JPS5812697B2 - image enhancer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electronics, and more particularly to single frame recording and photo chronography.
relates to an image intensifier or image intensifier designed for the investigation of high-speed processes in the mode of operation.

The image intensifier of the present invention can be used in diagnostic electro-optical devices which are fundamentally applicable to experimental work in the field of laser and laser plasma physics, thereby allowing controlled laser thermonuclear synthesis. , laser photobiosynthes
is) useful for investigating phenomena related to laser spectroscopy and laser position measurements.

Image intensifiers known in the art include an evacuated tubular envelope containing a photocathode, a focusing electrode in the form of a truncated cone, an anode diaphragm, and two pairs of gating diaphragms separated by a It accommodates an electronic gate in the form of a deflection plate, two deflection devices arranged at right angles to each other, and a series arrangement of fluorescent screens.

Prior art image intensifiers provide non-inertial control of the electronic image, which is accomplished by an electric field created by an electronic gate control plate and a deflection device.

The investigated scene is displayed on the screen with higher temporal resolution (
timeresolution), so that the separated phases follow one another at fairly small time intervals of the order of 10-11 seconds.

However, there are fast and very fast processes that require picosecond time resolution.

In this case, a suitable image intensifier must be able to resolve successive optical signals in time intervals of 10-12 seconds and less.

In the motion photography mode, the limiting time resolution is primarily due to the scattering of the electron transit time required for the electrons to pass from the photocathode to the plane where the electrons are deflected.

On the other hand, the above dispersion depends on the dispersion of the initial velocity of the electrons, and a smaller dispersion of the initial velocity provides better temporal resolution.

Reducing the dispersion of the electron transit time, holding constant the other parameters of the image intensifier, is achieved by increasing the electric field strength near the photocathode (UK Patent No. 132).
No. 9977, classification H01J, 31/50).

The image intensifier disclosed in the above reference includes an evacuated tubular envelope comprising a photocathode, an accelerating electrode having a fine mesh grid disposed in the vicinity of the photocathode. , a focusing electrode in the form of a frustoconical member;
It houses a serial arrangement of an anode diaphragm, an electronic gate in the form of two pairs of deflection plates separated by a gating diaphragm, an image scanning device and a fluorescent screen.

A fine-mesh grid having at least 300 meshes per square millimeter and spaced a distance of 1 to 3 mm from the photocathode is held at a positive potential on the order of 1 kilovolt with respect to the photocathode, and Provides an increase in electric field strength near the photocathode.

However, the use of a high potential grid results in a two-fold increase in the magnification of the image intensifier.

As a result, the brightness of the screen is reduced by a factor of four in single frame recording mode, while the resolution for the screen is reduced by a factor of two in motion photography mode.

Furthermore, in this case the focusing electrode must be held at a low potential in order to generate an image at the screen plane,
This will reduce the movement of electrons in the space between the grid and the anode diaphragm.

This reduced movement of electrons results in a tighter dispersion of electron transit times.

Another factor to consider is the dependence of the magnification of the image intensifier on the potential applied to the accelerating electrode.

Therefore, the reduction in the dispersion of the electron transit times achieved by the fact that the electric field strength in the vicinity of the photocathode increases is not realized to a sufficient extent and is of a magnitude required for resolutions in the sub-picosecond range. I can't reach it.

As an illustration, consider the difference Δt between the respective transit times t0 and t of two electrons moving in space between the grid and the deflection plane of the electron beam in a known image intensifier.

Here, E is the electric field strength near the photocathode, Δt is the difference in transit time of two electrons, m is the mass of the electron, e is the charge of the electron, and Voz is the amount of energy that escapes from the photocathode surface. is the vertical component of the initial velocity of the electron, U(Z) is the potential distributed along the Z axis, and to is V
is the transit time of an electron with a velocity of 0z=0, t is the transit time of an electron with a velocity of V02≠0, Z1 is the coordinate of the grid, and Z2 is the coordinate of the deflection plane of the electron beam. be.

The coefficient η represents a multiple by which the difference Δt increases compared to the case where the deflection plane coincides with the grid plane.

The coefficient η is equal to 1.75 in the case of the known image intensifier electro-optical arrangement.

This means that the dispersion of electron transit times increases by 75 percent.

The value of the coefficient, compared to the calculated resolution value corresponding to a given electric field strength near the photocathode, indicates the multiple by which the temporal resolution is reduced due to the low potential at the focusing electrode.

The deflection plates and electronic gates of the image scanning device are, in known image intensifiers, coupled to a capacitively terminated control circuit whose passband is limited by its resonant frequency.

Therefore, in known image intensifiers it is not possible to obtain an image scanning rate equal to one or two times the speed of light and providing adequate recording of phenomena with temporal resolution in the picosecond and sub-picosecond range. It's impossible.

If we increase the scanning speed by increasing the pulse amplitude,
As a result, the pulse amplitude exceeds that required for image scanning in the active portion of the screen, and the electron beam impinges on the walls of the vacuum envelope of the image intensifier tube during the deflection period.

As a result, electrons that are elastically reflected from the walls cause a reduction in image contrast and also reduce temporal resolution.

The present invention aims to solve the problems in the conventional type, and according to the present invention, an image intensifier is disclosed, and the image intensifier includes a photocathode, an accelerating electrode having a grid, , an evacuated tubular envelope comprising a series arrangement of a focusing electrode, an anode diaphragm, an electronic gate having a deflection plate and a diaphragm, an image scanning device, and a fluorescent screen; an accelerating electrode comprising a hollow cylinder accommodating an element having an electronic trap electrically coupled to the anode diaphragm, the grid disposed at the end facing the photocathode, having a diameter equal to the diameter of the hollow cylinder; a focusing electrode, an electronic gate and an image scanning device, each forming a two-conductor circuit of the through-type and disposed on the evacuated tubular envelope; has multiple terminals,
selected ones of the terminals are used to connect with a corresponding pulse generator, each other of the terminals is used to connect to a matching circuit with a respective terminating load;
Further, an electronic trap is disposed between the image scanning device and the fluorescent screen, a distance L between the photocathode and the fluorescent screen, a distance S between the accelerating electrode and the focusing electrode.
1, the distance S2 between the focusing electrode and the anode diaphragm, and the length l1 of the cylinder of the acceleration and focusing electrodes, respectively
, l2 have the following relationship with respect to the diameter d of the focusing electrode.

L=(7.1 to 8.6)d S1=(0.10 to 0.14)d S2=(0.08 to 0.19)d l1=(1.1 to 1.45)d l2= (0.57 to 0.77) d The accelerating electrode comprises an annular member disposed at the end of the cylinder of the accelerating electrode facing the photocathode, and a fixed relationship between said element and said annular member having a grid. It is advantageous to have a spring arranged on the side of the cylinder so as to provide.

Preferably, the diaphragm of the electronic gate is electrically coupled to the anode diaphragm, and each of the deflection plates of the electronic gate is an element of a respective two-conductor circuit and two conductor plates are mounted on the evacuated tubular envelope. one of the terminals is used to connect to an electronic gate pulse generator and a second of the terminals is used to connect to a matching circuit, the matching circuit having a resistor of has a terminating load equal to the wave resistance of the matching circuit.

The image scanning device is a broadband symmetrical circuit with distributed parameters, the circuit comprising two conductive wires with the same wave resistance, the outer conductor of the wire is connected to the anode diaphragm, and the inner conductor of the wire is deflected. configuring the device, the guide wire has coaxial connectors at its input and output ends, the input one of the coaxial connector is used to connect to the scanning pulse generator, and the output one of the connector corresponds to Advantageously, it is used to connect to a matching circuit with a terminating load having a resistance equal to the wave resistance of the conductor.

Preferably, the electronic trap comprises an element which is a frusto-conical member and whose more bottom side faces the fluorescent screen.

The image intensifier of the present invention provides a minimal dispersion of the electron transit times, thereby allowing the investigation of phenomena in the sub-picosecond range and ensuring that these phenomena are properly displayed on the intensifier screen, doubling the It is possible to maintain a level of magnification of , and to be independent of the voltage applied to the accelerating electrodes, so that the phenomena are recorded with higher temporal resolution.

The invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which: FIG.

The image intensifier of the present invention comprises a vacuum tubular envelope 1 comprising a photocathode 2, an accelerating electrode 3 with a grid 4, a focusing electrode 5, an anode diaphragm 6, a deflection plate 8,
It accommodates a series arrangement of an electronic gate 7 with 9, 10, 11 and a diaphragm 12, an image scanning device 13 and a fluorescent screen 14.

Also provided is an electronic trap 15, the central part of which constitutes an element 16 in the form of a truncated cone.

The bottom surface of the truncated conical member is a fluorescent screen 14.
facing.

Electron trap 15 is electrically connected to anode diaphragm 6 and is connected to image scanning device 13 and fluorescent screen 14.
is located between.

The accelerating electrode 3 comprises a hollow cylinder 17 accommodating an element 18 , which has a grid 4 arranged at its end facing the photocathode 2 .

The accelerating electrode 3 also includes an annular member 19 arranged at the end of the cylinder 17 facing the photocathode 2 and a cylinder 11 to provide a fixed relationship between the element 18 with the grid 4 and the annular member 19. A spring 20 is provided on the side surface of the holder.

The focusing electrode 5 is made as a hollow cylinder with a diameter equal to the diameter of the hollow cylinder of the accelerating electrode 3.

Electronic gate 1 is through-type
The deflection plates 8, 9, 10,
Each of 11 is an element of a respective two-conductor circuit and has terminals 21, 22 on the tubular envelope 1.

Terminal 21 is used to connect to an electronic gate pulse generator 24 via a connector 23, while terminal 22 is used to connect a matching circuit 25.

The length of the matching circuit 25 is selected to provide a condition such that twice the time required for a signal to pass through the circuit exceeds the maximum length of the electronic gating pulse.

The terminating load of the matching circuit 25 comprises a capacitor 28 and a resistor 27 connected via a connector 28.

The resistance of the terminating load is equal to the wave resistance of the matching circuit 25.

A diaphragm 12 of the electronic gate 7 is arranged between the deflection plates 8, 9 and 10, 11 and is electrically connected to the anode diaphragm 6.

The image scanning device 13 constitutes a broadband symmetrical circuit with distributed parameters, which circuit has two wave resistances with the same wave resistance.
It consists of conductive wires 29 and 30.

The outer conductors 31 of the conductors 29, 30 are electrically connected to the anode diaphragm 6, while the inner conductors 32 form the deflection device.

The conductors 29, 30 have coaxial connectors 33, 34 at their inputs.
is provided, and coaxial connectors 35 and 36 are provided at its output.

Input connectors 33, 34 are used to connect to a scanning panel generator 37, while output connectors 35, 36 are used to connect to matching circuits 38, 39, each of which allows the signal to pass through the matching circuit. 2 of the time it takes to pass
It has a length that provides conditions such that the double value exceeds the maximum length of the scanning pulse.

The terminal load of each of the matching circuits 38 and 39 is a capacitor 4.
0 and a resistor 41.

The resistance of the terminating load is equal to the wave resistance of the respective conductor 29,30.

A separating diaphragm 42 is arranged between the electronic gate 1 and the image scanning device 13.

An optical fiber disk 43 is provided on the outside of the fluorescent screen 14.
is provided.

the distance between the photocathode 2 and the fluorescent screen 14, the distance S1 between the accelerating electrode 3 and the focusing electrode 5, the distance S2 between the focusing electrode 5 and the anode diaphragm 6, and the accelerating and focusing electrode 3, The lengths l1 and l2 of the cylinder of No. 5 have the following relationship with the diameter d of the focusing electrode.

L=(7.1 to 8.6)d S1=(0.10 to 0.14)d S2=(0.08 to 0.19)d l1=(1.1 to 1.45)d 12= (0.57 to 0.77) d The ratio of each parameter of the image intensifier is selected as follows.

In existing image intensifiers for temporal analysis, the temporal resolution is improved (approximately 10
-12 seconds), the microstructured grid is placed near the photocathode and is given a high potential with respect to the potential of the photocathode, so that the electric field strength near the photocathode is approximately 3×1
06 volts/meter (this is limited by electrical strength).

The grid described above helps increase the electron-to-optical magnification by 4:1 and helps slow down the electrons considerably in the region of the focusing electrode where the potential is significantly reduced.

It is necessary to reduce the potential somewhat (about a few tens of volts) to prevent parasitic exposure to secondary electrons from the grid of the screen.

The following conditions were taken as a starting point in developing an electro-optical system with accelerating electrodes (grids).

a. High field strength near the photocathode (3 x 106 volts/meter) required to obtain high temporal resolution.

b. Approximately 2:1 electron-to-optical magnification to allow improved three-dimensional resolution and increased image brightness.

c. The absence of electric fields in the space surrounding the grid on the screen side allows mounts and functional elements to be placed within the grid cylinder without affecting the spatial resolution.

d. A blocking potential (several tens of volts) in the area of the focusing electrode to make it possible to prevent exposure to secondary electrons from the grid of the screen.

In order to achieve the object of the invention (taking into account the above conditions), the accelerating electrode of the image intensifier of the invention is designed in the form of a cylinder, the end of which is closer to the photocathode has a microstructure. A grid is provided and the focusing electrode is made in the form of a cylinder of the same diameter as the accelerating electrode.

The ratio between the diameter d of the focusing electrode and the length of each part was obtained with the aid of a computer and confirmed by testing a pilot model of the image intensifier.

The minimum decelerating electric field in the air gap between the grid and the anode is -30
In the case of from -180 volts, the change in the ratio described above corresponded to an electron-to-optical magnification factor of 1.8 to 2.4.

The image intensifier of the present invention operates as follows.

The incident light on the photocathode 2 causes the emission of photoelectrons from the photocathode, and the photoelectrons are accelerated by the electric field generated in the space between the photocathode 2 and the accelerating electrode 3.
, a focusing electrode 5 and an anode diaphragm 6, which are focused onto the screen 14 by an electron lens.

The image produced by the screen 14 is transmitted onto the surface of a fiber optic disk 43, which is external to the image intensifier and the image can be recorded by film or other sensing means.

When no signal appears at the photocathode 2, the image intensifier is deactivated by applying a cut-off voltage E1 to the deflection plates 8, 9, 10, 11 of the electronic gate 7.

The image intensifier is the deflection plate 8, 9, 10 of the electronic gate 7.
, 11 from an electronic gate pulse generator 24, so that a photoelectron beam passes through the gap in the gate diaphragm 12.

At the moment the photoelectron beam passes through the slit in the gating diaphragm 12, an image appears on the screen 14.

The voltage pulses from the electronic gate pulse generator 24 pass through the deflection plates 8, 9, 10, 11 of the electronic gate 7 and then through the high frequency matching circuit 25 to the terminating load.

Reflected signals generated by the load due to non-ideal matching conditions over a wide frequency range are caused by voltage waves crossing the matching circuit.
During the time required for the rotation, the light passes through the matching circuit 25 and reaches the deflection plates 8, 9, 10, and 11.

If the electrical length of the matching circuit 25 corresponds to twice the signal transmission time, and this time is greater than the maximum width of the gate voltage pulse, the reflected signal will be deflected after the intensifier image is cut off. Since the image returns to the plates 8, 9, 10, and 11, image distortion, which would otherwise cause deterioration of temporal resolution, does not occur.

The image shows that the voltage pulse from the scanning pulse generator 37 is connected to the conductor 2.
9 and 30, it is scanned onto the screen 14 using the two-conductor broadband conductors 29 and 30 of the image scanning device 13.

The scanning speed can be equal to several times the speed of light, which is required for adequate recording of phenomena requiring picosecond or sub-picosecond time resolution.

After passing through conductors 29, 30, the scanning pulse travels along matching circuits 38, 39 with terminating loads.

each terminating load generates a reflected signal due to non-ideal matching conditions over a wide frequency range, which reflected signal passes through a respective matching circuit 38 or 39 during the time required to travel through the matching circuit twice; It is then transmitted to conductors 29, 30, resulting in an abrupt change in scanning speed.

If the electrical length of each matching circuit 38 or 39 is selected such that a signal travels along the matching circuit from image scanning device 13 to the load and back during a time interval that exceeds the maximum width of the scan pulse. If so, the reflected signal will return to the device 13 after the image has been scanned, so that the quality of the image recording will not deteriorate.

After passing through the image scanning device 13, the electron beam, which has been deflected to an angle greater than that required for image scanning over the entire area of the screen 14, enters the conical element of the electronic trap 15, which is maintained at the potential of the anode diaphragm 6. Captured on 16th.

As a result, the contrast of the image on the screen 14 is
It does not drop as normally occurs due to the action of electrons that are elastically reflected from the side walls of the tubular envelope 1.

The image intensifier of the present invention is an electro-optical device widely used in various experimental tasks in physics, in particular when the phenomena to be investigated have temporal and spectral properties that cannot be handled by known devices. It can be part of the device.

Even compared to advanced competitors known in the art in Japan and abroad, the image intensifier of the present invention provides a higher degree of temporal resolution and therefore the information processing capacity of the device combined with the intensifier is Increased.

The image intensifier of the present invention can be used in motion photography systems that handle the recording of high velocity processes with picosecond and sub-picosecond temporal resolution.

[Brief explanation of drawings]

The accompanying drawing is a longitudinal sectional view of an image intensifier according to the invention. DESCRIPTION OF SYMBOLS 1... Vacuum tubular envelope, 2... Photocathode, 3... Accelerating electrode, 4... Grid, 5... Focusing electrode, 6... Anode diaphragm, 7... Electronic gate, 8, 9, 10
, 11... Deflector plate of electronic gate 7, 12...
...Electronic gate 7 diaphragm, 13...
...Image scanning device, 14... Fluorescent screen, 15... Electronic trap, 16...
- Elements of electronic trap 15, 17... hollow cylinder, 18... element including grid 4 of accelerating electrode 3, 19... annular member, 20...・・・
Spring, 21, 22... Deflection plate 8, 9, 1
0, 11 terminals, 24... electronic gate pulse generator, 25... matching circuit, 29, 30...
...2 conductor type conductor wire, 31...2 conductor type conductor wire 2
9, 30 external conductors, 32...2 conductor type conductor wire 2
9, 30 internal conductors, 33, 34, 35, 36...
...Coaxial connector, 37...Scanning pulse generator, 38, 39...Coaxial matching circuit, L...
Distance between photocathode 2 and fluorescent screen 14, S1
... Distance between the accelerating electrode 3 and the focusing electrode 5,
S2... Distance between focusing electrode 5 and anode diaphragm 6, l1... Cylinder 17 of accelerating electrode 3
12... Length of the cylinder of the focusing electrode 5, d... Diameter of the focusing electrode.

Claims (1)

[Claims] 1. Photocathode 2, accelerating electrode 3 with grid 4, focusing electrode 5, anode diaphragm 6, deflection plates 8, 9, 10, 1
1 and a diaphragm 12; an image scanning device 13; and a fluorescent screen 14. an electronic trap 15 electrically coupled to the anode diaphragm 6;
The accelerating electrode 3 comprises a hollow cylinder 17 housing an element 18 with a grid 4 arranged at the end facing the photocathode 2
, the focusing electrode 5 is a hollow cylinder having the same diameter as the hollow cylinder 11, the electronic cage 1 and the image scanning device 13 each constitute a through-type two-conductor circuit, and a vacuum tubular It has a plurality of terminals arranged on the enclosure 1, selected ones of which are used to connect to the corresponding pulse generator, and the other terminals are each connected to a terminating load. The electronic track 15 is arranged between the image scanning device 13 and the fluorescent screen 14, and the distance L between the photocathode 2 and the fluorescent screen 14, the acceleration Electrode 3
and the focusing electrode 5, the distance S2 between the focusing electrode 5 and the anode diaphragm 6, and the cylinder lengths l1, l2 of the acceleration and focusing electrodes 3, 5, respectively, with respect to the diameter d of the focusing electrode 5. The following relationships: L=(7.1 to 8.6) d S1=(0.10 to 0.14) d S2=(0.08 to 0.19) d l1=(1.1 to 1. 45) An image intensifier, characterized in that it has dl2=(0.57 to 0.77)d. 2. Image intensifier according to claim 1, in which the diaphragm 12 of the electronic gate 1 is electrically connected to the anode diaphragm 6 and the deflection plates 8, 9, 10, 11 of the electronic gate T each is an element of a respective two-conductor circuit and has two terminals 21, 22 on the evacuated tubular envelope 1, one terminal 21 connected to an electronic gate pulse generator 24. and the other terminal 22 is used to connect to a matching circuit 25 with a terminating load, characterized in that the terminating load has a resistance equal to the wave resistance of the matching circuit 25. vessel. 3 photocathode 2, accelerating electrode 3 with grid 4, focusing electrode 5, anode diaphragm 6, deflection plate 8, 9, 10, 1
1 and a diaphragm 12, an image scanning device 13, and a fluorescent screen 14 arranged in series, the image intensifier comprising: an electronic trap 15 electrically coupled to the anode diaphragm 6;
The accelerating electrode 3 comprises a hollow cylinder 17 housing an element 18 with a grid 4 arranged at the end facing the photocathode 2
, the focusing electrode 5 is a hollow cylinder with the same diameter as the hollow cylinder 11, the electronic gate 1 and the image scanning device 13 each constitute a passing two-conductor circuit, and a vacuum tubular It has a plurality of terminals arranged on the enclosure 1, selected ones of which are used to connect to the corresponding pulse generator, and the other terminals are each connected to a terminating load. The electronic trap 15 is arranged between the image scanning device 13 and the fluorescent screen 14, and the accelerating electrode 3 is connected to the end of the cylinder 17 facing the photocathode 2. having an annular member 19 arranged and having a spring 20 arranged on the side of said cylinder 11 such that a fixed relationship between the element 18 with the grid 4 and the annular member 19 is provided; Features: Image intensifier. 4 photocathode 2, accelerating electrode 3 with grid 4, focusing electrode 5, anode dianram 6, deflection plate 8, 9, 10, 1
1 and a guiaphragm 12, an image scanning device 13, and a fluorescent screen 14 arranged in series, the image intensifier comprising: an electronic trap 15 electrically coupled to the anode diaphragm 6;
The accelerating electrode 3 comprises a hollow cylinder 11 housing an element 18 with a grid 4 arranged at the end facing the photoelectric sheath 2
, the focusing electrode 5 is a hollow cylinder having the same diameter as that of the hollow cylinder 17, the electronic gate 7 and the image scanning device 13 each constitute a passing two-conductor circuit, and a vacuum tubular It has a plurality of terminals arranged on the enclosure 1, selected ones of which are used to connect to the corresponding pulse generator, and the other terminals are each connected to a terminating load. The electronic trap 15 is placed between the image scanning device 13 and the fluorescent screen 14, the image scanning device 13 being a broadband symmetrical circuit with distributed parameters. , the circuit has two identical wave resistances 2
It is equipped with conductive wires 29 and 30, and an outer conductor 31 of the wires.
is connected to the anode diaphragm 6, the inner conductor 32 constitutes a deflection device, the conductors 29, 30 having coaxial connectors 33, 34, 35, 36 at their input and output ends, the coaxial connectors 33, 34 being scanning The coaxial connectors 35, 36 are used to connect with a pulse generator 37, and the coaxial connectors 35, 36 are used to connect with a matching circuit 38, 39 having a terminating load with a resistance equal to the wave resistance of the conductors 29, 30, respectively. An image intensifier featuring: 5 photocathode 2, accelerating electrode 3 with grid 4, focusing electrode 5, anode diaphragm 6, deflection plate 8, 9, 10, 1
1 and a diaphragm 12, an image scanning device 13, and a fluorescent screen 14 arranged in series, the image intensifier comprising: an electronic trap 15 electrically coupled to the anode diaphragm 6;
The accelerating electrode 3 comprises a hollow cylinder 17 housing an element 18 with a grid 4 arranged at the end facing the photocathode 2
, the focusing electrode 5 is a hollow cylinder having the same diameter as that of the hollow cylinder 17, the electronic gate 7 and the image scanning device 13 each constitute a passing two-conductor circuit, and a vacuum tubular It has a plurality of terminals arranged on the enclosure 1, selected ones of which are used to connect to the corresponding pulse generator, and the other terminals are each connected to a terminating load. The electronic trap 15 is placed between the image scanning device 13 and the fluorescent screen 14, and the electronic trap has a larger bottom surface connected to the fluorescent screen 14. An image intensifier characterized in that it comprises an element that is a facing frustoconical member.