Luminance meter is a kind of light-color measuring instrument, which measures brightness and chroma. Generally, it consists of optical system, detector and signal output processing system. According to its measuring principle, it can be divided into three types: light-shielding barrel brightness meter, point-of-sight brightness meter and imaging brightness meter.
1. Shading barrel luminance meter
The calibration device of light shielding barrel brightness meter is composed of brightness measuring device, luminous intensity standard lamp group, standard white board, standard color board, transmission color board, standard color temperature lamp and standard brightness meter, and power supply of live measuring instrument. The photometric measuring device includes precision light measuring guide rail, pulley, lamp holder and filament plane adjuster, etc. Different brightness values can be obtained by adjusting the distance between the standard whiteboard and the standard lamp group.
Shading barrel luminance meter can only test the brightness of self-luminescent body. Its measuring area and area are difficult to control. It is generally used in occasions where the measurement accuracy is not high.
2. Point-of-sight luminance meter
Field-of-view angle is the angle of measuring the area of aiming measurement. It is one of the most important indicators of point-of-sight brightness meter. Under a certain measuring distance, the larger the field of view angle is, the larger the target point to be measured. When testing, the field of view angle corresponding to the area of the target to be measured should be selected. If the field of view angle is too large or too small, it will bring great errors. Point-of-sight brightness meter can measure the precise brightness of point-of-sight at different object distances by optical imaging.
The pointing brightness meter has a high measurement accuracy, but when analyzing and testing the brightness uniformity, it is necessary to test the luminous surface point by point, which is time-consuming and labor-consuming.
3. Imaging luminance meter
The imaging brightness meter uses the area array CCD as the photodetector. It can measure the brightness of millions of points in the plane at the same time with only one sampling, which is equivalent to millions of point-of-sight brightness meters working at the same time. Through the software macro mode, the imaging brightness meter can measure the field of view arbitrarily, and the field of view angle is flexible. However, compared with the point-of-sight luminance meter, the V (lambda) mismatch error of the imaging brightness meter is difficult to control. In order to meet the general measurement requirements, the V (lambda) mismatch error should reach the national level or above.
The imaging luminance meter can be used to analyze and test the brightness uniformity very conveniently. It has the characteristics of fast measurement speed and high accuracy. It is widely used in display screen, lighting engineering, indicator lamp and other occasions.
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