Digital camera-based image brightness meter and measuring method thereof

Abstract

The invention discloses a digital camera-based image brightness meter and a measuring method thereof. The digital camera-based image brightness meter is formed by connecting a CCD camera and a brightness measurement, control and analysis system by using a data wire, wherein the input and output module of the brightness measurement, control and analysis system is connected with a CPU; the CPU comprises an image decoding module, a data correction module for correcting the uniformity of an image field and a brightness computing and analysis module which is used for judging if the RGB channel values of all measured points of a shot scene image to be measured are all in an accurate measurement interval and converting the RGB channel values into brightness values; the CPU is connected with a storage module used for storing an operating system, analysis software, measurement accuracy, a noise change curve, the measured image and a measurement result; and the CPU is also connected with a display module. The brightness meter and the measuring method can improve measurement efficiency and measurement accuracy in an environment of strong light and shade contrast in background, have the advantage of acquiring the brightness data of all parts in a vision field, realize the reading of files in an RAW format and enlarge the linear range of camera measurement.

Description

technical field [0001] The invention relates to an image luminance meter and its measuring method, in particular to an image luminance meter based on a digital camera and its measuring method. Background technique [0002] Photometric measurement by using photography is not a new method. As early as the 1930s, people have carried out related research work on photometric measurement by photography. Transmittance infers the intensity of the light being measured. Because it can obtain very rich information in a short period of time, it is widely used in astronomical observation and other fields. In 1941, Meyers.G.I carried out road brightness testing by this method. However, because this test method needs to be quantified by a special densitometer or a special optical instrument such as a reflection interference microscope, and the resolution and accuracy are relatively low, it has not been further promoted. [0003] CCD (Charge coupled Device) is a new type of semiconductor...

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Problems solved by technology

[0006] Although these current studies have also carried out a preliminary quantitative analysis of the measurement error, because the influence of factors such as noise, aperture, and digital-to-analog conversion have not been fully considered, in-depth work is still needed to improve the error analysis method of the image brightness measurement method

[0007] At present, this research mostly uses jpeg image files with mature decoding technology. On the one hand, the image data has undergone many nonlinear transformations such as white balance and γ transformation, which not only increases unnecessary errors, but also greatly reduces the linear range of the camera ( Generally 90:1 or even lower), so that the advantages of CCD such as large dynamic range cannot be fully utilized

[0008] Based on the three primary color theory used by the image brightness measurement method of digital cameras, since the three primary colors in reality cannot match all the colors in nature, the previous research has not determined the accurate measurement range of this measurement method in the color space

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