扫描仪

扫描仪 scanner 是一种计算机外部仪器设备，通过捕获图像并将之转换成计算机可以显示、编辑、存储和输出的数字化输入设备。对照片、文本页面、图纸、美术图画、照相底片、菲林软片，甚至纺织品、标牌面板、印制板样品等三维对象都可作为扫描对象，提取和将原始的线条、图形、文字、照片、平面实物转换成可以编辑及加入文件中的装置。

扫描仪中属于计算机辅助设计（CAD）中的输入系统，通过计算机软件和计算机，输出设备（激光打印机、激光绘图机）接口，组成网印前计算机处理系统，而适用于办公自动化（OA），广泛应用在标牌面板、印制板、印刷行业等。

打开扫描仪的电源开关；（先要连到电脑）；

电脑---附件---打描仪和照相机向导---选择扫描仪首选项

2.1 对话框包括：彩色、灰度照片、黑白照片和文字、自定义设置亮度、对比度、分辨率；

2.2 预览：可拖动预览图像的四个控制点调整大小；

2.3 命名、文件格式、保存位置；

打开盖板：稿件下面朝下；

扫描仪是图像信号输入设备，它对原稿件进行光学扫描，然后将光学图像传送到光电转换器中变换为模拟信号，然后又将模拟信号转换为数字信号，最后通过计算机接口将信号送至计算机；

扫描仪可分为滚筒式、平板式、便携式；

scanner

There are many types of scanners in today's market:

1 Flatbed scanners are the most commonly used scanners.

平板扫描仪

2 Sheet-fed scanners are similar to flatbed scanners except the scan head is fixed and the document is movable.

走纸式扫描仪除了扫描头固定、文件移动以外，其余的与平板扫描仪相似；

3 Handheld scanners rely on the user to move the scan head.

手提式扫描仪是靠用户移动扫描头；

4 Drum scanners are used by the publishing industry to capture incredibly detailed images.

鼓形扫描仪被出版工业用来获取令人难以置信的详尽图像；

Main parts in a flatbed scanner

1 Lamp:a lamp is used to illuminate the document.the lamp is either a cold cathode fluorescent lamp(CCFL) or a xenon lamp.

扫描灯：用来照明文件。可以用冷阴极荧光灯或者氙灯。

2 Mirrors:The image of the document is reflected by an angled mirror to another mirror.In some scanners,there are three mirrors while others use a two mirror approach.Each mirror is slightly curved to focus the image it reflects onto a smaller surface.

镜子：文件的影像被一面带角度的镜子反射到另一面镜子上。一些扫描仪使用三面镜子，也有一些扫描仪使用两面镜子。每面镜子稍微有一点弯曲，使它反射的图像聚焦在一个缩小的表面上。

Lens and filters:the last mirror reflects the image onto a lens.The lens focuses the image through a filter on the CCD array.Most scanners today use the single pass method.The lens splits the image into three smaller versions of the original.Each smaller version passes through a color filter(red,green or blue)onto a section of the CCD array.The scanner combines the data from the three parts of the CCD array.The scanner combines the data from the three parts of the CCD array into a single full-color image.

透镜和滤色镜：最后的一面镜子把图像反射到一个透镜上。透镜通过一个滤色镜把图像聚焦在一个CCD阵列上。目前大多数扫描仪都使用一次扫描的方法。透镜把图像分裂为3个比原件小的图像。每个小的图像通过一个滤色镜（红、蓝或绿）反射到CCD阵列的一部分上面。由扫描仪把CCD阵列的三部分结合成为一个全色的图像；

CCD array:the core component of the scanner is the CCd(charge-coupled device)array,CCDis a collection of tiny light-sensitive diodes(photosites).which convert photons(light)into electrons(electrical charge).and the electrical charge is proportional to the brightness of the spot.

CCD阵列：扫描仪的核心部件是CCD（电荷耦合器件）阵列。CCD是许多微小的光敏二极管的集合。光敏二极管把光子（光）转换为电子（电荷）。而电荷的数量和该点的亮度成正比；

3 the scanning process

1 the document is placed on the glass plate and the cover is closed.The inside of the cover in most scanners is white,although a few are black.The cover provides a uniform background that the scanner software can use as a reference point ofr determining the size of the document being scanned.Most flatbed scanners allow the cover to be removed for scanning a bulky object.such as a page in a thick book.

2 A stepper motor moves the scan head(mirrors,lens,filter and CCD array)slowly across the document by an attached belt.A lamp illuminates the document.The image of the document is reflected by a series of mirrors.The last mirror reflects the image onto a lens.The lens focuses the image through a filter on the CCD array.

3 Another imaging array technology used in inexpensive flatbed scanners is contact image sensor(CIS).CIS replaces the CCD array,mirrors,filters,lamp and lens with row of red,green and blue light emitting diodes(LEDs).The image sensor mechanism,consisting of 300 to 600 sensors spanning the width of the scan area,is placed very close to the glass plate that the document rests upon.When the image is scanned,the LEDs combine to provide white light.The illuminated image is then captured by the row of sensors.CIS scanners are cheaper,lighter and thinner,but do not provide the same level of resolution found in most CCD scanners.

在廉价平板扫描仪中使用的另一种成像阵列技术是接触图像传感器。CIS用一排排红色、绿色和蓝色的发光两极管（LED）取代CCD阵列、镜子、滤色镜、扫描灯和透镜。由横跨扫描区宽度300-600个传感器组成的图像传感器被放置在很接近放文件的玻璃平板的地方。当图像被扫描的时候，各种颜色的发光二极管结合起来发出白光。然后，被照亮的图像被一行传感器接收。

Most scanner today use the single pass method.Some older scanners use a three pass scanning method.Each pass uses a different color filter(red,green or blue)between the lens and CCD array.After the three passes are completed,the scanner software assembles the three filtered images into a single full-color image.

For the scanned image to be useful,it must be transferred to a computer,Threr are three common connections used by scanners:Parallel pro(the slowest).SCSI,and USB(good speed,ease of use,and affordable).Some higher-end scanners use FireWire connection.

Most scanner manufacturer use resolution and color depth to meansure the performance of scanners.

3 Resolution

Most flatbed scannners have a true hardware resolution of a least 300-600 dots per inch(dpi).The first number in the dpi measure is the X-direction resolution,and the second number is the Y-direction resolution.

The X-direction resolution is determined by the number of sensors in a single row of the CCD.For example,if the X-direction resolution is 300 dpi and the scanner is capable of scanning a letter-size document(8.5 inch wide),then the CCD needs to have 300*8.5=2550 sensors arranged in each horizontal row.likewise,a scanner with an X-direction resolution of 600 dpi needs to have a CCD array with 5100 sensors in each horizontal row.A single-pass scanner would have three of these rows for a total of 15300 sensors.

X方向的分辨率取决于每一行CCD中传感器的数目。例如，X方向的分辨率是300dpi,扫描仪有能力扫描信纸大小的文件（8.5in宽），那么CCD在第行上需要有300*8.5＝2550个传感器。…

The Y-direction resolution is determined by the precision of the stepper motor.The Y-dirction resolution of 300 dpi means the stepper motor is able to move in increments eaual to 1/300 ths of an inch.

Many scanners proclaim resolutions of 4800*4800 or evne 9600*9600.These high resolutions are usually software-enhanced,interpolated resolution.Interpolation is a process that the scanning software uses to increase the perceived resolution of an image.It does this by creating extra pixels in between the ones actually scanned by the CCD array.These extra pixels are an average of the adjacent pixels.For example,if the hardware resolution is 300*300,and the interpolated resolution is 600*300,then the software is adding a pixel between every one scanned by a CCD sensor in each row.

很多扫描仪宣称分辨率为…,这样高的分辨率通常是经过由软件插值法来实现的。插值法是扫描仪软件用来增强图像的可察觉分辨的过程。这是通过在CCD阵列扫描的实际像素之间创造额外的像素来实现的。这些额外的像素是邻近像素的平均值。例如，假定硬件分辨率是300*300,而插值分辨率是600*300,那个软件在CCD传感器扫描的每两个之间又了一个像素。

4 color depth

Another term used when talking about scanners is bit depth,or color depth.This refers to the number of colors that the scanner is capable of reproducing.Each pixel requires 24 bits to create standard true color.Almost all new scanners on the market support 24-bit color depth.Some older versions support only 16-bit.

描述扫描仪性能的另一个指标是位深度，或称色深度。这个指标说明扫描仪能重现多少种色彩。每个像素需要24位才能创造标准的真实色彩。市场上几乎所有新的扫描仪都支持24位色深度。有些老机型只支持16位。