Edward Buckley

Eye‐safety analysis of current laser‐based scanned‐beam projection systems

Scanned-beam projection systems have attracted much interest recently, with claimed advantages including power efficiency and potential miniaturization consistent with embedding in mobile devices. However, the laser-safety classification and concomitant performance implications, which are arguably the most important issues pertaining to this technology, remain widely misunder- stood. In this paper, Class 1 and 2 laser-safety radiometric image power limits for scanned-beam sys- tems are derived with reference to the IEC 60825-1 standard. By calculating the equivalent photometric measure of luminous flux, it is possible to show that the brightness limits for scanned- beam projection systems using current technology are approximately 1 and 17 lm for Class 1 and 2 safety classifications, respectively.

Laser‐based multi‐user 3‐D display

Abstract— The development of a multi-user stereoscopic display that does not require the use of special glasses (autostereoscopic), and that enables a large degree of freedom of viewer movement and requires only the minimum amount of information (a stereo pair) for the displays described. The optics comprise an RGB holographic laser projector that is controlled by the output of a multi-target head-position head tracker, an optical assembly that converts the projector output into steerable exit pupils, and a screen assembly comprising a single liquid-crystal display (LCD) and image multiplexing screen. A stereo image pair is produced on the LCD by simultaneously displaying left and right images on alternate rows of pixels. Novel steering optics that replace the conventional backlight are used to direct viewing regions, referred to as exit pupils, to the appropriate viewers eyes. The results obtained from the first version of the display, where the illumination source consists of several thousand white LEDs, are given and the current status of the latest prototype being constructed on the basis of these results is described. The work indicates that a laser-based head-tracking display can provide the basis for the next generation of 3-D display.

Eye‐safety analysis of current laser‐based LCOS projection systems

Abstract— A laser safety analysis for liquid-crystal—on—silicon (LCOS) based imaging projection systems utilizing laser light sources is presented. It is shown that a typical laser-based imaging projector is capable of providing a D65 white-balanced luminous flux in excess of 20 lm while remaining Class 1 eye safe. By considering a Class 2 classification, it is shown that the same architecture is capable of providing several hundred lumens, a performance level which could potentially be applicable to a new class of high-brightness miniature projection systems.

Multi-viewer autostereoscopic display with dynamically addressable holographic backlight

— The Multi-User 3-D Television Display (MUTED), designed to provide three-dimensional television (3-D TV) by the display of autostereoscopic imagery to multiple viewers, each of whom should enjoy freedom of movement, is described. Such an autostereoscopic display system, which allows multiple viewers simultaneously by the use of head tracking, was previously demonstrated for TV applications in the ATTEST project. However, the requirement for a dynamically addressable, steerable backlight presented several problems for the illumination source. The MUTED system demonstrates significant advances in the realization of a multi-user autostereoscopic display, partly due to the provision of a dynamic backlight employing a novel holographic laser projector. Such a technology provides significant advantages in terms of brightness, efficiency, laser speckle, and the ability to correct for optical aberrations compared to both imaging and scanned-beam projection technologies.

European Research into Head Tracked Autostereoscopic Displays

Stereoscopic displays that do not require the wearing of special glasses (autostereoscopic), enable a large degree of freedom of viewer movement and show the minimum amount of information have been developed within several European Union-funded projects. In the ATTEST and MUTED projects a stereo image pair is produced on a single liquid crystal display (LCD) by simultaneously displaying left and right images on alternate rows or columns of pixels. Novel steering optics is used to direct regions, referred to as exit pupils, to the appropriate viewers eyes. The positions of these are controlled by the output of a head position tracker. In the HELIUM3D project an autostereoscopic image is produced with the use of a light engine and illumination is provided by an RGB laser. Exit pupil locations are determined by a head tracker controlling a spatial light modulator (SLM).

Letter: Scaling rules for pico-projector laser safety

— This letter presents a set of scaling rules for the laser safety analysis of scanned-beam and LCOS projection systems, providing a simple method for determining the impact of changes in key system parameters upon the maximum eye-safe luminous flux.

Letter: On proximity detection systems for pico‐projectors

— Proximity detection systems have been proposed as a potentially beneficial method for increasing the eye-safe luminous flux of laser-based pico-projectors. In this letter, it is shown that, while the benefit for panel-based systems could be significant, the impact upon scanned-beam projectors is far smaller.It has been suggested that proximity detection systems could potentially be beneficial in increasing the eye-safe luminous flux of laser-based picoprojectors. In this letter it is shown that, whilst the benefit for LCOS-based systems could be significant, the impact upon scanned-beam projectors is far smaller.

25.1: Distinguished Paper: Multi-Viewer Autostereoscopic Display with Dynamically-Addressable Holographic Backlight

An autostereoscopic display system, which allowed multiple viewers simultaneously by use of head-tracking, was previously demonstrated for TV applications in the ATTEST project. However, the requirement for a dynamically addressable, movable backlight presented several problems for the illumination source. In this paper, the authors demonstrate how the use of a novel laser-based holographic projection system can be used to address these problems.

Eye-safety analysis of phase-only holographic projection systems

— Recently, laser-safety analyses have been presented for scanned-beam and LCOS imaging projectors. A third class of projection technology, based on the properties of phase-only diffraction, is differentiated from scanned-beam and LCOS counterparts in its ability to provide a significantly higher effective luminous flux for video style images. In this paper, this desirable property is recognized by the definition of the “video lumen” and a detailed design fora hypothetical holographic projector and corresponding laser safety analysis is presented. As in the case of conventional amplitude-modulating LCOS projectors, a holographic projector is capable of delivering several hundred white lumens in Class 2; an appropriately specified holographic projector can also provide several tens of video lumens while maintaining a Class 1 classification.

Multi-user 3D display using a head tracker and RGB laser illumination source

A glasses-free (auto-stereoscopic) 3D display that will serve several viewers who have freedom of movement over a large viewing region is described. This operates on the principle of employing head position tracking to provide regions referred to as exit pupils that follow the positions ofthe viewers eyes in order for appropriate left and right images to be seen. A non-intrusive multi-user head tracker controls the light sources of a specially designed backlight that illuminates a direct-view LCD.