Figure 5. Simulated images of four different types of particles with the same needle-like morphology: negatively birefringent and transparent (first column), positively birefringent and transparent (second column), non-birefringent and transparent (third column), non-birefringent and absorptive (fourth column), imaged under two different analyzer orientations (0°: first row, 90°: second row) and the subtraction of the amplitudes (labeled as differential) at these two orientations (third row).

The differential step (third row) results in cancellation of non-birefringent particles that normally appear in both orientations of the analyzer.