Circumferentially Mounted Deformable Mirror for Iris Imaging
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Solution Overview
Problem
Conventional deformable mirrors used in adaptive optics systems, such as those for iris imaging, face limitations in cost, size, speed, and accuracy due to their design, which restricts their suitability across different applications and results in inadequate optical correction.
Innovation Solution
A circular deformable mirror substrate mounted by its circumference and driven by annular forces, allowing local tilting and deformation to achieve spherical or paraboloidal shapes, enhancing optical quality and adaptability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stack actuator mirror is used, then the deformable mirror can be constructed with multiple push rods, but the device becomes expensive, large, and relatively slow
Solution Approach 1:
The deformable mirror is segmented into multiple actuators distributed across the back surface, each capable of independent deformation. This segmentation allows the complex optical correction function to be achieved through multiple simpler actuation points, reducing the need for a single complex push rod mechanism while maintaining optical performance
Solution Approach 2:
The patent replaces the traditional mechanical push rod actuation system with a magnetic actuation system. Magnets are embedded in the back surface of the deformable mirror and are actuated by electromagnetic coils, eliminating the need for mechanical push rods and their associated complexity in construction, assembly, and alignment
2Reliability
If a stack actuator mirror is used, then the deformable mirror can correct optical aberrations, but the mirror exhibits waffle pattern and higher order modes due to print through
Solution Approach 1:
The magnetic actuation system replaces the mechanical push rod system, eliminating the source of waffle patterns and print-through artifacts. The magnetic fields act on the deformable mirror material without mechanical contact, producing smoother surface deformations and reducing higher order modes while maintaining optical correction accuracy
3Device complexity
If a small number of actuators are used, then the device complexity is reduced, but the regular geometry provides poor match to required correction modes
Solution Approach 1:
The patent employs actuators with varying strengths and positions distributed across the back surface of the deformable mirror. This non-uniform distribution allows each actuator to contribute differently to specific optical correction modes, enabling a small number of actuators to effectively match the required correction patterns through localized optimization rather than uniform geometry
4Device complexity
If all actuators have the same travel and are attached to a rigid reference surface, then the construction is simplified, but the stroke is inadequate for low order modes
Solution Approach 1:
The patent implements actuators with different travel ranges positioned at different locations on the deformable mirror back surface. This differential travel configuration allows actuators to be optimized for their specific roles in correcting different optical modes, with some actuators providing larger stroke for low order modes while others provide smaller stroke for higher order modes
Solution Approach 2:
The patent varies the travel parameter of the actuators rather than using uniform travel for all actuators. By changing the stroke length and actuation range of different actuators, the system achieves adequate correction range for both low order and high order optical modes while maintaining a relatively simple overall configuration
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 solution provides high optical quality with minimal high-frequency print-through, large operational temperature range, and reduced hysteresis, enabling effective correction of optical aberrations and improved image capture in iris imaging systems.
Implementation Method 1
A voice coil (solenoid coil) is positioned at some offset from the back side of the mirror substrate. When electrical current is applied to the voice coil, it induces a magnetic field. This attracts or repels the permanent magnet by some amount of force.
Implementation Method 2
the circumferential minor mount substantially prevents translation of the minor substrate (i.e., no up/down or side/side motion) but allows the minor substrate to tilt locally relative to the minor mount
Data Source
AI summary
A rapid iris acquisition, tracking, and imaging system can be used at longer standoff distances and over larger capture volumes, without the active cooperation of subjects. Eye reflections from the subjects' eyes are used to steer a high resolution camera to the eyes in order to capture images of the irises. A circular deformable minor driven by one or more annular forces can be used to focus the camera. A circular mirror substrate is mounted by its circumference onto a minor mount and driven by an annular drive element that contacts the minor substrate along a ring. If the annular drive element has a certain diameter relative to the circumference of the mirror substrate, the mirror substrate will be deformed in the shape of a sphere.