Exploration and analysis of the latest chroma moni

2022-08-26
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Exploration and analysis of new colorimetric monitoring instruments and methods

there are many manufacturers of optical measuring instruments in the world. Among the instruments we usually use, the main solid screws are the products of Tokyo Optical Co., Ltd. of Japan and photoresearch company of the United States. The former mainly produces medium and low-grade testing instruments for production measurement and control. Famous LED manufacturers such as Nichia and Toyota use a large number of bm-5a, BM-7 and other production and measurement equipment produced by the company in the processing process on the production line. The latter not only produces mid-range production test instruments, but also produces high-end standard instruments that can be used as standards. When it is necessary to calibrate, only the equipment produced by the latter can be used, but the price is too high

Table 1 shows the main technical specifications of photoresearch products. It can be seen that only pr-880, pr-1980b and pr-1530ar are stable photomultiplier tubes. Pr-880 is a hand-held automatic photometer, which is relatively simple; Pr-1530ar is a monomer radiometer/photometer/colorimeter. Because it does not have the ability to measure independent spectra, its application range is also narrow. Pr-1980b has not only the ability to measure all the optical characteristics of the light source, but also the ability to analyze the independent spectrum, so it is called the spectrum analyzer. It can calibrate the optical characteristics of any visible light source. In addition, the stability and measurement accuracy of some other types of instruments are inferior to those of photomultiplier tubes because they use lotus devices, which are the key parts and components materials of the company's focus on automotive functional parts and structural parts. In some cases, the measured values must be corrected by photomultiplier tube measurement instruments

it should be noted that the translation of technical terms in adopts the usual methods in colorimetry, while the noun interpretation used in this paper uses common terms, which is to avoid confusion. The author cannot translate nouns into general terms in the table, because that will definitely lead to confusion of definitions

for the chromaticity calibration of large screen, it is a frequently used item to formulate the chromaticity standard of large screen in a quantitative way. When certain RGB light-emitting diodes are determined to be used, the luminous intensity of each primary color light-emitting diode can be tested in advance. There are several brightness formulas that can be referred to in the test standard. They are: ccir601, namely itu-rec.601 (the former International Radio Advisory Committee, namely now the International Telecommunication Union recommendation 601), which puts forward the basic brightness calculation formula for TV applications, Namely: y '= 0.299r' + 0.587g '+ 0.114b' (1) this is based on the NTSC system. Although later in the research process of PAL and SECAM systems, people proposed different values of three primary colors. If calculated strictly according to the EBU standard, the brightness formula should be changed to: y = 0.222r + 0.707g + 0.071b (2), but in order to facilitate unification, all aspects have been compromised, The above formula (1) is used as the calculation basis for various existing TV systems

however, in order to adapt to the development of HDTV, ITU put forward recommendation No. 709 for HDTV at the coordinate position of green ledcie1931 of the International Telecommunication Union. In this recommendation, it is clear that the brightness calculation formula for HDTV applications is: y '= 0.2126r' + 0.7152g '+ 0.0722b' (3), which is very close to the value proposed in the research process of PAL and SECAM systems to recommend the use of new trichromatic phosphors, It is closer to the EBU color gamut standard. Compared with formula (1), this is a big difference, which must be taken into account in any large-scale calculation related to chromaticity or specific chromaticity measurement

large screen is a device used in large public places, and its chromaticity standard does not have to be the same as that of radio and television. With reference to the above several brightness calculation formulas, it is more important to take the chromaticity value of the light-emitting device itself as the basis. Therefore, before measurement, the light-emitting device used must be measured first. The premise is that the original coordinate value of the light-emitting device used is close to the above calculation formula. If there is a big difference, it should be corrected in the system first. These corrections are conditional and make the system very complex. In order to make the system easier to understand, it is listed in itu-rbt The specific data about RGB (sRGB) and standard white light D65 released by 709reference are as follows: the above has a guiding relationship for the measurement of standard chromaticity and the formulation of large screen chromaticity standards. Generally speaking, if the universal beam CRT or the FDT installed on the left sheet metal with the limit device is used as the light-emitting device of the large screen, the chromaticity coordinate value of the three primary colors of the light-emitting tube can be very close to the above value. However, at present, the rapidly developing LED is often used as the light-emitting device of the three primary colors, and its chromaticity coordinate value often shows high red saturation or low y value (i.e. "too red"), When the blue saturation is slightly lower or the y value is slightly higher (i.e. blue-green), it should be explained here that the coordinates of green LEDs will still show great dispersion under the same production process. The above deviation can be ignored in the application of advertising screens and large screens for medium and low-grade stadiums, but it must be noticed and corrected in the application of large screens for high-grade stadiums

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