Input & Output Devices Flashcards
2D Scanner
Paper placed on a glass panel
Bright light illuminates the document (modern scanners use a xenon light)
Scan head moves across the document
Lens focuses on the document image
Scanned image turned into electric form by the CCD
Applications of 2D Scanner
At airports to read passports OCR software used to read text Digital camera takes picture of face Images compared with passport photo using recognition software Key features compared
3D Scanner
Object has x,y coordinates
Scans along coordinates
Scanned image used by CAD
Application of 3D Scanners
CT Scanners
MRI Scanners
Barcode Scanner
Red laser shone add barcode Light is reflected back Sensors detect the light back Pattern converted to digital Microprocessor interprets the data Each digit made up of 2 dark and 2 white lines
Stock control
Barcode uniquely identifies product Stock level stored in DB Auto reduction of item when sold Auto reorder level of stock Can check stock level and location
QR Codes
QR Code scanned by camera
Three large squares used to define alignment
Light reflected back
Black squares reflect less than white squares
Squares data is decoded – each square has a binary value
Processed by an app
Links to website or document
QR code can be saved and used again
QR Code v Barcode
Barcode 1D QR is 2D
QR code can contain more data
QR code can be read from any angle
QR codes faster to scan than bar codes
Digital Cameras
Images converted from analogue to digital using ADC Image turned to pixels Each pixel given a value and colour Pixels form a grid Pixels stored in sequence E.g. jpg
Keyboards/Concept Keyboard
Circuit board under the keys Key press completes the circuit Location of press calculated Location corresponds to ASCII value ASCII binary value used by CPU
Types of Keyboard
Ergonomic
Virtual
Concept
Brail
Microphone
A diaphragm vibrates producing an electric signal
Signal goes to a sound card and is converted into digital values
Voice recognition system
Users voice converted into digital signal
Spoken words produce a digital pattern
Software compares wave pattern to patterns stored in memory
If they match person is identified
Speech recognition
Spoken words recognized and shown on screen
Problems: The software needs to be trained, Some dialects and accents can cause problems
Resistive Touchscreen
Uses multiple layers of material that transmit electric current
When top layer is touched into the lower layer current changes and location is found
Ads
Cheap to make
Can use when wearing a glove
Disads
Poor in sunlight
Easily scratched
Doesn’t allow multi-touch
Capacitive
Conductive layer
Current flows from 4 corners – electric field created
Sensors monitor field
When the screen is touched charge is transferred to the finger - current changes and location is calculated
Ads
Good in sunlight
Durable
Allows multi-touch
Disads
The screen can crack on impact
Can’t use wearing gloves
Gloves not conductive – block charge from finger
Infra-red
Invisible grid of infra-red beams on screen
When screen is touched beam is broken and location is calculated
Ads
Durable
Allows multi touch
Can use with gloves
Disads
Expensive to make
Screen can crack on impact
Sensitive to dirt
Printers
Interrupt - Signal sent to computer about no paper
Buffer – Area of memory used to temporarily store data being sent to the printer
Inkjet
Used for low quantities of documents
Used for photographs
Uses liquid ink cartridges Uses thermal bubble Rollers used to move the paper Uses a moving print head Sprays ink onto the paper Different colour inks are mixed to create the required colours
Laser
Used for high volume quality output
User toner cartridges
Uses charged print drum
Uses static electric charges
Toner is fused to the paper
3D
Used to make physical model from blueprint
Used to create physical model from CAD
Uses resin
Solid is built up in thin layers
Direct 3D printing
Uses inkjet technology with a moving head
Binder 3D printing
Similar to direct but uses two passes
1st pass sprays dry powder
2nd pass sprays a binder (type of glue)
Speakers & Headphones
Sound produced by passing digital data through a digital to analogue converter (DAC) then through an amplifier
Sound produced by voltage differences vibrating a cone
Rate with which DAC can translate the digital signals is know as sampling rate
LCD & LED Screens
Ads over CRT Brighter image Higher resolution Thinner screen Uses less power Last longer
OLED
Organic layers are thinner, lighter and more flexible
OLED layers can be made from plastic so are lighter
Brighter than LED
No backlighting required so use less power
Can be made into large thin sheets for advertising boards
Very large field of view
DLP projector
Uses millions of micro mirrors on a DLP chip
Micro mirrors can switch on/off thousands of times a second
Bright white light passes through colour filter on its way to the DLP chip
Light split into primary colours RGB
LCD
Older technology than DLP
Beam of light generated by a bulb
Light sent to group of chromatic-coated mirrors that reflect the light back at different wavelengths corresponding to RGB
Three different light components pass through three LCD screens
Images are then combined using a prism to create full colour image
Finally image passes through projector lens onto a screen
