With the development of projector products, various manufacturers continue to introduce projector products with higher brightness. The brightness of the projector has reached more than 2000 ANSI lumens. However, in the process of purchasing, the understanding of the brightness index of the projector is often biased. Brands and machines with the same brightness index are quite different in comparison, so how do you understand the brightness index of the projector? 'lightout' is the main technical index of the projector, and 'lightout' is usually expressed in terms of luminous flux, which is a description of unit time The ability of internal light source radiation to produce visual response, the unit is lumens. The unit of luminous flux for LCD projectors is ANSI lumens. ANSI lumens is a method for measuring the luminous flux of projectors established by the American National Standards Institute. It measures the illuminance of each point on the nine intersections of the 'Tian' shape on the screen, multiplying it by the area, and then calculating The average value of nine points is the ANSI lumen value of the projector. The light output of the liquid crystal projector is mainly determined by the brightness of the light source and the optical path system and the transmission or reflection ability of the liquid crystal panel. At present, high-brightness projectors use technology to improve the light utilization rate without increasing the power of the light source. A PS light conversion board is installed on the optical path to reflect and turn the vertical vibration of the S light after polarization, and the P light transmission to improve the light efficiency. efficiency. The lumens of mainstream models now exceed 1000 ANSI, which is about 1500 ANSI. The unit of brightness for DLP projectors is ANSI lumens. DLP projector (digital light processing technology Texas Instruments technology) uses digital micro-mirror devices as light valve imaging devices to amplify signals and output large-screen images. Most DLP projectors use a DMD light valve plate, and color filters are used to rotate the colors. LCD projectors and DLP projectors are currently the main types of models on the Chinese market. Due to the differences in the test environment, the ANSI lumen indicators of the machines of each brand are different. However, the ANSI lumens value provided by the manufacturer basically reflects the brightness level of the projector. However, most products on the market have an elevated ANSI index. It is recommended to directly look at the prototype for comparison when purchasing. The light output of a CRT (three-gun) projector is expressed by peak lumens, that is, on a test image of a white window, when the scan line is still clearly visible, measure the maximum illuminance (LUX) of the white window and multiply the white window area (m2) to determine the luminous flux of the projector, the peak lumens has a good practical significance, because any frame of video image you see can not be all white, the proportion of white generally occupies about 20% of the image area. At the same time, the CRT projector relies on the electron beam in the projection tube to scan the image on the fluorescent screen. The beam current depends on the emission capacity of the cathode. Under normal conditions, the electrons emitted by the cathode are controlled by the negative potential difference between the cathode and the grid. An electron cloud is formed. As the potential decreases, the electron flow is quickly drawn to the anode-the phosphor screen. The CRT tube can provide a higher pulse current, so the brightness of the window signal on the screen can be higher, and if the screen is completely white , Due to the limitation of the cathode emission capacity, it can only provide the average beam current, and the brightness on the screen will be greatly reduced, only about 1/5 of the peak current. Because the size of the cathode CRT projection and the adopted window signal is different (10%-25%), there is no absolute comparability in the brightness index of each manufacturer's product. The brightness of the projector has a lot to do with the distance of the projector from the screen, the viewing angle of the screen, and the gain index in the test and user use. It is also a point that needs to be paid attention to.