Structured Light Imaging Research Articles

Depth Edge Filtering Using Parameterized Structured Light Imaging.

This research features parameterized depth edge detection using structured light imaging that exploits a single color stripes pattern and an associated binary stripes pattern. By parameterized depth edge detection, we refer to the detection of all depth edges in a given range of distances with depth difference greater or equal to a specific value. While previous research has not properly dealt with shadow regions, which result in double edges, we effectively remove shadow regions using statistical learning through effective identification of color stripes in the structured light images. We also provide a much simpler control of involved parameters. We have compared the depth edge filtering performance of our method with that of the state-of-the-art method and depth edge detection from the Kinect depth map. Experimental results clearly show that our method finds the desired depth edges most correctly while the other methods cannot.

Predicting Gilthead Sea Bream (Sparus aurata) Freshness by a Novel Combined Technique of 3D Imaging and SW-NIR Spectral Analysis.

A technique that combines the spatial resolution of a 3D structured-light (SL) imaging system with the spectral analysis of a hyperspectral short-wave near infrared system was developed for freshness predictions of gilthead sea bream on the first storage days (Days 0–6). This novel approach allows the hyperspectral analysis of very specific fish areas, which provides more information for freshness estimations. The SL system obtains a 3D reconstruction of fish, and an automatic method locates gilthead’s pupils and irises. Once these regions are positioned, the hyperspectral camera acquires spectral information and a multivariate statistical study is done. The best region is the pupil with an R2 of 0.92 and an RMSE of 0.651 for predictions. We conclude that the combination of 3D technology with the hyperspectral analysis offers plenty of potential and is a very promising technique to non destructively predict gilthead freshness.

Color structured light imaging of skin.

We illustrate wide-field imaging of skin using a structured light (SL) approach that highlights the contrast from superficial tissue scattering. Setting the spatial frequency of the SL in a regime that limits the penetration depth effectively gates the image for photons that originate from the skin surface. Further, rendering the SL images in a color format provides an intuitive format for viewing skin pathologies. We demonstrate this approach in skin pathologies using a custom-built handheld SL imaging system.

레이저 구조광 영상기반 3차원 스캐너 개발

This paper addresses the development of 3D data acquisition system (3D scanner) based laser structured-light image. The 3D scanner consists of a stripe laser generator, a conventional camera, and a rotation table. The stripe laser onto an object has distortion according to 3D shape of an object. By analyzing the distortion of the laser stripe in a camera image, the scanner obtains a group of 3D point data of the object. A simple semiconductor stripe laser diode is adopted instead of an expensive LCD projector for complex structured-light pattern. The camera has an optical filter to remove illumination noise and improve the performance of the distance measurement. Experimental results show the 3D data acquisition performance of the scanner with less than 0.2㎜ measurement error in 2 minutes. It is possible to reconstruct a 3D shape of an object and to reproduce the object by a commercially available 3D printer.

레이저 구조광 영상기반 거리측정 센서 개발

레이저 구조광 영상기반 거리측정 센서 개발

Fresh meat color evaluation using a structured light imaging system

The objective of this study was to investigate the efficacy of a computer vision system (CVS) with structured light for meat color assessment. Three muscles (longissimus dorsi (LD), semimembranosus (SM), and psoas major (PM)) from eight beef carcasses were obtained at 1day postmortem, vacuum packaged and assigned to three aging periods (9, 16, and 23days). After aging, steaks were cut and displayed for 7days at 3°C under light. The surface colors were evaluated by using a Minolta, the CVS and trained color panel. In general, the CVS was highly correlated to the sensory scores, and showed an equivalent meat color assessment compared to the colorimeter. The CVS had a significantly higher correlation with the panel scores for the lighter and more color stable samples compared to the colorimeter. These results indicate that the CVS with structured light could be an appropriate alternative to the traditional colorimeter by offering improved precision and accuracy over the colorimeter.

Research of Image Information Extraction Method Based on Structured Light

In line structured light three-dimensional measurement systems, the position of shifted light in the structure light image reflects the three-dimensional profile information of the object. In this paper, according to the characteristics of structured light image, a approach of separating shifted pixels is proposed, and successfully extracts structured light image two-dimensional data with related mathematical methods, which contributes to the foundation for structured light three-dimensional reconstruction of three-dimensional measurement system work.

3D Palmprint Recognition Using Dempster-Shafer Fusion Theory

This paper proposed a novel 3D palmprint recognition algorithm by combining 3D palmprint features using D-S fusion theory. Firstly, the structured light imaging is used to acquire the 3D palmprint data. Secondly, two types of unique features, including mean curvature feature and Gaussian curvature feature, are extracted. Thirdly, the belief function of the mean curvature recognition and the Gaussian curvature recognition was assigned, respectively. Fourthly, the fusion belief function from the proposed method was determined by the Dempster-shafer (D-S) fusion theory. Finally, palmprint recognition was accomplished according to the classification criteria. A 3D palmprint database with 1000 range images from 100 individuals was established, on which extensive experiments were performed. The results show that the proposed method 3D palmprint recognition is much more robust to illumination variations and condition changes of palmprint than MCR and GCR. Meanwhile, by fusing mean curvature and Gaussian curvature feature, the experimental results are promising (the average equal error rate of 0.404%). In the future, imaging technique needs further improvement for a better recognition performance.

Meat color assessment using a structured light imaging system

Meat color assessment using a structured light imaging system

Vision Control System of Pipe Welding Robot

The author of this article designs a non-track automatic pipe welding robot, which mainly studies the image processing system of visual welding tracking. With the requirement of various interference noise and tracking accuracy in the welding process, this study adopts structure light CCD sensor checking system and image acquisition card processing images of computer software, in which sample filtering, edge checking, contour tracking, laser centerlines selection and checking of its characteristics. This processing method has the advantages of good effect and speedy processing that is able to meet the timely requirement of tracking system.

Multi-projector color structured-light vision

Research interest in rapid structured-light imaging has grown increasingly for the modeling of moving objects, and a number of methods have been suggested for the range capture in a single video frame. The imaging area of a 3D object using a single projector is restricted since the structured light is projected only onto a limited area of the object surface. Employing additional projectors to broaden the imaging area is a challenging problem since simultaneous projection of multiple patterns results in their superposition in the light-intersected areas and the recognition of original patterns is by no means trivial. This paper presents a novel method of multi-projector color structured-light vision based on projector–camera triangulation. By analyzing the behavior of superposed-light colors in a chromaticity domain, we show that the original light colors cannot be properly extracted by the conventional direct estimation. We disambiguate multiple projectors by multiplexing the orientations of projector patterns so that the superposed patterns can be separated by explicit derivative computations. Experimental studies are carried out to demonstrate the validity of the presented method. The proposed method increases the efficiency of range acquisition compared to conventional active stereo using multiple projectors.

이동로봇을 위한 링 배열 구조광 영상 기반 거리측정 센서 및 자율주행

In the paper, we proposed a ring type structured light image based embedded ranging sensor for a mobile robot. Since the proposed ranging sensor obtains omnidirectional object distance, it is useful for autonomous navigation of a mobile robot. By matching the local omnidirectional distance map with a given global object map, it is possible to get position and heading angle of mobile robot in the global coordinates. Experiments for matching and navigation were carried out to verify the performance of the proposed ranging sensor.

구조광 영상기반 전방향 거리측정 시스템 개발

In this paper, a ranging system is proposed that is able to measure 360 degree omnidirectional distances to environment objects. The ranging system is based on the structured light imaging system with catadioptric omnidirectional mirror. In order to make the ranging system robust against environmental illumination, efficient structured light image processing algorithms are developed; sequential integration of difference images with modulated structured light and radial search based on Bresenham line drawing algorithm. A dedicated FPGA image processor is developed to speed up the overall image processing. Also the distance equation is derived in the omnidirectional imaging system with a hyperbolic mirror. It is expected that the omnidirectional ranging system is useful for mapping and localization of mobile robot. Experiments are carried out to verify the performance of the proposed ranging system.

Feature points matching for face reconstruction based on the window unique property of pseudo-random coded image

Structured light vision systems have been successfully used for accurate measurement of the 3D surfaces of an object, in which a pseudo-random coded structured light image pattern is projected onto the target object through a projector, and the coded information image produced by its surface is captured by a CCD camera in order to recover its 3D surfaces. In this kind of computer vision technology, 3D face reconstruction is a hot research topic. This paper presents a method for feature points matching used in 3D reconstruction. In this method, the feature points can be identified exclusively taking advantage of the window unique property of a pseudo-random array. Thus, the matching problem can be solved by finding the correspondence between 2D coordinates of feature points in the pixel image and those in the code of the projected template. Then, the 3D reconstruction can be carried out with only a single image with the benefit of easy operation and simple calculation. An experiment for 3D face reconstruction with simulated data is given. The performances show that this method has high matching precision for object matching of feature points.

A Method for Measuring 3D Cardiac Surface Mechanics with High‐Speed Structured Light Imaging

Cardiac disease often manifests as a combination of electrical and mechanical remodeling. The relationship between whole‐heart epicardial mechanics and electrophysiology is crucial to our understanding of cardiac arrhythmias in the settings of heart failure. While advances in imaging technology have allowed for accurate descriptions of surface deformation in 2D and 3D, current imaging technologies are often hampered by poor temporal resolution that limits imaging to repeated patterns. Moreover, structural correspondences are often achieved with fiducial markers attached to finite locations—limiting the resolution for mechanical analysis. Here, we demonstrate the potential of a high‐speed structured light imaging system to capture and describe whole‐heart 3D epicardial motion. Additionally, we developed a novel motion‐tracking algorithm to form correspondences between 3D frames. All imaging was performed on isolated rabbits hearts (n = 4), Langendorff‐perfused with oxygenated Tyrode's solution at a constant pressure of 60 mmHg. By combining our structured light imaging system with surface registration, we are able to image and describe cardiac motion at more than 200,000 locations and kHz frames rates during normal sinus rhythm, ventricular pacing, and ventricular fibrillation. Our new method will allow combined electro‐mechanical imaging of intact hearts. Supported by NIH Grant RO1 HL067322.

A Novel 3-D Palmprint Acquisition System

Palmprints have been widely studied for personal authentication because they are highly accurate and incur low costs. Most of the previous work has focused on two-dimensional (2-D) palmprint identification. However, the inner surfaces of palms contain not only texture information but also shape information. Unfortunately, 2-D palmprint systems lose the shape information when capturing palmprint images. Hence, three-dimensional (3-D) information is important for palmprint systems. In this paper, we have designed and developed a novel 3-D palmprint acquisition system based on structured-light imaging technology. The acquisition system can obtain 3-D palmprint information and, at the same time, the corresponding 2-D texture, which are used for personal authentication. A 3-D palmprint database that contains 8000 samples has been established by using the developed acquisition system, and the test results illustrate the effectiveness of our system.

Improving signal-to-noise ratio of structured light microscopy based on photon reassignment

In this paper, we report a method for 3D visualization of a biological specimen utilizing a structured light wide-field microscopic imaging system. This method improves on existing structured light imaging modalities by reassigning fluorescence photons generated from off-focal plane excitation, improving in-focus signal strength. Utilizing a maximum likelihood approach, we identify the most likely fluorophore distribution in 3D that will produce the observed image stacks under structured and uniform illumination using an iterative maximization algorithm. Our results show the optical sectioning capability of tissue specimens while mostly preserving image stack photon count, which is usually not achievable with other existing structured light imaging methods.

A pilot study in the 3D registration of structured-light facial data with spiral CT images of the facial defect

The aim of this study was to assess the feasibility of merging surface images obtained individually by the structured-light scanning and the spiral computed-tomography (CT) scan. The study was conducted on six patients with various facial defects. A fast structured-light scanning of the face and a spiral CT scan of the head were carried out for each patient. The structured-light surface was superimposed on the reconstructed CT soft-tissue surface using initial positioning based on corresponding landmarks and then fine registration completed by the iterative closest point algorithm. For validity estimates, registration differences were calculated, and the average values were 0.5–0.8 mm. The virtual head can be displayed with different combinations of interior and exterior surface details. It was concluded that a structured-light surface and spiral CT images can be superimposed to create an accurate and complete 3D virtual head model of the facial defect with underlying skeletal structure using the registration method.

전방향 구조광 영상을 위한 Bresenham 래스터 알고리즘 기반 영상 탐색 방법

In this paper, we proposed a search method for structured light pixels of omnidirectional structured light image. Since the omnidirectional structured light image is composed of several circular arc segments, the proposed algorithm searches the structured light pixels in radial direction rather than horizontal or vertical directions. The proposed search algorithm is based on the well-known Bresenham raster algorithm for line drawing in discrete integer space, thereby computation of the algorithm is very efficient. Comparison results between the proposed search algorithm and the conventional horizontal search are presented in experiments.

조명잡음에 강인한 구조광 영상기반 거리측정 센서

This paper presents an active ranging system based on laser structured-light image. The structured-light image processing is computationally efficient in comparison with the conventional stereo image processing, since the burdensome correspondence problem is avoidable. In order to achieve robustness against environmental illumination noise, an efficient image processing algorithm, i.e., integration of difference images with structured-light modulation is proposed. Distance equation from the measured structured light pixel distance and system parameter calibration are addressed in this paper. Experiments and analysis are carried out to verify performance of the proposed ranging system.