EP2727334A1

EP2727334A1 - Matrix of pixels with programmable clusters

Info

Publication number: EP2727334A1
Application number: EP12733654.3A
Authority: EP
Inventors: Marc Arques
Original assignee: Commissariat a lEnergie Atomique CEA; Trixell SAS; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Trixell SAS; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2011-06-30
Filing date: 2012-06-29
Publication date: 2014-05-07
Also published as: JP2014523687A; FR2977371B1; WO2013001075A1; CN103782585A; FR2977371A1; US20140217302A1

Abstract

The invention relates to an imaging device comprising a matrix (10; 20; 30) of pixels (P(i,j); Q(ij); R(ij); X(ij); Y(ij)) organised in lines and columns, and a method for implementing said device. According to the invention, each current pixel (P(ij); Q(ij); R(ij); X(ij); Y(ij)) comprises : a line cluster interrupter (B(i,j)) allowing the current pixel (P(ij); Q(ij); R(ij); X(ij); Y(ij)) to be grouped with the following pixel (P(ij+1 ); Q(ij+1 ); R(ij+1 ); X(U+1 ); Y(U+1 )) of the same line; a column cluster interrupter (A(ij)) allowing the current pixel (P(i,j); Q(i,j); R(i,j); X(i,j); Y(i,j)) to be grouped with the following pixel (P(i+1,j); Q(i+1 j); R(i+1 J); X(i+1,j); Y(i+1 j)) of the same column; and storage means (M(i,j); U(i,j); V(i,j)) for defining the state, conducting or blocking, of the two cluster interrupters (A(i,j), B(U)).

Description

PIXEL MATRIX WITH PROGRAMMABLE GROUPS

The invention relates to an imaging device and a method implementing the device. The invention can be implemented for imaging in a detector. This type of device comprises a large number of sensitive points called pixels generally organized in matrix or bar.

The invention finds utility in producing visible images but is not limited to this field. In the context of the invention, the term imaging must be understood in a broad sense. For example, it is possible to carry out pressure or temperature mappings or two-dimensional representations of chemical or electrical potentials. These maps or representations form images of physical quantities.

In a detector, a pixel represents the elementary sensing element of the detector. Each pixel converts a physical phenomenon to which it is subjected into an electrical signal. The electrical signals from the different pixels are collected during a reading phase of the matrix and digitized so that they can be processed and stored to form an image. The pixels are formed of a zone sensitive to the physical phenomenon and delivering a current of electric charges. The physical phenomenon may be electromagnetic radiation and subsequently, the invention will be explained by means of this type of radiation and the charging current is a function of the photon flux received by the sensitive zone. Generalization to any imaging device will be easy.

The photosensitive zone generally comprises a photosensitive element, or photodetector, which may for example be a photodiode, a photoresistor or a phototransistor. There are large photosensitive matrices that can have many millions of pixels. Each pixel consists of a photosensitive element and an electronic circuit consisting for example of switches, capacitors, resistors, downstream of which is placed an actuator. The assembly constituted by the photosensitive element and the electronic circuit makes it possible to generate electrical charges and to collect them. The electronic circuit generally allows the charge collected in each pixel to be reset after a charge transfer. The role of the actuator is to transfer or copy the charges collected by the circuit into a reading electrode. This transfer is performed when the actuator receives the instruction. The output of the actuator corresponds to the output of the pixel.

In this type of detector, a pixel operates in two phases: an imaging phase, during which the electronic circuit of the pixel accumulates the electric charges generated by the photosensitive element, and a reading phase, during which the Collected charges are transferred or copied back into the reading electrode, thanks to the actuator.

During the imaging phase, the actuator is passive and the collected electrical charges change the potential at a point of connection between the photosensitive element and the actuator. This connection point is called the load collection node of the pixel or simply the node of the pixel. During the reading phase the actuator is active in order to release the accumulated charges at the photosensitive point in order to route or copy them, or to copy the potential of the node of the pixel to a reading circuit of the detector disposed downstream. of the actuator.

By passive actuator is meant an actuator not in electrical contact with the read circuit. Thus, when the actuator is passive, the charges collected in the pixel are neither transferred nor recopied in the read circuit.

An actuator may be a switch controlled by a clock signal. It is usually a transistor. It may also be a follower circuit or any other device making it possible to transfer or transfer the charge collected in the pixel to the read circuit, for example a device known by the acronym CTIA ("Capacitive").

Translmpedance Amplifier "for capacitive impedance transfer amplifier).

This type of pixel can be used for the imaging of ionizing radiation, including X or γ radiation detectors, in the medical field or that of non-destructive testing in the industrial field, for the detection of radiological images. In some detectors, the photosensitive elements make it possible to detect visible or near-visible electromagnetic radiation. These elements are not, or little, sensitive to radiation incident to the detector that is to be detected. A radiation converter called a scintillator is then used which converts the incident radiation, for example X-ray radiation, into radiation in a wavelength band to which the photosensitive elements present in the pixels are sensitive.

According to another type of detector, more and more widespread, the detector material is a semiconductor sensitive to radiation, for example X or gamma, to be detected. An interaction of radiation in the detector generates charge carriers. The charges generated by an interaction are collected at a terminal, called the pixel node.

During the imaging phase, the electromagnetic radiation, in the form of photons received by each photosensitive element, is converted into electrical charges (electron pairs / holes) and each pixel generally comprises a capacitance for accumulating these charges to make evolve the voltage of the pixel node. This capability may be intrinsic to the photosensitive element, so-called parasitic capacitance, or added as a capacitor connected in parallel with the photosensitive element.

Generally, the pixels are read individually. The matrix may for example comprise a reading electrode associated with each column of pixels of the matrix. In this case, a read instruction is sent to all the actuators of the same row of the matrix and each of the pixels of this line is read by transferring its electrical information, charge, voltage, current, frequency ... on the reading electrode with which it is associated.

You may have to group together several pixels to read them collectively. This grouping may be useful in order to increase the reading speed of the matrix or to improve the signal-to-noise ratio of each element read. The grouped pixels may have means for performing the sum or average operations of the electrical information of the grouped pixels. These means can be analog or digital.

Next, we will describe the case where the electrical information is available analogically in the pixels, in the form of quantities of charges stored on capacitors of the same value. It is understood that the invention can be implemented for any form of electrical information generated in each of the pixels.

Matrices have already been made which plan to group adjacent pixels by four or eight. The means for performing the averaging operation is simply a grouping switch contacting the adjacent pixel capacitors. The switches are controlled by row or column electrodes of the array, setting the on or off state of each switch. In order to limit the number of electrodes, the possible groupings are predetermined. An electrode can fix the state of several switches. For example, a set of electrodes arranged on every other line makes it possible to group all the pixels of the matrix in pairs. To make groupings by four it is necessary to add other group switch control electrodes for grouping two adjacent pairs.

As soon as it is desired to multiply the possible configurations of grouping, the number of electrodes increases which complicates the routing of the matrix and reduces the space available for the photosensitive elements. It is almost impossible to achieve variable groupings, this would require the implementation of an electrode by grouping switch.

This type of implementation also has a limit when some pixels are defective, which can be common in matrices comprising a large number of pixels. It can for example be a very noisy pixel, or a pixel shorted with a power supply. The false or missing information of this pixel is then replaced by the average of the information of its neighbors. But if this defective pixel pollutes or destroys a group of pixels, its acceptance becomes much more difficult, especially if the pollution or destruction extends to larger groups.

The invention aims to overcome all or part of the problems mentioned above by providing a pixel matrix in which group switches are programmable. To this end, the subject of the invention is an imaging device comprising a matrix of pixels organized in rows and columns, characterized in that each current pixel of the matrix comprises:

A line grouping switch for grouping the current pixel with the next pixel of the same line, if the next pixel exists in the line to which the current pixel belongs,

A column grouping switch for grouping the current pixel with the next pixel of the same column, if the next pixel exists in the column to which the current pixel belongs and

· Storage means for defining the state, passing or blocked two grouping switches.

The invention will be better understood and other advantages will appear on reading the detailed description of an embodiment given by way of example, a description illustrated by the accompanying drawings in which:

FIG. 1 represents an exemplary pixel matrix according to the invention, in which the electrical information collected during the reading of each of the pixels is a voltage;

FIG. 2 represents another example of a matrix of pixels according to the invention, in which the electrical information collected during the reading of each of the pixels is a charge;

FIG. 3 represents an example of means for adding or averaging the charges transiting in different column electrodes of the matrix of FIG. 2;

FIG. 4 represents a variant of the matrix of FIG. 2; FIG. 5 represents an example of a matrix according to the invention, the pixels of which comprise a shift register;

FIG. 6 represents another example of a pixel comprising a shift register;

Figures 7, 8 and 9 show several examples of pixel clusters.

For the sake of clarity, the same elements will bear the same references in the different figures. FIG. 1 represents a matrix 10 comprising sixteen pixels P (i, j) distributed in four rows and four columns. In this figure, the rows and columns are indicated by their rank, i for the rows and j for the columns. The pixels P (ij) are advantageously all identical, which simplifies the realization of the matrix. It is understood that the invention is not limited to a matrix of this size. Matrices having a much larger number of pixels are often found and in which the invention can be implemented.

Each pixel P (ij) comprises an element sensitive to a physical phenomenon, such as for example electromagnetic radiation. This phenomenon is, in the example shown, converted into electric charges. The sensitive element is represented in FIG. 1 in a simplified way by a capacitor C (ij) making it possible to accumulate the electric charges resulting from the conversion of the physical phenomenon. As has been seen previously, in the example of an electromagnetic radiation to be quantified, the sensitive element may be a photodiode and the capacitor C (i, j) represents its parasitic capacitance, or possibly an additional capacity connected in parallel. of the photodiode, on which accumulate the electric charges resulting from the conversion of the radiation. A first electrode of the capacitor C (ij) is connected to a mass of the matrix 10. The potential of the second electrode of the capacitor C (ij) changes as a function of the accumulated electrical charges. This second electrode forms the node of the pixel. As announced above, the physical phenomenon can be transformed by the sensitive element into other types of electrical information such as a voltage, a current or a frequency.

In the example of FIG. 1, each pixel P (ij) comprises a voltage follower S (i, j) making it possible to copy at the output of the pixel the voltage corresponding to the charges accumulated in the capacitor C (ij) and an actuator T. (ij) for transferring, during a reading phase, the voltage supplied by the follower S (ij) to a Col column electrode (j) of the matrix 10. The actuator T (ij) is controlled by a in-line electrode Phi- line (i) of the matrix 10. The follower S (ij) is connected at its input to the pixel node P (ij). The matrix 10 further comprises a row addressing register 1 1 for controlling the various in-line electrodes Phi-line (i) of the matrix 10 and a reading register of the columns 12 for collecting the voltages present on the different column electrodes Col (j) when actuators T (ij) are on.

Each pixel P (i, j) comprises a line grouping switch B (ij) making it possible to group it with the pixel P (ij + 1) of the same line situated in the following column and a column grouping switch A ( ij) for grouping it with the pixel P (i + 1 j) of the same column located in the following line.

The group switches A (ij) and B (ij) make it possible to connect the capacitors C (ij) of the different pixels P (i, j) concerned at the node of each of the pixels P (ij).

As we have seen previously, the pixels P (ij) are advantageously all identical in order to facilitate the definition of the masks allowing the realization of the matrix. In this case, even the pixels of the last line include the line grouping switch B (ij). Similarly, the pixels of the last column include the column group switch A (ij). These switches are useless and are simply not connected to the next pixel since it does not exist.

Each pixel P (ij) furthermore comprises storage means M (ij) making it possible to define the state of the two group switches A (ij) and B (ij) that are on or off. More precisely, the storage means M (ij) comprise two binary storage locations in each of which the state of one of the switches A (ij) and B (ij) is memorized. Each storage location comprises for example a flip-flop. The group switches A (ij) and B (ij) are, for example, field-effect transistors driven by their gate and an output of each of the storage locations controls the gate of the associated switch. For this purpose, in FIG. 1, in each of the storage locations, reference is made to the associated group switch A (ij) or B (ij).

Access to the storage means M (ij) for storing the necessary information is not shown in Figure 1 to not weigh it down. The addressing can be done by means of in-line and column electrodes making it possible to identify the pixel P (ij) addressed. Each pixel P (ij) can comprising an AND cell, two inputs of which are respectively connected to the on-line electrode and the addressing column electrode. The output of the AND cell thus defines the pixel to be programmed. An additional electrode, which can be routed either in line or in column, conveys the data to be memorized to each of the storage locations. There is therefore one data electrode per storage location and common to all the pixels P (ij). The addressing and data electrodes are driven by the registers 11 and 12.

The grouping of several neighboring pixels P (ij) is realized by connecting the different capacitors C (ij) of the pixels of the group at their respective nodes. This connection average the potentials of these different pixel nodes P (ij) of the grouping. The voltages available at the output of the different voltage followers S (ij) of the grouping are therefore equal and during the reading phase of the matrix 10, one of the voltage followers S (ij) of the group can be chosen indifferently to connect it to the Col column electrode (j) by means of the actuator T (ij) associated with the voltage follower S (ij) of the pixel P (ij) retained.

For example, it is desired to group four neighboring pixels forming a square pattern spread over two lines 2i and 2i + 1 and two columns 2j and 2j + 1. For any current value of i and j, the storage means M (ij) are programmed to group the coordinate pixels: (2i, 2j); (2i + 1, 2j); (2i + 1, 2j) and (2i + 1, 2j + 1). During the reading phase, the row addressing register 1 1 drives the actuators associated with the in-line electrodes Phi-line (2i) and the reading register of the columns 12 drives the column electrodes Col (2j). The pixels P (2i, 2j) therefore represent the group to which they belong.

Suppose a coordinate pixel other than (2i, 2j) is defective, the programming of the group switches A (ij) and B (ij) is done so that it does not belong to any group. It is not read, and does not pollute the group to which it would have belonged if the groupings had been systematic. We are simply with a group of three pixels instead of four.

If, on the contrary, a coordinate pixel (2i, 2j) is defective, as previously, the programming of the grouping switches is made so that it does not belong to any group. By cons in order to read the other pixels of this group, it is necessary in this case also modify the programming of the read register of the columns 12 so that, when the in-line electrode Phi-line (2i) is addressed, instead of addressing the electrode in column Col (2j), the column electrode Col (2j + 1) is addressed.

It is possible that several pixels are defective. Suppose that two coordinate pixels (2i, 2j) and (2i, 2j + 1) are defective. The programming of the grouping switches A (ij) and B (ij) is done so that the defective pixels do not belong to any group so as not to pollute the group to which they belonged if the groupings had been systematic. In order to read the other pixels of this group, it is also necessary to modify the programming of the row addressing register 1 1 so that the on-line electrode Phi-line (2i + 1) is addressed in place of the in-line electrode Phi-line (2i).

However, the solution of the preceding paragraph no longer works if on a pair of lines 2i, 2i + 1, there are at the same time pairs of defective pixels of coordinates (2i, 2j), (2i, 2j + 1) and couples of defective pixels of coordinates (2i + 1, 2k), (2i + 1, 2k + 1). In this case, to read the two groups having defective pairs, it is necessary to successively address the lines 2i and 2i + 1.

More generally, if all the pixels are good, during the reading phase, the addressing is done via lines 2i.

If a few rare pixels are defective, the addressing can take this into account and shift by a row the rows or columns to which the defective pixels belong.

If the number of pairs of defective pixels increases, it is necessary in certain cases to read the 2 rows or the 2 columns corresponding to the groups. This slows down the reading speed. Nevertheless, an interest is preserved by improving the signal-to-noise ratio of the voltages read.

If the number of pairs of defective pixels increases further, we tend to address all the rows and all the columns. The interest of groups in reading speed disappears completely. Interest in the signal-to-noise ratio, however, remains. This case is nevertheless unlikely in an imaging device made industrially. FIG. 2 represents a matrix 20 comprising, as previously, sixteen pixels Q (ij) distributed in four rows and four columns. In each pixel Q (i, j), there is the capacitor C (ij) for accumulating the electric charges resulting from the conversion of the physical phenomenon, the actuator T (ij), the grouping switches A (ij) and B (ij) and the storage means M (ij) associated with the group switches A (ij) and B (ij). In the matrix 20, the column electrodes Col (j) and in line Phi-line (i), the row addressing register 11 and the reading register of the columns 12 are found.

Unlike the matrix 10, the matrix 20 does not include a follower and the node of the pixel Q (ij) can be directly connected to the Col column electrode (j) through the actuator T (i, j ).

In the reading phase, the accumulated charges at the node of each pixel Q (i, j) are transferred to the column electrodes Col (j), through the actuator T (i, j), when the pixel Q (i, j) is addressed by the in-line electrode Phi-line (i). Note that in the matrix 20, the reading of the information of a pixel Q (ij) is destructive of the information. In other words, after transfer of the charges of the node of a pixel Q (i, j) to the column column Col (j) associated, the charges are no longer available on the node of the pixel Q (ij).

When one chooses to group pixels by means of the group switches A (i, j) and / or B (i, j), the potentials of the various connected nodes are averaged and the charges add up. When reading a group, one can drive the actuators T (ij) so that a single actuator T (ij) is closed in the same group. The charges added by the actuator T (ij) selected are then recovered. But this requires an individual control of the actuators T (ij) and therefore a system for addressing the actuators T (i, j) in line and in column, which greatly increases the routing of the matrix 20. It is easier to control actuators T (ij) per line by means of in-line electrodes Phi-line (i). In this case, if a group spreads over several consecutive columns, the charges of the group can simultaneously evacuate to column electrodes through several actuators T (ij) and therefore of several column electrodes Col (j). It is therefore useful for the matrix 20 to include reading means for adding or averaging the transiting charges. in the different column electrodes associated with the same grouping.

An example of such means is shown in Figure 2 by blocks B1 and B2 located at the end of the column electrodes. Each of the blocks makes it possible to average the electrical signals conveyed by two column electrodes Col (j). A more detailed diagram of one of these blocks is proposed in Figure 3.

In this block, two column electrodes Col (1) and Col (2) are respectively connected to the inverting input of two integrating amplifiers Ai (1) and Ai (2). The non-inverting inputs of the two integrating amplifiers Ai (1) and Ai (2) are connected to the ground of the matrix 20. A capacitor, respectively C (1) and C (2), and a switch, respectively li (1 ) and li (2) are connected in parallel between the inverting input and the output of each of the integrating amplifiers Ai (1) and Ai (2).

The charges received on the column electrodes Col (1) and Col (2) are converted into voltage on each of the capacitors C (1) and C (2). The switches li (1) and li (2) are controlled to reset the potential difference between the electrodes of the capacitors C (1) and C (2).

Capacitors, respectively Cmem (1) and Cmem (2), are connected between the output of each integrator amplifiers Ai (1) and Ai (2) and the mass of the matrix 20 via lech switches (1). and lech (2). The output voltages of these amplifiers are stored on the capacitors, respectively Cmem (1) and Cmem (2).

An Imelange mixing switch is used to connect the active (non-grounded) electrodes of the two capacitors Cmem (1) and Cmem (2). The Imelange switch is used to average the voltages present on each of two capacitors Cmem (1) and Cmem (2) when it is closed.

The voltage at the terminals of each of the capacitors Cmem (1) and Cmem (2), possibly averaged when the switch Imel is closed, is then read by means of follower amplifiers respectively As (1) and As (2). The block B1 shown in FIG. 3 makes it possible to average the available electrical information on the two electrodes in columns Col (1) and Col (2). It is of course possible to generalize the mixing switches between all the column electrodes Col (i) consecutive. The mixing switches will be maneuvered according to the definition of the pixel groups Q (ij) of the matrix 20.

FIG. 4 represents a matrix 30 forming an alternative embodiment of the matrix 20 in which the actuators T (ij) can be controlled individually without requiring individual addressing by means of electrodes dedicated to this addressing.

FIG. 4 represents a matrix 30 comprising, as before, sixteen pixels R (ij) distributed in four rows and four columns. In each pixel R (i, j), there is the capacitor C (i, j) for accumulating the electric charges resulting from the conversion of the physical phenomenon, the actuator T (ij) and the grouping switches A (ij ) and B (ij). In the matrix 30, there are the column electrodes Col (j) and online Phi-line (i), the row addressing register 1 1 and the read register columns 12. The node of the pixel R (ij ) is directly connected to the actuator T (ij) without follower.

Each of the pixels R (ij) also comprises memory means M (ij) associated with the group switches A (ij) and B (ij). Unlike the matrices 10 and 20, the storage means M (ij) of the matrix 30 further allow to allow the closing of the actuator T (ij). More precisely, the storage means M (ij) comprise an additional bit storage location, in which a closing authorization is authorized for the actuator T (ij).

The authorization to close the actuator T (ij) is made in connection with a reading command of the pixel R (ij). More specifically, the control of the actuator T (ij) is always done by means of the in-line electrode Phi-line (i). This command can be inhibited depending on the data stored in the additional location of the storage means M (ij). In practice, the pixel R (ij) may comprise an AND cell whose first input is connected to the on-line electrode Phi-line (i) and a second input of which is connected to the additional location whose data is denoted D (i, j). The output of the AND cell forms the gate control of the actuator T (ij).

It has been seen previously that the programming of the storage locations can be done by means of an electrode dedicated to each of the storage locations, in addition to the electrodes necessary for addressing the pixels. Increasing the number of storage locations therefore complicates the realization of the matrix 30 by imposing the routing of the electrodes further.

FIG. 5 represents four identical pixels X (lj) of a matrix

40 to overcome this problem by means of shift registers U (i, j) integrated with each of the pixels X (ij) and whose boxes form the different storage locations. As before, the invention is not limited to this number of pixels. Each pixel X (ij) comprises three electronic switches, T1 (i, j), T2 (i, j) and T3 (i, j). The switch T1 (i, j) allows the resetting of the potential of the sensitive element of the pixel represented here by a photodiode K (i, j). The switch T1 (i, j) is at the beginning of the integration cycle of a pixel X (ij). After this beginning of the cycle, the switch T1 (i, j) is blocked. The potential V of the node N (i, j) of the pixel X (ij) then changes as a function of the illumination, according to a law AV = Q / C, AV being the variation of potential at the node N (ij), Q being the photocharge collected (that is to say the charge collected due to the photon interactions in the detector) and C being the capacitance present at the integration node N (ij), generally essentially due to the parasitic capacitance of the photodiode K (j). At the end of the integration cycle, the switch T3 (i, j) is passed through the control electrode Phi-line (i). The assembly constituted by the switch T2 (i, j) and the current source lpol (j) located at the bottom of the column electrode Col (j) then constitutes a follower stage. An image potential is thus obtained from that of the node N (i, j) at the foot of the column electrode Col (j) and used by a circuit S (j), for example enabling the digitization of the potential.

Each pixel X (ij) also comprises a capacitor C (ij) for modifying the gain of the pixel X (ij). A switch G (ij) makes it possible to connect the capacitor C (ij) to the node N (ij) and thus to increase the capacitance value present at the integration node N (i, j). According to the invention, there are the group switches A (ij) and B (ij) and the storage means are here formed by a shift register U (i, j) with three boxes, each for controlling one of the switches A (i, j), B (i, j) and G (i, j).

The shift register U (i, j) comprises a clock input H (i, j) and a data input E (ij) on which the data to be stored in the different boxes of the shift register U (i, j) are conveyed in series. The data input E (i, j) is connected to an E-prog data electrode which may be common to all the pixels X (ij) of the matrix 40, which is why no markers are assigned ( i, j) to the E-prog data electrode. In FIG. 5, the E-prog electrode is routed along lines i of matrix 40. It is also possible to carry out this routing in column or grid.

The pixel X (ij) that one wishes to program is chosen by means of its clock input H (ij) and the data are presented in series on the data input E (i, j).

The clock input H (ij) is formed by the output of an AND cell, a first input of which is connected to the line bus Phi-line (i) and a second input of which is connected to an electrode in column H-Col (j) for choosing the column of pixels X (ij) to be programmed. A particular pixel X (ij) is selected by activating the in-line electrode Phi-line (i) concerned. The effective programming of the three boxes of the shift register U (ij) is performed by activating three times a command conveyed by the electrode in column H-Col (j) in agreement with three programming values conveyed in series on the input of given E (ij).

When acquiring an image, all the commands conveyed by the column electrode H-Col (j) are deactivated and the different pixels X (ij) can be selected with the on-line electrode Phi-line (i) , without disturbing the values programmed in the shift registers U (ij).

In this example, the in-line electrode Phi-line (i) has been reused as the pixel selection electrode X (ij) to be programmed. Alternatively, it is possible to implement a control electrode independent of the on-line electrode Phi-line (i) and dedicated to the programming of the different shift registers U (ij).

As a variant, it is possible to produce an E-prog electrode specific to each line of the matrix. In programming mode, it is then possible to activate all the commands carried by the online electrodes Phi-line (i) and simultaneously program all the pixels X (ij) of the same column. This makes it possible to accelerate the programming of the different shift registers U (i, j) of the matrix 40.

The programming of the different storage locations of a pixel requires only two specific electrodes: an H-Col clock electrode (j) and a data electrode proper E-prog, regardless of the number of storage locations. These two electrodes are connected to all the shift registers U (i, j) of the different pixels X (ij). Thus, without increasing the number of buses of the matrix 40, it is possible to increase the number of storage locations for other needs of the pixel X (i, j).

The programming of the storage locations being carried out in a specific phase, preceding that of taking pictures, the addressing electrodes of the pixels for programming and those for reading can be partially or completely merged.

Advantageously, the storage means are configured to store a plurality of pixel grouping configurations and the device comprises means for selecting among the stored configurations. FIG. 6 represents an example of a pixel Y (ij) in which the storage means are formed by a shift register V (ij) comprising six boxes making it possible to memorize two distinct control configurations of the different switches of the pixel Y (ij), either two configurations of three switches per pixel. More generally, the shift register V (i, j) contains several boxes and the number of boxes is equal to the number of storage locations multiplied by the number of distinct configurations that it is desired to store.

In the example shown, the shift register V (ij) operates in a circular loop through an additional control electrode Wax. The pixel Y (i, j) comprises the three switches T1 (i, j), T2 (i, j) and T3 (i, j) and an additional switch T4 (i, j) controlled by a control electrode Wax and for connecting the data input E (ij) to either the E-prog electrode or to the last box of the shift register V (i, j). Two programming configurations can be stored, respectively in the first 3 and last 3 boxes of the shift register V (ij). The programming of the shift register V (ij) is done by controlling the switch T4 (ij) so as to connect the data input E (ij) to the E-prog electrode in accordance with six pulses applied to the clock input H (i, j). The transition from one configuration to another is done by controlling the switch T4 (ij) so as to connect the data input E (ij) to the last box of the shift register V (ij) in concordance with three pulses applied to the clock input H (ij). The clock pulses are obtained by activating the commands present on the in-line electrode Phi-line (i) and by activating the command present on the electrode H-Col (j).

It is understood that the shift registers U (i, j) and V (ij) can be implemented for any type of matrix, such as matrices 10, 20 and 30 previously described.

The programming of the storage locations makes it possible to define any type of grouping: 2x2, 3x3, 4x4, ... nxn, nxm, even complex groupings of shapes, even groups that are not identical over the entire dimension of the matrix with for example smaller groups in the center than on the edges of the matrix, or groups alternatively small and large. Programming makes it possible to exclude groups of defective pixels.

By way of examples of complex shapes, FIG. 7 represents regular groups in the form of groups of eight pixels in cross-section. The outlines of the pixels are materialized in broken lines and the outlines of the groups in solid lines. Figure 8 shows regular groupings of three pixels organized in chevron. Figure 9 shows groupings of different sizes. Other forms of groupings are of course possible.

It may be interesting to be able to quickly switch from one cluster configuration to another. The programming of the storage locations makes it possible to quickly redefine the groupings between two images or between two successive image sequences. For example, if we group the 2x2 pixels in a dynamic imaging sequence, it may be interesting to move these groupings, from one image to the next, one pixel to the right, then up, then to the left, then finally down, so that after a cycle of 4 images, all the positions of these groups have been implemented. A spatial resolution close to that obtained without the groups is thus recovered while improving the signal-to-noise ratio of the image.

In the field of radiological imaging, the reconfiguration of the pixel groups is also of interest. For example in fluoroscopy, alternatively low dose fluoroscopy modes and high dose sequences can be used. In the fluoroscopy mode, one wishes to read quickly, and the spatial resolution is not sought. 2x2 or even larger groups are therefore desirable. In high dose sequences, the frame rate may be reduced, but the spatial resolution is sought and the size of the clusters reduced. You can not even group any pixel and read them all separately.

With the structures previously described in matrices 10,

20 and 30, it is necessary to reprogram completely the storage locations concerned by the group switches A (ij) and

B (ij) and this for all the pixels of the matrix. The programming time can be important.

Advantageously, to reduce the programming time, the storage means M (ij) are configured to store a plurality of pixel array configurations. The device then comprises means for choosing among the stored configurations.

When implementing a shift register, the number of cells can be multiplied by the number of distinct configurations that are to be memorized. For example, in the matrices 10 and 20 shown in FIGS. 1 and 2, if it is desired to store two configurations of pixel groups, a shift register comprising four cells and six cells in the matrix 30 is provided.

For the matrices 10 and 20 and two configurations, in a first programming phase, the four cells are filled from the serial input of the register, the first two cells corresponding to the first configuration and the last two cells corresponding to the second. This for all the pixels of the matrix.

Then the shift registers of all pixels are reconfigured to operate in a loop.

When you want to go from one group configuration to another, it is then sufficient to send two clock ticks simultaneously on all the registers of the matrix, which can be very fast.

Claims

1. An imaging device comprising a matrix (10; 20; 30) of pixels (P (i, j); Q (ij); R (ij); X (ij); Y (ij)) organized in rows and columns characterized in that each current pixel (P (ij); Q (ij); R (ij); X (ij); Y (ij)) of the matrix (10; 20; 30; 40) comprises:

A line grouping switch (B (i, j)) for grouping the current pixel (P (ij); Q (ij); R (ij); X (ij); Y (ij)) with the pixel; following (P (ij + 1); Q (ij + 1); R (ij + 1); X (ij + 1); Y (i, j + 1)) of the same line, if the following pixel exists, in the line to which the current pixel belongs (P (ij); Q (ij); R (ij); X (ij); Y (ij)),

"A column grouping switch (A (ij)) for grouping the current pixel (P (i, j); Q (i, j); R (i, j); X (i, j); i, j)) with the following pixel (P (i + 1, j); Q (i + 1 j); R (i + 1 j); X (i + 1 J); Y (i + 1 j); ) of the same column, if the next pixel exists, in the column to which the current pixel belongs (P (i, j); Q (i, j); R (i, j); X (i, j); Y (i, j)) and

Storage means (M (ij), U (ij), V (ij)) making it possible to define the on or off state of the two group switches (A (i, j), B (ij)).

2. Device according to claim 1, characterized in that the pixels (P (i, j); Q (i, j); R (i, j); X (i, j); Y (i, j)) are all identical.

3. Device according to one of the preceding claims, characterized in that the storage means (M (ij)) comprise two binary storage locations in each of which is stored the state of one of the switches A (ij) and B (ij).

4. Device according to one of the preceding claims, characterized in that each current pixel (R (ij)) further comprises an actuator (T (ij)) for reading the current pixel (R (ij)), and in that that the storage means (M (ij)) of the current pixel (R (ij)) make it possible to allow (D (ij)) the closing of the actuator (T (ij)) for reading the current pixel (R ( ij)) in connection with a read command (Phi-line (i)) of the current pixel (R (ij)).

5. Device according to claims 3 and 4, characterized in that the storage means (M (ij)) comprise an additional location for binary storage (D (i, j)), in which a closing authorization is stored. actuator T (i, j).

6. Device according to any one of claims 3 or 5, characterized in that the storage locations are addressed by means of in-line and column electrodes for identifying the pixel (P (i, j); ij); R (ij)) addressed and in that the device comprises a data electrode per storage location and common to all the pixels (P (i, j); Q (ij); R (i, j )).

7. Device according to any one of claims 3 or 5, characterized in that the storage locations are addressed by means of in-line and column electrodes for identifying the pixel (X (ij); Y (ij) ) addressed, in that each pixel (X (i, j); Y (ij)) comprises a shift register (U (i, j); Y (ij)) forming the storage means, and that the device comprises a clock electrode (H (i, j)) and a data electrode (E-prog) connected to all the shift registers (U (i, j); Y (i, j)) of different pixels (X (i, j); Y (i, j)).

8. Device according to one of the preceding claims, characterized in that the storage means (V (ij)) are configured to store a plurality of pixel array configurations (Y (ij)) and in that the device comprises means (T4 (i, j)) to choose among the stored configurations.

9. Device according to claims 7 and 8, characterized in that the shift register (V (i, j)) contains several boxes and in that the number of boxes is equal to the number of storage locations multiplied by the number different configurations that we want to memorize.

10. Method implementing an imaging device according to one of the preceding claims comprising a phase of imaging, characterized in that it consists in performing programming phase of the means for storing the pixels (P (i, j); Q (ij); R (ij); X (ij); Y (ij)) before the image-taking phase.