METHOD AND APPARATUS FOR PROVIDING SELECTIVELY-COLORED

LIGHT

Technical Field [0001] The invention relates in general to a method and apparatus for providing selectively-colored light.

Background

[0002] There appears to be a ubiquitous trend to provide customized goods, products or services. As such, a need appears to exist for a method and apparatus for providing selective light that may be associated with any desirable good, product or service, such as, for example, an automotive vehicle.

Brief Description of the Drawings [0003] The disclosure will now be described, by way of example, with reference to the accompanying drawings, in which:

[0004] Figure 1 is a circuit in accordance with an exemplary embodiment of the invention;

[0005] Figure 2 is a timing diagram associated with the circuit of Figure 1 in accordance with an exemplary embodiment of the invention;

[0006] Figure 3 is an International Commission on Illumination (CIE) chromaticity diagram; and

[0007] Figure 4 is an environmental view of a vehicle that includes the circuit of

Figure 1 in accordance with an exemplary embodiment of the invention.

Detailed Description

[0008] The Figures illustrate an exemplary embodiment of a method and apparatus for providing selective light in accordance with an embodiment of the invention. It is to be generally understood that the nomenclature used herein is simply

for convenience and the terms used to describe the invention should be given the broadest meaning by one of ordinary skill in the art.

[0009] Referring to Figure 1, a circuit is shown generally at 10 according to an embodiment. The circuit 10 includes a controller, which is shown generally at 12 and a plurality of light emitting diodes (LEDs), D1-D4, and resistors R1-R4 connected to controller 12. In an embodiment, four diodes, D1-D4, and four resistors, R1-R4, are included in circuit 10.

[0010] In an embodiment, first resistor, Rl, is connected to the cathode of the first diode, Dl . In an embodiment, second resistor, R2, is connected to the anode of the second diode, D2. In an embodiment, third resistor, R3, is connected to the anode of the third diode, D3. In an embodiment, fourth resistor, R4, is connected to the cathode of the fourth diode, D4. After consulting the present disclosure, it will be readily recognized that the position of the resistors with respect to the diodes are not limited to the exemplary embodiment such that one of ordinary skill will recognize alternate arrangements for the resistors which may be based on design considerations and desired output characteristics.

[0011] With continued references to Figure 1, controller 12 includes a plurality of output pins, three of which are labeled generally OUTl, OUT2 and OUT3. Connected, respectively, to each of the three output pins OUT1-OUT3 are a first transmission line 14, or first node, a second transmission line 16, or second node, and a third transmission line 18, or third node. It will be appreciated that any suitable controller may be provided and the invention hereof should not be limited by any aspect of the controller. [0012] In an embodiment, first transmission line 14 is directly connected to the anode of the first diode, Dl , and directly connected to the cathode of the second diode, D2. In an embodiment, second transmission line 16 is commonly, and directly, connected to each of the four resistors R1-R4. In an embodiment, third transmission line 18 is connected to the cathode of third diode, D3, and the anode of fourth diode, D4. The disclosure hereof will refer to high voltage and low voltage which, to facilitate ease of disclosure, will exemplarily refer to OV and 5V, respectively.

However, it is to be appreciated that the voltages thereof should not be used to limit the invention and one of ordinary skill in the art will recognize that various voltages may be used provided the voltages utilized are sufficient to activate the diode (i.e., the voltage may be designated at any level above the band gap energy of the diode) which may be dependent upon the diode chemistry that makes the emitted wavelength (commonly known as Vf- forward voltage drop). After considering the disclosure hereof, these and other considerations should become apparent and the invention should not be limited thereby. [0013] Moreover, and in the same regard, when considering the teachings of the disclosure hereof, one of ordinary skill will appreciate that the arrangement between the resistance elements and the transmissions lines may be alternatively arranged provided the polarity of the diodes is sufficiently maintained such that there exists a single current path when first transmission line 14 is high and second transmission line 16 is low, and second transmission line 16 is hi and first transmission line 14 is low. For example, it will be appreciated that, in an embodiment, cathodes of Dl and D2 cannot be connected to the same node or transmission line. [0014] In an embodiment, when controller 12 permits current to pass through one or more of the diodes, D1-D4, which resultant creates a voltage drop thereacross, such diode or diodes are activated to emit light, which is generally represented by L1-L4. In an embodiment, the light, L1-L4, emitted from each of the diodes, D1-D4, may defined by a unique wavelength that is different from each other. In an alternative embodiment, however, the light emitted from each of the diodes may not be unique. [0015] In an embodiment, a summation of one or more of the light, L1-L4, emitted from each diode, D1-D4, defines a selectively-colored light, Lj. In an embodiment, the selectively-colored light, L _T , is defined by light that is inclusive to the visible spectrum approximately ranging between 700nm and 400nm. However, it will be appreciated that any wavelength may be utilized and the invention should not be limited to the visible spectrum. For example, in an embodiment one or more of the diodes, in an embodiment, D4, may be provided to emit a wavelength in the ultraviolet ("UV") wavelength range, which may be arranged to excite phosphors

printed on a nearby substrate (or the like) which would appear when such UV diode is activated. Moreover, in an embodiment, one or more of the diodes, in an embodiment, D4, may be provided to emit a wavelength in the infrared range. [0016] Moreover, in an embodiment, one of the diodes, for example, D4, may be provided as a white light. It will be appreciated, however, that three diodes are sufficient to access any wavelength within the visible spectrum. [0017] In an embodiment, for example, the diode, Dl, may be defined to be a red diode by emitting light, Ll, having a wavelength between approximately 780nm- 622nm. The red diode, Dl, may comprise, for example, an aluminum gallium arsenide (AlGaAs) composition.

[0018] In an embodiment, for example, the diode, D2, may be defined to be a green diode by emitting light, L2, having a wavelength between approximately 577nm-492nm. The green diode, D2, may comprise, for example, an aluminum gallium phosphide (AlGaP) composition. [0019] In an embodiment, for example, the diode, D3, may be defined to be a blue diode by emitting light, L3, having a wavelength between approximately 492nm- 455nm. The blue diode, D3, may comprise, for example, a gallium nitride (GaN) composition, or, an indium gallium nitride (InGaN) composition. [0020] In an embodiment, for example, the diode, D4, may be a white diode. Although it is known in the art that "white light" is a mixture of colors of the visible spectra between approximately 780nm-390nm, the diode, D4, does not necessarily comprise a cluster of red, green and blue diodes. For example, the white diode, D4, may comprise a diode that is covered with, for example, a yellowish phosphor coating due to the fact that yellow stimulates the red and green receptors in the eye. Accordingly, in an embodiment, the diode may be, for example, a blue diode that emits blue light, and, when covered with a yellowish phosphor coating, the resulting mix of blue and yellow color gives the appearance of white light, L4, emitted from the diode, D4, to the eye. In an embodiment, the white diode, D4, may comprise, for example, GaN, and, the coating may comprise cerium (Ce).

[0021] In an embodiment, the current drop and corresponding on/off state of each of the diodes, D1-D4, is controlled by the activation signal directed to each diode, Dl- D4 via OUT1-OUT3. It will be recognized, based on this disclosure, that the intensity of the emitted light, L1-L4 can be a function of the duty cycle of OUT1-OUT3. After considering the inventive concepts described herein, it will be recognized that the variance of OUT2 defines the selective output of the lights L1-L4. [0022] Referring to the examples set forth Figure 2, a 50% duty cycle PWM control signal is provided from output pin OUT2. It will be appreciated that this exemplary duty cycle should not be used to limit the invention and the general principles of the invention can be practiced with any range of duty cycles. It is preferred, however, that when using the circuit to emit light in the visible spectrum, that the duty cycle is selected in a range that can not be perceived by the human eye (so as to avoid "flickering"). In an embodiment, the frequency of the PWM signal is preferably greater than approximately 120 Hz to prevent this phenomenon. [0023] In an embodiment and in conjunction with the arrangement of the diodes, D1-D4, shown in the circuit diagram 10, when the PWM control signal provided from OUT2 is low, only the first and fourth diodes Dl, D4 may be permitted to emit light Ll, L4, and, conversely, when the PWM control signal provided from OUT2 is high, only the second and third diodes D2, D3 may be permitted to emit light, L2, L3.In an embodiment, it will be appreciated that a diode activation signal provided from the controller 12 at output pins OUTl, OUT3 in combination with OUT2 determines the desired activation of each of the diodes, D1-D4. For example, in an embodiment as seen in Figure 2, from OT to 0.5T, OUTl is high, OUT2 is low and OUT3 is low thereby exclusively providing light, Ll, from the first diode, Dl . From 0.5T to T, OUTl and OUT3 are both low while OUT2 is high; accordingly, light, L2, L3 is provided from diodes, D2, D3.

[0024] In an embodiment, therefore, for the first period, 0 to T, the circuit 10 emits unsaturated, selectively-colored light, L _τ2 , that includes a mixture of light Ll, L2 and L3 emitted from the first, second and third diodes Dl, D2 and D3.

[0025] With continued reference to Figure 2, and specific reference to T to 1.5T, OUT1-OUT3 are all low such that none of the diodes are activated and the circuit does not emit light. Also, from 1.5T to 2T, OUT1-OUT3 are all high and none of the diodes are activated. Accordingly, for the second period, T to 2T, the circuit 10 emits no light.

[0026] In another embodiment as seen in Figure 2, between 2T and 2.5T, OUT2 is low and between 2.5T and 3T, OUT2 is high. OUTl and OUT3 are high for only a portion of this time, which results a selectively-colored light, Lχ3, that includes a mixture of light L1-L4 emitted from all of the diodes D1-D4. [0027] In another embodiment as seen in Figure 2, OUT 2 is low from 2T to 2.5T, while OUT2 is high between 2.5T and 3T. OUTl and OUT3 are high for only a portion of each of the first and second halves of the third period, 2T to 3T. Although OUTl and OUT 3 are high for only a portion of each of the first and second halves of the third period, 2T to 3T, OUTl and OUT3 are not high for the same length of time during each half of the third period, 2T to 3T.

[0028] As such, for the third period, 2T to 3T, the circuit 10 emits unsaturated, selectively-colored light, Lx ₃ , that includes a mixture of light L1-L4 emitted from all of the diodes Dl -D4. [0029] Referring to Figure 3, a mathematically defined color model is shown. The model is referred to as an International Commission on Illumination (CIE) chromaticity diagram that represents all of the chromaticities visible to the average person. The x, y parameters of the model define the chromaticity of a color. The outer curved boundary of the plot is referred to as the 'spectral locus,' with wavelengths being in nanometers, and corresponds to a saturated, monochromatic light. The straight edge on the lower part of the curve is called the 'line of purples,' that have no counterpart in monochromatic light. Unsaturated colors appear in the interior of the curve with white being approximately located within the middle of the spectral locus and line of purples boundary. [0030] Regarding the examples of the selectively-colored light, L _T i-L _T3 , from Figure 2 above, it will be appreciated that the amount of on time and selection of

diodes, D1-D4, that are to be activated will result in the circuit 10 being able to produce any saturated or unsaturated color appearing on the CIE chromaticity diagram. For example, the selectively-colored light, Ln, may be located on the saturated, outer portion of the curve (i.e., the spectral locus) proximate saturated red (e.g., 700nm). In another example, the selectively-colored light, Lτ2, may be any unsaturated color on the straight line between saturated green (e.g., 546. lnm) and saturated blue (e.g., 435.8 nm).

[0031] In another example, the selectively-colored light, L _T 3, may include an appearance of having any unsaturated color within or proximate the red-green-blue (RGB) color space formed by a triangle defined by saturated red, saturated green and saturated blue. The provision of the white diode, D4, assists in controlling the selectively-colored light, Lχ ₃ , to be located at any desirable location within the CIE chromaticity diagram. In this embodiment, where three or four diodes have been activated for a period, 2T to 3T, it will be appreciated that for the first half of the period, 2T to 3T, the available color of the emitted light is located between, for example, a saturated green diode, D2, and a saturated blue diode, D3, whereas, for the second half of the period, 2T to 3T, the available color of the emitted light is limited by, for example, a saturated red diode, Dl, located on the saturated, outer portion of the curve and a white diode, D4, that may be located at any position within the CIE chromaticity diagram. Because the PWM control signal from OUT2 regulates a very fast on/off time of the diodes, D1-D4, the resulting selectively-colored light, Ln, gives the appearance of having an unsaturated color selected from within or proximate the red-green-blue (RGB) color space rather than one color from the combination of the diodes D2, D3 from the first half of the period, 2T to 3T, and a another color from the combination of the diodes Dl, D4 from the second half of the period, 2T to 3T.

[0032] Further, as discussed above, it may be desirable to avoid using three diodes to emit white light. In an embodiment diode, D4, may be included as a white diode. In such an embodiment, therefore, D4, may be activated to provide the white light, L4. In this arrangement, OUT3 may be controlled to be high while OUT2 is

controlled to be low. In this method, none of the other diodes, D1-D3, are required to be activated to emit white light.

[0033] It will be appreciated that normalization of the selectively-colored light, L _T , may be provided in any desirable methodology. For example, the color scheme may be conducted by software stored within the controller 12. Alternatively, the color scheme may be provided by designing the circuit 10 to designate specific resistance values of each resistor, R1-R4.

[0034] If desired, the circuit 10 may include a user-input, I, that is provided to the controller 12 to manually change the selectively-colored light, L _T , to any desirable saturated or unsaturated color. Alternatively, if desired, the circuit 10 may be designed to be fixed in hardware or software to prevent any type of manual deviation of a selectively-colored light, L _τ , that is set by the designer. Such an implementation of the circuit 10 may be desirable when a designer is designing a color scheme for more than one client; for example, if client A requires a blue/green color, and client B requires a yellow/green color, the designer may work from one design of the circuit 10 while making minor changes in hardware or software to satisfy the each client's needs.

[0035] Further, it will be appreciated that the circuit 10 accommodates for a high level voltage of the system to be set to an arbitrary level that must be higher than the LED band gap energy or forward voltage drop. Further, it will be appreciated that circuit 10 may be set for either voltage control or current control. [0036] Referring to Figure 4, the circuit 10 may be implemented with or applied to any desirable good, product or service, such as, for example, a vehicle, V. In an embodiment the selectively-colored light, L _τ , may be provided to increase or enhance the visibility of the environment with respect to a passenger compartment interior, Pi, of the vehicle, V, and/or, an exterior of the passenger compartment, P _E , of the vehicle,

V.

[0037] If the selectively-colored light, L _τ , is utilized to increase or enhance the visibility of the environment with respect to the interior of the passenger compartment area, Pi, the selectively-colored light, L _τ , may be emitted from any portion of the

interior of the vehicle, such as, for example, an instrument panel cluster, the headliner, door panels, trim pillars, trim panels, beverage holders, glove compartments or the like. If, however, the selectively-colored light, Lx, is utilized to increase or enhance the visibility of the environment with respect to the exterior of the passenger compartment area, P _E , the selectively-colored light, L _τ , may be sourced to provide light from any portion of the exterior of the vehicle such as, for example, front or rear headlamps, turn-signal lamps, brake lamps, a vehicular chassis / underbody or the like. [0038] Although it is mentioned above that the circuit 10 may be applied to vehicular applications, it will be appreciated that the circuit 10 is not limited to vehicular applications. For example, it will be appreciated that the circuit 10 is applicable to any desirable good, product or service and is not limited to any particular mobile or immobile good, product or service. In an embodiment, the circuit 10 may be associated with a portable media device, such as a cell phone or digital music player. In another embodiment, for example, the circuit 10 may be associated with interior or exterior lighting scheme of a home, business or the like. [0039] The present invention has been described with reference to certain exemplary embodiments thereof. However, it will be readily apparent to those skilled in the art that it is possible to embody the invention in specific forms other than those of the exemplary embodiments described above. This may be done without departing from the spirit of the invention. The exemplary embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is defined by the appended claims and their equivalents, rather than by the preceding description.