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`
`~.A II!!! The Engineering
`Resource For
`Advancing Mobility
`
`400 COMMONWEALTH DRIVE WARRENDALE. PA 15096
`
`860347
`
`Light Control Systems for Automotive
`Instrumentation
`Diane Baum Verploegh
`3M Company
`Automotive Specialties Div.
`St. Paul, MN
`
`Reprinted from SP·654·
`Electronic Displays and Information Systems:
`Developments and Applications
`
`International Congress and Exposition
`Detroit, Michigan
`February 24-28, 1986
`
`MASIMO 2008
`Apple v. Masimo
`IPR2020-01526
`
`

`

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`
`No part of this pUblication may be reproduced in any form,
`in an electronic retrieval system or otherwise, without the
`prior written ~ermission of the publisher.
`
`ISSN 0148·7191
`Copyright 1986 Society of Automotive Engineers, Inc.
`
`This paper is subject to revision. Statements and opinions
`advanced in papers or discussion are the author's and are
`his responsibility, not SAE's; however, the paper has been
`edited by SAE for uniform styling and format. Discussion
`will be printed with the paper if it is published in SAE
`Transactions. For permission to publish this paper in full or
`in part, contact the SAE Publication Division.
`
`Persons wishing to submit papers to be considered for
`presentation or publication through SAE should send the
`manuscript or a 300 word abstract of a proposed manu·
`script to: Secretary, Engineering Activity Board, SAE.
`
`Printed in U.S.A.
`
`

`

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`860347
`
`light Contro~ Systems for AUltomotive
`InstrUlmentation
`Diane Baum Verploegh
`3M Company
`Automotive Specialties Div.
`St. Paul, MN
`
`instrument
`ABSTRACT Numerous optical problems for
`panel designers have been created by new trends in automo(cid:173)
`tive exterior and interior design, increasing use of electronic
`instrumentation, and new display packaging methods. The
`problems, nighttime reflections, glare, and daytime display
`viewability, were previously solved using conventional techni~
`ques of instrument panel hooding and recessing of displays.
`This paper will review the trends in automotive design and
`instrumentation technology and relate the design objectives
`to functional performance requirements. It will also describe a
`technology and product available from 3M which can reduce
`or eliminate many of the aesthetic and functional design prob(cid:173)
`lems now being addressed for automotive instrumentation.
`
`INTRODUCTION: Changing Vehicle Designs
`Concern for aerodynamic properties and reduction in fuel
`consumption has increased and is now resulting in dramatic
`changes to exterior vehicle designs. The significant changes
`that effect instrument panel design include:
`
`.. decreasing slope of the windshield
`o downsizing of vehicles
`e increasing passenger space
`
`Reducing the size of the conventional instrument panel is a
`method to increase interior passenger space. Reduction in
`the over-all physical size of the instrument panel is achieved
`by reducing its depth and intrusion into the passenger space.
`In the past, when passenger compartment space was abun~
`dant, and vehicle weight was not critical, hoods and shrouds
`were used to prevent optical problems of nighttimewindshield
`reflections and daytime glare on instrumentation. Hoods and
`shrouds consumed significant space, and when combined
`with recessed displays, were aesthetically unappealing.
`Recent changes in the slope of thewindshieid and reduction
`in the over-all size and amount of instrument panel shrouding
`have intensified the optical problems. These probiems could
`be solved with conventional techniques at the sacrifice of
`passengerspace, vehicle weight, and evolution of instrumen(cid:173)
`tation technology. Figure 1. illustrates nighttime windshield
`reflections with changing windshield position. With past vehi(cid:173)
`cle design, light emitted from instrumentation reflected onto
`the headliner, thus avoiding windshield reflections. However,
`given the same interior geometry and a reduction in the slope
`of the windshield, nighttime reflections occur and are in the
`driver's direct line of sight. In this example, shrouding the
`instrumentation is not an acceptable solution because of
`
`limited passenger space. Neither is recessing instrumenta·
`tion to block the windshield from stray light because of limited
`instrument panel package space. These problems exist with
`incandescent analog and electronic instrumentation.
`With the reduction of instrument panel size and the increase
`in the use of electronic instrumentation, another optical prob(cid:173)
`lem has been introduced - daytime display viewability or loss
`
`1 Past Vehicle design
`2 Present aerodynamic design
`
`Figure 1. Vehicle Design Changes and Effect on
`Windshield Reflections
`
`of display contrast. High levels of ambient light reduce the
`visibility of certain types of elecl1'onic displays. Numerous
`techniques are used to enhance the visibility of electronic dis(cid:173)
`plays in all ambient conditions. However, these techniques do
`not always yield satisfactory results, and sacrifice display life,
`performance, and efficiency.
`r
`In summary, changes in automobile design and increased
`performance requirements have created automotive interior
`needs which include:
`
`o Reduction of instrument panel size
`.. Elimination of daytime glare
`" Control of ambient and display generated light (day
`and night)
`" Elimination of nighttime windshield and window re(cid:173)
`flections
`" Enhanced daytime visibility of electronic instrumen(cid:173)
`tation
`.. New technology including electronics, instrumenta(cid:173)
`tion, and display packaging methods
`
`107
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`
`INSTRUMENTATION TRENDS
`Three levels of instrumentation exist today- conventional
`instrumentation, simulated electronic instrumentation, and
`electronic instrumentation. In all cases the instrumentation
`must provide information which is easiiy distinguished in all
`ambient condilions, be aesthetically pleasing, and provide
`long-term reliability.
`Conventional instrumentation uses passive, analog dis~
`plays. These types of displays present both quantitative and
`qualitative information. Daytime visibility is dependent upon
`ambient illumination of display pointers, scales, graphics, and
`isosymbols. Nighttime visibility is dependent upon auxiliary
`illumination, usually from incandescent, white lighting. Multi(cid:173)
`ple color graphics are achieved with screen printing techni(cid:173)
`ques on appliques and graphics panels.
`Simulated electronic instrumentation utilizes conventional
`instrumentation components, but has a psuedo electronic
`appearance because of variation in component packaging,
`screen printing techniques, and light source placement.
`Electronic instrumentation use is increasing, and dramatic
`growth is forecast into the mid-1990's, as shown in Figure 2.'
`U.S. automobile production is forecast to remain fairly stable
`into the same period. This growth in electronic instrumenta(cid:173)
`tion within a fairly stable automotive industry will provide
`numerous opportunities and challenges for designers,
`engineers, and suppliers. Figure 2 illustrates U.S. oppor(cid:173)
`tunities, but the growth trend is global in nature. On a global
`basis, this growth will require increased awareness of optical
`problems associated with new technology and design trends.
`Instrument panel designers must learn to effectively utilize
`new display technology to meet functional and aesthetic
`design objectives.
`
`Optical Performance Characteristics
`Electronic instrumentation must be easily read under all
`ambient conditions, from darkness to bright sunlight. Three
`significant factors contribute to display readability: display
`brightness, contrast, and glare. Brightness is the amount of
`light emitted by a display element, or the luminous sterance
`(intensity/unit area) of
`illuminated elements. Contrast, or
`luminance contrast, is the difference in brightness levels be(cid:173)
`tween display "on" elements, "off" elements, and their back(cid:173)
`ground. Glare, or front surface display reflectivity, can effect
`apparent contrast and reduce display viewability. Glare
`defines the response of light upon the external surface of a
`display or filter; contrast indicates the response of ambient
`light plus display generated light internal to a display sys(cid:173)
`tem.
`
`Contrast
`Luminance contrast ratios can be determined forelectronic
`displays with and without the use of filtration techniques.
`There is no single, standardized method forcalculation of con(cid:173)
`trast and contrast ratios. Luminance contrast ratios without
`the use of a filter are defined as the sum of the display
`generated light and ambient light reflected off the display ele(cid:173)
`ment divided by the amount of light reflected off the back(cid:173)
`ground, as shown in Equation 1.
`
`1.
`
`Luminance
`Contrast
`Ratio
`
`CR = LvS + 190FF
`Lv
`
`(2)
`
`where
`=Sterance of illuminated element ("on")
`LvS
`LvOFF =Sterance of light reflected off the element
`Lv B
`=Sterance of light reflected off the background
`
`Contrast ratios are optimized by maximizing "on" element
`brightness relative to background and "off" element reflec(cid:173)
`tance. Loss of display readability can be caused by loss of con(cid:173)
`trast between the "on" elements and the background re(cid:173)
`sulting in "washout", or by the loss of contrast between "on"
`and "off" elements, making "on" elements indistinguishable
`from other elements in a display.
`When the amount of element generated light equals jhe
`amount of light reflected from the background or "off" ele(cid:173)
`ments, the contrast ratio equals one. The contrast ratios of
`electronic displays are thus determined by:
`
`" Contrast between illuminated ("on") elements and
`background
`" Contrast between non-illuminated ("off") elements
`and background
`" Contrast between illuminated ("on") and non-illumi(cid:173)
`nated ("oW) elements
`
`Filtration
`Display brightness and contrast can be managed by proper
`filtration techniques. Filters attenuate incident ambient light
`and reduce the amount of light falling on the display. Neutral
`density filters can improve contrast by twice attenuating
`ambient light- by reducing the amount of ambient light enter(cid:173)
`ing and exiting a display. But,
`the disadvantage of
`low
`transmission neutral density filters is the attenuation of dis(cid:173)
`play generated light. Use of these filters has resulted in
`increased display brightness requirements. Low transmission
`filters have been required for automotive applications due to
`high ambient levels, and the potential for degradation of dis(cid:173)
`play readability.
`Filters also change display contrast by adding another vari(cid:173)
`able for analysis. This variable is glare, or reflection from the
`filter's front surface. Light that is not transmitted or absorbed
`by a filter is reflected at the air-filter interface. Depending
`
`u.s. Car Production
`
`Cars With
`Electronic IPS
`
`8 7
`
`6
`
`<I>
`
`~:¥ 5
`:E 4
`.,
`!?
`3
`u
`
`2 1 0
`
`1983
`
`1984
`
`1985
`
`1987
`
`1968
`
`1989
`
`1990 1993
`
`198e
`YeQr
`Figure 2. Total Car Production Vs. Cars with
`Electronic IPs
`
`ELECTRONIC INSTRUMENTATION: Electronic Display
`Types
`Electronic instrumentation offers unique appearance and
`performance features. If electronic displays are not properly
`utilized, numerous optical problems will plague their perfor(cid:173)
`mance and customer acceptance.
`Electronic instrumentation and displays can be divided in to
`two categories - active displays and passive displays. Active
`displays, such as vacuum fluorescent displays (VFD), light
`emitting diodes (LED), cathode ray lubes (CRT), and gas dis(cid:173)
`charge displays, are self-illuminating. The light source is also
`Ihe information source. Liquid crystal displays (LCD), as with
`conventional displays are passive and rely on external, aux(cid:173)
`iliary lighting for display viewablilily.
`Electronic instrumentation offers greater information den~
`sity within a defined area, when compared to conventional
`instrumentation. Significant emphasis is now being focused
`upon electronic displays which are large in display area, pro(cid:173)
`vide multi-color information, and offer multi-function capa(cid:173)
`bilities.
`
`108
`
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`
`upon the index of refraction of the filter material to the index of
`refraction of air, at least four percent of light can be reflected at
`each air~filter interface. Front surface glare can be either
`specular or diffuse. The human eye adds the light reflected off
`the filter surface to the display generated light and reflected
`background light. The luminance contrast ratio of a display
`with a filter is defined in Equation 2. as:
`
`2.
`
`Luminance
`Contrast
`Ratio
`
`CR = L"S + LyOFF + L"F
`LyB + LyF
`
`(3)
`
`where
`LyS
`
`=Sterance of illuminated element through the
`filter
`LyOFF =Sterance of light reflected off the element
`through the filter
`=Sterance of light reflected off the background
`through the filter
`=Sterance of light reflected off the filter
`
`LvB
`
`LvF
`
`For the purpose of measuring and determining actual con~
`trast ratios for active displays, the above equation can be
`expanded to:
`
`3.
`
`Contrast= CRoo
`Ratio
`(Display"on")
`= Element ON + Element OFF + Filter Reflectance
`Background ON + Filter Reflectance
`= LvSe + LyS O" + LyF
`VBon + LvF
`= LI/8 oo + LySou
`LVS on
`when including display reflectivity
`in LvSe", LvS O!!' and LvSo" measurements
`
`and
`
`4.
`Contrast
`Ratio
`(Display"off")
`
`= CR ov = Element OFF + Filter Reflectance
`Background OFF + Filter Reflectance
`
`=~
`Lv Boll
`when Including display reflectivity
`in Lv 8 ol! and LvBofi measurements
`
`Vacuum fluorescent displays have bright display areas and
`dark backgrounds. The bright display elements are very ap'
`parent without a filter in the OFF mode under high ambient
`levels. The use of a filter is needed to maximize the contrast of
`the "on" elements relative to the background and minimize the
`contrast of the "off" elements relative to the background. This
`relationship can be defined as:
`
`5. Contrast
`Ratio
`Improvement
`
`CRI is maximized when CRoN is maximized and CROFF is
`minimized.
`
`109
`
`Filters must minimize washout and maximize contrast ratios.
`In addition, filters for electronic instrumentation must:
`
`" Reduce glare by changing surface texture from glossy
`to a slight matte
`o Serve as an optical window
`" Be a durable, lightweight component
`" Hide the background and elements in the OFF mode
`o Provide color matching for display emission charac-
`teristics
`o Retain image quality and resolution
`o Be easy to mount
`" Seal off and enclose display and electronics
`
`LIGHT CONTROL SYSTEMS
`A technology known in product form as Light Control Film
`(LCF), can eliminate many of the aesthetic and functional
`design problems for automotive instrumentation. Automotive
`interior and exterior design trends, electronic instrumenta~
`tion, and new display packaging methods have created a need
`for LCF or a similar technology. Light Control Film is a unique
`optical film used for controlling light generated by instrument
`panel displays and ambient light in the interior of automobiles.
`The film is a powerful design tool to solve optical problems,
`and offers designers greater freedom and flexibility in instru(cid:173)
`ment panel design. The film, an optically clear, thin plastic,
`contains uniformly spaced microlouvers which control
`light
`ente,ing and exiting displays. Orientation of the louvers within
`the film determines the angles at which light can enter or exit
`displays. When the louvers are properly oriented, the film acts
`as an extended hood, thereby eliminating the need for hood·
`ing or recessing of displays.
`Light Control Film is used by many automotive manufac·
`turers on a global basis for functional and aesthetic interior
`applications. Specific interior automotive applications for the
`film are shown in Figure 3. The film has four major perfor·
`mance characteristics and can be designed in instrumenta(cid:173)
`tion and lighting assemblies to:
`
`o Eliminate nighttime windshield and window reflection
`o Improve daytime contrast and readability of elec(cid:173)
`tronic instrumentation
`o Internally direct light to specific locations within clus(cid:173)
`ter assemblies
`
`Figure 3. LCF Applications
`
`These combined characteristics could ultimately assist in
`providing:
`
`G Streamlined, smaller instrument panels
`o More efficient use of interior and cluster lighting
`o Increased passenger space
`" Vehicle weight reduction
`
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`

`Downloaded from SAE International by Vijay Madisetti, Thursday, May 06, 2021
`
`LCF Functional Characteristics
`Light Control Film combines function and aesthetics to con~
`trol and direct light, prevent nighttime reflections, and improve
`daytime contrast of electronic instrumentation. Figure 4
`demonstrates the performance of the film with a light emitting
`diode (LED) display. Display contrast is enhanced and reflec(cid:173)
`tions on a simulated windshield are eliminated. Thefilm is suit(cid:173)
`able for use with all major types of electronic instrumentation
`including vacuum fluorescent displays, light emitting diodes,
`backlighted liquid crystal displays, gas discharge displays,
`cathode ray tubes, and etectroluminescent panels. Further(cid:173)
`more, the film can be used with incandescent light sources for
`instrument panel clusters, switches and console displays.
`
`The viewing angle, or area allowing light to pass between the
`louvers, is determined by the length of the louver from one
`side of the film to the other. As shown in Figure 5, the shorter
`louver length provides a greater viewing angle or "open" area.
`By simple geometry, the longer louver length restricts the
`angle at which extreme rays of light can enter and exit the film,
`thus reducing the viewing angle. Standard viewing angles are
`48, 60, and 90 degrees. The louver angle and viewing angle
`are independent of each other and of over-all film thickness.
`Minimum film thickness isO.030 in. (0.76mm) and increases in
`increments of 0.020 in. (0.51 mm) to a maximum of 0.070 in.
`(1.78mm). The distance between each louver Is targeted
`either for 0.005 in. (0.13mm) or 0.010 in. (0.25mm). Louver
`thickness ',s targeted for 0.0005 in. (0.01 mm).
`The optical performance and transmission characteristics of
`the film can be graphically represented by a response curve of
`percent
`transmission and viewing angle. LCF having a 0
`degree angle and 60 degree viewing angle is represented In
`Figure 6. The on-axis, maximum nominal transmission is 75
`percent. With aO degree louver angle, the maximum transmis~
`sian occurs normai to the film surface, at the center of the
`viewing angle. The transmission decreases symmetrically
`about the louver angle or peak transmission (y axis), and
`neariy approaches zero at the limits olthe total viewing angle.
`Viewing in the z axis in unrestricted.
`
`75% Transmission
`
`35% Transmission
`
`1/ ~
`
`Visible
`Display
`
`I
`
`80
`
`60
`
`40
`
`o-
`
`20
`}~l/
`10 20
`0
`30 -20 -10
`Viewing Angle - Degrees
`
`/
`
`\
`
`"" j--.
`
`30
`
`Figure 6. Light Control Film Transmission Characteristics
`
`The louver angle defines where the maximum transmissic>n
`will occur on the response curve, either at points on the x axis
`equalling 0,18,30, or45 degrees. The viewing angle defines
`the shape of the response curve, whether it is narrow with a 48
`degree viewing angle or broader with a 90 degree viewing
`angle. The shape of the response curve is symmetrical about
`the peak transmission or louver angle.
`The peak transmission of LCF can move to the right or left of
`the y axis depending upon the louver angle and its tolerances.
`The tolerances of a 0 degree louver angle are +/- 6 degrees.
`Figure 7 shows the effect of tolerances on the location of
`peak transmission.
`
`Figure 4. Contrast Enhancement and Reflection Controt
`with Light Control Film
`
`Six parameters are used to describe LCF which include:
`
`e Louver Angle (maximum transmission angle)
`e Viewing Angle
`e Louver Type (louver transmission)
`e Filter Color
`e Surface Finish
`e Thickness
`
`The louver angle and viewing angle are the two most impor~
`tant parameters for characterizing the film. The louver angle
`defines how the louvers are positioned relative to the outer
`surfaces of the film. The louvers are positioned perpendicular
`to the film surfaces, oratan angle. Thisangle ismeasured from
`a normal to the film surface, and is the angle at which max(cid:173)
`imum transmission of light through the film occurs. Figure 5
`indicates the louver angles available, from 0 degrees to 45
`degrees.
`
`Louver Angle
`
`,.
`
`Vlewlr'lgAngle
`
`...
`'"'"
`
`~le
`
`1.1". TfOn,m\~,I(m
`An91e
`
`Figure 5. Light Control Film - Louver Orientation
`
`110
`
`

`

`Downloaded from SAE International by Vijay Madisetti, Thursday, May 06, 2021
`
`Percent Transmission
`100%
`
`7S%
`
`direction of light exiting a display and prevent windshield
`reflections, as shown in Figure 8. Louvers oriented perpen(cid:173)
`dicular to the top of the instrument panel can control display
`light and eliminate side window reflections. Various methods
`for LCF placement in cluster and display assemblies will be
`discussed in the Application Segments section. The use of the
`film makes hooding of displays unnecessary and allows for
`the design of consolidated, stream-lined instrument panels.
`
`rdSh ie ld
`
`LCF
`
`30~
`
`20'
`
`3D'
`
`20'
`
`10'
`0'
`10"
`Viewing Angle
`Figure 7. LCF Transmission Profile
`Louver Angle - 0 0
`Louver Type - Opaque black
`Viewing Angle - 60 0
`
`The amount of light transmitted through the louvers is
`defined by the louver type. Opaque black anti-ghosting
`louvers allow less than one percent of off-axis light to pass
`through the film. They are excellent for ImproVing contrast
`ratios and readability of electronic instrumentation at high
`ambient levels, as well as preventing nighttime reflections
`from both incandescent and electronic instrumentation.
`Transparent black louvers allow less than ten percent of off(cid:173)
`axis light to pass through the film. This louver type is recom(cid:173)
`mended for displays which rely on ambient light for daytime
`viewing but require incandescent, auxiliary illumination for
`nighttime viewing. The transparent black louvers allow some
`off-axis light to pass through to the display, and depending on
`the light source intensity, are sufficient for preventing or
`minimizing nighttime windshield reflections.
`Clear LCF can be transformed into a colored film with black
`louvers to maximize contrast, spectrally match display emis~
`sion characteristics, and minimize the number of filters for
`electronic instrumentation. Select filter colors and four levels
`of neutral density filters can be integrally combined with the
`film. In some applications, color can be achieved by screen
`printing on the surface of clear LCF.
`One surface of the film can be textured to either diffuse
`specular reflection (glare), orto allow the film to blend with tex(cid:173)
`tured finishes of instrument panel and Interior trim. The level of
`texture (matte level), from fine to heavy, is dependent upon
`display resolution and glare reducing requirements. Display
`character resolution and readability is Inversely proportional
`to the level of matte on the surface of a filter. Reflection from
`the front surface of filters will decrease contrast ratios, which
`is also true for LCF with a matte front surface. A highly matte,
`diffuse surface will scatterthe four percent of reflected light In
`all directions, and reduce the resolution of characters obser(cid:173)
`ved through the film, Including both screen printed characters
`and those of active electronic displays. A matte surface should
`maximize character resolution and minimize glare. Heavy
`matte, diffuse surfaces are not recommended for the high
`ambient environments of automobile instrument panels
`because of character
`resolution loss and the tendency
`towards decreasing contrast ratios, as shown by Equation 2.
`
`LCF Performance Characteristics
`
`Nighttime Reflections
`Light Control Film can effectively eliminate nighttime
`windshield and side window reflections. Louvers that are
`oriented parallel to the top oithe instrument panel, control the
`
`Instrument
`Panel
`
`Steering Column
`
`Figure 8. Light Control Fitm to Prevent Windshield
`Reflections
`
`Daytime Contrast Enhancement
`Electronic instrumentation requires filtration, mostly to
`Improve display contrast and over-all readability.
`In high
`ambient conditions, such as an automobile, maintaining dis~
`play contrast is a major objective.
`Incident sunlight upon
`instrument panels from the driver's side window has been
`measured at 4500 - 5500fc (48,000-60,000 lux).' Under
`these bright conditions, color or neutral density filters do not
`always maintain sufficient contrast ratios, and do not prevent
`diminished display readability (washout). High brightness dis(cid:173)
`plays emitting up to 1200 fL lose readability at such high
`ambient levels.
`Light Control Film can be used to prevent sunlight degrada(cid:173)
`tion of electronic Instrumentation, as shown In Figure 9. LCF Is
`a full-spectrum transmitting filter, allowing all wavelengths
`emitted by an electro-optical source to pass through the film.
`Simultaneously, all visible wavelengths of light incident upon
`the film outside the viewing angles, are blocked and never
`allowed to fall upon the display surface. The film improves
`luminance contrast ratios by m'lximizing the intensity of il(cid:173)
`luminated elements and minimizing the intensity of
`light
`reflected off the elements and background.
`
`Light Control Film
`
`Eleclro·OpliUlI
`Source
`
`All Visible
`WavelenglhS
`Blocked
`
`Figure g. LCF to Prevent Sunlight Degradation of
`Electronic Instrumentation
`
`111
`
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`

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`
`The improvement in contrast ratios with LCF can be
`demonstrated by experimental analysis, with results shown in
`Figures 10 and 11. A seven segment, vacuum fluorescent
`instrument panel clock was used to measure contrast ratios.
`Near-vehicle conditions were simulated at low and moderate
`ambient conditions. The display emitted an average of 840 fL
`without a filter. Contrast ratios for fhe "on" and "off" con(cid:173)
`ditions, and resultant contrast ratio improvements were deter~
`mined. Comparison is shown between the display without a
`filter, with a 22 percent neutral density filter used in a 1985
`automotive VFD application, and with LCF (0 degree AG 60
`degree), at ambient levels of 600 fc (6450 lux) and 2000 fc
`(21,500 lUx). LCF shows significant contrast ratio improve(cid:173)
`ment over the neutral density filter at incident ambient il(cid:173)
`lumination angles greater than 20 degrees.
`
`-0- NoFJIlor
`
`-0- LCF 60 009'1l0
`
`'0
`
`coo
`
`I
`t m
`r P
`
`40.,
`t v•R m 20
`
`s 0
`
`30
`
`o •
`t n
`;
`t
`o
`
`10
`
`6
`
`-0
`
`o ~ogL,C-"c-'--::":-dc'"f-"-"--::20:-d-l"-"-"--3::0-:"""-"-"--'-:0-d'+-Il'000
`Angle of Incident Ambient Illumination
`Figure 1O. Contrast Ratio Improvement of a Vacuum
`Fluorescent Display at 600 FC Ambient
`Illumination
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`LCF should be designed in applications from concept stage
`in order to maximize the features and performance charac(cid:173)
`teristics of thefilm. Properdesign of the film into an application
`requires that the functional and aesthetic objectives of the dis'
`play or lighting system be known. The type of display and its
`location relative to the driver's line of sight and windshield
`must be defined. The interior geometry of the vehicle and
`instrument panel orientation must also be determined. This
`collective information aids in determining properlouverorien~
`tation. The flexibility of louver orientation enables LCF to meet
`most optical requirements of the major application segments.
`
`Instrument Panel Cluster Displays
`This segment includes displays providing primary vehicle
`information to the driver, and could include both incandescent
`and electronic instrumentation. Light Control Film can be
`used as an optical window between the electronic display and
`lens coverto prevent nighttime windshield reflections or sun·
`light washout, as shown in Figures 12 and 13. The louvers con(cid:173)
`trol and direct light emitted from the display, or prevent off-axis
`sunlight from reaching the display. The electronic speedo(cid:173)
`meters of the 1985 Lincoln Continental and Mark VII, as well
`as the Uncoln Towncar, utilize LCF to prevent sunlight
`washout. The electronic instrument cluster of
`the 1985
`Oldsmobile Ninety Eight Regency, utilizes LCF with slanted
`louvers and 0.010 in.
`louver spacing. This combination
`simultaneously prevents sunlight washout and provides
`passenger viewing of the instrument cluster for aesthetic
`reasons.
`
`Cloe' Lon$
`U!lM Conl,o! Film
`Eloct,onlc Oi.ploy
`
`Figure 12. Cluster Display
`Nighttime Reflections
`
`C~",DO
`
`c"::=:""
`
`Ughl Control Film
`
`o dOllroO$
`10 dnG,eDo
`20 dellrOilS
`30 dogrQl,l!l
`40 dog.ooo
`Angle of Incident Ambient Illumination
`Figure 11. Contrast Ratio Improvement of a Vacuum
`Fluorescent Display at 2,000 FC Ambient
`illumination
`
`Contrast ratios can be maximized with the film, without sac(cid:173)
`rificing display brightness. With LCF, active displays do not
`have to emit such high levels of light to obtain similar contrast
`ratios when compared to low transmission filters and high dis(cid:173)
`play brightness levels. In the case of VFDs, lower brightness
`levels can result in longer display(phosphor) life with reduced
`power requirements.
`
`APPLICATION SEGMENTS
`Five major application segments have been identified forthe
`use of Light Control Film and include:
`
`Figure 13. Cluster Display
`Sunlight Washout
`
`Instrument Panel Cluster Displays
`"
`Instrument Panel Cluster Lighting (internal)
`"
`.. Instrument Panel Cluster Switches
`.. Center Mounted Console Displays
`.. Driver Information Center and Entertainment
`Modules
`
`In cluster display applications, LCF is an internal cluster
`component, with the driver looking at the display through the
`louvers. Resolution of the display elements is not sacrificed or
`reduced with LCF. The film does not change the spectral emis(cid:173)
`sion characteristics of the displays, and therefore can be used
`with multi-color clusters.
`
`112
`
`

`

`Downloaded from SAE International by Vijay Madisetti, Thursday, May 06, 2021
`
`Instrument Panel Cluster Lighting
`In this application segment, the film is used as an internal
`cluster component as in the cluster display segment, and is
`hidden from sight. LCF is used as a functional component only
`and controis secondary light internai to a cluster. Figure 14
`shows the use of the film as a light directing element, and
`demonstrates concept for simulated electronic instrumenta(cid:173)
`tion. The cluster graphics could be applied to an applique and
`light would pass through LCF and the applique in the non(cid:173)
`opaque areas, as shown In the figure. For optimum control of
`light, It is important that diffuse screen printing Inks not be
`used to generate color In the graphics and information areas
`as diffuse Inks tend to scatter light that Is to be controlled by
`the film. Combined techniques of screen printing negative
`Images on dark backgrounds with translucent Inks can op(cid:173)
`timize a system with LCF.
`
`methods for simultaneously Increasing space and placing key
`functions within a driver's easy reach. This placement of
`illuminated switches can cause nighttime windshield rellec(cid:173)
`tions. Hooding of Individual switches or the entire assembly
`becomes Impractical or aesthetically unappealing.
`LCF can provide the necessary nighttime reflection control
`oi these assemblies and offer greater design freedom which
`was previously near-Impossible. The film can be screen prin(cid:173)
`ted on both surfaces to provide Isosymbols, scales, indicators,'
`and color for night and day viewing. The screen printed film
`can be laminated with pressure sensitive adhesive and die~
`cut for easy switch construction and film mounting. Figure 16
`shows a specific screen printing configuration for the film to
`provide front surface, negative images on an opaque gray
`background, with color provided for nighttime viewing.
`
`CI".'"rCh,phl""
`Figure 14. Cluster Display
`
`Figure 15 Illustrates a cluster lighting application where the
`film is used only for Its light directing capabilities. Light from
`incandescent,
`fluorescent, or electroluminescent sources
`can be controlled to only illuminate specific regions of a clus(cid:173)
`ter, and not be allowed to fall upon the windshield and cause
`reflections. The geometry of the display face relative to the
`light source, and display face position relative to the wind(cid:173)
`shield determine the louver orientation required in the film.
`This type of design minimizes the depth of