Barcode Scanner Knowledgebase.
A barcode reader (or barcode scanner) is an electronic device for reading printed barcodes. Like a flatbed scanner, it consists of a light source, a lens and a photo conductor translating optical impulses into electrical ones. Additionally, nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the photo conductor and sending the barcode's content to the scanner's output port.
Types of barcode readers Methods
Barcode Readers are usually offered from three lines of heritage:
• Handheld readers for semi-automatic reading: The operator need not write, but must at least position the reader near the label
• Fix-mount readers for automatic reading: The reading is performed laterally passing the label over the reader. No operator is required, but the position of the code target must coincide with the imaging capability of the reader
• Reader gates for automatic scanning: The position of the code must be just under the gate for short time, enabling the scanner sweep to capture the code target successfully.
This leads to the segregation of in-line reading, semi-automatic reading, and automatic scanning.
Types of technology
The reader types can be distinguished as follows:
• Pen type readers
Pen type readers consist of a light source and a photodiode that are placed next to each other in the tip of a pen or wand. To read a bar code, the tip of the pen moves across the bars in a steady motion. The photodiode measures the intensity of the light reflected back from the light source and generates a waveform that is used to measure the widths of the bars and spaces in the bar code. Dark bars in the bar code absorb light and white spaces reflect light so that the voltage waveform generated by the photo diode is a representation of the bar and space pattern in the bar code. This waveform is decoded by the scanner in a manner similar to the way Morse code dots and dashes are decoded.
• Laser scanners
Laser scanners work the same way as pen type readers except that they use a laser beam as the light source and typically employ either a reciprocating mirror or a rotating prism to scan the laser beam back and forth across the bar code. As with the pen type reader, a photodiode is used to measure the intensity of the light reflected back from the bar code. In both pen readers and laser scanners, the light emitted by the reader is tuned to a specific frequency and the photodiode is designed to detect only this modulated light of the same frequency.
• CCD Readers
CCD readers (also referred to as LED scanner) use an array of hundreds of tiny light sensors lined up in a row in the head of the reader. Each sensor can be thought of as a single photodiode that measures the intensity of the light immediately in front of it. Each individual light sensor in the CCD reader is extremely small and because there are hundreds of sensors lined up in a row, a voltage pattern identical to the pattern in a bar code is generated in the reader by sequentially measuring the voltages across each sensor in the row. The important difference between a CCD reader and a pen or laser scanner is that the CCD reader is measuring emitted ambient light from the bar code whereas pen or laser scanners are measuring reflected light of a specific frequency originating from the scanner itself.
• Camera-Based Readers
2D imaging scanners are the fourth and newest type of bar code reader currently available. They use a small video camera to capture an image of a bar code. The reader then uses sophisticated digital image processing techniques to decode the bar code. Video cameras use the same CCD technology as in a CCD bar code reader except that instead of having a single row of sensors, a video camera has hundreds of rows of sensors arranged in a two dimensional array so that they can generate an image.
The reader packaging can be distinguished as follows:
• Handheld scanner : with a handle and typically a trigger button for switching on the light source.
• Pen scanner (or wand scanner) : a pen-shaped scanner that is swiped.
• Stationary scanner : wall- or table-mounted scanners that the barcode is passed under or beside. These are commonly found at the checkout counters of supermarkets and other retailers.
• Fixed position scanner : an industrial barcode reader used to identify products during manufacture or logistics. Most often used on conveyer tracks to identify cartons or pallets which need to be routed to another process or shipping location.
• PDA scanner : a PDA with a built-in barcode reader or attached barcode scanner e.g. Grabba.
• Automatic reader : a back office equipment to read barcoded documents at high speed (50,000/hour) e.g. Multiscan MT31 .
The scanner resolution is measured by the size of the dot of light emitted by the reader. If this dot of light is wider than any bar or space in the bar code, then it will overlap two elements (two spaces or two bars) and it may produce wrong output. On the other hand, if a too small dot of light is used, then it can misinterpret any spot on the bar code making the final output wrong.
The most commonly used dimension is 13 mils (0.3302 mm). As it is a very high resolution, it is extremely important to have bar codes created with a high resolution graphic application.
While cell phone cameras are not suitable for many traditional barcodes, there are 2D barcodes (such as Semacode) which are optimized for cell phones. These open up a number of applications for consumers:
• Movies: DVD/VHS movie catalogs
• Music: CD catalogs, play MP3 when scanned
• Book catalogs
• Groceries, nutrition information, making shopping lists when the last of an item is used, etc.
• Personal Property inventory (for insurance and other purposes)
• Calling cards: 2D barcodes can store contact information for importing.
• Brick and mortar shopping: Portable scanners can be used to record items of interest for looking up online at home.
• Coupon management: weeding expired coupons.
• Personal finance. Receipts can be tagged with a barcode label and the barcode scanned into personal finance software when entering. Later, scanned receipt images can then be automatically associated with the appropriate entries. Later, the bar codes can be used to rapidly weed out paper copies not required to be retained for tax or asset inventory purposes.
• If retailers put barcodes on receipts that allowed downloading an electronic copy or encoded the entire receipt in a 2D barcode, consumers could easily import data into personal finance, property inventory, and grocery management software. Receipts scanned on a scanner could be automatically identified and associated with the appropriate entries in finance and property inventory software.