JPH02253186A - Photosensitive apparatus and image detector comprising the same - Google Patents

Abstract

PURPOSE: To store two different information items at each photosensitive point by providing first and second photosensitive cells which can store information items at each photosensitive point. CONSTITUTION: In order to collect information items accumulated at points B of first, fourth, and seventh photosensitive points P1, P4, and P7, the collecting stages T1-Tn of a data collecting register 74 are shifted. Then a column switch M7 is conducted and a pulse outputted from a pulse generator 10 is impressed upon the first column array FB1 of a second column array FB and, accordingly, a second photosensitive cell JB connected to a column conductor. As a result, the collection of the information item A accumulated in a first photosensitive cell JA connected to the second column array FB 21 can be executed. The above-mentioned operations are repeated until the collection of the information items A and B is terminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the processing of images with photosensitive elements, and more particularly to a matrix structure of photosensitive elements that allows simultaneous acquisition of multiple images.

Furthermore, the present invention relates to a radiation detector using an array of photosensitive elements, and in particular to an X-ray detector that allows simultaneous processing of two images, each corresponding to a different energy spectrum of X-rays.

[Description of the Prior Art] For example, in the field of radiology and radiodiagnosis, in the process of diagnosing a patient, it is possible to distinguish between two plates, each corresponding to a different energy spectrum of X-rays. It is convenient to create the plate in such a way that specific information is obtained. This type of image, or two energy images, as currently constructed by X-ray technicians, can be created by modifying the conditions of the X-rays (different energy spectra of X-rays) from one image to the other; By using sensors sensitive to different energy windows of X-rays, two images of the same zone of the patient formed in succession are obtained. This can be achieved, for example, by changing the type of scintillator used in converting the X-rays into visible light that exposes the photographic film.

The scintillator is made of a material that is excited by Xil and has the property of emitting visible light or radiation of a wavelength close to visible light in response to this excitation. This scintillator has a maximum conversion function, ie maximum sensitivity, within a certain energy range of X-rays, the energy range of which is determined by the properties of the material of which the scintillator is constructed.

These methods of the prior art have the disadvantage of requiring mechanical movements, particularly of the film or sensor, since they employ two successive plates. Other important drawbacks are
In order to obtain these images continuously, movement of the patient is unavoidable. This results in insufficient superposition of the two plates and thus no improvement in spatial resolution.

One of the objects of the invention is to make it possible to process two images simultaneously by means of a surface-type photosensor device, so that perfect superposition can be obtained without the need for mechanical movements during the recording of the images. The goal is to make sure that the Such a light sensor is particularly suitable for use in radiology, where two images, referred to as two energy images, are processed, each corresponding to a different energy spectrum of the X-rays, e.g. A single x-ray exposure of the patient is referred to as two energy images.

For example, it is known to construct a matrix of several million high-capacity photosensitive elements. In conventional practice, these photosensitive element matrices include an array of line conductors and an array of column conductors. At the intersections of the line conductors and the intersections of the column conductors, photosensitive zones or spots are deposited and these spots are organized in the same manner as the lines and columns. The number of photosensitive points within a given plane determines the resolution of the image. Each photosensitive point is connected between a line conductor and a column conductor. In reality, each line conductor is connected to the same number of photosensitive points as there are columns of photosensitive points. Moreover, the same number of photosensitive points as the number of lines of photosensitive points are connected to each column conductor.

The number of photosensitive points in a given plane determines the resolution of the image. In order to reduce the space required for the photosensitive points and increase resolution by providing a large number of photosensitive points in a given plane, each photosensitive point has a matrix of photosensitive elements consisting of a photodiode in series with a capacitor. Eggplant.

French patent application no. 86100656, issued as no. is explained. Other French Patent Application No. 86100716 issued as No. 2.593.343
No. 1, as previously described, relates to a matrix having an array of photosensitive points, each consisting of a photodiode in series with a capacitor as previously described. This French patent cylinder 2.
No. 593.343 describes the process of manufacturing such a photosensitive matrix, as well as the process of reading this photosensitive matrix and the application of this photosensitive matrix to take images, especially radiation images. One of the advantages of structures of the type described in this patent is that they allow matrix structures of large dimensions, so that the deposition of thin films of e.g. amorphous silicon is now well controlled and therefore suitable for radiology. This can be applied as a useful method. The configuration disclosed in this patent includes
Contains a scintillator that illuminates the line. In response to these X-rays, the scintillator emits a second radiation that is detected by the photodiode.

The matrix of photosensitive elements described in the aforementioned French patent application no.
To obtain an image, it is sufficient to add a second scintillator, each with optimal sensitivity to X-rays of different energies. Further, certain photosensitive points are exposed only to light emitted from scintillators assigned to them, and other photosensitive points are exposed only to light emitted from other scintillators,
placed between the scintillator and photodiode.
It is necessary to introduce two additional levels of opaque-transparent into this structure.

However, although such a solution is technically relatively simple, the two adjacent photosensitive points, one affected by the first image and the other by the second image, The drawback is that the two-energy image has half the resolution and space factor compared to the one-energy image.

[Summary of the Invention] Yet another object of the invention is to make it possible to construct photosensitive point photodetectors, each capable of storing two different items of information. This is especially true for each
corresponding to different energies of il, and respectively −
It is possible to construct a radiation image detector that can simultaneously obtain two images exhibiting resolution and space factor comparable to the energy image.

According to the invention, a photosensitive device comprising an array of photosensitive points comprises:
Each photosensitive spot is defined to include two superimposed photosensitive elements each generating a signal proportional to its firing.

This invention will be better understood from the following description, and the features and effects of this invention will become clear. The following description is based on a non-limiting example and three figures are shown.

[Description of Embodiments] FIG. 1 shows an electrical block diagram of a photosensitive device 1 according to the present invention. The photosensitive device 1 has a plurality of photosensitive points P1 to P9. The photosensitive points P1 to P9 are arranged in lines and columns in a conventional manner that is obvious from the point of view of forming the photosensitive 7-trix 2. In this non-limiting example described, the number of photosensitive points P1-P9 is limited to nine by a 3.times.3 matrix assembly to simplify FIG. However, within the spirit of the invention, this matrix assembly can be made to even larger capacities.

According to the invention, each photosensitive point PL-P9 has two photosensitive cells JA. Consists of J.B. Each photosensitive cell JA. JB is capacitor CA. a photosensitive element DA connected in series with CB;
Equipped with DB.

According to another feature of the invention, the same photosensitive points P1 to 2
At least two photosensitive elements DA. DBs are superimposed. Regarding this, the photosensitive element DA. DB and capacitor CA. The following section will discuss a structure in which all CBs are stacked one on top of the other.

It further comprises line conductors L1-L3 of the photosensitive device 1, and according to another feature of the invention, two column arrays F of column conductors FA1-FA3 and column conductors FB1-FB3.
A. Equipped with FB. The line conductors L1-L3 are connected to the address device 8, and the first and second column conductors FA1-FA3 and column conductors FB1-FB3 are connected to the address device 8.
Array FA. FB is connected to first and second readout and multiplexer devices 9A, 9B. Photosensitive cell J
A. JB has a first end 3A, 3B and a second second end 4A, 4B, these photosensitive cells are connected to the line conductor L1
~L3 and column conductor FAI-FA3 and column conductor F
Connected to BI-FB3. In the case of the same photosensitive point, two photosensitive cells JA. JB is connected by one end to the same line conductor and by the other end to a different array/column conductor. Therefore, for example, the photosensitive point P1 is located between the first and second photosensitive cells JA. Equipped with JB,
Its first ends 3A, 3B are connected to the same line conductor L1. The second end 4A of the first photosensitive cell JA is coupled to the column conductor FAI of the first column array FA, and the second end 4B of the photosensitive cell JB is coupled to the column conductor FAI of the first column array FA.
It is connected to the column conductor FBI belonging to B. First and second photosensitive cells JA and JB of other photosensitive points P2 to P9
Similarly, line conductor LL-L3 and column conductor FAI-
It is connected to FA3 and column conductors FB1 to FB3. Actually, at the intersection, two superimposed photosensitive cells J
Photosensitive points consisting of A and JB are arranged.

Therefore, each of the photosensitive points P1 to P9 can be simultaneously or asynchronously such that two different information items form two radiation images, respectively corresponding to different energies of the X-rays. It is possible to obtain two different information items simultaneously or asynchronously. This is obtained by converting the X-rays into visible light and exposing each photosensitive element DA, DB to light with the desired light source, so that for each photosensitive point P1-P9:

That is, firstly, in a zone A arranged at the connection point of the photosensitive element DA and the capacitor CA, a first information item is stored in the form of a first charge amount proportional to the irradiation of the first photosensitive element DA. Can be memorized. Second, in a zone B arranged at the coupling point between the photosensitive element DB and the capacitor CB, a second information item is placed in the form of a second charge amount proportional to the irradiation of the first photosensitive element DB. Can be memorized.

In the description of non-limiting embodiments, the photosensitive elements DA, D
B is a photodiode. Each photodiode corresponds to the aforementioned French Patent Application No. 86100656 and 86
100716, it is connected in series with capacitors CA, CB, and with the operation of such a photosensitive cell,
The operation of the memory and the means that can be used to read the charge or information item is described in detail. Therefore,
These two French patent applications No. 86100656 and No. 86100716 should be considered as forming part of the description of this invention.

However, in the case of photosensitive cells JA, JB, the main steps of operation are as follows.

(a) Reverse biasing the photodiode; (b)
irradiating the photodiode (e.g., an X-ray flash irradiating the patient, converting the X-rays into visible light or radiation of wavelengths close to visible light, and storing information items corresponding to the irradiation; (C) reading) (Forward Biasing of the Photodiode) (d) The voltage level at the terminals of the photodiode is reset by either an electrical bias pulse applied to the line conductor, a calibrated standard illumination, or a strong light flash. step.

In this invention, each photosensitive point Pi-P9 has two photosensitive cells J.
A, JB, and thus providing two items of information, the operation described above is obtained in a manner similar in gist to the invention described in the two aforementioned French patent applications.

In the non-limiting embodiment described above, the line addressing device comprises a pulse generator IO for generating a pulse voltage VL. This pulse voltage VL is intended to be applied to the line conductors L1 to L3. For this purpose, the pulse generator 3 is connected to the MOS transistor M1. M2, M3
are connected to the line conductors L1-L3 via the outputs OLI, OL2, of the shift register 12;
It forms a line switch controlled by PL3. Line register 12 is controlled by line shift control signal SCL.

Therefore, the photosensitive points P1 to P3, P4 to
When lines P6, P7 to P9 are selected, the corresponding line conductors L1 to L3 are connected to the pulse generator IO so as to apply pulse voltage VL to the photosensitive points connected to the line conductors. . MOS) transistor M1, M
2. When M3 is open (non-conducting), line conductor L1~
To hold L3 at a fixed potential, each line conductor L1~
It should be noted that L3 is grounded by resistors R1-R3. These resistors R1-R3 have a higher value than the resistance value obtained by the MOS transistors M1, M2, M3 when the MOS transistors M1, M2, M3 are closed (conducting).

On the other hand, the readout and multiplexer devices 9A, 9B include integrating amplifiers GAI to GA3, G connecting the column conductors.
It is equipped with a readout amplifier consisting of BI to GB3.

Column conductors FA1 to FA of the first column array FA
3 are connected to the negative inputs °°-"° of the integrating amplifiers GAI-GA3. These integrating amplifiers GAI-GA3 are
Its negative human power °“−” and its output OAI~OA3 respectively
It is connected as an integrator to an integrating capacitor CL connected between the . Each integrating amplifier GA1~GA
The second or positive input -' is connected to the column reference potential CO, which may be, for example, ground.

Furthermore, each integrating amplifier GAI to GA3 has an integrating capacitor C.
An O reset switch IA is connected in parallel with L and reset to zero. 0 reset switch IA
consists of a MOS transistor controlled by a signal V, RAZ, which is reset to O. The zero reset switch IA of a given integrating amplifier GAI-GA3 is "closed" so as to short-circuit the integrating capacitor CL, except during the readout sequence of the photosensitive cell connected to the integrating amplifier GAI-GA3. That is, it is maintained in a "conductive" state. Integrating amplifier GAI~GA3 output OAI~OA3
is connected to the collection register 13A. The collection register 13A is, for example, a CCD type parallel manual input EAI to EA.
3 and a shift register with serial output S1.

The second column conductor FB is connected in a similar way to the integrating amplifiers GBI-GB3. These integrating amplifiers GBI
~GB3, in the same way as for the column conductor FAI-FA3, connect the integrating capacitor CL and the negative human power °
°−°′ and the outputs O of these integrating amplifiers GBI to GB3
A 0 reset switch IB is connected in parallel between BI and OB3. These integrating amplifiers G
The BI-GB3 outputs OBI-OB3 are connected to parallel inputs EAI-EA3 of the second acquisition register 13B, respectively. The acquisition register 13B likewise consists of a shift register of the type with a parallel input and a serial output S2.

The matrix configuration of the invention is described in French patent applications No. 86100656 and No. 86100716, which have already been described.
Compared to the photosensitive matrix disclosed in the above issue, each photosensitive point PI-P9 can collect two different information items (
The difference is that one can store point A and the other can store point B).

On the one hand, in the case of the same photosensitive points P1 to P9, the two photosensitive cells JA and JB are connected to the same line conductor, and on the other hand, the photosensitive cell A is connected to the column conductor FB1 to which the second photosensitive cell JB is connected. Column conductors FA1 to FA3 different from FB3
These photosensitive cells JA, JB each consist of a photosensitive element and one capacitor in series.
The operation in one of the positions remains essentially the same as that described in the two aforementioned French patent applications. The difference is that instead of having only the various first points A at the serial output S1 of the first acquisition register 13A, for example,
At the serial output S2 of the second acquisition register 13B, a plurality of signals relating to the information items stored at the various second points B are available, whether simultaneously or non-simultaneously.

Thus, for example, the overall operation of can be summarized into the following steps. The structure of the photosensitive device 1 is shown in FIG.

(a) Reverse biasing step: The pulse generator inputs one pulse to the front conductors L1 to L3 simultaneously or staggered. This pulse acts to reverse bias the photosensitive elements DA, DB.

(b) Therefore, all photosensitive points P1~
Step of irradiating P9: This usable signal, as a result of wavelength conversion by two scintillators (shown in Figure 3), irradiates all photosensitive points P1-P9 and illuminates these photosensitive points P1-P9.
The X-ray flash determines to store the information items of points A and B for each of P9.

(C) Point A of photosensitive points connected to the same line conductor
and point B (this may be done simultaneously for point A and point B of the photosensitive points): In the case of photosensitive cells JA and JB connected to the same line conductor L1 to L3, the number stored at point A is read. 1 and the second total information item stored at point B are stored in the first and second collection registers 13A, 1.
Each is transferred to 3B. These first and second acquisition registers 13A, 13B are then applied to one of the acquisition registers 13A, 13B such that the information item is transferred to a regular seed memory (not shown). It is unloaded under the control of shift signal SCH.

(d) A step of repeating the above step (c) for each line for all the line conductors L1 to L3. This results in two images of the object.

(e) Execute general reset to a level common to all photosensitive points P1 to P9 in the above steps.

In the non-limiting embodiment described above and in FIG. 1, all photosensitive cells JA, JB are arranged in a similar relationship to connecting line conductors L1-L3. However, within the spirit of the invention, one or the other of these two photosensitive cells JA, JB, or both, may be connected by connecting the photosensitive elements DA, DB with the anode P to the line conductor L1, as shown in FIG.
~ Connect to L3 and connect capacitors CA and CB to column conductor F.
A method different from that for connecting to AI-FA3 and column conductors FB1 to FB3 may be used.

- Thus, for example, within the photosensitive cells JA, JB, the arrangement of the photosensitive elements DA, DB and the capacitors CA, CB may be reversed. That is, the capacitors CA, CB are connected to the line conductors L1-L3, and the photosensitive elements DA, DB are connected to the column conductors.

Similarly, photosensitive cells JA and JB also have photosensitive elements DA and DB.
and irrespective of the relative arrangement of the capacitors CA, CB, opposite to the direction of conduction of the photosensitive elements DA, DB (in this case, of course, the polarity of the pulses applied to the photosensitive elements DA, DB also corresponds to French Patent Application No. 86100656 and No. 86100
The polarity is opposite to that described in No. 716. ),
and their anodes P or their cathodes N can be connected to capacitors CA, CB.

The arrangement of photosensitive cells JA and JB that can differ in this way is as follows:
In essence, it does not change the operation of the photosensitive cells JA, JB. Furthermore, other configurations are possible requiring only a series of integrating amplifiers. A diagram of such a configuration is shown in FIG.

FIG. 2 shows a block diagram of a second embodiment of the photosensitive device 1 of the invention. This embodiment, in contrast to the embodiment shown in FIG. 1, connects the readout amplifier to the line conductors L1 to L3.

The photosensitive points P1 to P9 and the two photosensitive cells JA and JB each containing these points are constructed in the same manner as in the first embodiment.

Each line conductor L1-L3 is connected to the negative input °°-°° of an integrator amplifier 61-G3. These integrator amplifiers 61
~G3 are each equipped with an integrating capacitor CL and an O-reset switch, as in the first embodiment described above. The 0 reset switch ■ is the integral capacitor CL.
is connected in parallel to the integrator amplifier 6 at one end.
1 to G3, and an O reset switch whose other end is connected to the outputs OFI to OF3. The 0 reset switch, as in the first embodiment, consists of a MOS transistor controlled by the 0 reset signal V, RAZ. The second or positive inputs of the integrator amplifiers G1-G3 are connected to ground or the column reference potential CO. The outputs l-OF3 of integrator amplifiers 61-G3 are connected to a third readout and multiplexer device or analog data acquisition register 74. The analog data collection register 74 is configured, for example, by parallel human power E1, E2,
. . . and a shift register of the type having n acquisition stages Tl to Tn with an output S.

In the non-limiting embodiment described above, two adjacent acquisition stages may be integrators, with a view to avoiding superposition of signals corresponding to the signals stored at points A and B within the same acquisition membrane. It is intended to be charged sequentially by the same outputs OFI-OF3 of amplifiers G1-G3. For this,
For example, loading the collection stage T2-T4 in a first period with the charge or information stored in the first photosensitive cell JA (photosensitive points P1-P9 connected to the same line conductors L1-L3); Third analog data collection register 7
After carrying out a multi-stage shift by means of the shift control signal SD applied to the acquisition stage T1. To load T3 and T5 within the second period, outputs 1 through OF3 are outputted to the second, third, and sixth registers of analog data collection register 74, respectively.
Connected to human power E2, E4, and E6.

Column conductors FA1 to FA3 and column conductor FBI-F
B3 is connected to the pulse generator IO through all MOS transistors M4 to M9 to form a column switch controlled by the outputs of two shift registers 15, 16, called column registers.

The first column register is connected to the first column control signal SCA.
outputs O controlling the three first column switches M4, M5, M6 respectively.
AI to OA3 are generated continuously. Three first column switches M4, M5, M6 connect the first, second and third column conductors FA1-FA3 respectively to the pulse generator 10.
is connected to.

In the same manner as the first column array FA, the second column register [6] is controlled by the column signal SCB to continuously generate outputs OBI to OB3. Output OB]~OB3 are column switches M7, M8, M9
are controlled by column switches M7, M8, and M9, respectively.
is the third column conductor FB1 of the second column array FB
~FB3 are connected respectively. Therefore, the end 4A of the metal 2 of the first photosensitive cell JA connected to the same column conductors FA1 to FA3 of the first column array FA,
4B is connected to the pulse generator 10 when the column conductors FA1 to FA3 are selected by the shift register 15. Also, the third column conductors FB1 to FB3 of the second column array FB are connected to the same column conductors FB1 to FB3 of the second column array FB. The end 4B of 2 is connected to the pulse generator 10 when the column conductors FB1 to FB3 are selected by the shift register 16.

In a second embodiment of the invention, the pulse generator 10
Apart from being connected by column conductors to the second ends 4A, 4B of the photosensitive cells JA, JB, especially in the reverse biasing stage, the pulse generator 10 sends one pulse to all the column conductors FA1-FA3 and the columns. Conductor FB1. -FB
3, the operation is the same as that of the first embodiment at the stage of reverse biasing during the period in which inputs are input simultaneously or with a time lag.

On the other hand, after the step of irradiating the photosensitive points P1-P9, the transfer of the information items stored at points A and B to the third analog data acquisition register 74 is carried out by all the points connected to the same column conductor. It is executed simultaneously for photosensitive cell JA or JB. Therefore, for example, assuming that the outputs OBI to OB3 of the second column register 16 are all inactive and only the first output OAI of the shift register 15°]6 is active, the first column・Switch 1.
14 is rendered conductive, and a pulse (not shown) output from pulse generator 10 is applied to the first column conductor FAI of column array FA. Therefore, the information items stored at point A of all the photosensitive points associated with this first column conductor F/11 (i.e., the first, fourth, and seventh photosensitive points P), , P4, P7) are integrator amplifiers G1-G
3 and analog data acquisition register 7
Transferred to 4. Then, as described above, point B of the same photosensitive points, that is, the first, fourth and seventh photosensitive points P], P4 and P7.
A shift of the acquisition stages Tl-Tn of the analog data acquisition register 74 is performed in order to acquire the information items stored in the analog data acquisition register 74. For this purpose, the first output OAI of the first shift register 15 is deactivated, and it is the second column register 16 that is activated. Then, the column switch M7 is made conductive, and the pulses output from the pulse generator IO are transferred to the second column array FB.
is applied to the first column array FB 1 of FB 1 and thus to the second photosensitive cell JB connected to this column conductor.

Therefore, the first, fourth and seventh photosensitive points P], , P4, P
The information items stored at point B of 7 are loaded into analog data collection registers 74. Analog data acquisition register 74 is emptied of its contents to the aforementioned main memory. Then only the second output OA2 of the first shift register 15.16 is activated;
As a result, the first photosensitive cell JA connected to the second column array FB21 of the second column array FB
Collection of information item A stored in . The operations described above are repeated until all information items A and B are completed.

Figures 3a and 3b are cross-sectional views taken from two orthogonal directions;
1 and 2 schematically illustrate, by way of non-limiting example, a preferred embodiment of a two-energy radiation image consisting of a matrix arrangement of photosensitive elements of the type previously described with reference to FIG. 1 or FIG.

Image detector 25 has a support or substrate 26, for example glass. A scintillator layer 27 is deposited on the substrate 26. The material of this scintillator layer 27 is selected as a function of maximum sensitivity within a certain energy range of incident X-rays. For example, gadolinium oxysulfide doped with terbium is known to exhibit optimum sensitivity to X-rays with energies on the order of 5 keV and in response emit green light at a wavelength of 0.54 μm.

Thus, for example, the scintillator layer 27 may consist of gadolinium oxysulfide powder embedded in a thermosetting resin in the form of two sheets. This sheet is then attached to substrate 26. scintillator layer 2
The thickness of 7 is selected to be optimal for proton generation efficiency without excessively impairing resolution. This thickness (not shown) is several tens of μm to several hundred μm for radiation imaging applications.
It is sufficient if it is within the range of .

The thin conductor layer 28 of electrically conductive material is transparent to the light emitted by the scintillator layer 27 and forms a barrier to the diffusion of impurities, for example directly or in particular to flatten the upper surface of the scintillator layer 27. covered with an intermediate insulating layer (not shown). The thin conductor layer 28 also includes a column conductor, for example, a second column array FB.
The column conductors FB1 to FB3 are carved.

On top of the thin conductor layer 28 there is an insulating layer 34 for forming the dielectric of the second capacitor CB. Insulating layer 34
forms a dielectric and is transparent, for example made of silicon nitride.

Further, after engraving, the insulating layer 34 includes a plurality of layers 30, 31, 32 constituting the above-mentioned second photodiode DB.
covered by a pile of In the non-limiting example described above, the second photodiode DB is of the NIP type. That is, on the insulating layer 34, an N-type impurity,
For example, hydrogenated amorphous doped with phosphorus.
A layer 30 of silicon is present. Above the layer 30 of N-doped silicon is then a layer 31 of intrinsically hydrogenated amorphous. In the layer of intrinsic silicon 31 there is then a layer of hydrogenated amorphous silicon 32 doped with a P-type impurity, for example boron. These last three layers30.
31 and 32 are carved according to a small island pattern so as to constitute the second photodiode DB. These second photodiodes DB in a small island pattern are connected to column conductors FAI-FA3 and line conductors L1-L3.
are located at each of the intersections between.

A new insulating layer 29 is deposited over the last layer 32 of P-type doped silicon. The insulating layer 29 is, for example, an insulating layer 34 forming a dielectric of the second capacitor CB.
Made of the same material as. Above the second photosensitive element DB in this last insulating layer 29 is called an intermediate conductor layer 51,
The photosensitive element DB is placed in contact with a layer of conductive material carved to form the line conductors L1 to L3.
A plurality of openings are formed.

When the resetting to the voltage level of the terminals of the aforementioned photosensitive elements DA, DB is carried out by means of electrical pulses, the intermediate conductor layer 51 may be opaque, for example consisting of a chromium or molybdenum deposit. However, when the reset to the voltage level is carried out by optical means, the intermediate conductor layer 5
1 must be transparent, for example made of the same material as the thin conductor layer 28 forming the column conductor FBI-FB3.

On the line conductors L1 to L3, that is, on the intermediate conductor layer 51,
There is a second stack of three layers 40.41.42 forming the PIN deposit. These three layers 40.41
．． 42 are a layer of hydrogenated amorphous silicon doped with P-type impurities, a layer of intrinsically hydrogenated amorphous silicon, and a layer of hydrogenated amorphous silicon doped with N-type impurities, respectively. These three layers 40, 41, 42 are carved according to a small island pattern so as to constitute a first photosensitive element DA superimposed on a second photodiode DB.

A deposit of an insulating layer 55 is formed on the photosensitive element DA, which constitutes the dielectric of the capacitor CA.

An upper conductor layer 56 is provided on the insulating layer 55 of the capacitor CA.
is formed. The upper conductor layer 56 is transparent and includes, for example, column conductors FB1 belonging to the second column array FB.
It is made of the same conductive material as the thin conductor layer 28 forming ~FB3. This upper conductor layer 56 is carved to constitute the first column conductor FAI-FA3 of the column array FB.

Finally, on the opposite side of the substrate 26, a second layer of scintillator material 58 terminates the structure and is glued or pressed onto a top conductor layer 56 by means of an optically transparent adhesive (not shown).
is covered.

The scintillator material forming the second scintillator material 58 is selected as a function of the X-ray energy range in which it exhibits maximum sensitivity. Of course, this maximum sensitivity is given for an energy range of X-rays that is different from the energy range of the first scintillator layer 27.

Thus, for example, in the case of the second scintillator material 58:
The scintillator material 58 is made of yttrium oxide, which exhibits optimal sensitivity to 20 keV X-rays. The yttrium oxide of the second scintillator layer 58 may be doped with terbium, for example.

In this structure, in the case of the same photosensitive point, the two photosensitive cells JA and JB, especially the first and second photosensitive elements DA and DB, are completely overlapped, so that the photosensitive point of the matrix device is It should be noted that the formation of

Therefore, at each photosensitive point, the required space in the lateral direction is minimized, so that the detection surfaces of the photosensitive elements DA, DB can be made as large as possible. Furthermore, this structure is advantageous because the first and second photosensitive elements DA, DB must be sensitive to the radiation (light) of different light sources. This is achieved by arranging the various superimposed layers constituting the first and second photosensitive cells JA, JB in a sandwich between the two scintillator layers 27 and the scintillator material 58.

Assuming that the X-rays (not shown) reach the side of the scintillator material 58 arranged on the opposite side of the substrate 26, and in relation to the direction of propagation of this scintillator material 58, the first scintillator SA will be referred to as the first scintillator SA in the following description. refer. The X-rays first pass through the first scintillator SA and the first photosensitive element DA, then through the second photodiode DB and another scintillator layer 27, referred to in the following part as the second scintillator layer SB.

The first scintillator SA mainly absorbs X-rays having an energy range centered around, for example, about 20 keV,
The amorphous silicon converts the absorbed X-rays into detectable radiation. The second scintillator SB has an energy corresponding to its maximum sensitivity and the first scintillator S
It primarily absorbs X-rays located at energies different from those applicable in case A (eg 50 keV). Absorbed X-rays are likewise converted into detectable radiation by amorphous silicon.

Photosensitive element D located close to the first scintillator SA
A and a photosensitive element DB located close to the second scintillator SB preferably detect the light emitted by this second scintillator SB. Each photodiode forms a screen between the other superimposed photodiodes and the closely located scintillator.

In photosensitive materials such as amorphous silicon,
The radiation, in particular the light emitted by the scintillator layers SA, SB, is absorbed or attenuated within the photosensitive material in such a way that the energy transferred to the material decreases exponentially with the length of the material. As a result, when the first and second photosensitive elements DA, DB have similar thicknesses El, E, the light emitted by the first scintillator SA is essentially absorbed by the first photodiode DA, i.e. Detected.

That is, the light emitted by the second scintillator SB is essentially absorbed, ie, detected, by the second photodiode DB. If the thicknesses El and E2 of the photodiodes DA and DB are sufficient to completely absorb the radiation, that is, the light emitted by the scintillator layer, the closer the thickness is, the more advantageous it is. A complete separation between the information provided and the information provided by the second scintillator SB. These information items are detected by first and second photodiodes DA and DA, respectively. Such a separation is, of course, only useful if the intermediate conductor layer 51 making up the line conductor is transparent. In this case, you can use a simple method to similarly
Optical level reset (RA
N) can be executed.

For this purpose, a light source 60 intended for a general reset to a common level can be directed, for example, at the substrate 26 facing the second scintillator SB.

This light source 60 consists of means known per se, for example a light-emitting plate, an array of light-emitting diodes or a French bulb.

Substrate 26 where light source 60 faces second scintillator SH
The substrate 26 itself must be transparent when directed toward the substrate. A conventional substrate made of glass is definitely suitable. In this case, the light source 60 is as in the embodiment described in French Patent Application No. 86106334.
It may also be made of light emitting diodes (not shown) mounted to form a panel.

According to another feature of the invention, the light source 60 has a red light beam, i.e. more than the light emitted by the first scintillator SA, SB, with a view to promoting a general reset to a common level by a single light source 60. Emit light with long wavelengths. This tends to reduce the absorption of the light used for the general reset to a common level relative to the absorption of the light emitted by the first scintillators SA, SB.

However, when the intermediate conductor layer 51 constituting the line conductor located between the first photosensitive cell JA and the second photosensitive cell JB is opaque and does not transmit visible light (or light close to visible light), , suitable for general resetting of photodiodes DA, DB to a common level to be performed by electrical pulses.

The embodiments shown in FIGS. 3a and 3b are realized by way of non-limiting embodiments, and in particular the layers constituting the first and second photosensitive cells JA, JB may be made of, for example, PIN or N
They can be arranged in different orders to form IP photodiodes or to change between photodiodes and capacitors of the same photosensitive cell. Furthermore, photodiodes DA and DB are NIPIN type or PIN type.
It should be noted that it may consist of an IP type photodiode.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing, as a non-limiting example, a photosensitive device according to the invention; FIG. 2 is a block diagram showing a second embodiment of the photosensitive device according to the invention; FIGS. 3a and 3b are 2 is a cross-sectional view along two orthogonal directions of a radiation image detector using the photosensitive device shown in FIG. 1. FIG. l...Photosensitive device l, 3A, 3B...first end, 4A, 4B...second end, 74...analog data collection register, 8A, 8B
...address device, 9A, 9B...readout and multiplexer device, 2
6... Substrate, 27... Scintillator layer, 30.31.31.40.41.42... Layer, 34.
55... Insulating layer, 28.58... Thin conductor layer, 51... Intermediate conductor layer, 60... Light source, DA, DB... Photosensitive element (photodiode),
FA Column array FA]~FA3, FB1~FB3... Column conductor, JA, JB Photosensitive cell, LAI~LA3 Line conductor, Ll, -L3 Line conductor, P1~P9... Photosensitive point, SA, SB scintillator. Patent Applicant Thomson CSF Patent Application Agent

Claims (18)

[Claims] (1) Line conductors (L1 to L3) and column conductors (FA
first and second photosensitive cells (JA, JB) each having a matrix of photosensitive points (P1 to P9) connected to the photosensitive points (1 to FA3, FB1 to FB3), each of which can store an information item; , and the two first and second photosensitive cells (JA, JB) are overlapped. (2) In the photosensitive device according to claim 1, the column conductors (FA1 to FA3, FB1 to FB3) are divided into two arrays (FA, FB), and the same photosensitive point (P
1 to P9) are connected to the same line conductor (JA, JB) by the first end (3A, 3B).
L1-L3) and their second ends (
4A, 4B) different column arrays (FA, FB)
A photosensitive device characterized in that it is connected to column conductors (FA1 to FA3, FA to FB) of ). (3) In the photosensitive device according to claim 2, each photosensitive cell (JA, JB) is a capacitor (CA, CB).
A photosensitive device comprising photosensitive elements (DA, DB) connected in series. (4) The photosensitive device according to claim 3, wherein the photosensitive elements (DA, DB) are photodiodes. (5) In the photosensitive device according to claim 3, the photosensitive elements (DA, DB) are of NIPIN type or PIN type.
A photosensitive device characterized by being an IP type phototransistor. (6) The photosensitive device according to claim 2, wherein the line conductor (L1 to L3) is an address device (87).
while the column conductors (FA1-FA3, FA-FB) of the first column array (FA) are connected to the readout and multiplexer device (9A), while the column conductors of the second column array (FB) Column conductor (FB1~FB3
) is connected to a readout and multiplexer device (9B). (7) The photosensitive device according to claim 2, wherein the line conductors (L1 to L3) are connected to a readout and multiplexer device (74), and the column conductors (FA1
~FA3, FA~FB) of the first and second arrays (
FA1 to FA3, FA to FB) are address devices (8A,
8B). (8) The photosensitive device according to claim 2, wherein the photosensitive cells (JA, JB) are supported by a substrate (26), and each of the photosensitive cells (JA, JB) is supported by a semiconductor layer (30, 31, 32 and 40).
, 41, 42) and an insulating layer (34), all said semiconductor layers being superimposed on each other between thin conductor layers (28, 58), one of which is connected to the second column.
The other is carved to form the column conductors (FB1-FB3) of the first column array (FB), and the other is carved to form the column conductors (FA1-FA3, FA-FB3) of the first column array (FA).
), characterized in that the two stacks or photosensitive cells (JA, JB) are separated by an intermediate conductor layer (51) forming line conductors (L1-L3). Photosensitive device. (9) The photosensitive device according to claim 8, wherein the intermediate conductor layer (51) is transparent to light. (10) The photosensitive device according to claim 9, wherein the photosensitive elements (DA, DB) have approximately equal thickness. (11) The photosensitive device according to claim 9 or 10, further comprising a light source (60) for performing a general reset of the voltage level at the terminals of the photosensitive element (DA, DB). Photosensitive device. (12) The photosensitive device according to claim 8, wherein the intermediate conductor layer 51 is opaque to light. (13) An image containing first and second scintillator materials (27, 58) that are sensitive to different energies of the incident radiation and generate visible or invisible light in response to the incident radiation. An image detector, further characterized in that the image detector comprises a photosensitive device (1) according to claims 1 to 12. (14) The image detector according to claim 13, wherein the two first and second scintillator materials (27, 58
) consists of first and second scintillators (SA, SB), and the photosensitive device (1) is arranged so as to construct a sandwich structure between the first and second scintillators (SA, SB). An image detector featuring: (15) The image detector according to claim 14, wherein the photosensitive device (1) has one substrate (26), and the substrate (26) has photosensitive cells superimposed by photosensitive cells (JA, JB). The second scintillator (SB) is deposited on the substrate (26), and the second scintillator (SB) is deposited on the substrate (26).
and a photosensitive cell (JA, JB). (16) Image detector according to claim 15, characterized in that it comprises at least one light source (60) used to set the voltage to the level of the photosensitive cells (JA, JB). vessel. (17) The image detector according to claim 16, wherein the light source (60) generates light having a longer wavelength than the light generated by the first scintillator SA. (18) The image detector according to any one of claims 13 to 17, wherein the incident radiation is an X-ray.