KR20000034846A - Laser CRT with electrostatic focusing of electron beam - Google Patents

Abstract

PURPOSE: A laser cathode ray tube is provided to increase a voltage difference between two electrodes in a focusing system without an accumulation of induction charges in a bulb and without giving rise to a discharge between the electrodes. CONSTITUTION: A laser cathode ray tube comprises a bulb(1) in which a laser screen(2) and an electron gun(3) are arranged. The electron gun(3) forms an electron beam, and comprises a cathode(4), a modulator(5), an acceleration electrode(6) and an anode(7). The laser cathode ray tube comprises a focusing system for focusing the electron beam to a screen(2), and consists of first and second cylindric electrodes(8,9). An addition electrode(12) surrounds the first and second cylindric electrodes(8,9) around a gap(11), and electrically insulates the first and second cylindric electrodes(8,9) sufficiently. The first electrode(8) and the addition electrode(12) are located at a position which is spaced apart from the gap(11), and are fixed by binding bars(13,14).

Description

Laser cathode ray tube with electrostatic focusing of electron beam {Laser CRT with electrostatic focusing of electron beam}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to quantum electronic devices, and more particularly to laser cathode ray tubes used in projection type television systems for representing images on large screens.

Projection-type television devices based on common cathode ray tubes with fluorescent film screens are widely used for displaying images on projection screens covering an area of several square meters. However, the size of the image represented on the projection screen of such a television device is limited because the fluorescent surface of the projection device cannot form a high density of light flux, thus making it difficult to form a television image having sufficient brightness and contrast. do.

An effective way to improve this characteristic of projection television systems is to use laser cathode ray tubes. (See US Pat. No. 3,558,956)

A distinct difference from conventional cathode ray tubes is that the light source of the laser cathode ray tube is a laser target, not a fluorescent screen. The laser target consists of a thin semiconductor single crystal plate with both parallel surfaces covered with a light reflecting coating. In general, one surface of the plate on which the electron beam is incident is provided with a metal coating film which is a fully reflective mirror, and a translucent mirror coating film is coated on the opposite surface of the plate. The mirror surfaces constitute an optical resonator, and the semiconductor plate between the mirror surfaces acts as an active medium of the laser excited by the electron beam. The laser target is fixed to a substrate which is a transparent dielectric material, which serves as an output window of the laser cathode ray tube and a heat sink of the laser target. Generally, the substrate is made of sapphire or the like having high thermal conductivity. The laser target, together with the transparent substrate, constitutes a laser screen of a laser cathode ray tube.

The electron beam is transmitted to the semiconductor plate through the metal coating film to induce spontaneous light emission. If the surface density of the current induced by the beam on the laser target exceeds the threshold, the power of the induced light emission is greater than the loss in the optical resonator, and the element on the target onto which the electron beam is incident causes laser light emission. As light passes through the resonators repeatedly, the spectrum of light narrows, resulting in monochromatic light. The laser light is radiated perpendicularly to the surface of the semiconductor plate through the translucent mirror coating and leaves the cathode ray tube through the sapphire output window.

Known laser cathode ray tubes (see VN Ulasjuk. Kvantoskopy. "Radio isvjaz", Moscow, 1988, page 105) have a bulb, a laser screen located inside the bulb, and an electron beam positioned inside the bulb to form an electron beam. An electron gun and a focusing system for focusing the electron beam on a laser screen. The focusing system consists of first and second electrodes which surround the electron beam and are arranged sequentially on the electron beam path, and ends of the first and second electrodes facing each other are separated from each other by a gap.

In known laser cathode ray tubes, the first electrode is provided with an adjustable low focusing voltage, while the second electrode is connected with a laser screen and is provided with a high acceleration voltage. Due to this potential difference, an electron lens is formed between the first electrode and the second electrode, and the electron lens electrostatics the electron beam on the laser screen by concentrating the divergent electron beam generated by the electron gun into a narrow converging beam. Provide focusing.

Because of the critical nature of the luminescence, the precise focusing of the beam in the laser cathode ray tube is much more important than the cathode ray tube with conventional fluorescent screens, especially when a high resolution can be provided through the laser cathode ray tube. At the same time, the electron beam of the laser cathode ray tube generally has much higher energy than a device with a fluorescent screen. In order to focus this beam correctly, it is necessary to increase the voltage difference between the first and second electrodes of the focusing system, which rises resulting in a discharge between the electrodes. When the gap between the first and second electrodes is enlarged to prevent such discharge, charges induced by the advancing electron beam accumulate on the inner surface of the cathode ray tube bulb near the gap. The induced charges affect the electron beam, and because the charge is scattered irregularly across the bulb surface, it interferes with the axial balance of the beam and renders the electron beam impossible for accurate focusing. In known laser cathode ray tubes, the gap size does not exceed 0.5 to 1.5 mm. However, the gap in the above range cannot increase the voltage difference between the electrodes more than 25 to 35 kV. This voltage is not sufficient in most cases to achieve the required focusing.

Therefore, the present invention has been devised to solve the above problems, and a specific object of the present invention is to provide a focusing system without inducing charges that adversely affect the focusing of the electron beam without causing discharge between the electrodes, without accumulating in the bulb of the cathode ray tube. The present invention provides a projection cathode ray tube, particularly a laser cathode ray tube, which can increase the voltage difference between two electrodes, thereby making the beam focus more accurately.

1 is a schematic view of a laser cathode ray tube according to the present invention;

The present invention to achieve the above object,

A gap between the bulb, a light emitting screen formed inside the bulb, an electron gun mounted inside the bulb to form an electron beam, and an end portion disposed sequentially on the electron beam path and facing each other and surrounded by the gap, separated by a gap A projection type cathode ray tube comprising a focusing system comprising a first electrode and a second electrode to focus the electron beam on a light emitting screen,

The projection cathode ray tube according to the invention further comprises an additional electrode surrounding the first electrode and the second electrode at least in the vicinity of the gap, the additional electrode being substantially insulated from the first electrode and the second electrode.

In addition, the present invention to achieve the above object,

A gap between the bulb, a laser screen mounted inside the bulb, an electron gun mounted inside the bulb to form an electron beam, and end portions disposed sequentially on the electron beam path and facing each other and surrounded by the gap, separated by a gap A laser cathode ray tube comprising a focusing system comprising a first electrode and a second electrode to focus the electron beam on a laser screen,

The laser cathode ray tube according to the invention further comprises an additional electrode surrounding the first electrode and the second electrode at least in the vicinity of the gap, the additional electrode being substantially insulated from the first electrode and the second electrode.

The additional electrode blocks the cathode ray tube bulb from the action of the electron beam to prevent accumulation of induced charges on the inner surface of the cathode ray tube bulb. The induced charge is symmetrically distributed at the inner surface of the additional electrode and does not interfere with the axial balance of the electron beam, and enables accurate focusing of the electron beam even with a relatively large gap between the electrodes. The enlargement of the gap makes it possible to increase the voltage difference between the electrodes without the occurrence of discharge and thus provide accurate focusing of the electron beam with large energy. In known devices the size of the gap is 0.5 to 1.5 mm or less, while the provision of the additional electrode according to the invention allows for an enlargement of the gap of at least 2 to 5 mm. Due to this widening of the gap, the voltage difference between the electrodes of the focusing system, which has not exceeded 25 to 35 kV in known devices, can be increased to 40 to 65 kV or more.

Preferably, the additional electrode can be mechanically connected to the electrodes of the focusing system, thereby simplifying the design of the cathode ray tube.

The projection cathode ray tube according to the present invention, in particular the laser cathode ray tube, is located at a position spaced apart from the gap and fixes the first electrode and the additional electrode, and is located at a position spaced apart from the gap and the second electrode. It is preferable to include a second dielectric coupling means for fixing the additional electrode and the additional electrode.

The first electrode of the focusing system is provided with an adjustable focusing voltage, and the second electrode may be a high voltage accelerating electrode and is connected to the laser target of the laser screen.

Preferably, at least one electrode in the electron gun is secured to the first dielectric coupling means for securing the first electrode and the additional electrode.

The electrode diameter of the focusing system in the vicinity of the gap is preferably larger than the electrode diameter in the vicinity of the dielectric coupling means. This diameter enlargement of the electrode enlarges the diameter of the focusing lens, which in turn reduces the influence of lens spherical aberration and increases the current density of the focused electron beam, thereby improving the laser emission power of the laser cathode ray tube.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Projection type cathode ray tube is a device that displays an image by expanding the image emitted from the cathode ray tube on a large-area projection screen. To this end, the projection type cathode ray tube includes a known cathode ray tube for forming an image, the cathode ray tube including a bulb forming a vacuum inside, a light emitting screen formed on the inner surface of the bulb, and an electron gun structure.

The electron gun emits an electron beam whose current density is controlled by an external signal to excite the light emitting screen, which is focused and accelerated by a focusing system to scan the light emitting screen with an optimal beam diameter.

The focusing system comprises a first cylindrical electrode to which an adjustable low focusing voltage is applied and a second cylindrical electrode to which a high voltage accelerating voltage is applied to form an electrostatic focus lens by the voltage difference between these electrodes. At this time, while further maintaining the voltage difference between the first and second cylindrical electrode, thereby further comprising an additional electrode surrounding the first and second electrode to prevent the induced charge is accumulated on the inner surface of the bulb. .

In the projection type cathode ray tube having such a configuration, the laser cathode tube adopting the laser screen instead of the fluorescent film screen as the light emitting screen will be described in more detail as follows.

1 is a schematic diagram of a laser cathode ray tube according to the present invention.

As shown, the laser cathode ray tube includes, for example, a bulb 1 which may be made of glass, and the inside of the bulb 1 forms a vacuum. Inside the bulb 1 is arranged a laser screen 2 and an electron gun 3 aligned for electron beam formation. In the illustrated embodiment, the electron gun 3 comprises a cathode 4 and a modulator 5 and an acceleration electrode 6 and an anode 7 but may further comprise other components of the known electron gun. The electrodes 4 to 7 are connected to an outer lead (not shown) of the laser cathode ray tube in order to be connected to an external circuit. The laser cathode ray tube further comprises a focusing system for focusing the electron beam on the laser screen 2. The focusing system comprises first and second cylindrical electrodes 8, 9, preferably these electrodes surround the electron beam 10 and are sequentially arranged along the electron beam path, with the ends facing each other by the gap 11. Are separated from each other. The laser cathode ray tube further comprises an additional electrode 12 surrounding the first and second electrodes 8, 9 in the vicinity of the gap 11 and substantially electrically insulated from the electrodes 8, 9. In the vicinity of the gap 11, the circumferential distance between the additional electrode 12 and the first electrode 8 and the circumferential distance between the additional electrode 12 and the second electrode 9 are these first and second electrodes. It is about 0.5 to 2 mm depending on the voltage applied to the fields 8 and 9. The electrodes 8, 9, 12 as well as other electrodes may be made of stainless steel or nickel.

The additional electrode 12 is mechanically coupled to the first and second electrodes 8, 9. In the illustrated embodiment, the coupling may be made by a first dielectric coupling means consisting of binding bars 13, 14 and a second dielectric coupling means consisting of binding bars 15, 16. The first electrode 8 and the additional electrode 12 are positioned at a distance from the gap 11 and fixed to the binding bars 13 and 14, which are glass components, for example. The binding bars 13 and 14 have a shape that approximates a parallelepiped and are manufactured in a manner similar to known binding bars commonly used to mechanically connect electrodes in various electronic devices. The first electrode 8 and the additional electrode 12 are connected by the binding bars 13 and 14, and as shown, for example, the flanges of the electrodes are sealed to the binding bar. The opposite end of the additional electrode 12 and the second electrode 9 are fixed in a similar manner to the pair of binding bars 15, 16. The number of binding bars constituting the first and second dielectric coupling means may not be two. If several binding bars are used to connect the respective electrodes, the binding bars are preferably arranged at equal intervals along the electrode circumference.

The connection of the first and second electrodes 8, 9 of the focusing system by the additional electrode 12 thus provides a mechanically strong and simplified design in the manufacturing process.

The first electrode 8 receives an adjustable focusing voltage, and the second electrode 9 is a high voltage accelerating electrode through a conductive coating film 17 and a laser target (not shown) of the laser screen 2. Connected. These electrodes 8, 9 are connected to respective external leads to receive the required voltage. The additional electrode 12 may have no external lead or may be connected to a separate external lead.

At least one or more other electrodes of the electron gun 3, for example the anode 7, may be secured to the first dielectric coupling means, ie the binding bars 13, 14, as shown.

In addition, as shown, the diameter of the electrodes 8 and 9 in the vicinity of the gap 11 exceeds the diameter in the vicinity of the binding bars 13-16. In one example, the diameters of the electrodes 8, 9 in the vicinity of the gap 11 may be 5-10 mm larger than the diameter in the vicinity of the coupling means, which may be approximately 25 mm.

The operation of the laser cathode ray tube is as follows.

The cathode 4 of the electron gun 3 is heated by an external current source (not shown) to emit electrons and form a beam 10. An acceleration voltage positive and approximately 40 to 65 kV relative to the cathode 4 is applied to the high voltage acceleration electrode 9 from an external voltage via a high voltage input (not shown). The acceleration voltage is applied to the target of the laser screen 2 through the conductive coating film 17. The electron beam 10 emitted from the electron gun 3 is advanced toward the laser screen 2 by the action of the high acceleration voltage applied to the second electrode 9 and the target of the laser screen 2.

The voltage, which typically does not exceed a few kilovolts applied to the first electrode 8, is adjusted to electrostatically focus the electron beam 10 on the target of the laser screen 2. During the electrostatic focusing, the electric field formed by the first and second electrodes 8, 9 forms an electron lens (shown in dashed lines) to concentrate the divergent electron beam emitted from the electron gun 3 into a narrow converging electron beam. .

Immediately after voltage is applied to the first and second electrodes 8, 9 of the focusing system, an intermediate voltage value between the voltages applied to the electrodes 8, 9 is applied to the additional electrode 12 due to the leakage current. . In some cases, this phenomenon may be a convenient way to provide a constant potential from the external power source to the additional electrode 12.

The additional electrode 12 blocks the bulb 1 from the action of the electron beam to prevent accumulation of induced charges on the inner surface of the bulb 1. The induced charges are symmetrically distributed to the inner surface of the additional electrode 12 surrounding the gap 11, whereby the axis of the electric field formed by the focusing system even when the size of the gap 11 is enlarged by approximately 2 to 5 mm. Directional balance and axial balance of the electron beam 10 focused by the focusing system is provided substantially completely. At the same time, the enlargement of the size of the gap 11 makes it possible to prevent the discharge from occurring between these electrodes 8, 9 even if a high potential difference exists between the first and second electrodes 8, 9. By providing the additional electrode 12 according to the present invention, the size of the gap 11, which is 0.5 to 1.5 mm or less in a known laser cathode ray tube, can be enlarged by at least 2 to 5 mm. This can also increase the voltage difference between the electrodes 8, 9 of the focusing system to 40-65 kV or more, which voltage value does not exceed 25-35 kV in known devices. The high voltage between the first and second electrodes 8, 9 of the focusing system enables accurate focusing of the electron beam 10 with high energy, thereby increasing the laser emission power of the cathode ray tube with high resolution.

The diameter enlargement of the first and second electrodes 8, 9 in the focusing system in the vicinity of the gap 11 also provides a diameter enlargement of the focusing lens. As is known, such diameter enlargement reduces the scattering of the beam caused by the spherical aberration of the lens, since this diffusion is determined as the ratio of the beam diameter to the lens diameter. The reduction of the influence of the spherical aberration increases the diameter of the electron beam 3 toward the electron lens on one side of the electron gun 3, thereby increasing the current density of the electron beam 10 focused on the target of the laser screen 2. . Thus, the laser emitting power of the cathode ray tube is further increased as compared with the known apparatus.

Although only one embodiment of the laser cathode ray tube has been described above, the laser cathode ray tube according to the present invention is a dielectric coupled to a known electron beam generating element and a known bulb design and electrodes used in such an electron beam device and a similar device. Means may be used.

As such, the present invention can provide a laser cathode ray tube having an electrostatic focusing of the electron beam without inducing discharge between the electrodes and without accumulating induced charge in the bulb, thereby ensuring more accurate focusing of the electron beam.

Claims (9)

Bulb; A light emitting screen mounted inside the bulb; An electron gun mounted inside the bulb and forming an electron beam; A focusing system surrounding the electron beam and sequentially disposed on the electron beam path so that the opposite ends are separated by a gap to focus the electron beam on the light emitting screen; And an additional electrode surrounding at least the first and second electrodes and substantially insulated from the first and second electrodes at least near the gap. Bulb; A laser screen mounted inside the bulb; An electron gun mounted inside the bulb and forming an electron beam; A focusing system surrounding the electron beam and sequentially disposed on the electron beam path such that opposite ends are separated by a gap to focus the electron beam on a laser screen; And an additional electrode surrounding said first and second electrodes at least near said gap and substantially insulated from said first and second electrodes. The laser cathode ray tube of claim 2, wherein the additional electrode is mechanically connected to the first and second electrodes. 4. The laser cathode ray tube according to claim 2 or 3, further comprising first dielectric coupling means positioned at a distance from the gap and fixing the additional electrode and the first electrode. The laser cathode ray tube according to any one of claims 2 to 4, further comprising a second dielectric coupling means positioned at a distance from the gap and fixing the additional electrode and the second electrode. The laser cathode ray tube according to any one of claims 2 to 5, wherein the first electrode is applied with an adjustable focusing voltage and the second electrode is applied with a high voltage accelerating voltage. The laser cathode ray tube of claim 2, wherein the second electrode is connected to a laser target of a laser screen. 8. The laser cathode ray tube according to any one of claims 4 to 7, wherein at least one electrode of the electron gun is mounted to the first dielectric coupling means. 9. A laser cathode ray tube according to any one of claims 4 to 8, wherein said first and second electrodes have a diameter in the vicinity of a gap exceeding a diameter in the vicinity of said first and second dielectric coupling means.