JPH06105958B2 - Horizontal deflection system linearity correction circuit - Google Patents

Description

The present invention relates to a linearity correction device for a horizontal deflection system of a CRT monitor, and more specifically, it automatically displays video signals from photographing devices having different scanning lines on the same CRT monitor. Therefore, the present invention relates to a linear deflection correction circuit of 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.

As a field for rapidly reproducing video signals with different scanning lines on the same CRT monitor, for example, CT (Computer Tomography), US (Ultrasonography), DF (Digital Fluorography) and other medical image diagnosis The medical imaging field using the device can be listed. The diagnostic system in the medical image field first displays image information introduced from the plurality of diagnostic devices on a CRT monitor, and then displays the displayed image with an imaging lens, a shutter device, a mirror, and the like. It is configured so that continuous filming can be performed on the film conveyed through the system.

And, in this field, by the CT, US, DF, etc., for example, since it is possible to continuously and quickly obtain image information around the affected part of the human body as its image information,
You can clearly understand the affected area itself and its surroundings,
It is convenient for doctors and the like to make a diagnosis. Further, in this field, it is important to obtain accurate and precise image information due to its nature. This is to avoid misdiagnosis and the like. Therefore, a CRT monitor with as little distortion as possible is adopted.

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

One of them is the occurrence of distortion as shown in Fig. 1, which occurs because the center of curvature of the phosphor screen of the CRT monitor and the deflection center of the electron beam are different from each other. Due to shrinkage and elongation at both ends. Referring to the drawings, FIG. 1a is a schematic view of a striped tube surface display without distortion correction, while FIG. 1b is its characteristic view. In FIG. 1b, the horizontal axis represents the deflection distance with respect to the horizontal direction of the tube surface, and the vertical axis represents the interval change rate on the phosphor screen with respect to the deflection distance.

Next, the second distortion is shown in FIG. That is, there is a distortion phenomenon in which the left side of the screen expands and the right side of the screen contracts because the horizontal deflection current does not change linearly due to the resistance of the horizontal deflection yoke and becomes an exponential saturation curve. The meaning of FIGS. 2a and 2b can be easily understood by referring to the explanation of FIGS. 1a and 1b.

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

The second distortion is corrected by connecting a saturable reactor biased by a DC magnetic field in series to the horizontal deflection yoke and utilizing the fact that the inductance changes at each point of the deflection current flowing through this. In this case, for example, if a plurality of saturable reactors are used, the combined impedance of the left side correction inductance and the right side correction inductance can be changed as shown in FIG. 3b.

FIG. 4 is an example of a conventional circuit diagram for correcting the above two types of distortions. In the circuit diagram, the horizontal deflection yoke 4 for horizontally deflecting the CRT 2 has an inductance via magnets 6a and 8a. The linearity correction coils 6a and 8a and the S-shaped correction capacitor 10 which are composed of a saturable reactor that can be changed depending on the current are connected in series. The horizontal linearity correction circuit relating to the first and second distortions composed of these components is a choke coil 20 connected to a horizontal drive transformer 12, a horizontal output transistor 14, a damper diode 16, a resonance capacitor 18 and a power source + V _BB. Is driven by a horizontal output circuit 22 composed of
It operates to correct distortion associated with character correction and exponential distortion.

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

Therefore, for example, in the case of 525 scanning lines (about 15 KHz at the horizontal oscillation frequency), it is assumed that the power supply voltage + V _BB = 15V is set, and the S-shaped correction capacitor 10 and the linearity correction coils 6b and 8b are adjusted to be optimum Even if the linearity correction constant is calculated, the number of scanning lines is 1125 (horizontal oscillation frequency about 33 KHz)
When the signal of (1) is introduced, the horizontal amplitude is reduced, and the accurate reproducibility of the image is not guaranteed. In this case, as shown in FIGS. 5A and 5B, the power supply voltage + V _{BB is set} to 15V × due to the requirement that the deflection width of the tube surface, that is, the amplitude of the current value is the same even for signals of different scanning lines. 33KHz / 15KHz = 33V, which needs to be doubled. As a result, the impedance of each element changes corresponding to the change of the horizontal oscillation frequency from 15 KHz to 33 KHz.
Unless the 10 and the linearity correction coils 6b and 8b are readjusted over time so as to match the changed horizontal oscillation frequency, it becomes impossible to maintain good horizontal linearity.

However, the loss of time associated with this readjustment is a fatal drawback in the field of using a medical image diagnostic apparatus that needs to display video signals from a plurality of imaging devices described above and display them on a CRT monitor quickly. Exposed as an inconvenience.

The present invention has been made in order to overcome the above-mentioned inconvenience, and the video signals having different numbers of scanning lines output from different types of imaging devices constituting various diagnostic apparatuses are output by the same CRT.
When displaying on the monitor, in order to automatically correct the non-linear distortion due to the horizontal deflection on the tube surface of the CRT monitor, the S-shaped correction capacitor, the linearity correction coil and the sub-yoke are used,
It is possible to dynamically change the current waveform supplied to the sub-yoke according to the number of scanning lines, and as a result, the non-linear distortion of the CRT monitor related to horizontal deflection is significantly reduced. It is an object of the present invention to provide a linearity correction circuit for a horizontal deflection system of a CRT monitor that can reduce time loss associated with readjustment of elements.

In order to achieve the above object, the present invention provides, for example, a sixth aspect.
As shown in the figure, in the linearity correction circuit of the horizontal deflection system corresponding to a plurality of horizontal oscillation frequencies, the horizontal correction capacitor 10 and the nonlinear correction coil 6b connected in series are connected in series. Horizontal output circuit having horizontal output transistor 14 for driving deflection yoke 4
22 and a linearity correction circuit 32 that drives the sub-yoke 24. The correction circuit 32 includes a frequency-voltage converter 44 that generates a voltage proportional to the horizontal oscillation frequency and n (n ≧ n) from the horizontal oscillation sawtooth wave.
2) It has an n-th power multiplier 42 for generating a power wave and a synthesizer 36 for synthesizing the outputs of the frequency-voltage converter 44 and the n-th power multiplier 42, and among the distortion generated on the tube surface of the CRT2, The horizontal output circuit 22 corrects the distortion on the substantially left side of the tube surface, and the correction circuit 32 corrects the distortion on the substantially right side of the tube surface of the CRT 2.

Next, a preferred embodiment of a linearity correction circuit for a horizontal deflection system according to the present invention will be described in detail below with reference to the accompanying drawings. The same components as those shown in FIG. 4 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 6, reference numeral 22 is a horizontal output circuit for driving the CRT 2, and the output terminal of the horizontal output circuit 22 is a straight line whose inductance characteristic is controlled by the S-shaped correction capacitor 10, the horizontal deflection yoke 4 and the magnet 6a. Sex correction coil 6b
Are connected in series and the other end is grounded.

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

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 linear correction wave H _{SF2 in} which the horizontal oscillation sawtooth wave H _SAW is shaped by the DC blocking capacitor 38, the half-wave rectifier 40 and the squarer 42 is introduced into one input terminal of the multiplier 36. Also, the other input terminal of the multiplier 36,
The horizontal synchronizing signal H _S is introduced after being converted into a function waveform described later via a frequency-voltage converter 44 (hereinafter referred to as F / V converter) and an operational amplifier 46. The operational amplifier 46 performs a level shift function by the resistors 48 and 50, the second variable resistor 52 and the power source voltage V ₁ together with the amplification function. Depending on the characteristics of the deflection system of the CRT, the squarer 42 in the function generating circuit 32 may be an n-th cuber such as a cuber.

The linearity correction circuit of the horizontal deflection system according to the present embodiment is basically constructed as described above, and its operation and effect will be described in detail below.

The operation method of the linearity correction circuit of the horizontal deflection system according to the present invention is basically such that the distortion on the left side of the screen of the CRT2 is corrected by the linearity correction coil 6b.
The sub-yoke 24 corrects the distortion on the right side of the screen.

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

Therefore, for example, the CRT monitor 2 now has the oscillation frequency related to the first scanning line number, for example, 15 KHz, and has the non-linear distortion characteristic shown in FIG. 7A, and the oscillation frequency related to the second scanning line number. For example, it is assumed that it has the nonlinear distortion characteristic of FIG. 7b at 33 KHz. In this case, it is easy to set the characteristic of the linearity correction coil 6b to the characteristic shown in FIG. 7c by rotating the magnet 6a. Next, the residual non-linear distortion corrected by the linearity correction coil 6b having the characteristic of FIG. 7C, that is, the distortion characteristic related to the correction of the residual distortion is shown in FIG. It becomes the characteristic shown by the characteristic curve shown in Fig.7.
It will be appreciated that the characteristics are represented by the characteristic curve shown in.

Therefore, the means for generating the distortion correction characteristic on the right side of the screen of the CRT according to FIGS. 7D and 7E will be described next. In this case, the distortion correction characteristic, that is, the horizontal oscillation frequency of 15 KHz
Horizontal oscillation of the input video signal indicates that the right side of the screen is corrected to the upper side on the characteristic curve of FIG. 7d, and the right side of the screen is set to the lower side of the characteristic curve of FIG. 7e at 33 KHz. If it is possible to automatically generate in response to a change in frequency, that is, the number of scanning lines, the video signals of the diagnostic device having different numbers of scanning lines can be displayed on the same CRT without distortion.
It is obvious that it can be displayed on the monitor. Next, a process of generating a correction signal related to the correction characteristic will be described.

First, from the horizontal oscillation sawtooth wave H _SAW shown in FIG.
8. Through the half-wave rectifier 40, the half-wave rectified wave H _{SF of the} horizontal oscillation sawtooth wave H _SAW can be obtained. Then, to convert the half-wave rectification wave H _SF, for example, by squarer 42 utilizing the square characteristic of the diode linearity correction wave H _SF2 right-up. Then, the upward-sloping linearity correction wave H _SF2 is introduced into one input terminal of the multiplier 36.

On the other hand, the horizontal synchronizing signal H _{S, 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 as shown in FIG.
The characteristic is that the correction voltage V _H1 increases in proportion to f _H.

Then, the correction voltage V _H1 is subjected to level shift processing and amplification processing correction by the operational amplifier 46 in the next stage, and is converted into a voltage signal V _H2 having a correction characteristic shown in FIG. 8B. In this case, the zero-cross point is, for example, the 24 KHz point of the horizontal oscillation frequency. The voltage signal V _H2 having the correction characteristic is the multiplier 36
Is introduced to the other input terminal of.

Next, the multiplier 36 multiplies the linearity correction wave H _SF2 by the radiation voltage signal V _H2 . At this time, if the horizontal oscillation frequency is 15 KHz, the input signal is inverted, so the first linearity correction voltage function H shown in FIG.
_C1 occurs. If the horizontal oscillation frequency is 33 KHz, the sign is not inverted and the second linearity correction voltage function
H _C2 is generated.

The two correction voltage functions H _C1 and H _C2 have waveforms similar to the waveform obtained by inverting the distortion characteristics shown in FIGS. 7d and 7e. Therefore, the correction voltage functions H _C1 and H _C2 are appropriately divided by the first variable resistor 34 and then introduced into the sub-yoke 24 of the CRT 2 to correct the horizontal nonlinear distortion. Can be done.

As described above, according to the present invention, when displaying video signals with different numbers of scanning lines output from different types of imaging devices constituting various diagnostic apparatuses on the same CRT monitor, the horizontal direction on the tube surface of the CRT monitor is used. In order to automatically correct the non-linear distortion due to the deflection, the S-shaped correction capacitor, the linearity correction coil, and the sub-yoke are properly arranged, and the function generator is arranged on the S-shaped correction capacitor, and the function is provided to the sub-yoke. It is possible to dynamically change the correction current according to the number of scanning lines. As a result, the non-linear distortion of the CRT monitor related to the horizontal deflection is remarkably reduced, so that the time loss related to the readjustment of the correction element can be remarkably reduced.

Although the present invention has been described with reference to the preferred embodiment, the present invention is not limited to this embodiment,
It goes without saying that various improvements and design changes can be made without departing from the scope of the present invention.

[Brief description of drawings]

Fig. 1 is a schematic diagram of the S-shaped correction capacitor of the CRT monitor and its characteristic diagram, Fig. 2 is a schematic diagram showing the exponential distortion of the CRT monitor and its characteristic diagram, and Fig. 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 a sawtooth wave relating to horizontal deflection, FIG. 6 is a linearity correction circuit diagram according to the present invention, and FIG. 7 is a present invention. FIG. 8 is a diagram for explaining the waveform of the linearity correction circuit, and FIG. 8 is an explanatory diagram for explaining a part of the characteristics of the linearity correction circuit according to the present invention. 2 ... CRT, 4 ... Horizontal deflection yoke 6b ... Linearity correction coil 10 ... S-shaped correction capacitor, 22 ... Horizontal output circuit 24 ... Sub-yoke

Claims (1)

[Claims] 1. A linear deflection correction circuit for a horizontal deflection system corresponding to a plurality of horizontal oscillation frequencies, wherein a horizontal deflection yoke connected in series with an S-shaped correction capacitor and a non-linear correction coil connected in series is provided. A horizontal output circuit having a horizontal output transistor for driving and a linearity correction circuit for driving the sub-yoke are provided, wherein the correction circuit is a frequency voltage converter for generating a voltage proportional to a horizontal oscillation frequency, and a horizontal oscillation sawtooth wave. To n (n ≧
2) It has an n-th power generator that generates a power wave, and a synthesizer that synthesizes the output of these frequency-voltage converters and n-th power. Is corrected by the horizontal output circuit, and the distortion on the substantially right side of the tube surface of the CRT is corrected by the correction circuit.