manufacturers have adopted digital keystone correction technology. Most projectors that adopt digital keystone correction support vertical keystone correction function, that is, the projector can adjust its height in the vertical direction. Through the vertical keystone correction of the projector, the generated trapezoid can make the picture rectangular and convenient for users to use.