A temporal wavelet analysis method is proposed for velocity, displacement, and three-dimensional surface-profile measurement of a continuously deforming object by use of the shadow moire technique. A grating is placed close to a deforming object, and its shadow is observed through the grating. The moire fringe patterns, generated by the interference of the grating lines and their shadows, are captured by a high-speed CCD camera with a telecentric gauging lens. Instantaneous frequency of gray-value variation is evaluated point by point with the continuous wavelet transform. From the instantaneous frequency of each point on the object, the velocity, displacement, and high-quality surface profile at different instants can be retrieved. In this application, two specimens are tested to demonstrate the validity of the proposed method: One is a small coin with a rigid body motion, and the other is a simply supported beam subjected to a central point load. The results are compared with those obtained from temporal Fourier-transform and mechanical stylus methods.

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Instantaneous velocity displacement and contour measurement by use of shadow moiré and temporal wavelet analysis.

A temporal wavelet analysis algorithm is proposed for shadow-moire-based three-dimensional surface profiling on objects having discontinuous height steps. A grating is positioned close to an object, and its shadow is observed through the grating. The moire fringe patterns vary when the grating is in-plane rotating. A series of fringe patterns are captured by a CCD camera at different rotating angles. Phase values are evaluated point by point with the continuous wavelet transform. From the phase values of each point on the object, the distance between the object and the grating can be retrieved. The surface profile is obtained without temporal or spatial phase unwrapping. This technique is applicable to objects with discontinuous height steps, which are impossible to measure with conventional shadow moire topography. Two specimens are tested to demonstrate the validity of the method: One is an object with a height step of 1.6 mm, and another is a small coin with unevenness of less than 0.2 mm. The experimental results are compared with test results by use of the mechanical stylus method.

/pdf/profiling-of-objects-with-height-steps-by-wavelet-analysis-4htvy21i0o.pdf

Profiling of objects with height steps by wavelet analysis of shadow moiré fringes

A 3D Fourier transform for vibration measurement of an object based on shadow moire technique is presented A
sinusoidal grating is placed closed to a vibrating object The moire fringe patterns generated by the interference of
grating lines and shadow lines are captured by a high-speed camera The joint spatial and temporal information of the
fringe sequence is processed by use of the 3D Fourier transform simultaneously rather than separately, then a 3D
space-time phase distribution can be obtained from the filtered spatiotemporal spectra From the phase values, the
surface profile, and displacement of the object at different time can be retrieved The experiment for measurement of a
vibrating cantilever beam is used to demonstrate the validity of the technique The results show that shadow moire with
spatiotemporal analysis can be applied to dynamic measurement

Vibration measurement by spatiotemporal analysis of shadow moiré fringes

Moire technique is a technique used for 2D and 3D imaging and surface characterization. Moire systems may have a
range of zooms to image an object at different levels of details or Moire images may be combined (or compared) with
images from other interferometers. So, it is needed to inter-relate images together in order to keep the continuity of the
images at different levels of zoom or images from different types of interferometers. This paper uses image registration
techniques to correlate images and find scale and translation between two images. Image registration is widely used in
medical imaging and range imaging to relate two different images from a single object or scene. In this work, only
interferograms from two successive levels of zooms of a Moire system are used. Saved interferograms are correlated
using one of the affine algorithms which are used in image registration and then relative scale and shift are calculated.
Calculation of these parameters makes it possible to locate the position of area that the Moire system is zoomed in,
related to the area with lower zoom level. Simulation results show that this technique is applicable and successful in
finding the scale and shift parameters and therefore can keep the continuity between images at different levels of zoom.

Image continuity at different levels of zoom for Moiré techniques

When dealing with production of Flip Chip Packages in semiconductor packaging the angle between the die and package substrate is critical for maintaining product yield and reliability. Current outgoing quality checks for die tilt can be time consuming to measure heights via point to point measurement techniques. Existing die tilt measurement approaches can also have reproducibility issues from user to user. Shadow moire technology is a full field optical inspection technique commonly used for flatness characterization in the semiconductor industry, particularly at elevated temperatures. Two limitations to shadow moire apply when discussing outgoing QC of die tilt: 1) shadow moire requires a diffuse reflective surface for measurement; 2) shadow moire is unable to measure sudden step heights. This paper focuses on case study data for samples with two or more separated planes. Die tilt measurement techniques from phase 1 of this study are applied to the case study data. Using shadow moire for this measurement technology can reduce measurement and user time as well as improve consistency of measurements from user to user. As shadow moire tools are often used for at temperature flatness measurements, this added application can reduce the number of different measurement tools needed in QA labs.

Measuring die tilt using shadow moiré optical measurements; new techniques for discontinuous and semi-reflective surfaces — Phase 2

The frequency sweeping technique is proposed to measure the shape of objects with discontinuous height steps and / or spatially separated surfaces, which have been impossible to measure with conventional shadow moire topography. By controlling the amount of the rotation angle of the grating, the spatiotemporal moire patterns are produced with different contour intervals. The Fourier transform technique has been applied to analyze these patterns and obtain the temporal carrier frequency in which the height distribution of the object is involved. Experimental results show the validity of this method.

Y. Otani

Papers

Shadow moiré profilometry by the frequency sweeping