JPS63171070A - Linearity correction circuit for horizontal deflection system - Google Patents

Abstract

PURPOSE:To correct the strain of non-linearity in relation to a horizontal deflection by correcting the strain of almost left side of the tube surface of a CRT with a S-shaped correction capacitor and a non-linear correction coil and correcting the strain of almost right side of the tube surface by supplying the output signal from a function generator to a sub yoke so as to correct. CONSTITUTION:The S-shaped correction capacitor 10, a horizontal deflection yoke 4 and a linearity correction coil 6b whose inductance characteristic is controlled by a magnet 6a are connected to the output terminal of a horizontal output circuit 22 which drives the CRT 2 in series. Meanwhile, the output from an adder 30 is supplied to the sub yoke 24 for correcting the linearity and the output signal of the function generator 32, whose output is controlled with a horizontal oscillation frequency, is supplied to the adder 30. Thus, the strain of almost left side of the tube surface of the CRT 2 can be corrected with the capacitor 10 and the coil 6b and also the strain of the almost right side of the tube surface can be corrected with the yoke 24.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a linearity correction device for a horizontal deflection system of a CRT monitor, and more particularly to a device for automatically displaying video signals from imaging devices having different numbers of scanning lines on the same CRT monitor. Therefore, the present invention relates to a linearity correction circuit for a horizontal deflection system that enables automatic correction using a function generator that generates a distortion correction function corresponding to the number of scanning lines of an input image signal.

For example, CT (computer tomography), US (ultra sonography),
One example is the medical imaging field that uses medical imaging diagnostic equipment such as DF (digital fluorography). A diagnostic system in the field of medical imaging first displays image information introduced from the plurality of diagnostic devices on a CRT monitor, and then displays the displayed image through a photographing optical system consisting of an imaging lens, a shutter device, a mirror, etc. It is constructed so that images can be taken continuously on the film being conveyed through the system.

In this field, for example, it is possible to continuously and quickly obtain image information of the affected area of the human body and its surroundings using CT, US, DF, etc. The surrounding situation can be clearly grasped, which is extremely convenient for doctors and others when making a diagnosis. Furthermore, in this field, it is essential to obtain accurate and detailed image information due to its nature. it is,
This is to avoid misdiagnosis, etc.

For this reason, CRT monitors with as little distortion as possible are employed.

By the way, in the CRT monitor, particularly in a flat face type CRT monitor, the following two factors can be cited as factors that deteriorate horizontal linearity.

One of these is the occurrence of distortion, as shown in Figure 1, which is caused by the difference between the center of curvature of the CRT monitor's phosphor screen and the center of deflection of the electron beam. Due to shrinkage and elongation at both ends. To explain the figures, FIG. 1a is a schematic diagram of a screen display of a striped pattern when no distortion correction is performed, while FIG. 1 is a characteristic diagram thereof. In FIG. 1, the horizontal axis shows the deflection distance with respect to the horizontal direction of the tube surface, and the vertical axis shows the rate of change in the interval on the phosphor screen with respect to the deflection distance.

Next, the second distortion is shown in FIG. That is, this is a distortion phenomenon in which the left side of the screen stretches and the right side of the screen contracts, which occurs because the horizontal deflection current does not change linearly but becomes an exponential saturation curve due to the resistance of the horizontal deflection yoke. This second figure a
, b will be easily understood by referring to the explanations of FIGS. 1a and 1b.

Here, the first distortion is corrected by superimposing the series resonant current of the horizontal deflection yoke of the CRT and the DC blocking capacitor (5-shaped correction capacitor) on the sawtooth current and bending the deflection current into an S-shape. . In this case, depending on the value of the five-figure correction capacitor, it is possible to change the resonant impedance in accordance with the tube surface, as shown in FIG. 3a.

The second distortion is corrected by connecting a saturable reactor biased by a DC magnetic field in series with the horizontal deflection yoke, and making use of the fact that the inductance changes at each point of the deflection current flowing through the reactor. In this case, for example, if a plurality of saturable reactors are used, it is possible to change the composite impedance consisting of the left correction inductance and the right correction inductance, as shown in FIG.

FIG. 4 is an example of a conventional circuit diagram for correcting the above two types of distortion. In this circuit diagram, an inductance is applied to the horizontal deflection yoke 4 that horizontally deflects the CRT 2 via magnets 6a and 8a. Linearity correction coils 6b, 8b and 3 consisting of saturable reactors that can be changed depending on the current
A character correction capacitor 10 is connected in series. The horizontal linearity correction circuit related to the first and second distortions made of these components includes a horizontal drive transformer 12) a horizontal output transistor 14, a damper diode 16, a resonant capacitor 18, and a choke coil 20 connected to the power supply +Vl1m. The horizontal output circuit 22 performs a horizontal deflection function and operates to correct the distortion and exponential distortion associated with the three-character correction.

However, the above-described conventional horizontal linearity correction circuit is only compatible with video signals corresponding to a specific number of scanning lines (horizontal oscillation frequency).

Therefore, for example, when the number of scanning lines is 525 (horizontal oscillation frequency is approximately 15 KHz), the power supply voltage is 10 V, II = 1
The 5-character correction capacitor 1 is set to 5V.
0 and the linearity correction coils 6b and 8b to find the optimal linearity correction constant, the number of scanning lines is 1125.
If a signal with a high frequency (horizontal oscillation frequency of approximately 33 KHz) is introduced, the horizontal amplitude will be reduced, and accurate reproducibility of the image cannot be guaranteed. In this case, as shown in Figure 5 a and b,
The power supply voltage +
It is necessary to increase VlB approximately twice as much as 15V x 33KHz/15KHz = 33V. As a result, since the impedance of each element changes corresponding to the change in the horizontal oscillation frequency from 15Ktz to 33KHz, the horizontal oscillation after changing the three-figure correction capacitor 10 and the linearity correction coils 6b and 8b changes. Good horizontal linearity cannot be maintained unless readjusted over time to suit the frequency.

However, the loss of time associated with this readjustment is fatal in the field of using medical image diagnostic equipment, which requires video signals to be introduced from the plurality of imaging devices mentioned above and quickly displayed on a CRT monitor. It is exposed as an inconvenience that becomes a disadvantage.

The present invention has been made in order to overcome the above-mentioned disadvantages, and it is possible to transfer video signals with different numbers of scanning lines output from different types of imaging devices constituting various diagnostic apparatuses to the same CR.
When displaying on a T monitor, in order to automatically correct nonlinear distortion related to horizontal deflection on the CRT monitor screen, a three-figure correction capacitor, a linearity correction coil, and a sub-yoke are used. It is possible to dynamically change the current waveform corresponding to the number of scanning lines, and as a result, the non-linear distortion of the CRT monitor related to horizontal deflection can be significantly reduced, and as a result, the correction element can be readjusted. It is an object of the present invention to provide a linearity correction circuit for a horizontal deflection system of a CRT monitor, which makes it possible to reduce such time loss.

In order to achieve the above object, the present invention corrects the distortion on the substantially left side of the CRT tube surface using a three-figure correction capacitor and a nonlinear correction coil connected in series with the horizontal deflection yoke, and corrects the distortion on the substantially right side of the tube surface horizontally. The present invention is characterized in that the output signal of a function generator whose output is controlled by the oscillation frequency is supplied to the sub-yoke for correction.

Next, preferred embodiments of the horizontal deflection system linearity correction circuit according to the present invention will be described in detail with reference to the accompanying drawings. Components that are the same as those shown in FIG. 4 are given the same reference numerals, and detailed explanations thereof will be omitted.

In FIG. 6, reference numeral 22 is a horizontal output circuit that drives the CRT 2, and the output terminal of the horizontal output circuit 22 has a straight line whose inductance characteristics are controlled by the three-figure correction capacitor 10, the horizontal deflection yoke 4, and the magnet 6a. The gender correction coils 6b are connected in series, and the other end is grounded.

On the other hand, one terminal of the sub-yoke 24 for linearity correction is grounded, and the other terminal is connected to the output terminal of the adder 30. The input terminal of the adder 30 is the first terminal in the function generating circuit 32 that generates various function voltages corresponding to the number of scanning lines.
is connected to the sliding terminal of the variable resistor 34.

One terminal of the first variable resistor 34 in the function generating circuit 32 is grounded, and the other terminal is connected to the output terminal of the multiplier 36. A linearity correction wave HSFK is introduced into one input terminal of the multiplier 36, which is a horizontally oscillated sawtooth wave HSAW shaped into a waveform by a DC blocking capacitor 38, a half-wave rectifier 40, and a squarer 42. Further, the multiplier 3
6, the horizontal synchronizing signal H8 is connected to the other input terminal of
The signal is converted into a function waveform to be described later and introduced via a voltage converter 44 (hereinafter referred to as an F/V converter) and an operational amplifier 46. This operational amplifier 46 has an amplifying effect and a resistor 48.
50, the second variable resistor 52, and the power supply voltage (2) perform the level shifting function. Note that, as the squarer 42 in the function generating circuit 32, depending on the characteristics of the deflection system of the CRT, an n-power generator such as a cube generator may be selected depending on the case.

The horizontal deflection system linearity correction circuit according to this embodiment is basically constructed as described above, and its operation and effects will be explained in detail below.

The operating system of the horizontal deflection system linearity correction circuit according to the present invention is basically a method in which the distortion on the left side of the screen of the CRT 2 is corrected by the linearity correction coil 6b, and the distortion on the right side of the screen is corrected by the sub-yoke 24. be.

In the characteristic curve shown in FIG. 7, the horizontal axis represents the deflection distance, and the vertical axis represents the interval change rate.

Therefore, for example, if the CRT monitor 2 has the nonlinear distortion characteristic shown in FIG. , for example, at 33 KHz, it is assumed that the non-linear distortion characteristic shown in FIG. 7 is obtained. In this case, it is easy to change the characteristics of the linearity correction coil 6b to the characteristics shown in FIG. 7C by rotating the magnet 6a.

Next, the linearity correction coil 6 having the characteristics shown in FIG.
The residual nonlinear distortion corrected by b, that is, the distortion characteristics related to the correction of the residual distortion, have the characteristics expressed by the characteristic curve shown in FIG. 7, it will be understood that the characteristics are expressed by the characteristic curve shown in FIG. 7e.

Next, a description will be given of the means for generating the distortion correction characteristic on the right side of the screen of the CRT shown in FIG. 7dSe. In this case, the distortion correction characteristic, that is, the horizontal oscillation frequency 1
At 5 KHz, the right side of the screen is corrected above the characteristic curve shown in Figure 7 d, and at 33 KHz, the right side of the screen is corrected below the characteristic curve shown in Figure 7 e, depending on the horizontal direction of the input video signal. If it were possible to automatically generate the oscillation frequency in response to changes in the number of scanning lines,
It is obvious that video signals of the diagnostic equipment having different numbers of scanning lines can be displayed on the same CRT monitor without distortion. Next, a process of generating a correction signal related to the correction characteristic will be explained.

First, a half-wave rectified wave H3F of the horizontal oscillation harmonic H3□ is obtained from the horizontal oscillation harmonics H and A shown in FIG. 6 through the capacitor 38 and the half-wave rectifier 40. Next, the half-wave rectified wave H
sF is converted into a linearity correction wave H, , 2 with an upward slope to the right by, for example, a squarer 42 that utilizes the square characteristic of a diode. And this upward-sloping linearity correction wave H! F4 is introduced into one input terminal of multiplier 36.

On the other hand, the horizontal synchronizing signal Hs, which is synchronously separated and introduced from the composite video signal output from the diagnostic device, is converted by the F/V converter 44 into a voltage proportional to the frequency. In this case, the conversion characteristic is such that the correction voltage V141 increases in proportion to the horizontal oscillation frequency fH, as shown in FIG. 8a.

Then, the correction voltage VNI is subjected to level shift processing and amplification processing correction in the next stage operational amplifier 46, and is converted into a voltage signal VHz having correction characteristics shown in FIG. In this case, the zero crossing point is, for example, 24K of the horizontal oscillation frequency.
Hz point. Voltage signal with the relevant correction characteristics■. is introduced into the other input terminal of the multiplier 36.

Next, the multiplier 36 multiplies the linearity correction wave H3F2 and the radiation voltage signal vnz. At this time, if the horizontal oscillation frequency is 15 KHz, the input signal is inverted, so that the first linearity correction voltage function Hel shown in FIG. 6 is generated. If the horizontal oscillation frequency is 33 to 1 (z), the sign is not inverted and the second
A linearity correction voltage function I(cz is generated).

These two correction voltage functions HcI and HCZ are shown in Fig. 7d above.
The waveforms are similar to the waveforms obtained by inverting the distortion characteristics shown in and e. Therefore, the correction voltage functions HCI and HCZ
Horizontal nonlinear distortion can be corrected by appropriately dividing the voltage using the first variable resistor 34 and introducing the voltage into the sub-yoke 24 of the CRT 2.

As described above, according to the present invention, when displaying video signals with different numbers of scanning lines outputted from different types of imaging devices constituting various diagnostic devices on the same CRT monitor, horizontal In order to automatically correct nonlinear distortion related to deflection, a figure-8 correction capacitor, a linearity correction coil, and a sub-yoke are appropriately arranged, and a function generator is provided on top of the 8-character correction capacitor, which is supplied to the sub-yoke. It becomes possible to dynamically change the correction current in accordance with the number of scanning lines. As a result, the non-linear distortion of the CRT monitor related to horizontal deflection is significantly reduced, and therefore the time loss related to readjustment of the correction element can be significantly reduced.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram and its characteristic diagram related to the three-figure correction capacitor of a CRT monitor. Figure 2 is a schematic diagram showing the exponential distortion of a CRT monitor and its characteristic diagram. Figure 3 is an impedance characteristic diagram of the correction element. , FIG. 4 is a conventional horizontal linearity correction circuit diagram, FIG. 5 is a diagram showing harmonics related to horizontal deflection, and FIG. 6 is a linearity correction circuit diagram according to the present invention.
FIG. 7 is an explanatory diagram of waveforms of the linearity correction circuit according to the invention, and FIG. 8 is an explanatory diagram illustrating part of the characteristics of the linearity correction circuit according to the invention. 2...CRT 4...Horizontal deflection yoke 6b...Linearity correction coil 10...3-character correction capacitor 22...Horizontal output circuit 24...Sub yoke ← Deflection distance. FIG, 3 ↑ Left - biased 1'1lffn! = Right left −
Deflection distance - right FIG, 5

Claims (2)

[Claims] (1) A function in which the distortion on the left side of the CRT tube surface is corrected by an S-shaped correction capacitor and a nonlinear correction coil connected in series with the horizontal deflection yoke, and the output of distortion on the right side of the tube surface is controlled by the horizontal oscillation frequency. A linearity correction circuit for a horizontal deflection system, characterized in that it is configured to supply an output signal of a generator to a sub-yoke for correction. (2) In the circuit described in claim 1, the function generator has a multiplier, one input terminal of the multiplier is connected to a series circuit of a half-wave rectifier and a squarer, and the other input terminal is connected to a series circuit of a half-wave rectifier and a squarer. A horizontal deflection system linearity correction circuit configured to connect a series circuit consisting of an F/V converter and a level shifter to the input terminal.