CA1297672C - Display for contrast enhancement - Google Patents

Abstract

ABSTRACT

A display comprising optical means for presenting an absence of light over a controlled viewing angle and means for selectively scattering or transmitting light in response to a prescribed input to effect a display of information within said viewing angle.

Description

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A DISPLAY FOR CONTRAS~ ENHANCEM~NT

The present invention relate~ generally to displays, and more particularly to di~plays including an optical system for enhancing a display o~ information.

Visual display devices may utilize liquid crystals. The property of liquid crystals that enables thPm ~o h~ used in visual displays is t~e ability of liquid crystals to transmit llght in a ~trictly aligned or field-on ~tate, and ` ~ tQ ~catter light and/or to absor~ it (especially when comb~ned wlth an appropriate dye) in a relatively free or field-o~f stat~. ~n elsctric field may be ~electively applied acro~s the liquid crystal~ to switch between field-of~ and ~ield-on ~tates.

Frequently a v~sual display device using liquid crystals displays dark ~haracter6 on a gray or relatively light background. In such devices, it iF de~irable to improve ; the effective contrast between the characters displayed and the background, and to reduce or ellminate ~ront sur~ace : ylare from t~e display.

; ~ There ar ~hree categories of~ liquid crystal materials, namely, cholesteric, nematic and smectic. Th~ present lnvention relates in a pref~rred embodiment described hereinafter to the use of nematia liquid crystal which is operationally nematic. ~y 'loperationally nematic" is meant that, in the a~sence of ext~rnal ieldsl ~tructural dis-tortion of the liquid crystal is dominated by th~ ori~nta-.

7~72 tion of the liquid crystal at its boundaries rather than bybulk effects, such as very strong twists (as in cholesteric material) or layering (as in smectic material). Thus, for example, a liquid crystal material including chiral ingredients which induce a tend-ency to twist but which cannot overcome the effects of the boundary alignment of the liquid crystal material would be considered to be operationally nematic. A more detailed explanation of operation-ally nematic liquid crystal material is provided in U.S. Patent No. 4,616,903 in the name of Fergason, entitled ENCAPSULATED LIQUID
CRYST~L AND ~ETHOD, assigned to Manchester R&D Partnership. Refer-ence may also be made to U.S. Patent No. 4,435,047, issued March 6, 1984, in the name of Fergason, entitled ENCAPSULATED LIQUID
CRYSTAL ~ND METHOD, assigned to Manchester R&D Partnership.
The operationally nematic liquid crystal is contained in a containment medium that forms volumes of liquid crystal material.
The liquid crystal may be contained in discrete capsules or in a containment medium that tends to form a multitude of capsule-like environments wherein the capsules may be interconnected by channels containing liquid crystal material. In the field-off condition, or any other condition which results in the liquid crystal being in a distorted or randomly aligned state, the liquid crystal structure is distorted to a curved form (hence curvilinearly aligned) wherein the spatial average orientation of the liquid crystal over a capsule -like volume, for instance, is stronyly curved and there is no sub-stantial parallel directional orientation of the liquid crystal in the absence of a prescribed input.

Preferably, the operationally nematic liquid crystal has a positive dielectric anisotropy, and has an ordinary index ~ B

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of refraction that ~ubstantially matches that of the containment medium. Such material will cause ~cattering of light incident thereon in the field-off or relatively free ctate. This liquid crystal material, described in detail in the above-identified U.S. Patent 4,435,047, ~ay be designated encapsulated operationally nematic liquid crystal material or nematic curvilinearly aligned phases (9'NC~P") liquid crystal material~

The present invention, however, is not limited in use to NCAP con~igured liquid crystal. Cextain embodiments of the invention may be employed with any o~ the various types of liguid cryskal materials or configurations thereof that selectively scatter and/or absorb or transmit light in respons~ to a prescribed input.

Usually liquid crystal is anisotropic both optically and, for example in the ca~e of nematic liguid crystal, elec-trically. Th~ optical anisotropy is manifest by the ~cattering of light when the liquid crystal is in random alignment, and the transmission of light through the liquid crystal when it is in ordered alignment. The electrical aniaotropy may be a relationship betw~en the dielectric constant or dielectric coefficient with respect to the alignment o~ the liguid cry~tal ~aterial.

The present invention relates to improvements in displays as w~ll as to the utilization o~ the light ~cattering characteristic of liguid crys~al materials in displays.
The invention also relates to the use of ~uch materials and characteristics, for example, to obtain relatively dark characters or information displayed on a rela~ively bright background in both ~mall and large ~ize displays.
Additlonally, an embodiment of ~he presen~ invention provides a di~play in which front surface glare is all but eliminated.

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An object of the present invention is to provide a dis~
play having a relatively high ~uality of optical brightness and contrast.
Another object of the present invention is to provide a display including an optical system for enhancing the display of information, the information displayed being vividly contrasted to its background.
A further object of the present invention is to provide a liquid crystal display wherein focused light and scattered light are utilized to create a dark character on a very bright background.
A still further object of the present invention is to provide a display wherein front surface glare is all but eliminated.
According to the present invention there is provided a display comprising means for selectively scattering or transmitting light in response to a prescribed input, and optical means for Eocusing light transmitted b~ said scattering or transmitting means within a controlled viewing angle onto a light absorbing target means for enhancing the contrast of the display.
The invention further provides a display comprising:
means selectively operable for affecting light incident there-on by selectively scattering or transmitting light in response to a prescribed input; and reflecting means located on a non-viewing side of said select-ively operable means for focusing light transmitted by said select-ively opexable means within a prescribed viewing angle onto a tar-get means disposed between sald selectively operable means and said reflecting means for absorbing light incident thereon to enhance the contrast of the display. ~

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The invention also provides a display, comprising means selectlvely operable for affecting light incident thereon by selectively scattering or transmitting light in response to a prescribed input;
a target means located on a non-viewing side of said selectively operable means for absorbiny light incldent thereon;
and a lens means diæposed between said selectively operable means and said target means for focusing light transmitted by said selectively operable means ~ithin a controlled viewing angle onto said target means to enhance the contrast of tha display.
The invention further provides an apparatus for reducing glare comprising a light absorbing targek and a concave reflector means for focusing specular xeflection onto said target, said reflec~or means havlng a radius of curvature R and said target located on a vlewing side of said re~lector at a distance of between .4R and .5R there~rom and said target comprising vertically and horizontally extending light absorbing surfaces.
A liquid crystal means may be utilized for selectively scattering or transmittiny light in response to a prescribed lnpuk. The optical means may presen~ an absence of light over the view1ng angle by foausing light transmitted by the liquid crystal means onto a targe~ means. The llquid crys~al means may comprise NCAP light crystal. Ma~erials othex than liquid crystal, such as electrophoretic materials, which scatter light on one hand and transmlt it on the oth~r, however, may also be utilized in ~he contexk o~ the present invention.

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The target means may comprise a black absorber for absorb-ing at least substantially all of ths light incident thereon. The optical means may comprise a reflecting concave means for focusing light transmitted by the liquid crystal means wi~hin a controlled viewing angle onto a target means disposed between the liquid crystal means and the reflecting means.

In another embodiment, the optical mean~ may comprise a lens means di6posed between the liquid crystal means and the target means for focusing light ~rom an ob~erver within a prescribed viewing angle onto the target means. This embodiment also is preferably illuminated from the rear.

In yet another embodiment, the optical means may comprise a concave reflector means located on a non-~iewing side of the liquid crystal means to focus light onto a light absorbing target means located on a viewing side of the liquid crystal means. The reflector means and the liquid crystal means present a concave surface to light incident thereon. This embodiment not only enhances contrast but eliminates front surface glare.

The concept of this embodiment provides a method and apparatus ~or reducing glaxe from a display hy focusing specular reflection from a aoncave reflecting surface onto a light absorbing target means. This embodiment is not limited to u~e with materials that transmit or scatter light in response to a prescribed input. The concave configuration of this embodimen~ pxovides ~or glare reduction in both elec~ro-optical and non-electro-optical devices. For example, the concept of this embodiment may be utilized to reduce glare from a white-faced chalkboard or a glossy-faced sign.

The prescribed input is pre~erably o~ the electroma~netic type and, more particularly, an electric field. The ~7i~7~

apparatus may include electrodes ~or applying the electric field. The electrodes may be located on opposite sides of the liquid crystal means. Substantially optically trans-parent substrate means may support ~he electrode means, and a circuit means may be provided to selectively energize the electrode means to apply the electric ~ield.

In accordance with one aspect of the present invention, a liquid cryætal display, 8uch as a billboard, can produce relatively dark characters, information, etc. on a rela-tively bright or white background. The bright backgroundmay be produced by liquid crystal material that is randomly aligned in the field-off state wherein light incident on the liquid crystal material is scattered. The dark char-acter is caused, ~or example, by liquid crystal material 15 that ls in a field-on ~tate or in ordered alignment and, thus, substantially optically transparent such that inci-dent light is appropria~ely focused onto the target means.
When the liquid cry~tal material is randomly aligned, only the relatively bright background appears. When a selected portion of the liquid crystal material is orderly aligned, a very dark charact2r may appear against the very bright background to an observer within the viewing cone or viewing angle of the display. The foregoing may be accom-pli~hed u6ing relatively low power re~uirements and minimum liquid crystal material.

The display of the present invention will be described in more detail hereinafter in conjunction wi~h the drawings wherein:

Figures 1 and 2 are schematic YieWS that illustrate a liquid crystal apparatus in the ~ield-off and field-on states, respectively, that may be utili~ed in ~he present invention:

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Figure 3 i~ a schematic t side elevational v~ew illustrating one embodiment of the di~play o~ the present invention;

Figure 4 i6 a ~chematic ray trace illu~trating the opera-tion of the embodiment of Fisure 3;

Figure 5A i6 a schematic, ~ide elevational view illustra-ting another embodiment of the display o~ the present invention;

Figure 5B i6 a perspective view illustrating a further embodiment of thP display of ~he present invention:

Flgure 6 i8 a schema~ic ray trace illustrating the opera-tion o~ the embodiment of Figure 5B:

Figure 7 is a schematic, side elevational view illu~trating yet another embodiment of the display of the present invention;

Figure 8 i~ a front elevational view of the embodiment of Figure 7: and Figure 9 i~ schematic ray trace illustrating the operation of the embodiment of Figures 7 and 8.

Referring now to the drawings, attention is first directed to Figures 1 and 2. Figures 1 and 2 show a liquid crystal apparatus indicated generally by reference numeral 10. The apparatus includes a layer or layers of liquid crystal 11 supp~rted on a 6ubstrate 12 having an electrode 13 located thereon. The apparatus may further include a ~eoond ~lectrode 14 mounted on a ~ubstrat2 1~.

The liquid crystal may comprise any liquid cry~tal material or configuration of liquid cry~t~l material which selec-tiv~ly 6catters or txansmit~ light in respons2 to a pre-. ~

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~cri~ed input. For exampl~, the liguid crystal may ~yconfigured as a twisted nematic apparatus. In a preferred embodiment, the liquid crystal is configured in a curvilinear manner (NCAP). A primary feature of the pre~ent invention i6 that the liquid crystal material will scatter light impinging thereon when in a field-o~f or random alignmen~ e~a~e, and in the field-on or orderly aligned ~tate the liquid crystal material will be ~ub-stantially optically transparent.

Additionally, materials other than liquid crystal which scatter light on one hand and transmit it on the other in response to a prescribed input ~ay ~e utiliz~d in the context of the present invention. For instance, an electrophoretic material may be used.

~he use of NCAP configured liquid crystal permits 6ub~trates 12 and 18 to be flexibleO This allows, as will be discussed in more detail below, the construction of a display in which front ~urface glare is all but eliminated.
Particularly, the NCAP configured liquid crystal material disposed between the ~lexible electrode-coated substrates provide~ a flexible film that may be utilized to form a curved ~ront ~urface of a display.

A voltage may be applied to electrode6 13 and 14, and hence across liquid crystal 11 ~rom a conventional voltage source 16. Voltage source 16 may be connected to the electrodes by electrical leads through a 6witch 17. When the switch 17 i5 closed, the electrod0s axe energized and apparatus 10 i~ in a field-on 6tat~ with the molecule~ of the liquid crystal material in the desired alignment to permit the tran mission of ligh~. When the switch is open, the : electrodes are de-energized and apparatus 10 is in a fi~ld-of~ state 6uch that the liquid crystal scatters light.

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The NCAP configured liquid crystal material, which is schematically illustxated in Figures 1 and 2, may include a liquid crystal material 20 more or le~s contained within the confines or the in~erior volume 21 of a capsule 22 or an encapsulating medium. The NC~P configured liquid crystal material comprise~ a plurality of 6uch capsules or an encapsula~ing medium in which liquid crystal material is dispersed.

Each capsule may be discrete or alternatively the liquid crystal material 20 may be contained in a containment medium 23, such as a latex medium as will be hereinafter discussed, that tends to form a multitude of capsule-like environments containing the liquid crystal material. In this regard, the liquid cry~tal material 20 may be more or less con~ined to an approximately spherical or otherwise curvilinear surface of a containment cavity. Such cavi-ties, however, may be interconnected, for example, by one or more channels or passages. ~he liguid crystal material would preferably be in both the discrete volumes or cavi-ties and in the interconnecting passages. Thus, theinternal volumes o~ respective aapsules may be fluidly coupled v.ia one or more interconnecting passages. All of tha aspects and features of the present invention vis-a-vis individual unconnected cap~ule6 have been found to be applicable to an arxangement of cap6ules that have one or more interconnecting pas~ages.

Preferably, liquid crystal material 20 is nematic liquid crystal material having positive dielectric anisotropy.
Nematic liquid crystal material has ~luid-like properties that facilitate the conformance or the distortion thereof to ths 6hape of the capsule wall in the absence of an electxic fiel~. On ~he other hand, in the pre ence o~ an - electric field 6uch nematic material will relatively easily change to ordered alignment with respect to such field.

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Li~uid crystal material o~ a type other than nematic or combinations of var.ious types of liquid crystal material and/or other additives may be used with or substituted for the nematic liquid crystal material as long as it i~
operationally nema~ic in ~he containment medium. However, cholesteric and smectic liquid crystal material generally are bulk driven. It is more difficul~ to break up the bulk structure thereof for conformance to capsule wall shape and energy considerations in the capsule.

As shown in Figure 1, in the fi~ld-of~ ~tate, the molecules o~ liquid crystal, depicted as dashed lines, conform to the shape of the cavity containing the liquid crystal. The directional orientation of a layer of liquid crystal molecules may be distorted to curve in the direction that is parallel to a proximate area of the wall surface 25 of a cavity. More generally, all that is required is that ~he interaction between the cavity wall 25 and the liquid crystal material 20 produces an orientation in the liquid crystal near that wall that i~ generally uni~orm and piecewise aontinuous, so that the ~patial average orien-tation of the liquid crystal material over the capsule volume is strongly cur~ed and there is no substantial parallel direction of orientation o~ the liquid crystal structure. It is ~his strongly curved orientation that results in the scattering and polarization insensitivity (the liquid crystal material is insensitive to the direc-tion of optical polarization ~ incident light) in the ~ield~off condition.

In the field-on condition (See Figure 2), or any other condition which results in the liquid cry6tal being in ordered or parallel alignment, the li~uid cry~tal material 20 will transmit æubstantially all the light incident thereon and will t~nd not to ~e visible. The light that is transmittd is ~ha~ which is ~ocused onto a target means to optically enhance a display, as discussed below. On the 3~7~;7~

other hand, as noted, in the ~ield-off condition when the liquid crystal is in distorted or random alignment, some of the incident light will be absorbed, but most of the incident light will be scattered.

The index of refraction of containment ~edium 23 and the ordin~ry index of refrac~ion (the index when an electric field i8 applied) of the liquid crystal material 20 ~hould be matched as much as possible when ln the fi~ld-on ~tate to avoid cattering. However, when the liquid crystal material i~ in the field--off ~tate, there will be a differ-ence in the indice~ of refrac~ion at the boundary of the liquid crystal material 20 and the wall of capsule 22, for example. Specifically, the extraordinary index of refrac-tion (the index with no electric field) of the liquid crystal is greater than the index of refraction of medium 23. This causes refraction at that interface or boundary and, thus, scattering.

As long as the ordinary index of refraction of the liquid crystal material is closer to the index of refraction of the containment medium, than is the extraordinary index of refraction, a change in ~cattering will result when going ~rom field on to field-off 8tate5, and vice-versa. For any given index of refraation, maximum contrast results when the ordinary index of refraction of the liquid crystal matches the index of re~raction of the medium. ~he close-nes~ of the index matching wlll be dependent on the dasired degree of contra6t and tran~parency in the device, but the ordinary index of refraction of the liquid crystal and the index of the containment medium will preferably diffQr by no more than 0.03, more pre~erably, 0.01, especially 0.001.

Preferably, the electric field E ~See Figure 2) i appliedto the li~uid cry ~al ma~erial 20 ~or the most part rather than ~eing di~sipated or dropped substantially in the containment medium~ There ehould not be a substantial -12~
voltage drop across or through the material o~ which the containment medium is formed. Rather, the voltage drop should occur across the liquid crystal material 20 within the volume 21 of the capsule 22.

Additionally, the electrical impedance of the containment medium preferably should in effect be large enough relative to that of the liquid crystal such that a short circuit will not occur exclusively through the medium to bypass the liquid crystal.

The dielectric constant of the material of which the containment medium is formed and the dielectric coefficient of the liquid crystal, and the effactive capacitance values of the containmen~ medium, par~icularly in a radial direc-tion, and o~ the liguid crystal material across which the electric ~ield E is imposed, all should be so related that the containment m~dium does not substantially drop the magnitude o~ the applied electric ~ield E. Ideally the capacitance dielectric con~tants (coe~ficients) of the entire layex of NCAP liquid arystal should be substantially the same for thz field-on condition.

Tha liquid crystal ma~erial 20 will have a dielectric coefficient value that i8 anisotropic. It is preferable that the dielectric constant of the containment medium be greater than the dielectric coefficient of th~ liquid crystal material 20. The differential between the dielectric coef~icient for the li~uid crystal material 20 when no electric field is applied, which should be rather small, and the dielectric coe~ficient ~or the liquid crystal materlal when it is aligned upon the application of the elec~ric field, which should be rela~ively large, Ghould be a~ large as possible. ~he critical relationship of diel~ctric values an~ applied electric ~ield should be such that the field ~pplied across the liquid crystal material in the containmen~ me~ium is adequate ~o cause 7~
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alignment of the liquid crystal with respect to the field.
The relationship between the dielectric constant of the containment medium and the dielectric coefficient of the liquid crystal 20 may be achieved when the liquid crystal has a positive dielectric anisotropy.

In accordance with the present invention, ~ubstrates 12 and 18, and electrodes 13 and 14 are optically tran~missive so that liquid crystal apparatus 10 can control the trans-mission of light therethrough in response to the applica-tion of an electric field. Electrode 13 may, for 2xample,form a ~ingl~ common electrode surface while electrode 14 comprises a patterned electrode having multiple electrode portion~ that can be ~electively energized to apply the electric field to selected portions of the liquid crystal material. For instance, as is well known in the art, electrode 14 may be divided into ~even electrically isolat-ed segments, each of which may be selectively energized to di~play various numerical characters. ~lectrode 14 could alGo be configured to form a dot matrix display comprising a plurality o~ ~o~s or pixels arrange~ in column and rows.
A row is enabled to accept display information in parallel via the column lines.

Preferably, a plurality of NCAP liquid crystals are applied to substrate 18 in a manner such that the NCAP liquid crystals adhere to electrode 14 and substrate 18. The material of which capsule 22 is formed is suitable for binding or otherwise adhering the capsule to the electrode and/or sukstrate. In one embodiment, capsule 22 is formed of a polyvinyl ~lcohol (PVA). In a preferred embodiment, the li~uid cry~tal material is dispersed or entrapped in a latex containment mediumO In elther embodimen~, eubstrate 18 may be a polyester film, ~uch as MylarR, t~at has been precoated with a layer o~ indium tin oxide (IT0) to form electrode 14. Preferably, the film has been precoated with a 90 ~o 500 ohms per square layer of IT0~ and most prefer-ably with a 450 + 150 ohm~ per ~quare layer of IT0. Of :

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course, materials other than ITO may be used to form the electrodes of the apparatus of the present invention. A Mylar film with a precoated ITO electrode, known as Intrex, may be purchased from Sierracin of Sylmar, California. Such an electrode-coated film is very flexible.
As noted, latex entrapped NCAP liquid crystal is used in a preferred embodiment. Latex entrapped NCAP liquid crystal com-prises the entrapment of liquid crystal in a latex medium. The latex is a suspension of particles. The particles may be natural rubber or synthetic polymers or copolymers. A latex medium is formed by drying a suspension of such particles.
Briefly, latex entrapped NCAP liquid crystal may be form-ed by mixing a suspension of latex particles and liquid crystal material wherein the liquid crystal material has been previously emulsified in an aqueous phase. Alternatively, all components may be combined prior to emulsifying the liquid crystal material. The mixture may then be applied to substrate 18 and electrode 14. As the mixture dries, it adheres to the electrode-coated side of the polyester film. When dried, the latex particles form a latex medium 2Q with particles of liquid crystal dispersed therein.
A specific method for making latex entrapped NCAP liquid crystal may comprise first emulsifying 36 grams of the liquid cry-stal ROTN701 (manufactured by Hoffman La Roche of - 1~ --~1 New York, New York) ~n a solution containing 14 grams of a 12% aqueous solution of PVA and 1 gram of the Rurfactant TWEEN 20 (available through ICI Americas Incorporated of Wilmington, Dalaware). The liquid crystal is added contin-uously while the solution is mixed with an impeller blade at 3500 RPM. When the particle ~ize of the liquid crystal is about 1-5 microns, 49 grams of Neorez R-967 (manu-factured by Polyvinyl Chemical Industries, Wilmington, Massachusetts), containing 40% latex particles by weight, is added with slow mixing of less than 1000 RPM until the mixture is homogenous. This material may then be cast with a doctor blade or other sui~able means onto subs~rate 18 and electrode 1~.

After the NCAP liguid crystal material has dried onto electrode 14 and substrate 18, 6ubstrate 12 and electrode 13 may be laminated onto the surface of the latex entrapped NCAP liquid crystal material. Substrate 12 may also be a flexible, MylarR film precoated with a 90 to 5000 ohms per square, most pre~erably a 450 ~ 150 ohms per square, layer o~ IT0 to form electrode 13.

In accordance with an aspect of the present in~ention, lightl ~or example that represented by a light beam 19 (see Figures 1 and 2), incident on the liquid crystal material will be scattered to yield a white or bright appearance from a viewing area or side 30 when the liquid crystal is in a ~ield-off or random alignment state, and a dark appearance when the liquid crystal material, or a selected portion thereof, is in a field-on or ordered alignment state. The present invention enhances the effective contra~t between the characters or information displayed and the background.

It is noted ~hat light inciden~ on apparatus 10 will be refracted, due to a mismatch in indices of refraction, as it passes through the di~ferent material~ that comprise s ~ ~

apparatus 10. Apparatus 10 may be used, for example, in an air environment, represented by the reference numeral 40.
The air forms an interface 42 with the substrate 12 at the front side or from the viewing direction 30.

As shown in Figure 1, the liguid crystal material 20 is in a random alignment when in the field-off state. Incident light beam 65 enters substrate 12 a~ the interface 42 and is refracted, (see light beam 65a) ultimately impinging as incident light beam 70a on the layPr of liquid crystal.
The random or distorted liquid crystal material will scatter the light incident thereon There are several possibilities of how such incident light beam 70a would tend to be scattered.

For example, one possibility is t~at the incident light beam 70a will be directed according to ~he dotted line 70b through the layer of liquid crystal material toward the non-~iewing side 32 thereof. Llght beam 70b may impinge, as will be disaussed below, on a xeflective surface at the non-viewing side to be reflected a~ light beam 70c back to the layer of li~uid crystal material where it will be treated as ano~her independently incident light beam thereto, just like the light beam 70a from which it was derived. ~here~ore, such light beam 70c will undergo scattering, further enhancing the brightness of the back-ground of the display.

Another possibility is that the in¢ident light beam 70a, orthat derived there~rom, such as the light beam 70c, will be ~cattered toward the interface 42 at an angle that is so nlose to normal at tha~ interfaca that the light beam will pass through the interface 42 into the medium 40 to be vi~wed by an ohserver or ob erving instrument. Light beam 70d represents such a light beam emi~ed from ~he apparatus 10. It is that ligh~, for example, the sum of such emitted light beams 70d, which exits at the interface 42 that causes the liquid crystals to give the appearance of a white or bright background when viewed from the viewing side 30.

Referring to Figure 2, the ~ield-on or ordered alignment state and operation of the liquid crystal apparatus are shown. Particularly, an electric field E has been applied between electrode 13 and electrode 14. For instance, if electrode 14 is con~igured to form a figur~-eight p~ttern, selected conductive se~ments may be energized to display the desired numeral. The light beams 72 and 74, for instance, would be transmitted through the aligned and, thus, ~ffectively transparent or non-scattering liquid crystal material located be~ween the energized electrodes.

Light beams 72 and 74 will be focused, as disaussed below, by an optical means on a target means. The sum of such focused light beams display the ~elected numeral, character or other information to an observer at the viewing location 30. Particularly, to an observer at viewing side 30, the area between the energized electrodes may appear very dark wherein the light beams are ~ocused onto a target means comprising a black absorber ~or absorbing at least substan-tially all of the light incident thereon.

The li~uid crystal material that is not located between the energized electrodes is still in the field-of~ state.
Thus, that material still ~catters light incident thereon from bokh the viewing and non-viewiny sides. Th~refore, the numerals or o~her infvrmation displayed appear as very dark characters against a very brilliant or white back-ground.

One embodiment o~ the present invention is illustrated in Figure 3. This embodiment includes a li~uid crystal apparatus 10 as part o~ a laminated display assembly comprising a target means 50 and a re~lecting means 52.

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The target means and the reflecting means form a back plane of the display. Light incident on apparatus 10 from the front or viewing side 30 thereof i~ either ~catt~red or transmitted thexethrough. ~he transmitted light iB focused onto the target means by the reflecting m~ans. Whether such incident light is focused or defocused (scattered) depends on whether an electric field is applied to the liquid crystal or some portion thereof.

The reflecting means may comprise an array of cylindrical mirror~ 54 having a radius of curvature R. Mirrors 54 present a concave sur~ace to light incident thereon. The mirrors may be formed by partial cylinders; for example, they may be formed from one-eighth to one-quarter cylinderæ. The dimensions of the mirrors in the "x" or horizontal direction is substan~ially equal to the dimension of the display in that direction. The number of mirrors in the array is dependent upon the height or dimension o~ the display in the "y" or vertical direction.

The target means is disposed between the reflecting means and the liquid crystal means. The target mean~ may com-prise a plurality of black stripes 56 ~or ab~orbing sub-skantially all of the light incident thereon~ Stripes 56 may be formed on an optically transparent substrate 57.
Alternatively, for a colored display, the target means could comprisP colored stripes for absorbing only one or more specified wavelengths of liyht.

Targets 56 may be located at a distance "d" o~ be~ween .~R
and o5R from mirrors 54 (See Figure 4). Most preferably, targets 56 are located inwardly of the focal point of the mirrors. Optimally, in order to prevent the phenomenon of coma, they are located at a di6tance S'd" of .469R from the mirrors.

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The targets' dimension in the "x" direction i~ substan-tially equal to ~he dimension of the mirrors in thak direction. AS a result, the viewing angle o~ the display in the "x" direction or plane is approximately 180. For instance, if the display is located in a room, an observer at the front or viewing side 30 of the display would be able to see the information displayed, ignoring ~or the moment the limitation on the viewing angle in the "y"
direction, from a wide angle wlthin the room.

The angle of view i'A" of the display in the "y" dir ction or plane is limited. This angle of view is dependent upon the height "h" of the target (See Figure 4). Particularly, the greater the height "h" the wider the angle of view IlA".
Mathematically, the angle o~ view "A" is represented by the equation 2 arctan h/2f where "h" is the height o~ the target and "f" is the focal length of the mirrors of the optical system. As is known, f = R/2.

Therefore, an increase in the viewing angle "A" may be obtained by increasing the height of the target. An increase in the viewing angle is, however, achieved at the expense of a loss of contras~ between ~he informa~ion displayed and its background. That is, the taller the target the less bxilliant is the display. A good trade off between viewing angle and contrast is obtained for a target height "h'l oE about 0.125R. This height provides a viewing angle "A" of approximately 20 (+ 10), and the loss of brightne~s of the display is only about 20~. A viewing angle "Ai' of ~ 10 is suitable fox most applications, for example, hillboard displays which are viewed from relatively long distances and au~omobile dashboard displays which are viewed at relatively short distances. Generally ; speaking, if a display is ko be viewed from a relatively short distance, the viewing angle "A" should b~ wider than a display which is to be viewed at a relatively long distance.

The liqui~ crystal apparatus 10 i~ preferably located at a distance R from mirrors 54. As noted, light transmitted by apparatus 10 is focused onto a target disposed between a mirror and the salected portion o~ the liquid crystal apparatus 10 to which a prescribed ~nput, ~uch as an electric field, has been applied.

The ray trace of Flgure 4 illustrates that light, repre-sented by light beams 58a, transmitted by the liquid crystal apparatus in the field-on state impinges on the concave surfaca of mirror S4 disposed in back of the eneryized portion of the liquid crystal apparatus. This light i~ focu~ed, as illustrat~d by light beams 5~b, onto target 56~ More particularly, within a prescribed viewing angle or viewing cone "A", light ~rom an observer or observing instrument 90 from viewing side 30 of the display is ~ocused onto the target. Thus, if the target comprises a black absorber, the information displayed by the ener-gized porti~n of the liquid crystal will appear as a very dark character, numeral, etc. against a very white or brilliant background to an observer 90 within the pre-scribed viewing angle. The appearance of the display is further enhanced by the fact that some o~ the light imping-ing upon the reflecti~g means will be reflected back to the liquid crystal apparatus to undergo scattering~ thereby further increasing the brightness o~ the display.

~he display assembly illustrated in Figure 3 may be structured in an air environment. However/ improved result~ ars obtained, in the sense that the angle of view is increased, if the a~sembly, including th~ liquid crys~21 means, the target means and ~he re~lectors, are support~d and contained in a support medium 60 having an lndex of refraction greater than tha~ o~ air. Thus, ~upport medium 60 may be ~ormed of such materials as acrylic, polyvinyl alcohol, or polycarbonate.

:
.
, - . .
- . `

- . :

7~
. .

The above assembly may form one of a plurality of modules which can be stacked in rows and columns to form a larger display. An illumination source on the v$ewing side of the display may also be provided to enhance the appearance of the display, ~hat i~, ~h~ con~rast between the character or other information displayed and the background.

Figures 5A and 5B illustrate alternate embodiments o~ the present invention. These embodiments include a lens system 62, preferably comprising convex lenses, disposed between liquid crystal apparatus 10 and a target means 64. These embodiments also preferably include a backlighting scheme represented by light source~ 2~ an~ di~user 29 (not shown in Figure 5B).

As shown in Figure 5A, the lens system 62 may comprise an array of spheres 66 stacked on top of and adjacent to one another to form a plurality of columns and rows of spheres.
Alternatively and more preferably, as shown in Figure 5B, lens system 62 comprises a plurality of cylindrical rods 75 dispo~ed adjacent to one another. The lens means (the rods or spheres) may be foxmed from such materials as acrylic, polyester, polystyrene, glass, polycarbonates, or various other optically ~ransmissive materials.

In the embodiment of Figure 5A, the targets comprise a plurality of ~pots or dots 68 located at the backside o~
2~ each of the spherical lenses. Preferably, spots 68 are located at the focal point of the lenses, and ~re thus spaced from the back ~urface of the lenses for optimum results. In such an arrangemen~, the ~arget~ or spots 68 may be ~ormed in the ~upport medium mean~ 60, or in a ~ubstantially optically ~ransparen~ 6ubstrate located behind the lenses. ~n accep~able display is al80 obtained if the dot~ are formed on the back surface~ of the spheres.
As di6cu~sed heretofore, the targets may comprise black or colored absorbers.

. ~9~ ~2 In th~ embodiment of Figure 5B, the targets may romprise a line or stripe 77 extending along the back ~ur~ace of each cylindrical rod 75. Optimally, stripes 77 are spaced from the back ~urface of the rods to be located at the ~ocal point thereof. The ~tripes, however, may be coated on the back ~urface of the cylindrical rods. Stripes 77 may be black or colored ahsorbers.

The angle of view or viewing cone of the displays of Figures 5~ and 5B in the "y" direction is limited and dependent upon the ~ize of their re~pective targets. The angle of view in the "x" direc~ion o~ ~he embodiment of Fi~ure 5B is approximately 180 as discussed with respect to the embodiment of Figure 3. ~he angle of view in the "x" direction of the embo~iment of Figure 5A i8, however, limited by the size of the target. For a circular spot or target, the angle of view in the "x" diraction is equal to the angle of view in the "y" direction.

The ray trace of the embodiment o~ Figure 5B is shown in Figure 6. The height "hl" of the respective ~tripes 77 determines the angle of view "B" of the display in the "y"
direction. The greater the height "hl" the larger is tha angle of view. However, as discussed previously, an increase in the angle of view is achieved by a decrease in the brightness of the display.

In the embodiment of Figure 5B, ~or an angl~ of ~iew of 20 (+ 10), the height "hl" of stripes 77 i8 approximat~ly equal to one-sixth the diame~er of cylindrical rods 75. In the embodiment of Figur~ 5A, to achieve approximately the same angle of view, the angle of vlew in the ~Ix~ and 9'y"
directions being equal for a circular target, the diameter of spots 68 may be approximately one-sixth the diàmeter of ~` spheres 66. The embodiment of Figure 5A iG especially suitable for displays that are to be viewed by an observer at a relatively fixed position, for instance, an automobile .

.

~7~2 .

dashboard display. This embodiment is less ~uitable for displays which are to be viewed from widely-varying positions in the "x" direction, for example, a 6coreboard di~play.

The liquid crystal means o. either embodiment i~ preferably spaced from the lens ~ystem a distance approximately egual to twice the diameker of the spheres or cylindrical rods.
Such positioning provides better uniformity o~ illumina-tion.

As noted, tha embodiments o~ Figures 5~ and 5B preferably include a backlighting scheme represented by light sources 28 at the back or non-viewing side 32 of the di~play (See Figure 5A). The backlighting scheme may include a diffuser 29 to soften the light ~rom illumination ~ources 28. The backlighting scheme is utilized to overcome front æurf~ce ylare, and to enhance the appearance of the di6play especially when operated other than in bright sunlight.

The light provided by light sources 28 is scattered by the liquid crystal of apparatus 10 in the field-off state to increase the brightness of ~he background of the display.
If the liquid crystal is in the field~on state, the back-light is invisible to an observer ~0 within the prescribed viewing angle "B." Such an observer i8 only able to see the black image Pstablished by the lens system and the target means. Particularly, the target means obscures the light from illumina~ion sources 28 and the lens sy~tem ~ocu~es the parallel light rays, represented by rays 67a tSee Figure 6), originating from an observer within the prescribed viewing angle "B" onto ~o the target means as 30 shown by ligh~ beams ~7b. Therefore, to an observer 90 within the viewing angle IIBII, the charactars or other - in~ormation in back of the ~elected energized portion of the liquid crystal will appear very dark agains~ a very white background.

6~
", The embodiment illustrated in Figures 7 and 8 is an improved display that eliminates front surfac2 glare. This embodiment utilizes the ~lexible nature of the substrates between which the NCAP liquld crystal i5 disposed to eliminate front ~urface glare. Liguid crystal apparatus not utilizing ~lexible substrates could not perform satisfactorily in this embodiment.

The NCAP liquid crystal apparatu~ lO, which comprises a ~lexible film, i6 formed to present a concave surface to incident light, such as that repre~ented by light beam 19.
Disposed immediately hehind the NCAP liquid crystal appara-tus is a reflector means 80 presPnting a concave, reflect-ing surface to incident light. The reflector means may comprise a positive concave mirror having a radius of curvature R. The radius of curvature o~ the NCAP apparatus would also be R.

The re~lector means 80 may be constructed by coating ~h~
surface of a substrate 80a, such as one made from glass, metal or plastic, with a thin layer of a reflecting metal 80b, such as aluminum or silver. The electrode 14 of NCAP
apparatus lO may be formed on substrate 18, and reflector means 80 suitably laminated to that substrate. Alterna-tively, substrate 18 may be eliminated, and electrode 14 ~ormed on the surface of the reflector means by etching that surface to form the desired electrode pattern.

A target 82 is disposed in ~ront of or on the viewing sid~
30 o~ the liquid crystal apparatus. The target may be located at a distance "d2'~ of betwePn .4R and .5R from : reflector ~0. Preferably, the target is located inwardly of ~he focal point of reflector 80 at a distance of .469R
~rom the reflector. In a pre~erred embodiment, the target is L-shaped comprising vertical and horizon~al surfaces 82a and 82b, respectively. These ~urfaces may comprise black or colored absorbers.
; , , ~
~, . . . .

7~72 The viewing angle in the "x" direction of the display is a function of the width "w2" of Rurfaces 82a and 82b. For a viewing angle of 90, the width "w2" is preferably equal to tha width of the display plus the radius of curva~ure R of r~flector means 80. Particularly, 6urfaces 82a and 82b extend beyond the display by a distance R/2 at each side thereof such that the dimension ~Iw3~ is equal to R/2 (see Figure ~).

The height "h2" of surface g2a and th~ length "12" of surface 8~b (See Figure 8~ det~rmine ~iewing angle "C" in the "y" direction. For a viewing angle "C" o~ 20 (+
10), the height "h2" is approximately 0.0625R, and the length "12" of horizontal surface 82b is approximately .lR
or greater. The angle of view "C" is related to the height of the ~arget by the equation 2 arctan h2/2f where "~" is the focal length o~ re~lector means 80.

~he taxget 82 may be modified by replacing the horizon~al and vertical absorbing surfaces with a single vertical absorbing surface located at approximately the focal point of the reflector. For a vîewing angle in the "y" or vertical direction of 20 (+10), the height of the single vertical surface would be approximately 0.125R. The width of such a vertical surface determines the angle of view in the "x" direction, as discussed with respect to surfaces 82a~ B2b. The target may also include a hood for shielding the light-absorbing ~ur~aces o~ the target from direct sunlight. For instance, a hood 86 may be utilized to shield surfaces 82a and 82b.

As shown by Figure 9, light incident on the display, represented by light beams 85a, within a controlled viewi~g angle "C" impinges on the reflecting surface of reflac~or 80 where it i5 focused onto the horizontal and v~r~ical surfaces of target 82, as shown by light beams 85b. The light that is focused on the ~arget, where the target is a ~lack absorber, presents an extremely dark image or display to an ohserver 90 within the prescribed viewing angle.

The glare on the ~ront surface of the display of this embodiment is specular. This embodiment eliminates that glare by focusing it onto the target, or at least the glare at tha energiæed portion of the NCAP liquid cry~tal. The glare at tha de-energized portion of the liquid crystal is not a problem.
.

The glare-reduction display of Figure 7 ~s well as ~he other embodiments discussed are adaptable to such displays as outdoor billboards, indoor display signs, automobile dashboard displays, window mounted displays, gas price signs, time and t~mperature signs,and scoreboards both portable and fixed.

Ideally, if the display of in~ormation is to b observed from above, the targat should be located at bottom of the display. Conversely, if the display of information is to be observed from below, the target should be a~ the top of the display. The embodiment ~epicted in Figure 7 may be utilized~as billboard which would be observed ~rom below the display. In thia embodimant, the target is located at the bottom of the display to prevent shadows from being cast onto the displ~y, which is contrary to the preferred arrangement of the target and the display.

The display of Figure 7 may use cylindrical, hyperbolic, parabolic, or elliptical cross sections to reduce target size or improve the dimensions of the display apparatus. A
support medium means 60 may be used to support and contain the reflector and liquid crystal means.
.~ f~
~s noted, presen~ invention ie not limi~ed to use with liquid crystal materials. The ~mbodiment of Figure 7, for instance, may be used to reduce or eliminate specular glare ' A

~76 ~

from almost any type of display where such glare is a problem, ~or example, a white-faced chalkboard or a glossy-faced billboard. In this context, this embodiment will comprise a light absorbing target and a concave reflector means for focusing 6pecular reflection onto the target.

p-~ The present inven~ion may also be used in~alternate embodi-ment wherein bright characters are displayed on a rela-tively dark background. In such an embodiment, the liquid crystal material located in the display segments used to form the character or information di~played would be in a field-off state such that light is scattered to create characters having a bright appearance. The liquid crystal material in the display segments surrounding tha character segments would be in a field-on state such that light is appropriately focused onto ~uitable targets to create a relatively dark background.

Although certain specific embodiments of the invention have been described herein in detail, the invention is not to be .limited only to such embodiments, bu~ rather only by the appended claim~.

Claims (52)

1. A display comprising means for selectively scattering or transmitting light in response to a prescribed input, and optical means for focusing light transmitted by said scattering or trans-mitting means within a controlled viewing angle onto a light absorb-ing target means for enhancing the contrast of the display.

2. The display of claim 1 wherein said scattering or trans-mitting means comprises a liquid crystal means.

3. The display of claim 2 wherein said liquid crystal means comprises at least one layer of nematic curvilinearly aligned phases liquid crystal material.

4. The display of claim 1 wherein said optical means has a focal point and said target means is located at approximately said focal point.

5. The liquid crystal apparatus of claim 4 wherein said target means comprises a black absorber for absorbing substantially all of the light incident thereon or a colored absorber for absorb-ing only one or more specified wavelengths of light.

6. A display comprising:
means selectively operable for affecting light incident thereon by selectively scattering or transmitting light in response to a prescribed input; and reflecting means located on a non-viewing side of said select-ively operable means for focusing light transmitted by said select-ively operable means within a prescribed viewing angle onto a target means disposed between said selectively operable means and said reflecting means for absorbing light incident thereon to enhance the contrast of the display.

7. The display of claim 6 wherein said selectively oper-able means comprises a liquid crystal means.

8. The liquid crystal apparatus of claim 7 wherein said liquid crystal means comprises at least one layer of nematic curvi-linearly aligned phases liquid crystal material.

9. The display of claim 6, 7 or 8 wherein said reflecting means comprises a crylindrical mirror presenting a concave surface to incident light and having a radius of curvature R.

10. The display of claim 6, 7 or 8 wherein said reflecting means comprises a cylindrical mirror presenting a concave surface to incident light and having a radius of curvature R, and said target means is located a distance approximately R/2 from said mirror.

11. The display of claim 6, 7 or 8 wherein said reflecting means comprises a cylindrical mirror presenting a concave surface to incident light and having a radius of curvature R, and said target means is located a distance of between 0.4R and 0.5R from said mirror.

12. The display of claim 6, 7 or 8 wherein said reflect-ing means comprises a cylindrical mirror presenting a concave surface to incident light and having a radius of curvature R, and said target means is located a distance of 0.469R from said mirror.

13. The display of claim 6, 7 or 8 wherein said reflecting means comprises a cylindrical mirror presenting a concave surface to incident light and having a radius of curvature R, said target means is located a distance of 0.469R from said mirror and said selectively operable means is located a distance approximately R
from said mirror.

14. The display of claim 6, 7 or 8 wherein said reflecting means comprises a cylindrical mirror presenting a concave surface to incident light and having a radius of curvature R, said target means is located a distance of 0.469R from said mirror and said selectively operable means is located a distance approximately R
from said mirror the height of said target means is approximately .125R and the length of said target means is greater than or equal to the length of said mirror.

15. The display of claim 6, 7 or 8 wherein said reflecting means comprises a cylindrical mirror presenting a concave surface to incident light and having a radius of curvature R, said target means is located a distance of 0.469R from said mirror and said selectively operable means is located a distance approximately R
from said mirror the height of said target means is approximately .125R and the length of said target means is greater than or equal to the length of said mirror including a plurality of said mirrors and target means, a respective one of said mirrors adapted to focus light onto a respective target means.

16. The display of claim 6, 7 or 8 wherein said reflecting means comprises a cylindrical mirror presenting a concave surface to incident light and having a radius of curvature R, said target means is located a distance of 0.469R from said mirror and said selectively operable means is located a distance approximately R
from said mirror the height of said target means is approximately .125R and the length of said target means is greater than or equal to the length of said mirror including a plurality of said mirrors and target means, a respective one of said mirrors adapted to focus light onto a respective target means and further including a sub-stantially optically transparent support medium means for support-ing and containing said liquid crystal means, said mirrors and said target means.

17. The display of claim 6, 7 or 8 wherein said reflecting means comprises a cylindrical mirror presenting a concave surface to incident light and having a radius of curvature R, and said target means is located a distance of between 0.4R and 0.5R from said mirror and said target means comprises a black stripe for absorbing at least substantially all of the light incident thereon.

18. The display of claim 6, 7 or 8 wherein said reflecting means comprises a cylindrical mirror presenting a concave surface to incident light and having a radius of curvature R, and said target means is located a distance of between 0.4R and 0.5R from said mirror and said target means comprises a colored stripe for absorbing only one or more specified wavelengths of light.

19. A display, comprising means selectively operable for affecting light incident there-on by selectively scattering or transmitting light in response to a prescribed input;
a target means located on a non-viewing side of said select-ively operable means for absorbing light incident thereon; and a lens means disposed between said selectively operable means and said target means for focusing light transmitted by said sel-ectively operable means within a controlled viewing angle onto said target means to enhance the contrast of the display.

20. The display of claim 19 wherein said selectively operable means comprises a liquid crystal means.

21. The display of claim 20 wherein said liquid crystal means comprises at least one layer of nematic curvilinearly aligned phases liquid crystal material.

22. The display of claim 19, 20 or 21 further including an illumination source on the non-viewing side of the display for directing light toward said lens means.

23. The display of claim 19, 20 or 21 wherein said lens means comprises a plurality of cylindrical rods disposed adjacent to one another, and further including an illumination source on the non-viewing side of the display for directing light toward said lens means.

24. The display of claim 19, 20 or 21 wherein said lens means comprises a plurality of cylindrical rods disposed adjacent to one another and further including an illumination source on the non-viewing side of the display for directing light toward said lens means and said target means comprises a stripe extending substantially along the length of each of said cylindrical rods.

25. The display of claim 19, 20 or 21 wherein said lens means comprises a plurality of cylindrical rods disposed adjacent to one another and further including an illumination source on the non-viewing side of the display for directing light toward said lens means and said target means comprises a stripe extending substantially along the length of each of said cylindrical rods and said target means is positioned between the backsurface of said lens means and the focal point thereof.

26. The display of claim 19, 20 or 21 wherein said lens means comprises a plurality of cylindrical rods disposed adjacent to one another and further including an illumination source on the non-viewing side of the display for directing light toward said lens means and said target means comprises a stripe extending substantially along the length of each of said cylindrical rods and said target means is positioned between the backsurface of said lens means and the focal point thereof and said stripe comprises a black absorber for absorbing at least substantially all of the light incident thereon or a colored absorber for absorbing only one or more specified wavelengths of light.

27. The display of claim 19, 20 or 21 wherein said lens means comprises a plurality of cylindrical rods disposed adjacent to one another and further including an illumination source on the non-viewing side of the display for directing light toward said lens means and said target means comprises a stripe extending substantially along the length of each of said cylindrical rods and said target means is positioned between the backsurface of said lens means and the focal point thereof and the height of said stripes is approximately equal to one sixth the diameter of said cylindrical rods.

28. The display of claim 19, 20 or 21 wherein said lens means comprises a plurality of cylindrical rods disposed adjacent to one another and further including an illumination source on the non-viewing side of the display for directing light toward said lens means and said target means comprises a stripe extending substantially along the length of each of said cylindrical rods and said target means is positioned between the backsurface of said lens means and the focal point thereof and said selectively operable means is spaced from said cylindrical rods a distance approximately equal to twice the diameter thereof.

29. The display of claim 19, 20 or 21 further including an illumination source on the non-viewing side of the display for directing light toward said lens means and said lens means comprises a plurality of spheres disposed adjacent to one another.

30. The display of claim 19, 20 or 21 wherein further in-cluding an illumination source on the non-viewing side of the display for directing light toward said lens means and said lens means comprises a plurality of spheres disposed adjacent to one another and said target means comprises a dot located at the backside of each of said spheres.

31. The display of claim 19, 20 or 21 wherein further in-cluding an illumination source on the non-viewing side of the display for directing light toward said lens means and said lens means comprises a plurality of spheres disposed adjacent to one another and said target means comprises a dot located at the backside of each of said spheres, said dot being positioned between the backside of said spheres and the focal point thereof.

32. The display of claim 19, 20 or 21 wherein further in-cluding an illumination source on the non-viewing side of the display for directing light toward said lens means and said lens means comprises a plurality of spheres disposed adjacent to one another and said target means comprises a dot located at the backside of each of said spheres, said dot being positioned between the backside of said spheres and the focal point thereof, the diameter of said dot is approximately equal to one-sixth the diameter of said spheres.

33. The display of claim 19, 20 or 21 wherein further in-cluding an illumination source on the non-viewing side of the display for directing light toward said lens means and said lens means comprises a plurality of spheres disposed adjacent to one another and said target means comprises a dot located at the backside of each of said spheres, said dot being positioned be-tween the backside of said spheres and the focal point thereof, the diameter of said dot is approximately equal to one-sixth the diameter of said spheres and said dot comprises a black absorber for absorbing at least substantially all of the light incident thereon or a colored absorber for absorbing only one or more specified wavelengths of light.

34. The display of claim 19, 20 or 21 wherein further in-cluding an illumination source on the non-viewing side of the display for directing light toward said lens means and said lens means comprises a plurality of spheres disposed adjacent to one another and said target means comprises a dot located at the backside of each of said spheres, said dot being positioned be-tween the backside of said spheres and the focal point thereof, the diameter of said dot is approximately equal to one-sixth the diameter of said spheres and said dot comprises a black absorber for absorbing at least substantially all of the light incident thereon or a colored absorber for absorbing only one or more specified wavelengths of light, said selectively operable means being spaced from said spheres a distance approximately equal to twice the diameter thereof.

35. An apparatus for reducing glare comprising a light absorbing target and a concave reflector means for focusing specular reflection onto said target, said reflector means having a radius of curvature R and said target located on a viewing side of said reflector at a distance of between .4R and .5R therefrom and said target comprising vertically and horizontally extending light absorbing surfaces, wherein the height of said vertically extending surface is approximately 0.0625R and the length of said horizontally extending surface is at least 0.1R.

36. A display for enhancing contrast and reducing glare, comprising:
a target means for absorbing light;
a concave reflector means for focusing light incident thereon including specular reflection onto said target means; and means selectively operable for affecting light incident thereon by selectively scattering or transmitting light in response to a prescribed input, said selectively operable means including first and second major surfaces having a concave configuration substantially the same as said concave reflector means, and said target means located in front of and on a viewing side of said selectively operable means.

37. A display comprising:
a film of nematic curvilinearly aligned phases liquid crystal material having first and second surfaces, and selectively operable for affecting light incident thereon by transmitting light in response to a prescribed input, and at least one of scattering and absorbing light in the absence of said prescribed input;
target means located in front of and on a viewing side of said film for absorbing light incident thereon; and reflector means disposed on a non-viewing side of said film, said reflector means having a concave surface and said film disposed along said surface so that said first and second surfaces and said reflector means present a concave surface to light incident thereon from the viewing side thereof for focusing light transmitted by said film within a viewing angle onto said target means to enhance the contrast of and reduce glare from the display.

38. The display of claim 37 wherein said liquid crystal material is in a containment medium, said liquid crystal material having positive dielectric anisotropy and indices of refraction substantially matched to said containment medium to maximize optical transmission in the presence of said prescribed input and to effect substantial isotropic scattering in the absence of said prescribed input.

39. The display of claim 37 wherein said target means is located approximately at the focal point of said reflector means.

40. The display of claim 37 wherein said reflector means has a radius or curvature R and said target means is located a distance of between .4R and .5R from said reflector means.

41. The display of claim 40 wherein said target means is located at a distance of .469R from said reflector means.

42. The display of claim 40 wherein said target means comprises vertically and horizontally extending light absorbing surfaces.

43. The display of claim 42 wherein the height of said vertically extending surface is approximately .0625R, the width of said horizontally and vertically extending surfaces are approximately equal to the width of the display plus R, and the length of said horizontally extending surface is at least .1R.

44. The display of claim 37 or 42 wherein said target means comprises a black absorber for absorbing at least substantially all of the light incident thereon.

45. The display of claim 42 wherein said target means comprises a coloured absorber for absorbing only one or more specified wavelengths of light.

46. The display of claim 37 further including a substantially optically transparent support medium means for supporting and containing said film and said reflector means.

47. The display of claim 37 wherein said target means comprises a vertically extending light absorbing surface.

48. A method for reducing glare from a display comprising focusing specular reflection from a concave reflecting surface having a radius of curvature R onto a light absorbing target means having vertically and horizontally extending light absorbing surfaces and located in front of said concave reflecting surface at a distance of between 0.4R and 0.5R wherein the height of said vertically extending surface is approximately 0.0625R and the length of said horizontally extending surface is at least 0.1R.

49. The display of claim 48 wherein said target is located at a distance of .469R from said reflector means.

50. A method for contrast enhancement, comprising:
scattering or transmitting incident light by means of an electro-optical device as a response to a given electrical input independent of incident light, said electro-optical device having two states, a first state for scattering light and a second state for transmitting light; and focusing unscattered light transmitted through said electro-optical device onto a light absorbing target means external to and on a non-viewing side of said electro-optical device for enhancing contrast.

51. A display, comprising:
liquid crystal means operable for affecting light incident thereon and having two states, one state for scattering light and a second state for transmitting light in response to a prescribed input independent of the incident light;
a target means located on a non-viewing side of said liquid crystal means for absorbing light incident thereon; and a plurality of cylindrical lenses disposed between said liquid crystal means and said target means for directing light transmitted through said liquid crystal means onto said target means to enhance the contrast of the display.

52. The display of claim 51 wherein said lenses comprise cylindrical rods.