WO2017143742A1 - Tft平板图像传感器的图像采集方法 - Google Patents

Tft平板图像传感器的图像采集方法 Download PDF

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Publication number
WO2017143742A1
WO2017143742A1 PCT/CN2016/095847 CN2016095847W WO2017143742A1 WO 2017143742 A1 WO2017143742 A1 WO 2017143742A1 CN 2016095847 W CN2016095847 W CN 2016095847W WO 2017143742 A1 WO2017143742 A1 WO 2017143742A1
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time
signal
driving
period
chip
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PCT/CN2016/095847
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English (en)
French (fr)
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凌严
朱虹
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上海箩箕技术有限公司
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Priority to US15/550,583 priority Critical patent/US10044965B2/en
Publication of WO2017143742A1 publication Critical patent/WO2017143742A1/zh

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    • 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
    • H04N25/75—Circuitry for providing, modifying or processing image signals from the pixel array
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers
    • H01L27/12—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being other than a semiconductor body, e.g. an insulating body
    • H01L27/1214—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being other than a semiconductor body, e.g. an insulating body comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
    • H01L27/124—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being other than a semiconductor body, e.g. an insulating body comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs with a particular composition, shape or layout of the wiring layers specially adapted to the circuit arrangement, e.g. scanning lines in LCD pixel circuits
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
    • H04N25/50—Control of the SSIS exposure
    • H04N25/57—Control of the dynamic range
    • H04N25/58—Control of the dynamic range involving two or more exposures
    • H04N25/587—Control of the dynamic range involving two or more exposures acquired sequentially, e.g. using the combination of odd and even image fields
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/30—Transforming light or analogous information into electric information
    • H04N5/32—Transforming X-rays
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/18—Printed circuits structurally associated with non-printed electric components

Definitions

  • the present invention relates to the field of TFT flat panel image sensors, and more particularly to an image acquisition method for a TFT flat panel image sensor.
  • CMOS image sensors cannot fully meet the market demand.
  • the largest wafer in the current silicon-based CMOS process is 12 inches, and the production cost of the 12-inch production line is still relatively high, while the low-cost production line is mainly 8-inch, 8 The production cost of the inch production line is still too high for the market demand.
  • TFT Thin Film Transistor
  • the optical signal is usually concentrated by a focusing lens to a small image plane for photoelectric conversion, which is a conventional imaging method of a CMOS sensor and a CCD sensor.
  • the more common X-ray flat panel image sensor has a large pixel area, which can be as large as 17 inches by 17 inches. If you use a CMOS image sensor to make it, you need a lot of small sensors to be spliced together, and the cost is very high. Therefore, the TFT flat panel image sensor can greatly reduce the cost.
  • Optical fingerprint sensors as a general consumer product, require lower cost and require as thin a structure as possible, so instead of using a focusing lens, a similar flat panel image sensor is used. Therefore, optical fingerprint sensor products using TFT flat panel image sensors have been available.
  • the TFT flat panel image sensor is formed on a substrate (glass, stainless steel, or plastic) through an amorphous silicon thin film transistor (a-Si TFT) or a low temperature polysilicon thin film transistor (Low Temperature Poly Silicon Thin Film Transistor, A pixel region and a peripheral region circuit are fabricated by an LTPS TFT or Oxide Semiconductor Thin Film Transistor (OS TFT) technology.
  • a-Si TFT amorphous silicon thin film transistor
  • a low temperature polysilicon thin film transistor Low Temperature Poly Silicon Thin Film Transistor
  • the pixel signal amplification and digital-to-analog conversion functions are usually realized by an external chip, which is usually called a readout IC (ROIC). That is to say, the pixel electronic signal of the TFT flat panel image sensor is connected to the external signal readout chip through the data line, and the signal readout chip performs photoelectric conversion and signal processing to realize image acquisition.
  • ROIC readout IC
  • the external mode of the signal readout chip is mainly divided into three cases: in the first case, the chip direct COG (Chip On Glass) is bound to the TFT flat panel image sensor; the second case, the chip Directly bonded to a Flexible Printed Circuit (FPC), then the flexible printed circuit board is bonded to the TFT flat panel image sensor; the third case: the chip is directly bonded to a Printed Circuit Board (PCB) The above rigid printed circuit board is then bonded to the TFT flat panel image sensor by another flexible printed circuit board.
  • FPC Flexible Printed Circuit
  • the TFT flat panel image sensor includes a substrate 10 and a signal readout chip (not shown), and is located on the substrate 10.
  • the device layer on the top (not labeled).
  • the device layer is fabricated on a substrate 10 which is glass, stainless steel, or plastic.
  • the device layer has a pixel array region and a peripheral circuit region, and the device layer is fabricated by a technical process of an amorphous silicon TFT, a low temperature polysilicon TFT, or an oxide semiconductor TFT.
  • the pixel array area has a plurality of data lines 11 and a plurality of scan lines 12, and the data lines 11 and the scan lines 12 define a grid arranged in an array, and the area where the grid is located corresponds to the pixels 13.
  • the pixel 13 includes at least one pixel switch 131 (the pixel switch 131 is typically a TFT device), and at least one device 132 (such as a photosensitive device, an electrode plate, a thermal device, etc.).
  • Device 132 is used to collect external input signals (such as light, electrostatic fields, heat, etc.) and convert them into electrical signals, which are then stored in pixels 13.
  • the pixel switch 131 is turned on, the electrical signal in the device 132 is conducted to the data line 11, and then the external signal readout chip realizes signal acquisition.
  • the scan line is controlled by a peripheral driving circuit to realize progressive opening of the pixel switch 131.
  • the driving circuit is an external driving chip or integrated in the device layer in a manner of a TFT device circuit.
  • the external driver chip is also divided into three cases: in the first case, the chip is directly bound to the periphery of the TFT flat panel image sensor; in the second case, the chip is directly bonded to the flexible printed circuit board, and then the flexible printing The board is bonded to the TFT flat panel image sensor; the third case: the chip is directly bonded to the rigid printed circuit board, and then the rigid printed circuit board is bonded to the TFT flat panel image sensor through another flexible printed circuit board.
  • the image acquisition method of the existing TFT flat panel image sensor needs to be improved.
  • the problem to be solved by the present invention is to provide an image acquisition method for a TFT flat panel image sensor to improve the stability of the signal readout chip and reduce the design difficulty of the entire circuit system.
  • the present invention provides an image acquisition method for a TFT flat panel image sensor, the TFT flat panel image sensor comprising: a substrate and a signal readout chip, and a device layer on the substrate; the device layer includes an array row a plurality of pixels of the cloth, and a plurality of data lines and a plurality of scan lines; wherein each of the pixels passes through a column of the pixels a pixel switch is connected to the same data line; in the row of pixels, the pixel switch connected to each of the pixels is connected to the same scan line; and the image collecting method includes: setting the signal a signal acquisition period of the read chip is a first period; setting a time for the scan line to complete one drive is a drive time; setting a length of time of the first period and the driving time is equal; setting a mth The end time of the first period overlaps with the start time of the m+1th first period, where m is a positive integer; the end time of the nth driving time and the n+1th setting
  • the first period includes: a first operation time for performing an operation of clearing a data line signal; a second operation time for performing a first signal sampling operation; and a third operation time for performing a second operation time a sub-signal sampling operation; setting the i-th first period to start before the i-th driving time, and the starting time interval of the two is less than the length of time of the two, where i is a positive integer; setting the jth During the first operation time and the second operation time of the first period, the j-1th driving time is correspondingly performed; the third operation time of the jth first period During the execution, the jth driving time is correspondingly performed; wherein j is an integer of 2 or more.
  • the scanning line corresponding to the k-1th driving time still controls the pixel switch to remain in an on state, thereby And causing, at the first operation time of the kth first period, to perform a clear signal operation on the pixels of the corresponding row, where k is an integer of 2 or more.
  • the signal reading chip performs a difference between the signal obtained by the second signal sampling operation and the signal obtained by the first signal sampling operation, and the obtained result is output as a final signal.
  • the first period further includes a signal release time after the second operation time and before the third operation time.
  • a first interval time is between the start time of the first period and the first operation time
  • the second interval time is between the first operation time and the second operation time
  • a third interval between the second operation time and the third operation time Time
  • a fourth interval time between the third operation time and an end time of the first cycle
  • the third interval time including the signal release time
  • the signal release time ensures that more than 80% of the electronic signals in the pixels of the corresponding row are transmitted to the signal readout chip.
  • the driving circuit of the scan line is an external driving chip or integrated in the device layer in a manner of a TFT device circuit.
  • the signal reading chip is directly bound to the substrate by using a COG method, or the signal reading chip is bound to an external printed circuit board electrically connected to the TFT flat panel image sensor.
  • the external driving chip is directly bonded to the substrate by using a COG method, or the external driving chip is bound to an external printed circuit board electrically connected to the TFT flat panel image sensor.
  • setting a signal acquisition period of the signal readout chip to a first period; setting a time when the scan line completes one drive is a driving time; setting the first period and the The length of time of the driving time is equal; setting an end time of the mth first cycle to overlap with a start time of the m+1th first cycle, where m is a positive integer; setting the nth The end time of the driving time overlaps with the start time of the n+1th driving time, where n is a positive integer.
  • the majority of the electrons come from the electrons released when the pixel switch is turned off, thus achieving almost cancel each other out of the extracted electrons and the released electrons, thereby minimizing the amount of electrons extracted or released when the pixel switch is turned on or off.
  • the charge impact of the pixel switch on the signal readout chip is reduced, the stability of the signal readout chip is improved, and the design difficulty of the entire circuit system is reduced.
  • FIG. 1 is a schematic structural view of a portion of a conventional TFT flat panel image sensor
  • FIG. 2 shows a corresponding driving sequence diagram of the TFT flat panel image sensor of FIG. 1 when the existing image capturing method is used;
  • Figure 3 is a diagram showing the specific time included in the first cycle of Figure 2;
  • FIG. 4 is a corresponding driving timing diagram of the TFT flat panel image sensor of FIG. 1 when the image capturing method provided by the embodiment of the present invention is used;
  • Figure 5 is a graph showing the specific time included in the first cycle of Figure 4.
  • the driving timing includes the driving timing of the scanning line and the driving timing of the signal sensing chip
  • each scanning line 12 shown in FIG. 1
  • the line 12z, the scanning line 12a, the scanning line 12b, the scanning line 12c, and the scanning line 12d, but only the scanning line 12a, the scanning line 12b, and the scanning line 12c and the nth scanning line 12n not shown in FIG. 1 are shown in FIG.
  • the driving timing is turned on line by line, the driving time of each scanning line 12 is the driving time B, and the signal acquisition period of the signal reading chip (labeled as ROIC in the timing chart) is the first period A of the signal.
  • the driving time of the scanning line 12a is before the driving time of the scanning line 12b
  • the driving time of the scanning line 12b is before the driving time of the scanning line 12c.
  • the signal readout chip (the corresponding signal line in Fig. 2 is labeled as the signal readout chip) corresponds to the progressive signal acquisition.
  • FIG. 3 shows a more specific timing diagram of the signal readout chip and the scan line 12 (specifically, two adjacent scan lines - scan line 12a and scan line 12b), specifically showing the first period. For each part of A, the situation of more scan lines can be analogized.
  • a signal acquisition period of the signal readout chip generally includes three actions, namely: clearing the data line signal action, corresponding to the first operation time R1; the first signal sampling action, Corresponding to the second operation time R2; the second signal sampling action corresponds to driving the third time R3.
  • the scan lines 12 are respectively turned on line by row, and the drive time B of one scan line 12 corresponds to a signal first period A of the signal read chip.
  • Each drive time B is after the second operation time R2 before the third time R3 is driven.
  • the pixel switch 131 corresponding to the scan line 12 (the pixel switch 131 is a TFT device as described above) is turned on and off, a large amount of charge is extracted and discharged from the data line 13. Many times, this extracted and released charge is much larger than the image signal produced by the pixel 13 itself.
  • the internal circuit of the signal readout chip needs to be continuously connected to the data line 11, and therefore, the extraction and release of the charge of the pixel switch 131 are directly related to the signal read. Out of the chip internal circuit. Therefore, the on and off of the pixel switch 131 have a large charge shock to the signal readout chip, thereby affecting its stability and response speed.
  • the pixel signal i.e., electronic signal
  • the signal readout chip needs to be designed to be very sensitive to make a large amplification of the input signal. The more sensitive the signal readout chip is, the less the amount of charge that can withstand the charge impact, which makes the signal readout chip more susceptible to the charge of the pixel switch being turned on or off, that is, the poorer the stability of the signal readout chip. .
  • the present invention provides a new image acquisition method for a TFT flat panel image sensor, which reduces the charge impact of the pixel switch on the signal readout chip by the cooperation of the scan line drive timing and the signal readout chip drive timing.
  • the stability of the signal readout chip reduces the design difficulty of the entire circuit system.
  • Embodiments of the present invention provide an image acquisition method for a TFT flat panel image sensor. Please refer to FIG. 1, FIG. 4 and FIG. 5 in combination.
  • the structure of the TFT flat panel image sensor can be referred to FIG. 1 (which can be combined with reference to the background art), which includes a substrate 10 and a signal readout chip (not shown), and a device on the substrate 10.
  • Layer (not labeled).
  • the substrate material is glass, stainless steel, or plastic, and the device layer is fabricated by an amorphous silicon TFT, a low temperature polysilicon TFT, or an oxide semiconductor TFT technology.
  • the device layer includes a plurality of pixels 13 arranged in an array, and a plurality of data lines 11 and a plurality of scan lines 12.
  • the device layer includes a pixel array area, and the pixel array area is an area where the pixel 13 is located.
  • Pixel 13 is used for the reception, conversion and temporary storage of optical signals.
  • the plurality of data lines 11 and the plurality of scan lines 12 define a grid (not labeled), and the pixels 13 are located in the grid (i.e., one of the grids has a pixel 13).
  • the pixel 13 includes at least one pixel switch 131 (the pixel switch 131 is typically a TFT device), and at least one device 132 (such as a photosensitive device, an electrode plate, a thermal device, etc.).
  • Device 132 is used to collect external input signals (such as light, electrostatic fields, heat, etc.) and convert them into electrical signals, which are then stored in pixels 13.
  • external input signals such as light, electrostatic fields, heat, etc.
  • the electrical signal in the device 132 is conducted to the data line 11, and then the external signal readout chip realizes signal acquisition.
  • the scan line is controlled by a peripheral driving circuit to realize progressive opening of the pixel switch 131.
  • the driving circuit is an external driving chip or integrated in the device layer in a manner of a TFT device circuit.
  • the TFT flat panel image sensor may be an optical image sensor (including an optical fingerprint sensor, etc.), an X-ray flat panel image sensor, or other flat panel image sensor, as long as it is based on amorphous silicon.
  • the flat panel image sensor of the low temperature polysilicon/oxide semiconductor can be (not limited to an optical image sensor, nor is it limited to a fingerprint sensor).
  • each of the pixels 13 may have a light transmitting region and a non-light transmitting region.
  • the non-transmissive region may have a photosensitive element 132.
  • the light transmissive region enables light to pass through the TFT device layer.
  • each of the pixels 13 may also be a non-transparent area, which is usually The visible light does not pass through the TFT device layer.
  • the TFT flat panel image sensor is an X-ray flat panel image sensor, especially a low dose dynamic X-ray sensor, as described above
  • the corresponding signal readout chip needs to be designed to be sensitive to greatly enlarge the input signal. .
  • X-rays have certain damage to the human body.
  • the X-rays that are irradiated to the human body per unit time cannot be too high, that is, they cannot be illuminated with strong X-rays, and the total length (for example, 1 year)
  • the amount of X-ray exposure should not be too high. That is, it is not possible to use a strong X-ray, or to use a very low X-ray for a long time.
  • X-ray intensity can be larger, and a static X-ray sensor can be used; and sometimes, continuous filming is required.
  • a static X-ray sensor can be used; and sometimes, continuous filming is required.
  • dynamic real-time monitoring during the interventional procedure cardiac stent surgery, radiotherapy surgery pre-positioning, etc.
  • the intensity of each X-ray corresponds to very low, only a few tenths of a static X-ray.
  • the sensor used at this time is called a low-dose dynamic X-ray sensor.
  • FIG. 1 specifically shows five scanning lines 12 as representatives (the number of all scanning lines 12 may be more).
  • the five scanning lines 12 are a scanning line 12z, a scanning line 12a, a scanning line 12b, a scanning line 12c, and a scanning line 12d, respectively.
  • the scan line 12z is a virtual scan line.
  • the scan line 12z is located at the lowermost side (or the outermost side) of all the scan lines 12, and is used to ensure that the most downstream (or outermost) pixels 13 and the pixels 13 of other rows are in the same structural environment as much as possible.
  • the substrate 10 may be a light transmissive substrate or a non-transparent substrate.
  • the substrate 10 may be a glass material, a plastic material, or a stainless steel material or the like.
  • the pixel 13 further includes at least one pixel switch 131, and at least one device 132 (the device 132 may be, for example, a photosensitive device, an electrode plate, a heat sensitive device, etc., which is selected as a photosensitive device in this embodiment, and the photosensitive device
  • the device can include a photodiode).
  • the pixel switch 131 can typically be a TFT device (TFT switch).
  • Device 132 can be used to collect external input signals (such as light, electrostatic fields, and heat, etc.) It is converted into an electrical signal and then stored in the pixel 13.
  • external input signals such as light, electrostatic fields, and heat, etc.
  • the electronic signal in the pixel 13 is conducted to the corresponding data line 11, and then the signal is transmitted to the outside.
  • the chip is read out to realize fingerprint image signal acquisition.
  • the device layer (which may be referred to as a TFT device layer due to various TFT processes) may also include a portion of peripheral circuits.
  • the partial peripheral circuit includes a driving circuit, a signal sensing chip bonding area (not labeled), and a flexible printed circuit board bonding area, and between the signal sensing chip binding area and the flexible printed circuit board binding area Connection lines (each connection line is not shown in Figure 1).
  • the fabrication process of the device layer may be a semiconductor process such as an amorphous silicon TFT process, a low temperature polysilicon TFT process, or an oxide semiconductor TFT process.
  • the signal reading chip may be directly bonded to the substrate 10 by using a COG method (the binding position may be on the device layer of the substrate 10 or may not be in the device layer). Upper) such that the signal reading chip is electrically connected to the data line 11.
  • the signal readout chip can also be electrically connected to the data line 11 on the substrate 10 by being bonded to a corresponding external printed circuit board.
  • the chip is directly bonded to the flexible printed circuit board, and then the flexible printed circuit board is bound to the TFT flat panel image sensor; the second case: the chip is directly bonded to the rigid printed circuit board, The rigid printed circuit board is then bonded to the TFT flat panel image sensor by another flexible printed circuit board.
  • each pixel 13 is connected to the same data line 11 through one pixel switch 131. Further, in the row of pixels 13, the pixel switch 131 to which each pixel 13 is connected is connected to the same scanning line.
  • the purpose is to make the pixel switch 131 connected to each pixel 13 in the row of pixels 13 to be scanned by the same scanning.
  • Drive control of line 12 ie a line image In the pixel 13, the pixel switch 131 connected to each of the pixels 13 is in an on state, or both are in an off state, or both are switched between the two states, and the same scanning line is connected by them. 12 drive controls.
  • the pixel switch 131 is generally a TFT device, it is only necessary to ensure that the gate of the pixel switch 131 to which each pixel 13 is connected is connected to the same scan line 12 in a row of pixels 13, so that "each pixel 13 is connected"
  • the pixel switch 131 is controlled by the drive of the same scanning line 12.
  • FIG. 4 shows the driving sequence corresponding to the image capturing method of the TFT flat panel image sensor of FIG. 1 (the driving sequence includes the driving timing of the scanning line and the driving timing of the signal sensing chip), and the scanning line is shown in FIG. 12z, scan line 12a, scan line 12b, scan line 12c, and scan line 12d, but the drive of scan line 12a, scan line 12b, scan line 12c, and nth scan line 12n not shown in FIG. 1 is shown in FIG. Timing.
  • the image acquisition method includes: setting a signal acquisition period of the signal readout chip to a first period A; setting a scan line 12 to complete a driving time as a driving time B; setting a first period A and The driving time B is equal in length; the end time of the mth first period A is overlapped with the starting time of the m+1th first period A (ie, the mth first period A and the m+1th number) There is no time interval between one cycle A), where m is a positive integer; the end time of the nth drive time B is set to overlap with the start time of the n+1th drive time B (ie, the nth drive time B and There is no time interval between the n+1th driving time B), where n is a positive integer; setting the i-th first period starts before the ith driving time, and the starting time interval of the two (or the time difference between the start times of the two) is less than the length of time of the two, where i is a positive integer (for example, when i is equal
  • the present embodiment makes the time lengths of the first period A and the driving time B equal, but the starting point (starting point, that is, the starting time) is shifted, and the starting point of each driving time B falls during the period of the first period A. That is to say, in the present embodiment, the scan lines 12 are turned on row by row (the scan line 12 is turned on row by row does not mean that the scan lines 12 of adjacent rows in the structural position are sequentially turned on, that is, the guides of the scan lines 12 of the respective rows. Pass time can not be based on structural position In order, as long as one line of scan lines 12 is turned on, another line of scan lines 12 is turned on. The signal readout chip performs signal acquisition successively, but the time of the two does not coincide.
  • the scan line 12 By setting the scan line 12 to be turned on line by line, and ensuring that adjacent lines do not overlap (ie, the drive time B between different scan lines does not overlap), so as to avoid crosstalk of pixel signals of different rows; and simultaneously ensure adjacent conduction in time. There is no interval between the scan lines 12 (the end time of the previous line happens to be the start time of the current line), that is, when the previous row of pixel switches 131 is just turned off, the current row of pixel switches 131 is just turned on, thereby implementing different rows of pixel switches 131.
  • the first period A specifically includes:
  • a first operation time R1 (shown by the first narrow elongated bar from the left in the first cycle A) for performing the operation of clearing the data line 11 signal;
  • a second operation time R2 (shown by a second narrow slender strip from the left in the first period A) for performing the first signal sampling operation
  • the third operation time R3 (shown by the third narrow slender square from the left in the first period A) is used to perform the second signal sampling operation.
  • the first interval time (not labeled) is between the start time of the first period A and the first operation time R1
  • the second interval time E is between the first operation time R1 and the second operation time R2.
  • the role of the first operation time R1 is to clear the upper row of pixels 13 on the data line 11 and the letter
  • the signal residual on the readout chip circuit prepares for the next line of signal acquisition, thereby ensuring that the signals sampled by the subsequent second operation time R2 are stable and consistent.
  • the purpose of the second operation time R2 sampling is to collect the background signal for subsequent operations such as performing a difference with the pixel integrated signal, thereby subtracting the influence of the background signal on the final signal.
  • the third operation time R3 samples the acquired signal (this signal is the pixel integrated signal) including the (background) signal sampled by the second operation time R2 and the output signal of the pixel.
  • the first signal sampling is started, that is, the second operation time R2 is entered.
  • the length of the second interval E is related to the design of the actual signal readout chip and the parasitic parameters of the data line 11 (e.g., capacitance and resistance, etc.).
  • One of the purposes of setting the second interval time E is to stabilize the circuit of the signal readout chip, thereby ensuring stable and efficient sampling when the subsequent second sampling time R2 performs the first signal sampling operation.
  • the first period A further includes a signal release time F after the second operation time R2 and before the third operation time R3.
  • the third interval time includes a signal release time F, that is, the signal release time F is a part of the third interval time.
  • the signal reading chip performs a difference between the signal sampled by the third operation time R3 (ie, the pixel integrated signal) and the signal sampled by the second operation time R2 (ie, the background signal) as a final signal. , output out, to achieve analog to digital conversion.
  • the purpose of the two sampling is to remove the low-frequency noise of the analog circuit (including the internal analog circuit of the signal readout chip, the data line 11 and the pixel 13 circuit, etc.) and the difference between the channels inside the signal read chip, etc., to increase the fingerprint collected.
  • the signal to noise ratio of the image That is, the signal readout chip performs a difference between the signal obtained by the second signal sampling operation and the signal obtained by the first signal sampling operation, and the obtained result is output as a final signal, thereby making the final signal output accurate. More sexual.
  • the signal release time F is only required to ensure 80% of the pixels 13 of the corresponding row.
  • the above electronic signal can be transmitted to the signal readout chip.
  • all the electronic signals are transmitted, which requires an infinite amount of time. Therefore, as long as a sufficient number of signals in the pixel are released in the actual application, this embodiment can be used. It is sufficient to ensure that more than 80% of the electronic signals are transmitted to the signal readout chip.
  • the j-1th driving time B is correspondingly performed; the first stage of the jth first period A During the third operation time R3, the jth driving time B is correspondingly performed; where j is an integer of 2 or more.
  • the above process is: when the first operation time R1 and the second operation time R2 of the second first period A are set, the first drive is performed correspondingly (the same time).
  • One of the time B (corresponding to the driving time B of 12a in FIG. 5) (substantially the latter part of the first driving time B), and the third operating time R3 of the second first period A are performed during the same time.
  • a part of the second driving time B (corresponding to the driving time B of 12b in FIG.
  • the second driving time B (corresponding to the driving time B of 12b in FIG. 5) is performed correspondingly.
  • One of the parts (corresponding to the latter part of the second driving time B) is performed, and the third driving time R3 of the third first period A is performed, and the third driving time B is performed correspondingly (corresponding to the figure) Part of the drive time B) of 12c in 5 (corresponding to approximately the third drive time) The front part of B); continuously in this way.
  • FIG. 5 shows the cooperation between the driving time of the scanning line and the signal reading of the signal reading chip.
  • the k-1th driving time B corresponds to The scan line 12 still controls the pixel switch 131 to remain in an on state, where k is an integer greater than 2, such that at the first operational time R1, the clearing signal operation is simultaneously performed on the pixels 13 of the corresponding row.
  • the scan line 12a corresponding to the first driving time B still controls the pixel switch 131 to remain in an on state, thereby causing
  • the pixel 13 of the corresponding row is simultaneously cleared.
  • the scan line 12b corresponding to the second driving time B still controls the pixel.
  • the switch 131 remains in an on state, so that at the first operation time R1, the clearing signal operation is simultaneously performed on the pixels 13 of the corresponding row.
  • nth scan line 12 and the n+1th scan line 12 do not refer to the case of two adjacent scan lines, but refer to the temporal relationship, regardless of the position. That is, the nth scan line 12 and the n+1th scan line 12 may be two adjacent scan lines 12 or two scan lines 12 separated by one or more lines.
  • the present embodiment makes the first period A and the driving time B of each scanning line 12 match each other.
  • the row driving of the pixel 13 (ie, driving the scan line 12) is relatively simple, and can be implemented by an external driving chip, that is, the scanning line of the pixel array region is connected to the external driving chip.
  • the driving circuit of the scan line 12 can be integrated in the device layer in the manner of a TFT device circuit.
  • the driving circuit of the scan line 12 is an external driving chip
  • the external driving chip may be directly bonded to the substrate 10 by COG (to electrically connect the scanning line 12), or be bound to the corresponding external printed circuit board.
  • Upper to electrically connect to scan line 12 on substrate 10).
  • the external driving chip For the external driving chip to be bound to the corresponding external printed circuit board, there are two cases: in the first case, the chip is directly bonded to the flexible printed circuit board, and then the flexible printed circuit board is bound to the TFT flat panel. Image sensor; the second case: the chip is directly bonded to the rigid printed circuit board, and then the printed circuit board is bonded to the TFT flat panel image sensor through another flexible printed circuit board.
  • the channel layer of the pixel switch 131 is required.
  • the circuit connected to the drain and the source ie, the data line, etc.
  • the pixel switch 131 is switched from off to on, it is necessary to extract electrons from the circuit connected to the drain and the source, and inject into the pixel switch 131.
  • the channel layer In the channel layer. Therefore, when the pixel switch 131 is turned off and turned on, electrons are released and extracted to the signal readout chip, thereby generating a charge shock and affecting the stability of the signal readout chip.
  • the first period A and the driving time B are mutually matched by the corresponding image acquisition method, so that when one row of the pixel switches 131 is switched from on to off, another row of the pixel switches 131 is disconnected.
  • the electrons extracted when the pixel switch 131 is turned on may basically come from the electrons released when the pixel switch 131 is turned off, thereby achieving mutual cancellation of the extracted electrons and the released electrons, thereby minimizing the pixel switch 131.
  • the amount of extracted or released electrons generated when turned on or off reduces the charge shock of the pixel switch 131 on the signal readout chip, improves the stability of the signal readout chip, and reduces the design difficulty of the entire circuit system.

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Abstract

一种TFT平板图像传感器的图像采集方法，所述图像采集方法包括：设定所述信号读出芯片的一个信号采集周期为第一周期；设定一条所述扫描线完成一次驱动的时间为驱动时间；设定所述第一周期和所述驱动时间的时间长度相等；设定第m个所述第一周期的结束时刻与第m+1个所述第一周期的开始时刻重叠，其中m为正整数；设定第n个所述驱动时间的结束时刻与第n+1个所述驱动时间的开始时刻重叠，其中n为正整数。所述图像采集方法提高所述信号读出芯片的稳定性，降低整个电路系统的设计难度。

Description

TFT平板图像传感器的图像采集方法
本申请要求于2016年2月26日提交中国专利局、申请号为201610107910.9、发明名称为“TFT平板图像传感器的图像采集方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及TFT平板图像传感器领域，尤其涉及一种TFT平板图像传感器的图像采集方法。
背景技术
随着硅基CMOS技术的飞速发展，硅基CMOS电路产品的性能效果大幅提升，生产效率大大提升，CMOS图像传感器的制作成本也因此大大降低。但是，CMOS图像传感器的制作成本还是无法完全满足市场需求。例如对于CMOS图像传感器而言，由于目前硅基CMOS工艺的最大晶圆(wafer)是12英寸，并且12英寸产线的制作成本仍比较高，而低成本的生产线还是以8英寸为主，8英寸产线的制作成本对于市场需求而言还是太高。
而TFT(Thin Film Transistor，薄膜晶体管)图像传感器成本可以做到更低。这是因为，TFT工艺的生产线，基板都是在1米×1米左右，甚至达到3米×3米左右。基板越大，就可以切割的单个产品越多，单个产品的最终成本就越低。
在图像传感器领域中，为了降低传感器成本，减小机构尺寸，通常通过聚焦透镜将光信号聚集到很小的像面的再进行光电转化，这就是传统的CMOS传感器和CCD传感器等的成像方式。
但是有些领域，为了提高图像性能，优化结构设计，就不能使用聚焦透镜，而是1比1成像，比如X射线平板图像传感器。此处的“平板”的含义就是指入射光信号没有经过聚焦，而是1比1直接成像。
比较常见的X射线平板图像传感器的像素区面积都很大，大的可以达到17英寸×17英寸。如果使用CMOS图像传感器来制作，就需要很多个小的传感器拼接而成，成本就非常高。所以用TFT平板图像传感器就可以大大降低成本。
而光学指纹传感器作为一种通常消费品，要求成本就更低，同时要求结构上尽量薄，所以也都不使用聚焦透镜，而是使用类似的平板图像传感器。因此已有使用TFT平板图像传感器的光学指纹传感器产品问世。
TFT平板图像传感器是在一个基板上(玻璃、不锈钢、或塑料等材料)，通过非晶硅TFT(amorphous Silicon Thin Film Transistor，a-Si TFT)、低温多晶硅TFT(Low Temperature Poly Silicon Thin Film Transistor，LTPS TFT)或氧化物半导体TFT(Oxide Semiconductor Thin Film Transistor，OS TFT)技术工艺制作像素区和外围区电路。
然而，由于TFT的器件特性相比于Si基CMOS的器件特性而言，性能上仍然差很多。所以，采用TFT技术工艺制作的平板图像传感器中，像素信号放大和数模转换功能通常是通过外置的芯片来实现，这个芯片通常叫信号读出芯片(Readout IC，ROIC)。也就是说，TFT平板图像传感器的像素电子信号通过数据线连接到外置的信号读出芯片，所述信号读出芯片进行光电转换和信号处理，实现图像的采集。信号读出芯片的外置方式主要分三种情况：第一种情况，芯片直接COG(Chip On Glass，玻璃上芯片工艺)绑定的方式绑定到TFT平板图像传感器；第二种情况，芯片直接绑定在柔性印刷电路板(Flexible Printed Circuit，FPC)上，然后柔性印刷电路板绑定到TFT平板图像传感器；第三种情况：芯片直接绑定在硬性印刷电路板(Printed Circuit Board，PCB)上，然后通过另外一个柔性印刷电路板将上述硬性印刷电路板绑定到TFT平板图像传感器。
一种现有TFT平板图像传感器的如图1所示，所述TFT平板图像传感器包括基板10和信号读出芯片(未示出)，以及位于基板10 上的器件层(未标注)。器件层制作在基板10上，所述基板材料是玻璃、不锈钢、或塑料。器件层中有像素阵列区和外围电路区，所述器件层通过非晶硅TFT、低温多晶硅TFT、或氧化物半导体TFT的技术工艺制作而成。所述像素阵列区中具有多条数据线11和多条扫描线12，数据线11和扫描线12限定出一个个阵列排布的网格，网格所在区域对应具有像素13。像素13包括至少一个像素开关131(像素开关131通常为TFT器件)，以及至少一个器件132(比如感光器件、电极板、热敏器件等)。器件132用于收集外部输入信号(比如光、静电场、热等)，并转化为电子信号，然后存储在像素13中。像素开关131导通，则器件132中的电信号就传导到数据线11上，然后外部的信号读出芯片实现信号采集。所述扫描线由外围的驱动电路控制，来实现像素开关131的逐行开启，所述驱动电路为外置驱动芯片或者以TFT器件电路的方式集成在所述器件层中。外置驱动芯片同样分三种情况：第一种情况，芯片直接绑定的方式绑定到TFT平板图像传感器的外围；第二种情况，芯片直接绑定在柔性印刷电路板上，然后柔性印刷电路板绑定到TFT平板图像传感器；第三种情况：芯片直接绑定在硬性印刷电路板上，然后通过另外一个柔性印刷电路板将上述硬性印刷电路板绑定到TFT平板图像传感器。
现有TFT平板图像传感器的图像采集方法有待改进。
发明内容
本发明解决的问题是提供一种TFT平板图像传感器的图像采集方法，以提高所述信号读出芯片的稳定性，降低整个电路系统的设计难度。
为解决上述问题，本发明提供了TFT平板图像传感器的图像采集方法，所述TFT平板图像传感器包括：基板和信号读出芯片，以及位于所述基板上的器件层；所述器件层包括阵列排布的多个像素，以及多条数据线和多条扫描线；一列所述像素中，每个所述像素通过 一个像素开关连接同一条所述数据线；一行所述像素中，每个所述像素所连接的所述像素开关连接同一条所述扫描线；所述图像采集方法，包括：设定所述信号读出芯片的一个信号采集周期为第一周期；设定一条所述扫描线完成一次驱动的时间为驱动时间；设定所述第一周期和所述驱动时间的时间长度相等；设定第m个所述第一周期的结束时刻与第m+1个所述第一周期的开始时刻重叠，其中m为正整数；设定第n个所述驱动时间的结束时刻与第n+1个所述驱动时间的开始时刻重叠，其中n为正整数。
可选的，所述第一周期包括：第一操作时间，用于进行清空数据线信号操作；第二操作时间，用于进行第一次信号采样操作；第三操作时间，用于进行第二次信号采样操作；设定第i个所述第一周期先于第i个所述驱动时间开始，并且两者的开始时刻间隔小于两者的时间长度，其中i为正整数；设定第j个所述第一周期的所述第一操作时间和所述第二操作时间进行期间，对应进行第j-1个所述驱动时间；第j个所述第一周期的所述第三操作时间进行期间，对应进行第j个所述驱动时间；其中j为2以上的整数。
可选的，在进行第k个所述第一周期的所述第一操作时间时，第k-1个所述驱动时间对应的所述扫描线仍然控制所述像素开关保持导通状态，从而使得在第k个所述第一周期的所述第一操作时间时，同时对相应行的所述像素进行清空信号操作，其中k为2以上的整数。
可选的，所述信号读出芯片将所述第二次信号采样操作获得的信号与所述第一次信号采样操作获得的信号进行作差，得到的结果作为最终信号输出。
可选的，所述第一周期还包括位于第二操作时间之后，且位于所述第三操作时间之前的信号释放时间。
可选的，所述第一周期的开始时刻和所述第一操作时间之间具有第一间隔时间，所述第一操作时间和所述第二操作时间之间具有第二间隔时间，所述第二操作时间和所述第三操作时间之间具有第三间隔 时间，所述第三操作时间与所述第一周期的结束时刻之间具有第四间隔时间；所述第三间隔时间包括所述信号释放时间。
可选的，所述信号释放时间保证相应行的所述像素中，80％以上的电子信号传输至所述信号读出芯片中。
可选的，所述扫描线的驱动电路为外置驱动芯片或者以TFT器件电路的方式集成在所述器件层中。
可选的，所述信号读取芯片采用COG方式直接绑定在所述基板上，或者所述信号读取芯片绑定在与所述TFT平板图像传感器电性连接的外部印刷电路板上。
可选的，所述外置驱动芯片采用COG方式直接绑定在所述基板上，或者所述外置驱动芯片绑定在与所述TFT平板图像传感器电性连接的外部印刷电路板上。
与现有技术相比，本发明的技术方案具有以下优点：
本发明的技术方案中，设定所述信号读出芯片的一个信号采集周期为第一周期；设定一条所述扫描线完成一次驱动的时间为驱动时间；设定所述第一周期和所述驱动时间的时间长度相等；设定第m个所述第一周期的结束时刻与第m+1个所述第一周期的开始时刻重叠，其中m为正整数；设定第n个所述驱动时间的结束时刻与第n+1个所述驱动时间的开始时刻重叠，其中n为正整数。通过上述设定，使第一周期与驱动时间之间相互配合，从而使得在一行像素开关由导通切换为断开时，另外一行像素开关由断开切换为导通，导通像素开关时抽取的电子可以绝大部分来自于断开像素开关时释放的电子，因此实现了抽取电子和释放电子的几乎相互抵消，从而最大程度降低像素开关导通或断开时产生的抽取或释放的电子数量，减小像素开关对所述信号读出芯片的电荷冲击，提高所述信号读出芯片的稳定性，降低整个电路系统的设计难度。
附图说明
图1是现有TFT平板图像传感器部分结构示意图；
图2显示了图1中TFT平板图像传感器采用现有图像采集方法时对应的驱动时序图；
图3是显示了图2中第一周期所包括的具体时间；
图4显示了图1中TFT平板图像传感器采用本发明实施例所提供的图像采集方法时对应的驱动时序图；
图5是显示了图4中第一周期所包括的具体时间。
具体实施方式
图2显示了图1中TFT平板图像传感器采用现有图像采集方法的驱动时序(驱动时序包括扫描线的驱动时序和信号读出芯片的驱动时序)，各扫描线12(图1中显示了扫描线12z、扫描线12a、扫描线12b、扫描线12c和扫描线12d，但图2中仅显示了扫描线12a、扫描线12b和扫描线12c以及图1中未显示的第n条扫描线12n的驱动时序)逐行导通，各扫描线12的驱动时间均为驱动时间B，信号读出芯片(时序图中标注为ROIC)的一个信号采集周期为信号第一周期A。其中，扫描线12a的驱动时间在扫描线12b的驱动时间之前，扫描线12b的驱动时间在扫描线12c的驱动时间之前。而信号读出芯片(图2中对应信号线标注为信号读出芯片)对应逐行信号采集。
请参考图3，图3表示了信号读出芯片和扫描线12(具体为相邻的两条扫描线——扫描线12a和扫描线12b)的更加具体的时序图，具体显示了第一周期A中的各部分时间，更多扫描线的情况可以类推。
如图3中所示，所述信号读出芯片的一个信号采集周期通常主要包括有3个动作，即：清空数据线信号动作，对应的是第一操作时间R1；第一次信号采样动作，对应的是第二操作时间R2；第二次信号采样动作，对应的是驱动第三时间R3。
如图3中所示，扫描线12是逐行分别导通的，一条扫描线12的驱动时间B对应信号读出芯片的一个信号第一周期A。时间上先后相邻的两条扫描线之间具有时间间隔H，即时间上先后相邻的两条扫描线12线之间，驱动时间B不是连续进行的，而是存在时间间隔H(亦可参考图2)。每个驱动时间B都在第二操作时间R2之后，在驱动第三时间R3之前。
由于扫描线12对应的像素开关131(如前所述像素开关131为TFT器件)在导通和断开的时候，会从数据线13上抽取和释放大量电荷。很多时候，此抽取和释放的电荷甚至远远大于像素13本身产生的图像信号。而且，在像素开关131导通和断开的时候，为了防止信号丢失，所述信号读出芯片内部电路需要持续连接至数据线11，因此，像素开关131的抽取和释放电荷直接关联到了信号读出芯片内部电路。以至于，像素开关131的导通和断开对信号读出芯片具有很大的电荷冲击，从而影响其稳定性和响应速度。
在TFT平板图像传感器的像素尺寸很小(例如像素尺寸仅为50μm左右时)或输入的图像信号很小时(例如为低剂量动态X射线传感器)时，像素信号(即电子信号)就很少。为了实现足够的信号输出，信号读出芯片就需要设计得很灵敏，以对输入信号做很大的放大。而信号读出芯片越灵敏，能够承受的电荷冲击的电荷量就越少，导致信号读出芯片越容易受像素开关的导通或断开的电荷冲击，即信号读出芯片的稳定性越差。
为此，本发明提供一种新的TFT平板图像传感器的图像采集方法，通过扫描线驱动时序和信号读出芯片驱动时序的配合，减小像素开关对所述信号读出芯片的电荷冲击，提高所述信号读出芯片的稳定性，降低整个电路系统的设计难度。
为使本发明的上述目的、特征和优点能够更为明显易懂，下面结合附图对本发明的具体实施例做详细的说明。
本发明实施例提供一种TFT平板图像传感器的图像采集方法， 请结合参考图1、图4和图5。
所述TFT平板图像传感器的结构可以参考图1(可结合参考背景技术所述内容)，所述TFT平板图像传感器包括基板10和信号读出芯片(未示出)，以及位于基板10上的器件层(未标注)。所述基板材料是玻璃、不锈钢、或塑料，所述器件层通过非晶硅TFT、低温多晶硅TFT、或氧化物半导体TFT技术工艺制作而成。所述器件层包括阵列排布的多个像素13，以及多条数据线11和多条扫描线12。
本实施例中，所述器件层包括像素阵列区，所述像素阵列区为像素13所在区域。像素13用于光学信号的接收、转化和暂存。多条数据线11和多条扫描线12限定出一个个网格(未标注)，像素13位于所述网格中(即一个所述网格所在区域中，具有一个像素13)。像素13包括至少一个像素开关131(像素开关131通常为TFT器件)，以及至少一个器件132(比如感光器件、电极板、热敏器件等)。器件132用于收集外部输入信号(比如光、静电场、热等)，并转化为电子信号，然后存储在像素13中。像素开关131导通，则器件132中的电信号就传导到数据线11上，然后外部的信号读出芯片实现信号采集。所述扫描线由外围的驱动电路控制，来实现像素开关131的逐行开启，所述驱动电路为外置驱动芯片或者以TFT器件电路的方式集成在所述器件层中。
本实施例中，根据器件132的不同，所述TFT平板图像传感器具体可以为光学图像传感器(包括光学指纹传感器等)、X射线平板图像传感器或者其它的平板图像传感器等，只要是基于非晶硅/低温多晶硅/氧化物半导体的平板图像传感器都可以(不限于光学图像传感器，也不限于指纹传感器)。
本实施例中，当所述TFT平板图像传感器为光学指纹传感器时，每个像素13可以具有透光区域和非透光区域。所述非透光区域可以具有感光元件132。所述透光区域使光线能够透过所述TFT器件层。其它实施例中，每个像素13也可以全部为非透光区域，此时通常的 可见光线不会透过所述TFT器件层。
所述TFT平板图像传感器为X射线平板图像传感器，特别是低剂量动态X射线传感器时，正如前面所述，相应的信号读出芯片就需要设计得很灵敏，以对输入信号做很大的放大。这是因为，X射线对人体是有一定的伤害的，单位时间内照射到人体的X射线不能太高，即不能用很强的X射线照人，而且长时间(比如1年)内总的X射线照射量也不能太高。即，不能用很强的X射线照，也不能用很低的X射线长时间照。一般只拍一张X光片时，(比如胸透，骨折拍片等静态片)，由于只拍一张，所以X射线强度可以大一点，可以采用静态X射线传感器；而有些时候，需要连续拍片，比如介入手术(心脏支架手术，放疗手术预定位等)过程中的动态实时监测，整个过程需要连续拍几十，甚至几百张，这个时候，就需要控制总的X射线的照射量，所以每一张X射线对应的强度就很低，只有静态X片的几十分之一。这种时候用的传感器就叫低剂量动态X射线传感器。
本实施例中，图1具体显示了其中的五条扫描线12作为代表(全部扫描线12的数量可以更多)。五条扫描线12分别为扫描线12z、扫描线12a、扫描线12b、扫描线12c和扫描线12d。
其中，扫描线12z为虚拟扫描线。扫描线12z位于全部扫描线12的最下侧(或最外侧)，用于保证最下行(或最外行)的像素13与其它行的像素13尽量处于相同的结构环境中。
本实施例中，基板10可以为透光基板，也可以为非透光基板。基板10可以是玻璃材料、塑料材料或者不锈钢材料等。
本实施例中，像素13还包括至少一个像素开关131，以及至少一个器件132(器件132可以为例如感光器件、电极板和热敏器件等，本实施例中选择为感光器件，并且所述感光器件可以包括光电二极管)。像素开关131通常可以为TFT器件(TFT开关)。
器件132可以用于收集外部输入信号(比如光、静电场、和热等)， 转化为电子信号，然后存储在像素13中。当像素开关131导通(像素开关131的导通和断开受相应的扫描线12控制)，则像素13中的电子信号就传导到相应的数据线11上，然后传输到外部的所述信号读出芯片，实现指纹图像信号采集。
本实施例中，所述器件层(由于采用各种TFT工艺制作而成，所述器件层也可以称为TFT器件层)还可以包括部分外围电路。所述部分外围电路包括驱动电路、信号读出芯片绑定区(未标注)和柔性印刷电路板绑定区，以及所述信号读出芯片绑定区和柔性印刷电路板绑定区之间的连接线(各连接线在图1中未画出)。
本实施例中，器件层的制作工艺可以采用非晶硅TFT工艺、低温多晶硅TFT工艺或氧化物半导体TFT工艺等半导体工艺。
需要说明的是，其它实施例中，所述信号读取芯片可以采用COG方式直接绑定在基板10上(绑定位置可以是在基板10的所述器件层上，也可以不在所述器件层上)，以使得所述信号读取芯片电连接数据线11。
其它实施例中，所述信号读出芯片也可以通过绑定在相应的外部印刷电路板上，从而电连接到基板10上的数据线11。分两种情况:第一种情况，芯片直接绑定在柔性印刷电路板上，然后柔性印刷电路板绑定到TFT平板图像传感器；第二种情况：芯片直接绑定在硬性印刷电路板上，然后通过另外一个柔性印刷电路板将上述硬性印刷电路板绑定到TFT平板图像传感器。
本实施例中，如图1所示，一列像素13中，每个像素13通过一个像素开关131连接至同一条数据线11。并且，一行像素13中，每个像素13所连接的像素开关131连接同一条所述扫描线。
对于“一行像素13中，每个像素13所连接的像素开关131连接同一条所述扫描线”的设置，目的是使得一行像素13中，每个像素13所连接的像素开关131受同一条扫描线12的驱动控制，即一行像 素13中，每个像素13所连接的像素开关131，是都处于导通状态，还是都处于断开状态，或是都在两种状态之间切换，都由它们共同连接的同一条扫描线12所驱动控制。由于像素开关131通常为TFT器件，只需要保证一行像素13中，每个像素13所连接的像素开关131的栅极都连接至同一条扫描线12，即可实现“每个像素13所连接的像素开关131受同一条扫描线12的驱动控制”。
请参考图4，图4显示了图1中TFT平板图像传感器的图像采集方法对应的驱动时序(驱动时序包括扫描线的驱动时序和信号读出芯片的驱动时序)，图1中显示了扫描线12z、扫描线12a、扫描线12b、扫描线12c和扫描线12d，但图4中显示了扫描线12a、扫描线12b、扫描线12c以及图1中未显示的第n条扫描线12n的驱动时序。
所述图像采集方法，包括：设定所述信号读出芯片的一个信号采集周期为第一周期A；设定一条扫描线12完成一次驱动的时间为驱动时间B；设定第一周期A和驱动时间B的时间长度相等；设定第m个第一周期A的结束时刻与第m+1个第一周期A的开始时刻重叠(即第m个第一周期A和第m+1个第一周期A之间不存在时间间隔)，其中m为正整数；设定第n个驱动时间B的结束时刻与第n+1个驱动时间B的开始时刻重叠(即第n个驱动时间B和第n+1个驱动时间B之间不存在时间间隔)，其中n为正整数；设定第i个所述第一周期先于第i个所述驱动时间开始，并且两者的开始时刻间隔(或者说两者开始时刻之间的时间差)小于两者的时间长度，其中i为正整数(例如i等于1时，即为设定第一个第一周期A先于第一个驱动时间B开始，并且两者的开始时刻间隔小于两者的时间长度)。
通过上述方法过程，本实施例使得第一周期A和驱动时间B的时间长度相等，但是起点(起点即开始时刻)错开，每个驱动时间B的起点落在第一周期A的期间。也就是说，本实施例中，扫描线12逐行导通(扫描线12逐行导通并不意味着是结构位置上相邻行的扫描线12依次导通，即各行扫描线12的导通时间可以不按结构位置的 顺序，只要保证一行扫描线12导通完成，有另外一行扫描线12导通即可)，信号读出芯片逐次进行信号采集，但两者的时间并不重合。
通过将扫描线12设置为逐行导通，并且保证相邻行没有重叠(即不同扫描线之间的驱动时间B不重叠)，以免不同行的像素信号串扰；同时保证时间上相邻导通的扫描线12之间没有间隔(前一行的结束时刻恰好是当前行的开始时刻)，即上一行像素开关131恰好断开时，当前行像素开关131恰好导通，从而实现不同行像素开关131导通和断开时，其中一行像素开关131由数据线11抽取的电荷与另一行像素开关131向数据线11释放的电荷基本相互抵消，或者说，其中一行像素开关131向数据线11释放的电荷基本等于另一行像素开关131由数据线11抽取的电荷。
虽然不同行的像素开关131实际释放和抽取电子的速度和个数(电荷量)都无法完全一致，但当不同行像素开关131中，恰好一行导通时另一行断开，则此时可以实现绝大部分电荷的相互抵消。
请参考图5，本实施例中，第一周期A具体包括：
第一操作时间R1(第一周期A中左起第一个窄细长方条所示)，用于进行清空数据线11信号操作；
第二操作时间R2(第一周期A中左起第二个窄细长方条所示)，用于进行第一次信号采样操作；
第三操作时间R3(第一周期A中左起第三个窄细长方条所示)，用于进行第二次信号采样操作。
其中，第一周期A的开始时刻和第一操作时间R1之间具有第一间隔时间(未标注)，第一操作时间R1和第二操作时间R2之间具有第二间隔时间E，第二操作时间R2和第三操作时间R3之间具有第三间隔时间(未标注)，第三操作时间R3与第一周期A的结束时刻之间具有第四间隔时间(未标注)。
第一操作时间R1的作用是清空上一行像素13在数据线11和信 号读出芯片电路上的信号残留，为下一行信号采集做准备，从而保证后续第二操作时间R2采样到的信号都是稳定和一致的。
第二操作时间R2采样的目的是采集本底信号，以备后续与像素综合信号进行作差等操作，从而扣除本底信号对最终信号的影响。
第三操作时间R3采样采集到的信号(此信号为所述像素综合信号)包括上述第二操作时间R2采样到的(本底)信号和像素的输出信号。
本实施例中，在第一操作时间R1完成之后，再经过一个第二间隔时间E之后，开始第一次信号采样，即进入第二操作时间R2。第二间隔时间E的长短根据实际的信号读出芯片的设计和数据线11寄生参数(例如电容和电阻等)有关。设定第二间隔时间E的其中一个目的是使信号读出芯片的电路稳定，从而保证后续第二操作时间R2进行第一次信号采样操作时，能够稳定有效地进行采样。
本实施例中，第一周期A还包括位于第二操作时间R2之后，且位于第三操作时间R3之前的信号释放时间F。并且本实施例中，所述第三间隔时间包括信号释放时间F，即信号释放时间F为所述第三间隔时间的一部分。
本实施例中，所述信号读出芯片将第三操作时间R3采样的信号(即上述像素综合信号)与第二操作时间R2采样的信号(即上述本底信号)进行作差，作为最后信号，输出出去，实现模数转化为数字信号。两次采样的目的是去掉传感器前段模拟电路系统(包括信号读出芯片内部模拟电路、数据线11和像素13电路等)的低频噪音以及信号读出芯片内部的通道间差异等，增加所采集指纹图像的信噪比。即所述信号读出芯片将所述第二次信号采样操作获得的信号与所述第一次信号采样操作获得的信号进行作差，得到的结果作为最终信号输出，从而使最终信号输出的准确性更高。
本实施例中，信号释放时间F只要保证相应行的像素13中，80％ 以上的电子信号传输至所述信号读出芯片中即可。理论上，根据RC充电电路原理(即电阻电容充电电路原理)，全部电子信号都传到出来，需要无穷长的时间，故实际应用中只要像素中足够多的信号释放出来就可以，本实施例保证80％以上的电子信号传输至所述信号读出芯片时即可。
本实施例中，继续设定第j个第一周期A的第一操作时间R1和第二操作时间R2进行期间，对应进行第j-1个驱动时间B；第j个第一周期A的第三操作时间R3进行期间，对应进行第j个驱动时间B；其中j为2以上的整数。
例如，当j等于2时，上述过程即为：设定第2个第一周期A的第一操作时间R1和第二操作时间R2进行期间，(相同时间内)对应进行的是第1个驱动时间B(相当于图5中的12a的驱动时间B)的其中一部分(大致为第1个驱动时间B的后面部分)，第2个第一周期A的第三操作时间R3进行期间，相同时间内，对应进行的是第2个驱动时间B(相当于图5中的12b的驱动时间B)的其中一部分(大致为第2个驱动时间B的前面部分)；当j等于3时，上述过程即为：设定第3个第一周期A的第一操作时间R1和第二操作时间R2进行期间，对应进行的是第2个驱动时间B(相当于图5中的12b的驱动时间B)的其中一部分(对应进行的大致为第2个驱动时间B的后面部分)，第3个第一周期A的第三操作时间R3进行期间，对应进行的是第3个驱动时间B(相当于图5中的12c的驱动时间B)的其中一部分(对应进行的大致为第3个驱动时间B的前面部分)；以此方式不断进行。
图5给出了扫描线的驱动时间和信号读出芯片的信号读取之间的配合，在进行第k个第一周期A的第一操作时间R1时，第k-1个驱动时间B对应的扫描线12仍然控制像素开关131保持导通状态，其中k为2以上的整数，从而使得在第一操作时间R1时，同时对相应行的像素13进行清空信号操作。
例如，在进行第2个(即k等于2时)第一周期A的第一操作时间R1时，第1个驱动时间B对应的扫描线12a仍然控制像素开关131保持导通状态，从而使得在第一操作时间R1时，同时对相应行的像素13进行清空信号操作；在进行第3个第一周期A的第一操作时间R1时，第2个驱动时间B对应的扫描线12b仍然控制像素开关131保持导通状态，从而使得在第一操作时间R1时，同时对相应行的像素13进行清空信号操作。
需要特别说明的是，第n个扫描线12和第n+1个扫描线12并不是指两条相邻扫描线的情况，而是指时间上的先后关系，与位置无关。也就是说，第n个扫描线12和第n+1个扫描线12既可以是相邻的两条扫描线12，也可以是隔一行以上的两条扫描线12。
通过上述设定，本实施例使得第一周期A和各扫描线12的驱动时间B相互配合。
本实施例中，像素13的行驱动(即对扫描线12的驱动)功能比较简单，可以通过外置驱动芯片来实现，即像素阵列区的扫描线连接到外置驱动芯片。但是，由于指纹识别对图像分辨率要求不高的领域，也可以通过相应TFT器件来实现行扫描驱动信号。因此，扫描线12的驱动电路可以为以TFT器件电路的方式集成在器件层中。当扫描线12的驱动电路为外置驱动芯片时，所述外置驱动芯片可以采用COG方式直接绑定在基板10上(以电连接扫描线12)，或者绑定在相应的外部印刷电路板上(以电连接到基板10上的扫描线12)。对于所述外置驱动芯片绑定在相应的外部印刷电路板上，可以分两种情况:第一种情况，芯片直接绑定在柔性印刷电路板上，然后柔性印刷电路板绑定到TFT平板图像传感器；第二种情况：芯片直接绑定在硬性印刷电路板上，然后通过另外一个柔性印刷电路板将上述印刷电路板绑定到TFT平板图像传感器。
本实施例的TFT平板图像传感器中，像素开关131(如前所述，通常为TFT器件)由导通切换为断开时，像素开关131的沟道层需 要向漏极和源极所连电路(即数据线等)释放电子；像素开关131由断开切换为导通时，需要由漏极和源极所连电路抽取电子，注入到像素开关131的沟道层中。所以，像素开关131断开和导通时，会向所述信号读出芯片释放和抽取电子，从而对其产生电荷冲击，影响信号读出芯片的稳定性。
而本实施例通过相应的图像采集方法，设定第一周期A与驱动时间B之间相互配合，从而使得在一行像素开关131由导通切换为断开时，另外一行像素开关131由断开切换为导通，这个时候，导通像素开关131时抽取的电子可以基本来自于断开像素开关131时释放的电子，因此实现了抽取电子和释放电子的相互抵消，从而最大程度降低像素开关131导通或断开时产生的抽取或释放的电子数量，减小像素开关131对所述信号读出芯片的电荷冲击，提高所述信号读出芯片的稳定性，降低整个电路系统的设计难度。
虽然本发明披露如上，但本发明并非限定于此。任何本领域技术人员，在不脱离本发明的精神和范围内，均可作各种更动与修改，因此本发明的保护范围应当以权利要求所限定的范围为准。

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  1. 一种TFT平板图像传感器的图像采集方法，所述TFT平板图像传感器包括：
    基板和信号读出芯片，以及位于所述基板上的器件层；
    所述器件层包括阵列排布的多个像素，以及多条数据线和多条扫描线；
    一列所述像素中，每个所述像素通过一个像素开关连接同一条所述数据线；
    一行所述像素中，每个所述像素所连接的所述像素开关连接同一条所述扫描线；
    其特征在于，所述图像采集方法，包括：
    设定所述信号读出芯片的一个信号采集周期为第一周期；
    设定一条所述扫描线完成一次驱动的时间为驱动时间；
    设定所述第一周期和所述驱动时间的时间长度相等；
    设定第m个所述第一周期的结束时刻与第m+1个所述第一周期的开始时刻重叠，其中m为正整数；
    设定第n个所述驱动时间的结束时刻与第n+1个所述驱动时间的开始时刻重叠，其中n为正整数。
  2. 如权利要求1所述的图像采集方法，其特征在于，所述第 一周期包括：
    第一操作时间，用于进行清空数据线信号操作；
    第二操作时间，用于进行第一次信号采样操作；
    第三操作时间，用于进行第二次信号采样操作；
    设定第i个所述第一周期先于第i个所述驱动时间开始，并且两者的开始时刻间隔小于两者的时间长度，其中i为正整数；
    设定第j个所述第一周期的所述第一操作时间和所述第二操作时间进行期间，对应进行第j-1个所述驱动时间；第j个所述第一周期的所述第三操作时间进行期间，对应进行第j个所述驱动时间；其中j为2以上的整数。
  3. 如权利要求2所述的图像采集方法，其特征在于，在进行第k个所述第一周期的所述第一操作时间时，第k-1个所述驱动时间对应的所述扫描线仍然控制所述像素开关保持导通状态，从而使得在第k个所述第一周期的所述第一操作时间时，同时对相应行的所述像素进行清空信号操作，其中k为2以上的整数。
  4. 如权利要求3所述的图像采集方法，其特征在于，所述信号读出芯片将所述第二次信号采样操作获得的信号与所述第一次信号采样操作获得的信号进行作差，得到的结果作为最终信号输出。
  5. 如权利要求4所述的图像采集方法，其特征在于，所述第 一周期还包括位于第二操作时间之后，且位于所述第三操作时间之前的信号释放时间。
  6. 如权利要求5所述的图像采集方法，其特征在于，所述第一周期的开始时刻和所述第一操作时间之间具有第一间隔时间，所述第一操作时间和所述第二操作时间之间具有第二间隔时间，所述第二操作时间和所述第三操作时间之间具有第三间隔时间，所述第三操作时间与所述第一周期的结束时刻之间具有第四间隔时间；所述第三间隔时间包括所述信号释放时间。
  7. 如权利要求6所述的图像采集方法，其特征在于，所述信号释放时间保证相应行的所述像素中，80％以上的电子信号传输至所述信号读出芯片中。
  8. 如权利要求7所述的图像采集方法，其特征在于，所述扫描线的驱动电路为外置驱动芯片或者以TFT器件电路的方式集成在所述器件层中。
  9. 如权利要求8所述的图像采集方法，其特征在于，所述信号读取芯片采用COG方式直接绑定在所述基板上，或者所述信号读取芯片绑定在与所述TFT平板图像传感器电性连接的外部印刷电路板上。
  10. 如权利要求8所述的图像采集方法，其特征在于，所述外置驱动芯片采用COG方式直接绑定在所述基板上，或者所述外 置驱动芯片绑定在与所述TFT平板图像传感器电性连接的外部印刷电路板上。
PCT/CN2016/095847 2016-02-26 2016-08-18 Tft平板图像传感器的图像采集方法 WO2017143742A1 (zh)

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