Introducing sub-wavelength pixel THz camera for the understanding of close pixel-to-wavelength imaging challenges
2012
Conventional guidelines and approximations useful in macro-scale system design can become invalidated when applied
to the smaller scales. An illustration of this is when camera pixel size becomes smaller than the diffraction-limited
resolution of the incident light. It is sometimes believed that there is no benefit in having a pixel width smaller than the
resolving limit defined by the Raleigh criterion, 1.22 λ F/#. Though this rarely occurs in today's imaging technology,
terahertz (THz) imaging is one emerging area where the pixel dimensions can be made smaller than the imaging
wavelength. With terahertz camera technology, we are able to achieve sub-wavelength pixel sampling pitch, and
therefore capable of directly measuring if there are image quality benefits to be derived from sub-wavelength sampling.
Interest in terahertz imaging is high due to potential uses in security applications because of the greater penetration depth
of terahertz radiation compared to the infrared and the visible. This paper discusses the modification by INO of its
infrared MEMS microbolometer detector technology toward a THz imaging platform yielding a sub-wavelength pixel
THz camera. Images obtained with this camera are reviewed in this paper. Measurements were also obtained using
microscanning to increase sampling resolution. Parameters such as imaging resolution and sampling are addressed. A
comparison is also made with results obtained with an 8-12 μm band camera having a pixel pitch close to the diffractionlimit.
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