The performance index of projector is a standard to distinguish the grade of projector, mainly including the following indexes:
Light output: It refers to the light energy output by the projector in "lumens" (lm). A physical quantity related to light output is brightness, which refers to the ratio of the light energy emitted by the surface of the screen irradiated by light to the screen area. The commonly used unit of brightness is "Lux" (lx, 1lx=1lm/m2). When the light output by the projector passes through a certain amount, the larger the projection area is, the lower the brightness is, if not, the higher the brightness is. The factors that determine the projector's light output include projection and screen area, performance and lens performance. Usually, if the screen area is large, the light output will be large, too. The projector lens with the liquid coupling lens has good performance, and the light output of the projector can be correspondingly improved.
Horizontal scanning frequency: The movement of electrons from left to right on the screen is called horizontal scanning, also called line scanning. The scanning times per second are called horizontal scanning frequency. The horizontal scanning frequency of the video projector is fixed, which is 15.625KHz(PAL system) or 15.725KHz(NTSC system) data and the scanning frequency of the graphic projector are not different frequency bands. In this frequency band, the projector can automatically track the line frequency of the input signal, and the phase-locked circuit realizes complete synchronization with the line frequency of the input signal. Horizontal scanning frequency is an important projector index to distinguish projector grades. Projectors with frequencies ranging from 15kHz-60kHz are usually called data projectors. Those whose upper frequency exceeds 60kHz are usually called graphic projectors.
Vertical scanning frequency: The electron beam moves from top to bottom while scanning horizontally. This process is called vertical scanning. Every time an image is scanned, the number of scans per second is called the vertical scanning frequency, and the vertical scanning frequency is also called the refresh frequency, which indicates the times this image is refreshed per second. The vertical scanning frequency is generally not lower than 50Hz, otherwise the image will have flicker.
Video Bandwidth: The total bandwidth of the video channel of the projector, which is defined as the upper limit frequency of the corresponding signal when the amplitude of the video signal drops to 0.707 times. The corresponding increment of 0.707 times is -3db, so it is also called -3db bandwidth.
Resolution: The resolution includes addressable resolution, RGB resolution and video resolution.
- For projectors, addressable resolution refers to the highest resolution pixel of the projection tube, which is mainly determined by the focusing performance of the projection tube and is an important parameter of the quality index of the projection tube. Addressable resolution should be higher than RGB resolution.
- RGB resolution refers to the highest pixel that the projector can reach when receiving RGB resolution video signals. For example, the resolution is 1024×768, which means the horizontal resolution is 1024 and the vertical resolution is 768,RGB resolution is related to horizontal scanning frequency, vertical scanning frequency and video bandwidth.
- Video resolution refers to the highest resolution when the projector displays composite video. Here, it is necessary to analyze the relationship between video band, horizontal scanning frequency, vertical scanning frequency and RGB resolution: First, realize the relationship between horizontal scanning frequency and vertical scanning frequency.