17 - Efficient, High Quality, Silicon Microdisplays
Submitting InstitutionsHeriot-Watt University,
University of Edinburgh
Unit of AssessmentGeneral Engineering
Summary Impact TypeTechnological
Research Subject Area(s)
Physical Sciences: Optical Physics
Information and Computing Sciences: Artificial Intelligence and Image Processing
Engineering: Materials Engineering
Summary of the impact
Micropix were formed in 1997 as a result of ERPE research (1993-08) into
microdisplays. Following a major investment in 2004 the company was
re-branded as Forth
Dimension Displays (ForthDD).
Due to its unique microdisplay technology, based on the ERPE underpinning
research, the ForthDD
commercial activity has, since 2008, increased its annual revenue by more
than 25% to around $5M
and, over the same period, has increased its global workforce from 25 to
35 with exports to 15
Kopin Corporation, the world's largest producer of microdisplays,
acquired ForthDD in 2011 for
This ERPE research team comprised Professors: Underwood; Walton; and
Stevenson (to 2012) and
Smith (PDRA to 2012 then Lecturer) all in post throughout unless stated
are: PDRA Bodammer and PhD students: Lee; Miremont; Rankin; and Seunarine.
Physics researchers are Senior Lecturer Hossack and Professor Emeritus
Liquid Crystal on Silicon (LCoS) spatial light modulators (SLMs) were
conceived then researched
and developed within ERPE and the School of Physics. The team developed
Ferroelectric Liquid Crystal on Silicon (FLCoS) SLMs in the late 1980s and
early 1990s and
deployed them in a range of applications with primarily industrial
collaborators.  reports the state
of the art of LCoS technology around 1993. Around that time it became
clear that a major application
for FLCoS SLMs was as miniature active-matrix liquid crystal displays
(also called microdisplays) to
be viewed under optical magnification in electronic projection systems and
The most important underpinning ERPE research contributions were:
Achieving colour without colour filters by pulsed illumination of red,
green and blue LEDs.
To be successful in mainstream applications, a display technology must be
capable of producing
moving colour images. The first LCoS SLM-based microdisplays used
single-colour LED illumination
and so produced monochrome images. In 1996 a method for producing 3-bit
colour images on a low
resolution microdisplay using short rapid pulses of illumination from red,
green and blue LEDs in
sequence  was reported. The method was refined to produce 16-bit colour
and high resolution 
via the DTI-LINK project SLIMDIS (1995-7; ca £200k; with ERPE, GEC
Marconi, Swindon Silicon
Systems, Admit Design Systems, Davin Optical Holdings).
Improving image quality through improved manufacturing techniques.
Image quality is one of the most important factors in determining the
competitiveness of a new
display technology. Certainly a minimum level of image quality is
essential. In the case of LCoS
displays, the optical quality of the surface of the CMOS (active matrix)
substrate has a huge
influence on the perceived image quality. In the late 1990s this was the
main topic of the EPSRC-funded
PACMAN project (1998 - 2001; ca £800k; led by Underwood with Micropix,
Design Systems).  reported techniques to planarise the substrate at the
pixel-array level (i.e.,
reduce excess curvature that can lead to colour artefacts). While 
reports detailed process
characterisation and optimisation to planarise the substrate at the
sub-pixel level by filling narrow
trenches in the substrate that, if unfilled, would adversely affect the
alignment of the LC and,
hereby, the image quality.
Infrastructure for the design and characterisation of the technology.
A robust generic infrastructure for the design and characterisation of
FLCoS microdisplays was an
essential part of the industrialisation of the technology. This
requirement was addressed in the
EPSRC-funded ELITE project (1999-2001; ca £310k; led by Underwood with
Marconi, Avant!, Domain Solutions). A key outcome, by way of example, was
the development of an
advancement to the widely used SPICE circuit description model for the FLC
 which has made the
overall design process much more efficient, accurate and robust.
References to the research
References identified with * are those which best indicate the quality of
the underpinning research.
* Johnson, K.M., McKnight, D.J. and Underwood, I., "Smart Spatial
Light Modulators Using Liquid
Crystals On Silicon", IEEE Journal of Quantum Electronics, Vol. 29,
No. 2, 1993.
. Google scholar (GS) 187
This invited paper reports progress, state-of-the-art and future
prospects for LCOS technology.
 Rankin, I.D., Underwood, I., Vass, D.G. and Worboys, M.R., "Full
Colour Miniature Display",
Proc SPIE on "Liquid Crystal Materials, Devices and Applications", Vol.
2651, pp. 16-24, 1996.
DOI (Full Proceedings):10.1117/12.235358. 10 GS citations.
First report of novel technique (field-sequential colour illumination)
applied to a LC microdisplay
to achieve energy-efficient full colour without the use of colour filters.
 Vass, D.G., Hossack, W., Rankin, I.D., Underwood, I., et. al., "A
High Resolution Full Colour
Head Mounted Ferroelectric Liquid Crystal-Over-Silicon Display",
Ferroelectrics, Vol. 213, Issue
1-4, pp. 603-12, 1998. DOI:10.1080/00150199808016486.
10 GS citations.
The first high-resolution full colour FLCoS microdisplay-based
head-mounted display system
suitable for productisation.
* Seunarine, K., Calton, D.W., Underwood, I., Stevenson, J.T.M.,
Gundlach, A.M. and Begbie, M.,
"Techniques To Improve The Flatness Of Reflective Micro-Optical Arrays"
Actuators, Vol. 78, pp. 18-27, 1999. DOI:10.1016/S0924-4247(99)00199-5.
14 GS citations.
Reports research to increase the image quality and energy efficiency of
improving the flatness and fill factor of the in-pixel metal mirrors on
* Lee, Y., Parkes, W., Bodammer G. and Underwood, I., "Characterisation
Dielectric Deposition Processes On CMOS Backplanes For Liquid Crystal On
Microdisplays", IEE Proceedings Optoelectronics, Vol. 151, No. 1,
Reports detailed process characterisation and comparison for local
planarization by filling
trenches in CMOS active matrix substrates.
 Smith, S., Walton, A.J., Underwood, I., Miremont, C., Vass, D.G.,
Hossack, W.J., et. al., "SPICE
Modeling Of Ferroelectric Liquid Crystal On Silicon Microdisplays",
in IEEE International
Conference on Microelectronic Test Structures, pp. 148-152, 2003
Reports a SPICE circuit model that relates the electronic and
electro-optical characteristics of
Details of the impact
Since its formation ForthDD (originally Micropix) has raised in excess of
$33M in investment
including the 2011 injection of $11M by leading US microdisplay company,
Kopin Corporation [S5].
Headquartered in Fife, Scotland, ForthDD has maintained and continues to
technical links with the ERPE research team. ForthDD designs, develops and
chip micro-displays used in the most demanding segments of markets such as
simulation systems, HD video camera viewfinders, medical imaging systems
and virtual-reality and
head-mounted displays [S5]. Entirely digital, providing 24-bit full-colour
images, capable of
handling high-speed motion and with no visible artefacts, ForthDD's single
chip imagers are
especially well-matched to the new solid state LED and laser diode light
sources and provide very
high native resolution. ForthDD now has offices in Spain, Germany and the
In late 2012, ForthDD reaffirmed its position as the world's leading
supplier of advanced
microdisplays when it released the world's highest resolution full colour
Underwood was employed as a consultant in the feasibility stage of
defining the new product.
"ForthDD's premium quality components are deployed and used in the most
and applications imaginable. Forth Dimension Displays' product range
has, from the beginning,
been targeted at high-end markets. In these applications, image quality
is of the utmost
importance. The ability to provide colour has always been absolutely
essential throughout our
product range and the pioneering research done at ERPE on field
sequential colour, using
switched LED illumination, provided the foundation for our products to
produce deep, saturated,
satisfying colour." CEO, ForthDD [S2].
The Near-To-Eye displays market comprises Head-Mounted Displays (HMDs)
Viewfinders (EVFs). While other companies and other divisions of Kopin
address the mainstream,
the Unique Selling Point (USP) of ForthDD is that its products achieve the
highest image quality
available in LCoS microdisplays and can thus command a high price from
those customers with
the most demanding applications. The foundations of the ability to meet
the requirements of the
most demanding applications lies in the research carried out by ERPE: "A
key selling point for
Forth Dimension Displays is our ability to produce high quality images
in applications where competing
technologies do not quite make the grade. Underpinning this image
quality are product features
enabled by technical specifications such as high pixel aperture ratio
and accurate liquid crystal
alignment, that were first established through the ERPE research on
backplane surface quality
improvement. The backplane surface quality improvement techniques
described by the ERPE research
have been adopted by CMOS foundries, such as those from which ForthDD
obtains the substrates for
its current product range." Director of Product Design, ForthDD
Achieving colour with pulsed RGB LED illumination.
The combined fast switching capability of digital CMOS active matrix
drivers and Binary
Ferroelectric Liquid Crystal allowed the achievement of colour images by
using fast pulses from
Red, Green and Blue (RGB) LEDs to create the illusion of full colour
images without colour filters
and with no spatial separation of RGB sub-pixels. It also allowed an
all-digital video signal path.
This ERPE research [2, 3], was quickly incorporated into early products
and has been continually
developed and refined within the company to encompass higher colour depth,
higher frame rates
and higher definition. "Thus every Forth Dimension Displays product,
including the most recent
product range, the QXGA (2048 x 1536 pixel) microdisplay launched in
October 2012, has used
and continues to use pulsed RGB LED illumination based upon the original
ERPE scheme that
was published [2, 3] as an outcome of the foundational ERPE research."
CEO, ForthDD [S2]
Improving image quality through improved manufacturing techniques
The improvements in surface planarity and pixel fill factor achieved by
ERPE researchers [4, 5],
were critical to allowing FLCoS microdisplays to exceed the threshold of
image quality necessary
to satisfy customers. The underlying manufacturing processes were made
available to ForthDD's
commercial CMOS foundry supplier, through publication and direct transfer,
and thus were
incorporated into product manufacture. The CMOS foundry has continued to
refine these. Thus the
manufacturability, image quality and optical efficiency of the current
product range and the recently
released product range rely upon the ERPE foundational research in
pioneered in the Scottish Microelectronics Centre.
Infrastructure for the design and characterisation of the technology
The development of infrastructure linking the design and
manufacturability of FLCoS microdisplays
(such as the developed SPICE model for the FLC ) assisted the
productisation of the
technology. "GarField Matrics is the integrated circuit design
subcontractor to ForthDD. ERPE
researchers have made many successful technical advances to the design
microdisplays. Specifically they developed a SPICE simulation model to
represent the electrical
load that the ferroelectric liquid crystal places on the drive circuit.
It is essential to have SPICE
models of components that are both robust and accurate. Thus the ERPE
SPICE models have
been used directly in the design of FLCoS active matrix backplanes. Thus
the design-flow for new
products has benefited directly from the ERPE research on design and
Managing Director, GarField Matrics [S4].
The electronic architecture and pixel drive circuit of every product
generation designed by ForthDD
have been based upon architectures and designs first pioneered by ERPE
researchers. Thus the
prosperity of the company is comprehensively underpinned by ERPE research.
And that prosperity
is evident in that, today, ForthDD is the division of Kopin Corporation —
the world's largest
microdisplay company — whose products address the most demanding markets
such as electronic
viewfinders for professional cinematography cameras plus commercial and
military flight simulators
(97% of military flight simulators based on head-mounted displays use
Customers in these markets include Rockwell Collins, ARRI and L-3
products are focused on Virtual Reality [S6] for consumer applications.
"ForthDD develops and manufactures the world's highest performance
microdisplays for use in
Near-to-Eye and Head-Mounted Display Systems in market sectors such as
training and defence. Operating in these very demanding market sectors,
ForthDD has, since
2008, increased its annual revenue by more than 25% to $5M, almost
entirely in exports, and over
the same period has increased its global workforce from 25 to 35
employees, as well as providing
competitive edge to its customer companies and benefits to the end-users
of its display products. It
now makes sales to 15 countries." CEO, ForthDD [S2]
Sources to corroborate the impact
highest resolution micro-display.
[S2] CEO, ForthDD, see comments included in Section 4.
[S3] Director of Product Design, ForthDD, see comments included in
[S4] Managing Director, GarField Matrics Ltd., see comments included in
Forth DD in 2011.
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