JPH0750149A - Photoelectric cathode, photoelectric tube, and photo-detecting device - Google Patents

Abstract

PURPOSE:To provide a photoelectric cathode, a photoelectric tube, and a photo- detecting device having position resolution and high sensitivity. CONSTITUTION:The surface electrode 105 of a photoelectric cathode 1 is divided into a plurality of picture element electrode 1051-105n and photoelectrons generated inside can be emitted to the outside for only the picture elements applied with bias. The one-dimensional position resolution can be attained when picture elements are aligned in a one-dimensional array shape, and the two-dimensional position resolution can be attained when picture elements are aligned in a two-dimensional matrix. A photoelectric tube is provided with the photoelectric cathode in a vacuum container 21 and a bias switching control means of a plurality of picture element electrodes, and it has the one-dimensional or two-dimensional position resolution. A photo-detector is provided with the photoelectric tube, a power source, a timing control means, and a memory means, and the memory means stores the output of an anode in response to the position information of the picture element electrodes in the photoelectron emittable state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocathode, a phototube, and a photodetector, and more particularly, for obtaining one-dimensional or two-dimensional information such as an incident position or an incident light image of weak light. Related to photodetection technology.

[0002]

2. Description of the Related Art As a general device for detecting light of weak light including one-dimensional or two-dimensional position information, there is a device formed by combining an image intensifier and a solid-state image pickup device. In this device, photoelectrons are excited by photons incident on the photocathode through the input window of the envelope,
After the photoelectrons emitted from the photocathode into the vacuum are focused and accelerated by the electron lens system, they are imaged by the phosphor and converted into optical signals again to enhance light. This enhanced optical signal is photoelectrically converted again by a solid-state image sensor such as CCD, and the position information is taken out as an electric signal.

Besides, there is a photomultiplier tube having a position detecting function. In this example, the position information is obtained by dividing the anode of the photomultiplier tube, dividing it into multiple tubes, and detecting light. Another example in which the photomultiplier tube has a position detecting function is described in Japanese Patent Application Laid-Open No. 60-20441.

In this photomultiplier tube, a photocathode is formed on the inner wall surface of the face plate. A mesh electrode is provided between the photocathode and a focusing electrode for forming an electric field that guides the photoelectrons emitted from the photocathode to the first-stage dynode. It is arranged only on one side at a position of about 1/10 of the distance between. Then, an electric field distribution is formed so as to gradually prevent the photoelectrons from reaching the first stage dynode from one side to the other side. By applying the bias voltage to the mesh electrode, one of the photoelectrons emitted from the entire photoelectron emission surface of the photocathode is prevented from reaching the first stage dynode. That is, the orbits of photoelectrons are changed, and only those emitted from a predetermined portion of the emission surface are multiplied and output as an electric signal. Based on this output signal level and the level of the bias voltage applied to the mesh electrode, an external discriminating device performs light detection with position resolution. Thus
The position is detected by detecting only the photoelectrons that are excited by the light incident on the specific position and have not blocked the orbit.

[0005]

In the conventional example in which the image intensifier and the solid-state image pickup device are combined, it is essentially unavoidable to convert optical signal → electrical signal → optical signal → electrical signal. The efficiency deteriorates and the performance decreases due to loss.

In the photomultiplier tube in which the anode is divided, crosstalk between the photocathode and the multiplication section and between the multiplication section and the anode becomes a problem, and the position resolution is not essentially improved.

Further, in the photomultiplier tube having the mesh electrode, only a part of the photoelectrons emitted from the entire photoelectron emission surface of the photocathode is detected and the position is detected at the time of measurement. There is an inherent problem in terms of ratio. Furthermore, since position resolution is also determined by changing the orbit of the photoelectron, crosstalk is structurally increased, and only one photomultiplier tube can determine the position at about two locations. It is inherently difficult to convert.

Therefore, an object of the present invention is to realize a photocathode having a position detecting function with less crosstalk, and a phototube and a photodetector using the photocathode.

[0009]

The photocathode of the present invention includes a photoelectric conversion layer in which photoelectrons are excited by incident photons, and photoelectrons generated inside the photoelectric conversion layer and accelerated are emitted from the photoelectron emission surface. A semiconductor layer to be emitted to the outside,
A front electrode formed on the semiconductor layer of the photoelectron emission surface and a back electrode formed on the opposite surface of the photoelectron emission surface so as to face the front electrode. The front electrode is divided to form a plurality of pixel electrodes. In addition, the plurality of pixel electrodes are electrically insulated from each other, and the plurality of pixel electrodes are connected to a plurality of bias application lines that independently apply a positive bias potential as compared with the back surface electrode.

The photoelectric tube of the present invention comprises a vacuum container, a photocathode arranged inside the vacuum container, and an anode arranged inside the vacuum container for receiving photoelectrons emitted from the photocathode. The photocathode includes a photoelectric conversion layer that internally excites photoelectrons by incident photons, a semiconductor layer that emits photoelectrons generated and accelerated inside the photoelectric conversion layer to the outside from the photoelectron emission surface, and a photoelectron emission surface. And a back electrode formed on the semiconductor layer on the opposite surface of the photoelectron emission surface so as to face the front electrode, and the front electrode is divided into a plurality of pixel electrodes and mutually formed. The plurality of pixel electrodes are electrically insulated and are connected to a plurality of bias application wirings that independently apply a positive bias potential as compared with the back surface electrode. Furthermore, a plurality of bias applications are applied inside the vacuum container. A plurality of switch elements for individually switching the bias application by individually turning on and off the connection between the wiring and the plurality of pixel electrodes, a switching circuit for individually turning on and off the plurality of switch elements, and a plurality of switch elements At least one of a plurality of stem pins led to the outside from the vacuum container is provided with a switching control means having a plurality of switching wires that individually connect a plurality of output terminals of the switching circuit to each control terminal. It is characterized in that the book is connected to the back electrode, at least one is connected to the bias applying wiring, at least two is connected to the input terminal of the switching circuit, and at least one is connected to the anode.

The photodetector of the present invention comprises a phototube having a photocathode and an anode inside a vacuum container, a power supply for applying a potential to the photocathode and the anode, a timing control means, and a memory means. The photocathode includes a photoelectric conversion layer that internally excites photoelectrons by incident photons, and a semiconductor layer that emits photoelectrons generated and accelerated inside the photoelectric conversion layer to the outside from the photoelectron emission surface, and photoelectron emission. A front surface electrode formed on the surface semiconductor layer and a back surface electrode formed on the semiconductor layer on the surface opposite to the photoelectron emission surface to face the front surface electrode, and the front surface electrode is divided into a plurality of pixel electrodes. And electrically insulated from each other, the plurality of pixel electrodes are respectively connected to a plurality of bias application wirings that independently apply a positive bias potential as compared with the back surface electrode, and further, inside the vacuum container, A plurality of switch elements that individually switch the bias application by individually turning on and off the connection between the plurality of bias applying wirings and the plurality of pixel electrodes, and a plurality of switch elements individually. A switching circuit for turning on and off and a plurality of switching wirings for individually connecting the plurality of output terminals of the switching circuit to the respective control terminals of the plurality of switching elements are provided. Then, the timing pulse is continuously applied to the switching circuit, the switching circuit sequentially turns on and off the plurality of switching elements in response to the timing pulse, and the memory means starts the storage operation when the activation signal is given. It is characterized in that the output of the anode is stored in correspondence with the positions of the pixel electrodes which are in the photoelectron emission ready state in sequence based on the timing pulse.

[0012]

According to the photocathode of the present invention, the surface electrode is divided into a plurality of pixel electrodes, and the pixel electrodes are independently applied with a bias potential. Only for the selected pixels, the photoelectrons generated inside can be emitted to the outside. Therefore, when the pixel electrodes are arranged in a one-dimensional array, a one-dimensional position dividing ability can be realized, and when they are arranged in a two-dimensional matrix, a two-dimensional position dividing ability can be realized.

According to the photoelectric tube of the present invention, the vacuum container has the above-mentioned photocathode, and the switching control means for switching the application of the bias to the plurality of pixel electrodes is provided. It is possible to realize a photoelectric tube having a positional resolution of.

According to the photodetector of the present invention, in addition to the above-mentioned photoelectric tube and the power supply, the timing control means and the memory means are provided. Since the timing control means stores the output of the anode in the memory means in correspondence with the position information of the pixel electrode in the phototube in the photoelectron dischargeable state, the one-dimensional image or the two-dimensional image of weak light is obtained. Can be stored in the memory means.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below with reference to the accompanying drawings. The same elements will be denoted by the same reference symbols, without redundant description.

As shown in FIG. 1, the semiconductor layer 100 as the main body of the photocathode 1 is composed of InGaAs on the InP substrate 101.
The light absorption layer 102 is formed, and the InP contact layer 103 is formed thereon. An ohmic electrode 104 made of Au (gold) or the like is formed on the back surface of the InP substrate 101.
Is formed as a back electrode, and the InP contact layer 103 is formed.
A Schottky electrode 105 made of Al (aluminum) or the like is formed as a surface electrode on the surface of the. Here, the ohmic electrode 104 is formed thin so as to allow incident light to pass therethrough, or is formed with a large number of openings, and the Schottky electrode 105 is divided into pixel electrodes 105 ₁ and 105 arranged in a one-dimensional array. ₂ , ..., 105 _n . Each pixel electrode is patterned in a mesh shape, and photoelectrons can pass through the openings. InP
Of the surface of the contact layer 103, in particular, the openings of the mesh-shaped pixel electrode are thinly coated with Cs (cesium) or the like for lowering the work function of the surface, so that the photoelectrons from the inside of the semiconductor layer 100 to the outside vacuum. Are easily released.

As shown in FIG. 1, such a photocathode 1 is attached to a vacuum container 21, and an anode 22 is provided at a position facing the photocathode 1. Each pixel electrode 105 ₁ ,
105 ₂ , ..., 105 _n are bias applying wirings 106.
₁ , 106 ₂ , ..., 106 _n are connected, and these are connected to the power supply terminal 301 via the switch SW. on the other hand,
The ohmic electrode 104 is connected to the power supply terminal 302, but the terminal 301 has a positive high potential as compared with the terminal 302. Therefore, the switch SW causes the terminal 301
Pixel electrodes 105 _{1 to} 105 to which a bias from
Only _n has a higher positive potential than the ohmic electrode 104, and the opening and the photoelectron emission surface in the vicinity thereof are in a state capable of emitting photoelectrons. The photoelectrons emitted into the vacuum travel toward the anode 22. This is because the anode 22 is further biased to a positive high voltage via the power supply terminal 303.

As shown in FIG. 2, ohmic electrode 104
When the light to be detected (hν) is transmitted through the optical path and is photoelectrically converted in the InGaAs light absorption layer 102 having a narrow band cap, photoelectrons (-e) are generated. At this time, if a bias is applied between the ohmic electrode 104 and the Schottky electrode 105, photoelectrons are accelerated in the semiconductor layer 100 in the direction of the photoelectron emission surface as shown in the lower figure, and high energy is obtained. Emitted in vacuum (level VL). Therefore, the switch SW is used to apply the bias to the individual pixel electrodes 105 _{1 to} 105 _n obtained by dividing the Schottky electrode 105.
By individually turning on and off with, the photoelectrons generated inside the InGaAs light absorption layer 102 can be emitted from the photoelectron emission surface to the outside of the semiconductor layer 100, that is, in vacuum only for the pixel electrode whose switch SW is turned on. .

In the photocathode of FIG. 3, pixel electrodes form a one-dimensional array and are fixed to a holder. The long semiconductor layer 100 is fixed to a ceramic holder 401, which is fixed to a molybdenum die 402.
0 and the mold 402 are insulated. The mold 402 terminal pins 403 _1, 403 _2, 403 _3, 403 ₄ is fixed through an insulator, pin 403 ₁ a positive bias power supply +
Is connected to V _B on the semiconductor layer 100 of the biasing line (not shown), the pin 403 ₂ is connected to ground (the ground) to the ohmic electrode 104 on the semiconductor layer 100,
Pin 403 _3, 403 ₄ is connected to the input terminal of the shift register 5 on the semiconductor layer 100. Here, the shift register 5 is a switching control means for sequentially applying a bias to the pixel electrodes 105 _{1 to} 105 _n , and the terminal pin 40
3 _3, 403 ₄ via the start pulse SP and clock pulse CLK to be described later is input. The semiconductor layer 10
Surfaces other than the photoelectron emission surface of 0 are covered with an insulating film 120 such as SiO ₂ .

The pixel electrodes 105 _{1 to} 105 _n shown in FIG.
If the −1, i, i + 1th are expressed in perspective, FIG.
As shown in. That is, the pixel electrode 105 _i
Is patterned in a mesh shape having 15 openings, and has field effect transistor (FET) switch elements S _i at the corners. Then, the gate electrode is connected to the i-th output terminal of the shift register 5 by the Al wiring 501 _i . Therefore, when a pulse is input from the shift register 5 through the Al wiring 501 _i , the i-th switch element S _i is turned on and the bias applying wiring 1
Bias + V _B is applied from 06 _i to the pixel electrode 105 _i. Such operation is performed for 1 to i−1 other than the i-th,
The same applies to the i + 1 to n-th pixels.

As shown in a three-dimensional equivalent circuit in FIG. 5, the ohmic electrode 104 and the respective pixel electrodes 105 _{1 to} 105.
_{Between n} , diodes D _{1 to} D _n whose ohmic electrodes 104 serve as cathodes are equivalently formed. Then, the switches S _{1 to} S _n are turned on by the output from the shift register 5, so that the diodes D _{1 to} D of the respective pixels are
_n is reverse biased individually. Then, due to the electric field inside the semiconductor layer 100 under the reverse bias, the photoelectrons are accelerated toward the pixel electrode 105 to obtain high energy as shown in FIG. 2, and are emitted to the outside of the semiconductor layer 100.
The clock pulse CLK is input to the input terminal 502 of the shift register 5, and the start pulse SP is input to the terminal 503.

The operation in this case will be described with reference to FIGS. 6 and 7. Here, the light detection outputs in the pixels corresponding to the pixel electrodes 105 _{1 to} 105 _n are P _{1 to} P _n . The outputs P _{1 to} P _n are taken out to the outside as the output A _OUT of the anode 22 when configured as shown in FIG. As shown in FIG. 7, the start pulse SP is given to activate the shift register 5, and when this pulse SP is given, the shift register 5 receives pulses from the output terminals 501 _{1 to} 501 _n in response to the clock pulse CLK. Then, the switch elements S _{1 to} S _{n formed of} FETs are sequentially turned on, and the bias + V _B is sequentially applied to the pixel electrodes 105 _{1 to} 105 _n . As a result, photoelectrons can be sequentially emitted from each pixel, and the outputs P _{1 to} P _n are sequentially taken out as the anode output A _OUT .

Referring to FIG. 8, a photo-detecting device to which the photocathode according to the above embodiment is applied will be described. As shown,
A transmission type photocathode 1 is attached to the input window of the vacuum container 21, and a switching control unit 50, an anode 22, and a dynode 25 for multiplying photoelectrons by two-dimensional electrons are provided inside. The power supply 61 supplies an anode potential + V _A to the anode 22 through a stem pin penetrating the vacuum container 21, supplies a dynode potential V _D to the dynode 25, and supplies a bias potential + V _B to the switching control unit 50. The timing control unit 62 outputs a start pulse SP according to an operator's instruction and the clock pulse CL having a constant cycle.
K is output continuously. The signal processing circuit 63 amplifies the anode output A _OUT , performs threshold processing for noise removal, or performs analog / digital conversion, and supplies the output signal to a memory device 64 with a controller such as a microprocessor. A display device 65 is connected to the storage device 64.

In this configuration, the timing controller 62
When the start pulse SP is output from the switch controller 5
0 and the memory device 64 are activated, and each operates in response to the clock pulse CLK. That is, the switching control unit 50
Each time a clock pulse CLK is input, a pulse is sequentially output from the output terminal corresponding to each pixel electrode, and each pixel is brought into a state in which photoelectrons can be sequentially emitted. The photoelectrons thus emitted are multiplied by the dynode 25 and given to the storage device 64 via the signal processing circuit 63.

At this time, since the clock pulse CLK is also given from the timing controller 62 to the memory device 64, the controller of the memory device 64 has the anode output A according to the result value obtained by counting the clock pulse CLK.
_OUT is stored in correspondence with the position of the pixel that is in a state capable of emitting photoelectrons. For example, the count value of the clock pulse CLK is used as an address and the value (digitally converted value) of the anode output A _OUT is stored as data. Such processing can be understood from the timing chart of FIG. 7. Sequential on / off switching is repeated a plurality of times for all pixel electrodes, and if the anode output A _OUT is added to each pixel and stored in a storage area corresponding to the position of the pixel in the storage device 64, an image is formed. Image data of the detected light is obtained. This image is C
It is displayed on the display 65 equipped with RT and the like.

FIG. 9 shows a photocathode of another embodiment. The upper side is a top view, the center is a side view showing a part of the section, and the lower side is a bottom view. An InGaAsP light absorption layer 102 and an InP contact layer 103 are formed on the InP substrate 101 by epitaxial growth, and an Au ohmic electrode 104 is formed on the back surface of the InP substrate 101. A plurality of Al Schottky electrodes 105 to be joined are formed in a pattern. Here, the semiconductor layer 100 composed of the substrate 101, the light absorption layer 102 and the contact layer 103 may have a heterojunction structure composed of GaAs and AlAs or a mixed crystal thereof, and Ge (germanium) and Si (silicon) or these A heterojunction structure made of a mixed crystal of Schottky electrode 1
For 05, for example, Al, Au, Ag (silver), W
(Tungsten), Ni (nickel), Ti (titanium), or alloys thereof.

The pattern of the Schottky electrode 105 may be a mesh electrode composed of orthogonal linear members as shown in FIG. 9, but may be a pattern as shown in FIG. In FIG. 10, the upper diagram shows a pattern of mesh-shaped electrodes having hexagonal openings, the central diagram shows a stripe pattern of grid-shaped electrodes made of parallel members, and the lower diagram shows a comb-shaped pattern. Is shown. In both cases, the openings for the passage of photoelectrons are arranged at intervals of about 10 μm or less. The light may be incident on the back surface, that is, the ohmic electrode 104, but may be incident on the front surface, that is, the opening of the Schottky electrode 105. When light is incident from the back surface, the ohmic electrode 104 is formed of a transmissive material or a metal film that is thin enough to transmit light,
Alternatively, it is formed of a metal film having a large number of apertures through which light can pass.

In FIG. 9, each pixel electrode 105
The switches S _{1 to} S _n of the FET are formed in the vicinity corresponding to _{1 to} 105 _n , and the switching function of the FET turns on and off the bias voltage to the electrodes 105 _{1 to} 105 _n . The surface of the photoelectron emission surface is lightly coated with Cs (cesium) for lowering the work function of the surface. Such coating materials are alkali metals or their compounds, alkali metal oxides or fluorides. Alkali metals include Ks in addition to Cs
(Potassium), Na (sodium) Rb (rubidium)
Is included. The substrate 101 is fixed by a ceramic holder 401, and its surface has an Al Schottky electrode 105.
Except for the above portion, it is covered with an insulating film 120 of SiO ₂ or SiN.

Further, in the example of FIG. 9, the shift register 5 composed of a transistor is formed on the semiconductor layer 100, and the gates of the FETs S _{1 to} S _n are respectively wired to the n output terminals of the shift register 5. ing. The shift register 5 generates a scanning pulse by a start pulse SP and a clock pulse CLK from the outside, and each of the FETS ₁ to
S _n is sequentially turned on to turn each Al Schottky electrode 105 ₁ to
Address 105 _n . In addition, the terminal 403 _1, 403
Reference numeral ₄ is for connecting a circuit on the substrate 100 and an external circuit.
Terminal 403 _3, 403 ₄ are for signals input to the shift register 5, the terminal 403 _1, FETS ₁ ~
This is also for externally applying a bias voltage + V _B to the Schottky diodes D _{1 to} D _n via S _n .

FIG. 11 shows an example of a structure in which the photocathode of the embodiment is applied to a head-on type photomultiplier tube.
The upper side is a schematic view of the face plate viewed from the inside, and the lower side is a cross-sectional view of the envelope 21 in the axial direction. Note that, due to space limitations, n = 6. The ceramic holder 402 for fixing the semiconductor substrate as the photocathode is fixed to the fixing fitting 405 made of molybdenum by spot welding, and the electrode terminal 403 is connected to the outside of the face plate. A focusing electrode 26 is provided inside the vacuum container, that is, the envelope 21, and eight dynodes 25 _{1 to} 25 ₈ are provided.
Are arranged. An anode 22 is provided on the front side of the ninth-stage reflective dynode 25 ₉ . In this photomultiplier tube, six sets of terminal pins 403 are provided corresponding to each of the six pixels, and the pixels capable of emitting photoelectrons are switched by the output of the external control circuit.

In the photomultiplier tube of FIG. 12, the control circuit has a shift register 5 provided on the face plate 405.
Has been realized in. The input of the start pulse SP and the clock pulse CLK to the shift register 5 is realized by the stem pin 406.

11 and 12 are both transmission type photocathodes, that is, photoelectrons are emitted in the same direction as the incident direction of photons (therefore, the incident surface of the photons is the opposite surface of the photoelectron emission surface). A type of photocathode is used. The embodiment of FIG. 13 uses a reflective photocathode, that is, a photocathode of the type that emits photoelectrons in the direction opposite to the incident direction of photons (therefore, the incident surface of photons is the same surface as the photoelectron emission surface). Such a photomultiplier tube is called a side-on type, and the structure of its cross section is shown in FIG. Photons incident from a vacuum container 21 such as glass pass through a focusing electrode (mesh-shaped electrode) and enter the photocathode 1. The emitted photoelectrons are multiplied by the dynodes 25 _{1 to} 25 ₈ ,
It is incident on the anode 22.

The operation of the photomultiplier tubes of FIGS. 11, 12, and 13 can be explained with reference to the timing chart of FIG. 7 mentioned above. In FIG. 7, “S _{1 to} S _n ” denotes the output level from the shift register to the FET switch, and when it is high, the switch is on. Start pulse SP
Becomes high level, the shift register 5 starts to operate, the FETs are sequentially operated by the clock pulse CLK, and the switches S _{1 to} S _n are turned on. Switch S ₁ ~
When S _n is turned on, the photoelectron emission surface to which the predetermined bias voltage is applied to the pixel electrodes 105 _{1 to} 105 _n (that is, the Schottky diode to which the bias voltage is applied) operates.
Of course, at this time, since the Schottky electrode to which the bias voltage is not applied does not operate as a photoelectron emitting surface, photoelectrons are not emitted regardless of the presence of incident light. “P _{1 to} P _n ” in FIG. 7 indicates the bias voltage of each photoelectron emitting surface, and when it is high, it is in the operating state.

Assuming that P _{3 on the} photoemission surface of the photomultiplier tube is
If light is incident on this portion, photoelectrons are emitted when a bias voltage is applied to this portion. Photoelectron emission surface P
_The photoelectrons emitted from _{3 have} their trajectories corrected by the focusing electrode and enter the first stage dynode. The first-stage dynode produces and emits several times as many secondary electrons as the incident primary electrons (photoelectrons), and these secondary electrons are multiplied by the second-stage dynode, the third-stage dynode ... ^It reaches about ⁶ times and is detected as photocurrent at the anode 22.

Since the photoelectron emission surfaces P _{1 to} P _n are sequentially operated by the address signal from the shift register 5, the photoelectrons from each part of the photoelectron emission surface are multiplied and detected as a photocurrent. By synchronizing the clock pulse CLK input to the shift register 5 and the signal read by the anode 22, the anode output A _OUT is changed to the photoelectron emission surface P.
_It is determined from which position of _{1 to} P ₆ the photoelectron is emitted. Therefore, the anode output A _OUT and the clock pulse CL
One-dimensional position information about the incident light can be obtained from the timing of K.

Here, an example has been described in which the shift register 5 is formed on the same substrate as the photoelectron emission surface to perform switching and addressing of the FET, but as shown in FIG. 11, the bias voltage of the Schottky electrode 105 is applied from the terminal of each pixel. It is also possible to directly control and to control without using the shift register 5. Further, if the wiring is not complicated, the shift register 5 can be formed outside the semiconductor substrate forming the photocathode.

The operation of the photomultiplier tube of FIG.
11 is the same as the photomultiplier tube. P on the photoemission surface₃
Assuming that light is incident on a part, the light from the shift register 5
Photoelectron emission surface P by address signal₁~ P₆Work sequentially
Therefore, the photoelectron emission surface P ₃Photoelectrons emitted from
The orbit is modified by the focusing electrode and the first stage dynode is
Incident. Number of incident primary electrons at the first stage dynode
Twice as many secondary electrons are generated and emitted, and these secondary electrons are generated in the second stage.
Dynode, 3rd-stage dynode ... are multiplied and finally 1
0⁶Doubled and detected as photocurrent at anode 22
To be done. Therefore, the input clock to the shift register 5 is
Sync pulse CLK and the signal read by the anode 22
As a result, the anode output is changed to the photoelectron emission surface P₁~
P₆It is possible to determine from which position of the photoelectron is emitted.

Further, it can be applied to a side-on type photomultiplier tube, and FIG. 13 shows a configuration example in that case. A reflection type photoelectron emitting surface having a one-dimensional position detecting function is provided at the place where the light hν is incident, and the generated photoelectrons are dynodes 25 ₁ to 2 2 like the above-described embodiment.
It is multiplied by 5 ₈ and detected at the anode 22. Although the emission direction of photoelectrons is different from that of the above-mentioned transmission type photoelectron emission surface, the operation method is exactly the same as that of the head-on type.
The present invention enables position detection by the reflection type photoelectron emission surface, which has been impossible in the past.

FIG. 14 shows an embodiment of the present invention of the photoelectron emission surface when the photoelectron emission surface is constructed to have a two-dimensional position detecting function. In this embodiment, a plurality (m rows) of those having the one-dimensional position detecting function as described above are arranged in the vertical direction of FIG. Further, although not included in FIG.
A shift register for addressing the vertical direction is formed outside (on the left side of the figure). That is, the pixel electrodes 10 of each row
5 _{11 to} 105 _1n , 105 _{21 to} 105 _2n , ..., 105 _m1 to
M shift registers 5A _{1 to} 5A corresponding to 105 _mn
m is formed on the substrate 100 on which the photocathode 1 is formed.
In addition, the bias applying wirings 106 ₁ to 10 10 in each of m rows.
An external shift register is connected to 6 _m via a terminal pin. Here, the first shift registers 5A _{1 to} 5A _m respectively input the clock pulse CLK and the start pulse SP from the outside via the terminal pins,
There are n output terminals corresponding to each pixel electrode. Further, a second shift register provided outside also inputs CLK and SP, and the output thereof realizes a photocathode arranged in a two-dimensional matrix of m rows and n columns of pixel electrodes.

FIG. 15 shows an equivalent circuit when operating the photoelectron emission surface of the m × n pixel structure of FIG. 14, and the portion surrounded by the dotted line is a circuit formed on the substrate of FIG. Is shown. Lateral first shift register 5A
₁ , 5A ₂ , ..., 5A _m have the same circuit configuration as in FIG. 2, and have a start pulse SP and a clock pulse CLK _2.
Thus, the switches S _{11 to} S _mn operate in parallel at exactly the same time to sequentially turn on the switches. The switches SB _{1 to} SB _m are provided so as to be connected to the output of the vertical second shift register 5B,
The shift pulse is addressed by the shift register 5B by the clock pulse CLK ₁ and sequentially turned on. Shift register 5A
Switches S provided at the outputs of ₁ , 5A ₂ , ..., 5A _{m
11 to} S _mn are switches SB for the bias power supply + V _B
Bias voltage + V _B from the outside is applied to the Schottky diodes D _{11 to} D _mn in series with _{1 to} SB _m when both switches in series with the power supply are turned on.

A photomultiplier tube having a two-dimensional position detecting function can be constructed by using the photoelectron emitting surfaces shown in FIGS. 14 and 15 in the same manner as in the one-dimensional case. FIG. 16 is a timing chart showing the operation of the photomultiplier tube in this case. “S” in FIG. 16 indicates the output level from the shift register to the FET switch, and when it is high, the switch is on.

When the start pulse SP becomes high level, all the shift registers start operating at the same time.
Input of clock pulse CLK ₁ shift register 5
The FETs in the column of B are turned on sequentially, and first, the switch SB ₁
Is addressed and turned on. The horizontal shift registers are simultaneously operated in parallel by the clock pulse CLK ₂ . When any of the outputs of these shift registers is high, a bias voltage + V _B is applied, and photoelectrons can be emitted from the photoelectron emission surfaces P _{11 to} P _mn . In the timing chart of FIG. 16, the switch S
_{When 11} is on, the longitudinal direction of the switch S ₂₁ to S
_{Although 2 m is} also on, if the switch SB ₁ is on, the bias voltage + V _B is applied only to the photoelectron emission surface P ₁₁ , and this operates. When the switch SB ₁ is on, the vertical ones of the switches S _{11 to} S _mn are sequentially turned on, and the photoelectron emission surfaces P _{11 to} P _1n sequentially operate. This is the switch SB ₂ , SB ₃ , ...
This is also done for SB _m .

The clock pulse CLK ₁ is synchronized with the clock pulse CLK ₂ of the shift registers A _{11 to} A _mn , and the width of the clock pulse CLK ₁ is set to be n times the cycle of the clock pulse CLK ₂ to make the Schottky diode P ₁₁
~ P _mn sequentially bias voltage + V _B from the upper left to the lower right of the figure
Will turn on the switch to give. Then, the photoelectron emission surfaces P _{11 to} P _mn are sequentially arranged from the upper left to the lower right in the figure.
The photoelectrons generated by the excitation of the incident light are emitted from, and are multiplied and detected.

As in the previous embodiment, the clock pulse C
By synchronizing LK ₁ and the clock pulse CLK ₂ with the read signal, it is possible to obtain two-dimensional position information about the incident light. Therefore, the clock pulse CLK
Two-dimensional position detection is possible by synchronizing ₁ , CLK ₂ and the anode output. Of course, as mentioned above, shift register or FE for switching
T may be formed on the same substrate as the photoelectron emitting surface or may be formed on the other portion.

As shown in FIG. 17, the first and second shift registers may all be formed on the substrate 100 forming the photocathode. In this way, the number of terminal pins on the substrate 100 can be significantly reduced, and the positional resolution can be improved as a large number of pixels. Note that each reference numeral in FIG.
The same reference numerals are used for the same elements as 4 and 15.

FIG. 18 shows an example of a configuration system of an optical position detecting device using the above-described photomultiplier tube according to the present invention. This system includes a photomultiplier tube PMT, a drive circuit section for driving the photomultiplier tube PMT, a read circuit section 82 for reading a signal, a DC power supply section 81 for supplying a high voltage to the photomultiplier tube PMT, Input clock pulse (CLK, CL to the PMT PMT)
Pulse generator 8 for generating K ₁ , CLK _2, etc.)
3. An A / D conversion unit 84 for a read signal from the photomultiplier tube PMT, an oscilloscope (or a display device such as a CRT or LCD) 85, and a computer unit 86 for control. Other than the photomultiplier tube PMT, conventional ones are used. As described above, the position of the incident light on the photomultiplier tube PMT is controlled by controlling the generation timing of the input clock pulse to the photomultiplier tube PMT by the computer 86 and capturing the signal read from the photomultiplier tube PMT. It is possible to easily obtain information, and it is also possible to display this on a display device in the form of an image.

Thus, the photoelectron emission surface of the present invention is 1
Despite being the photoelectron emission surfaces formed on one substrate, they can be operated as a plurality of independent photoelectron emission surfaces by applying a bias voltage to each of the plurality of pixel electrodes individually. Therefore, as compared with a conventional photodetector having a photoelectron emitting surface, it is possible to realize a photodetector capable of position detection with a much simpler structure and very little crosstalk.

On the photoelectron emission surface of the present invention, since it is possible to detect light with ultra-high sensitivity and low noise by multiplying secondary electrons of photoelectrons, it is possible to easily detect position and image information under weak light. It can be carried out. Furthermore, since the portion to which the bias voltage is not applied does not emit electrons due to the dark current, noise is not generated from the portion that does not operate as the photoelectron emission surface, and the photodetector is essentially very low noise. Therefore, in the photodetector using the photoelectron emitting surface according to the present invention and the photodetector using the photodetector, the sensitivity is extremely high, and
Position detection with low noise is possible.

Further, conventionally, the photoelectron emitting surface having this kind of position detecting function had to be essentially a so-called transmissive structure in which the incident direction of light is different from the emitting direction of photoelectrons. However, according to the present invention, a position detection function can be provided even in a so-called reflective structure in which the incident direction of light is the same as the emitting direction of photoelectrons, and the degree of freedom in device structure and design is greatly expanded.

The present invention does not select and multiply photoelectrons from the entire photoelectron emission surface for photoelectrically converting incident light, but
A bias voltage is applied to make some of it work. Therefore, it is possible to easily obtain a photoelectron emitting surface having low noise and a position detecting function with very little crosstalk. Further, by adding a multiplication section to form a photoelectron multiplication section, it is possible to realize a photodetector having a supersensitive position detection function.

The present invention is not limited to the above-described embodiment, but various modifications can be made. For example, if the main material of the photoelectron emission surface is I
Although description has been made by using nP and InGaAsP, the invention is not limited to this. Further, the Schottky electrode, ohmic electrode, alkali metal, etc. are not limited to those used in this embodiment. Further, by using the shift register as an address decoder and applying an additional input address pulse, it is possible to detect a position that allows random access.

By the way, "US PAT. 3,958
143 ”discloses an example of a photoelectron emission surface that accelerates photoelectrons by utilizing an internal electric field and emits them into a vacuum.
However, position information cannot be obtained on the photoelectron emission surface described in this document. In addition, Japanese Patent Laid-Open No. 4-26941
9 ”shows a photoelectron emission surface in which Schottky electrodes are formed in a pattern. However, since this does not similarly form a plurality of electrodes and does not individually apply a bias voltage, No location information can be obtained.

[0053]

As described above, according to the photomultiplier tube of the present invention, it is possible to obtain a detection output according to the incident position of the light on the photocathode, and it is possible to make it small and compact. The photomultiplier tube can be constructed by using the photoelectron emitting surface of the present invention. Further, according to the photodetector using the photomultiplier tube of the present invention, it is possible to obtain one-dimensional or two-dimensional information about the incident light even if the incident light on the photocathode is weak. .

[Brief description of drawings]

1 shows a photocathode according to an example and a phototube having the same, the upper side is a top view of the photocathode, and the lower side is a vertical cross-sectional view of the phototube taken along line X ₁ -X ₁ in the upper figure.

2 shows an energy band structure of the photocathode of FIG. 1, in which the upper side is a state in which a bias voltage is not applied, and the lower side is a state in which a bias voltage is applied.

FIG. 3 is a perspective view showing a photocathode assembly according to an embodiment.

FIG. 4 is a perspective view showing an example of a pattern of a pixel electrode in an example.

FIG. 5 is a three-dimensional view of an equivalent circuit of the photocathode of the example.

FIG. 6 is a plan view showing an equivalent circuit of the photocathode of the embodiment.

FIG. 7 is a timing chart showing the operation of the embodiment.

FIG. 8 is a diagram showing a photodetector using the photocathode of the example.

FIG. 9 is a top view, a side view, and a bottom view showing the photocathode assembly of the embodiment.

FIG. 10 is a top view showing another example of the pixel electrode of the embodiment.

FIG. 11 is a diagram showing a head-on type photomultiplier tube using the photocathode of the example.

FIG. 12 is a diagram showing a head-on type photomultiplier tube using the photocathode of the example.

FIG. 13 is a view showing a side-on type photomultiplier tube using the photocathode of the example.

FIG. 14 is a diagram showing an example in which a two-dimensional matrix is formed.

FIG. 15 is a diagram showing an example in which a two-dimensional matrix is formed.

FIG. 16 is a timing chart showing the operation of the original embodiment.

FIG. 17 is a diagram showing another embodiment in the form of a two-dimensional matrix.

FIG. 18 is a block diagram showing a photodetector according to an example.

[Explanation of symbols]

100 ... Semiconductor layer, 104 ... Ohmic electrode (back surface electrode), 105 ... Schottky electrode (front surface electrode), 5 ... Shift register, 21 ... Vacuum container, 22 ... Anode, 25 ... Dynode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsuneo Yubara 1126-1 Nono Ichi, Hamamatsu, Shizuoka Prefecture 1126 Hamamatsu Photonics Co., Ltd. (72) Masami Yamada 1126 1126 Nomachi, Hamamatsu, Shizuoka Prefecture (72) Inventor Norio Asakura 1 Hamamatsu Photonics Co., 1126, Nomachi, Hamamatsu City, Shizuoka Prefecture Inside (72) Inventor Yasuharu Negi 1 126, Nomachi, Hamamatsu, Shizuoka Prefecture Hamamatsu Photonics Co., Ltd. ( 72) Inventor Tomoko Suzuki 1 1126, Nomachi, Hamamatsu, Shizuoka Prefecture 1 Hamamatsu Photonics Co., Ltd.

Claims (21)

[Claims] 1. A semiconductor layer comprising a photoelectric conversion layer for internally exciting photoelectrons by incident photons, and emitting the photoelectrons generated and accelerated inside the photoelectric conversion layer to the outside from a photoelectron emission surface, and the photoelectrons. A front surface electrode formed on the semiconductor layer on the emission surface, and a back surface electrode formed on the semiconductor layer on the surface opposite to the photoelectron emission surface so as to face the front surface electrode, and the front surface electrode is divided. A plurality of pixel electrodes and electrically insulated from each other, and the plurality of pixel electrodes are respectively connected to a plurality of bias applying wirings that independently apply a positive bias potential as compared with the back surface electrode. Photocathode characterized by. 2. The photocathode according to claim 1, wherein the semiconductor layer has a heterojunction structure. 3. The photocathode according to claim 2, wherein the semiconductor layer has a heterojunction structure of GaAs, AlAs or a mixed crystal thereof. 4. The photocathode according to claim 2, wherein the semiconductor layer has a heterojunction structure of InP, GaAs or a mixed crystal thereof. 5. The photocathode according to claim 2, wherein the semiconductor layer has a heterojunction structure of Si, Ge or a mixed crystal thereof. 6. The photoelectron emitting surface of the semiconductor layer is coated with an alkali metal, a compound of an alkali metal or an oxide or fluoride thereof, and the alkali metal is Cs, K, Na or Rb. The photocathode according to claim 1, wherein 7. The photocathode according to claim 1, wherein the semiconductor layer and the front surface electrode are in Schottky contact, and the semiconductor layer and the back surface electrode are in ohmic contact. 8. The photocathode according to claim 1, wherein the plurality of pixel electrodes are arranged in a one-dimensional array form or a two-dimensional matrix form. 9. The photocathode according to claim 1, wherein the surface electrode has an electron transmitting portion that allows the photoelectrons generated in the photoelectric conversion layer and accelerated in the semiconductor layer to pass therethrough to be emitted to the outside. . 10. The surface electrode is made of Al, Au, Ag,
The photocathode according to claim 1, which is made of W, Ti, Ni, WSi, or an alloy thereof. 11. The photocathode according to claim 1, wherein the surface electrode has a large number of openings through which the photoelectrons can pass. 12. The photocathode according to claim 1, wherein the surface electrode has a stripe, mesh or grid pattern with a pitch of 10 μm or less. 13. The back electrode is made of a translucent material, is a metal electrode that is thin enough to transmit incident photons, or is a metal electrode having a large number of apertures that can transmit incident photons. 1. The photocathode according to 1. 14. The photoelectric conversion layer is formed on a semiconductor substrate, and a plurality of bias applying wirings provided corresponding to the plurality of pixel electrodes respectively on the semiconductor substrate, and a plurality of the bias applying wirings. The photocathode according to claim 1, wherein a plurality of switch elements are formed to individually switch the bias application by individually turning on and off the connection between the bias applying wiring and the plurality of pixel electrodes. 15. A switching circuit for individually turning on and off the plurality of switching elements on the semiconductor substrate, and a plurality of output terminals of the switching circuit individually connected to respective control terminals of the plurality of switching elements. 15. The photocathode according to claim 14, wherein a plurality of switching wirings are formed. 16. The photocathode according to claim 15, wherein the switch element is a transistor, and the switching circuit is a shift register in which an output terminal is connected to a gate terminal of the transistor. 17. The plurality of pixel electrodes are arranged in a two-dimensional matrix with m rows and n columns (m and n are integers of 2 or more), and the plurality of switch elements are pixels of the m rows and n columns. M corresponding to each electrode and connected in parallel in each row
xn first switches, and each of the n first switches of each row and m second switches serially connected for each row, the switching circuit for each row of the pixel electrode. Corresponding to, and n first shift registers each having n output terminals connected to the control terminals of the n first switches in each row, and m second switches. A second output terminal in which m output terminals are respectively connected to the control terminals of
16. The photocathode of claim 15 including the shift register of claim 1. 18. A photoelectric conversion device comprising: a vacuum container; a photocathode arranged inside the vacuum container; and an anode arranged inside the vacuum container for receiving photoelectrons emitted from the photocathode. The cathode includes a photoelectric conversion layer that internally excites photoelectrons by incident photons, and a semiconductor layer that emits the accelerated photoelectrons generated inside the photoelectric conversion layer to the outside from the photoelectron emission surface, and the photoelectron emission surface. A front surface electrode formed on the semiconductor layer and a back surface electrode formed on the semiconductor layer on the opposite surface of the photoelectron emission surface to face the front surface electrode, and the front surface electrode is divided. A plurality of pixel electrodes are formed and are electrically insulated from each other, and the plurality of pixel electrodes are respectively connected to a plurality of bias application wirings that independently apply a positive bias potential as compared with the back surface electrode, In the vacuum container, a plurality of switch elements for individually switching the bias application by individually turning on and off the connection between the plurality of bias applying wirings and the plurality of pixel electrodes, and the plurality of switching elements are provided. A switching control means having a switching circuit for individually turning on and off the switch element and a plurality of switching wirings for individually connecting a plurality of output terminals of the switching circuit to respective control terminals of the plurality of switch elements. Of the plurality of stem pins that are provided and are led out from the vacuum container, at least one is to the back electrode, at least one is to the bias applying wiring, and at least two are to the input terminals of the switching circuit. , At least one of which is connected to the anode. 19. The photoelectric tube according to claim 18, wherein the photoelectric conversion layer is formed on a semiconductor substrate, and the switching control means is formed on the semiconductor substrate. 20. The photoelectric tube according to claim 18, further comprising an electron multiplying means for two-dimensionally multiplying photoelectrons emitted from the photocathode, inside the vacuum container. 21. A phototube having a photocathode and an anode inside a vacuum container; a power supply for applying a potential to the photocathode and the anode; a timing control means; and a memory means. A semiconductor layer that includes a photoelectric conversion layer that internally excites photoelectrons by incident photons, and that emits the accelerated photoelectrons generated inside the photoelectric conversion layer from a photoelectron emission surface to the outside, and the semiconductor on the photoelectron emission surface. A front surface electrode formed on a layer and a back surface electrode formed on the semiconductor layer opposite to the photoelectron emission surface so as to face the front surface electrode, and the front surface electrode is divided into a plurality of pixels. The plurality of pixel electrodes, which form an electrode and are electrically insulated from each other, are connected to a plurality of bias applying lines that independently apply a positive bias potential as compared with the back electrode. Further, inside the vacuum container, a plurality of switch elements for individually switching the bias application by individually turning on and off the connection between the plurality of bias applying wirings and the plurality of pixel electrodes, A switching circuit that individually turns on and off a plurality of switching elements, and a plurality of switching wirings that individually connect a plurality of output terminals of the switching circuit to individual control terminals of the plurality of switching elements, The timing control means continuously applies a timing pulse to the switching circuit when a start signal is given, and the switching circuit sequentially switches on and off of the plurality of switch elements in response to the timing pulse, The memory means starts the storage operation when the activation signal is given, and sequentially becomes the photoelectron emission enable state based on the timing pulse. An optical detection device, which stores the output of the anode in correspondence with the position of the pixel electrode.