Time-to-Digital Converter Peak-Bin Histogram Refinement
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Solution Overview
Problem
Existing time-to-digital converters (TDCs) in time-of-flight (ToF) systems face challenges in achieving high resolution depth detection without increasing the number of histogram bins, which leads to higher area consumption and power usage.
Innovation Solution
A method and circuit implementation that involves generating a coarse histogram to detect a peak bin, followed by generating a fine histogram with a narrower depth range centered around the peak bin, allowing for higher resolution depth detection with a reduced number of bins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of histogram bins is increased to achieve higher resolution depth detection, then measurement precision is improved, but area consumption and power usage increase
Solution Approach 1:
The patent divides the depth detection process into two segments: a first pass using a smaller number of histogram bins to identify a peak depth range, and a second pass focusing only on that identified range with higher resolution binning. This segmentation allows high resolution depth detection in the region of interest without maintaining high resolution across the entire depth range, thus reducing overall area consumption while improving measurement precision where needed.
2Measurement precision
If the number of histogram bins is increased to achieve higher resolution depth detection, then measurement precision is improved, but power usage increases
Solution Approach 1:
The patent segments the histogram binning operation into two phases: an initial phase with fewer bins that consumes less power to identify the peak depth range, and a focused second phase with higher resolution bins only in the region of interest. This reduces the total number of bin operations performed, thereby lowering power usage while still achieving high resolution depth detection where required.
3Measurement precision
If a fixed large number of histogram bins is used to cover the full depth range, then measurement precision is maintained across all depths, but device complexity increases
Solution Approach 1:
The patent implements a dynamic histogram binning approach where the number and distribution of bins change between two operational passes. In the first pass, fewer bins are used to quickly identify the peak depth range. In the second pass, the bin structure is dynamically adjusted to concentrate higher resolution bins only in the identified region of interest. This dynamic adaptation reduces device complexity compared to maintaining a fixed large bin structure across the entire depth range.
Data Source
AI summary
In an embodiment, a method includes: receiving a first plurality of digital codes from a time-to-digital converter (TDC); generating a coarse histogram from the first plurality of digital codes; detecting a peak coarse bin from the plurality of coarse bins; after receiving the first plurality of digital codes, receiving a second plurality of digital codes from the TDC; and generating a fine histogram from the second plurality of digital codes based on the detected peak coarse bin, where a fine histogram depth range is narrower than a coarse histogram depth range, where a lowest fine histogram depth is lower or equal to a lowest coarse peak depth, and where a highest fine histogram depth is higher or equal to a highest coarse peak depth.