Throughout the 1980s and 1990s, barcode scanning became a critical component of automated material handling systems in operations of all sizes and across all industries. As technology advanced, laser-based barcode reading equipment became smaller, more powerful and easier to use and maintain. Over the last four years, CCD-based cameras have steadily been replacing laser scanners in many automatic identification applications. During this time, CCD technology has matured, camera designs have evolved to meet the most demanding material handling requirements, and the cost to implement and maintain cameras has come down. Once common only in postal applications, where cameras are necessary to read very low aspect ratio codes such as Postnet and 4-State codes, cameras for barcode reading and image capture are now commonly found worldwide in manufacturers' warehouses, retail distribution centers, parcel distribution centers and even on the factory floor.
Until recently, camera technology was considered too complex, costly and maintenance intensive for most parcel shipping and distribution applications. But cameras have come of age; today, they are cost competitive with high-end omnidirectional laser scanners. And because they have fewer moving parts, cameras are more reliable. Complexity is a thing of the past as end users regularly install cameras with flexible configurations and user friendly Windows-based setup software. The widespread acceptance of cameras is directly related to the benefits they provide. These benefits result in an immediate and positive impact on the bottom line of material handling operations.
High read rates Read rate improvements, particularly in instances where the barcodes are poorly printed or have been damaged in the material handling process, are a result of the high scan rates and optimized decode software offered by cameras. Cameras also enable the reading of low aspect ratio codes, which can translate into reduced barcode heights and ultimately reduced label costs.
Image archiving The ability to capture and archive images of the objects passing the camera for quality review, sort and ship confirmation and verification of vendor applied barcode compliance are a few additional benefits resulting from the implementation of cameras.
Video encoding High-volume parcel distribution centers with a significant percentage of non-barcoded parcels can eliminate manual handling of these parcels by implementing a camera-based video-encoding system. Video-encoding systems automatically send images of no-read parcels to a workstation where an operator enters the appropriate sort information via a keyboard. This information can be used to sort a parcel or automatically print a label for future sorts.
Dimensioning CCD technology can also be used for dimen-sioning parcels on a conveyor. A single CCD camera can provide high-speed barcode scanning while dimensioning to an accuracy of one quarter inch by one quarter inch by half an inch. CCD dimensioning facilitates revenue recovery, product verification and trailer-load optimization.
Side-by-side detect Another key benefit of imaging technology in high-speed parcel sortation systems is the capability for side-by-side carton detection. CCD camera systems can analyze images to determine carton pairs that are not detected by photocells. When these cartons are identified, the sortation system can track the parcels to a jackpot area, eliminating incorrect shipments and the costly loss of goods.
Cameras are uniquely suited for multi-sided scanning tunnel applications. Laser tunnels have been used for years to eliminate the need for manual "facing" of an object toward the scanner. Depending on the size of the object and the orientation of the barcode, a laser scanner tunnel can be comprised of as many as 20 individual scanners. The large coverage (field of view and depth of field) offered by cameras and their ability to provide coverage of multiple sides of an object can reduce that number down to five or fewer. Additionally, the use of cameras can reduce the length of transport required for reading in tunnel configuration.
Cameras can read codes omnidirectionally (360° rotation of the label as is presented to the camera) with a scan pattern no larger than a fraction of an inch wide across the transport, while the scan pattern of an equivalent omnidirectional laser scanner can span from 20 inches to 40 inches. The narrow scan area of a line CCD camera also facilitates omnidirectional scanning and image capture on the bottom of cartons.
A new tunnel design takes full advantage of all the features and benefits of cameras as previously described while further simplifying a camera-based tunnel solution as compared to a laser-based solution. The new design provides the ability to cover five sides of a 36 inch by 36 inch box (of any length) at transport speeds up to 450 feet per minute using only three cameras. A laser tunnel providing similar coverage would be comprised of 16 to 18 laser line scanners.
The tunnel consists of a camera mounted above the transport to read the top of the box and two additional cameras one mounted on each side of the conveyor to read the front, both sides and rear of the box (see Figure 1).
A range-finding device triggers the cameras and determines the position of the object on the transport. These devices provide the additional benefit of enabling the cameras to focus at high speeds on the contours of irregularly shaped objects, thereby ensuring good images and high read rates on objects such as soft-sided shipping bags and garment bags as well as non-square shipping containers.
Further enhancing multi-side reading capabilities are new sensors and lens technology in the side-read cameras to enable coverage over 50 inches. Each camera requires an illumination assembly, range-finding device and mirror. All of these components are arranged together and pre-aligned in a mounting cradle. This arrangement further simplifies the tunnel and reduces installation time.
An image captured by a CCD camera can provide much more value than a simple string of data read by a simple barcode scanner. Image technology for barcode reading, 2D code reading, OCR, image archiving, dimensioning and side-by-side detection is bringing more flexibility, performance and value to material handling and parcel sortation systems worldwide. It is a powerful tool that offers immediate benefits for today's high-speed operations.
Diane Nowakowski is product manager for Accu-Sort Systems. For more information, email her at dmnowak@accusort.com.
