A fast autofocus method based on virtual differential optical path in digital holography: Theory and applications

Wen, Yongfu; Wang, Huaying; Asundi, Anand; Qu, Wei-Jun; Cheng, Haobo; Dong, Zhao; Wu, Yayu

doi:10.1016/j.optlaseng.2019.04.006

Cited by 15 publications

(10 citation statements)

References 26 publications

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“…One of the outstanding advantages of DH is that it can simulate the diffraction process of object waves from the hologram plane to the reconstructed image plane through numerical calculations, and achieve a digitally focused reconstructed image from a single recorded digital hologram. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] The typical autofocusing method in DH calculates the focusing evaluation function values of a series of reconstructed images, and then ascertains the focus plane by finding the extreme value of the focusing evaluation function, thereby achieves a high quality reconstructed image.…”

Section: Introductionmentioning

confidence: 99%

“…Various focusing evaluation approaches suitable for autofocusing of digital holographic reconstructed images have successively proposed, for instance, by analysis of amplitude differential, 12,13) by analysis of phase difference, 14) by virtual differential optical path, 15) by spectral l 1 norm, 16) by use of a Fresnelet sparsity criterion, 17) by sparsity measurement, 18) by critical resampling of the contained complex field, 19) by correlation coefficient method, 20) by a connected domain, 21) by Cosine score algorithm, 22) by an area metric focusing method, 23) by using structure tensor and schatten norm, 24) by using eigenvalue, 25) by compressive sensing autofocusing, 26,27) learning based nonparametric autofocusing, 28) by convolutional neural network algorithm, 29) by use of hybrid autofocusing method, 30,31) by clustering based particle detection method, 32) by use of the local variance of the image gradient in the wavelet domain, 33) by use of spatial correlation of focus metric curves, 34) by a phase retrieval autofocusing method, 35) by the edge sparsity of the complex optical wavefront gradient, 36) by the variance of the dark-field gradient, 37) etc. Most of the proposed autofocusing approaches are in combination with the angular spectrum or convolution method as the numerical hologram reconstruction algorithms.…”

Section: Introductionmentioning

confidence: 99%

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Autofocusing in off-axis digital Fresnel holography using S-th power weighted neighborhood correlation coefficient

Zhang,

Song,

Qiu

2023

Jpn. J. Appl. Phys.

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Accurately determining the focus plane of the reconstructed image is crucial for obtaining high-quality reconstructed images in the process of digital hologram reconstruction. In this paper, a focusing evaluation function based on S-th power weighted neighborhood correlation coefficient (SPWNCC) is proposed to realize automatic focusing of the reconstructed image in off-axis digital Fresnel holography. The Fresnel transform method is utilized as the off-axis digital holographic reconstruction algorithm. Both the numerical simulation and optical experiment results are given to verify the validity of the proposed autofocusing method. The obtained focusing curve can maintain good unimodality and noise immunity performance over a large search range (approximately 800 mm). The proposed SPWNCC based focusing evaluation function has a certain guiding significance on the automatic focusing of off axis digital holographic reconstructed images of long distance recorded objects.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Autofocusing in off-axis digital Fresnel holography using S-th power weighted neighborhood correlation coefficient

Zhang,

Song,

Qiu

2023

Jpn. J. Appl. Phys.

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“…It has been widely used in life, medicine, environment, materials, manufacturing, microelectronics, and other fields [7][8][9][10][11][12]. Common-path off-axis digital holographic microscopy (CO-DHM) system based on grating diffraction, as a typical and simple DHM, can realize high-stability non-contact real-time dynamic monitoring of samples [13,14]. The system uses a classic optical microscope and is equipped with an additional diffraction module [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Single-Shot Common-Path Off-Axis Dual-Wavelength Digital Holographic Microscopy Based on Two-Dimensional Grating Diffraction

Wang

Zhao

et al. 2022

Front. Phys.

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We present a single-shot dual-wavelength common-path off-axis digital holographic microscopic (CO-DHM) imaging method based on two-dimensional grating diffraction. This method improves the utilization rate of the interference field under the limited photosensitive size of the camera, and further expands the original camera’s field of view (FOV). In addition, the mode of orthogonal carrier frequencies close to the diagonal direction can optimize the utilization of the camera’s spatial bandwidth. Compared with the traditional dual-wavelength CO-DHM using one-dimensional grating or prism beam splitting, this method effectively avoids the aliasing of high-frequency components of the +1-order spectrum of different wavelengths in the frequency domain. We provide quantitative phase imaging experiments for the full FOV of USAF resolution chart, onion epidermal cells and standard polystyrene beads. The results prove that the system can enlarge the interferometric FOV by nearly 74.0% without changing the imaging parameters, such as magnification and resolution, and can achieve high-precision quantitative phase imaging with only a single hologram.

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“…In the past decades, various autofocusing methods have been proposed for digital holography [21][22][23][24][25][26][27][28][29][30][31]. Automatic evaluation function is the primary consideration of image definition, which is mainly determined from the spatial domain and the frequency domain.…”

Section: Introductionmentioning

confidence: 99%

Autofocusing Algorithm for Pixel-Super-Resolved Lensfree On-Chip Microscopy

Zhang

et al. 2021

Front. Phys.

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In recent years, lensfree on-chip microscopy has developed into a promising and powerful computational optical microscopy technique that allows for wide-field, high-throughput microscopic imaging without using any lenses. However, due to the limited pixel size of the state-of-the-art image sensors, lens-free on-chip microscopy generally suffers from low imaging resolution, which is far from enough to meet the current demand for high-resolution microscopy. Many pixel super-resolution techniques have been developed to solve or at least partially solve this problem by acquiring a series of low-resolution holograms with multiple lateral sub-pixel shifting or axial distances. However, the prerequisite of these pixel super-resolution techniques is that the propagation distance of each low-resolution hologram can be obtained precisely, which faces two major challenges. On the one hand, the captured hologram is inherent pixelated and of low resolution, making it difficult to determine the focal plane by evaluating the image sharpness accurately. On the other hand, the twin-image is superimposed on the backpropagated raw hologram, further exacerbating the difficulties in accurate focal plane determination. In this study, we proposed a high-precision autofocusing algorithm for multi-height pixel-super-resolved lensfree on-chip microscopy. Our approach consists of two major steps: individual preliminary estimation and global precise estimation. First, an improved critical function that combines differential critical function and frequency domain critical function is proposed to obtain the preliminary focus distances of different holograms. Then, the precise focus distances can be determined by further evaluating the global offset of the averaged, low-noise reconstruction from all backpropagated holograms with preliminary focus distances. Simulations and experimental results verified the validity and effectiveness of the proposed algorithm.

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A fast autofocus method based on virtual differential optical path in digital holography: Theory and applications

Cited by 15 publications

References 26 publications

Autofocusing in off-axis digital Fresnel holography using S-th power weighted neighborhood correlation coefficient

Autofocusing in off-axis digital Fresnel holography using S-th power weighted neighborhood correlation coefficient

Single-Shot Common-Path Off-Axis Dual-Wavelength Digital Holographic Microscopy Based on Two-Dimensional Grating Diffraction

Autofocusing Algorithm for Pixel-Super-Resolved Lensfree On-Chip Microscopy

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