Monochrome Camera Research Articles

Intra-abdominal laparoscopic assessment of organs perfusion using imaging photoplethysmography.

An objective evaluation of the functional state and viability of biological tissues during minimally invasive surgery remains unsolved task. Various non-contact methods for evaluating perfusion during laparoscopic surgery are discussed in the literature, but so far there have been no reports of their use in clinical settings. Imaging photoplethysmography (iPPG) is a new method for quantitative assessment of perfusion distribution along the tissue. This is the first study in which we demonstrate successful use of iPPG to assess perfusion of organs during laparoscopic surgery in an operation theater. We used a standard rigid laparoscope connected to a standard digital monochrome camera, and abdominal organs were illuminated by green light. A distinctive feature is the synchronous recording of video frames and electrocardiogram with subsequent correlation data processing. During the laparoscopically assisted surgeries in nine cancer patients, the gradient of perfusion of the affected organs was evaluated. In particular, measurements were carried out before preparing a part of the intestine or stomach for resection, after anastomosis, or during physiological tests. The spatial distribution of perfusion and its changes over time were successfully measured in all surgical cases. In particular, perfusion gradient of an intestine before resection was visualized and quantified by our iPPG laparoscope in all respective cases. It was also demonstrated that systemic administration of norepinephrine leads to a sharper gradient between well and poorly perfused areas of the colon. In four surgical cases, we have shown capability of the laparoscopic iPPG system for intra-abdominal assessment of perfusion in the anastomosed organs. Moreover, good repeatability of continuous long-term measurements of tissue perfusion inside the abdominal cavity was experimentally demonstrated. Our study carried out in real clinical settings has shown that iPPG laparoscope is feasible for intra-abdominal visualization and quantitative assessment of perfusion distribution.

Simultaneous three-dimensional deformation measurement using tri-wavelength and monochrome camera imaging with a pyramid prism.

What we believe to be a new electronic speckle pattern interferometry (ESPI) configuration is being developed for simultaneous three-dimensional deformation measurements. In this ESPI system, two pairs of symmetrical illuminating arrangement with dual-wavelength lights were used to independently sense two in-plane deformation components, one Michelson interferometer-based set illuminating with the other wavelength light was utilized to measure out-of-plane deformation. The color speckle interferogram was split into four sub-patterns by a prism, three of them were filtered by three different bandpass dichroic filters and recorded by one monochrome camera. Micro-rotation testing work firstly verifies the validation of the proposed phase-shifting device. Three-dimensional deformation information was simultaneous obtained by using temporal phase-shift method. All strain components related to the specimen surface deformation were further determined by numerical differential. The experimental results of a tested specimen were excellently consistent with those of FEM simulation, which verified the validation and feasibility of the proposed ESPI system for measuring 3D deformation.

Single-frame two-color illumination computational imaging based on Kramers–Kronig relations

Annular-illumination quantitative phase imaging based on Kramers–Kronig relations (AIKK) achieves a large space-bandwidth-time product. The reconstruction algorithm is non-iteration, parameter-free, and object-independent constitutionally. Based on the observation and analyticity of intensity spectrum characteristics and symmetry in spatial and frequency domains, we propose a single-frame two-color illumination imaging based AIKK (SFTC-AIKK). In addition, we apply the two-color mode to synthetic aperture imaging, and only one measurement is sufficient with a monochrome camera. We employ SFTC-AIKK to achieve resolution corresponding to nearly two times the objective NA at camera-limited frame rate to applications with observing dynamic target at various spatial and temporal scales.

Observation of beamlet displacement and parallelism in NIO1

In the compact radiofrequency negative ion source NIO1 (Negative Ion Optimization phase 1), beamlet images are recorded from visible light monochrome cameras, for which several mounting positions are available. For two cameras, named CAM1 and CAM2, looking in directions perpendicular to each other and to the z axis of the beam drift tube, an extensive database of images is available, with methods and results of analysis discussed here. All NIO1 beamlets, arranged in a 3 × 3 matrix, are extracted, so CAM1 can record 3 beamlet projection groups and CAM2 also. Both cameras can be used to estimate the beam optics, depending on extracted beamlet currents, their uniformity and applied voltages; moreover CAM1 shows the filter current effects, while CAM2 images may give information on the deflection field (due to magnets inserted in the extraction grid EG and the post-acceleration grid PA). Light reflection is reduced by careful set-up, and by considering image central portion for analysis. Image luminosity can be simply fitted by Gaussian shapes, when the 3 projection groups are fairly separated. This analysis allows to estimate beamlet displacement and deflection. In general, optional algorithms for noise rejection and pre-smoothing for improving automatic recognizing of beamlet peaks is discussed, as well as the classes of available fits. Results for beamlet size, deflection and rms divergence are reported for selected datasets (within the 10 or 20 mrad goal). In some datasets, beamlet convergence was observed, indicating the need for further analysis and beam optics adjustments.

A-143 Imaging Flow Cytometry: A Novel Method Using ADVIA 2120i System Reagents and Microscopic Image Analysis

Abstract Background Flow cytometry based ADVIA 2120i Hematology System reagents are used to modify blood cells. Laser-scattering flow cytometry replaced with digital microscopic image analysis significantly simplifies the complex system to a compact, low-cost microscope. A novel method for imaging flow cytometry is proposed here that simultaneously generates complete blood count (CBC) and high-resolution images of blood cells. Methods Image processing algorithms are implemented to process the pixels containing blood cells. RBCs are made isovolumetrically spherical using the RBC reagent (Fig. 1A) and imaged. RBC volumes are easily determined from the diameter of the isovolumetrically spherical RBCs. By illuminating the spherical RBCs with approximately400 nm light, the increasing grayscale values of the pixels corresponds to increasing haemoglobin concentration due to absorption. WBC nuclei are stained using the Perox reagent (Fig. 1B). The grayscale values of the nuclei pixels can be used to determine the peroxidase stain component, thereby obtaining cell size-to-peroxidase activity scatter plots similar to those on the ADVIA 2120i system. Using the Baso reagent, the cytoplasm of all WBCs are stripped off except for basophils, as shown in Fig. 1C. All the microscopic images have good contrast and high resolution. Image processing techniques can thus provide a 5-part differential using the nuclei/lobular density of WBCs. Results Images were obtained under a 20×x Nikon microscope with a Thorlabs DCC1545M monochrome camera. ADVIA reagents were mixed with venous blood and <5 µL of reagent treated sample was spotted between a microscopic slide and coverslip. Image analysis was performed using ImageJ particle analysis tools. Conclusion Analysis of digital microscopic images of blood cells acted upon by ADVIA 2120i system reagents can offer a novel, simplified, cost-effective method of hematology analysis. Simultaneous CBC scatter plots and high-resolution images of the blood cells can be obtained using this new approach.Fig. 1.(a) Isovolumetricallly spherical RBCs, (b) peroxidase stain of WBC nuclei, and (c) cytoplasm of WBCs stripped off (except for basophils). Images taken under a 20× Nikon microscope. *Under development and not available for commercial sale.

Joint polarization-color coding strategy based on Stokes parameter for robust strip-edge detection in 3D measurement

Stripe-edge detection of color fringe is crucial in structured light measurement. However, the robustness of color stripe-edge detection is affected by the color crosstalk, scattering, and the color filter in the color camera. This can lead to a decrease in imaging quality. In order to avoid the influence of color crosstalk, this paper analyzes the polarization properties of RGB channels and proposes a joint polarization-color coding strategy based on the Stokes parameter and a corresponding stripe-edge detection method. Compared with the traditional color-coded fringe measurement system, the monochrome camera can distinguish the color-coded fringe so that the influence induced by color crosstalk is eliminated completely. Furthermore, the influence induced by the scattering is reduced. The experiment shows that the robustness of strip-edge detection is remarkably improved, the nonparallelism of detected edges reduced by 32.4%, and the nonuniformity of detected edges reduced by 44.1%.

Videocapillaroscopic monitoring of microcirculation in rats during photodynamic therapy

The proposed approach to microcirculation assessment is non-invasive, informative, and can be implemented during photoactivation, and thus is perspective both for research tasks and clinical practice. The functional principles of the vasculature response to photodynamic exposure, identified using this technique, also foster the efficiency and safety of photodynamic therapy. The developed setup allows simultaneous photodynamic exposure and studying the microcirculation parameters by videocapillaroscopy and photoplethysmography techniques. Photodynamic action is carried out by 662 nm laser radiation with a power density of 15 mW/cm2 in continuous and pulsed modes. The imaging system of the setup consists of a large working distance microscope, an optical filter, and a monochrome camera. The illumination system is based on LED with a central wavelength of 532 nm. The acquired images were processed in order to obtain morphometric and hemodynamic microcirculation data in the inspected skin area. To compare the proposed approach with existing methods, we measured blood flow parameters by a laser Doppler flowmeter. We tested the developed setup on rats injected with a photosensitizer and obtained active vessel maps, photoplethysmograms, and skin vessel density values before, during, and after photoactivation in both generation modes. The proposed approach allows to reveal differences in the microcirculation response to photodynamic effects of low power densities in different modes, in particular, the discrepancy between the time from the start of exposure to the cessation of blood flow and the start of the recovery period.

Surface structured light sensor with simultaneous color mapping

To obtain geometric information and color texture simultaneously, a surface structured light sensor consisting of a monochrome camera, a color camera, and a projector is proposed. The sensor uses a color camera to acquire surface color information while using it as a geometric measurement unit and matching with the monochrome camera to obtain geometric information. Due to the Bayer array and demosaicing algorithm of the color camera, pixel RGB components are always coupled with interference from other channels. However, existing color de-crosstalk in reconstruction is merely applied to the decoupling of color composite patterns, ignoring the intensity errors present in color fringe patterns under monochrome illumination. In our sensor, de-crosstalk of monochromatic patterns is considered to guarantee the reconstruction accuracy. The high-accuracy measurement of the sensor is validated by reconstructing standard steps, yielding a mean absolute error of 0.008 mm for distance measurements. In addition, the reconstruction experiment of a terracotta warrior verifies that the proposed sensor has potential application in the digital preservation of cultural relics.

Sequential RGB color imaging with amillimeter-scale monochrome camera with a rolling shutter.

Applications are growing for ultracompact millimeter-scale cameras. For color images, these sensors commonly utilize a Bayer mask, which can negatively and perceptibly have an impact on image resolution and quality, especially for low pixel-count submillimeter sensors. To alleviate this, we built a time-multiplexed RGB LED illumination system synchronized to the rolling shutter of a monochrome camera. The sequential images are processed and displayed as near real-time color video. Experimental comparison with an identical sensor with a Bayer color mask showed significant improvement in the MTF curves and to perceived image clarity. Trade-offs with respect to system complexity and color motion artifacts are discussed.

Method for Evaluation of Linearity of Image Sensors in High Dynamic Range Mode

Image sensors in cameras that are used for outdoor imaging, such as for automotive applications, are typically operated in high dynamic range (HDR) mode. Photo-response linearity is a key performance indicator of image sensors. Existing procedures for evaluation of image sensor linearity are based on exposure variation. They are efficient when image sensors are operated in the basic mode, which has a limited dynamic range, however, they are difficult or impractical to implement with image sensors in HDR mode. This work presents a method to evaluate linearity of image sensors in HDR mode. The method uses an indirect approach, which is based on the relative response between color channels in color cameras. It is independent of the HDR mechanism and the actual photoresponse ratios between color channels; it can be applied to monochrome cameras with attenuation filters. We demonstrate the method with a camera module that includes a color image sensor that is activated in HDR mode with the recommended configuration file and with a file that was modified to produce a non-linear HDR response. Raw image data were collected with test targets in a controlled lab environment, and outdoors in a representative HDR scene. The data were used to calculate signal and noise properties to construct signal-to-noise ratio and relative channel response curves, and to evaluate color properties. Analysis of the relative response curves show that the proposed method is highly sensitive to deviation from linearity and that it correlates well with color artifacts.

Highly multicolored light-emitting arrays for compressive spectroscopy

Miniaturized, multicolored light-emitting device arrays are promising for applications in sensing, imaging, computing, and more, but the range of emission colors achievable by a conventional light-emitting diode is limited by material or device constraints. In this work, we demonstrate a highly multicolored light-emitting array with 49 different, individually addressable colors on a single chip. The array consists of pulsed-driven metal-oxide-semiconductor capacitors, which generate electroluminescence from microdispensed materials spanning a diverse range of colors and spectral shapes, enabling facile generation of arbitrary light spectra across a broad wavelength range (400 to 1400nm). When combined with compressive reconstruction algorithms, these arrays can be used to perform spectroscopic measurements in a compact manner without diffractive optics. As an example, we demonstrate microscale spectral imaging of samples using a multiplexed electroluminescent array in conjunction with a monochrome camera.

High-Resolution, Broad-Range Detection Setup for Polarimetric Optical Fiber Sensors

A common-path polarization interferometer using a Wollaston prism and an area detector for the measurement of retardation or optical path difference is presented. Employing a moderate-resolution 1280 by 1024 pixel monochrome camera, it offers a measurement range of approximately 780 radians at 830 nm and 1350 radians at 515 nm while maintaining a high measurement resolution. Retardation introduced by a zero-order waveplate or a Soleil–Babinet compensator was measured to evaluate the performance of the interferometer. Based on the presented measurement results, the resolution of the measurement is estimated to be better than 0.002 rad.

Color triangle color separation system for colorimetric research in microscopy

The paper presents studies of the color separation system based on the developed color triangle for conducting scientific research in microscopy which will allow identifying genetic or chemical deviations of the samples under study by an accurate change in color. The color triangle covers the entire visible range and is focused on the physiological RGB and XYZ colorimetric systems. Based on the method of converting color spaces, the addition curves of the developed systems were found. Based on the curves, sets of color separating light filters were selected to fit the shapes of these curves based on the selected monochrome camera. Three sets are presented. An analytical study of these sets was carried out and one optimal set was selected. An analytical study of this system is presented in the form of mathematical modeling with 14 control colors from the Munsell atlas. The selected set of the system was experimentally studied on the developed optoelectronic setup placed in a black box to exclude light and color flare. One important part of the setup is the reflective screen: the location follows the lighting/observation recommendations of the International Commission on Illumination for colorimetric measurement of samples. For an objective analysis of measurements, reference test objects were selected — standardized colored optical glasses. The study was based on the evaluation of glass groups: yellow, yellow-green, green, blue-green, since the work has expanded the color space in the direction of the selected colors to obtain color accuracy. Previously, the author, in an analytical study of modern color separation systems, obtained results where the best value was found with a wide color triangle of 0.009, the worst 0.04 — with a small one. Thus, it has been proven: the larger the coverage of the color triangle, the smaller the change in color. The obtained values of the developed KZS system are better than modern ones –0.0088 on average. During the mathematical modeling of the experiment, the change in color was obtained 0.016 on average, the practical result — 0.027 on average. The obtained parameters and characteristics will be taken into account when introducing the developed color separation system into a monochrome digital microscope to improve color rendering in microscopy.

Underwater 3D Scanning System for Cultural Heritage Documentation

Three-dimensional capturing of underwater archeological sites or sunken shipwrecks can support important documentation purposes. In this study, a novel 3D scanning system based on structured illumination is introduced, which supports cultural heritage documentation and measurement tasks in underwater environments. The newly developed system consists of two monochrome measurement cameras, a projection unit that produces aperiodic sinusoidal fringe patterns, two flashlights, a color camera, an inertial measurement unit (IMU), and an electronic control box. The opportunities and limitations of the measurement principles of the 3D scanning system are discussed and compared to other 3D recording methods such as laser scanning, ultrasound, and photogrammetry, in the context of underwater applications. Some possible operational scenarios concerning cultural heritage documentation are introduced and discussed. A report on application activities in water basins and offshore environments including measurement examples and results of the accuracy measurements is given. The study shows that the new 3D scanning system can be used for both the topographic documentation of underwater sites and to generate detailed true-scale 3D models including the texture and color information of objects that must remain under water.

Full-Field Vibration Measurements by Using High-Speed Two-Dimensional Digital Image Correlation

This work developed a method that uses a single monochrome high-speed camera without sacrificing the spatial resolution to measure both in-plane and out-of-plane full-field vibrations. By using the high-speed camera and a two-dimensional digital image correlation (2D-DIC) algorithm, the method first extracts the out-of-plane displacement field from the measured virtual in-plane strains. Then it retrieves the in-plane displacement field after eliminating the out-of-plane motion-induced virtual component. For validation, in-plane and out-of-plane translation tests and single-frequency vibration experiments were carried out. The measurement results show good agreement with the reference values, indicating the effectiveness of the proposed high-speed 2D-DIC (HS-2D-DIC). Further, the natural frequencies and mode shapes of a rectangular cantilever panel were also measured successfully, exhibiting the method’s effectiveness in practical applications. Since the HS-2D-DIC requires only a single monochrome camera, no complex optical setup, and no complicated calibration process, the method can be developed as a competitive tool for full-field vibration characterizations.

Plasma diagnostics using fast cameras at the GOLEM tokamak

Tomographic inversion of radiation determines spatial distribution of tokamak plasma radiation sources using line integrated plasma projections data. For measurements of the projections, fast visible radiation matrix cameras became broadly applied on tokamaks in recent past. These novel cameras opened new possibilities in high temperature plasma studies.The GOLEM tokamak of the Czech Technical University in Prague strives to implement up-to-date diagnostics with enhanced temporal and spatial resolution. Therefore, a novel diagnostic system of two crossed monochrome cameras Photron FASTCAM MINI UX50 was integrated into the GOLEM diagnostics. The proposed contribution will detail their novel port mounts (vertical and horizontal) at the GOLEM tokamak which have been designed so that additional optical measurements of the plasma core (e.g. plasma spectroscopy) is possible.As the main purpose of this study, we shall focus in particular on the frame rate potential which is high enough to make detection and observation of highly transient phenomena in the GOLEM plasmas possible. Progress in solving specific challenges of the ill-conditioned tomographic inversion via the algorithm optimization and testing for the GOLEM tokamak will be presented together with the first tomographic results.

Chlorophyll Fluorescence Imaging for Early Detection of Drought and Heat Stress in Strawberry Plants.

The efficiency of photosynthesis in strawberry plants is measured to maintain the quality and quantity of strawberries produced. The latest method used to measure the photosynthetic status of plants is chlorophyll fluorescence imaging (CFI), which has the advantage of obtaining plant spatiotemporal data non-destructively. This study developed a CFI system to measure the maximum quantum efficiency of photochemistry (Fv/Fm). The main components of this system include a chamber for plants to adapt to dark environments, blue LED light sources to excite the chlorophyll in plants, and a monochrome camera with a lens filter attached to capture the emission spectra. In this study, 120 pots of strawberry plants were cultivated for 15 days and divided into four treatment groups: control, drought stress, heat stress, and a combination of drought and heat stress, resulting in Fv/Fm values of 0.802 ± 0.0036, 0.780 ± 0.0026, 0.768 ± 0.0023, and 0.749 ± 0.0099, respectively. A strong correlation was found between the developed system and a chlorophyll meter (r = 0.75). These results prove that the developed CFI system can accurately capture the spatial and temporal dynamics resulting from the response of strawberry plants to abiotic stresses.

Sensor simulation using a spectrum tunable LED system.

This study developed a method to simulate the sensor responses and verify the effectiveness on spectral reconstruction by a spectrum tunable LED system. Studies have shown that the spectral reconstruction accuracy could be improved by including multiple channels in a digital camera. However, the real sensors with designed spectral sensitivities were hard to manufacture and validate. Therefore, the presence of a quick and reliable validation mechanism was preferred when performing evaluation. In this study, two novel approaches, i.e., channel-first and illumination-first simulations, were proposed to replicate the designed sensors with the use of a monochrome camera and a spectrum-tunable LED illumination system. In the channel-first method, the spectral sensitivities of three extra sensor channels were optimized theoretically for an RGB camera and then simulated by matching the corresponding illuminants in the LED system. The illumination-first method optimized the spectral power distribution (SPD) of the lights using the LED system, and the extra channels could be determined accordingly. The results of practical experiments showed that the proposed methods were effective to simulate the responses of the extra sensor channels.

Internal defect detection method based on dual-channel speckle interferometry

A novel dual-channel speckle interferometry based on a monochromatic camera is proposed to quantitatively characterize internal defects in materials. The sensor of the monochromatic camera is divided into two independent and simultaneous imaging channels by integrating dual-biprism and dichroic filters. The combination of electronic speckle pattern interferometry and digital shearography allows for the simultaneous measurement of out-of-plane displacement and slope. The [4+1] phase-shifting algorithm is employed to dynamically detect of the sequential phase. The effectiveness and accuracy of the proposed method are verified by testing a centre-loaded circular plate. Furthermore, the developed system performs non-destructive testing on a thin metallic plate with internal defects. The experimental results show that the proposed method can successfully localize and detect internal defects.

Ivrr-PPG: An Illumination Variation Robust Remote-PPG Algorithm for Monitoring Heart Rate of Drivers

Heart rate can be accurately measured by Remote PhotoPlethysmoGraphy (rPPG) in stable illumination and noise-controlled environments such as indoors. However, heart rate measure in automotive scene is still faced with several challenges since the lighting illumination in the cab often changes dramatically. To address such issues, a novel method named Illumination Variation Robust Remote-PhotoPlethysmoGraphy (Ivrr-PPG) is proposed for monitoring the heart rate of drivers during on-road driving. The prototype is based on a commercial off-the-shelf imaging system, which includes a monochrome camera with 940 nm narrowband NIR filter and two 940 nm NIR active light sources to collect real-time video of drivers. Based on a dichromatic model, the core idea of our method is to model the non-linear relationship between illumination changing and the rPPG signal. This paper also proposed to use a background region to sense the illumination changing and consequently suppress its impact on the pulse signal. A singletone sinusoidal signal-based frequency estimation method is then used to compute the heart rate. Experimental results conducted on four different on-road driving scenarios show that the Ivrr-PPG significantly outperforms the state-of-the-art single-channel narrowband NIR algorithms.