JPH0235490A - Image display device - Google Patents

Abstract

PURPOSE:To correct a vertical deflected signal by a small number of bits by storing only waveform correcting data taking consideration of distortion in a correction value generating circuit for each unit of dots on a horizontal scan line. CONSTITUTION:Since the contents of dot clock signals CK counted up in an X counter circuit 11 are cleared whenever a horizontal synchronizing signal HS is added, dot included in one horizontal scan line are outputted from the circuit 11 by bits (x). Signals HS are sequentially added to a Y counter circuit 12 and counted up. Whenever a vertical synchronizing signal VS is added, the circuit 12 is cleared, whereby horizontal scan lines included during one vertical scan period are outputted by bits (y) from the circuit 12. Both outputs are added to the correction value generating circuit 17. It previously stores the waveform correction data taking consideration of the distortion of the vertical deflected signal as digital memory. By using an output from a counter circuit 10 as an address, desired waveform correction is carried out and an optimum voltage is outputted as a digital value of bits (n). Thus, the vertical deflected signal can be corrected by a small number of bits.

Description

Detailed Description of the Invention (Objective of the Invention) (Industrial Application Field) The present invention provides an image display device that displays a desired image on a fluorescent screen by controlling an electron beam using a horizontal deflection circuit and a vertical deflection circuit. Regarding.

(Prior Art) An image display device using a cathode ray tube (CRT) uses a horizontal deflection circuit and a vertical deflection circuit to scan an electron beam horizontally and vertically on the fluorescent screen of the tube, as shown in FIG. The desired image is displayed using the following method. When scanning the electron beam over the tube surface in this way,
The horizontal deflection circuit and the vertical deflection circuit control the electron beam using a magnetic field formed by supplying sawtooth current to horizontal deflection coils and vertical deflection coils arranged around the tube, respectively.

In particular, the period of the sawtooth wave current for vertical deflection is much longer than that of the sawtooth wave current for horizontal deflection, so the waveform of the sawtooth wave current must have excellent linearity over the entire period to achieve distortion-free quality. This is a necessary condition for obtaining good images.

This sawtooth current is obtained by utilizing the charging and discharging characteristics of time constant circuits such as resistor R and capacitor C.

However, in actual situations, the sawtooth wave for vertical deflection that is obtained may be caused by variations in the time constant of the time constant circuit, the presence of a choke coil in the vertical deflection circuit, or variations in the characteristics of the transistors making up the vertical deflection circuit. The current waveform becomes distorted. As a result, the magnetic field formed is not uniform, and the scanning speed of the electron beam controlled by this magnetic field is not constant, as shown in Figures 7(a) and (b).
An image containing distortion called thread distortion or barrel distortion will be displayed.

Images containing such distortion do not pose much of a problem when the display target can be roughly distinguished, such as in a normal broadcasting television receiver. However, when used as an image display device for medical diagnostic equipment, the display target is selected to be a minute sample or a sample that changes minutely, so distortion in the image can greatly impede the collection of basic data for diagnosis. I will come. For example, when a curve is displayed, it is difficult to distinguish whether the curve is an original curve of the specimen or a curve based on waveform distortion of the sawtooth current. In order to eliminate such drawbacks, the present applicant has previously provided a vertical deflection circuit that takes into consideration waveform correction as disclosed in Japanese Patent Laid-Open No. 62-230167.

As shown in FIG. 5, in this vertical deflection circuit, desired waveform correction data of a vertical deflection signal is stored in advance in a waveform generation circuit 13 as a digital memory, and the X counter circuit 11 and Y counter circuit 12
Using the output as an address, the waveform generation circuit 13 outputs the optimum voltage after the desired waveform correction, and converts it into an analog value Vo by the D/A conversion circuit 14 to the vertical amplifier circuit 15.
, a sawtooth wave current is applied to the vertical deflection coil via the vertical output circuit 16.

(Problem to be Solved by the Invention) Incidentally, the vertical output circuit of such a conventional image display device can generate a sawtooth wave current with excellent linearity, but it is necessary to store all desired waveform correction data in advance. As a result, the number of bits forming the waveform generation circuit and the D/A conversion circuit increases, resulting in an unavoidable increase in cost. For example, 14 bits or more are required to perform sufficient correction, preferably 16 bits. Another problem is that it is difficult to perform adjustment work for accurate correction.

The present invention has been made in response to the above-mentioned problems.
It is an object of the present invention to provide an image display device equipped with a vertical deflection circuit that has a small number of bits and is easy to adjust.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention includes Y and X counter circuits each counting the number of horizontal scanning lines and the number of dots forming one screen, and vertical a correction value generation circuit that stores in advance waveform correction data that takes into account the distortion of the deflection signal and generates a digital value of the correction value using the output of the counter circuit as an address, and each output from the Y counter circuit and the correction value generation circuit. D/A converts digital voltage to analog voltage
The variable-conversion circuit includes an analog addition circuit that adds the outputs of the respective D/A conversion circuits, and a vertical output circuit that supplies the sawtooth wave current output from the analog addition circuit to the vertical deflection coil.

(Function) In the correction value generation circuit, only waveform correction data that takes into account distortion in advance is stored as a digital memory in units of dots on the horizontal scanning line, so the desired correction of the vertical deflection signal can be performed with a small number of bits. Can be done. As a result, the vertical deflection signal can be corrected without unnecessarily increasing the number of bits, and adjustment work can be easily performed accordingly.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a vertical deflection circuit used in an image display device according to an embodiment of the present invention. A counter circuit 10 consists of an X counter circuit 11 and an X counter circuit 12, and both counter circuits 11 and 12 have horizontal A signal Hs is commonly applied, and a dot (pixel) clock signal GK and a vertical synchronization signal VS are applied to the X counter circuit 11 and the X counter circuit 12, respectively. The frequency of the dot clock signal GK is determined depending on the required image resolution. The dot clock signal CK, which is sequentially applied to the X counter circuit 11 and counted up, is a horizontal synchronization signal)-1
Each time s is added, its content is added to I, so
The X counter circuit 11 outputs the number of dots included in one horizontal scanning line H in X bits. On the other hand, the horizontal synchronizing signal Hs is sequentially applied to the X counter circuit 12 to count up, but the contents are cleared each time the vertical synchronizing signal Vs is applied, so the X counter circuit 1
From 2, the number of horizontal scanning lines included in one vertical scanning period is
Bits will be output. The number of horizontal scan lines to be scanned up can be determined depending on the resolution of the image. Therefore, the X counter circuit 11 and the Y counter 1
The X bit and y bit output from the second
One screen as shown in the figure will be configured. For example, if 10 is determined as X and y, 210 (dots) x 210 (dots) = 1,024 (dots) xl,
A screen consisting of 024 (dots) will be constructed. This X.

The value of y can be arbitrarily selected depending on the required image resolution.

The outputs of the X counter circuit 11 and the X counter circuit 12 are applied to a correction value generation circuit 17. This correction value generation circuit 1
In 7, waveform correction data that takes into account the distortion of the vertical deflection signal is stored in advance as a digital memory, and when the output of the counter circuit 10 is added, the desired waveform correction is performed using this output as an address to obtain the optimum voltage. Output as an n-bit digital value. The value of n is determined depending on the content of the correction, and is set to n=6, for example.

The Y counter circuit 12 outputs a period T having excellent linearity, for example, as shown in FIG.
A sawtooth wave voltage is output.

On the other hand, correction value data having a waveform as shown in FIG. 4(b) is stored in advance in the correction value generation circuit 17 as a 6-bit digital memory, taking into account the distortion of the sawtooth voltage. The digital outputs from the X counter circuit 12 and the correction value generation circuit 17 are provided by a D/A conversion circuit 14A,
After being converted into an analog voltage by 14B, it is applied to the analog tta calculation circuit 18. The waveform of FIG. 4(C) obtained by howing the waveforms of FIGS. 4(a) and (b) by this analog adder circuit 1B is output as a sawtooth wave voltage vO, and the voltage is amplified by the vertical amplifier circuit 15, and the vertical output is The power is further amplified by the circuit 16 and then supplied to the deflection coil as a sawtooth current IO.

FIGS. 3(a) to (f>) show time charts of signals 1q converted by the vertical deflection circuit of FIG. 1. FIG.

The waveform of the vertical deflection voltage VO changes stepwise in accordance with the count up of the X counter circuit 12 of the counter circuit 10, and one step corresponds to one horizontal scanning line.

For example, if the X counter circuit 12 is composed of 10 bits as in the above example, one screen will be composed of 210 = 1,024 (dots) = 1,024 horizontal scanning lines, so 1, A vertical deflection voltage Vo is formed by the steps of 024, which becomes a sawtooth voltage when viewed macroscopically. Moreover, since the steps are regularly formed, it is possible to obtain an excellent sawtooth wave voltage in a linear manner. Therefore, a sawtooth wave current Io having excellent waveform linearity corresponding to this sawtooth wave voltage can be supplied to the deflection coil. Moreover, the sawtooth wave current obtained in this manner is subjected to desired waveform correction by the correction value generation circuit 17 based on waveform correction data that takes into account the distortion of a small number of bits.
Any kind of distortion can be corrected with a small number of bits. This makes it possible to easily perform adjustment work for accurate correction.

That is, each of the 2y horizontal scanning lines output from the X counter circuit 12 is composed of 2X dots output from the X counter circuit 11, so by specifying Since it is possible to address a specific dot, such as the number of dots in the horizontal scanning line, waveform correction can be performed in units of dots, and it is possible to deal with any kind of distortion. Furthermore, it becomes possible to correct a plurality of distortions using one correction circuit. Therefore, it is possible to perform partial correction at arbitrary dot positions for each horizontal scanning line on the image, so it is possible to display an image free of string distortion, barrel distortion, and the like. Therefore, it is particularly effective when applied to an image display device of a medical diagnostic device in which minute display objects are selected.

[Effects of the Invention] As explained above, according to the present invention, a vertical deflection signal is corrected by a correction value generation circuit in which only waveform correction data that takes into account distortion in advance is stored as a digital memory with a small number of bits. Therefore, it is possible to supply a sawtooth waveform flow for vertical deflection with excellent linearity without increasing costs, and therefore, it is possible to display an image without distortion.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a vertical deflection circuit of an image display device according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing a tube surface of an embodiment of the present invention, and FIG. Timing chart showing signals of the vertical deflection circuit of the embodiment of the invention, FIG. 4(a)
to (C) are signal waveform diagrams explaining this embodiment, FIG. 5 is a block diagram of the conventional example, and FIGS. 6 and 7 (a) and (b).
1 is a diagram showing a display pattern on a tube surface of a conventional example. 10... Counter circuit, 11... X counter circuit,
12... Y counter circuit, 14A, 14B... D/A conversion circuit, 15... Vertical amplifier circuit, 16... Vertical output circuit, 17... Correction value generation circuit, 18... Analog addition circuit. , 1077 se 4th round b (e) Sting (5) @IS so Vs (f) Horizontal chanting stick 4 呵 H5 Fig. 2 Fig. 3

Claims (1)

[Claims] In an image display device that displays a desired image on a phosphor screen by controlling an electron beam using a horizontal deflection circuit and a vertical deflection circuit, the vertical deflection circuit controls the number of horizontal scanning lines and the number of dots constituting one screen. Y and X counter circuits that count Y and X respectively; a correction value generation circuit that stores waveform correction data in consideration of the distortion of the vertical deflection signal in advance and generates a digital value of the correction value using the output of the counter circuit as an address; A D/A conversion circuit that converts each digital voltage output from the counter circuit and the correction value generation circuit into an analog voltage, an analog addition circuit that adds the outputs of each D/A conversion circuit, and an output from the analog addition circuit. An image display device comprising: a vertical output circuit that supplies a sawtooth wave current to a vertical deflection coil.