Phase Shifting Inspection System for Edge Break Measurement
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Solution Overview
Problem
Existing inspection systems for edge breaks are time-consuming and inexact due to challenges in making accurate replicas, particularly in measuring sharp edges of objects like turbine airfoils and compressor fans under thermal and mechanical stress.
Innovation Solution
A phase shifting inspection system comprising a light source, grating, phase shifting unit, and imager that projects phase shifted patterns onto an object surface, allowing for high-resolution reconstruction of the surface with a processor, enabling accurate measurement of edge breaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a wax or soft-metal impression process is used to measure edge breaks, then the inspection can be performed offline, but the process is time-consuming and inexact due to challenges in making accurate replicas
Solution Approach 1:
The patent replaces the mechanical impression process with an optical system. A phase-shifting projector projects grating patterns onto the object surface, and a camera captures the deformed patterns. The mechanical contact method is substituted with non-contact optical projection and capture, enabling rapid acquisition of surface geometry data without time-consuming physical impressions.
Solution Approach 2:
Instead of creating physical replicas through wax or soft-metal impressions, the system creates digital copies of the surface geometry. The phase-shifting interferometry technique captures optical information from the surface and reconstructs a digital 3D model, allowing multiple measurements without repeated physical contact and eliminating the time required for physical replica creation.
2Measurement precision
If a stylus or tracer-type mechanical gauge is used to measure the impression, then the measurement can be obtained, but the process is inexact due to challenges in making an accurate replica of the edge break
Solution Approach 1:
The patent replaces mechanical stylus or tracer gauges with an optical measurement system. Phase-shifting projectors and cameras are used to capture surface geometry optically, eliminating the need for mechanical contact instruments and their associated alignment and operation complexities.
Solution Approach 2:
The patent introduces phase-shifting optical patterns as an intermediary between the measurement system and the object surface. These projected grating patterns serve as a mediator that interacts with the surface geometry and provides measurement information through optical deformation, simplifying the measurement process compared to direct mechanical contact methods.
3Measurement precision
If traditional offline impression methods are used, then the inspection process is simpler, but the resolution and accuracy for sharp edges are insufficient
Solution Approach 1:
The patent changes the fundamental measurement parameter from mechanical contact to optical phase information. By measuring the phase shift of projected optical patterns rather than physical contact, the system achieves higher resolution (less than 10 microns) for sharp edges while maintaining operational simplicity through automated image capture and processing.
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 precise and efficient inspection of edge breaks with a resolution of less than 10 microns, overcoming the limitations of traditional offline methods by generating accurate phase shifted patterns and reconstructing the object surface effectively.
Implementation Method 1
The grating is in a path of the generated light and is configured to produce a grating image after the light passes through the grating
Implementation Method 2
The phase shifting unit is configured to form and reflect a plurality of phase shifting patterns of the grating image onto an object surface
Data Source
AI summary
An inspection system is provided. The inspection system comprises a light source, a grating, a phase shifting unit, an imager, and a processor. The light source is configured to generate light. The grating is in a path of the generated light and is configured to produce a grating image after the light passes through the grating. The phase shifting unit is configured to form and reflect a plurality of phase shifted patterns of the grating image onto an object surface to form a plurality of projected phase shifting patterns. The imager is configured to obtain image data of the projected phase shifted patterns. The processor is configured to reconstruct the object surface from the image data. An inspection method and a phase shifting projector are also presented.