BACKGROUND

Holographic display devices may present holographic images in a variety of applications including automotive heads up displays (HUDs), augmented reality (AR) displays, virtual reality (VR) displays, and others. Such holographic display devices have advantages over other displays including an inherent ability to focus light at different distances, very high light efficiency, and small size, to name a few. In the context of presenting holographic images, a spatial light modulator (SLM) is a key component. An SLM has many small pixels that are capable of modulating either the phase of light or its amplitude, but not both. Although devices that combine both phase and amplitude modulation are possible, technical constraints make such devices large, costly, and extremely complex. Therefore, SLMs that modulate only one of phase or amplitude are typically used with phase modulation being employed more frequently.

In the context of phase or amplitude modulation SLMs, given a particular holographic image that is to be displayed, the corresponding pattern, a holographic diffraction image, to be displayed on the SLM must be determined. In image generation, the holographic diffraction image displayed on the SLM in combination with highly coherent light emitted onto the SLM generates the holographic image viewed by a user. Typically, the holographic diffraction image is generated based on a constrained optimization problem that is, in turn, based on the display being implemented and the configuration of the imaging set up of the display as well as the particular holographic image to be displayed. For example, the constrained optimization problem may model forward propagation of light for the display set up. The constrained optimization problem is typically solved using iterative approaches that require tens or hundreds of iterations with each iteration being computationally expensive. For example, one iteration may include multiple passes across an entire image including application of a non-linear function, inverse fast Fourier transform (IFFT), non-linear function, fast Fourier transform (FFT), etc. with each being performed on a complex image (i.e., an image having two floating point values: one each for amplitude and phase).

Current techniques for generating holographic diffraction images are computationally expensive and have other limitations. It is with respect to these and other considerations that the present improvements have been needed. Such improvements may become critical as the desire to present holographic images in a variety of contexts becomes more widespread.

