Digital Image Speckle Correlation Research Articles

Real-time emotion detection by quantitative facial motion analysis.

Research into mood and emotion has often depended on slow and subjective self-report, highlighting a need for rapid, accurate, and objective assessment tools. To address this gap, we developed a method using digital image speckle correlation (DISC), which tracks subtle changes in facial expressions invisible to the naked eye, to assess emotions in real-time. We presented ten participants with visual stimuli triggering neutral, happy, and sad emotions and quantified their associated facial responses via detailed DISC analysis. We identified key alterations in facial expression (facial maps) that reliably signal changes in mood state across all individuals based on these data. Furthermore, principal component analysis of these facial maps identified regions associated with happy and sad emotions. Compared with commercial deep learning solutions that use individual images to detect facial expressions and classify emotions, such as Amazon Rekognition, our DISC-based classifiers utilize frame-to-frame changes. Our data show that DISC-based classifiers deliver substantially better predictions, and they are inherently free of racial or gender bias. Our sample size was limited, and participants were aware their faces were recorded on video. Despite this, our results remained consistent across individuals. We demonstrate that DISC-based facial analysis can be used to reliably identify an individual's emotion and may provide a robust and economic modality for real-time, noninvasive clinical monitoring in the future.

Noise reduction in high-resolution speckle displacement measurements through ensemble averaging

To measure surface displacement on micro samples, a non-invasive method with both a low displacement measurement uncertainty below 100 nm and high spatial resolution of around 20 µm is required. In digital image speckle correlation, both requirements can be fulfilled individually but not simultaneously. To lower the displacement measurement uncertainty without deteriorating the spatial resolution, an ensemble averaging technique over multiple uncorrelated speckle patterns is presented. To generate and reproduce different speckle patterns, two concepts for the respective modulation of laser light illumination are investigated: a low-cost concept with a rotating glass diffuser, as well as a faster concept using a digital micromirror device combined with a stationary diffuser with a maximum pattern rate of 17.9 kHz. Both setups lead to a measurement uncertainty reduction by one order of magnitude over a wide range of spatial resolutions. As a result, displacements in the micrometer range are measured with a measurement uncertainty of 40 nm and spatial resolution of 20 µm.

In situ digital image speckle correlation (DISC) observation of plastic strain increment in low-carbon steel

In situ digital image speckle correlation (DISC) observation of plastic strain increment in low-carbon steel

Digital Image Speckle Correlation to Optimize Botulinum Toxin Type A Injection: A Prospective, Randomized, Crossover Trial.

Historically, physicians have relied on their subjective measures when determining the site and dosages for botulinum toxin type A injections. Digital image speckle correlation is a technology that tracks pore movement from rest to maximal exertion, allowing for the determination of the optimal sites of injection. In this prospective, randomized, crossover trial, the efficacy of using digital image speckle correlation was compared to physician assessment in choosing botulinum toxin type A injection sites. Ten female patients were analyzed in this blinded crossover study. Subjects were randomized to either injections based on digital image speckle correlation analysis or injections based on the 2004 facial aesthetics consensus recommendations. All patients received 20 U of botulinum toxin type A in the glabellar region and were crossed over and reinjected after 6 months. Follow-up was completed with the Facial Line Outcomes 11-item survey and repeated imaging with digital image speckle correlation, to measure patient satisfaction and degree of paralysis, respectively. Statistical comparison was completed by means of matched sample t test. On average, the digital image speckle correlation analysis provided 4.8 injection sites, whereas the practitioner chose five injections sites. Patients receiving digital image-directed injections had higher rates of satisfaction on the Facial Line Outcomes instrument (p = 0.0003) and a larger degree of paralysis (p = 0.003). Furthermore, muscle function returned to normal later in patients injected with digital image speckle correlation (17.9 weeks versus 20 weeks; p = 0.03). This study demonstrates the benefits of using digital image speckle correlation in determining optimal botulinum toxin type A injection location. Digital analysis allows practitioners to better treat facial rhytides by eliminating subjective decisions regarding dose and site of injection. Therapeutic, II.

An Analysis of Facial Nerve Function in Patients with Vestibular Schwannomas Using Digital Image Speckle Correlation

An Analysis of Facial Nerve Function in Patients with Vestibular Schwannomas Using Digital Image Speckle Correlation

Deformation Gradients Imprint the Direction and Speed of En Masse Fibroblast Migration for Fast Healing

En masse cell migration is more relevant than single cell migration in physiological processes of tissue formation, such as embryogenesis, morphogenesis and wound healing. In these situations, cells are influenced by the proximity of other cells including interactions facilitated by substrate mechanics. Here we found that when fibroblasts migrated en masse over a hydrogel, they established a well-defined deformation field by traction forces and migrated along a trajectory defined by field gradients. The mechanics of the hydrogel determined the magnitude of the gradient. For materials stiff enough to withstand deformation related to cellular traction forces, such patterns did not form. Furthermore, migration patterns functioned poorly on very soft matrices where only a minimal traction gradient could be established. The largest degree of alignment and migration velocity occurred on the gels with the largest gradients. Granulation tissue formation in punch wounds of juvenile pigs was correlated strongly with the modulus of the implanted gel in agreement with in vitro en masse cell migration studies. These findings provide basic insight into the biomechanical influences on fibroblast movement in early wounds and relevant design criteria for development of tissue-engineered constructs that aim to stimulate en masse cell recruitment for rapid wound healing.

Digital Image Speckle Correlation (DISC) Analysis for Targeted Cosmetic Treatment and Effect Quantification of Botulinum Toxin Type A

Digital Image Speckle Correlation (DISC) Analysis for Targeted Cosmetic Treatment and Effect Quantification of Botulinum Toxin Type A

An in vivo analysis of the effect and duration of treatment with botulinum toxin type A using digital image speckle correlation

Use of Botulinum toxin type A (BTX-A) for facial wrinkles is well-documented, but current methods of subjective evaluation by clinicians and patients fail to objectively quantify the magnitude and duration of facial muscle paralysis. (a) Determine the locus of facial muscular tension; (b) Quantify and monitor muscular paralysis and subsequent return; (c) Continuously correlate the appearance of wrinkles and muscular tension using non-invasive digital image speckle correlation (DISC) to measure treatment efficacy; (d) Corroborate objective data with existing rating scales (subject global assessment and facial lines outcome-11). Two sequential images of slight facial motion (frowning, raising eyebrows) are taken with acamera for n=6 patients pre- and post-treatment at different time points up to 24weeks. DISC processes the images to produce a vector map of muscular displacement to obtain spatially resolved information regarding facial tension. We observed maximum paralysis (≥70%) at 2weeks, and the rate of recovery varied widely ranging from 2 to 5months, with two patients continuing to exhibit reduced contraction at 24weeks. Vector analysis of pre-treatment contraction correctly predicted injection site and illustrated lines of maximum tension. Digital image speckle correlation can precisely track the degree of contraction of different muscle groups following BTX-A injection. It can help predict injection site, quantify muscle paralysis, and monitor the recovery following BTX-A injection. Results were found to be reproducible across six patients.

Comparison of Native Porcine Skin and a Dermal Substitute Using Tensiometry and Digital Image Speckle Correlation

Dermal substitutes are currently used in plastic surgery to cover various soft tissue defects caused by trauma, burns, or ablative cancer surgery. Little information is available on the biomechanical properties of these dermal substitutes after adequate incorporation as compared to normal skin. Determining parameters such as tensile strength in these skin substitutes will help us further understand their wound healing properties and potential in developing artificial tissue constructs. We hypothesize that a dermal substitute has a lower stress-strain curve and altered stress-induced deformation quantified with tensiometry and digital image speckle correlation (DISC) analysis. Two separate 5×10-cm full-thickness wounds were created on the dorsum of 3 female swine. Fibrin glue was applied before either a full-thickness skin graft (FTSG) or application of artificial dermal matrix. On day 42, cultured autologous keratinocytes were applied as a cell sheet to the wound covered with Integra. On day 56, the wounds were fully excised and fresh tissue specimens, including normal skin, were stored in a physiological solution and prepared for analysis. Rectangular samples were excised from the center of each specimen measuring 4×4×30 mm. Using a tensiometer and DISC analysis, we evaluated the tensile strength of 3 different groups of skin, namely, normal, FTSG, and Integra. There is a significant difference between the Integra specimen when compared to normal skin and FTSG. We found a minimal difference in the stress-strain curves of the latter two. Integra alone shows plastic deformation with continued stretching before ultimate midline fracture. There is significant change between the Young's moduli of the normal skin and the Integra, whereas there is little difference between the FTSG and the normal skin; DISC confirms this analysis. The normal skin and FTSG show a convergence of vectors to a linear plane, whereas Integra shows very little organization. Using 2 different methods of analysis, we have shown a dermal substitute does not display similar biomechanical properties after adequate incorporation. These major tensile strength differences are shown between normal, grafted, and Integra constructs under physiological conditions. These properties will lead to further understanding of artificial tissue and engineered constructs in laboratory and clinical applications.

Numerical and Experimental Investigation of Thermomechanical Deformation in High-Aspect-Ratio Electroplated Through-Silicon Vias

In this paper we present the numerical and experimental analysis of thermomechanical deformation in high-aspect-ratio copper electroplated through-silicon vias (TSVs), which were fabricated by deep reactive ion etching, thermal oxidation, and bottom-up electroplating processes. Later, these TSVs were subjected to thermal cyclic loading of . Due to the significant mismatch in the coefficients of thermal expansion of silicon and copper, thermomechanical stress was generated at the copper–silicon interface. Detailed investigation of this stress is of prime importance as it is one of the main root-causes behind the crack formation and dielectric delamination at the interface. A three-dimensional finite element model of the copper-filled TSVs was built and simulation was performed to predict the theoretical distribution of thermomechanical deformation. A noncontact digital image speckle correlation technique was used for the in situ measurement of the thermal deformation and the thermomechanical stress. Thermomechanical shear strain at the copper–silicon oxide–silicon interface was found to be the significant deformation mode in these TSVs.

Measurement of skin stretch using digital image speckle correlation

The surface of the skin is covered by intersecting grooves and ridges which produce characteristic skin surface patterns. It has been suggested that these folds provide a reserve of tissue, allowing the skin to stretch during normal muscle movements. More so, skin is anisotropic and under constant tension. Therefore, to characterize skin displacement following stretch, a discrete, description of the in-plane skin displacement during stretch is of interest. We introduce the use of digital image speckle correlation (DISC), a non-contact technique, to map, in two dimensions, the surface deformation patterns resulting from skin stretching. We analyze skin stretch under the mechanical action of a film former applied on a defined square surface on the back of the hand. This is achieved by taking a series of images, during the drying process of the film former. The images are then analyzed with DISC to create vector diagram and projection maps, from which we can obtain spatially resolved information regarding the skin displacement. We first show that DISC can provide spatially resolved information at any time point during the drying process: areas of de-wetting, wetting were identified using projection maps; we then extracted the value of the drying time. Finally using a vector map, we show the orientation of the skin displacement during stretching and calculated the magnitude of the total stretch. We have shown previously that DISC can be used to determine skin mechanical properties and muscular activity. We show here that DISC, as a non-contact technique, can map, in two dimensions, the surface deformation patterns of a polymer solution on a substrate at any time point during the drying process. DISC analysis generates for each speckle of the sample analyzed, the orientation and magnitude of displacement of the polymer solution. DISC can map in two dimensions the deformation undergone by the substrate and skin stretch is measured in this particular case. We therefore show that the DISC method, as a non-contact technique has great potential for characterization of film formation and is a potential clinical research tool for the measurement of epidermis stretch and epidermis properties.

Mechanical and microstructural characterization of high aspect ratio through-wafer electroplated copper interconnects

In this paper we present the mechanical and microstructural characterization results of through-wafer electroplated copper interconnects. Copper was deposited in very high aspect ratio (∼15), narrow (15 µm) through-vias in silicon, which were earlier created by deep reactive ion etching. The two critical mechanical properties, i.e. hardness and modulus of elasticity, and the microstructure of the electroplated copper interconnect were determined by nanoindentation, atomic force microscope and x-ray diffraction techniques. A location-dependent hardness characteristic was shown along the length of electroplated copper interconnects. The modulus and the hardness of copper interconnects at the bottom segment (124 GPa and 1.8 GPa) were found to be higher than those at the top segment (116 GPa and 1.1 GPa). The reason behind these variable hardness values in the copper interconnect was due to the different grain sizes and the microstructure in the electroplated copper. These varying grain sizes were caused by the incremental current densities used during electrodeposition. The thermal strain, generated due to the coefficient of thermal expansion mismatch, was measured by the digital image speckle correlation technique. From the results, the thermal strain in the Y-direction was found to be more dominant than that in the X-direction. The grain sizes and the preferred texture orientation in the electroplated copper were characterized by the x-ray diffraction technique.

An in vivo study of the mechanical properties of facial skin and influence of aging using digital image speckle correlation

The skin on the face is directly attached to the muscle through the superficial musculoaponeurotic system. We show that this can be used to probe skin mechanical properties, in vivo, using, digital image speckle correlation (DISC), a technique that measures the intrinsic cutaneous pore structure displacement following a natural facial deformation. We take a series of images, which are then analyzed with DISC to create a displacement vector diagram, from which we can obtain spatially resolved information regarding facial deformation. We then studied the functional form of the displacement as a function of age, location on the face, and skin treatment. Finally, through DISC vector field analysis we investigate the mechanism of wrinkle formation. We first show that facial skin displacement follows the direction of muscular movement and reflects the magnitude of the applied forces. Using DISC vector field analysis, we find that as the skin ages the distribution of forces becomes more condensed, with a marked spatial asymmetry. Analysis of the data, in the perioral region, we find that the skin elasticity decreases exponentially with age, with a decay constant of approximately 32 years. Similar results, but with a larger amplitude, were also found for the periorbital region. Finally, DISC vector field analysis also shows that the location of maximal stress correlated with the location of existing facial wrinkles. The DISC method, as a non-contact technique, is a potential clinical research tool for the diagnosis of facial skin condition and underlying muscular activity. We demonstrate how these factors can be used to monitor the effects of aging, formation of wrinkles, and the efficacy of topical applications of skin creams.

In-Situ Micro-Digital Image Speckle Correlation Technique for Characterization of Materials' Properties and Verification of Numerical Models

In this study, improved cross-search, bicubic spline interpolation and finite element (FE) methods are implemented into conventional digital image speckle correlation algorithm in order to reduce correlation computational time, to increase deformation measurement accuracy, and to smooth deformation distribution. With the improved correlation algorithms, an integrated computer-aided-measurement system, called micro-digital image speckle correlation (/spl mu/-DiSC) is built. This system is then applied to characterize the thermal property and fracture behavior of the plastic ball grid array (BGA) assembly and underfill thin film, and employed to validate the material constitutive relationship for a flip chip package and the fatigue life prediction model for a BGA assembly. The demonstration results are found to be in good agreement with those obtained from thermo-mechanical analyzer (TMA), finite element modeling (FEM), moire/spl acute/ interferometry (MI), and accelerated temperature cycling (ATC) test. Therefore, the system can be used as an effective experimental tool to characterize properties of electronic materials and verify findings of theoretical and numerical models for the establishment of reliability design methodology.

ATOMIC FORCE MICROSCOPE (AFM)-BASED DIGITAL IMAGE SPECKLE CORRELATION (DiSC) TECHNIQUE FOR THE MEASUREMENT OF DEFORMATION IN NANOSCALE

Experimental measurement techniques for the determination of stress levels and distributions will be one of most important keys for the optimization of the design of the next generation electronic packages, e.g., nano-wafer-level packages. However, current experimental photo-mechanics techniques are often found to be insufficiently sensitive but also lacking in sufficient resolution to determine stress distributions of nanoscale electronic packages. In this study, the digital image speckle correlation method was combined with the atomic force microscopy (AFM) to develop a new experimental measurement technique, so-called nanodigital image speckle correlation (Nano-DiSC), for the determination of deformation on the nanometer scale. With the developed theoretical model, computational algorithms and nanospeckle pattern preparation method, the Nano-DiSC methodology was found to be able to measure the in-plane deformation on the sub-10 nm scale.

Determining the Mechanical Properties of Rat Skin with Digital Image Speckle Correlation

Background: Accurate measurement of the mechanical properties of skin has numerous implications in surgical repair, dermal disorders and the diagnosis and treatment of trauma to the skin. Investigation of facial wrinkle formation, as well as research in the areas of skin aging and cosmetic product assessment can also benefit from alternative methodologies for the measurement of mechanical properties. Objective: A noncontact, noninvasive technique, digital image speckle correlation (DISC), has been successfully introduced to measure the deformation field of a skin sample loaded by a material test machine. With the force information obtained from the loading device, the mechanical properties of the skin, such as Young’s modulus, linear limitation and material strength, can be calculated using elastic or viscoelastic theory. Methods: The DISC method was used to measure the deformation of neonatal rat skin, with and without a glycerin-fruit-oil-based cream under uniaxial tension. Results: Deformation to failure procedure of newborn rat skin was recorded and analyzed. Single skin layer failures were observed and located by finding the strain concentration. Young’s moduli of freshly excised rat skin, cream-processed rat skin and unprocessed rat skin, 24 h after excision, were found with tensile tests to be 1.6, 1.4 and 0.7 MPa, respectively. Conclusion: Our results have shown that DISC provides a novel technique for numerous applications in dermatology and reconstructive surgeries.

Subpixel displacement and deformation gradient measurement using digital image/speckle correlation (DISC)

Experimental solid mechanics relies heavily on surface dis- placement and deformation gradient measurements. Digital image/ speckle correlation (DISC) uses digital image processing to resolve dis- placement and deformation gradient fields. The practical implementation of DISC involves important challenges such as computation complexity and the discrepancy of the sensitivities and accuracies claimed in previ- ous studies. We develop an iterative, spatial-gradient based algorithm, which uses only first-order spatial derivatives of the images before and after deformation. Simulated images are then used to verify this algo- rithm, as well as to study the impact of speckle size on the accuracy. Based on these simulations, the sensitivity of DISC to displacement and deformation gradient, as well as an optimal speckle size for optimal ac- curacy, is recommended. The algorithm is then calibrated using rigid body translation and rotation, and an application of DISC to thermome- chanical diagnostics of electronic packaging is also presented. © 2001