11/5/2014
`
`The First Head Up Display Introduced by General Motors
`
`INTERNATIONAL...
`
`I Learn I Publications I Technical Papers
`
`The First Head Up Display Introduced by General Motors
`
`Paper #1 890288
`
`DOI:
`
`10.4271/890288
`
`Published: 1989-02-01
`
`Citation: Weihrauch, M., Meloeny, G., and Goesch, T., “The First Head Up Display
`Introduced by General Motors," SAE Technical Paper 890288, 1989,
`doi:10.4271/S90288.
`
`Author(s): M. Weihrauch G. G. Meloeny
`
`T. C. Goesch
`
`Affiliated: Hughes Aircraft Co. C-P-C Group, General Motors Corp. Delco Electronirs Corp.
`
`Abstract: The first production configured head up display (HDD) wa8 introduced in
`the United States in the 1988 Oldsmobile Cutlass Supreme Indianapolis
`500 Pace Car Parade Convertibles. The design and performance of this
`HUD uses a vacuum fluorescent display tube (VFD) and reflective optics,
`including the standard production windshield as the final element, and
`produces a virtual image of a digital speedometer and selected telltales
`just above the hood line
`in
`the driver's central vision area at
`approximately front bumper range. The unit's functional and physical
`design minimize modification of existing instrument panel structures and
`interfaces while providing essential
`features and performance for
`consumer satisfaction. Human factors engineering contributed to this
`application; supporting studies and simulation efforts are summarized to
`substantiate the design decisions.
`Automotive
`
`Sector:
`
`Topic:
`
`Electrical, Electronics and Avionics Human Factors Displays
`
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`~ For Advancing Mobility
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`rm
`
`890288
`
`The First Head Up Display Introduced by
`General Motors
`T. C. Goesch
`Advanced Instrumentation Engineering
`Delco Electronics Corp.
`Kokomo, IN
`
`M. Weihrauch
`Automotive Systems
`Hughes Aircraft Co.
`Los Angeles, CA
`
`G. G. Meloeny
`Advanced Electrical Systems
`C-P-C Group
`General Motors Corp.
`Pontiac, MI
`
`Reprinted from SP·nG-Automotive Information
`Systems and Electronic Displays;
`Recent Developments
`
`International Congress and Exposition
`Detroit, Michigan
`February 27 - March 3, 1989
`
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`The papers inCluded ,n thiS volume
`are abstracted and mdeJfed In rhe
`SAE G/{)bal MomMy Darabase.
`
`SAE GLOBAL MOBIUTY DATABASE
`
`No part of this publication may be reproduced in any form, in
`an electronic retrieval system or otherwise, without the prior
`written permission of the publisher.
`
`ISSN 0148-7191
`Copyright 1989 Society of Automotive Engineers, Inc.
`
`Positions and opinions advanced in this paper are those of the
`author(s) and not necessarily those of SAE. The author is
`solely responsible for the content of the paper. A process is
`available by which diScussions will be printed with the paper
`iI
`it is published in SAE Transactions. For permission to
`publish this paper in full or in part, contact the SAE Publica(cid:173)
`tions Division.
`
`Persons wishing to submit papers to be considered for pres(cid:173)
`entation or pUblication through SAE should send the manu(cid:173)
`script or a 300 word abstract of a proposed manuscript to:
`Secretary, Engineering Activity Board, SAE.
`
`Printed in U.S.A.
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`890288
`
`The First Head Up Display Introduced by
`General Motors
`T. C. Goesch
`Advanced Instrumentation Engineering
`Delco Electronics Corp.
`Kokomo, IN
`
`M. Weihrauch
`Automotive Systems
`Hughes Aircraft Co.
`Los Angeles, CA
`G. G. Meloeny
`Advanced Electrical Systems
`C-P-C Group
`General Motors Corp.
`Pontiac, MI
`
`ABSTRACT
`
`first production configured head up
`The
`display (RUD) was
`introduced in the United
`States in the 1988 Oldsmobile Cutlass Supreme
`Indianapolis 500 Pace Car Parade Convertibles.
`The design and performance of
`this HUD uses a
`vacuum fluorescent
`display
`tube
`(VFD)
`and
`reflective
`optics,
`including
`the
`standard
`production windshield as the final element,and
`produces
`a
`virtual
`image
`of
`a
`digital
`speedometer and selected telltales just above
`the hood line in the driver' B central vision
`area at approximately front bumper range.
`The
`unit's functional and physical design minimize
`modi fieation
`of
`existing
`instrument
`panel
`str.uctur.es
`and
`interfaces while
`providing
`essential features and performance for consumer
`satisfaction.
`Human
`factors
`engineering
`to
`contributed
`this
`application;
`suppor.ting
`studies and simulation efforts are summarized
`to substantiate the design decisions.
`
`is an instrument
`A Head Up Diaplay (RUD)
`which allows
`the driver of a vehicle to view
`key driving/status data superimposed on
`the
`visual field through the windshield rather than
`requiring looking down at
`the instrument panel
`for necessary or useful
`information.
`The HOD
`feature has
`come
`into widespread use in the
`aircraft industry over the past 20 years and is
`suited
`for
`adaptation
`to
`today's modern
`automobiles.
`is
`concept
`HUD
`automotive
`The
`basic
`illustrated in Figure 1. There are two ways in
`which the HUD can facilitate the driving task:
`First, with key driving data such as vehicle
`speed as part of the HUD image,
`the driver can
`keep his eyes
`looking toward the road ahead
`while
`accessing
`and
`responding
`to
`the
`information;
`in
`addition.
`his
`eyes
`remain
`
`Figure 1 - Basic Automotive HUD Concept
`
`in his
`level
`light
`adapted to the ambient
`primary visual field. Secondly, with the image
`focused to appear two or more meters forward of
`the driver,
`the need to re-accommodate from the
`road to the image is reduced.
`The first production-configured automotive
`HUD introduced in the U. S. was developed by a
`General Motors
`team from Oldsmobile,CPC(cid:173)
`Advanced Vehicle Engineering, Delco Electronics
`and Hughes Aircraft Co.
`Its design was guided
`by human factors considerations such as those
`mentioned
`above
`and
`its
`implementation was
`based on technology derived from HUDs used in
`the world's
`foremost
`fighter aircraft.
`This
`pioneering
`HUD
`system
`was
`engineered
`specifically for
`the 1988 Oldsmobile Cutlass
`Supreme Indianapolis 500 Pace Cars and limited
`edition Parade Convertibles.
`This
`advanced
`technology feature
`is
`ideally suited to the
`Cutlass Supreme
`since
`it matches well
`the
`innovations in design and styling of
`this new
`family of mid-size,
`front wheel drive coupes.
`Based on the response to this introductory
`system, it Is expected that HUDs will
`find
`widespread acceptance in the automotive market
`8S they have in the aerospace industry.
`
`55
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`REFLECTlVE AUTOMOTIVE HUD CONCEPT
`
`Head Up displays are used routinely by
`pilots of mlllt.-3.ry and commercial aircraft
`to
`perform very complex and difficult tasks which
`require cognizance of auxiliary information in
`An obvious
`the context of
`the visual
`field.
`advantage of Hun over
`in-cockpit. panel-mounted
`instruments and displays is that the pilots can
`maintain visual contact with airspace and/or
`targets while monttoring information (without
`looking down)
`that
`is needed for effective
`control of
`the vehicle and/or weapon systems to
`llccompltsh
`the
`desired mission
`objectives.
`While
`the
`detailed
`tasks, missions,
`and
`environments of automohUe drivers and pilots
`are different,
`they nevertheless have much in
`common, not
`the least of which is the need, or
`desire
`to maintain continuous visual contact
`with ~he real world.
`It
`is therefore not
`surprising that drivers
`react very positively
`to fWn-equipped vehicles, particularly if the
`HUDs
`are carefully designed
`for.
`the driving
`task.
`As
`in
`airborne
`systems)
`the
`right
`information should be presented in the proper
`locat ion wi th
`cIa ri ty)
`in
`natural,
`east ly
`formats.
`Unlike
`airborne
`interpretabl~
`systems,
`automotive
`HUDs
`are
`not
`used
`as
`sighting,
`tracking
`or
`comprehensive
`system
`mon ttoring/ cant rol
`devices;
`therefore,
`high
`accuracy and
`voluminous
`infonnation content,
`which account
`for much of
`the complexity and
`cost of airborne systems, are not critical
`in
`automotive applications. Clearly the design of
`a cost- efF.ective automotive HUn
`is not a
`simple adaptation of an airborne design. but a
`carefully
`taIlored
`application
`of
`aerospace
`technology and experlence to the specific needs
`of drivers and the automotive envir.onment.
`The
`HUD
`described
`herein
`and
`illustrated
`conceptually in Fig. 2 is such a design.
`
`.. CHECK GAUGES ..
`
`ilH::'U:'hD
`
`REFLECTIVE
`WINDSHIELD
`
`Iq"·m~
`. . _II MPH
`(
`~-_. ---- ---- ---- ---------------
`/t~.,;~{-------------~.~:-
`!
`
`"\... MIRROR
`{CURVED)
`
`.
`.
`
`HUD
`IMAGE
`
`MIRROR
`
`iff~~JE
`(VFD)
`
`Figure 2 . Pace Car HUD Optical Schematic Diagram
`
`Human factors analysis, preliminary design
`studies,
`and evaluation of early engineering
`models led to the conclusion that,
`for optimum
`utility,
`the HUD image
`should be
`simple and
`located in the lower central
`region of
`the
`
`56
`
`the image should
`field. Also,
`driver's visual
`be at a range greater than two meters from the
`driver's nominal eye position, preferably at,
`or
`just
`forward of
`the front bumper. where
`re-accommodation time
`can be
`reduced.
`This
`contrasts with windshield-reflected instruments
`which have no optical power and place the image
`off
`axis
`at
`relatively
`close
`range where
`typical drivers will need greater re-accommoda(cid:173)
`tion and divert their atten~ion from the visual
`field time.
`were
`alternatives
`design
`Numerous
`refractive, diffractive
`considered,
`including;
`integral combiners and
`and reflective optics,
`various windshield combined
`treatments) VFD,
`LED and LCD display devices.
`integral, separate
`and
`shared
`electronics,
`absorption
`and
`diversion
`type
`glare
`traps,
`spherical
`and
`aspheric
`imaging
`elements,
`large
`optical
`apertures and small apertures with manual tilt
`control.
`After careful consideration of
`the
`various
`tradeoffs,
`the reflective HUD concept
`was
`selected for
`the Pace Car HUD, which is
`classifie~ as
`a
`secondary
`instrument;
`this
`concept is characterized as follows~
`
`1.
`
`2.
`
`3.
`
`4.
`
`5.
`
`A high-brightness
`segmented graphics
`is
`"source".
`
`VFD with discrete
`used as
`the
`image
`
`is limited to a digital
`Image content
`digits)
`and
`units
`of
`speedometer
`(3
`measure
`(English/Metric)
`along
`with
`selected
`telltales
`(turn/hazard
`arrows,
`headlight high beam on indicator,
`low fuel
`a
`indicator
`and
`provIsIons
`for
`"check
`gages ll summary advisory message); graphics
`style,composition
`and
`image
`size
`are
`consistent with easy legibility, Figure 8.
`
`is
`the VFn graphics
`image of
`A virtual
`produced at front bumper
`range using a
`relatively small aperture,
`folded
`reflective optical system with manual tilt
`control
`to
`suit
`driver
`position
`preference,
`a flat window with a louver(cid:173)
`type
`absorptive
`glare
`trap,
`and
`the
`unmodified production windshield as
`the
`combining glas8.
`
`A complete set of electronics is included
`in
`the
`unit
`(power
`supplies,
`signal
`processing,
`VFn
`drivers
`and
`dimming
`circuits), making HUn operation totally
`independent of,
`and redundant wi th,
`the
`instrument cluster.
`
`The Hun unit and aUKiliary components
`(dimming control module) mounting brackets
`and Wiring
`harness
`components)
`are
`packaged in and on the top pad of
`the
`instrument
`panel
`to minimize
`vehicle
`integration impact.
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`performance
`respectively) •
`
`(p
`
`<
`
`0.001
`
`and
`
`p
`
`<0.01,
`
`1 . 6 ; - - - - - - -
`
`,
`
`tii 1.5
`
`w~ ~
`
`1.4
`
`1.40
`
`~i
`
`ii 1.3
`
`1.2
`~ 1.1
`
`~ ~~
`
`~ww~
`
`HUD
`
`HDD
`
`DISPLAY TYPE
`Figure 3 . Steering Variability as a Function of
`Display Type
`
`1 .40 . . . - - - - - - - - - - - - - - -__,
`1.35
`
`1.35
`
`zg1Il 1.30
`hl~
`tu 8 1.25
`Ow
`~": 1.20
`U w
`~ ~ 1.15
`mo
`
`1.10
`0"'---
`
`HUO
`
`HOD
`
`DISPLAY TYPE
`Figure 4 - Pop-up Response Time as a Function of
`Display Type
`
`Brightness (luminance) of the HUD image is
`an important factor in legibility and consumer
`acceptance.
`HUD luminance
`requirements
`are
`very demanding because the image must be easily
`readable against
`road scene backgrounds
`that
`range from less than 0.1 foot Lamberts at night
`(for
`headlight-
`illuminated
`black
`top)
`to
`bright
`sun-lit
`snow in
`daytime.
`Visual
`perception data were used to define contrast
`ratio
`design
`goals
`and minimum acceptable
`requirements of 1.5 and 1.2:1,
`respectively.
`These
`requirements
`take many
`interacting
`factors into account,
`such as:
`image size,
`image luminance,
`stroke width-to-height ratio,
`driver age,
`task criticality, etc.
`A related luminance design consideration
`the possibility of veiling glare.
`To
`is
`determine
`the
`allowable HUD night
`luminance
`without
`causing visually degrading glare,
`a
`glare model originally developed by Moon and
`Spencer
`(1945)
`and visual
`threshold data by
`Blackwell were used
`to evaluate effect upon
`driver performance as a result of ambient light
`level, RUD image luminance, driver age, object
`(target) size, viewing time, etc.
`Packaging
`of
`the
`introductory
`
`HUDs
`
`57
`
`design
`optical
`reflective
`folded
`The
`is
`particularly well-suited
`to
`approach
`automothl'e HUDs because it allows for compact
`packaging
`in
`irregularly
`shaped
`space
`envelopes.
`It also involves a minimum number
`of surfaces in the optical path, only one of
`which is not flat.
`Thus it is simple, easy to
`align and should be producible at low cost.
`It
`has
`the
`added
`advantage
`of
`high
`optical
`efficiency and
`low susceptibility to
`stray
`light
`and multiple
`reflections which
`are
`difficult
`to
`control
`in
`refractive optical
`systems.
`Human factors issues were addressed in the
`development of
`this system.
`Summaries of
`the
`more significant studies and results follow.
`
`HUMAN FACTORS CONSIDERATIONS
`
`experiments,
`laboratory
`Analysis,
`driver-in- the-loop simulation, and in-vehicle,
`on-the-
`road
`test
`and
`evaluation techniques
`were used to address driver
`interface design
`issues for
`the RUD.
`Special studies were
`conducted to address specific design issues for
`which no adequate or applicable information was
`found in Human Factors literature.
`the
`A major optical design question was
`definition of
`the maximum acceptable vertical
`binocular image disparity in an automotive HUD.
`Military HUDs are generally limited to one
`milliradian,
`which
`demands
`high
`optical
`precision and commensurately high cost.
`Three
`laboratory investigations were
`conducted
`to
`determine
`the
`tolerable
`level
`of
`optical
`disparity for
`automobile drivers.
`It was
`determined
`that
`disparities
`up
`to
`25
`milliradians did not affect
`instrument
`reading
`performance and that
`reported diplopia (double
`vIsion) started to increase substantially only
`above 17 milliradians.
`Based on these results
`a maximum, conservative 5 milliradian vertical
`disparity design goal was established.
`The optimum location of
`the RUD image (in
`and
`angle) was
`also a major
`design
`range
`question.
`A variable geometry HUD simulation
`fixture was
`installed in a test vehicle and a
`driver-in-
`the-loop, dynamic
`simulation study
`was
`conducted to determine driver preference
`and
`performance
`as
`a
`function
`of
`azimuth,
`elevation and range of
`the image.
`It was
`concluded that
`the image should be
`low (just
`above the hood line), centered directly in
`front of
`the driver in azimuth, and beyond two
`meters near
`the vehicle's front bumper. With
`respect
`to the nominal driver's eye position,
`this is approximately -8 degrees vertically, 0
`degrees horizontally,
`and 2.4 meters
`in range
`(depending nn the specific vehicle).
`As part of
`the HUD driVing simulation
`study,
`the HUD was compared to a head-down
`instrument panel display.
`As shown in Figures
`3 and 4,
`the RUD resulted in superior steering
`control
`and
`roadway
`obstacle
`detection
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`
`to minimize
`units
`profile
`low
`required
`modifications of existing vehicle structures.
`This
`height
`limitation
`neccessitated
`development of a low profile,
`louver-type glare
`trap to block ambient reflections from the
`HUD's flat glass window toward the driver's eye
`position envelope.
`One effect of
`the louvers
`is
`to modulate
`the
`HUO
`image with
`dark
`A driVing
`horizontal
`lines.
`test
`was
`conducted,
`using HUD-equipped vehicles with
`various louver configuratIons,
`to determine the
`best
`design
`from
`the
`standpoint
`of
`functionality
`and
`driver
`acceptance;
`an
`elliptical
`diversion-
`type
`glare
`trap
`(significantly deeper
`than the louver plates)
`was
`included
`in
`this
`test
`along with
`six
`different
`louver plate configuratlons varying
`in pitch (spacing between blades and depth) and
`blade thicknesA.
`The
`study results
`indicate
`that
`the
`louver blades
`should be as
`thin as
`possible, consistent with strength and handling
`consideratlons.
`For the Pace Car HUD graphics,
`the
`optimum louver pitch is apprOXimately 9
`millimeters.
`The
`drivers
`rated
`the
`9
`pitch
`millimeter
`and
`0.4 millimeter
`thick
`louver configuration equally acceptable 85 the
`elliptical glare trap without
`louvers.
`is
`The
`research
`described
`above
`representative of
`the Human Factors activities
`which were
`included
`in
`the
`Pace Car
`HUD
`development
`to make these units easier
`to Use
`and to enhance driver satisfaction.
`
`HUD DESIGN
`
`influenced by
`The HUD system design was
`considerations.
`Human Factors
`and Marketing
`Marketing needs
`included meeting the Indy 500
`Vehicle
`program dates,
`a
`compact HUD design
`that
`could
`easily
`be
`integrated
`in
`a
`pre-eXisting vehicle design,
`and
`flexibility
`for
`easy,
`rapid adaptation to other vehiCle
`models. Human Factors considerations drove and
`constrained the design, as indicated above,
`to
`enhance driver
`performance
`and
`satisfaction.
`Its mechanizatlon
`is
`blending
`of
`advanced
`aerospace and traditional automotive technology
`as described below.
`
`system
`HUD
`The
`SYSTEM DESIGN
`HUD
`HUD Dimmer
`a
`unit,
`of
`the
`HUD
`consists
`control/switch module, a mounting bracket, and
`wiring harness adapters,
`illustrated in Figure
`5.
`These system components are mounted in/on
`the instrument panel
`top pad which is the only
`vehicle structure that needed to be modified to
`accommodate the HUD system.
`
`Figure 5 - Pace Car HUD System
`
`The HUD is a self-contained unit which
`functions
`independently
`of
`the
`instrument
`cluster.
`The harness adapters simply route
`f ..om
`existing signals and power,
`in parallel,
`the
`instrument cluster wiring to the HUD and
`between the HUD unit and HUD Dimmer module.
`HUD brightness levels and control reqUire(cid:173)
`ments differ significantly from those of
`the
`instrument cluster.
`Therefore a separate HUD
`Dimmer module was developed. This module has a
`thumbwheel-operaterl dimming potentiometer with
`a detented on/off switch position at
`the lower
`end of
`its range.
`The switch is used to turn
`the HUn on or off and the voltage from the
`potentiometer is used to control VFD brightness
`via a pulse width modulation circuit.
`Two
`brightness
`range8 were mechanized:
`one
`for
`daytime
`use
`(providing maximum Hun
`image
`brightness of apprOXimately 500 foot Lamberts
`at
`the upper
`limit of
`the thumbwheel's control
`range) and the other for nighttime and twilight
`operation
`(with
`the
`control
`sensltivity
`attenuaten by a
`factor of 6: 1 so that
`the
`maximum
`image
`brightness
`is
`reduced
`to
`approximately 90 foot Lamberts).
`The nighttime
`dimming range
`is automatically selected when
`the parking lamps or headlights are turned on
`and the daytime range is available whenever
`the
`lights are off.
`A cutout was made in the top surface of
`the instrument panel
`to fit
`the HUD's chassis
`outline and a metal mounting bracket was
`added as
`shown in Figure 5.
`The mounting
`bracket secures
`the HUD in place and also
`stiffens the pad area around the cutout for
`stable HUD operation.
`the HUD unit protrudes
`The
`top cover of
`the top pad and is styled to harmonize
`above
`with the vehicle's interior design.
`A slider
`control
`is located on the top right surface of
`
`58
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`
`is used to tilt the
`This control
`the cover.
`imaging mirror
`in the optical
`system to suit
`the driver's
`seating position and
`personal
`preference.
`
`OPTICAL 08SIGN - The HUD's optical system,
`illustrated in Figure 2, is designed to produce
`a magnified virtual
`image of
`the symbology on
`the VFn at approximately front bumper range in
`the
`lower
`central
`section of
`the driver's
`visual field.
`Key design goals of the optical
`system include:
`
`degree
`1.0
`x
`vertical
`degree
`a) 1.5
`horizontal field of view corresponding to
`a VFD image size of 10 x 20 millimeters.
`
`b) 2.4 meters
`posItion
`range) •
`
`range
`image
`(approximately
`
`from nominal eye
`front
`bumper
`
`c) 0 degree image azimuth and minimum height
`above the hood line when viewed from the
`nominal eye position.
`
`image visibility over at
`d) Full monocular
`least
`the
`95% e,ellipse
`(125
`x
`125
`millimeter minimum vertical
`total
`eye
`motlon box).
`
`including compensation
`e) Minimum distortion,
`for
`the skewed, asphed.c windshield which
`is used as the combiner.
`
`to
`f) Minimum vertical disparity (average not
`exceed 1 milliradian and maximum to be
`less than 5 milliradiana for all positions
`of
`two eyes,
`separated 63. ') millimeters
`horizontally,
`in the Eye Motion Box).
`
`for HUn packaglng
`g) Geometric constraints
`and vehicle installation were defined for
`minimum modification
`of
`the
`existing
`the HUn may
`instrument panel: no part of
`extend above a 5 degree downward sloping
`plane
`from
`the
`bottom of
`the
`95%
`eyelltpse,
`the
`defroster
`and
`speaker
`grilles must
`remain intact, no strllctural
`elements
`below the
`top
`pad
`of
`the
`instrument panel may be modified,
`space
`must be allowed for efficient packaging of
`the electronics within the HUD unit, etc.
`
`h) Optical efficiency must be maximized for
`effective use of the VFD's light output.
`
`the optical system
`form of
`The general
`on
`the
`basis
`of
`selected
`2)
`was
`(Fig.
`preliminary design studies using first order
`approximations
`of
`the
`individual
`optical
`elements;
`it was
`subsequently
`refined
`and
`optimized,
`iteratively,
`using a proprietary,
`comprehensive computer ray trace program.
`A simple, flat, first surface glass mirror
`
`was used to fold the optical path between the
`VFD and the imaging mirror.
`This
`fold is
`necessary
`for
`efficient utilization of
`the
`available space and to facilitate packaging at
`the top.
`In order
`to prevent excessive glare
`and sunball reflections in the direction of the
`Eye Motion Box, a glare trap is mounted on top
`of the window.
`This glare trap is a flat black
`metal plate with louver blades oriented so that
`light from the imaging mirror is transmitted to
`the windshield and hence reflected toward the
`Eye Motion Box while ambient
`reflections are
`blocked.
`Louver
`blade
`height,
`pitch,
`thickness,
`and orientation are designed
`for
`minimum impact on Hun image quality, maximum
`ambient
`light blocking effectiveness, minimum
`glare trap depth, and durability.
`The louver
`plate is removable for access to the glass
`window for cleaning. Alternate light
`trapping
`techniques were considered during the initial
`design
`phases,
`including
`curved
`windows,
`filters, meshes, coatings, etc.; none was found
`to
`be
`competitive
`in
`terms
`of
`functional
`performance,
`low profile and cost.
`The windshield is the final element of the
`HUD's optical
`acting as
`a partial
`system~
`mirror to reflect the HUD's image and as a
`window for direct
`real
`observation of
`the
`FMVSS design requirements constrain the
`world.
`transmission and reflecting
`the
`characteristics of automotive windshields;
`former must exceed 70% at normal
`incidence and
`the latter must be minimized to provide a low
`level of veiling glare;
`in addition,
`the design
`and construction
`of windshields must meet
`stringent
`environmental,
`durability,
`styling
`and impact safety requirements.
`Ideally,
`from
`the point of view of HUD performance alone, a
`very
`thin,
`flat,
`very
`accurate,
`highly
`reflective windshield
`(possibly selective in
`angle
`and/or
`spectrally,
`depending
`on
`the
`geometry and emissive characteristics of
`the
`display)
`is desired. Clearly,
`a practical
`solution
`for
`an
`existing
`vehicle
`design
`required optimizing these
`characteristiCS of
`the system.
`For
`the introductory Pace Car HUD
`system,
`this goal was achieved with unmodified
`production windshields. Windshield treatment
`options
`for
`improved HUD performance
`(image
`brightness/ contract/ visibility,
`image quality
`and
`uniformity)
`are
`being
`pursued
`for
`performance improvements and for future HUD's.
`a
`Typical
`reflection characteristics for
`production windshield are shown in Figure 6.
`Light
`is
`reflected toward the Eye Motion Box
`from both
`the
`inside
`(No.4)
`and
`outside
`surfaces (No.1) of
`the windshield.
`This
`results in two slightly displaced virtual
`images.
`Careful design of
`the geometrical
`relationship
`between
`the
`HUn
`and
`the
`windshield,
`the specific graphics
`composition
`and the range at which these images are formed
`cause them to overlap when viewed from the
`
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`
`a)
`
`for
`togie
`vehicle speed
`
`calculation and
`
`display of
`
`III
`
`I
`V.POL~IlIZATION
`
`TRANSMISSION
`
`"-
`
`~O~ARLlleo
`
`-------~ 'i'
`N'''''''N
`
`b) Display brightness controls
`
`c)
`
`Input signal conditioning
`
`d)
`
`Vehicle
`pr.otection
`
`Electrical
`
`system transient
`
`H.POLAIlI1Z:1
`
`e) Display Power Supply
`
`. / UNP~LAlllleO
`
`REFLECTION
`
`V
`
`--..
`
`-I.---'" ,
`
`V.~IZATION
`
`..
`
`1.00
`
`0
`
`0.80
`
`0
`
`0.""
`
`0.400
`
`0.20
`
`0
`
`0.""
`
`o
`
`20
`
`40
`
`&0
`
`INCIDENCE ANGLE, DEGREES
`
`,
`PACE CAll OPEIlATlNG ANGLE
`
`Figure 6 - Typical Windshield Transmlssionl
`Reflection Characteristics
`
`central region of the Eye Motion Box t providing
`one
`sharp composite image;
`relatively bright t
`some
`"ghost ll
`image
`separation will occur at
`peripheral positions in the Eye Motion Box and
`field of view, particularly for
`fine graphics
`details.
`These separations tend to be masked
`by the glare shield louvers and do not appear
`to be disturbing to HUD users.
`The aggregate
`windshield reflectivity at
`the HUD's operating
`angle (approximately 70 degrees)
`is in the 25%
`range, which,
`when
`factored
`in with
`the
`of
`efficiencies
`the
`internal optical
`HUD1~
`elements
`(folding mirror t
`imaging mirror,
`window)
`provides
`a
`composite maximum image
`brightness of 500 ft Lamberts
`(predicted and
`measured) when the VFD is operating at its
`brightness
`limit of
`around 3000 ft Lamberts.
`This is sufficient for visibility under normal
`driving conditions.
`Higher
`image brightness/
`contrast is desirable for extreme ambient light
`levels.
`This can be achieved by a variety of
`means,
`including the use of brighter or narrow
`spectral
`band
`display
`devices,
`increased
`optical
`efficiency
`of
`the
`HUD' s
`internal
`components,
`polarization
`effects,
`spectral
`selectivity (filtering, diffraction effects)t
`improved reflectivity of
`the windshields, etc.
`Work progressing in all of
`these areas is
`expected to lead to future HUD's which are
`clearly visible
`under all
`ambient
`lighting
`conditions and which opens up the possibility
`that a HUD could become the primary instrument.
`
`ELECTRONICS - The HUD electronics package
`was designed as
`a
`stand alone system with
`special
`emphasis
`on
`low
`cost
`and
`high
`reliability.
`This provided a design which can
`easily be
`used with all
`types
`of
`vehicle
`intrumentation,
`not
`solely
`vehicles with
`digital
`electronic
`speedometers.
`The
`HUD
`electronic package consists of:
`
`reduced cost and high
`the purposes of
`For
`desireable
`to
`hold
`reliability,
`it
`was
`electronic component count
`to a minimum.
`This
`was accomplished through the use of
`a set of
`application
`specific
`integrated
`circuits
`(ASICls) designed to provide the required logic
`and VF segment drivers from a single CMOS
`integrated circuit.
`Use of
`this chip set
`eliminated
`the
`need
`for
`development
`of
`microprocessor
`software,
`saving
`valuable
`program time.
`A high brightness VFD tube is used as
`Ilimage
`source"
`in the optical
`system of
`HUD.
`This tube was specially developed to
`meet
`the brightness, contrast and image quality
`requirements of
`the HUD.
`The graphics are
`composed
`of discrete
`segments
`as
`shown
`in
`Figure 7.
`The tube is rated for 3000 foot
`Lambert brightness with a half-life greater
`than
`5,000
`operating
`hours
`(equivalent
`to
`100,000 miles).
`
`the
`the
`
`HUDNFD GRAPHICS
`Figure 7 - Pace Car HUD Graphics
`
`The VFD faceplate is registered precisely
`in the optical system.
`The tube is mounted on
`a
`simple printed circuit board module
`along
`with the necessary filament
`power.
`supply and
`drive electronics.
`The HUD dimming circuit has a discrete
`turn-on
`step
`and
`an
`adjustment
`range
`of
`approximately 80:1 between minimum and maximum
`display brightness
`in each control mode;
`the
`night mode characteristic is attenuated by a
`factor of 6:1 relative to the day mode 90 that
`
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`
`the total available HUD brightness adjustment
`range is approximately 500:1.
`the
`design of
`Care was
`taken
`in the
`printed circuit module and selection of readily
`available, automotive grade electronic
`components
`to provide high reliability as well
`as
`immunity
`to
`transients,
`input
`power
`and
`variations,
`electromagnetic interference;
`care was also taken to preclude interference by
`the HUD with other vehicle electr.onics.
`The
`electronics module is located in the HUD's
`optical
`cavity where
`it
`is
`necessary
`to
`minimize
`the
`possibility
`of
`stray
`light
`reflections from the electronic components into
`the primary optic~l path. Therefore the module
`iR conformally coated and painted dull black.
`
`HUD STRUCTURES - The HUD unit consists of
`two major
`subassemblies;
`the Chassis
`and the
`HUD cover.
`injection molded,
`The Chassis is a stable,
`structure which serves as the "optical bench".
`The printed circuit module, which contains the
`VFD tube and folding mirror on a bracket above
`it,
`is mounted directly to the chassis and
`registered in the optical path by a set of
`locator pins.
`The aspheric imaging mirror
`is
`bonded into a frame which is mounted to a set
`of hinge blocks on the chassis.
`The frame
`includes a bolt-on tilt arm which is coupled to
`the sl ider mechanism on the HUD cover via cam
`action for manual
`ttl t control.
`The chassis
`also includes capttve nuts
`for attachment of
`the HUD assembly to the mounting bracket
`in the
`top pad of
`the instrument clustp.r.The HUD cover
`is also an inj ection molded part.
`The glass
`window is
`bonded
`into
`the
`final
`optical
`aperture and the louver-type glare trap is
`retained above it by a cam lever.
`It can be
`removed with the HUD installed in the vehicle
`for access to the window (for inspection and/or
`cleaning). A detent-action slider mechanism is
`bonded to the inside of
`the cover with a button
`protruding
`in
`a
`slot
`on
`top.
`The
`outside
`surface of
`the cover
`is styled,
`textured and
`fI.nished to harmonize with the top pad of
`the
`instrument panel.
`It
`is registered with touch
`points on the HUD chassis and attached to it by
`two screws.
`Care was
`taken in its design to
`prOVide a good contour match with the top pad
`which is a pliable plastic part.
`Figure 8 is a
`photograph of
`the HUD as
`installed in the
`vehicle.
`
`Figure 8 - Typicai HUD Installation
`
`HUD PERFORMANCE
`
`The Pace Car HUD's design and performance
`are summarized in Table 5.1.
`Its performance.
`acceptability. utility and compatibility with
`the automotive envir.onment has been evaluated
`in the laboratory and on the road.
`this
`to
`Positive
`consumer
`response
`introductory system will
`lead to increase of
`the HUD feature in the near future.
`
`TABLE I
`
`PACE CAR HUD DESIGN AND PERFORMANCE
`SUMMARY
`
`Features and
`Parameters
`
`Design Concept
`
`Image Content
`
`Operation
`
`Values and Limits
`
`Reflective
`with high
`coplanar VFD
`windshield
`glass.
`
`system
`optical
`brightness,
`using standard
`as
`combining
`
`Digital speed with units of
`measure,
`turn/hazard
`low
`arrows,
`fuel.
`high
`(plus
`beam.
`growth
`for
`"check gages").
`
`Self-contained unit.
`independent
`of
`instrument
`cluster..
`
`image/eye
`dimmer,
`Operating Controls On/off
`(day/night
`tilt>
`box
`dimming range selection is
`automatic
`via
`light
`swi tch).
`
`Image Size
`
`Image Location
`
`degrees
`1.5
`degrees wide.
`
`high
`
`x
`
`3
`
`Azimuth: near driver Center
`line.
`
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`
`TABLE 1 PACE CAR HUD DESIGN AND PERFORMANCE
`SUMMARY (continued)
`
`tiltable (-2
`Elevation:
`to -6.5 degrees).
`Range:
`2.4 meters
`front bumpe r).
`
`(near
`
`Brightness
`
`Color
`
`Eye Motion Box
`
`2
`
`modes:
`
`Contr.ol
`(day/night)
`Maximum:
`500 ft L (day)
`Minimum:
`1 ft L (night)
`Adjust.
`range: 80:1 (each
`mode)
`Blue-green (50S nm peak)
`
`130 mm x 130 mm
`Total:
`Instantaneous: 130 x 6S mm
`with manual tilt.
`
`Vertical Binocular Average:
`Disparity
`Maximum:
`
`les8 than 0.7 mr
`less than 1.5 mr
`
`Dimensions
`
`270 x 180 x 90mm,
`
`irregular
`
`Weight
`
`Power
`
`SUMMARY
`
`0.75 kg
`
`3 watts, 12 v