Digital Holographic Imaging Limiter for Aliasing Suppression
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Solution Overview
Problem
Digital holographic imaging apparatuses face issues with false signals or 'aliases' due to high-frequency components exceeding the Nyquist frequency, which affect the reconstruction of phase or magnitude distribution information, particularly in specimens with small, similar components like cultured cells.
Innovation Solution
Incorporating a limiter, such as an optical low-pass filter or incident angle limiter, between the specimen and the image sensor to restrict spatial frequencies and incident angles, ensuring only frequencies up to the Nyquist limit are captured, thereby suppressing false signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If no limiter is used in the digital holographic imaging apparatus, then high spatial frequency information can be captured, but false signals (aliases) occur in the reconstructed image
Solution Approach 1:
The patent introduces a limiter as an intermediary component positioned between the image sensor and the specimen. This limiter acts as a mediator that selectively transmits light within a specific angular range, thereby controlling the spatial frequency components that reach the image sensor. By doing so, it prevents high-frequency components that would cause aliasing while preserving the necessary information for accurate image reconstruction.
Solution Approach 2:
The patent changes the angular parameter of light incident on the image sensor by introducing a limiter with specific angular transmission characteristics. The limiter is designed to transmit only light within a predetermined angular range, effectively filtering out high-angle (high-frequency) components. This parameter-based filtering approach resolves the contradiction by controlling which spatial frequencies are captured.
2Reliability
If a limiter is added to remove high-frequency components, then false signals are suppressed, but device complexity increases
Solution Approach 1:
The limiter serves as a simple intermediary element that can be integrated into the existing optical path without requiring complex additional systems. By positioning the limiter in the optical path between the specimen and image sensor, it provides the necessary filtering function with minimal structural addition, thus resolving the contradiction between reliability improvement and device complexity.
3Reliability
If the limiter restricts spatial frequency to Nyquist limit, then aliasing is prevented, but information loss occurs
Solution Approach 1:
The patent converts the potentially harmful effect of high-frequency components (which cause aliasing) into a beneficial filtering mechanism. By deliberately limiting the spatial frequency range to match the Nyquist criterion, the system prevents aliasing artifacts while maintaining optimal image reconstruction quality. The 'loss' of high-frequency information is actually a beneficial reduction of problematic frequencies.
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
The limiter effectively reduces or removes high-frequency components, minimizing false signals in the reconstructed images and maintaining image quality without increasing computational complexity.
Implementation Method 1
an image sensor comprising multiple pixels arranged on a photoelectric surface (also called as photosensitive surface or conversion surface) thereof in a two-dimensional manner, and structured to capture an image of a magnitude distribution of an interference pattern
Data Source
AI summary
An illumination unit emits illumination light to a specimen. An image sensor includes multiple pixels arranged in a two-dimensional manner on a photoelectric surface. The image sensor captures an image of a magnitude distribution of an interference pattern formed due to the illumination light that has interacted with the specimen. A limiter limits at least one from among the spatial frequency of the interference pattern formed on the photoelectric surface and the incident angle of the light input to the photoelectric surface.