MEMS Technology: The New Class of Bar Code

By Stuart Scott, Intermec's Senior Director, International Marketing

Bar code technology users no longer need to choose between the reliability provided by solid-state CCD readers and the speed associated with laser scanners. A major innovation in laser scanner design and manufacturing provides outstanding reliability and performance. By adapting proven, reliable microelectromechanical systems (MEMS) technology for bar code reading, MEMS-based laser scanners provide faster reading, better recognition of poor quality bar codes than traditional lasers, and reliability even in demanding environments. MEMS scan engines are also extremely compact – about the size of a sugar cube – which leads to lightweight, ergonomic, power-friendly scanners.

MEMS, first developed in the 1970s, combine electronic circuitry with miniaturised mechanical devices on a silicon substrate smaller than a grain of sand. MEMS is the underlying technology behind antilock brakes and airbags, and used in numerous other products.

MEMS components, assembled on silicon, can be smaller in diameter than a human hair. Further processing is used to etch away parts of the silicon wafer or to add components. The assembly may include sensors to collect input, electronics to process it, and a mechanics to perform actions based on the processed input.

In 1997, the Fraunhofer Institute for Photonic Microsystems (IPMS) began developing a MEMS scanning mirror. Intermec Technologies and IPMS collaborated for five years to develop the EL10 MEMS laser scan engine, which was successfully tested commercially for more than a year before release.

Like traditional scanners, the EL10 uses a mirror to focus and direct a laser to scan a bar code. A sensor measures the light reflected, which is converted to a digital signal and decoded. Traditional laser designs cannot accommodate separate lenses and mirrors, so the mirrors reflect and collect light. MEMS technology enables separate lens and mirror components to be built into the scanner, optimising laser scanning processes.

Motorised mirrors are problematic. The mirrors are soldered or wired into place, often failing when scanners are dropped or bumped. MEMS components have less mass than traditional laser scanners, making them more durable. They also better resist wear. Motors produce friction, wearing down components. Mirrors can also misalign over time, degrading performance. These dangers are mitigated in MEMS designs.

Many users choose charge-coupled device (CCD) bar code readers. CCDs are reliable because they lack moving parts. Light emitting diodes (LEDs) illuminate the symbol and convert reflected light into a digital signal that is decoded. CCDs have solid construction that performs in challenging environments.

MEMS scanners deliver the reliability of CCDs to the laser category. MEMS scanners do not use a motor, eliminating an important source of failure. In MEMS scanners, the mirror, etched on silicon, utilises a method of frictionless oscillation that requires less power at faster speeds with two-dimensional (2D) matrix scanning capability and other benefits.

The assembly uses power efficiently to oscillate the mirror very quickly. The scan rate for the EL 10 is about 500 per second- approximately 14 times faster than traditional laser scanners and 5 times faster than traditional “high speed” models. The high rate makes the scanner more tolerant of low contrast, torn labels and other problems. The speed advantage should widen as MEMS scanning matures.

The EL10s compact assembly is ideal for integrating into handheld and wearable computers, weighing less than other scan engines.

Frictionless scanning and solid-state construction eliminate leading causes of failure in motor scanners. MEMS scanners are produced to the same drop and shock resistance standards as other readers. MEMS have been implemented and proven reliable in more demanding environments than scanning. In automotive collisions, MEMS measure force, process information and deploy airbags milliseconds after impact. Others provide real-time views of battlefields during combat.

First-generation MEMS scanners have a range comparable to common laser scanners. They can read a UPC/EAN symbol from about 30 centimetres- 5 to 7.6 cm better than many common lasers. Range should improve as technology matures.

However, like all linear laser scanners, current MEMS devices are limited in their ability to process two-dimensional (2D) symbologies and read omnidirectional bar codes and do not yet process matrix-style symbologies. Future mirror assemblies and design changes already on the drawing board will enable omnidirectional and faster scanning, and extended range.

MEMS provides an important new option for bar code scanning. It should be considered when extreme reliability and responsiveness are desirable in scanning. Until speciality MEMS scanners are released, the technology is not an option for long-range and select 2D reading applications. MEMS scanning is advantageous for operations in many environments, providing reliability and total cost of ownership benefits. MEMS scanners meet or exceed the speed and range users expect from common scanners while setting new standards for dependability and size. Future innovations in materials, components and design that are expected to rapidly improve scanning performance may also help make MEMS scanners even smaller and more efficient.

View video that describes MEMS laser technology (7 mb)