Optical Computing has long been heralded as the solution to the world’s thirst for data processing. As speed and resolution limits are approached and power requirements become ever more impractical, serial electronic processing begins to show its limitations...

Optical processing uses the fastest medium there is to perform the same calculations serial electronic systems grind away at: light. CCL’s optical processing technology applies the principles of Fourier and Diffractive optics to create solutions in areas requiring processing capabilities beyond those of current and future serial electronic methods – in low power, compact, rugged architectures. Coupled with expert consultancy and technical support, the technology may be used as the basis of a custom solution, or provide step increases in processing power to existing systems for OEM customers.

Optical Correlation and the Optical Fourier Transform

Correlation is a method of comparing two sets of data. By definition, a two-dimensional correlation between two real objects, an input, s(x,y), and a reference, r(x,y), is defined as the Fourier Transform of the product of the two original function, which have themselves been Fourier transformed:

Correlation Diagram

The Fourier Transform is one of the fundamental building blocks of frequency analysis and signal processing. It is the decomposition of a signal or image into its constituent frequency parts. The Fast Fourier Transform (FFT) algorithm and its many variants have equipped electronic processors with the tools to perform 1-D Fourier transforms at speed, largely responsible for the field of Digital Signal Processing.

However, 2-D data processing using the same techniques is highly processor intensive and process time is badly affected by increases in resolution. The Fourier Transform is by nature a parallel process, where each element of the transform is derived from a calculation involving every element in the input signal. By contrast, electronic systems are by their nature serial and therefore less well suited to processes involving large Fourier Transforms.

Diffractive optics diagram

By exploiting the fact that the 2-D Fourier Transform of an image is analagous to its Far Field (Fraunhofer) Diffraction pattern, the two-dimensional Fourier transform of an image may be produced using a simple optical system: But that is not all, because the process is parallel in nature, the process time does not scale with resolution. Every pixel of the image is compared with every other simultaneously, independent of resolution. This allows very large images to be Fourier transformed at the speed of light – orders of magnitude faster than the electronic equivalents.


CCL Fourier Transform Engine

Optical Correlators

Types of Optical Correlator

Correlator Operation

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