Light sources that increase object chroma when dimmed

A method of increasing the color gamut of a multi-emitter light emitting device when dimming includes the steps of independently driving each emitter in the device, and increasing the lumen output of at least one emitter while simultaneously decreasing the lumen output of at least one other emitter, such that total color gamut increases while total lumen output of the light emitting device decreases. A light emitting device is also disclosed.

BACKGROUND OF THE INVENTION

When conventional light sources are dimmed, color perceptions of the objects being illuminated by the light source become muted (e.g. duller, less saturated, less vivid, and less vibrant). This phenomenon of human vision is known as the Hunt Effect, where at low light levels, objects essentially appear less colorful than at high light levels. For many applications, such as residential lighting, museum lighting, theater lighting, hospitality lighting, and any other application where color perceptions and dimming are important components of the lighting solution, it would be beneficial to compensate for the reduced sensitivity to color as the light source is dimmed.

There are numerous recently introduced LED products that feature a “dim-to-warm” technology. Filament lamps also become warmer when they dim. With “dim-to-warm” LED products, a light source featuring multiple LEDs is independently adjusted so that the correlated color temperature (CCT) of the light source becomes warmer during dimming. However, there is no physiological reason that dim-to-warm should be a preferable or attractive lighting modality to humans. There is, however a physiological reason that “dim-to-vibrant” should be preferable and desirable, namely for overcoming the Hunt Effect.

Thus, what is needed in the art is a device, system and method for counteracting the Hunt Effect and increasing object chroma when the light source is dimmed.

SUMMARY OF THE INVENTION

In one embodiment, a method of increasing the color gamut of a multi-emitter light emitting device when dimming, includes the steps of independently driving each emitter in the device; and increasing the lumen output of at least one emitter while simultaneously decreasing the lumen output of at least one other emitter, such that total color gamut increases while total lumen output of the light emitting device decreases. In one embodiment, the multiple LED emitters include at least 7 LED emitters. In one embodiment, the at least 7 LED emitters include a red emitter, an amber emitter, a lime emitter, a green emitter, a cyan emitter, a blue emitter and an indigo emitter. In one embodiment, the plurality of LED emitters includes at least 4 LED emitters. In one embodiment, the at least 4 LED emitters include a red emitter, a green emitter, a royal blue (indigo) emitter, and a white emitter. In one embodiment, the plurality of LED emitters includes at least 5 LED emitters. In one embodiment, the at least 5 LED emitters include a red emitter, a lime emitter, a green emitter, a cyan emitter, and a royal blue (indigo) emitter.

In one embodiment, the method includes the step of linearly decreasing the IES TM-30-15 fidelity index (Rf) as lumen output decreases. In one embodiment, the method includes the step of linearly decreasing the IES TM-30-15 fidelity index (Rf) from about 96 at full output to about 48 at minimum dimmed level. In one embodiment, the method includes the step of linearly increasing the IES TM-30-15 gamut index (Rg) as lumen output decreases. In one embodiment, the method includes the step of linearly increasing the IES TM-30-15 gamut index (Rg) from about 101 at full output to about 140 at minimum dimmed level. In one embodiment, the method includes the step of linearly decreasing Duv as lumen output decreases. In one embodiment, the method includes the step of linearly decreasing Duv from about 0.0 at full output to about −0.03 at minimum dimmed level. In one embodiment, the method includes the step of linearly increasing the IES TM-30-15 chroma shift in hue bin one (Rcs,h1) as lumen output decreases. In one embodiment, the method includes the step of linearly increasing the IES TM-30-15 chroma shift in hue bin one (Rcs,h1) from about −0.1% at full output to about +35.4% at minimum dimmed level. In one embodiment, the method includes the step of maintaining a constant correlated color temperature as lumen output decreases. In one embodiment, the light emitting device is a luminaire. In one embodiment, the light emitting device is a lamp with an integrated base that can screw into an existing light socket or insert into a pin-base.

In one embodiment, a light emitting device includes at least 2 LED emitters, at least one internal controller, multiple driver circuits configured to independently drive the plurality of LED emitters via the at least one internal controller, and programming logic configured to increase the lumen output of at least one emitter while simultaneously decreasing the lumen output of at least one other emitter, such that total color gamut increases while total lumen output of the light emitting device decreases. In one embodiment, each of the LED emitters is configured to emit a different color. In one embodiment, the at least 2 LED emitters are selected from a group including a red emitter, a lime emitter, an amber emitter, a green emitter, a cyan emitter, a blue emitter, an indigo emitter, and a white emitter. In one embodiment, the light emitting device is further configured to linearly decrease the IES TM-30-15 fidelity index (Rf) as lumen output decreases. In one embodiment, the light emitting device is further configured to linearly decrease the IES TM-30-15 fidelity index (Rf) from about 96 at full output to about 48 at minimum dimmed level. In one embodiment, the light emitting device is further configured to linearly increase the IES TM-30-15 gamut index (Rg) as lumen output decreases. In one embodiment, the light emitting device is further configured to linearly increase the IES TM-30-15 gamut index (Rg) from about 101 at full output to about 140 at minimum dimmed level. In one embodiment, the light emitting device is further configured to increase the IES TM-30-15 gamut index (Rg) to at least 120 at a 50% dimmed level. In one embodiment, the light emitting device is further configured to linearly decrease Duv as lumen output decreases. In one embodiment, the light emitting device is further configured to linearly decrease Duv from about 0.0 at full output to about −0.03 at minimum dimmed level. In one embodiment, the light emitting device is further configured to linearly increase the IES TM-30-15 chroma shift in hue bin one (Rcs,h1) as lumen output decreases. In one embodiment, the light emitting device is further configured to linearly increase the IES TM-30-15 chroma shift in hue bin one (Rcs,h1) from about −0.1% at full output to about +35.4% at minimum dimmed level. In one embodiment, the light emitting device is further configured to maintain a constant correlated color temperature as lumen output decreases. In one embodiment, each of the multiple LED emitters comprises an LED die. In one embodiment, the multiple LED emitters are arranged in a single LED package. In one embodiment, the light emitting device is a luminaire. In one embodiment, the light emitting device further comprises an external controller interface communicatively connected to an external controller and the internal controller.

In another aspect, a light emitting device comprises at least 2 LED emitters and a plurality of driver circuits configured to independently drive the plurality of LED emitters, wherein the light emitting device emits light at a first fixed output level, the output level having a lower total lumen output and a higher total color gamut than would be emitted if all the LED emitters were driven equally. In one embodiment, the light emitting device is also configured to emit light at a second fixed output level, the second fixed output level having a lower total lumen output and a higher total color gamut than the first fixed output level. In one embodiment, the light emitting device is configured to emit light at an ordered set of fixed output levels, and each subsequent fixed output level in the set has a lower total lumen output and a higher total color gamut than all previous fixed output levels in the set.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a more clear comprehension of the present invention, while eliminating, for the purpose of clarity, many other elements found in systems and methods of increasing object chroma when dimming a light source. Those of ordinary skill in the art may recognize that other elements and/or steps are desirable and/or required in implementing the present invention. However, because such elements and steps are well known in the art, and because they do not facilitate a better understanding of the present invention, a discussion of such elements and steps is not provided herein. The disclosure herein is directed to all such variations and modifications to such elements and methods known to those skilled in the art.

Referring now in detail to the drawings, in which like reference numerals indicate like parts or elements throughout the several views, in various embodiments, presented herein are light sources that increase object chroma when dimmed.

With reference now toFIG. 1, an exemplary light emitting device40is shown according to one embodiment. The light emitting device40includes multiple LED emitters1,2,3,4,5,6,7that are each respectively connected to a driver circuit21,22,23,24,25,26,27. Each driver circuit21,22,23,24,25,26,27is connected to an internal controller30that is configured to drive each respective LED emitter1,2,3,4,5,6,7independently. The internal controller30individually manipulates power to each LED1,2,3,4,5,6,7as the light emitting device40transitions between full output and minimum dimmed levels. It should be appreciated that there is no limitation to the exact number of emitters, for example, the device might include two or more emitters, or might include two or more emitters of at least two different colors of light. The device can also include multiple emitters with groups of two or more emitters emitting the same color of light.

In some embodiments, the device comprises one or more phosphor-converted LEDs (PC-LEDs). A PC-LED is known in the art as an LED emitter having a peak emission wavelength and also including one or more phosphors, wherein the one or more phosphors converts some of the light emitted to a longer wavelength. In some embodiments, the combination of emitters and phosphors is capable of producing a broad spectral emission with a high color-fidelity score. In one embodiment, the combination of emitters and phosphors is capable of creating a spectral emission with an IES TM-30-15 Rf fidelity score greater than 90. In one embodiment, the invention comprises one blue emitter and two narrow-emitting phosphors, one in the green range (with a peak wavelength of about 530 nm) and one in the red range (with a peak wavelength of about 630 nm).

The internal controller30can be a hardwired circuit that automatically adjusts power driven to each LED emitter1,2,3,4,5,6,7at various levels of lumen output. The internal controller30can also be a digital component including a chip that is programmable to control how power is driven individually to each LED emitter1,2,3,4,5,6,7at various levels of lumen output. Thus, the internal controller can include computer logic to individually manipulate the output of the emitters. The logic can operate on a computer platform, such as a local or remote executable software platform, or as a hosted Internet or network program or portal. Any computing device as would be understood by those skilled in the art may be used with the system to drive emitter signals, including desktop or mobile devices, laptops, desktops, tablets, smartphones or other wireless digital/cellular phones, or other devices as would be understood by those skilled in the art. The light emitting device40is configured to independently drive power to the multiple LED emitters to increase gamut as overall lumen output of the device decreases during the process of dimming.

In some embodiments, the light emitting device40further includes at least one external controller interface, configured to communicate with an external controller. Examples of external controllers for use with the external controller interface include, but are not limited to, commercially-available controllers that are already in widespread use. For example, an external controller interface of the present invention might connect to a 0-10V wall-box dimmer, a DMX512 controller, a DALI controller, a wireless lighting controller, a smart home controller, an ambient light sensor, a daylight photocell sensor, or a time clock. In these embodiments, the external controller interface serves as a bridge between the internal controller, which sets the relative intensities of the various LED emitters of the device, and the external controller, which in some embodiments includes a human interface such as a switch, a dimmer switch, or voice control.

In one embodiment, each of the LED emitters1,2,3,4,5,6,7is configured to emit a different color, however, certain embodiments may include one or more sets of LED emitters that are the same color. In one embodiment, at least 4 LED emitters emit different colors, while in another embodiment, at least 7 LED emitters emit different colors. With reference now toFIG. 2A, in an embodiment where at least 7 LED emitters emit different colors, an LED array is shown where colors and peak wavelengths include a red emitter (630 nm)1, an amber emitter (590 nm)2, a lime emitter (568 nm)3, a green emitter (530 nm)4, a cyan emitter (500 nm)5, a blue emitter (460 nm)6and a royal blue (indigo) emitter (445 nm)7. The emitters can be for example part of an LED package containing the seven LED array. As would be understood by one skilled in the art, the wavelengths listed above are only one example of a possible combination of emitters and are not meant to be exclusive. In some embodiments, for example, the red emitter may have a peak wavelength of 640 nm. In other embodiments, the 7 emitters may include a white emitter with multiple peak wavelengths. The wattage or power supplied to each emitter is independently controlled by a digital controller or a control circuit as described above. For illustrative purposes, the light emitting device40ofFIG. 2Ais shown in an environment depicted inFIG. 2Bas an overhead room light40illuminating an object14that is being observed by a person12.

In certain embodiments, one or more LED packages are configured on a printed circuit board or substrate. A single internal controller or control circuit can be used to control multiple LED arrays, for example by using a common driver circuit to control the same colored LEDs found in different arrays. The emitters can be any of the various types known in the art, such as for example emitters known by the trade name of Luxeon Rebel (Lumileds Holding B.V.). In certain embodiments, the emitters include an organic material and are OLED emitters. In certain embodiments, the one or more internal controllers and the one or more LED packages are disposed on the same substrate. In certain embodiments, the emitters are configured as a liquid crystal on silicon (LCoS) lighting device. In certain embodiments, the emitters are laser diodes. In certain embodiments, the one or more LED packages are PC-LEDs.

The physical arrangement of emitters within the array can take various forms. Arrangements can for example be symmetrical or asymmetrical. With reference now toFIG. 3, a light emitting device140is shown having nine LED emitters31,32,33,34,35,36,37,38,39. In this example, the arrangement of the dies is three in-line rows and columns, versus the offset arrangement shown inFIG. 2A. In addition, the embodiment shown inFIG. 3includes emitters of the colors and peak wavelengths of deep-red (650 nm)31, red (620 nm)32, red-orange (610 nm)33, amber (585 nm)34, lime (566 nm)35, green (520 nm)36, cyan (490 nm)37, blue (460 nm)38, and violet (420 nm)39. As with embodiments described above, the power driven to each die by the internal controller or control circuit is independent of the others.

In one embodiment having at least four LED emitters emitting different colors, the LED array may include emitters with peak wavelengths of red (630 nm), lime (568 nm), green (530 nm), royal blue or indigo (445 nm), and white, having a broad phosphor converted emission. In another embodiment where at least five LED emitters emit different colors, the LED array may include emitters with peak wavelengths of red (630 nm), lime (568 nm), green (530 nm), cyan (500 nm), and royal blue or indigo (445 nm).

Another example of an LED array is shown inFIG. 4A. In this example, the emitters are unequal in number to balance for different lumen outputs. The power driven to each emitter is controlled independently. In this example, the emitters include the colors red (1), amber (2), lime (3), green (4), cyan (5), blue (6), and royal blue (indigo) (7). The example ofFIG. 4Acomprises five red emitters, ten amber emitters, seven lime emitters, five green emitters, three cyan emitters, three blue emitters, and three royal blue (indigo) emitters.

Another example of an LED array is shown inFIG. 4B. In this example, 22 emitters are used in a substantially round configuration. The colors corresponding to each number 1-7 inFIG. 4Bare red (1), amber (2), green (3), cyan (4), blue (5), royal blue (indigo) (6), and white (7).

There are two primary advantages to this configuration. First, adding more emitters to a package increases the maximum lumen output possible by the package as a whole. Second, emitters of the same type but of a different color will often have different maximum lumen outputs, due to differences in efficiency and in the underlying chemistry necessary to produce light of the required spectral range. One can compensate for the variation in efficiency by using more emitters of lower efficiency to reach the same total luminous output as fewer emitters of higher efficiency.

One example of emitter color distribution is shown inFIG. 5A. The individual SPDs of seven emitters are shown. InFIG. 5A, the curves are numbered as follows, with the corresponding peak wavelengths: 1) Red (634 nm), 2) Amber (597 nm), 3) Green (525 nm), 4) Cyan (500 nm), 5) Blue (475 nm), 6) Royal Blue (Indigo) (445 nm), and 7) White (564 and 436 nm). The SPDs ofFIG. 5Aare normalized to show the shape of each curve, so that the peak emission wavelength of all curves are shown at the same level. This is not meant to indicate that all seven LED dies are emitting light at the same luminous power level.

FIG. 5Bshows an alternative representation of the SPDs of the seven emitters indicated above in the description ofFIG. 5A. Each curve inFIG. 5Brepresents the total relative radiant watts generated by each group of emitters with the peak wavelengths indicated above in the description ofFIG. 5A, and arranged as in the set of 22 emitters shown inFIG. 4B.

By adjusting the power driven to the various emitters, systematic variations in color characteristics are created in order to increase the gamut index of the light source (hereinafter “Rg”). The invention does so while systematically controlling changes to the fidelity index (hereinafter “Rf”), correlated color temperature (hereinafter “CCT”), “Duv”, (which is understood in the art to be a metric that quantifies the distance between the chromacity of a given light source and a black body radiator of equal CCT), and chroma shift in hue bin1(hereinafter “Rcs,h1”). The systematic control of these variables counteracts the Hunt effect and increases object chroma during dimming according to embodiments of the invention. Fractional (i.e. relative) percentages of each of the various LED channels are used to create systematic variations in color characteristics. In one embodiment, the light emitting device is configured to limit the decrease in the IES TM-30-15 fidelity index (Rf) as lumen output decreases. In one embodiment, the light emitting device is configured specifically to limit the decrease in the IES TM-30-15 fidelity index (Rf) from about 96 at full output to about 48 at minimum dimmed level. In one embodiment, the light emitting device is configured to linearly increase the IES TM-30-15 gamut index (Rg) as lumen output decreases. In one embodiment, the light emitting device is configured specifically to linearly increase the IES TM-30-15 gamut index (Rg) from about 101 at full output to about 140 at minimum dimmed level. In one embodiment, the light emitting device is configured to linearly decrease Duv as lumen output decreases. In one embodiment, the light emitting device is configured specifically to linearly decrease Duv from about 0.0 at full output to about −0.03 at minimum dimmed level. In other embodiments, the light emitting device is configured to hold Duv nearly or completely constant. In some embodiments, the light emitting device is configured to hold CCT approximately or completely constant. In other embodiments, the light emitting device is configured to change both CCT and gamut, independently or in parallel. In one embodiment, the light emitting device is configured to linearly increase the IES TM-30-15 chroma shift in hue bin one (Rcs,h1) as lumen output decreases. In one embodiment, the light emitting device is configured specifically to linearly increase the IES TM-30-15 chroma shift in hue bin one (Rcs,h1) from about −0.1% at full output to about +35.4% at minimum dimmed level. In one embodiment, the light emitting device is configured to maintain a constant correlated color temperature as lumen output decreases. These systematic changes increase object chroma during dimming, and this is demonstrated in the experimental examples described in further detail below.

The light emitting device can be any type of light emitting device known in the art for illuminating objects or a general space. In one embodiment, the light emitting device is a luminaire such as a lamp, or a light fixture such as overhead room lighting. In another embodiment, the light emitting device is packaged into a replacement bulb that can screw into an existing light socket or insert into a pin-base. The LED module can be incorporated into luminaires, or be a luminaire inclusive of housing and circuitry. The light emitting device can be used in various applications, such as residential, commercial, museum, theater and hospitality lighting.

Advantageously, embodiments of the invention manipulate the relative proportions of optical radiation at different wavelengths (i.e. the spectral power distribution) to alter the appearance of illuminated objects. At high output (100%) the color gamut of the spectral power distribution will be comparable to a reference illuminant, which has a gamut index (e.g., IES Rg, GAI) of about 100. As the light source is dimmed, not only will lumen output decrease, but the gamut will increase (e.g., IES Rg>100).

In some embodiments, the internal controller of the present invention may include or be replaced by a single, fixed output configuration or a set of fixed output levels that accomplish the wider spectral emission at a lower relative light output of the present invention. For example, in one embodiment, a light emitting device of the present invention will have only “on” and “off” states, but while in the “on” state, the light emitting device will have a lower total lumen output than a reference illuminant, while also having a larger gamut (e.g., IES Rg>100). In exemplary embodiments, an emitter in the “on” state will have a fixed output as shown inFIG. 7H, 7I, or7J. Alternatively, the fixed output state of an emitter of the present invention may be defined by any single column inFIG. 6A or 6B. It is understood that the embodiments shown inFIGS. 6A, 6B, 7H, 7I, and 7Jare not meant to be limiting, and that a fixed output embodiment of a light emitting device of the present invention may have any fixed output wherein the total lumen output is lower than a reference illuminant (i.e. dim), but the total color gamut output will be higher than normal, in order to show illuminated objects in a wider, more radiant color gamut. Embodiments of the present invention may alternatively have a fixed set of output levels, wherein the output level decreases and the color gamut increases in steps rather than continuously.

In one embodiment, a method of generating light output from a light emitting device includes the steps of independently driving multiple LED emitters to increase gamut as lumen output decreases. In one embodiment, the method includes the step of limiting the decrease in the IES TM-30-15 fidelity index (Rf) as lumen output decreases. In one embodiment, the method includes the step of limiting the decrease in the IES TM-30-15 fidelity index (Rf) from about 96 at full output to about 48 at minimum dimmed level. In one embodiment, the method includes the step of linearly increasing the IES TM-30-15 gamut index (Rg) as lumen output decreases. In one embodiment, the method includes the step of linearly increasing the IES TM-30-15 gamut index (Rg) from about 101 at full output to about 140 at minimum dimmed level. In one embodiment, the method includes the step of linearly decreasing Duv as lumen output decreases. In one embodiment, the method includes the step of linearly decreasing Duv from about 0.0 at full output to about −0.03 at minimum dimmed level. In one embodiment, the method includes the step of linearly increasing the IES TM-30-15 chroma shift in hue bin one (Rcs,h1) as lumen output decreases. In one embodiment, the method includes the step of linearly increasing the IES TM-30-15 chroma shift in hue bin one (Rcs,h1) from about −0.1% at full output to about +35.4% at minimum dimmed level. In one embodiment, the method includes the step of maintaining a constant correlated color temperature as lumen output decreases.

Experimental Examples

With reference now toFIGS. 6A and 6D, fractional (i.e. relative) percentages of each of the seven LED channels are used to create systematic variations in color characteristics. They are adjusted for lumen output based on the array of 22 LED emitters described inFIGS. 4B and 5B. In this example CCT is held constant at 3500 K. The IES TM-30-15 fidelity index (Rf) changes linearly from 96 at full output to 48 at the minimum dimmed level. The IES TM-30-15 gamut index (Rg) changes linearly from 101 to 140. Duv changes linearly from 0.0 to −0.03. IES TM-30-15 chroma shift in hue bin one (Rcs,h1), representing red saturation, varies linearly from −0.001 (−0.1%) to +0.354 (+35.4%). Relative DMX (digital multiplex) values associated with the fractional values given inFIG. 6Aare shown inFIG. 6B. These DMX values have been adjusted for lumen output. With reference now to the example shown inFIG. 6C, systematic changes in Rf, Rg, CCT, Duv, and Rcs,h1 are shown from full output to the minimum dimmed level in 10% increments. CCT was held constant and luminous efficacy of radiation (LER) is shown for reference.

FIGS. 7A-7K, provide TM-30-15 Color Vector Graphics (CVGs) [top] and associated Spectral Power Distributions (SPDs) [bottom] for dimming from full output to minimum dim level in increments of 10 percent. The CVGs are divided into 16 hue bins, each represented by a point and representing the average of the TM-30-15 hue samples taken in that radial section of the hue graph. The vectors represent the difference in hue and saturation of each bin between the test illuminant (dark circle) and a reference illuminator (white circle). Vectors of increasing distance from the center represent an increase in saturation, vectors decreasing distance to the center represent a decrease in saturation. The component of each vector tangent to the reference illuminator circle represents a hue shift in that hue bin. The Rg is determined by the difference in the area enclosed by the polygons defined by the test illuminant points and the reference illuminator points, where Rg=100 represents a match with the reference illuminator.