Birefringent Device Pupil Function Shaping
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Solution Overview
Problem
Conventional optical systems face limitations in achieving extended depth of field (EDoF) due to limitations in shaping the pupil function, leading to issues like intensity loss, lateral displacement of spatial structures, and asymmetry in through focus modulation transfer function (MTF), which affect imaging quality.
Innovation Solution
A birefringent device is designed to shape distinct pupil functions for different polarization directions, using variations in crystal axes orientation, refractive indices, and thickness across the pupil plane, allowing for complex conjugate pupil functions that maintain symmetry and improve depth of field without intensity loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional wavefront coding techniques are used to shape the phase of the pupil function, then extended depth of field is achieved, but intensity loss occurs in the transmitted light
Solution Approach 1:
The patent changes the physical parameters of the optical system by introducing a birefringent element with specific optical properties (birefringence value, thickness, orientation) to modify the pupil function without causing intensity loss. The birefringent element introduces a phase shift between orthogonal polarization components, enabling extended depth of field while preserving light intensity through proper parameter selection.
Solution Approach 2:
The patent employs a composite optical system combining a birefringent element (such as a liquid crystal layer or birefringent material) with the imaging lens. This composite structure allows simultaneous achievement of extended depth of field and maintained intensity by utilizing the unique optical properties of birefringent materials to shape the pupil function differently for different polarization states.
2Stability of the object's composition
If the pupil function is shaped to extend depth of field, then through focus MTF symmetry is improved, but lateral displacement of spatial structures occurs
Solution Approach 1:
The patent introduces asymmetric phase modulation through the birefringent element, where the phase shift varies across the pupil plane in a controlled asymmetric manner. This asymmetric phase profile compensates for the lateral displacement effects while maintaining through-focus MTF symmetry, as the birefringent element creates opposite phase shifts for different polarization components that counterbalance the displacement.
Solution Approach 2:
The birefringent element acts as an intermediary component between the imaging lens and the image sensor, mediating the optical path by introducing polarization-dependent phase shifts. This intermediary element enables independent control of the pupil function for different polarization states, allowing correction of lateral displacement while preserving MTF symmetry through proper design of the birefringent element's optical parameters.
3Measurement precision
If amplitude manipulation techniques are used to shape the pupil function, then depth of field is extended, but manufacturing complexity increases
Solution Approach 1:
The patent replaces complex mechanical or physical amplitude manipulation structures with a birefringent element that achieves pupil function shaping through optical phase modulation. Instead of using complex amplitude masks or mechanical focusing devices, the birefringent element uses its intrinsic optical properties to modify the wavefront, significantly simplifying the manufacturing process while achieving extended depth of field.
Solution Approach 2:
The patent simplifies manufacturing by changing the approach from physical structure modification to optical parameter control. By adjusting the birefringent element's parameters (thickness, birefringence value, orientation angle), the desired pupil function is achieved without complex manufacturing processes, making the system easier to manufacture and align compared to conventional amplitude manipulation 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
The birefringent device achieves a symmetric through focus MTF and real optical transfer function, enhancing depth of field and reducing imaging artifacts, while avoiding the limitations of conventional wavefront coding and amplitude manipulation techniques.
Implementation Method 1
A birefringent device is designed to shape distinct pupil functions for different polarization directions, using variations in crystal axes orientation, refractive indices, and thickness across the pupil plane
Implementation Method 2
The birefringent device achieves a symmetric through focus MTF and real optical transfer function, enhancing depth of field and reducing imaging artifacts
Data Source
AI summary
A birefringent device, which is configured to be mounted in an optical path of an optical system, has an effective area in a pupil plane. The birefringent device affects different polarization states differently and position-dependently. The birefringent device realizes a first pupil function assigned to a first polarization state and a second different pupil function assigned to a second polarization state. The pupil functions may be optimized to achieve various specific optical properties like extended depth of field.