Barcodes and Scanners Flashcards
What is a scanner?
scanner, uses a charge-coupled device (CCD) to turn a picture into a digital representation of a picture. Digital cameras and optical mice also use CCDs - in fact there are dozens of peripherals that use CCDs.
All scanners follow the same steps to scan an image.
How does a scanner work?
The page is illuminated with a powerful lamp. The page reflects light, but the light reflected depends on what is on the page:
White parts of the page, such as the paper itself, reflect the most light. Black parts of the page reflect the least light. Grey parts reflect an amount of light that is between white and black - the intensity of the reflection depends on how dark the page is at that point.
Coloured parts of the page reflect coloured light. Purple text, for example, would reflect purple light and red text reflects red light.
The reflected light is focused onto a charge-coupled device (CCD), which detects what colour light is reflected and how bright that reflected light is. The CCD returns digital information about the page to the computer. You learnt about CCDs earlier this lesson. Flat-bed scanners use a system of mirrors to bring the light to the CCD.
What are the four different types of scanners?
Handheld scanner
Roller Scanner
Flatbed scanner
Drum scanner
What are the charateristics of a handheld scanner?
Small scanner that you hold in your hand and drag over a piece of paper
Cheap, slow
$100 - $400
Typically 150dpi, 200dpi although 1200dpi is available
Monochrome and colour (12 bit (4,096 colours), 24 bit (16,777,216 colours))
Requires a steady hand
Some requires multiple passes and stitching software for A4, although some can scan a full A4 page
What are the characteristics of a roller scanner
Generally built into printers
$200-$600
300dpi - 1200dpi
Monochrome and colour (16 bit (65,536 colours), 24 bit (16,777,216 colours) and 30 bit (1,073,741,824 colours)
Rolls the paper past the scanner head, difficult to photocopy pages out of a book
What are the characteristics of a flatbed scanner?
Document scanned on A4 glass plate
Optical Character Recognition (OCR) software
$50 - $400
600dpi - 2400dpi
Monochrome and colour (24 bit (16,777,216 colours), 32 bit (4,294,967,296 colours))
Typically found now-a-days built into multifunction printers (printer, scanner, photocopier, and fax) (can price up to $5,000 plus)
Document feeder for multiple pages
What are the characteristics of a drum scanner?
Expensive
Fast scan
Traditional photographic scanner
Uses PMT (photomultiplier tubes)
Rotates image on a drum around intense mercury vapour light
2400dpi plus, 40 bit colour plus, $5,000 plus
Used for publishing, glossy photos
What is Optical character recognition (OCR)?
When a scanner has scanned a document, you have an image of that document. In effect, you have a picture of the text. The problem is that word processors can’t recognise text in an image.
OCR software will turn scanned text into the ASCII text that a word processor can use. This allows you to edit files. The process of turning pictures of text into ASCII text is called optical character recognition (OCR).
Technically difficult for computer
Pattern recognition
Often use neural networks – attempts to simulate human brain, and learn by example rather than by being programmed with algorithm
What is a barcode?
Barcodes are ways of storing numbers so that they can be read rapidly
Numbers and letters are encoded as black and white lines of different thicknesses
The ratio of black to white identifies the number to a barcode reader
The code used to represent each number is designed so that the same number will be read, even if the barcode is upside down when it is read
What are the two different types of barcode scanner?
Handheld barcode reader
Flatbed barcode reader
What are the characteristics of the handheld barcode reader?
Cheap, slow
Works over a short range - 0.1m range
Approximately $30 plus
Used in small shops, libraries
What are the characteristics of the flatbed barcode reader?
Uses laser Approximately $100 plus 0.5m range Scans via X and Y axes Used in supermarkets
How does a barcode reader work?
Barcode reader shines a light on the barcode
Different reflections of light are reflected depending on whether it is a white or black line/segment/part/ratio/width
Barcode is decoded and the numbers are returned to the CPU in turn delivering its output to the required device/s
Describe a magnetic swipe card.
Magnetic particles on strip of tape
Encrypted for security
Ferric oxide coloration on stripes
Stores only account number and pin number – rest is stored in secure site
Examples: EFTPOS cards, credit cards, Student ID cards, bus/phone cards
Describe a smartcard
Contains CPU and non-volatile memory
Chip with gold contact points
Store transactions and account balances on card
Problems with hacking – all information is loaded onto chip
Examples: Cell phones, plastic money, rechargeable bus/phone cards, pay TV (i.e. Sky TV)
