What Is Tube Drawing?

The image storage tube, also known as the electronically excited conductive storage tube, is a storage tube that converts electrical signals into electrical signal outputs instead of optical signal outputs. When the input signal scanning system is different from the output signal scanning system, scanning can be achieved The conversion of the standard, this map storage tube can also be called the scanning standard conversion tube. For example, the radar scanning method is converted into a TV raster scan output signal, and a TV system with one TV scanning line number is converted into a TV system with another scanning line number (frame rate should be unchanged).

Chinese name: Save tube

Types of: A memory

The structure of the save tube

There are either single-sided targets or double-sided targets in the map storage tube, but there are two electron guns. In the single-sided target storage tube, the recording electron gun and the reading electron gun are placed on the same side of the target, and in the double-sided target tube, the two guns are placed on both sides of the target respectively.

Figure 1 Schematic diagram of typical structure of double-sided target storage tube A fine metal mesh with a layer of aluminum film deposited as a signal board. Figure 1 is a schematic diagram of a typical structure of a double-sided target image storage tube, which will be used as an example to explain the working process of the image storage tube. The cathode potential of the recording gun is 10kV-15kV, and the cathode potential of the reading gun is only 1/10 of the cathode potential of the recording gun, about -1kV. The collector is grounded to zero potential ^[1] .

Among them, 1 is a recording gun; 2 is a double-sided target; 3 is a collector; 4 is a reading gun; 5 is a recording gun deflection system; 6 is a reading gun deflection system

The working principle of the save tube

Erasure of saved tube signals

Add a target pressure of -50V to the signal board, turn off the recording gun, and the reading gun sends out a non-modulated electron beam to scan the target surface. Because the energy of the electron beam is 1 keV, it is not enough to excite the conduction phenomenon, but it is sufficient to be the target surface, so the potential of the target surface rises due to the accumulation of positive charges, and finally reaches the equilibrium potential equal to the collector potential, that is, the zero potential, so that the target surface The potential difference between the capacitor and the signal board reaches 50V.

Recording of the tube signal

Turn off the reading gun and turn on the recording gun. The input signal is applied to the modulation pole of the recording gun to control the beam current. The high-speed electron beam with an energy of 10keV-15keV passes through the signal plate and enters the dielectric target, which causes the excitation conduction phenomenon, which causes the longitudinal conductance of the target to increase, causing the capacitor to discharge between the target surface and the signal plate, and the potential of the target surface decreases to the signal. The plate potential (-50V) is close. The size of the beam determines how quickly the potential of each pixel on the target surface decreases. After one frame scan, a negative potential fluctuation corresponding to the input signal is formed on the entire target surface, and the maximum depth of the fluctuation can reach 50V.

The characteristic of this recording is that the vertical resistance of each pixel is modulated by the input signal, so that the target capacitor discharge time constant of each pixel is different, so that potential fluctuations are formed on the target surface in the same frame scanning time. This method of using electrons to stimulate conduction causes the recording signal of the target surface potential to fluctuate between the equilibrium potential (zero potential) and the signal plate potential (-50V) to become an electronically excited conductive recording, so the tube is also called an electron. Excitation of conductive storage tube ^[1] .

Reading of the saved tube signal

Turn off the recording gun and turn on the reading gun. The non-modulated fast electron beam emitted by the reading gun scans the target surface. As already pointed out during the erasure of the signal, the pixels on the target surface will return to the same equilibrium potential again. The potential fluctuations have been established on the surface, that is, the initial potential of each pixel on the target surface is different, so when they are balanced to the same potential, the charging current required by the target capacitance of each pixel is different. A signal output will be generated on the load resistor in the circuit formed by the signal board and the collector. The larger the signal, the more the potential drop caused on the target surface during recording, the greater the potential difference between the target surface and the collector during reading, the more secondary electrons from the target, the greater the charging current, The more secondary electrons there are, the greater the positive polarity output signal generated on the load resistance.

Because the potential of the recorded electrical signal fluctuates deeply, the reading beam is likely to return the target surface to the equilibrium potential in one reading, and a satisfactory output signal can be obtained even after several minutes of continuous reading. Such deep potential fluctuations can be read thousands of times after recording a signal, or stored for several days or even tens of days.

The final result of reading or saving is that the potential of the target surface returns to the equilibrium potential, and the target capacitance between the target surface and the signal board is recharged to a potential difference of 50V, so this reading method is a recharge reading method.

In the actual work of the image saving tube, the input signal is continuous, and the recording of the current frame signal and the reading of the previous frame signal are performed simultaneously, and the input signal during recording and the output signal during reading pass through the load resistance of the signal board. Therefore, in order to prevent interference between the two, the reading beam is usually modulated in advance with a radio frequency of 30MHz-60MHz, and then the signal output circuit is tuned to the radio frequency, and the output signal can be obtained after mediation, thereby avoiding input Signal interference.

Summary of Saved Graphs

Because the information recording gun and the reading gun of the picture tube are separated, they can adopt different scanning systems as required, so they can achieve system conversion while transmitting TV images. The output signal of the image saving tube can be used for oscilloscope or CRT tube for observation. Because the image saving tube can save the signal for a long time and read it many times, it is superior to the long afterglow tube in positioning display.