High time for simple 3D imaging!
2 août 2012
The Canadians use the principle of triangulation for measuring objects three- dimensionally in their Gocator series. The basic idea of triangulation is to observe the line profile projected by a laser, i.e. using line optics on an object, with a camera. As the geometrical layout of the camera and laser are known, the height of the object can, for example, be calculated via line displacement using trigonometric formulae (see images 1 and 2). This principle is employed in numerous applications and products and is in itself not a new development in imaging.
Simple configuration surface
A main characteristic of the Gocator products by LMI is their easy handling: the intelligent 3D sensors are distinguished by a simple configuration surface (see image 3) which allow the user to connect via a standard browser entering the IP address of the Gocator used. This has the advantage that configuration is independent of the operating system used and that no additional software needs to be installed. This means that no additional PC system is necessary for industrial use in a production plant or line, other than the initial configuration.
Tools for different measuring tasks
Two basic modes are available to the user for processing the laser profiles: the »Profile Mode«, which was developed for observing single profiles, and the »Whole Part Mode«, which enables viewing several combined line profiles (see image 4). Both modes offer various tools for different measuring tasks. The Whole Part Mode converts the 3D sensors into intelligent 3D cameras as they allow the automatic detection, display and evaluation of the beginnings and ends of objects and capture entire objects as point clouds.
Several LMI sensors in a single system
Another characteristic of the family is the possible use of several Gocator sensors in a single system, which can be implemented using a so-called Dual Sensor Mode. If required, two LMI sensors can be combined to form a system. In this configuration the captured profile data of the two sensors is simply combined. This method can, for example, be used if the inspection range of a sensor is insufficient and requires extending or doubling. Even if objects are to be inspected prior to and following a production step, two Gocator units can be switched in sequence to check the success of the process. A further use of the Dual Sensor Mode is to apply two systems opposite to each other and thus enable measuring of the overall measurements of an object.
Calibrated metrically, robust and well suited for installation
Compared with triangulation systems which consist of individual components, the LMI products also offer the major advantage that they are calibrated metrically for a predefined object field and thus offer the user direct metric distances as a result of the measuring tools. Furthermore, the LMI 3D sensors are extremely robust mechanically: they are supplied in tough casings with IP67 Protection Class and, by virtue of their small size and low weight, are also well suited for installation in restricted spaces or on robot arms. Using the industrial connector, the device can be connected for configuration and communication with machine controls, i.e. via Ethernet communications, as well as provided with power. The Genicam Transportlayer (GenTL) used takes on image transfer to suitable software packages such as , for example, the Common Vision Blox (CVB) by STEMMER IMAGING.
At present, there are two families of Gocator sensors, available in laser classes from 2M to 3B: The Gocator 2000 series features a pre-calibrated sensor with a horizontal resolution of 640 pixels and two connectors for 100 Mbit-LAN and I/O with power supply, where the different-sized models allow the measurement of small to large objects. This series offers the user a good balance of VGA resolution and scan rate.
The Gocator 2300 family differs from the 2000 series by having a sensor with greater horizontal resolution of 1280 pixels and higher speed. The models in this series are also available in various pre-calibrated sizes and are suitable for measuring small to large objects at higher speed. The 3D sensors in this family provide 3D profile data down to micrometer range.
Suited for various sectors
With its two Gocator families, LMI addresses 3D solutions in different sectors, i.e. metal, wood, automotive, electronics and transport. Examples for possible applications include, among others:
- Capturing and measuring objects such as wood planks or car tyres,
- The general inspection of surfaces for various defects,
- The inspection of electronic components,
- Measuring gaps and junctions in automotive applications,
- Checking shaped parts or continuous casting profiles as well as
- Sorting by size via volume determination, i.e. sorting potatoes or other natural objects.
With these two families of intelligent 3D sensors, LMI opens the way to simple 3D imaging in a number of sectors and applications.