TOF Sensor Processing Circuit With Counter-Based Depth Readout
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Solution Overview
Problem
Current time-of-flight (TOF) image sensors require complex processing circuits for distance determination, leading to increased power consumption and area usage, and are not compatible with existing image sensor designs without significant redesign.
Innovation Solution
A TOF imaging device with a pixel array and signal processing circuit that includes a time-of-flight processing circuit performing logical operations on first and second tap signals, outputting digital signals through a counter, allowing for efficient depth sensing with minimal power consumption and reduced area, while being compatible with existing designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex processing circuits are used for TOF distance determination, then measurement precision is improved, but use of energy increases and device complexity increases
Solution Approach 1:
The patent extracts the essential TOF measurement function from complex processing circuits and implements it using a simplified counter-based approach. The counter circuit counts clock cycles between emitted and reflected light wave detections, eliminating the need for complex signal processing while maintaining distance measurement precision.
Solution Approach 2:
The patent replaces complex electronic processing circuits with a simpler counter-based timing system. Instead of using sophisticated signal processing to determine distance, the system uses a clock signal and counter to measure the time of flight directly, reducing power consumption and circuit complexity.
2Measurement precision
If complex processing circuits are used for TOF distance determination, then measurement precision is improved, but area of stationary object increases
Solution Approach 1:
The patent extracts the core TOF measurement capability from complex processing circuits and implements it using a minimal counter circuit. This extraction reduces the circuit area significantly while preserving the essential distance measurement function.
Solution Approach 2:
The patent uses a clock signal copy approach where a reference clock is divided and used for timing measurements. This copying method allows precise time measurement without requiring complex processing circuits, thereby reducing the area occupied by the processing circuitry.
3Ease of manufacture
If existing image sensor designs are maintained, then ease of manufacture is improved, but adaptability worsens
Solution Approach 1:
The patent implements a universal counter circuit that can support multiple operating modes (different distance measurement techniques and binning operations) through software control. This single counter-based architecture replaces the need for separate processing circuits for each mode, enabling existing image sensor designs to support multiple functions without hardware changes.
Solution Approach 2:
The patent enables mode switching by changing operational parameters of the counter circuit rather than changing the hardware architecture. Different distance determination modes are achieved by modifying timing parameters, clock division ratios, and counter initialization values, allowing existing designs to adapt to different requirements.
Data Source
AI summary
A time-of-flight imaging device comprises an image sensor comprising a pixel array including a plurality of pixel circuits, respective ones of the plurality of pixel circuits including a first tap output configured to output a first tap signal, and a second tap output configured to output a second tap signal; and a signal processing circuit including a time-of-flight processing circuit configured to perform at least one logical operation on the first tap signal and the second tap signal based on a mode of the signal processing circuit, and a counter configured to output a digital signal based on an output of the time-of-flight processing circuit.