I/O Flashcards
What are the 4 main types of barcode reader?
Pen-style readers, laser scanners, CCD, camera based
How does a pen-style barcode readers work?
Physically looks like a pen that you drag across the barcode.
Contains a light source and photo diode in the tip.
The diode measures the intensity of light reflected back as it passes over the barcode.
How do laser scanner barcode readers work?
A laser is reflected of a moving mirror to read the barcode
How does a charge-coupled device (CCD) work?
Has an array of tiny light sensors in a row, that measure intensity of light
How does a camera based barcode work?
Uses a camera and image processing software
What are the 2 sensors in a camera?
CCD = high quality, more power CMOS = lower quality, less power
What happens when you take a photo on a digital camera?
- Shutter opens
- Light enters camera
- Image projected on to sensor in the lens
- Each tiny sensor measures brightness
- Turned into an electrical signal stored in binary
How is a coloured image produced in digital camera?
The sensors are placed behind coloured filters. RGB
Can either be mosaic or mirrors
How does a laser printer work?
- Ink stored in cartridges
- Print software generates bitmap
- Drum is negatively charged
- Laser draws a mirror negative onto the drum
- Laser light cause areas of drum to loose their charge, then rotates
- Charges particles are attached to areas of page not layered
- Particles then bonded to the page with heat and pressure
What is an RFID card?
They store information without being in line of site i.e dog tag
What are the 2 types of RFID?
and what are their properties?
Active tags - Larger, contain battery, constantly transmit signal
Passive tags - smaller, rely on radio waves to provide electromagnetic to energise antenna coil
Why would QR codes be used over barcode readers?
It can encode more complex information
