There is provided a spatial light modulator arranged to display a light modulation pattern comprising a hologram. The spatial light modulator comprises a liquid crystal on silicon spatial light modulator having a plurality of pixels. The hologram has a plurality of pixels. The spatial light modulator comprises a silicon backplane. Each pixel of the spatial light modulator comprises a light-modulating element and a respective pixel circuit. Each pixel circuit is embedded in the silicon backplane. Each pixel circuit is arranged to drive the corresponding light-modulating element. Each pixel circuit is further arranged to combine a received pixel value of the hologram with a corresponding pixel value of the light processing function such that the light modulation pattern further comprises the light processing function. The light processing function comprises a lens function and/or a grating function.

A volume holographic film (such as a photopolymer) that is pre-recorded with patterns subsequently is used to encode LED or low-power laser light reflections from an eye into a binary pattern that can be read at very high speeds by a relatively simple complementary metal-oxide-semiconductor (CMOS) sensor that may be similar to a high framerate, low resolution mouse sensor. The low-resolution mono images from the film are translated into eye poses using, for instance, a look up table that correlates binary patterns to X, Y positions or using a pre-trained convolutional neural network to robustly interpret many variations of the binary patterns for conversion to X, Y positions.