Modeling, Calibration, and Rendition of Color Logarithmic CMOS Image Sensors

CONTENTS
1. Introduction 1. Introduction Infrared camera model 2. 2. Infrared Noise measurements 3. 3. Noise noise spatial noise of postcorrection spatial Sources of 4. Sources 4.1. 4.1. Nonlinear nonuniformities Chromatic spatial noise 4.2. 4.2. Chromatic 4.3. Excess Excess low frequency noise 4.3. 4.4. Residual nonuniformity nonuniformity after correction correction 4.4. noise effect of Combined effect 5. 5. Combined of spatial spatial and and temporal noise signal-to-noise Signal-to-noise 6. 6. Signal -to -noiseand and contrast contrast signal -to -noiseratios: ratios: figures figures of of merit Comparison of spectral bands 7. 7. Comparison Conclusions 8. 8. Conclusions Acknowledgments 9. 9. Acknowledgments References 10. References 10.
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Rolling shutter distortion correctionChia-Kai Liang*, Yu-Chun Peng**, and Homer Chen***Graduate Institute of Communication Engineering, National Taiwan University, TaiwanABSTRACTAs opposed to the global shutter, which starts and stops the light integration of each pixel at the same time by incorporating a sample-and-hold switch with analog storage in each pixel, the electronic rolling shutter found in most low-end CMOS image sensors today collects the image data row by row, analogous to an open slit that scans over the image sequentially. Each row integrates the light when the slit passes over it. Therefore, the scanlines of the image are not exposed at the same time. This sensor architecture creates an objectionable geometric distortion, known as the rolling shutter effect, for moving objects. In this paper, we address this problem by using digital image processing techniques. A mathematical model of the rolling shutter is developed. The relative image motion between the moving objects and the camera is determined by block-based motion estimation. A Bezier curve fitting is applied to smooth the resulting motion data , which are then used for the alignment of scanlines. The basic ideas behind the algorithm presented here can be generalized to deal with other complicated cases.Keywords: rolling shutter, motion estimation1.INTRODUCTIONMore and more low-cost imaging devices are equipped with CMOS image sensor array. Unlike the CCD sensor array that normally has interline connections, the CMOS sensor array does not hold and store all the pixels. An electronic rolling shutter is thus resulted because each scanline of the CMOS sensor array is exposed, sampled, and stored sequentially. An annoying effect of the electronic rolling shutter is that it introduces geometric distortion to moving objects. A graphical illustration of this annoying effect is shown in Figure 1. We can see that the image of a vertical object becomes slanted. In this simple example, we assume that the object is stationary and the camera is moving. Note that the same effect occurs when the image of a moving object is captured by a still camera. In general, as long as there is a relative motion between the camera the scene, the rolling shutter effect would appear. The extent of the geometrical distortion depends on the magnitude and direction of the relative motion.Many circuit architectures have been developed to address the rolling shutter problem1, 2 by implementing a sample-and-hold circuit for the CMOS sensor. However, the transistor count of such architectures becomes two to four times more than that of the original architecture, introducing new problems, such as the requirement of more advanced IC process, that are more costly to solve.Little has been studied to overcome the rolling shutter effect by digital image processing. C. Geyer et al. have derived a camera model for rolling shutter cameras3. They developed a general rolling-shutter constraint on the motion of each image point. However, this approach involves an elaborated procedure to compute the 3-D motion of object that is sensitive to image errors..In this paper, we develop a simple model to characterize the rolling shutter effect without resorting to 3-D analysis. With this model, the rolling shutter distortion can be corrected by the alignment of scanlines. An attractive feature of this algorithm is that it is relatively easy to implement.The paper is organized as follows. Section 2 describes our approach to the compensation of rolling shutter distortion, including a basic mathematical model of the rolling shutter, an algorithm for rolling shutter compensation, and the extension of the algorithm to more general image motions . Section 3 describes the setup of our experiments in detail and shows the simulation results. This is followed by a conclusion in Section 4.*r93942031@.tw **b88901049@.tw ***homer@.twVisual Communications and Image Processing 2005, edited by Shipeng Li,Fernando Pereira, Heung-Yeung Shum, Andrew G. Tescher, Proc. of SPIE Vol. 5960(SPIE, Bellingham, WA, 2005) · 0277-786X/05/$15 · doi: 10.1117/12.6326712.APPROACHWithout loss of generality, we start the derivation of our approach with the case where the object is stationary and thecamera moves horizontally from right to left, as shown in Figure 1(a). Since the camera is moving, by the time thecamera finishes storing the sampled data of the first scanline and is ready to scan the second line, the object wouldappear to have moved by a certain distance horizontally. Therefore, a displacement between the sampled data along thetwo scanlines is resulted. This is shown in Figure 1(b). In effect, the shape of the object is seriously distorted whenthe entire image of the object is captured. The basic idea of our approach, as shown in Figure 2(a), is to correct thisgeometric distortion by aligning the scanlines according to the apparent object movement detected in the image. InFigure 2(a), x i is the displacement between scanlines l i and l i+1. Note that x i is equivalent to the displacement between the horizontal object segments shown in Figure 2(b).(a) (b) Figure 1. Illustration of the rolling shutter effect. (a) A vertical object appears to move to the left of the image while a rolling shuttercamera moving horizontally to the right of the object acquires the image data line-by-line. (b) The resulting image of the verticalobject (partial view). Note the inevitable distortion on the object caused by the rolling shutter.(a) (b)Figure 2. (a) Correcting the rolling shutter distortion by aligning the scanlines. (b) The object displacement x i betweenscanlines.For the approach to work, the displacement (or offset) x i along each scanline has to be determined. This displacementof scaneline l i is related to the velocity v(t) of the object, measured in the image plane, by1,nT i ti nT i t x v t dt ' ' ³ (1)where n is the frame index, Ϧt is the exposure time of each scanline, and T is the time interval between two consecutivevideo frames. For most commercial cameras, we may consider that there is a constant time lapse d between the end of theprevious frame and the beginning of the current frame. Assuming a constant frame rate f , we have T=1/f . Then theexposure time of the scaneline can be determined by,t T d S '(2) where S denotes the total number of effective scanlines in a video frame.Based on v (t ), we can determine the displacement x i line-by-line and hence compensate the rolling shutter distortion.Since the object is stationary, we determine v (t ) by global motion estimation. The global motion vector of the n th frameis related to the camera motion by³nT T n dt t v nT GMV 1 (3) ³¦ nT n i dt t v iT GMV nT AGMV 00 (4)where GMV (nT ) is the global motion vector of the n th frame and AGMV (nT ) denotes the accumulated global motion vector with respect to the first frame.If v (t ) varies slowly, it can be computed by the finite difference method as followsT nT GMV T T n AGMV nT AGMV dt t dAGMV nT v nT t 1)( (5)The block diagram of our rolling shutter correction algorithm is shown in Figure 3. In this algorithm, a block-based motion estimation is applied to the image sequence. The global motion is determined by clustering and classifying the motion vectors thus obtained.5 Then v (t ) is calculated by equation (5), and x i is obtained by (1). Finally each scanline of the distorted image is compensated by x ito generate the corrected image.Figure 3.Block diagram of the rolling shutter correction algorithm.Note that a constant velocity for the entire frame is assumed in (5). However, this constant velocity assumption may not always be a good approximation. This is illustrated in Figure 5, where the solid curve is the actual accumulated global motion, and the piecewise linear segment represents the accumulated global motion under the constant velocity assumption. An ideal case occurs when the two curves completely overlap. In such a case, the estimated x i leads to accurate rolling shutter compensation. When the two curves are apart from each other during a frame interval, the algorithm may not generate good result.To improve the performance of the algorithm, we reconstruct the value of AGMV (t ) from the sampled AGMV (nT )and obtain dAGMV (t )/dt at the time instant of interest. Here, we are dealing with the case where the sampling rate of AGMV (t ), which is equal to the frame rate, is potentially smaller than the bandwidth of AGMV (t ). According to the Nyquist theorem, this may lead to an aliasing effect. If the reconstructed AGMV (t ) is larger than the real one, an over-compensated frame is resulted, as shown in the 45th compensated frame in Figure 4(b) where the Christmas tree is slightly tilted over to the left. Note that the over-compensation can happen to the finite difference method and thereconstruction method.(a)(b)Figure 4. (a) The 39th (left) and 45th (right) frames of the original sequence (6 frames/sec). (b) The corrected frames.Figure 5. Accumulated Global Motion Vector.We have observed the over-compensation degrade the video quality much seriously than under-compensation. Therefore, we need to apply a low pass filter upon AGMV (t ) to make it smoother. However, it is difficult to find a filter suitable for AGMV (t ). Even it can be found, it normally requires a large number of samples as input, resulting in a large output delay. Instead, we adopt the Bezier method to approximate the curve. A Bezier curve for AGMV (t ) between nT and (n +1)T is described by,1313143322213P t P t t P t t P t t Q (6)where P i ’s are the control points of the curve, which can be derived by using the following boundary conditionsT n AGMV Q 20 (7) T n AGMV Q 11 (8) nT AGMV Q 32 (9)T n AGMV Q 11 (10)Once the control points are obtained, the velocity v (t ) can be calculated by ¸¹·¨©§ T T t Q dt d t v 32 (11)The dotted curve in Figure 5 shows the reconstructed curve based on AGMV(nT). The Bezier method removes the high frequency components of AGMV(t). Unlike deterministic low pass filters, the Bezier method is a low pass filter with adaptive control points and introduces only one frame delay. The control points are updated frame-by-frame according to the local characteristics of AGMV(t). The result of Bezier curve method is shown in Figure 6, where the over-compensation is removed.(a)(b)Figure 6. (a) The 39th (left) and 45th (right) frames of the original sequence (6 frames/sec). (b) The corrected frames using Bezier curve approximation.We have shown how to correct the rolling shutter distortion for the simple horizontal motion case. Now we discuss how to generalize it to other types of motions. For the case where the scene is static and the camera moves perpendicularly to the scanlines, the rolling shutter compensation can be achieved in a similar way. However, an extra step is required to interpolate the missing scanlines. An illustration of the problem is shown in Figure 7.(a) (b)Figure 7. The rolling shutter effect due to vertical camera motion. (a) The distorted image. (b) The compensated image.If the objects in the scene are at different depths, our algorithm in general can still restore the image because the global motion obtained by the algorithm represents the motion of most parts of the image. For the case where the camera is stationary and the objects are moving, the algorithm can be further enhanced by supplementing it with a segmentation technique to distinguish the objects from each other and from the background.Figure 8. VGA frame timing of OmniVision 1.3 MegaPixel CameraChip3.SIMULATION RESULTSWe implement our algorithm on two different video sequences captured by OmniVision 1.3 MegaPixel CameraChip4. This chip only performs image format conversion and color interpolation on the captured images. The timing parameters of this chip shown in Figure 8 are obtained from the user’s manual. Both simulation sequences are in VGA size. In our simulations, the search range of motion estimation is r120 pixels and the vertical compensation is turned off.Figures 9 and 10 show the results of our first simulation. The frame rate of this sequence is 6 frames per second. The blank region of the corrected images is filled with black pixels. Based on the black region, it can be clearly seen that the velocity v(t) of (1) is not constant.Figure 9. The original and corrected 1st, 5th and 6th, and frames of the first sequenceFigure 10. The original and corrected 12th, 26th, and 38th frames of the second sequence Figures 11 and 12 show the simulation result of our second sequence. In this simulation, the frame rate is 12 frames per second. Because of the smoothing effect on the global motion vectors, no over-compensation occurs in the corrected images.Figure 11. The original and corrected 1st, 15th, and 30th frames of the second sequenceFigure 12. The original and corrected 45th, 60th , and 75th frames of the second sequence Our algorithm corrects most distortions caused by translational movements, even if there are moving objects in the scene. However, non-translational movements, such as rotation and zooming, are not analyzed yet. The information loss in non-translational motion is serious and block-based motion estimation is not suitable to detect such movements. We will construct a more robust distortion model of the rolling shutter effect in non-translational motion.4.CONCLUSIONIn this paper, we have described an algorithm for compensating the rolling shutter effect. A mathematical model for rolling shutter cameras is developed. Two different correction methods, the finite difference method and the reconstruction method, are examined and their drawbacks are discussed. Because over-compensation degrades the video quality, a Bezier curve fitting technique is adopted to smooth the global motion and improve the video quality. Compared with other techniques, this algorithm only involves digital image processing and does not need any sample-and-hold circuit. The algorithm is relative easy to implement.REFERNECES1.S. Lauxtermann et al., “A mega-pixel high speed CMOS imager with sustainable gigapixel/sec readout rate”, inProc. 2001 IEEE Workshop on Charge-Coupled Devices and Advanced Image Sensors, pp. 48-51, Lake Tahoe, NV, June 7-9, 20012.M. Wäny and G.Paul, “CMOS image sensor with NMOS-only global shutter and enhanced responsivity”, in IEEETransactions on Electron Devices, vol. 50, no. 1, pp. 57-62, January, 20033. C. Geyer, M. Meingast and S. Sastry, “Geometric Models of Rolling-Shutter Cameras”, 4.OmniVision Technologies, Inc. 5.Chia-Kai Liang, Yu-Chun Peng, Hung-Au Chang, Che-Chun Su and Homer Chen, “The effect of digital imagestabilization on coding performance”, International Symposium on Intelligent Multimedia, Video and SpeechProcessing, October, 2004。

Whilst e2v technologies has taken care to ensure the accuracy of the information contained herein it accepts no responsibility for the consequences of any use thereof and also reserves the right to change the specification of goods without notice. e2v technologies accepts no liability beyond the set out in its standard conditions of sale in respect of infringement of third party patents arising from the use of tubes or other devices in accordance with information contained herein.e2v technologies limited, Waterhouse Lane, Chelmsford, Essex CM1 2QU United Kingdom Telephone: +44 (0)1245 493493 Facsimile: +44 (0)1245 492492e-mail: enquiries@ Internet: Holding Company: e2v technologies plce2v technologies inc. 4 Westchester Plaza, PO Box 1482, Elmsford, NY10523-1482 USA Telephone: (914) 592-6050 Facsimile: (914) 592-5148 e-mail: enquiries@INTRODUCTIONThe CCD55-30 is one of the CCD55 range of large area image sensors primarily intended to suit the requirements of astronomy, medical diagnostic and scientific measuring instruments. The device utilises Advanced Inverted-Mode Operation (AIMO) for lowest dark current. It operates with standard three-phase clocking and buried channel charge transfer. The read-out register has a low-noise amplifier at one end for slow-scan applications and a high speed amplifier at the other end.DESCRIPTIONThe sensor has an image area with 1252 x 1152 pixels for Full Frame variants. Frame Transfer variants can also be produced by application of a metal “store shield” leaving an unobstructed image area of 1242 x 574 usable pixels. There is a single output register that has charge detection circuits incorporated at each end. One output (A1) is intended for high-speed operation and has an associated dummy output circuit. By design the maximum speed of this output is approximately 6 MHz, as set by being sufficiently settled for reliable CDS with ≤10 pF load, but operation up to 9 MHz should be achievable if incomplete settling can be tolerated. This output is designed to have charge handling capacity of at least two image pixels. The second output (A2) is designed for lower noise performance whilst still being able to handle the full well capacity of one pixel and by design has a maximum speed of approximately 3 MHz.VARIANTSMultiple AR coatings are available as well as the choice between Full Frame and Frame Transfer variants. Attachment of permanent windows is also an option and should be discussed directly with e2v.Non-inverted-mode options (N I MO) and other formats (e.g. CCD55-20) can also be provided and are described in other data sheets.Consult e2v technologies for any further information.The device pictured is without a store shield.SUMMARY SPECIFICATIONNumber of usable image pixels 1242 (H) x 574 (V)Read-out noise A1 6.5 e at 18.5 kHz−Quoted performance parameters given here are “typical” values. Specification limits are shown later.CCD55-30 AIMO Back Illuminated High Performance CCD SensorPERFORMANCEElectro-Optical SpecificationNote 1 Min Typical Max Units Note Peak charge storage (image) 400,000 e−/pixel 2,3Peak charge storage (register) 1,300,000 e−/pixel 2,3Output node capacity A1 1,300,000 e−2,3 A2 600,000 e−Output amplifier responsivity A1 0.8 1.2 1.6 µV/e−A2 2 3 4 µV/e−Read-out noise A1 6.5 e− rms4 A2 3.5 5 e− rmsDark signal at 273 K 70 110 e−/pixel/s5 at 293 K 800 1300 e−/pixel/sDark Signal Non-Uniformity at 273 K 30 53 e−/pixel/s5 at 293 K 185 325 e−/pixel/sCharge transfer efficiencyserial 99.9999 %2,6 parallel 99.9993 %NOTES1. Device performance will be within the limits specified by “max” and “min” when operated at the recommended voltagessupplied with the test data and when measured at a typical register clock frequency of 50 kHz. Performance at higher readout frequencies is not measured for production testing at e2v. The readout frequency for noise is defined separately in note 3.2. Typical values are provided from results of previous measurement or by design and by default are not measured per device.3. Signal level at which resolution begins to degrade.4. Measured at 253 K with an 18.5 kHz readout frequency.5. Dark signal (or current) is measured with the substrate voltage at +9V and the device temperature 273 K. It is a strongfunction of temperature and the typical AIMO average dark current Q d any temperature T (Kelvin) between 230 K and 300 K is given by:Q d/Q do = 1.14x106T³e -9080 /Twhere Q do is the dark current at 293 K.Note, DSNU scales with temperature generally following the NIMO scaling of Q d/Q do = 122T³e -6400 /T.Transfer through the image sections can give rise to an additional temperature-independent signal component called “clock-induced charge” The CIC generated depends on the bias levels used, whether the device operates in inverted or non-inverted mode, and the details of the clock timings employed. Further details can be found on the e2v website or by contacting e2v.6. The CTE value is quoted for the complete clock cycle (i.e. all phases). If fitted, the permanent window on Frame Transfervariants would hamper CTE measurements. If it were to be measured, the reported results may under-estimate the true CTE performance.COSMETIC SPECIFICATIONSMaximum allowed defect levels are indicated below.Grade0 1 2 Column defects Black 0 2 6 White0 0 2 White spots 80 100 150 Black spots 50 100 400 Traps > 200e −2512Grade 5 devices are fully functional but with an image quality below that of grade 2, and may not meet all other specifications. Not all parameters may be tested.DEFINITIONSWhite spotsA defect is counted as a white spot if the dark generation rate is 50 times the specified maximum dark signal generation rate at 293 K. The typical temperature dependence of white spot defects is different from the average dark signal and is given by:Q d /Q do = 122T³e -6400/TBlack spots A black spot defect is a pixel with less than 80% of the local mean at a signal level of approximately half full well.Column defects A column is counted as a defect if it contains at least 9 white or dark single pixel defects. TrapsA trap causes charge to be temporarily held in a pixel and these are counted as defects ifthe quantity of trapped charge is greater than 200 e - at the specified test temperature (nominally 273 K).TYPICAL OUTPUT AMPLIFIER NOISEThe theoretical variation of typical read noise with operating frequency is shown below, if measured using correlated double sampling with a pre-sampling bandwidth equal to twice the pixel rate at approximately 253 K.SPECTRAL RESPONSE AT 253 K (−20 °C)Wavelength(nm)Minimum QE (%)Maximum Pixel Response Non-UniformityPRNU (1σ) (%)Basic Process Mid Band CoatedBasic Process Broad Band CoatedBasic ProcessUncoated [7]350 15 25 10 - 400 40 55 25 3 500 85 75 55 - 650 85 75 50 3 9003030305NOTE7. Only available in Full Frame format.TYPICAL QE VALUES FROM MODEL CALCULATIONModel inputs: Basic back thinning process, temperature -20 °C, silicon thickness 16.00 µm, typical AR coating layer thickness, incoherent reflection.NOTES8 Manufacturing process variation can mean actual sensor QE performance may differ from the typical values in these curves,but will meet minimum QE values from the spectral response table above. QE measurements are averaged over many pixels and over the pass band of the optical filter. 9 The values here represent performance at -20 °C. QE at longer wavelengths will decrease at much lower temperatures andincrease when temperature rises. Contact e2v for more information.DEFINITIONSBack-ThinningA back-thinned CCD is fabricated on the front surface of the silicon and is subsequently processed for illumination from the reverse side. This avoids loss of transmission in the electrode layer (particularly significant at shorter wavelengths or with low energy X-rays). This process requires the silicon to be reduced to a thin layer by a combination of chemical and mechanical means. The surface is “passivated” and an anti-reflection coating may be added.AR CoatingAnti-reflection coatings are normally applied to the back illuminated CCD to further improve the quantum efficiency. Standard coatings optimise the response in the visible, ultra-violet or infrared regions. For X-ray detection, an uncoated device may be preferable.Inverted Mode (IMO)An inverted mode CCD has an additional implant that allows charge integration to be carried out with all clock phases low. With a high voltage applied to the substrate (typically +9 V) this causes the whole of the device to be flooded with holes (inverted or pinned), which suppresses the surface component of dark signal. This leaves only the much lower bulk component, reducing the overall dark signal by a factor of approximately 100.Inverted mode operation is also referred to as multi-phase pinning (MPP).Readout NoiseReadout noise is the random noise from the CCD output stage in the absence of signal. This noise introduces a random fluctuation in the output voltage that is superimposed on the detected signal.The method of measurement involves reverse-clocking the register and determining the standard deviation of the output fluctuations, and then converting the result to an equivalent number of electrons using the known amplifier responsivity. Dummy OutputOutput A1 has an associated “dummy” circuit on-chip, which is of identical design to the “real” circuit but receives no signal charge. The dummy output should have the same levels of clock feed-through, and can thus be used to suppress the similar component in the “real” signal output by means of a differential pre-amplifier. The penalty is that the noise is increased by a factor of √2. If not required the dummy outputs may be powered down.Dark SignalThis is the output signal of the device with zero illumination. This typically consists of thermally generated electrons within the semiconductor material, which are accumulated during signal integration. Dark signal is a strong function of temperature as described in note 5.Correlated Double SamplingA technique for reducing the noise associated with the charge detection process by subtracting a first output sample taken just after reset from a second sample taken with charge present.Charge Transfer EfficiencyThe fraction of charge stored in a CCD element that is transferred to the adjacent element by a single clock cycle. The charge not transferred remains in the original element, possibly in trapping states and may possibly be released into later elements. The value of CTE is not constant but varies with signal size, temperature and clock frequency.ARCHITECTUREDevice SchematicFrame Transfer Image AreaABD AØ3AØ2AØ1SS BØ1BØ2BØ3DD DGI OD2OS2RD2ØR2CØ2CØ3G 6789101112131415163451217181920212239383736353433323130294241404443282726252423ABD AØ3AØ2AØ1SS BØ1BØ2BØ3DGI G OD1OS1DOS1RD1ØR1CØ1OGOUTPUT CIRCUITSLarge Signal (A1)Low Noise (A2)NOTES10. The DC restoration circuitry requires a pulse at the start of line read-out, and this is automatically obtained by an internalconnection to the BØ3 image clock, as can be seen in the schematics.11. The external load on the large signal output is not critical, but can be 7.5 mA constant current supply or a 3.3 kΩ resistor Theamplifier output impedance is typically 250 Ω for A1.12. The external load on the low noise output is not critical, but can be 5 mA constant current supply or a 5 kΩresistor. Theamplifier output impedance is typically 400 Ω for A2.ELECTRICAL INTERFACECONNECTIONS, TYPICAL VOLTAGES AND ABSOLUTE MAXIMUM RATINGSNOTES13. Reset and the A and B section clock pulse low levels should be 0 ± 0.5 V. The C section clock pulse low level should be set1 V higher.14. Charge can be reverse-clocked into the drain at the top of the device. During this period of clocking, I G should be 13 ± 1 Vfor 12 V image clocks.15. Non-charge dumping level shown. For charge dumping, DG should be 13 ± 1 V for 12 V register clocks.16. The device has no anti-blooming but a drain bus is present above section A and must be biased to prevent charge injection.The isolation gate I G is positioned between this bus and the first AØ1 electrode.17. The substrate voltage may need to be adjusted within the range indicated to achieve correct inverted mode operation.18. Various guard diodes are connected to the output drains and bias must be maintained. It is not therefore possible to switchoff an unused amplifier.19. Do not connect to voltage supply but use an external load, note 8. With a 5 mA constant-current load, VOS ~ VRD + 6 V.The current through this pin must not exceed 20 mA. Permanent damage may result if, in operation, OS experiences short circuit conditions.20. Phase 2 for read-out through amplifier A2, phase 1 for read-out through amplifier A1.21. Phase 1 for read-out through amplifier A2, phase 2 for read-out through amplifier A1.22. Do not connect to voltage supply but use an external load, note 9. With a 7.5 mA constant-current load, VOS ~ VRD + 6V.The current through this pin must not exceed 20 mA. Permanent damage may result if, in operation, OS or DOS experience short circuit conditions.PIN CONNECTIONS (View facing underside of package)ELECTRICAL INTERFACE CHARACTERISTICSElectrode Capacitances (calculated at mid-clock level)The total load to be driven per phase is the sum of the capacitance of the phase to substrate plus the inter-phase capacitance to each of the adjacent phases. For the AØ1 and BØ1 phases the total is 26.6 nF, for the AØ2, AØ3, BØ2 and BØ3 phases the total is 14 nF and for all CØ phases the total is 355 pF.POWER UP/POWER DOWNWhen powering the device up or down, it is critical that any specified maximum rating is not exceeded. Specifically the voltage for the amplifier and dump drains must never be taken negative with respect to the substrate. Hence, since the substrate is to be operated at a positive voltage, then the drive electronics should have a switch-on sequence which powers up all the drains to their positive voltages before the substrate voltage starts to increase from zero.It is also important to ensure that excess currents (see notes 19 and 22) do not flow in the OS or DOS pins. Such currents could arise from rapid charging of a signal coupling capacitor or from an incorrectly biased DC-coupled preamplifier.Similarly, for powering down, the substrate must be taken to zero voltage before the drains.POWER CONSUMPTIONThe power dissipated within the CCD is a combination of the static dissipation of the amplifiers and the dynamic dissipation from the parallel and serial clocking (i.e. driving the capacitive loads).The table below gives calculated values for the components of the power dissipation for different frame rates. The frequency is that for clocking the serial register. The clock period for parallel transfer is taken to be 20 µs (near the minimum).The amplifier power dissipation is the on-chip component for both A1 and A2. The clocked power dissipation is distributed between the device and the clock buffers.The dissipation reduces to only that of the amplifiers during any time that charge is being collected in the image sections with both the parallel and serial clocks static.TIMING DIAGRAMDETAIL OF LINE TRANSFERNote: For Full Frame readout, IØ = AØ = BØ. For Frame Transfer, IØ = BØ whilst AØ is low for charge collection.DETAIL OF OUTPUT CLOCKINGLINE OUTPUT FORMATCLOCK TIMING REQUIREMENTSThe table below details some limitations on the clock timing. Where no value is shown, the timing is either not critical or will be defined by the required readout rate.For AIMO operation, the first image electrode to be taken high after the all-low integrate phase should be Ø3 and the standard four pulse sequence, as shown in the detail of line transfer, is necessary to transfer a row to the register. For correct image row transfer, the voltage on the electrode should rise to at least 90% clock amplitude before the voltage on the previous phase electrode begins to fall. This in turn should reduce to below 10% clock pulse amplitude before the voltage on the next phase electrode begins to rise.For the register section, CØ1 and CØ2 should be high to receive charge from the last image row. The order of clock pulses to CØ1 and CØ2 determine the direction of readout to either A1 or A2, with A2 shown above by default.Symbol Description Min Typ Max UnitT i Image clock period15 3t op + 3t ip- µst wi Image clock pulse width8 2t op + 1t ip -t ri Image clock pulse rise time (10 to 90%)0.5 - 0.5t oiµst fi Image clock pulse fall time (10 to 90%)0.5 - 0.5t oiµst oi Image clock pulse overlap 3 - - µst li Image clock pulse, two phase low 2 - - µst dir Delay time, BØ stop to CØ start 3 - - µst dri Delay time, CØ stop to BØ start 1 - - µsT r Register clock period (note 23)150 - - nst rr Register pulse rise time (at 10-90% levels) 10 - 0.3T r nst fr Register pulse fall time (at 90-10% levels) 10 - 0.3T r nst or Register pulse overlap 10 - - nst wx Reset pulse width (at 50% levels) 20 - - nst rx, t fx Reset pulse rise and fall times 10 - - nsNOTE23 With the device pinned, the register clock overlaps required limit the maximum readout frequency to ~6 MHz for maximumcharge signal transfer, but faster operation could be possible for some loss in peak signal. At readout frequencies below the maximum it can be advantageous to use an asymmetrical timing, where, the CØ2 pulse can be minimised to only the width required to contain the reset pulse thereby maximising the reset and signal sampling windows.PACKAGE DETAILHANDLING CCD SENSORSCCD sensors, in common with most high performance MOS IC devices, are static sensitive. In certain cases, a discharge of static electricity may destroy or irreversibly degrade the device. Accordingly, full antistatic handling precautions should be taken whenever using a CCD sensor or module. These include: •Working at a fully grounded workbench•Operator wearing a grounded wrist strap•All receiving sockets to be positively groundedEvidence of incorrect handling will invalidate the warranty. All devices are provided with internal protection circuits to the gate electrodes (i.e. all CCD pins except SS, DD, RD, OD and OS) but not to the other pins.The devices are assembled in a clean room environment. e2v technologies recommend that similar precautions are taken to avoid contaminating the active surface.PART REFERENCESFor ordering information, some existing part numbers are below. Contact e2v for other variants.CCD55-30-*-xxx* = cosmetic gradexxx = device specific part numberPart Number DescriptionCCD55-30-*-348 Full Frame, Basic Midband, No Window CCD55-30-*-359 Full Frame, Basic Uncoated, No Window CCD55-30-*-S17 Full Frame, Basic Broadband, No WindowDimension Distance (mm) TolerancesA 53.34 ~ 1 %B 33.00 ~ 1 %C 2.54 -D 3.81 -E 2.3 ~ 10 %F <1.8 ~ 10 %G 43.18 ~ 1 %H 48.26 ~ 1 %The dimensions are provided for information.“E” is the thickness of the package at the greatest point where the temporary window sits on an outer ledge.HIGH ENERGY RADIATIONPerformance parameters will begin to change if the device is subject to ionising radiation. Characterisation data is held at e2v technologies with whom it is recommended that contact be made if devices are to be operated in any high radiation environment.TEMPERATURE RANGEOperating temperature range 153 - 323 KStorage temperature range 143 - 373 K Operation or storage in humid conditions may give rise to ice on the surface when the sensor taken to low ambient temperatures, thereby causing irreversible damage.Maximum rate of heating or cooling: 5 K/min.。

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References
Design of Physical-to-Digital Converters
References for emerging trends (cont'ed)
• M. Yip and A.P. Chandrakasan, "A Resolution-Reconfigurable 5-to-lOBit 0.4-to-l V Power Scalable SAR ADC for Sensor Applications," 7SSC, vol. 48, no. 6, pp. 1453-1464, June 2013. P. Harpe, etal., "A 10b/12b 40 kS/s SAR ADC With Data-Driven Noise Reduction Achieving up to 10.1b ENOB at 2.2 fJ/Conversion-Step," JSSC, vol. 48, no. 12, pp. 3011-3018, Dec. 2013. D.A. Hall, etal., "A 256 Pixel Magnetoresistive Biosensor Microarray in 0.18 pm CMOS," JSSC, vol. 48, no. 5, pp. 1290-1301, May 2013. S. Gambini, et al., "A 10 kPixel CMOS Hall Sensor Array With Baseline Suppression and Parallel Readout for Immunoassays," JSSC, vol. 48, no. 1, Jan. 2013. L.H.C. Braga, etal., "A Fully Digital 8x 16 SiPM Array for PET Applications With Per-Pixel TDCs and Real-Time Energy Output," JSSC, vol. 49, no. 1, Jan. 2014. Y. Maruyama, etal., "A 1024 x 8, 700-ps Time-Gated SPAD Line Sensor for Planetary Surface Exploration With Laser Raman Spectroscopy and LIBS," JSSC, vol. 49, no. 1, Jan. 2014.