Lensless CMOS Edge Localizer Using Diffractive Fresnel Optics
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Solution Overview
Problem
Existing optics systems for automated inspection and alignment tasks face challenges due to size, cost, and complexity constraints, requiring a solution that provides wide angle-of-view, low computational complexity, and ease of manufacturing while accurately estimating the position of visual edges without the need for focusing optics.
Innovation Solution
The use of a Panchromatic Fresnel Zone Plate or Fractal Fresnel phase plate as a diffractive optic, which exhibits low wavelength dependence and allows for accurate measurement of incident angles by aligning responses from different wavelengths within a single pixel pitch over a wide range of angles, enabling precise alignment without the bulk and complexity of traditional focusing optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional focusing optics are used to accurately estimate the position of visual edges, then measurement precision is improved, but device complexity and size increase
Solution Approach 1:
The patent extracts the focusing function from the optical system by removing traditional lenses and focusing optics. Instead, it uses a diffractive optic (Fresnel zone plate or Fractal Fresnel phase plate) that performs both diffraction and focusing in a single integrated element, thereby eliminating the need for separate focusing components and reducing overall system complexity.
Solution Approach 2:
The patent replaces the mechanical focusing system (lenses, mirrors, and adjustment mechanisms) with a diffractive optical system based on wave optics principles. The Fresnel zone plate or Fractal Fresnel phase plate uses diffraction patterns to achieve focusing and edge localization without mechanical moving parts, significantly reducing device complexity.
2Measurement precision
If traditional focusing optics are used for accurate alignment measurement, then measurement precision is improved, but the device size increases
Solution Approach 1:
The patent removes bulky focusing optics from the system and replaces them with a thin diffractive optic element. The Fresnel zone plate or Fractal Fresnel phase plate can be manufactured as a thin transparent plate with micrometer-scale features, reducing the optical system volume from centimeters to millimeters or micrometers while maintaining measurement precision.
Solution Approach 2:
The diffractive optic is implemented as a thin transparent plate or film containing micrometer-scale grating structures. This thin-film approach replaces thick lens systems with a lightweight, space-efficient element that achieves the same optical function with minimal volume, enabling integration into compact automated inspection systems.
3Adaptability or versatility
If a wide angle-of-view is implemented to meet spatial constraints, then adaptability is improved, but measurement precision deteriorates
Solution Approach 1:
The patent applies local quality by designing the diffractive optic with spatially varying grating structures. The Fractal Fresnel phase plate uses different grating patterns in different regions of the plate, optimized for specific angular ranges. This allows the system to maintain high measurement precision across a wide field of view by adapting the local optical properties to different incident angles.
Solution Approach 2:
The patent transitions from conventional two-dimensional image sensors to a three-dimensional diffractive optical system. The Fresnel zone plate or Fractal Fresnel phase plate introduces a third dimension (depth/focusing distance) through its diffractive structure, enabling wide angle-of-view coverage while maintaining precision through the z-axis optical path control.
4Device complexity
If diffractive optics are used to reduce system size, then device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses parameter changes by scaling the grating structure dimensions to the micrometer range. The Fractal Fresnel phase plate employs micrometer-scale features that can be manufactured using standard semiconductor fabrication techniques or precision lithography. This scaling approach balances manufacturing feasibility with the need for high precision, as micrometer-scale features are within the capability of modern manufacturing processes.
Solution Approach 2:
The diffractive optic can be implemented using composite structures, such as transparent plates with embedded grating patterns or multi-layer structures. This allows the system to achieve the required optical precision through material composition and structural design rather than relying solely on extremely tight dimensional tolerances, making manufacturing more feasible.
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 solution enables accurate and wavelength-insensitive measurement of incident angles with low computational overhead, supporting precise alignment of visual edges in automated inspection systems, even under severe spatial constraints, using simple image processing algorithms and materials like lanthanum dense flint glass.
Implementation Method 1
the right diffractive optic can perform an operation other than the identity function
Implementation Method 2
Fractal Fresnel phase plate
Implementation Method 3
transforming light intensities from different incident angles to locations on a two-dimensional image sensor
Data Source
AI summary
Described are imaging systems that employ diffractive structures as focusing optics optimized to detect visual edges (e.g., slits or bars). The diffractive structures produce edge responses that are relatively insensitive to wavelength, and can thus be used to precisely measure edge position for panchromatic sources over a wide angle of view. Simple image processing can improve measurement precision. Field-angle measurements can be made without the aid of lenses, or the concomitant cost, bulk, and complexity.