JPS5925423B2 - Cathode ray tube beam control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a beam control method when recording images on printing paper using a cathode ray tube.

In a cathode ray tube (hereinafter referred to as CRT), an electron gun consisting of a cathode and two or three electrodes accelerates and focuses an electron beam, and causes it to collide with a screen coated with a fluorescent substance, causing it to emit light. In order to project an arbitrary image on the screen, it is necessary to adjust the brightness by adjusting the magnitude of the beam current using control electrodes, and to deflect the beam electrostatically or electromagnetically. There are different focusing and deflection methods: electrostatic focusing electromagnetic deflection type, electromagnetic focusing electromagnetic deflection type,
There are four types of CRTs: electrostatic focusing electrostatic deflection type and composite deflection type, but the electrostatic focusing electromagnetic deflection type CRT is most often used because it is easy to use and can provide a large screen.

In addition, there are CRTs that are suitable for recording images on printing paper and making so-called hard copies, such as flyshield spot tubes, pin tubes, and optical fiber tubes that utilize electron guns.

FIG. 1 shows, as an example, beam control when recording an image on printing paper using an optical fiber tube OFT.

As shown in figure a, from the left end LFT of the screen to the right end RGT
When a character synchronization signal for one line is generated, a high frequency sawtooth wave shown in FIG. b is generated for each character and scans in the vertical (Y-axis) direction. Furthermore, since the horizontal scanning is performed by a low-frequency sawtooth wave as shown in Figure c, each character in one line can be handled as a temporal unit. Further, the drive current of the deflection coil is controlled so that a negative polarity current flows at the left end LFT'('i2) of the screen, and a positive polarity current il flows at the right end RGT. The beam will be swung from the left end to the right end.When the recording of one row is completed, the driving current is applied to the coil in order to record the next row.
Or, by setting it to ←■2, it is returned to the initial recording position and waits for the arrival of the video signal.

However, the time required for line feed of the printing paper is extremely long compared to the return time of the beam, that is, the power consumption of the drive circuit during the pause period of the video signal that arrives after the line feed operation is completed cannot be ignored.

The present invention provides a means for solving the above-mentioned conventional drawbacks, and its purpose is to minimize the power consumption of the CRT drive circuit, prevent heat generation, and provide a simple means. The object of the present invention is to provide a CRT beam control method that can be realized economically.

The above object is to position the beam at the center of the screen by keeping the content of the beam digit position counter at zero during the period when no video signal arrives, and to position the beam at the center of the screen in synchronization with the arrival of the video signal. This is accomplished by setting the position counter to a predetermined value and returning the beam to the initial recording position on the screen.

Hereinafter, the present invention will be described by way of examples with reference to the drawings.

2 and 3 are connection diagrams of a coil drive circuit showing one embodiment of the present invention, and time charts of beam control,
FIG. 4 is a block diagram showing the configuration of an example of a cathode ray tube display device embodying the present invention.

In the figure, a line printing machine using an optical fiber tube 0FT will be explained. In FIG. 4, a display signal and display information inputted to an input terminal 1N are received by an interface section 1NT, and a display control section DCON controls the timing necessary for display based on the received signal. The display pattern generation unit DPG stores display patterns (characters), and sends display information to the brightness modulation unit BM with a signal from the display control unit DCON, and the brightness modulation unit BM receives the display information and converts it into a video signal. The signal is converted and input to the cathode ray tube CRT via the amplifier AMP2. Beam digit position counter B
P-CTR is set to a predetermined content by a signal from the display control unit DCON as described later, and the digital signal indicating the content is sent to the digital-to-analog conversion circuit DA-C.
The signal is converted into an analog signal by the NV, and is input to the deflection coil of the cathode ray tube CRT via the amplifier AMP. The sawtooth wave generating section STWG generates a sawtooth wave for beam deflection based on a signal from the display control section DCON, and the sawtooth wave is applied to the cathode ray tube CTR via the amplifier AMPL. The voltage waveform VlN input from the beam digit position counter BP-CTR to the amplifier AMP via the digital-to-analog conversion circuit DA-CNV has 0V at the center and changes from negative to positive as shown on the left side of Figure 2. It is a voltage that changes over time.

In Fig. 2, when the output of the amplifier AMP (corresponding to AMP in Fig. 4) is a negative voltage -E, only the diode D1 becomes conductive, and the pace potential of the transistor Tr2 becomes -E, so only the transistor Tr2 is turned on. , deflection coil C
A current of I2 flows through L.

When the output voltage of the amplifier AMP changes from negative to positive, the current of the transistor Tr2 decreases and is cut off.
The transistor Trl is turned on and the current of 11 increases little by little. When the output voltage of the amplifier AMP reaches a constant positive value +E, the diode D1 is cut off and the maximum positive current 11 flows from the transistor Trl to the deflection coil CL. Therefore, the beam on the screen of the cathode ray tube CRT shown in FIG. 4 is swung from the left end to the right end.
Here, when it comes to the rest period, conventionally +i1 or -12
Since it is necessary to flow a current of 5 A to 10 A into the deflection coil CL, a corresponding voltage is applied from the amplifier AMP and the beam position is held at the edge of the screen. By setting the content of the digit position counter to zero, the voltage is set to O, making both diodes Dl and D2 conductive, and both transistors Trl and T
The current flowing through the deflection coil CL is made zero by cutting off r2. Therefore, the beam position on the screen stops at the center. In this case, since a blanking voltage is applied, there is no need to worry about the light shining at the center of the screen and burning the fluorescent surface. In order to apply the O voltage to the drive circuit during the rest period, this is controlled by the beam digit position counter BP-CTR at the previous stage.

In Figure 3, Figure a is the one-line recording command signal, Figure b is the recording execution period, Figure c is the count output of the beam digit position counter, Figure d is the center value return signal, and Figure e is the output voltage of the digital-to-analog conversion circuit. shows.

When a one-line recording command as shown in FIG. For the digit position on the screen,
The beam digit position counter BP-CTR performs calculations to digitally calculate the position, which is converted into an analog signal voltage by the digital-to-analog conversion circuit DA-CNV. When the beam digit position counter BP-CTR issues a one-line recording command, it counts -n when it is at the left end, and sequentially records n-1, . n-2, ・・・・・・・・・
, -2, -1, O, +1, +2, and counts up to +n until reaching the right end. Then, while the printing paper is line-feeding, or when the video to be recorded ends at this line, it is stopped at the count 0 position, and at the same time a center value return signal shown in FIG. d is output.

During the recording period TWR, the digital-to-analog conversion circuit DA-CNV converts the signal into a step-like analog signal from -E to +E, as shown in Figure e, and applies it to the amplifier AMP.

When entering the pause period Tps, the analog signal is held at 0V by the center return signal. Then, in response to the recording command of the next row, the beam digit position counter BP-CTR starts counting again from -n, and the DA converter generates a stepped analog signal from -E to +E. As explained above, according to the present invention, the beam digit position counter is set to zero during the recording suspension period such as the printing paper changing operation period, and no deflection current is applied, so that the power consumption in the drive circuit can be reduced. Moreover, heat generation in the deflection coil can also be reduced.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an example of a beam control method for a cathode ray tube, Fig. 2 is a connection diagram of a coil drive circuit showing an embodiment of the present invention, and Fig. 3 is a beam control diagram showing an embodiment of the present invention. FIG. 4 is a block diagram showing the configuration of an example of a cathode ray tube display device embodying the present invention. In the figure, CL is a deflection coil, i1 is a right-end deflection current,
I2 is the left end deflection current, Trl and Tr2 are transistors,
Dl and D2 are diodes, TWR is a recording period, Tps is a rest period, CRT is a cathode ray tube, and BP-CTR is a beam digit position counter.

Claims (1)

[Claims] 1. In a drive circuit that deflects the beam in the digit direction (left/right direction) of the cathode ray tube by supplying voltage and current according to the contents of the beam digit position counter to the deflection element of the cathode ray tube, the beam is turned off during the period when no video signal arrives. By keeping the content of the digit position counter at zero, the beam is positioned at the center of the screen, and in synchronization with the arrival of the video signal, the number of the beam digit position counter is set to a predetermined value, and the beam is returned to the initial screen recording position. A beam control method for a cathode ray tube.