3D Shape of Specular Surface Measurement Using Five Degrees of Freedom Camera System (original) (raw)
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New optical sensing system for obtaining the three‐dimensional shape of specular objects
Optical Engineering, 1996
A specular surface reflects light only in the direction such that the angle of incidence equals the angle of reflection. Due to this characteristic, conventional approaches to obtain the shape of specular objects have not guaranteed accurate results. Taking into account this characteristic, an optical sensing system is proposed to obtain the threedimensional surface shape of specular objects. Its principle is that a highly focused laser beam strikes the object surface and the specular components of the reflected light are then detected by a beam receiving unit. To achieve this, the system is to be composed of a galvanometer that steers the laser beam's direction to the desired surface point, a parabolic mirror that reflects the specular component of surface reflection toward its center line and a beam receiving unit positioned along the mirror center line. To evaluate the performance of the proposed optical sensing system, a series of experiments was performed for various measurement conditions. The sensing principle and measurement accuracy are discussed in detail for various objects of simple geometrical shapes.
3D freeform surface measurement on coordinate measuring machine using photometric stereo method
2017
Surface metrology has been widely used in manufacturing for many years. There has been a wide range of techniques applied for measuring surface topography. A photometric stereo technique is one of the best ways for the analysis of threedimensional (3D) surface textural patterns. Many published works are concerned the developed approach for recovering the 3D profiles from surface normal. This research I am also thankful to my beloved family, my father, and mother who always support and encourage me until submitting this research study. I have also to say many thanks, my wife, to look after our daughter during this research study alone.
Surface structure reconstruction using a multispectral variable angle light source
2017 18th International Carpathian Control Conference (ICCC), 2017
The paper presents a method for obtaining a surface gradient using photometric stereo method. A described technique deals with the limitations of the photometric stereo method to make it more suitable for use in industrial, rather than laboratory conditions. The image is captured with a RGB camera paired with a light source which light direction and wavelength composition can be externally controlled. The information carried by three image channels is used in order to get a full resolution surface gradient. The reconstruction is then possible with a single image acquisition, which is crucial when a measured element is in motion. As an addition, the paper presents an easy and efficient method for working with non telecentric light source. The paper contains a details of computational algorithm, description of a measurement stand and an analysis of the obtained results.
Surface profile measurement using color fringe projection
Machine Vision and Applications, 1991
A novel method for noncontact visual measurement of the profile of surfaces is described. Sinusoidal color fringe patterns are projected onto the surface to be measured, which is then viewed with a color camera. From examination of the red, green, and blue components of a single color image the depth at each point on the surface is determined from the calculation of relative phase shifts.
Optical Systems Design 2015: Optical Fabrication, Testing, and Metrology V, 2015
With the advent of techniques devised for the mass production of optical components made with surfaces of arbitrary form (also known as free form surfaces) in the last years, a parallel development of measuring systems adapted for these new kind of surfaces constitutes a real necessity for the industry. Profilometry is one of the preferred methods for the assessment of the quality of a surface, and is widely employed in the optical fabrication industry for the quality control of its products. In this work, we present the design, development and assembly of a new profilometer with five axis of movement, specifically suited to the measurement of medium size (up to 150 mm of diameter) "free-form" optical surfaces with sub-micrometer accuracy and low measuring times. The apparatus is formed by three X, Y, Z linear motorized positioners plus and additional angular and a tilt positioner employed to locate accurately the surface to be measured and the probe which can be a mechanical or an optical one, being optical one a confocal sensor based on chromatic aberration. Both optical and mechanical probes guarantee an accuracy lower than the micrometer in the determination of the surface height, thus ensuring an accuracy in the surface curvatures of the order of 0.01 D or better. An original calibration procedure based on the measurement of a precision sphere has been developed in order to correct the perpendicularity error between the axes of the linear positioners. To reduce the measuring time of the profilometer, a custom electronics, based on an Arduino TM controller, have been designed and produced in order to synchronize the five motorized positioners and the optical and mechanical probes so that a medium size surface (around 10 cm of diameter) with a dynamic range in curvatures of around 10 D, can be measured in less than 300 seconds (using three axes) keeping the resolution in height and curvature in the figures mentioned above.
Optics & Photonics News, 2000
The use of optical sensors to evaluate threedimensional shapes plays an increasingly important role in a number of applications. One important advantage of optical sensors is that no contact is required with the object being measured; another is that they are significantly faster than contact probes. Typical industrial applications for optical sensors are production quality control, both in the micro and the macro ranges, 1 the digitization of freeshape surfaces in reverse engineering, 2 and a number of 3-D computer vision problems. 3 Examples of the latter are object manipulation by means of robots 4 and obstacle detection for robotic vehicles. 5 New areas in which opti cal sensors have been successfully introduced include the measurement and preservation of antiquities, and 3-D virtual reality entertainment products. 7 A number of recent publications have described the optical techniques developed for both active and passive 3-D measurement. In passive methods, no controlled source of light is necessary. Surface reflectance, stereo disparity and camera motion are examples of tech niques based on the passive approach. The main draw back associated with these techniques is the intense computational effort required to obtain information on depth. 8 In active methods, use of a pattern of radiation simplifies the problem of depth measurement. Interfer ometric and moire techniques yield very accurate mea surements over small depth ranges. 9 Time of flight methods are suitable for medium and long distances. 10 Triangulation-based methods match the short distance interval: in this context, systems based on coherent light scanning are widely used, 11 as are whole field pro filometers, based on the projection of structured light. In this final category are a number of pattern projection schemes, which differ from each other in the coding used to express the direction of light. Since its inception, the Optoelectronics Laboratory at the University of Brescia has been active in the field of optical sensing, especially in the context of distance mea surements 6 ; the Imaging Group at the Lab has been involved in the design and implementation of techniques and systems for 3-D vision since 1992. The Group has recently developed an optical instrument for 3-D based on the projection of structured light. The basic compo nents of the system are a liquid crystal projector, which projects fringe patterns on the target, and a video camera for the acquisition of the patterns. The measurement technique designed to elaborate the patterns and obtain the depth information is based on a combination of the Gray Code and the Phase Shift methods. 17,18 It produces an extended measuring range and high resolution, and allows for measurement of a wide variety of targets char acterized by shape discontinuities and fine surface details.
Comparison and verification of optical 3-d surface measurement systems
The international archives of …, 2008
ABSTRACT: The following paper is a summary and comparison of different optical measuring systems for free-form surface measurement according to their achieved accuracy. The investigation includes three fringe projection systems, two stereo image-based ...
A structured lighting for 3D shape measurement of glass surface
2009
This paper describes an optical technique that enables 3D measurement of a shiny surface by reflection of a regular pattern. The technique called “deflectometry” has already been used to detect curvature defects. We have developed a calibration procedure in order to quantify the gathered information and enable a 3D reconstruction of the surface. We give a detailed description of the setup as well as the calibration procedure. Then we present the results of a metrology study that allows an assessment of the global uncertainty of the measurements. Applications in the car industry are then presented. Introduction – The 3D measurement of shiny surfaces Optical techniques that enable quick and global 3D measurement of surfaces are more and more accepted and used in industry, in particular because of a better knowledge of their metrological characteristics. Structured lighting is an optical technology based on fringes projection that allows quick 3D digitization of manufactured parts. The...