Depth Sensing System Using Period Number Calculation
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Solution Overview
Problem
Conventional indirect time-of-flight (iToF) modules for depth sensing are limited in their measurement range due to the phase delay of modulated light being restricted to a period of 0˜2π, making it difficult to distinguish between different phase delays and calculate accurate depth values.
Innovation Solution
A depth sensing system and method that utilizes a single-frequency modulated light to calculate the period number corresponding to the phase delay, allowing for the determination of an actual depth or range value by calculating a spatial ratio, basic range, and period number using pixel data and range data from a depth sensing module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional iToF modules use modulated light for depth sensing, then depth measurement can be performed, but the measurement range is limited to 0-2π due to phase delay constraints
Solution Approach 1:
The depth measurement process is segmented into multiple components: phase delay measurement (0-2π range) and period number calculation (additional full periods). By dividing the total depth measurement into these segments, the system overcomes the limitation of single-period measurement while maintaining precision.
Solution Approach 2:
The system performs preliminary actions by calculating the period number N based on spatial ratios and basic ranges before finalizing the depth measurement. This preliminary calculation of N allows the system to determine how many full periods are contained in the total depth, enabling extended measurement range.
2Ease of operation
If the phase delay is limited to one period (0-2π), then the measurement process is simple, but the system cannot distinguish between different phase delays corresponding to different periods
Solution Approach 1:
The system introduces an intermediary calculation process that uses spatial ratios and basic ranges derived from optical center and measuring pixel positions to determine the period number N. This intermediary step recovers the lost period information without complicating the fundamental phase measurement process.
Solution Approach 2:
The system transitions from one-dimensional phase delay measurement (0-2π) to two-dimensional measurement by adding the period number dimension. The final depth is calculated as D = N×P + d, where N represents the period dimension and d represents the phase delay dimension within one period.
3Length of stationary object
If multiple frequencies are used to extend measurement range, then period number can be determined, but device complexity increases
Solution Approach 1:
Instead of using multiple frequencies, the system creates a computational copy of the depth measurement process by calculating virtual depth values D1 and D2 from different spatial positions. By comparing these copied measurements and their spatial ratios, the system determines the period number without requiring multiple physical frequencies or complex hardware modifications.
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
Enables accurate calculation of actual depth or range values beyond the limited measurement range of conventional iToF modules by effectively determining the period number and using it to compute the actual depth or range value.
Implementation Method 1
a distance (i.e., a depth) between the depth sensing module and the target object is calculated according to a phase delay φ caused by the back-and-forth flight time of the modulated light
Implementation Method 2
indirect time-of-flight (iToF) module is a conventional device used for sensing a distance from the iToF module to a target object
Data Source
AI summary
A depth sensing system and a depth sensing method are provided. The sensing system includes depth sensing module and a processor for performing the sensing method. The depth sensing method incudes: obtaining a sensed target data set via a depth sensing module; calculating a period number corresponding to a measuring pixel; and calculating an actual range value or an actual depth of the measuring pixel in accordance with a period number and a range value of the measuring pixel. The step of calculating the period number of the target data set includes: calculating a spatial ratio in accordance with the position values of the pixel of optical center and measuring pixel, and a focal length of the depth sensing module; calculating a basic range in accordance with the spatial ratio and an unit depth; and calculating the period number corresponding to the measuring pixel.