CRT显示器原理简介

CRT显示器原理简介---摘自《 FPGA PROTOTYPING BY VERILOG EXAMPLES 》By-- Pong P. Chu   (Cleveland State University)

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CRT(cathode ray  tube)---阴极射线管

The  conceptual sketch  of a monochrome(单色的;黑白的) CRT monitor is  shown in Figure 13.1.

 

The electron gun (cathode) generates a focused electron beam, which traverses a vacuum

tube and eventually hits the phosphorescent  [,fɔsfə'resnt]  发出磷光的；磷光性的  screen.

Light is emitted at the instant that electrons hit a phosphor dot on the screen.

The intensity of the electron beam and thebrightness of the dot are determined by the

voltage  level of  the external video input signal,labeled mono in Figure 13.1.

The mono  signal is an analog signal whose voltage level is between 0 and 0.7 V. 

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A vertical deflection coil (偏转线圈) and a horizontal deflection coil outside the tube produce

magnetic fields to control how the electron beam travels and to determine

where on the screen the electrons hit.  In  today's monitors,  the electron beam

traverses  (i.e.,  scans) the screen systematically  in  a fixed pattern,  from  left

to right  and  from top to bottom,  as shown  in Figure 13.2. 

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The monitor's internal oscillators and amplifiers generate sawtooth(锯齿) waveforms  to control the  

two deflection  coils.  For example, the electron beam moves from the  left edge to the right edge

as the voltage applied to the horizontal deflection coil gradually increases. After reaching the right edge,

the beam  returns rapidly to the  left edge (i.e.,  retraces) when the voltage changes to 0.  The relationship

between the sawtooth waveform and  the  scan is shown  in  Figure 13.4. Two external  synchronization signals,

hsync  and vsync,  control generation of the sawtooth waveforms.  These signals are digital signals.  

The relationship between  the hsync  signal and the horizontal sawtooth is also shown in Figure  13.4.

Note that the "  1  " and "0" periods of  the hsync  signal correspond to the rising and falling ramps of the

sawtooth waveform. 

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总结一下就是:

行场同步信号(hsync_vsync)--->经振荡器、放大器---->锯齿波(电压从低到高)--->

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偏转线圈随加在其上的从低到高的电压,从左偏转向右,完成扫描。

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 (1)The screen of a CRT monitor usually  includes a small black border.The middle rectangle is the visible portion.

 (2)Note  that the CRT monitor should be black in the right and left borders and during retrace. 

 (3)For  a human eye, the refresh rate must be at least 30 screens per  second to make the motion  appear to be continuous.    

 (4)To reduce flickering,  the monitor usually has a much higher rate, such as the 60 screens per  second  specification above.