Digital Hologram Reconstruction Using Auxiliary Height Data
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Solution Overview
Problem
Existing digital holography systems face challenges in resolving phase ambiguities during the reconstruction of digital holograms, leading to inaccurate measurements of three-dimensional features, particularly in highly discontinuous surfaces.
Innovation Solution
A method and system that utilize additional images, such as incoherent light images or AI-generated images, to resolve phase ambiguities by deriving height data with lower precision, which is then used to enhance the precision of phase map resolution, achieving higher accuracy in measuring three-dimensional features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase unwrapping techniques are used to reconstruct digital holograms, then the measurement process is simple, but the measurement precision deteriorates due to phase ambiguities in highly discontinuous surfaces
Solution Approach 1:
The patent introduces an intermediary low-precision height measurement system (such as a time-of-flight camera or structured light scanner) that provides initial height estimates. These estimates serve as a mediator to guide the phase unwrapping process in the high-precision digital holography system, resolving phase ambiguities without requiring complex multi-wavelength or multi-step procedures. The intermediary system bridges the gap between the ambiguous phase data and the true height values.
Solution Approach 2:
The patent performs preliminary height measurement using a lower precision system before conducting the high-precision phase unwrapping process. This preliminary action provides initial estimates of height values that constrain the possible solutions during phase unwrapping, effectively pre-resolving ambiguities before the main measurement process begins. This approach simplifies the overall system while maintaining high precision in the final measurements.
2Measurement precision
If additional imaging systems are integrated to resolve phase ambiguities, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent makes the additional imaging system serve multiple functions: it provides height estimates for phase unwrapping, guides the reconstruction process, and validates the final results. By making this single auxiliary system multi-functional, the patent avoids the need for multiple specialized systems, thereby reducing overall device complexity while maintaining high measurement precision.
Solution Approach 2:
The patent designs the system so that the additional imaging system works passively to provide height constraints, while the main digital holography system performs the heavy computational lifting. The auxiliary system essentially 'services' the main system by providing guidance information, rather than requiring active coordination between multiple complex subsystems. This self-service arrangement reduces system complexity.
3Adaptability or versatility
If low-precision height data is used to resolve phase ambiguities, then the effective measuring range extends, but the final measurement accuracy may be compromised
Solution Approach 1:
The patent uses low-precision height data not to provide the final measurement, but to provide sufficient guidance for resolving phase ambiguities. The low-precision data performs a partial function (constraining the solution space) while the high-precision digital holography system performs the excessive action of delivering ultra-precise final measurements. This division of labor allows the system to handle large height variations (extending measuring range) while maintaining nanometer-level accuracy in the final output.
Solution Approach 2:
The patent transitions from the ambiguous phase dimension (wrapped between -π and π) to the true height dimension by using the low-precision height data as a reference. This dimensional transformation allows the system to map the wrapped phase information onto the true height scale, effectively extending the measuring range beyond what a single phase wrap can represent, while the high-precision system ensures the final accuracy is not compromised by the initial low-precision input.
Data Source
AI summary
A method for reconstructing a digital hologram of a surface having at least one three-dimensional feature thereon, including acquiring a digital hologram of the surface, reconstructing a wavefront based on the digital hologram, generating a phase map of at least a portion of the surface based on the wavefront, the phase map including phase ambiguities, obtaining at least one additional image of the surface, obtaining height data relating to the three-dimensional feature from the at least one additional image of the surface, the height data being obtained with a first precision, resolving the phase ambiguities based on the height data and deriving a height of the at least one three-dimensional feature based on the phase map following the resolving of the phase ambiguities therein, the height being derived with a second precision more precise than the first precision.