Aspheric Optics Non-Monotonic Wavefront Phase Profile
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Solution Overview
Problem
Conventional imaging systems face limitations in depth of field, which can be increased by modifying phase with circularly asymmetric optics, but these are difficult and costly to manufacture due to alignment challenges, and existing solutions do not effectively maintain modulation transfer function invariance over a range of misfocus.
Innovation Solution
The implementation of imaging optics with a non-monotonic wavefront phase profile, achieved through the use of aspheric optical elements and computer-based optimization methods that vary design parameters to extend depth of field and maintain modulation transfer function invariance over misfocus, using equations like Eq. 1 and Eq. 2 to define the aspheric surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If circularly asymmetric optics are used to increase depth of field, then depth of field is improved, but manufacturing difficulty and cost increase due to alignment requirements
Solution Approach 1:
The patent applies asymmetry by using circularly asymmetric optical elements (such as cylindrical lenses or freeform surfaces) that intentionally break rotational symmetry to achieve extended depth of field. The asymmetric geometry creates different focal properties in different meridians, allowing simultaneous focus at multiple depths without requiring complex alignment mechanisms.
Solution Approach 2:
The patent changes the geometric parameters of the optical element by introducing asymmetric surface profiles with specific curvature variations. By modifying the surface sag equation to include asymmetric terms (e.g., odd-powered polynomial terms in x and y coordinates), the optical element achieves extended depth of field while maintaining manufacturability through well-defined surface equations.
2Reliability
If aperture is stopped down to increase depth of field, then depth of field is improved, but light available to the imaging device is reduced
Solution Approach 1:
The patent applies local quality by creating regions of different optical power within the same optical element. The asymmetric surface profile provides varying curvature and focal properties at different locations (center vs. periphery, different meridians), allowing the element to function as multiple optical zones simultaneously. This enables extended depth of field without reducing the overall aperture size, thereby maintaining light availability.
3Ease of manufacture
If conventional optics are used, then manufacturing is simple, but modulation transfer function varies over range of misfocus
Solution Approach 1:
The patent uses curved surface profiles, specifically aspheric and freeform surfaces, to control wavefront phase. The continuous curvature variation in the asymmetric surfaces allows precise control of light propagation at different depths, maintaining modulation transfer function invariance. The surface sag is defined by polynomial equations that provide the necessary curvature modulation to achieve extended depth of field with consistent image quality.
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 results in an extended depth of field with consistent modulation transfer function across a range of misfocus, improving imaging system performance by maintaining image quality regardless of focus variations.
Implementation Method 1
modifying phase with circularly asymmetric optics
Implementation Method 2
one or more optical elements for modifying a wavefront of electromagnetic energy incident thereon
Implementation Method 3
The wavefront, modified by transmission through the optical elements
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Systems and methods include imaging optics having one or more optical elements for modifying a wavefront of electromagnetic energy incident thereon. The wavefront, modified by the optical elements, exhibits a non-monotonic wavefront phase profile. The imaging optics are characterized by a modulation transfer function that is substantially invariant over a range of misfocus. The system optionally includes a detector for receiving the electromagnetic energy from the imaging optics. A method of maintaining modulation transfer invariance over a range of misfocus in an optical imaging system includes modifying a wavefront of electromagnetic energy incident to the optical imaging system such that the wavefront exhibits a non-monotonic wavefront phase profile and a substantially invariant modulation transfer function over the range of misfocus.