TDC Coarse-Fine Histogram Circuit for High-Resolution Depth Sensing
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Solution Overview
Problem
Time-to-digital converters (TDCs) in ranging systems face limitations in achieving high resolution without increasing the number of histogram bins, which can lead to higher area consumption and power usage in ToF image sensors.
Innovation Solution
A method and circuit that generate coarse and fine histograms using a TDC, where the fine histogram focuses on a narrower depth range around a detected peak bin, allowing for higher resolution depth detection with fewer bins, reducing area consumption and power usage.
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 histogram into multiple levels (coarse histogram and fine histogram). The coarse histogram covers a wide depth range with fewer bins, and the fine histogram focuses on a specific region of interest with higher resolution bins. This segmentation allows the system to achieve high resolution where needed while using fewer total bins, reducing area consumption in the ToF image sensor.
Solution Approach 2:
The patent applies different histogram bin resolutions to different depth ranges. Instead of using uniform high-resolution bins across the entire depth range, the system uses fine bins only in the region of interest (where targets are most likely to be found) and coarser bins elsewhere. This local quality approach maintains measurement precision in critical areas while reducing overall area consumption.
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 into coarse and fine levels, processing only the necessary portions at high resolution. By using a coarse histogram for initial analysis and only generating fine histogram bins in regions of interest, the system reduces the total computational load and power consumption compared to maintaining high-resolution bins across the entire depth range.
Solution Approach 2:
The patent applies partial action by generating fine histogram bins only for the region of interest rather than for the entire depth range. This selective approach provides sufficient measurement precision for actual targets while avoiding the excessive power consumption that would result from uniformly high-resolution processing across all possible depth values.
3Adaptability or versatility
If a fixed deep histogram is used to cover the entire depth range, then adaptability is improved, but measurement precision in specific regions deteriorates
Solution Approach 1:
The patent segments the depth range coverage into a coarse histogram that spans the entire depth range and fine histograms that focus on specific regions of interest. The coarse histogram provides broad adaptability and coverage, while the fine histograms deliver high measurement precision in critical areas. This multi-level segmentation resolves the contradiction between covering the entire depth range and achieving high precision in specific regions.
Solution Approach 2:
The patent implements a dynamic histogram generation approach where fine bins are selectively created based on detected peaks or regions of interest in the coarse histogram. Rather than using a static fixed-depth histogram, the system dynamically adjusts the histogram resolution and focus based on the actual scene content, maintaining adaptability while improving precision where needed.
Data Source
AI summary
In an embodiment, a method includes: receiving a first plurality of digital codes from a time-to-digital converter (TDC); 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.