Video camera-based machine vision systems have been used for industrial inspection and quality control for a number of years. However, they have only recently been integrated into AIDC applications because 1D linear barcodes were scanned far more cost-effectively with laser scanners. The recent development and use of 2D matrix barcodes has rapidly driven technology refinements and cost-efficiencies in vision-based scanning used for AIDC applications.

Vision-based scanners use a CCD-based video imager, very similar to a video camera, to capture an image and convert it into a digital format. Fluorescent lighting, high-speed strobe flash, or an array of LEDs most usually provide the illumination source. Specialized electronic circuitry and/or software processes the digitized image to obtain the encoded data.

Decoding algorithms have been developed for both 1D and 2D symbologies (as well as for Optical Character Recognition applications). Because a vision-based system captures a symbol’s complete image, more information is gathered than can be obtained from a single or raster-scanned laser beam. Processing this wealth of information allows for reading at lower contrast ratios and a greater ability to work around impairments.

Configurations
The first machine vision scanners were sophisticated fixed-mount devices used for expensive inspection applications. However, within the last few years the widespread interest in 2D symbologies, spearheaded by the electronics and automotive industries, has resulted in rapid developments in dedicated 2D scanning systems.

Several years ago, United Parcel Service (UPS) in USA pioneered the development of the 2D matrix code MaxiCode as well as the vision-based CCD scanner to read it, in order to encode package address and handling data that would stay with the package. UPS’s fixed-mount scanner (its manufacture was later licensed to two AIDC vendors) uses an array of sensors positioned ahead of the scanner to detect the height of packages. The sensors instantly adjust the scanner’s autofocus, thus achieving an unheard-of 36-inch DOF. Fixed-mount vision-based scanners (with more modest DOFs) are also used by the United States Postal Service (U.S.P.S.).

Two different handheld CCD-based image reading scanners have lately come to market that can read both 1D and 2D stacked and matrix barcodes. The scanners operate in a working zone that extends approximately three inches from target.

• Feature extraction technology
• Automated continuous surveillance
• Flexible vision systems and processing platforms available
• Sophisticated processing systems available
• Application specific processing generally required
• Can be cost effective in applications where continuous automated inspection is required and the technology is applied as part of a statistical process control system
• Illumination can be an important consideration

Acknowledgement: Some of the information on AIDC pages is based on the information in AIMGlobal's website. We would like to thank AIMGlobal for this.