CA2072191C - Display apparatus - Google Patents
Display apparatusInfo
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- CA2072191C CA2072191C CA 2072191 CA2072191A CA2072191C CA 2072191 C CA2072191 C CA 2072191C CA 2072191 CA2072191 CA 2072191 CA 2072191 A CA2072191 A CA 2072191A CA 2072191 C CA2072191 C CA 2072191C
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Abstract
A display apparatus in which the focus shift and astigmatism of the electron beam caused in the CRT and its vicinity portion are reduced. Picture scenes of higher fidelity, higher acuteness and higher resolution can be obtained. In the electron beam shaped control circuit, signals corresponding to a high-pass component, a brightness component in the image signals from the horizontal direction electron beam shaped detection deciding portion, and signals corresponding to the low-pass component in the image signals from the vertical direction electron beam shaped detection deciding portion are composed. Composite signals of parabolic waves are obtained by a driving voltage generating portion so as to apply the output to the auxiliary acceleration focusing electrode of the CRT.
Description
DISPLAY APPARATUS
The present invention generally relates to a display apparatus for image reproduction, character display or the like using a cathode-ray tube (hereinafter referred to as CRT).
An in line shaped self convergence CRT system (hereinafter referred to as non-uniform magnetic system) in a television field causes considerable resolution deterioration when electronic beams are deflected with deflection yokes.
Especially, the deterioration in picture scenes and their circumferences is noticeable. Various proposals have been made to settle this problem. A dynamic focusing system is available to remove the difference in focusing, for example, between the central portion of the picture scene and the circumference portion. In order to remove the deflection distortion in the circumference, there are an electromagnetic correcting system as disclosed in Japanese Laid-Open Patent Publication No. 57-84683, and an electrostatic system represented by a DAF system.
Exceptional resolution deterioration is caused in the deflection of an electron beam in a wide range, even if the yoke is a uniform magnetic field deflection yoke. Especially, the deterioration in the picture scene circumference is exceptional. A proposal similar to the above description is provided and introduced.
The above described Japanese Laid-Open Patent Publication No. 57-84683 is complicated in construction and composition, and is of high cost. The electrostatic system to be represented by the DAF system is high in applied voltage, with problems in terms of reliability and cost.
Accordingly, the present invention has been developed with a view to substantially eliminating the above discussed drawbacks inherent in the prior art and has for its essential object to provide an improved display apparatus.
Another object of the present invention is to provide an improved apparatus in which the resolution deterioration in the picture scene and its vicinities is corrected with a prefocus lens portion of an electron gun to obtain an optimum image, with the electronic beam shape being modulated with parabolic wave forms of horizontal, vertical periods of the parabolic wave forms and frequency components of the image signals (hereinafter referred to as to a dynamic prefocus system).
Still another object of the present invention is to provide an improved display apparatus in which a moire phenomenon caused by correlation between the electronic beam spot and a shadow mask is removed so as to reduce the light emission saturation phenomenon of the phosphor caused by concentration of the electron beam spots.
In accomplishing these and other objects, the present invention adopts a dynamic prefocusing system. In accordance with one aspect of the present invention there is provided a display apparatus including a CRT, said apparatus comprising:
a dynamic focus correction voltage generator, said dynamic focus correction voltage generator generating a dynamic focus correction voltage signal consisting of vertical and horizontal cyclic parabolic waveforms and supplying said signal to at least one main focus grid of the CRT; a horizontal direction electron beam focusing determination circuit, said horizontal direction electron beam focusing determination circuit generating a horizontal direction spot size signal in accordance with a high-pass component and luminance component contained within an image signal input thereto; a vertical direction electron beam focusing determination circuit, said vertical direction electron beam focusing determination circuit generating a vertical direction spot size signal in accordance with a low-pass component contained within said image signal input thereto; and an electron beam focusing controller, said electron beam focusing controller receiving said horizontal direction spot size signal generated by said horizontal direction electron beam -2a focusing determination circuit and said vertical direction spot size signal generated by said vertical direction electron beam focusing determination circuit and outputting a signal in response thereto; and a driving voltage generator, said driving voltage generator receiving said dynamic focus correction voltage signal and adding it to the output signal of said electron beam focusing controller and supplying a resultant added signal to at least one prefocus grid of the CRT.
In accordance with another aspect of the present invention there is provided a method of controlling a focus of a CRT included within a display apparatus, said method comprising the steps of: generating a signal consisting of a vertical cyclic parabolic waveform and a horizontal cyclic parabolic waveform and using the generated signal to control a dynamic focus of the CRT by supplying the generated signal to a main focus lens of the CRT; generating a horizontal direction spot size signal generated in accordance with a high-pass component and luminance component contained within an image signal and a vertical direction spot size signal generated in accordance with a low-pass component contained within the image signal; combining the horizontal and vertical direction spot size signals to form a combined signal; adding the generated signal to the combined signal to generate a signal which is applied to a prefocus lens of the CRT for controlling a dynamic prefocus of the CRT.
As disclosed in laid-open Japanese Patent Publication No.
53-105168, published September 13, 1978 in the name of Kouzou Tateishi, when a cathode-ray-tube having an electron gun is used so that auxiliary acceleration, focusing electrodes are provided on the cathode side of the accelerating electrode or on the main lens side, rectangular or similarly shaped electronic transmission apertures are formed in each of a control electrode, an accelerating electrode and an auxiliary accelerating electrode, the above described control electrode is arranged so that the major axis direction of the electronic transmission aperture can become vertical to the main scanning 2b direction of the electron beam, the electronic transmission aperture of either the above described accelerating electrode or the auxiliary acceleration focusing electrode are arranged so that the major axis direction thereof can become orthogonal to the major axis direction of the electronic transmission aperture of the above described control electrode, the electronic transmission aperture of the other electrode is arranged so that the major axis direction can become parallel to the major axis direction of the electronic transmission aperture of the above described control electrode, or when a cathode-ray-tube having an electron gun is used so that an auxiliary acceleration, focusing electrode is arranged on the cathode side of the accelerating electrode or on the main control electrode, a round shaped or a rectangular electronic transmission aperture is formed at each of the control electrode, accelerating electrode and auxiliary accelerating electrode, the dynamic voltage is applied to the auxiliary acceleration focusing electrode so as to reduce the deterioration of the resolution with the voltage for correcting the focusing shift and astigmatism distortion in the picture scene vicinity portion being piled.
At the same time when the high frequency components are many through the detection of the frequency components of the reproducing image signal, the electron beams are made long vertically. When the low frequency components are many, the electron beams are made long horizontally. Higher fidelity, higher acuteness and higher resolution of the reproduced images may be achieved across the whole picture scenes without the moire phenomenon being caused.
The present invention corrects the focus shift of the electronic beam spot of the picture scene and its vicinity portion, and reduces astigmatism by the above described construction. The present invention controls the shape of the electron beam spot in accordance with the frequency component of the image signal across the whole picture scene, so that the bright point shape on the fluorescent screen can be selectively determined. An electron beam bright point of high current density is obtained and the light emitting saturation of the phosphor can be removed.
In the drawings:
Fig. 1 is a perspective exploded view showing an electron gun electrode construction of a CRT of a first embodiment of the present invention;
Fig. 2 is a perspective exploded view showing an electron gun electrode construction of a CRT of a second embodiment of the present invention;
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Fig. 3 is a spot shaped, control, dynamic prefocus driving circuit diagram of an electron beam in the first embodiment of the present invention;
Fig. 4 is a dynamic prefocus driving circuit diagram in the second embodiment of the present invention;
Figs. 5(a) to (j), show signal wave-form charts of the construction of Fig. 3 in the first embodiment of the present invention, and Figs. 6(a) to (j), show signal wave-form charts of the construction of Fig. 4 in the second embodiment of the present invention.
The present invention reduces the peripheral focus deterioration due to a large image scene, by the flattening operation by a dynamic prefocus driving circuit composed of five blocks to achieve improvements in the fidelity, acuteness and resolution of the images across the whole picture scene.
(Embodiment 1) One embodiment of the present invention will now be described with reference to the drawings.
Fig. 1 shows the electrode construction of a CRT to be used in the present circuit. Secondary electrodes are two in number. They are both rectangular and in the shape of the electron beam transmission aperture. The major axes of the respective rectangles are orthogonal. It is characteristic that the spot shape of the electron beam by the voltage applied to the electrode can be controlled (Japanese Patent Publication No. 61-6970).
First, a dynamic astigmatism correcting voltage generating portion 19 will be described in Fig. 3. Image signals of the terminal 10 pass through a vertical saw tooth wave generating circuit 11 and a vertical parabolic wave generating circuit 12 to form vertical parabolic waves. The same image signals pass through a horizontal pulse wave generating circuit 13, a phase shift control circuit 14, and a horizontal parabolic wave generating circuit 15 to obtain the horizontal parabolic waves. The vertical parabolic waves of the outputs of these circuits and the horizontal parabolic wave of the outputs of these circuits are added at a first adding circuit 16, and are inputted into a V G2S driving voltage generating portion 59.
A horizontal direction electron beam shaped detecting deciding portion 29 is composed of a high-pass component detecting circuit 21, a brightness signal component detecting circuit 22 and a second adding circuit 23. An image signal on the terminal 10 passes through the high-pass component detecting circuit 21, and signals equivalent to the outline among the image signals are outputted. The same image signal passes through the brightness signal component detecting circuit 22 and signals equivalent to the brightness among the image signals are outputted. Both the above described outputs are added by the second adding circuit 23 and are inputted to an electron beam form control circuit 49. The signal decides the spot size in the horizontal direction and at the same time, has a level adjusting function.
A vertical direction electron beam form detection deciding portion 39 is composed of a delay line 31 and a subtracting circuit 32 ~or delaying the image signal by lH.
A signal of the difference between the original signal and the signal delayed by lH is made by a subtracting circuit 32, and is inputted to an electron beam form controlling circuit 49.
The signal decides the spot size in the vertical direction and, at the same time, has a level adjusting function.
In the electron beam shaped control circuit 49, signals for a horizontal direction electron beam from the detection deciding portion 29 and signals for the vertical direction electron beam from the detection deciding portion 39 are inputted. They are converted into signals for controlling the electron beam form to input the output signal into a third adding circuit 51.
The V G2S driving voltage generating portion 59 is composed of the third adding circuit 51 and a V G2 voltage generating circuit 52. A voltage V G2S controlled by the third adding circuit 51 is applied to an auxiliary acceleration focusing electrode G2S (4 of Fig. 1).
Figs. 5(a) to (j) show signal wave-form charts of the above described operations. Figs. 5(a) to (j) use asymmetrical shafts in Fig. 1. The beam spot form in the focus is controlled in the electron beam shape.
By the use of the above described prefocus driving circuit, the deflection distortion and the geometric distortion of the electronic beam by the non-uniform magnetic deflection are improved. Further, the vertical direction and horizontal direction frequency component of the image signals are detected. The electron beam form is controlled (the formation of the vertical length beam spot and the horizontal length beam spot are freely effected so that the brightness point shape on the fluorescent screen can be selectively determined) so that a display apparatus of higher acuteness, higher resolution can be obtained.
(Embodiment 2) A second embodiment of the present invention will be described hereinafter with reference to the drawings.
The electrode construction of a CRT to be used in the circuit of the presen~ invention will be described in Fig. 2.
The second electrodes are two in number. They are both round and square in the shape of the electron beam transmission aperture. It is characteristic that the focusing of the electronic beam spot can be controlled by the voltage to be applied to the electrode. The dynamic focusing voltage generating portion 60 will be described in Fig. 4. The image signals of the terminal 10 pass through a vertical saw tooth wave generating circuit 11 and a vertical parabolic wave generating circuit 12 to form vertical parabolic waves. The same image signals pass through the horizontal pulse wave generating circuit 13, the phase-shifting control circuit 14, and the horizontal parabolic wave generating circuit 15 to obtain the horizontal parabolic waves. The vertical parabolic waves of the output of the vertical parabolic wave generating circuit 12 and the horizontal parabolic waves of the output of the horizontal parabolic wave generating circuit 15 are added by the first adding circuit 16, and are inputted to the V G2S
driving voltage generating portion 59.
The horizontal direction beam focusing detection deciding portion 29 is composed of the high-pass component detecting circuit 21, the brightness signal component detecting circuit 22, and the second adding circuit 23. The image signals of the terminal 10 pass through the high-pass component detecting circuit 21, and signals equivalent to the outlines among the image signals are outputted. The same image signals pass through the brightness signal component detecting circuit 22, and signals equivalent to the brightness in the image signal are outputted. Both the above described outputs are added by the second adding circuit 23 and are inputted to the electron beam focus control circuit 63. The signal decides the spot size, and at the same time, has a level adjusting function.
The vertical direction beam focus detection deciding portion 62 is composed of the delay line 31 and the subtracting circuit 32 for delaying by lH the image signals.
Signals of difference between the original signals and the lH
delayed signals by the subtracting circuit 32 are made and are inputted to the electron beam focus control circuit 63. The signal decides the spot size and, at the same time, has a level adjusting function.
In the electron beam focusing control circuit 63, signals for the horizontal direction beam focus detection deciding portion 61 and the signals for the vertical direction beam focus detection deciding portion 62 are inputted. They are converted into the electron beam focusing signals to input the output signals into a third adding circuit 51.
The V G2S driving voltage generating portion 59 is composed of the third adding circuit 51 and a V G2S voltage generating circuit 52 so as to apply a voltage V G2S
controlled by the third adding circuit 51 to the auxiliary acceleration focusing electrode G2S (8 of Fig. 2).
By the use of the above described dynamic prefocus driving circuit, the difference in focus between the central portion of the picture screen and its vicinity portion is removed. Further, the vertical direction and horizontal direction frequency component of the image signal is detected to control the focusing of the electron beam, so that a display apparatus of higher acuteness and higher resolution may be obtained. Figs. 6(a) to (j) show signal wave-form charts of the above described operations. Figs. 6(a) to (j) use a symmetrical shaft of Fig. 2 as a CRT. The beam spot in focus changes with respect to the increase or decrease in the beam current.
As is clear from the above described embodiment, the present invention improves the focus shift of the electron beam around the picture screen of the CRT, and further controls the focus of the electron beam in accordance with the component of the image signal across the whole picture screen, so that a display apparatus of higher fidelity, higher acuteness and higher resolution can be obtained.
As is clear from the above described embodiment, according to the present invention, the focusing shift, astigmatism distortion of the electron beam causing the picture scene peripheral portion to be accompanied by a flattening of the large picture scene CRT, are reduced or prevented. The spot shape of the electron beam is controlled in its vertical length, and horizontal length in accordance with the components of the image signals across the whole picture scene, so that a display apparatus of higher fidelity, higher acuteness and higher resolution of the images can be obtained.
Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be noted here that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as included therein.
" ,~
The present invention generally relates to a display apparatus for image reproduction, character display or the like using a cathode-ray tube (hereinafter referred to as CRT).
An in line shaped self convergence CRT system (hereinafter referred to as non-uniform magnetic system) in a television field causes considerable resolution deterioration when electronic beams are deflected with deflection yokes.
Especially, the deterioration in picture scenes and their circumferences is noticeable. Various proposals have been made to settle this problem. A dynamic focusing system is available to remove the difference in focusing, for example, between the central portion of the picture scene and the circumference portion. In order to remove the deflection distortion in the circumference, there are an electromagnetic correcting system as disclosed in Japanese Laid-Open Patent Publication No. 57-84683, and an electrostatic system represented by a DAF system.
Exceptional resolution deterioration is caused in the deflection of an electron beam in a wide range, even if the yoke is a uniform magnetic field deflection yoke. Especially, the deterioration in the picture scene circumference is exceptional. A proposal similar to the above description is provided and introduced.
The above described Japanese Laid-Open Patent Publication No. 57-84683 is complicated in construction and composition, and is of high cost. The electrostatic system to be represented by the DAF system is high in applied voltage, with problems in terms of reliability and cost.
Accordingly, the present invention has been developed with a view to substantially eliminating the above discussed drawbacks inherent in the prior art and has for its essential object to provide an improved display apparatus.
Another object of the present invention is to provide an improved apparatus in which the resolution deterioration in the picture scene and its vicinities is corrected with a prefocus lens portion of an electron gun to obtain an optimum image, with the electronic beam shape being modulated with parabolic wave forms of horizontal, vertical periods of the parabolic wave forms and frequency components of the image signals (hereinafter referred to as to a dynamic prefocus system).
Still another object of the present invention is to provide an improved display apparatus in which a moire phenomenon caused by correlation between the electronic beam spot and a shadow mask is removed so as to reduce the light emission saturation phenomenon of the phosphor caused by concentration of the electron beam spots.
In accomplishing these and other objects, the present invention adopts a dynamic prefocusing system. In accordance with one aspect of the present invention there is provided a display apparatus including a CRT, said apparatus comprising:
a dynamic focus correction voltage generator, said dynamic focus correction voltage generator generating a dynamic focus correction voltage signal consisting of vertical and horizontal cyclic parabolic waveforms and supplying said signal to at least one main focus grid of the CRT; a horizontal direction electron beam focusing determination circuit, said horizontal direction electron beam focusing determination circuit generating a horizontal direction spot size signal in accordance with a high-pass component and luminance component contained within an image signal input thereto; a vertical direction electron beam focusing determination circuit, said vertical direction electron beam focusing determination circuit generating a vertical direction spot size signal in accordance with a low-pass component contained within said image signal input thereto; and an electron beam focusing controller, said electron beam focusing controller receiving said horizontal direction spot size signal generated by said horizontal direction electron beam -2a focusing determination circuit and said vertical direction spot size signal generated by said vertical direction electron beam focusing determination circuit and outputting a signal in response thereto; and a driving voltage generator, said driving voltage generator receiving said dynamic focus correction voltage signal and adding it to the output signal of said electron beam focusing controller and supplying a resultant added signal to at least one prefocus grid of the CRT.
In accordance with another aspect of the present invention there is provided a method of controlling a focus of a CRT included within a display apparatus, said method comprising the steps of: generating a signal consisting of a vertical cyclic parabolic waveform and a horizontal cyclic parabolic waveform and using the generated signal to control a dynamic focus of the CRT by supplying the generated signal to a main focus lens of the CRT; generating a horizontal direction spot size signal generated in accordance with a high-pass component and luminance component contained within an image signal and a vertical direction spot size signal generated in accordance with a low-pass component contained within the image signal; combining the horizontal and vertical direction spot size signals to form a combined signal; adding the generated signal to the combined signal to generate a signal which is applied to a prefocus lens of the CRT for controlling a dynamic prefocus of the CRT.
As disclosed in laid-open Japanese Patent Publication No.
53-105168, published September 13, 1978 in the name of Kouzou Tateishi, when a cathode-ray-tube having an electron gun is used so that auxiliary acceleration, focusing electrodes are provided on the cathode side of the accelerating electrode or on the main lens side, rectangular or similarly shaped electronic transmission apertures are formed in each of a control electrode, an accelerating electrode and an auxiliary accelerating electrode, the above described control electrode is arranged so that the major axis direction of the electronic transmission aperture can become vertical to the main scanning 2b direction of the electron beam, the electronic transmission aperture of either the above described accelerating electrode or the auxiliary acceleration focusing electrode are arranged so that the major axis direction thereof can become orthogonal to the major axis direction of the electronic transmission aperture of the above described control electrode, the electronic transmission aperture of the other electrode is arranged so that the major axis direction can become parallel to the major axis direction of the electronic transmission aperture of the above described control electrode, or when a cathode-ray-tube having an electron gun is used so that an auxiliary acceleration, focusing electrode is arranged on the cathode side of the accelerating electrode or on the main control electrode, a round shaped or a rectangular electronic transmission aperture is formed at each of the control electrode, accelerating electrode and auxiliary accelerating electrode, the dynamic voltage is applied to the auxiliary acceleration focusing electrode so as to reduce the deterioration of the resolution with the voltage for correcting the focusing shift and astigmatism distortion in the picture scene vicinity portion being piled.
At the same time when the high frequency components are many through the detection of the frequency components of the reproducing image signal, the electron beams are made long vertically. When the low frequency components are many, the electron beams are made long horizontally. Higher fidelity, higher acuteness and higher resolution of the reproduced images may be achieved across the whole picture scenes without the moire phenomenon being caused.
The present invention corrects the focus shift of the electronic beam spot of the picture scene and its vicinity portion, and reduces astigmatism by the above described construction. The present invention controls the shape of the electron beam spot in accordance with the frequency component of the image signal across the whole picture scene, so that the bright point shape on the fluorescent screen can be selectively determined. An electron beam bright point of high current density is obtained and the light emitting saturation of the phosphor can be removed.
In the drawings:
Fig. 1 is a perspective exploded view showing an electron gun electrode construction of a CRT of a first embodiment of the present invention;
Fig. 2 is a perspective exploded view showing an electron gun electrode construction of a CRT of a second embodiment of the present invention;
,~ ~.
Fig. 3 is a spot shaped, control, dynamic prefocus driving circuit diagram of an electron beam in the first embodiment of the present invention;
Fig. 4 is a dynamic prefocus driving circuit diagram in the second embodiment of the present invention;
Figs. 5(a) to (j), show signal wave-form charts of the construction of Fig. 3 in the first embodiment of the present invention, and Figs. 6(a) to (j), show signal wave-form charts of the construction of Fig. 4 in the second embodiment of the present invention.
The present invention reduces the peripheral focus deterioration due to a large image scene, by the flattening operation by a dynamic prefocus driving circuit composed of five blocks to achieve improvements in the fidelity, acuteness and resolution of the images across the whole picture scene.
(Embodiment 1) One embodiment of the present invention will now be described with reference to the drawings.
Fig. 1 shows the electrode construction of a CRT to be used in the present circuit. Secondary electrodes are two in number. They are both rectangular and in the shape of the electron beam transmission aperture. The major axes of the respective rectangles are orthogonal. It is characteristic that the spot shape of the electron beam by the voltage applied to the electrode can be controlled (Japanese Patent Publication No. 61-6970).
First, a dynamic astigmatism correcting voltage generating portion 19 will be described in Fig. 3. Image signals of the terminal 10 pass through a vertical saw tooth wave generating circuit 11 and a vertical parabolic wave generating circuit 12 to form vertical parabolic waves. The same image signals pass through a horizontal pulse wave generating circuit 13, a phase shift control circuit 14, and a horizontal parabolic wave generating circuit 15 to obtain the horizontal parabolic waves. The vertical parabolic waves of the outputs of these circuits and the horizontal parabolic wave of the outputs of these circuits are added at a first adding circuit 16, and are inputted into a V G2S driving voltage generating portion 59.
A horizontal direction electron beam shaped detecting deciding portion 29 is composed of a high-pass component detecting circuit 21, a brightness signal component detecting circuit 22 and a second adding circuit 23. An image signal on the terminal 10 passes through the high-pass component detecting circuit 21, and signals equivalent to the outline among the image signals are outputted. The same image signal passes through the brightness signal component detecting circuit 22 and signals equivalent to the brightness among the image signals are outputted. Both the above described outputs are added by the second adding circuit 23 and are inputted to an electron beam form control circuit 49. The signal decides the spot size in the horizontal direction and at the same time, has a level adjusting function.
A vertical direction electron beam form detection deciding portion 39 is composed of a delay line 31 and a subtracting circuit 32 ~or delaying the image signal by lH.
A signal of the difference between the original signal and the signal delayed by lH is made by a subtracting circuit 32, and is inputted to an electron beam form controlling circuit 49.
The signal decides the spot size in the vertical direction and, at the same time, has a level adjusting function.
In the electron beam shaped control circuit 49, signals for a horizontal direction electron beam from the detection deciding portion 29 and signals for the vertical direction electron beam from the detection deciding portion 39 are inputted. They are converted into signals for controlling the electron beam form to input the output signal into a third adding circuit 51.
The V G2S driving voltage generating portion 59 is composed of the third adding circuit 51 and a V G2 voltage generating circuit 52. A voltage V G2S controlled by the third adding circuit 51 is applied to an auxiliary acceleration focusing electrode G2S (4 of Fig. 1).
Figs. 5(a) to (j) show signal wave-form charts of the above described operations. Figs. 5(a) to (j) use asymmetrical shafts in Fig. 1. The beam spot form in the focus is controlled in the electron beam shape.
By the use of the above described prefocus driving circuit, the deflection distortion and the geometric distortion of the electronic beam by the non-uniform magnetic deflection are improved. Further, the vertical direction and horizontal direction frequency component of the image signals are detected. The electron beam form is controlled (the formation of the vertical length beam spot and the horizontal length beam spot are freely effected so that the brightness point shape on the fluorescent screen can be selectively determined) so that a display apparatus of higher acuteness, higher resolution can be obtained.
(Embodiment 2) A second embodiment of the present invention will be described hereinafter with reference to the drawings.
The electrode construction of a CRT to be used in the circuit of the presen~ invention will be described in Fig. 2.
The second electrodes are two in number. They are both round and square in the shape of the electron beam transmission aperture. It is characteristic that the focusing of the electronic beam spot can be controlled by the voltage to be applied to the electrode. The dynamic focusing voltage generating portion 60 will be described in Fig. 4. The image signals of the terminal 10 pass through a vertical saw tooth wave generating circuit 11 and a vertical parabolic wave generating circuit 12 to form vertical parabolic waves. The same image signals pass through the horizontal pulse wave generating circuit 13, the phase-shifting control circuit 14, and the horizontal parabolic wave generating circuit 15 to obtain the horizontal parabolic waves. The vertical parabolic waves of the output of the vertical parabolic wave generating circuit 12 and the horizontal parabolic waves of the output of the horizontal parabolic wave generating circuit 15 are added by the first adding circuit 16, and are inputted to the V G2S
driving voltage generating portion 59.
The horizontal direction beam focusing detection deciding portion 29 is composed of the high-pass component detecting circuit 21, the brightness signal component detecting circuit 22, and the second adding circuit 23. The image signals of the terminal 10 pass through the high-pass component detecting circuit 21, and signals equivalent to the outlines among the image signals are outputted. The same image signals pass through the brightness signal component detecting circuit 22, and signals equivalent to the brightness in the image signal are outputted. Both the above described outputs are added by the second adding circuit 23 and are inputted to the electron beam focus control circuit 63. The signal decides the spot size, and at the same time, has a level adjusting function.
The vertical direction beam focus detection deciding portion 62 is composed of the delay line 31 and the subtracting circuit 32 for delaying by lH the image signals.
Signals of difference between the original signals and the lH
delayed signals by the subtracting circuit 32 are made and are inputted to the electron beam focus control circuit 63. The signal decides the spot size and, at the same time, has a level adjusting function.
In the electron beam focusing control circuit 63, signals for the horizontal direction beam focus detection deciding portion 61 and the signals for the vertical direction beam focus detection deciding portion 62 are inputted. They are converted into the electron beam focusing signals to input the output signals into a third adding circuit 51.
The V G2S driving voltage generating portion 59 is composed of the third adding circuit 51 and a V G2S voltage generating circuit 52 so as to apply a voltage V G2S
controlled by the third adding circuit 51 to the auxiliary acceleration focusing electrode G2S (8 of Fig. 2).
By the use of the above described dynamic prefocus driving circuit, the difference in focus between the central portion of the picture screen and its vicinity portion is removed. Further, the vertical direction and horizontal direction frequency component of the image signal is detected to control the focusing of the electron beam, so that a display apparatus of higher acuteness and higher resolution may be obtained. Figs. 6(a) to (j) show signal wave-form charts of the above described operations. Figs. 6(a) to (j) use a symmetrical shaft of Fig. 2 as a CRT. The beam spot in focus changes with respect to the increase or decrease in the beam current.
As is clear from the above described embodiment, the present invention improves the focus shift of the electron beam around the picture screen of the CRT, and further controls the focus of the electron beam in accordance with the component of the image signal across the whole picture screen, so that a display apparatus of higher fidelity, higher acuteness and higher resolution can be obtained.
As is clear from the above described embodiment, according to the present invention, the focusing shift, astigmatism distortion of the electron beam causing the picture scene peripheral portion to be accompanied by a flattening of the large picture scene CRT, are reduced or prevented. The spot shape of the electron beam is controlled in its vertical length, and horizontal length in accordance with the components of the image signals across the whole picture scene, so that a display apparatus of higher fidelity, higher acuteness and higher resolution of the images can be obtained.
Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be noted here that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as included therein.
" ,~
Claims (3)
1. A display apparatus including a CRT, said apparatus comprising:
a dynamic focus correction voltage generator, said dynamic focus correction voltage generator generating a dynamic focus correction voltage signal consisting of vertical and horizontal cyclic parabolic waveforms and supplying said signal to at least one main focus grid of the CRT;
a horizontal direction electron beam focusing determination circuit, said horizontal direction electron beam focusing determination circuit generating a horizontal direction spot size signal in accordance with a high-pass component and luminance component contained within an image signal input thereto;
a vertical direction electron beam focusing determination circuit, said vertical direction electron beam focusing determination circuit generating a vertical direction spot size signal in accordance with a low-pass component contained within said image signal input thereto; and an electron beam focusing controller, said electron beam focusing controller receiving said horizontal direction spot size signal generated by said horizontal direction electron beam focusing determination circuit and said vertical direction spot size signal generated by said vertical direction electron beam focusing determination circuit and outputting a signal in response thereto; and a driving voltage generator, said driving voltage generator receiving said dynamic focus correction voltage signal and adding it to the output signal of said electron beam focusing controller and supplying a resultant added signal to at least one prefocus grid of the CRT.
a dynamic focus correction voltage generator, said dynamic focus correction voltage generator generating a dynamic focus correction voltage signal consisting of vertical and horizontal cyclic parabolic waveforms and supplying said signal to at least one main focus grid of the CRT;
a horizontal direction electron beam focusing determination circuit, said horizontal direction electron beam focusing determination circuit generating a horizontal direction spot size signal in accordance with a high-pass component and luminance component contained within an image signal input thereto;
a vertical direction electron beam focusing determination circuit, said vertical direction electron beam focusing determination circuit generating a vertical direction spot size signal in accordance with a low-pass component contained within said image signal input thereto; and an electron beam focusing controller, said electron beam focusing controller receiving said horizontal direction spot size signal generated by said horizontal direction electron beam focusing determination circuit and said vertical direction spot size signal generated by said vertical direction electron beam focusing determination circuit and outputting a signal in response thereto; and a driving voltage generator, said driving voltage generator receiving said dynamic focus correction voltage signal and adding it to the output signal of said electron beam focusing controller and supplying a resultant added signal to at least one prefocus grid of the CRT.
2. A method of controlling a focus of a CRT included within a display apparatus, said method comprising the steps of:
generating a signal consisting of a vertical cyclic parabolic waveform and a horizontal cyclic parabolic waveform and using the generated signal to control a dynamic focus of the CRT by supplying the generated signal to a main focus lens of the CRT;
generating a horizontal direction spot size signal generated in accordance with a high-pass component and luminance component contained within an image signal and a vertical direction spot size signal generated in accordance with a low-pass component contained within the image signal;
combining the horizontal and vertical direction spot size signals to form a combined signal;
adding the generated signal to the combined signal to generate a signal which is applied to a prefocus lens of the CRT for controlling a dynamic prefocus of the CRT.
generating a signal consisting of a vertical cyclic parabolic waveform and a horizontal cyclic parabolic waveform and using the generated signal to control a dynamic focus of the CRT by supplying the generated signal to a main focus lens of the CRT;
generating a horizontal direction spot size signal generated in accordance with a high-pass component and luminance component contained within an image signal and a vertical direction spot size signal generated in accordance with a low-pass component contained within the image signal;
combining the horizontal and vertical direction spot size signals to form a combined signal;
adding the generated signal to the combined signal to generate a signal which is applied to a prefocus lens of the CRT for controlling a dynamic prefocus of the CRT.
3. A display apparatus including a CRT, said apparatus comprising:
a first generator for generating a first generated signal based on vertical and horizontal cyclic parabolic waveforms, and applying said first generated signal to a main focus lens of the CRT for controlling a dynamic focus of the CRT;
a controller for generating a second generated signal based on a high-pass component and a luminance component contained within an image signal and a low-pass component contained within the image signal; and a voltage generator for adding said first and second generated signals, generating a dynamic prefocus voltage in response thereto, and applying said dynamic prefocus voltage to a prefocus lens of the CRT to control the prefocus of the CRT.
a first generator for generating a first generated signal based on vertical and horizontal cyclic parabolic waveforms, and applying said first generated signal to a main focus lens of the CRT for controlling a dynamic focus of the CRT;
a controller for generating a second generated signal based on a high-pass component and a luminance component contained within an image signal and a low-pass component contained within the image signal; and a voltage generator for adding said first and second generated signals, generating a dynamic prefocus voltage in response thereto, and applying said dynamic prefocus voltage to a prefocus lens of the CRT to control the prefocus of the CRT.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3154437A JP2822694B2 (en) | 1991-06-26 | 1991-06-26 | Display device |
| JP3-154437 | 1991-06-26 | ||
| JP3-336537 | 1991-12-19 | ||
| JP3336537A JP3057864B2 (en) | 1991-12-19 | 1991-12-19 | Display device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2072191A1 CA2072191A1 (en) | 1992-12-27 |
| CA2072191C true CA2072191C (en) | 1999-01-12 |
Family
ID=26482715
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2072191 Expired - Fee Related CA2072191C (en) | 1991-06-26 | 1992-06-23 | Display apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2072191C (en) |
-
1992
- 1992-06-23 CA CA 2072191 patent/CA2072191C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2072191A1 (en) | 1992-12-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |