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

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OPTICAL TOF RANGE MEASUREMENT 35 f1 f2 TW TW measurement signal spurious signal resulting input signal ⎛ ⎞ ⎜ t rect ⎟ ⎝ TW ⎠ f1 0 2 f t t t t t signal distortion by spurious signal ⎛ T sinc ⎜2π ⋅ ∆f ⋅ W ⎝ 2 Figure 2.11 Spectral selectivity of digital lock-in. measurement signal ⎞ ⎟ ⎠ f spurious signal input signal 0 f1 f1 f2 f2 ⎛ T sinc ⎜2π ⋅ f ⋅ W ⎝ 2 1 TW ∆f 0 f1 2 f We only have to consider the superimposed signal power of the spurious signal’s sinc-spectrum into the spectrum of the measurement signal at its center frequency. This is because the DFT detection is only sensitive to discrete frequencies, as ⎞ ⎟ ⎠ f f f f f
36 CHAPTER 2 mentioned before. The demodulation result for the measurement signal is then falsified due to frequency dispersion by: ⎛ T ⎞ sinc⎜2π ⋅ ∆f ⋅ w ⎟ Equation 2.21 ⎝ 2 ⎠ With TW=observation window/ integration time and ∆f=difference frequency of measurement and spurious signal. If we postulate a signal suppression of better than 40 dB (factor 100) for neighboring frequencies, we need to choose integration times as listed below: f1 f2 ∆f TW 20 MHz 21.0000 MHz 1 MHz 100 µsec 20 MHz 20.1000 MHz 100 kHz 1 msec 20 MHz 20.0100 MHz 10 kHz 10 msec 20 MHz 20.0010 MHz 1 kHz 100 msec 20 MHz 20.0001 MHz 100 Hz 1 sec These considerations are of special importance if two or more TOF cameras observe the same area so that their radiation fields are superimposed. If for any reason these modulation signals can’t be separated by using light of different wavelengths, one might want to separate the signals by using slightly different modulation frequencies. In that case the observation window defines the spectral selectivity concerning modulation frequency. Note that the above estimation presumes equal amplitudes of spurious signal and measurement signal. 2.2.2 Aliasing Obviously the shape of the modulation signal has an influence on the measurement result. As already mentioned, we only use four sampling points to sample the offset containing signal. Therefore, Shannon’s law is only obeyed for a pure sinusoidal wave. If we consider using a square-wave modulated signal (infinite spectrum), taking only four sampling points will lead to aliasing effects. In most of the literature aliasing is only treated together with the amplitude spectrum. We, however, are especially interested in the influence of aliasing on the phase spectrum. For that purpose we first take a simple signal consisting of a cosine wave and one harmonic frequency of the same amplitude and triple frequency. This is to simplify the spectra
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Page 3 and 4: To my parents
Page 5 and 6: Meinen Eltern
Page 7 and 8: II 4. Power budget and resolution l
Page 10 and 11: Abstract Since we are living in a t
Page 12: centimeter accuracy. With the singl
Page 15 and 16: X Eine elegantere Methode zur Entfe
Page 18 and 19: INTRODUCTION 1 1. Introduction One
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Page 89 and 90: 72 CHAPTER 3 A s = sf ⋅ q C ⎡ V
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Page 95 and 96: 78 CHAPTER 3 charge carriers the CT
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86 CHAPTER 4 Figure 4.1 P lens Lamb
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88 CHAPTER 4 Required optical power
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90 CHAPTER 4 4.2 Noise limitation o
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92 CHAPTER 4 number of pseudo-backg
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94 CHAPTER 4 Cmod = 1 QE(λ) = 0.65
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96 CHAPTER 4 Range accuracy (std) i
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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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