[Understand the four main screen technical indicators] Projection screen technology introduction
Gain The ability of the screen to reflect incident light. When the incident light angle is constant and the incident luminous flux is constant, the ratio of the brightness in a certain direction of the screen to the brightness in the ideal state is called the brightness coefficient in that direction, and the maximum value is called the gain of the screen. Usually the gain of a matt white wall is set to 1. If the screen gain is less than 1, the incident light will be weakened; if the screen gain is greater than 1, more incident light will be reflected or refracted.
Viewing angle The reflection of the screen in all directions is different. The farther away from the center of the screen in the horizontal direction, the lower the brightness; the viewing angle when the brightness drops to 50% is defined as the viewing angle. Viewing the image within the viewing angle, the brightness is satisfactory; viewing the image outside the viewing angle, the brightness is insufficient. Generally speaking, the larger the gain of the screen, the smaller the viewing angle (metal screen); the smaller the gain, the larger the viewing angle (white plastic screen, due to the care of students, education screens mostly use white plastic screens) glass bead screens are more popular.
Classification screens are divided into two types: reflective and transmissive in terms of function. The reflective type is used for front projection, and the transmissive type is used for rear projection. Front projection screens are divided into flat screens and curved screens. The gain of the flat screen is small, the viewing angle is large, and the ambient light must be weak; the gain of the arc-type screen is large, the viewing angle is small, and the ambient light can be strong, but the incident light reflected by the screen is different in all directions. In terms of texture, it is divided into glass curtain, metal curtain, embossed plastic curtain, etc., which are generally applicable.
Size The size of the screen is defined by the size of its diagonal. Generally, the aspect ratio of the video image is 4:3, and the educational screen is square. For example, a 1.83m (72-inch) screen, according to the Pythagorean theorem, can quickly conclude that the screen has a width of 1.5m and a height of 1.1m.