No abstract

Optimum filters for optical correlators have been the topic of several papers in the last few years. How can there be more than one optimum? Because, different approaches optimize different functions. Most research to date has optimized some internal working function of the correlator, such as optical efficiency, or narrowness of the correlation peak. However, in the real world, there is usually some application oriented function to optimize. For example, in a tracking system, the robustness to break-lock may be the most critical function. There is a threshold in the signal to noise required for single pixel tracking. Beyond that, "optimization power" might better be spent on increasing tolerance to aspect change, rather than increasing signal to noise. This paper will discuss the attention the filter designer must pay to bore slope error, tolerances for distortions, signal to noise, correlation width, transport delay, and other variables.

Advanced Optical Systems has developed the world's smallest and lowest cost, fully functional target recognition and tracking system. The heart of the ULTOR™ target recognition and tracking system is an optical correlator. The system includes real-time preprocessing, large filter stores, filter management logic, correlation detection and thresholding, correlation tracking, and data output. It is self contained, receiving operational commands as an Internet appliance. We will present a demonstration of some of the capabilities of the system using live video signals and real target models.The ULTOR™ system has wide application in both military and commercial settings. The Navy is considering use of the ULTOR™ system in several programs, including missile systems and unmanned aerial vehicles.

We describe a technique for constructing beam splitter cubes in which we monitor the optical path difference with a wavelength tunable laser. A white light interferometer should have path lengths equal to within λ/4. A larger path difference results in reduced fringe visibility and loss of signal-to-noise ratio. The beam splitter must be manufactured so that the two paths through glass are equal. We discuss the tolerance placed on the cube. One can assemble the cube from two right angle prisms in optical contact and in near perfect alignment. Alternatively, we adjust the OPD to zero by sliding the prisms into proper alignment on a layer of uncured cement. Using a dye laser, we have readily achieved acceptable path differences. This method of measuring the OPD with a tunable laser is shown to be useful for alignment of interferometers and measurement of aberrations in lens systems. A laser diode can be tuned by changing its operating current or temperature. We report results of optical path difference measurements using a laser diode.

This paper discusses an optical correlator interfaced to a FUR and laser rangefinder to aid aircraft landing aboard an aircraft carrier. The purpose was to recognize aircraft and provide precision track in spite of the engine plume which is visible in JR images. Toward the end of the program, an opportunity arose to piggyback on tests of a Navy FUR system, on board the USS Enterprise. The Navy's developmental FUR and laser rangefinder were mounted on the carrier and provided excellent imagery with concurrent range data. The correlator performed a limited set of experiments at sea, tracking an aircraft from 8000 feet until almost touchdown. The challenges to the correlator were operation in a harsh environment and real time interfacing with other hardware. Real time range information controlled a series of filters in the correlator. The system fit into a standard panel rack and utilized remote alignment. The system operated during the shock of aircraft launch and landing, with no need to open up the optical box.