The influence of additional phase modulation of an amplitude liquid crystal STLM on the image recognition characteristics in the invariant optical digital correlator

We present the results of measurements of additional phase modulation characteristics of a serial amplitude liquid crystal spatial light modulator HoloEye LC 2002. It is found in which way the phase shift of the liquid crystal spatial light modulator depends on the applied signal. The mathematical simulation of the performance of an invariant diffractive optical-digital correlator based on a liquid crystal spatial light modulator with the amplitude-dependent phase shift is carried out using previously measured data. The correlation filters used in the work are an optimal tradeoff maximum average correlation height filter and a minimum noise and correlation energy optical correlation filter. A method for correlation filters optimization was proposed to compensate for the recognition error caused by the presence of the additional phase modulation. In some cases, the optimization allows one not only to compensate for the recognition error, but also to reduce it.

EVALUATION NOISE IMMUNITY OF THE BINARY DIGITAL MODEM WITH SIGNALS TYPE NOISE USING THE CHARACTERISTIC FUNCTION METHOD

The issue of improving modems with noise signals implies increasing the accuracy of theoretical estimation of noise immunity of the proposed methods of demodulation of information components of signals. Important is the task of assessing the immunity of digital modems, enabling engineers to ascertain the prospect of system development at the design stage. The article investigates the noise immunity of a binary digital modem with phase manipulation of the noise signal and the autocorrelation algorithm of its reception, which uses as noise carrier Gaussian signals. The paper presents a technique for calculating the bit error rate (BER) in a demodulator, which is characterized by the fact that the functional for estimating the received information bit contains components with different laws of probability distribution. The presented methodology is based on a mathematical apparatus of characte­ristic functions, which allows determining the potential noise immunity of a digital modem, providing a reduction of the discrepancies between theoretical and experimental data for determining the BER. Summing up the whole research it is worth noting the following research results: 1 noise immunity analysis of digital binary modem of noise signals was performed using mathematical apparatus of characteristic functions at autocorrelation method of operation of Gaussian type noise signal demodulator in the presence of Gaussian additive interference; 2 an analytical expression was found to calculate the characteristic density function of the random variable distribution at the output of a binary digital correlator; 3 the ratio was obtained to determine the potential noise immunity of the demodulator. The results of the study showed that the application of this technique eli­minates significant differences between the results of the theoretical evaluation of the noise immunity of the demodulator and the results of its simulation.