When you need to scan objects in all kinds of settings at up to 120,000 3D measurements per second and with a +/- 3 mm accuracy at 25m, your technology platform had better be precise and robust.
That’s the challenge that faced FARO Technologies, a global company with headquarters in Lake Mary, FL, as its engineers developed the latest version of the Laser Scanner LS. With more than 13,500 installations worldwide, FARO offers a suite of portable measurement devices for applications ranging from architecture and road building to OEM manufactured products.
The FARO Laser Scanner LS is a portable, computerized measurement device that scans, digitally recreates,and then records all of an object’s dimensions, creating what looks like a “photograph” on the computer screen – but in 3-D. Engineers use the captured datato create a digital model for inspection, reverse-engineering, CAD-to-part comparison or factory planning.
Birth of a Scanner
For its third-generation Laser Scanner LS, which this year includes new color and mobile versions, FARO engineers had to make key changes in every major system. In the mechanical realm, the scanner incorporates a new pan axis that rotates the device 360 deg horizontally, as well as a mirror axis to deflect the laser beam 90 deg and send it out in a circular fashion in a 320 deg vertical sweep.
In the system’s optics, engineers added a sensor unit that sends a modulated laser beam via a mirror to an object, and then receives the reflected light from the same mirror through a lens system.
New electronic components include sensors that create a 3X modulated voltage, detect the reflected light and compare the phase shift of sent and received light in three frequencies. A PC controls the whole scanner and, in a synchronized fashion, adds the 3X phase into the mirror angle and the pan angle to polar coordinates.
Blending all these technologies into a highly precise product demands both a mechatronics design approach and close cooperation among the engineering disciplines designing the scanner, notes Dr. Bernd-Dietmar Becker, an electrical engineer and director of product management for FARO.
“The scanner is an excellent example of a complex instrument that brings together mechanical, optical, electrical, control and software technology,” says Becker. “It is not very easy to achieve this large field of view and precise 3D representation of reality. If, for example, the mechanical and optical systems do not perform precisely as they should, you will see it immediately in the scanned image.”
A key challenge in the electronics area was adjusting for what engineers refer to as “noise” in the photomultiplier component. “If you send a laser beam 10 times to the same spot, it won’t measure the exact same distance all the time,” says Becker. “Only the average of the points will reflect the accurate distance.”
To counter the noise problems, engineers used a combination of software-based noise compression, shielding and preamplifier components.
As for engineering tools on the Laser Scanner LS project, engineers used Autodesk’s Inventor 3D modeling for mechanical design, Intusoft’s SPICE for circuit design and proprietary software for optics design and FPGA simulation. They also turned to MATLAB to simulate noise levels in the system.
Responding to User Needs
In the OEM world, the new scanner is becoming a key fixture in such industries as aerospace and shipbuilding, notes Becker. For example, metrology specialists at Direct Dimensions, Owings Mills, MD, relied on the Laser Scanner LS to generate a digital model of the outer airflow surface of a business jet. The goal was to gather enough detailed data to perform a virtual wind tunnel analysis on the plane, which had undergone numerous modifications over the years. With the scanner, Direct Dimensions needed only six hours to digitally capture the entire surface, nose to tail. The data was later converted to a wire frame and then imported to a CAD model using NURBS tools.
“Because the FARO LS brings in so much data at once,” says Michael Raphael, owner of Direct Dimensions, “it really compresses the time we spend on site collecting data and tying up the client’s assets.
But FARO isn’t resting on its laurels. This year, it is launching new color and “super mobile” versions of the Laser Scanner LS. “Scans are usually in black and white because adding high-quality, color information to millions of 3-D pixels was difficult and time consuming,” says Becker.
When combined with a specially calibrated color bracket, Nikon D200 camera and FARO Scene v4.1 software, the FARO Laser Scanner LS provides high-speed capture of 50 million color pixels in just 2.5 minutes.
Increasingly, too, customers want to reposition laser scanners to get a more comprehensive view or take scanners into dirty or hazardous environments, such as mines or even nuclear reactors. This led to the recent introduction of a Super Mobile Laser Scanner Kit for the LS. Among other components, the kit includes a Wi-Fi/WLAN Scanner Connection that enables users to control scanning from their PDA, mobile phone, laptop or other Internet-equipped devices. There’s also a scanner-based web server, which gives scanning control to as many as different users as needed, without additional license fees.
What’s next for FARO? The company is currently developing a “pulse-based” scanner that promises to give customers more capability in taking long-distance scans.Customers will be able to exchange this new module with the existing phase-based LS modules to gain more than 250m range.