VWGoA - Ex. 1007
`Volkswagen Group of America, Inc., Petitioner
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`1
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`U.S. Patent
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`Nov. 14, 1995
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`Sheet 1 of 4
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`5,467,417
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`7
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`III/II/III/II/I’II/IIIIIIIIIIIIIIIII/IIIIIIIIIIIIA
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`6
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`2
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`1
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`5
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`mmnmmumm
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`1+
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`3
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`1
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`FIG. 2
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`2
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`U.S. Patent
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`Nov. 14, 1995
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`Sheet 2 of 4
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`5,467,417
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`/-75. 3
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`t*—'°—%
`O
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`6
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`3
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`U.S. Patent
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`Nov. 14, 1995
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`Sheet 3 of 4
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`5,467,417
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`F/G. 5
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`LUMINANCE(RELATIVEVALUE)
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`2.0
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`1.8
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`1.6
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`1.4
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`1.2
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`1.0
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`0.8
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`0.6
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`0.1+
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`0.2
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`0.0
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`-80
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`-60
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`-1+0
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`-20
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`0
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`20
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`1+0
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`60
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`80
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`VISUAL ANGLE (DEGREE)
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`FIG. 6
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`63
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`62
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`63
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`62
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`\A
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`6°
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`61
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`4
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`U.S. Patent
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`Nov. 14, 1995
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`Sheet 4 of 4
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`5,467,417
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`FIG. 7
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`VALUE)
`LUMINANCE(RELATIVE
`
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`VISUAL ANGLE (DEGREE)
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`/=/5. 8(a)
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`/=/5. 3/12)
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`Aw @
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`5
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`5,467,417
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`2
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`1
`PRISM PLATE FOR EFFICIENTLY
`EMITTING LIGHT FLUX WITHIN A
`PREDETERMINED RANGE, AND LIQUID
`CRYSTAL INDICATOR AND INDICATOR
`ILLUNHNATION METHOD USING THE
`SANIE
`
`BACKGROUND AND SUMMARY OF THE
`INVENTION
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`5
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`10
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`light intensity of the ray of light 61 incident on the prism
`plate 60 which corresponds to the visual angle characteristic
`as if there is no prism plate 60. As shown by the solid line
`70 in FIG. 7, the luminance is increased by more than 1.4
`times over an effective range of visual angle of from -35
`degree to 35 degrees. However, the light is also emitted over
`ineffective ranges of visual angle from -80 degrees to -60
`degrees and from 60 degrees to 80 degrees resulting in
`wasteful consumption of electric power. When viewed from
`these directions, the indicator is unnecessarily bright. The
`cause is attributed, as shown in FIG. 6, to the fact that the
`ray of light 61 incident on the prism plate 60 is totally
`reflected by the prism plane 62 and is emitted from the prism
`plane 63.
`An object of the present invention is to solve the above-
`rnentioned problems by providing an indicator which pre-
`vents light from being emitted into ineffective ranges of
`visual angle, so as to increase the intensity of light emitted
`within an efiective range of visual angle. It is another object
`of the present invention to provide an indicator which has a
`small thickness and consumes a small amount of electric
`power, thereby being particularly suitable for portable infor-
`mation processors.
`
`In order to achieve the above objects, the basic concept of
`the present invention is the recognition that the prism plate
`gathers the light from the scattering plate in the direction of
`an eifective visual angle (for example from -60 degree to
`+60 degree as shown in FIG. 7), and minimizes intensity of
`outgoing light in the direction of a noneffective visual angle.
`And more desirably, the present invention is elfective to
`assure that there is no peak of the intensity of outgoing light
`in the direction of the noneffective angle.
`Another aspect of the present invention is a prism plate
`having prism-like protuberances formed at a side thereof, in
`which the vertex angle 26 formed by two planes of each
`prism-like protuberance is defined by the formula,
`
`26>’/3><(1t/2+2xarcsin (l/n))
`
`where n is the refractive index of the prism plate medium.
`According to yet another feature of the present invention,
`an data indicator for an information processor comprises a
`light source, a scattering plate which scatters light from the
`light source, an indicator plate irradiated with scattered light
`from the scattering plate, and a prism plate having many
`prism-like protuberances formed on one side thereof and
`being disposed between the scattering plate and the indicator
`plate such that the prism-like protuberances face the scat-
`tering plate, and, the vertical angle 26 formed by two planes
`of each of the prism-like protuberances is,
`
`26>’/3X(1:l2+2Xarcsin (n 7n))
`
`where n is the refractive index of the prism plate, and n' is
`the refractive index of the material in which the prism plate
`is arranged.
`Accordingly, in a prism plate whose prism vertex angle 26
`satisfies the above inequalities, the totally reflected scattered
`light from one surface of the prism-like protuberance is also
`totally reflected on the other surface of the prism-like
`protuberance, thereby making it possible to gather the emit-
`ted light only in the effective range of visual angle.
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`BRIEF DESCRIPTION OF THE DRAWINGS
`
`These and other objects, features and advantages of the
`present invention will become more readily apparent from
`
`The present invention relates to a prism plate which
`efliciently emits within a predetermined range of angles a
`flux of light that is incident over a wide range of angles, to
`an indicator, such as a liquid crystal indicator, incorporating
`such a prism plate that is used for information indication in 15
`information processors such as personal computers, word
`processors, and the like, and to an indicator illumination
`method which efliciently emits the flux of light within the
`predetermined range.
`
`It has been desired to develop portable information pro- 20
`cessors such as personal computers and word processors,
`with the growth in an information-oriented society. Perfor-
`mance required for the portable information processors is
`that they should be small in size,
`light in weight, and
`consume a small amount of electric power so that they can 25
`be used for a long time on a small capacity power source.
`In portable information processors, in particular, the infor-
`mation indicator unit roughly determines the shape of the
`apparatus and always consumes electric power; hence it is
`desired that such unit have a small thickness and be of a type 30
`which consumes only a small amount of electric power.
`Such an indicator can be represented by a liquid crystal
`indicator of back-light type as described in Japanese Patent
`Laid-Open No. 67016/ 1992.
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`Referring to FIGS. 1 and 2 of Japanese Patent Laid-Open
`No. 67016/1992, the light rays emitted from light sources 23
`and 24 and the light rays reflected by reflectors 25 are
`scattered by a scattering plate 26, pass through optical
`device 27 such as a prism plate whose light incident side is
`a flat plane 28 and whose light outgoing side is a prism plane
`29, and are incident on a liquid crystal indicator element 12.
`In an embodiment of Japanese Patent Laid-Open No. 6701 6/
`1992, the optical device 27 such as the prism plate is made
`of a polycarbonate resin or a like resin, and the vertex angle
`between two planes of each prism on the prism plane 29 is,
`for example, 90 degrees (a half vertex angle is 45 degrees).
`The optical device 27 such as the prism plate disposed on the
`scattering plate 26 can collect light scattered over a wide
`range of angles by the scattering plate 26 in the normal
`direction of the optical device 27, increasing the luminance
`within an effective range of visual angle.
`A problem arises, however, with a conventional prism
`plate made of a polycarbonate resin or a like resin having a
`vertex angle of about 90 degrees (with a half vertex angle of 55
`45 degrees) as shown in the above-mentioned Japanese
`patent document.
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`50
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`FIG. 6 is a sectional view illustrating the conventional
`prism plate on an enlarged scale. Reference numeral 60
`denotes a prism plate and 61 denotes a ray of light. A solid
`line 70 in FIG. 7 represents the visual angle characteristic of
`outgoing light of the prism plate 60 illustrated in FIG. 6,
`which characteristic is found by a ray tracing calculation
`under the condition where the vertex angle 26 between a
`prism plane 62 and a prism plane 63 is 90 degrees (a half 65
`vertex angle 6245 degrees) and the refractive index n is
`1.585. A dotted line 71 represents the angle dependency of
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`60
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`5,467,417
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`the following detailed description when taken in conjunction
`with the accompanying drawing wherein:
`-
`FIG. 1 is a sectional view of a liquid crystal indicator of
`the side light type in accordance with one embodiment of the
`present invention;
`FIG. 2 is an exploded perspective view of the indicator of
`FIG. 1 showing the liquid crystal indicator of the present
`invention;
`FIG. 3 is an enlarged sectional view which illustrates a
`prism plate embodying the present invention;
`FIG. 4 is a diagram showing a ray trace of the prism plate;
`FIG. 5 shows the visual angle characteristic of the prism
`plate of the present invention;
`FIG. 6 is an enlarged sectional view which illustrates a
`conventional prism plate;
`FIG. 7 shows the visual angle characteristic of the con-
`ventional prism plate of FIG. 6; and
`FIGS. 8(a) and (b) are enlarged perspective views show-
`ing two protuberance structures at the surface of the prism
`plate of the type shown in FIGS. 3 and 4 in accordance with
`the present invention.
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`DETAILED DESCRIPTION OF THE DRAWINGS
`
`In FIGS. 1 and 2, reference numeral 1 denotes a cold
`cathode-ray tube, 2 denotes a reflector plate, and 3 denotes
`a lightguide plate made of an acrylic resin or the like resin
`and having a reflector 4 such as white paint applied to the
`lower surface thereof. Reference numeral 5 denotes a thin
`scattering plate having fine roughness on the surface thereof
`which is placed on the upper surface of the lightguide plate
`3, reference numeral 6 denotes a prism plate whose lower
`side is flat and which has prism protuberances formed on the
`upper side thereof, and reference number 7 denotes a liquid
`crystal indicator element.
`The principle of the present invention will be described
`with reference to FIG. 4 which is a ray-trace diagram of light
`of the prism plate. Reference numeral 40 denotes a prism
`plate having a vertex angle between a prism plane 42 and a
`prism plane 43 of 26 (a half vertex angle is 9) and a
`refractive index of n, and 41 denotes a ray of light having an
`angle of incidence of on (the direction indicated by arrow in
`FIG. 4 is assumed to be negative). The angle of refraction on’
`on a plane 44 (direction indicated by arrow in FIG. 4 is
`assumed to be negative) and the angle of incidence B on the
`prism plane 42 (direction indicated by arrow in FIG. 4 is
`assumed to be negative) are given by:
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`ot'=arcsin (1/nxsin oz)
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`B=o:'+e—n/2
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`(1)
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`(2)
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`The ray of light that satisfies the condition of nxsin B<—l is
`totally reflected by the prism plane 42 and is incident on the
`prism plane 43. The angle of incidence 8 on the prism plane
`43 is given as the following formula:
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`20
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`25
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`30
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`35
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`40
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`45
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`50
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`55
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`5=—B—26
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`(3)
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`60
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`the incidence [5
`As the incidence or becomes smaller,
`becomes larger. The smallest angle of incidence on is -1:/2.
`So if sin 0: is —l and if
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`nxsin 5<—1
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`(4)
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`65
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`then, the rays of light incident on the prism plane 43 are all
`totally reflected, emitted from the plane 44 of the prism plate
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`40, scattered by the scattering plate and the like, and become
`rays of light that are incident again on the prism plate 40.
`When this inequality is transformed,
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`8<arcsin (—1/n)
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`Based on formulas (3) and (5),
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`[3>26+arcsin (1/21)
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`Based on fonnulas (2) and (6),
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`6>'/a><(1't/2+arcsin (l/n)—ot')
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`I
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`Moreover, ot'=—arcsin (l/n) since sin ot=—l
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`29>‘/3(n:/2+2><arcsin (1/n))
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`(5)
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`(6)
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`(7)
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`(8)
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`Accordingly, in a prism plate whose prism vertex angle 26
`satisfies the above inequality (8), the totally reflected scat-
`tered light fiom the surface 42 is also totally reflected on the
`surface 43. And such prism plate makes it possible to
`prevent the light from being emitted in the ineffective range
`of visual angle that has been a problem inherent in the prior
`art, and further makes it possible to utilize the light that has
`hitherto been emitted to ineffective ranges of visual angle, as
`incident light that falls on the prism plate. This enables the
`light intensity within an effective range of visual angle to be
`increased substantially more than that of the prior art.
`In the above explanation, the material around the prism
`plate is, for example, air or vacuum whose refractive index
`is 1. If the material around the prism plate is another material
`(for example, liquid such as oil or water, or transparent solid
`matter such as resin or glass) whose refractive index is n‘, the
`inequality (8) should be rewritten to inequality (9) as fol-
`lows;
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`29>Z/a(1t/2+2><arcsin (:1 7n))
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`(9)
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`Because, when the light irradiated from a material 1 (whose
`refractive index is nl) to a material 2 (whose refractive index
`is n2), the relative refractive index n2,
`is n2/nl. We can
`obtain formula (9) by rewriting “l/n” to “n'/n” in formula
`(8)-
`Next, described below is the operation of the liquid crystal
`indicator element of this embodiment. The light emitted
`from the cold cathode-ray tube 1 is incident on the side
`surface of the lightguide plate 3 directly or after-reflected
`from the reflector plate 2, reflected by the reflection member
`4 applied to the lower side of the lightguide plate 3, and
`emitted from the upper side of the lightguide plate 3. The
`light emitted from the lightguide plate 3 is distributed
`through the scattering plate 5, and hence the light intensity
`is of a uniform distribution over a wide range of angles. The
`prism plate 6 utilizing the principles of the present invention
`emits light only within an effective range of visual angle, so
`that
`information is indicated through the liquid crystal
`indicator element 7.
`
`FIG. 3 is an enlarged sectional view of the prism plate 6.
`In this embodiment, the prism plate 6 is made of an acrylic
`resin and has a refractive index n of 1.585. By substituting
`the refractive index n=l .585 of the prism plate 6 for the right
`side of the inequality (8),
`2/3(1t/2+2xarcsin (1/n))=1l2.2 degrees
`Therefore, the inequality (8) becomes,
`29>112.2 degrees
`Thus, the vertex 26 of the prism formed on the upper side
`is set to an angle which is greater than ll2.2 degrees. For
`instance, 120 degrees (half vertex angle 6 is 60 degrees) is
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`desirable. Moreover, the pitch P of the prism is, for example,
`50 pm. In FIGS. 1 to 3, the shapes of the prisms are shown
`in an exaggerated manner with respect to the thickness of the
`prism plate. The prism plate has a thickness of, for example,
`1 mm.
`
`a light guide plate to transmit light irradiated from the
`light source,
`
`a scattering plate for scattering the transmitted light being
`located at a surface of the light guide plate,
`a prism plate having a plurality of prism-shaped protu-
`berances formed at a surface thereof and located at a
`surface of the scattering plate, and
`an indicator configured and arranged to be irradiated by
`the light from the prism plate.
`2. An information indicator according to claim 1, wherein
`a reflector is located at another surface of the light guide
`plate.
`3. An information indicator according to claim 2, wherein
`an angle 26 constituting said prism-like protuberance struc-
`ture is defined by theformula,
`
`29>‘/3X(7I:/2+b<arcsin (n 7n))
`
`where n is the refractive index of the prism plate, n' is the
`refractive index of a material in which the prism plate is
`arranged.
`4. An infonnation indicator according to claim 1, wherein
`the prism plate is configured to gather the light from the
`scattering plate so that there is no peak in the intensity of the
`outgoing light in the direction of the noneifective visual
`angle.
`5. An information indicator according to claim 4, wherein
`the noneffective visual angle is visual angle of smaller than
`about -60 degrees and greater than about +60 degrees.
`6. An information indicator comprising:
`a light source,
`
`a light guide plate configured to transmit light irradiated
`from the light source,
`
`a scattering plate located at a surface of the light guide
`plate configured to scatter the transmitted light,
`a prism plate having a plurality of cone-shaped protuber-
`ances formed at a surface thereof and located at a
`surface of the scattering plate, and
`an indicator arranged to be irradiated by the light from the
`prism plate.
`7. An information indicator comprising:
`a light source,
`
`a light guide plate configured to transmit light irradiated
`from the light source,
`a scattering plate located at a surface of the light guide
`plate to scatter the transmitted light,
`a prism plate having a plurality of pyramid shaped pro-
`tuberances formed at a surface thereof and located at a
`surface of the scattering plate, and
`an indicator arranged to be irradiated by the light from the
`prism plate.
`
`A solid line 50 of FIG. 5 represents the visual angle
`characteristic of the outgoing light of the prism plate 6 found
`by the ray trace calculation, similar to that of FIG. 7.
`Furthermore, a dotted line 71 corresponds to the visual angle
`characteristic of the scattering plate 5 as would occur when
`there is noprism plate 6, similar to that of FIG. 7, and shows
`a uniform distribution of light intensity over a wide range of
`angle of about i(plus/minus) 80 degrees. As shown by the _
`solid line 50 in FIG. 5, no light is enritted over inelfective
`ranges of visual angle of smaller than -60 degrees and
`greater than 60 degrees, and the electric power is thus not
`wastefully consumed. Even when viewed from these direc-
`tions, the indicator is not unnecessarily bright. Moreover, the
`effective range of visual angle is $45 degrees which is wider
`than the effective range of visual angle of ‘£35 degrees as
`shown by the solid line 70 of FIG. 7, and the luminance is
`increased by more than 1.4 times.
`The present invention is in no way limited only to the
`above-described embodiment, and the prism plate need only
`have a refractive index and a vertex angle which satisfy the
`inequality (8). Furthermore, the prism plate is not limited to
`the one that has a prism shape only in one direction as shown
`in FIGS. 1 and 2, but can be those of a pyramid shape as
`shown in FIG. 8(a) or a conical shape having a prism shape
`in cross section in two directions, which is shown in FIG.
`8(b). Moreover, the invention is not limited to the specific
`features shown in FIGS. 1 and 2, but can also include an
`embodiment in which the positions of the prism plate and the
`liquid crystal indicator element are exchanged. It is also
`within the scope of the present invention that the indicator
`can be a liquid crystal indicator of the back-light type as
`shown in FIGS. 1 and 2 of Japanese Patent Laid-Open No.
`67016! 1992.
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`10
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`15
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`20
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`25
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`30
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`35
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`In summary, the present invention provides an indicator
`which prevents light from being emitted into ineffective
`ranges of visual angle,
`increases the intensity of light
`emitted within an elfective range of visual angle, has a small
`thickness and consumes a small amount of electric power,
`and hence is particularly suitable for use in a portable
`information processor.
`Although the invention has been described and illustrated
`in detail, it is to be clearly understood that the same is by
`way of illustration and example, and is not to be taken by
`way of linritation. The spirit and scope of the present
`invention are to be limited only by the terms of the appended
`claims.
`We claim:
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`1. An information indicator comprising:
`a light source,
`
`8