Automatic focusing method in high-noise environment and digital imaging device thereof

Abstract

The invention discloses an automatic focusing method in a high-noise environment and a digital imaging device thereof. The automatic focusing method in the high-noise environment is used for deciding an object distance of the digital imaging device to an object and comprises the following steps of: respectively obtaining two digital images with a first exposure condition and a second exposure condition at a farthest object distance; obtaining two digital images with the first exposure condition and the second exposure condition at a nearest object distance; capturing digital images with the first exposure condition at a plurality of object distances except the farthest object distance and the nearest object distance; selecting at least two images with adjacent object distances and generating a composite image by an image superposition unit; calculating the object distance of the composite image; calculating high-frequency signals in focusing frames of an image with the second farthestobject distance, an image with the second nearest object distance and the composite image; and deciding the object distances corresponding to the high-frequency signals of the images from the images and moving an automatic focusing lens to the object distance to complete focusing.

Description

technical field [0001] The invention relates to an automatic focus method and a digital image pickup device thereof, in particular to an automatic focus method in a high-noise environment and a digital image pickup device using the method. Background technique [0002] With the development of digital cameras, photography is no longer an expensive expense. Users can freely shoot desired images to record memorable moments or scenes. Generally speaking, in order to obtain clear images when shooting, most cameras have an auto-focus function. [0003] For the existing focusing technology, please refer to Figure 1a. When capturing corresponding digital images at different object distances, the digital camera will calculate the high-frequency signal in the focus frame for each digital image, and obtain the result as shown in Figure 1b. The object distance and high frequency signal curve. Then, the existing curve fitting and evaluation techniques are used to find the object dista...

AI Technical Summary

Problems solved by technology

[0004] However, when shooting under high ISO conditions in a low-light environment, digital images are prone to noise.

The denoising ability of existing denoising algorithms For digital images captured under low-illumination and high-sensitivity conditions, the noise suppression effect of denoising algorithms is quite limited

Moreover, the details of the scene in the digital image are usually blurred, so that the autofocus module of the digital camera still cannot obtain effective high-frequency signals in the case of extremely high noise.

Under such circumstances, the existing focusing technology can easily obtain the object distance and high-frequency signal curve shown in Figure 1c, and there is no obvious global maximum in the figure, which leads to the Focus distance is not the most accurate

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