3D movie display is a wonderful entertainment innovation but not when viewing discomfort — particularly on a small portable screen — comes into play. Chinese researchers have created a "dense arrangement of viewpoints" on the screen to address this issue.

Scientists from Sun Yan-Sen University have developed a new display boasting of comfortable three-dimensional visual effects based on a "super multi-view technique" working to reduce viewing discomfort and the ensuing headache or nausea.

Author and associate professor Lilin Liu said there are many reasons behind 3D viewing discomfort, among which is vergence-accommodation conflict, a mismatch between the point at which the eyes converge on an image and the distance to which they focus while viewing 3D images.

The two eyes view slightly different images when a person looks at an object because of a six-centimeter distance between them.

The brain, in order to keep the binocular vision going, directs the eyes to maintain the focus on the lens within each eye, leading to the image projecting sharply on the retina.

Vergence distance is the distance at which the sight lines of the eyes cross, while accommodative distance is the distance to which the eye is focused. The conflict occurs when the eyes' focal point and convergence point on a given image fail to correlate and adjust simultaneously.

This synchronization between vergence and accommodation in the human eye ensures that the image before the eyes is undistorted. Now, most 3D displays manipulate vergence-accommodation by recreating the natural viewing process.

These 3D pictures simulate vergence changes yet the accommodation distance stays unchanged. This leads to vergence-accommodation conflict, the source of viewer's discomfort.

Liu explained that this conflict happens as conventional 3D displays typically provide view of the displayed spatial spot to only one eye pupil, leading accommodative distance to remain fixed on the screen and unable to adjust along with vergence distance.

The researchers sought to project a number of 2D prospective views to viewpoints with intervals that are smaller than the eye's pupil diameter. This delivers more than two views to an eye pupil and allows the eyes to focus naturally on the displayed image.

"The prototype in our study is 65-millimeter-thin, and the system could become thinner with improvements in structural elements," says co-author Dongdong Teng, highlighting their work as promising for comfortable 3D portable displays or wearables.

The prototype is also made up of 11 elementary projecting units, each of which is formed by an organic light-emitting diode or OLED microdisplay, a rectangle-shaped projecting lens, a pair of vertical baffles, and gating apertures attached to the projecting lens.

The team tested eight individuals' reaction to the prototype by having them watch a 3D image of an apple in the lab setting, with no viewing discomfort reported afterwards.

Future work is concentrated on making the device even thinner.

The findings were published in the journal Optics Express.