Because the projector is installed, it is difficult to be perpendicular to the projection screen and to the center of the projection screen. In order to facilitate the placement and make the projector does not affect the viewer's line of sight, when the projector installation location deviation, trapezoidal will appear.

This is due to the projection screen is closer to the side of the projection of light diffusion is smaller than the far side of the spread, the image will be placed on the opposite sides of the width of the different, so that the rectangular image becomes a ladder;

So how to solve this problem? For example, when the projector and projector are fixed, we have to find a way to make the projector have the function to solve the problem. This function is called the projector calibration function.

We present the projector keystone technology has two kinds: optical trapezoidal correction and digital keystone correction

Optical Trapezoidal Correction refers to the physical optical adjustment of the position of the lens, the image on the projector beam width and placement of reverse zoom, so to achieve the purpose of adjusting the ladder, usually use the projector in the engineering level, home theater projector, optical trapezoidal correction has no effect on the projection image;

Digital Keystone Correction is realized by the built-in software. Digital trapezoidal correction is an electronic device to adjust and compensate the image before the projection by the difference algorithm. Digital keystone correction for those applications of image accuracy is not high, a good image can solve the trapezoidal distortion, practicality is very strong; but for the application of higher requirements on the accuracy of the image display, such as CAD map, it is not suitable. Because, after correction of the image, some lines and edges of the image will appear burr and non smooth, resulting in poor clarity.