Flashcards in I/O Devices Deck (18):
What is a digital camera?
Device for recording still and moving images in digital form that can then be processed further using specialised software.
What are the principles of operation of a digital camera?
• When a photo is taken the shutter opens and lets light in through the lens.
• Light is focused onto a sensor, which is either a charge coupled device ( CCD ) , or a complementary metal oxide semiconductor ( CMOS )
• Sensors are made up of millions of transistors, each of which stores data for one or more pixels.
• As the light hits the sensor, it is converted into electrons and the amount of charge is recorded for each pixel in digital form
• With light, all colours can be created from RGB combinations, a camera will therefore have three different sensors.
• Digital data can be decoded and manipulated using specialist software.
Where is data typically stored for a camera?
• Removable storage devices
• Data are usually stored in compressed files.
What are RAW files?
Uncompressed files containing all data from the original photograph
What are the principles of operation for a camera ( shorthand )?
• Light let in through the shutter
• Focused by the lens
• Directed through RGB filters
• Before being focused onto the CCD or CMOS sensor
How is the capability of digital cameras quantified?
How many megapixels it uses to record images.
What is the consequence of higher megapixel cameras?
• Higher megapixels mean the sensor is breaking down the image into very small units and taking readings for each unit.
• Image can therefore be recreated very accurately without blurring or pixellation.
• Creating high res images and is useful if the image is going to be printed and enlarged.
What are the four types of barcode reader?
• Camera based
• Pen Type
What are barcode readers?
Series of input devices that use scanner technology
What are the principles of operation of barcode readers?
• A light ( usually LED ) is passed over an image
• Some form of light sensor is used to measure the intensity of light being reflected back, this is converted into a current effectively generating a waveform, this could be achieved using a photo-diode or a CCD sensor in the same way as a digital camera
• White areas reflect most light and black areas the least, making it possible to use the waveform to distinguish patterns of black and white bars
• Waveform is analogue and needs to be converted into digital form using an analogue to digital converter
• Encoding will convert the black and white into binary codes.
• Signal is decoded into a form that can be interpreted by software.
Where are barcodes used?
• Primarily for inputting product details at the point of sale.
What is RFID?
• Small wireless tracking devices or tags are embedded onto or into other items.
• Tags contain data about the item being tracked.
How does RFID work?
• Tag contains a chip which contains the data about the item and a modem to modulate and demodulate the radio signals
• Tag contains an antennae to send and receive signals
• Tags can be active, where they have their own power source, or passive which means they will pick up electromagnetic power when they are in range of an RFID tracker
• Signals and therefore data can be transmitted in both directions using radio frequencies.
What are some uses of tags?
• Transmit location
• Transmit data back
What are some applications of RFID?
• Tracking individuals
• Use in electronic passports
What are the principles of operation of laser printer?
• Rotating drum inside the printer is coated in a chemical which holds an electrical charge
• Laser beam is reflected onto the drum and where the light hits the drum the charge is discharged, effectively creating an image on the drum
• As the drum rotates it picks up toner which is attracted to the charged part of the drum
• Paper is passed over the drum and by charging the paper with the opposite charge to the toner, the toner is attracted to the paper and away from the drum
• Paper is heat treated to fuse the toner onto the paper
How is colour printing achieved?
• Four different coloured toners are used, and the process of transferring the toner to the drum is repeated for each colour