Optical Interference Filter Angle Sensing for Free-Space Beam Detection
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Solution Overview
Problem
Existing methods for determining the angle of incidence of an optical beam in free-space optical communication systems are inaccurate and limited by spectral range, complexity, and sensitivity to beam irradiance distribution, leading to high energy consumption and detection errors.
Innovation Solution
A detection device and method using optical interference filters (OIFs) rotated with respect to the optical axis, combined with multiple detectors, to measure optical power ratios and determine the angle of incidence accurately, expanding the spectral range and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If array sensors (CCD/CMOS) are used to determine beam direction, then unambiguous direction determination is achieved, but device complexity and energy consumption increase significantly
Solution Approach 1:
The patent extracts only the essential function of beam direction detection from complex array sensors by using a single photodiode with angular-dependent optical filters. This eliminates the need for multiple active elements while preserving the core measurement capability through the angular selectivity of the filters.
Solution Approach 2:
The patent replaces the mechanical/electronic complexity of array sensor readout and data processing with an optical solution where filter characteristics inherently encode angular information. The optical system performs the measurement function through physical optics rather than electronic scanning or matrix operations.
2Measurement precision
If array sensors (CCD/CMOS) are used to determine beam direction, then unambiguous direction determination is achieved, but response speed decreases to 100-300 Hz
Solution Approach 1:
The patent extracts only the essential function of beam direction detection from complex array sensors by using a single photodiode with angular-dependent optical filters. This eliminates the need for multiple active elements while preserving the core measurement capability through the angular selectivity of the filters.
Solution Approach 2:
The patent replaces the mechanical/electronic complexity of array sensor readout and data processing with an optical solution where filter characteristics inherently encode angular information. The optical system performs the measurement function through physical optics rather than electronic scanning or matrix operations.
3Measurement precision
If segmented photodiodes are used for beam angle detection, then beam position can be determined, but detection accuracy decreases due to sensitivity to beam irradiance distribution
Solution Approach 1:
The patent changes the detection parameter from direct photodiode current (which depends on total power and irradiance distribution) to the ratio of currents from filters with different angular characteristics. This ratio is independent of total beam power and irradiance distribution, making the measurement robust against atmospheric turbulence and beam distortion.
4Measurement precision
If lateral effect photodiodes are used for beam position detection, then beam direction can be determined independently of optical power, but device complexity and spectral limitations increase
Solution Approach 1:
The patent uses conventional photodiodes that can detect a broad spectral range, making the system universal rather than limited to specific spectral regions. The angular selectivity is achieved through optical filters rather than specialized photodiode structures, allowing the same detector to work across different wavelengths by simply changing filters.
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 proposed method provides unambiguous and accurate determination of the optical beam angle, reducing complexity and energy consumption while enhancing the range of applications.
Implementation Method 1
optical interference filter (OIF), whose spectral response changes depending on the angle of incidence of the beam
Data Source
AI summary
The invention relates to the fields of optical technologies and telecommunication technologies, and is dedicated to determination of the direction of optical beam in free-space optical communication systems. The invention is based on the property of interference optical filters (IOF), that transmittance and reflectance of such filters, for a beam with given optical spectrum, depends on the angle of the beam with respect to IOF surface normal. According to the proposed method, at least one IOF is used, which is rotated by defined angle with respect to the optical axis of the detection device. In the implementation of the detection device with one IOF, two optical power detectors are used, which measure optical power of the beam reflected from the IOF and transmitted through the IOF.