JPH06138831A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To obtain a display image of high quality by preventing an electron beam from traveling zigzag along a horizontal line and becoming beltlike and a black stripe separating the image from being generated at the time of low resolution. CONSTITUTION:The cathode-ray tube which makes a raster scan with the electron beam and is selectable in resolution is constituted by arranging an electrostatic deflector 24 which deflects the electron beam vertically between the electron gun 40 and electromagnetic yoke 36; when the cathode-ray tube operates with low resolution, a deflection signal generator 60 supplies a high-frequency, low-amplitude deflection signal to the electrostatic deflector.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a cathode ray tube, and more particularly to a cathode ray tube including a high frequency deflection device.

[0002]

In some display systems, the display image is formed by scanning an electron beam over a target surface in a raster scan pattern. The pattern consists of about 200-2000 horizontal lines arranged side by side along the vertical axis. If the number of lines is different, the resolution is different,
The higher the number of lines, the higher the resolution.

Some raster scan display systems have multiple format display capabilities. These systems are capable of selectively forming display images in a number of different formats corresponding to different resolutions. A multi-format display system is desirable because it can be used with several video formats as well as computer graphics generators with different resolutions. The multi-format display function is incorporated in, for example, direct-view CRT displays and electron beam addressed light modulators used in projection displays.

When the electron beam impinges on the target surface of a cathode ray tube (hereinafter CRT), the electron beam forms an image spot of unique spot size. In conventional multi-format display systems, the electron beam spot size is single and fixed for all display formats. Usually, the fixed spot size is relatively small so that the vertical width of the horizontal line of the electron beam in the raster scan can be used in the highest resolution display format. However, a single fixed spot size horizontal line will have the same fixed width for all other display formats.

[0005]

5A and 5B show a target plane 1 showing a conventional raster scan display format.
0 is a front view of FIG. 0, and a substantially horizontal line 12 has a vertical axis 14
Are spaced along. The width 15 of the line 12 along the vertical axis 14 is substantially fixed and relatively narrow.

FIG. 5A illustrates a high resolution format condition in which adjacent lines 12 are separated by a relatively small gap 16 (larger for clarity in the figure). FIG. 5B shows the low resolution format with adjacent lines 12 separated by a relatively large gap 18. Gaps 18 are an undesired result of using lines 12 of width 15 for all display formats.

In particular, the gap 18 separates the displayed image, that is, makes it discontinuous, thus degrading the quality of the displayed image. In a projection display system, a large gap 18 between the lines 12 on the target surface 10 that is unacceptable causes a large black stripe in the projected display image, reducing the light output of the display. In some low resolution formats, the projected line 12 is narrower than the black stripe, so there is insufficient light in the projected image to form a discernible display.

A large gap 18 that exceeds the allowable range between adjacent lines 12 of the displayed image occurs when the range of resolution is relatively wide. For example, a large gap 1 that exceeds the allowable range
8 occurs when the highest resolution display format consists of about 1.5 times more lines than the lowest resolution display format. In order to prevent the occurrence of a large gap 18 that exceeds the allowable range, the resolution range of the multi-format display is set so that the highest resolution display format is smaller than about 1.5 times the lowest resolution display format. Restrict.

Therefore, an object of the present invention is to provide a multi-format display CRT which can obtain a good display in any of the multi-display formats in which the number of horizontal lines is widely varied.

Another object of the present invention is to provide a CRT which does not produce black stripes which discontinue a displayed image at low resolution even with an electron beam having a small spot size.

[0011]

SUMMARY OF THE INVENTION The present invention is a multiple format raster scan display capable of providing high quality display images in a wide range of resolutions. In the preferred embodiment, the display includes a CRT that emits an electron beam along a beam axis toward a target surface. C
The RT includes an electromagnetic deflection yoke that deflects the electron beam in the horizontal and vertical directions to form a raster scan pattern on the target surface. The raster scan pattern is formed by selectively including 200 to 2000 substantially parallel horizontal lines arranged along the vertical axis.

The electrostatic deflector is located between the electron gun and the electromagnetic yoke and is oriented so as to deflect the electron beam in the vertical direction. The deflection signal generator supplies a high frequency, low amplitude deflection signal to the electrostatic deflector when the display device operates at a low resolution. The electrostatic deflector imparts high frequency and low amplitude deflection so that the electron beam travels in a zigzag manner along a horizontal line, and a wide band is formed instead of the conventional thin line.

For each of the low resolution raster scan patterns, the deflection signal generator produces a high frequency deflection signal of a corresponding signal amplitude. Therefore, the electrostatic deflector acts to form a horizontal band of sufficient width to obtain a high quality displayed image.

[0014]

1 is a sectional view of a CRT 20 of the present invention. The CRT 20 has an evacuated bulb 22 containing a high frequency deflector 24. The bulb 22 includes a tubular glass neck 26, a glass funnel 28 and a light transmissive or transparent glass faceplate 30. Fluorescent material layer 3
2 is attached to the inner surface of the face plate 30 to form a target surface 34. In conventional direct view display systems, the target surface 34 acts as a display screen.

The electromagnetic deflection yoke 36 is arranged at the end of the funnel portion 28 that is connected to the neck portion 26, and scans the target surface 34 with an electron beam in a raster scanning pattern (not shown). The deflection yoke 36 includes horizontal and vertical deflection coils (not shown) that deflect the electron beam in the horizontal direction 38a and the vertical direction 38b, respectively.

The electron gun 40 is disposed within the glass neck 16 and includes a cathode 42 mounted at the end of the CRT 20 opposite the target surface 34. Cathode 42
Is supplied with a potential of about 0V. An appropriate video control signal having an amplitude of several tens of volts is supplied to the electron gun 40, and the electron beam is modulated according to the video signal. The acceleration element 46 is normally supplied with a potential of about 500V.

FIG. 2 is a perspective view of an electrostatic deflection element used in the CRT of the present invention. The electron gun 40 has a target surface 3
An electron beam is generated which propagates along the tube axis 48 in a direction 50 towards 4. The beam passes through a high frequency deflector 24 that includes a pair of tubular deflection elements 52 and 54. Deflector 5
As shown in the side view of FIG. 1, reference numeral 2 denotes an upstream end 56a perpendicular to the pipe shaft 48 and a downstream end 56 forming an acute angle with the pipe shaft 48.
b. Similarly, as shown in the cross-sectional view of FIG. 1, the deflection element 54 has an upstream end 58a forming an acute angle with the tube axis 48 and a downstream end 58b forming a right angle with the tube axis. The ends 56b and 58a of the cross-section are substantially parallel to each other and intersect the axis 48, preferably at an angle of 45 °.

The deflection signal generator 60 supplies a DC anode voltage of approximately 800V to each of the deflection elements 52 and 54 via deflection signal input terminals 62a and 62b, respectively. Further, the deflection signal generator 60 supplies a sinusoidal deflection signal having an amplitude in the range of 0 to about 10 V (peak-peak voltage) to the deflection element 54 via the input terminal 62b. The deflection signal has a high frequency which is about twice, and preferably about three times greater than the predetermined highest video signal. The predetermined maximum video signal frequency is about 5 MHz for the NTSC video standard and 100 MHz for high resolution graphic display systems. The amplitude of the deflection signal is selected according to the resolution with which the CRT 20 operates.

The high frequency deflection signal provided to deflection element 54 functions with deflection element 52, which is an electrostatic deflector.
In particular, the ends 56b and 58a form a region 64 in which the elements 52 and 54 are arranged facing each other in the direction perpendicular to the axis 48, and by this configuration the elements 52 and 54 are arranged so that the electrostatic deflector 2 is provided.
Function as 4. Tubular elements 52 and 54 are typically cylindrical in shape and are preferred over conventional parallel plate electrostatic deflectors for simplicity of manufacture. Moreover, electromagnetic deflectors that are deflectable at sufficiently high frequencies are relatively expensive, which makes them undesirable.

The CRT 20 includes a set of aberration correction plates 70 and a bipotential focusing lens 72 that operate in a known manner. Aberration correction by the corrector plate 70 and focusing by the focus lens 72 work together to form a relatively small electron beam spot size on the target surface 34 that can also be used in high resolution display formats.

FIGS. 3A and 3B show bands 74a and 74, respectively.
3b is a front view of target surface 34 formed in accordance with the present invention. FIG. Bands 74a and 74b oscillate vertically on the target surface 34 and extend horizontally in a dense sinusoidal electron beam scan (in the figure, the bands are horizontal except for the bottom). It has been enlarged in.). The sinusoidal shape of bands 74a and 74b is produced by the sinusoidal form of the deflection signal. The sinusoidal signal is desired to be sinusoidal in shape because it is simple to generate and the deflection signal generator 60 can be relatively simple and inexpensive to manufacture. However, other periodic waveforms may be used, for example triangular waves or other complex waveforms.

3A and 3B show bands 74a and 74b.
Shows different low resolution formats formed with different widths 76a and 76b. The widths 76a and 76b are determined by the amplitude of the deflection signal generated by the deflection signal generator 60. The signal amplitude is adjusted so that the adjacent bands 74a and 74b of FIGS. 3A and 3B contact in the direction of the vertical axis 14. CRT20 for high resolution formats
Draws a raster scan pattern in the form of a CRT shown in FIG. 5A.

FIG. 4 illustrates a preferred electron beam addressed projection display system 110 using the CRT of the present invention.
The display system 110 includes an exhaust bulb 112 having a ceramic body 114 having a light transmissive input window or faceplate 116 and a light transmissive output window 118 mounted on opposite sides thereof.

The light source 120 includes a projection lamp 122 and a reflector 124, which in turn directs light rays through an input lens system 126, a field lens 128 and a linear polarizer 130 to a faceplate 116. The input lens system 126 formats the size of the area illuminated by the light source 120, and the field lens system 128 directs the rays in the proper direction to propagate the output window 118.

The light exiting the output window 118 is projected by the projection lens system 132 through the linear polarizer 134 towards a distant display surface (not shown). The polarization filter 130 and the linear polarizer 134 are arranged such that their light transmission axes are parallel to each other. Light valve 110
However, it will be apparent to those skilled in the art to configure the polarizing filter 128 and analyzer 132 to operate such that the light transmission axes are orthogonal.

The light valve 110 includes the face plate 11
An internal liquid crystal cell 140 (see FIG. 4 for clarity) arranged in the path of the polarized projected light entering the bulb 112 via
Has been expanded. ) Has. The cell 140 includes a layer of nematic liquid crystal material sandwiched between a faceplate 116 and a thin optically transparent target substrate 144 having a target surface 145. Target substrate 144
Is formed of a suitable dielectric material such as glass, polyimide or mica.

The ends of the face plate 116 and substrate 144 are sealed to the body 140 with a ceramic frit seal material 150 or other suitable material. The transparent conductive film 146 of indium tin oxide (ITO) is
It covers the inner surface of the face plate 116 and acts as a back electrode for the cell. The target substrate 144 is separated from the film 146 by a predetermined distance by a plurality of spacers 148 having a substantially uniform height. Preferably, a large number of spacers (glass beads, or spacers made by photolithography) are fairly evenly distributed in the gap between the faceplate 116 and the target substrate 144.

The opposing surfaces of the target substrate 144 and the ITO film 146 are treated as homogenous or parallel surfaces to sandwich the nematic liquid crystal material therebetween. The alignment directions of the two faces are processed at right angles to produce a 90 ° twist cell. The desired surface orientation is performed by known methods such as vacuum deposition of silicon monoxide on the surface at an angle of about 5 °. Nematic liquid crystal materials suitable for use in cell 140 are available from E.I. ZL from Mark
I 2244 nematic liquid crystal material marketed under the trade name,
Or other similar material.

The molecules of the nematic liquid crystal material of layer 142 are
The polarization direction of the plane-polarized light transmitted through the cell is aligned such that it is rotated about 90 ° in the absence of the applied electric field or in the off state. When a potential difference is applied to a particular region of the liquid crystal material, the longitudinal axes of the liquid crystal molecules in that region tend to be oriented parallel to the generated electric field, thereby causing the cell 1
The amount of rotation in the polarization direction of light passing through the region of 40 is reduced.

If the potential difference across the cell 140 is large enough, the polarization direction of light passing through that region of the cell is
Substantially unchanged. Polarization filter 128 and analyzer 1
Since the light transmission axes of 32 are arranged in the same direction, they pass through the analyzer 132 when the cell is in the on state, and are sufficiently blocked by the analyzer 132 when the cell is in the off state. An intermediate amount of light transmission occurs in the area of the cell to which the intermediate amplitude potential difference is applied.

Tube 112 includes elongated first and second tubular glass necks 152a and 152b, one end of each neck being frit sealed to body 114 adjacent window 118. The writing electron gun 154a has a neck 1
It is attached in 52a. The electron gun 154a has substantially the same configuration as the electron gun 40 of FIG.
Directs the writing electron beam toward the target surface 145 instead of the direct-view target surface 34. Similarly, an erase electron gun (not shown) is mounted within neck 152b. The erasing electron gun has substantially the same configuration as the electron gun 40 in FIG.
Turn to 5.

The writing beam formed by the gun 154a is responsive to a video signal and is responsive to an appropriate electrical signal supplied from a deflection circuit (not shown) to an electromagnetic deflection yoke 162a supported on the neck portion 152a. Then, the target surface 145 of the target substrate 144 is raster-scanned. When the writing beam is scanned along a horizontal line on the target surface 145, the collector electrode 166.
Is supplied with a positive potential. Due to this positive potential, the collecting electrode 166 collects the secondary electrons emitted from the target surface 145 when the writing electron beam strikes the target surface. As a result, the areas of the target surface 145 that have been written or addressed by the writing electron beam have a positive electrostatic potential image that conveys video information to the liquid crystal layer 142, forming a display image.

The erasing beam formed by the erasing electron gun responds to an appropriate signal supplied from a deflection circuit (not shown) to the electromagnetic deflection yoke 162b supported by the neck portion 152b. The surface 145 is raster-scanned. The erasing beam causes
Collecting electrode 1 when scanned along a horizontal line above the
No positive potential is supplied to 66. As a result, the secondary electrons emitted from the target surface 145 return to the target surface, and the area of the target surface 145 near and at the point of impact of the erase beam loses the positive potential previously generated by the writing beam.

The erase beam is scanned along a horizontal line during the horizontal blanking period of the write beam, and conversely, the write beam is scanned along the horizontal line during the horizontal blanking period of the erase beam. The erase beam raster scan lags the write beam raster scan by about one-half image field. Thus, the horizontal line drawn by the writing beam is erased after 1/2 image field period.

Although the preferred embodiments of the present invention have been described above, it will be apparent to those skilled in the art that various modifications can be made without departing from the gist of the present invention. For example, C
RT10 may use electrostatic deflectors to form the raster scan pattern.

[0036]

According to the present invention, an electrostatic deflector for vertically deflecting an electron beam is arranged between the electron gun and the electromagnetic yoke, and when the display device operates at a low resolution, the deflection signal generator is used. , High frequency, low amplitude deflection signals are supplied to the electrostatic deflector. This prevents the electron beam from advancing in a zigzag pattern along the horizontal line to form a strip, and black stripes that separate the images at low resolution can be prevented, and a high-quality display image can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a CRT of the present invention.

FIG. 2 is a perspective view showing an electrostatic deflector which is a part of the CRT of the present invention.

FIG. 3 is a front view of a target surface for showing a raster scanning pattern according to the CRT of the present invention.

FIG. 4 is a perspective view showing an electron beam addressed liquid crystal light modulator using the CRT of the present invention.

FIG. 5 is a front view of a target surface for showing a conventional raster scanning pattern.

[Explanation of symbols]

 24 Electrostatic Deflection Means 34 Target Surface 36 Main Deflection Means 60 Deflection Signal Generator

Claims (1)

[Claims] 1. A main deflection means for deflecting an electron beam by drawing a raster scanning pattern on a target surface in a first direction in which a plurality of lines extend and in a second direction in which the plurality of lines are arranged at predetermined intervals, An electrostatic deflection unit that deflects the electron beam in a second direction, and a deflection signal that oscillates the electron beam in the second direction by a distance smaller than a predetermined interval between the plurality of lines are supplied to the electrostatic deflection unit. A cathode ray tube comprising a deflection signal generating means.