LCOS Spatial Light Modulator Laser Beam Alignment
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Solution Overview
Problem
Optical communication systems face challenges in pointing and tracking between transmitter and receiver, particularly in satellite communication, due to mechanical complexity, weight, maintenance needs, and reliability issues with existing mechanical implementations like servomotor-controlled systems and MEMS micro-mirrors, which are not suitable for long missions.
Innovation Solution
A method and device using a liquid crystal on silicon spatial light modulator (LCOS-SLM) for diffracting and reflecting a laser beam, controlled by a microprocessor, to project and align the beam without mechanical parts, by dividing the beam into quadrants, pulsating, and using pointing and tracking diffraction masks to adjust the beam's direction based on displacement, allowing for precise alignment and tracking without mechanical movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical implementations (servomotor-controlled systems or MEMS micro-mirrors) are used for pointing and tracking, then alignment precision can be achieved, but device complexity, weight, and maintenance needs increase
Solution Approach 1:
The patent replaces mechanical pointing and tracking systems (servomotors, MEMS micro-mirrors) with a purely optical system using a spatial light modulator. The SLM uses liquid crystal technology to diffract and steer the laser beam electronically without any moving mechanical parts, thereby eliminating mechanical complexity while maintaining alignment precision through phase modulation of the light wavefront
Solution Approach 2:
The patent changes the operational parameters of the optical system by using a spatial light modulator that dynamically adjusts the phase of light across different regions of the beam. By modifying the phase parameters electronically through liquid crystal modulation, the system achieves precise beam steering and tracking without mechanical movement, resolving the contradiction between precision and complexity
2Measurement precision
If mechanical implementations (servomotor-controlled systems or MEMS micro-mirrors) are used for pointing and tracking, then alignment precision can be achieved, but weight increases
Solution Approach 1:
The patent substitutes heavy mechanical components (servomotors, actuators, moving mirrors) with a lightweight spatial light modulator based on liquid crystal technology. The SLM achieves beam steering through phase modulation rather than physical movement, dramatically reducing the weight of the pointing and tracking subsystem while maintaining the required alignment precision for optical communication
3Measurement precision
If mechanical implementations are used for pointing and tracking, then alignment can be achieved, but reliability decreases due to wear and maintenance needs
Solution Approach 1:
The patent eliminates mechanical wear and failure modes by replacing moving mechanical parts with a solid-state spatial light modulator. The liquid crystal-based SLM has no moving components that can wear out, eliminating the reliability issues associated with mechanical friction, lubrication degradation, and component fatigue, while maintaining precise alignment capability through electronic phase control
Solution Approach 2:
The spatial light modulator performs self-adjustment through electronic control of liquid crystal phases, requiring no mechanical maintenance or intervention. The system automatically compensates for alignment variations through phase modulation without mechanical adjustment, enhancing reliability by eliminating the need for maintenance that would otherwise be required for mechanical systems
4Measurement precision
If mechanical implementations are used for pointing and tracking, then alignment can be achieved, but the system becomes unsuitable for long missions due to fuel and energy restrictions
Solution Approach 1:
The patent replaces energy-intensive mechanical systems (servomotors requiring power for continuous positioning, fuel for propulsor-based adjustments) with a low-power spatial light modulator. The liquid crystal SLM consumes minimal energy to switch liquid crystal phases and steer the beam, eliminating the need for fuel and reducing electrical power requirements, making the system suitable for long-duration missions with limited energy resources
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 reduces mechanical complexity, weight, and maintenance needs while enhancing reliability, enabling efficient and precise alignment and tracking of laser beams in optical communication systems, particularly suitable for small satellite platforms, by concentrating light over a small area and maintaining the communication link despite movement.
Implementation Method 1
a liquid crystal on silicon spatial light modulator (24) comprising an element for diffracting and reflecting said laser beam
Implementation Method 2
a liquid crystal on silicon spatial light modulator (24) comprising an element for diffracting and reflecting said laser beam
Implementation Method 3
by distortion of the wavefront of said laser beam using a pointing diffraction mask generated in said element for diffracting and reflecting said laser beam
Implementation Method 4
a laser (16)... wherein said laser and said element for diffracting and reflecting said laser beam are controlled by said microprocessor
Implementation Method 5
interrupting the projection of each quadrant of said laser beam during each interval of a set of consecutive intervals by pulsation of said laser beam using amplitude modulation
Implementation Method 6
said receiving station comprises a photodiode receiver (52) for detecting said transmitted laser beam
Data Source
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AI summary
The present invention relates to a method, system and device for transmitting information from an optical communication transmitter to a receiving station via a laser beam and for alignment of said laser beam emitted from said optical communication transmitter with said receiving station, wherein: - said optical communication transmitter is displaced relative to said receiving station and comprises a laser, a radio receiver, a microprocessor and a liquid crystal on silicon spatial light modulator comprising a diffractive element, whereby said laser beam is emitted from said laser and is projected over an area by diffraction and reflection using said liquid crystal on silicon spatial light modulator, wherein said laser and said diffractive element are controlled by said microprocessor, wherein said laser beam has a longitudinal axis parallel to the propagation path of said laser beam, - said receiving station comprises a photodiode receiver for detecting said transmitted laser beam and a radio transmitter, and - said method comprises using a pointing diffraction mask and a tracking diffraction mask, wherein each pointing diffraction mask is generated in combination with a tracking diffraction mask in said diffractive element.