Studio Software

In-plane strain and CTE measurement Technique

Digital Image Correlation (DIC) is a non-contact, full-field optical technique for measuring both in-plane and out-of-plane displacements of an object surface. A high contrast, random speckle pattern is applied to the surface of interest. Two cameras are mounted above the oven, viewing the sample from different angles.

Two simultaneous images from both cameras are digitized. Software identifies the same point on the surface from both perspectives, using pattern recognition of the speckles within a small pixel window. Using the principle of stereo triangulation, the spatial position of the pixel window relative to the cameras is determined in 3D space. Stepping the pixel window across the sample, the displacement of the surface can be mapped out in 3 axes.

The strengths of the DIC measurement technique include:

• In-plane strain measurement at <150 microstrain
• Calculate average surface CTE from strain and temperature data

The DIC technique is offered in the form of the DIC 2.0 module on the following Akrometrix tools:

• AXP
• PS200S

Flatness Measurement and Analysis Technique

Shadow Moiré is a non-contact, full-field optical technique that uses geometric interference between a reference grating and its shadow on a sample to measure relative vertical displacement at each pixel position in the resulting image. It requires a Ronchi-ruled grating, a white line light source at approximately 45 degrees to the grating and a camera perpendicular to the grating. Its optical configuration is shown in the figure to the right. A technique, known as phase stepping, is applied to shadow moiré to increase measurement resolution and provide automatic ordering of the interference fringes. This technique is implemented by vertically translating the sample relative to the grating

The strengths of the shadow moiré measurement technique include:

• Full field data acquired in less than 2 seconds
• Resolution down to <1 micron
• Resolution is unchanged by field of view
• Highly robust with minimal moving parts

The shadow moiré technique is offered on the following Akrometrix tools:

• AXP
• PS200S
• PS600S
• AKM600P