WO1997043788A1 - Dispositif a transfert de charge - Google Patents

Dispositif a transfert de charge Download PDF

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Publication number
WO1997043788A1
WO1997043788A1 PCT/GB1997/001269 GB9701269W WO9743788A1 WO 1997043788 A1 WO1997043788 A1 WO 1997043788A1 GB 9701269 W GB9701269 W GB 9701269W WO 9743788 A1 WO9743788 A1 WO 9743788A1
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WO
WIPO (PCT)
Prior art keywords
charge
pixels
ctd
active
sub
Prior art date
Application number
PCT/GB1997/001269
Other languages
English (en)
Inventor
Mark Riches
Original Assignee
Nac Incorporated
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nac Incorporated filed Critical Nac Incorporated
Priority to AU27091/97A priority Critical patent/AU2709197A/en
Publication of WO1997043788A1 publication Critical patent/WO1997043788A1/fr

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Classifications

    • 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

Definitions

  • This invention relates to a charge-transfer device (CTD) and, in particular, a high speed charge-transfer device having a high sensitivity
  • CCD charge-transfer device
  • the invention may be used, for example, in a framing camera for permitting photography of high or ultra high speed events which typically occur over time scales of the order of nanoseconds to milliseconds
  • Framing cameras are known in the art with speeds of 2,000 to 100,000,000 frames per second Framing cameras of this type are used for taking pictures of high or ultra high speed events such as lightening and sparks resulting from electrical discharge, or events to be analysed to a high resolution such as in shock waves, fluid dynamics and fuel injection
  • An image tube of the type described in European Patent specification no 0 315 435 can be used in such a framing camera for recording these high speed events
  • the duration of the event which can be recorded by the image tube is inversely proportional to the number of frames per second Consequently, if the event being recorded is required to be analysed at a high temporal resolution, then the running time of the image tube will be relatively short In these circumstances, it is necessary to predict the precise timing of the event so the image tube can be triggered to record the event as it occurs
  • a previously proposed method of overcoming this problem is to use a film or video camera, having a much slower frame rate and hence poor temporal resolution
  • the camera is triggered to start before the event is expected to occur and is run continuously across the event of interest It is simple to stop the camera once the event has occurred, and wind the film or video tape back to the frames of interest
  • a CCD is a type of CTD which takes the form of a multiple-gate semiconductor fabricated on a silicon chip as an MOS integrated circuit Information is stored by minority carriers as a charge packet in a potential well under a gate electrode at a particular site The charge can be moved to another gate at a particular site by means of clocked pulses
  • some of the sites are photo-sensitive Light falling on these sites produces electron-hole pairs proportional in number to the light intensity
  • the charge that collects under the gate electrodes is a charge pattern of the incident light which can be transferred to other gate electrodes and then extracted as an analogue signal by clocking of the gate voltages whilst the photo-sensitive sites record a new image
  • One type of CCD for use in imaging systems generally comprises a matrix of 2048 x 2048 sites, each defining a pixel In use, a
  • a charge-transfer device comprising a plurality of active pixels adapted to produce a charge pattern in response to incident light, and a plurality of non-active pixels, a respective group of the said non-active pixels being associated with each active pixel, the device being arranged such that a charge packet formed in an active pixel can be shifted sequentially from the active pixel to each non-active pixel within its associated group
  • the CTD may be a CCD
  • the non-active pixels act as storage pixels for receiving a charge pattern from the associated active pixel, leaving the active pixels free to record another charge pattern.
  • Each shift of the charge packets stores a complete new frame
  • the charge patterns are preferably shifted at intervals, for example in response to a clock signal, to each of the non-active pixels before being read out or dumped
  • the charge pattern formed by the charge packets produced in all of the active pixels together in response to a single clock signal form one frame of the event of interest
  • the readout may be sequential, in parallel, or a combination of both
  • the plurality of active pixels are preferably substantially evenly dispersed across a surface of the CTD
  • the charge-transfer device may comprise a two-dimensional array of pixels, the array being split into a plurality of groups of pixels Each group of pixels preferably includes at least one active pixel and several non-active pixels
  • One type of standard CTD comp ⁇ ses a two-dimensional array of 2048 x 2048 pixels In the case of the present invention, such an array could be split up into 256 x 256 'super pixels ' , each of which could be defined
  • a clock signal is generated to advance the charges stored in the pixels by one pixel This frees the active pixels to capture the next frame More specifically, the charge packet formed in each active pixel is shifted, in response to a clock signal, to an adjacent storage pixel, and a new charge packet is formed in the active pixel In response to another clock signal, the charge packet stored in the adjacent storage pixel is shifted to a second non-active pixel, the charge packet currently stored in the active pixel is shifted to the adjacent non-active pixel, leaving the active pixel free to form another charge packet This process is repeated in response to each clock signal such that each charge packet is shifted through the sub-array until it reaches the final storage pixel At this point, another clock signal will cause the charge packet stored in the final storage pixel to be dumped or deposited into the read-out structure
  • the charge packets may be shifted around the sub-array in a generally spiral configuration towards a final storage pixel situated at the periphery of the sub-array.
  • the charge packets may be shifted from one side of the sub-array to the other in a zig-zag configuration.
  • the charge packets output from each of the sub-arrays may be fed into a conventional horizontal or vertical line of pixels, which in turn deposits its charge into a conventional readout register at the top, bottom or side of the CTD.
  • the CTD of the present invention need only have one actual output, as all of the stored data can be shifted sequentially at slow scan speed out of this port.
  • the device can run continuously, with the stored frames providing a post-triggering retrieval capability
  • Figure 1 is a schematic view of a CTD according to a first embodiment of the present invention.
  • Figure 2 is a schematic view of a CTD according to a second embodiment of the present invention.
  • a CTD 10 according to a first embodiment of the present invention comprises a matrix 12 of 2048 x 2048 pixels.
  • the CTD is a CCD, but other types of CTD could be used.
  • the matrix 12 is divided into 256 x 256 'super pixels', each 'super pixel' consisting of a sub-array 15 comprising 8 x 8 (64) normal pixels or sub-pixels 16.
  • Each sub-array 15 includes only one active photo-sensitive pixel 18.
  • the remaining 63 pixels (storage pixels 19) are masked off from incident light or are not photo-sensitive.
  • the pixel size of this CCD is envisaged as being around 9 to 22 ⁇ m. However, this is not essential and is merely convenient in view of currently available technology P B97/01269
  • incident light from the image to be recorded falls on the device 10 and produces in the active pixel 18 of each sub-array 15 a charge packet characteristic of the incident light
  • the charge packets formed in all of the active pixels at a particular instant form a single frame of the image of interest
  • Clock signals are provided, each signal being arranged to cause each charge packet to shift to an adjacent pixel in response thereto
  • the pulses are provided at the desired frame rate, I e in this embodiment at a frequency of 1,000,000Hz (l e every 1 ⁇ s) or 500,000 Hz (l e every 2 ⁇ s)
  • the charge packet currently in the active pixel is shifted to the adjacent pixel 20 and stored, and a new charge packet is produced and stored in the active pixel
  • the charge packet in each of the occupied pixels is shifted to a pixel adjacent thereto and stored The above process is repeated every 1 ⁇ s (or 2 ⁇ s) until all of the pixels are occupied
  • the active pixel 18 is situated at a generally central position within the sub-array 15
  • the charge packets are shifted around the matrix 15 in a spiral-type direction as indicated bv the arrow until all of the pixels are occupied
  • the charge packet stored in the 64 pixel 22 must either be dumped or read out in order to create space for the rest of the charge packets to be shifted
  • the charge packets output from each of the sub- arrays can be fed into a conventional horizontal or vertical line, which in turn deposits its charge into a conventional readout register at the bottom, top or side of the CCD
  • the CCD need only have one actual output as all of the stored data can be shifted sequentialh at slow scan speed out of this port
  • the 64 pixels could be adapted to dump their charge packets or shift them into a readout line or pixel
  • the readout pixel could be made large enough to integrate or sum many of the high-speed frames into one 'slow' frame for the live access at, say, 50 Hz Whilst the image is being shifted in this way, further images are dumped at the 64 pixels.
  • a stop trigger pulse is used to start or stop the capture process For example, it may be programmed to start the capture of 64 frames, mark the point at which, say, the preceding 64 frames should be captured, or mark a point at which the preceding 32 frames and the next 32 frames should be captured This can be determined by the user.
  • the output of the CCD could be sub-sampled in real time to give a live mode at 50/60 Hz (or faster)
  • the camera could output information onto a tape or into a RAM at 500 frames per second but, upon a clock signal, the camera could read out the 64 backed up frames which were taken at 50,000 frames per second or even 500.000 frames per second before the trigger
  • the active pixel may be made larger than the other 63 pixels in a sub-array and have a relatively shallow electron well In this case, the remaining pixels would taper to a geometrically smaller size, but have deeper electron wells so as to maintain full well capacity Alternatively, the well depths of all of the pixels could be substantially the same, in which case the full well capacity of the imaging pixel should be adjusted, so as not to over-fill the smaller storage pixels - which would lead to blooming of the image This can be achieved by the provision of anti-blooming gates This option offers independent gating mode for the CCD
  • the normal exposure provided by the device is (1/ frame rate)
  • the anti-blooming gate should allow the exposure to be reduced beyond this down to a fundamental limit In other words, the provision of gated anti-blooming gates on the active pixel gives electronic exposure control, down to the order of 1 ⁇ s or less even at slow frame rates
  • the readout analogue electronic circuitry required for the present invention is relatively simple slow scan technology optimised for dynamic range and noise performance
  • the resultant device exhibits not only a high spatial resolution, but also a high temporal resolution (on demand)
  • the sensitivity of the device may be further improved by the provision of a lens over each of the sub-arrays to concentrate the available light into the active pixel
  • colour may be added with a combined micro-lens array and colour filters, possibly even user-switchable between monochrome and colour
  • each active pixel 18 is situated in a corner of a respective sub-array 15
  • Each charge packet is shifted through the sub-array in a zig ⁇ zag configuration (as indicated by the arrow) to the final pixel 22, where the charge packet is either dumped or read out
  • charge packets may be shifted through the device using a number of configurations
  • a number of active pixels may situated adjacent each other, and the non-active pixels may radiate from the respective active pixel, in a horizontal, vertical or diagonal direction
  • an interlaced linear arrangement may be used
  • Another alternative is a nested arrangement, for example wherein each sub-array includes two active pixels which are adjacent each other and are situated in a generally central position on a surface of the CTD.
  • the charge packets may be transmitted to two associated non-active pixels which are adjacent each other and situated at a point at or adjacent the periphery of the CTD, by shifting the charge packet through a series of non-active pixels in a nested spiral configuration, for example
  • the CTD may even be three-dimensional the active pixels may cover one or more of the surfaces of a three-dimensional CTD, and the associated non-active pixels could be buried within the three-dimensional CCD
  • a CTD according to the present invention could be coated with a fluorescent material, or backthinned with appropriate masking at the storage pixels for UV. x-ray or other spectral sensitivity It could also be applied to cadmium-telluride (infra-red cameras)
  • the present invention has been described in terms of a device which provides an output of 64 frames at a 256 x 256 resolution, it will be appreciated that the CTD of the present invention may be split into any convenient groups of pixels For instance, the device may be arranged to provide 32 frames at a 512 x 256 resolution
  • each sub-group of pixels may be arranged in any convenient manner
  • CTD computed time difference

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Transforming Light Signals Into Electric Signals (AREA)
  • Solid State Image Pick-Up Elements (AREA)

Abstract

Dispositif à transfert de charge (CTD) (10) destiné à un appareil d'imagerie à vitesse élevée particulier. Le CTD comprend une matrice (12) de pixels, divisée en un certain nombre de 'superpixels' (15). Chaque superpixel (15) se présente sous la forme d'un sous-ensemble et se subdivise en une pluralité de pixels (16). L'un des pixels (16) de chaque sous-ensemble (15) est actif, c'est-à-dire photosensible, les autres (pixels de stockage) étant masqués ou non photosensibles. En fonctionnement, la lumière provenant de l'image à enregistrer tombe sur le dispositif (10) et produit dans le pixel actif (18) de chaque sous-ensemble (15) un paquet de charge caractéristique de la lumière incidente. Les paquets de charge formés dans tous les pixels actifs (18) à un instant particulier forment un motif qui représente une seule trame de l'image à enregistrer. Des signaux d'horloge sont générés et, en réponse auxdits signaux, le paquet de charge stocké dans chaque pixel actif (18) est décalé vers un pixel de stockage adjacent, laissant les pixels actifs libres pour enregistrer une autre trame. Ce processus est répété en réponse à chaque signal d'horloge, chaque paquet de charge étant décalé dans tout le sous-ensemble, de façon à former, par exemple, une configuration en spirale, jusqu'au moment où il atteint le pixel de stockage final. A ce niveau, la survenue d'un autre signal d'horloge fait que le paquet est soit affiché, soit déchargé. Ainsi, une pluralité de trames peuvent être stockées dans le CTD de la présente invention, et le circuit électronique analogue d'affichage nécessaire est relativement simple, c'est-à-dire qu'il s'agit d'une technologie à balayage lent optimisée quant à la gamme dynamique et au niveau sonore. Le CTD peut être un dispositif à couplage de charge (CCD).
PCT/GB1997/001269 1996-05-09 1997-05-09 Dispositif a transfert de charge WO1997043788A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU27091/97A AU2709197A (en) 1996-05-09 1997-05-09 Charge-transfer device

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9609660A GB2313186A (en) 1996-05-09 1996-05-09 Charge-transfer device for imaging
GB9609660.7 1996-05-09

Publications (1)

Publication Number Publication Date
WO1997043788A1 true WO1997043788A1 (fr) 1997-11-20

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PCT/GB1997/001269 WO1997043788A1 (fr) 1996-05-09 1997-05-09 Dispositif a transfert de charge

Country Status (3)

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AU (1) AU2709197A (fr)
GB (1) GB2313186A (fr)
WO (1) WO1997043788A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9462202B2 (en) 2013-06-06 2016-10-04 Samsung Electronics Co., Ltd. Pixel arrays and imaging devices with reduced blooming, controllers and methods
US9979905B2 (en) 2015-11-17 2018-05-22 Microsoft Technology Licensing, Llc. Multimode photosensor

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4120623A1 (de) * 1991-06-22 1993-01-07 Fraunhofer Ges Forschung Schmierbildkamera und verfahren zum herstellen von schmierbildern
US5210613A (en) * 1990-10-13 1993-05-11 Goldstar Electron Co., Ltd. Zigzag interline transfer type CCD image sensor
DE4243116A1 (de) * 1992-12-21 1994-07-07 Fraunhofer Ges Forschung Verfahren und Vorrichtung zum Herstellen von Bildern
WO1994030004A1 (fr) * 1993-06-16 1994-12-22 Cambridge Imaging Limited Systeme de prise d'images perfectionne

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8314300D0 (en) * 1983-05-24 1983-06-29 Gen Electric Co Plc Image sensors
GB2262383B (en) * 1991-12-09 1995-06-14 Sony Broadcast & Communication Charge-coupled image sensor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5210613A (en) * 1990-10-13 1993-05-11 Goldstar Electron Co., Ltd. Zigzag interline transfer type CCD image sensor
DE4120623A1 (de) * 1991-06-22 1993-01-07 Fraunhofer Ges Forschung Schmierbildkamera und verfahren zum herstellen von schmierbildern
DE4243116A1 (de) * 1992-12-21 1994-07-07 Fraunhofer Ges Forschung Verfahren und Vorrichtung zum Herstellen von Bildern
WO1994030004A1 (fr) * 1993-06-16 1994-12-22 Cambridge Imaging Limited Systeme de prise d'images perfectionne

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9462202B2 (en) 2013-06-06 2016-10-04 Samsung Electronics Co., Ltd. Pixel arrays and imaging devices with reduced blooming, controllers and methods
US9979905B2 (en) 2015-11-17 2018-05-22 Microsoft Technology Licensing, Llc. Multimode photosensor

Also Published As

Publication number Publication date
GB2313186A (en) 1997-11-19
GB9609660D0 (en) 1996-07-10
AU2709197A (en) 1997-12-05

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