RU2210137C2 - Dynamically focused electron-beam laser device - Google Patents

Abstract

FIELD: electronic engineering; projection television units. SUBSTANCE: device has envelope with at least part of its inner surface covered with low-resistance coat; electron gun for generating electron beam, laser screen; focusing system for focusing electron beam generated by electron gun on laser screen; and means for dynamic focusing of mentioned electron beam that includes electrode installed at location point of magnetic focusing system; mentioned low-resistance coat applied to inner surface of envelope has discontinuity in vicinity of mentioned electrode where inner surface of envelope is covered with high-resistance coat. EFFECT: reduced size of device and provision for additional focusing at higher frequency. 11 cl, 1 dwg

Description

 The invention relates to electronic and quantum devices, namely to laser electron-beam devices used, for example, in projection television devices for forming images on large-area screens.

 Projection television devices based on conventional electron-beam devices (EBLs) with a fluorescent screen are widely used to form images on projection screens up to several square meters in area. However, the size of the image on the projection screen of such television devices is limited by the inability of the luminescent screens of projection EBLs to generate the required luminous fluxes with high intensity, which makes it difficult to obtain television images with the necessary brightness and contrast.

 An effective way to improve the parameters of projection television devices is through the use of laser EBLs (see, for example, US Pat. No. 3,558,956, H 01 J 29/18, 1971).

 Unlike a conventional EBL, the source of radiation in a laser EBL is not a phosphor layer, but a laser target, which is a thin semiconductor single crystal wafer, on which parallel surfaces light-reflecting coatings are deposited. From the side of incidence, an opaque mirror metallic coating is usually applied to the electron beam plate, and from the opposite side, a translucent mirror coating. Mirror surfaces form an optical resonator, and the semiconductor wafer between them serves as the active medium of an electronically excited laser. The laser target is attached to a substrate of transparent dielectric material, which plays the role of the exit window of a laser EBL, as well as a heat sink for the laser target. The substrate is usually made of sapphire, which has high thermal conductivity. The laser target together with the substrate form the screen of the laser ELP (laser screen).

 A beam of electrons, penetrating into a semiconductor wafer through a metal coating, induces spontaneous light emission. When the surface current density of the beam on the laser target is equal to the threshold value, the power of the induced light radiation compensates for the loss in the optical cavity and the element of the target onto which the electron beam is incident becomes a source of laser radiation. In the process of multiple passage of light through the resonator, its frequency spectrum is narrowed, as a result of which the emitted light is monochromatic. Laser light is emitted through a translucent mirror coating almost perpendicular to the surface of the semiconductor wafer and exits the EBL through the sapphire exit window.

 Known laser electron-beam device (Ulasyuk VN Quantoscopes. -M.: Radio and communications, 1988, p.105, 107, 108), containing a flask, at least part of the inner surface of which is applied low resistance conductive coating, electronic a spotlight for forming an electron beam, a laser screen and a magnetic focusing system for focusing the electron beam formed by the electronic spotlight on the laser screen.

 A conductive coating deposited on the inner surface of the flask prevents the appearance of charges induced by an electron beam on this surface. It is known that the absence of induced charges is a prerequisite for the formation of a highly directional axisymmetric beam, and due to the threshold nature of the radiation in a laser EBL, accurate focusing is much more important for it than for conventional phosphor EBLs, especially if it is necessary to achieve a high resolution that can provide laser EBP.

 The use of a magnetic focusing system in laser EBs allows one to obtain high resolution and is often preferred. However, when the electron beam moves along the laser screen during image formation, a certain defocusing of the beam occurs due to a change in the distance from the magnetic focusing lens formed by the magnetic focusing system to the laser screen. In addition, some defocusing of the beam also occurs when its current changes during image formation. These circumstances make it necessary to use dynamic electron beam focusing in a laser EBL.

 In some designs of laser EBLs, a subfocus signal is applied to the accelerating electrode and the laser screen of the EBL. However, this requires special measures to be taken to protect the dynamic focusing signal generation circuits from high accelerating voltage, which greatly complicates and increases the cost of the device design.

 In the aforementioned well-known EBL, the means of dynamically focusing the electron beam are made in the form of an additional focusing coil mounted on the flask, into which a current of focusing is applied, which varies depending on the position of the electron beam. However, due to the high electron energies and high beam current density in a laser EBL, in this case it is necessary to use an additional coil with a high inductance and a focusing current with a large amplitude value, which leads to a significant increase in the dimensions of the dynamic focusing means. In addition, the high inductance of the additional focusing coil makes it extremely difficult to dynamically focus the beam depending on the focusing current, since the frequency of the focusing signal in high-resolution laser EBLs can reach 100 MHz or more.

 The objective of the present invention is to provide a laser EBL with a non-induction element of dynamic focusing and thereby reduce the size of the dynamic focusing tools and enable dynamic focusing with a higher frequency.

 The problem is solved in that in a laser EBL containing a flask, at least part of the inner surface of which is coated with a low resistance coating, an electronic searchlight for forming an electron beam, a laser screen, a magnetic focusing system for focusing an electron beam formed by an electronic searchlight on a laser screen and means for dynamically focusing said electron beam, according to the invention, means for dynamically focusing include an electrode mounted at the installation site and a magnetic focusing system, and said low-resistance coating on the inner surface of the bulb, in the region of said electrode has a gap in which the inner surface of the bulb coated with a high resistance coating.

 The dynamic focusing means electrode is preferably made in the form of a conductive coating deposited on the outer surface of the bulb.

 Due to the presence of a gap in the low-resistance coating under the electrode, the electric field of this electrode created when a dynamic focus signal is applied to it induces a corresponding dynamic signal on the part of the high-resistance coating under the electrode. The electric field of this dynamic signal acts on the electron beam and changes the speed of the electrons depending on the sign and amplitude of the supplied dynamic focus signal. This, in turn, leads to a change in the residence time of electrons in the field of the magnetic focusing lens, which provides the necessary dynamic focusing of the electron beam. The proposed means of dynamic focusing, due to their non-induction nature, practically do not increase the dimensions of the EBL and provide the ability to supply a high-frequency AF signal, which is necessary for laser EBLs. The presence of a high-resistance coating in the gap region in a low-resistance coating provides an effective elimination of charges induced on the inner wall of the EBL bulb by an electron beam. In this case, the EBF bulb reliably isolates the electrode of the dynamic focusing means from the coating located at high potential on the inner side of the bulb. Due to this, it is not necessary to take special measures to protect the dynamic focusing signal generation circuits, which would be necessary when applying dynamic focusing voltage directly to the coating applied to the inner side of the EBF bulb.

 An insulating film may be applied over the conductive coating forming the electrode of the dynamic focusing means.

 The resistance of said high resistance coating is preferably from about 30 to 500 MΩ. It may include a coating applied in the form of a cylindrical spiral and / or in the form of a continuous layer and consisting, for example, of chromium oxide or titanium.

 The low-resistance coating deposited on the inner surface of the bulb is preferably electrically connected to the target of the laser screen to supply an appropriate voltage through it to the target.

 The distance, measured along the axis of the device, from any edge of the electrode of the dynamic focusing means to the nearest edge of the specified low-resistance coating is preferably at least about half the inner diameter of the bulb of the device in the region where the electrode is placed.

 A high-resistance coating deposited on the inner surface of the bulb directly below said electrode may have a gap in which a conductive coating is applied to the inner surface of the bulb.

 1 schematically shows a laser EBL made according to the invention.

 In FIG. 2 schematically shows a portion of a laser EBP made according to an embodiment of the invention.

 In accordance with figure 1, the laser EBL contains a flask 1 made, for example, of glass, from which air is evacuated. On the inner surface of the flask 1 applied low resistance coating 2, made, for example, of aquadag. An electronic spotlight 3 is placed in the neck of the bulb 1 to form an electron beam, and a laser screen 4 is mounted opposite it. A magnetic focusing system 5 of a conventional design, formed by electromagnetic coils (not shown separately), is installed on the outside of the bulb 1. In accordance with the invention, a laser EBL also contains means for dynamically focusing the electron beam, including an electrode 6 mounted on the outside of the bulb 1 at the installation site of the magnetic focusing system 5. In the region of the electrode 6 koomnoe coating 2 applied to the inner surface of the bulb 1 has a gap in which the inner surface of the bulb 1 7 deposited high-resistance coating.

 The distance L, measured along the axis of the device, from any edge of the electrode 6 to the nearest edge of the low-resistance coating 2 in the preferred embodiment of the invention is at least half the inner diameter D of the EBV bulb in the region where the electrode 6 is placed.

 The electrode 6 is located directly below the magnetic focusing system 5 and can protrude somewhat beyond its borders, for example, approximately 10% of its length, or, conversely, be slightly shorter than it. In the embodiment shown in FIG. 1, the electrode 6 is made in the form of a conductive coating, for example, from an aquadag deposited on the outer surface of the bulb 1, over which an insulating film 8 is applied for electrical insulation and protection against external influences.

 The resistance of the high-resistance coating 1, measured between its edges adjacent to the low-resistance coating 2, is preferably from about 30 to 500 MΩ. High resistance coating 7 may include a coating applied on the inner surface of the bulb 1 in a spiral fashion, i.e. having the form of a cylindrical spiral, the axis of which coincides with the axis of the bulb 1. Coating 7 can also be applied in the form of a continuous layer or a continuous layer superimposed on top of each other and a cylindrical spiral. As the material for coating 7, chromium or titanium oxide or any other material suitable for applying high resistance coatings can be used. For example, a high-resistance coating 7 can be formed by a continuous layer of titanium oxide with a thickness of about 50-100 μm and a resistance of about 5000 MΩ, on top of which a cylindrical spiral of chromium oxide with a thickness of about 50-100 μm and a resistance of about 30-500 MΩ, including about 30 turns, is applied 0.5 mm wide in 1 mm increments.

 The electronic spotlight 3 in the laser EWL shown in FIG. 1 includes a cathode 9, a modulator 10, an accelerating electrode 11, and an anode 12. The proposed laser EWP may include other known electrodes or elements of an electronic searchlight used in such devices. Between the magnetic focusing system 5 and the laser screen 4, a deflecting system 13, for example, of a magnetic type, is installed on the outside of the bulb 1. The electrodes 9-11 of the electronic spotlight 3 and the electrode 6 of the means of dynamic AF are connected to the leads (not shown), intended for connection with external circuits of the EBL (not shown).

 The low-resistance coating 2 is electrically connected to a target (not shown) of the laser screen 4, a high-voltage input 14 and the anode 12.

 In the embodiment shown in FIG. 2, the high-resistance coating 7 applied to the inner surface of the bulb 1, directly below the electrode 6, has a gap in which a conductive coating 15 is applied to the inner surface of the bulb.

 It is easy to see that the dynamic focusing means used in the proposed laser EBL practically do not increase the dimensions of the device.

 Laser EBL works as follows.

 The cathode 9 is heated using an external current source (not shown), which causes the emission of electrons. Accelerating voltages positive with respect to the cathode 9 are supplied to the high-voltage input 14 and the accelerating electrode 11 from external sources (not shown). The accelerating voltage from the high-voltage input 14 is applied to the target of the laser screen 4 through a low-resistance coating 2, and also through a part of the low-resistance coating 2, the high-resistance coating 7, applied in the gap of the low-resistance coating 2, and the other part of the low-resistance coating 2 on the other side of the gap, to the anode 12. Moreover, there is essentially no voltage drop on the high-resistance coating 7. The electrons of the beam 16 formed by the electronic searchlight 3, under the action of a high accelerating voltage applied to the electrodes 11 and 12, as well as to the laser screen 4, move from the cathode 9 to the screen 4.

 A current is passed through the electromagnetic coils of the magnetic focusing system 5, which ensures sharp magnetic focusing of the electron beam 16 at the center point 17 of the target of the laser screen 6. As is known, with magnetic focusing, the magnetic field created by the focusing system, in this case system 5, forms a magnetic lens, which collects a diverging electron beam into a narrow converging beam.

 Into the electromagnetic coils of the deflecting system 13, they are fed with line and frame signals of a sawtooth shape. The magnetic fields of the electromagnetic coils deflect a beam of 16 electrons in the horizontal and vertical directions, providing the formation of a television raster, similar to what happens in known electron-beam devices. At the same time, voltage is supplied to the modulator 10 from an external video source (not shown), which controls the current of the electron beam 16. The synchronized supply of scanning signals and a video signal allows you to create a television image that is projected from a laser EBP onto an external projection screen (not shown).

 When the electron beam deviates under the action of the deflecting system 13 from the center point 17 of the target of the laser screen, this beam is defocused due to a change in the distance from the magnetic focusing lens formed by the magnetic focusing system 5 to the target of the laser screen 4. In addition, the current of the electron beam 16 is changed in accordance with the voltage of the video signal applied to the modulator 10, causes additional defocusing, depending on the brightness change of the corresponding image point.

 To eliminate these defocusings on the electrode 6 means dynamic focusing from an external source (not shown) supply voltage focusing. To eliminate the defocusing associated with a change in the distance to the target of the laser screen 4, the focusing voltage includes two components, which are functions of the deviation of the electron beam 16 from the center 17 of the target of the laser screen 4, respectively, horizontally (with the horizontal frequency) and vertically (with the frequency HR scan). To eliminate the defocus associated with a change in the beam current 16, the focus voltage includes a component that is a function of the video signal. The specific amplitude and time parameters of the components of the focusing voltage can easily be selected by specialists for any particular embodiment of the invention based on the measured experimental or calculated characteristics of a particular laser EBP. Electronic circuits that allow the formation of such a voltage are also well known to specialists and are not considered here.

 The electric field of the electrode 6 created when a dynamic focus signal is applied to it induces a corresponding dynamic signal on the part of the high-resistance coating 7 under the electrode 6 (in the embodiment of the invention shown in FIG. 1) or on the conductive coating 15 under the electrode 6 (in the embodiment the invention shown in figure 2). The electric field of this dynamic signal acts on the beam 16, changing the speed of the electrons of this beam, depending on the sign and amplitude of the supplied signal dynamic focusing. A change in the electron velocities in the region of the focusing lens formed by the magnetic focusing system 5 leads to a change in their residence time in the focusing magnetic field of the lens, which ensures the required dynamic focusing of the electron beam 16.

 At the same time, the conductivity of the high-resistance coating 7 is sufficient so that the charges induced by the electron beam do not accumulate on the inner surface of the bulb 1 under the electrode 6 of the dynamic focusing means.

 If the distance L from the edge of the electrode 6 to the edge of the low-resistance coating 2 is chosen equal to at least about half the inner diameter D of the EBW bulb, then the resistance between the low-resistance coating 2 on the inner surface of the bulb 1 and the coating area under the electrode 6 will be high enough to maintain the level of the induced dynamic focus signal during the playback time of the television image element.

 As indicated above, the coating 7 may be in the form of a continuous layer or spiral. The coating in the form of a continuous layer provides better protection against the accumulation of charges in comparison with a spiral coating, which does not completely cover the surface beneath it (the gaps between the turns of the spiral remain uncoated). On the other hand, when applying a continuous coating to the inner surface of the flask 1, it is almost impossible to achieve high uniformity, since it is technologically impossible to apply a continuous coating of the same thickness. At the same time, the inhomogeneity of the coating leads to non-uniformity of the focusing electric field and thereby to distortion of the shape of the electron beam 16, which negatively affects its focusing. In the case of using a spiral coating, it is possible to achieve high uniformity by applying it with a rotating sliding slider.

 The best results can be achieved by using a coating 7 comprising a continuous layer and an additional layer having a cylindrical spiral shape applied over it.

 Due to the non-inductive nature of the dynamic focusing means made according to the invention, it is possible to supply a high-frequency focusing signal, which is a function of the voltage of the video signal, and thus eliminating the defocusing associated with a high-frequency variation of the beam current 16. The presence of a high-resistance coating 7 in the gap region in the low-resistance coating 2 provides an effective elimination of charges induced on the inner wall of the flask 1 by an electron beam 16. The absence of induced charges provides the formation of a highly directional axisymmetric beam 16.

 The wall of the glass flask 1 reliably isolates the dynamic focusing means electrode 6 from the coating 2, which is under high potential. Therefore, no special measures are required to electrically protect the dynamic focusing signal generation circuits, which would be necessary when applying dynamic focusing voltage directly to the coating 2.

 Thus, the present invention provides the creation of a laser EBL with a non-induction small-sized element of dynamic focusing, which provides the possibility of effective high-frequency focusing of the electron beam.

 The design of a laser EBL considered above is given only as an example. In the laser EBL according to the invention, any known elements for generating, modulating, accelerating and deflecting electron beams, as well as any known EBW bulb designs used in electron beam devices and other similar devices, can be used.

Claims (11)

 1. Laser electron-beam device containing a bulb, at least part of the inner surface of which is coated with a low resistance coating, an electronic searchlight for forming an electron beam, a laser screen, a magnetic focusing system for focusing an electron beam formed by an electronic searchlight on a laser screen and means dynamic focusing of said electron beam, characterized in that the dynamic focusing means include an electrode installed at the installation site of the magnetic Ushiro system, and said low-resistance coating on the inner surface of the bulb in the area of finding said electrode has a gap in which the inner surface of the bulb coated with a high resistance coating.  2. The laser electron-beam device according to claim 1, characterized in that the electrode of the dynamic focusing means is made in the form of a conductive coating deposited on the outer surface of the bulb.  3. The laser electron-beam device according to claim 2, characterized in that an insulating film is deposited on top of the conductive coating forming the electrode of the dynamic focusing means.  4. Laser electron-beam device according to one of paragraphs. 1-3, characterized in that the resistance of the specified high-resistance coating is approximately 30-500 MΩ.  5. Laser electron-beam device according to one of paragraphs. 1-4, characterized in that the high-resistance coating includes a coating applied in the form of a cylindrical spiral.  6. The laser electron-beam device according to claim 5, characterized in that said coating, applied in the form of a spiral, consists of chromium oxide or titanium.  7. Laser electron beam device according to one of paragraphs. 1-6, characterized in that the high-resistance coating includes a coating applied in the form of a continuous layer.  8. The laser electron-beam device according to claim 7, characterized in that said coating, applied as a continuous layer, consists of chromium oxide or titanium.  9. Laser electron-beam device according to one of paragraphs. 1-8, characterized in that the said low-resistance coating is electrically connected to the target of the laser screen.  10. Laser electron beam device according to one of paragraphs. 1-9, characterized in that the distance measured along the longitudinal axis of the device, from any edge of the electrode means dynamic focusing to the nearest edge of the specified low resistance coating is at least about half the inner diameter of the bulb of the device.  11. Laser electron beam device according to one of paragraphs. 1-10, characterized in that the specified high-resistance coating deposited on the inner surface of the flask, directly below the specified electrode has a gap in which a conductive coating is applied to the inner surface of the flask.

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