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DEMODULATION PIXELS IN CMOS/CCD 101 This chapter is divided into three main sections: In Section 5.1 we introduce different realizations of demodulation pixels. They have all been realized in Orbit 2 µm CMOS/CCD technology, a process offered as MPW. This process has two different polysilicon layers (poly1 and poly2) that can both be used as transistor gates. Additionally the design rules allow these poly gates to overlap over the thin gate oxide. Hence it is possible to realize CCDs with this CMOS/CCD process (c.f. Section 3.2). The realized demodulation pixels vary in operational architecture, maximum demodulation frequency and fill factor, the latter being a very important parameter for realizing highly sensitive devices. All pixels fulfill the four physical demodulation demands described above. The characteristic features of the pixels introduced are summarized in Table 5.1 and Figure 5.8. Section 5.2 then summarizes the results of a detailed characterization of the demodulation performance for the 1-tap pixel, which is the pixel-realization with the best electrooptical properties (demodulation bandwidth and optical fill factor). This pixel has been fabricated twice; (1) with surface channel (SCCD) CCD structures and (2) with buried channel (BCCD) structures, allowing a direct comparison of both CCD types. Especially we focus on the efficiency of the shutter mechanism (sampling efficiency or demodulation contrast) and its dependency on sampling frequency and wavelength. Also, we present the measured phase accuracy as a function of the optical power received in the pixel and compare these results to the theory presented in Section 4.2. The 1-tap pixel is the basis for two lock-in sensor arrays we realized, a line-sensor with 108 pixels and an image sensor with 64x25 pixels. Both arrays are implemented as range cameras, which are introduced in Chapter 6. Motivated by the outstanding results presented in Section 5.2, we present a very simple and only slightly modified pixel structure in Section 5.3 that overcomes the restrictions of the 1-tap pixel (serial integration of the single sampling points) by offering two optically identical photosites.
102 CHAPTER 5 5.1 Pixel concepts 5.1.1 Multitap lock-in CCD This device, introduced in [SP2] and [SP4], consists of a light sensitive photogate that is connected to a 4-phase CCD-line, the pipeline-CCD. Every CCD-element, consisting of four CCD gates, is connected to an identical CCD-line, the readout- CCD, by so-called transfer gates (see Figure 5.2). metal wire contact n+ diffusion poly 2 poly 1 CCD channel light opening Dimensions: photogate: 45x15 µm 2 , pixel: 45x270 µm 2 , aspect ratio: 1:6, fill factor: 5.6%. potential light shield a 0 vertical transfer for charge addition in readout CCD a 1 CCD3 CCD1 CCD4 CCD2 Figure 5.2 Multitap lock-in pixel: layout and cross-sectional view. a 2 PG DG dump diff. During the demodulation operation the upper CCD-line is clocked at maximum lossless speed so that photoelectrons from the photogate are transported into this CCD line. With an appropriate choice of the modulation frequency (modulation period equals the time of four CCD shifts) each CCD element within the pipeline CCD carries one sampling point of the received modulated light after four CCD shifts. By clocking the pipeline CCD, the temporal modulation is converted into spatial charge distribution. This is the actual process of demodulation in the multitap-pixel. After these four sampling points have been taken, they can be stored into the readout- CCD by activating the transfer gates. During this transfer the additional photoelectrons generated under the photogate can be dumped to a diffusion so that a 3
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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 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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Page 67 and 68: 50 CHAPTER 3 the smearing effect, r
Page 69 and 70: 52 CHAPTER 3 3.1 Silicon properties
Page 71 and 72: 54 CHAPTER 3 (a) Figure 3.3 Optical
Page 73 and 74: 56 CHAPTER 3 Quantum efficiency in
Page 75 and 76: 58 CHAPTER 3 The different operatio
Page 77 and 78: 60 CHAPTER 3 (a) (b) Depletion widt
Page 79 and 80: 62 CHAPTER 3 Very special processes
Page 81 and 82: 64 CHAPTER 3 1 kT Dn = ⋅ vth ⋅
Page 83 and 84: 66 CHAPTER 3 The proportionality fa
Page 85 and 86: 68 CHAPTER 3 difference of only 1 V
Page 87 and 88: 70 CHAPTER 3 Flicker noise is cause
Page 89 and 90: 72 CHAPTER 3 A s = sf ⋅ q C ⎡ V
Page 91 and 92: 74 CHAPTER 3 amount of the charge p
Page 93 and 94: 76 CHAPTER 3 substrate (Equation 3.
Page 95 and 96: 78 CHAPTER 3 charge carriers the CT
Page 97 and 98: 80 CHAPTER 3 without causing short
Page 99 and 100: 82 CHAPTER 3 Over an address decode
Page 101 and 102: 84 CHAPTER 3 Orbit’s 2.0µm CMOS/
Page 103 and 104: 86 CHAPTER 4 Figure 4.1 P lens Lamb
Page 105 and 106: 88 CHAPTER 4 Required optical power
Page 107 and 108: 90 CHAPTER 4 4.2 Noise limitation o
Page 109 and 110: 92 CHAPTER 4 number of pseudo-backg
Page 111 and 112: 94 CHAPTER 4 Cmod = 1 QE(λ) = 0.65
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Page 116 and 117: DEMODULATION PIXELS IN CMOS/CCD 99
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IMAGING TOF RANGE CAMERAS 151 6. Im
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IMAGING TOF RANGE CAMERAS 153 contr
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IMAGING TOF RANGE CAMERAS 155 6.1.2
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IMAGING TOF RANGE CAMERAS 157 gate
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IMAGING TOF RANGE CAMERAS 159 6.2 2
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IMAGING TOF RANGE CAMERAS 161 n+ di
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IMAGING TOF RANGE CAMERAS 163 pixel
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IMAGING TOF RANGE CAMERAS 165 Power
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IMAGING TOF RANGE CAMERAS 167 Delay
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IMAGING TOF RANGE CAMERAS 169 6.3 3
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IMAGING TOF RANGE CAMERAS 171 Gate
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IMAGING TOF RANGE CAMERAS 173 Bound
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IMAGING TOF RANGE CAMERAS 175 Figur
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IMAGING TOF RANGE CAMERAS 177 Final
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IMAGING TOF RANGE CAMERAS 179 #5 #6
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SUMMARY AND PERSPECTIVE 181 7. Summ
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SUMMARY AND PERSPECTIVE 183 into th
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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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