A head-up display for a windscreen having spatially variant optical power. The head-up display includes a diffuser arranged to display an image. The diffuser is shaped to compensate for the spatially variant optical power of the windscreen. A holographic projector may be provided, which is arranged to project the image for display onto the diffuser and includes a spatial light modulator arranged to apply a phase-delay distribution to incident light. The phase-delay distribution includes phase-only data representative of an object. The projector further includes Fourier transform means arranged to perform a Fourier transform of phase modulated light received from the spatial light modulator and to form the image on the diffuser.