The accelerated advancement of micro-electro-mechanical systems (MEMS) and microelectronic integrated circuits has led to a growing necessity for the dynamic detection and performance assessment of micro-nano sensors. Digital holography is a highly precise non-destructive measurement method that is capable of meeting the detection requirements of a range of parameters in both dynamic and static conditions. This paper presents a new method for measuring the dynamic parameters of MEMS mirror using a combination of digital holography and event cameras. By analyzing the full hologram recorded by the event camera of the MEMS mirror at a specific time sequence, the vibration frequency of the mirror can be obtained. Under identical experimental conditions, the vibration frequency that can be measured by the event camera is several times to several tens of times higher than that of a general high-speed camera, and it exhibits superior anti-interference performance.
Holographic displays are widely regarded as the pinnacle of three-dimensional (3D) visualization technology. In these displays, real objects must be either photographed or converted into 3D models, which are then processed through neural networks or sophisticated algorithms to generate 3D holograms. To address this challenge, we propose an end-to-end 3D hologram generation strategy that integrates the Transport of Intensity Equation (TIE) phase retrieval technique with the Double Phase-Amplitude Coding (DPAC) method. Under coherent light illumination, phase-only holograms containing depth information can be directly generated by capturing out-of-focus amplitude maps of object light waves propagating to the holographic plane via a camera. The TIE module processes the two out-of-focus amplitude maps to resolve the phase and subsequently generates a phase-only hologram through DPAC. We further conduct simulations to validate the phase retrieval capability of the TIE on complex holograms and demonstrate the feasibility of our proposed strategy.
Defect detection is an important part of heritage conservation and speckle pattern interferometry is a common technique for inspecting surface and internal defects. A speckle pattern interferometry coupled with pulsed laser system for non-destructive detection and prediction of different size cracks is introduced and tested. According to photoacoustic effect, ultrasonic waves are generated by pumping a pulsed laser beam to the rear surface of the sample. The ultrasonic waves serve as carrier propagating from the rear surface to the front, thus conveying deformation and crack size information. For obtaining information about simulated crack size, the front surface is detected by a speckle pattern interferometry system. And simultaneously, the generated ultrasound waves are detected by air-coupled transducer. In this study, the introduced system and method were validated by detecting medium density fiberboards with simulated cracks of different width and depth. Differentiated speckle pattern and ultrasound signals are compared and combined to indicate crack presence and to figure out different crack size qualitatively.
Microelectromechanical systems (MEMS) are electronic devices with movable micromechanical structures, which possess morphology and deformation in scales difficult to observe by traditional microscopic methods. In this paper, the surface morphology and deformation value of MEMS with complex structure was recovered by digital holographic technology, and the high precision detection of MEMS was realized. The local magnification was carried out through the microscope objective lens, and the magnification was calibrated by the resolution test chart. Due to the introduction of spherical wave by the magnification of the objective lens, this paper carried out the elimination of the quadratic term error. The shape of the comb tooth was reconstructed by setting a mask in the phase disturbance area. The deformation of the surface before and after voltage applied was measured, and the actual displacement deformation value was solved.
Fluorescence spectroscopy has been successfully applied to the identification of colorants in oil paintings and murals due to the advantage of non-destructive detection, but the traditional equipment uses xenon lamp as the excitation light source, which is energy inefficient in the process of using, and the monochromatic light output power is weak and unstable. This paper proposes the use of ultra-continuous spectrum broad-band tunable laser with fiber optic sensors to achieve effective detection of weak fluorescence signals of silk dyes, compared with the traditional 3D-fluorescence equipment, single-wavelength excitation light output power is greatly increased, higher monochromaticity and energy density to achieve better spatial resolution and faster detection efficiency, while adding fiber optic sensors can be done to achieve the surface of the painted artifacts in situ non-destructive detection. The proposed method can detect more weak fluorescence information under the comparison results of multiple dyed silk samples with different fluorescence emission effects. Acknowledgement: This project is funded by National Key R&D Program of China No.2020YFE0204600.
KEYWORDS: Holograms, Denoising, Education and training, Speckle, Image processing, Holography, Digital holography, Histograms, Deep learning, 3D image reconstruction
Digital holographic microscopy (DHM) is a non-contact and high accuracy measurement technique widely used in biomedicine, microstructure,and other fields.The quality of the reconstructed image and the effectiveness of holographic microscopy were easily affected by speckle noise. Inspired by the idea of Noise2Noise, we propose a self-supervised noise2noise hologram speckle noise removal method. From the holograms that need denoising to generate the input and labels with the same noise distribution to form a training pair for training. Solve the problem that clean holograms are difficult to obtain.The training sets of this self-supervised method are generated from the holograms to be processed. As such, it avoids the need of collectting a large number of training sets. The proposed method is therefore less vulnerable to the background noises and more convenient and reliable for practical hologram speckle denoising applications.
We have investigated the internal structure of materials by use of a digital acousto-optic holographic technique. The innovative technique is effective in detecting the internal structure information of functional gradient materials. The present visible-light-source-based digital holographic techniques are not able to detect the internal structure information of non-transparent objects and that motivates us to seek the ultrasound-based digital optical holography alternative. The characteristic model of functional gradient materials is modeled through finite element modeling software. The effects of material composition, shape and density on the ultrasound field distribution are simulated, which reveal the propagation pattern of the ultrasound in functional gradient materials as the shape, density and elastic modulus of the medium affect the acoustic properties. The dynamic changes of quantitative mapping relationship between the internal structural information and the sound field is also analyzed. Results indicate that the change is correlated with the internal structural information of the object. The simulation results provide useful quantifiable information for the subsequent research of digital acousto-optic holography to detect the internal structure of materials. Our research is applicable to various industrial problems where traditional digital holographic techniques alone fail to deliver solutions.
Digital holographic imaging systems are promising as they provide 3-D information of the object. However, the acquisition of holograms during experiments can be adversely affected by the speckle noise in coherent digital holographic systems. Several different denoising algorithms have been proposed. Traditional denoising algorithms average several holograms under different experimental conditions or use conventional filters to remove the speckle noise. However, these traditional methods require complex holographic experimental conditions. Besides time-consuming, the use of traditional neural networks has been difficult to extract speckle noise characteristics from holograms and the resulting holographic reconstructions have not been ideal. To address tradeoff between speckle noise reduction and efficiency, we analyze holograms in the spectrum domain for fast speckle noise reduction, which can remove multiple-levels speckle noise based on convolutional neural networks using only a single hologram. In order to effectively reduce the speckle noise associated with the hologram, the data set of the neural network training cannot use the current popular image data set. To achieve powerful noise reduction performance, neural networks use multiple-level speckle noise data sets for training. In contrast to existing traditional denoising algorithms, we use convolutional neural networks in spectral denoising for digital hologram. The proposed technique enjoys several desirable properties, including (i) the use of only a single hologram to efficiently handle various speckle noise levels, and (ii) faster speed than traditional approaches without sacrificing denoising performance. Experimental results and holographic reconstruction demonstrate the efficiency of our proposed neural network.
In this research, we systematically investigated the image classification accuracy of Fourier Ptychography Microscopy (FPM). Multiple linear regression of image classification accuracy (dependent variable), PSNR and SSIM (independent variables) was performed. Notebly, results show that PSNR, SSIM, and image classification accuracy has a linear relationship. It is therefore feasible to predict the image classification accuracy only based on PSNR and SSIM. It is also found that image classification accuracy of the FPM is not universally significantly differed from the lower resolution image under the higher numerical aperture (NA) condition. The difference is yet much more pronounced under the lower NA condition.
This paper presents a simple and effective method, without the need for any additional recording of the intensity maps or tremendous iterative computations, to remove the complex zeroth-order term in the complex hologram for phase retrieval in two-step quadrature phase-shifting holography by utilizing the intensity in certain area in the complex hologram. We select a particular area in the complex hologram where there is negligible diffraction from the test sample to calculate the intensity. The calculated intensity value allows us to eliminate the complex zeroth-order term from the complex hologram. Exact phase distribution can then be reconstructed by using the new complex hologram without the zeroth-order and twin image noise. Experiment results have been performed to verify the effectiveness and feasibility of our proposed method.
Lossy and near-lossless digital hologram compression methods are investigated to compress different complexities of wafer surface structures. In the lossy compression method, we apply row- and column-based uniform downsampling together with spline interpolation, whereas in the near-lossless compression method, we use wavelet local modulus maxima and spline interpolation. Results have shown that the lossy compression method is able to achieve a compression ratio of up to 100 for simpler wafer surface structures than that for complex surface structures. However, the near-lossless compression method is able to yield almost lossless compression even for complex wafer surface structures with a compression of about two. The proposed compression methods are computationally friendly for wafer surface structures as there is no time-consuming iterative computation involved.
Phase retrieval based on the transport of intensity equation (TIE) is a non-interferometric and quantitative technique for phase reconstruction which has been applied to many fields of physics. The TIE expresses the relationship between the object-plane phase and the axial intensity derivative in the Fresnel region for coherent and partially coherent fields and there have been many methods to solve it. In this paper, the Fourier transform method that was an approximate but a widely used solution to the TIE was studied. The concrete steps of the solution were given and two simulations were performed to study the influence of the intensity on the phase retrieval accuracy. Finally, a fiber was selected as the sample to reconstruct its phase using Fourier transform method in practice and the phase was retrieved with acceptable accuracy.
Off-axis holography records a three-dimensional object into a two dimensional hologram through Leith-Upatneiks geometry. The recovery of 3D object from off-axial hologram, termed as an inverse problem, has been previously implemented by back-propagating (BP) reconstruction. Here we demonstrate the possibility of reconstruction of 3D object from off-axis hologram by combining back-propagating with two-step iterative shrinkage/thresholding algorithms (Twist) and compare it with back-propagating reconstruction of off-axis holography. The results of simulations and experiments show that Twist-BP reconstruction has better performance in eliminating out of focus noise.
This paper presents a novel approach to generate object-adapted fringe, which based on scattered data
interpolation. It can effectively solve the problems of the existing methods, such as complicated
computation process and low accuracy. It needn't map the projector pixels coordinate onto the camera
coordinate, only map the camera pixels coordinate onto projector coordinate. The phase of integer
pixels of projector coordinate can be interpolated in the term of phase distribution of wanted fringe
pattern. Compared to the presently algorithms, the advantages of this algorithm are simple and highly
efficiency. This paper expatiates on the principle of the object-adapted fringe generation method using
scattered data points. Simulation analysis and experiment results prove the validity and feasibility of
the new approach. We also have compared the result between this new approach and other existing
methods.
In this paper, we validate experimentally the potential of off-axis digital micro-holography for 3D image reconstruction of a live Human Embryonic Kidney 293(HEK293) cell that is widely used as transfection and expression. A subtraction method of two off-axis holograms to reconstruct the phase of the live microscopic object is discussed. The presented subtraction method can remove some main noise, for example, the quadratic phase aberration introduced by microscope objective (MO), other phase aberration introduced by the liquid in tank and other interference noise introduced by the
optical parts. Thus an improvement in the measurement precision of live cells in aqueous solution is observed. The potential of this method is demonstrated by providing the phase reconstruction results of a phase grating and a single HEK293 cell. The results showed good correspondence to the actual character of HEK293 cell prove the capability of digital micro-holography as a tool to monitor the dynamic transfection process of the living HEK 293 cells.
KEYWORDS: Holograms, Molybdenum, Digital holography, Charge-coupled devices, 3D image reconstruction, Reconstruction algorithms, Phase measurement, Optical filters, Holography, Digital signal processing
It develops a digital micro-holographic optical system to record the magnified hologram (named post-magnification
digital micro-holography in this paper), which can suppress the quadratic phase aberration introduced by
micro-objective (MO) and the wave-front difference between the object wave and reference wave. In order to show its
remarkable trait, post-magnification micro-holography is compared with the traditional digital micro-holography (DMH)
(named pre-magnification DMH) from the view of digital processing and aberration eliminating. Their differences are
also analyzed by the measurement results of a phase grating with period 30lines/mm and depth 0.3 μm. Fresnel
approximation algorithm is used to reconstruct the phase-contrast one of this phase grating. The results show that the
presented system is greatly helpful to restrain the quadratic phase error.
In-line digital holographic microscopy as a phase measurement tool for the inspection of micro-components is presented.
Light diffracted by the micro-components interferes with the directly propagating beams to give the in-line digital
hologram recorded by the CCD camera. The convolution method is used to calculate the diffractive propagation of the
light in order to reconstruct the wavefront of the test specimen. A reference hologram without the test specimen is
recorded for the phase reconstruction. Finally, the method is applied on a phase grating to test its refractive index of the
coating material.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.