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

108 CHAPTER 5
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Quantized sensor output
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Measured delay in nanoseconds
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Quantized sensor output
Measured delay
Error
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Figure 5.5 4-tap lock-in pixel (with one output diffusion): Phase measurements
at 10 MHz, (a) without and (b) with correction of 3 rd sampling point.
(c) Measured delay vs. real delay after correction of 3 rd sampling
point. Standard deviation of measurement error: 1.2 ns. (1.2% of
modulation period).
Phase measurements performed with the 4-tap pixel at 10 MHz modulation
frequency (40 MHz sampling frequency) are shown in Figure 5.5. For these
measurements an offset value of 250 quantization levels (estimated empirically)
had to be subtracted from the 3 rd sampling point. Figure 5.5 (a) illustrates the
originally measured sampling point data for different signal delays, (b) shows the
same data after the offset subtraction from the 3 rd sampling point. The achieved
time resolution is pretty poor: 1.2 nanoseconds. Also, in a real application, the
measurement of the different sampling point sensitivities for each pixel in the array
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Error in nanoseconds
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