Wavefront Coding 3D Imaging Depth of Field Extension
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Solution Overview
Problem
Conventional structured illumination systems face limitations in capturing high-resolution 3D images over a wide depth of field due to limited depth of field and high costs associated with existing methods, and struggle to accurately detect grid lines and their crossing points over large capture volumes.
Innovation Solution
The integration of a first phase-modulating element and an optional second element in the optical system to extend the depth of field, using specially designed phase masks to produce a point spread function that allows for accurate detection of grid lines over a wider range, while reducing chromatic aberration and compensating for lateral shifts, thereby enhancing the system's ability to capture 3D images at a lower cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional structured illumination systems are used, then the system can capture 3D images, but the depth of field is limited and detection accuracy decreases over large capture volumes
Solution Approach 1:
The patent applies wavefront coding by modifying the optical transfer function of the system through a cubic phase mask. This changes the parameter of the point spread function to extend the depth of field while maintaining measurement precision through computational reconstruction algorithms that reverse the phase modulation effects.
Solution Approach 2:
The patent introduces a cubic phase mask as an intermediary element in the optical path. This mask modulates the wavefront of light passing through the system, encoding depth information in a way that extends the effective depth of field while preserving the ability to accurately detect grid line positions through computational processing.
2Measurement precision
If laser interference method is used for stripe pattern generation, then fine patterns with unlimited depth of field can be obtained, but the cost is high and individual stripe modulation is not possible
Solution Approach 1:
The patent uses a projector with a display device to generate stripe patterns, which is a simplified copy or alternative implementation compared to the complex laser interference system. This approach achieves sufficient pattern fineness for 3D reconstruction while dramatically reducing system cost and enabling individual stripe modulation through digital control of the display device.
Solution Approach 2:
The patent changes the light source parameter from coherent laser beams to incoherent projector light, and uses digital modulation of the display device to generate the required stripe patterns. This parameter change maintains pattern quality while reducing system complexity and cost, and enables flexible individual stripe control.
3Device complexity
If projection method is used with incoherent light source, then cost is reduced, but depth of field remains limited
Solution Approach 1:
The patent applies wavefront coding by introducing a cubic phase mask that modifies the optical transfer function. This parameter change in the optical system extends the depth of field for incoherent light projection systems, allowing the lower-cost projector-based approach to achieve extended depth of field performance previously only available with complex laser interference systems.
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 the capture of high-resolution 3D images over an extended depth of field with improved signal-to-noise ratio and reduced noise amplification, allowing for accurate determination of grid line centroids and increased volumetric resolution, even at larger depths of field.
Implementation Method 1
a first phase-modulating element and an optional second element in the optical system to extend the depth of field, using specially designed phase masks to produce a point spread function
Implementation Method 2
Structured illumination (SI) or patterned illumination projects a narrow band of light onto a three-dimensional scene to produce lines of illumination that appear distorted
Implementation Method 3
The distortions can be imaged and used to reconstruct the surface shape of one or more objects within the scene, by triangulation of the position of the distorted lines
Data Source
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AI summary
An optical system for capturing three-dimensional images of a three-dimensional object is provided. The optical system includes a projector for structured illumination of the object. The projector includes a light source, a grid mask positioned between the light source and the object for structured illumination of the object, and a first Wavefront Coding (WFC) element having a phase modulating mask positioned between the grid mask and the object to receive patterned light from the light source through the grid mask. The first WFC element is constructed and arranged such that a point spread function of the projector is substantially invariant over a wider range of depth of field of the grid mask than a point spread function of the projector without the first WFC element.