 |
Claims  |
|
|
What is claimed is:
1. A charge transfer signal processor, comprising:
vacuum housing means defining longitudinally spaced and confronting
two-dimensional input and output external ports for providing an evacuated
region between the external input and output ports;
input electromagnetic signal means coupled to said vacuum housing means for
writing an input electromagnetic signal defining a two-dimensional (the
2-D) spacially-varying input intensity distribution into the evacuated
region as a selectable two-dimensional spacially-varying electronic charge
intensity distribution;
imaging means for transporting said selectable two-dimensional
spacially-varying electronic charge intensity distribution of said input
electromagnetic signal proximate to said output port; and
two-dimensional electronic charge collecting and electrically conductive
feedthrough means vacuum-mounted at said external output port to said
vacuum housing means and cooperative with said imaging means for receiving
said two-dimensional electronic charge intensity distribution proximate
said output port and electrically transferring it externally of said
vacuum housing means;
said two-dimensional electronic charge collecting said electrically
conducting feedthrough means including a preselected high resolution 2-D
array of electrically isolated longitudinally extending conductors having
ends terminating in first and second surfaces, with the ends terminating
in said first surface being located inside said evacuated region
confronting said input port, and with the ends terminating in said second
surface being located outside said evacuated region and facing externally
of said vacuum housing means;
said preselected resolution of said high resolution 2-D array being
selected to substantially preserve the fidelity of the input 2-D
electromagnetic signal;
said 2-D electronic charge intensity distribution being locally received by
said ends of said two dimensional electronic charge collecting and
electrically conductive feedthrough means terminating in said first
surface of said high-resolution 2-D array of electrically isolated and
longitudinally extending conductors and individually electrically
transferred thereby to associated ones of the ends thereof terminating in
said second surface of said high-resolution 2-D array of electrically
isolated longitudinally extending conductors of said feedthrough means so
as to provide at said second ends and externally of the housing an
electrical 2-D output signal having a spacially varying output intensity
distribution corresponding to that of the input electromagnetic signal.
2. The charge transfer signal processor of claim 1, wherein said input
electromagnetic signal means includes an electron gun vacuum-mounted
proximate said external input port of said vacuum housing means.
3. The invention of claim 1, wherein said input electromagnetic signal
means includes an optically transmissive window vacuum-mounted at said
external input port of said vacuum housing means, and a layer of a
photo-emissive material disposed on said window and on the side thereof
confronting the evacuated region of said vacuum housing means.
4. The charge transfer signal processor of claim 1, wherein said input
electromagnetic signal means includes an electron gun vacuum-mounted to
said vacuum housing means; and further includes an optically transmissive
window vacuum-mounted to said external input port of said vacuum housing
means and a layer of a photoemissive material deposited on the surface of
said window confronting the evacuated region of said vacuum housing means.
5. The charge transfer signal processor of claim 1, wherein said imaging
means includes means for establishing an electric field in said evacuated
region of said vacuum housing means.
6. The charge transfer signal processor of claim 5, wherein said electric
field establishing means includes an acceleration grid for providing said
longitudinally extending electric fields.
7. The charge transfer signal processor of claim 1, wherein said imaging
means includes means for establishing a magnetic field in said evacuated
region of said vacuum housing means.
8. The charge transfer signal processor of claim 1, wherein said imaging
means includes means for providing electromagnetic fields in said
evacuated region of said vacuum housing means.
9. The charge transfer signal processor of claim 1, further including a
coating of a high-charge gain enhancer coating disposed on said ends of
said 2-D array of electrically-isolated elongated conductors that
terminate in said first surface thereof.
10. The charge transfer signal processor of claim 1, wherein said 2-D array
of electrically-isolated elongated conductors is constituted as a
lamination of insulative substrates each having spaced-apart and
generally-parallel conductive filaments disposed on a surface thereof.
11. The charge transfer signal processor of claim 10, wherein said
insulative substrates are glass substrates, and wherein said conductive
filaments are photolithographically-deposited metalization traces.
12. The charge transfer signal processor of claim 9, further including
means coupled to said vacuum housing means for erasing electronic charge
on said enhancer coating.
13. The charge transfer signal processor of claim 1, wherein said
collecting and feedthrough means is constituted as an apertured
electrically insulating plate having an electrically conductive material
disposed in the apertures thereof.
14. The charge transfer signal processor of claim 13, wherein said apetured
plate includes a glass capillary array, and wherein said conductive
material is a metal.
15. The charge transfer signal processor of claim 1, wherein said
two-dimensional charge collecting and feedthrough means includes plural
drawable longitudinally extending filaments each constituted as an outer
insulative sheath and an inner conductive core.
16. The charge transfer signal processor of claim 15, wherein each of said
filaments include a glass sheath and a drawable conductive glass core.
17. The charge transfer signal processor of claim 15, wherein each of said
filaments includes an outer glass sheath and an inner conductive flowable
metal.
18. The charge transfer signal processor of claim 1, further including a
microchannel plate subassembly operatively disposed in said evacuated
region of said vacuum housing means intermediate said input port thereof
and said collecting and feedthrough means.
19. The charge transfer signal processor of claim 1, further including
means disposed in said evacuated region of said vacuum housing means
intermediate said input port thereof and said collecting and feedthrough
means for providing current amplification of said two-dimensional
electronic charge distribution of said input electromagnetic signal.
20. The charge transfer signal processor of claim 19, wherein said current
amplification means includes a power microchannel plate.
21. The charge transfer signal processor of claim 20, wherein said power
microchannel plate includes a 2-D array of cross-talk free channels each
containing plural discrete dynodes.
22. The charge transfer signal processor of claim 21, wherein said 2-D
array of said power microchannel plate is constituted as a lamination of
high-efficiency secondary electron emitting conductive layers and
alternating apertured insulative layers.
23. The charge transfer signal processor of claim 22, wherein said emitting
conductive layers include an electrically conductive grid defining
interstitices, and a layer of a high secondary electron emitting
conductive material disposed onto said grid.
24. The charge transfer signal processor of claim 22, wherein said emitting
conductive layers include a grid of a secondary electron emitting
conductive material.
25. The charge transfer signal processor of claim 21, wherein said power
microchannel plate is constituted as a stack of high secondary electron
emitting conductive material coating apertured insulative layers.
26. The charge transfer signal processor of claim 25, wherein said high
secondary electron emitting conductive material is composite.
27. The charge transfer signal processor of claim 26, wherein said
composite material includes a layer of a conductive material and an
overlaid layer of a high secondary electron emitting material.
28. The charge transfer signal processor of claim 26, wherein said high
secondary emission conductive material is single.
29. The charge transfer signal processor of claim 28, wherein said single
material is a high secondary electron emitting conductive layer.
30. The charge transfer signal processor of claim 22, further including
means for applying a potential gradient across the lamination of the
several high-efficiency secondary electron emitting conductive layers.
31. The charge transfer signal processor of claim 25, further including
means for applying a potential gradient across said stack of high
secondary electron emitting conductive material coated apertured
insulative layers.
32. The charge transfer signal processor of claim 20, wherein said high
secondary electron emitting conductive material is magnesium oxide.
33. The charge transfer signal processor of any one of claims 10, 13, 15,
or 19, further including an output device mounted to said ends of said 2-D
array of electrically-isolated and longitudinally extending conductors
that terminate in said second plane external of said vacuum housing means.
34. The charge transfer signal processor of claim 33, wherein said output
device includes an electronic circuit having contacts that are
electrically connected to preselected ones of the conductors of the 2-D
array of the electrically-isolated and longitudinally extending conductors
that lie in said second plane external to said vacuum housing means.
35. The charge transfer signal processor of claim 33, wherein said
electronic circuit is an electronic parallel-to-serial converter.
36. The charge transfer signal processor of claim 34, wherein said
electronic circuit is an integrated circuit.
37. The charge transfer signal processor of claim 33, wherein said output
device includes a two-dimensional photo-conductor mounted to the ends of
the 2-D array of conductors that terminate in said second external plane,
a two-dimensional transparent conductor mounted to said photo-conductor,
and means for selectively illuminating different regions of said
photo-conductor through said transparent conductor for providing a read
control output signal.
38. The charge transfer signal processor of claim 33, wherein said output
device includes a two-dimensional light modulating element and a conductor
operatively mounted to the ends of the conductors of the 2-D array that
terminate in said second external plane in such a way that the light
modulating element is responsive to the electric fields produced by the
electronic charge distribution thereon.
39. The charge transfer signal processor of claim 38, wherein said light
modulating element includes an electro-optic material.
40. The charge transfer signal processor of claim 39, wherein said
electro-optic material includes organic crystals.
41. The charge transfer signal processor of claim 39, wherein said
electro-optic material includes inorganic crystals.
42. The charge transfer processor of claim 39, wherein said electro-optic
material includes a transparent ceramic.
43. The charge transfer signal processor of claim 38, wherein said light
modulating element includes an electro-absorptive material.
44. The charge transfer signal processor of claim 38, wherein said light
modulating element includes an elastomer.
45. The charge transfer signal processor of claim 38, wherein said light
modulating element includes a flexible membrane.
46. The charge transfer signal processor of claim 45, wherein said membrane
is nitrocellulose.
47. The charge transfer signal processor of claim 38, wherein said light
modulating element includes liquid crystals.
48. The charge transfer signal processor of claim 38, wherein said light
modulating element material includes an oil film.
49. The charge transfer signal processor of claim 33, wherein said output
device includes an electrically addressable conductive grid, and means for
applying opaque toner particles onto said grid.
50. The charge transfer signal processor of claim 38, wherein said output
device includes a piezoelectric device.
51. The charge transfer signal processor of claim 50, wherein said
piezoelectric device is constituted as several stacks of plural
laminations of a piezoelectric material.
52. The charge transfer signal processor of claim 33, wherein said output
device includes an electron gun operation in the Vidicon mode.
53. A high spacial resolution, high-current gain, power microchannel plate
assembly, comprising:
means for providing a two-dimensional array of high-efficiency, secondary
electron emitting discrete dynode chains that each define an electron
amplification channel and that together define a cross-talk free and high
spacial-resolution high-current two-dimensional charge amplifier; and
means coupled to the two-dimensional array of high-efficiency, secondary
electron emitting discrete dynode chains for applying a potential gradient
across the constituative discrete dynodes of each of the chains of dynodes
to control the electron amplification of the channels and for feeding
charge into the constituative dynodes of each chain of dynodes to provide
high-current and non-saturation-limited electron amplification channels;
said array providing means including a lamination of first layers of
high-efficiency secondary electron emitting conductive grids defining a
2-D array of conductive windows alternating with second layers of
apertured insulative sheets, with the windows of the grids longitudinally
alternating with the apertures of the apertured insulative sheets to
provide said two-dimensional charge amplifier.
54. The power microchannel plate subassembly of claim 53, wherein said
potential gradient applying means includes a voltage divider network
connected to each of the several first layers of the high-efficiency
secondary electron emitting conductive grids.
55. A high spacial-resolution charge transfer feedthrough plate subassembly
for a charge transfer signal processor, comprising:
plural longitudinally extending electrically conductive members;
means coupled to said members for supporting said members in a high-spacial
resolution two-dimensional array in such a way that each of the conductors
is electrically isolated from all of the other conductors in the
two-dimensional array; and
means cooperative with said supporting means for providing vacuum-tight
sealing between all of the electrically conductive and mutually
electrically isolated conductors of the two-dimensional array;
said conductive members are mutually parallel metallic traces disposed in
spaced apart relation on one surface of each of plural insulative sheets
that are laminated together in a vacuum-tight sealing relation.
56. The power microchannel plate assembly of claim 53, wherein the
conductive windows of the grids define a center-to-center spacing and the
apertures of the apertured insulative sheets define a center-to-center
spacing, the center-to-center spacing of the conductive windows being
smaller than the center-to-center spacing of the apertures of the
insulative sheets to maximize the secondary electron emitting processes
that occur in each of the electron amplification channels thereof.
57. A high spacial resolution, high-current gain, power microchannel plate
assembly, comprising:
means for providing a two-dimensional array of high-efficiency, secondary
electron emitting discrete dynode chains that each define an electron
amplification channel and that together define a cross-talk-free and
high-spacial-resolution high-current two-dimensional charge amplifier; and
means coupled to the two-dimensional array of high-efficiency, secondary
electron emitting discrete dynode chains for applying a potential across
the constituative dynodes of each of the chains of dynodes to control the
electron amplification of the channels and for feeding charge into the
constituative dynodes of each chain of dynodes to provide high-current and
non-saturation-limited electron amplification channels;
said array providing means including a lamination of plural, apertured
insulative sheets each having opposing two-dimensional surfaces and a
coating of a high-efficiency secondary electron emitting conductive
material disposed on the same one of the opposed surfaces of each of the
apertured insulative sheets which material partially extends into the
apertures of each of the insulative apertured sheets;
the several layers of the high-efficiency secondary electron emitting
conductive material disposed on the same one of the opposing surfaces of
each of the apertured insulative sheets being electrically isolated from
adjacent layers by the intervening insulative sheets.
58. The power microchannel plate assembly of claim 57, wherein said
material is composite and includes an electrically conductive underlayer
and a high-efficiency secondary electron emitting overlayer.
59. The power microchannel plate assembly of claim 57, wherein said
material is a single electrically conductive and high-efficiency secondary
electron emitting material
60. The power microchannel plate assembly of claim 57, wherein said
potential gradient applying means includes a voltage divider network
connected to each of the several coatings of the high-efficiency secondary
electron emitting conductive material of the plural sheets.
61. The power microchannel plate assembly of claim 57, wherein each of said
plural apertured insulative sheets includes a high-resolution glass
capillary array.
62. A high-spacial-resolution charge transfer feedthrough plate subassembly
for a charge transfer signal processor, comprising:
plural, longitudinally extending electrically conductive members;
means coupled to said members for supporting said members in a high-spacial
resolution two-dimensional array in such a way that each of the conductors
is electrically isolated from all of the other conductors in the
two-dimensional array; and
means cooperative with said supporting means for providing vacuum-tight
sealing between all of the electrically conductive and mutually
electrically isolated conductors of the two-dimensional array;
said electrically conductive members including plural longitudinally
extending filaments traversely arrayed in a closely-packed and
vacuum-tight two-dimensional array that each include an electrically
insulative sheath surrounding a co-axially disposed electrically
conductive core. |
|
 |
|
 |
Claims |
|
|
|
Description |
|
|
FIELD OF THE INVENTION
This invention is directed to the field of signal processing, and more
particularly, to a novel charge transfer signal processor.
BACKGROUND OF THE INVENTION
In many applications, it is desirable to convert the spatially-varying
signal intensity of an input 2-D electromagnetic signal into an amplified
electrical 2-D output signal having a spatially-varying output intensity
distribution corresponding to that of the input electromagnetic signal.
The output electrical signal in this way preserves the information content
of the input electromagnetic signal, but in such a way that it may be
advantageously utilized in a host of applications environments that
include, but are not limited to, imaging detectors, optical signal
processors, real-time adaptive optical systems, and target recognition,
tracking and optical communications systems. Such 2-D conversion devices
are often called upon to provide a high degree of spatial resolution, wide
spectral bandwidths, fast cycle times, the capability to accommodate the
heat produced by high-power output utilization devices, control of the
electron energy distribution, high-current-level output signals,
sensitivity to low input-intensity signal levels, and, among other things,
to provide the capability to be fabricated at a reasonably low cost.
Reference may be had to U.S. Pat. No. 4,481,531 for an exemplary
microchannel spatial light modulator, incorporated herein by reference.
The utility of the heretofore known devices has been limited in one or
more of the foregoing respects.
SUMMARY OF THE INVENTION
In one embodiment, the charge transfer signal processor of the present
invention includes an enclosure defining a vacuum chamber having a first
generally planar surface defining an input port and a second generally
planar surface spaced from and confronting the first surface defining an
output port. A generally planar photocathode member is in communication
with the first surface and responsive to incident electromagnetic energy
received through the input port for providing an electrical signal having
a charge distribution that corresponds to the intensity distribution of
the incident electromagnetic energy. A 2-D array of electrically-isolated
longitudinally-extending conductors having ends that terminate in first
and second planes is coupled to the second surface of the enclosure and
mounted within the enclosure with the ends thereof terminating in one of
the planes in external communication with the second surface of the
enclosure and with the other of the planes thereof internally confronting
and in spaced relation to the photocathode member. An enhancer coating of
an efficient electron/hole generator is provided over the ends of the 2-D
array of electrically-isolated elongated conductors confronting the
photocathode. An acceleration grid is provided in the vacuum chamber
intermediate the photocathode member and the enhancer coating for
providing controlled transport of the photocathode electron distribution
to the coated 2-D array of electrically-isolated elongated conductors. The
intensity of the transported electrons is amplified by the enhancer
coating, and the amplified electrons are locally fed through the
conductors providing a spatially varying electron intensity distribution
at the output port that corresponds to the intensity distribution at the
input port. In this embodiment, the charge transfer signal processor is
operable as a high-spatial-resolution, high-temporal-resolution, gen-I
type charge transfer amplifier.
In a further embodiment, one or more microchannel plates are operatively
connected between the photocathode member and the acceleration grid within
the vacuum enclosure of the charge transfer signal processor. The one or
more microchannel plates are operative in response to the photocathode
electron distribution to locally amplify the electron charge distribution
in such a way that it is everywhere representative of the spatial
intensity distribution of the input electromagnetic signal. The electric
field provided by the grid proximity focuses the amplified charge
distribution onto the enhancer coating of the output conductor array,
which, in turn, feeds it externally of the enclosure. In this embodiment,
the charge transfer signal processor is operable as a high-gain charge
transfer amplifier.
In a further embodiment, the charge transfer signal processor further
includes a power microchannel plate operatively connected in the vacuum
chamber intermediate the input port and the acceleration grid of the
vacuum enclosure. The power microchannel plate includes a laminated stack
of perforated insulative sheets alternating with secondary-electron
emitting and electrically conductive layers. The several layers cooperate
with the several perforated insulative sheets to provide a 2-D array of
plural axially-aligned discrete dynodes. A potential gradient is applied
across the several layers in such a way that the power microchannel plate
is operative as an electron amplifier capable of delivering high output
current densities. In this embodiment, the charge transfer signal
processor is operable as a high-current charge transfer amplifier.
Different light modulating elements or electronic signal output devices are
selectively couplable to the output port of the charge transfer signal
processor and externally of the enclosure. In dependence on the type of
output device selected and on the particular embodiment, the novel charge
transfer signal processor of the present invention is operative, among
others, to provide high-speed, low-light-level, deformable mirrors for
adaptive optics applications; ultra-high-speed, low-light-level,
high-resolution spatial phase and amplitude modulators for optical
computing, target recognition, tracking and signal processing; and, among
others, ultra-fast, low-light-level, high-resolution detectors for
astronomy and for optical communications applications.
In each of the several embodiments, the input electromagnetic signal can be
optical, electrical, or a combination of the two. The optical input
signals may be either coherent or incoherent. The input electrical signal
may be a controlled electron-beam write source. For operation in a hybrid
input mode, both a light input and an electron-beam input can be
simultaneously and/or successively applied.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features and attendant advantages of the present invention
will become apparent as the invention becomes better understood by
referring to the following solely exemplary and non-limiting detailed
description of the preferred embodiments thereof, and to the drawings,
wherein:
FIG. 1 illustrates in FIGS. 1A-1C thereof diagrammatic views of a first
embodiment of the charge transfer signal processor according to the
present invention respectively showing three different input
electromagnetic structures;
FIG. 2 is a schematic diagram useful in illustrating two modes by which
information is written in the charge transfer signal processor according
to the present invention;
FIG. 3 is a perspective view illustrating in FIGS. 3A and 3B thereof one
embodiment of a charge collecting and feed-through plate assembly of the
charge transfer signal processor according to the present invention;
FIG. 4 illustrates in FIG. 4A a perspective view and in FIG. 4B a partial
sectional view illustrating a second embodiment of the charge collecting
and feed-through plate assembly of the charge transfer signal processor
according to the present invention;
FIG. 5 illustrates in FIG. 5A a perspective view and in FIG. 5B a partial
sectional view illustrating a third embodiment of the charge collecting
and feed-through plate assembly of the charge transfer signal processor
according to the present invention;
FIG. 6 illustrates in FIGS. 6A through 6C thereof diagrammatic views of a
second embodiment of the charge transfer signal processor according to the
present invention respectively showing three different input
electromagnetic structures;
FIG. 7 is a perspective view illustrating a microchannel plate of the
charge transfer signal processor according to the present invention;
FIG. 8 illustrates in FIG. 8A a side view of and illustrates in FIG. 8B a
fragmentary perspective diagram of one embodiment of a power microchannel
plate of the charge transfer signal processor according to the present
invention;
FIG. 9 illustrates in FIG. 9A a side view of and illustrates in FIG. 9B a
fragmentary perspective diagram of a further embodiment of the power
microchannel plate of the charge transfer signal processor according to a
further embodiment of the present invention;
FIG. 10 illustrates a diagrammatic view of a third embodiment of the charge
transfer signal processor according to the present invention;
FIG. 11 illustrates in FIGS. 11A, 11B, 11C thereof diagrammatic views
illustrating a fourth embodiment of the charge transfer siganl processor
according to the present invention respectively showing three different
input electromagnetic structures; and
FIGS. 12 through 23 are pictorial diagrams respectively illustrating
different output devices of the charge transfer signal processor according
to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, respectively generally designated at 10, 12, and
14 in FIGS. 1A, 1B, and 1C are three embodiments of a gen-I type charge
transfer signal processor according to the present invention. The charge
transfer devices 10, 12, 14 are substantially identical and principally
differ in the structure of the input electromagnetic excitation signal
source. The charge transfer devices 10, 12, 14 each include a housing 16
defining an enclosed vacuum generally designated 18. The housings 16 each
include top input and bottom output faces 20, 22 of a
generally-cylindrical shape that respectively define 2-D input and output
ports.
A source of electrons, such as from an electron gun 24 vacuum-mounted
through the face 20, is provided for writing an input 2-D electromagnetic
signal into the charge transfer signal processor 10 of FIG. 1A. An
electron control signal 25 marked "V.sub.s " is controllably applied to
the gun 24. An optically-transmissive window 26 having a deposited layer
of a photoemissive material 28 defining a photocathode is vacuum-mounted
to the face 20 of the charge transfer signal processor 12 of FIG. 1B. The
photocathode 28 cooperates with incident 2-D write light schematically
illustrated by an arrow 30 for providing an input 2-D electrical charge
distribution, schematically illustrated by variable-length arrows 32, that
everywhere locally corresponds to the 2-D intensity distribution of the
input write light 30. An optically transmissive window 34 having a
desposited layer 36 of any suitable photoemissive material defining a
photocathode, and a source 38 of write electrons, such as from an electron
gun 38, are vacuum-mounted to the top input face 20 of the charge transfer
signal processor 14 in FIG. 1C. An electron control signal 39 marked
"V.sub.s " is controllably applied to the gun 38. The photocathode 36 is
cooperative with write light schematically illustrated by an arrow 41 to
provide a spatially-varying 2-D electron distribution that everywhere
locally corresponds to the intensity distribution of the write light 41,
as schematically illustrated by variable length arrows 42, and the
electron source 38 is operative to provide a 2-D electron pattern
illustrated by arrows 44. The write light, which may be either coherent or
incoherent, and the write electrons, can be either sequentially or
simultaneously applied. A biasing network generally designated 45 and
marked "V.sub.m.sup.(1) " is operatively coupled to the photocathodes 28,
36 in FIGS. 1B, 1C, and a biasing network generally designated 47 and
marked "V.sub.c " is operatively coupled to the cathodes of the guns 24,
38 in FIGS. 1A, 1C. Conventional magnetic, electrostatic, or
electromagnetic techniques are employed in the electron guns 24, 38 for
electron beam focus and deflection.
A charge transfer feedthrough plate subassembly generally designated 46, to
be described, is vacuum-mounted within the bottom output face 22 of the
housings 16 of the charge transfer signal processors 10, 12, and 14. The
charge transfer feedthrough plate subassemblies 46 each include plural
electrically-isolated elongated conductors 50 therethrough the ends of
which respectively terminate in a first planar surface internally of the
housings 16 and a second planar surface externally of the housings 16. The
conductors 50 of the charge transfer feedthrough plate subassembly have a
very high spatial density, and are operative to controllably transfer a
2-D electronic charge pattern to the exterior of the housing 16 with a
very high spatial resolution. An output device 52 to be described is
externally mountable to the output port of the housing 16 and operatively
connected electrically to the elongated conductors 50 of the corresponding
charge transfer feedthrough plate subassembly 46. The external mounting of
the output device 52 makes possible the selection of a wide variety of
devices to be described. For example, the output devices then need not be
vacuum compatible. Further, they can be externally cooled for high-power
applications, and can be readily removably replaced without requiring
substantial system disconnection.
A layer of a charge enhancing material 54 is deposited over the inner plane
at which the conductor 50 of the charge transfer feedthrough plate
subassembly 46 terminate. The layer 54 may be, for example, either a
coating of a high secondary electron emitter substance such as MgO or
Cu:BeO or an efficient electron/hole generating substance such as silicon
or germanium. In the case of the high secondary electron emitter
substances the gain provided by the enhancing layer 54 provides for
high-sensitivity to the level of the input signal, a high temporal
bandwidth, and for control of the write modes to be described of the
charge transfer signal processor.
In the case of the electron/hole generating substances, the gain provided
by the enhancing layer 54 provides for high-sensitivity to the level of
the input signal and provides for a high temporal bandwidth.
A grid 56, maintained at a positive potential by a variable voltage source
generally designated 58 and marked "V.sub.a ", is positioned in the vacuum
chamber 18 intermediate the front face 20 and the enhancer coating 54. The
grid 56 provides an electric field within the vacuum chamber 18
predominately having only longitudinal electric field components. This
field accelerates the 2-D input charge distribution by Coulombic
attraction, and images it on the enchancer coating 54 by proximity
focusing. Erasure may be provided by flooding the coating 54 from either
of the sources of the input electromagnetic signal. An optional electron
gun 60 is vacuum-mounted to the housings 16 in position to conveniently
flood the coatings 54 for image erasure purposes. It will be appreciated
that although electrostatic proximity focusing is disclosed in the
preferred embodiments, other suitable charge imaging techniques, such as
magnetic, electric, or a combination of the electric and the magnetic, can
as well be employed without departing from the inventive concept.
The voltage selected for the grid 56 controls the acceleration of the
electrons through the vacuum chamber 18 and therewith controls the kinetic
energy of the charges incident on the enhancer coating 54. Where high
secondary electron emitting coatings are used, as will be appreciated by
those skilled in the art, the gain, DELTA, of the particular material
selected for the enhancer coating 54 is a function of the kinetic energy
of the incident electron stream. The gain can then be selected to be
either greater than or less than unity by varying the grid voltage
accordingly. For comparatively-low voltages and corresponding kinetic
energies, the gain is selectable to be less-than-unity. In this case, more
electrons arrive that are given off the less-than-unity gain coating, so
that the electrons that are incident on the enhancer coating accumulate
thereon as generally designated at 62 in FIG. 2. For comparatively-high
grid voltages and corresponding kinetic energies, the gain is selectable
to be greater-than-unity. In this case, more electrons are emitted off of
the coating than are accumulated thereon, due to the selected high gain
coefficient, so that electrons are locally depleted about the surface of
the enhancer coating in accordance with the incident intensity of the 2-D
electronic charge distribution as generally designated at 64 in FIG. 2. If
a comparatively-high resistance enhancer coating 54 is selected, the
incident electronic charge integrates during image writing thereonto, and
if a comparatively low-resistance enhancer coating 54 is selected, the
electronic charges bleed off the enhancer coating at a specific rate. The
charge transfer signal processor of the present invention is then in this
manner selectably operable in either of a framed or a continuous mode.
In the framed mode, images may be written either by electron depletion or
by electron accumulation. If the potential of the source 58 is selected
such that the incident electronic charges have a kinetic energy that
corresponds to operation in the greater-than-unity gain regime, more
electrons are given off the enhancer coating by secondary emission than
are received so that the image is written in an electron depletion write
mode. At the termination of the write period, the accumulated image is
erased by flooding the enhancer coating 54 with electrons as from the gun
60. If the potential of the source 58 is selected so that the kinetic
energy of the incident electronic charges corresponds to operation in the
less-than-unity gain regime, the number of the incident electrons is
greater than the electrons knocked thereout by secondary emission such
that the image is written by electron accumulation. At the end of the
write period, the image is erasable as by controlled emission from the
flood gun 60, by flooding the photocathode with light, or by defocusing
the signal electron gun 24, 38 as appropriate.
Where efficient electron/hole generators are used for the enhancer
coatings, the voltage selected for the grid controls the acceleration of
the electrons, and correspondingly their kinetic energy at incidence on
the enhancer coating 54. An intended gain, as will be appreciated by those
skilled in the art, is provided by selecting the magnitude of the incident
kinetic energy of the electron stream, whereby corresponding quantities of
electron/hole pairs are generated within the semiconductor material of the
enhancer coatings in dependence on the kinetic energy selected. Where
necessary, and in accord with the particular output device utilized, the
electron erasure gun then floods the enhancer coatings with a uniform
electron flux for image erasure purposes.
Referring now to FIG. 3, generally designated at 66 in FIG. 3A is a
perspective view of one embodiment of the charge transfer feedthrough
plate subassembly of the charge transfer signal processor according to the
present invention. The assembly 66 inlcudes an upper, optically-flat
generally-planar surface generally designated 68, a lower, o | | |
