Optical Wave Surface Inspection Using Density Gradient Filter
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Solution Overview
Problem
Current measuring apparatuses for optical wave surfaces, such as interferometers and wavefront sensors, are cumbersome, lack accuracy, and are not well-suited for observing extended objects like galaxies or globular clusters, and pose usage problems in ophthalmology with point laser sources.
Innovation Solution
A system comprising an optical head with a density gradient filter, a matrix frame of identical lenses, and a photodetector array, along with image processing to compute partial derivatives of the wave surface, allowing for precise inspection of optical wave surfaces with improved accuracy and ease of production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If interferometers are used for measuring optical surfaces, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The invention segments the complex interferometric measurement process into simpler components: a diffuser element that creates multiple scattered beams, a detector array that captures intensity variations, and computational processing that reconstructs wavefront information. This segmentation allows achieving interferometer-level precision with a less complex, more compact system architecture.
Solution Approach 2:
The invention replaces traditional mechanical interferometer components (mirrors, beam splitters, precise alignment mechanisms) with a diffuser-based optical system combined with digital computation. This substitution eliminates cumbersome mechanical structures while maintaining measurement precision through computational analysis of intensity patterns.
2Device complexity
If wavefront sensors are used instead of interferometers, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The invention changes the measurement parameter from direct wavefront slope detection (traditional wavefront sensors) to intensity variation analysis through a diffuser. By computing derivatives of intensity patterns with respect to diffuser position, the system recovers precise wavefront information from simpler intensity measurements, thereby maintaining precision while reducing device complexity.
Solution Approach 2:
The diffuser element acts as an intermediary between the optical wave and the detector array. It transforms wavefront information into intensity variations that can be captured by simple detectors, while computational processing extracts precise wavefront parameters. This intermediary approach enables high precision measurement without complex sensor hardware.
3Adaptability or versatility
If adaptive optics systems with multiple artificial stars are used, then measurement coverage is improved, but device complexity increases
Solution Approach 1:
The invention creates a universal measurement system that can handle multiple field points and extended objects simultaneously through computational processing of a single diffuser pattern. The system achieves multi-functionality by mathematically reconstructing wavefronts across the entire field of view from intensity measurements, eliminating the need for multiple specialized sensors or artificial stars.
Solution Approach 2:
The invention merges the functions of multiple wavefront sensors (one per artificial star) into a single integrated system using one diffuser and one detector array. Computational algorithms combine information from all field points simultaneously, achieving the coverage of multiple sensors with a single unified apparatus, thereby reducing overall system complexity.
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 system provides accurate and efficient inspection of optical wave surfaces with high spatial resolution and short measurement times, overcoming the limitations of existing technologies by using a compact and easy-to-produce optical head with enhanced image processing capabilities.
Implementation Method 1
a density gradient filter, in a plane referenced (x′, y′) perpendicular to the optical axis of the optical measuring head, the transmission T(x′, y′) of said filter being governed by the equation: T(x′, y′) = 0.5{1 + cos[2π(x′−y′)/px]}{1 + cos[2π(x′+y′)/py]}
Implementation Method 2
a matrix frame of identical lenses of square shape and of the same focal length, said matrix frame comprising at least four lenses, each centre of one of the four lenses being arranged on an axis passing through the centre of the exit pupil and a point O′M′(i, j) of the density gradient filter
Implementation Method 3
a photodetector array, each of the four lenses forming an image of the pupil in the plane of this array
Data Source
AI summary
Systems for inspecting a surface of an optical wave originating from an optical device are provided. The optical device includes an exit pupil, and the inspection system includes an optical measuring head and a computer for processing the images from said optical measuring head. The optical measuring head includes a density gradient filter, the density varying periodically in the two directions in space, a matrix frame having at least four identical lenses of square shape of the same focal length and being arranged symmetrically, and a photodetector array, each of the four lenses forming an image of the pupil in the plane of this array. The image processing computer includes computing means for computing the partial derivatives∂Δ∂x(x,y)and∂Δ∂y(x,y)of the wave surface Δ(x, y) in the plane of the exit pupil.