Equipment within the LIMA lab is available for a wide range of measurement, metrology integrated automation and calibration processes. Our equipment includes:
- Equipment for Materials Research and non Destructive Evaluation
- 3D Vision
- Indoor GPS (iGPS) with the latest 'Surveyor' interface software
- A Faro Laser Tracker with both IFM and ADM ranging technologies
- A laser line scanner for the characterization of free form surfaces
- Spatial Analyzer software
Faro Laser Tracker
Laser trackers are the state of the art in production ready large scale measurements. These instruments are widely used in aerospace manufacturing.
Generically the laser tracker is a laser-based spherical coordinate measurement system. Such systems combine a laser distance measurement with two angle measurements to give coordinate measurements in 3 dimensions. The main body of the instrument emits a laser from a gimballed head; in the case of a laser tracker a spherically mounted retroreflector (SMR) is then used to reflect the laser back to the unit allowing the distance to be measured. In the case of laser radar the light is scattered off the object being measured and the scattered light is detected at the instrument.
In the case of the laser tracker sensors detect the position of the returned laser and provide feedback to sensors in the gimbal in order to track the reflector so that as the reflector moves so does the gimballed head; keeping the laser aimed at the reflector. Encoders in the gimbal measure the azimuth and elevation angle to the reflector.
In this way the laser tracker is able to measure the coordinates to the center of the SMR. The SMR has a known calibrated radius and so can be used as a probe with which objects can be measured.
There are two different approaches to distance measurement used by laser trackers. The original and still the most accurate method is to measure the displacement from a known reference using a fringe counting interferometer. The second approach to distance measurement is known as absolute distance measurement (ADM). This gives a distance rather than a displacement and so the laser beam can be broken and then picked up by the SMR at a new location. The Faro tracker in LIMA has both interferometer and ADM capabilities.
Indoor GPS (iGPS)
The Indoor GPS system (iGPS) is a new type of active triangulation device. iGPS uses a number of transmitters placed around the working volume to fix the position of a single sensor. Communication from transmitter to sensor is one-way and so it is possible to have a large number of sensors simultaneously receiving signals and detecting their position. In this sense it is similar to the NAVSTAR GPS system where signals from a number of satellites allow any number of GPS receivers to fix their position. In every other aspect the function of iGPS is fundamentally different from NAVSTAR GPS. iGPS is a proprietary technology owned by Metris.
Each transmitter acts as a rotary-laser automatic theodolite (R-LAT) providing the sensor with optical signals which allow the horizontal and vertical angle from the transmitter to the sensor to be calculated. Once these angles have been determined from at least two transmitters the coordinates of the sensor can be calculated in the same way as for a theodolite network, typically using a bundle adjustment.
Equipment at UCL
- Arius 3D Foundation system - colour laser scanner on a UMEL CMM under environmental control
- Metris K Scan - optically tracked triangulation scanner
- Leica ECDS - four theodolite industrial measurement system
- Several bespoke digital photogrammetric systems
- Stereo Photogrammetric Workstations running BAESystems SocetSet
- 3D Geowall
- Camera calibration facility, for the past 30 years we have calibrated photogrammetric cameras for most of the UK's photogrammetry and surveying industry.
Equipment at UWE
A well equipped machine vision laboratory comprising state of the art cameras, optics and lighting equipment. We have a number of systems developed in-house for three- and four-dimensional (moving 3D) data acquisition based on laser triangulation, photometric stereo and stereo triangulation. We also have a number of commercial systems including a three pod 3DMD system.