Spatial Light Modulator Zero-Order Suppression via Aberration
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Solution Overview
Problem
Spatial light modulators produce an unmodulated 'zero-order' part of the light beam that cannot be suppressed or moved away, leading to unwanted excitation of biological samples and artifacts in holographic projections, with existing techniques either introducing blind zones or decreasing diffraction efficiency.
Innovation Solution
An optical system that includes a perturbing aberrant optical element to spread the unmodulated 'zero-order' part throughout the replay volume, introducing optical aberrations to distribute the unmodulated light evenly, while a correction signal component adjusts for the distortions caused by these aberrations, ensuring the modulated part can be projected without interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the unmodulated 'zero-order' part is blocked in an intermediate plane, then the harmful excitation of the sample is reduced, but a blind zone is introduced at the center of the excitation field and diffraction efficiency is degraded
Solution Approach 1:
The patent shifts the problem from spatial blocking (2D plane blocking) to temporal/spatial distribution by spreading the zero-order beam across the entire replay volume through axial displacement. This transforms the concentrated harmful effect into a distributed low-intensity background, eliminating the need for physical blocking and avoiding blind zones while preserving diffraction efficiency.
Solution Approach 2:
The patent changes the axial position parameter of the zero-order beam relative to the sample, displacing it along the optical axis to distribute its intensity throughout the replay volume. This parameter change transforms the high-intensity concentrated spot into a low-intensity distributed background, reducing harmful excitation without requiring beam blocking.
2Object-affected harmful factors
If the unmodulated 'zero-order' part is shifted away from the region of interest, then direct illumination of the sample is reduced, but unwanted excitation still occurs and diffraction efficiency decreases
Solution Approach 1:
Instead of lateral shifting (2D plane displacement), the patent employs axial displacement along the optical axis to distribute the zero-order beam throughout the replay volume. This dimensional change allows the zero-order energy to be spread in three-dimensional space, reducing peak intensity at any single location while maintaining overall diffraction efficiency.
Solution Approach 2:
The patent converts the harmful concentrated zero-order beam into a beneficial distributed background by axial displacement. The zero-order energy that would otherwise create harmful hotspots is transformed into a uniform low-intensity illumination across the replay volume, which can even provide useful background lighting without causing artifacts.
3Object-affected harmful factors
If a beam block is introduced to eliminate the zero-order beam, then the alignment precision must be very high, but this increases device complexity and alignment difficulty
Solution Approach 1:
The patent extracts the zero-order beam from the problematic concentrated state and redistributes it axially throughout the replay volume. By removing the need for physical beam blocking and its associated alignment requirements, the system eliminates the complex alignment procedures while still achieving the goal of reducing zero-order harmful effects.
Solution Approach 2:
The axial displacement mechanism acts as an intermediary that transforms the zero-order beam characteristics without requiring physical blocking elements. This intermediary approach (axial position control) replaces the need for precisely aligned beam blocks, simplifying the overall system while maintaining effectiveness in reducing zero-order artifacts.
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 effectively suppresses the unmodulated 'zero-order' part's impact without creating blind zones or unwanted excitation, maintaining high diffraction efficiency and allowing for precise control over the projection area.
Implementation Method 1
A spatial light modulator usually comprises an array of controllable elements adapted for generating a modulated light beam by diffracting an incident light beam
Implementation Method 2
a perturbing aberrant optical element for introducing optical aberrations in the incident light beam and/or the modulated light beam so as to spread the unmodulated 'zero order' part of the modulated light beam in all the replay volume
Data Source
AI summary
The invention concerns an optical system (10) comprising:a spatial light modulator (13) comprising an array of controllable elements adapted for generating a modulated light beam (17) by diffracting an incident light beam (12), the modulated light beam (17) comprising a modulated part and an unmodulated “zero order” part, the modulated part carrying an image to be projected into a replay volume (18),a control unit for applying a control signal to the controllable elements so as to control the modulated light beam (17) generated by the controllable elements,a perturbing optical element (30) for introducing optical aberrations in the incident light beam (12) and/or the modulated light beam (17) so as to spread the unmodulated “zero order” part of the modulated light beam in the replay volume (18), the perturbing optical element (30) generating distortions in the image to be projected, wherein the control signal comprises an image signal component carrying data representative of the image to be projected and a correction signal component representative of a correction pattern for correcting the distortions generated by the perturbing optical element (30) in the image to be projected.