Pen-type readers

Pen-type readers consist of a light source and photodiode that are placed next to each other in the tip of a pen. To read a barcode, the person holding the pen must move the tip of it across the bars at a relatively uniform speed. The photodiode measures the intensity of the light reflected back from the light source as the tip crosses each bar and space in the printed code. The photodiode generates a waveform that is used to measure the widths of the bars and spaces in the barcode. Dark bars in the barcode absorb light and white spaces reflect light so that the voltage waveform generated by the photodiode is a representation of the bar and space pattern in the barcode. This waveform is decoded by the scanner in a manner similar to the way Morse code dots and dashes are decoded.

Laser scanners

Laser barcode scanners utilize a semiconductor laser diode to produce a laser beam. This beam is directed by a deflection mirror onto a polygon mirror wheel. The design may include a focusing device, enabling the scanner to adjust the beam to scan at various distances.^[1]

The scanner deflects the laser beam using a rotating mirror wheel. This wheel deflects the beam line by line over the barcode at frequencies between 200 Hz and 1200 Hz in most scanners. The deflected beam exits the scanner spread at an opening angle, which is dependent on scanner design. The deflection allows it to traverse the barcode in a reading plane, effectively turning it into a "reading beam." To accommodate stationary items, laser scanners incorporate oscillating mirrors that provide additional deflection perpendicular to the main scanning line. These mirrors function at frequencies that can vary from 0.1 Hz to about 5 Hz, ensuring that barcodes can be read at different orientations.^[1]

Photodetector receives light through the optical system consisting of the mirror wheel and an optical filter. The reflected light, rapidly varying in brightness with a data pattern, is then converted into an electrical signal and is subsequently amplified to a usable level for digital processing.^[1]

CCD readers (also known as LED scanners)

CCD Barcode Scanner

Charge-coupled device (CCD) readers use an array of hundreds of tiny light sensors lined up in a row in the head of the reader. Each sensor 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 barcode 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 barcode whereas pen or laser scanners are measuring reflected light of a specific frequency originating from the scanner itself. LED scanners can also be made using CMOS sensors, and are replacing earlier Laser-based readers.^[2]

Camera-based readers

Two-dimensional imaging scanners are a newer type of barcode reader. They use a camera and image processing techniques to decode the barcode.

Video camera readers use small video cameras with the same CCD technology as in a CCD barcode 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.

Large field-of-view readers use high resolution industrial cameras to capture multiple bar codes simultaneously. All the bar codes appearing in the photo are decoded instantly (ImageID patents and code creation tools) or by use of plugins (e.g. the Barcodepedia used a flash application and some web cam for querying a database), have been realized options for resolving the given tasks.

Omnidirectional barcode scanners

Omnidirectional scanning uses "series of straight or curved scanning lines of varying directions in the form of a starburst, a Lissajous curve, or other multiangle arrangement are projected at the symbol and one or more of them will be able to cross all of the symbol's bars and spaces, no matter what the orientation.^[3] Almost all of them use a laser. Unlike the simpler single-line laser scanners, they produce a pattern of beams in varying orientations allowing them to read barcodes presented to it at different angles. Most of them use a single rotating polygonal mirror and an arrangement of several fixed mirrors to generate their complex scan patterns.

Omnidirectional scanners are most familiar through the horizontal scanners in supermarkets, where packages are slid over a glass or sapphire window. There are a range of different omnidirectional units available which can be used for differing scanning applications, ranging from retail type applications with the barcodes read only a few centimetres away from the scanner to industrial conveyor scanning where the unit can be a couple of metres away or more from the code. Omnidirectional scanners are also better at reading poorly printed, wrinkled, or even torn barcodes.

Cell phone cameras

While cell phone cameras without auto-focus are not ideal for reading some common barcode formats, there are 2D barcodes which are optimized for cell phones, as well as QR Codes (Quick Response) codes and Data Matrix codes which can be read quickly and accurately with or without auto-focus.^[4]

Cell phone cameras open up a number of applications for consumers. For example:

• Movies: DVD/VHS movie catalogs.
• Music: CD catalogs – playing an MP3 when scanned.
• Book catalogs and device.
• Groceries, nutrition information, making shopping lists when the last of an item is used, etc.
• Personal Property inventory (for insurance and other purposes) code scanned into personal finance software when entering. Later, scanned receipt images can then be automatically associated with the appropriate entries. Later, the barcodes 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.
• Consumer tracking from the retailer perspective (for example, loyalty card programs that track consumers purchases at the point of sale by having them scan a QR code).

A number of enterprise applications using cell phones are appearing:

• Access control (for example, ticket validation at venues), inventory reporting (for example, tracking deliveries), asset tracking (for example, anti-counterfeiting).^[5]
• Recent versions of the Android, iOS, and Windows Phone mobile phone operating systems feature QR or barcode scanners built in, usually accessible from their respective camera application.