About Instruments Today No. 219

3D Imaging and Manufacturing Technology

3D Image Scanning Technology and The Application to Indoor Positioning

Ching-Cherng Sun

In the new IT technology development, capture of 3D indoor space information has become more and more important. Besides, the associated applications have attracted intensive attention. In this report, we discuss three main optical scanning technologies for 3D indoor space information, including structured light, time of flight and stereo image detection. The characteristics, including advantages and shortages, of the three approaches are discussed. Finally, we introduce the developed technologies by the CIVIS team of National Central University, including auto-guided 3D scanning vehicle and point cloud processing technology. This report is expected to provide a useful reference to the people who are working or interested in this field.

The Application of Vertical-Cavity Surface-Emitting Lasers (VCSELs) Array for 3D Sensing

Jin-Wei Hsu

In this paper, we briefly review the applications of vertical-cavity surface-emitting lasers (VCSELs) array for 3D sensing and gesture monitoring. We compare its working principles and device performances with those of the edge-emitting high-power distributed feedback (DFB) laser, which is the major competitor of VCSEL array for the above-mentioned applications. Besides, we discuss the difference between coherent and non-coherent VCSEL array. In the end of this article, we illustrate the Zn-diffusion and oxide-relief techniques developed by our research group and demonstrate the high performance quasi-coherent VCSEL array based on these two techniques.

Structured Light 3D Imaging and Its Encoding Technology

Chi-Chung Lau, Si-Min Chou

Mobile and automatic devices inspire the demand of high-precision positioning and object recognition. Traditional 2D image detection cannot satisfy the demand of accuracy, and measurement turns to 3D imaging to fulfil the requirement. Structured light reconstruction method is one of the most adopted method in many optical 3D measurement techniques. Due to its acceptable cost, robustness, and data accuracy, structured Light method has been applied in many mobile consumer products. In this article, we briefly introduce some general methods of optical 3D measurement, then explain the principle of structured light imaging, and the coding technology that affects the efficiency and accuracy of structural light imaging.

Repairing IR-depth Image with Use of 2D Color Image

Yeh-Wei Yu, Tzu-Kai Wang

The most popular depth imaging methods including structure light, time-of-flight, and stereoscopic image. Since no point cloud detection method can prevent depth information loss, the complement methods is therefore important. Conventional 3D-image technologies produce RGBD images use 2D RGB image combing with depth image. Therefore, we proposed a depth information complement method that repair the IR-depth image with use of 2D RGB image. Besides, we propose a novel iterative low-pass pervasion method for depth image pervasion. In the experiment, we use strong IR noise to destroy parts of the depth image. Then we successfully complement the depth image by the proposed method. This research also builds a simulation analyzing process. It demonstrates that iterative low-pass pervasion method has good accuracy and precision.

Applications of Fringe Projection Techniques to 3D Profile Inspection, Velocity Detection, and Deformation Sensing

Wei-Hung Su, Yu-Heng Lo

Profile measurements performed by fringe projection techniques have been commonly studied for a while. In this article, we extent its applications to the fields of velocity sensing and deformation inspection. Advantages of the proposed method include: (1) capacity of non-scanning and full-field measurements, (2) system simplicity, (3) fast measurement speed, (4) easiness for calibration, and (5) low environmental vulnerability (a major problem for interferometers). Only one-shot measurement is required for data processing. The full-field property makes it possible to inspect several objects at the same time.

Semantic Loop Closure in Simultaneous Localization and Mapping Systems

Che-Yu Yang, Yu-Cheng Zhang, Yu-Shiu Chen, Chih-Wei Huang

Simultaneous localization and mapping (SLAM) algorithm is one of the core technologies to build 3D environment data using optical sensors. The technology is widely utilized on machines such as automated guided vehicles (AGV) and domestic robots. The performance of SLAM algorithms is highly depending on both the software and the quality of optical sensors, like cameras, LIDAR, etc. Loop closure, one of the crucial SLAM function component to highlight, is responsible for detecting visited locations and correcting accumulated errors. Conventionally, loop Closure calculates the similarity of scenes by comparing geometric features, but in scenarios where different scenes appears nearly identical, the performance of feature-based methods degrade significantly. Therefore, instead of using geometric feature, we introduce object recognition combining with time-spatial sequences to evaluate the similarity and improve the SLAM process. In this article, we first overview the SLAM process, and then give the introduction with object recognition and time-spatial comparing schemes. By identifying landmarks objects or signs, we can better classify similar scenes and improve 3D indoor mapping results.

Optical Scanning Holography for 3D Imaging

Jung-Ping Liu, Hsuan-Hsuan Wen

Optical scanning holography (OSH) is a kind of digital holography. OSH applies the techniques of heterodyne interference, two-dimensional scanning, and single-pixel detection. In addition, OSH has some unique features, including the recordings of the incoherent hologram, the pupil-modulation hologram, the fusion hologram, and the tilted hologram. In this article, we will introduce the principle and features of OSH. Techniques of OSH for three-dimensional imaging will also be discussed.

Multiplexed Holographic Non-axial-scanning Slit Confocal Fluorescence Microscopy

Tso-Hua Wu, Hung-Chun Wang, Chou-Min Chia, Yuan Luo

A non-axial-scanning multi-plane microscopic system incorporating multiplexed volume holographic gratings and slit array detection to simultaneously acquire optically sectioned images from different depths is presented. The proposed microscopic system is configured such that multiplexed volume holographic gratings are utilized to selectively produce axial focal points in two or more planes inside the sample, and then to use confocal slit apertures to simultaneously image these multiple planes onto corresponding detection areas of a CCD. We describe the design, implementation, and experimental data demonstrating this microscopic system’s ability to obtain optically sectioned multi-plane images of fluorescently labeled standard micro-spheres and tissue samples without scanning in axial directions.

Introduction and Application of 3D Manufacturing Technology

Yu-Fang Shen, Ming-You Shie, Yi-Wen Chen

With the rapid development of 3D printing technology, the precision and structural strength of printed objects have been continuously improved, and this technology has had wider applications. In addition to the consumer product industry, industrial machinery field, automobile industry, aerospace industry, and education industry, its main application fi elds have practical applications in medicine. This article will introduce the development status of 3D printing, 3D printing process, 3D scanning imaging technology and principle, various 3D manufacturing technologies and principles, and the practical application of 3D printing technology in medicine.