US3862795A

US3862795A - Solid state crystal display having two isolated end cell regions

Info

Publication number: US3862795A
Application number: US069289A
Authority: US
Inventors: Jacob Tellerman
Original assignee: Sun Chemical Corp
Current assignee: Sequa Corp
Priority date: 1970-09-03
Filing date: 1970-09-03
Publication date: 1975-01-28
Anticipated expiration: 1992-01-28

Abstract

A single crystal material, such as gadolinium molybdate, is electrically excited to modulate transmission of plane polarized light. The memory characteristics and the sharp threshold characteristics are relied on to produce selection switching of the domains. Domain injection techniques are utilized for reducing domain coupling characteristics.

Description

' a fazw an 0 United State Q [H1 3,862,795

f Tellerman X51024 1 Jan. 28, 1975 [54] SOLID STATE CRYSTAL DISPLAY HAVING 3.374.473 3/!968 Cummins 350/150 TWO ISOLATED END CELL REGIONS 3.53l.l82 9/l970 Land et al ISO/I50 3.559.125 l/l97l it 1-1 .350150 [75] lnventor: Jacob Tellerman. Baysidc. N.Y. OTHER :SLLZATIONS I 7 A z 3] Sslgnee git z z New Land. Ferroelectric Ceramlc Electrooptic Storage and Display Devices, Sandia Corp. Reprint ScR-6- [22] Filed: Sept. 3, 1970 7-l2l9. Oct. 1967. pp. l7-20. 42-44.

' 2l A l. N ,1 69,289

[ 1 pp 0 Primary Examiner-John K. Corbin Attorney. Agent, or Firm-Cynthia Berlow [52] U.S. Cl 350/150, 340/1732. 350/l57 [5 1] Int. Cl. G02 1/26 57 ABSTRACT [58] Field of Search 350/l50. I51, 320;

340/!73 LS A single crystal material, such as gadolinium molybdate, is electrically excited to modulate transmission [56] References Cited of plane polarized light. The memory characteristics and the sharp threshold characteristics are relied on to UNITED STATES PATENTS produce selection switching of the domains. Domain 350/15) injection techniques are utilized for reducing domain 2.928.317 3/1960 Haines 350/50 coupling characteristics.

3.027.806 4/1962 Koelsch 3.l64.8l6 l/l965 Chang et al 350/l5l 3.374.358 3/1968 Majima 350/l50 13 Claims, 19 Drawing Figures PATENTEB JMIZBIWS sum 10? 5 22 2.6 PULSE AMPLITUDE- RATIO TO DC THRESHOLD VOLTAGE o 0 0 0 0 0 0 mozoummjfli z 1.5:: wm 5m mvsmon fic'ai fifmw 'y p ATTORNEY SOLID STATE CRYSTAL DISPLAY HAVING TWO ISOLATED END CELL REGIONS BACKGROUND OF THE INVENTION Optical activity and birefringence has been observed in many crystal materials, especially crystals that have piezoelectric activity. The gadolinium molybdate crystal materials are of particular interest because they exhibit the optical effect and memory. That is, when properly excited, the dipoles are switched into a new direction and remain there until re-excited to switch back to original position. The dipole reversal introduces a change in mechanical strain and in optical effects. Domain is used herein'to designate a group of dipoles oriented in the same direction.

SUMMARY OF TI-IE INVENTION This invention relates to the use of a single crystal material (such as gadolinium molybdate) for modulating the transmission of light by means of electrical excitation to achieve an information display panel. While the gadolinium molybdate crystal has shown birefringence and effective changes in the birefringence characteristics, the present invention is concerned with a display technique which utilizes the ability of the crystal to rotate plane polarized light 90 in response to electrical excitation. The memory characteristics of the crystal wherein its domains remain oriented in the directions given by electric field polarization makes the crystal uniquely suited to display applications. The crystal provides particularly desirable'effects because of another factor, namely, its threshold characteristics. The threshold characteristic for gadolinium molybdate, for example, dictates that an electric field of at least 12 volts per mil of thickness is required before domain switching can occur. Thus, a change in the optical effect is created only by exceeding the threshold field. It is necessary, however, to exceed the threshold by only a small amount in order to cause all dipoles to switch in the direction of the applied field to form a single domain.

In the illustrated display panel embodiments, a gadolinium molybdate crystal controls the transmission of impinging light in selected regions or cells which, after electrical activation, remain in the condition thus determined.

The single crystal panel has its C-axis normal to the plane of the panel and plane polarized light is incident upon the panel at an angle within a few degrees of its C-axis. XY electrical matrix selection networks are provided for selective control of the panel. The crystal material is arranged in a matrix array to reduce domain coupling sufficiently to allow individual control of adjacent crystal cells. A domain injection technique is also utilized for reducing the inherent domain coupling characteristics of the material. In particular, domain injection is utilized to provide oppositely polarized domain traps at opposite ends of stick-type crystal elements. Other applications of stick crystals are shown to exhibit one-dimensional type scanning such as tliermometer or window shade effects.

Other features and advantages of the invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which show structure embodying preferred features of the present invention and the principles thereof, and what is now considered to be the best mode in which to apply these principles.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings forming a part of the specification. and in which like numerals are employed to designate like parts throughout the same:

FIG. 1 is a diagrammatic view illustrating a direct view type display panel arrangement in accordance with the present invention;

FIG. 2 is an enlarged fragmentary view showing a sandwich-type arrangement comprising a polarizer. a panel and an analyzer;

FIG. 3 is a diagrammatic view showing a projection screen type of display panel arrangement in accordance with the present invention;

FIG. 4 is a diagrammatic view showing the effective electrical matrix network of the display panel;

FIG. 5 is an enlarged fragmentary perspective view of a display panel having a crystal matrix wherein individual crystal cells are mechanically isolated;

FIGS. 6 and 7 are fragmentary detailed sectional views taken as indicated on the lines 66 and 7-7, respectively on FIG. 5;

FIG. 8 illustrates a display panel having a crystal matrix utilizing a crystal stick array;

FIGS. 9 and 10 are fragmentary detailed sectional views taken as indicated by the lines 9-9 and 10-10 on FIG. 8;

FIG. 11 is a perspective diagrammatic illustration of a computer memory application utilizing a display panel in accordance with this invention;

FIG. 12 is a fragmentary perspective view similar to FIG. 8 and showing another embodiment of the invention wherein crystal sticks have domain traps at opposite ends;

FIG. 13 is an enlarged fragmentary sectional view taken as indicated on the line 13-13 of FIG. 12;

FIG. 14 is a view similar to FIG. 13 and showing an alternative stick arrangement;

FIG. 15 is a side view of a crystal stick and electrical energizing circuit combination;

FIG. 16 is a graph showing the electrical field profile DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, and particularly to FIG. 1, a diagrammatic illustration is given of a display panel embodiment for presenting black and white display of information. The arrangement utilizes a flat planar panel 10 of a single crystal material having transparent electrodes 10E on opposite sides to be voltage controllable by means of electrical field excitation for modulating the transmission of light through the panel.

In the illustrated embodiment, the panel is of gadolinium molybdate crystal having its C axis or axis of symmetry oriented perpendicular to the plane of the slab. Plane polarized light, as indicated at 11, is shown incident upon the panel at an angle of incidence aligned with or at least within a few degrees of the crystals C axis. The transmission of such plane polarized light through the panel is modulated by application to the crystal material of an electric field oriented in the direction of the C axis.

To provide plane polarized light, a light source 12 is shown at the focus of a parabolic reflector 13 to create collimated light which, after passage through a polarizer 14, provides only plane polarized light incident upon the panel. An analyzer 15 is located on the opposite face of the panel. For initial adjustment. the analyzer 15 is rotated to a position allowing maximum light transmission. The transmission of light through the panel 10 is reduced by a large factor by exciting the crystal material with an electrical field to switch it to a condition opposite to that which existed for the initial setting. Substantially complete extinction of light transmission can be approached in the case of single crystal material such as gadolinium molybdate.

The effect of altering the electric field excitation appears to cause the plane of polarization of the incident light to be rotated 90 with respect to the initial condition. The apparent range of the modulation effect can be increased somewhat by utilizing monochromatic light as the source 12. As is shown in FIG. 2, the single crystal panel 10, the polarizer 14, and the analyzer 15, are mounted in sandwiched relation rather than being spaced apart as in the diagrammatic representation of FIG. I.

The light emerging from the analyzer 15, being plane polarized, presents a field of view spanning only a few degrees, so that a viewer would have to be located substantially directly in line with the direction of transmission. For practical information display systems, a diffuser plate 16 is shown intercepting the light projected from the analyzer 15 to create a display having a field of view of approximately 180. The diffuser plate 16, as shown herein, is an opal flashed glass plate having a coating 16C of opal material upon its upstream face. The diffuse surface can also be a ground or etched plate of glass.

As shown in FIG. 3, a modified embodiment for enlarging the illuminated display includes a projection lens 17 located downstream of the analyzer 15, with a light diffuser screen 18 being provided to receive the light projected from the lens 17.

In the preferred practice of the invention, the single crystal panel 10 effectively constitutes a twodimensional matrix for which an electrical schematic is shown in FIG. 4. The matrix is controlled from any suitable signal source which incorporates an X-Y coincident voltage addressing function analogous to the coincident current addressing technique utilized in magnetic core memory systems. Thus, the signal source has provisions for energizing any one of the horizontal row electrodes Y, to Y; and has provisions for energizing any selected ones of the vertical ro electrodes X to X These rows of electrodes, as explained hereinafter, are located on opposite faces of the panel and the crossing points of the energized electrodes define and control the individual crystal elements or cells which collectively constitute the matrix. As shown in FIG. 4, each crossing ofthe row and column electrodes on the opposite faces of the crystal may be represented by an equivalent discrete capacitor. Thus. by exciting one of the column electrodes, for example. X and one of the row electrodes, for example, Y the excited crystal element is element 20 shown in FIG. 4. The manner of excita-' tion is to apply a positive halfvoltage (+V/2) to the column electrode X and a negative half voltage (-V/Z) to the row electrode Y so that full voltage (V) is applied across the selected crystal element to effect the desired optical switching action of such element. By applying opposite voltage polarities, the element 20 may be switched back to its initial condition.

It should be noted that the signal selector source operates so that all of the electrodes which are not cnergized are connected to ground during the excitation of electrodes X and Y Thus, all of the remaining crystal elements controlled by the horizontal electrode Y and all of the elements controlled by the column electrode X have only a half voltage, or respectively, acting thereacross, and will not be switched from their assumed initial condition. Once an element of the display is excited. it remains excited, without further or continued excitation because of the optical memory characteristic of the crystal material that is utilized. In addition, any element of the display may be reset by reversing its previous state of electrical excitation so that full or partial erasure can be provided as desired. I

While gadolinium molybdate is the currently preferred material for the practice of the invention, other materials having comparable characteristics are contemplated within the scope of this invention. In particular, the characteristics which are of principal impor tance are the ability of the crystal material to effect a rotation of the plane of polarization of the light incident upon the crystal, the optical memory effect which enables the crystal material to remain in its set state and to be switched from that state only by reverse polarization, and the sharp threshold characteristic. In the case of gadolinium molybdate, the electric field should be 12 volts per mil of thickness or greater in order to cause it to switch states of light transmission. The applied voltage is thus set to exceed the threshold value to a limited extent so that the half voltage level remains well below the threshold. This enables selective switching of discrete regions of the matrix and it enables the entirety of each such discrete region to switch instantaneously and uniformly.

In the case of gadolinium molybdate, the ratios of maximum light transmission to light transmission at cutoff are larger where the crystal thickness is above 0.010 inches.

A number of mosaic or semi-mosaic structural arrangements are provided in the preferred practice of the invention. The crystal material can be shown to be comprised of groups of dipoles oriented in the same direction, such a group of dipoles being referred to as a domain. If one element or cell of the matrix is switched, it is necessary that all dipoles therein undergo rotation in order to achieve the desired optical change for the element. The domain in one element, upon being switched, tends to produce a switching effect in neighboring unexcited regions where only a half strength electric field exists. Domains have a strong coupling in one direction but a comparatively weak coupling in a perpendicular direction.

The matrix arrangement in FIG. 5 is comprised of a two-dimensional array of square crystal elements, each of which represents a separately switchable element of the display. 'Ihcse individual squares are interconnected into a composite matrix panel by means of a mechanical grid work of intersecting webs W of suitable filler material, such as an elastomer.

The raw electrodes 74,, X etc. are shown as including connection tabs 21 leading from the edge cells X,Y,, X Y etc., bridging tabs 22 (FIG. 6) overlying the webs W and full surface conductive coatings 23 on the corresponding cell surfaces and interconnected by the bridging tabs 22.

Similarly, the column electrodes Y,, Y etc., are shown as including connection tabs 24 leading from the edge cells X,Y,, X,Y etc., bridging tabs 25 (FIG. 7) overlying the webs W and full surface conductive coatings 26 on the corresponding cell surfaces and interconnected by the bridging tabs 25.

In this mosaic arrangement, the elastomer webbing W between the discrete crystal elements prevents mechanical coupling and stressing effects due to the domain switching characteristic of the material. The mosaic is manufactured by first growing a single crystal structure which is cut into panels by slicing in a plane perpendicular to the C axis. Each panel is the approximate size of the final mosaic panel and is further processed by providing

conductive coatings

23, 26 on its opposite faces. A thin vacuum deposited metallic film may be used with some sacrifice in light transmission. Metallic oxides, such as stannons, cadmium or indium oxides, provide less light attenuation.

The electroded panel is then slit into elemental squares or cells by cutting with a wire saw, first in one direction and then in an orthogonal direction, with the slots formed by the cutting being filled with elastomer material which is cured in situ.

Finally, the bridging

electrode tabs

22, 25 are vacuum deposited upon the webs to complete the desired grid work of electrode connections.

Another mosaic panel arrangement is shown in FIGS. 8,9 and 10. It employs a glass substrate 27 having crystal strips or sticks 28 in closely spaced side-by-side relation. Opposite faces of the panel from which the sticks 28 are cut are coated as previously indicated so that the underface of each stick is provided with a transparent electrode 29 extending along its full length. Each stick is effectively subdivided by providing a set of grooves 28G in spaced relation along the upper surface to provide mechanical discontinuities which minimize the domain coupling effect between neighboring cells of the are shown connected to the underface electrode coatings 29. Column electrode tabs 33 are shown connected to the upper face electrode coatings 30.

The arrangement of FIG. I as already indicated is particularly useful in an information display system wherein the light transmission characteristic of the crystal material is selectively controlled by the strength and polarity of the electrical field excitation so that a true black and white visible indication is produced for viewing.

The same basic panel structure, such as is shown in FIGS. 5 and 8, is useful in other information systems such as a computer memory arrangement wherein the information to be stored is in the form ofa binary code. In a computer memory application as shown in FIG. I I, the storage matrix 35 is selectively excited and the pattern of domain polarization which is thus established will remain after the excitation is removed. For readout, the matrix 35 is shown associated with a single output photocell 36 and with a flying spot scanner 37 which generates a line-by-Iine raster pattern so that the individual data bits are read out in sequence.

A further panel embodiment is shown in FIG. 12

'where a matrix arrangement is comprised of a set of crystal sticks 38 which are arranged in parallel relation upon a glass substrate and spaced apart by webs W. In this form, each stick is provided with a separate groove 38G adjacent each end and serving to define

end cells

38A,38B which function as domain traps in the final matrix. Scribe lines are shown in phantom as indicated at 388 to define the intermediate cell regions of each stick. The scribe lines 388, as shown in the enlarged fragmentary view of FIG. 13, represent discontinuities in the surface electrode coatings 39 and may be formed by discrete electrode coatings as initially applied or by etching of full surfaced coatings or by saw cuts (that is, similar to the grooves 280 of FIGS. 8 and 9).

Each of the sticks 38, as described more completely hereinafter, is subdivided into a set of intermediate cells which are part of the electrical matrix and end cells or domain traps 38A, 383 which are not part of the electrical matrix. The domain traps of each stick are oppositely polarized electrically by means of a domain injection process described hereinafter and remain unchanged during use of the matrix. The intermediate cells are of random polarization and are capable of individual polarization in accordance with the applied matrix voltages. The provision of the domain traps 38A,38B at opposite ends of the sticks 38 allows the independent switching of the domains in the intermediate cells. It is believed that since the domain traps prevent the domains from aligning along the entire length of the stick, as is the normal tendency due to the domain coupling relationshipof such crystal materials, the domain coupling is essentially disrupted thereby allowing the intermediate cells to be independently oriented in accordance with the applied electric fields.

It may be noted that the grooves 28G between adjacent cells in the embodiment of FIGS. 8 and 9 are provided for reducing domain coupling between adjacent cells. As shown in FIG. 14, a stick 39 may be provided with domain traps 39A,39B and with isolation grooves 39G for use in a matrix arrangement as shown in FIG. 12.

DOMAIN INJECTION The domain trap configuration as previously referred to consists in providing domain traps of opposite orientation at opposite ends of the stick. The stick is provided with grooves to delineate the trap regions and as indicated previously the intermediate region of the stick may be smooth or may be provided with grooves to delineate the individual cells. With either stick configuration, the process of domain injection is the same and consists of:

l. Bringing the stick up to Curie temperature, ap-

proximately l60C, so that the domains assume a random pattern of orientation;

2. Applying opposite voltage bias to successive intermediate cells;

3. Applying positive voltage to one end region and negative voltage to the other end region;

4. Slowly bring the temperature of the stick down from Curie temperature to provide domain traps of opposite orientation at extreme ends, these domains being oriented perpendicular to the long axis.

The domain trap principle is utilized in gadolinium molybdate stick arrangement for providing other optical display effects. For example, in FIG. a stick 40 is shown with grooves 406 to define

domain traps

40A,40B which are oppositely polarized as previously described to reduce the domain coupling and allow the intermediate stick regions to be selectively polarized.

The stick 40 has an underface coating 41 of any suitable transparent conductive material and has an upper face coating 42 of a high resistive material, such as indium oxide, which spans the stick region intermediate the grooves 400. Domain traps 40A,40B of opposite polarity are defined at the ends of the stick 40. Typically, the resistance of the indium oxide coating from terminal to terminal is 200 K ohms.

The stick is arranged for connection in circuit with a source S of variable DC voltage and, as shown, includes a connection terminal 43 at one extreme end which is to be connected to the positive polarity terminal of the source and a connection terminal 44 at the opposite end of the indium oxide coating which is connected to ground through a voltage dropping resistor 45. The under face coating 41 is connected directly to ground. The indium oxide coating 42 electrically is in series with the resistor 45 to function as a voltage dropping network which determines the voltage gradient profile across the stick.

The profile chart of FIG. 16 shows a pair of voltage gradient profile lines A,B to illustrate the control of domain switching that can be achieved by the combination illustrated in FIG. 15. For example, voltage profile line A which is for a relatively low applied voltage indicates that the voltage gradient across the stick is a maximum at the left end of the indium oxide coating and is a minimum at the right end. A typical voltage gradient threshold line T, for example for a gadolinium molybdate crystal stick, is shown in the graph. Domain switching occurs at regions of the stick where the voltage gradient exceeds the threshold level T.

Thus, application of a DC voltage corresponding to the profile line A will cause the entire region of the stick between the left hand terminal and the intersection point P to switch domains because the field strength at such region exceeds the threshold field strength T. The portions of the stick to the right of the point P will not switch domains. The resultant optical effect in a system such as shown in FIG. 1 is a bar type indication in the nature of a thermometer or window shade action.

If the applied voltage is increased to a higher level to determine a voltage profile line B, the entire region of the stick intermediate of the grooves 400 will switch domains. Therefore, the length of the stick region which switches domains is a function of the level of the applied voltage. The optical contrast ratio between the I fashion to stop short of the end of the opaque region. v

switched regions and the remainder is about 10 to 20 to one.

An alternative stick 50, as shown in FIG. 17, is of uni-' form taper from end to end and is provided with grooves 506 to define

domain traps

50A,50B of opposite orientation. The stick 50 has a trnsparent conductive coating 51 on its underface and a transparent conductive coating 52 spanning the region of its upper face intermediate the grooves 500. DC voltage from a variable voltage source S is applied directly across the

coatings

51,52 to produce a voltage gradient varying linearly along the length of the stick. the gradient being greatest at the narrow end and lowest at the thick end. The point at which the gradient exceeds the threshold value determines the region of the stick which will undergo domain switching. The length of the region that switches is directly proportional to the level of the applied voltage so that the stick arrangement of FIG. 17 provides a thermometer or window shade effect analogous to that of the stick of FIG. 15.

Another stick arrangement for producing this same effect is shown in FIG. 18. In this form, the stick 60 is tapered in the direction of its width and is provided with

electrode coatings

61,62 in the fashion of the stick of FIG. 17 such that DC voltage applied from a source S produces a field which is uniform along the length of the stick. The stick 60 is shown with grooves 60G that define oppositely oriented domain traps 60A,60B.

The domains near the wide end of the stick are easiest to switch while the domains closer to the crowded or converging end of the stick present increasing resistance to domain switching. An applied voltage from the source S produces domain switching beginning at the left end and progressing lengthwise to a point determined by the value of the applied voltage. If the applied voltage is increased the region of domain switching elongates.

Any of the stick configurations of FIGS. l5, l7 and 18 can be controlled in accordance with a further property exhibited by the crystal material, namely, the property wherein domain switching begins at one end and propagates lengthwise at a predetermined rate. Accordingly, the invention contemplates the use of a gated source S that is adjustable for applying voltage pulses of variable time duration selected to terminate the domain propagation. Typically, the time constant of domain propagation for gadolinium molybdate is about 20 milliseconds per inch, though there is a time delay associated with initiation of the domain switching. After the initial time delay, the propagation itself is rapid. The chart of FIG. 19 provides a response time curve taken for gadolinium molybdate crystals threeeighths inches in diameter and 0.15 to 0.20 inches thick.

Additional optical display characteristics can be provided with the domain trap-type stick arrangements. For example, a stick may be domain switched in a fashion to propagate black" from left to right to produce a continuous opaque region of predetermined length. The stick is then excited with DC voltage of opposite polarity to propagate white" from left to right in a The length of each propagation may be controlled as a function of voltage level or time, as previously indicated. An opaque mark will remain of a width determined by the amount of the black propagation that is not erased by the subsequent white propagation.

In any of the embodiments disclosed herein, the matrix cells may be formed with discrete coatings, for example, a separate coating for each cell quadrant so that the X-Y address system is subdivided by a factor of 4. Each cell is in effect four subcells. A relatively small composite grouping, such as 4, makes it possible to domain switch each sub-region individually even though the cell is not subdivided mechanically. This allows development of gray tones by reason of the higher resolution that is made possible. The gray tone effect is more easily achieved in cell structures of sticks having domain traps as described herein.

A further concept for producing gray tones is based on the use of partial switching. in this approach. any selected cell is excited by a very narrow pulse timed to effect switching ofonly part of a cell. Thus, the fraction of the cell that switches is determined by the duration of the pulse to permit the effect of gray shade to be generated.

Thus, while preferred constructional features of the invention are embodied in the structure illustrated herein, it is to be understood that changes and variations may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

What is claimed is:

l. A system for electronic control of optical transmission comprising panel means having an axis of symmetry perpendicular thereto, said panel means comprising a mosaic of parallel spaced apart gadolinium molybdate crystal sticks arranged in side by side relation to providea matrix array of individually controllable crystal cells, each stick including an equal number of intermediate crystal cells collectively constituting said cells of said matrix and two isolated end cell regions, electrical means controlling selective energization of any of said matrix cells, optical means for directing plane polarized light upon said panel means at an angle of incidence within a few degrees of said axis, said electrical means effecting selective electric field excitation of the matrix crystal cells in the direction of said axis for producing domain switching activity within each selected crystal cell for rotating plane polarized light to effect modulation of the light transmission characteristics thereof, and said isolated end cell regions of each stick being of predetermined, fixed and opposite polarization for limiting domain coupling effects between said cells of said matrix.

2. A system for electronic control of optical transmission as defined in claim 1 wherein said electrical means includes row electrode means and column electrode means overlying opposite faces of the panel means.

3. A system as defined in claim 1 wherein said optical means includes a source of collimated light, a polarizer between said source and said panel means and an analyzer on the opposite side of said panel.

4. A system as defined in claim 1 and including a display screen intercepting light transmitted through said panel means, said screen having a diffusion surface to provide a display characterized by a wide angle field of view.

5. A single crystal element responsive to electric field actuation to effect control of optical transmission, said element comprising a stick of crystal material exhibiting a bistable optical memory characteristic and further exhibiting domain switching activity at a sharply defined threshold level capable of rotating plane polarized light, said stick having two isolated end cell regions of predetermined, fixed and opposite polarization for limiting domain coupling effects at the non-isolated intermediate regions thereof and electrode means connected to opposite intermediate face regions of the stick to control selective electrical field excitation thereof.

6. A single crystal element as defined in claim 5 and wherein said stick has transverse surface grooves in one of said faces defining and isolating said end cell regions.

7. A single crystal element as defined in claim 5 wherein said stick has transverse surface grooves in one of said faces defining and isolating said end cell regions, one of said electrode means includes a transparent conductive coating overlying substantially the entire intermediate region of one of said faces and the other ofsaid electrode means includes a transparent high resistance coating overlying substantially the entire intermediate region of the other of said faces.

8. A single crystal element as defined in claim 5 wherein said stick has transverse surface grooves in one of said faces defining and isolating said end cell regions, said stick being tapered in thickness to progressively vary the spacing of said faces.

9. A single crystal element as defined in claim 5 wherein said stick has transverse surface grooves in one of said faces defining and isolating the end cell regions, said stick being tapered in width to provide uniformly spaced faces of tapering width.

10. A single crystal element as defined in claim 5- wherein said crystal material is gadolinium molybdate;

11. A system for electronic control of optical transmission comprising a stick of single crystal gadolinium molybdate exhibiting a sharp electric field threshold of domain switching activity capable of rotating plane polarized light, said stick having two isolated end cell regions of predetermined, fixed and opposite polarization for limiting domain coupling at the non-isolated intermediate regions thereof, and electrical source means including electrode means connected to opposite intermediate face regions of the stick for applying an electric field adjacent one extreme of the intermediate face regions to propagate domain switching activity a controlled distance lengthwise along the stick.

12. A method of manufacturing a stick of single crystal materialthat exhibits selective domain switching activity capable of rotating plane polarized light in response to selective electric field actuation, said method including providing end cell regions of opposite orientation at opposite ends of the stick by bringing the stick material up to Curie temperature to allow the domains to assume random orientation, applying opposite voltage bias to successive intermediate cells, applying positive voltage at one end and negative voltage to the other end of the stick and maintaining the applied voltage relationships while bringing the temperature of the stick down from Curie temperature to provide end cell regions at the ends of the stick oriented perpendicular to the long axis of the stick.

13. A method as defined in claim 12 and including the step of forming surface grooves to border and define the end cell regions.

Claims

1. A system for electronic control of optical transmission comprising panel means having an axis of symmetry perpendicular thereto, said panel means comprising a mosaic of parallel spaced apart gadolinium molybdate crystal sticks arranged in side by side relation to provide a matrix array of individually controllable crystal cells, each stick including an equal number of intermediate crystal cells collectively constituting said cells of said matrix and two isolated end cell regions, electrical means controlling selective energization of any of said matrix cells, optical means for directing plane polarized light upon said panel means at an angle of incidence within a few degrees of said axis, said electrical means effecting selective electric field excitation of the matrix crystal cells in the direction of said axis for producing domain switching activity within each selected crystal cell for rotating plane polarized light to effect modulation of the light transmission characteristics thereof, and said isolated end cell regions of each stick being of predetermined, fixed and opposite polarization for limiting domain coupling effects between said cells of said matrix.

5. A single crystal element responsive to electric field actuation to effect control of opTical transmission, said element comprising a stick of crystal material exhibiting a bistable optical memory characteristic and further exhibiting domain switching activity at a sharply defined threshold level capable of rotating plane polarized light, said stick having two isolated end cell regions of predetermined, fixed and opposite polarization for limiting domain coupling effects at the nonisolated intermediate regions thereof and electrode means connected to opposite intermediate face regions of the stick to control selective electrical field excitation thereof.

7. A single crystal element as defined in claim 5 wherein said stick has transverse surface grooves in one of said faces defining and isolating said end cell regions, one of said electrode means includes a transparent conductive coating overlying substantially the entire intermediate region of one of said faces and the other of said electrode means includes a transparent high resistance coating overlying substantially the entire intermediate region of the other of said faces.

10. A single crystal element as defined in claim 5 wherein said crystal material is gadolinium molybdate.

12. A method of manufacturing a stick of single crystal material that exhibits selective domain switching activity capable of rotating plane polarized light in response to selective electric field actuation, said method including providing end cell regions of opposite orientation at opposite ends of the stick by bringing the stick material up to Curie temperature to allow the domains to assume random orientation, applying opposite voltage bias to successive intermediate cells, applying positive voltage at one end and negative voltage to the other end of the stick and maintaining the applied voltage relationships while bringing the temperature of the stick down from Curie temperature to provide end cell regions at the ends of the stick oriented perpendicular to the long axis of the stick.