We present a method for simulating multiple diffraction in imaging systems based on the Huygens–Fresnel principle. The method accounts for the effects of both aberrations and diffraction and is entirely performed using Monte Carlo ray tracing.We compare the results of this method to those of reference simulations for field propagation through optical systems and for the calculation of point spread functions. The method can accurately model a wide variety of optical systems beyond the exit pupil approximation.@en

To predict the quality of an optical system we need to simulate the effects of aberrations and diffraction. Aberrations can be calculated by tracing rays from a source point through a digital model of the system and evaluating the spot size of these rays on the detector. For a system without aberrations, the rays will intersect at a single point. However, the real spot size will be larger due to diffraction. This increase in size is due to the wave nature of light, which cannot be fully captured by regular ray-tracing methods. This thesis presents two ray-tracing methods that can simulate wave-optical effects by initiating secondary rays at diffracting surfaces. The first method uses rays to transport the Wigner distribution function. The second method combines the Huygens-Fresnel principle with ray tracing. The methods, particularly the latter, can be used to assess the quality of an optical system, especially when the system has multiple diffracting surfaces.@en

We study a simulation method that uses the Wigner distribution function to incorporate wave optical effects in an established framework based on geometrical optics, i.e., a ray tracing engine. We use the method to calculate point spread functions and show that it is accurate for paraxial systems but produces unphysical results in the presence of aberrations. The cause of these anomalies is explained using an analytical model.@en

The electric field at the output of an optical system is in general affected by both aberrations and diffraction. Many simulation techniques treat the two phenomena separately, using a geometrical propagator to calculate the effects of aberrations and a wave-optical propagator to simulate the effects of diffraction. We present a ray-based simulation method that accounts for the effects of both aberrations and diffraction within a single framework. The method is based on the Huygens–Fresnel principle, is entirely performed using Monte Carlo ray tracing, and, in contrast to our previously published work, is able to calculate the full electromagnetic field. The method can simulate the effects of multiple diffraction in systems with a high numerical aperture.@en