JPS62230167A - Picture display device - Google Patents

Abstract

PURPOSE:To prevent pincushion distortion and barrel distortion by storing necessary waveform correction data as digital memory in a waveform generating circuit beforehand and generating saw tooth wave for vertical deflection high in linearity. CONSTITUTION:Counter circuits 11 and 12 count the number of horizontal scanning lines constituting a picture and dot clocks and output the output as a reading address to a waveform generating circuit 13. Desired waveform correction data of a vertical deflection signal are stored beforehand as digital memory in the waveform generating circuit 13. When the output of above-mentioned counter circuit 10 is added, desired waveform correction is made making it an address, and optimum voltage is outputted as digital value of (n) bits. The digital output is converted to analog by a D/A converter 14, and amplified by a vertical amplifier circuit 15, power amplified by a vertical output circuit 16, and supplied to a deflecting coil as saw tooth wave current.

Description

Detailed Description of the Invention [Objective of the Invention 1 (Industrial Application Field) The present invention provides 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. 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 on the fluorescent screen of the tube in the left-right direction and in the downward direction, as shown in FIG. By doing so, the desired ryokai can be displayed. When scanning an electron beam over a tube surface in this way, a horizontal deflection circuit and a vertical deflection circuit generate a magnetic field by supplying a sawtooth wave current to horizontal and vertical deflection coils placed around the tube, respectively. This is used to control the electron beam.

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 has a linearity over its circumference as shown in Figure 5(a). Excellent quality is a necessary condition for obtaining distortion-free, high-quality images.

This sawtooth wave current is obtained by utilizing the charging and discharging characteristics of the time constant circuit of the resistor R and the capacitor FjC.

However, in reality, the sawtooth wave current for vertical deflection (q) is The waveform of is shown in Fig. 5(b).

The image will be distorted as shown in (C). 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 Figure 7(a).
, (b), an image containing distortion called threading distortion is now displayed.

Images containing such distortion do not pose much of a problem in cases where the display distortion can be roughly discerned, such as in a normal broadcasting television receiver. However, when used as an image display device for medical diagnostic equipment, the display target is a minute specimen or a specimen that changes minutely, so distortion in the image can be a major hindrance to the collection of basic data for diagnosis. This is what will happen. 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, a vertical deflection circuit as shown in FIG. 4 is provided in which waveform correction is taken into consideration.

In synchronization with the vertical synchronization signal Vs separated from the received video signal, the vertical oscillation circuit 1 generates a sawtooth voltage Vo for vertical deflection and applies it to the waveform adjustment circuit 2.

The sawtooth voltage Vo, which has undergone desired waveform adjustment by the waveform adjustment circuit 2, is applied to the vertical excitation circuit 3, and after desired voltage amplification is applied to the vertical output circuit 4.

The vertical output circuit 4 performs power amplification of the sawtooth voltage Vo to the extent necessary to supply a large sawtooth current to to the vertical deflection coil 5, and also supplies a portion of the input voltage to the vertical deflection coil 5 through a line 6. It functions to correct the waveform by providing negative feedback to the excitation circuit 3.

By the way, since such conventional waveform correction is performed by analog means, it is necessary to provide individual correction circuits depending on the cause of distortion. Further, since the circuit components vary, manual adjustment is necessary, but since there is little freedom in adjustment, it is difficult to generate a sawtooth wave current for vertical deflection with excellent linearity and no distortion.

(Problems to be Solved by the Invention) As described above, it is said that the vertical deflection circuit of the conventional image display device cannot obtain an image without distortion because it is difficult to generate a sawtooth wave current with excellent linearity. There's a problem.

The present invention was made in response to such problems, and an object of the present invention is to provide an image display device that generates a sawtooth wave current with excellent linearity to obtain an image free of distortion. It is something to do.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a vertical deflection circuit of an image display device that counts the number of horizontal scanning lines and the number of dots constituting one screen. a waveform generating circuit that stores waveform correction data of the vertical deflection signal in advance and generates a digital value of an optimum voltage using the output of the counter circuit as an address; and D that converts the digital voltage into an analog voltage.
The present invention is characterized by comprising a /A conversion circuit and a vertical output circuit that supplies a sawtooth current according to an analog voltage to a vertical deflection coil.

(Function) Since all desired waveform correction data is stored in advance in the waveform generation circuit as a digital memory in units of dots on the horizontal scanning line, the output of the counter circuit is added to the waveform using the output as the address. The generating circuit outputs the lH suitable voltage with desired correction. By storing all necessary waveform correction data in advance in the waveform generation circuit as a digital memory in this way, a plurality of distortions can be corrected by one correction circuit (waveform generation circuit).

(Embodiment) FIG. 1 shows a vertical deflection circuit used in an image display device according to an embodiment of the present invention, in which a counter circuit 10 consists of an X counter circuit 11 and a Y color 29 circuit 12; A horizontal synchronizing signal 1s is commonly applied to the X counter circuit 11 and a Y color 29 circuit 12, and a dot (pixel) clock signal CK and a vertical synchronizing signal S are applied to the X counter circuit 11 and the Y color circuit 12, respectively. The frequency of the dot clock signal QCK 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 connected to the horizontal synchronization signal Hs.
Since the contents are cleared each time .times. is added, the X counter circuit 11 outputs the number of dots included in one horizontal scanning line H in X bits. On the other hand, Y color 29
The horizontal synchronizing image gl-1s is sequentially applied to the circuit 12 and counted up, but its contents are cleared each time the vertical synchronizing signal Vs is applied, so that the Y color 29 circuit 12 counts up one vertical scanning period. The number of horizontal scanning lines included in is outputted in y bits. The number of horizontal scanning lines counted up can be determined depending on the resolution of the image. Therefore, the X counter circuit 11 and the Y counter 1
By the X bit and y pit output from 2,
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
, 024 (dots).

The values of X and y can be arbitrarily selected depending on the required image resolution.

The outputs of the X counter circuit 11 and the Y collar 29 circuit 12 are applied to a waveform generation circuit 13. Desired waveform correction data of the vertical deflection signal is stored in advance in this waveform generation circuit 13 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. is output as an n-bit digital value. The value of n is determined depending on the content of the correction.

The digital output is converted into an analog voltage by the D/A conversion circuit 14, voltage amplified by the vertical amplifier circuit 15, further power amplified by the vertical output circuit 16, and then supplied to the deflection coil as a sawtooth current IO.

3(a) to 3(f)' show time charts 1 to 1 of signals obtained by the vertical deflection circuit of FIG. 1.

The waveform of the vertical deflection voltage (2) 0 changes stepwise in accordance with the count up of the Y color 29 circuit 12 of the counter circuit 10, and one step corresponds to one horizontal scanning line.

For example, if the Y color 29 circuit 12 is configured with 10 bits as in the previous example, 210 = 1,024 (dots)
Since one screen is composed of =1,024 horizontal scanning lines, the vertical deflection voltage Vo is formed by 1,024 steps, which becomes a sawtooth voltage from a macroscopic perspective. Moreover, since the steps are regularly formed, it is possible to obtain an excellent sawtooth voltage in a straight line. Therefore, it is possible to supply the deflection coil with a sawtooth wave current IO having an excellent waveform linearity corresponding to this sawtooth wave voltage. Also like this 1
Since the waveform generation circuit 13 performs desired waveform correction on the sawtooth wave current, it can be corrected to correspond to any distortion.

In other words, the 2y horizontal scanning lines output from the Y color 29 circuit 12 are composed of 2x dots output from the X counter circuit 11, so by specifying x and y, the number of horizontal scanning lines can be changed. Since it is possible to address specific dots, such as the number of dots in the horizontal scanning line of the mouth, waveform correction can be performed on a dot-by-dot basis, making it possible to deal with any distortion. Furthermore, it becomes possible to correct a plurality of distortions using one correction circuit. Therefore, since partial correction can be made at arbitrary dot positions on each horizontal scanning line on the image, 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, since the vertical deflection signal is corrected by the waveform generation circuit in which all desired waveform correction data is stored in advance as a digital memory, the linearity is improved. Since it is possible to supply a sawtooth waveform flow for excellent vertical deflection, it is possible to display an image without distortion.

[Brief explanation of drawings]

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 FIGS. Timing dilation showing the signals of the vertical deflection circuit of the embodiment of the invention, FIG. 4 is a block diagram of the conventional example, FIGS. 5(a) to (C) are signal waveform charts of the conventional example, FIGS. 6 and 7 (a) and (b) are diagrams of display patterns of snow surfaces in conventional examples. 10... Counter circuit, 11... X counter circuit,
12... Y counter circuit, 13... Waveform generation circuit,
14... D/A conversion circuit, 15... Vertical amplifier circuit,
16... Vertical output circuit. (e) Bottle j [πtl [Month] Kankochi) 〆S (f) 7 to 14 deposits 1 [Roi 11 mi qtbu δ Fig. 3 (a) (b) Fig. 7

Claims (1)

[Claims] In 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, the vertical deflection circuit counts the number of horizontal scanning lines and the number of dots forming one screen. a waveform generating circuit that stores waveform correction data of the vertical deflection signal in advance and generates a digital value of an optimum voltage using the output of the counter circuit as an address; and a D/A converter circuit that converts the digital voltage into an analog voltage. and a vertical output circuit that supplies a sawtooth current according to an analog voltage to a vertical deflection coil.