打印机
打印机（printer) 是计算机的输出设备之一，用于将计算机处理结果打印在相关介质上。衡量打印机好坏的指标有三项：打印分辨率，打印速度和噪声。
针式打印机：wire printer,Lattice printer,Dot matrix printer也称点阵式打印机；
它是由打印头上的钢针经过色带在纸上打印，形成一些点玻璃钢组成的字符和图像；
将喷出的墨点落在纸上的不同位置，形成各种字符和图像；
激光打印机：Laser printer，使用硒鼓与碳粉；
原理类似于复印机，然而它使用的是激光；
故障处理：
4.1 总提示缺纸：a 连线或接口损坏；b 传感器上灰尘堆积；c 需重装或升级驱动；d 其他物理故障；
4.2 一次送入多张纸：a 纸粘在了一起；b 放入的纸太多；c 厚度不一样的纸；
4.3 出现打印乱码：a 更换数据线；b 升级驱动；c 扩充内存；
分为点阵打印机，针式打印机，喷墨式打印机，激光打印机等。针式打印机通过打印机和纸张的物理接触来打印字符图形，而后两种是通过喷射墨粉来印刷字符图形的。
laser printer
The term laser printer is a bit mysterious_how can a laser,a highly focused beam of light,write letters and draw pictures on papers? In this chapter we'll learn the principle of work,the main parts in the laser printer,and the printing process.
激光打印机这个名词有点神秘。激光，一束高度汇聚的光，怎么能在纸张上写字和画画呢？在这一章中我们将学习激光打印机的工作原理、它的主要部件以及打印的过程。
1) The Principle of Work
1）工作原理
The primary principle of work in a laser printer is static electricity.Static electricity is an electrical charge built up on an insulated object.Since oppositely charged objects are attracted to each other,a laser printer uses this phenomenon as a sort of "temporary glue."
激光打印机最基本的工作原理是静电。静电是在绝缘体上累积起来的电荷。激光打印机利用带相反电荷的物体彼此吸引这个现象作为一种暂时性的“胶”。
2）The Main Parts in a Laser Printer
2）激光打印机的主要部件
2.1 the drum:The core component of a laser printer is the photoreceptor,a revolving drum.This drum is made out of highly photoconductive material that can be charged by static electricity,and discharged by light photons.The drum rotates a notch every time the laser finisheds scanning a line.A small print-engine synchronizes all of this perfectly.
2.1 硒鼓：激光打印机的核心部件感光器是一个旋转的硒鼓。这个硒鼓是用高光导性材料做成的。它能够被静电充电，而靠光子放电。激光每打描完一条线，硒鼓就旋转一点点。由一个小型的打印机引擎完美地完成所有这些同步。
2.2 The laser assembly:The laser assembly is composed of a laser,a movable mirror,and a series of lenses.Alaser beam is used to draw the printint pattern.As the beam moves across the drum,the laser emits a pulse of light for every dot to be printed,and no pulse for empty space.The laser doesn't actually move.It bounces the beam off a movable mirror instead.As the mirror moves,it shines the beam through a series of a lenses.This system compensates for the image distortion caused by the varying distance between the mirror and points along the drum.
2.2 激光组件是由激光、一面可移动的镜子和一系列透镜组成的。一个激光光束被用来画要打印的图案。当光束顺着硒鼓移动的时候，激光在每个要打印点上发一个光脉冲，在空白的点就不发脉冲。激光实际上并不移动。它是用一面可移动的镜子反光。当镜子移动的时候，通过一系统透镜照出光束。用这个系统弥补因为镜子和硒鼓上的点之间距离不同的而导致的图像失真。
2.3 Toner:It's electrically-charged powder with two main ingredients:pigment and plastic.Pigment provides the coloring that fills in the text and images.The plastic will melt when it passes through the heat of the fuser.
2.3 炭粉是一种带电的粉末。它含有两个主要的成分：颜料和塑料。颜料提供文字和图像的色彩，而塑料在通过熔化器的高热时会熔化。
2.4 The fuser:The fuser is a pair of rollers heated by internal quartz tube lamps,so the plastic in the toner melts as it passes through.The fuser rolls are coated with Telfon,an anti-sticky material.Thus,it keeps the toner from collecting on the fuser rollers.
2.4 熔化器是一对滚轮，内部由石英管灯加热。炭粉中的塑料在经过这对滚轮的时候熔化。熔化器滚轮表面涂有一层防粘材料特氟隆，炭粉就不会粘着在熔化器滚轮上面。
3） The printing Process
Initially,the drum is given a total positive charge by the charge corona wire.As the drum revolves,the printer shines a tiny laser beam across the surface to discharge certain points,In this way,the laser draws an electrostatic image on the drum.
一开始，硒鼓表面被电晕充电线完全充上正电荷。当硒鼓旋转时，打印机用一束用细的激光光束横扫硒鼓表面，让要打印的点放电成负电荷。以这种方式，激光在硒鼓表面画出一幅静电的图案。
After a pattern is set,the printer coats the drum with positively charged toner.Since the toner has a positive charge,it clings to the negative discharged areas of the drum,but not to the positively charged background.So you end up with a pattern written in powder.
在图案画好以后，打印机使硒鼓的表面裹上一层带正电荷的炭粉。带有正电荷的炭粉吸附在硒鼓表面被放电的地方，而不吸附在大面积带正电荷的背景区域。这样的结果就得一幅由炭粉画出的图案。
With the powder pattern affixed,the drum rolls over a sheet of negative charged paper.The charge on paper is stronger than the negative charge of the electrostatic image,so the paper can pull the toner powder away from the drum.Since it is moving at same speed as the drum,the paper picks up the image pattern exactly.To keep the paper from clinging to the drum,it is discharged by the discharge corona wire immediately after picking up the toner.At this point,the only thins keeping the toner on the page is gravity-if you were to blow on the page,you would completely lose the image.
硒鼓带着一幅由炭粉画出的图案滚过一张带负电荷的纸张。由于纸张上的电荷比比静电图像的负电荷更强，所以纸张上的电荷能够吸引炭粉离开硒鼓。因为纸张和硒鼓以同样速度滚动，使图案精确地转移到纸面上。为了防止纸张吸住硒鼓不放，就在纸面接受炭粉之后立即用电晕放电线释放纸张上的电荷。在这时，让炭粉继续留在纸面上的唯一力量是重力。如果在纸面上吹一口气，就会完全失掉图案。
Finally,the paper passes through the fuser,a pair of heated roller.As the paper passes through these rollers,the plastic inside the loose toner powder melts,fusing with the fibers in the paper.The fuser rolls the paper to the output tray,and you have your finished page.
最后，纸张经过熔化器，当纸张通过这副加热的滚轮的时候，在炭粉中的塑料熔化，并且熔合到纸张的纤维中。然后，熔化器将纸张推到输出筐，一页打印就到此完成。
After depositing toner on the paper,the drum surface passes the discharge lamp.This bright light exposes the entire photoreceptor surface,erasing the electrical images.The drum surface then passes the charge corona wire,repeating the entire process.
在纸张上转移炭粉以后，硒鼓经过明亮的放电灯，使整个感光器表面曝光，完全清除静电图像。硒鼓表面然后通过电晕充电线，重复上述过程；
4）color Printers
Essentially,color printers work the same way as monochrome printers,except they go through the entire printing process four times-one pass each for cyan(blue),magenta(red),yellow and black.By combining these four colors of toner in varying proportions,you can generate the full spectrum of color.
本质上，彩色打印机和单色打印机以同样的方式工作，只不过它们重复整个打印过程4次，一次蓝色、一次红色、一次黄色和一次黑色。通过改变这4种彩色的组合比例，可以产生完全的彩色系列。
There are several different ways of doing this,Some models have four toner units on a rotating wheel.The printer lays down the electrostatic image for one color and puts that toner unit into position.It then applies this color to the paper and goes through the process again for the next color.Some printers add all four colors to a plate before placing the image on paper.
彩色打印机有几种不同的工作模式。有些打印机把4套盒放在一个转轮上。打印机先描出一种颜色的静电图像，把那个颜色的粉末加上去，并且把这种颜色转印到纸张上。然后再换下一个颜色，重复上述过程。而有些打印机则是把所有4种色彩都加到一个平板上，然后再把图像一起转移到纸张上。
Some more expensive printers actually have a complete printer unit-a laser assembly,a drum and a toner system-for each color.The paper simply moves past the different drum heads,collecting all the colors in a sort of assembly line.
还有一些更昂贵的打印机实际上使用4套独立的打印单元。每一种色彩都有一个激光组件、一只硒鼓和一个色粉盒。纸张就像在套色胶印的流水线那样传送，经过4个不同的硒鼓头，印上4种不同的颜色。
Inkjet Printers
Since their introduction in the late 1980s,inkjet printers have grown to popularity and performance while dropping significantly in price.
1) Inkjet Printers Basics
The basic function of an inkjet printer is to place tiny droplets of ink onto paper to create an image:
喷墨打印机的基本功能是往纸上喷射墨水微滴，用以打印出一幅图像；
1.1 The dot size is usually between 50 and 60 microns in diameter,comparing to the diameter of a human hair of 70 microns.
墨水微滴的直径通常是50-60um，而人的头发的直径是70um;
1.2 The dots are positioned pricisely with resolution of up to 1440*720 dpi(dots per inch)
喷射微滴的位置精确到分辨率1440*720dpi;
1.3 The dots can have different colors combined together to create photo-quality images.
微滴可以有不同的色彩，结合在一起创造出相当于质量的图像；
2） Inkjet Technologies
There are two main technologies currently in use to form droplets of ink.
a) Thermal bubble
热气泡技术
This technology uses tiny resistors to create heat,which vaporizes ink to create a bubble.As the bubble expands,some of the ink is pushed out of a nozzle onto the paper.When the bubble"pops"(collapses),a vacuum is created.This pulls more ink into the print head from the cartridge.A typical bubble jet print head has 300 or 600 tiny nozzles,and all of them can fire a droplet simultaneously.
这项技术使用很小的电阻产生热量，使墨水蒸发形成气泡。当气泡扩大的时候，有些墨水就被推到喷嘴外面，沾到纸上。当气泡爆裂的时候产生真空，就从墨水盒吸进一些墨水到打印头中。一个典型的喷墨打印机的打印头有300-600个很细的喷嘴，它们可以同时分别喷射出墨水微滴。
2) Piezoelectric [pai7i:zEui5lektrik] [物]压电的
This technology uses a crystal located at the back of the ink reservoir of each nozzle.The crystal receives a tiny electric charge that causes it to vibrate.When the crystal vibrates inward,it forces a tiny amount of ink out of the nozzle.When it vibrates out,it pulls some more ink into the reservoir to replace the ink sprayed out.
这项技术在每个喷嘴的墨斗后面放置一小片晶体。晶体得到很小量的电荷就能振动。当晶体向内侧振动的时候，这把很小量的墨水推到喷嘴外面；当它向外侧振动的时候，就把墨水吸进墨斗来补充喷出的墨水；
3）The Main Parts in Inkjet Printers
Inkjet printers of different manufacturers and different models are very different in structure.However,they have some main parts in common.
3.1 Print Head:It contains a series of nozzles that are used to spray droplets of ink.
3.2 Ink cartridges:The containers hold the black or color inks.The cartridges of some inkjet printers include the print head itself.
3.3 Paper Feed Stepper Motor:It powers a set of rollers to pull the paper in from the paper tray or feeder,move the paper in the exact increment needed for a continuous image,and advance the paper when the current page is finished.
3.4 Control circuitry:A microprocessor controls all the mechanical operations of the printer.A memory buffer receives and stores data of the following pages while it is printing the current page.It makes the printing process faster.
3.5 Interface port:The parallel port is still used by many printers,but more and more printers use the USB port.Printers also have network interface,so that users can share them via the network.
4) The Printing Process
When you click on a button to print,there is a sequence of events that take place.
4.1 The software application you are using sends the data to be printed to the printer driver.
4.2 The driver translates the data into a format that the printer can understand,and checks if the printer is online and available to print.
4.3 The driver sends the data to the printer via the interface port or the network.The printer receives the data and stores it in a buffer.
4.4 If the printer has been idle for a period of time,it will normally go through a short clean cycle to make sure that the print head(s) are clean.Once the clean cycle is complete,the printer is ready to begin printing.
4.5 The control circuitry activates the paper feed stepper motor.This engages the rollers,which feed a sheet of paper from the paper tray/feeder into the printer.A small trigger mechanism in the tray/feeder is depressed when there is paper in the tray or feeder.If the trigger is not depreesed,the printer lights up the "Out of Paper" LED and sends an alert to the computer.
4.6 Once the paper is fed into the printer and positioned at the start of the page,the print head stepper motor moves the print head across the page.The motor pauses for the merest fraction of a second each time that the print head sprays dots of ink on the page and then moves a tiny bit before stopping again.This stepping happens so fast that it seems like a continuous motion.
4.7 Multiple dots are made at each stop.It sprays the colors in precise amounts to make any other color imaginable.
4.8 At the end of each complete pass,the paper feed stepper motor advances the paper a fraction of an inch.Depending on the inkjet model,the print head is reset to the beginning side of the page,or,in most cases,simply reverses direction and begins to move back across the page as it prints.
Once the printing is complete,the print head is parked.The paper feed stepper motor spins the rollers to finish pushing the completed page into the output tray.