3,241,256
`A, P, vlRET ETAL
`March 22, 1966
`METHOD AND MEANS FOR INTEGRALLY LIGHTING AN INDICATOR
`WITH UNIFORM BRIGHTNESS AND WITH LIGHT CONSERVATION
`Filed May 13, 1963
`4 Sheets~Sheet 1
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`WOLFGANG FUHR‘
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`
`LGD_000705
`
`LG Display Ex. 1015
`
`

`
`3,241,256
`A P, VIRET ETAL
`March 22, 1966
`METHOD AND MEANS FO.R INTEGRALLY LIGHTING AN INDICATOR
`WITH UNIFORM BRIGHTNESS AND WITH LIGHT CONSERVATION
`Filed May 13, 1965
`4 Sheets-Sheet 2
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`LGD_000706
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`3,241,256
`A. P. VIRET ETAL
`March 22, 1966
`METHOD AND MEANS FOR INTEGRALLY LIGHTING AN INDICATOR
`WITH UNIFORM BRIGHTNESS AND WITH LIGHT CONSERVATION
`_ Filed May 13, 1965
`4 Sheets-Sheet ‘5
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`ANDRE P. V/PET
`WOLFGANG FUHR’
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`LGD_000707
`
`

`
`March 22, 1966
`METHOD AND MEANS FO.R INTEGRALLY LIGHTING AN IND 3,241,256
`A P. VIRET ETAL
`ICATOR
`WITH UNIFORM BRIGHTNESS AND WITH LIGHT CONSERVATION
`Filed May 13, 1965
`4 Sheets-Sheet 4.
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`INVENTORS
`ANDRE F? V/RET
`WOLFGANG FUHR
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`
`LGD_000708
`
`

`
`"Ice
`United States Patent 0
`
`3,241,256
`Patented Mar. 22, 1966
`
`1
`
`3,241,256
`METHOD AND MEANS FOR INTEGRALLY LIGHT
`ING AN INDICATOR WITH UNIFORM BRIGHT
`NESS AND WITH LIGHT CONSERVATION
`Andre P. Viret, Ridgewood, and Wolfgang Fuhr, Has
`brouck Heights, N.J., assignors to The Bendix Corpora
`tion, Teterboro, N.J., a corporation of Delaware
`Filed May 13, 1963. Ser. No. 279,723
`6 Claims. (Cl. 40-130)
`
`This invention relates to a method and means for inte
`grally lighting an indicator with uniform brightness
`throughout and with light conservation and more par
`ticularly to improvements in the illumination of instru
`ment dials, scales, and indicator tapes so as to achieve
`light conservation and uniform brightness in a lighting
`system by a novel pattern of light re?ecting (diffuse re
`?ection) areas or dots, hereinafter called the “dot pat
`tern,” at appropriate locations on the back surface of a
`light conducting block or panel and in which “dot pat
`tern” the dots or diffusing areas are either larger in size
`or more densely distributed or both, the greater the dis
`tance thereof from the light source.
`One of the basic methods of integrally lighting an in
`dicator has been to transilluminate the indicator dial.
`This has often been done by using a dial with translucent
`indicia (not necessarily white) in a black background.
`Behind the dial there has been placed a light conducting
`block in which are inserted illuminating lamps so ar
`ranged that light rays from the lamps diffuse through the
`block so as to emmanate from the front surface thereof
`(as well as from its other surfaces) so as to pass through
`the dial and thereby transilluminate it. This technique,
`While very simple, has not been found entirely satisfac
`tory in that there has developed a considerable loss of
`light, and there is an undesirable nonuniform brightness
`distribution over the face of the dial.
`Heretofore, diffusion areas of predetermined size and
`shape have been provided on the back surface of a light
`conducting block immediately opposite areas to be il
`luminated such as indicia in order to diffusely re?ect light
`rays impinging on the diffusing areas up and through the
`indicia immediately above them. This produced more
`uniform illumination of the indicia. In the present in
`vention, there is provided a novel pattern of diffusing
`surfaces or dots so formed upon the lower surface of the
`light conducting block as to di?use the internally re
`?ected light rays with uniform intensity from the light
`conducting block through a translucent dial, scale, or in
`dicator tape situated above said block and optically sep
`arated from it in order to produce a uniform brightness
`of the dial, scale, or tape.
`This allows a dial or scale to be uniformly illuminated
`throughout its surface including the background thereof
`as well as the indicia thereon. It also allows a tape with
`indicia thereon to be moved over the light conducting
`block with a constantly uniform illumination of the in
`dicia and background thereof.
`An object of the invention, therefore, is to provide a
`method and means of achieving light conservation and
`uniform distribution of light rays over the entire face of
`an indicator dial or tape by putting light re?ecting (dif
`fuse re?ection) dots or areas at appropriate locations on
`the back of the light conducting block.
`Another object of the invention is to provide such dots
`in a so-called dot pattern to effect a more uniform bright
`ness distribution throughout a dial, scale, or tape (in
`cluding background) by providing dots of large size and/
`or more dense distribution the greater the distance of
`the dots from the light source.
`Another object of the invention is to provide a light
`
`2
`re?ecting dot pattern on the lower side of a light con
`ducting block, in which arrangement light rays which are
`not re?ected off the dots the ?rst time around are not
`lost since such light rays may be internally re?ected off
`the polished surfaces of the light conducting material be
`tween the dots and off the re?ective coatings on the edges
`of the block so as to be kept within the block until such
`time as they are diffused by striking a light re?ecting dot.
`Another object of the invention is to provide in such
`arrangement a novel dot pattern in which. the dots act
`to effect diffused re?ections so that the light rays re?ect
`ing off of them are so spread out that by the time they
`pass through the dial, scale, or tape a uniform brightness
`distribution is effected over the entire surface of the dial,
`scale, or tape, including background.
`Another object of the invention is to provide in such
`a dot pattern dots of varying size and shape convenient
`to provide the desired brightness distribution. and in which
`arrangement normally the dots are larger and more
`densely distributed the greater the distance thereof from
`the light source.
`Another object of the invention is to provide from
`the foregoing technique a reduction in the quantity of
`lamps needed to effect the desired illumination by con
`serving the light rays through appropriate coating at
`peripheral edges of the light conducting block with a
`suitable specular re?ecting material and further by pre
`venting the formation of a bright spot which normally
`occurs directly above the illumination lamp by inserting
`some sort of light ba?le immediately above the lamps.
`These and other objects and features of the invention
`are pointed out in the following description in terms of
`the embodiment thereof which is shown in the accom
`panying drawings. It is to be understood, however, that
`the drawings are for the purpose of illustration only and
`are not a de?nition of the limits of the invention. Refer
`ence is to be had to the appended claims for this purpose.
`In the drawings:
`FIGURE 1 is a sectional view illustrating one embodi
`ment of the invention wherein light rays from light
`sources pass through a light conducting member and may
`be diffused from light re?ecting areas or dots of different
`size and variously located so as to effect a uniform dis
`tribution of the light rays through a translucent movable
`indicator tape and in which the dots may be of larger
`size and of greater density the greater the distance there
`of from the source of light so as to effect the desired
`uniform brightness.
`FIGURE 2 is a front plan view of a modi?ed form
`of the invention as applied to an indicator dial.
`FIGURE 3 is a side view of FIGURE 2 with certain
`parts broken ‘away to illustrate the lamps in the light
`conducting block.
`FIGURE 4 is a rear view of FIGURE 2 showing the
`electrical conductors for energizing the lamps.
`FIGURE 5 is a rear plan view of the under surface of
`the light conducting block of FIGURES l and 2 showing
`the novel pattern of light diffusing dots to effect the uni
`form distribution of the light rays through an indicator
`dial, as shown in FIGURE 2, or translucent tape, as
`shown in FIGURE 1.
`FIGURE 6 is an edge view of a modi?ed form of
`the invention.
`‘
`FIGURE 7 is an underside of the illuminating block
`of FIGURE 6 showing the pattern of the light re?ecting
`areas or dots to effect the desired uniform distribution
`of the light rays through an indicator dial and with illumi
`nating lamps arranged at opposite ends of the light con
`ducting block.
`FIGURE 8 is an end view of the illuminating block of
`FIGURE 7 with the mounting bracket removed and il
`
`15
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`20
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`40
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`50
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`60
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`LGD_000709
`
`

`
`3
`lustrating the arrangement of the illuminating lamps in
`the end of the block.
`Referring now to the drawings wherein like reference
`characteristics designate like or corresponding parts
`throughout the views, there is shown in FIGURE 1 a
`sectional view of one form of the illuminating system
`comprising the invention including a light transmitting
`block or panel 12, a translucent tape 16 having suitable
`translucent indicator markings formed in a translucent
`black background thereon and separated by an air space
`17 from the front surface of the panel 12. The tape 16
`may be positioned relative to the light transmitting block
`or panel 12 by suitable drive means such as shown, for
`example, in US. Patent No. 3,117,312 granted January 7,
`1964, by William F. Watson, for a Vertical Scale Con
`dition Indicator, and which patent has been assigned to
`The Bendix Corporation, assignee of the present inven
`tion.
`In the light conducting block 12, there may be pro
`vided suitable sources of light energy such as electric
`lamps 13 and 20 positioned in the panel 12 in spaced
`relation and carried by a supporting plate 21. The
`lamps 18 and 20 are arranged to introduce light energy
`in the form of light rays into the light transmitting block
`or panel 12 by transmission therethrough and by internal
`re?ection from the adjacent upper and lower surfaces of
`the panel or block 12 and by re?ection from the outer
`edges of the panel 12, as indicated in FIGURE 1 by the
`dash lines indicating the paths of internal re?ection of the
`light trays therein.
`Moreover, in order to prevent the formation of a
`bright spot directly in front of the lamps 18 and 20, there
`may be inserted a light baffle 19 in the lamp hole directly
`in front of the lamps 18 and 20, as shown in FIGURES
`1 and 3, or in the alternative the front of the lamps or
`the ?lter over the lamps 18 and 20 may be painted black.
`Further, as shown in FIGURE 1, diffusing areas 22 of
`predetermined size and shape are provided upon the back
`surface of the panel 12 for causing the light rays inter
`nally transmitted and re?ected in the block 12 to be
`diffusely re?ected through the upper surface of the light
`transmitting block 12 upon impinging on the area 22 so
`as to transilluminate the translucent indicator tape 16
`with uniform brightness (that is, the indicia have uniform
`brightness values and the background has an equally
`uniform but lower brightness value).
`Any ray of light within a transparent medium which
`encounters an air interface at the critical angle (for ex
`ample, 42.2 degrees off the normal for Plexiglas) or
`greater will not be transmitted—but totally re?ected.
`When a light ray strikes a diffuse re?ector (such as
`white paint) the re?ected light distribution is independ
`ent of the angle at which the light strikes the surface.
`No matter what this angle may be, the maximum in
`tensity of the light re?ected is normal to the surface and
`the light is spread throughout an angle of one hundred
`and eighty degrees (180° ).
`The diffusing areas 22 may be of different predeter
`mined size and shape to effect the desired illumination
`with uniform brightness over the entire viewable area
`of the translucent indicator tape 16 of FIGURE 1 or indi~
`cator dial 14 of FIGURE 3. Normally, as shown in
`FIGURES 5 and 7, the light diffusing dots are larger
`and/or more densely distributed the further away they
`are located from the light source in order to diffuse the
`light rays impinging thereon and produce a uniform
`transillumination of the dial or tape above the light con
`ducting block 12.
`As shown in FIGURE 1, the re?ecting light rays which
`exceed the complement of the critical angle of the ma
`terial comprising the light transmitting block 12 are
`transmitted from its outer surface through the air space
`17 and translucent tape 16 so as to illuminate the indicia
`and background of tape 16 with uniform brightness over
`the entire viewable area of the indicator tape 16.
`
`A
`The diffusing block illumination system, herein de
`scribed may serve to illuminate an indicator dial, tape,
`scale or the like by the transmission of light energy by
`diffuse re?ection from a ?rst light transmitting block or
`panel so as to illuminate with uniform brightness an
`indicator panel, scale, dial or translucent tape optically
`separated therefrom. Moreover, by the diffused re?ec
`tion of the internally transmitted light rays uniform
`brightness in illumination may be obtained over the en
`tire viewable surface of the indicator panel or translucent
`indicator tape including the background of the panel or
`tape.
`The light transmitting block or member 12 may com
`prise a ?at transparent plate having upper and lower
`surfaces in parallel relation to each other polished to pro
`vide an optically smooth and clear surface. Member
`12 is of such suitable physical dimensions as to effectively
`transmit light energy to all portions of a juxta-positioned
`indicator panel 14, ‘as in FIGURE 3, or translucent tape
`16, as in FIGURE 1.
`Although any clear, colorless, transparent light trans
`mitting material may be used in forming the light trans
`mitting member 12, the member 12 may be fabricated
`from an acrylic resin or methyl methacrylate plastic ma
`terial of the thermoplastic type such as, for example,
`“Lucite” or “Plexiglas.” Thermosetting materials such
`as the allyl resins also are applicable as in glass.
`The feature of the present invention resides in the pro
`vision of the back surface of the light transmitting block
`12 with a predetermined pattern of light diffusing sur
`faces 22 which may be formed in the back surface of
`the light transmitting block 12 by etching with an en
`graving tool or the like or by photoetching or by apply
`ing a dot coating or translucent or opaque material, such
`as paint, directly to the surface. The dot coatings may
`be applied by the silk screen, paint spray process, or any
`other suitable process in which the dot coatings of paint
`are applied in optical contact with the light transmitting
`element.
`Further, the peripheral edges 25 of the light conduct
`ing block 12 may be coated with specular re?ecting ma
`terial (such as silver or aluminum) for maximum con
`servation of light. Diffused re?ector material such as
`white paint may also be used, but this has been found to
`be not as effective a light conserver as materials such as
`silver or aluminum. In the alternative, the peripheral
`edges 25 may be left clear if light conservation is un
`important.
`Moreover, since the dots or areas 22 are diffused re
`?ectors, the light rays re?ected off them spread out as
`such rays pass through the block 12 and indicator dial
`114 of FIGURES 2 and 3 or translucent indicator tape 16
`of FIGURE 1 so that the dot pattern is not reproduced
`as such on the dial or indicator tape. The dots may be
`any size or shape necessary or convenient to produce the
`desired distribution of the light rays with uniform bright
`ness.
`A second form of the invention is illustrated in FIG
`URES 2, 3, 4 and 5 wherein like numerals indicate cor
`responding parts to those described with reference to
`FIGURE 1.
`Moreover, as shown in FIGURE 3, there is positioned
`adjacent the front surface of the light conducting block
`or panel 12 a light diffusing or transmitting panel 14
`having on the front face thereof suitable indicator mark
`ings, as shown in FIGURE 2.
`In the drawing of FIGURE 4, there are shown elec
`trical conductor bars 30 and 31 connected to sources of
`electrical energy through conductors 32 and 33, respec—
`tively. The conductor bar 30 includes conductors 35 and
`36 while the conductor bar 31 includes conductors 37 and
`38 which lead respectively to the input terminals of the
`electric lamps 18 and 20 so as to provide electrical energy
`for the illumination of the respective lamps 18 and 20
`
`3,241,256
`
`15
`
`20
`
`25
`
`30
`
`35
`
`70
`
`LGD_000710
`
`

`
`3,241,256
`
`mounted in the light conducting block 12 of FIGURE 3
`and providing sources of illumination thereof.
`In FIGURES 6 and 7, there is illustrated a further
`modi?ed form of the invention in which corresponding
`parts to those described with reference to FIGURE 1
`have been indicated by corresponding numerals.
`In the form of the invention of FIGURES 6 and 7,
`the sources‘of light rays for illuminating the light con
`ducting block 12 are electric lamps 50 and 51 mounted
`at opposite ends of the light conducting block 12. These
`lamps may be electrically connected to a suitable source
`of electrical energy through conductors 52, 53, and 54.
`Further, as shown in FIGURE 7, there is provided at the
`under or back side of the light conducting block 12 a
`pattern of light diffusing areas or dots 22 in which dots 22
`of larger size are arranged in the central area and at a
`greater distance from the lamps 50 and 51 mounted at
`opposite ends of the light conducting block 12. These
`light diffusing areas or dots diminish in size as the same
`approach the outer ends of the block 12 so as to effect
`the desired uniform diffusion or distribution of the light
`rays through the light diffusing panel, indicator dial or
`indicia bearing surface 14.
`While several embodiments of the invention have been
`illustrated and described, various changes in the form and
`relative arrangement of the parts, which will now appear
`to those skilled in the art may be made without depart
`ing from the scope of the invention. Reference is, there
`fore, to be had to the appended claims for a de?nition
`of the limits of the invention.
`What is claimed is:
`1. In an illumination system of a type including a light
`conducting block of transparent material having substan
`tially parallel front and rear re?ecting surfaces, said sur
`faces being polished and operative to specularly re?ect
`light rays in said block, a member of translucent mate
`rial extending parallel to said surfaces and positioned ad
`jacent to the front face of said light conducting block,
`and said member of translucent material having indicia in
`an obverse face thereof; the improvement comprising a
`light diffusing means in optical contact with the rear re
`?ecting surface of the light’ conducting block, said light
`diffusing means including light diffusing areas of differ
`ent size arranged in spaced relation in a predetermined
`pattern in such a manner as to diffuse a portion of said
`specularly re?ected light rays from the rear surfaces of
`the block of light conductor material into and through
`the member of translucent material so as to illuminate
`the entire viewable surface area of the member of trans
`lucent material with uniform brightness, said light diffus
`ing means includes a series of paint dots arranged in a
`predetermined pattern, said dots being of different size
`and having a different spaced relation so as to effect a
`diffusion of the light rays through the translucent member
`with uniform brightness.
`2. In an illumination system of a type including a light
`conducting block of transparent material having substan
`tially parallel front and rear re?ecting surfaces, said sur
`faces being polished and operative to specularly re?ect
`light rays in said block, a member of translucent mate
`rial extending parallel to said surfaces and positioned
`adjacent to the front face of said light conducting block,
`and said member of translucent material having indicia
`in an obverse face thereof; the improvement comprising
`a light diffusing means in optical contact with the rear
`re?ecting surface of the light conducting block, said light
`diffusing means including light diffusing areas of different
`size arranged in spaced relation in a predetermined pat~
`tern in such a manner as to diffuse a portion of said
`specularly re?ected light rays from the rear surface of
`the block of light conductor material into and through
`the member of translucent material so as to illuminate the
`entire viewable surface area of the member of translucent
`material with uniform brightness, the light diffusing means
`includes a plurality of light diffusing re?ecting dots placed
`in optical contact with the rear polished surface of the
`
`50
`
`65
`
`70
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`10
`
`15
`
`20
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`25
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`30
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`6
`block of light conducting material and in a predetermined
`patern so as to provide the dots of a larger size and more
`dense distribution, the gerater the distance thereof from
`the light source.
`3. In a diffusing block illumination system of a type
`including means for illuminating an indicia bearing sur~
`face comprising a transparent light transmitting block
`having plane, polished, and parallel front and rear re?ect
`ing surfaces for specularly re?ecting light rays introduced
`therein from a light source; the improvement comprising
`a predetermined pattern of light diffusing elements po
`sitioned on the rear surface of said light transmitting
`block, said pattern including a plurality of said elements
`of different size arranged in different spaced relation, and
`said pattern being such that a portion of the light rays
`specularly re?ected in said light transmitting block may
`be diffusely re?ected by said diffusing elements from the
`rear re?ecting surface of the light transmitting block into
`and through the indicia bearing surface so as to illumi
`nate the last-mentioned surface with uniform brightness,
`said light diffusing elements include a series of paint dots
`arranged in a predetermined pattern, said dots being of
`different size and having different spaced relation so as
`to effect diffusion of the light rays through the indicia
`bearing surface with said uniform brightness.
`4. In a diffusing block illumination system of a type
`including means for illuminating an indicia bearing sur
`face comprising a transparent light transmitting block
`having plane, polished, and parallel front and rear re
`?ecting surfaces for specularly re?ecting light rays intro
`duced therein from a light source; the improvement com
`prising a predetermined pattern of light diffusing ele'nents
`positioned on the rear surface of said light transmitting
`block, said pattern including a plurality of said elements
`of different size arranged in different spaced relation, and
`said pattern being such that a portion of the light rays
`specularly re?ected in said light transmitting block may
`be diffusely re?ected by said diffusing elements from the
`rear re?ecting surface of the light transmitting block into
`and through the indicia bearing surface so as to illumi
`nate the last-mentioned surface with uniform brightness,
`the light diffusing elements include a plurality of light
`diffusing re?ection dots placed in optical contact with the
`rear polished surface of the block of a light conducting
`material and in a predetermined pattern in which the dots
`are of a larger size and more densely distributed, the
`greater the distance thereof from the light source.
`5. Means for illuminating a translucent indicia bearing
`surface, said means comprising a light conducting block
`of transparent material having opposite ends and substan
`tially front and rear re?ecting surfaces, said front and
`rear surfaces being operative to specularly re?ect light
`rays in said block, said front and rear surfaces being sub
`stantially parallel to said translucent indicia bearing sur
`face, sources of light rays mounted at the opposite ends
`of said light conducting block, light diffusing means in
`optical contact with the rear re?ecting surface of the light
`conducting block, said light diffusing means including
`light diffusing areas of different size and spaced relation
`in a predetermined pattern in which light diffusing areas
`of relatively greater size may be located intermediate the
`sources of light rays, and in which light diffusing areas of
`relatively lesser size are located nearer the source of light
`rays at one of said ends and in greater spaced relation to
`the other of said light diffusing areas than the light dif
`fusing areas of said relatively greater size, and said pre
`determined pattern of light diffusing areas being so ar
`ranged in such a manner as to diffuse a portion of said
`specularly re?ected light rays from the rear surface of
`the light conducting block into and through the translu
`cent indicia bearing surface so as to uniformly illuminate
`the last-mentioned surface.
`6. In a diffusing block illumination system of a type
`including means for illuminating an indicia bearing sur
`face comprising a transparent light transmitting block hav
`ing plane, polished, and parallel front and rear re?ecting
`
`LGD_000711
`
`

`
`3,241,256
`
`8
`indicia bearing surface may be of a movable translucent
`indicator tape operable for receiving the uniform diffused
`light therethrough so as to be illuminated with uniform
`brightness.
`
`7
`surfaces for specularly re?ecting light rays introduced
`therein from a light source; the improvement comprising
`a predetermined pattern of light diffusing elements posi
`tioned on the rear surface of said light transmitting block,
`said pattern including a plurality of said elements of dif
`ferent size arranged in different spaced relation, and said
`pattern being such that a portion of the light rays spec
`ularly re?ected in said light transmitting block may be
`diffusely re?ected by said diffusing elements from the
`rear re?ecting surface of the light transmitting block into
`and through the indicia bearing surface so as to illumi
`nate the last-mentioned surface with uniform brightness,
`the light diffusing elements include a plurality of light
`di?using re?ection dots placed in optical contact with
`the rear polished surface of the light transmitting block
`and in a predetermined pattern in which the dots are of
`a larger size and more densely distributed, the greater the
`distance thereof from the light source, and in which said
`
`References Cited by the Examiner
`UNITED STATES PATENTS
`
`2,561,885
`2,629,043
`2,824,399
`2,880,536
`2,945,313
`3,043,038
`3,043,947
`
`7/ 1951 Prideaux __________ __ 40—130
`2/1953 Holtje ___________ __ 40-—l30 X
`2/1958 Neugass ___________ __ 40-130
`4/1959 Sullivan __________ __, 40—130
`7/1960 Hardesty _________ __ 40-130
`7/1962 Marble ___________ __ 40—130
`7/1962 Albinger ________ __ 40-—130 X
`
`10
`
`15
`
`EUGENE R. CAPOZIO, Primary Examiner.
`JEROME SCHNALL, Examiner.
`
`LGD_000712