Spatial and angular resolution measurement of a tensor light field display

Dependent on the way in which the images are formed, some light field three-dimensional (3D) displays are less straightforward to characterize than two-dimensional (2D) displays. They do not have an effective screen position that physically exists, they do not have pixels in the conventional sense that can be simply measured with a microscope and, in common with all 3D displays they have light emission that varies with angle, giving them the characteristic of angular resolution. In our previous work on light field characterisation, subjective evaluation was used to determine perceived spatial resolution and some other characteristics; however, the measurement of angular resolution eluded us. As this is the vital characteristic that distinguishes 3D displays from 2D displays, we set out to determine a method of obtaining this parameter from existing data collected. Crucial to this was the realisation that, first, the meanings of the characteristics must be defined. It was observed that the overall display system, including; capture, processing and display, behaves as a low-pass filter. Regarding the system as such enables the spatial resolution to be expressed in terms of spatial cut-off frequency and angular resolution in terms of angular cut-off frequency. This led us to determine the angular resolution indirectly from the variation of spatial resolution with depth. In this paper, we describe the rationale behind our method, which also dispenses with the need to conduct lengthy and unreliable user trials, and give the results of the measurements.