Commercial Video Camera Research Articles

Effect of unpredictable timing on the hip, knee, and ankle kinematics and center of mass during deceleration tasks.

Unpredictable stopping or deceleration tasks are crucial to prevent ACL injury. The purpose of this study was to reveal differences and relationships in kinematics during different deceleration tasks with and without anticipation. Twenty-four collegiate athletes were recruited. Three commercial video cameras were used to capture frontal and sagittal lower-extremity kinematics. Participants were instructed to perform three deceleration tasks: 1) anticipated stopping and running backward at a point indicated previously (SRB-P); 2) anticipated stopping and running backward in front of a badminton net (SRB-N); and 3) unanticipated stopping and running backward upon random flashing of a light (SRB-U). Differences and relationships between hip, knee, and ankle kinematics at stopping (SS) and deceleration steps (DS) and the height of the great trochanter (HGT) at SS were analyzed. For all tasks, the knee flexion angle was less than 25° at SS. There were no significant differences in hip, knee, and ankle kinematics between tasks. HGT during SRB-U was higher than that in the other tasks at DS. Hip flexion angle at SS and DS was significantly correlated with HGT at SS. During SRB_P and SRB_N, only knee flexion angle at DS was significantly correlated with HGT at SS. The deceleration task in this study, SRB, causes a low knee-flexion angle at SS. The COM remained higher during unanticipated stopping, which is related only to hip flexion angle during the task. Knee flexion movement does not contribute to lowering COM during an unpredictable deceleration task.

Respiratory Feature Extraction for Contactless Breathing Pattern Recognition Using a Single Digital Camera

Non-contact respiratory monitoring is gaining attention due to its unobtrusive form of measurement. Among all other non-contact sensing modalities, optical sensors integrated with commercial video cameras have received more attention due to their ease of use and low cost, allowing non-experts to employ these methods without any prior knowledge. Prior research mostly focused on extracting breathing rate and heart rate-related information for sedentary breathing patterns using camera to determine health status. However, for abnormal breathing patterns, a range of respiratory-pattern-related signatures need to be monitored to investigate the associated primary cause of pattern change. In this paper, we propose a novel feature extraction technique to recognize respiratory patterns such as eupnea, tachypnea, bradypnea, and apnea retrieved from videos captured using a single digital camera working in the visible range. At this aim, a hyper-feature algorithm has been implemented to extract distinguishable air-flow-related from videos collected on twenty-four participants having four different respiratory patterns. After the training of the algorithm using the reference respiratory signal obtained from a medical-grade chest strap, the performance of the system has been evaluated on additional five participants whose measurement was not used for algorithm development and on seven patients. Results demonstrated an accuracy of 96.07% in the recognition of all the respiratory patterns, with minimum performances (81.81%) in detecting bradypnea and 100% in detecting apnea events. Additionally, including the patient’s dataset with the apnea and the normal breathing pattern, the accuracy of the proposed algorithm becomes 97.39%, demonstrating its robustness on the patient’s dataset.

Reliability and Repeatability of ACL Quick Check®: A Methodology for on Field Lower Limb Joint Kinematics and Kinetics Assessment in Sport Applications.

Anterior cruciate ligament (ACL) lesion represents one of the most dramatic sport injuries. Even though clinical screenings aiming at identifying subjects at risk of injuries are gaining popularity, the use of sophisticated equipment still represents a barrier towards their widespread use. This study aimed to test both reliability and repeatability of a new methodology to assess lower limb joints kinematics and kinetics directly on field with the aid of video cameras and plantar pressure insoles. Ten athletes and one case study (post ACL surgery) were assessed in a gait laboratory, while performing double leg squats, through the simultaneous acquisition of stereophotogrammetry, force plates, commercial video cameras and plantar pressure insoles. Different sources of errors were investigated and both reliability and repeatability analysis performed. Minimum and maximum RMSE values of 0.74% (right knee joint center trajectory) and 64.51%, respectively (ankle dorsi-plantarflexion moment), were detected. Excellent to good correlation was found for the majority of the measures, even though very poor and inverse between-trials correlation was found on a restricted number of trials especially for the ankle dorsi-plantarflexion moment. These findings could be used in combination with already available screening tools in order to provide more repeatable results.

Application in Process Industry of the Solid Particles Displacement on a Flat Oscillating Surface

In this paper we present a series of obtained results from the analysis of the behavior of a solid particle on a flat oscillating surface, a process that is found in separation operations of a heterogeneous mixture of solid particles. In this study, the inclination angle of the flat surface (7 or 10 degrees) and the eccentric device speed (91, 244 and 405 rpm) were varied. The results are extracted from video analysis using two commercial video cameras (Sony DCR-SR 36) with a recording speed of 25 frames per second, using the SynthEyes and Mathcad processing software. The obtained results from the analysis helped us to extract data showing the movement on the three axes OX, OY and OZ, average travel distance, average moving time of the solid particle on working surface and average velocity of the solid particle displacement.

Subpixel Motion Detection Using a Commercial Video Camera

Performance metrics for detecting subpixel motion are calculated for a commercial video camera using image difference data processed with three Neyman–Pearson-based algorithms. High-signal-to-noise-ratio data are collected and analyzed for a thin black bar that slowly oscillates against a white background. The position and velocity of the bar are estimated using Fourier-based processing techniques. The probability of detecting subpixel motion as a function of false alarm rate, number of pixels tested, subpixel shift, and detection algorithm are calculated with Monte Carlo simulations using the experimental data. The results characterize the best performance curves for detecting subpixel motion for most commercial video cameras and targets.

Lock-in technique for extraction of pulse rates and associated confidence levels from video.

We investigate the practical applicability of video photoplethysmography (VPPG) to extract heart rates of subjects using noncontact color video recordings of human faces collected under typical indoor laboratory conditions using commercial video cameras. Videos were processed following three previously described simple VPPG algorithms to produce a time-varying plethysmographic signal. These time signals were then analyzed using, to the best of our knowledge, a novel, lock-in algorithm that was developed to extract the pulsatile frequency component. A protocol to associate confidence estimates for the extracted heart rates for each video stream is presented. Results indicate that the difference between heart rates extracted using the lock-in technique and gold-standard measurements, for videos with high-confidence metrics, was less than 4 beats per minute. Constraints on video acquisition and processing, including natural subject motion and the total duration of video recorded required for evaluating these confidence metrics, are discussed.

Detection of vibrations on windows and doors excited by a speaker using video cameras

Algorithms were developed and tested to estimate acoustic coupled vibrations on doors and windows in a small building using data from commercial video cameras. The building was excited with a speaker that emitted low frequency tones. Image processing based algorithms were developed to estimate the frequency, amplitude, and signal-to-interference-plus-noise ratio (SINR) of the tones. Sensors such as Laser Doppler Vibrometers (LVDs) and accelerometers are much more sensitive than video cameras for measuring small vibrations and have a higher cutoff frequency. However, video cameras are ubiquitous, passive, and can potentially monitor a large area. Their performance is limited by the target range due to increased pixel size and atmospheric turbulence, lighting conditions, the contrast of the object of interest and the sample rate of the camera. Given these limitations, there are still potential new applications and niches for using video cameras to remotely measure vibrations of objects.

An Affordable Temporal Calibration Method for Common Video Camera

The temporal synchronization between video capture and sensor data acquisition are provided by most of advanced data gathering systems using dedicated (and expensive) hardware. This paper raises the question that one could obtain accurate temporal assessment with a normal commercial video camera. With the help of an affordable ATmega328 microcontroller enabled board – for real time programming, and an inexpensive LED based circuit together with some image recognition software an affordable temporal calibration method was proposed that address two of the issues concerning timing of video capture: the real time for image capture and usage of external recorded timers for synchronization between various acquisition systems.

A Prospective Evaluation of the Landing Error Scoring System (LESS) as a Screening Tool for Anterior Cruciate Ligament Injury Risk

Background: Anterior cruciate ligament (ACL) injuries are immediately disabling, costly, take a significant amount of time to rehabilitate, and are associated with an increased risk of developing posttraumatic osteoarthritis of the knee. Specific multiplanar movement patterns of the lower extremity, such as those associated with the drop vertical jump (DVJ) test, have been shown to be associated with an increased risk of suffering noncontact ACL injuries. The Landing Error Scoring System (LESS) has been developed as a tool that can be applied to identify individuals who display at-risk movement patterns during the DVJ. Hypothesis: An increase in LESS score is associated with an increased risk of noncontact ACL injury. Study Design: Case-control study; Level of evidence, 3. Methods: Over a 3-year interval, 5047 high school and college participants performed preseason DVJ tests that were recorded using commercial video cameras. All participants were followed for ACL injury during their sports season, and video data from injured participants and matched controls were then assessed with the LESS. Conditional logistic regression analysis was used to examine the association between LESS score and ACL injury risk in all participants as well as subgroups of female, male, high school, and college participants. Results: There was no relationship between the risk of suffering ACL injury and LESS score whether measured as a continuous or a categorical variable. This was the case for all participants combined (odds ratio, 1.04 per unit increase in LESS score; 95% confidence interval, 0.80-1.35) as well as within each subgroup (odds ratio range, 0.99-1.14). Conclusion: The LESS did not predict ACL injury in our cohort of high school and college athletes.

Commercial Video Frame Rates Can Produce Reliable Results for Both Normal and CP Spastic Gait’s Spatiotemporal, Angular, and Linear Displacement Variables

To investigate what sampling frequency is adequate for gait, the correlation of spatiotemporal parameters and the kinematic differences, between normal and CP spastic gait, for three sampling frequencies (100 Hz, 50 Hz, 25 Hz) were assessed. Spatiotemporal, angular, and linear displacement variables in the sagittal plane along with their 1st and 2nd derivatives were analyzed. Spatiotemporal stride parameters were highly correlated among the three sampling frequencies. The statistical model (2 × 3 ANOVA) gave no interactions between the factors group and frequency, indicating that group differences were invariant of sampling frequency. Lower frequencies led to smoother curves for all the variables, with a loss of information though, especially for the 2nd derivatives, having a homologous effect as the one of oversmoothing. It is proposed that in the circumstance that only spatiotemporal stride parameters, as well as angular and linear displacements are to be used, in gait reports, then commercial video camera speeds (25/30 Hz, 50/60 Hz when deinterlaced) can be considered as a low-cost solution to produce acceptable results.

Development of a Point Tracking System for Measuring Structural Deformations Using Commercial Video Cameras

This paper deals with the creation of a new, low-cost point/position tracking system that can measure deformations in engineering structures with simple commercially widespread cameras. Though point tracking systems do exist today, such as Stereo Pattern Recognition (SPR) and Projection Moir<TEX>$\acute{e}$</TEX> Interferometry (PMI) systems, they are far too costly to use to analyze small, simple structures because complex optical components such as large flashes, high-resolution cameras and data acquisition systems with several computers are required. We developed a point tracking system using commercial cameras. This system used IR LEDs and commercial IR CCD cameras to minimize the interference posed by other extraneous light sources. The main algorithm used for this system is an optical point tracking algorithm, which is composed of the point extraction algorithm and the point matching algorithm for 3-D motion estimation. a series of verification tests were performed. Then, the developed point tracking system was applied to measure deformations of an acrylic plate under a mechanical load. The measured deformations of the acrylic plate matched well with the numerical analysis results. The results indicate that the developed point tracking system is reliable enough to measure continuous deformed shapes of various engineering structures.

ACQUISITION AND ANALYSIS OF GROUND REACTION FORCES AND FOOT ORIENTATION ON IN-LINE SKATES DURING TRACK SPEED SKATING

METHODS The thin curved arches of a marathon roller-skate frame were directly strain gauged for a total number of 8 full bridges in order to collect information about the vertical load FZ and the lateral load FY acting on each of the four wheels (100 mm diameters). A total number of 32 strain gauges was applied to each frame: cables were properly grouped and joined to a rear plug as shown in Figure 1. The 8 channels were statically and cyclically calibrated with a servohydraulic testing machine loading each wheel and with a calibrated force platform, using a dummy silicon foot as a support. Two additional inertial platforms X-sense Mti were applied to the skate frame and acquired at 100 Hz: three accelerations, three gyro meters and the magnetic heading of the platform were synchronously recorded. Track field measures were taken at 400 Hz by means of a portable data acquisition system installed in a backpack: tests were performed by an Olympic gold medallist (700 N B.W.) during speed skating in an oval track of 200 m and video recorded with two commercial video cameras. Recorded data were analysed in order to estimate the peak values of the loads, the load distribution at the wheels and the force pattern in straight skating or cornering events. RESULTS AND DISCUSSION The peak values of the total resultant loads in the vertical Z and lateral Y directions are reported in Table 1: peak values appeared at the outer skate during a curve, higher than twice the body weight. The loads at each wheel were plotted and wheels 1 and 2 (anteriors) showed highest loads. The skating pattern was steadily repeated by the skilled tester and allowed to clearly distinguish between external and internal foot. Kinematical data, properly combined with mechanical data, allowed to transform the load recorded in the skate reference system into an absolute reference system.

A Television System for Determining Dynamic Thermal Fields in Self-Propagating High-Temperature Synthesis Processes

A television measuring-computing system based on a standard commercial color video camera (analog or digital) and a computer, which enables the thermal space-time characteristics of a combustion wave to be measured in self-propagating high-temperature synthesis processes, is described. The procedure for measuring temperature is outlined.

Measurement of the Emission Profiles of Cylindrical Light Diffusers Using a Video Technique

The uniformity of the emission profile produced by a cylindrical light diffuser is an important parameter for determining the light dose received by the target tissue during laser therapies such as photodynamic therapy (PDT) and interstitial laser photocoagulation (ILP). A technique originally used for determining the profile of a laser beam with a commercial video camera is adapted in order to measure the distribution of light from a cylindrical diffuser. The method can produce quantitative one-dimensional beam profiles in both the circumferential and axial direction of the light diffuser. The system allows the use of tissue phantoms that provide a convenient and effective method for comparing manufacturer's measurements often made in air with those to be expected in vivo. The technique is a quick and easy method for assessing light diffusers before treatment, and utilises readily available equipment that does not require specialist knowledge. Also, the response of the video camera facilitates the assessment of diffusers over a relatively broad optical spectrum, which encompasses the range of wavelengths currently used for both PDT (515-675 nm) and ILP (800-1064 nm).

Flexible method to obtain high sensitivity, low-cost CCD cameras for video microscopy

A simple method is described to extend image exposure times in video-rate CCD cameras and thereby, increase their sensitivity and reduce noise level of low-light images. Most commercial video cameras lack the capability of extending image exposures since they operate regular television timing formats. The technique described here implements the control of the exposure times by selectively gating the image readout from the CCD sensor. This prevents the cyclic clearing of photo-charges occurring at regular video-rates, allowing image integration beyond the duration of single video field periods. Image readout is controlled by the duration of external gating pulses, giving the camera an efficient operational versatility under different light conditions. This technique is applicable to standard monochrome and color CCD cameras. The evaluations described here using this technique show that the light sensitivity of an standard video-rate CCD camera can be significantly improved, generating high quality images at low-light levels. These were comparable to those obtained with image intensifiers or intensified video cameras. Cameras are still compatible with regular video equipment, since this technique preserves the normal TV synchronization signals. Results in simulated and real experimental situations confirmed that this technique enables the use of affordable video-rate CCD cameras for a variety of fluorescence microscopy and optical recording applications.

Video systems for PIV recording

CCD video cameras have been used extensively in recent years for image capture in fluid flow measurements with the particle image velocimetry (PIV) technique. Recent advances in CCD imaging technology have improved and extended the PIV technique to new applications, ranging from rotating machinery to 3D measurements. The progressive scan interline transfer CCD allows the time interval between two consecutive frames to be very small. Combined with frame straddling technique and the cross correlation analysis method, video cameras with such CCD design can be used for high-speed flow measurements, without the need for image shifting or image tagging methods to resolve directional ambiguity. Investigation of the pixel fill factor in CCD designs has indicated that the particle image diameter of two pixels or more is required to minimize the error in particle image location, which is important for accurate PIV measurements. Results of the investigation on a commercial video camera with the progressive scan interline transfer CCD design for its capability in high-speed flow measurements are presented. It is shown that this camera can achieve images for a time interval as small as s and for velocities of up to 250 m in the experiment.

Measurement of laser-beam profile by using a video camera

Laser-beam profile is an important laser parameter that is frequently ignored because conventional measurement techniques are cumbersome. A technique for accurately and rapidly measuring laser-beam profile with a commercial video camera and oscilloscope is described. Both two-dimensional pictures of the beam and quantitative, one-dimensional beam profiles can be obtained. The technique is particularly well suited for biomedical applications because it is compatible with most pulsed and continuous wave visible lasers, it uses readily available and relatively inexpensive components, and it is easy to implement.