3.4 Printers and Scanners
3.4.a 2D Printers
There are three types of 2D printers: Laser printer, Inkjet printer and Graphics Plotter.
|Step||Operation on |
|1||Given electric charge (+).||Given (-) electric charge.|
The drum starts to spin.
|2||A laser beam is directed by a mirror and lens, moving across the drum (from left to right) to remove charge.|
For each location, if:
* Laser off: Charge remains on drum
* Laser on: Charge removed from the drum.
|[Repeat step 1-2, until a full page of electrostatic image is created.]|
|3||Drum is coated with charged (-) toner.|
The toner only sticks on the discharged parts of the drum.
|4||The drum rolls over the paper.|
The ink is transferred to the paper.
|5||The paper pass through heated rollers to fuse the toner particles onto the paper.|
|6||The drum is discharged.|
Excess toner is collected.
|[Page print complete. Start form step 1 again.]|
Smaller in size, cheeper to buy, but quality is poorer.
- The printhead moves across the sheet, deposing ink.
- Release: Either by thermal bubble or piezoelectric.
- Ink: Cyan, Magenta, Yellow, and black. (NOT RGB!)
- By a combination of different ink, any color could be formed.
- The paper moves forward a fraction.
- Repeat step 1-2.
Two factors denominate the accuracy:
- Mechanical Precision
- e.g. How far to move the paper for every sweep of inched
- Nozzle accuracy
- i.e. How many nozzles are in the printhead (>Thousands)
Uses a pen to write on a large sheet of paper. Allows the drawing to created directly from vector files – instead of being bitmapped.
The paper is constrained by sprockets, which moves the paper. The pen can move up and down at any time to draw / not draw.
- The design is splitter into layers.
- For every layer, the nozzle squirt material onto the previous layer.
- Some way is ensured that the layers are welded together.
- Steps 1 and 2 are repeated.
For traditional 2-D scanners:
- The paper is fixed.
- A light source moves from one end of sheet to another.
- The reflected light passes through mirror and lenses to a charged-coupled device. (CCD)
- The CCD has an array of photo-sensitive cells. It creates an electrical response proportional to the light intensity.
- An analogue-to-digitial converter is required to create the bitmap image.
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