Fast autofocusing in digital holography using scaled holograms

İlhan, Hazar Aytekin; Doğar, Mert; Özcan, Meriç

doi:10.1016/j.optcom.2012.09.036

Cited by 32 publications

(6 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The automatic depth measurement from a digital hologram is important on 3D measurements because it saves a lot of time and man hours and realizes more accurate determination. 37,38 Therefore, we are considering automatic depth measurement for this PPSDHM in the future.…”

Section: Discussionmentioning

confidence: 99%

Modularized microscope based on parallel phase-shifting digital holography for imaging of living biospecimens

et al. 2020

View full text Add to dashboard Cite

Section: Discussionmentioning

confidence: 99%

Modularized microscope based on parallel phase-shifting digital holography for imaging of living biospecimens

et al. 2020

View full text Add to dashboard Cite

“…A reliable technology to estimate the focal position is considered by calculating a value for the quantification of the image sharpness. Based on this concept, the total sum of the gradient (GRA) 7,8 , the Laplace operator (LAP) 9,10 and the Variance of Gray Value Distribution (VAR) 7,11,12 of the reconstructed images have been invented as the refocusing critical functions, which are more applicable for pure phase objects. These critical function curves have wide full-widths at half maximum (FWHM), which increases the difficulty of determining the best focused distance.…”

Section: Introductionmentioning

confidence: 99%

Research on autofocus critical function in digital holography based on the discrete cosine transform

Chen¹,

Li²,

Shen³

et al. 2022

Holography, Diffractive Optics, and Applications XII

View full text Add to dashboard Cite

Selecting a suitable autofocus critical function to accurately obtain the defocused distance in a digital holographic microscope (DHM) is the key to digital reconstruction. Several typical autofocus methods have been proposed to calculate the defocused distance by ascertaining the global extreme value of the critical functions to determine the best focused plane. However, these typical methods are easily affected by noise, or exhibit parameter dependence. In this work, a novel digital holographic autofocus algorithm based on the weighting factor of the discrete cosine transform (DCT) is proposed. We compare the proposed method with several typical methods involving SPEC, DIF, GRA and LAP to evaluate the capability of our method under noise-free condition and different noise conditions. Futhermore, to avoid artificially selecting the filter window and to find the optimal interval where the extreme value is located, we filter the high-frequency components in the form of percentages during the process of bandpass-filtering. The experimental results of HeLa cells and phase resolution target verify that our method has a good performance in terms of applicability and noise-resistance.

show abstract

“…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.

View full text Add to dashboard Cite

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.

show abstract

Fast autofocusing in digital holography using scaled holograms

Cited by 32 publications

References 7 publications

Modularized microscope based on parallel phase-shifting digital holography for imaging of living biospecimens

Modularized microscope based on parallel phase-shifting digital holography for imaging of living biospecimens

Research on autofocus critical function in digital holography based on the discrete cosine transform

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

Contact Info

Product

Resources

About