A fast high-precision six-degree-of-freedom relative position sensor

Lasers are commonly used in high-precision measurement and profiling systems. Some laser measurement systems are based on interferometry principles, and others are based on active triangulation, depending on requirements of the application. This paper describes an active triangulation laser measurement system for a specific application wherein the relative position of two fixed, rigid mechanical components is to be measured dynamically with high precision in six degrees of freedom (DOF). Potential applications include optical systems with feedback to control for mechanical vibration, such as target acquisition devices with multiple focal planes. The method uses an array of several laser emitters mounted on one component. The lasers are directed at a reflective surface on the second component. The reflective surface consists of a piecewise-planar pattern such as a pyramid, or more generally a curved reflective surface such as a hyperbolic paraboloid. The reflected spots are sensed at 2-dimensional photodiode arrays on the emitter component. Changes in the relative position of the emitter component and reflective surface will shift the location of the reflected spots within photodiode arrays. Relative motion in any degree of freedom produces independent shifts in the reflected spot locations, allowing full six-DOF relative position determination between the two component positions. Response time of the sensor is limited by the read-out rate of the photodiode arrays. Algorithms are given for position determination with limits on uncertainty and sensitivity, based on laser and spot-sensor characteristics, and assuming regular surfaces. Additional uncertainty analysis is achievable for surface irregularities based on calibration data

Optimized Position Sensors for Flying-Spot Active Triangulation Systems

A description of the integrated sensors developed for flying-spot active triangulation will be given. All the sensors have been fabricated using standard CMOS technology that allows the monolithic integration of photo-sensors, together with readout circuits, and digital signal processors. Position sensors are classified into two classes that allow a better understanding of the pros and cons of each one. A description of the proposed position sensor that is optimized for accurate and fast 3D acquisition is given alongside some experimental results.Nous d\ue9crivons les capteurs int\ue9gr\ue9s d\ue9velopp\ue9s pour la triangulation active \ue0 faisceau explorateur. Tous les capteurs ont \ue9t\ue9 fabriqu\ue9s \ue0 l'aide de la technologie CMOS standard qui permet l'int\ue9gration monolithique de photocapteurs, combin\ue9s \ue0 des circuits d'affichage et \ue0 des processeurs num\ue9riques de signaux. Les capteurs de position sont class\ue9s en deux classes qui permettent une meilleure compr\ue9hension des avantages et des inconv\ue9nients de chacune. Une description du capteur de position propos\ue9 qui est optimis\ue9 en vue d'une acquisition 3D rapide et de pr\ue9cision est accompagn\ue9e de certains r\ue9sultats exp\ue9rimentaux.NRC publication: Ye

Optimized Position Sensors for Flying-Spot Active Triangulation Systems

A description of the integrated sensors developed for flying-spot active triangulation will be given. All the sensors have been fabricated using standard CMOS technology that allows the monolithic integration of photo-sensors, together with readout circuits, and digital signal processors. Position sensors are classified into two classes that allow a better understanding of the pros and cons of each one. A description of the proposed position sensor that is optimized for accurate and fast 3D acquisition is given alongside some experimental results.Nous d\ue9crivons les capteurs int\ue9gr\ue9s d\ue9velopp\ue9s pour la triangulation active \ue0 faisceau explorateur. Tous les capteurs ont \ue9t\ue9 fabriqu\ue9s \ue0 l'aide de la technologie CMOS standard qui permet l'int\ue9gration monolithique de photocapteurs, combin\ue9s \ue0 des circuits d'affichage et \ue0 des processeurs num\ue9riques de signaux. Les capteurs de position sont class\ue9s en deux classes qui permettent une meilleure compr\ue9hension des avantages et des inconv\ue9nients de chacune. Une description du capteur de position propos\ue9 qui est optimis\ue9 en vue d'une acquisition 3D rapide et de pr\ue9cision est accompagn\ue9e de certains r\ue9sultats exp\ue9rimentaux.NRC publication: Ye

Optimized Position Sensors for Flying-Spot Active Triangulation Systems

A description of the integrated sensors developed for flying-spot active triangulation will be given. All the sensors have been fabricated using standard CMOS technology that allows the monolithic integration of photo-sensors, together with readout circuits, and digital signal processors. Position sensors are categorized into two classes that allow a better understanding of the pros and cons of each one. A description of the proposed position sensor that is optimized for accurate and fast 3D acquisition is given alongside some experimental result

A vector light sensor for 3D proximity applications: Designs, materials, and applications

In this thesis, a three-dimensional design of a vector light sensor for angular proximity detection applications is realized. 3D printed mesa pyramid designs, along with commercial photodiodes, were used as a prototype for the experimental verification of single-pixel and two-pixel systems. The operation principles, microfabrication details, and experimental verification of micro-sized mesa and CMOS-compatible inverse vector light pixels in silicon are presented, where p-n junctions are created on pyramid’s facets as photodiodes. The one-pixel system allows for angular estimations, providing spatial proximity of incident light in 2D and 3D. A two-pixel system was further demonstrated to have a wider-angle detection. Multilayered carbon nanotubes, graphene, and vanadium oxide thin films as well as carbon nanoparticles-based composites were studied along with cost effective deposition processes to incorporate these films onto 3D mesa structures. Combining such design and materials optimizations produces sensors with a unique design, simple fabrication process, and readout integrated circuits’ compatibility. Finally, an approach to utilize such sensors in smart energy system applications as solar trackers, for automated power generation optimizations, is explored. However, integration optimizations in complementary-Si PV solar modules were first required. In this multi-step approach, custom composite materials are utilized to significantly enhance the reliability in bifacial silicon PV solar modules. Thermal measurements and process optimizations in the development of imec’s novel interconnection technology in solar applications are discussed. The interconnection technology is used to improve solar modules’ performance and enhance the connectivity between modules’ cells and components. This essential precursor allows for the effective powering and consistent operations of standalone module-associated components, such as the solar tracker and Internet of Things sensing devices, typically used in remote monitoring of modules’ performance or smart energy systems. Such integrations and optimizations in the interconnection technology improve solar modules’ performance and reliability, while further reducing materials and production costs. Such advantages further promote solar (Si) PV as a continuously evolving renewable energy source that is compatible with new waves of smart city technology and systems

Design of an Active Stereo Vision 3D Scene Reconstruction System Based on the Linear Position Sensor Module

Active vision systems and passive vision systems currently exist for three-dimensional (3D) scene reconstruction. Active systems use a laser that interacts with the scene. Passive systems implement stereo vision, using two cameras and geometry to reconstruct the scene. Each type of system has advantages and disadvantages in resolution, speed, and scene depth. It may be possible to combine the advantages of both systems as well as new hardware technologies such as position sensitive devices (PSDs) and field programmable gate arrays (FPGAs) to create a real-time, mid-range 3D scene reconstruction system. Active systems usually reconstruct long-range scenes so that a measurable amount of time can pass for the laser to travel to the scene and back. Passive systems usually reconstruct close-range scenes but must overcome the correspondence problem. If PSDs are placed in a stereo vision configuration and a laser is directed at the scene, the correspondence problem can be eliminated. The laser can scan the entire scene as the PSDs continually pick up points, and the scene can be reconstructed. By eliminating the correspondence problem, much of the computation time of stereo vision is removed, allowing larger scenes, possibly at mid-range, to be modeled. To give good resolution at a real-time frame rate, points would have to be recorded very quickly. PSDs are analog devices that give the position of a light spot and have very fast response times. The cameras in the system can be replaced by PSDs to help achieve real- time refresh rates and better resolution. A contribution of this thesis is to design a 3D scene reconstruction system by placing two PSDs in a stereo vision configuration and to use FPGAs to perform calculations to achieve real-time frame rates of mid-range scenes. The linear position sensor module (LPSM) made by Noah Corp is based on a PSD and outputs a position in terms of voltage. The LPSM is characterized for this application by testing it with different power lasers while also varying environment variables such as background light, scene type, and scene distance. It is determined that the LPSM is sensitive to red wavelength lasers. When the laser is reflected off of diffuse surfaces, the laser must output at least 500 mW to be picked up by the LPSM and the scene must be within 15 inches, or the power intensity will not meet the intensity requirements of the LPSM. The establishment of these performance boundaries is a contribution of the thesis along with characterizing and testing the LPSM as a vision sensor in the proposed scene reconstruction system. Once performance boundaries are set, the LPSM is used to model calibrated objects. LPSM sensitivity to power intensity changes seems to cause considerable error. The change in power appears to be a function of depth due to the dispersion of the laser beam. The model is improved by using a correction factor to find the position of the light spot. Using a better-focused laser may improve the results. Another option is to place two PSDs in the same configuration and test to see whether the intensity problem is intrinsic to all PSDs or if the problem is unique to the LPSM

Non contact surface metrology in a hazardous environment

The EFDA-JET tokamak is an experimental fusion device researching fusion as a means of energy production. Inside the toroidal vessel, plasma with temperature in excess of 100 million degrees Celsius is generated and constrained by high power magnetic fields. Additional protection is provided by tiles which clad the inside of the machine. As part of a major upgrade existing heat protective tiles are to be replaced with an advanced design, and renewed interest has been shown in dimensional measurement of the surface. Measurement must occur during shutdown periods where temperature and pressure are at ambient levels. Manned entry is not permissible and all work should be performed remotely. To avoid contamination which could affect the fusion reaction and experimental results, contact with the measurement surface is not permitted. This work assesses non-contact surface measurement technologies, along with standards and guidelines for dimensional surface measurement. Existing measurement test artefacts do not offer the required surface finish and features, so specific test artefacts have been designed and produced. These artefacts are traceable to the national length standard, as traceability is a pre-requisite to evaluate accuracy. Exploratory tests highlighted two technologies for further investigation, laser triangulation and white light fringe projection. Two commercially available, state-ofthe- art examples of each technology have been evaluated using a processing method developed to highlight performance in key areas relevant to EFDA-JET. These areas include quantitative assessments of the effect of surface angle on measurement quality, the effect of depth of field for fringe projection systems and the ability of technologies to record gap and flush from tens of micrometres to millimetres. Tests enable a user to begin to assess the impact the measurement system has on the measurement result, how different technologies and systems used alone or in combination may resolve or compound erroneous results, clarifying or disrupting the meaning of results