There are three resolutions: addressable resolution, RGB resolution and video resolution. For CRT 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 that 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 of the projector when displaying composite video. Here we need to analyze the relationship between video band, horizontal scanning frequency, vertical scanning frequency and RGB resolution: First, look at the relationship between horizontal scanning frequency and vertical scanning frequency.

2. Vertical scanning frequency

When scanning horizontally, the electron beam moves from top to bottom. This process is called vertical scanning. Each scan forms an image, and the number of scans per second is called vertical scanning frequency, also known as refresh frequency, which indicates the number of times to refresh the image per second. The vertical scanning frequency is generally not less than 50Hz, otherwise the image will flicker.

3. Focusing performance of cathode ray tube

The smallest unit of a graph is a pixel. The smaller the pixel, the higher the resolution of the graph. In CRT kinescope, the minimum pixel is determined by focusing performance, and the so-called addressable resolution refers to the minimum number of pixels.

There are three focusing mechanisms for CRT projectors: electrostatic focusing, magnetic focusing and electromagnetic compound focusing. Among them, electromagnetic compound focusing is more advanced and has the advantages of good focusing performance, especially defocusing under high brightness and high focusing accuracy. It can focus on different areas, edges and corners, so that every point on the screen is clear.

4. Convergence; gather

Convergence refers to the superposition of RGB colors on the screen. For CRT projectors, convergence control is particularly important, because it has three kinds of RGB CRT tubes, which are installed in parallel on the bracket. In order to achieve complete convergence of images, various image distortions must be corrected.

With the change of machine position, the connection needs to be readjusted, so the requirements for connection are full-featured and convenient. Convergence includes static convergence and dynamic convergence, in which dynamic convergence has functions such as tilt, bow, amplitude, linearity, trapezoid and pillow, and each function can be adjusted in both horizontal and vertical directions.

In addition, nonlinear balance, trapezoidal balance and pillow balance can be adjusted. Some projectors have a convergence function, which divides the whole screen into 208 points and adjusts them point by point, so that every point on the screen can converge accurately.

Extended data:

Application classification of projectors:

1, home theater type: it is characterized by a brightness of about 2000 lumens (this number is increasing with the development of projection, and the contrast is high), and the aspect ratio of the projected picture is mostly 16: 9, and various video ports are complete, which is suitable for playing movies and HDTV, and suitable for home users.

2. Portable business projector: Generally, a projector weighing less than 2kg is defined as a business portable projector, which is comparable to a thin notebook computer. The advantages of business portable projector are small size, light weight and strong mobility. It is a substitute for traditional slide projectors and large and medium-sized projectors, and a combination of thin and light notebook computers and business portable projectors.

3. Educational conference projector: generally used in schools and enterprises, with mainstream resolution and brightness of about 2000-3000 lumens, moderate weight, good heat dissipation and dust prevention, suitable for installation and short-distance movement, rich functional interfaces, easy maintenance, relatively high cost performance, and suitable for public purchase and promotion.

4. Mainstream engineering projector: Compared with mainstream ordinary projectors, engineering projectors have larger projection area, longer distance and higher brightness, generally support multi-bulb mode, and can better cope with large and changeable installation environment, which is very suitable for education, media and government.

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