No-reference structural sharpness-based automatic focusing method

Abstract

The invention discloses a no-reference structural sharpness-based automatic focusing method. The method includes the following steps that: step S1, grayscale processing is performed on an original image; step S2, image preprocessing is performed with a downsampling method; step S3, low-pass smoothing filtering is performed on a downsampled image, so that a reference image is obtained; step S4, overlapped blocking is performed on the downsampled image and the reference image according to a set block size and a moving step size, so that image sub-blocks are obtained; intra-block variances are calculated, a threshold parameter is set, and image sub-blocks of which the intra-block variances are greater than the threshold are selected; step S5, SSIM values are calculated for the selected imagesub-blocks corresponding to the down-sampled image and the reference image sequentially, and the image sharpness evaluation value, namely NRSS value, of the original image is calculated; and step S6,the NRSS value is converted into a voltage signal, and a lens receives the voltage signal and thereafter completes real-time automatic focusing. The method of the invention has strong robustness, saves calculation time, and well satisfies the real-time requirement of micro-circulation monitoring for automatic focusing.

Description

technical field [0001] The invention belongs to the technical field of automatic focusing, and in particular relates to an automatic focusing method based on no-reference structure definition. Background technique [0002] In the field of microcirculation monitoring, it is very important to obtain clear medical images, which puts forward high requirements for focusing accuracy and real-time performance. Traditional manual focusing relies too much on the judgment of the human eye. To obtain a clear image, repeated manual operations are required until a seemingly clear image is obtained. Due to the limited response speed of the human eye, the accuracy of focusing is difficult to guarantee. In recent years, with the continuous development of computer hardware level and digital image processing technology, the automatic focusing technology based on digital image processing has begun to flourish. [0003] The digital image processing auto-focus technology in the prior art starts...

AI Technical Summary

Problems solved by technology

[0004] However, there are still various defects in the existing auto-focus technology applied to the field of medical imaging, for example, the focus accuracy is not high enough, and it is easy to make focus mistakes; the focus stability is not strong, and it is easily affected by the environment, resulting in image distortion; Low, unable to meet the real-time requirements of microcirculation image monitoring, etc.

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