10-07-2012, 10:08 AM
Computer Peripherals
[attachment=27310]
Impact vs. Non-Impact
Impact printers physically transfer a dot or shape to the paper
Of those in the preceding slide, only dot-matrix uses impact printing
Non-impact printers spray or lay down the image with impact
Impact printers remain important because they can print multi-part forms
Specifications
cps
characters per second
Varies by quality of print (e.g., draft vs. final)
lpm
lines per minute (related to cps)
Forms
Maximum number of layers of paper that can by printed simultaneously
Specified as n-part forms (e.g., 4-part forms)
mtbf
Mean time between failure (e.g., 6000 hours)
How it works
Four steps
A laser is fired in correspondence to the dots to be printed. A spinning mirror causes the dots to be fanned out across the drum. The drum rotates to the next line, usually 1000th or 1600th of an inch. The drum is photosensitive. As a result of the laser light, the drum becomes electrically charged wherever a dot is to be printed.
Operation of a Laser Printer
Four steps
A laser is fired in correspondence to the dots to be printed. A spinning mirror causes the dots to be fanned out across the drum. The drum rotates to the next line, usually 1000th or 1600th of an inch. The drum is photosensitive. As a result of the laser light, the drum becomes electrically charged wherever a dot is to be printed.
Operation of a Laser Printer
2. As the drum continues to rotate, the charged part of the drum passes through a tank of black powder called toner. Toner sticks to the drum wherever the charge is present. Thus, the pattern of toner on the drum matches the image.
Operation of a Laser Printer
3. A sheet of paper is fed toward the drum. A charge wire coats the paper with electrical charges. When the paper contacts the drum, it picks up the toner from the drum
Operation of a Laser Printer
4. As the paper rolls from the drum, it passes over a heat and pressure area known as the fusing system. The fusing system melts the toner to the paper. The printed page then exits the printer. As the same time, the surface of the drum passes over another wire, called a corona wire. This wire resets the charge on the drum, to ready it for the next page.
Background
Inkjet technology was developed in the 1960s
First commercialized by IBM in 1976 with the 6640 printer
Cannon and Hewlett Packard developed similar technology
Also called bubble jet
How it works
Characters and graphics are 'painted‘ line by line to from a pattern of dots as a print head scans horizontally across the paper. An ink-filled print cartridge is attached to the inkjet's print head. The print head contains 50 or more ink-filled chambers, each attached to a nozzle. An electrical pulse flows through thin resistors at the bottom of each chamber. When current flows through a resistor, the resistor heats a thin layer of ink at the bottom of the chamber to more than 900 degrees Fahrenheit for several millionths of a second . The ink boils and forms a bubble of vapour. As the vapour bubble expands, it pushes ink through the nozzle to form a droplet at the tip of the nozzle. The droplet sprays onto the paper.
The volume of the ejected ink is about one millionth that of a drop of water from an eye-dropper. A typical character is formed by an array of these drops 20 across and 20 high. As the resistor cools, the bubble collapses. The resulting suction pulls fresh ink from the attached reservoir into the firing chamber.
How it works
A scanner works by digitizing an image. A scanning mechanism consists of a light source and a row of light sensors. As light is reflected from individual points on the page, it is received by the light sensors and translated to digital signals that correspond to the brightness of each point. Colour filters can be used to produce colour images, either by providing multiple sensors or by scanning the image three times with a separate colour filter for each pass. The resolution of scanners is similar to that of printers, approximately 300-600 dpi (dots per inch).
[attachment=27310]
Impact vs. Non-Impact
Impact printers physically transfer a dot or shape to the paper
Of those in the preceding slide, only dot-matrix uses impact printing
Non-impact printers spray or lay down the image with impact
Impact printers remain important because they can print multi-part forms
Specifications
cps
characters per second
Varies by quality of print (e.g., draft vs. final)
lpm
lines per minute (related to cps)
Forms
Maximum number of layers of paper that can by printed simultaneously
Specified as n-part forms (e.g., 4-part forms)
mtbf
Mean time between failure (e.g., 6000 hours)
How it works
Four steps
A laser is fired in correspondence to the dots to be printed. A spinning mirror causes the dots to be fanned out across the drum. The drum rotates to the next line, usually 1000th or 1600th of an inch. The drum is photosensitive. As a result of the laser light, the drum becomes electrically charged wherever a dot is to be printed.
Operation of a Laser Printer
Four steps
A laser is fired in correspondence to the dots to be printed. A spinning mirror causes the dots to be fanned out across the drum. The drum rotates to the next line, usually 1000th or 1600th of an inch. The drum is photosensitive. As a result of the laser light, the drum becomes electrically charged wherever a dot is to be printed.
Operation of a Laser Printer
2. As the drum continues to rotate, the charged part of the drum passes through a tank of black powder called toner. Toner sticks to the drum wherever the charge is present. Thus, the pattern of toner on the drum matches the image.
Operation of a Laser Printer
3. A sheet of paper is fed toward the drum. A charge wire coats the paper with electrical charges. When the paper contacts the drum, it picks up the toner from the drum
Operation of a Laser Printer
4. As the paper rolls from the drum, it passes over a heat and pressure area known as the fusing system. The fusing system melts the toner to the paper. The printed page then exits the printer. As the same time, the surface of the drum passes over another wire, called a corona wire. This wire resets the charge on the drum, to ready it for the next page.
Background
Inkjet technology was developed in the 1960s
First commercialized by IBM in 1976 with the 6640 printer
Cannon and Hewlett Packard developed similar technology
Also called bubble jet
How it works
Characters and graphics are 'painted‘ line by line to from a pattern of dots as a print head scans horizontally across the paper. An ink-filled print cartridge is attached to the inkjet's print head. The print head contains 50 or more ink-filled chambers, each attached to a nozzle. An electrical pulse flows through thin resistors at the bottom of each chamber. When current flows through a resistor, the resistor heats a thin layer of ink at the bottom of the chamber to more than 900 degrees Fahrenheit for several millionths of a second . The ink boils and forms a bubble of vapour. As the vapour bubble expands, it pushes ink through the nozzle to form a droplet at the tip of the nozzle. The droplet sprays onto the paper.
The volume of the ejected ink is about one millionth that of a drop of water from an eye-dropper. A typical character is formed by an array of these drops 20 across and 20 high. As the resistor cools, the bubble collapses. The resulting suction pulls fresh ink from the attached reservoir into the firing chamber.
How it works
A scanner works by digitizing an image. A scanning mechanism consists of a light source and a row of light sensors. As light is reflected from individual points on the page, it is received by the light sensors and translated to digital signals that correspond to the brightness of each point. Colour filters can be used to produce colour images, either by providing multiple sensors or by scanning the image three times with a separate colour filter for each pass. The resolution of scanners is similar to that of printers, approximately 300-600 dpi (dots per inch).