An opto-electronic model of a cricket POL1-neuron. Skylight transmitted through a blue-filter and a polarizer tuned to horizontal and vertical e-vector orientations, respectively (see double arrows), is viewed by two photodiodes. Their visual fields are restricted by cylindrical tubes. Simulating polarization opponency, the two photodiode signals are logarithmized and subtracted from each other. To record responses for each azimuthal direction, the model makes a 360° rotation about the vertical axis.