Acousto-Optic Tunable Filter Design to Reduce Angular Spread
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Solution Overview
Problem
Conventional acousto-optic tunable filters suffer from significant wavelength-dependent angular spread of output light, which is detrimental in high-resolution imaging applications like confocal microscopy.
Innovation Solution
A novel filter design deviating from the parallel-tangent condition to reduce angular spread by limiting the angular acceptance range to collinear light incidence, using parameters such as entrance and emission surface orientations and transducer dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a parallel-tangent condition filter design is used, then the angular acceptance range is wide, but the angular spread of output light is large
Solution Approach 1:
The patent applies parameter changes by modifying the filter design parameters, specifically the interaction length of the acousto-optic filter and the orientation of the light propagation direction relative to the crystal axes. By changing these parameters away from the conventional parallel-tangent condition, the patent achieves a new operating point where both angular acceptance range and angular spread are optimized for confocal microscopy applications.
2Quantity of substance
If the angular acceptance range is widened, then more light can be received, but the collinearity of output light is degraded
Solution Approach 1:
The patent resolves this contradiction by changing the operating parameters of the acousto-optic filter, specifically the interaction length and the angle of light propagation relative to crystal axes. This parameter change enables the system to maintain good collinearity while accepting sufficient light throughput for confocal microscopy operation.
Solution Approach 2:
Instead of following the conventional parallel-tangent design approach that prioritizes wide angular acceptance, the patent inverts the design philosophy by prioritizing collinearity of output light and adjusting the angular acceptance range accordingly. This inversion of design priorities leads to optimal performance for confocal microscopy where collinearity is critical.
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
Significantly reduces angular spread of output light while maintaining a broad spectral bandwidth, enabling collinear light emission for improved image quality in confocal microscopy.
Implementation Method 1
a piezoelectric transducer which generates an acoustic wave in the filter crystal
Implementation Method 2
The acoustic wave causes refractive index fluctuations in the filter material, these fluctuations acting as a diffraction grating. Thus, the light propagating through the filter material is diffracted in case that the light wavelength matches the diffraction grating.
Data Source
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AI summary
An optical filter device (102) comprises an acousto-optic tunable filter (112) which includes a transducer (114) tunable with a radio frequency signal for wavelength-dependent light diffraction. The acousto-optic tunable filter (112) has a transducer surface (232) on which the transducer (14) is attached, a light entrance surface (230) configured to receive input light (110) of a predetermined spectral bandwidth within an angular acceptance range (A), and a light emission surface (234) configured to emit diffracted output light (126) including multiple wavelengths from the spectral bandwidth at exit angles defining an angular spread (C) among the multiple wavelengths of the output light (126). The acousto-optic tunable filter (112) is formed in accordance with a filter design determining the angular acceptance range (A) with respect to the input light (110) and the angular spread (C) among the multiple wavelengths of the output light (126). The filter design deviates from a parallel-tangent condition to reduce the angular spread (C) among the multiple wavelengths of the output light (126) while limiting the angular acceptance range (A) with respect to the input light (110) over the spectral bandwidth thereof to collinear light incidence.