DETAILED DESCRIPTION

[0083] Various embodiments of the present invention are directed to methods and apparatus for generating and modulating white light illumination conditions. Examples of applications in which such methods and apparatus may be implemented include, but are not limited to, retail environments (e.g., food, clothing, jewelry, paint, furniture, fabrics, etc.) or service environments (e.g., cosmetics, hair and beauty salons and spas, photography, etc.) where visible aspects of the products/services being offered are significant in attracting sales of the products/services. Other applications include theatre and cinema, medical and dental implementations, as well as vehicle-based (automotive) implementations.

[0084] The description below pertains to several illustrative embodiments of the invention. Although many variations of the invention may be envisioned by one skilled in the art, such variations and improvements are intended to fall within the scope of this disclosure. Thus, the scope of the invention is not to be unduly limited in any way by the disclosure below.

[0085] As used in this document, the following terms generally have the following meanings; however, these definitions are in no way intended to limit the scope of the term as would be understood by one of skill in the art.

[0086] The term “LED” generally includes light emitting diodes of all types and also includes, but is not limited to, light emitting polymers, semiconductor dies that produce light in response to a current, organic LEDs, electron luminescent strips, super luminescent diodes (SLDs) and other such devices. In an embodiment, an “LED” may refer to a single light emitting diode having multiple semiconductor dies that are individually controlled. The term LEDs does not restrict the physical or electrical packaging of any of the above and that packaging could include, but is not limited to, surface mount, chip-on-board, or T-package mount LEDs and LEDs of all other configurations. The term “LED” also includes LEDs packaged or associated with material (e.g. a phosphor) wherein the material may convert energy from the LED to a different wavelength. For example, the term “LED” also includes constructions that include a phosphor where the LED emission pumps the phosphor and the phosphor converts the energy to longer wavelength energy. White LEDs typically use an LED chip that produces short wavelength radiation and the phosphor is used to convert the energy to longer wavelengths. This construction also typically results in broadband radiation as compared to the original chip radiation.

[0087] “Illumination source” includes all illumination sources, including, but not limited to, LEDs; incandescent sources including filament lamps; pyro-luminescent sources such as flames; candle-luminescent sources such as gas mantles and carbon arc radiation sources; photo-luminescent sources including gaseous discharges; fluorescent sources; phosphorescence sources; lasers; electro-luminescent sources such as electro-luminescent lamps; cathode luminescent sources using electronic satiation; and miscellaneous luminescent sources including galvano-luminescent sources, crystallo-luminescent sources, kine-luminescent sources, thermo-luminescent sources, tribo-luminescent sources, sono-luminescent sources, and radio-luminescent sources. Illumination sources may also include luminescent polymers. An illumination source can produce electromagnetic radiation within the visible spectrum, outside the visible spectrum, or a combination of both. A component illumination source is any illumination source that is part of a lighting fixture.

[0088] “Lighting fixture” or “fixture” is any device or housing containing at least one illumination source for the purposes of providing illumination.

[0089] “Color,” “temperature” and “spectrum” are used interchangeably within this document unless otherwise indicated. The three terms generally refer to the resultant combination of wavelengths of light that result in the light produced by a lighting fixture. That combination of wavelengths defines a color or temperature of the light. Color is generally used for light which is not white, while temperature is for light that is white, but either term could be used for any type of light. A white light has a color and a nonwhite light could have a temperature. A spectrum will generally refer to the spectral composition of a combination of the individual wavelengths, while a color or temperature will generally refer to the human perceived properties of that light. However, the above usages are not intended to limit the scope of these terms.

[0090] The recent advent of colored LEDs bright enough to provide illumination has prompted a revolution in illumination technology because of the ease with which the color and brightness of these light sources may be modulated. One such modulation method is discussed in U.S. Pat. No. 6,016,038 the entire disclosure of which is herein incorporated by reference. The systems and methods described herein discuss how to use and build LED light fixtures or systems, or other light fixtures or systems utilizing component illumination sources. These systems have certain advantages over other lighting fixtures. In particular, the systems disclosed herein enable previously unknown control in the light which can be produced by a lighting fixture. In particular, the following disclosure discusses systems and methods for the predetermination of the range of light, and type of light, that can be produced by a lighting fixture and the systems and methods for utilizing the predetermined range of that lighting fixture in a variety of applications.

[0091] To understand these systems and methods it is first useful to understand a lighting fixture which could be built and used in embodiments of this invention. FIG. 2 depicts one embodiment of a lighting module which could be used in one embodiment of the invention, wherein a lighting fixture ( 300 ) is depicted in block diagram format. The lighting fixture ( 300 ) includes two components, a processor ( 316 ) and a collection of component illumination sources ( 320 ), which is depicted in FIG. 2 as an array of light emitting diodes. In one embodiment of the invention, the collection of component illumination sources comprises at least two illumination sources that produce different spectrums of light.

[0092] The collection of component illumination sources ( 320 ) are arranged within said lighting fixture ( 300 ) on a mounting ( 350 ) in such a way that the light from the different component illumination sources is allowed to mix to produce a resultant spectrum of light which is basically the additive spectrum of the different component illumination sources. In FIG. 2 , this is done my placing the component illumination sources ( 320 ) in a generally circular area; it could also be done in any other manner as would be understood by one of skill in the art, such as a line of component illumination sources, or another geometric shape of component illumination sources.

[0093] The term “processor” is used herein to refer to any method or system for processing, for example, those that process in response to a signal or data and/or those that process autonomously. A processor should be understood to encompass microprocessors, microcontrollers, programmable digital signal processors, integrated circuits, computer-software, computer hardware, electrical circuits, application specific integrated circuits, programmable logic devices, programmable gate arrays, programmable array logic, personal computers, chips, and any other combination of discrete analog, digital, or programmable components, or other devices capable of providing processing functions.

[0094] The collection of illumination sources ( 320 ) is controlled by the processor ( 316 ) to produce controlled illumination. In particular, the processor ( 316 ) controls the intensity of different color individual LEDs in the array of LEDs so as to control the collection of illumination sources ( 320 ) to produce illumination in any color within a range bounded by the spectra of the individual LEDs and any filters or other spectrum-altering devices associated therewith. Instantaneous changes in color, strobing and other effects, can also be produced with lighting fixtures such as the light module ( 300 ) depicted in FIG. 2 . The lighting fixture ( 300 ) may be configured to receive power and data from an external source in one embodiment of the invention, the receipt of such data being over data line ( 330 ) and power over power line ( 340 ). The lighting fixture ( 300 ), through the processor ( 316 ), may be made to provide the various functions ascribed to the various embodiments of the invention disclosed herein. In another embodiment, the processor ( 316 ) may be replaced by hard wiring or another type of control whereby the lighting fixture ( 300 ) produces only a single color of light.

[0095] Referring to FIG. 3 , the lighting fixture ( 300 ) may be constructed to be used either alone or as part of a set of such lighting fixtures ( 300 ). An individual lighting fixture ( 300 ) or a set of lighting fixtures ( 300 ) can be provided with a data connection ( 350 ) to one or more external devices, or, in certain embodiments of the invention, with other light modules ( 300 ).

[0096] As used herein, the term “data connection” should be understood to encompass any system for delivering data, such as a network, a data bus, a wire, a transmitter and receiver, a circuit, a video tape, a compact disc, a DVD disc, a video tape, an audio tape, a computer tape, a card, or the like. A data connection may thus include any system or method to deliver data by radio frequency, ultrasonic, auditory, infrared, optical, microwave, laser, electromagnetic, or other transmission or connection method or system. That is, any use of the electromagnetic spectrum or other energy transmission mechanism could provide a data connection as disclosed herein.

[0097] In an embodiment of the invention, the lighting fixture ( 300 ) may be equipped with a transmitter, receiver, or both to facilitate communication, and the processor ( 316 ) may be programmed to control the communication capabilities in a conventional manner. The light fixtures ( 300 ) may receive data over the data connection ( 350 ) from a transmitter ( 352 ), which may be a conventional transmitter of a communications signal, or may be part of a circuit or network connected to the lighting fixture ( 300 ). That is, the transmitter ( 352 ) should be understood to encompass any device or method for transmitting data to the light fixture ( 300 ). The transmitter ( 352 ) may be linked to or be part of a control device ( 354 ) that generates control data for controlling the light modules ( 300 ). In one embodiment of the invention, the control device ( 354 ) is a computer, such as a laptop computer.

[0098] The control data may be in any form suitable for controlling the processor ( 316 ) to control the collection of component illumination sources ( 320 ). In one embodiment of the invention, the control data is formatted according to the DMX- 512 protocol, and conventional software for generating DMX- 512 instructions is used on a laptop or personal computer as the control device ( 354 ) to control the lighting fixtures ( 300 ). The lighting fixture ( 300 ) may also be provided with memory for storing instructions to control the processor ( 316 ), so that the lighting fixture ( 300 ) may act in stand alone mode according to pre-programmed instructions.

[0099] The foregoing embodiments of a lighting fixture ( 300 ) will generally reside in one of any number of different housings. Such housing is, however, not necessary, and the lighting fixture ( 300 ) could be used without a housing to still form a lighting fixture. A housing may provide for lensing of the resultant light produced and may provide protection of the lighting fixture ( 300 ) and its components. A housing may be included in a lighting fixture as this term is used throughout this document.

[0100] FIG. 4 shows an exploded view of one embodiment of a lighting fixture of the present invention. The depicted embodiment comprises a substantially cylindrical body section ( 362 ), a lighting fixture ( 364 ), a conductive sleeve ( 368 ), a power module ( 372 ), a second conductive sleeve ( 374 ), and an enclosure plate ( 378 ). It is to be assumed here that the lighting fixture ( 364 ) and the power module ( 372 ) contain the electrical structure and software of lighting fixture ( 300 ), a different power module and lighting fixture ( 300 ) as known to the art, or as described in U.S. patent application Ser. No. 09/215,624, the entire disclosure of which is herein incorporated by reference. Screws ( 382 ), ( 384 ), ( 386 ), ( 388 ) allow the entire apparatus to be mechanically connected. Body section ( 362 ), conductive sleeves ( 364 ) and ( 374 ) and enclosure plate ( 378 ) are preferably made from a material that conducts heat, such as aluminum.

[0101] Body section ( 362 ) has an emission end ( 361 ), a reflective interior portion (not shown) and an illumination end ( 363 ). Lighting module ( 364 ) is mechanically affixed to said illumination end ( 363 ). Said emission end ( 361 ) may be open, or, in one embodiment may have affixed thereto a filter ( 391 ). Filter ( 391 ) may be a clear filter, a diffusing filter, a colored filter, or any other type of filter known to the art. In one embodiment, the filter will be permanently attached to the body section ( 362 ), but in other embodiments, the filter could be removably attached. In a still further embodiment, the filter ( 391 ) need not be attached to the emission end ( 361 ) of body portion ( 362 ) but may be inserted anywhere in the direction of light emission from the lighting fixture ( 364 ).

[0102] Lighting fixture ( 364 ) may be disk-shaped with two sides. The illumination side (not shown) comprises a plurality of component light sources which produce a predetermined selection of different spectrums of light. The connection side may hold an electrical connector male pin assembly ( 392 ). Both the illumination side and the connection side can be coated with aluminum surfaces to better allow the conduction of heat outward from the plurality of component light sources to the body section ( 362 ). Likewise, power module ( 372 ) is generally disk shaped and may have every available surface covered with aluminum for the same reason. Power module ( 372 ) has a connection side holding an electrical connector female pin assembly ( 394 ) adapted to fit the pins from assembly ( 392 ). Power module ( 372 ) has a power terminal side holding a terminal ( 398 ) for connection to a source of power such as an AC or DC electrical source. Any standard AC or DC jack may be used, as appropriate.

[0103] Interposed between lighting fixture ( 364 ) and power module ( 372 ) is a conductive aluminum sleeve ( 368 ), which substantially encloses the space between modules ( 362 ) and ( 372 ). As shown, a disk-shaped enclosure plate ( 378 ) and screws ( 382 ), ( 384 ), ( 386 ) and ( 388 ) can seal all of the components together, and conductive sleeve ( 374 ) is thus interposed between enclosure plate ( 378 ) and power module ( 372 ). Alternatively, a method of connection other than screws ( 382 ), ( 384 ), ( 386 ), and ( 388 ) may be used to seal the structure together. Once sealed together as a unit, the lighting fixture ( 362 ) may be connected to a data network as described above and may be mounted in any convenient manner to illuminate an area.

[0104] FIGS. 5 a and 5 b show an alternative lighting fixture ( 5000 ) including a housing that could be used in another embodiment of the invention. The depicted embodiment comprises a lower body section ( 5001 ), an upper body section ( 5003 ) and a lighting platform ( 5005 ). Again, the lighting fixture can contain the lighting fixture ( 300 ), a different lighting fixture known to the art, or a lighting fixture described anywhere else in this document. The lighting platform ( 5005 ) shown here is designed to have a linear track of component illumination devices (in this case LEDs ( 5007 )) although such a design is not necessary. Such a design is desirable for an embodiment of the invention, however. In addition, although the linear track of component illumination sources in depicted in FIG. 5 a as a single track, multiple linear tracks could be used as would be understood by one of skill in the art. In one embodiment of the invention, the upper body section ( 5003 ) can comprise a filter as discussed above, or may be translucent, transparent, semi-translucent, or semi-transparent.

[0105] Further shown in FIG. 5 a is the optional holder ( 5010 ) which may be used to hold the lighting fixture ( 5000 ). This holder ( 5010 ) comprises clip attachments ( 5012 ) which may be used to frictionally engage the lighting fixture ( 5000 ) to enable a particular alignment of lighting fixture ( 5000 ) relative to the holder ( 5010 ). The mounting also contains attachment plate ( 5014 ) which may be attached to the clip attachments ( 5012 ) by any type of attachment known to the art whether permanent, removable, or temporary. Attachment plate ( 5014 ) may then be used to attach the entire apparatus to a surface such as, but not limited to, a wall or ceiling.

[0106] In one embodiment, the lighting fixture ( 5000 ) is generally cylindrical in shape when assembled (as shown in FIG. 5 b ) and therefore can move or “roll” on a surface. In addition, in one embodiment, the lighting fixture ( 5000 ) only can emit light through the upper body section ( 5003 ) and not through the lower body section ( 5001 ). Without a holder ( 5010 ), directing the light emitted from such a lighting fixture ( 5000 ) could be difficult and motion could cause the directionality of the light to undesirably alter.

[0107] In one embodiment of the invention, it is recognized that prespecified ranges of available colors may be desirable and it may also be desirable to build lighting fixtures in such a way as to maximize the illumination of the lighting apparatus for particular color therein. This is best shown through a numerical example. Let us assume that a lighting fixture contains 30 component illumination sources in three different wavelengths, primary red, primary blue, and primary green (such as individual LEDs). In addition, let us assume that each of these illumination sources produces the same intensity of light, they just produce at different colors. Now, there are multiple different ways that the thirty illumination sources for any given lighting fixture can be chosen. There could be 10 of each of the illumination sources, or alternatively there could be 30 primary blue colored illumination sources. It should be readily apparent that these light fixtures would be useful for different types of lighting. The second light apparatus produces more intense primary blue light (there are 30 sources of blue light) than the first light source (which only has 10 primary blue light sources, the remaining 20 light sources have to be off to produce primary blue light), but is limited to only producing primary blue light. The second light fixture can produce more colors of light, because the spectrums of the component illumination sources can be mixed in different percentages, but cannot produce as intense blue light. It should be readily apparent from this example that the selection of the individual component illumination sources can change the resultant spectrum of light the fixture can produce. It should also be apparent that the same selection of components can produce lights which can produce the same colors, but can produce those colors at different intensities. To put this another way, the full-on point of a lighting fixture (the point where all the component illumination sources are at maximum) will be different depending on what the component illumination sources are.

[0108] A lighting system may accordingly be specified using a full-on point and a range of selectable colors. This system has many potential applications such as, but not limited to, retail display lighting and theater lighting. Often times numerous lighting fixtures of a plurality of different colors are used to present a stage or other area with interesting shadows and desirable features. Problems can arise, however, because lamps used regularly have similar intensities before lighting filters are used to specify colors of those fixtures. Due to differences in transmission of the various filters (for instance blue filters often loose significantly more intensity than red filters), lighting fixtures must have their intensity controlled to compensate. For this reason, lighting fixtures are often operated at less than their full capability (to allow mixing) requiring additional lighting fixtures to be used. With the lighting fixtures of the instant invention, the lighting fixtures can be designed to produce particular colors at identical intensities of chosen colors when operating at their full potential; this can allow easier mixing of the resultant light, and can result in more options for a lighting design scheme.

[0109] Such a system enables the person building or designing lighting fixtures to generate lights that can produce a pre-selected range of colors, while still maximizing the intensity of light at certain more desirable colors. These lighting fixtures would therefore allow a user to select certain color(s) of lighting fixtures for an application independent of relative intensity. The lighting fixtures can then be built so that the intensities at these colors are the same. Only the spectrum is altered. It also enables a user to select lighting fixtures that produce a particular high-intensity color of light, and also have the ability to select nearby colors of light in a range.

[0110] The range of colors which can be produced by the lighting fixture can be specified instead of, or in addition to, the full-on point. The lighting fixture can then be provided with control systems that enable a user of the lighting fixture to intuitively and easily select a desired color from the available range.

[0111] One embodiment of such a system works by storing the spectrums of each of the component illumination sources. In this example embodiment, the illumination sources are LEDs. By selecting different component LEDs with different spectrums, the designer can define the color range of a lighting fixture. An easy way to visualize the color range is to use the CIE diagram which shows the entire lighting range of all colors of light which can exist. One embodiment of a system provides a light-authoring interface such as an interactive computer interface.

[0112] FIG. 6 shows an embodiment of an interactive computer interface enabling a user to see a CIE diagram ( 508 ) on which is displayed the spectrum of color a lighting fixture can produce. In FIG. 6 individual LED spectra are saved in memory and can be recalled from memory to be used for calculating a combined color control area. The interface has several channels ( 502 ) for selecting LEDs. Once selected, varying the intensity slide bar ( 504 ) can change the relative number of LEDs of that type in the resultant lighting fixture. The color of each LED is represented on a color chart such as a CIE diagram ( 508 ) as a point (for example, point ( 506 )). A second LED can be selected on a different channel to create a second point (for example, point ( 501 )) on the CIE chart. A line connecting these two points represents the extent that the color from these two LEDs can be mixed to produce additional colors. When a third and fourth channel are used, an area ( 510 ) can be plotted on the CIE diagram representing the possible combinations of the selected LEDs. Although the area ( 510 ) shown here is a polygon of four sides it would be understood by one of skill in the art that the area ( 510 ) could be a point line or a polygon with any number of sides depending on the LEDs chosen.

[0113] In addition to specifying the color range, the intensities at any given color can be calculated from the LED spectrums. By knowing the number of LEDs for a given color and the maximum intensity of any of these LEDs, the total light output at a particular color is calculated. A diamond or other symbol ( 512 ) may be plotted on the diagram to represent the color when all of the LEDs are on full brightness or the point may represent the present intensity setting.

[0114] Because a lighting fixture can be made of a plurality of component illumination sources, when designing a lighting fixture, a color that is most desirable can be selected, and a lighting fixture can be designed that maximizes the intensity of that color. Alternatively, a fixture may be chosen and the point of maximum intensity can be determined from this selection. A tool may be provided to allow calculation of a particular color at a maximum intensity. FIG. 6 shows such a tool as symbol ( 512 ), where the CIE diagram has been placed on a computer and calculations can be automatically performed to compute a total number of LEDs necessary to produce a particular intensity, as well as the ratio of LEDs of different spectrums to produce particular colors. Alternatively, a selection of LEDs may be chosen and the point of maximum intensity determined; both directions of calculation are included in embodiments of this invention.

[0115] In FIG. 6 as the number of LEDs are altered, the maximum intensity points move so that a user can design a light which has a maximum intensity at a desired point.

[0116] Therefore the system in one embodiment of the invention contains a collection of the spectrums of a number of different LEDs, provides an interface for a user to select LEDs that will produce a range of color that encloses the desirable area, and allows a user to select the number of each LED type such that when the unit is on full, a target color is produced. In an alternative embodiment, the user would simply need to provide a desired spectrum, or color and intensity, and the system could produce a lighting fixture which could generate light according to the requests.

[0117] Once the light has been designed, in one embodiment, it is further desirable to make the light's spectrum easily accessible to the lighting fixture's user. As was discussed above, the lighting fixture may have been chosen to have a particular array of illumination sources such that a particular color is obtained at maximum intensity. However, there may be other colors that can be produced by varying the relative intensities of the component illumination sources. The spectrum of the lighting fixture can be controlled within the predetermined range specified by the area ( 510 ). To control the lighting color within the range, it is recognized that each color within the polygon is the additive mix of the component LEDs with each color contained in the components having a varied intensity. That is, to move from one point in FIG. 6 to a second point in FIG. 6 , it is necessary to alter the relative intensities of the component LEDs. This may be less than intuitive for the final user of the lighting fixture who simply wants a particular color, or a particular transition between colors and does not know the relative intensities to shift to. This is particularly true if the LEDs used do not have spectra with a single well-determined peak of color. A lighting fixture may be able to generate several shades of orange, but how to get to each of those shades may require control.

[0118] In order to be able to carry out such control of the spectrum of the light, it is desirable in one embodiment to create a system and method for linking the color of the light to a control device for controlling the light's color. Since a lighting fixture can be custom designed, it may, in one embodiment, be desirable to have the intensities of each of the component illumination sources “mapped” to a desirable resultant spectrum of light and allowing a point on the map to be selected by the controller. That is, a method whereby, with the specification of a particular color of light by a controller, the lighting fixture can turn on the appropriate illumination sources at the appropriate intensity to create that color of light. In one embodiment, the lighting fixture design software shown in FIG. 6 can be configured in such a way that it can generate a mapping between a desirable color that can be produced (within the area ( 510 )), and the intensities of the component LEDs that make up the lighting fixture. This mapping will generally take one of two forms: 1) a lookup table, or 2) a parametric equation, although other forms could be used as would be known to one of skill in the art. Software on board the lighting fixture (such as in the processor ( 316 ) above) or on board a lighting controller, such as one of those known to the art, or described above, can be configured to accept the input of a user in selecting a color, and producing a desired light.

[0119] This mapping may be performed by a variety of methods. In one embodiment, statistics are known about each individual component illumination sources within the lighting fixture, so mathematical calculations may be made to produce a relationship between the resulting spectrum and the component spectrums. Such calculations would be well understood by one of skill in the art.

[0120] In another embodiment, an external calibration system may be used. One layout of such a system is disclosed in FIG. 7 . Here the calibration system includes a lighting fixture ( 2010 ) that is connected to a processor ( 2020 ) and which receives input from a light sensor or transducer ( 2034 ). The processor ( 2020 ) may be processor ( 316 ) or may be an additional or alternative processor. The sensor ( 2034 ) measures color characteristics, and optionally brightness, of the light output by the lighting fixture ( 2010 ) and/or the ambient light, and the processor ( 2020 ) varies the output of the lighting fixture ( 2010 ). Between these two devices modulating the brightness or color of the output and measuring the brightness and color of the output, the lighting fixture can be calibrated where the relative settings of the component illumination sources (or processor settings ( 2020 )) are directly related to the output of the fixture ( 2010 ) (the light sensor ( 2034 ) settings). Since the sensor ( 2034 ) can detect the net spectrum produced by the lighting fixture, it can be used to provide a direct mapping by relating the output of the lighting fixture to the settings of the component LEDs.

[0121] Once the mapping has been completed, other methods or systems may be used for the light fixture's control. Such methods or systems will enable the determination of a desired color, and the production by the lighting fixture of that color.

[0122] FIG. 8 a shows one embodiment of the system ( 2000 ) where a control system ( 2030 ) may be used in conjunction with a lighting fixture ( 2010 ) to enable control of the lighting fixture ( 2010 ). The control system ( 2030 ) may be automatic, may accept input from a user, or may be any combination of these two. The system ( 2000 ) may also include a processor ( 2020 ) which may be processor ( 316 ) or another processor to enable the light to change color.

[0123] FIG. 9 shows a more particular embodiment of a system ( 2000 ). A user computer interface control system ( 2032 ) with which a user may select a desired color of light is used as a control system ( 2030 ). The interface could enable any type of user interaction in the determination of color. For example, the interface may provide a palette, chromaticity diagram, or other color scheme from which a user may select a color, e.g., by clicking with a mouse on a suitable color or color temperature on the interface, changing a variable using a keyboard, etc. The interface may include a display screen, a computer keyboard, a mouse, a trackpad, or any other suitable system for interaction between the processor and a user. In certain embodiments, the system may permit a user to select a set of colors for repeated use, capable of being rapidly accessed, e.g., by providing a simple code, such as a single letter or digit, or by selecting one of a set of preset colors through an interface as described above. In certain embodiments, the interface may also include a look-up table capable of correlating color names with approximate shades, converting color coordinates from one system, (e.g., RGB, CYM, YIQ, YUV, HSV, HLS, XYZ, etc.) to a different color coordinate system or to a display or illumination color, or any other conversion function for assisting a user in manipulating the illumination color. The interface may also include one or more closed-form equations for converting from, for example, a user-specified color temperature (associated with a particular color of white light) into suitable signals for the different component illumination sources of the lighting fixture ( 2010 ). The system may further include a sensor as discussed below for providing information to the processor ( 2020 ), e.g., for automatically calibrating the color of emitted light of the lighting fixture ( 2010 ) to achieve the color selected by the user on the interface.

[0124] In another embodiment, a manual control system ( 2031 ) is used in the system ( 2000 ), as depicted in FIG. 10 a , such as a dial, slider, switch, multiple switch, console, other lighting control unit, or any other controller or combination of controllers to permit a user to modify the illumination conditions until the illumination conditions or the appearance of a subject being illuminated is desirable. For example, a dial or slider may be used in a system to modulate the net color spectrum produced, the illumination along the color temperature curve, or any other modulation of the color of the lighting fixture. Alternatively, a joystick, trackball, trackpad, mouse, thumb-wheel, touch-sensitive surface, or a console with two or more sliders, dials, or other controls may be used to modulate the color, temperature, or spectrum. These manual controls may be used in conjunction with a computer interface control system ( 2032 ) as discussed above, or may be used independently, possibly with related markings to enable a user to scan through an available color range.

[0125] One such manual control system ( 2036 ) is shown in greater detail in FIG. 10 b . The depicted control unit features a dial marked to indicate a range of color temperatures, e.g., from 3000K to 10,500K. This device would be useful on a lighting fixture used to produce a range of temperatures (“colors”) of white light. It would be understood by one of skill in the art that broader, narrower, or overlapping ranges may be employed, and a similar system could be employed to control lighting fixtures that can produce light of a spectrum beyond white, or not including white. A manual control system ( 2036 ) may be included as part of a processor controlling an array of lighting units, coupled to a processor, e.g., as a peripheral component of a lighting control system, disposed on a remote control capable of transmitting a signal, such as an infrared or microwave signal, to a system controlling a lighting unit, or employed or configured in any other manner, as will readily be understood by one of skill in the art.

[0126] Additionally, instead of a dial, a manual control system ( 2036 ) may employ a slider, a mouse, or any other control or input device suitable for use in the systems and methods described herein.

[0127] In another embodiment, the calibration system depicted in FIG. 7 may function as a control system or as a portion of a control system. For instance a selected color could be input by the user and the calibration system could measure the spectrum of ambient light; compare the measured spectrum with the selected spectrum, adjust the color of light produced by the lighting fixture ( 2010 ), and repeat the procedure to minimize the difference between the desired spectrum and the measured spectrum. For example, if the measured spectrum is deficient in red wavelengths when compared with the target spectrum, the processor may increase the brightness of red LEDs in the lighting fixture, decrease the brightness of blue and green LEDs in the lighting fixture, or both, in order to minimize the difference between the measured spectrum and the target spectrum and potentially also achieve a target brightness (i.e. such as the maximum possible brightness of that color). The system could also be used to match a color produced by a lighting fixture to a color existing naturally. For instance, a film director could find light in a location where filming does not occur and measure that light using the sensor. This could then provide the desired color which is to be produced by the lighting fixture. In one embodiment, these tasks can be performed simultaneously (potentially using two separate sensors). In a yet further embodiment, the director can remotely measure a lighting condition with a sensor ( 2034 ) and store that lighting condition on memory associated with that sensor ( 2034 ). The sensor's memory may then be transferred at a later time to the processor ( 2020 ) which may set the lighting fixture to mimic the light recorded. This allows a director to create a “memory of desired lighting” which can be stored and recreated later by lighting fixtures such as those described above.

[0128] The sensor ( 2034 ) used to measure the illumination conditions may be a photodiode, a phototransistor, a photoresistor, a radiometer, a photometer, a calorimeter, a spectral radiometer, a camera, a combination of two or more of the preceding devices, or any other system capable of measuring the color or brightness of illumination conditions. An example of a sensor may be the IL2000 SpectroCube Spectroradiometer offered for sale by International Light Inc., although any other sensor may be used. A colorimeter or spectral radiometer is advantageous because a number of wavelengths can be simultaneously detected, permitting accurate measurements of color and brightness simultaneously. A color temperature sensor which may be employed in the systems methods described herein is disclosed in U.S. Pat. No. 5,521,708.

[0129] In embodiments wherein the sensor ( 2034 ) detects an image, e.g., includes a camera or other video capture device, the processor ( 2020 ) may modulate the illumination conditions with the lighting fixture ( 2010 ) until an illuminated object appears substantially the same, e.g., of substantially the same color, as in a previously recorded image. Such a system simplifies procedures employed by cinematographers, for example, attempting to produce a consistent appearance of an object to promote continuity between scenes of a film, or by photographers, for example, trying to reproduce lighting conditions from an earlier shoot.

[0130] In certain embodiments, the lighting fixture ( 2010 ) may be used as the sole light source, while in other embodiments, such as is depicted in FIG. 8 b , the lighting fixture ( 2010 ) may be used in combination with a second source of light ( 2040 ), such as an incandescent, fluorescent, halogen, or other LED sources or component light sources (including those with and without control), lights that are controlled with pulse width modulation, sunlight, moonlight, candlelight, etc. This use can be to supplement the output of the second source. For example, a fluorescent light emitting illumination weak in red portions of the spectrum may be supplemented with a lighting fixture emitting primarily red wavelengths to provide illumination conditions more closely resembling natural sunlight. Similarly, such a system may also be useful in outdoor image capture situations, because the color temperature of natural light varies as the position of the sun changes. A lighting fixture ( 2010 ) may be used in conjunction with a sensor ( 2034 ) as controller ( 2030 ) to compensate for changes in sunlight to maintain constant illumination conditions for the duration of a session.

[0131] Any of the above systems could be deployed in the system disclosed in FIG. 11 . A lighting system for a location may comprise a plurality of lighting fixtures ( 2301 ) which are controllable by a central control system ( 2303 ). The light within the location (or on a particular location such as the stage ( 2305 ) depicted here) is now desired to mimic another type of light such as sunlight. A first sensor ( 2307 ) is taken outside and the natural sunlight ( 2309 ) is measured and recorded. This recording is then provided to central control system ( 2303 ). A second sensor (which may be the same sensor in one embodiment) ( 2317 ) is present on the stage ( 2305 ). The central control system ( 2309 ) now controls the intensity and color of the plurality of lighting fixtures ( 2301 ) and attempts to match the input spectrum of said second sensor ( 2317 ) with the prerecorded natural sunlight's ( 2309 ) spectrum. In this manner, interior lighting design can be dramatically simplified as desired colors of light can be reproduced or simulated in a closed setting. This can be in a theatre (as depicted here), or in any other location such as a home, an office, a soundstage, a retail store, or any other location where artificial lighting is used. Such a system could also be used in conjunction with other secondary light sources to create a desired lighting effect.

[0132] The above systems allow for the creation of lighting fixtures with virtually any type of spectrum. It is often desirable to produce light that appears “natural” or light which is a high-quality, especially white light.

[0133] A lighting fixture which produces white light according to the above invention can comprise any collection of component illumination sources such that the area defined by the illumination sources can encapsulate at least a portion of the black body curve. The black body curve ( 104 ) in FIG. 1 is a physical construct that shows different color white light with regards to the temperature of the white light. In a preferred embodiment, the entire black body curve would be encapsulated allowing the lighting fixture to produce any temperature of white light.

[0134] For a variable color white light with the highest possible intensity, a significant portion of the black body curve may be enclosed. The intensity at different color whites along the black body curve can then be simulated. The maximum intensity produced by this light could be placed along the black body curve. By varying the number of each color LED (in FIG. 6 red, blue, amber, and blue-green) it is possible to change the location of the full-on point (the symbol ( 512 ) in FIG. 6 ). For example, the full-on color could be placed at approximately 5400K (noon day sunlight shown by point ( 106 ) in FIG. 1 ), but any other point could be used (two other points are shown in FIG. 1 corresponding to a fire glow and an incandescent bulb). Such a lighting apparatus would then be able to produce 5400 K light at a high intensity; in addition, the light may adjust for differences in temperature (for instance cloudy sunlight) by moving around in the defined area.

[0135] Although this system generates white light with a variable color temperature, it is not necessarily a high quality white light source. A number of combinations of colors of illumination sources can be chosen which enclose the black body curve, and the quality of the resulting lighting fixtures may vary depending on the illumination sources chosen.

[0136] Since white light is a mixture of different wavelengths of light, it is possible to characterize white light based on the component colors of light that are used to generate it. Red, green, and blue (RGB) can combine to form white; as can light blue, amber, and lavender; or cyan, magenta and yellow. Natural white light (sunlight) contains a virtually continuous spectrum of wavelengths across the human visible band (and beyond). This can be seen by examining sunlight through a prism, or looking at a rainbow. Many artificial white lights are technically white to the human eye, however, they can appear quite different when shown on colored surfaces because they lack a virtually continuous spectrum.

[0137] As an extreme example one could create a white light source using two lasers (or other narrow band optical sources) with complimentary wavelengths. These sources would have an extremely narrow spectral width perhaps 1 nm wide. To exemplify this, we will choose wavelengths of 635 nm and 493 nm. These are considered complimentary since they will additively combine to make light which the human eye perceives as white light. The intensity levels of these two lasers can be adjusted to some ratio of powers that will produce white light that appears to have a color temperature of 5000K. If this source were directed at a white surface, the reflected light will appear as 5000K white light.

[0138] The problem with this type of white light is that it will appear extremely artificial when shown on a colored surface. A colored surface (as opposed to colored light) is produced because the surface absorbs and reflects different wavelengths of light. If hit by white light comprising a full spectrum (light with all wavelengths of the visible band at reasonable intensity), the surface will absorb and reflect perfectly. However, the white light above does not provide the complete spectrum. To again use an extreme example, if a surface only reflected light from 500 nm-550 nm it will appear a fairly deep green in full-spectrum light, but will appear black (it absorbs all the spectrums present) in the above described laser-generated artificial white light.

[0139] Further, since the CRI index relies on a limited number of observations, there are mathematical loopholes in the method. Since the spectrums for CRI color samples are known, it is a relatively straightforward exercise to determine the optimal wavelengths and minimum numbers of narrow band sources needed to achieve a high CRI. This source will fool the CRI measurement, but not the human observer. The CRI method is at best an estimator of the spectrum that the human eye can see. An everyday example is the modem compact fluorescent lamp. It has a fairly high CRI of 80 and a color temperature of 2980K but still appears unnatural. The spectrum of a compact fluorescent is shown in FIG. 27 .

[0140] Due to the desirability of high-quality light (in particular high-quality white light) that can be varied over different temperatures or spectrums, a further embodiment of this invention comprises systems and method for generating higher-quality white light by mixing the electromagnetic radiation from a plurality of component illumination sources such as LEDs. This is accomplished by choosing LEDs that provide a white light that is targeted to the human eye's interpretation of light, as well as the mathematical CRI index. That light can then be maximized in intensity using the above system. Further, because the color temperature of the light can be controlled, this high quality white light can therefore still have the control discussed above and can be a controllable, high-quality, light which can produce high-quality light across a range of colors.

[0141] To produce a high-quality white light, it is necessary to examine the human eye's ability to see light of different wavelengths and determine what makes a light high-quality. In it's simplest definition, a high-quality white light provides low distortion to colored objects when they are viewed under it. It therefore makes sense to begin by examining a high-quality light based on what the human eye sees. Generally the highest quality white light is considered to be sunlight or full-spectrum light, as this is the only source of “natural” light. For the purposes of this disclosure, it will be accepted that sunlight is a high-quality white light.

[0142] The sensitivity of the human eye is known as the Photopic response. The Photopic response can be thought of as a spectral transfer function for the eye, meaning that it indicates how much of each wavelength of light input is seen by the human observer. This sensitivity can be expressed graphically as the spectral luminosity function V ( 501 ), which is represented in FIG. 12 .

[0143] The eye's Photopic response is important since it can be used to describe the boundaries on the problem of generating white light (or of any color of light). In one embodiment of the invention, a high quality white light will need to comprise only what the human eye can “see.” In another embodiment of the invention, it can be recognized that high-quality white light may contain electromagnetic radiation which cannot be seen by the human eye but may result in a photobiological response. Therefore a high-quality white light may include only visible light, or may include visible light and other electromagnetic radiation which may result in a photobiological response. This will generally be electromagnetic radiation less than 400 nm (ultraviolet light) or greater than 700 nm (infrared light).

[0144] Using the first part of the description, the source is not required to have any power above 700 nm or below 400 nm since the eye has only minimal response at these wavelengths. A high-quality source would preferably be substantially continuous between these wavelengths (otherwise colors could be distorted) but can fall-off towards higher or lower wavelengths due to the sensitivity of the eye. Further, the spectral distribution of different temperatures of white light will be different. To illustrate this, spectral distributions for two blackbody sources with temperatures of 5000K ( 601 ) and 2500K ( 603 ) are shown in FIG. 13 along with the spectral luminosity function ( 501 ) from FIG. 12 .

[0145] As seen in FIG. 13 , the 5000K curve is smooth and centered about 555 nm with only a slight fall-off in both the increasing and decreasing wavelength directions. The 2500K curve is heavily weighted towards higher wavelengths. This distribution makes sense intuitively, since lower color temperatures appear to be yellow-to-reddish. One point that arises from the observation of these curves, against the spectral luminosity curve, is that the Photopic response of the eye is “filled.” This means that every color that is illuminated by one of these sources will be perceived by a human observer. Any holes, i.e., areas with no spectral power, will make certain objects appear abnormal. This is why many “white” light sources seem to disrupt colors. Since the blackbody curves are continuous, even the dramatic change from 5000K to 2500K will only shift colors towards red, making them appear warmer but not devoid of color. This comparison shows that an important specification of any high-quality artificial light fixture is a continuous spectrum across the photopic response of the human observer.

[0146] Having examined these relationships of the human eye, a fixture for producing controllable high-quality white light would need to have the following characteristic. The light has a substantially continuous spectrum over the wavelengths visible to the human eye, with any holes or gaps locked in the areas where the human eye is less responsive. In addition, in order to make a high-quality white light controllable over a range of temperatures, it would be desirable to produce a light spectrum which can have relatively equal values of each wavelength of light, but can also make different wavelengths dramatically more or less intense with regards to other wavelengths depending on the color temperature desired. The clearest waveform which would have such control would need to mirror the scope of the photopic response of the eye, while still being controllable at the various different wavelengths.

[0147] As was discussed above, the traditional mixing methods which create white light can create light which is technically “white” but sill produces an abnormal appearance to the human eye. The CRI rating for these values is usually extremely low or possibly negative. This is because if there is not a wavelength of light present in the generation of white light, it is impossible for an object of a color to reflect/absorb that wavelength. In an additional case, since the CRI rating relies on eight particular color samples, it is possible to get a high CRI, while not having a particularly high-quality light because the white light functions well for those particular color samples specified by the CRI rating. That is, a high CRI index could be obtained by a white light composed of eight 1 nm sources which were perfectly lined up with the eight CRI color structures. This would, however, not be a high-quality light source for illuminating other colors.

[0148] The fluorescent lamp shown in FIG. 27 provides a good example of a high CRI light that is not high-quality. Although the light from a fluorescent lamp is white, it is comprised of many spikes (such as ( 201 ) and ( 203 )). The position of these spikes has been carefully designed so that when measured using the CRI samples they yield a high rating. In other words, these spikes fool the CRI calculation but not the human observer. The result is a white light that is usable but not optimal (i.e., it appears artificial). The dramatic peaks in the spectrum of a fluorescent light are also clear in FIG. 27 . These peaks are part of the reason that fluorescent light looks very artificial. Even if light is produced within the spectral valleys, it is so dominated by the peaks that a human eye has difficulty seeing it. A high-quality white light may be produced according to this disclosure without the dramatic peaks and valleys of a florescent lamp.

[0149] A spectral peak is the point of intensity of a particular color of light which has less intensity at points immediately to either side of it. A maximum spectral peak is the highest spectral peak within the region of interest. It is therefore possible to have multiple peaks within a chosen portion of the electromagnetic spectrum, only a single maximum peak, or to have no peaks at all. For instance, FIG. 12 in the region 500 nm to 510 nm has no spectral peaks because there is no point in that region that has lower points on both sides of it.

[0150] A valley is the opposite of a peak and is a point that is a minimum and has points of higher intensity on either side of it (an inverted plateau is also a valley). A special plateau can also be a spectrum peak. A plateau involves a series of concurrent points of the same intensity with the points on either side of the series having less intensity.

[0151] It should be clear that high-quality white light simulating black-body sources do not have significant peaks and valleys within the area of the human eye's photopic response as is shown in FIG. 13 .

[0152] Most artificial light, does however have some peaks and valleys in this region such shown in FIG. 27 , however the less difference between these points the better. This is especially true for higher temperature light whereas for lower temperature light the continuous line has a positive upward slope with no peaks or valleys and shallow valleys in the shorter wavelength areas would be less noticeable, as would slight peaks in the longer wavelengths.

[0153] To take into account this peak and valley relationship to high-quality white light, the following is desirable in a high-quality white light of one embodiment of this invention. The lowest valley in the visible range should have a greater intensity than the intensity attributable to background noise as would be understood by one of skill in the art. It is further desirable to close the gap between the lowest valley and the maximum peak; and other embodiments of the invention have lowest valleys with at least 5% 10%, 25%, 33%, 50%, and 75% of the intensity of the maximum peaks. One skilled in the art would see that other percentages could be used anywhere up to 100%.

[0154] In another embodiment, it is desirable to mimic the shape of the black body spectra at different temperatures; for higher temperatures (4,000 K to 10,000 K) this may be similar to the peaks and valleys analysis above. For lower temperatures, another analysis would be that most valleys should be at a shorter wavelength than the highest peak. This would be desirable in one embodiment for color temperatures less than 2500 K. In another embodiment it would be desirable to have this in the region 500 K to 2500 K.

[0155] From the above analysis high-quality artificial white light should therefore have a spectrum that is substantially continuous between the 400 nm and 700 nm without dramatic spikes. Further, to be controllable, the light should be able to produce a spectrum that resembles natural light at various color temperatures. Due to the use of mathematical models in the industry, it is also desirable for the source to yield a high CRI indicative that the reference colors are being preserved and showing that the high-quality white light of the instant invention does not fail on previously known tests.

[0156] In order to build a high-quality white light lighting fixture using LEDs as the component illumination sources, it is desirable in one embodiment to have LEDs with particular maximum spectral peaks and spectral widths. It is also desirable to have the lighting fixture allow for controllability, that is that the color temperature can be controlled to select a particular spectrum of “white” light or even to have a spectrum of colored light in addition to the white light. It would also be desirable for each of the LEDs to produce equal intensities of light to allow for easy mixing.

[0157] One system for creating white light includes a large number (for example around 300) of LEDs, each of which has a narrow spectral width and each of which has a maximum spectral peak spanning a predetermined portion of the range from about 400 nm to about 700 nm, possibly with some overlap, and possibly beyond the boundaries of visible light. This light source may produce essentially white light, and may be controllable to produce any color temperature (and also any color). It allows for smaller variation than the human eye can see and therefore the light fixture can make changes more finely than a human can perceive. Such a light fixture is therefore one embodiment of the invention, but other embodiments can use fewer LEDs when perception by humans is the focus.

[0158] In another embodiment of the invention, a significantly smaller number of LEDs can be used with the spectral width of each LED increased to generate a high-quality white light. One embodiment of such a light fixture is shown in FIG. 14 . FIG. 14 shows the spectrums of nine LEDs ( 701 ) with 25 nm spectral widths spaced every 25 nm. It should be recognized here that a nine LED lighting fixture does not necessarily contain exactly nine total illumination sources. It contains some number of each of nine different colored illuminating sources. This number will usually be the same for each color, but need not be. High-brightness LEDs with a spectral width of about 25 nm are generally available. The solid line ( 703 ) indicates the additive spectrum of all of the LED spectrums at equal power as could be created using the above method lighting fixture. The powers of the LEDs may be adjusted to generate a range of color temperature (and colors as well) by adjusting the relative intensities of the nine LEDs. FIGS. 15 a and 15 b are spectrums for the 5000K ( 801 ) and 2500K ( 803 ) white-light from this lighting fixture. This nine LED lighting fixture has the ability to reproduce a wide range of color temperatures as well as a wide range of colors as the area of the CIE diagram enclosed by the component LEDs covers most of the available colors. It enables control over the production of non-continuous spectrums and the generation of particular high-quality colors by choosing to use only a subset of the available LED illumination sources. It should be noted that the choice of location of the dominant wavelength of the nine LEDs could be moved without significant variation in the ability to produce white light. In addition, different colored LEDs may be added. Such additions may improve the resolution as was discussed in the 300 LED example above. Any of these light fixtures may meet the quality standards above. They may produce a spectrum that is continuous over the photopic response of the eye, that is without dramatic peaks, and that can be controlled to produce a white light of multiple desired color temperatures.

[0159] The nine LED white light source is effective since its spectral resolution is sufficient to accurately simulate spectral distributions within human-perceptible limits. However, fewer LEDs may be used. If the specifications of making high-quality white light are followed, the fewer LEDs may have an increased spectral width to maintain the substantially continuous spectrum that fills the Photopic response of the eye. The decrease could be from any number of LEDs from 8 to 2. The 1 LED case allows for no color mixing and therefore no control. To have a temperature controllable white light fixture at least two colors of LEDs may be required.

[0160] One embodiment of the current invention includes three different colored LEDs. Three LEDs allow for a two dimensional area (a triangle) to be available as the spectrum for the resultant fixture. One embodiment of a three LED source is shown in FIG. 16 .

[0161] The additive spectrum of the three LEDs ( 903 ) offers less control than the nine LED lighting fixture, but may meet the criteria for a high-quality white light source as discussed above. The spectrum may be continuous without dramatic peaks. It is also controllable, since the triangle of available white light encloses the black body curve. This source may lose fine control over certain colors or temperatures that were obtained with a greater number of LEDs as the area enclosed on the CIE diagram is a triangle, but the power of these LEDs can still be controlled to simulate sources of different color temperatures. Such an alteration is shown in FIGS. 17 a and 17 b for 5000K ( 1001 ) and 2500K ( 1003 ) sources. One skilled in the art would see that alternative temperatures may also be generated.

[0162] Both the nine LED and three LED examples demonstrate that combinations of LEDs can be used to create high-quality white lighting fixtures. These spectrums fill the photopic response of the eye and are continuous, which means they appear more natural than artificial light sources such as fluorescent lights. Both spectra may be characterized as high-quality since the CRIs measure in the high 90 s.

[0163] In the design of a white lighting fixture, one impediment is the lack of availability for LEDs with a maximum spectral peak of 555 nm. This wavelength is at the center of the Photopic response of the eye and one of the clearest colors to the eye. The introduction of an LED with a dominant wavelength at or near 555 nm would simplify the generation of LED-based white light, and a white light fixture with such an LED comprises one embodiment of this invention. In another embodiment of the invention, a non-LED illumination source that produces light with a maximum spectral peak from about 510 nm to about 570 nm could also be used to fill this particular spectral gap. In a still further embodiment, this non-LED source could comprise an existing white light source and a filter to make that resulting light source have a maximum spectral peak in this general area.

[0164] In another embodiment high-quality white light may be generated using LEDs without spectral peaks around 555 nm to fill in the gap in the Photopic response left by the absence of green LEDs. One possibility is to fill the gap with a non-LED illumination source. Another, as described below, is that a high-quality controllable white light source can be generated using a collection of one or more different colored LEDs where none of the LEDs have a maximum spectral peak in the range of about 510 nm to 570 nm.

[0165] To build a white light lighting fixture that is controllable over a generally desired range of color temperatures, it is first necessary to determine the criteria of temperature desired.

[0166] In one embodiment, this is chosen to be color temperatures from about 2300K to about 4500K which is commonly used by lighting designers in industry. However, any range could be chosen for other embodiments including the range from 500K to 10,000K which covers most variation in visible white light or any sub-range thereof. The overall output spectrum of this light may achieve a CRI comparable to standard light sources already existing. Specifically, a high CRI (greater than 80) at 4500K and lower CRI (greater than 50) at 2300K may be specified although again any value could be chosen. Peaks and valleys may also be minimized in the range as much as possible and particularly to have a continuous curve where no intensity is zero (there is at least some spectral content at each wavelength throughout the range).

[0167] In recent years, white LEDs have become available. These LEDs operate using a blue LED to pump a layer of phosphor. The phosphor down-coverts some of the blue light into green and red. The result is a spectrum that has a wide spectrum and is roughly centered about 555 nm, and is referred to as “cool white.” An example spectrum for such a white LED (in particular for a Nichia NSPW510 BS (bin A) LED), is shown in FIG. 18 as the spectrum ( 1201 ).

[0168] The spectrum ( 1201 ) shown in FIG. 18 is different from the Gaussian-like spectrums for some LEDs. This is because not all of the pump energy from the blue LED is down-converted. This has the effect of cooling the overall spectrum since the higher portion of the spectrum is considered to be warm. The resulting CRI for this LED is 84 but it has a color temperature of 20,000K. Therefore the LED on its own does not meet the above lighting criteria. This spectrum ( 1201 ) contains a maximum spectral peak at about 450 nm and does not accurately fill the photopic response of the human eye. A single LED also allows for no control of color temperature and therefore a system of the desired range of color temperatures cannot be generated with this LED alone.

[0169]