Toru Iwane

Light-field Display Combined with an Aerial Image Display Device, Aerial Imaging by Retro-Reflection (AIRR)

By combining a light-field 3D display with an aerial image display device on aerial imaging by retro-reflection (AIRR), we have succeeded in forming aerial 3D volumetric images, both computer-generated and acquired by a light-field camera.

Light field camera and integral 3D display: 3D image reconstruction based on lightfield data

Recently, light field cameras have become popular as cameras with which you can refocus images after having taken pictures. In this paper I report that combination of this light field camera and integral display has useful features for 3D image capture and reconstruction. Refocusing function is based on 3D information contained in light field data and this fact means that a light field camera captures 3D images and encodes them in the 2D sensor plane by micro lens array. This 3D capturing is unique in two points; one is that a light field camera acquires not real 3D object images but 3D image plane compressed in axial direction by the object lens in proportion to ratio of longitudinal and lateral magnification. So when captured 3D image plane is shown on the integral display, the actual 3D image is reconstructed near display screen like an embossed carving. The other point is that the reconstructed image is of higher resolution than density of micro lens. Light filed data by the light field camera basically contain full resolution information not limited by density of micro lens. This implicit resolution in encoded data comes out, when the light field data is decoded by the integral display thorough optical convolutional process.

Light-field displays and light-field optics

Light-field optics is a novel system in which image is exchangeable in between 2D (light-field data) and real 3D, although this technology is well known just for refocusing camera Light-filed optics has two useful features both of which are different from previous imaging optics. One is a feature that 3D scene can be expressed in 2D-data (light-field data) as 4D data and reconstructed from these encoded 2D data through reverse optical path. The other is that reconstructed image is not necessary to be conjugated with display device, in other words, image appears in different plane from displays screen. With the former feature, an integral 3D-display whose data are of light-field optics is realized. There is no difference in this display in structure from previous integral 3Ddisplays. It consists of flat display and lens array attached directly above to the display. Lens array decodes light-filed data and this display reconstructs 3D scene. So, 3D scene acquired by a light-field camera or computer generated light-field data appear nearby lens array. With the latter feature, a simple head mounted display(HMD) can be developed for example. In previous HMDs development, problem is to find out a solution of optical design to form display image on the retina of a speculator in trade-off relation between maneuverability and size of optical system. Using light-field optics, display device can be set in directly front of eyes, because image is generated in a different plane you can see.

Light-field optics as optical encoding and decoding system for 3-D scene

Film-based cameras were replaced with digital cameras in a very short period. Saving film costs for each shot is not only of advantage of this transition. The more important advantage by this digitization is that forming optically a completed image on detector is not necessary and acquired data are processable by a computer. We can think that, with optional optical system-lens array-, acquired data can be nuggets of information which contains both image and its depth or bunch of incident rays which are equal value to actual 3-D scene. These data represent 3-D situations and by computing them, various optical effect, e.g. focusing and changing field of depth, can also be realized or simulated virtually. My issue is to clarify how 3-D scene is transformed and expressed on 2-D detector and how this 2-D information is retrieved back again into 3-D scene through lens array and other optical devices. Light-field optics or lens array is one of those exchangeable methods of the transformation between actual 3-D scene and information encoded on 2-D plane. Recently new method for lens array was introduced; a circular zone plate instead of lens array. As for a 3-D Display which consists of flat display and lens array, the encoded data shown on a flat display and they are retrieved into real 3-D image by a lens-array. I will mention not only its advantage but its limitation of ability for 3-D image reconstruction.

Aerial light-field image augmented between you and your mirrored image

This paper proposes a method to form an aerial light-field image in front of a mirror. Our system consists of a specially fabricated punctured retro-reflector covered with a quarter-wave retarder and a reflective polarizer. The floating aerial 3D image is augmented between you and your mirrored image.