CA1237167A - Multicolour display device - Google Patents
Multicolour display deviceInfo
- Publication number
- CA1237167A CA1237167A CA000535364A CA535364A CA1237167A CA 1237167 A CA1237167 A CA 1237167A CA 000535364 A CA000535364 A CA 000535364A CA 535364 A CA535364 A CA 535364A CA 1237167 A CA1237167 A CA 1237167A
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- light emitting
- light
- emitting diode
- display
- auxiliary
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- 239000003086 colorant Substances 0.000 claims abstract description 12
- 239000002131 composite material Substances 0.000 claims abstract description 12
- 238000002156 mixing Methods 0.000 claims description 11
- 230000000694 effects Effects 0.000 claims description 5
- 230000004913 activation Effects 0.000 claims description 3
- 238000005286 illumination Methods 0.000 claims description 3
- 230000003287 optical effect Effects 0.000 abstract description 6
- 238000010586 diagram Methods 0.000 description 4
- 238000000149 argon plasma sintering Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000001747 exhibiting effect Effects 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 230000005465 channeling Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000012358 sourcing Methods 0.000 description 1
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Abstract
MULTICOLOUR DISPLAY DEVICE
ABSTRACT OF THE DISCLOSURE
A multicolour display device having seven illuminated optically stable states includes three triads of associated electro-optical components. In each triad, a light sensor is electrically coupled with a display light emitting diode and auxiliary light emitting diode. An optical feedback is established in each triad between the auxiliary light emitting diode and the light sensor tending to maintain its associated display light emitting diode either in the illuminated or extinguished condition. Light signals of respectively different colours emitted by three display light emitting diodes are blended to obtain a composite light signal of a colour in accordance with the conditions of respective display light emitting diodes.
ABSTRACT OF THE DISCLOSURE
A multicolour display device having seven illuminated optically stable states includes three triads of associated electro-optical components. In each triad, a light sensor is electrically coupled with a display light emitting diode and auxiliary light emitting diode. An optical feedback is established in each triad between the auxiliary light emitting diode and the light sensor tending to maintain its associated display light emitting diode either in the illuminated or extinguished condition. Light signals of respectively different colours emitted by three display light emitting diodes are blended to obtain a composite light signal of a colour in accordance with the conditions of respective display light emitting diodes.
Description
6~
MULTICOL.OUR DISPL,AY DEVICE
~ACKGROUND OF THE INVENTION
1. Field of the Invention This invention generally relates to display devices for emitting light of several different colours and more specifically to a display device having several stable states characterized by respectively different colours.
MULTICOL.OUR DISPL,AY DEVICE
~ACKGROUND OF THE INVENTION
1. Field of the Invention This invention generally relates to display devices for emitting light of several different colours and more specifically to a display device having several stable states characterized by respectively different colours.
2. Description of the Prior Art A multicolour semiconductor lamp comprising a plurality of light emitting diodes for emitting light of respectively different colours is disclosed in U. S. Patent No. 3,875,456 issued on April 1, 1975 to Tsuyoshi Kano et al. The light emitting diodes are closely adjacent and covered by a layer of light scattering material to provide an appearance of a single light source.
A circuit for selectively illuminating one of a pair of parallel back-to-back coupled light emitting dlodes is disclosed in U. S. Patent No. 4,484,105 issued on Nov. 20, 1984 to Rlchard J. Kriete et al. Two photon-emitting devices and two photon-responsive devices are additionally provided for selectively reversing current flow through the back-to-back coupled light emitting diodes to illuminate them either in red or green colour. Since the two light emitting diodes are coupled to conduct current in opposite directions, they cannot be illuminated simultaneously to blend their emissions.
A display device capable of exhibiting more than two stable states characterized by respectively different colours is unknown.
., ,7~
SUMMARY OF T~IE INVENTlON
Accordingly, it is the principal object of this invention to provide an improved multicolour display device exhibiting more than two stable optical states.
The invention resides in physical arrangernent and electrical and optical coupling of three electro-optical triads, each including a light sensor, display light emitting diode, and auxiliary light emitting diode. As will be more fully pointed out subsequently, the display and ~0 auxiliary light emitting diodes in each triad may be electrically coupled either in series or in parallel.
The auxiliary light emitting diode in each triad serves to maintain its associated display light emitting diode either fully illuminated or completely extinguished. Since light signals emitted by the auxiliary light emitting diodes are not viewed externally, their colour may be selected at will .
Light signals of respectively different primary colours emitted by the display light emitting diodes are combined to obtain a composite light signal, which may be viewed externally, of a colour in accordance with the conditions of respective display light emitting diodes.
Further objects of the invention will become obvious from the accompanying drawings and their descriptlon.
A circuit for selectively illuminating one of a pair of parallel back-to-back coupled light emitting dlodes is disclosed in U. S. Patent No. 4,484,105 issued on Nov. 20, 1984 to Rlchard J. Kriete et al. Two photon-emitting devices and two photon-responsive devices are additionally provided for selectively reversing current flow through the back-to-back coupled light emitting diodes to illuminate them either in red or green colour. Since the two light emitting diodes are coupled to conduct current in opposite directions, they cannot be illuminated simultaneously to blend their emissions.
A display device capable of exhibiting more than two stable states characterized by respectively different colours is unknown.
., ,7~
SUMMARY OF T~IE INVENTlON
Accordingly, it is the principal object of this invention to provide an improved multicolour display device exhibiting more than two stable optical states.
The invention resides in physical arrangernent and electrical and optical coupling of three electro-optical triads, each including a light sensor, display light emitting diode, and auxiliary light emitting diode. As will be more fully pointed out subsequently, the display and ~0 auxiliary light emitting diodes in each triad may be electrically coupled either in series or in parallel.
The auxiliary light emitting diode in each triad serves to maintain its associated display light emitting diode either fully illuminated or completely extinguished. Since light signals emitted by the auxiliary light emitting diodes are not viewed externally, their colour may be selected at will .
Light signals of respectively different primary colours emitted by the display light emitting diodes are combined to obtain a composite light signal, which may be viewed externally, of a colour in accordance with the conditions of respective display light emitting diodes.
Further objects of the invention will become obvious from the accompanying drawings and their descriptlon.
3~.6'7 BRIEF DESCR-[PTION OF TIIE nRAWINGS
In the drawings in which are shown several possible embodiments of the invention, FIG. 1 is a generalized block diagram illustrating the inventive principles.
FIG. 2 is a schematic diagram of a two primary colours display device.
FIG. 3 is a schematic diagram of a three primary colours display device.
FIG. 4 is a cross-sectional view revealing internal structure of a multicolour display device shown in FIG. 3.
Throughout the drawings, like characters indicate like parts.
lX~
DESCRIPTION OF T~IE PREFI~RRED EMBODIMENTS
Referring now, more particuLarly, to the drawings, in FIG. 1 is shown, in very general configuration, a multicolour display device of the present invention which comprises three triads of electrically coupled electro-optical components. The first triad includes a display red LED (light emitting diode) 13a, auxiliary LED 14a, and LAD
(light activated device) 12a. The second triad includes a display green LED 13b, auxiliary LED 14b, and LAD 12b. The third triad includes a display blue LED 13c, auxiliary LED
14c, and LAD 12c. The light activated devices, or light sensors, typically exhibit resistance variable in accordance with illumination. An optical feedback is established in each triad from the auxiliary LED to its associated LAD to exert a toggle effect by varying its resistance in a sense tending to maintain its associated display LED either in the illuminated or extinguished condition. The light signals emitted by the three display LE~s are blended to form a composite light signal of a colour in accordance with the conditions of respective display LEDs. Consequently, the device has eight possible states: emitting light of red colour, green colour, blue colour, yellow colour, purple colour, blue-green colour, white colour, or being extinguished. As will be more specifically revealed subsequently, all these states are optically and electrically stable.
The terms 'light source', 'light activated device', and 'light sensor' as used throughout the description of the invention are intended to be interpreted in a broad sense.
'7~6~7 Light sources may include light emitting diodes, liquid crystal devices, plasma devices, and the like. Light sensors may include phototransistors, photodiodes, photodarlingtons, phototriacs, photo sensitive silicon controlled rectifiers, photodetectors, photoresistors, photoconductive cells, and the like. Optical Eeedback between the auxiliary LED and ].ight sensor in each triad may be established either by suitable physical arrangement therebetween or, alternatively, by use of light channeling devices which may include mirrors, prismatic devices, lenses, optical fibers, reflectors, directors, filters, and the like.
A display device incorporating the features of the present invention is illustrated in a schematic diagram form in FIG. 2. Two voltage levels, referred to as a logic high and low, respectively, are used throughout the description of the circuit. The device employs commercially well known phototransistors which exhibit very high resistance, typically hundreds of Megaohms, when maintain~d in dark and very low resistance, typically tens of Ohms, when illuminated.
To extinguish the device, a low logic level is momentarily applied to its Clear input GLR. As a consequence, the output of a preferably TTL (Transistor Transistor Logic) buffer 19a also drops to a low logic level. Since a TTL device is not capable of sourcing current from a low logic level output, no current can flow therefrom to ground. All LEDs 13a, 13b, 14a, and 14b therefore extinguish, and resistances of the phototransistors 16a and 16b rise to very high values. When ~3'7~
a high logic Level 20a returns to the input CLR, the output of buffer 19a also rises to a high logic Level. ~lowever, the currents flowing via resistor 17a, high resistance of phototransistor 16a and LEDs 13a, 14a in parallel to ground, and via resistor 17b, high resistance of phototransistor 16b and LEDs 13b, 14b in parallel to ground, are very small and not sufficient to illuminate the I.EDs. This state is therefore stable and will exist until either of or both inputs R, G are activated.
To illuminate the device in red colour, a relatively narrow positive going pulse 20b is applied to its input R
(Red). The width of the pulse depends on the response time of the phototransistor and should be sufficient to allow its resistance to drop below a predetermined triggering point.
As a consequence, current flows from the input R, via current limiting resistor 17c, which confines the current flow, and LEDs 13a, 14a in parallel to ground. The auxiliary LED l~a illuminates, and its emission causes the resistance of its associated phototransistor 16a to rapidly drop to a very low value. As a result of positive optical feedback, whereby the increase in luminance of the auxiliary LED causes the decrease in resistance of the phototransistor which in turn has an effect of further increase in the luminance and further decrease in the resistance, the current in the display red LED branch, from buffer l9a, via resistor 17a and phototransistor 16a, sharply rises to a value sufficient to maintain the LEDs 13a and 14a fully illuminated. At the conclusion of the pulse 20b, the magnitude of the LED current is limited substantially by the value of the current limiting resistor 17a. It is readily ~ 3~
apparent that t~is state is stable and wilL e~ist until another input of the device is activated.
To illuminate the device in green colour, a positive going pulse 20c is applied to its input G (Green). As a consequence, current flows from the input G, via current limiting resistor 17d and LEDs 13b, 14b in parallel to ground. The auxiliary LED 14b illuminates, and its emission causes the resistance oE its associated phototransistor 16b to drop to a very low value. The current in the display green LED branch, from buffer l9a, via resistor 17b and phototransistor 16b, sharply rises to a value sufficient to maintain the LEDs 13b and 14b illuminated.
To illuminate the device in yellow colour, both pulses 20b and 20c are applied, either simultaneously or sequentially, to respective inputs R and G. As a consequence, currents flow from the input R, via current limiting resistor 17c and LEDs 13a, 14a in parallel to ground and from the input G, via current limiting resistor 17d and LEDs 13b, 14b in parallel to ground. Both auxiliary LEDs 14a and 14b illuminate, and their emissions respectively cause the resistances o~ associated phototransistors 16a and 16b to drop to very low values.
The currents in the display red LED and display green LED
branches sharply rise to values sufficient to maintain all LEDs 13a, 13b, 14a, and 14b illuminated. The red and green light signals emitted by the display LEDs 13a and 13b are blended to form a composite light signal of substantially yellow colour. The hue of the composite light signal may be accurately adjusted by varying the values of current limiting resistors 17a and 17b.
~ ~t,~317~
Since the dispLay device shown in FIG. 3 is similar to the one shown in FIG. 2, it wilL ~e described only briefly.
The light emitting diodes 13a, L3b, 13c, 14a, l~b, and 14c are reversed with respect to like LEDs in FIG. 2, and a positive voltage +VCC (typically + 5 V) is applied to the interconnected anodes of the display LEDs. Logic levels of the control pulses are also reversed. The device may he extinguished by applying a high logic level to its Clear input CLR; a low logic level therein will maintain its instant condition. To illuminate the device in blue colour, a negative going pulse 20g is applied to its input B (Blue).
As a consequence, current flows from the source ~VCC, via display LED 13c, auxiliary LED 14c, coupled in series, and current limiting resistor 17j to input terminal B. The auxiliary LED 14c illuminates, and its emission causes the resistance of its associated phototransistor 16c to drop to a very low value. The current in the display blue LED
branch sharply rises to a value sufficient to maintain the LED 13c illuminated, being limited only by the value of current limiting resistor 17g.
To illuminate the device in purple colour, both pulses 20e and 20g are applied, either simultaneously or sequentially, to respective inputs R and B. As a consequence, currents flow from the source +VCC, via display LED 13a, auxiliary LED 14a and resistor 17h to input terminal R and from the source +VCC, via display LED 13c, auxiliary LED 14c, and resistor 17j to input terminal B.
Both auxiliary LEDs 14a and 14c illuminate, and their emissions respectively cause the resistances of associated phototransistors 16a and 16c to drop to very low values~
6'7 The currents in the dispLay red LED and dlsplay blue LED
branches sharply rise to values s~lfficient to maintain all LEDs 13a, 13c, 14a, and 14c illuminated. The red and blue light signals emitted by the display LEDs 13a and 13c are blended to form a composite light signal of substantially purple colour.
To illuminate the device in blue-green colour, both pulses 20f and 20g are applied, either simultaneously or sequentially, to respective inputs G and B. As a consequence, currents flow from the source +VCC, via display LED 13b, auxiliary LED 14b, and resistor 17i to input terminal G and from the source +VCC, via display LED 13c, auxiliary LED 14c, and resistor 17j to input terminal B.
Both auxiliary LEDs 14b and 14c illuminate, and their emissions respectively cause the resistances of associated phototransistors 16b and 16c to drop to very low values.
The currents in the display green LED and display blue LED
branches sharply rise to values sufficient to maintain all LEDs 13b, 13c, 14b, and 14c illuminated. The green and blue light signals emitted by the display LEDs 13b and 13c are blended to form a composite light signal of substantially blue-green colour.
To illuminate the device in white colour, all three pulses 20e, 20f, and 20g are applied, either simultaneously or sequentially, to respecti-ve inputs R, G, and B. As a consequence, currents flow from the voltage supply +VCC, via display LED 13a, auxiliary LED 14a, and resistor 17h to terminal R, from the voltage supply ~VCC, via display LED
13b, auxiliary LED 14b, and resistor 17i to terminal G, and from the voltage supply +VCC, via display LED 13c, auxiliary LED 14c, and reslstor 17j to termlnal B. The three auxiLlary LEDs 14a, 14b, and 14c llluminate, and their emissions respectively cause the resistances of associated phototransistors 16a, 16b, and 16c to drop to very low values. The currents in the display red LED, display green LED, and display blue LED branches sharply rise to values sufficient to maintain all LEDs 13a, 13b, 13c, l4a, 14b, and 14c illuminated. The red, green, and blue light signals emitted by the display LEDs 13a, 13b, and 13c are blended to form a composite light signal of substantially white colour.
An important consideration has been given to physical arrangement of the light sources and sensors in the display device of the invention, to simultaneously provide the blending of primary colours and optically separated feedbacks in respective triads.
Referring additionally to FIG. 4, which should be considered together with FIG. 3, the display device is comprised of a housing 30 having two opaque walls 22a and 22b disposed therein which are tapered in the thickness toward the top of the housing. The inner inclined surfaces of the walls define therebetween a light blending cavity 23.
The dimensions of the housing should be considered as merely illustrative and may be modified. The display light emitting diodes 13a, 13b, and 13c, adapted for emitting upon activation light signals of red, green, and blue primary colours, respectively, are mounted within the light blending cavity on a base portion 29. The- three display LEDs are completely surrounded by light scattering material 25 serving to disperse the light signals to form a composite light signal of a composite colour that emerges at the top '7~
surface 24 of the light blending cavity. Three chambers 21a, 21b, and 21c, which are secured from the presence of ambient light and optically isolated from one another, are formed in the opaque walLs 22a and 22b for accommodating respective pairs of auxiliary LED and phototransistor 14a and 16a, 14b and 16b, 14c and 16c. In each pair, the active area of the phototransistor is oriented to intercept light signals emitted by the associated auxiliary LED to exert a toggle effect by varying resistance of the phototransistor in a sense tending to maintain its serially coupled display LED either in the illuminated or extinguished condition.
All matter herein described and illustrated in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. It would be obvious that numerous modifications can be made in the construction of the preferred embodiments shown herein, without departing from the spirit of the invention as defined in the appended claims.
~l23'~6'7 CORRELATION TABLE
This is a correlation table of reEerence characters used in the drawings herein, their descripti.ons, and examples of commercially available parts.
# DESCRIPTION E~AMPLE
12 light activated device 13a red display LED
13b green display LED
10 13c blue display LED
14 auxiliary LED
16 phototransistor MRD310 17 resistor 19 buffer 74LS244 20 pulse 21 chamber 22 opaque wall 23 light blending cavity 24 top surface of light blending cavity 20 25 light scattering material 29 base portion 30 housing
In the drawings in which are shown several possible embodiments of the invention, FIG. 1 is a generalized block diagram illustrating the inventive principles.
FIG. 2 is a schematic diagram of a two primary colours display device.
FIG. 3 is a schematic diagram of a three primary colours display device.
FIG. 4 is a cross-sectional view revealing internal structure of a multicolour display device shown in FIG. 3.
Throughout the drawings, like characters indicate like parts.
lX~
DESCRIPTION OF T~IE PREFI~RRED EMBODIMENTS
Referring now, more particuLarly, to the drawings, in FIG. 1 is shown, in very general configuration, a multicolour display device of the present invention which comprises three triads of electrically coupled electro-optical components. The first triad includes a display red LED (light emitting diode) 13a, auxiliary LED 14a, and LAD
(light activated device) 12a. The second triad includes a display green LED 13b, auxiliary LED 14b, and LAD 12b. The third triad includes a display blue LED 13c, auxiliary LED
14c, and LAD 12c. The light activated devices, or light sensors, typically exhibit resistance variable in accordance with illumination. An optical feedback is established in each triad from the auxiliary LED to its associated LAD to exert a toggle effect by varying its resistance in a sense tending to maintain its associated display LED either in the illuminated or extinguished condition. The light signals emitted by the three display LE~s are blended to form a composite light signal of a colour in accordance with the conditions of respective display LEDs. Consequently, the device has eight possible states: emitting light of red colour, green colour, blue colour, yellow colour, purple colour, blue-green colour, white colour, or being extinguished. As will be more specifically revealed subsequently, all these states are optically and electrically stable.
The terms 'light source', 'light activated device', and 'light sensor' as used throughout the description of the invention are intended to be interpreted in a broad sense.
'7~6~7 Light sources may include light emitting diodes, liquid crystal devices, plasma devices, and the like. Light sensors may include phototransistors, photodiodes, photodarlingtons, phototriacs, photo sensitive silicon controlled rectifiers, photodetectors, photoresistors, photoconductive cells, and the like. Optical Eeedback between the auxiliary LED and ].ight sensor in each triad may be established either by suitable physical arrangement therebetween or, alternatively, by use of light channeling devices which may include mirrors, prismatic devices, lenses, optical fibers, reflectors, directors, filters, and the like.
A display device incorporating the features of the present invention is illustrated in a schematic diagram form in FIG. 2. Two voltage levels, referred to as a logic high and low, respectively, are used throughout the description of the circuit. The device employs commercially well known phototransistors which exhibit very high resistance, typically hundreds of Megaohms, when maintain~d in dark and very low resistance, typically tens of Ohms, when illuminated.
To extinguish the device, a low logic level is momentarily applied to its Clear input GLR. As a consequence, the output of a preferably TTL (Transistor Transistor Logic) buffer 19a also drops to a low logic level. Since a TTL device is not capable of sourcing current from a low logic level output, no current can flow therefrom to ground. All LEDs 13a, 13b, 14a, and 14b therefore extinguish, and resistances of the phototransistors 16a and 16b rise to very high values. When ~3'7~
a high logic Level 20a returns to the input CLR, the output of buffer 19a also rises to a high logic Level. ~lowever, the currents flowing via resistor 17a, high resistance of phototransistor 16a and LEDs 13a, 14a in parallel to ground, and via resistor 17b, high resistance of phototransistor 16b and LEDs 13b, 14b in parallel to ground, are very small and not sufficient to illuminate the I.EDs. This state is therefore stable and will exist until either of or both inputs R, G are activated.
To illuminate the device in red colour, a relatively narrow positive going pulse 20b is applied to its input R
(Red). The width of the pulse depends on the response time of the phototransistor and should be sufficient to allow its resistance to drop below a predetermined triggering point.
As a consequence, current flows from the input R, via current limiting resistor 17c, which confines the current flow, and LEDs 13a, 14a in parallel to ground. The auxiliary LED l~a illuminates, and its emission causes the resistance of its associated phototransistor 16a to rapidly drop to a very low value. As a result of positive optical feedback, whereby the increase in luminance of the auxiliary LED causes the decrease in resistance of the phototransistor which in turn has an effect of further increase in the luminance and further decrease in the resistance, the current in the display red LED branch, from buffer l9a, via resistor 17a and phototransistor 16a, sharply rises to a value sufficient to maintain the LEDs 13a and 14a fully illuminated. At the conclusion of the pulse 20b, the magnitude of the LED current is limited substantially by the value of the current limiting resistor 17a. It is readily ~ 3~
apparent that t~is state is stable and wilL e~ist until another input of the device is activated.
To illuminate the device in green colour, a positive going pulse 20c is applied to its input G (Green). As a consequence, current flows from the input G, via current limiting resistor 17d and LEDs 13b, 14b in parallel to ground. The auxiliary LED 14b illuminates, and its emission causes the resistance oE its associated phototransistor 16b to drop to a very low value. The current in the display green LED branch, from buffer l9a, via resistor 17b and phototransistor 16b, sharply rises to a value sufficient to maintain the LEDs 13b and 14b illuminated.
To illuminate the device in yellow colour, both pulses 20b and 20c are applied, either simultaneously or sequentially, to respective inputs R and G. As a consequence, currents flow from the input R, via current limiting resistor 17c and LEDs 13a, 14a in parallel to ground and from the input G, via current limiting resistor 17d and LEDs 13b, 14b in parallel to ground. Both auxiliary LEDs 14a and 14b illuminate, and their emissions respectively cause the resistances o~ associated phototransistors 16a and 16b to drop to very low values.
The currents in the display red LED and display green LED
branches sharply rise to values sufficient to maintain all LEDs 13a, 13b, 14a, and 14b illuminated. The red and green light signals emitted by the display LEDs 13a and 13b are blended to form a composite light signal of substantially yellow colour. The hue of the composite light signal may be accurately adjusted by varying the values of current limiting resistors 17a and 17b.
~ ~t,~317~
Since the dispLay device shown in FIG. 3 is similar to the one shown in FIG. 2, it wilL ~e described only briefly.
The light emitting diodes 13a, L3b, 13c, 14a, l~b, and 14c are reversed with respect to like LEDs in FIG. 2, and a positive voltage +VCC (typically + 5 V) is applied to the interconnected anodes of the display LEDs. Logic levels of the control pulses are also reversed. The device may he extinguished by applying a high logic level to its Clear input CLR; a low logic level therein will maintain its instant condition. To illuminate the device in blue colour, a negative going pulse 20g is applied to its input B (Blue).
As a consequence, current flows from the source ~VCC, via display LED 13c, auxiliary LED 14c, coupled in series, and current limiting resistor 17j to input terminal B. The auxiliary LED 14c illuminates, and its emission causes the resistance of its associated phototransistor 16c to drop to a very low value. The current in the display blue LED
branch sharply rises to a value sufficient to maintain the LED 13c illuminated, being limited only by the value of current limiting resistor 17g.
To illuminate the device in purple colour, both pulses 20e and 20g are applied, either simultaneously or sequentially, to respective inputs R and B. As a consequence, currents flow from the source +VCC, via display LED 13a, auxiliary LED 14a and resistor 17h to input terminal R and from the source +VCC, via display LED 13c, auxiliary LED 14c, and resistor 17j to input terminal B.
Both auxiliary LEDs 14a and 14c illuminate, and their emissions respectively cause the resistances of associated phototransistors 16a and 16c to drop to very low values~
6'7 The currents in the dispLay red LED and dlsplay blue LED
branches sharply rise to values s~lfficient to maintain all LEDs 13a, 13c, 14a, and 14c illuminated. The red and blue light signals emitted by the display LEDs 13a and 13c are blended to form a composite light signal of substantially purple colour.
To illuminate the device in blue-green colour, both pulses 20f and 20g are applied, either simultaneously or sequentially, to respective inputs G and B. As a consequence, currents flow from the source +VCC, via display LED 13b, auxiliary LED 14b, and resistor 17i to input terminal G and from the source +VCC, via display LED 13c, auxiliary LED 14c, and resistor 17j to input terminal B.
Both auxiliary LEDs 14b and 14c illuminate, and their emissions respectively cause the resistances of associated phototransistors 16b and 16c to drop to very low values.
The currents in the display green LED and display blue LED
branches sharply rise to values sufficient to maintain all LEDs 13b, 13c, 14b, and 14c illuminated. The green and blue light signals emitted by the display LEDs 13b and 13c are blended to form a composite light signal of substantially blue-green colour.
To illuminate the device in white colour, all three pulses 20e, 20f, and 20g are applied, either simultaneously or sequentially, to respecti-ve inputs R, G, and B. As a consequence, currents flow from the voltage supply +VCC, via display LED 13a, auxiliary LED 14a, and resistor 17h to terminal R, from the voltage supply ~VCC, via display LED
13b, auxiliary LED 14b, and resistor 17i to terminal G, and from the voltage supply +VCC, via display LED 13c, auxiliary LED 14c, and reslstor 17j to termlnal B. The three auxiLlary LEDs 14a, 14b, and 14c llluminate, and their emissions respectively cause the resistances of associated phototransistors 16a, 16b, and 16c to drop to very low values. The currents in the display red LED, display green LED, and display blue LED branches sharply rise to values sufficient to maintain all LEDs 13a, 13b, 13c, l4a, 14b, and 14c illuminated. The red, green, and blue light signals emitted by the display LEDs 13a, 13b, and 13c are blended to form a composite light signal of substantially white colour.
An important consideration has been given to physical arrangement of the light sources and sensors in the display device of the invention, to simultaneously provide the blending of primary colours and optically separated feedbacks in respective triads.
Referring additionally to FIG. 4, which should be considered together with FIG. 3, the display device is comprised of a housing 30 having two opaque walls 22a and 22b disposed therein which are tapered in the thickness toward the top of the housing. The inner inclined surfaces of the walls define therebetween a light blending cavity 23.
The dimensions of the housing should be considered as merely illustrative and may be modified. The display light emitting diodes 13a, 13b, and 13c, adapted for emitting upon activation light signals of red, green, and blue primary colours, respectively, are mounted within the light blending cavity on a base portion 29. The- three display LEDs are completely surrounded by light scattering material 25 serving to disperse the light signals to form a composite light signal of a composite colour that emerges at the top '7~
surface 24 of the light blending cavity. Three chambers 21a, 21b, and 21c, which are secured from the presence of ambient light and optically isolated from one another, are formed in the opaque walLs 22a and 22b for accommodating respective pairs of auxiliary LED and phototransistor 14a and 16a, 14b and 16b, 14c and 16c. In each pair, the active area of the phototransistor is oriented to intercept light signals emitted by the associated auxiliary LED to exert a toggle effect by varying resistance of the phototransistor in a sense tending to maintain its serially coupled display LED either in the illuminated or extinguished condition.
All matter herein described and illustrated in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. It would be obvious that numerous modifications can be made in the construction of the preferred embodiments shown herein, without departing from the spirit of the invention as defined in the appended claims.
~l23'~6'7 CORRELATION TABLE
This is a correlation table of reEerence characters used in the drawings herein, their descripti.ons, and examples of commercially available parts.
# DESCRIPTION E~AMPLE
12 light activated device 13a red display LED
13b green display LED
10 13c blue display LED
14 auxiliary LED
16 phototransistor MRD310 17 resistor 19 buffer 74LS244 20 pulse 21 chamber 22 opaque wall 23 light blending cavity 24 top surface of light blending cavity 20 25 light scattering material 29 base portion 30 housing
Claims (2)
1. A multicolour display device comprising:
three display light emitting diodes for emitting upon activation light signals of respectively different primary colours, each said display light emitting diode being capable either of an illuminated or extinguished condition;
means for blending said light signals to obtain a composite light signal of a colour in accordance with the conditions of respective display light emitting diodes;
three auxiliary light emitting diodes respectively electrically coupled to said display light emitting diodes, thereby forming three pairs of associated display light emitting diode and auxiliary light emitting diode;
three light sensors respectively electrically serially coupled to said pairs of associated display light emitting diode and auxiliary light emitting diode, each said light sensor having resistance variable with illumination; and three chambers secured from the presence of ambient light for respectively accommodating the pairs of serially coupled light sensor and auxiliary light emitting diode, in each said pair the active area of said light sensor being oriented to intercept light signals emitted by its associated auxiliary light emitting diode to exert a toggle effect by varying the resistance of said light sensor in a sense tending to maintain its serially coupled display light emitting diode either in the illuminated or extinguished condition.
three display light emitting diodes for emitting upon activation light signals of respectively different primary colours, each said display light emitting diode being capable either of an illuminated or extinguished condition;
means for blending said light signals to obtain a composite light signal of a colour in accordance with the conditions of respective display light emitting diodes;
three auxiliary light emitting diodes respectively electrically coupled to said display light emitting diodes, thereby forming three pairs of associated display light emitting diode and auxiliary light emitting diode;
three light sensors respectively electrically serially coupled to said pairs of associated display light emitting diode and auxiliary light emitting diode, each said light sensor having resistance variable with illumination; and three chambers secured from the presence of ambient light for respectively accommodating the pairs of serially coupled light sensor and auxiliary light emitting diode, in each said pair the active area of said light sensor being oriented to intercept light signals emitted by its associated auxiliary light emitting diode to exert a toggle effect by varying the resistance of said light sensor in a sense tending to maintain its serially coupled display light emitting diode either in the illuminated or extinguished condition.
2. A multicolour display device comprising:
a housing having a base and two opaque walls secured to said base, said walls being tapered in the thickness toward the top of said housing and having inner inclined surfaces defining a light blending cavity therebetween;
three display light emitting diodes disposed in said light blending cavity for emitting upon activation light signals of respectively different primary colours, each said display light emitting diode being capable either of an illuminated or extinguished condition;
means for blending within said light blending cavity said light signals to obtain a composite light signal of a colour in accordance with the conditions of respective display light emitting diodes;
three auxiliary light emitting diodes respectively electrically coupled to said display light emitting diodes, thereby forming three pairs of associated display light emitting diode and auxiliary light emitting diode;
three light sensors respectively electrically serially coupled to said pairs of associated display light emitting diode and auxiliary light emitting diode, each said light sensor having resistance variable with illumination; and three chambers disposed in said opaque walls and secured from the presence of ambient light for respectively accommodating the pairs of serially coupled light sensor and auxiliary light emitting diode, in each said pair the active area of said light sensor being oriented to intercept light signals emitted by its associated auxiliary light emitting diode to exert a toggle effect by varying the resistance of said light sensor in a sense tending to maintain its serially coupled display light emitting diode either in the illuminated or extinguished condition.
a housing having a base and two opaque walls secured to said base, said walls being tapered in the thickness toward the top of said housing and having inner inclined surfaces defining a light blending cavity therebetween;
three display light emitting diodes disposed in said light blending cavity for emitting upon activation light signals of respectively different primary colours, each said display light emitting diode being capable either of an illuminated or extinguished condition;
means for blending within said light blending cavity said light signals to obtain a composite light signal of a colour in accordance with the conditions of respective display light emitting diodes;
three auxiliary light emitting diodes respectively electrically coupled to said display light emitting diodes, thereby forming three pairs of associated display light emitting diode and auxiliary light emitting diode;
three light sensors respectively electrically serially coupled to said pairs of associated display light emitting diode and auxiliary light emitting diode, each said light sensor having resistance variable with illumination; and three chambers disposed in said opaque walls and secured from the presence of ambient light for respectively accommodating the pairs of serially coupled light sensor and auxiliary light emitting diode, in each said pair the active area of said light sensor being oriented to intercept light signals emitted by its associated auxiliary light emitting diode to exert a toggle effect by varying the resistance of said light sensor in a sense tending to maintain its serially coupled display light emitting diode either in the illuminated or extinguished condition.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/892,837 | 1986-08-04 | ||
| US06/892,837 US4686425A (en) | 1986-04-28 | 1986-08-04 | Multicolor display device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1237167A true CA1237167A (en) | 1988-05-24 |
Family
ID=25400584
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000535364A Expired CA1237167A (en) | 1986-08-04 | 1987-04-23 | Multicolour display device |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1237167A (en) |
-
1987
- 1987-04-23 CA CA000535364A patent/CA1237167A/en not_active Expired
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