Autofocusing of digital holographic microscopy based on off-axis illuminations

Gao, Peng; Yao, Baoli; Min, Junwei; Guo, Ren; Ma, Bo; Zheng, Juanjuan; Lei, Ming; Yan, Shaohui; Dan, Dan; Ye, Tong

doi:10.1364/ol.37.003630

Cited by 62 publications

(27 citation statements)

References 23 publications

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“…Hitherto, there have been many reports on image plane detection, which are based on amplitude analysis, 7–9 intensity gradient, 10 self-entropy, 11 local intensity variance, 12 spectral norms, 13 wavelet theory, 14 and so on. 15–20 Recently, we also reported non-conventional illumination based image plane determination approaches, which are based on two-wavelength illumination, 21 off-axis illuminations 22 or structured illumination. 23 The image plane was determined by finding the minimal difference between the reconstructed object waves which are aligned with two wavelength illuminations, two off-axis illuminations, or two diffraction orders of structured illumination.…”

Section: Introductionmentioning

confidence: 99%

Opposite-view digital holographic microscopy with autofocusing capability

Zheng

Gao

Shao

2017

Sci Rep

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Digital holographic microscopy (DHM) has its intrinsic ability to refocusing a sample by numerically propagating an object wave from its hologram plane to its image plane. In this paper opposite-view digital holographic microscopy (OV-DHM) is demonstrated for autofocusing, namely, digitally determining the location of the image plane, and refocusing the object wave without human intervention. In OV-DHM, a specimen is illuminated from two sides in a 4π-alike configuration, and two holograms are generated and recorded by a CCD camera along two orthogonal polarization orientations. The image plane of the sample is determined by finding the minimal variation between the two object waves, and consequently refocusing is performed by propagating the waves to the image plane. Furthermore, the field of view (FOV) of OV-DHM can be extended by combining the two object waves which have an angle in-between. The proposed technique also has the potential to reduce speckle noise and out-of-focus background.

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Section: Introductionmentioning

confidence: 99%

Opposite-view digital holographic microscopy with autofocusing capability

Zheng

Gao

Shao

2017

Sci Rep

Self Cite

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“…It means that the topography measurements on tested surface with optical interferometric precision and without vibration isolation. Moreover, due to the inherent advantages of DH such as numerical focusing [41][42][43][44], numerical aberration correcting [38,40,45,46], synthetic aperture imaging [47][48][49][50][51] and super-resolution imaging [52][53][54][55], the morphology measurement can be achieved with a large field of view and high resolution. Therefore, it has the potential for addressing rapid measurement of surface quality in realistic workshop conditions (e.g., under mechanical vibration, air turbulence, and so on) with high resolution and precision.…”

Section: Introductionmentioning

confidence: 99%

Subaperture stitching interferometry based on digital holography

Pan

Dong

et al. 2016

Optics and Lasers in Engineering

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a b s t r a c tA novel subaperture stitching interferometry based on digital holography is developed to measure the deformation of spherical surfaces. The subaperture measurement is performed by off-axis digital holography on single exposure. Then, the subaperture phase maps are obtained by digital holographic reconstruction, in which the phase aberration caused by position errors of each subaperture measurement is effectively compensated by the method of numerical parametric lens. After that, the full aperture phase map is retrieved by a subaperture stitching algorithm, in which the relative alignment errors of adjacent subapertures are eliminated with an iterative process of stitching optimization. The experiments demonstrate the feasibility and effectiveness of the proposed interferometry, which provides a rapid and robust way to measure spherical surfaces with high resolution and precision. A practical example is given to demonstrate the performance of this method. The stitching result shows good agreement with the full-aperture result.

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“…A digital holographic autofocusing algorithm makes it possible to make an automated evaluation without any mechanical components. And an in-focus plane can be obtained via searching for the optimized distance based on the intensity gradient, amplitude analysis, spectral norms and some other criterions [17][18][19][20]. Nevertheless, the autofocusing method has not been utilized in terahertz in-line digital holography experiments due to the low signal-to-noise ratio of the reconstructed image and the disturbance of twin image in the reconstruction.…”

Section: Introductionmentioning

confidence: 99%