Spatial Multiplexing Phase Modulation for iTOF Depth Mapping
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Solution Overview
Problem
Indirect Time of Flight (iTOF) depth mapping systems face challenges in accurately measuring depth due to range-folding ambiguities and multi-path interference, requiring multiple acquisition phases and sensitive image sensing arrays, which can be complex and prone to errors.
Innovation Solution
The system employs spatial modulation of the carrier wave phase or frequency across the target scene, using an array of beams with varying phase angles or frequencies, allowing for single-frame depth mapping without phase-shifting sensing intervals, and mitigating multi-path interference by canceling stray reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If indirect TOF systems use multiple acquisition phases to measure depth, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the depth measurement process by assigning different phase angles to different spatial regions (columns) of the scene. Instead of sequentially acquiring multiple phases for the entire scene, each column is illuminated with a specific phase angle simultaneously, enabling parallel depth measurement across the scene and reducing acquisition time while maintaining accuracy
Solution Approach 2:
The patent introduces spatial dimensionality to the phase encoding process by varying phase angles across different columns of the scene. This spatial multiplexing approach transforms the temporal sequence of phase acquisitions into a spatial parallel process, where multiple phase measurements are captured simultaneously in a single frame
2Measurement precision
If indirect TOF systems use sensitive image sensing arrays for phase shift measurement, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the sensing array into column groups, where each group corresponds to a specific phase angle. This segmentation allows the system to process phase information from different spatial regions independently and simultaneously, simplifying the overall measurement process while maintaining high measurement accuracy through dedicated phase processing for each column group
3Measurement precision
If indirect TOF systems use multiple phase acquisition intervals, then depth mapping accuracy is improved, but loss of time increases
Solution Approach 1:
The patent employs periodic modulation of the illumination beams with different phase angles, where each column is modulated at a unique phase offset. This periodic spatial modulation enables the system to capture all phase information simultaneously in a single frame, eliminating the need for sequential phase acquisitions and dramatically reducing the time required for depth mapping
Solution Approach 2:
By transforming the temporal phase acquisition process into a spatial encoding scheme, the patent captures multiple phase measurements simultaneously across different columns. This dimensional transformation converts a time-consuming sequential process into a parallel spatial operation, achieving high-speed depth mapping without sacrificing measurement accuracy
4Productivity
If spatial multiplexing with varying phase angles is used, then productivity is improved, but device complexity increases
Solution Approach 1:
The patent segments the illumination control into column-specific phase modulations, where each column is independently controlled with a specific phase angle. This segmentation approach, while increasing control complexity, enables parallel processing of depth information from all columns simultaneously, dramatically improving productivity and depth mapping speed
Solution Approach 2:
The patent introduces spatial dimensionality to the phase modulation control, varying phase angles across different columns rather than applying uniform phase control. This spatial multiplexing strategy increases the complexity of illumination control but enables simultaneous depth measurement across the entire scene, achieving high productivity through parallel acquisition
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 enables accurate single-frame depth mapping, reduces peak illumination power, enhances security by unique modulation patterns, and improves measurement accuracy by canceling phase errors, while being adaptable to various iTOF detection and processing methods.
Implementation Method 1
an array of beams of optical radiation toward different, respective areas in a target scene while modulating the beams with respective carrier waves having a common carrier frequency and different respective phase angles
Implementation Method 2
measuring the phase shift of that carrier wave in the radiation that is reflected back from the target scene. The phase shift can be measured by imaging the scene onto an optical sensor array
Implementation Method 3
objective optics, which are configured to form an image of the target scene on the second array
Implementation Method 4
Processing circuitry is configured to process the signals output by the sensing elements in order to generate a depth map of the target scene
Data Source
AI summary
Apparatus for optical sensing includes an illumination assembly, which is configured to direct a first array of beams of optical radiation toward different, respective areas in a target scene while modulating the beams with respective carrier waves having a common carrier frequency and different respective phase angles, which vary across the first array in a predefined spatial pattern. A detection assembly includes a second array of sensing elements, which are configured to output respective signals in response to the optical radiation that is incident on the sensing elements during one or more detection intervals, which are synchronized with the carrier frequency, and objective optics, which are configured to form an image of the target scene on the second array. Processing circuitry processes the signals output by the sensing elements in order to generate a depth map of the target scene.