Kevin W Houser | The Pennsylvania State University (original) (raw)

Papers by Kevin W Houser

We have developed a two-measure system for evaluating light sources' color rendition that builds ... more We have developed a two-measure system for evaluating light sources' color rendition that builds upon conceptual progress of numerous researchers over the last two decades. The system quantifies the color fidelity and color gamut (change in object chroma) of a light source in comparison to a reference illuminant. The calculations are based on a newly developed set of reflectance data from real samples uniformly distributed in color space (thereby fairly representing all colors) and in wavelength space (thereby precluding artificial optimization of the color rendition scores by spectral engineering). The color fidelity score R f is an improved version of the CIE color rendering index. The color gamut score R g is an improved version of the Gamut Area Index. In combination, they provide two complementary assessments to guide the optimization of future light sources. This method summarizes the findings of the Color Metric Task

This tutorial explains how the human perception of color rendering arises, in terms of the underl... more This tutorial explains how the human perception of color rendering arises, in terms of the underlying phenomena of light and vision, and using those concepts it presents a clear explanation of the CIE Color Rendering Index. The strengths and weaknesses of the CIE Color Rendering Index are reviewed and some common misunderstandings about color rendering are addressed. It is suitable for self-study, with learning outcomes stated at the beginning and a conceptual summary provided at the end.

Office buildings don’t have opinions about saving or using energy; their occupants do. Of the tot... more Office buildings don’t have opinions about saving or using energy; their occupants do. Of the total energy consumed by commercial buildings, an increasing proportion is directly under the control of building occupants, who to this point have rarely been challenged to conserve energy in any consistent way. While improved devices and controls achieve some efficiencies, the biggest potential savings are in the hands of ordinary office occupants deciding which device to turn on or off, up or down. Broadly speaking the decision to save energy comprises two parts: an initial learning and commitment phase, and a refining and monitoring phase. Our implementations of Serious Games and Dashboards educate users and prompt behavioral change; games oriented toward the engagement and commitment phase, dashboards to monitoring and persistence. These studies evaluated the effectiveness of a virtual pet game and an energy dashboard in reducing plug-loads in mid-size commercial offices. Initial energ...

CITATIONS 0 READS 20 6 authors, including:

Energy and Buildings, 2014

Serious Games are virtual simulations of real-world activities that can both educate users and pr... more Serious Games are virtual simulations of real-world activities that can both educate users and prompt behavioral change. This study evaluated the effectiveness of a virtual pet game in reducing plug-loads in a mid-size commercial office. Participants were 61 resident workers. The energy consumption of 288 appliances was monitored for 24 weeks using plug-load sensors. After 4-weeks of baseline, 42 participants were introduced to the "Energy Chickens" serious game, which they played for 12 weeks. Within the game, daily energy consumption data for each individual's devices were used to manipulate animated chickens living on a personalized virtual farm. Changes in device-specific energy consumption were reflected in the improving or declining "health" of the corresponding chickens. Healthy, energy-saving chickens laid eggs that the user could collect and use to purchase accessories for their virtual farm. Across all intervention days, average energy consumption declined by 13%. Participants achieved 23% reductions on non-work days and 7% reductions on workdays. At the conclusion of the intervention, 69% of participants indicated that the game helped them be more energy conscious, with some indicating changes in their energy use outside the office. Results highlight the effectiveness of behavioral interventions on plug-load energy consumption within commercial office settings.

LEUKOS, 2014

ABSTRACT Visual perception of many manufactured white objects is driven by the concentration of f... more ABSTRACT Visual perception of many manufactured white objects is driven by the concentration of fluorescent whitening agents (FWAs) that they contain. FWAs serve to increase overall whiteness perception by enhancing luminance and providing a chromatic blue shift. White objects with FWAs have been engineered for many decades to interact with conventional illuminants such as daylight and incandescent light in order to provide desirable whiteness perception. Whiteness perception has not previously been investigated under light emitting diodes (LEDs). In this study, three psychophysical experiments—forced choice, selection, and sorting—were conducted to investigate the whiteness perception of a series of whiteness standards containing predetermined amounts of FWAs, illuminated by five sources: a typical blue-pumped LED (BLED), a filtered halogen lamp, and violet-pumped LEDs with three violet emission levels. Thirty-nine participants with normal color vision completed the experiments. Results from the sorting experiment can be explained by FWA excitation: the BLED induced no fluorescence and standards could not be ordered properly, whereas for other sources the perceived whiteness increased with the amount of FWAs. Results from the other two experiments can be explained by FWA excitation together with shifts in source chromaticity. Overall, all results are compatible with the known trend for blue shifts to induce whiteness perception. Adaptations of the CIE whiteness formula are also shown to agree well with the experimental results. The results indicate that engineering of an LED source’s spectrum is necessary for an accurate rendering of whiteness.

LEUKOS, 2011

ABSTRACT This paper analyzes the illuminance uniformity of 30 outdoor sports fields at various po... more ABSTRACT This paper analyzes the illuminance uniformity of 30 outdoor sports fields at various points in their service lives. The study was limited to the fields that employ 1500 W metal halide lamps with a rated life of 3000 hours. The sample was comprised of 12 soccer fields, 14 baseball fields, and 4 softball fields, all of which are owned and maintained by municipal parks and recreation departments. Five uniformity indices were computed for both measured illuminance and initial design calculations: maximum to minimum ratio (Max:Min), maximum to average ratio (Max:Ave), average to minimum ratio (Ave: Min), coefficient of variation (CV), and uniformity gradient (UG). Measured uniformity was rarely as good as the uniformity predicted by the design calculations. The uniformity of the baseball and softball fields was better with hours-of-use, with infields and outfields exhibiting similar trends. Max:Min, UG, and CV indices, as well as the illuminance of the transition area between infield and outfield, are suggested as key evaluation parameters. Group vs. spot lamp replacement, as-built vs. as-designed, dirt accumulation, and outgassing are factors that contribute to sports lighting uniformity.

ABSTRACT This paper analyzes the performance of 138 LED luminaires comprised of 95 indoor and 43 ... more ABSTRACT This paper analyzes the performance of 138 LED luminaires comprised of 95 indoor and 43 outdoor, all of which were within the judging phase of the 2010 U.S. Department of Energy Next Generation Luminaire™ (NGL) competition. The analyses focus on three areas derived from LM-79 and LM-80 test reports that were supplied by the manufacturers: energy efficiency, color, and long-term performance. Indoor recessed downlights and street lighting luminaires had the most entries. All luminaires employed phosphor-converted LED (PC-LED) packages or remote phosphor technology, reflecting the fact that these technologies now have better performance than color-mixed light emitting diodes (LEDs) for white-light applications. Comparisons of luminaire efficacy and luminous efficacy of radiation (LER) were made among the NGL 2010 submissions, luminaires with conventional light sources, and the expected performance of LED luminaires in the near future. 0–10V and reverse-phase control were the prominent dimming methods among the luminaires studied. High correlation (r = 0.98) was found between the CIE color rendering index (CRI) and NIST’s Color Quality Scale (CQS). Compared to the luminaires recognized in 2009, a better balance was achieved between efficacy and CRI in 2010. The need to standardize the methods for evaluating LED products is discussed, including dimming performance, color-shift, long-term performance, and luminaire rated life. In person evaluation and mockups are recommended prior to specifying LED products

Optics Express, 2013

Twenty-two measures of color rendition have been reviewed and summarized. Each measure was comput... more Twenty-two measures of color rendition have been reviewed and summarized. Each measure was computed for 401 illuminants comprising incandescent, light-emitting diode (LED) -phosphor, LED-mixed, fluorescent, high-intensity discharge (HID), and theoretical illuminants. A multidimensional scaling analysis (Matrix Stress = 0.0731, R 2 = 0.976) illustrates that the 22 measures cluster into three neighborhoods in a twodimensional space, where the dimensions relate to color discrimination and color preference. When just two measures are used to characterize overall color rendition, the most information can be conveyed if one is a referencebased measure that is consistent with the concept of color fidelity or quality (e.g., Q a ) and the other is a measure of relative gamut (e.g., Q g ).

LEUKOS The Journal of the Illuminating Engineering Society of North America

We have developed a two-measure system for evaluating light sources' color rendition that builds ... more We have developed a two-measure system for evaluating light sources' color rendition that builds upon conceptual progress of numerous researchers over the last two decades. The system quantifies the color fidelity and color gamut (change in object chroma) of a light source in comparison to a reference illuminant. The calculations are based on a newly developed set of reflectance data from real samples uniformly distributed in color space (thereby fairly representing all colors) and in wavelength space (thereby precluding artificial optimization of the color rendition scores by spectral engineering). The color fidelity score R f is an improved version of the CIE color rendering index. The color gamut score R g is an improved version of the Gamut Area Index. In combination, they provide two complementary assessments to guide the optimization of future light sources. This method summarizes the findings of the Color Metric Task

This tutorial explains how the human perception of color rendering arises, in terms of the underl... more This tutorial explains how the human perception of color rendering arises, in terms of the underlying phenomena of light and vision, and using those concepts it presents a clear explanation of the CIE Color Rendering Index. The strengths and weaknesses of the CIE Color Rendering Index are reviewed and some common misunderstandings about color rendering are addressed. It is suitable for self-study, with learning outcomes stated at the beginning and a conceptual summary provided at the end.

Office buildings don’t have opinions about saving or using energy; their occupants do. Of the tot... more Office buildings don’t have opinions about saving or using energy; their occupants do. Of the total energy consumed by commercial buildings, an increasing proportion is directly under the control of building occupants, who to this point have rarely been challenged to conserve energy in any consistent way. While improved devices and controls achieve some efficiencies, the biggest potential savings are in the hands of ordinary office occupants deciding which device to turn on or off, up or down. Broadly speaking the decision to save energy comprises two parts: an initial learning and commitment phase, and a refining and monitoring phase. Our implementations of Serious Games and Dashboards educate users and prompt behavioral change; games oriented toward the engagement and commitment phase, dashboards to monitoring and persistence. These studies evaluated the effectiveness of a virtual pet game and an energy dashboard in reducing plug-loads in mid-size commercial offices. Initial energ...

CITATIONS 0 READS 20 6 authors, including:

Energy and Buildings, 2014

Serious Games are virtual simulations of real-world activities that can both educate users and pr... more Serious Games are virtual simulations of real-world activities that can both educate users and prompt behavioral change. This study evaluated the effectiveness of a virtual pet game in reducing plug-loads in a mid-size commercial office. Participants were 61 resident workers. The energy consumption of 288 appliances was monitored for 24 weeks using plug-load sensors. After 4-weeks of baseline, 42 participants were introduced to the "Energy Chickens" serious game, which they played for 12 weeks. Within the game, daily energy consumption data for each individual's devices were used to manipulate animated chickens living on a personalized virtual farm. Changes in device-specific energy consumption were reflected in the improving or declining "health" of the corresponding chickens. Healthy, energy-saving chickens laid eggs that the user could collect and use to purchase accessories for their virtual farm. Across all intervention days, average energy consumption declined by 13%. Participants achieved 23% reductions on non-work days and 7% reductions on workdays. At the conclusion of the intervention, 69% of participants indicated that the game helped them be more energy conscious, with some indicating changes in their energy use outside the office. Results highlight the effectiveness of behavioral interventions on plug-load energy consumption within commercial office settings.

LEUKOS, 2014

ABSTRACT Visual perception of many manufactured white objects is driven by the concentration of f... more ABSTRACT Visual perception of many manufactured white objects is driven by the concentration of fluorescent whitening agents (FWAs) that they contain. FWAs serve to increase overall whiteness perception by enhancing luminance and providing a chromatic blue shift. White objects with FWAs have been engineered for many decades to interact with conventional illuminants such as daylight and incandescent light in order to provide desirable whiteness perception. Whiteness perception has not previously been investigated under light emitting diodes (LEDs). In this study, three psychophysical experiments—forced choice, selection, and sorting—were conducted to investigate the whiteness perception of a series of whiteness standards containing predetermined amounts of FWAs, illuminated by five sources: a typical blue-pumped LED (BLED), a filtered halogen lamp, and violet-pumped LEDs with three violet emission levels. Thirty-nine participants with normal color vision completed the experiments. Results from the sorting experiment can be explained by FWA excitation: the BLED induced no fluorescence and standards could not be ordered properly, whereas for other sources the perceived whiteness increased with the amount of FWAs. Results from the other two experiments can be explained by FWA excitation together with shifts in source chromaticity. Overall, all results are compatible with the known trend for blue shifts to induce whiteness perception. Adaptations of the CIE whiteness formula are also shown to agree well with the experimental results. The results indicate that engineering of an LED source’s spectrum is necessary for an accurate rendering of whiteness.

LEUKOS, 2011

ABSTRACT This paper analyzes the illuminance uniformity of 30 outdoor sports fields at various po... more ABSTRACT This paper analyzes the illuminance uniformity of 30 outdoor sports fields at various points in their service lives. The study was limited to the fields that employ 1500 W metal halide lamps with a rated life of 3000 hours. The sample was comprised of 12 soccer fields, 14 baseball fields, and 4 softball fields, all of which are owned and maintained by municipal parks and recreation departments. Five uniformity indices were computed for both measured illuminance and initial design calculations: maximum to minimum ratio (Max:Min), maximum to average ratio (Max:Ave), average to minimum ratio (Ave: Min), coefficient of variation (CV), and uniformity gradient (UG). Measured uniformity was rarely as good as the uniformity predicted by the design calculations. The uniformity of the baseball and softball fields was better with hours-of-use, with infields and outfields exhibiting similar trends. Max:Min, UG, and CV indices, as well as the illuminance of the transition area between infield and outfield, are suggested as key evaluation parameters. Group vs. spot lamp replacement, as-built vs. as-designed, dirt accumulation, and outgassing are factors that contribute to sports lighting uniformity.

ABSTRACT This paper analyzes the performance of 138 LED luminaires comprised of 95 indoor and 43 ... more ABSTRACT This paper analyzes the performance of 138 LED luminaires comprised of 95 indoor and 43 outdoor, all of which were within the judging phase of the 2010 U.S. Department of Energy Next Generation Luminaire™ (NGL) competition. The analyses focus on three areas derived from LM-79 and LM-80 test reports that were supplied by the manufacturers: energy efficiency, color, and long-term performance. Indoor recessed downlights and street lighting luminaires had the most entries. All luminaires employed phosphor-converted LED (PC-LED) packages or remote phosphor technology, reflecting the fact that these technologies now have better performance than color-mixed light emitting diodes (LEDs) for white-light applications. Comparisons of luminaire efficacy and luminous efficacy of radiation (LER) were made among the NGL 2010 submissions, luminaires with conventional light sources, and the expected performance of LED luminaires in the near future. 0–10V and reverse-phase control were the prominent dimming methods among the luminaires studied. High correlation (r = 0.98) was found between the CIE color rendering index (CRI) and NIST’s Color Quality Scale (CQS). Compared to the luminaires recognized in 2009, a better balance was achieved between efficacy and CRI in 2010. The need to standardize the methods for evaluating LED products is discussed, including dimming performance, color-shift, long-term performance, and luminaire rated life. In person evaluation and mockups are recommended prior to specifying LED products

Optics Express, 2013

Twenty-two measures of color rendition have been reviewed and summarized. Each measure was comput... more Twenty-two measures of color rendition have been reviewed and summarized. Each measure was computed for 401 illuminants comprising incandescent, light-emitting diode (LED) -phosphor, LED-mixed, fluorescent, high-intensity discharge (HID), and theoretical illuminants. A multidimensional scaling analysis (Matrix Stress = 0.0731, R 2 = 0.976) illustrates that the 22 measures cluster into three neighborhoods in a twodimensional space, where the dimensions relate to color discrimination and color preference. When just two measures are used to characterize overall color rendition, the most information can be conveyed if one is a referencebased measure that is consistent with the concept of color fidelity or quality (e.g., Q a ) and the other is a measure of relative gamut (e.g., Q g ).

LEUKOS The Journal of the Illuminating Engineering Society of North America