Automatic exposure method and device based on brightness histogram

Abstract

An automatic exposure method based on a brightness column diagram includes the following steps: (1) dividing an input image into N*N image blocks; (2) calculating the average imaging brightness; (3) calculating and accounting the column diagram; (4) dividing the bright column diagram into three areas; (5) dividing an underexposure area into m sub-areas; (6) dividing an overexposure area into n sub-areas; (7) for the N*N average bright values, judging whether each average brightness value falls in each sub-area of the underexposure area or the overexposure area; (8) calculating the overexposure value; (9) calculating the underexposure value; (10) adjusting the exposure time. A device for applying the automatic exposure method includes an imaging sensor, an image processing module, a column diagram accounting module and an exposure calculating module. The invention can obtain quicker and more accurate automatic exposure adjustment under different brightness and contrast conditions.

Description

technical field [0001] The invention relates to the field of automatic exposure control of a digital camera, in particular to an automatic exposure method and device based on a brightness histogram. Background technique [0002] The main function of automatic exposure is to control the brightness of the captured image by adjusting the exposure time of the imaging sensor of the digital camera. [0003] Automatic exposure has a great influence on the quality of the output image. The goal of automatic exposure is to not lose details in the dark part of the captured image, not to expose the bright part, and at the same time, the average brightness is suitable for human eyes. [0004] Most traditional automatic exposure methods search for the optimal exposure time and gain based on the area-weighted average brightness value of the captured image. The disadvantage of this method is that it oversimplifies the image information and does not work well when the image contrast is hig...

AI Technical Summary

Problems solved by technology

If the exposure time adjustment step is too small, it will increase the number of searches and reduce the search speed; if the exposure time adjustment step is too long, it may cause the search to fail to converge, and the phenomenon of swinging around the best exposure point is unstable

Most of the existing automatic exposure methods cannot dynamically adjust the search step according to the brightness of different scenes

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