Dot matrix fluorescent display device

A dot matrix, fluorescent display tube having a filament, a grid and array of anodes on which light emitters are placed. Two or more light emitters are placed on at least one of the anodes.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a dot-matrix fluorescent display device. 
More particularly, it relates to a dot-matrix fluorescent display device 
employing a fluorescent display tube. 
2. Background Art 
A dot-matrix fluorescent display device employing a fluorescent display 
tube is often used for a video or audio device to indicate by a selected 
lit numeral or character a received frequency, a selected mode or the 
like. The general operation of the fluorescent display tube is hereafter 
described with reference to FIG. 1. In the tube, a filament 1 is heated by 
electric power from an AC power supply 2 to thereby emit thermoelectrons. 
The electrons are accelerated and diffused by a grid g.sub.i to which a 
grid drive voltage VG.sub.i is applied. After passing through the grid 
g.sub.i, the electrons collide against a plurality of anodes A.sub.ij to 
which a separate anode drive voltage VA.sub.ij is applied to each of the 
plurality of anodes A.sub.11 -A.sub.mn. As a result, a light emitter (not 
shown in the drawing) provided on the surface of each anode A.sub.ij emits 
light. If the fluorescent display tube has 5.times.7 (35) image elements, 
5.times.7 (35) anodes A.sub.ij are disposed in a matrix to form an anode 
group AG.sub.i, as shown in FIG. 2. Anode lead wires 1.sub.11 to 1.sub.75 
are connected to the anodes A.sub.11 -A.sub.75. The grid g.sub.i is 
provided in opposition to every matrix-disposed anode group AG.sub.i, as 
shown in FIG. 4. Multiple anode groups AG.sub.i provide multiple displayed 
characters. 
FIG. 3 shows an enlarged sectional view of the anode A.sub.ij included in 
the fluorescent display tube. The light emitter 3 is provided on the 
surface of the anode A.sub.ij. The anode lead wire 1.sub.ij is connected 
to the anode A.sub.ij. 
FIG. 4 shows a schematic view of a conventional dot-matrix fluorescent 
display device employing such a fluorescent display tube as described 
above. In the device, each of a number n of anode groups AG.sub.1 
-AG.sub.n corresponds to one character. The n anode groups AG.sub.1 
-AG.sub.n correspond to a line of characters. In each anode group 
AG.sub.i, 5.times.7 (35) anodes A.sub.ij are disposed in a matrix, as 
shown in FIG. 2. The anode lead wire 1.sub.ij for the anode A.sub.ij of 
the anode group AG.sub.i is connected to the anode lead wire 1.sub.ij for 
the anode A.sub.ij of the adjacent anode group AG.sub.i+1. An anode drive 
voltage VA.sub.ij is applied through the anode lead wire 1.sub.ij to the 
anode A.sub.ij with its attached light emitter 3, to cause it to emit 
light. It is probable that the anode drive voltage VA.sub.ij is applied to 
a plurality of similarly situated anodes A.sub.ij simultaneously. Grids 
g.sub.1 -g.sub.n are independently provided for the anode groups AG.sub.1 
-AG.sub.n. Grid drive voltages VG.sub.1 -VG.sub.n are sequentially applied 
to the grids g.sub.1 -g.sub.n in a time division multiplex manner. 
FIG. 5 shows a timing diagram of examples of the grid drive voltages 
VG.sub.1 -VG.sub.n and the anode drive voltage VA.sub.ij for the 
dot-matrix fluorescent display device shown in FIG. 4. Since the grid 
drive voltages VG.sub.1 -VG.sub.n are applied to the grids g.sub.1 
-g.sub.n in time division multiplex and the anode drive voltage VA.sub.ij 
is applied to the anodes A.sub.ij of the anode groups AG.sub.1 -AG.sub.n, 
the light emitter 3 emits light only if it is located on the anode 
A.sub.ij of the anode group AG.sub.i for which the grid drive voltage 
VG.sub.1 and the anode drive voltage VA.sub.ij are simultaneously applied. 
For the same reason, the light emitter 3 provided on the anode A.sub.ij of 
the anode group AG.sub.n later emits light as well for a different 
combination of grid drive voltage VG.sub.n and anode drive voltage 
VA.sub.ij. 
The above-mentioned conventional dot-matrix fluorescent display device 
needs a number of anode lead wires 1.sub.ij, which number corresponds to 
that of the number of anodes A.sub.ij which constitute each of the anode 
groups AG.sub.i. If each anode group AG.sub.i is composed of 5.times.7 
(35) anodes A.sub.ij in a matrix group, 35 anode lead wires 1.sub.ij are 
needed. However, in reality, anode drive voltage is simultaneously applied 
to several anodes A.sub.ij through the corresponding anode lead wires 
1.sub.ij. When only a predetermined image such as "PLAY" and "FF" is to be 
indicated by the dot-matrix fluorescent display device for a video or 
audio device, anode drive voltages are always simultaneously applied to a 
plurality of anodes A.sub.ij in predetermined anode groups AG.sub.i 
through the corresponding anode lead wires 1.sub.ij. For that reason, the 
number of all the anode lead wires 1.sub.ij of the device is so large that 
the device is very complicated. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide a dot-matrix 
fluorescent display device including a fluorescent display tube in which 
image elements are lit by using a number of anodes which is less than the 
number of image elements. 
In the dot-matrix fluorescent display device of the invention, a plurality 
of light emitters are provided on at least one of the plural anodes so 
that the plurality of light emitters simultaneously emit light when drive 
voltages are applied to the anode and a grid, respectively. For that 
reason, the dot-matrix fluorescent display device can be made of fewer 
anodes than the image elements. 
When the dot-matrix fluorescent display device is used for a video or audio 
device in which a displayed image is limited, dot-matrix displaying with a 
high quality image can be easily performed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An embodiment of the present invention is hereafter described with 
reference to the drawings. 
According to the invention, FIG. 6 shows an enlarged sectional view of an 
anode A.sub.pq included in a dot-matrix fluorescent display device. Two 
light emitters 3a and 3b are provided on the surface of at least one anode 
A.sub.pq included in an anode group AG.sub.i. An anode lead wire 1.sub.pq 
is connected to the anode A.sub.pq. When an anode drive voltage VA.sub.pq 
is applied to the anode A.sub.pq through the anode lead wire 1.sub.pq, the 
light emitters 3a and 3b both emit light. For that reason, the single 
anode A.sub.pq can function for two image elements. For example, a 
dot-matrix fluorescent display device includes such anodes A.sub.pq 
instead of conventional anodes A.sub.25 and A.sub.35 belonging to an anode 
group AG.sub.1, as shown in FIG. 4. Such light emitters 3a and 3b 
simultaneously emit light, as shown by the hatching in FIG. 7, when a grid 
drive voltage VG.sub.1 and an anode drive voltage VA.sub.25 are 
simultaneously applied. 
If a plurality of light emitters are provided on the surface of one anode, 
as described above, so as to reduce the number of all anodes, two grids 
for two adjacent anode groups can be decreased to one grid for the two 
adjacent anode groups. The number of all grids can thus be reduced as 
well. 
If a dot-matrix fluorescent display device, in which the numbers of anodes 
and grids are reduced as described above, is driven and controlled through 
a microcomputer, a displayed image can be easily regulated. If the output 
terminals of the microcomputer are designed to resist a high voltage, the 
fluorescent display tube of the device can be directly driven so as to 
make the cost of the device low and its operation easy.