CA1252505A - Middle-infrared imaging device - Google Patents
Middle-infrared imaging deviceInfo
- Publication number
- CA1252505A CA1252505A CA000506528A CA506528A CA1252505A CA 1252505 A CA1252505 A CA 1252505A CA 000506528 A CA000506528 A CA 000506528A CA 506528 A CA506528 A CA 506528A CA 1252505 A CA1252505 A CA 1252505A
- Authority
- CA
- Canada
- Prior art keywords
- membrane
- intensifier
- image
- visible light
- light generating
- 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
- H01J31/50—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output
- H01J31/506—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output tubes using secondary emission effect
- H01J31/507—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output tubes using secondary emission effect using a large number of channels, e.g. microchannel plates
Abstract
Abstract of the Disclosure A middle-infrared image intensifier including an image-forming microchannel plate, a thermionic emissive membrane in front of the microchannel plate, and a lens system to form a middle-infrared image on the membrane, whereby electrons emitted from the membrane are multiplied in channels of the microchannel plate.
Description
S~5 6~20~-103 Field of the Invention The invention relates to middle-infrared image intensifiers.
sackground of the Invention Present direct-view, night-vision, image intensifiers employ photoelectron emission for the primary photodetection process, and thus are limited to visible, near-infrared wavelengths not greater than one micron, e.g., provided by moonlight or starlight, in order to obtain the energy necessary for photoelectron emission.
In these devices microchannel plates are typically used to amplify 10 the electrons, which are then directed to a phosphor screen, to provide a visible image, Imaging systems for middle-infrared radiation (i.e., result-ing from heat), which has insufficient energy for photoelectron emission, are indirect, employing arrays of semiconductor elements connected to display devices by pluralities of wires. These systems are thus complicated, large, heavy, and expensive.
Summary of the Invention I have discovered that middle-infrared image intensification can be achieved at room temperature and without the need for a cooling system by using a lens to form a s middle-infrared image on a thermionic emissive membrane and multiplying the electrons emi-t-ted from the back of -the membrane in response to middle-infrared radiation on the front of the membrane in channels of a microchannel plate.
According to a broad aspect of the invention there is provided a middle-infrared image intensifier comprising an i.mage-forming microchannel plate, a thermionic emissive membrane in front of said microchannel plate, said membrane emitting electrons when exposed to middle-infrared radiation, and a lens system to form a middle-infrared image on said membrane, said membrane being sufficiently thin and mounted to have two dimensional temperature differences develop across its surface conforming to said middle-infrared image so that electrons emitted from said membrane are emitted in an amount related to the temperature of the membrane at the position from which they are emitted and are multiplied in channels of said microchannel plate.
In preferred embodiments the electron flux from the microchannel plate is directed to an electroluminescent display to provide a visible image; and a modulator is used to repetitively admit and block incoming middle-infrared radiation, and an image extraction stage is used to provide signals related to the difference between the electron flux from the microchannel plate when the incoming middle-infrared radiation is admitted and the electron flux when the incoming middle-infrared radiation is blocked.
.
5~S~5 Other advantages and features ofthe invention will be apparent from the claims and from the following description of the preferred embodiments.
Description of the Preferred Embodiments -The drawings are briefly described first.
Drawings Figure l is a diagrammatic vertical sectional view of a middle-infrared image intensifier according to the invention.
Figure 2 is a diagrammatic vertical sectional view of an image extraction stage of the Figure l apparatus according to the invention.
2a ~2~S(?5 Figure 3 is the equivalent circuit for a unit of the Figure
sackground of the Invention Present direct-view, night-vision, image intensifiers employ photoelectron emission for the primary photodetection process, and thus are limited to visible, near-infrared wavelengths not greater than one micron, e.g., provided by moonlight or starlight, in order to obtain the energy necessary for photoelectron emission.
In these devices microchannel plates are typically used to amplify 10 the electrons, which are then directed to a phosphor screen, to provide a visible image, Imaging systems for middle-infrared radiation (i.e., result-ing from heat), which has insufficient energy for photoelectron emission, are indirect, employing arrays of semiconductor elements connected to display devices by pluralities of wires. These systems are thus complicated, large, heavy, and expensive.
Summary of the Invention I have discovered that middle-infrared image intensification can be achieved at room temperature and without the need for a cooling system by using a lens to form a s middle-infrared image on a thermionic emissive membrane and multiplying the electrons emi-t-ted from the back of -the membrane in response to middle-infrared radiation on the front of the membrane in channels of a microchannel plate.
According to a broad aspect of the invention there is provided a middle-infrared image intensifier comprising an i.mage-forming microchannel plate, a thermionic emissive membrane in front of said microchannel plate, said membrane emitting electrons when exposed to middle-infrared radiation, and a lens system to form a middle-infrared image on said membrane, said membrane being sufficiently thin and mounted to have two dimensional temperature differences develop across its surface conforming to said middle-infrared image so that electrons emitted from said membrane are emitted in an amount related to the temperature of the membrane at the position from which they are emitted and are multiplied in channels of said microchannel plate.
In preferred embodiments the electron flux from the microchannel plate is directed to an electroluminescent display to provide a visible image; and a modulator is used to repetitively admit and block incoming middle-infrared radiation, and an image extraction stage is used to provide signals related to the difference between the electron flux from the microchannel plate when the incoming middle-infrared radiation is admitted and the electron flux when the incoming middle-infrared radiation is blocked.
.
5~S~5 Other advantages and features ofthe invention will be apparent from the claims and from the following description of the preferred embodiments.
Description of the Preferred Embodiments -The drawings are briefly described first.
Drawings Figure l is a diagrammatic vertical sectional view of a middle-infrared image intensifier according to the invention.
Figure 2 is a diagrammatic vertical sectional view of an image extraction stage of the Figure l apparatus according to the invention.
2a ~2~S(?5 Figure 3 is the equivalent circuit for a unit of the Figure
2 image extraction stage.
Figure 4 is a diagrammatic, partially schematic, ver-tical sectional view of an alternative image extraction stage according to the invention.
Figure 5 is the equivalent circuit for a unit of the Figure 4 image extraction stage.
Structure Referring to Figure 1, there is shown middle-infrared (middle-IR) image intensifier 10 including middle-IR transparent lens system 11, middle-IR transparent window 12, middle-IR image modulator 14 ( a Pockels cell, which transmits radiation for a period of Td and blocks radiation for an equal period during each cycle), microchannel plate 16 (having conductive channels spaced 50-100 microns center-to-center, a maximum gain of 104 and a maximum output of 108 (electrons/channel-second), membrane 18 supported on the front of microchannel plate 16 and including silicon dioxide support layer 19 and cathode 20 (Cs-0-~g ma-terial, Sl code, having a low work function of approximately 1.2 eV), and image extraction stage 22. Components 12 through 22 are contained within a vacuum seal formed between components 12 and 22.
Membrane 18 is between 100 angstroms and 10 microns thick, preferably between about 1 and 10 microns; it should not be so thin that radiation passes through it without absorption, and it should not be so thick that there is a temperature gradient across it, owing to colling at the periphery. It exhibits " 3 ~S~5(~5 substantial thermionic emission at only moderately elevated temperatures and has sufficient electrical conductivity to replace electron emission losses without the creation of a per-turbing lateral electric field.
Referring to Figure 2, the first embodiment of image extrac-tion stage 22 includes glass output window 24 carrying layer 26 of vacuum deposited, transparent, electrically conductive tin oxide thereon. Supported across the surface of tin oxide layer 26 are units 23, each approximately 80 microns wide, spaced from each other by 100 microns center-to-center, generally square in plan view and arranged in rows and columns on glass window 24.
Each unit 23 includes electroluminescent layer 28 (e.g., a member of the zinc sulfide family of electroluminescent material and between 10 and 100 microns thick), electrically conductive, metallic layer 30 (e.g., of a nickel-chrome alloy available under the trade designation Inconel) thereabove, 1-10 micron thick glass layer 32 thereabove, electrically conductive, metallic collector layer 34 thereabove, and resistor material 36 adjacent to layers 28 through 32 and underneath collector layer 34.
Referring to Figure 3, which is the equivalent circuit for a single unit 23, I~ represents the electron flux hitting collector layer 34. Resistor Rl is provided by glass layer 32, and capacitor Cl is provided by glass layer 32 and conductive layers 30, 34 on opposite sides of it. Resistor R2 is provided by zinc sulfide layer 28, and capacitor C2 is provided by zinc . ~
~s~s~
6920~-103 sulfide layer 28 and overlapping portions of conductive layers 26, 30 on opposite sides of it. Bypass resistor R3 is provided by material 36. Capacitor C3 is outside of the sealed components of intensifier 10 and is connected to tin oxide layer 26. Power supply Ps is also connected to tin oxide layer 26 through exter-nal resistor R4. The materials and dimensions of components in each unit 23 are selected to provide certain electrical character-istics. The resistance of resistor Rl is much greater than the resistance of resistor R2; to achieve this glass layer 32 is designed to have as little leakage current as possible. The capacitance of capacitro Cl is much greater than the capacitance of capacitor C2, and the capacitance of capacitor C3 is much greater than the capacitance of capacitor C2, so that the ratio 1:(1 + C2/C3 ~ C2/Cl), which determines the fraction of the modulated component of the electron flux that is applied to electroluminescent layer 28, is as high as possible. The pro-duct of the capacitance of capacitor C2 times the resistance of R2 is much greater than the value of l/Wm, where Wm/2~ is the input radiation modulation frequency of modulator 14. The actual values are as follows:
Cl lo-llF
Rl 1015 ohms R2 1013 ohms R3 5 x 1nl2 ohms This makes the relaxation time-constant of electroluminescent layer 28 long compared to the radiation modulation period, to ~S~5~5 minimize resistive losses from the modulated signal. The maximum dielectric strength required of the capacitors is 105 V/cm.
Referring to Figure 4, there is shown a partially schematic, vertical sectional view of a second embodiment of image extraction stage 22, this one designated 22'. It includes lower glass output window 50, on which is deposited transparent, electrically conduc-tive tin oxide layer 52. Thereabove are supported units 54, each approximately 80 microns wide, spaced from adjacent units by about 100 microns center-to-center, generally square in shape in plan view, and arranged in rows and columns on glass window 50.
Each unit 54 includes glass layer 58, electrically conductive metallic layer 60 thereabove, electroluminescent layer 62 there-above, and electrically conductive collector layer 64 on top.
Adjacent to layers 58-64 are electrically conductive collector layer 66 and diodes Dl, D2 and resistor R4, positioned below layer 66 and indicated schematically in Figure 4. Suspended between 100 microns and 1 mm above, and aligned with, collector layers 64, 66 are tungsten wires 68 about 10 microns in diameter.
Referring to Figure 5, the equivalent circuit for a unit 54 is shown. Capacitor C4 is provided by electroluminescent layer 62 and conductive layers 60, 64 on opposite sides of it. Capaci-tor C5 is provided predominantly by glass layer 58 and overlapping portions of conductive layers 52, 60 on opposite sides of it and also by overlapping portions of conductive layers 52, 66 and the components between them. The materials and dimensions of the components are such that the resistance of resistor R4 is between ~5~5~5 1012 and 1013 ohms, preferably 1013 ohms and the capacitance of capacitor C5 is between 1o~14 and 10-15 farads, also the capaci-tance of capacitor C5 is at least 10 times larger than the capacitance of capacitor C4, and the maximum dielectric strength of the capacitors is 105 V/cm.
Operation _ In operation middle-IR radiation is projected by lens system 11 to form a middle-IR image on the front of membrane 18, heating up portions of the membrane to varying extents. Modulator 14 repetitively admits incoming middle-IR for a period Td and blocks incoming middle-IR for a period Td , at a frequency of 100 H~.
Electrons are emitted from the rear of membrane 18 in an amount related to the temperature of the membrane at the positions from which they are emitted, and enter the various channels of micro-channel plate 16. The electrons are multiplied within the channels of microchannel plate 16. The electron flux from micro-channel plate 16 is directed to image extraction stage 22, where the electron flux resulting from background thermionic emission (i.e., that not due to the image formed on membrane 18) is ~0 subtracted from the total flux, and the visible image that is displayed by stage 22 is based upon the difference.
Image extraction stage 22, shown in detail in Figures 2 and
Figure 4 is a diagrammatic, partially schematic, ver-tical sectional view of an alternative image extraction stage according to the invention.
Figure 5 is the equivalent circuit for a unit of the Figure 4 image extraction stage.
Structure Referring to Figure 1, there is shown middle-infrared (middle-IR) image intensifier 10 including middle-IR transparent lens system 11, middle-IR transparent window 12, middle-IR image modulator 14 ( a Pockels cell, which transmits radiation for a period of Td and blocks radiation for an equal period during each cycle), microchannel plate 16 (having conductive channels spaced 50-100 microns center-to-center, a maximum gain of 104 and a maximum output of 108 (electrons/channel-second), membrane 18 supported on the front of microchannel plate 16 and including silicon dioxide support layer 19 and cathode 20 (Cs-0-~g ma-terial, Sl code, having a low work function of approximately 1.2 eV), and image extraction stage 22. Components 12 through 22 are contained within a vacuum seal formed between components 12 and 22.
Membrane 18 is between 100 angstroms and 10 microns thick, preferably between about 1 and 10 microns; it should not be so thin that radiation passes through it without absorption, and it should not be so thick that there is a temperature gradient across it, owing to colling at the periphery. It exhibits " 3 ~S~5(~5 substantial thermionic emission at only moderately elevated temperatures and has sufficient electrical conductivity to replace electron emission losses without the creation of a per-turbing lateral electric field.
Referring to Figure 2, the first embodiment of image extrac-tion stage 22 includes glass output window 24 carrying layer 26 of vacuum deposited, transparent, electrically conductive tin oxide thereon. Supported across the surface of tin oxide layer 26 are units 23, each approximately 80 microns wide, spaced from each other by 100 microns center-to-center, generally square in plan view and arranged in rows and columns on glass window 24.
Each unit 23 includes electroluminescent layer 28 (e.g., a member of the zinc sulfide family of electroluminescent material and between 10 and 100 microns thick), electrically conductive, metallic layer 30 (e.g., of a nickel-chrome alloy available under the trade designation Inconel) thereabove, 1-10 micron thick glass layer 32 thereabove, electrically conductive, metallic collector layer 34 thereabove, and resistor material 36 adjacent to layers 28 through 32 and underneath collector layer 34.
Referring to Figure 3, which is the equivalent circuit for a single unit 23, I~ represents the electron flux hitting collector layer 34. Resistor Rl is provided by glass layer 32, and capacitor Cl is provided by glass layer 32 and conductive layers 30, 34 on opposite sides of it. Resistor R2 is provided by zinc sulfide layer 28, and capacitor C2 is provided by zinc . ~
~s~s~
6920~-103 sulfide layer 28 and overlapping portions of conductive layers 26, 30 on opposite sides of it. Bypass resistor R3 is provided by material 36. Capacitor C3 is outside of the sealed components of intensifier 10 and is connected to tin oxide layer 26. Power supply Ps is also connected to tin oxide layer 26 through exter-nal resistor R4. The materials and dimensions of components in each unit 23 are selected to provide certain electrical character-istics. The resistance of resistor Rl is much greater than the resistance of resistor R2; to achieve this glass layer 32 is designed to have as little leakage current as possible. The capacitance of capacitro Cl is much greater than the capacitance of capacitor C2, and the capacitance of capacitor C3 is much greater than the capacitance of capacitor C2, so that the ratio 1:(1 + C2/C3 ~ C2/Cl), which determines the fraction of the modulated component of the electron flux that is applied to electroluminescent layer 28, is as high as possible. The pro-duct of the capacitance of capacitor C2 times the resistance of R2 is much greater than the value of l/Wm, where Wm/2~ is the input radiation modulation frequency of modulator 14. The actual values are as follows:
Cl lo-llF
Rl 1015 ohms R2 1013 ohms R3 5 x 1nl2 ohms This makes the relaxation time-constant of electroluminescent layer 28 long compared to the radiation modulation period, to ~S~5~5 minimize resistive losses from the modulated signal. The maximum dielectric strength required of the capacitors is 105 V/cm.
Referring to Figure 4, there is shown a partially schematic, vertical sectional view of a second embodiment of image extraction stage 22, this one designated 22'. It includes lower glass output window 50, on which is deposited transparent, electrically conduc-tive tin oxide layer 52. Thereabove are supported units 54, each approximately 80 microns wide, spaced from adjacent units by about 100 microns center-to-center, generally square in shape in plan view, and arranged in rows and columns on glass window 50.
Each unit 54 includes glass layer 58, electrically conductive metallic layer 60 thereabove, electroluminescent layer 62 there-above, and electrically conductive collector layer 64 on top.
Adjacent to layers 58-64 are electrically conductive collector layer 66 and diodes Dl, D2 and resistor R4, positioned below layer 66 and indicated schematically in Figure 4. Suspended between 100 microns and 1 mm above, and aligned with, collector layers 64, 66 are tungsten wires 68 about 10 microns in diameter.
Referring to Figure 5, the equivalent circuit for a unit 54 is shown. Capacitor C4 is provided by electroluminescent layer 62 and conductive layers 60, 64 on opposite sides of it. Capaci-tor C5 is provided predominantly by glass layer 58 and overlapping portions of conductive layers 52, 60 on opposite sides of it and also by overlapping portions of conductive layers 52, 66 and the components between them. The materials and dimensions of the components are such that the resistance of resistor R4 is between ~5~5~5 1012 and 1013 ohms, preferably 1013 ohms and the capacitance of capacitor C5 is between 1o~14 and 10-15 farads, also the capaci-tance of capacitor C5 is at least 10 times larger than the capacitance of capacitor C4, and the maximum dielectric strength of the capacitors is 105 V/cm.
Operation _ In operation middle-IR radiation is projected by lens system 11 to form a middle-IR image on the front of membrane 18, heating up portions of the membrane to varying extents. Modulator 14 repetitively admits incoming middle-IR for a period Td and blocks incoming middle-IR for a period Td , at a frequency of 100 H~.
Electrons are emitted from the rear of membrane 18 in an amount related to the temperature of the membrane at the positions from which they are emitted, and enter the various channels of micro-channel plate 16. The electrons are multiplied within the channels of microchannel plate 16. The electron flux from micro-channel plate 16 is directed to image extraction stage 22, where the electron flux resulting from background thermionic emission (i.e., that not due to the image formed on membrane 18) is ~0 subtracted from the total flux, and the visible image that is displayed by stage 22 is based upon the difference.
Image extraction stage 22, shown in detail in Figures 2 and
3, can be used when the thermionic emission based upon the middle-IR image is comparable in magnitude to the background emission of membrane 18 at room temperature. Image extraction stage 22, shown in detail in Figures 4 and 5, can be used when ., ~ .
~s~s the thermionic emission based upon the middle-IR image is much smaller than the background emission of membrane 18 at room temperature.
In operation of the Figures 2-3 image extraction stage, because the resistance oE resistor Rl is very large, essentially all of the DC component of the microchannel plate electron flux Ie passes through bypass resistor R3, and only the ~C component of the electron flux, based upon the middle-IR image on membrane 18, is directed to electroluminescent layer 28, and provides a visible image of the middle-IR radiation image on membrane 18.
In operation of the Figures 4-5 image extraction stage, wires 68 associated with collector layers 64 and wires 68 associated with collector layers 66 are alternately switched between positive and negative voltages in synchronization with the admission and rejection of middle-IR by modulator 14. When middle-IR radiation is admitted by modulator 14, the electrons from microchannel plate 16 are all deflected to collector layers 64 by providing a positive voltage on the wires in front of collector layers 64 and a negative voltage on the wires in front of collector layers 66.
When middle-IR radiation is rejected by modulator 14, the electrons from microchannel plate 16 are all directed to collector layers 66, by providing a negative voltage on the wires in front of collector layers 64 and a positive voltage on the wires in front of collector layers 66.
If no middle-IR radiation is projected onto membrane 18, the electron fluxes hitting collector layers 64, 66 are the same; the potentials at collector layers 64, 66 are equal, and there is no ~S~5~5 potential across electroluminescent layer 62 (capacitor C4 in Figure 5). When a middle-IR image is projected on membrane 18, the electron fluxes hitting collector layers 64, 66 differ, and a potential equal to the difference in electron flux times the resistance of resistor R4 appears across electroluminescent layer 62, and causes a visible image to be displayed.
Other Embodiments Other embodiments of the invention are wi-thin the scope of the following claims.
For example, other membrane and cathode materials can be used (e.g., depending on the operating temperatures and the radiation being monitored), and different means can be used to extract from the electron flux the signals related to the middle-infrared images. The Cs-O-Ag cathode material described above has useful thermionic emission near 300K. Ba 0/SrOor Ni has useful emissions in the 400-700K range, and Ba-W has useful emission in the 375 to 500K range. Other candidates for low work function cathode material are those listed in Table 4.1 of Bleaney et al., Electricity and Magnetism, (Oxford at the Clarendon Press, 1965) p. 92. Different materials and components can be used to obtain the equivalent circuits shown in Figures 3 and 5, and these circuits can be modified to rely on the same principles for extracting image signals. Also, in the image extraction stage a visible image can be provided by light emitting diodes, liquid crystals or plasma-cell panels (e.g., as described in G.F. Weston and R. Bittleston, Alphanumeric Disl~lays (McGraw Hill, 1982)) ~z~zs~s could be used in place of the electroluminescent materials. The brightness display provided by any of these means could be increased by a second stage or even second and third stayes of image intensification, as is common in some existing night vision instruments. Another alternative is having the electron flux emerging from the microchannel plate directly strike a phosphor screen, and extracting the infrared image from the resultant visible display by known optical image-processing techniques.
~s~s the thermionic emission based upon the middle-IR image is much smaller than the background emission of membrane 18 at room temperature.
In operation of the Figures 2-3 image extraction stage, because the resistance oE resistor Rl is very large, essentially all of the DC component of the microchannel plate electron flux Ie passes through bypass resistor R3, and only the ~C component of the electron flux, based upon the middle-IR image on membrane 18, is directed to electroluminescent layer 28, and provides a visible image of the middle-IR radiation image on membrane 18.
In operation of the Figures 4-5 image extraction stage, wires 68 associated with collector layers 64 and wires 68 associated with collector layers 66 are alternately switched between positive and negative voltages in synchronization with the admission and rejection of middle-IR by modulator 14. When middle-IR radiation is admitted by modulator 14, the electrons from microchannel plate 16 are all deflected to collector layers 64 by providing a positive voltage on the wires in front of collector layers 64 and a negative voltage on the wires in front of collector layers 66.
When middle-IR radiation is rejected by modulator 14, the electrons from microchannel plate 16 are all directed to collector layers 66, by providing a negative voltage on the wires in front of collector layers 64 and a positive voltage on the wires in front of collector layers 66.
If no middle-IR radiation is projected onto membrane 18, the electron fluxes hitting collector layers 64, 66 are the same; the potentials at collector layers 64, 66 are equal, and there is no ~S~5~5 potential across electroluminescent layer 62 (capacitor C4 in Figure 5). When a middle-IR image is projected on membrane 18, the electron fluxes hitting collector layers 64, 66 differ, and a potential equal to the difference in electron flux times the resistance of resistor R4 appears across electroluminescent layer 62, and causes a visible image to be displayed.
Other Embodiments Other embodiments of the invention are wi-thin the scope of the following claims.
For example, other membrane and cathode materials can be used (e.g., depending on the operating temperatures and the radiation being monitored), and different means can be used to extract from the electron flux the signals related to the middle-infrared images. The Cs-O-Ag cathode material described above has useful thermionic emission near 300K. Ba 0/SrOor Ni has useful emissions in the 400-700K range, and Ba-W has useful emission in the 375 to 500K range. Other candidates for low work function cathode material are those listed in Table 4.1 of Bleaney et al., Electricity and Magnetism, (Oxford at the Clarendon Press, 1965) p. 92. Different materials and components can be used to obtain the equivalent circuits shown in Figures 3 and 5, and these circuits can be modified to rely on the same principles for extracting image signals. Also, in the image extraction stage a visible image can be provided by light emitting diodes, liquid crystals or plasma-cell panels (e.g., as described in G.F. Weston and R. Bittleston, Alphanumeric Disl~lays (McGraw Hill, 1982)) ~z~zs~s could be used in place of the electroluminescent materials. The brightness display provided by any of these means could be increased by a second stage or even second and third stayes of image intensification, as is common in some existing night vision instruments. Another alternative is having the electron flux emerging from the microchannel plate directly strike a phosphor screen, and extracting the infrared image from the resultant visible display by known optical image-processing techniques.
Claims (13)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A middle-infrared image intensifier comprising an image-forming microchannel plate, a thermionic emissive membrane in front of said microchannel plate, said membrane emitting electrons when exposed to middle-infrared radiation, and a lens system to form a middle-infrared image on said membrane, said membrane being sufficiently thin and mounted to have two dimensional temperature differences develop across its surface conforming to said middle-infrared image so that electrons emitted from said membrane are emitted in an amount related to the temperature of the membrane at the position from which they are emitted and are multiplied in channels of said microchannel plate.
2. The intensifier of claim 1, further comprising visi-ble image means for providing a visible image of said middle-infrared image based upon electron flux provided by said micro-channel plate.
3. The intensifier of claim 2 further comprising a modulator to repetitively admit middle-infrared radiation to said membrane and block middle-infrared radiation from said membrane, and image extraction means for obtaining signals related in magnitude to the difference of the electron flux when no middle-infrared image appears on said membrane and the electron flux when a middle infrared image appears on said membrane.
4. The intensifier of claim 3 wherein said visible image means and said image extraction menas are provided by a plurality of discrete units supported by a glass plate, each said unit including a visible light generating element.
5. The intensifier of claim 4 wherein the electron flux has a varying component of a nonvarying component, and each said unit includes a resistor-capacitor network so that the varying component of the electron flux from said microchannel plate appears at said visible light generating element and the nonvarying component passes through other electrical components in said unit.
6. The intensifier of claim 4 wherein each said unit includes two collectors to receive said electron flux, and means are provided for alternately directing said electron flux to one collector and then the other collector in synchronization with the admitting and rejecting of said middle-infrared radiation by said modulator.
7. The intensifier of claim 6 wherein each said unit includes means for providing to said visible light generating element signals related to the difference in magnitude of the electron fluxes received by said collectors.
8. The intensifier of claim 7 wherein electrodes of said visible light generating element are directly connected to, or integral with, said two collectors, which are each connected to a common resistor.
9. The intensifier of claim 4, 5 or 6 in which said visible light generating element is an electroluminescent element.
10. The intensifier of claim 5 or 8 in which said visible light generating element is made of a member of the zinc sulfide family or electroluminescent materials.
11. The intensifier of claim 4, 5 or 7 in which said visible light generating element is one of the group of a light emitting diode, a liquid crystal element and a plasma panel element.
12. The intensifier of claim 1 or 4 in which said membrane includes a cathode of material of one of the group of Cs-O-Ag, BaO/SiO/-Ni, and Ba-W.
13. The intensifier of claim 7 or 8 in which said visible light generating element is an electroluminescent element.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/738,353 US4701618A (en) | 1985-05-28 | 1985-05-28 | Middle-infrared imaging device |
| US738,353 | 1985-05-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1252505A true CA1252505A (en) | 1989-04-11 |
Family
ID=24967637
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000506528A Expired CA1252505A (en) | 1985-05-28 | 1986-04-14 | Middle-infrared imaging device |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US4701618A (en) |
| JP (1) | JPS61273838A (en) |
| BE (1) | BE904837A (en) |
| CA (1) | CA1252505A (en) |
| CH (1) | CH671640A5 (en) |
| DE (1) | DE3617929A1 (en) |
| FR (1) | FR2582859A1 (en) |
| GB (1) | GB2175742B (en) |
| IT (1) | IT1189676B (en) |
| NL (1) | NL8600841A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4914296A (en) * | 1988-04-21 | 1990-04-03 | The Boeing Company | Infrared converter |
| GB8812957D0 (en) * | 1988-06-01 | 1988-10-05 | Thorn Emi Electronics Ltd | Thermal imaging |
| US5132586A (en) * | 1991-04-04 | 1992-07-21 | The United States Of America As Represented By The Secretary Of The Navy | Microchannel electron source |
| DE19827094A1 (en) * | 1998-06-18 | 1999-12-23 | Treo Elektrooptik Gmbh | Image converter e.g. image amplifier tube |
| JP2011517044A (en) * | 2008-04-10 | 2011-05-26 | アラディアンス インコーポレイテッド | Image intensifier |
Family Cites Families (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3056062A (en) * | 1952-08-15 | 1962-09-25 | Westinghouse Electric Corp | Thermal image converter |
| US3130309A (en) * | 1961-10-03 | 1964-04-21 | Honeywell Regulator Co | Infrared visual image converter with lens mirror coated with infrared absorbing material |
| FR83070E (en) * | 1963-02-12 | 1964-06-05 | Electronique & Physique | Image transformer tube |
| GB1090406A (en) * | 1963-08-19 | 1967-11-08 | Mullard Ltd | Improvements in or relating to image intensifiers and the like |
| US3407324A (en) * | 1967-06-21 | 1968-10-22 | Electro Mechanical Res Inc | Electron multiplier comprising wafer having secondary-emissive channels |
| US3681606A (en) * | 1969-04-10 | 1972-08-01 | Bendix Corp | Image intensifier using radiation sensitive metallic screen and electron multiplier tubes |
| GB1303889A (en) * | 1970-08-13 | 1973-01-24 | ||
| GB1321022A (en) * | 1971-04-22 | 1973-06-20 | Standard Telephones Cables Ltd | Channel plate |
| JPS5759624B2 (en) * | 1974-04-01 | 1982-12-15 | Nippon Electric Co | |
| US3983395A (en) * | 1974-11-29 | 1976-09-28 | General Electric Company | MIS structures for background rejection in infrared imaging devices |
| CA1098615A (en) * | 1975-12-29 | 1981-03-31 | George S. Hopper | Ferroelectric imaging system |
| US4100445A (en) * | 1976-03-15 | 1978-07-11 | The Machlett Laboratories, Inc. | Image output screen comprising juxtaposed doped alkali-halide crystalline rods |
| DE2752704A1 (en) * | 1976-11-26 | 1978-06-01 | Texas Instruments Inc | IR detector system using optical and electronic devices - collects and focusses energy from scene via lens to convert into electric signals (NL 30.5.78) |
| US4147932A (en) * | 1977-09-06 | 1979-04-03 | Xonics, Inc. | Low light level and infrared viewing system |
| US4316103A (en) * | 1979-05-15 | 1982-02-16 | Westinghouse Electric Corp. | Circuit for coupling signals from a sensor |
| US4550251A (en) * | 1983-07-08 | 1985-10-29 | Varian Associates, Inc. | Image intensifier tube with increased contrast ratio |
-
1985
- 1985-05-28 US US06/738,353 patent/US4701618A/en not_active Expired - Fee Related
-
1986
- 1986-04-02 NL NL8600841A patent/NL8600841A/en not_active Application Discontinuation
- 1986-04-14 CA CA000506528A patent/CA1252505A/en not_active Expired
- 1986-04-23 GB GB8609924A patent/GB2175742B/en not_active Expired
- 1986-05-12 JP JP61108390A patent/JPS61273838A/en active Pending
- 1986-05-23 IT IT67426/86A patent/IT1189676B/en active
- 1986-05-28 FR FR8607647A patent/FR2582859A1/en not_active Withdrawn
- 1986-05-28 DE DE19863617929 patent/DE3617929A1/en active Granted
- 1986-05-28 BE BE0/216715A patent/BE904837A/en not_active IP Right Cessation
- 1986-05-28 CH CH2167/86A patent/CH671640A5/de not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| CH671640A5 (en) | 1989-09-15 |
| US4701618A (en) | 1987-10-20 |
| JPS61273838A (en) | 1986-12-04 |
| IT8667426A0 (en) | 1986-05-23 |
| GB8609924D0 (en) | 1986-05-29 |
| DE3617929A1 (en) | 1986-12-04 |
| GB2175742A (en) | 1986-12-03 |
| GB2175742B (en) | 1989-09-20 |
| DE3617929C2 (en) | 1989-11-30 |
| NL8600841A (en) | 1986-12-16 |
| FR2582859A1 (en) | 1986-12-05 |
| IT1189676B (en) | 1988-02-04 |
| BE904837A (en) | 1986-09-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4639379B2 (en) | Detector for bipolar time-of-flight mass spectrometer | |
| CA2458532C (en) | Intensified hybrid solid-state sensor | |
| JPS5915977A (en) | Display unit | |
| CA1252505A (en) | Middle-infrared imaging device | |
| US3585439A (en) | A camera tube with porous switching layer | |
| US6278104B1 (en) | Power supply for night viewers | |
| EP1018143A1 (en) | Night vision device having improved automatic brightness control | |
| US4870265A (en) | Position-sensitive radiation detector | |
| WO1999005697A1 (en) | Night vision device having improved automatic brightness control | |
| US5045754A (en) | Planar light source | |
| US6320180B1 (en) | Method and system for enhanced vision employing an improved image intensifier and gated power supply | |
| US4608519A (en) | Middle-infrared image intensifier | |
| Geller | Field emission from metals into alkali halide crystals | |
| US6049168A (en) | Method and system for manufacturing microchannel plates | |
| US3921031A (en) | Electroemissive component | |
| EP0803910B1 (en) | Infrared to visible light image conversion device | |
| US6297494B1 (en) | Method and system for enhanced vision employing an improved image intensifier with a gated power supply and reduced halo | |
| US2153163A (en) | Television transmitting and the like system | |
| EP2690644B1 (en) | Microplasma night vision device | |
| US4385232A (en) | Image intensifier devices | |
| Johnson | Photoelectronic detector technology review and update (Keynote Address) | |
| US4134010A (en) | Bistable image tube | |
| SU1078495A1 (en) | Electronic switching device | |
| MNKA | Microchannel Plate Photodetectors | |
| Lynch | Development of intensified charge-coupled devices (CCDs) and solid state arrays |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |