| What is a barcode? | o Barcodes are printed diagrams that consist of light and dark portions |
| Describe the operation of an RFID system | Reader emits radio waves which are picked up by the tag’s antenna
The power induced in the tag’s antenna from these waves is
enough to power the chip which then uses its antenna to emit its own radio wave, which contains the information held on the chip
This wave is picked up by the reader which decodes the information and returns the information to a computer. |
| Give the differrence betweens a passive and an active transponder | - Passive transponders can be powered by energy from the reader whereas active transponders the energy is stored with it in the form of batteries
- Passive transponders are less bulky
- Passive transponders cant broadcast constantly
- Passive transponders have a shorter read range
- Passive transponders are cheaper |
| What are the uses of RFIDs | o Protect goods in shops
1 bit transponder
Removed or deactivated at the till
A reader installed at the shops exit goes off if an items transponder is still active (Not been removed/ probably not been paid for) passes through it
o Attached to products
Gives them a unique code
Items can be individually recognised
o Passive transponders have access control which is means of restriction of certain areas
o Passive transponders can be used for smart labels
o Passive transponders can be used for races
o Smart cards |
| Explain the process of capturing an image | o Light from objects is focused on the sensor by the lens
Sensors consist of a 2D array of cells which are light sensitive photosensors
• Each cell having an electric charge proportional to the brightness
o This is converted into a digital format with an analogue to digital converter
This ADC conversion is done by a CMOS or a CCD converter |
| What are the advatages of CMOS against CCD | CMOS has Lower Power consumption
Usually cheaper cost |
| · Explain how a CCD sensor works, and how data is acquired | o Array of photodiodes
o 1 red filter, 1 blue filter, 2 green filters cover the photodiodes (Bayer filter mosaic)
o Each row shares an ADC converter
Located to the right
o Charge is accumulated based on light exposure and frequency
o The charges are shifted to the right one cell at a time
o Converted into analogue and then into the digital equivalent |
| · What is a barcode reader? | o It’s a device that allows computers to be able to receive data |
| What are the principles of operation for a barcode reader | o Barcode readers consist of a laser light source, a lens, photodiodes and a mirror
o The mirror directs light from the laser onto a printed barcode
o The light reflected by the barcode passes through the lens and is incident on the photodiode which turns light into electrical charge
o This electrical charge can be measured and processed to form a digital signal representing the content of a barcode |
| · What is the output of a barcode reader? | Electrical charge |
| · Explain the difference between one-dimensional barcode and 2D barcode | o 2D barcodes contain more info
o 2D require more processing to extract info |
| Name the two types of 2D barcode | Aztec, Tag |
| Name the two types of 1D barcode | ISSN, ISBN |
| What are the advantages/ good things about barcodes and barcode readers | o Very reliable
Even if the item is continuously moving very fast
Can complete thousand of scans a second
• So even if dirt is covering the barcode it carries on
o Well refined
Great for mass commercial use
o Cheap
Been around for years
High volume of use
o Easy to use
Just point at the barcode and shoot |
| What are the parts to a laser printer | o Laser
o Mirror
o Lens
o Toner
o Drum
o Fusing section |
| · Explain in detail the operation of printing (monochrome) | o The page description language describes how the page should be printed (as lines, arcs and polygons)
o This is translated to a bit map image by the processor and saved in raster memory
o A negative charge is applied to the photosensitive drum
o Laser beams are directed onto the rotating drums surface
o The lasers are then turned on or off by positrons determined by the saved bitmap image
o This results in the negatively charged drum being positively charged in these sections hit by the lasers- this corresponds to the black parts of the printing
o The charged surface of the drum is then exposed to a toner
o * Darker areas are achieved by applying more layers of toner *
o * A higher voltage difference between the toner and the drum achieves more toner being deposited into the drum quicker *
o The drum is then rolled and pressed onto a sheet of paper which transfers the contents of the projected image onto the page
* not needed * |
| which primary colours are used in colour laser printing? | Cyan, magenta, yellow
+ black |
| What is the simple explanation of the process of colour printing | Goes through the printing cycle 4 times- one for each colour
Layering the colours on top of each other |
| What are the advatages of monochrome laser printers compared to colour laser printers? | Faster printing speeds
Cheaper per page
Lighter |
| What are the advatages of colour laser printers compared to monochrome laser printers? | Has colour
Two in one- still have black and white
More versatile (Images, leaflets etc...) |
| Describe an RFID generally | o Transmission of data using radio frequencies |
| List the components of a RFID system | o Transponder
o Reader
o Clock
o Coupling element (Antenna)
o ‘Energy’
o ‘Data’ |
| What are the two types of RFID transponders called | Active
Passive |
| What are the advatges of RFIDs against barcode scanning | RFIDs can scan many tags at one time
RFIDs does not to be in LOS
RFIDs can add timestamps to avoid multiple counting
RFIDs uniquely tags and labels each item |
| Why donesnt barcode scanning timestamp items | because items are not unique |
| What are the two types of sensor called | CMOS and CCD |
| What are both types of sensor fabricated from | from metal oxide semiconductors |
| Has CMOS or CCD been around longer and since when? | CMOS since 1975 |
| Why for a CCD sensor are there 2 green filters? | 2 green represent that the human eye is most sensitive to green light |
| State how for printing the toner can be applied to the drum quicker | Applying a higher voltage difference between the toner and th drum |
| Explain how darkeer areas are acheived when priting | Applying more layers of toner |
