全息投影

Colour holographic laser projection technology for heads-up and instrument

cluster displays

Dr. Edward Buckley

Director of Business Development

Light Blue Optics Ltd.

2nd floor Platinum Building, St. John’s Innovation Park , Cowley Road, Cambridge, CB4 0WS, United Kingdom

edward@lightblueoptics.com

Abstract: Light Blue Optics’ holographic laser projection

technology has significant competitive advantages

compared to imaging and scanning projection technology.

This paper describes the system, its operation, and

advantages. It is shown that the particular combination of

benefits that LBO’s technology offers provides compelling

and differentiating advantages for automotive head-up and

instrument cluster displays.

1 Introduction

Light Blue Optics’ projection technology represents a

revolutionary approach to the projection and display of

information. Unlike other commercially-available

projection technologies, this projection engine exploits the

physical process of two-dimensional diffraction to form

video images, enabling the realisation of miniature, highly

efficient and robust miniature projectors. Such attributes

are uniquely suited to vehicular displays applications,

providing several compelling competitive advantages.

This paper describes the functionality, properties and

advantages of this technology and potential opportunities

for its use in both head-up and instrument cluster displays.

2 Holographic laser projection technology

Light Blue Optics (LBO) has developed a novel

projection architecture in which images are formed using

diffraction, a physical optical effect generally regarded as

an undesired phenomenon in conventional imaging

systems. The basic architecture of the system is shown in

Figure 1, in which coherent light is launched into free

space and then collimated by a lens, before being

reflected by a microdisplay, which in this case is a binary

ferroelectric liquid crystal on silicon (FLCOS) device.

The size of the collimated beam is set to match the

microdisplay’s active area.

The essential difference between an imaging projector

and the LBO system lies both in the nature of the pattern

on the microdisplay, and the way it is written. Unlike a

normal projection system in which the desired image

itself is shown on the microdisplay, the LBO system

works by writing sets of diffraction (or hologram) patterns

h(n) to the display. The microdisplay therefore acts to spatially phase-modulate incident coherent light, forming

the projected image entirely by coherent interference.

λr

λg

λbL2

L1

Microdisplay

Figure 1 - Schematic diagram of LBO’s holographic

laser projector.

If just a single hologram is calculated for each video frame,

unacceptable image noise is manifest as a result of the

necessary phase quantisation of the interference pattern.

This limitation has thus far prevented the construction of a

high quality holographic display, despite the obvious

benefits of high optical efficiency and fault tolerance [1].

Furthermore, the computational load of calculating

holograms using conventional approaches was previously

found to be incompatible with real-time operation.

LBO has demonstrated a novel approach to the calculation

and display of holograms that, for the first time, enables

high quality image formation in real time. LBO’s

technology works on the principle of calculating – using

proprietary, patented algorithms – N sets of interference

patterns per input video image, which are displayed

sufficiently rapidly on the microdisplay such that the

resultant noise is effectively cancelled out by the

integrating action of the eye.

A desired image is converted into sets of holograms by

LBO’s proprietary algorithms and displayed on a phase

modulating microdisplay which is time-sequentially

illuminated by red, green and blue laser light of

wavelengths λr, λg and λb respectively. The subsequent

diffraction pattern passes through a simple

demagnification lens pair L1 and L2, thereby generating

the required output image. The resultant instantaneous

projected image is a direct consequence of Fourier optics,

and is the Fourier transform F [h(n)] (where n = 1,…,N)

of the pattern on the display. Since the image is created in

the far field (or Fraunhofer regime) unlike normal

projectors, in which the image is always created by means

of converging rays, the image is in focus at all distances

from the lens L2.

3 Competitive advantages

LBO’s technology has significant advantages for

automotive applications compared to both scanning and

imaging technologies, and two completely differentiating

features in the ability to remove speckle and provide ultra-