Digital Holographic Interferometry Research Articles

Simultaneous acquisition of 3D shape and deformation by combination of interferometric and correlation-based laser speckle metrology.

A metrology system combining three laser speckle measurement techniques for simultaneous determination of 3D shape and micro- and macroscopic deformations is presented. While microscopic deformations are determined by a combination of Digital Holographic Interferometry (DHI) and Digital Speckle Photography (DSP), macroscopic 3D shape, position and deformation are retrieved by photogrammetry based on digital image correlation of a projected laser speckle pattern. The photogrammetrically obtained data extend the measurement range of the DHI-DSP system and also increase the accuracy of the calculation of the sensitivity vector. Furthermore, a precise assignment of microscopic displacements to the object's macroscopic shape for enhanced visualization is achieved. The approach allows for fast measurements with a simple setup. Key parameters of the system are optimized, and its precision and measurement range are demonstrated. As application examples, the deformation of a mandible model and the shrinkage of dental impression material are measured.

Phase estimation from noisy phase fringe patterns using linearly independent basis functions

A novel technique is proposed for obtaining unwrapped phase estimation from a highly noisy exponential phase field. In this technique, the interference phase is represented as a linear combination of linearly independent and pre-defined basis functions along each row/column of the phase field at a time. Consequently, the problem of phase estimation is converted into the problem of the estimation of the weights of the basis functions. The extended Kalman filter formulation allows for the accurate estimation of these weights. The simulation results indicate that the formulation offers a strong noise robustness in the phase estimation. Experimental results obtained using digital holographic interferometry and digital speckle pattern interferometry set-ups are provided to demonstrate the practical applicability of the proposed method.

Study of the measurement for the diffusion coefficient by digital holographic interferometry.

In the measurement of the diffusion coefficient by digital holographic interferometry, the conformity between the experiment and the ideal physical model is lacking analysis. Two data processing methods are put forward to overcome this problem. By these methods, it is found that there is obvious asymmetry in the experiment and the asymmetry is becoming smaller with time. Besides, the initial time for diffusion cannot be treated as a constant throughout the whole experiment. This means that there is a difference between the experiment and the physical model. With these methods, the diffusion coefficient of KCl in water at 0.33 mol/L and 25°C is measured. When the asymmetry is ignored, the result is 1.839×10(-9) m2/s, which is in good agreement with the data in the literature. Because the asymmetry is becoming smaller with time, the experimental data in the latter time period conforms to the ideal physical model. With this idea, a more accurate diffusion coefficient is 2.003×10(-9) m2/s, which is about 10% larger than the data in the literature.

Dynamical measurement of refractive index distribution using digital holographic interferometry based on total internal reflection

We present a method for dynamically measuring the refractive index distribution in a large range based on the combination of digital holographic interferometry and total internal reflection. A series of holograms, carrying the index information of mixed liquids adhered on a total reflection prism surface, are recorded with CCD during the diffusion process. Phase shift differences of the reflected light are reconstructed exploiting the principle of double-exposure holographic interferometry. According to the relationship between the reflection phase shift difference and the liquid index, two dimensional index distributions can be directly figured out, assuming that the index of air near the prism surface is constant. The proposed method can also be applied to measure the index of solid media and monitor the index variation during some chemical reaction processes.

Iterative signal separation based multiple phase estimation in digital holographic interferometry.

We propose a new method for signal separation from a multicomponent interference field recorded in a digital holographic interferometry setup. The setup consisting of multiple object illuminating beams results in an interference field containing multiple signal components. The proposed method utilizes an amplitude discrimination criteria established by setting different intensities to the object illuminating beams in order to separate the signal components iteratively. The signal separation is performed in a small block of the interference field at a time. The augmentation of the block matrix with its own rows and columns is performed which has an effect of noise subspace inflation. This operation offers an improved noise robustness to the signal separation capability of the proposed method. The simulation and experimental results are provided to substantiate the applicability of the proposed method in multidimensional deformation measurement.

Optical diagnostics of the process of free liquid convection

A technique for complex investigation of the process of free liquid convection under the action of a heat source is presented, which is based on the use of digital holographic interferometry. The mode of studying an object, which is a flat liquid layer in a glass cell, has been developed. Experimental results have been obtained in the form of space–time temperature distributions for water, glycerol, and a mixture thereof. A dominant mechanism of heat transfer in different stages of heating the liquids under study has been revealed. A mathematical model of the process of free convection is constructed and the space–time temperature distribution is calculated for the case in which water is used as a test object. The results of mathematical simulation correctly describe the experimentally observed character of changes in the thermal field.

Acquisition of multiple phase derivatives from a single frame in digital holographic interferometry

This paper proposes a technique to extract two-dimensional multiple phase derivatives (strains, slopes, and shearing strains) from a single frame of the interference fringe pattern recorded in an optical setup with multiple illumination beams. In the proposed method, the interference field is modeled as a multicomponent complex sinusoid in an analysis window around each pixel. The frequencies of these sinusoids provide the estimates of the spatially varying phase derivatives. Matrix enhancement and matrix pencil-based technique is utilized to accurately estimate the multiple frequencies. A numerical example is provided to test the performance of the proposed method in the presence of noise. Experimental results are given to substantiate its applicability in the simultaneous estimation of multiple phase derivatives in a multiwave digital holographic interferometry setup.

Visualization of Spatial–Temporal Evolution of Light-Induced Refractive Index in Mn:Fe:KTN Co-Doped Crystal Based on Digital Holographic Interferometry

The dynamic refractive-index-change behavior of the light-induced process in an Mn:Fe:KTN crystal illuminated by a focused light sheet can be observed experimentally by digital holographic interferometry. By numerically retrieving a series of sequential phase maps from recording digital holograms, the spatial and temporal evolution of the light-induced refractive-index-change distribution inside the material is visualized in situ and monitored in a quantitative and in full field way. With this technique, the effect of recording parameters, such as writing laser power and polarization, bias voltage, temperature, and writing time, on the Mn:Fe:KTN crystal in the photorefractive effect can be explored. Therefore, optimized recording parameters will be achieved according to the dynamic behavior. The method provides an access to explore the evolution of the photorefractive (PR) effect of electrooptic crystal under various situations.

Temperature dependence of Kerr coefficient and quadratic polarized optical coefficient of a paraelectric Mn:Fe:KTN crystal

We measure temperature dependence on Kerr coefficient and quadratic polarized optical coefficient of a paraelectric Mn:Fe:KTN crystal simultaneously in this work, based on digital holographic interferometry (DHI). And the spatial distribution of the field-induced refractive index change can also be visualized and estimated by numerically retrieving sequential phase maps of Mn:Fe:KTN crystal from recording digital holograms in different states. The refractive indices decrease with increasing temperature and quadratic polarized optical coefficient is insensitive to temperature. The experimental results suggest that the DHI method presented here is highly applicable in both visualizing the temporal and spatial behavior of the internal electric field and accurately measuring electro-optic coefficient for electrooptical media.

Multiple phase estimation via signal separation using a windowed Fourier transform in digital holographic interferometry

This paper proposes a novel method for the simultaneous estimation of multiple interference phases from a single recording of the interference field in a multi-wave digital holographic interferometry set-up. The method involves the separation of signal components from the recorded interference field based on windowed Fourier transform based filtering and amplitude discrimination criteria. The proposed method possesses the advantages offered by windowed Fourier transform based filtering such as noise robustness and a high quality reconstruction of the signal components. The performance of the method is validated with numerical and experimental examples.

Development of measuring diffusion coefficients by digital holographic interferometry in transparent liquid mixtures.

As for the measurement of diffusion coefficient in transparent liquids by digital holographic interferometry, there are many kinds depending on the mathematical model and experimental setup. The method of using the distance of the peaks in concentration difference profile to determine diffusion coefficient by Mach-Zehnder interferometric experimental setup, is easy to handle. In order to improve the accuracy and convenience of measurement in this method, we combine procedures of hologram analysis used by Mialdun et al (2011) and those by He et al (2009). By using polynomial to fit the continuous phase difference (interference phase) of object beam, it can be more convenient and accurate to determine the distance between the two peaks. Besides, the shift of initial time has been discussed as a separated topic at the first time and two functions for minimization have been given for determination of the initial time in this paper. With the development, diffusion coefficient of KCl in water at 0.33mol/L and 25 °C has been measured. The diffusion coefficient is 1.844 × 10(-9) m2/s with the uncertainty of ± 0.012 × 10(-9) m2/s. Our measurement has more similar result with other methods than holographic interferometry. The relative uncertainty of diffusion coefficient in our experiment is less than 1% and total uncertainty of temperature is within ± 0.04 K.

Three-dimensional displacement measurement from phase signals embedded in a frame in digital holographic interferometry.

A novel technique is proposed for the simultaneous measurement of all three components of displacement from a single recording of the interference field in digital holographic interferometry. The interference field is divided into a number of rectangular segments, and in each of these segments, the interference field is represented as a multicomponent low-order two-dimensional (2D) polynomial phase signal. 2D-product high-order ambiguity function based analysis is applied to obtain an accurate estimation of the 2D polynomial coefficients. These coefficients are further used to compute the interference phases. The simulation and experimental results show the robustness of the proposed method to noise and its effectiveness in multiple phase estimation.

In situ visualizing the evolution of the light-induced refractive index change of Mn:KLTN crystal with digital holographic interferometry

The light-induced refractive index change in Mn:KLTN crystal, illuminated by focused light sheet, is visualized in situ and quantified by digital holographic interferometry. By numerically retrieving a series of sequential phase maps from recording digital holograms, the spatial distribution of the induced refractive index change can be visualized and estimated readily. This technique enables the observation of the temporal evolution of the refractive index change under different recording situations such as writing laser power, applied voltage, and temperature, and the photoconductivity of Mn:KLTN crystal can be calculated as well, the experimental results are in good agreement with the theory. The research results suggest that the presented method is successful and feasible.

Solution to the Boundary problem for Fourier and Multigrid transport equation of intensity based solvers

In this work we present a solution for the boundary problem for phase retrieval techniques based on the Transport of intensity Equation (TIE). The solution presented here is based on the Neumann Boundary condition and the mirror padding scheme of the captured intensities. The obtained results are derived for the widely used Fourier Transform based TIE solver, but it is shown that they can also be applied to Multigrid based techniques. Full Text: PDF References K. A. Nugent, D. Paganin, and T. E. Gureyev, "A phase odyssey", Phys. Today 54, 27 (2001). CrossRef R. Porras-Aguilar, M. Kujawinska, and W. Zaperty, "Capture and display mismatch compensation for real-time digital holographic interferometry", Appl. Opt. 53, 2870 (2014). CrossRef R. Porras-Aguilar, K. Falaggis, J. C. Ramirez-San-Juan, and R. Ramos-Garcia, "Self-calibrating common-path interferometry", Opt. Express 23, 3327 (2015). CrossRef I. A. Shevkunov, N. S. Balbekin, and N. V. Petrov, "Comparison of digital holography and iterative phase retrieval methods for wavefront reconstruction", Proc. SPIE 9271, 927128 (2014). CrossRef N. Streibl, "Phase imaging by the transport equation of intensity", Opt. Commun. 49(1984). DirectLink J. Martinez-Carranza, K. Falaggis, and T. Kozacki, "Optimum measurement criteria for the axial derivative intensity used in transport of intensity-equation-based solvers", Opt. Lett. 39, 182 (2014). CrossRef J. Martinez-Carranza, K. Falaggis, and T. Kozacki, "Optimum plane selection for transport-of-intensity-equation-based solvers", Appl. Opt. 53, 7050(2014). CrossRef K. Falaggis, T. Kozacki, and M. Kujawinska, "Optimum plane selection criteria for single-beam phase retrieval techniques based on the contrast transfer function", Opt. Lett. 39, 30(2014). CrossRef Z. Jingshan, R. Claus, J. Dauwels, and L. Tian, "Transport of Intensity phase imaging by intensity spectrum fitting of exponentially spaced defocus planes", Opt. Express 22, 18125 (2014). CrossRef J. Martinez-Carranza, K. Falaggis, T. Kozacki, and M. Kujawinska, "Effect of imposed boundary conditions on the accuracy of transport of intensity equation based solvers", Proc. SPIE 8789, 87890N (2013). CrossRef F. Roddier and C. Roddier, "Curvature sensing and compensation: a new concept in adaptive optics", Appl. Opt. 27, 1223 (1988). CrossRef C. Zuo, Q. Chen, and A. Asundi, "Boundary-artifact-free phase retrieval with the transport of intensity equation: fast solution with use of discrete cosine transform", Opt. Express 22, 9220 (2014). CrossRef K. Falaggis, T. Kozacki, and M. Kujawinska, "Computation of highly off-axis diffracted fields using the band-limited angular spectrum method with suppressed Gibbs related artifacts", Appl. Opt. 52, 3288 (2013). CrossRef V. V. Volkov, Y. Zhu, and M. De Graef, "A new symmetrized solution for phase retrieval using the transport of intensity equation", Micron 33, 411 (2002). CrossRef K. Falaggis, T. Kozacki, and M. Kujawinska, "Accelerated single-beam wavefront reconstruction techniques based on relaxation and multiresolution strategies", Opt. Lett. 38, 1660(2013). CrossRef W. L. Briggs, V. E. Henson, and S. F. McCormick, A Multigrid Tutorial, Second (SIAM, 2000). CrossRef

Surface strain-field determination of tympanic membrane using 3D-digital holographic interferometry

In order to increase the understanding of soft tissues mechanical properties, 3D Digital Holographic Interferometry (3D-DHI) was used to quantify the strain-field on a cat tympanic membrane (TM) surface. The experiments were carried out applying a constant sound-stimuli pressure of 90dB SPL (0.632Pa) on the TM at 1.2kHz. The technique allows the accurate acquisition of the micro-displacement data along the x, y and z directions, which is a must for a full characterization of the tissue mechanical behavior under load, and for the calculation of the strain-field in situ. The displacements repeatability in z direction shows a standard deviation of 0.062µm at 95% confidence level. In order to realize the full 3D characterization correctly the contour of the TM surface was measured employing the optically non-contact two-illumination positions contouring method. The x, y and z displacements combined with the TM contour data allow the evaluation its strain-field by spatially differentiating the u(m,n), v(m,n), and w(m,n) deformation components. The accurate and correct determination of the TM strain-field leads to describing its elasticity, which is an important parameter needed to improve ear biomechanics studies, audition processes and TM mobility in both experimental measurements and theoretical analysis of ear functionality and its modeling.

HOLOGRAPHIC MEASUREMENT OF SURFACE ACOUSTIC WAVE CHARACTERISTICS IN CRYSTALS

Holographic interferometry allows visualizing SAW on the entire specimen surface simultaneously and measuring wave characteristics directly. A special method of SAW characteristics measurements by digital holographic interferometry was developed. The use of a picosecond laser allowed registering high frequency SAW two−exposure interferograms, and optical magnification of the CCD input image was used to increase spatial resolution.As a result we reach a sensitivity and resolution of visu-alization and SAW characteristics measurements that significantly exceeded the commonly known limitations of standard holographic methods.

Matrix pencil based phase derivative estimation in digital holographic interferometry

A novel technique is proposed for the direct two-dimensional phase derivatives estimation based on the matrix pencil approach in digital holographic interferometry. The interference field is represented as a two-dimensional complex sinusoidal signal in an analysis window around each pixel. The method provides high resolution frequency estimates and does not require the two-dimensional search in the spectral domain. A simple denoising procedure is proposed based on singular value decomposition of the interference field. The uncertainty in the frequency estimate is utilized as a parameter to identify the regions containing high fringe concentration on the object surface. Simulation and experimental results are provided to show the noise robustness and the practical applicability of the proposed method.

Study of heat dissipation process from heat sink using lensless Fourier transform digital holographic interferometry.

This paper presents the results of experimental investigations about the heat dissipation process of plate fin heat sink using digital holographic interferometry. Visual inspection of reconstructed phase difference maps of the air field around the heat sink with and without electric power in the load resistor provides qualitative information about the variation of temperature and the heat dissipation process. Quantitative information about the temperature distribution is obtained from the relationship between the digitally reconstructed phase difference map of ambient air and heated air. Experimental results are presented for different current and voltage in the load resistor to investigate the heat dissipation process. The effect of fin spacing on the heat dissipation performance of the heat sink is also investigated in the case of natural heat convection. From experimental data, heat transfer parameters, such as local heat flux and convective heat transfer coefficients, are also calculated.

Visualized measurement of the electric field in large aperture LiNbO3 crystal by digital holographic interferometry

The electric field distribution in LiNbO3 crystal under different electrode shape is presented by using the digital holographic interferometry. Three configurations of phase modulator including the rectangular electrode type, single-triangle electrode type, and dual-triangle electrode type are performed in this experiment. The nonuniform electric field distribution in these phase modulators are observed and the electric field increases with voltage increasing. The digital holographic interferometry with high electro-optic effect improves the measurement precision. The digital holographic interferometry provides an effective way for studying the electric field distribution. Such in situ quantitative analysis of electric field distribution is a key to optimizing electrode shape.

Digital Holographic Interferometry of a Wide Spectral Range in the Systems of Nondestructive Testing of Dynamics of Micro- and Macrosystems

Modern digital holographic interferometry is used to study the objects of various nature and various spatial scales. In this case, a wide spectral range of coherent electromagnetic radiation from long-wavelength infrared to deep ultraviolet is used. In this work, we present the results of studying dynamic processes in construction materials by the methods of digital holographic interferometry using radiation with a wavelength of up to 9.3 μm. The holographic method for testing of microelectromechanical structures is also considered. The method of digital holographic interferometry, which uses an automated holographic microscope, is proposed to study microscopic biological objects.