Acousto-Optic Modulator for Coherent Illumination Artifact Suppression
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Solution Overview
Problem
High temporal and spatial coherence of laser illumination leads to unwanted speckle and diffraction artifacts in coherent optical systems, affecting image quality and measurement accuracy in laser-based three-dimensional sensing and microscopy.
Innovation Solution
The use of an acousto-optic device or spatial light modulator to modulate laser illumination, imparting a time-varying phase gradient across the illumination image plane, which suppresses speckle and diffraction artifacts by varying the interference pattern orientation during detector integration, thereby reducing errors in coherent structured illumination systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If laser illumination with high temporal and spatial coherence is used, then illumination intensity and directionality are improved, but speckle and diffraction artifacts increase
Solution Approach 1:
The patent applies dynamics by making the illumination pattern move or change over time during the detector integration period. The spatial light modulator dynamically alters the phase gradient, causing the interference pattern to shift. This temporal variation prevents coherent artifacts from forming stable patterns that would be detected, while maintaining high illumination intensity throughout the integration period.
Solution Approach 2:
The patent changes the phase gradient parameter of the illumination pattern over time. By modulating the phase gradient applied by the spatial light modulator during the integration period, the interference pattern's orientation and position change dynamically. This parameter variation suppresses coherent artifacts while preserving the beneficial high intensity and directionality of laser illumination.
2Object-generated harmful factors
If a spatial light modulator is used to suppress coherent artifacts, then speckle and diffraction artifacts are reduced, but device complexity increases
Solution Approach 1:
The patent introduces a spatial light modulator as an intermediary device between the laser source and the object. This mediator imparts the necessary phase gradients to shape the illumination pattern dynamically. While the device complexity increases due to adding this component, it enables effective suppression of coherent artifacts through controlled phase modulation, achieving a worthwhile trade-off in system performance.
3Object-generated harmful factors
If the interference pattern is varied during integration period, then coherent artifacts are suppressed, but measurement precision may be affected
Solution Approach 1:
The patent employs periodic action by varying the interference pattern in a controlled, periodic manner during the integration period. The spatial light modulator applies time-varying phase gradients that create systematic changes in the illumination pattern. This periodic variation suppresses coherent artifacts while the structured nature of the modulation allows for computational recovery of precise measurements through correlation techniques.
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 reduces speckle and diffraction artifacts, maintaining the depth of field while enhancing image quality and measurement accuracy in laser-based systems, enabling high-speed, power-efficient, and light-efficient pattern projection and imaging.
Implementation Method 1
Some embodiments may provide flexible and efficient methods and systems for suppressing coherent artifacts in laser-based pattern projection and detection systems by modulating the laser illumination with an acousto-optic device or another spatial light modulator
Implementation Method 2
The methods include illuminating an object with a first radiation, the first radiation forming an interference pattern at an illumination image plane, so as to produce a second radiation from the object
Data Source
AI summary
Methods and systems are provided for suppressing speckle and/or diffraction artifacts in coherent structured illumination sensing systems. A coherent radiation pattern forms an interference pattern at an illumination image plane and illuminates an object. Radiation scattered or otherwise emitted by the object is detected to produce a signal, which is integrated in time. Coherent artifact suppression is attained by using a spatial modulator, such as an acousto-optic device, to vary a phase gradient at the illumination image plane during the signal integration time. Various embodiments are provided for purposes including without limitation: preserving the depth of field of the coherent illumination; using the same acousto-optic device for pattern generation and coherent artifact suppression; electronically controlling the effective spatial coherence of the illumination system; and reducing errors due to coherent artifacts in a laser-based three dimensional imaging system.