As you may know, when we use the term scanner we refer to image scanners, but if we check the definition of the term scan, we can see that more devices fit in the description: Scan is to examine some object systematically (usually by passing a beam of radiation over or through) in order to obtain data especially for display or storage In this lesson we are going to review some of the most used scanning devices.
First we will speak about image scanners. Image scanners are devices that capture an image of a printed document or photo and create a digital representation of it. Nowadays we can do the same by taking a photo with a digital photo camera or even with a smartphone, but the image you will get with a scanner will be better as they do so in a controlled environment with the right amount of light. There are several technologies used for image scanners and most of them are based on using a controlled source of light to illuminate the document and moving an image capturing device along it to scan the document or photo located over it. Nowadays most of them are connected to the computer using an USB port.
First scanners didn t use a platen to put the documents, they were hand held and had to be dragged across the surface of the image to be scanned by hand. Scanning documents in this manner requires a steady hand, as an uneven scanning rate produces distorted images; an indicator light on the scanner indicates if motion is too fast. As hand scanners are much narrower than most normal document or book sizes, software (or the end user) needed to combine several narrow "strips" of scanned document to produce the finished image.
A flatbed scanner is usually composed of a glass pane (also called a platen) under which there is a bright light which illuminates the pane, and a moving CCD sensor that captures the image. They have accessories as film supports to scan photo films and document feeders to help when scanning several sheets. They can be used with optical character recognition software (called OCR) to get a text version of the content of the scanned image
If you need a very portable scanner or you are going to use it mainly to scan documents with several sheets, scanners that pull a flat sheet over the scanning element between rotating rollers are available. They can only handle single sheets up to a specified width, but can be very compact, just requiring a pair of narrow rollers between which the document is passed. Some are portable, battery powered and have their own storage, transferring stored scans later to a computer over a USB or other interface.
Modern photocopiers are scanner based machines. They can have a network interface and send the scanned documents to the user s computer.
Fax machines, sometimes called telecopying or telefax, print material (both text and images) to another fax machine using the telephone network. They include a scanner. The original document is scanned with a fax machine (or a telecopier), which processes the contents (text or images) as a single fixed graphic image, converting it into a bitmap, and then transmitting it through the telephone system in the form of audio-frequency tones. The receiving fax machine interprets the tones and reconstructs the image, printing a paper copy. You can find modem expansion cards that connect to the telephone network and are able to act as a fax machine, sending and receiving documents.
Optical mark readers (OMRs, also known as Scantron machines) are scanners designed to read specially designed sheets marked with a pencil (such as reading the answers to a multiple-choice questions test)
A 3D scanner is a device that analyses a realworld object or environment to collect data on its shape and possibly its appearance (e.g. colour). The collected data can then be used to construct digital three-dimensional models
Magnetic ink character recognition readers (MICR) are technology used by banks to speed up the clearance of issued checks by reading information such as the bank identifier, check routing number, and a customer's account number
Bar code readers read information coded in printed bars, usually numeric codes. They are used in a lot of different applications as in speeding the payment in retail stores or classifying luggage in airports. There are unidirectional bar codes and bidirectional bar codes known as QR with greater readability and greater storage capacity. They are connected to the computer using an USB port or, in legacy cases, a serial port.
Magnetic card readers are used to read credit cards, identification cards, ATM cards, and any other card that has a magnetic strip that stores customer information. There are manual swipe readers and automatic readers in which the card is inserted.
Radio frequency identification tags (RFIDs) are attached to objects and use radio waves to identify and track its movements. Some of them collect energy from the interrogating radio waves of the reader and act as a passive transponder, others have a battery and can operate at hundreds of meters from the reader. Their advantage is that they don t need to be within line of sight of the reader and may be embedded in the tracked object, so they are substituting barcodes in a lot of applications