Raster-Scan Displays

　　The most common type of graphics monitor employing a CRT is the raster-scan display, based on television technology [1]. In a raster-scan system, the electron beam is swept across the screen, one row at a time from top to bottom. As the electron beam moves across each row, the beam intensity is turned on and off to create a pattern of illuminated spots.

　　光栅扫描显示器

　　使用CRT的普通图形监视器是基于电视技术的光栅扫描显示器。在光栅扫描系统中，电子束横向扫描屏幕，一次一行，从顶到底依次进行。当电子束沿横向逐行移动时，电子束的强度不断变化，从而建立亮点的可显示模式。

　　Picture definition is stored in a memory area called the refresh buffer or frame buffer. This memory area holds the intensity values for all the screen points. Stored intensity values are then retrieved from the frame buffer and “ painted” on the screen one row (scan line) at a time. Each screen point is referred to as a pixel or pel (shortened forms of picture element). The capability of a raster-scan system to store intensity information for each screen point makes it well suited for the realistic display of scenes containing subtle shading and color patterns. Home television sets and printers are examples of other systems using raster-scan methods.

　　图形定义保存在称为刷新缓冲器或帧缓冲器的存储器中。该存储器保存一组对应屏幕所有点的强度值。然后再从刷新缓冲器取出存储的强度值，并在屏幕上逐行(扫描行)画出。每个屏幕点作为一个像素。光栅扫描系统对于屏幕每一点都有存储强度信息的能力，从而使之较好地适用于包含细微阴影和彩色模式的场景的逼真显示。家用电视和打印机是另一类使用光栅扫描方式的例子。

　　Random-Scan Displays

　　When operated as a random-scan display unit, a CRT has the electron beam directed only to the parts of the screen where a picture is to be drawn. Random-scan monitors draw a picture one line at a time and for this reason are also referred to as a vector displays(or stroke-writing or calligraphic displays). The component lines of a picture can be drawn and refreshed by a random-scan system in any specified order. A pen plotter operates in a similar way and is an example of a random-scan, hard-copy device.

　　随机扫描显示器

　　当使用随机扫描显示器时，CRT的电子束只在屏幕的图形部分移动。随机扫描显示器一次只绘制图形中的一条线，因此也称为向量显示器(或笔划显示器，或笔迹显示器)。图形的组成线条由随机扫描系统按任意指定的顺序绘制并刷新。笔式绘图仪也以类似的方式工作，它是随机扫描、硬拷贝设备的一个例子。

　　Direct-View Storage Tubes

　　An alternative method for maintaining a screen image is to store the picture information inside the CRT instead of refreshing the screen. A direct-view storage tube (DVST) stores the picture information as a charge distribution just behind the phosphor-coated screen [3]. Two electron guns are used in a DVST. One, the primary gun, is used to store the picture pattern; the second, the flood gun, maintains the picture display.

　　直视存储管

　　保持屏幕图形的另一种方法是把图形信息存储在CRT内，而不再是刷新屏幕。直视存储管(DVST)通过紧贴在屏幕荧光层后的电荷分布来存储图形信息。DVST使用两支电子枪。一支是基本枪，用来存储图形图案;另一支是泛流枪，用来保持图形显示。

　　Flat-Panel Displays

　　The term flat-panel display refers to a class of video devices that have reduced volume, weight, and power requirements compared to a CRT. A significant feature of flat-panel displays is that they are thinner than CRTs, and we can hang them on walls or wear them on our wrists. Since we can even write on some flat-panel displays, they will soon be available as pocket notepads. Current uses for flat-panel displays include small TV monitors, calculators, pocket video games, laptop computers, armrest viewing of movies on airlines, as advertisement boards in elevators, and as graphics displays in applications requiring rugged, portable monitors.

　　平板显示器

　　平板显示器代表一类能比CRT减少体积、减轻重量并节省功耗的视频设备。平板显示器的一个有意义的特性是比CRT要薄，可把它们挂在墙上或戴在手腕上。因为有些平板显示器上甚至可以书写，不久它们即可作为袖珍式笔记本。平板显示器目前的应用包括小型TV监视器、计算器、袖珍式视频游戏机、折叠式计算机、航空座椅上的电影屏幕、电梯内的告示牌，以及在要求不高的便携式监视器的应用场合中，作为图形显示器。