Driving a focus-tunable liquid lens in an innovative way and synchronizing the display with it, the researchers propose a multifocal display that goes well beyond the typical limitations of focus-tunable lenses. In a paper titled “Towards Multifocal Displays with Dense Focal Stacks” presented at the SIGGRAPH Asia conference last December, the researchers describe an optical system able to produce thousands of focal planes per second, which if the display is fast enough, could be used to project just the images relevant to each focal plane.
In that case, an observer could look anywhere at the display and would naturally get a coordinated vergence and focus thanks to the images’ depth maps sequentially assigned to a dense stack of focal planes. Multifocal displays are not a new concept per se, but previous demonstrations often found their limitation due to the focus-tunable liquid lens’ relatively slow settling time. Based on an input driving voltage, such lenses can take about 5ms to settle onto a particular focal length, which would limit their output at 200 focal planes per second at most. Taking in consideration a display operating in the range of 30 to 60 frames per second (fps), this would limit the number of available focal planes to between three and six focal planes per frame, creating accommodation artefacts for the viewer.