CA1093627A - Vacuum fluorescent indicator - Google Patents
Vacuum fluorescent indicatorInfo
- Publication number
- CA1093627A CA1093627A CA286,441A CA286441A CA1093627A CA 1093627 A CA1093627 A CA 1093627A CA 286441 A CA286441 A CA 286441A CA 1093627 A CA1093627 A CA 1093627A
- Authority
- CA
- Canada
- Prior art keywords
- filament
- anode
- voltage
- holes
- screen
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J31/00—Cathode ray tubes; Electron beam tubes
- H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
- H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
- H01J31/12—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen
- H01J31/15—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen with ray or beam selectively directed to luminescent anode segments
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
- H01J29/08—Electrodes intimately associated with a screen on or from which an image or pattern is formed, picked-up, converted or stored, e.g. backing-plates for storage tubes or collecting secondary electrons
Abstract
VACUUM FLUORESCENT INDICATOR
Abstract of the Disclosure A vacuum fluorescent display has a filament heated below incandescence and phosphor coated anodes. A foraminous charge-control electrostatic lens between the filament and the viewer both controls uniform illumination of the anodes and also comprises part of a contrast-enhance-ment element. An embodiment of the in-vention with a linear array of anodes and an analog-to-digital power supply forms a linear scale indicator.
Abstract of the Disclosure A vacuum fluorescent display has a filament heated below incandescence and phosphor coated anodes. A foraminous charge-control electrostatic lens between the filament and the viewer both controls uniform illumination of the anodes and also comprises part of a contrast-enhance-ment element. An embodiment of the in-vention with a linear array of anodes and an analog-to-digital power supply forms a linear scale indicator.
Description
1(~93627 Background of the Invention Display devices which can be selectably illuminated .
to convey changing information have become increasingly important. The earliest illuminated display devices were fixed-message signs, such as "exit" or "no smoking" signs which contained a source of light capable of being turned on and off, and a partially translucent face plate containing the message. This type of display suffered washout by strong front illumination. U.S. Patent 3,682,531, issued to A.R. Jeffers teaches a light trap consisting of a circular polarizer and optionally also of a specular foraminous screen to trap ambient light entering the face of the sign.
Electronically controllable display devices have grown particularly with the growth of computers. For example, a gas-discharge device containing a stacked set of ;
bm:
- . - .
,~
1093~;~';i' transparent plates having shaped discharge regions therein has been in use for many years. The shaped discharge regions may for example form the numerals 0 through 9, one to a transparent plate. When the discharge regions in one plate are electrically energized, the characteristic glow of the gas discharge regions forms one of the numerals.
Except when the particular plate illuminated is nearest the viewer, the illuminated numeral is viewed through one or more transparent deenergized plates. When an array of these gas-discharge devices are used to display multiple numerals, the varying distance of the illuminated plates from the viewer gives rise to annoying parallax.
In an attempt to eliminate parallax in a gas-discharge display device, S.M. Frouws, in U.S. Patent 3,418,509, disclosed a planar gas discharge tube containing individually energizable segments spaced away from a counter electrode of transparent conductive material or a fine gauge wire screen through which the viewer observed the segments. The gas discharge was set up between the counter electrode and the energized segments.
This device suffered, in common with all gas discharge devices, the need for high voltages and inductive current limiting. This made it impractical to directly drive bm:
i2~7 gas-discharge display devices from modern solid state electronics.
The modern development of vacuum fluorescent display has solved the parallax and high-voltage problems of the gas discharge display devices while requiring the solution of a number of problems of its own.
A vacuum fluorescent display device uses a filament, heated to below incandescent temperature, as a source of thermionic electrons which are then accelerated toward an anode coated with a phosphor capable of fluorescing under bombardment by low-energy electr~ns.
The accelerating voltage can be from a few volts to hundreds of volts but is preferably in the range of from 10 to 30 volts. By selectively accelerating thermionic electrons to desired regions of the phosphor-coated anode, a bright changeable planar display is achieyed.
It was discovered by R. DuBois that natural electrostatic charges, such as from a comb run through a person's hair and brought into proximity of a vacuum fluorescent display of the type described, could completely extinguish the display for an extended time. His solution, disclosed in U.S. Patent 3,S84,252, consisted in partially encircling the rear and side regions of the anode with a conductive electrostatic shield.
A second problem of unequal illumination of the anode by thermoelectrons has engendered a number of solutions.
The problem arises because a convenient method of fabrication includes an insulating substrate, usually glass, bm:
iOS~3~;~Z'7 behind or embedding the anodes. Charges stored in the insulating substrates so distort the electric field within the vacuum fluorescent device that widely variable illumination of the phosphor occurs. Solutions by R.
Raago in U.S. Patent 4,780,326 and by S. Shimada in U.S.
Patent 3,668,466 taught the use of an auxiliary electrode in substantially the same plane as the anodes.
Application of the correct voltages on the auxiliary electrode could adjust the electrostatic field to achieve 10 uniform illumination or alternatively could extinguish the device. R. Raago in U.S. Patent 3,688,147 solved the problem in a different way by spacing the anode segments on cantilevers far enough forward from the insulating substrate to avoid the distortion of the electrostatic field from charges stored in the insulator. Still another solution, disclosed in varying forms by M. Tanji in U.S. Patents 3,619,694 and 3,508,101 and by R. DuBois in U.S.' Patent 3,566,187 uses a mesh grid interposed between the filament and the anodes operating in a fashion analogous to a normal 20 electron-tube screen grid to accelerate electrons toward the anode using positive voltage or to cut off electron flow to the anode using negative voltage. Proper adjustment of the positive voltage on the grid was effective to cancel the bm:
10~
effect of charges stored in the insulating substrate. In addition, the grid shields the anodes from external electro~
static disturbances. The location of the grid between the filament and the anodes fails to protect the filament from disturbances by external electrostatic fields. In addition, the grid, being positive, attracts electrons to itself. Thus a large current, not contributing to display output, is set up with consequent heating and waste of power.
Summary of the Invention The present invention provides an improvement in a vacuum fluorescent display device having at least one electrically heated thermoelectron-emitting filament, at least one phosphor-coated anode, wherein the filament and anode are sealed in an enclosure having a hard vacuum therein, the improvement comprising:
an electrostatic lens inside the enclosure interposed in the line of sight between the viewer and the filament; the electrostatic lens being a metallic sheet having a regular pattern of holes therethrough, the sheet and holes forming a foraminous screen; ;
the holes comprising from about 20 to about 50 per cent of the screen area; a circular polarizer interposed in the line of sight between the viewer and the screen; the side of the foraminous screen nearest the circular polarizer being specularly reflecting; and the foraminous screen being connected to a positive voltage with respect to the filament.
Brief Description of the Drawings Fig. 1 shows a ghost pictorial perspective view of one embodiment of a vacuum fluorescent display device and a block diagram of power supplies therefor according to the teachings of this invention.
~7 --5 -~!ICr rw/
iZ'7 Fig. 2 shows an embodiment of the present invention which includes a contrast enhancement device.
Fig. 3 shows a close up view of one embodiment of the foraminous screen taken along 3-3 in Fig. 2.
Fig. 4 shows an embodiment of the present invention especially adapted to use as a linear scale indicator.
Fig. 5, adjacent Figures 2 and 3, shows a simplified schematic diagram of a power supply for a linear scale indicator --of the type shown in Fig. 4.
Detailed Description of the Preferred Embodiment . . _ A vacuum fluorescent display device 10 according to the teachings of the present invention is shown in Fig. 1. A
substrate 12 of insulating material, such as glass or ceramic, has a shaped phosphor-coated conductive anode 14 upon or embedded within it. Methods of forming shaped conductive areas on or embedded within insulating materials are well known and do not form part of the present invention. The phosphor coating on the conduetive anode 14 is applied using any method sueh as masked spraying or brushing. The eonduetive anode 14 may be of any eonvenient rw/
lU~3~
planar shape and may comprise a single conduc-tive region or it may be divided into independently controllable subregions of any shape. In the figure, the anode 14 is shown to comprise a -~ shape, for purposes of illustration, made up of a horizontal bar 16 and two vertical half-bars 18, 18a. Each vertical half-bar 18, 18a is separated from the horizontal bar 16 by an insulating gap 19, l9a, An electrical conductor 20 passes sealably through the substrate 12 electrically connecting the horizontal bar 16 to one output of an anode supply 22. Similarly, electrical conductors 24, 24a pass sealably through the substrate 12 electrically connecting the vertical half-bars 18, 18a to the anode supply 22. It will be evident to one skilled in the art that any anode pattern can be formed and independently connected to the anode supply 22. The anode supply 22 is capable of independently controlling the application of accelerating voltages to the parts of the anode 14 according to anode control signals 16 received from an external source, not shown. Thus, the anode segments 16, 18, 18a can be energized in any desired pattern under the control of the anode control signals 26 as will be described.
One or more heater filaments 28 (only one lS
shown) preferably in the form of a fine wire is suspended above the anode 14 by two filament supports 30, 30a. The heater filament 28 is treated with a rare-earth oxide coating bm:
lV93~;z ,~
or by other methods known or which become known to enable it to emit thermoelectrons at dull red color or cooler.
Filament leads 32, 32a sealably penetrate the substrate 12 connecting the filament supports 30, 30a to a filament supply 34.
A reference signal 36 is connected from filament lead 32 to the anode supply 22, When a positive voltage with respect to the reference signal 36 is connected to one or more segments of the anode 14, thermoelectrons are accelerated toward those segments of the anode 14. When a negative or neutral voltage is connected to certain anode 14 segments, thermoelectrons are not accelerated toward those anode 14 segments, The phosphor coating on the positively biased anode 14 segments glows under the bombardment of the thermoelectrons whereas the negatively biased segments remain dark. Thus, a variable illuminated pattern can be set up in the anode 14 by selection of those segments to be positively and negatively biased, Due to the electrostatic charge distribution set up in the substrate 12 and also due to external electrostatic fields, a vacuum fluorescent display device 10 containing only the elements heretofore described will display segments of variable brightness and will be subject to electrostatic disruption of the display. An electrostatic lens 38 connected to an electrostatic lens power supply 40 adjusts the electrostatic field within the display device 10 to bm:
1093~Z'~
overcome the internal electrostatic charge distribution and also shields the filament 28 and anode 14 from ex~
ternal electrostatic disturbances. The electrostatic lens 38 is a transparent conductive surface or a foraminous screen placed in the line of sight 42 between the viewer and the illuminated segments of the anode 14.
A cover 44 having a transparent portion at least in the line of sight 42 is sealed to the substrate 12. The cover 44 and substrate 12 together form a hermetically sealed enclosure within which the anode 14 and the filament 28, with associated parts, are contained. The electrostatic lens 38 is inside the cover 44 to avoid interference from a charge gradient which may be set up across the cover 44.
The hermetically sealed enclosure is evacuated to a hard vacuum between 10 6 and 10 9 torr using methods well known in the art.
Referring now to Fig. 2, there is shown a second embodiment of the invention containing a circular polarizer 46 interposed in the line of sight 42. As is explained in U.S. Patent 3,682,531, the interposition of a circular , polarizer in the line of sight to an internally illuminated display enhances the contrast of the display by trapping incident light while permitting the exit of internally generated light relatively unattenuated.
_ g _ rw/
109~ 7 In Fig. 3, an embodiment of the electrostatic lens 38 which may advantageously be combined with the circular polarizer 46 shown in Fig. 2 to yield an additional contrast enhancement. The electrostatic lens 38 is a foraminous screen containing a plurality of holes 48.
The holes may be in any shape and regular placement but their area should comprise from about 10 to about 70 percent, but best contrast enhancement is obtained with hole openings in the range of from about 20 to about 50 percent of the screen area. The preferred range of hole spacing is from about 100 to about 750 lines per inch.
The holes may be located at the corners of right squares as in Fig. 3 or they may be along skewed or curved lines.
For contrast enhancement with the circular polarizer 46, the side of the foraminous screen 38 nearest the viewer is specularly reflecting. The theory whereby specular reflection in the foraminous screen 38 enhances optical contrast is covered in detail in U.S. Patent 3,682,531.
The foraminous screen 38 is made of electrically conductive material and is electrically connected to the electrostatic lens power supply 40 as shown in Fig. 1.
An embodiment of the invention especially adapted to use as a linear scale indicator is shown in Fig. 4~
Linear scale indicators are advantageously employed in aircraft, automotive and other applications to indicate the status of measured parameters by the length of an illuminated line.
The substrate 12 is in the shape of a rectangular plate made of a suitable glass or ceramic material but preferably is of black glass due to the fact that it bm:
109~ 7 absorbs incident light. An evacuation opening 50 passes through the substrate 12 and is used in a manner well known in the art during the process of evacuating the enclosure. A plurality of bar-shaped anodes 14a, 14b, etc. are disposed in a contiguous parallel array. The anode is partially embedded in the glass substrate 12 and is further retained in position by the passage through the substrate of electrical conductors 20a, 20b, etc.
The electrical conductors 20a, 20b, etc. are conveniently shaped at their outer ends for insertion into standard electrical connectors. Alternatively, the electrical conductors 20a, 20b, etc. may be of wire or may have solder fittings adapted to electrical connection by other conventional methods.
The filament supports 30, 30a (30 is hidden) are supported and power is supplied through filament leads 32, 32a. A flat filament tensioning spring 52 applies endwise force to the filament 28 to prevent sagging.
The filament may also be supported in its run by a filament support wire 54 which extends laterally from pegs 56, 56a. The foraminous screen 38 is placed above the - filament on support legs 58a tthe remaining support legs are not shown). At least one of the support legs 58a extends through the substrate 12 and provides external connection for the control voltage. Thus, connection of the foraminous screen 32 to the control voltage performs the functions of the electrostatic lens previously described. A non-flashing or flashing getter bar 60 is supported within the enclosure on a pair of getter bar support legs 62, 62a which provide external electrical connection, not shown. The non-flashing . ' .
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~093~i~t~
getter bar 60 is used in the final stages of evacuation of the enclosure in a manner well known in the art.
The box shaped cover 44 preferably formed of glass is sealably attached to the upper perimeter of the substrate thereby forming the hermetically sealed enclosure. The outer regions 64, 64a of the glass cover 44 may optionally be blackened to prevent the lateral entry of extraneous light. A rectangular shaped central clear region 66 allows viewing of the illuminated anodes 14a, 14b, etc. through the openings in the foraminous screen 38.
The foraminous screen 38, instead of being independently formed and supported on support legs 58a, could alternatively be produced as a plating photo chemically formed upon the inner surface of the cover 44 with electrical connection to the exterior provided by conventional means.
The circular polarizer 46 may be installed on top of the cover 44 covering at least the clear region 66.
Alternatively, the cover 44 itself may be fabricated in such a manner that it, itself, performs the function of a circular polarizer. For best results, the contrast enhancement device described in United States Patent 3,682,531 requires that the foraminous screen 38 should be specularly reflecting on its side facing the circular polarizer 46 and that there should be no intervening diffusive or further retarding means interposed between them. Although the presence of the clear glass region 66 between the circular polarizer of the foraminous screen as shown in Fig. 4 somewhat degrades the performance of the current enhancement device, the applicant has discovered bm:
lO!~;Z'7 that the degradation is of acceptahle degree.
A portion of an analog to digital anode supply 22 is shown in Fig. 5. For simplicity of description only two anodes 14a and 14b are shown with the associated supply components. It will be understood that the number of anodes may be increased to a large number with each additional anode requiring the addition of a modular set of supply components as shown in Fig, 5. A resistive voltage divider composed of resistors Rl, R2 and R3 between the positive supply voltage and ground provides inputs to ,~
the negative input terminals of voltage comparators Al and A2. The second input to the voltage comparators Al, A2 is provided in parallel from a device which generates a measured voltage to be indicated on the display. For purposes of illustration the measured voltage-generating device is shown as a variable resistor R4. Resistors R5 and R6 between the outputs of Al and A2 respectively and the positive supply allow the zero outputs of Al and A2 to clamp the voltage at anodes 14a and 14b to ground.
Assuming essentially that the wiper of variable resistor R4 is at its ground end, the voltage fed to the input of Al from variable resistor R4 is less positive than the voltage at the junction of voltage divider resistors Rl and R2. Consequently, voltage comparator Al provides a zero output to anode 14a. Similarlyj voltage comparator A2 provides a zero output to anode 14b. As the wiper of variable resistor R4 is moved toward its positive end, when the voltage thus supplied to voltage comparator Al just exceeds the voltage at the junction of voltage divider resistors Rl and R2, the output of voltage comparator Al switches abruptly from zero to positive voltage. Anode bm:~O
lO'~;Zt^~
14a thereupon becomes positive, attracts thermal electrons from the filament and begins to glow. The positive voltage at the input of voltage comparator A2 from the junction of the divider resistors R2 and R3, being more positive than the voltage fed to voltage comparator Al, retains voltage comparator A2 in the cutoff condition providing a zero output to anode 14b. As the wiper of variable resistor R4 continues to be moved toward its positive end, when the voltage thus fed to voltage comparator A2 exceeds the voltage at the junction of voltage divider resistors R2 and R3 the output of voltage comparator A2 abruptly changes from zero to positive thereby illuminating anode 14b. Additional anode sections 14c, 14d, etc. can be acco~dated by adding one additional voltage divider resistor, voltage comparator and resistor on the output for each section to be added. If all corresponding resistors have the same value, the voltage resolution of the indicator equals the total voltage divided by the number of anode segments. The response of the indicator can be made stepwise non-linear to approximate any desired mathematical curve by suitably choosing the values of the voltage divider resistors.
It will be understood that the claims are intended to cover all changes and modifications of the preferred embodiments of the invention, herein chosen for the purpose of illustration which do not constitute departures from the spirit and scope of the invention, bm:
to convey changing information have become increasingly important. The earliest illuminated display devices were fixed-message signs, such as "exit" or "no smoking" signs which contained a source of light capable of being turned on and off, and a partially translucent face plate containing the message. This type of display suffered washout by strong front illumination. U.S. Patent 3,682,531, issued to A.R. Jeffers teaches a light trap consisting of a circular polarizer and optionally also of a specular foraminous screen to trap ambient light entering the face of the sign.
Electronically controllable display devices have grown particularly with the growth of computers. For example, a gas-discharge device containing a stacked set of ;
bm:
- . - .
,~
1093~;~';i' transparent plates having shaped discharge regions therein has been in use for many years. The shaped discharge regions may for example form the numerals 0 through 9, one to a transparent plate. When the discharge regions in one plate are electrically energized, the characteristic glow of the gas discharge regions forms one of the numerals.
Except when the particular plate illuminated is nearest the viewer, the illuminated numeral is viewed through one or more transparent deenergized plates. When an array of these gas-discharge devices are used to display multiple numerals, the varying distance of the illuminated plates from the viewer gives rise to annoying parallax.
In an attempt to eliminate parallax in a gas-discharge display device, S.M. Frouws, in U.S. Patent 3,418,509, disclosed a planar gas discharge tube containing individually energizable segments spaced away from a counter electrode of transparent conductive material or a fine gauge wire screen through which the viewer observed the segments. The gas discharge was set up between the counter electrode and the energized segments.
This device suffered, in common with all gas discharge devices, the need for high voltages and inductive current limiting. This made it impractical to directly drive bm:
i2~7 gas-discharge display devices from modern solid state electronics.
The modern development of vacuum fluorescent display has solved the parallax and high-voltage problems of the gas discharge display devices while requiring the solution of a number of problems of its own.
A vacuum fluorescent display device uses a filament, heated to below incandescent temperature, as a source of thermionic electrons which are then accelerated toward an anode coated with a phosphor capable of fluorescing under bombardment by low-energy electr~ns.
The accelerating voltage can be from a few volts to hundreds of volts but is preferably in the range of from 10 to 30 volts. By selectively accelerating thermionic electrons to desired regions of the phosphor-coated anode, a bright changeable planar display is achieyed.
It was discovered by R. DuBois that natural electrostatic charges, such as from a comb run through a person's hair and brought into proximity of a vacuum fluorescent display of the type described, could completely extinguish the display for an extended time. His solution, disclosed in U.S. Patent 3,S84,252, consisted in partially encircling the rear and side regions of the anode with a conductive electrostatic shield.
A second problem of unequal illumination of the anode by thermoelectrons has engendered a number of solutions.
The problem arises because a convenient method of fabrication includes an insulating substrate, usually glass, bm:
iOS~3~;~Z'7 behind or embedding the anodes. Charges stored in the insulating substrates so distort the electric field within the vacuum fluorescent device that widely variable illumination of the phosphor occurs. Solutions by R.
Raago in U.S. Patent 4,780,326 and by S. Shimada in U.S.
Patent 3,668,466 taught the use of an auxiliary electrode in substantially the same plane as the anodes.
Application of the correct voltages on the auxiliary electrode could adjust the electrostatic field to achieve 10 uniform illumination or alternatively could extinguish the device. R. Raago in U.S. Patent 3,688,147 solved the problem in a different way by spacing the anode segments on cantilevers far enough forward from the insulating substrate to avoid the distortion of the electrostatic field from charges stored in the insulator. Still another solution, disclosed in varying forms by M. Tanji in U.S. Patents 3,619,694 and 3,508,101 and by R. DuBois in U.S.' Patent 3,566,187 uses a mesh grid interposed between the filament and the anodes operating in a fashion analogous to a normal 20 electron-tube screen grid to accelerate electrons toward the anode using positive voltage or to cut off electron flow to the anode using negative voltage. Proper adjustment of the positive voltage on the grid was effective to cancel the bm:
10~
effect of charges stored in the insulating substrate. In addition, the grid shields the anodes from external electro~
static disturbances. The location of the grid between the filament and the anodes fails to protect the filament from disturbances by external electrostatic fields. In addition, the grid, being positive, attracts electrons to itself. Thus a large current, not contributing to display output, is set up with consequent heating and waste of power.
Summary of the Invention The present invention provides an improvement in a vacuum fluorescent display device having at least one electrically heated thermoelectron-emitting filament, at least one phosphor-coated anode, wherein the filament and anode are sealed in an enclosure having a hard vacuum therein, the improvement comprising:
an electrostatic lens inside the enclosure interposed in the line of sight between the viewer and the filament; the electrostatic lens being a metallic sheet having a regular pattern of holes therethrough, the sheet and holes forming a foraminous screen; ;
the holes comprising from about 20 to about 50 per cent of the screen area; a circular polarizer interposed in the line of sight between the viewer and the screen; the side of the foraminous screen nearest the circular polarizer being specularly reflecting; and the foraminous screen being connected to a positive voltage with respect to the filament.
Brief Description of the Drawings Fig. 1 shows a ghost pictorial perspective view of one embodiment of a vacuum fluorescent display device and a block diagram of power supplies therefor according to the teachings of this invention.
~7 --5 -~!ICr rw/
iZ'7 Fig. 2 shows an embodiment of the present invention which includes a contrast enhancement device.
Fig. 3 shows a close up view of one embodiment of the foraminous screen taken along 3-3 in Fig. 2.
Fig. 4 shows an embodiment of the present invention especially adapted to use as a linear scale indicator.
Fig. 5, adjacent Figures 2 and 3, shows a simplified schematic diagram of a power supply for a linear scale indicator --of the type shown in Fig. 4.
Detailed Description of the Preferred Embodiment . . _ A vacuum fluorescent display device 10 according to the teachings of the present invention is shown in Fig. 1. A
substrate 12 of insulating material, such as glass or ceramic, has a shaped phosphor-coated conductive anode 14 upon or embedded within it. Methods of forming shaped conductive areas on or embedded within insulating materials are well known and do not form part of the present invention. The phosphor coating on the conduetive anode 14 is applied using any method sueh as masked spraying or brushing. The eonduetive anode 14 may be of any eonvenient rw/
lU~3~
planar shape and may comprise a single conduc-tive region or it may be divided into independently controllable subregions of any shape. In the figure, the anode 14 is shown to comprise a -~ shape, for purposes of illustration, made up of a horizontal bar 16 and two vertical half-bars 18, 18a. Each vertical half-bar 18, 18a is separated from the horizontal bar 16 by an insulating gap 19, l9a, An electrical conductor 20 passes sealably through the substrate 12 electrically connecting the horizontal bar 16 to one output of an anode supply 22. Similarly, electrical conductors 24, 24a pass sealably through the substrate 12 electrically connecting the vertical half-bars 18, 18a to the anode supply 22. It will be evident to one skilled in the art that any anode pattern can be formed and independently connected to the anode supply 22. The anode supply 22 is capable of independently controlling the application of accelerating voltages to the parts of the anode 14 according to anode control signals 16 received from an external source, not shown. Thus, the anode segments 16, 18, 18a can be energized in any desired pattern under the control of the anode control signals 26 as will be described.
One or more heater filaments 28 (only one lS
shown) preferably in the form of a fine wire is suspended above the anode 14 by two filament supports 30, 30a. The heater filament 28 is treated with a rare-earth oxide coating bm:
lV93~;z ,~
or by other methods known or which become known to enable it to emit thermoelectrons at dull red color or cooler.
Filament leads 32, 32a sealably penetrate the substrate 12 connecting the filament supports 30, 30a to a filament supply 34.
A reference signal 36 is connected from filament lead 32 to the anode supply 22, When a positive voltage with respect to the reference signal 36 is connected to one or more segments of the anode 14, thermoelectrons are accelerated toward those segments of the anode 14. When a negative or neutral voltage is connected to certain anode 14 segments, thermoelectrons are not accelerated toward those anode 14 segments, The phosphor coating on the positively biased anode 14 segments glows under the bombardment of the thermoelectrons whereas the negatively biased segments remain dark. Thus, a variable illuminated pattern can be set up in the anode 14 by selection of those segments to be positively and negatively biased, Due to the electrostatic charge distribution set up in the substrate 12 and also due to external electrostatic fields, a vacuum fluorescent display device 10 containing only the elements heretofore described will display segments of variable brightness and will be subject to electrostatic disruption of the display. An electrostatic lens 38 connected to an electrostatic lens power supply 40 adjusts the electrostatic field within the display device 10 to bm:
1093~Z'~
overcome the internal electrostatic charge distribution and also shields the filament 28 and anode 14 from ex~
ternal electrostatic disturbances. The electrostatic lens 38 is a transparent conductive surface or a foraminous screen placed in the line of sight 42 between the viewer and the illuminated segments of the anode 14.
A cover 44 having a transparent portion at least in the line of sight 42 is sealed to the substrate 12. The cover 44 and substrate 12 together form a hermetically sealed enclosure within which the anode 14 and the filament 28, with associated parts, are contained. The electrostatic lens 38 is inside the cover 44 to avoid interference from a charge gradient which may be set up across the cover 44.
The hermetically sealed enclosure is evacuated to a hard vacuum between 10 6 and 10 9 torr using methods well known in the art.
Referring now to Fig. 2, there is shown a second embodiment of the invention containing a circular polarizer 46 interposed in the line of sight 42. As is explained in U.S. Patent 3,682,531, the interposition of a circular , polarizer in the line of sight to an internally illuminated display enhances the contrast of the display by trapping incident light while permitting the exit of internally generated light relatively unattenuated.
_ g _ rw/
109~ 7 In Fig. 3, an embodiment of the electrostatic lens 38 which may advantageously be combined with the circular polarizer 46 shown in Fig. 2 to yield an additional contrast enhancement. The electrostatic lens 38 is a foraminous screen containing a plurality of holes 48.
The holes may be in any shape and regular placement but their area should comprise from about 10 to about 70 percent, but best contrast enhancement is obtained with hole openings in the range of from about 20 to about 50 percent of the screen area. The preferred range of hole spacing is from about 100 to about 750 lines per inch.
The holes may be located at the corners of right squares as in Fig. 3 or they may be along skewed or curved lines.
For contrast enhancement with the circular polarizer 46, the side of the foraminous screen 38 nearest the viewer is specularly reflecting. The theory whereby specular reflection in the foraminous screen 38 enhances optical contrast is covered in detail in U.S. Patent 3,682,531.
The foraminous screen 38 is made of electrically conductive material and is electrically connected to the electrostatic lens power supply 40 as shown in Fig. 1.
An embodiment of the invention especially adapted to use as a linear scale indicator is shown in Fig. 4~
Linear scale indicators are advantageously employed in aircraft, automotive and other applications to indicate the status of measured parameters by the length of an illuminated line.
The substrate 12 is in the shape of a rectangular plate made of a suitable glass or ceramic material but preferably is of black glass due to the fact that it bm:
109~ 7 absorbs incident light. An evacuation opening 50 passes through the substrate 12 and is used in a manner well known in the art during the process of evacuating the enclosure. A plurality of bar-shaped anodes 14a, 14b, etc. are disposed in a contiguous parallel array. The anode is partially embedded in the glass substrate 12 and is further retained in position by the passage through the substrate of electrical conductors 20a, 20b, etc.
The electrical conductors 20a, 20b, etc. are conveniently shaped at their outer ends for insertion into standard electrical connectors. Alternatively, the electrical conductors 20a, 20b, etc. may be of wire or may have solder fittings adapted to electrical connection by other conventional methods.
The filament supports 30, 30a (30 is hidden) are supported and power is supplied through filament leads 32, 32a. A flat filament tensioning spring 52 applies endwise force to the filament 28 to prevent sagging.
The filament may also be supported in its run by a filament support wire 54 which extends laterally from pegs 56, 56a. The foraminous screen 38 is placed above the - filament on support legs 58a tthe remaining support legs are not shown). At least one of the support legs 58a extends through the substrate 12 and provides external connection for the control voltage. Thus, connection of the foraminous screen 32 to the control voltage performs the functions of the electrostatic lens previously described. A non-flashing or flashing getter bar 60 is supported within the enclosure on a pair of getter bar support legs 62, 62a which provide external electrical connection, not shown. The non-flashing . ' .
bm:
~093~i~t~
getter bar 60 is used in the final stages of evacuation of the enclosure in a manner well known in the art.
The box shaped cover 44 preferably formed of glass is sealably attached to the upper perimeter of the substrate thereby forming the hermetically sealed enclosure. The outer regions 64, 64a of the glass cover 44 may optionally be blackened to prevent the lateral entry of extraneous light. A rectangular shaped central clear region 66 allows viewing of the illuminated anodes 14a, 14b, etc. through the openings in the foraminous screen 38.
The foraminous screen 38, instead of being independently formed and supported on support legs 58a, could alternatively be produced as a plating photo chemically formed upon the inner surface of the cover 44 with electrical connection to the exterior provided by conventional means.
The circular polarizer 46 may be installed on top of the cover 44 covering at least the clear region 66.
Alternatively, the cover 44 itself may be fabricated in such a manner that it, itself, performs the function of a circular polarizer. For best results, the contrast enhancement device described in United States Patent 3,682,531 requires that the foraminous screen 38 should be specularly reflecting on its side facing the circular polarizer 46 and that there should be no intervening diffusive or further retarding means interposed between them. Although the presence of the clear glass region 66 between the circular polarizer of the foraminous screen as shown in Fig. 4 somewhat degrades the performance of the current enhancement device, the applicant has discovered bm:
lO!~;Z'7 that the degradation is of acceptahle degree.
A portion of an analog to digital anode supply 22 is shown in Fig. 5. For simplicity of description only two anodes 14a and 14b are shown with the associated supply components. It will be understood that the number of anodes may be increased to a large number with each additional anode requiring the addition of a modular set of supply components as shown in Fig, 5. A resistive voltage divider composed of resistors Rl, R2 and R3 between the positive supply voltage and ground provides inputs to ,~
the negative input terminals of voltage comparators Al and A2. The second input to the voltage comparators Al, A2 is provided in parallel from a device which generates a measured voltage to be indicated on the display. For purposes of illustration the measured voltage-generating device is shown as a variable resistor R4. Resistors R5 and R6 between the outputs of Al and A2 respectively and the positive supply allow the zero outputs of Al and A2 to clamp the voltage at anodes 14a and 14b to ground.
Assuming essentially that the wiper of variable resistor R4 is at its ground end, the voltage fed to the input of Al from variable resistor R4 is less positive than the voltage at the junction of voltage divider resistors Rl and R2. Consequently, voltage comparator Al provides a zero output to anode 14a. Similarlyj voltage comparator A2 provides a zero output to anode 14b. As the wiper of variable resistor R4 is moved toward its positive end, when the voltage thus supplied to voltage comparator Al just exceeds the voltage at the junction of voltage divider resistors Rl and R2, the output of voltage comparator Al switches abruptly from zero to positive voltage. Anode bm:~O
lO'~;Zt^~
14a thereupon becomes positive, attracts thermal electrons from the filament and begins to glow. The positive voltage at the input of voltage comparator A2 from the junction of the divider resistors R2 and R3, being more positive than the voltage fed to voltage comparator Al, retains voltage comparator A2 in the cutoff condition providing a zero output to anode 14b. As the wiper of variable resistor R4 continues to be moved toward its positive end, when the voltage thus fed to voltage comparator A2 exceeds the voltage at the junction of voltage divider resistors R2 and R3 the output of voltage comparator A2 abruptly changes from zero to positive thereby illuminating anode 14b. Additional anode sections 14c, 14d, etc. can be acco~dated by adding one additional voltage divider resistor, voltage comparator and resistor on the output for each section to be added. If all corresponding resistors have the same value, the voltage resolution of the indicator equals the total voltage divided by the number of anode segments. The response of the indicator can be made stepwise non-linear to approximate any desired mathematical curve by suitably choosing the values of the voltage divider resistors.
It will be understood that the claims are intended to cover all changes and modifications of the preferred embodiments of the invention, herein chosen for the purpose of illustration which do not constitute departures from the spirit and scope of the invention, bm:
Claims (2)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a vacuum fluorescent display device having at least one electrically heated thermoelectron-emitting filament, at least one phosphor-coated anode, wherein said filament and anode are sealed in an enclosure having a hard vacuum therein, the improvement comprising:
(a) an electrostatic lens inside said enclosure interposed in the line of sight between the viewer and said filament;
(b) said electrostatic lens being a metallic sheet having a regular pattern of holes therethrough, said sheet and holes forming a foraminous screen;
(c) said holes comprising from about 20 to about 50 per cent of the screen area;
(d) a circular polarizer interposed in the line of sight between the viewer and said screen;
(e) the side of said foraminous screen nearest said circular polarizer being specularly reflecting; and (f) said foraminous screen being connected to a positive voltage with respect to said filament.
(a) an electrostatic lens inside said enclosure interposed in the line of sight between the viewer and said filament;
(b) said electrostatic lens being a metallic sheet having a regular pattern of holes therethrough, said sheet and holes forming a foraminous screen;
(c) said holes comprising from about 20 to about 50 per cent of the screen area;
(d) a circular polarizer interposed in the line of sight between the viewer and said screen;
(e) the side of said foraminous screen nearest said circular polarizer being specularly reflecting; and (f) said foraminous screen being connected to a positive voltage with respect to said filament.
2. The improvement recited in claim 1 wherein said holes are in a regular pattern of from about 100 to about 750 holes per linear inch.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA354,539A CA1108216A (en) | 1976-10-14 | 1980-06-20 | Vacuum fluorescent indicator |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/732,330 US4100455A (en) | 1976-10-14 | 1976-10-14 | Vacuum fluorescent display device with circular polarizer |
| US732,330 | 1976-10-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1093627A true CA1093627A (en) | 1981-01-13 |
Family
ID=24943116
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA286,441A Expired CA1093627A (en) | 1976-10-14 | 1977-09-09 | Vacuum fluorescent indicator |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4100455A (en) |
| JP (3) | JPS5348663A (en) |
| CA (1) | CA1093627A (en) |
| DE (2) | DE7730946U1 (en) |
| FR (1) | FR2368107A1 (en) |
| GB (1) | GB1555385A (en) |
| IT (1) | IT1090158B (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53126560U (en) * | 1977-03-15 | 1978-10-07 | ||
| US6630970B2 (en) | 2001-07-02 | 2003-10-07 | 3M Innovative Properties Company | Polarizers for use with liquid crystal displays |
| JPS5625445U (en) * | 1979-08-03 | 1981-03-09 | ||
| GB2133935A (en) * | 1982-12-17 | 1984-08-01 | Payne John M | Dissipating electrical charge from the screen of a visual display unit |
| JPH061674B2 (en) * | 1984-12-04 | 1994-01-05 | ソニー株式会社 | Fluorescent display tube |
| FR2586508B1 (en) * | 1985-08-23 | 1988-08-26 | Thomson Csf | RADIOLOGICAL IMAGE ENHANCER TUBE ENTRY SCREEN SCINTILLER AND METHOD FOR MANUFACTURING SUCH A SCINTILLATOR |
| EP0529090B1 (en) * | 1991-03-06 | 1996-11-27 | Miyota Kabushiki Kaisha | Cathode luminescence device |
| JP3485530B2 (en) * | 2000-07-12 | 2004-01-13 | 双葉電子工業株式会社 | Fluorescent display tube |
| US6549335B1 (en) * | 2000-07-28 | 2003-04-15 | 3M Innovative Properties Company | High durability circular polarizer for use with emissive displays |
| US20050088084A1 (en) * | 2003-10-27 | 2005-04-28 | Eastman Kodak Company | Organic polarized light emitting diode display with polarizer |
| JP6393197B2 (en) * | 2015-01-20 | 2018-09-19 | ノリタケ伊勢電子株式会社 | Vacuum tube |
| US11881373B2 (en) | 2022-01-11 | 2024-01-23 | Thomas Koschmieder | Triode with wirebonded structure and method of making |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2016737A1 (en) * | 1969-04-17 | 1970-11-05 | Sony Corp., Tokio | Electron tube |
| US3682531A (en) * | 1970-11-05 | 1972-08-08 | Andrew R Jeffers | High contrast display device |
| JPS4928364A (en) * | 1972-07-04 | 1974-03-13 | ||
| JPS5011179A (en) * | 1973-05-28 | 1975-02-05 | ||
| GB1522145A (en) * | 1974-11-06 | 1978-08-23 | Marconi Co Ltd | Light emissive diode displays |
| US4004186A (en) * | 1975-12-01 | 1977-01-18 | Texas Instruments Incorporated | Vacuum fluorescent display having a grid plate coplanar with the anode |
-
1976
- 1976-10-14 US US05/732,330 patent/US4100455A/en not_active Expired - Lifetime
-
1977
- 1977-09-09 CA CA286,441A patent/CA1093627A/en not_active Expired
- 1977-09-12 GB GB37883/77A patent/GB1555385A/en not_active Expired
- 1977-09-28 IT IT51183/77A patent/IT1090158B/en active
- 1977-10-06 DE DE19777730946U patent/DE7730946U1/en not_active Expired
- 1977-10-06 DE DE19772745029 patent/DE2745029A1/en not_active Withdrawn
- 1977-10-13 JP JP12195577A patent/JPS5348663A/en active Pending
- 1977-10-13 FR FR7730885A patent/FR2368107A1/en active Granted
-
1980
- 1980-02-22 JP JP2064480A patent/JPS55163592A/en active Pending
-
1981
- 1981-06-02 JP JP1981080667U patent/JPS5725455U/ja active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| FR2368107B1 (en) | 1982-02-05 |
| FR2368107A1 (en) | 1978-05-12 |
| JPS5725455U (en) | 1982-02-09 |
| GB1555385A (en) | 1979-11-07 |
| JPS55163592A (en) | 1980-12-19 |
| IT1090158B (en) | 1985-06-18 |
| JPS5348663A (en) | 1978-05-02 |
| DE7730946U1 (en) | 1978-09-21 |
| DE2745029A1 (en) | 1978-04-27 |
| US4100455A (en) | 1978-07-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |