Moiré Microscope
Moiré Microscope
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Described is a Moiré microscope proposed in 1996 by Steve Hines that helps identify the geometric structure of materials. For example, a fly's eye, crystal growth, half-tone printing screens, perforated metal filters, image-coherent fiber-optic bundles, CCD and CMOS image sensors, nano-particles, and the honeycomb lattices of graphene. This device optically super-imposes the image of the test sample onto a reference pattern, and rotates the reference pattern with respect to the image of the sample to create a Moiré interference pattern. It becomes quite clear whether the sample has a hexagonal, square-packed or parallel-line structure.
The sample being examined is laid on the base of the microscope which provides both front and back lighting. A lens relays the image of the sample to the test patterns in the rotatable turret. Each test pattern in the turret can be turned, and the relay lens can be zoomed to find the best match. It is obvious when the correct pattern is compared to the image of the sample at a matching magnification.
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A variation of the Moiré microscope requires only the test sample, without anything to compare it to because two images are created of the sample using a beam splitter. To make the comparison, a dove prism in the optical path (or one in both paths, as shown at right) can be used to rotate the images for comparison. Rotation of the dove prisms zooms the Moiré pattern larger or smaller. For example, a half-tone printing screen has from 12,000 – 90,000 dots/sq. inch. When the printing screen is just held up to the light and viewed, it would appear to be a gray filter, as would any of the three patterns above when viewed alone. However, when viewed with the Moiré microscope, the structure of the sample is immediately apparent. The magnification reaches infinite power as the two patterns are aligned, a magnification that is not possible in a conventional microscope. Advantages of this device are (1) the low cost due to the absence of lenses, (2) a reference sample not being required, and (3) the magnification reaching infinite power. |
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Moiré patterns are never sharp images, but rather varying phase relationships between two patterns. The strength of the Moiré microscope is not to provide sharp images or measure samples, but as a field instrument to quickly categorizes the geometric structure for further examination using other techniques.
Hines' lab notebook #1, p. 81:
This is a technology being offered for license. Please contact Steve Hines at: