JPH0452964B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluorescent display tube widely used as a flat display in various industrial measuring instruments, computer terminals, etc., and particularly relates to its driving method.

[Prior art]

Conventionally, in computer systems, light pens have been used in combination with CRTs (cathode ray tubes) as devices that enable direct interaction with the computer. The input method using a light pen is
Since the light emission is captured as time-series data and its designated dot is identified, in beam spot scan methods such as CRTs, where the light emission of each dot is temporally shifted, the position of each point can be determined simply by measuring the light emission time. input can be made.

[Problem that the invention seeks to solve]

However, as is well known, CRTs generally have the disadvantage of being large in size. Therefore, if a fluorescent display tube, which is a flat type display, can be used instead, it would greatly contribute to downsizing the device.

However, in the conventional column scanning (line sequential scanning) dot matrix type fluorescent display tube, the dots in one column emit light at the same time.
It is impossible to identify each dot in a row by its luminescence time. This problem can be solved by using a dot-sequential method in which each light-emitting dot is lit sequentially, but if the light-emitting duty is m rows and n columns, then 1/m×
n, and the luminance is 1/m of the column scanning method, making it impractical. Increasing the brightness by increasing the accelerating voltage is also difficult due to limitations in terms of electrode (grid) loss and drive.

[Means for solving problems]

In order to solve such problems, the first driving method of the present invention inserts a non-light emitting period at mutually shifted timing within the light emitting period of the anode dot segments to which driving pulses are applied at the same time. This is what I did.

Further, in the second driving method of the present invention, a light emitting period is further inserted into the non-light emitting period of the anode dot segments at mutually shifted timings.

[Effect]

In the first driving method, each dot within the same group (for example, column) can be identified based on the timing of the non-emission period. Furthermore, in the second driving method, each dot can be identified by the timing of the non-emission period.

〔Example〕

FIG. 4 is a diagram showing an example of an arrangement pattern of anode dot segments of a fluorescent display tube. The illustrated example is a dot matrix type fluorescent display tube with m rows and n columns, which is scanned by a grid provided in the column direction and applies a light emitting voltage to the anode dot segments Px, y. Therefore, Px, 1 to Px,
m (x=1~n) segments emit light at the same time.
Segments from P ₁ ,y to Pn,y (y=1 to m) are sequentially scanned.

That is, basically, drive pulses as shown by broken lines in FIG. As shown, each drive pulse is incised at a timing corresponding to the row position of the dot. In other words, the k-th dot has a light emission waveform that falls by a predetermined width at the timing _tk . In other words, a non-light emitting period is inserted within the light emitting period at that timing, albeit for a very short time. Since this timing is mutually shifted depending on the row position as described above, it is determined by the light detection element 21 of the light pen 2 disposed on the face plate 11 of the fluorescent display tube 1 as shown in FIG. t _k
By detecting the length of , the line position can be recognized. In Fig. 5, 12 is a back plate, 13 is a filament, 14 is a scanning grid, and 15 is an anode dot segment.Each dot emits light through a lens 22 through a photodiode or phototransistor (the example shown is a photodiode). ) photodetecting element 21 consisting of
is taken, amplified and shaped by the amplification and waveform shaping circuit 23, and a falling differential output as shown in FIG. 1e, for example, is sent to a circuit for detecting the dot position.

The width T1 of the cut in the drive pulse may be a minimum value depending on the characteristics of the drive and detection elements, and generally several μsec is sufficient. This is a few tenths of the entire light emission period and has almost no effect on the luminance of light emission.

Although the case where a dot which is emitting display light is detected has been described above, it is also possible to similarly detect a dot which is not emitting display light. That is, as shown in FIGS. 2a to 2d, during the non-emission period when there is no driving pulse, a positive driving pulse that falls at the same timing as the falling pulse in the emitting period is applied, and each dot is Make it emit light. That is, the dots in the same column sequentially emit light due to this pulse, and the falling differential output is sent to a circuit for detecting the dot position, as shown in FIG. 2e, for example, as described above. The pulse width T2 of this light emission is
Depending on the characteristics of the driving and sensing elements, the minimum is sufficient;
Generally, detection is possible even at a few microseconds or less, but this light emission duty is extremely small. For example, even if the pulse width is 5 microseconds, a 16 microsecond refresh is 1/3200.
Therefore, from the perspective of human vision, the brightness is so low that it does not appear to be emitting light.

In this embodiment, the rising timing of the break of the drive pulse inserted into the display light emitting period and the falling timing of the drive pulse inserted into the non-light emitting period are aligned, but in order to simplify the circuit configuration, the third Figure a (light emitting period) and b (non-emitting period)
As shown in FIG. 2, one may fall and the other rise at the same timing.

By detecting dots that are not emitting display light in this manner, it becomes possible to designate a position that has not emitted display light and cause a light emitting display to be performed there, that is, to write a new figure or the like. As described above, by aligning the output timings of the photodetecting elements for both the dots emitting display light and the dots not emitting display light, the coordinates can be detected from the outputs using exactly the same process. At this time, it can be easily determined whether the detected dot is a display light-emitting dot or not by checking the polarity of the detection pulse.

In addition, in a fluorescent display tube, there is generally a distance of several millimeters from the surface of the face plate constituting the vacuum container to the light emitting surface, and it is difficult to completely focus the photodetector element 21 on one dot. As shown by the broken line in FIG. 5, light emission from neighboring dots is also detected. In this case, in the driving method according to the present invention, since the emission pulse waveforms of adjacent dots are temporally shifted in both the row and column directions, multiple pulses are generated around the maximum amplitude pulse corresponding to the indicator dot as shown in FIG. A pulse is obtained. In the figure, T _j indicates one grid time, and T _k indicates one dot time.

In order to detect the correct pulse from this pulse train, for example, a Schmitt trigger circuit or the like is used.
As shown in Figure 7a, using the threshold level Ath,
It is only necessary to perform shaping as shown in FIG. 2 and detect the central pulse from the pulse train after this shaping. As a method of detecting this median value, for example, the value of y is determined using a timing matching circuit, and the obtained values y _jp ,...
..., y _j , y _j+p are input into a microprocessor or the like and the average value is calculated, and that value becomes the indicated center value in the y direction (column direction). Also in the x direction (row direction), by treating the pulse train of y _jp to _{y j+p} as one pulse, the indicated center value can be obtained by the same process as in the y direction.

〔Effect of the invention〕

As explained above, according to the present invention, a non-emission period is inserted at mutually shifted timings into the emission period of a plurality of anode dot segments driven simultaneously, or the non-emission period is further caused to emit light at the same timing in the non-emission period. By inserting a period, it becomes possible to optically identify each dot that emits light simultaneously in the same row, which was previously impossible, and it becomes possible to input arbitrary coordinates using a light pen, making it possible to A simple graphic/character input/output system can be realized.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram showing an example of the anode dot segment drive pulse waveform and photodetector element output when the display is on, showing an embodiment of the present invention, and FIG. 2 is a waveform diagram of the anode dot segment drive pulse when the display is not on. 3 is a waveform diagram showing an example of the output of a photodetector element, FIG. 3 is an anode dot segment driving pulse waveform diagram during display lighting and non-display lighting, showing another embodiment of the present invention. FIG. A diagram showing an example of the arrangement pattern of anode dot segments, FIG. 5 is a diagram for explaining the coordinate input method using a light pen, and FIG. 6 is a waveform diagram showing an example of the detection output when considering the influence of adjacent dots. , FIG. 7 is a diagram for explaining a method for determining a correct indicator dot in such a case. 1... Fluorescent display tube, 2... Light pen, 15...
...Anode dot segment, 21...Photodetection element.

Claims (1)

[Scope of Claims] 1. In a drive method for a fluorescent display tube in which a plurality of anode dot segments each constituting one light emitting point are divided into groups, and a drive pulse is applied to all anode dot segments in the same group at the same time, A method for driving a fluorescent display tube characterized by inserting a non-light emitting period into the light emitting period of each anode dot segment in the same group at mutually shifted timings. 2. In a fluorescent display tube drive method in which a plurality of anode dot segments each constituting one light emitting point are divided into groups and a drive pulse is applied to all anode dot segments in the same group at the same time, each anode in the same group A method for driving a fluorescent display tube, characterized in that a non-light emitting period is inserted into a light emitting period of a dot segment at a mutually shifted timing, and a light emitting period is inserted within a non-light emitting period at a mutually shifted timing.