Holographic spatial light modulator (SLM) display with coherent beam profile detection using light sensing pixels

Apparatus and methods for generating holographic images are disclosed, as well as a spatial light modulator (SLM) for use in such techniques. A spatial light modulator (SLM) comprises plural light modulating pixels 502 for diffracting a beam of coherent light to generate an image from a hologram displayed on said SLM, with at least one of the light modulating pixels replaced with a light sensing pixel (e.g. CMOS device or photodiode; 504) to sense a beam intensity of coherent light at the light sensing pixel position. Also claimed is a method including providing a light sensing pixel on an SLM, detecting beam coherent light intensity, and determining the intensity of a generated image accordingly, e.g. spatial light distribution. Plural light detecting pixels may be used, with spatial illumination intensity determined via a space-frequency transform, allowing brightness compensation, e.g. using average intensity. A second SLM modulator may be used. The SLM may be incorporated in an optical assembly for a holographic image projection system, in combination with a laser illumination system to illuminate the SLM and an optical output system to output an image. Microelectromechanical systems (MEMS) may used (Figure 5b).