Time-of-Flight Sensor Q/I Calculation Circuit
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Solution Overview
Problem
Current time-of-flight image sensors require multiple frames to calculate distance and depth, leading to high power consumption and increased chip area due to the need for multiple counters and analog-to-digital conversions.
Innovation Solution
The implementation of a time-of-flight sensor with a pixel array and processing circuitry that includes comparators and a counter, utilizing an exponential reference signal to calculate quantities Q and I in two frames, reducing the need for multiple counters and analog-to-digital conversions, thereby decreasing power consumption and chip area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple frames are used to calculate distance and depth, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent combines multiple functions into a single counter circuit that can handle multiple frames of distance and depth calculation. Instead of using separate counters for each frame and calculation type, one counter is designed to sequentially process multiple frames and perform both distance (Q) and depth (I) calculations, thereby reducing the number of active components and lowering power consumption while maintaining measurement precision.
Solution Approach 2:
The counter circuit is designed with multi-functionality to perform various operations including distance calculation, depth calculation, and handling multiple frames sequentially. This universal counter can be configured through control signals to execute different calculation modes, eliminating the need for dedicated hardware for each function and reducing overall power consumption while preserving accuracy.
2Measurement precision
If multiple counters and analog-to-digital converters are used to calculate distance and depth, then measurement precision is improved, but chip area increases
Solution Approach 1:
The patent merges multiple counters and analog-to-digital conversion functions into a single integrated counter circuit. This counter is capable of performing sequential counting and calculation operations for both distance (Q) and depth (I) measurements across multiple frames, significantly reducing the chip area required compared to having separate dedicated counters and ADCs for each function.
Solution Approach 2:
The counter circuit is designed as a universal processing unit that can be dynamically configured to perform different measurement functions. Through control signals and state machine logic, the same hardware resources are reused across multiple frames and calculation types, minimizing the total chip area while maintaining the precision required for accurate distance and depth measurement.
3Measurement precision
If multiple frames are used for calculation, then measurement precision is improved, but processing time increases
Solution Approach 1:
The patent employs periodic action by using a state machine to sequentially process multiple frames in a systematic manner. The counter is controlled to switch between different calculation modes (distance, depth, different frames) in a periodic sequence, optimizing the processing flow to minimize idle time and ensure that each frame is processed efficiently, thereby reducing overall processing time while maintaining the precision benefits of multi-frame calculation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for efficient calculation of distance and depth with reduced power consumption and chip area, achieving accurate results with improved processing efficiency.
Implementation Method 1
charge is collected in a photoelectric conversion device of the pixel circuit as a result of the impingement of light
Implementation Method 2
time-of-flight sensor... distance and depth determination... calculate quantities Q and I in two frames
Data Source
AI summary
A time-of-flight device comprises a pixel array including an array of pixel circuits respectively including a photodiode, a first tap, and a second tap; a first signal line coupled to the first tap; a second signal line coupled to the second tap; and processing circuitry coupled to the first signal line and the second signal line, the processing circuitry including: a first comparator configured to receive a first phase signal, to receive a reference signal having an exponential waveform, and to output a first comparison signal, a second comparator configured to receive a second phase signal, to receive the reference signal, and to output a second comparison signal, and a counter configured to perform a count based on the first comparison signal and the second comparison signal.