Diffraction Grating Light Field Imaging for Passive 3D Depth Sensing
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Solution Overview
Problem
Traditional imaging systems, such as plenoptic cameras, struggle to capture depth information effectively due to the limitations of square-law detectors, requiring complex reconstruction techniques or additional sensors, which increase power consumption and device footprint, and are sensitive to interfering signals and specular reflections.
Innovation Solution
A light field imaging device incorporating a diffraction grating assembly and a pixel array with a smaller pixel pitch than the grating period, allowing direct measurement of phase, angle, and wavelength through diffracted wavefronts, enabling depth mapping and 3D imaging without active illuminators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors or sensor segmentation is used to capture depth information, then depth measurement precision is improved, but device footprint and complexity increase
Solution Approach 1:
The patent segments the optical wavefront into multiple diffraction orders using a diffraction grating, where each order carries depth information encoded through its spatial frequency. This allows a single sensor to capture depth data that would traditionally require multiple sensors, resolving the contradiction between measurement precision and device footprint.
Solution Approach 2:
The patent transforms the problem from capturing depth in the spatial domain using multiple sensors to capturing depth in the frequency domain through diffraction. By encoding depth information in the spatial frequencies of diffracted wavefronts, the system achieves depth measurement with a single sensor, reducing device footprint while maintaining precision.
2Measurement precision
If complex machine learning and reconstruction techniques are used to recover depth information, then depth measurement precision is improved, but computational expense and processing time increase
Solution Approach 1:
The patent performs preliminary encoding of depth information directly in the optical domain through diffraction before detection. The diffraction grating pre-processes the wavefront to embed depth data in the spatial frequencies of diffracted orders, which can then be decoded through simpler computational methods compared to full machine learning reconstruction, reducing processing time while maintaining precision.
3Measurement precision
If active illuminators and sensors are used for depth sensing, then depth measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent makes the imaging system self-sufficient by using the scene's reflected ambient light as the illumination source. The diffraction grating assembly processes this passive light to extract depth information, eliminating the need for active illuminators and significantly reducing power consumption while maintaining depth measurement precision through the passive light field analysis.
4Ease of operation
If time-averaged intensity measurement is used with square-law detectors, then ease of operation is improved, but loss of information increases due to inability to measure phase or wave vector
Solution Approach 1:
The patent introduces a diffraction grating as an intermediary element between the scene and the detector. This grating transforms the light field to encode phase and wave vector information into the spatial frequencies of diffracted wavefronts, which can then be measured by simple intensity detectors. This resolves the contradiction by preserving information content while maintaining detection simplicity.
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 passive depth sensing with reduced power consumption and device footprint, preserving 2D image quality, and providing enhanced depth mapping capabilities using a single sensor architecture.
Implementation Method 1
the diffraction grating diffracting the optical wavefront to generate a diffracted wavefront
Data Source
AI summary
A light field imaging device and method are provided. The device can include a diffraction grating assembly receiving a wavefront from a scene and including one or more diffraction gratings, each having a grating period along a grating axis and diffracting the wavefront to generate a diffracted wavefront. The device can also include a pixel array disposed under the diffraction grating assembly and detecting the diffracted wavefront in a near-field diffraction regime to provide light field image data about the scene. The pixel array has a pixel pitch along the grating axis that is smaller than the grating period. The device can further include a color filter array disposed over the pixel array to spatio-chromatically sample the diffracted wavefront prior to detection by the pixel array. The device and method can be implemented in backside-illuminated sensor architectures. Diffraction grating assemblies for use in the device and method are also disclosed.