There are two methods to measure the light efficiency, including the wide value method and the brightness contrast method. The latter is the direct comparison method. The direct comparison method will be compared with the reference light, monochromatic light is compared to an arbitrary regulation of light intensity (energy), so that both brightness and brightness feeling are equal, the standard fixed side light intensity and monochromatic light energy ratio, and luminous efficiency. There is a difference between the reference light and the monochromatic light, and it is very difficult to compare only the brightness.
In order to eliminate because of the different colors to brightness than the difficulty caused by the phase comparison method will be used as the standard monochromatic light, choose relatively close to the wavelength of monochromatic light, when compared with the change of spectrum, the standard light wavelength will change, this is the brightness ratio. Because of the small color difference of this method, the brightness ratio is relatively easy. But to note exhausted is the standard light wavelength change, which increases the complexity of operation, but also to avoid increasing the strength of error measurement.
The method of intersection is the interaction between standard light and comparative light in one place. When the flicker between the two becomes smaller, it can be considered that this is the same brightness, and only the residual brightness of color difference. At the same time, the ratio of luminous efficiency is calculated from the energy ratio. When this method is used, it will be difficult to determine the number of times when the interaction time is reduced, but too many times, the two will be unable to separate because of the fusion, so it is necessary to choose the appropriate number of flashes.
The schematic diagram of the measurement system of light efficiency is shown in the figure. Usually used for the brightness of the sensitivity of the flash, the color is not sensitive to the number of sensitive.
Schematic diagram of the measurement system of light efficiency
The flicker method is the simplest method of brightness comparison, and the error is small.