SAE TECHNICAL
`PAPER SERIES
`
`920812
`
`Optical System for Illuminating the Lateral
`Section of Wraparound Lamps
`
`H. Satsukawa, A. Yamada, H. Kawashima, and 0. Hiraguchi
`Koito Manufacturing Co., Ltd.
`
`~A~ The Engineering Society
`-=----=' For Advancing Mobility
`.._..---Land Sea Air and Space®
`INTERNATIONAL
`
`liB
`J);lr~
`International Congress & Exposition
`Detroit, Michigan
`February 24-28, 1992
`
`4 0 0 C 0 M M 0 N W E A L T H D R I V E, W A R R E N D A L E, P A 1 5 0 9 6 - 0 0 0 1 U. S. A.
`
`Page 1 of 10
`
`Mercedes-Benz USA, LLC, Petitioner - Ex. 1013
`
`

`

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`ISSN 0148·7191
`Copyright 1992 Society of Automotive Engineers, Inc.
`
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`
`Printed in USA
`
`Page 2 of 10
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`

`

`920812
`
`Optical System for Illuminating the Lateral
`Section of Wraparound Lamps
`H. Satsukawa, A. Yamada, H. Kawashima, and 0. Hiraguchi
`Koito Manufacturing Co., Ltd.
`
`1. ABSTRACT
`
`With the increased use of
`wraparound lamps in automotive design,
`the problem of how to illuminate the
`lateral section which is blocked from
`the light source by the chassis has
`become a point of concern. This report
`describes the development of an optical
`system which makes use of a
`photoconductive panel in order to
`resolve this problem.
`
`INTRODUCTION
`
`Automobile signalling lamps play an
`important role in ensuring safety during
`night driving by indicating one's
`presence and intentions to not only
`oncoming and following vehicles, but
`also to adjacent vehicles and
`pedestrians. Recent automotive design
`has favored curved, uniform lines to
`permit increased streamlining. These
`designs preclude the protruding lamp
`
`Curved Corner
`
`systems which formerly served the
`purpose of lateral signalling.
`Instead,
`wraparound units, particularly for the
`rear combination and front turn signal
`lamps, have become the norm (fig. 1).
`The demands for increased trunk
`space and engine room have also had a
`significant effect on today's lamps, and
`current specifications require
`ultra-slim, space-saving designs.
`However, as lamps have become ever
`slimmer and the wraparound portion more
`pronounced, the range of direct
`illumination from the light source has
`become reduced.
`In particular, the
`lateral wraparound portion of lamps has
`remained largely unilluminated up to
`now. Consequently this portion fails to
`serve its function as a lateral
`indicator, and the overall appearance of
`the lamp also suffers (figs. 2 & 3).
`The goal of our research was to
`overcome these drawbacks of wraparound
`lamp designs, and to provide overall
`illumination.
`
`Rear
`Combination/
`Lamp
`
`Fig.l Trends in Recent Auto Designs
`
`Direction
`of Travel
`
`Front Turn
`Signal Lamp
`
`Page 3 of 10
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`

`

`Range beyond Direct
`Illumination from Light
`Source
`
`920812
`
`I
`
`Range of
`Direct Illumination
`from Source
`
`Fig.2 A Typical Lorge Size Wraparound Rear Combination Lamp
`
`n= l3 [ Rear Combination Lamp
`Front Turn Signal Lamp
`
`11 models J
`
`2 models
`
`Range beyond Direct
`Illumination from Light
`Source
`
`---
`
`Number
`of
`Models
`5
`
`4
`
`3
`
`2
`
`0
`
`a
`
`n
`
`1 D 20 30 40 50 60 70 80 90 100
`
`0
`
`b/a
`.....
`
`Range of
`Direct Illumination
`from Source
`
`When viewing a vehicle from the side.
`only about 50% of the lamp Is illuminated.
`
`Fig.3 Percentage of Illumination of Lateral Portion of Wraparound Lamps
`
`Page 4 of 10
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`

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`920812
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`3. CHOOSING A SOLUTION
`
`In the first step of our research,
`various possible methods of illuminating
`the lateral wraparound portion were
`examined and evaluated by their
`comparative merits.
`
`3
`
`Considering the relative merits of
`each of these five methods, it was clear
`that the photoconductive panel with
`conical dots held the greatest promise,
`and from this point we began working on
`the development of such a system.
`
`NO.
`
`METHOD
`
`ABILITY TO DEPTH OF
`ILLUMINATE LAMP BODY
`
`COST
`
`GENERAL
`EVAL.
`
`1 Photoconductive Panel with
`Conical Dot Reflectors.
`A light-conducting acrylic
`panel is used to bend light
`from the light source to the
`wraparound portion (fig.4).
`
`2 Multiple Miniature Bulbs.
`An array of miniature white
`bulbs are distributed within
`the wraparound portion to
`provide illumination(fig.5).
`
`3 LED. - -LED's are distributed within
`the wraparound portion to
`provide illumination(fig.6).
`
`@
`
`0
`
`@ @
`
`f:J.
`
`f:J.
`
`f:J. ~
`
`~ 0
`
`~ ~
`
`4 Electro Luminescence ( EL) •
`An EL system is installed
`within the lateral wraparound
`portion( fig. 7).
`
`5 Fiber O_etics.
`Light is conducted from the
`light source to the wrap-
`around portion through the
`use of a network of optical
`fibers(fig.8).
`
`6
`
`6
`
`@
`
`6
`
`X
`
`X
`
`X
`
`X
`
`@: Excellent
`
`Q: Good
`
`6: Poor
`
`X: Bad
`
`Page 5 of 10
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`

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`920812
`
`Photoconductive
`Panel with
`conical oots
`
`Fig.S ~ultiple ~iniature Bulb ~ethOd
`
`Fig.6 LED Method
`
`Page 6 of 10
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`

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`920812
`
`/ I
`
`Fiber Optics
`
`Fig.S Fiber Optics Method
`
`4. HOW DOES A PHOTOCONDUCTIVE PANEL WITH
`CONICAL DOTS WORK?
`
`The photoconductive panel is
`basically a means of converting a point
`light source into a planar light source
`with uniform illumination (fig. 9).
`Light rays emitted from a source
`(bulb filament) enter the edge of a
`transparent acrylic photoconductive
`panel. The rays reflect off the inner
`surface of the panel at angles which
`permit total reflection, and the light
`is thereby transmitted along the panel.
`Ultimately the light will come into
`contact with one of many strategically
`located conical protrusions. The light
`is then reflected back out of the panel.
`In order to achieve even
`illumination over the surface of the
`panel, the density of conical dots must
`be varied from section to section.
`In
`general, to provide uniform
`illumination, it is required that the
`density of conical dots increase with
`the distance from the light source.
`
`0
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`0
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`0
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`0
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`0
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`0
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`0
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`0
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`0
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`0
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`0
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`0
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`0
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`0
`0
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`0
`0
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`0
`0
`
`0
`0
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`0
`0
`
`0
`0
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`0
`0
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`0
`0
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`0
`0
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`0
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`0
`0
`0
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`0
`0
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`0
`0
`0
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`0
`0
`0
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`0
`
`0 0000000
`0000000
`0 0000
`0
`0 0000000
`0 0 00000
`0000000
`0 0000000
`0 000000
`0 0000000
`
`Lens
`
`6
`
`~-------Conical
`Dots
`
`Photoconductive Panel with
`Conical Dots
`
`~-L_o_w~~-----D-e_n_s_i_t_y __ o __ f __ C_o_n_i_c_a_l __ D_o __ t_s----~~1 High I
`
`Fig.9 Basic Principle of Photoconductive Panel with Conical Dots
`
`Page 7 of 10
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`

`

`6
`
`Because of their slim, lightweight
`construction, photoconductive panels are
`suitable for use in display units.
`Up to now, they have found application
`in heater control and audio control
`indicator panels, etc., as well as
`character and marking panels.
`These all represent applications
`within a planar format, however the
`product which we have developed is
`ground-breaking in that it represents
`the first application of a
`photoconductive panel with conical dots
`over an L-shaped, curved surface.
`
`5. DESIGN PROCESS
`
`5-1 HARDWARE
`
`The photoconductive panel makes use
`of the space within the lamp body
`existing forward and lateral of the
`light source as a light transmission
`path. The panel is roughly L-shaped,
`its specific shape depending on the lamp
`body dimensions (fig. 10).
`Light enters the panel at the edge
`closest to the light source, and is
`
`920812
`
`transmitted by total reflection along
`the panel's surfaces to lateral areas
`where direct rays from the light source
`cannot reach. Conical dots are located
`at these areas on the inner surface of
`the panel adjacent to the lamp body.
`Opposite the panel surface with
`conical dots, the lamp body surface is
`coated with white paint to ensure
`uniform reflection.
`After light rays have been
`transmitted through the photoconductive
`panel , there exist three patterns by
`which they are directed outward,
`resulting in the illumination of the
`wraparound portion of the lamp (fig.11).
`
`(1) The ray reaches a conical dot, from
`which it is reflected out of the panel.
`
`(2) The ray exits from the inner surface
`of the panel, is reflected off the white
`surface of the lamp body, and then
`passes out through the panel.
`
`(3) The ray exits directly from the
`outer surface of the panel.
`
`Range of
`Conical Dots
`
`White Coated
`Inner Surface
`of Lamp
`Housing
`
`White Coated
`Inner Surface of
`Lamp Housing
`
`Housing
`
`Conical Dots
`
`Photoconductive
`Panel with Conical
`Dots
`
`Fig.lO Configuration of Hardware
`
`Fig.ll Light Emission Paths from Photoconductive Panel
`
`Page 8 of 10
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`

`

`920812
`
`5-2 SOFTWARE
`
`To ensure bright and even
`illumination at all points along the
`lamp, the shape of the edge surface
`closest to the light source, as well as
`the arrangement and density of the
`conical dot pattern, must be carefully
`chosen. By using light beam tracking
`computer simulation programs, luminance
`estimates were calculated with speed and
`accuracy, and in this way it was
`possible to arrive at a configuration
`providing optimal illumination at the
`design stage.
`
`(1) Light Beam Tracking
`
`1. Refraction at Incident Light Surface
`
`normal vector to incident
`surface
`incident ray vector
`refracted ray vector
`refractive index
`
`2. Total Reflection within
`Photoconductive Panel
`
`~ E2
`
`normal vector to reflective
`surface
`incident ray vector
`reflected ray vector
`
`(2) Luminous Exitance Approximation
`To facilitate calculations,
`luminance is approximated by the
`luminous exitance. The luminous
`exitance M of a photoconductive panel
`surface S is represented by the
`following equation (fig. 12):
`
`M =
`Fl· f (xly I z) • a.(l-8) +Fl (1-f (xl y I z)) o.-8) 3 r+F2 (1-8)
`s
`M : luminous exitance of panel surface S
`S : area of panel surface S
`F1: incident luminous flux on inner
`surface of panel S
`F2 : incident luminous flux on outer
`surface of panel S
`f(x,y,z) : Conical dot density function
`: refractive index of conical dots
`a.
`8
`reflectance of panel surface S
`reflectance of lamp body reflector
`y
`
`White Coated
`
`Conical Dots
`
`s
`
`Lamp Housing
`
`F1
`F1
`F2
`
`f( x, y, z ) · a (1- f3)
`(1-f(x,y,z))(l-{3)3 "(
`(l-j3)
`
`Photoconductive
`Panel with Conical
`Dots
`
`Fig.l2 Luminous Exitance Approximation
`
`Page 9 of 10
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`

`

`6. PROTOTYPE TESTS AND RESULTS
`
`A prototype lamp was built using
`the specifications arrived at through
`our light beam tracking analysis.
`Performance evaluations revealed the
`following points.
`
`(1) When lit, no irregularities in
`illumination were evident along the
`surface of the lamp. The lamp was
`uniformly illuminated at the front and
`throughout the lateral, wraparound
`surface (fig. 13).
`
`(2) The luminous exitance of the
`
`920812
`
`prototype lamp corresponded closely with
`the estimate arrived at through our
`computer simulation program (fig. 14).
`
`7. SUMMARY
`
`The lamp system we have developed
`allows for total illumination of
`wraparound units. This represents a
`significant improvement not only in the
`signalling ability of the lamp, but also
`in the overall appearance of the unit.
`The technology may also be used in a
`wide range of illuminated display panel
`applications, opening new doors in the
`concept of contoured illumination.
`
`Front View
`
`Luminance
`(nit)
`
`....----Prototype Test of Lamp Side
`
`200
`
`100
`
`Without
`Photoconductive
`Panel with Conical
`Dots
`
`0
`
`50
`
`Approximation
`
`----~ --
`
`100 Dista nee
`Cmm)
`
`Lateral View tAbove: Prototype
`
`Below: Conventional
`Type
`
`Fig13. Photographs of Lamp when
`Illuminated
`
`Photoconductive Panel
`
`Light Beam
`
`Light Source
`
`Fig.14 Light Beam Tracking & Approximation +~
`Prototype Test of Luminance
`
`Page 10 of 10
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