3D Time-of-flight distance measurement with custom - Universität ...

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DEMODULATION PIXELS IN CMOS/CCD 135 Figure 5.19 Figure 5.20 Contrast in % 45 40 35 30 25 20 15 10 5 0 10 100 1000 10000 100000 1000000 Optical power in femtowatts T_int=1.25ms T_int=12.5ms T_int=125ms Demodulation contrast versus optical power per pixel for different integration times (fmod=20 MHz). [MCD05]. Contrast in % 45 40 35 30 25 20 15 10 5 0 0 500 1000 1500 2000 Output voltage swing in mV (average value) T_int=1.25ms T_int=12.5ms T_int=125ms Demodulation contrast versus total number of integrated electrons (output voltage swing) for different integration times (fmod=20 MHz). (Same data as for Figure 5.19). [MCD05]. We see that the demodulation contrast does not depend on the optical power but only on the energy in each pixel (product of power and integration time). Assuming a reasonable integration time (optically generated signal must dominate the dark current signal), a large output voltage swing, either caused by high optical input power or by a long integration time, leads to a good demodulation contrast.
136 CHAPTER 5 This is only possible, since the CCD-performance of adding and storing signals in the charge domain is nearly noise-free. Normally, one would expect a lower optical power to lead to a worse demodulation contrast, since we know, from CTE measurements of CCDs that are realized in the same technology, that the CTE is better, the more charge is to be transported (c.f. Figure 3.20). This is because all three transport mechanisms (self-induced drift, diffusion and fringing fields) contribute to the charge transport. Self-induced drift strongly depends on the number of integrated electrons, because a smaller number of electrons leads to a reduced influence of self-induced drift on the overall charge transfer. For 20 MHz modulation, the short-time integration lasts only 25 ns (50 ns modulation period). In this period, only few electrons are generated and transported to the integration gate. In fact, as one can see from MCD05, for 175,000 femtowatts, the highest optical power used, only 18 electrons are generated within 50ns, statistically speaking, i.e. only 9 electrons within the active sampling time. For the lowest optical power used the conditions are much worse: one electron is generated, statistically speaking, only every 300 th modulation period. From these numbers, we understand that, under the above conditions, self-induced drift can have no influence at all on the charge transfer. We really move single electrons. Demodulation only works here with the help of statistics. This enormous performance is a big welcome surprise. In addition to the total optical power on one photogate, the average resulting output voltage swing is also listed in MCD05. This can be calculated with known quantum efficiency, wavelength, integration time, conversion capacitance and amplification of the output stage. Also the total number of electrons generated during the integration time is listed, as well as the number of electrons statistically generated during only one modulation period. Since these values are smaller than one, it is more meaningful to list the inverse value, which is the number of modulation cycles that have to pass until one electron is optically generated by the modulated light source, statistically speaking.
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3D Time-of-flight distance measurem
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To my parents
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Meinen Eltern
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II 4. Power budget and resolution l
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Abstract Since we are living in a t
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centimeter accuracy. With the singl
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X Eine elegantere Methode zur Entfe
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INTRODUCTION 1 1. Introduction One
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INTRODUCTION 3 light source observe
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INTRODUCTION 5 Propagation time, ho
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INTRODUCTION 7 Chapter 3 gives a sh
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OPTICAL TOF RANGE MEASUREMENT 9 2.
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OPTICAL TOF RANGE MEASUREMENT 13 pr
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OPTICAL TOF RANGE MEASUREMENT 15 hi
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OPTICAL TOF RANGE MEASUREMENT 17 Pu
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OPTICAL TOF RANGE MEASUREMENT 19 Ad
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OPTICAL TOF RANGE MEASUREMENT 21 pr
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OPTICAL TOF RANGE MEASUREMENT 23 wh
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OPTICAL TOF RANGE MEASUREMENT 25 δ
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OPTICAL TOF RANGE MEASUREMENT 27 c(
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OPTICAL TOF RANGE MEASUREMENT 29 A
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OPTICAL TOF RANGE MEASUREMENT 31 ph
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OPTICAL TOF RANGE MEASUREMENT 33 Ts
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OPTICAL TOF RANGE MEASUREMENT 35 f1
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OPTICAL TOF RANGE MEASUREMENT 37 an
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OPTICAL TOF RANGE MEASUREMENT 39 in
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OPTICAL TOF RANGE MEASUREMENT 41 Ss
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OPTICAL TOF RANGE MEASUREMENT 43 Fr
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OPTICAL TOF RANGE MEASUREMENT 45 1
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50 CHAPTER 3 the smearing effect, r
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52 CHAPTER 3 3.1 Silicon properties
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54 CHAPTER 3 (a) Figure 3.3 Optical
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56 CHAPTER 3 Quantum efficiency in
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58 CHAPTER 3 The different operatio
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60 CHAPTER 3 (a) (b) Depletion widt
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62 CHAPTER 3 Very special processes
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64 CHAPTER 3 1 kT Dn = ⋅ vth ⋅
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66 CHAPTER 3 The proportionality fa
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68 CHAPTER 3 difference of only 1 V
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70 CHAPTER 3 Flicker noise is cause
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72 CHAPTER 3 A s = sf ⋅ q C ⎡ V
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74 CHAPTER 3 amount of the charge p
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76 CHAPTER 3 substrate (Equation 3.
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78 CHAPTER 3 charge carriers the CT
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80 CHAPTER 3 without causing short
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82 CHAPTER 3 Over an address decode
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Page 182 and 183: IMAGING TOF RANGE CAMERAS 165 Power
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SUMMARY AND PERSPECTIVE 185 or phas
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188 CHAPTER 8 8.2 Typical parameter
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190 CHAPTER 8 Spectral luminous int
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192 CHAPTER 8 MCD03S: Conditions SC
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194 CHAPTER 8 MCD06S: Measurement c
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196 [BRK] Brockhaus, “Naturwissen
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198 [KAI] I. Kaisto, et al., “Opt
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200 [SP1] T. Spirig et al., “The
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ACKNOWLEDGMENTS 203 Acknowledgments
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206 Publication list 1. R. Lange, P
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