CA1253268A

CA1253268A - Point of purchase flat panel electroluminescent display

Info

Publication number: CA1253268A
Application number: CA000511109A
Authority: CA
Inventors: Reuben Michaels
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-06-09
Filing date: 1986-06-09
Publication date: 1989-04-25

Abstract

POINT OF PURCHASE FLAT PANEL
ELECTROLUMINESCENT DISPLAY

ABSTRACT OF THE INVENTION
A shelf edge-mounted electroluminescent display (10) is disclosed. Plural electroluminescent lights (16, 26) provide illumination through a template (18) which has opaque graphical indicia (20, 28) thereon. The lights (16, 26) are flashed by pulsing ac power thereto. One light (26) is flashed at a first rate, while the other background light (16) is flashed at a slower rate. A
proximity sensor (25) detects the presence or movement of approaching objects and activates the flashing lights (16, 26). An age compensating circuit comprising a light sensor (98), a sample and hold amplifier (92) and an integrator (100) which automatically adjusts the ac voltage applied to the lights (16, 26) to compensate for deteriorating output brightness due to lamp age.

Description

~3~8 BACKGROUND OF THE INVENTION
Electroluminescent material has previously been utilized for various displays and~ signs. Displays of this type have gained popularity because there are no sudden burnouts, very little heat is generated and large surfaces can be illuminated with low power consumption.
Substantial resources have heretofore been devoted to further refinements of electroluminescent materials to provide a variety of colors and to reduce the deleterious - affects of moisture and aging. ~he electroluminescent material is constructed similar to a capacitor, i.e., having a dielectric insulator between spaced-apart plates.
One of the plates is generally constructed of a transparent material. Heterogenous phosphor particles are embedded in the insulator and are energized by the application of an alternating current applied to the plates.
A major adverse characteristic of electroluminescent materials is the deterioration of the brightness of the light over a period of time. This is apparently due primarily to the affects of humidity. The deterioration is so noticeable that the life of such a display is measured by its half life - the length of time expended until the brightness decays to one half the original value. Attempts have been made to reduce this deterioration by insulating the pho~phor surface from the environment by vapor barriers and desiccants. While this approach has provided a certain degree of additional

2 ~

longevity, the deterioration in the brightness is not entirely eliminated.
Another inherent characteristic of electroluminescent lights is that the brightness varies directly with the fre~uency of the ac driving power.
While an increase in the driving frequency can restore the brightness, an offsetting characteristic is that the life of the lamp is inversely proportioned to the driving frequency.
The replacement of one electroluminescent display located amongst other similar displays results in an undesirable contrasting brightness of the new light.
Preaging new electroluminescent lights tends to provide uniform brightness between new lamps and old lamps.
However, this solution is not without the disadvantage that a portion of the life of the lamp has been expended without useful utility. Brightness controls have been provided in which an operator can man~ally adjust the power applied to the light, thereby adjusting its brightness to a desired luminescence. U.S. Patent 4,266,164 discloses such a brightness control for use with an electroluminescent backlighting application.
Electroluminescent lighting systems have been adapted primarily for backlighting instrument panels in automobiles and aircraft, as well as bacXlighting overlays or templates in display and advertising applications.
U.S. Patent Nos. 4,420,898; 3,188,761; 2,975,318;

3,110,882 and 3,037,189 illustrate these principles.

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These patents illustrate various applications of electroluminescent lights utilized merely as a backlighting medium. However, prior displays and signs have not been completely satisfactory with respect to 5 visibility and commercial accaptcmce, or with respect to brightness and longevity of the elecroluminescent device.
From the foregoing, it may be seen that a need has arisen for further improvements in electroluminescent displays, both in improving the useful life, and for highlighting the display for attention-getting purposes.
An associated need has also arisen for an improved electroluminescent light with a high level of brightness and with an increased usable life.

SUMMARY OF THE INVENTION
In accordance with the present invention, an improved electroluminescent display is provided which substantially eliminates or reduces the problems associated with the prior art devices. In the preferred form of the invention, the electroluminescent light is provided with many features, including the adaptation for attachment to a merchandise shelf edge.
The useful life of the electroluminescent display is improved, especially when used as a high intensity display light, by providing an adjustable power source for supplying ac power to the light, and a photosensor device for detecting the brightness of the display. The photosensor is opticalIy coupled to the electroluminescent light and automatically causes lS adjustment of the voltage of the power source in response to a decrease in the brightness of the light.
The display also includes plural electroluminescent elaments which are individually powered. The lighting of aach element i3 separately controlled by a timer circuit which permits the elements to flash at different rates, thereby giving an enhanced visual affect to the display~ When used in the merchandising field, a template or overlay is lighted, showing price, size or bargain information. This information is disposed in front of the electroluminescent elements, there~y flashing and highlighting certain of the information with respect to the other.

53;~

An additional and significant improvement in the electroluminescent display of the invention comprises a proximity sensor for sensing an approaching person or object. The proximity sensor i.s responsive either to movement of an object, or the interruption of ambient light thereto. Th proximity sensor is coupled to the power supply for switching the electroluminescent elements on in response to the presence or movement of the person or object.

Provided with the display is a case for housing the electroluminescent element~ and replaceable templates.
A front access cover in hinged to the case to provide ready access for interchanging templates. Other 1~ applications of the electroluminescent display o the invention pertain to automobile license plates. In this application the template would be generally transparent, with opaque license ~bers. Alternatively, there is embedded within the electroluminescent background contact sockets for making contact with a plurality of separate electroluminescent number elements. Each number element is provided with electrical contact pins insertable within the socket~.

2~
6a In accordance with the invention, there is provided a passive advertising display for displaying indicia associated therewith, and for use in an ambient light condition in connection with advertising merchandise. The passive advertising display comprises:
a display light switchable between an off and an on state for illuminating said indicia;
a proximity sensor responsive to the ambient light for sensing a person approaching proximate said display by sensing a small change in said ambient light and providing an output indication of the proximity of the object; and means responsive to the output indication of said proximity sensor for switching said display light to the on state to illuminate said indicia.

Another feature of the invention constitutes a method of highlighting merchandise stored on a shelf and attracting the attention of prospective customers. The method comprises the steps of:
positioning a display on a shelf area proximate the merchandise;
activating lighting of the display only when a shopper approaches within an area proximate the display; and deactivating the lighting of the display after the shopper moves beyond the proximate area.

.26B

BRIEF DESCRIPTION OF THE DRAWINGS
Further features and advantages of the present invention will become apparent from the description of an illustrative embodiment thereof, taken in conjunction wlth the accompanying drawings, in which:
FIGURE 1 is an isometric view of the electroluminescent display according to the invention, shown opened with the template and filter elements removed therefrom;
FIGURE 2 iB a side view of the invention as attached to a shelf edge, with the access cover thereof shown in phantom and hinged open;
FIGURE 3 is a sectional view of the display, taken along line 3-3 of FIGURE 2;
FIGURE 4 is a block diagram of the sensing and control circuitry for operating the electroluminescent light;
FIGURE 5 is an isometric view of the proximity sensor, shown in exploded form;
FIGURES 6a-6 are front views of various embodiments of proximity sensor aperture masks;
FIGUXE 7 is an isometric view of an alternative embodiment of the proximity sensor, also shown in exploded form;
FIGURE 8 is a detailed electrical schematic drawing of the circuits of the invention;

;3268 FIGURE 9 is a frontal isometric ~iew of an alternative form of the invention, utilized as an automobile license display;
FIGURE 10 is yet another embodiment of the S invention, showing electroluminescent number elements pluggable into the Plectroluminescent background; and FIGURE 11 illustrates the invention utilized as a lapel button.

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DETAILED DESCRIPTION OF THE INVENTION
Referring to FIGURE 1 of the drawings, the electroluminescent display, generally designated 10, is shown attached to the edge of a merchandising shelf 12.
The display comprises primarily an integral case 14 housing a high intensity electroluminescent light 16 and a power supply (not shown in FIGURE 1). A replaceable and transparent graphic overlay 18 is placed in front of the electroluminescent light 16. The template 18 is provided with opaque graphic information 20, thereby providing a contrast between the information 20 and the light shining through the template 18. The light ~6 itself may also have printed information on its face. An optional color filter 22 may be placed between the electroluminescent display 16 and the template 18 for providing a color different than the color of the electroluminescent light 16. Hinged to the case 14 is a front access cover 24 for closing and sealing the template 18 and/or filter 22 adjacent the electroluminescent light 16. A proximity sensor 25 is located at the front of the display ~0. A
s~cond electroluminescent elemen-t 26 may be provided for separately lighting other graphical information 28 on the template 18. To be discussed in more detail below, the electroluminescent elements 16 and 26 may be separately powered, emit light of different colors, and be separately switched with the power supply to flash at different rates. Shown in phanton in FIGURE 1, and to be described in detail below is a light intensity sensor sandwiched Lr~2d~3 between the electroluminescent elements 16 and 26. The light intensity sensor senses th~a brightness of the large electroluminescent element 16.
As shown in FIG~RE 2, and when embodied as a shelf edge display, the electroluminescent display 10 can be mounted rigidly to the shelf 12 by a flat-headed screw 30. The top edge 32 of the hinging cover 24 is substantially level with the top of the shelf 12. With this construction, there is minimal interference of the display 10 with the stocking or removal of items from the shelf 12.
The case 14 of the display 10 is formed in two parts. Eirst, a shelf mounting bracket part 34 of the display 10 is formed by the extrusion of a plastic material. The shelf mounting bracket part 34 includes a large area base 36, an elongate hollow component enclosure 38, both connected by a solid plastic arm 40. The open ends of the enclosure 38 ara covered by plastic plates 42, secured by screws 44. O~her suitable fastening means can be used. The top surface 48 of the enclosur~ mounts flush with the undersurface of the shelf 12. The display 10 is particularly useful where standardized shelve~ are available with a shelf front "talker" 46. The top 50 of the large area base is spaced from the top of the enclosure 48 a distance such that the bottom of the shelf talker 46 engages the top of the base 36. When fastened to the shelf 12 by the screw 30, the display 10 is thus provided with an additional degree of stability. Formed, 3~ ~

or otherwise drilled in the connecting arm 40 is a channel 51 through which electrical conductors can be routed from the component enclosure 38 to the electroluminescent light 16. The enclosure 38 houses the electrical circuitry for 5 controlling the light 16 and the proximity sensor 25.
The second part of the case 14 comprises a back support 52 to which the electroluminescent light 16 is supported. Also, the front access covar 24 is hinged by a pin 54 to the back support 52. The front access cover 24 is shell-like in construction, in that it covers the front and sides of the back support 52. Located on the top of the back support 52 ara a plurality of raised projections 56 which are engage~ble with a plurality of correspondingly located dimpled area~ 58 formed in the access cover 24. The projections 56 are frictionally engageable with the dimple~ 58 to provide a snap lock type of latch. Of course, other means for locking the access cover 24 to the case 14 may be provided.
The hingeable cover 24 i~ shown in phantom in FIGURE 2 in the open position. The cover 24 swings open sligh~ly more than 90 to provide ready access for replacement of the advertising template 18 or color filter 22. The cover 24 is constructed with a hole (not shown) through which the proximity sensor 25 projects. Because f the highly nondirectional sensing features of the sensor 25, it is preferred that the cover does not block ambient light from reaching the sensor 25. While a nonapertured clear plastic cover 24 may not impede light ~ ~ 5~

directly in front of the proximity sensor 25, light from the sides of the display lO may be reflected and prevented from reaching the proximity sensor 25. To provide an enclosure which is environmentall.y tight, the cover 24 can be bubbled out slightly in front of the proximity sensor 25, and the cover hole eliminated. The bubbled portion can even form a lens for collimating ambient light toward the proximity sensor 25.
FIGURE 3 is a sectional view of the invention, taken along line 3-3 of FIGURE 2, illustrating additional features of the invention. Specifically, in the cross section of the component enclosure 38 there is illustrated in module form electrical components and circuitry 60. The top sidewall 62 and the bottom sidewall 64 of the component enclosure 38 are apertured. A hole 66 is placed in the bottom sidewall 64 for routing therethrough power wires 68 connected to the circuit module 60. A transverse channel 51 is drilled, or otherwise formed, in the bottom sidewall 64 for routing therethrough control signal wires 72 to the display and sensing apparatus mounted to the back support 52. The enclosur~ end covers 42 are secured by the screws 44 to angle brackets 74 secured by adhesive to the top and bottom sidewalls 62 and 64. A knurled threaded in~ert 76 is press fit within a hole 78 in the enclosure top sidewall 62. Other techniques may be used to secure the anchor screw 30 through the shelf 12 to the display lO.

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The electrical control and sensing operation of the invention are shown in block form in FIGURE 4. The proximity sensing circuit comprises the proximity sensor 25 connected to the input of an amplifier 80, the output of which is connscted to a Schmitt trigger circuit 82.
The output of the Schmitt trigger circuit 82 controls a counter 84 which, in turn, is toggled by a clock 86. The counter 84 is provided with a first output 88 and a second output 90. The repatition rate of the first output 88 is pulsed at a higher rate than that of the second output 90.
The first output 88 is connected to the control input of a switch 94. The second counter output 90, having the lower repetition rate, is coupled to a sample and hold amplifier 92, and to the control input of a switch 96. A light intensity sensor 98, located between the electroluminescent elements 16 and 26, i5 coupled to the input of the sample and hold circuit 92. The output of the sample and hold circuit 92 is connected to an integrator 100. The integrator 100 provides an output voltage to the inputs of the first and second switches 94 and 96. The output of switches 94 and 96 are connected respectively to power ~mplifiers 102 and 104. The power amplifiers 102 and 104 drive respective oscillators 106 and 108 with a voltage pulse having a certain current level. The oscillator outputs are transformer coupled Dy transformers 110 and 112 for supplying an alternating current power to the respective electroluminescent elements 26 and 16.

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The operation of the circuit of FIGURE 4 functions generally as follows. The proximity sensor 25 comprises a photoconductive element which is responsive to ambient light, shown by arrows 114. The proximity sensor 25 is characterized as having a low resistance when receiving ambient light 114, and characterized by a high resistance when an object changes the intensity of the ambient light 114 reaching the proximity sansor 25. The variations in resistance are applied as varying electrical signals to the amplifier 80, and are amplified accordingly. A Schmitt trigger 82 provides a degree of hysteresis in the signal output by amplifier 80 so as to define the presence or absence of an object within the fringe area of sensitivity of ~he proximity sensor ~5. In other words, an object approaching the proximity sensor 25, but yet at a distance, is interpreted by the circuit as a resistance of the sensor 25 which is somewhat between its low resistance and high resistance state. The hysteresis circuit 82 resolves this indeterminate state, and will be discussed in detail below.
When it is determined that an object has approached the display 10, the hysteresis circuit 82 enables the counting of the counter 84 by the clock 86.
Counter 84 i9 toggled at its input by an etght hertz clock signal. Counter 84 is of the type which provides a four hert2 signal on the first output 88, and a one hertz signal on the second output 90. For different visual effects, other frequencies can be used. Because of the provision of automatic compensation or decreased light intensity due to accelerated aging, higher driving frequencies can now be used as the automatic compensation will adjust the driving voltage to the set brightness.
S In accordance with a primary feature of the invention, when a person approaches the display 10, it is desired that one or both of the electroluminescent elements 16 and 26 become lighted to attract the attention of the person. Moreover, an additional feature of the invention enables the large electroluminescent element 16 to be flashed at a first rate, and the second smaller electroluminescent element 26 to be flashed at a higher rate. Accordingly, the graphical information on the template which is in fron~ o the small element 26 is highlighted at a different rate than the information illuminated by the large element 16. It can be seen that with the em~odiment of FIGURE 1, the word "special" 28 embossed on the template 18 would appear to flash at a rate higher than the surrounding graphical indicia 20.
Eirst and second switches 94 and 96 are alternately opened and closed at pulse rates corresponding to the counter first and second outputs 88 and 90. The output voltage of the integrator 100 is thus switched at different rates to the respective inputs of power 25 amplifiers 102 and 104. The switched signal at the input of the power amplifier 102 is amplified for driving the oscillator 106, thereby gating the o~cillator 106 and driving the primary of transformer 110. The secondary o ;2 transformer 110 thus provides the small electroluminescent element 26 with bursts of alternating current power occurring at the higher repetit:ion rate of four hertz.
Similarly, the switched input of power amplifier 104 provides bursts of alternating current power to the Largsr electroluminescent element 16 at the lower repetition rate of one hertz.
In accordance with another feature of the invention, the brightness of the large electroluminescent element 16 is sensed by a sensor 98 which comprises a photoconducive or photosensitive element. The sensor 98 is responsive only to light emitted from element 16, as it is shielded from external ambient light by the small light element 26. Other techniques for shielding the light sensor 98 from ambient light include taping the sensor 98 to the outer surface of the large light element 16 by an opaque tape. An opaque glue or other similar substance may work with equal effectiveness.
Photoconductive light sensor 98 provides a voltage output to the sample and hold amplifier 92 proportional to the intensity of the light emitted by electroluminescent element 16. The output voltage of the light sensor 98 is sampled by the sample and hold amplifier 92 at the rate of the counter second output 90.
The amplifier 92 thereby provides voltages to the integrator 100 based upon the brightness of the large electroluminescent element 16 existing during the periods of time in which the element 16 is flashed or pulsed to 3.~

its lighted state. The integrator 100 provides a dc output voltage to both switches 94 and 96, which voltage is inversely proportional to the brightness or intensity produced by the large electroluminescent element 16. As the switches 94 and 96 are alternately switched between the output voltage of the integrator 100 and ground, the respective amplifiers 102 and 104 provide amplified counterpart signals to the oscillators 106 and 108.
Because of the eff~cts of humidity and age on the electroluminescent light 16, the brightness thereof is known to deteriorate. The decreasing light intensity is manifest as an increasing output voltage of integrator 100. Therefore, the amplitude of the one hertz and four hertz pulses applied to the power amplifiers 102 and lQ4 ~ill also increase. The oscillators 106 and 108 are of the type which are responsive to the incr~ased pulse amplitude by increasing the ac signal amplitude applied to the primaries of transformers 110 and 112. Accordingly, drive voltages of incre~sed amplitudes will be applied to both electroluminescent elements 16 and 26, thereby restoriny the intensity of light emitted by both elements 16 and 26. The electroluminescent light 16 of the invention is driven so as to produce a highly illuminated background light of about thirty to forty-five foot lamberts. This contrasts with three-seven foot lamberts normally used with such type of lights. Thus, it is of paramount importance to maintain the light 16 at a constant high luminescence to maintain a high ~ ; 3 r~

1~3 attention getting aspect. It can be seen that an effective and cost efficient aging compensator is provided. However, the invention is not limited to this form of compensator. From the foregoing, one skilled in the art can devise a compensator which increases the drive frequency, rather than the voltage amplitude, to increase the lamp brightness due to the effects of aging or humidity.
It is preferable that the electroluminescent material of both elements 16 and 26 be of the same type, whereby each such element ages at approximately the same rate. It is thus expected that the decrease in luminescity of one display 16 will be equal to that of the other 26, and thus the amount of increased drive to the lS large element 16 will be also sufficient for restoring the light intensity light of the smaller element 26. However, those skilled in the art may prefer to provide independent aging compensation circuits in which the ac drive voltage to each element is i~dependently sensed and controlled in response to the intensity o light emitted by each such electroluminescent element.
The details of the proximity sensor 25 are shown in more detail in FIGURES 5 and 6. The proximity sensor 2S comprises a photoconductive cell 116 having a thin lined serpentine-shaped photosensitive resistance element 118. Contact pins 120 are connected to the ends of the resistance element 118. Many conventional photoconductive cells of the type described are suitable for operation in ~2~3 the invention. Located adjacent the serpentine resistance element 118 is an apertured mask 122. Th~ illustrated mask has a plurality of holes 124 spaced apart in accordance with the resistance element 118. The apertured mask 122 is held firmly against the case of the photoconductive cell 116 by a bezel 126.
FIGURE 6a illustrates the optical alignment of the apertured mask 122 with the serpentine resistance element 118. It is noted that each hole 124 of the apertured mask 122 is spaced so that a section of the serpentine resistance element 118 lies directly therebehin~. Thus, light which enters through the holes 124 impinges directly on a portion of the resistance element 118, thereby causing a decrease in the total resistance of such element. The construction of the apertured mask 122 is highly significant in that it renders the photoconductive cell 116 responsive to the blockage or change of light to any of the apertures by an object po~itioned within a wide angle in front of the 20 sensor 25. In practice, with apertures 124 of approximately 30mm in diameter. The photoconductive cell 116 is responsive to approaching persons located about twenty-five feet directly in front of the cell 116. This is based upon the general ambient light conditions found in a retail store. In addition, with the proximity sensor of the invention, the photoconductive cell 116 is responsive to the approach of a person from the side thereof at a distance of about 8-10 feet. Thus, there is s~ ~3.~B

essentially an area of 180 in front of the proximity sensor 25 to which the unit is responsive.
FIGURE 6b shows an alternative construction of an apertured mask 127 and an associated photosensitive resistance element 129. The mask 127 includes three holes 131 disposed in the mask 127 in a position nonaligned with the resistive element shapes 129. As shown in FIGURE 6c, the invention functions quite well with an apertured mask 236 having a single hole 238 disposed in front of either a straight thin line photosensitive element or a serpentine element. A peep-hole arrangement, much like that used in entrance doors can be used in connection with a photoconduetive cell to provide wide angle coverage sensitivity to approaching persons or objects.
Other embodiments of the apertured mask according to the invention are shown in FIGURES 6d-6f. In EIGURE 6d there is illustrate~ an apertured mask 240 having closely spaced apertures 242 arranged in a triangular form. The apertures 242 are more closely spaced than those in the mask shown in FIGURE 6b, and is thus more sensitive to persons or objects in close proximity with the proximity sensor 25. Thus, the mask 240 would work well in store aisles of small widths.
FIGURE 6e shows an apertured mask 244 with a vertical slit 246. Thi5 embodiment exhibits good sensitivity to the blockage of ambient light when, for example, the store overhead lights are aligned in rows with the aisles.

. ~ ~2 ~3 In FIGURE 6f there is shown another embodiment of an apertured mask 248 which has good sensitivity to ceiling lights aligned with the store aisles. In this embodiment the light sensitive material comprise a series of interleaved vertical elements 250. Each element is somewhat longer (or shorter) than an adjacent element.
Th~ slit 25~ is diagonally disposed with respect to the elements 250. The principles of the proximity sensor 25 may find a variety of applications in apparatus other than described herein.
FIGURE 7 illustrate~ an alternative e~'aodiment of a proximity sensor 128. With thiR embodiment, a lens 130 is located between the ba2el 126 and the apertured mask 122. The lens 130 provides an increased sensitivity for detecting blockage or change of the ambient light to the resistance element 118. A larger area of light is focused through ~ch of ~he holes 124, thereby providing increa~ed light intensity to the photoconductive cell 116.
The blockage or change of the ambiant light to any of the apertures 1?4 is also acc~ntuated, and manifest as a higher change in resistance between the terminals 120.
Other effects on the light reaching the proximity sensor cell 115 can be realized by selecting other optical characteristics of th~ lens 130.
The specific operations of the electroluminescent display in accordance with the preferred embodiment of the invention are carried out by the electrical circuit shown in FIGURE 8. It shauld be noted that throughout the description hereof, like and corresponding elements are identified by the same reference characters. The proximity sensor 25 is connected in series with a resistor 132, and a voltage is impressed across the two resistiv~e elements. The blockage or change in the transmission of ambient light intensity to the proximity sensor 25 causes a varying voltage at the junction 131 betwe^n the resistor 132 and the sensor 25.
Th~ varying voltage is applied to the noninverting input of a differential amplifier 134.
Preferably, the proximity sensor 25 is of the photoconductive type having a cadmium selenide resistive element which is nonresponsive to sixty cycle ac variations in ambient light generated by overhead florescent or incandescent lights. Moreover, the differential amplifier 134 is provided with a feedback capacitor 136 of .1 microfarad to further reduce the effects of undesired sixty cycle ac variations in the sensor voltage. The ratio of the value of resistors 138 and 140 are chosen to provide an amplifier ac gain of about ten. The dc gain of the amplifier is unity. Thus, any steady state voltage appearing across the proximity sensor 25 is reproduced at the output of the amplifier 134 without gain. On the other hand, any variation in voltage acro~s the proximity sensor 25, caused by object movements, is amplified by a factor of ten.
Significantly, a capacitor 142 provides an ac ground to the inverting terminal of the differential 3~B

amplifier 134. As a consequence, the output of amplifier 134 is an amplified version of only the voltage changes occurring across the proximity slensor 25. With this arrangement, the amplifier circuit 80 is responsive to the S movement of objects between the almbient light and the proximity sensor 25. Should a person approach the electroluminescent display 10 and remain stationary, the amplifier 80 would provida an output corresponding to the initial approach, but would return to its initial state shortly thereafter. Capacitor 142 is chosen to be about 22 microfarads, and resistor 140 is about 47 kilohm, thereby providing approximately a one second delay before the amplifier output returns to its initial state after ~he last detected movement. Other delay periods can be accommodated by changing the values of these components.
Also contributing to the time delay in Which it takes the differential amplifier 134 to return to its initial state are components located in tha\\~Schmitt trigger circuit 82. Coupling capacitors ~144~and 146, together with respective resistor~ 148 and 150 contribute to the time in which it takes the differential amplifier to settle to it~ quiescent state. The Schmitt trigger circuit 82 is conventional in design, and is responsive to either a negative or positive voltage transition, once an input voltage threshold is exceeded. Variable resistance 152 is provided for adjusting the input threshold of the Schmitt trigger 82 such that the output is responsive only to signals exceeding a desired threshold. When active, the output of the Schmitt trigger circuit is a logic low voltage, which is inverted to a logic high voltage by an inverter 154.
: The counter circuit 84 i.s comprised of a pair of four-bit synchronous binary counters 156 and 158 ir.terconnected to provide a first output 88 which counts at a rate four times that of the second output 90.
Counters of the 4520 type manufactured by RCA ar~ suitable for u~e as described below. The logic high output of the inverter 154 is coupled to the reset input of counter 156, and thereby clears the output of such counter to a logic low level. The clear input of counter 156 is connected to tha "eight" output of counter 158. The "eight" output of counter 156 is connected to the clock input of counter 158. Counter 158 is clocked on its enable input at an eight hertz rate by clocX 86. The enable input of counter 156 and ~he reset input of counter 158 are both grounded.
Qther counting arrangements may be used to suit other needs.
Clock 86 comprises two inverters 160 and 162 connected in a conventional manner by resistor 164 and capacitor 166 to provide an oscillator. Variable resistance 168 is adjusted to provide an output frequency of eight hertz. Accordingly, counter output 88 toggles at a four hertz rate, while output 90 toggles at a one hertz rate. These rates correspond to the respective blinking rates of the smaller electroluminescent element 26 and the larger electroluminescent element 16. As noted above, counter output 88 controls the switching rate of swltch 96. Counter output 90 controls the sampling of the sample and hold amplifier 92, as well as the switching rate of switch 94. While shown as mechanical embodiments in 5 FIGURE 8, switches 94 and 96, as well as the switch 170 of the sample and hold amplifier 92 are single pole double-throw MOSFET analog switch devices.
A voltage divider is established between the electroluminescent element brightness detector 98 and a resistor 172. The voltage at node 174 is representative o the brightness of the light emitted by electroluminescent element 16, which voltage is sampled by amplifier 176 of the sample and hold circuit 92. When the switch 17~ closes and samples the voltage at node 174, a low-loss capacitor 178 stores the nodal voltage. During the flashing period when the electroluminescent element 16 is not lit, the capacitor 178 is connected by the switch 170 through resistor 180 to the output of amplifier 176.
The integrator 100 is provided with a brightness adjustment 182 which establishes a desired intensity or brigntness of the light emitted by the electroluminescent light 16. A capacitor 184 and resistor 186 provide a time constant sufficient for maintaining the integrator output at a dc voltage corresponding to the sampled brightness of the large element 16. When the intensity of the electroluminescent element 16 changes, for whatever reason, the output dc voltage of the integrator 100 changes in an inverse manner.

;3~

The output of tha integrator lOO is coupled to an input contact of each switch 94 and 96. The other input contact of the switches are connected to ground, and the poles of the switches are connected to the inputs of respective amplifiers 102 and 104. In this manner, when the counter outputs 88 and 90 are at lo~ic highs, the output of the integrator 100 is switched at the respective rates to the inputs of amplifiers 102 and 104. On the other hand, when the counter output 88 and 90 are ~t logic lows, ~he inputs of amplifiers 102 and 104 are switched to ground. The respective inputs of amplifiers 102 and 104 are thus switched between ground and a dc voltage representative of the light intensity desired to be emitted by electroluminescent light 16.
Each power amplifier 102 and 104 includes a differential amplifier 188 and 190 configured with a voltage gain of unity. NPN driver transistors 192 and 194 provide a current gain for coupling the respective switching rates to oscillators 106 and 108. The dc output voltage of the integrator 100 is thus converted into a corresponding current by transistors 192 and 194 representative of the light intensity of the electroluminescent display 16.
Oscillator 106 and transformer 110 comprise a conventional inverter for converting the dc l~vel of the current supplied by transistor 192 into an ac voltage for driving the electroluminescent display 16. Thus, when the proximity sensor 2~ senses the movement of an object, the output of the integrator 100 is applied at the rate of the counter outputs 88 and 90 to the power amplifiers 102 and 104. Particularly, the output of amplifier 102 comprises current pulses at the repetition rate of four hertz, and with an amplitude corresponding to the voltage of the integrator lOO outputO Accordingly, the amplitude of the current pulse applied to the oscillator 106 is related to the ac voltage amplitude driving the electroluminescent element 16. As the amplitude of the current pulse applied to oscillator 106 increases or decreases, corresponding to an increase or decrease in the intensity output of the electroluminescent element 16, the ac voltage applied to the element 16 decreases or increases. The brightness of the element 16 is then restored in accordance with the value established by adjustment resistor 182. Oscillator 108 and transformer 112 operate in a comparable manner.
Inverters of the type suitable for the operation described above are identified by series E 600, unit no. E 0003, and obtainable from Endicott Research Group, Inc., Endicott, New York. It can be appreciated that 2 major portion of the electrical circuitry of FIGURE 8 can be constructed in integrated form. Indeed, a single silicon integrated circuit can easily accommodate a majority of the circuit functions.
The operation of the electroluminescent display lO can be understood from the following example. First of all, it will be assumed that the ambient light shining on the proximity sensor 25 has not been impeded by an r ~

approaching object or person. The resistance of the element 118 of the proximity sensor will be high, and thus the voltaga coupled to the noninverting input o operational amplifier 134 will be high. As a result, the output of amplifier 134 will be at a static high voltage level and the Schmidt trigger 82 will not be triggered.
The inverter 154 will not enable the reset input of counter 156, and the counter will not be toggled by the clock 86. Thus, the input to amplifiers 102 and 104 will be grounded, and the electroluminescent displays 16 and 26 will remain off.
When a person approaches the display 10 either from the front or sides thereof, the ambient light striking the proximity sensor ~5 will be decreased, thereby lowering tha resistance of element 118. The voltage applied to the noninverting input of operational amplifier 134 will thus be decreased, whereupon the amplifier output experiences a transition from the high voltage to a logic low voltage. The Schmitt trigger 82 will then be operated, and the output thereof will go to a logic low. The output of inverter 154 will thus be at a logic high and reset counter 156 allowing counter 158 to count. The one hert~ signal on conductor 90 will operate switch 94 at such rate and alternately connect to the input of amplifier 10~ a ground and the output voltage of integrator 100. The amplifier 102, in conjunction with the oscillator 106 and transormer 110 will drive the electroluminescent display 16 with bursts of ac power.

;3,~2~

The bursts of ac power occur at a one hertz rat~, and thereby illuminate the element :L6 at such rate. In a comparable manner, the four hertz output of counter 84 is coupled by conductor 88 to switch 96, where the amplifier 104, oscillator 108 and transformer 112 illuminate the small electroluminescent element 26 at such rate.
Because of the design of the delay elements in the amplifier 80 and Schmidt trigger 82, the initial detection of the object movement causes the pulsing illumination of the electroluminescent elements 16 and 26 only for a short predetermined period of time. As described in detail above, the magnitude of the output voltage of integrator 100 is representative of intensity of light output by element 16. The light intensity of 15 element 16 is stored as a voltage on capacitor 178, and coupled by amplifier 176 to the integrator 100. Thus, the sample and hold amplifier 92 continuously monitors the light intensity of the electroluminescent element 16, and provides such information for compariso~ with the setting 20 of potentiometer 182 by the amplifier of integrator 100.
Switches 94 and 96 thus couple signals to amplifiers 102 and 104 which correspond to drive signal levels which will illuminate the elements 16 and 26 at the desired intensities.
While the foregoing display 10 described in connection with the circuit o FIGURE 8 includes many features, it is not necessary to incorporate every feature to realize thei.r individual advantages. Accordingly, in some applications it may be des:irable to eliminate the electroluminescent element aging compensation circuit, and in still other applications it may be desirable to eliminate the proximity sensing feature. In yet other S applications, it may be desirable to provide a sin~le electroluminescent display, and dispense with the blinking or flashing feature.
With reference now to FIGURE 9, there is shown another embodiment and application of the invention.
Particularly, an automobile license plate structure is shown having an electroluminescent backlight 200 and a transparent license number template 202. The numbers or letters 204 th~mselves are preferably formed with an opaque material to provida a contrast with the background lS light 200. Furthermore, an electroluminescent peripheral light element 206 is provided separate and apart from the background light 200. Likewise, an electroluminescent light 208 forms a third independent light source. With this construction, the state or province 210 formed on the template 202 is illuminated by light section 208.
Preferably, light 208 is a different color than background 200.
The license plate embodiment of FIGURE 9 is also provided with a proximity sensor 212, operating by the same principles described abov~. In this situation, however, the proximity sensor 212 comprises a photoconductive cell which is rPsponsive to the lights of an approaching automobile, rather than ambient light.

~3~

Because the intensity of an automobile headlamp is generally greater than that of ambient room lights, the proximity sensor 212 can detect automobiles approaching several hundred feet behind. In the application, the amplifier which amplifies the light detected by the proximity sensor 212 is not responsive to movement, but rather is responsive to light. Thus, as long as the lights of an automobile are shining on the pro~imity detector 212, selected electroluminescent elements flash.
- 10 Preferably, the peripheral light element 206 is selected as the element to flash, thereby bringing attention to the driver in the approaching car. Neither the background light 200 nor the light section 208 function and thus the identification of the automobile is not impeded. The foregoing application provides a significant advantage in that the proximity sensor 212 can be adjusted to cause flashing when the approaching car reaches a predetermined distance. It can be appreciated that there is a correlation between the headlamp intensity of a rearwardly approaching automobile, and the distance separating the two automobiles. While the tail lights of a car provide a ganeral indication of the presence of the front automobile, it is not always possible by the rear driver to judge the distance o the automobile ahead.
This is true especially at night when, indeed, it is not always possible to even judge whether the car ahead is completely stopped or traveling at an appreciable rate of speed. Accordin~ly, the present invention provides both 3~

an alertness of the car ahead, and a means for roughly judging the distance separatins the cars. Also, the lighting system of the invention can be mounted within the automobile so as to be visible t:hrough the rear window.
This allows further awareness to following drivers in critical driving conditions, such as in traffic jams or when drivers are confronted with highway driving speeds interspersed with frequent stops. The invention also facilitate~ safety in the event the auto tail lights or stop lights are obscurad with mud, snow, grime, etc.
The sense and control circuit of the automobile license display can be powered from the automobile light switch, wherein the electroluminescent elements 200, 206 and 208 operate only when the headlights of the automobile are switched on, and/or the braka pedal depressed.
In FIGURE 10, the automobile license embodiment is shown including separate letter or number elements 216 pluggable into the background electroluminescent light 218. Particularly, the number or letter elements 216 include contact pins 220 which fit into corresponding contact sockets 222 embedded within the background light element 218. The pair of pins 220 provide power to both plates of the capacitor-like electroluminascent material, thereby causing the letter or number element 216 to be illuminated. With this arrangement, license numbers can be changed or replaced to accommodate changes in the identification of the automobile. Moreover, each electroluminescent number or element may be driven 5~2 individually, or in different se~uences, such as with the two display elements of FIGURE 8. As with the embodiment of FIGURE 9, the front access cover 224 is sealed against the entry of moisture into the case 226 by a closed cell foam gasket 228.
With reference to FIGURE ll, there is illustrated the concepts and principles of the invention embodied into a lapel button 230. Because of the inherent low power consumption of an electroluminescent display, the-battery for the display may include a small watch or calculator-type battery mounted within the button 230.
Since the lapel button 230 is generally worn close to a pocket, a battery wired externally to the button ~30 can be conveniently held within the pocket. Moreover, power can be conserved by providing the flashing feature described above. Power is then consumed only during the illuminated portion of the flashing cycle. A proximity sensor 232 can also be provided in the manner described above, for illuminating one or more electroluminescent sactions 23~ of the button.
From the foregoing, an electroluminescent display has been disclosed which provides features and advantages not heretoore known, including a technique for combining multiple electroluminescent elements in one display. Plural colored displays may also be used. Also disclosed is a technique for compensating for the deteriorating brightness of an electroluminescent light, thus maintaining a constant light intensity irrespective of the age of the light. An electroluminescent display is provided with a feature which en~bles one or more elements thereof to be flashed at different rates, thereby attracting attention to the display. Moreover, a proximity sensor with highly nondirectional attributes is disclosed for activating the electroluminescent light on detecting the movement of an approaching object. The display with all the foregoing features is well adapted for shelf edge mounting to highlight merchandise. The concepts of the invention may also be applied, for example, to singage, advertising placards on vehicles, as well as many other applications.
While the preferred embodiments of the method and apparatus have been disclosed with reference to specific sensors, lights and circuits, it is to be understood that many changes in detail may be made as a matter of engineering choice without departing from the spirit and scope of the invention as defined by the appended claims. Indeed, those skilled in the art may prefer not to adopt all or various advantages or features of the presant invention into a single composite display in order to realize their individual advantages.

Claims

1. A passive advertising display for displaying indicia associated therewith, and for use in an ambient light condition in connection with advertising merchandise, comprising:
a display light switchable between an off and an on state for illuminating said indicia;
a proximity sensor responsive to the ambient light for sensing a person approaching proximate said display by sensing a small change in said ambient light and providing an output indication of the proximity of the object; and means responsive to the output indication of said proximity sensor for switching said display light to the on state to illuminate said indicia.

2. The lighted display of Claim 1 further including timer means for maintaining said display light switched on for a predetermined period of time.

3. The lighted display of Claim 1 wherein said proximity sensor is responsive to changes in the ambient light as a result of the movement of said object when proximate thereto.

4. The lighted display of Claim 3 further including timer means for maintaining said display light switched on for a predetermined period of time in the absence of the movement of said object.

5. The lighted display of Claim 1 wherein said proximity sensor comprises photoconductive means located proximate the front of the display and responsive to the intrusion of an object between the photoconductive means and an ambient light for providing said output indication.

6. The lighted display of Claim 5 wherein said photoconductive means includes directional means for focusing said ambient light to said photoconductive means.

7. The lighted display of Claim 5 wherein said photoconductive means includes an apertured mask for directing ambient light onto said photoconductive means.

8. The lighted display of Claim 7 wherein said photoconductive means includes a photoconductive material responsive to light, said photoconductive material being formed in a narrow width, and said apertures are aligned with a portion of the photoconductive material.

9. The lighted display of Claim 8 wherein the apertures in said mask are spaced from each other.

10. The light display of Claim 1 further including means for resolving the remoteness and nearness of said object when said object is disposed in the fringe area to which said proximity sensor is responsive.

11. The lighted display of Claim 10 wherein said resolving means includes hysteresis means operable in said fringe area for establishing proximity on the first indication thereof and holding said indication a predetermined period of time after said object is moved from the proximate area.

12. A lighted shelf display for use in attracting attention to merchandise displayed on a shelf which is generally illuminated by overhead store lights to provide ambient light to the merchandise, comprising:
a light;
a display case for housing said light, including an access cover for providing access to the interior of said case;
information bearing means disposed adjacent said light for providing information bearing contrast when said light is illuminated;
bracket means for fastening said case to said shelf adjacent the front edge thereof;
power means for supplying power to said light;
means for sensing the intensity of ambient light external to said shelf display so that when a person approaches said display anywhere in a peripheral area of said display said sensing means causes said power to be coupled to said light to thereby illuminate the information bearing means; and means for removing power from said light when no person is located in said peripheral area to thereby restore said shelf display to a quiescent state.

13. The lighted display of Claim 12 wherein said light is an electroluminescent light, and further including another electroluminescent light powered by said power means.

14. The lighted display of Claim 13 further including control means for automatically controlling the brightness of at least one said light.

15. The lighted display of Claim 14 wherein said control means includes means for flashing ones of said electroluminescent lights at different rates when said sensing means senses a person in said peripheral area.

16. The lighted display of Claim 12 further including means for sensing the intensity of light emitted by said display and for automatically adjusting the power supply to increase the light emitted when the sensing of the light intensity indicates a decreased intensity.

17. The lighted display of Claim 12 wherein said bracket means includes means for fastening said case so that the top thereof is substantially flush with the top surface of the shelf, and said power means is disposed under said shelf.

18. The lighted display of Claim 17 further including a housing integral with said case for containing said power means, and means for fixing said housing to the underside of the shelf.

19. The lighted display of Claim 17 further including for use with a shelf of the type having a shelf talker, means for engaging the shelf talker so that said case is stabilized.

20. A method of highlighting merchandise stored on a shelf and attracting the attention of prospective customers comprising the steps of:
positioning a display on a shelf area proximate the merchandise;
activating lighting of the display only when a shopper approaches within an area proximate the display; and deactivating the lighting of the display after the shopper moves beyond the proximate area.

21. The method of Claim 20 further including the steps of operating the light when activated.

22. The method of Claim 21 further including lighting a plurality of areas proximate the shelf edge and controlling at least one said area.

23. The method of Claim 22 further including operating both lighted areas at different rates.

24. The method of Claim 23 further including illuminating different advertising indicia with each said light.

25. An attention attracting lapel button, comprising:
a button having an electroluminescent lighted area;
a proximity sensor responsive to ambient light intensity for causing said lighted area to illuminate; and a source of electrical power connected to said lighted area and to said sensor for powering said lighted area in response to the ambient light intensity detected by said sensor.

26. The lapel button of Claim 25 further including means for flashing said lighted area when powered in response to the ambient light intensity.

27. A proximity sensor responsive to the change of ambient light directed thereto, comprising:
a photoelectric element providing an output indication of the intensity of the ambient light striking said element;
an apertured mask disposed between said photoelectric element and the ambient light, said aperture being arranged in the mask so as to provide a change in the intensity of light striking said element in response to the change of the ambient light by an object located within an arcuate range in front of said photoelectric element.

28. The proximity sensor of Claim 27 wherein said mask includes a plurality of apertures.

29. The proximity sensor of Claim 28 wherein said photoelectric element comprises a narrow line of light sensitive material, a portion of said light sensitive material being disposed behind each said aperture.

30. The proximity sensor of Claim 29 further including a lens for focusing the ambient light on the light sensitive material.

31. The proximity sensor of Claim 28 wherein said photoelectric element comprises a plurality of vertically oriented lines, and the apertured mask includes a diagonal slit.

32. The proximity sensor of Claim 28 wherein said apertures are arranged in a triangular shape.

33. The proximity sensor of Claim 27 wherein said mask includes a single vertical slit.

34. The proximity sensor of Claim 27 wherein said mask includes an aperture of about 30mm in diameter.