Nonlinearly recorded matched filter: a technique to reduce the false alarm rate

The effect of film nonlinearity in recording a spatial matched filter for optical signal detection is to record a distorted signal rather than the original target signal. This distorted signal could cause a large false alarm rate if it is severely distorted. We propose a method that requires an additional mask immediately before the holographic matched filter to convert the original signal to the distorted signal before processing the signal through the nonlinear matched filter. This process will, in theory, eliminate all the false alarm signal caused by film nonlinearity. The transmittance function of the mask is calculated for a given target signal and given matched filter recording parameters. For a particular choice of recording parameter, the mask can be fabricated by directly exposing the Fourier spectrum of the target signal. A computer simulation using a square function as target signal proves the validity of this technique.