JPS5826613B2 - Yuuki Film Target - Google Patents

Description

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

The outline of the two-electron gun type scanning converter tube using the organic film target is described in, for example, Nikkei Electronics, No. 19747-15 (N(L86)J), but its operation will be briefly described here. state

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 polyimide acid of m.

This polyimide film can be obtained by applying liquid polyimide acid 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 such that when the first crossover voltage is 60 to 70V,
It shows a higher value than cases such as 5i02.

A two-electron gun type scanning conversion tube using this organic film as a target has two electron guns facing each other with the organic film target T in the middle, as shown in FIG.

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 an electric field protruding from the holes in the mesh controls and modulates the readout beam scanning the mesh side.

The controlled electron beam is extracted from the mesh electrode as an output signal.

In the erase mode, the target voltage is set to 100V, which is in the range of δ>■ in FIG. 1, and in the write mode, it is set to 30V, which is in the range of δ×1.

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

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

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

In this case, since δ is less than 1, negative charges proportional to the electron beam are accumulated, and a charge pattern corresponding to the video signal is formed.

During 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 writing individual organic film.

In order to ensure reliable operation of a two-electron gun type scan converter tube that uses the organic film Targera T as described above, it is important to perform mode switching reliably.

Particularly likely to be a problem is the transient characteristics when switching modes.
In particular, it is necessary to pay attention to the transient characteristics when switching from "write operation" to "erase operation".

The reason for this will be explained with reference to FIG.

In write mode, the charge image formed on the organic film surface is when the target voltage is 30V, and the polyimide surface has a maximum potential of -30V-1 with respect to the target.
It is.

After such a state, when the erase mode is set, the polyimide surface potential becomes -1oov, and the potential difference with the previously formed charge image becomes (-30V) - (-100V) = 70V, which is In the graph of secondary electron emissivity in Figure 1, δ
>1, and a predetermined erasing operation is performed.

However, if we consider a case where the switching time of the target voltage, especially the time to switch from 30V to 1oov, is long, as shown in ■ in Figure 3, the target voltage changes instantly from 30V to 70V, Then 100V
It is assumed that the change occurs gradually in the housing.

In other words, when the erase beam current starts flowing when the target voltage is 70V, when the target voltage m is 70V,
The polyimide surface potential is -70V, so the potential difference with the previously formed charge image is (-30V) - (-70V
)=40V.

This is a range of δ times 1. This state is in write mode, so the polyimide surface is storing charge rather than releasing it, until it reaches -70V.

Therefore, even if the target voltage becomes 100V after this, the potential difference on the polyimide surface will be (-70V) - (
-100V)=30VL, and remains in the range of δ<1.

Therefore, a charge equal to -100V is accumulated on the surface of the polyimide, and what was intended to be an erase operation ends up being an accumulation of charges.

In such a state, normal function can no longer be expected.

The present invention reliably prevents such inconveniences.

The present invention will be described in detail below with reference to FIG. 4. Time t
1 to t2, the first grid G1 electrode for writing and erasing is
A video signal is applied to form a charge image on the target.

The charge image thus formed is simultaneously read out by the read-out electron gun and can be observed on a monitor.

On the other hand, time t2 to t is an erasure period, and after this erasure, a new video is written again at time t to t6.

The problem here is the period from t2 to t, which is the transition time at the time of switching, in the erasing period.

That is, if the beam current begins to flow during l/#i (between t2 and t13) when the target voltage has not completely changed from the write voltage to the erase voltage, problems will occur for the reasons explained above.

Therefore, the present invention can be used between times t2 and t60, or between t4 and t
The scanning converter tube is cut off during this period so that no beam current flows during this period.

If mode switching is to be performed simultaneously with other electrode voltages other than the target voltage, time t2 to t3 may be added to the electrode with the longest transition time among those electrodes.

As described above, according to the present invention, by controlling the beam current so that it does not flow during the mode switching transition time, mode switching can be performed reliably, and a scan conversion tube device that always operates stably can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the secondary electron emissivity of the organic film target, Fig. 2 is a block diagram showing the operation of the organic film target 2-electron gun type scan conversion tube in the present invention, and Fig. 3 is a graph showing the secondary electron emissivity of the organic film target. FIG. 4 is a diagram for explaining the operation in detail, and FIG. 4 is a diagram for explaining the present invention in detail.

Claims (1)

[Claims] 1 A circuit for switching between an erase mode and a write mode by switching a target voltage or a target voltage and a grid voltage, and a circuit for controlling a beam current, and a circuit for controlling a beam current during a switching transition time of the mode switching circuit. An organic film target type scanning converter tube device characterized by preventing a beam from flowing.