JPS5826612B2 - Yuuki Film Target - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-electron gun type scan converter tube using an organic film target.

For an overview of the two-electron gun type scan conversion using the above organic film target, see, for example, "Nikkei Electronics,
No. 19747-16 (A86) J, etc., and its operation will be briefly described here.

This is characterized in that the target part is composed of a metal mesh and an organic film, and the organic film has a thickness of 2 to 3 μm.
It is composed of a polyimide film of m.

This polyimide film can be obtained by applying a liquid polyimide film to one side of a metal mesh and curing it at a certain high temperature.

Compared to conventional silicon targets, this organic film target has the advantage of being very inexpensive.

As shown in Figure 1, the secondary electron emissivity characteristics of such a polyimide film are as follows: when the first crossover voltage is 60 to 70V,
It shows a higher value than cases such as in2.

A two-electron gun type scanning converter tube using this organic film as a target is shown in Figure 2.
With T in the middle, two electron guns are facing each other.

Here, the video signal is applied to the first grid G1 of the write electron gun, and the electron beam is modulated and scanned to accumulate and form a two-dimensional charge pattern on the organic film surface.

Next, based on this charge image, a potential image of the electric field protruding from the holes in the mesh controls and modulates the readout beam scanning the mesh side.

A controlled electron flow is extracted from the mesh electrode as an output signal.

In erase mode, the target voltage is set to δ〉 in Figure 1.
1 in the range of 100V, and in write mode δ〈l
Set to 30V, which is within the range of .

In the erase mode, the unmodulated electron beam on the write side scans the organic film surface for several frames of standard television scanning.

In this case, since δ>1, all the accumulated charges on the organic film surface are in a state where there is no emission pattern.

In one writing mode, a writing electron beam modulated by a video signal scans the organic film surface.

In this case, since δ<1, negative charges proportional to the electron beam are accumulated on the organic film surface, forming a charge pattern corresponding to the video signal.

In readout, by scanning the target on the readout side with an unmodulated beam, it is possible to extract a signal output proportional to the charge pattern accumulated on the surface of the organic film on the writing side.

In the operation of the organic film target type two-electron gun scan converter tube described above, the voltage of the fourth grid G4 on the write side is constant in both erase and write modes. time) must be precisely controlled.

That is, if the erasing time is too short, the charges accumulated on the surface of the organic film will remain without being released.

On the other hand, if the erasing time is too long, positive charges will accumulate on the organic film surface, making writing operations impossible.

In this case, the reason why positive charges are accumulated on the organic film surface is that in the erase mode, the target voltage is 10
For 0V, the fourth crid voltage on the write side is 450V.
This is because it is v.

In other words, when an unmodulated beam hits the organic film surface, δ
>1, more electrons than incident electrons exit from the organic film surface and are at a higher potential.

It is captured by the fourth grid G4.

As a result, the potential on the organic film surface increases by the amount of electrons reduced.

In normal operation, when all the charge images due to negative charge accumulation are released and the potential on the organic film surface reaches 100V, the erase beam is turned off and the erase mode ends, but this erase time is long. If too much, the exchange of electrons between the organic film surface and the fourth grid continues until both become the same potential, and eventually the organic film surface becomes the fourth grid.
It rises at 450V, the same potential as the grid.

If you fall into this state, even in write mode, the organic film surface will be one of δ〉l! At 1, write operations are no longer possible.

It can be seen that in order to eliminate such a drawback, it is sufficient to set the fourth grid voltage in the erase mode to 100V, which is the same as that of the target.

Lowering the fourth grid by 100Vt also has other positive effects.

In the erase mode, the focusing ratio of the electron beam of the write-side electron gun is different compared to the writing mode, and in the erase mode where the fourth grid voltage is low, the focusing ratio is smaller, and therefore the organic film surface is more This means that it is possible to scan a wide area with an electron beam.

Therefore, safer and more reliable erasing can be performed.

The present invention further improves this, and specifically, the voltage of the fourth grit in the erase mode is made slightly higher than the voltage of the target (for example, 20 to 30 V).

In this way, the effect of making the fourth grid voltage and the target voltage the same can be achieved without any loss, and at the same time it is possible to improve the image quality and increase the readout signal level.

This is for the following reasons.

In the writing mode, the charge pattern on the organic film surface written by the writing electron beam modulated by the video signal is mostly formed on the surface of the organic film, but the second pattern penetrates into the deep layer of the organic film. .

This deep charge is generated by the fourth grid voltage in erase mode = (
target voltage), it is difficult to remove.

If deep charge remains, the image quality deteriorates and at the same time, it is difficult to form a charge image with higher density.

Therefore, if the fourth grid voltage)>(target voltage) is set in the erase mode, charges can be released in the deep layer 1 of the organic film.

((4th crit voltage) - (target voltage) 1
The point at which 1 can be increased can be predicted from the secondary electron emissivity δ in Figure 1.

That is, ((4th grid voltage) - (target voltage)
) is set to 30V and an erase operation is performed in this state, the organic film surface reaches a maximum of +30V, and even in write mode, the potential of the organic film surface remains at the target voltage (30V).
V)+30V=60V, which is within the range of δ×1, so the write operation is possible.

As explained above, according to the present invention, in the erase mode, the fourth
By raising the grid voltage by several tens of volts above the target voltage, it is possible to operate the organic film target type scan converter tube more safely and reliably, and at the same time, it is possible to improve the image quality and to adjust the readout signal level. This is something that can be increased.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the secondary electron emissivity of an organic film target, FIG. 2 is a diagram showing the configuration of a conventional organic film target 2-electron gun type scan converter tube, and FIG. 3 is an embodiment of the present invention. FIG. 2 is a diagram showing the configuration of an example organic film target type scan converter tube. T...Organic film target, G4...
...4th grid.

Claims (1)

[Claims] 1. The fourth grid voltage of the writing side electron gun is switched in conjunction with the switching operation of the target voltage that is switched according to the erase mode and the write mode, and in the erase mode, the fourth grid voltage is set to several +V higher than the target voltage. An organic film target type scan converter tube characterized in that it can be used in a highly advanced manner.