Moiré contour-sum contour-difference, and vibration analysis of arbitrary objects

Area of Science:

• Optics and Photonics
• Mechanical Engineering
• Image Processing

Background:

• Moiré patterns arise from the superposition of two or more grids or gratings.
• Optical projection techniques are valuable for non-contact measurement and analysis.
• Existing methods may have limitations in real-time dynamic analysis.

Purpose of the Study:

• To introduce and analyze a moiré fringe technique for contour measurement and image enhancement.
• To extend the moiré method for real-time vibration analysis.
• To investigate the properties, limitations, and sensitivity of the proposed technique.

Main Methods:

• Projecting a grid onto an object and capturing the image with an offset camera.
• Utilizing double exposure or filtering for superimposing images to generate contour-difference moiré fringes.
• Employing two offset projectors for contour sum or doubling measurements.
• Applying time-average moiré fringes for vibration analysis.

Main Results:

• Contour-difference moiré fringes are generated, enabling contour measurement.
• The method demonstrates utility for image enhancement.
• Real-time vibration analysis is achieved, with fringes described by the zeroth-order Bessel function.
• The modal amplitude function is contained within the Bessel function argument.

Conclusions:

• The described moiré fringe technique offers a versatile approach for object contour measurement and image enhancement.
• The extension to real-time vibration analysis provides a powerful tool for dynamic studies.
• The mathematical framework, particularly the Bessel function in vibration analysis, offers insights into modal behavior.