Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N3/00—Scanning details of television systems; Combination thereof with generation of supply voltages
  • H04N3/10—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical
  • H04N3/14—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by means of electrically scanned solid-state devices
  • H04N3/15—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by means of electrically scanned solid-state devices for picture signal generation
  • H04N3/155—Control of the image-sensor operation, e.g. image processing within the image-sensor
  • H04N3/1562—Control of the image-sensor operation, e.g. image processing within the image-sensor for selective scanning, e.g. windowing, zooming
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
  • H04N25/40—Extracting pixel data from image sensors by controlling scanning circuits, e.g. by modifying the number of pixels sampled or to be sampled
  • H04N25/44—Extracting pixel data from image sensors by controlling scanning circuits, e.g. by modifying the number of pixels sampled or to be sampled by partially reading an SSIS array
  • H04N25/443—Extracting pixel data from image sensors by controlling scanning circuits, e.g. by modifying the number of pixels sampled or to be sampled by partially reading an SSIS array by reading pixels from selected 2D regions of the array, e.g. for windowing or digital zooming
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
  • H04N25/40—Extracting pixel data from image sensors by controlling scanning circuits, e.g. by modifying the number of pixels sampled or to be sampled
  • H04N25/44—Extracting pixel data from image sensors by controlling scanning circuits, e.g. by modifying the number of pixels sampled or to be sampled by partially reading an SSIS array
  • H04N25/445—Extracting pixel data from image sensors by controlling scanning circuits, e.g. by modifying the number of pixels sampled or to be sampled by partially reading an SSIS array by skipping some contiguous pixels within the read portion of the array
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
  • H04N25/40—Extracting pixel data from image sensors by controlling scanning circuits, e.g. by modifying the number of pixels sampled or to be sampled
  • H04N25/46—Extracting pixel data from image sensors by controlling scanning circuits, e.g. by modifying the number of pixels sampled or to be sampled by combining or binning pixels
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
  • H04N25/70—SSIS architectures; Circuits associated therewith
  • H04N25/71—Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors
  • H04N25/74—Circuitry for scanning or addressing the pixel array
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
  • H04N25/70—SSIS architectures; Circuits associated therewith
  • H04N25/71—Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors
  • H04N25/745—Circuitry for generating timing or clock signals

Definitions

• the present invention relates to matrix optical sensors.
• the invention applies for example to the use of such sensors for the detection of an object in the image of a detection plane on the sensor, for example to locate the position of a pointer in front of a screen touch.
• the invention can still be applied to video surveillance or telemetry.
• matrix CCD optical sensors These sensors are relatively expensive and the image formed on the pixels is read en bloc, sequentially. The processing of the image is relatively complex because all the pixels must be memorized.
• CMOS matrix sensors called "snapshot".
• the pixels are each associated with an analog memory. The size of the pixels is relatively large and the memory may have a large information leak under strong illumination.
• touch screens include a screen and a location system of a pointer in the image of a detection plane associated with the screen, for example placed just in front of it.
• Light sources and sensors are arranged relative to the screen so that the pointer intercepts the light emitted by these sources or reflected by reflective surfaces disposed around the screen and forms an image on the sensors.
• the analysis of the formed image makes it possible, by triangulation, to determine the position of the object.
• FIG. 15 shows an example of a touch screen known from application US 2007/0089915.
• two matrix sensors 101 and 102 are respectively disposed at each corner of the screen.
• the Cartesian coordinates X and Y of the finger D in the detection plane 103 can be determined from the angles a and ⁇ corresponding to the occlusion induced by the pointer D in the detection plane 103.
• Touch screens equipped with linear sensors are also known. Unlike touch screens employing matrix sensors, linear sensors must be arranged with great precision relative to the detection plane. A disadvantage of this configuration is the sensitivity of these sensors to games or mechanical deformations encountered during manufacture and during use, which would make the image of the pointer would form out of the sensor.
• the linear sensors used have pixels of rectangular shape, of large side oriented perpendicularly to the detection plane.
• a disadvantage related to the use of rectangular pixels is the decrease in the sensitivity of the pixels due to a greater parasitic capacitance of the photodiode. In addition, such pixels collect more stray light.
• matrix sensors incorporating a windowing function are known.
• the sensor receives an input window address, for example the address of the upper corner, and outputs the values of the pixels in the window.
• the size of this window may still be quite large and suddenly greatly increase the number of pixels to be processed.
• the reading speed of a matrix sensor is not symmetrical in line and in column, the enlargement of the reading window in the vertical direction significantly increases the reading time of an image.
• the application US 2004/0155175 discloses a matrix sensor associated with a reading means configured to read an image formed on the pixel matrix of the sensor.
• the reading means sequentially reads the columns of the pixel matrix.
• Such a sensor does not allow parallel processing of the columns of pixels, and the reading of an image with such a sensor can be relatively long.
• the object of the invention is, according to one of its aspects, a matrix optical sensor, comprising: a matrix of pixels, each pixel being identified by a line address and a column address and,
• a programmable electronic circuit comprising a plurality of programmable units for reading pixels, each programmable unit being associated with at least one pixel column address and being configured for:
• the invention more particularly relates to a matrix optical sensor comprising: a plurality of programmable units for reading the pixels, each connected to at least one column of pixels and each being configured for:
• At least one line address is for example dedicated to a function other than reading the value of a pixel and the readable programmable unit receiving this line address as read address is for example configured to allow the execution of said function, which can save the number of sensor control signals.
• the programmable reading unit is capable of delivering the value of the pixel either outside the sensor or to another component of the sensor, for example in view of its storage and / or its treatment within the sensor, for example to undergo a differential treatment.
• the reading can be done first by line addressing then column addressing.
• value of the corresponding pixel it is necessary to understand the value of the pixel directly acquired by the sensor, or the value after filtering treatment, for example.
• the sensor according to the invention makes it possible to program a selection of pixels and to read only the values of the programmed pixels, this reading being performed by means of the programmable reading units, which can work in parallel.
• the invention makes it possible to avoid reading each of the 256 lines of the image, thus to speed up the processing.
• pixel line is meant a row of pixels according to the size of the pixel array having the most pixels.
• column of pixels is meant a row of pixels according to the size of the matrix of pixels having the fewest pixels.
• the senor has 256 rows of 1600 pixels each and 1600 columns of 256 pixels each.
• At least one readable readout unit including each readable readout unit, may be associated with only one pixel column address.
• the programmable read unit is connected to only one column of pixels.
• the senor can be integrated in a system for locating a pointer in an image of a detection plane formed on the sensor by detecting the occultation by the pointer of the light rays directed towards the sensor.
• This image can define straight line segments having a relatively low angle of inclination relative to the lines of the sensor.
• the image read may be in one dimension only, that is, read only for one pixel per column. This reading can be done in parallel, that is to say simultaneously, for all the reading units.
• At least one readable readout unit in particular each readable readout unit, can be associated with several pixel column addresses, for example at consecutive column addresses or, in other words, be connected to several columns of pixels, for example to consecutive columns of pixels. This further simplifies sensor construction and processing.
• the number of rows of the pixel array is for example equal to 2 n and each readable readout unit can be associated with n consecutive addresses of columns of pixels.
• n n consecutive addresses of columns of pixels.
• eight consecutive column addresses are for example associated with the same programmable read unit.
• the invention also makes it possible to reduce the reading clock frequency of the sensor, to the benefit of energy consumption and parasitic electromagnetic radiation.
• the power consumed by a sensor according to the invention is for example less than 100 mW, under a supply voltage of the order of 3.3V.
• the matrix sensor according to the invention is for example embodied in the form of an integrated electronic chip of reduced size.
• Each programmable reading unit comprises for example: at least one memory register including in memory the line address programmed in the readable programmable unit, a comparator receiving:
• the line address programmed in the memory register the line address programmed in the memory register, and at least one buffer memory.
• the comparator can be configured to compare the addresses on the first and second inputs and, in case of equality, allow the buffer value to be stored in the pixel whose line address has been programmed into the unit. programmable reading.
• the readable programmable unit When a readable programmable unit is associated with several pixel column addresses or, in other words, is connected to several columns of pixels, the readable programmable unit may comprise a single memory register, a single comparator for the whole said pixel column addresses and a buffer memory per pixel column address. According to a first embodiment of a programmable read unit, the latter comprises only one memory register, a single comparator and at least one buffer memory.
• the programmable reading unit comprises several buffers associated with the same column address or, in other words, connected to the same column, the latter can make it possible to record successively over time the values of the pixels identified by the same addresses of the column. row and column. This may make it possible to perform a differential treatment between two images successively formed on the sensor, in order to eliminate the contribution of ambient light for example.
• the sensor may comprise a differential amplifier for delivering a value corresponding to the difference of the values of a pixel at two successive instants, which correspond, for example, to the switching on and off of the light source serving to form the image of the image. detection plan on the sensor.
• a programmable reading unit comprises several memory registers, a single comparator and one or more buffers.
• the user can program different line addresses in each memory register, which can read in the buffer or buffers of the readable programmable unit the values of different pixels of the memory. same column of pixels.
• Each readable programmable unit comprises for example two memory registers, which makes it possible, for example, to read pixels defining an open or closed loop-shaped pattern on the image formed on the sensor.
• the programmable unit may further comprise memory registers, for example four, in order to read pixels of a more complex shape image formed on the sensor, for example defining a reniform pattern.
• the sensor comprises a matrix of photodetectors, a pixel being for example associated with a photodetector.
• a pixel is associated with several photodetectors. These photodetectors can be made according to CMOS technology.
• the matrix sensor may be configured to perform at least one binomial filtering within a column of the photodetector array, which may make it possible to smooth out, according to the filtered dimension, the distribution of the electric charges acquired by the photodetectors.
• Binomial filtering may make it possible to compensate for disturbances occurring during the operation of the matrix sensor, for example caused by mechanical stresses exerted on a screen to which the sensor is associated or by ambient temperature. Binomial filtering can be done in two different configurations.
• two photodetectors of at least one column of the respective coordinate matrix 2k and 2k + 1 are connected according to the filtered column, where k is a natural integer, for example 2k and 2k + 1 line addresses.
• the binomial filtering is performed by connecting two photodetectors of at least one column of the respective coordinate matrix 2k + 1 and 2k + 2 according to the filtered column, where k is a natural integer, for example lines 2k + l and 2k + 2.
• the matrix sensor comprises, for example, a plurality of controllable switches, each of these controllable switches connecting two photodetectors adjacent to the photodetector matrix, in particular two neighboring photodetectors of the same column.
• binomial filtering can be activated by two signals.
• at least one line address dedicated to a function other than the pixel value reading is dedicated to a configuration described above for binomial filtering, and the reception by the readable programmable unit of said address as an address of For example, reading causes the controllable switches to close according to one of the filtering configurations described above.
• a pixel line address is for example dedicated to each binomial filter configuration.
• the subject of the invention is a system for locating a pointer in the image of a detection plane, comprising at least one matrix sensor as defined above.
• the sensor is for example configured to acquire an image of a detection plane and the pixels whose line address is stored in the programmable reading units are the pixels on which the image of the detection plane is formed.
• the analysis of the read pixels makes it possible to detect the position of the pointer in the detection plane, the pointer blocking the light arriving at different pixels according to its location.
• the location system is for example integrated in a screen to form a touch screen and the image of the detection plane formed on the sensor is for example that of one or more light sources distributed around the screen or their reflection by a reflector located on the edge of the screen.
• the screen to which the location system is integrated comprises one or more LEDs located near the optical axis of the sensors and illuminating the edges of the screen, which are provided with catadioptric reflectors. The light from the LEDs is sent back to each sensor with a given light output. The presence of a pointer near the screen causes a significant decrease in this output and creates an occultation on the sensor.
• the value of the sensor pixel or pixels may be changed as a function of the position of the pointer in the image of the detection plane and not all the pixels of the sensor, which reduces the processing time and the need for RAM.
• the set of pixel values of the sensor does not have to be stored. The cost of the location system is reduced.
• the location system advantageously comprises two matrix sensors according to the invention, and the location can be performed by a triangulation calculation.
• the readable readout unit may receive as input as a read address only the pixel line addresses where the detection plane image is formed, which may avoid processing the lines of sensor pixels on which the image of the pointer useful to the location of the latter has no chance of forming.
• the invention further relates to a touch screen, comprising:
• Another object of the invention is, according to another of its aspects, a method of reading a selection of pixels within a matrix of pixels, each pixel being identified by a column address and a line address, the selected line addresses having been programmed in associated readable programmable units or, in other words, each connected to at least one column of pixels, in which method: at least one read address is provided with programmable read units, for some read address values, the read address thus received as input is compared with at least one programmed line address in each readable readable unit, and in the case of equality, a buffer memory is recorded in value of the pixel having the programmed line address.
• At least one line address is for example dedicated to a function other than the reading of the pixel value and the readable programmable unit receiving this line address as read address is for example configured to allow the execution of said function .
• a single line address can be programmed per programmable read unit, for example during a sensor calibration phase.
• a plurality of line addresses are programmed per programmable read unit and it is compared whether the read address received at the input is equal to any of these addresses programmed in the readable programmable unit.
• the programmable read unit can have as many buffers as programmed line addresses.
• the programmable read unit can still be reprogrammed on the fly. Once the value of the pixel corresponding to the line address programmed in the register memory of the readable programmable unit stored in a buffer of this readable programmable unit, the user can program a new line address in the memory register, the value of the pixel identified by this new line address being subsequently stored in the same buffer of the readable programmable unit, after reading and erasing the previous data, or in another buffer of the readable programmable unit. This can read the value of several pixels of the same column associated with a programmable read unit.
• the matrix of pixels is associated with a matrix of photodetectors and the method may comprise a binomial filtering step of the photodetectors as defined above prior to the step of providing the programmable read units with a read address.
• At least one line address is for example dedicated to a binomial filter configuration and, during the binomial filtering step, for example sends to at least one readable programmable unit said line address as read address.
• the subject of the invention is also a method for locating a pointer in the image of a detection plane, in which: the acquisition of the image of the detection plane is allowed with a matrix of photodetectors, each pixel of the image being marked in the image of the detection plane by a line address and a column address and reading is allowed a selection of pixels of the image of the detection plane according to the method above.
• the method may comprise the steps of: acquiring a first image of at least a part of the detection plane, in particular of the entire detection plane, when the observation field of the photodetector matrix is illuminated by a source artificial light, acquire a second image of said portion of the detection plane, in the absence of illumination of the field of view of the matrix of photodetectors by the artificial source, - perform a differential reading of the images.
• Such a differential reading reduces the noise due to ambient lighting.
• To acquire the first and the second image it is carried out for example by iteration by acquiring at each iteration during a lighting / extinction elementary cycle of the artificial light source only part of the image of the detection plane. .
• At each iteration for example, a single line of pixels is acquired from the image of the detection plane.
• Such an iterative acquisition method makes it possible, for example, to expose the photodetectors associated with the line to be acquired to the light of the artificial source only for a reduced duration, which may be desirable when the light intensity of the source artificial, is high, and this can avoid to saturate the photodetectors.
• the artificial light source is acquired, for the first and second images, the entire image of the detection plane, which can reduce the duty cycle of the artificial source, and to obtain light pulses of higher energy.
• the artificial light source comprises for example at least one light emitting diode.
• the invention further relates, in another of its aspects, in combination with the foregoing, a matrix optical sensor comprising: a matrix of two-dimensional pixels whose reading is performed first by line addressing and then by addressing of columns, a plurality of read units, each being connected to at least one column of pixels, each read unit storing a reading result selectively for one or more given line addresses the sensor being configured to allow to obtain after scanning all or part of the rows of the pixel array a one-dimensional image corresponding to a given pixel line of the pixel array.
• FIG. 1 schematically represents an example of a matrix sensor according to the invention
• FIG. 2 schematically represents a plurality of programmable readout units according to the invention
• FIG. 3a represents an exemplary image of the detection formed on a part of the matrix sensor in the presence of a pointer
• FIGS. 3b to 3d represent different steps during the location, by the location system of the pointer in the image of the detection plane
• FIG. schematic various steps of a method of location of the pointer in the image of the detection plane
• Figure 5 shows different elements of an exemplary matrix sensor according to the invention
• Figures 6a to 6e show different steps of an example binomial filtering
• - Figure 7 shows an example of differential reading
• Figure 8 shows an example of programming method of a prog unit
• FIG. 9 is a timing diagram representing an exemplary reading of the buffers
• FIG. 10a is a timing diagram representing a first example of differential reading according to the invention
• FIG. 10b is a timing diagram representing a second reading example.
• FIG. 11 is an example of integration of a location system according to the invention into an apparatus
• FIG. 12 schematically represents a variant of the matrix sensor shown in FIG. and 14 represent further examples of programmable read units according to the invention
• - Figure 15 shows an example of detecting the position of a finger on a touch screen according to the prior art.
• FIG. 1 shows very schematically an example of a matrix sensor 1 according to the invention.
• the sensor 1 may be incorporated into a positioning system 100 and comprises in the example shown an image acquisition device 2, a programmable electronic circuit 3 having a plurality of sense programmable units 3 J5 and a decoder 5.
• the matrix sensor 1 according to the invention is for example integrated with a chip of reduced dimensions, for example of size less than 25 mm 2 .
• the resolution of the sensor 2 is, for example, 256 lines of 1600 pixels and each pixel has for example a size of 5 ⁇ m, but the invention is not limited to a resolution and a particular pixel size.
• the pixels are for example pixels without respective memories, also called "active pixel”.
• the sensor 1 exchanges data with a digital processing unit 4 which comprises for example a microprocessor as well as a random access memory.
• a digital processing unit 4 which comprises for example a microprocessor as well as a random access memory.
• the decoder 5 is for example made using conventional logic gates, being for example configured to transform a natural binary code into a vector of binary signals of which one and only one is worth “1". This logic "1" makes it possible to select the line of pixels to be read.
• the decoder 5 receives from the processing unit 4 the address of a line to be read via a bus 11, as illustrated in FIG. 2.
• a readable programmable unit 3 j is associated with a single pixel column address.
• Each programmable reading unit 3 j comprises in the example of this figure a programmable memory register 7 ,, a comparator 8, associated with the memory register 7 ,, a buffer memory 9 ,, and an electronic switch 10,.
• each comparator 8 can comprise two inputs: a first input connected to the bus 11 and a second input connected to the memory register 7 j of the readable programmable unit 3 j .
• each memory register 7 , each comparator 8, and each buffer memory 9 are associated with a single column of pixels.
• FIGS. 13 and 14 show further examples of programmable reading units 3 j .
• a programmable read unit 3 j includes two memory registers 7 and 7 ', a comparator 8 ,, a buffer memory 9, and an electronic switch 1 Y j.
• the invention is not limited to a particular number of memory registers 7 j per programmable reading unit 3 j . These can each comprise more than two memory registers 7,.
• each programmable read unit 3 j may also include a memory register 7 a comparator 8 J5 , two buffers 9a, 9b and j and an electronic switch 10 ,.
• the invention is not limited to a particular number of buffers 9, per programmable read unit. These can each comprise more than two buffers 9,.
• each programmable read unit comprises a comparator, several memory registers and several buffers.
• FIG. 5 shows an example of an image acquisition device according to the invention.
• This acquisition device 2 comprises, for example, a matrix of detection elements, which in the example described are 20 nm photodetectors.
• the sensor 1 also comprises a plurality of controllable switches 21, for example field effect transistors 21, connecting two neighboring photodetectors along a column of the matrix sensor and a plurality of controllable switches 22 allowing the reading of the charge acquired by the sensors.
• the sensor 1 comprises for example, as illustrated in FIG. 11, a plurality of inputs 60, 61 to 6x and 70
• the input 60 is for example connected to a power supply, the inputs 61 to 6x are for example connected to a processor of the apparatus in which the sensor 1 is integrated and the input 70 is for example connected to ground.
• the inlet 60 and the inlet 70 can be connected by a decoupling capacitor.
• the system 1 comprises for example two outputs 72 and 73 respectively connected to a transistor 74 and 75 respectively.
• Application to the location of a pointer in front of a touch screen We will now describe with reference to FIGS. 3a to 3d and in FIG. 4 an example of application of the invention to the location of a pointer in the image of a plan for detecting a touch screen using a locating system 100 comprising a sensor 1 comprising programmable reading units 3 j as represented in FIG. 2.
• FIG. 3a only six lines and nineteen columns of the pixel array of the sensor have been shown.
• the columns are numbered from left to right and the lines from bottom to top.
• the pixels represented in dark color correspond to the occlusion of a light source due to the presence of the pointer.
• the pixels making it possible to locate the pointer in the image of the detection plane for the columns of address j to j + 2 are all located at the address line i + 2 and are respectively designated 6i + 2j , 6 1+ 2 j + i and 6i + 2j + 2 in the illustrated example.
• the values of the set of pixels making it possible to locate the pointer in the image of the detection plane can fill a one-dimensional array.
• the digital processing unit 4 causes the erasure of the information previously recorded in the memory registers 7, each programmable reading unit 3_.
• the digital processing unit 4 scans each line of the image of the detection plane and determines in step 42 for each pixel column the line address of the pixel corresponding to the image of the detection plan.
• the row address of the pixel of each column for locating the pointer in the image of the detection plane is programmed in each of the memory registers 7 J + 1 to 7 J + i9.
• the line address "i + 2" is in the illustrated example recorded in registers 7 J + i, 7 J + 2 and 7 J + 3.
• FIG. 8 shows an example of programming a line address in a memory register 7, according to step 43.
• the digital processing unit 4 sends to the memory register 7, associated with the column of column address pixels j via a bus, not represented, an ADR signal [7: 0] corresponding to the line address of the pixel of this column to program.
• the line address is eight-bit coded and the memory register 7 ⁇ of this line address is bit-by-bit recorded sequentially.
• the memory register receives each bit of the address coding successively, each of the bits being recorded in the memory register on receipt of a rising edge of the clock signal CLK, as shown in FIG. 8.
• This recording in FIG. a memory register 7 is for example carried out at a rate greater than 12 MHz.
• the digital processing unit 4 sends to the step 44 via the bus 11 to the decoder 5 and each readable readout unit 3 j to 3 J + 1 s a pixel reading address of the image, this read address corresponding to a line address.
• the first read address sent at this step 44 corresponds to the lowest line address associated with one or more pixels on which the image of the detection plane is formed.
• Each comparator 8 compares this read address received at the first input to the line address programmed in step 43 in the memory register 7, to which it is associated and which it receives as a second input.
• the comparator 8 j acts on the switch 10, to allow the recording in the buffer memory 9, the value of the corresponding pixel.
• steps 44 and 45 are performed again, the digital processing unit 4 sending via the bus 11 to the decoder 5 and the reading of programmable units 3 j 3 J + i8 the next reading address by incrementing the number of line.
• the read address "i + 2" is sent and comparators 8, 8 J + 2 on the one hand, 8 J + 10 to 8 J + 14 on the other hand, having their first and second values With equal input, the values of the corresponding pixels are recorded in the buffers 9, 9 J + 2 and 9 J + 10 to 9 J + 14 .
• the read address "i + 3" is sent via the bus 11 to the decoder 5 and the readable programmable units 3 j to 3 J + 1 s and is performed in a manner similar to that described above, This leads to the recording in the buffers 9 j + 4 to 9 J + 9 of the values of the pixels 6 1+ 3, J + 4 to 6 1+ 3, J + 9.
• the invention is not limited to the use of a programmable reading unit 3 j per column of pixels.
• a programmable reading unit 3 j can thus be associated with several columns of consecutive pixels, especially in the case where the pixels making it possible to locate the pointer in the detection plane define a plurality of segments each having a zero or low inclination angle. relative to the lines of the matrix sensor 2.
• the combination of a single readable programmable unit 3 j to several columns of consecutive pixels of the image of the detection plane can simplify the realization of the location system. It is possible to program in the memory register of the readable programmable unit associated with these columns of pixels a single line address.
• the programmable readout units are as shown in FIGS. 13 and 14.
• the arrangement of the switches 22 in the acquisition device 2 makes it possible to carry out a binomial filtering according to a dimension of the photodetector matrix, for example a filtering according to each column called "vertical filtering".
• the switches 21 connect neighboring photodetectors 20 nm in the matrix in a column and make it possible to perform vertical filtering.
• the invention makes it possible to implement binomial filtering, in two configurations, as explained below with reference to FIGS. 6a to 6e.
• the photodetectors are numbered 20 lm to 2Oio m and two neighboring photodetectors are connected via controllable switches 21k m - the film switches 21, 21 2m,
• 21 3m ... 21 9m connect respectively the photodetectors 20 lm and 2 ⁇ 2 m , 2 ⁇ 2 m and 2 ⁇ 3 m , 2 ⁇ 3 m and
• FIG. 6a shows the photodetectors 20 nm after acquisition of an image. As can be seen, only the photodetector 20m has recorded a charge which is set, for the purposes of the example, equal to one.
• the controllable switches 21,2k + i, m, of coordinate 2k + 1 according to the filtering dimension, k being a natural integer, are controlled in closing so as to connect the photodetectors 2 ⁇ 2k + i, m and 2 ⁇ 2k + 2, m , with coordinates 2k + 1 and 2k + 2 depending on the filtering dimension, for example vertical within a column.
• the charge acquired by a 20 nm photodetector is calculated by summing the charges acquired by each of the photodetectors connected by a controllable switch and dividing this sum by two. As can be seen in FIG. 6b, at the end of this operation, the photodetectors 20s m and 20m each have a charge equal to 0.5, the charge being no longer only carried by the photodetector 20 m, as before filtering.
• a second filter configuration can be applied to the photodetectors of the matrix, according to FIG. 6c.
• the switches controllable 212k, m, coordinated 2k according to the filter size, k is a natural number, are controlled in the closed so as to connect the photodetectors 20 2k, m and 202k + i, m , with 2k and 2k + 1 coordinates depending on the filtering dimension.
• the charge acquired by a photodetector 20 nm is calculated, as in the first configuration, by summation of the charges acquired by each of the photodetectors connected by a controllable switch and by dividing this sum by two.
• the photodetectors 2 ⁇ 4 m to 2 ⁇ 7 m both have a load equal to a quarter of the charge initially borne by the single photodetector 206 m .
• binomial filtering can again be performed according to the first configuration, as shown in FIG. 6d and then in the second configuration, as shown in FIG. 6e, so as to further smooth the distribution of charges.
• Each of the two filtering configurations is for example coded by an address ⁇ 1, respectively ⁇ 2.
• ⁇ 1 and ⁇ 2 are in the example described particular pixel line addresses, these addresses being dedicated to binomial filtering.
• ⁇ l corresponds for example in hexadecimal code to the address 00 and ⁇ 2 to the address FF.
• the sending by the digital processing unit 4 of one of these addresses to the image acquisition device 2 and to the programmable reading units causes the closing of the controllable switches 2 1 and 2k of index 2k according to the dimension or filter 21 n, i + 2k 2k + l index, according to the filter configuration.
• Differential reading The invention can also allow the removal of ambient light by implementing a differential reading.
• FIG. 7 illustrates in the form of a timing diagram an example of differential reading according to which: a first image of a part of the detection plane is acquired when the field of observation of the photodetector matrix is illuminated by an artificial light source; acquires a second image of the same part of the detection plane in the absence of illumination by the light source, and eliminates the noise component related to ambient lighting by subtracting the second image to the first image, by example using a differential amplifier.
• the ambient lighting even when it is intense, remains largely stationary, so that if the image acquisition speed is high, the influence of the ambient light can be strongly attenuated after subtraction of the first and second images.
• the differential reading is applied to one line of pixels at a time but it can go differently.
• the digital processing unit 4 is, for example, configured to send the acquisition device 2 and the programmable electronic circuit 3 the address AD1 of a first pixel line of the image of the detection plane to be processed.
• the digital processing unit 4 can cause the erasure of the charges that would have previously been acquired by the photodetectors 20, this corresponding charge erasure on the timing chart at the activation of the signal RST.
• the digital processing unit 4 can then cause the illumination of the field of view of the acquisition device 2 by the artificial light source.
• the latter is for example a light-emitting diode whose state is represented on the timing diagram of FIG. 7 by the LED signal.
• the digital processing unit 4 then causes the acquisition by the image acquisition device 2 of a first image of the processed line and the recording of the values of the pixels of the line acquired by the programmable electronic circuit, such as for example shown in one of Figures 3b to 3d, which corresponds in the timing chart to the activation of the RDI signal.
• the digital processing unit can then cause erasure of the charges acquired by the photodetectors during the previous step and cause the extinction of the artificial light source.
• the digital processing unit 4 can then cause the acquisition by the image acquisition device of a second image of the processed line and the recording by the programmable electronic circuit 3 of the values of the pixels of the acquired line, which corresponds in the timing diagram to the activation of the signal RD2.
• the digital processing unit 4 for example sends the address of the next line of pixels to be processed and the steps described above are reproduced.
• FIG. 9 shows an example of implementation of differential reading in a matrix sensor 1 according to the invention.
• each readable readout unit 3 j is associated with a column of pixels and is as shown in Figure 14, having a memory register 7 ,, comparator 8, and two buffers 9a, and 9b.
• the assembly 9a formed by the joining of the buffers 9a of each readable programmable unit 3 j contains, for example, the values of pixels recorded according to the method described above during the processing of the first image acquired with illumination of the artificial light source. .
• the assembly 9b formed by the meeting of the buffers 9b, of each readable programmable unit 3 j contains for example the values of pixels recorded according to the method described above during the processing of the second image acquired without illumination by the artificial light source. .
• the invention implements in the example described a sequential reading of the contents of memory sets 9a and 9b by a shift register 15 whose state is represented in FIG. 9 by the signal HD. Zeroing this HD signal causes the previously acquired information to be erased by the shift register.
• the shift register Upon reception by the shift register of the clock signal HCLK, the shift register reads the contents of a buffer memory 9a, or 9b,.
• the signal OUTP corresponding to the reading of the set 9a associated with the first image and the signal OUTN corresponding to the reading of the set 9b associated with the second image is also represented in the timing diagram of FIG. 9.
• the information read in the memory sets 9a and 9b can then be subjected to a subtraction processing, for example by means of a differential amplifier connected to the read buses of the memory assemblies 9a and 9b.
• the differential reading can be implemented by acquiring, during an on / off cycle of the artificial light source only a line of pixels of the first image and the second image and proceeding by iteration for each row of pixels to acquire.
• FIG. 10a shows a timing diagram corresponding to such a differential reading example.
• the digital processing unit 4 firstly causes the erasure of the charges previously acquired by the photodetectors 20 of the acquisition device 2 and the activation of the artificial light source, which causes corresponds respectively to the timing diagram of FIG. 10a at the activation of the signal RST and the signal LED
• the digital processing unit then sends the acquisition device 2 and the programmable electronic circuit 3 the addresses ⁇ 1 and ⁇ 2 associated with the two vertical binomial filtering configurations.
• the digital processing unit 4 then sends the acquisition device 2 and the programmable electronic circuit 3 the ADl address of the pixel line to be processed, then activates the RDI signal.
• the activation of the signal RD 1 successively causes: the acquisition by the acquisition device 2 of the address line AD1 of the first image, the vertical binomial filtering of the electrical charge recorded by the photodetectors of the acquisition device according to the two configurations, according to the addresses ⁇ 1 and ⁇ 2 previously received and - the reading by the programmable electronic circuit 3 of the pixel values of this line for locating the pointer in the image of the detection plane.
• the values of these pixels are recorded in the buffers 9aj as previously described.
• the digital processing unit 4 then causes the erasure of the charges previously acquired by the photodetectors and the extinction of the artificial light source, which respectively corresponds in the timing diagram of FIG. 10a to the activation of the RST signal and to the deactivation of the LED signal.
• the digital processing unit 4 then sends to the sensor 1 and the programmable electronic circuit 3 the addresses ⁇ 1 and ⁇ 2 associated with the two vertical binomial filtering configurations and then activates the signal RD2.
• the activation of the signal RD2 successively causes: the acquisition by the acquisition device 2 of the address line AD1 of the second image, the vertical binomial filtering of the electric charge recorded by the photodetectors of the acquisition device according to the two configurations, according to the previously received addresses ⁇ 1 and ⁇ 2 and, the reading by the programmable electronic circuit 3 pixel values of this line for locating the pointer in the image of the detection plane.
• the values of these pixels are recorded in the buffers 9bj, as previously described.
• the invention is not limited to carrying out binomial filtering according to its two configurations prior to processing the first and second images. As a variant, it could only be previously done according to only one of the binomial filtering configurations. In another variant, no binomial filtering is performed before acquisition of the first and second images.
• an on / off cycle of the artificial light source corresponds to the acquisition of first and second images only of a single line of pixels.
• FIG. 10b Another example of implementation of differential filtering according to the invention is shown in FIG. 10b.
• a single on / off cycle of the artificial light source makes it possible to acquire all the lines of pixels.
• the charges previously acquired by each photodetector are first erased by sending the address of each line and activating the signal RST for each of these lines.
• the digital processing unit 4 then fires the artificial light source and then extinguishes it.
• the addresses ⁇ 1 and ⁇ 2 are sent, similar to what has been described with reference to FIG. 10a.
• the address AD1 is then sent, which causes the reading of the pixels of the address line AD1 making it possible to locate the pointer in the image of the detection plane, in accordance with what has been described with reference to FIGS. 3a to 3d , then the RST signal is activated, causing the erasure of the electric charges acquired.
• the first image is thus acquired at the end of a single ignition / extinction cycle of the artificial light source.
• the addresses ⁇ 1 and ⁇ 2 are then sent again as well as the line addresses, which allows the acquisition of the second image.
• each readable readout unit 3 j is associated with several successive column addresses, eight in the example described.
• Each readable readout unit 3 j has a memory register 7 ,, a comparator 8, and eight pairs of buffers 9a, at 9a, J + 7 and 9b, at 9b J + 7
• a line address is programmed in the memory register 7 J5 this programmed line address being common to the eight columns of column address pixels between j and j + 7.
• the sending by the digital processing unit 4 via the bus 11 of a read address is received at the input by each readable readable unit 3 j which transmits it to the comparator 8, the latter verifying if this received address is equal to that programmed in the memory register 7, associated with the eight column address columns between j and j + 7.
• the device represented in FIG. 12 comprises two buffers 9a, and 9b, associated with each column, the buffers 9a, and 9b respectively relating to a first image and to a second image of the detection.
• the expression "having one” shall be understood as being synonymous with the expression “containing at least one”, except when the opposite is specified.

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• Transforming Light Signals Into Electric Signals (AREA)

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