Time-of-Flight Depth Calculation Using Lookup Tables
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current time-of-flight depth calculation methods are inefficient due to complex calculations involving inverse trigonometric functions, high memory consumption, and inability to perform parallel processing, leading to low frame rates and increased costs with high-capability processors.
Innovation Solution
A time-of-flight depth calculation method that obtains a phase image, calculates a differential ratio of charge signals, and uses a phase conversion model to determine a depth value when the differential ratio exceeds a threshold, improving accuracy and calculation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inverse trigonometric function calculation is used to obtain phase from phase images, then depth measurement accuracy is improved, but calculation time increases and frame rate decreases
Solution Approach 1:
The patent pre-calculates and stores phase-to-depth conversion data in a lookup table during system initialization. This preliminary action allows the system to replace complex real-time inverse trigonometric calculations with simple table lookups during actual depth measurement, thereby improving frame rate while maintaining accuracy.
Solution Approach 2:
The patent creates a simplified copy of the phase-to-depth conversion relationship by storing pre-computed values in a lookup table. Instead of performing the original complex inverse trigonometric function calculations in real-time, the system uses this copied data structure to quickly retrieve depth values corresponding to measured phases.
2Measurement precision
If inverse trigonometric function calculation is used to obtain phase from phase images, then depth measurement is achieved, but memory consumption increases due to table lookup requirements
Solution Approach 1:
The patent changes the parameter representation by storing phase-to-depth conversion data in a discrete lookup table format rather than maintaining the continuous mathematical relationship. This parameter transformation allows the system to trade a controlled amount of memory for dramatically reduced computational complexity during real-time operation.
3Measurement precision
If floating-point number calculation is used for phase calculation, then calculation precision is improved, but calculation speed decreases significantly
Solution Approach 1:
The patent replaces expensive floating-point arithmetic operations with inexpensive integer-based lookup table indexing. The lookup table stores pre-computed floating-point results, allowing the system to retrieve precise phase values through simple integer indexing and array access operations that are much faster and less computationally intensive than real-time floating-point calculations.
4Speed
If table lookup method is used to obtain phase values, then calculation speed is improved, but parallel processing capability is lost
Solution Approach 1:
The patent segments the phase-to-depth conversion process into independent per-pixel operations. Each pixel's depth calculation becomes an independent lookup operation that can be performed in parallel across the image sensor array. This segmentation maintains the speed benefits of table lookup while enabling parallel processing architecture.
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 ensures more accurate depth measurements with faster calculation speeds, reducing the need for high-capability processors and enabling higher frame rates.
Implementation Method 1
an image sensor, including at least one tap, configured to acquire charge signals of reflected signals reflected by the target region at different times
Implementation Method 2
Depth calculation method and system based on time of flight
Data Source
AI summary
A time-of-flight depth calculation method includes: obtaining a phase image, and obtaining, based on the phase image, a differential ratio of charge signals corresponding to reflected signals acquired by an image sensor at different times; in response to that the differential ratio of the charge signals is greater than or equal to a threshold, obtaining a first phase based on a phase conversion model and the differential ratio of the charge signals; and calculating a depth value of a target region based on the first phase.