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Automatic Color Compensation in a Daylight Harvesting Lighting Control System

IP.com Disclosure Number: IPCOM000245348D
Publication Date: 2016-Mar-02
Document File: 6 page(s) / 187K

Publishing Venue

The IP.com Prior Art Database

Abstract

This disclosure is directed to a system that can extend automatic lighting control systems to control not only the light level in an environment but also the spectral (e.g. color) content. This system has applicability to health care facilities, work spaces, classrooms, residential environments, and other uses. For example, this system can be use anywhere the color of the light is desired to change to influence the circadian rhythm, alertness levels, and/or mood of individuals. It is anticipated that this will extend the existing automated lighting control to new areas of use. Existing systems to control color content may be based on schedule operation only or also involve manual intervention to compensate for natural daylight contributions. This present concept may automatically compensate for light spectrum content and level and provide for changes that can automatically adjust for intended light level and spectrum content in the environment. Alternatively, the present system can also compensate the light level and spectrum content based on the time of day and a stored schedule This differs from existing daylight harvesting systems because it detects and uses color in addition to normal photonic light level. The system uses a color sensing photocell to identify key spectrum content. In addition to the current light level and a time/day based schedule that identifies overall light level, the schedule contains both the desired color spectrum in addition to the overall light level. In turn, this allows the system to perform automatic color tuning of the artificial light in an environment. This is different from existing solutions because it uses feedback from the target environment to make tailored color adjustments in addition to light level adjustments. The system is comprised of similar components as a normal daylight harvesting lighting control system. The basic system can be as simple as including: a color adjustable luminaire, a control unit with an optional time/day clock, an optional configurable time of day schedule with target light level and target spectral content, and a photocell that is capable of sensing both light intensity and color or spectral content. This system can be extended to include occupancy/vacancy sensors to turn the lights off when no one is present and switches that can be used to complement the occupancy sensors and photocell control for special conditions (see Figure 1). The spectrum sensing photocell detects the spectral content to determine the current environmental lighting parameters. This is then reported to the processing unit. The processing unit then compares the environmental parameters to the desired lighting parameters which may optionally be based on the time of day. Based on the current environmental parameters and the desired target level, the artificial lighting will be adjusted for both light intensity and spectral content (or color temperature). This can also be done in a dynamic manner. In one implementation of this invention the Luminaire control might be controlled using multiple 0-10V signals, one for light intensity and one 0-10V signal for color temperature. In another implementation there could be one 0-10V for light intensity and multiple 0-10V signals to adjust the key color components to achieve the desired color content of the artificial light.

The ability to capture a desired spectral content can be done multiple ways as well. In one implementation of the photocell, the color temperature could be used to provide an approximation of the spectral content. Another implementation could provide the levels of five key frequencies that correspond to the five known detection mechanisms of the human eye. A third implementation would be to do a full spectrographic measurement and convey this measurement to the processing unit. Another implementation would be to use the standard Red, Green, Blue (RGB) colors to approximate the spectral content. The implementation of the light level and spectral content (and optional stored schedule) would use a mechanism that would match either the manner that the photocell provides the spectral content or the mechanism used to control the color content from the luminaire. If a schedule is used, depending on the manner it is used to specify the desired environmental lighting parameters, a transformation function may be used to translate the photocell information into the representation of the schedule information. Alternatively, the result of the schedule information may be transformed into the format needed to control the luminaire (see Figure 2). In addition to the 0-10V control described, other analog or digital control schemes common to lighting control could also be used. The general processing to accomplish this would start with a sampling of the lighting in the controlled area for both light level and color content. This sample would be compared to the currently desired or scheduled target for the controlled area and an adjustment to the light level and color would be sent to the light (see Figure 3). This can be done continuously or on a periodically updating basis. The general algorithm to accomplish this automatic color compensation starts with information from the light level and spectral content sensor comparing it to the currently desired level and spectral content and making adjustments to the controlled luminaires to achieve the desired target lighting (see Figure 4). In an alternative implementation, this concept may work with a mixture of both natural and artificial light sources, with some ability for further manipulation. An example of this would be to control window coverings to reduce the contribution from the natural light when the limits of artificial light control have been reached.

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Automatic Color Compensation in a Daylight Harvesting Lighting Control System

This disclosure is directed to a system that can extend automatic lighting control systems to control not only the light level in an environment but also the spectral (e.g. color) content. This system has applicability to health care facilities, work spaces, classrooms, residential environments, and other uses. For example, this system can be use anywhere the color of the light is desired to change to influence the circadian rhythm, alertness levels, and/or mood of individuals. It is anticipated that this will extend the existing automated lighting control to new areas of use.

Existing systems to control color content may be based on schedule operation only or also involve manual intervention to compensate for natural daylight contributions. This present concept may automatically compensate for light spectrum content and level and provide for changes that can automatically adjust for intended light level and spectrum content in the environment. Alternatively, the present system can also compensate the light level and spectrum content based on the time of day and a stored schedule

This differs from existing daylight harvesting systems because it detects and uses color in addition to normal photonic light level. The system uses a color sensing photocell to identify key spectrum content. In addition to the current light level and a time/day based schedule that identifies overall light level, the schedule contains both the desired color spectrum in addition to the overall light level. In turn, this allows the system to perform automatic color tuning of the artificial light in an environment. This is different from existing solutions because it uses feedback from the target environment to make tailored color adjustments in addition to light level adjustments.

The system is comprised of similar components as a normal daylight harvesting lighting control system. The basic system can be as simple as including: a color adjustable luminaire, a control unit with an optional time/day clock, an optional configurable time of day schedule with target light level and target spectral content, and a photocell that is capable of sensing both light intensity and color or spectral content. This system can be extended to include occupancy/vacancy sensors to turn the lights off when no one is present and switches that can be used to complement the occupancy sensors and photocell control for special conditions (see Figure 1).

The spectrum sensing photocell detects the spectral content to determine the current environmental lighting parameters. This is then reported to the processing unit. The processing unit then compares the environmental parameters to the desired lighting parameters which may optionally be based on the time of day. Based on the current environmental parameters and the desired target level, the artificial lighting will be adjusted for both light intensity and...