novel human machine interface (hmi) design enabled by holographic laser projection

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Despite the current proliferation of in-car flat panel displays, designers continue to investigate alternatives to flat and rectangular thin-film transistor (TFT) panels - principally to obtain differentiation by freedom of design using, for example, free-form shapes, round displays, flexible displays or mechanical 3D solutions. A perfect demonstration was provided at the 2008 Paris Motor Show by the BMW Mini Center Globe, a novel instrument cluster design which combines lighting, a circular flat panel and a holographic laser projector provided by Light Blue Optics (LBO) to redefine the state of the art in human-machine interface (HMI).In this paper, the authors will show how the incorporation of LBO’s holographic laser projection technology can allow the construction of a unique display technology like the Mini Center Globe, and how such a combination of technologies represents a significant advance in the current state of the art in automotive displays. From UK based. from light blue optics (LBS)

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  • 1.14.4 / E. Buckley 14.4: Novel Human-Machine Interface (HMI) Design Enabled by HolographicLaser Projection Edward BuckleyLight Blue Optics Inc., 4775 Centennial Blvd., Colorado Springs, CO 80919, USADominik Stindt Light Blue Optics Ltd., Platinum Building, Cowley Road, Cambridge CB4 0WS, UK Robert IseleBMW AG, Knorrstrasse 147, 80788 Muenchen, GermanyAbstract of display makers, lighting companies and laser projector Despite the current proliferation of in-car flat panel displays, manufacturers, has been employed in realising an automotive designers continue to investigate alternatives to flat and display. rectangular thin-film transistor (TFT) panels - principally to obtain differentiation by freedom of design using, for example, free-form shapes, round displays, flexible displays or mechanical 3D solutions. A perfect demonstration was provided at the 2008 Paris Motor Show by the BMW Mini Center Globe, a novel instrument cluster design which combines lighting, a circular flat panel and a holographic laser projector provided by Light Blue Optics (LBO) to redefine the state of the art in human-machine interface (HMI). In this paper, the authors will show how the incorporation of LBOs holographic laser projection technology can allow the construction of a unique display technology like the Mini Center Globe, and how such a combination of technologies represents a significant advance in the current state of the art in automotive displays.Figure 1 - Artists rendition of the BMW Mini Center Globeinstrument cluster, incorporating circular TFT, laser 1.Introduction projection and lighting technologies. In the last decade, thin-film transistor (TFT) panels have reigned supreme in automotive applications and a continued increase in In this paper, the authors will show how the incorporation of volume sales of automotive TFT panels is expected in the nextLight Blue Optics holographic laser projection technology few years. The proliferation of such displays is driven both by theprovides unique features which can revolutionise the HMI, increased desire for more communication and entertainmentcreating a new class of automotive display technologies and functions and by the steep, and continued, price erosion in flat-further increasing the in-car display density. panel display technologies. Indeed, the extent to which these twin market forces have influenced the human-machine interface2.Holographic Laser Projection (HMI) is aptly demonstrated by the availability of automotive- Technology qualified TFT displays with diagonals in excess of 40 [1].LBOs technology represents a revolutionary approach to theprojection and display of information. Unlike other commercially- Despite the popularity of flat panel displays they areavailable projection technologies, LBOs projection engine fundamentally limited as a design element since, by definition,exploits the physical process of two-dimensional diffraction to they are flat, regular and opaque. This conflicts with the desire of form video images. the automotive industry for HMI differentiation by freedom of design using, for example, free-form shapes, round displays, A typical imaging projection system works by displaying the flexible displays or mechanical 3D solutions. For this reason, andesired image Fxy on a microdisplay, which is usually sequentially increasing number of car manufacturers are discussing andilluminated by red, green and blue light to form colour. In this exploring free-programmable cluster concepts [2] employing case, the microdisplay simply acts to selectively block (or large displays and hybrid solutions. amplitude modulate) the incident light; after passing throughsome magnification optics, the projected image Fxy appears. A perfect example of such a hybrid solution was provided by theConversely, holographic laser projection forms the image Fxy by BMW Mini Crossover concept car demonstrated at the 2008 Parisilluminating a diffraction (or hologram) pattern huv by laser light Motor Show. The instrument cluster design, termed the Miniof wavelength . If the hologram pattern is represented by a Center Globe and shown in Figure 1, presented a completelydisplay element with pixel size then the image Fxy formed in the revolutionary approach to transforming displays to real 3D components by combining TFT, laser projection and lighting focal plane of the lens is related to the pixellated hologram pattern technologies into a complete solution. It is the first time that a huv by the discrete Fourier transform F [], and is written as multi-disciplinary approach, combining the common development

2. 14.4 / E. Buckley Uniquely, the key to holographic laser projection technology liesFxy = F [huv ] (1)not in the optical design but in the algorithms used to calculate the as shown in Figure 2 below.hologram patterns huv from the desired image Fxy. LBO hasdeveloped and patented proprietary algorithms for the purposes ofcalculating sets of N holograms both efficiently and in real time,as first demonstrated in 2004 [4]. Crucially, such algorithms canbe efficiently implemented in a custom silicon chip.A practical realisation is rather simple and is shown in theschematic of Figure 4. A desired image is converted into sets ofholograms by LBOs proprietary algorithms and displayed on aphase-modulating microdisplay which is time-sequentiallyilluminated by red, green and blue laser light respectively. Thesubsequent diffraction pattern passes through a demagnificationlens pair L1 and L2, which can be chosen to provide ultra-wideprojection angles in excess of 100. Due to the nature ofFraunhofer diffraction, the image remains in focus at all distancesfrom the lens L2. Figure 2 The relationship between hologram huv and image Fxypresent at the back focal plane of a lens of focal length f,when illuminated by coherent monochromatic light of L2wavelength .L1 The crucial efficiency advantage of LBOs system occurs because the hologram huv is quantised to a set of phase only values uv, where huv = exp juv, so that the incident light is steered into theMicrodisplay desired image pixels without blocking by the process of coherent interference, and the resultant instantaneous projected image appears as a direct consequence of Fourier optics. To achieve video-rate holographic display, a dynamically- addressable display element is required to display the hologram patterns; LBOs system uses a custom-manufactured ferroelectric liquid crystal on silicon (LCOS) microdisplay manufactured by Displaytech, Inc.Lasers To achieve high image quality, a fast microdisplay is used to display N holograms per video frame within the 40ms temporal bandwidth of the eye, each of which produces an image FxyFigure 4 - A schematic diagram of LBOs holographic laser exhibiting quantisation noise [3]. If the intensity of the ith projection technology illustrating lasers, phase-2 displayed image isI xy = Fxy )(ithen the time-averaged perceptmodulating microdisplay and demagnification lens pairL1, L2. over N subframes is3.Advantages of Holographic Laser1 N2 V xy =Ni =1Fxyi )( (2)Projection TechnologyThere are several exacting requirements imposed upon the light which is noise-free, as illustrated in Figure 3. engine by automotive applications. In addition to the highbrightness and contrast ratios required to display cluster imagery[5], the entire projection subsystem must be robust, fault-tolerantand optically efficient whilst maintaining wide operating andstorage temperature ranges. Finally, the projection subsystemmust be small and exhibit a wide throw angle to enable integrationinto space-limited dashboards.To the authors knowledge, only LBOs system is able to achievethese requirements whilst simultaneously providing efficientHologram Video SubframeVideo Framedisplay of bright symbology and cluster imagery, with low 1 Nspeckle contrast. A number of these important advantages are (i ) 2huv = exp juv I xy = F(i ) 2xy Vxy = N F i =1xydescribed in more detail below. Figure 3 - The relationship between hologram huv, subframe Fxyand frame Vxy in LBOs holographic projectiontechnology. 3. 14.4 / E. BuckleyLong depth of field - The combination of the diffractive nature of resultant aberration in software; in the same way, the optical LBOs technology and the use of laser light sources ensures that subsystem can be designed with a far wider range of tolerances the projected image is always in focus, regardless of projection than would ordinarily be possible. Not only does this allow cost distance or projection surface geometry. This property, coupledeffective assembly, but it provides a degree of insensitivity to with the ability to correct for distortion in the projected image [6], process tolerances which is crucially important when integrating allows the projection of images of arbitrary non-plane geometriesoptical subsystems into, for example, automotive instrument - thereby allowing the realisation of curved displays which cannot clusters. A demonstration of this powerful capability is provided be achieved with current flat panel display technologies.in Figure 5 below. The laser spot shape of Figure 5(a), after Aberration correction - Due to the diffractive nature of LBOs propagation through the projector optics, demonstrates that technology, which by definition exerts accurate control over the significant aberration is present. As a result, the quality of the optical wavefront, it is possible to correct for aberrations causedprojected images (b) and (c) is severely impacted. Appropriate by the projector optics by appropriate modification of the correction for the optical aberrations, however, results in a laser hologram patterns. It is therefore possible to construct a projector spot that is almost diffraction limited (d), leading to recovery of using simple, cost effective optical elements and correct for anythe image fidelity in (e) and (f). (a) Laser spot shape after (b) Aberrated projected image(c) Close