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Papers by Apiparn Borisuit

Sustainability, Dec 13, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Scientific Reports, 2016

Circadian rhythms in physiology and behavior are modulated by external factors such as light or t... more Circadian rhythms in physiology and behavior are modulated by external factors such as light or temperature. We studied whether self-selected office lighting during the habitual waking period had a different impact on alertness, cognitive performance and hormonal secretion in extreme morning and evening chronotypes (N = 32), whose preferred bed-and wake-up times differed by several hours. The self-selected lighting condition was compared with constant bright light and a control condition in dim light. Saliva samples for hormonal analyses, subjective ratings of alertness, wellbeing, visual comfort and cognitive performance were regularly collected. Between the self-selected and the bright, but not the dim lighting condition, the onset of melatonin secretion in the evening (as marker for circadian phase) was significantly different for both chronotypes. Morning chronotypes reported a faster increase in sleepiness during the day than evening chronotypes, which was associated with higher cortisol secretion. Wellbeing, mood and performance in more difficult cognitive tasks were better in bright and self-selected lighting than in dim light for both chronotypes, whereas visual comfort was best in the self-selected lighting. To conclude, self-selection of lighting at work might positively influence biological and cognitive functions, and allow for inter-individual differences.

Proceedings of Cisbat 2011 Cleantech For Sustainable Buildings, 2011

The intensive use of daylight in buildings is beneficial at many levels: it provides sufficient l... more The intensive use of daylight in buildings is beneficial at many levels: it provides sufficient levels of illumination to perform working activities throughout the day and it reduces the use of artificial light, which in turn leads to lower electricity consumption [1-3]. The spectral composition of daylight often leads to higher visual comfort in humans, compared to electric lighting. There are also illuminance and spectrally-dependent light effects on the human circadian system, which regulate hormonal rhythms, alertness and (visual) performance across 24 hours [4-6]. The main objective of this work was to assess luminous performance in office buildings and to test optimizations by virtually applying different daylighting strategies by computer simulations.We first assessed the daylight distribution in two different office rooms, set-up as test modules on the EPFL campus in Lausanne (46° 32'N, 6° 39'E). One of these test modules is equipped with a standard double-glazing; the second one comprises anidolic daylighting systems [7], which convey diffuse daylight and sunlight deeper in the room, and reduce glare risk. In both rooms, we also assessed vertical spectral irradiance in the visible range, which gave us additional information with respect to photo biological properties of the available daylight. We then measured the real daylighting situation in an office room located in the city of Zacatecas, Mexico (22°47'N 102°34'W), which is equipped with a standard double-glazing window. In a next step we tested, whether the daylight distribution for this room could be improved by virtually applying different complex fenestration systems (such as prismatic panels and laser cut panels) by using computer simulations. The results of these simulations showed higher indoor luminous performance with the two advanced daylighting systems. This new method may contribute to an improved and tailored design of daylight availability in real buildings at different geographical locations.

Proceedings of Cisbat 2011 Cleantech For Sustainable Buildings, 2011

Visual comfort is a key element at work places and at home. Besides task illuminance and color re... more Visual comfort is a key element at work places and at home. Besides task illuminance and color rendering it is the indoor light distribution, which strongly impacts visual comfort. We aimed to show possible relations between subjective and objective visual comfort and nonvisual functions such as mood, alertness, and wellbeing. Twenty-two healthy young volunteers were recruited to spend six hours in the afternoon in a testing room at our laboratory. They were exposed to daylight in the range between 1000 and 2000 lx. Artificial lighting was added when daylight illuminance decreased below this target range. In order to determine objective visual comfort, luminance ratios of the room were extracted from high dynamic range (HDR) images, taken three times during the afternoon. From these HDR images we calculated glare indexes by using specialized software (Evalglare v0.9, Fraunhofer ISE). Those glare indexes served as objective visual comfort assessments. At several occasions we asked subjects to assess their subjective visual comfort and glare as well as alertness, mood and well-being on visual analogue scales. We correlated objective and subjective glare assessments with those from alertness, mood and wellbeing. We found that objective visual comfort exhibited a time of day-dependent positive or negative association with subjective physical wellbeing, visual comfort and alertness. Higher objective glare indexes at the beginning of the afternoon slightly correlated with greater physical wellbeing (p<0.1); whereas in the middle of the afternoon, higher objective glare indexes were significantly correlated with lower subjective visual comfort and lower alertness. Towards the end of the afternoon, we found that higher objective glare was associated with significantly lower physical wellbeing (for all significant results: p<0.05). Taken together, our results show that objective glare indexes were associated not only with subjective visual comfort but also with non-visual functions such as subjective physical wellbeing and alertness. However, these assessments varied with the time of day, reflecting the effects of dynamic light conditions on subjective homeostatic and circadian functions. This might have implications on the lighting environment at many work places and homes in the future.

Nonimaging Optics: Efficient Design for Illumination and Solar Concentration IX, 2012

Behavioral Neuroscience, 2012

In sighted humans, light intensity, timing, exposure duration, and spectral composition of light ... more In sighted humans, light intensity, timing, exposure duration, and spectral composition of light are important to entrain the endogenous circadian pacemaker to the 24-h day-night cycle. We tested the impact of two realistic office lighting conditions during the afternoon on subjective sleepiness, hormonal secretion, and cognitive performance in the early evening hours. Twenty-nine young subjects came twice and spent 8 h (12:00-20:00) in our laboratory, where they were exposed for 6 h to either artificial light (AL) or to mainly daylight (DL). In the early evening, we assessed their salivary cortisol and melatonin secretion, subjective sleepiness, and cognitive performance (n-back test) under dim light conditions. Subjects felt significantly more alert at the beginning of the evening after the DL condition, and they became sleepier at the end of the evening after the AL condition. For cognitive performance we found a significant interaction between light conditions, mental load (2-or 3-back task) and the order of light administration. On their first evening, subjects performed with similar accuracy after both light conditions, but on their second evening, subjects performed significantly more accurately after the DL in both n-back versions and committed fewer false alarms in the 2-back task compared to the AL group. Lower sleepiness in the evening was significantly correlated with better cognitive performance (p Ͻ .05). In summary, even short-term lighting conditions during the afternoon had an impact on cognitive task performance in the evening. This rapid effect was only distinguishable on the second day of training, when a difficult task had been sufficiently practiced.

Architectural Science Review, 2010

The integration of daylighting and electric lighting systems within buildings (also designated as... more The integration of daylighting and electric lighting systems within buildings (also designated as ‘green lighting’) is a recent issue for the lighting research community: it allows achieving better lighting conditions for building occupants, in particular within office rooms. Besides the substitution of electric light, daylighting can contribute in a significant way to improve the users&amp;amp;amp;amp;amp;amp;#39; visual comfort and performance, with

Suboptimal light distribution in a room can cause visual discomfort and glare. Next to rods and c... more Suboptimal light distribution in a room can cause visual discomfort and glare. Next to rods and cones, perception of light is also governed by a third class of photoreceptors, important for circadian rhythm regulation and non-visual functions such as alertness, mood and hormonal secretion. These receptors show greatest sensitivity in the blue part of the visible light spectrum. In order to assess light distribution with respect to non-visual sensitivity functions, we aimed at validating a new device to create light distribution maps with a circadian weighted radiance (Lec) which accounts for this difference in sensitivity. We utilized a camera-like light sensor (CLLS) to assess the distribution of Lec. For this purpose, we equipped the device with customized filters to adapt the camera’s spectral sensitivity to circadian sensitivity, similarly, as we had previously reported for the photometric calibration with the same device [1]. After spectral calibration and circadian weighted ra...

Lighting Research & Technology, 2014

Lighting conditions in workplaces contribute to a variety of factors related to work satisfaction... more Lighting conditions in workplaces contribute to a variety of factors related to work satisfaction, productivity and well-being. We tested whether different photometric variables also influence visual perception and the comfort of the lighting, as well as subjective non-visual variables such as mood, alertness and well-being. Twenty-five young subjects spent two afternoons either under electric light or daylighting conditions (without view from the window). Subjects overall preferred the daylighting for visual acceptance and glare. Changes of photometric variables modulated changes in visual light perception, alertness and mood in the course of the afternoon. Finally, we found several associations of visual and non-visual functions, indicating a potential relationship of visual comfort with other circadian and wake-dependent functions in humans, which consequently could impact office lighting scenarios in the future.

Solar Energy, 2016

We previously developed a Camera-Like Light Sensor (CLLS) to record images using a novel High Dyn... more We previously developed a Camera-Like Light Sensor (CLLS) to record images using a novel High Dynamic Range (HDR) imaging vision sensor. The device was equipped with customized filters for adapting the camera's spectral sensitivity to both photopic and circadian sensitivities. Here, we aim at investigating photometric and circadian metrics to assess and simulate the potential of light on non-visual functions. The CLLS was used to monitor luminance and circadian weighted radiance (L ec) over time in two test rooms, equipped with different daylight redirecting devices: venetian blinds (VB) and optical louver systems (OLS). Additionally, a computer simulation was performed for the two test rooms using the software RADIANCE: false colour images were used to demonstrate distribution of luminance and absolute values of L ec. Circadian weighted irradiance (E ec) was also computed at different positions corresponding to the gaze directions of a seated office worker. From our results, the VB provided overall higher illuminance compared to the OLS, but when a virtually seated observer was facing desk, the OLS provided larger circadian weighted irradiance in the afternoon. Our results illustrate the use of simulations for circadian metrics, which will be applicable in the future to predict the potential impact of light on non-visual functions for daylighting optimization in buildings.

Proceedings of Clima Conference, 2013

Proceedings of Cisbat 2013 Cleantech For Smart Cities and Buildings, 2013

Suboptimal light distribution in a room can cause visual discomfort and glare. Next to rods and c... more Suboptimal light distribution in a room can cause visual discomfort and glare. Next to rods and cones, perception of light is also governed by a third class of photoreceptors, important for circadian rhythm regulation and non-visual functions such as alertness, mood and hormonal secretion. These receptors show greatest sensitivity in the blue part of the visible light spectrum. In order to assess light distribution with respect to non-visual sensitivity functions, we aimed at validating a new device to create light distribution maps with a circadian weighted radiance (L ec) which accounts for this difference in sensitivity. We utilized a camera-like light sensor (CLLS) to assess the distribution of L ec. For this purpose, we equipped the device with customized filters to adapt the camera's spectral sensitivity to circadian sensitivity, similarly, as we had previously reported for the photometric calibration with the same device [1]. After spectral calibration and circadian weighted radiance calibration, we validated the CLLS in real scenes. The results showed that circadian luminance maps of a room can be efficiently assessed in a very short time (i.e. within 100 ms) under electric lighting as well as under daylighting conditions. We also used the CLLS to compare the L ec values between two rooms, equipped with different daylighting systems such as LightLouver TM and standard venetian blinds. Our results showed different dynamics of luminance and L ec in the course of the day with highest values at noon. We also found higher luminance and L ec values in the test room with the venetian blinds, when compared to the room equipped with LightLouvers TM. Taken together, the validation of circadian luminance maps under real dynamic lighting conditions offers new possibilities to integrate the CLLS into advanced (day-) light sensors systems. This would allow to instantly adapting ambient lighting conditions with respect to tailored biological user needs.

Visual comfort at workplaces has often been considered in terms of discomfort glare, luminance di... more Visual comfort at workplaces has often been considered in terms of discomfort glare, luminance distribution and task visibility. Besides visual effects, the lighting environment has also impact on human physiology and behaviour. These effects of light are transmitted via a novel class of photoreceptors in the mammalian retina, which was discovered only a decade ago. Since then, it has become evident that light also plays an important role in regulating Non-Image Forming (NIF) functions such as circadian rhythms, alertness, well-being and mood. In lighting design it is accordingly necessary to take into account not only luminous intensity, but also light's spectral composition, since the novel class of photoreceptors is more maximally sensitive to different luminous wavelengths than the classical photoreceptors (e.g. rods and cones). The main focus of this doctoral thesis is on visual comfort assessment at workplaces. It was hypothesized that the impact of light on visual comfort comprises not only luminance distribution and/or luminous intensity, but also other qualitative aspects of the lighting environment. Office lighting influences building occupants in terms of visual task performance, alertness, health and well-being. The aim of this thesis was to assess the impact of office lighting on visual comfort including NIF effects. Firstly, in order to monitor the luminance distribution within a scene, a new photometric device based on a high dynamic range logarithmic visual sensor (IcyCAM TM) was set up. After calibrations and validations, the photometric device was used to assess luminance distribution of office spaces in a very efficient way. Secondly, two experimental studies were performed with human subjects, aiming to test the acute effects of light on visual comfort variables, subjective alertness, mood and well-being. Lastly, the novel device was also used during one of the studies to monitor the impacts of luminous distribution over time and under various lighting conditions. The novel photometric device enables to assess luminous distribution also in circadian metrics with respect to NIF effects of light. The results from the two studies showed the effects of office lighting including different sky conditions and time-of-day changes on visual comfort and NIF functions. Inter-individual differences, as assessed in extreme chronotypes, also had an influence on visual comfort. Interestingly, luminance distribution was not only found to impact on visual comfort but also on subjective alertness, mood and well-being. To conclude, the results obtained with the new device provide a more comprehensive scientific framework and practical basis for indoor lighting design at workplaces.

Sustainability, Dec 13, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Scientific Reports, 2016

Circadian rhythms in physiology and behavior are modulated by external factors such as light or t... more Circadian rhythms in physiology and behavior are modulated by external factors such as light or temperature. We studied whether self-selected office lighting during the habitual waking period had a different impact on alertness, cognitive performance and hormonal secretion in extreme morning and evening chronotypes (N = 32), whose preferred bed-and wake-up times differed by several hours. The self-selected lighting condition was compared with constant bright light and a control condition in dim light. Saliva samples for hormonal analyses, subjective ratings of alertness, wellbeing, visual comfort and cognitive performance were regularly collected. Between the self-selected and the bright, but not the dim lighting condition, the onset of melatonin secretion in the evening (as marker for circadian phase) was significantly different for both chronotypes. Morning chronotypes reported a faster increase in sleepiness during the day than evening chronotypes, which was associated with higher cortisol secretion. Wellbeing, mood and performance in more difficult cognitive tasks were better in bright and self-selected lighting than in dim light for both chronotypes, whereas visual comfort was best in the self-selected lighting. To conclude, self-selection of lighting at work might positively influence biological and cognitive functions, and allow for inter-individual differences.

Proceedings of Cisbat 2011 Cleantech For Sustainable Buildings, 2011

The intensive use of daylight in buildings is beneficial at many levels: it provides sufficient l... more The intensive use of daylight in buildings is beneficial at many levels: it provides sufficient levels of illumination to perform working activities throughout the day and it reduces the use of artificial light, which in turn leads to lower electricity consumption [1-3]. The spectral composition of daylight often leads to higher visual comfort in humans, compared to electric lighting. There are also illuminance and spectrally-dependent light effects on the human circadian system, which regulate hormonal rhythms, alertness and (visual) performance across 24 hours [4-6]. The main objective of this work was to assess luminous performance in office buildings and to test optimizations by virtually applying different daylighting strategies by computer simulations.We first assessed the daylight distribution in two different office rooms, set-up as test modules on the EPFL campus in Lausanne (46° 32'N, 6° 39'E). One of these test modules is equipped with a standard double-glazing; the second one comprises anidolic daylighting systems [7], which convey diffuse daylight and sunlight deeper in the room, and reduce glare risk. In both rooms, we also assessed vertical spectral irradiance in the visible range, which gave us additional information with respect to photo biological properties of the available daylight. We then measured the real daylighting situation in an office room located in the city of Zacatecas, Mexico (22°47'N 102°34'W), which is equipped with a standard double-glazing window. In a next step we tested, whether the daylight distribution for this room could be improved by virtually applying different complex fenestration systems (such as prismatic panels and laser cut panels) by using computer simulations. The results of these simulations showed higher indoor luminous performance with the two advanced daylighting systems. This new method may contribute to an improved and tailored design of daylight availability in real buildings at different geographical locations.

Proceedings of Cisbat 2011 Cleantech For Sustainable Buildings, 2011

Visual comfort is a key element at work places and at home. Besides task illuminance and color re... more Visual comfort is a key element at work places and at home. Besides task illuminance and color rendering it is the indoor light distribution, which strongly impacts visual comfort. We aimed to show possible relations between subjective and objective visual comfort and nonvisual functions such as mood, alertness, and wellbeing. Twenty-two healthy young volunteers were recruited to spend six hours in the afternoon in a testing room at our laboratory. They were exposed to daylight in the range between 1000 and 2000 lx. Artificial lighting was added when daylight illuminance decreased below this target range. In order to determine objective visual comfort, luminance ratios of the room were extracted from high dynamic range (HDR) images, taken three times during the afternoon. From these HDR images we calculated glare indexes by using specialized software (Evalglare v0.9, Fraunhofer ISE). Those glare indexes served as objective visual comfort assessments. At several occasions we asked subjects to assess their subjective visual comfort and glare as well as alertness, mood and well-being on visual analogue scales. We correlated objective and subjective glare assessments with those from alertness, mood and wellbeing. We found that objective visual comfort exhibited a time of day-dependent positive or negative association with subjective physical wellbeing, visual comfort and alertness. Higher objective glare indexes at the beginning of the afternoon slightly correlated with greater physical wellbeing (p<0.1); whereas in the middle of the afternoon, higher objective glare indexes were significantly correlated with lower subjective visual comfort and lower alertness. Towards the end of the afternoon, we found that higher objective glare was associated with significantly lower physical wellbeing (for all significant results: p<0.05). Taken together, our results show that objective glare indexes were associated not only with subjective visual comfort but also with non-visual functions such as subjective physical wellbeing and alertness. However, these assessments varied with the time of day, reflecting the effects of dynamic light conditions on subjective homeostatic and circadian functions. This might have implications on the lighting environment at many work places and homes in the future.

Nonimaging Optics: Efficient Design for Illumination and Solar Concentration IX, 2012

Behavioral Neuroscience, 2012

In sighted humans, light intensity, timing, exposure duration, and spectral composition of light ... more In sighted humans, light intensity, timing, exposure duration, and spectral composition of light are important to entrain the endogenous circadian pacemaker to the 24-h day-night cycle. We tested the impact of two realistic office lighting conditions during the afternoon on subjective sleepiness, hormonal secretion, and cognitive performance in the early evening hours. Twenty-nine young subjects came twice and spent 8 h (12:00-20:00) in our laboratory, where they were exposed for 6 h to either artificial light (AL) or to mainly daylight (DL). In the early evening, we assessed their salivary cortisol and melatonin secretion, subjective sleepiness, and cognitive performance (n-back test) under dim light conditions. Subjects felt significantly more alert at the beginning of the evening after the DL condition, and they became sleepier at the end of the evening after the AL condition. For cognitive performance we found a significant interaction between light conditions, mental load (2-or 3-back task) and the order of light administration. On their first evening, subjects performed with similar accuracy after both light conditions, but on their second evening, subjects performed significantly more accurately after the DL in both n-back versions and committed fewer false alarms in the 2-back task compared to the AL group. Lower sleepiness in the evening was significantly correlated with better cognitive performance (p Ͻ .05). In summary, even short-term lighting conditions during the afternoon had an impact on cognitive task performance in the evening. This rapid effect was only distinguishable on the second day of training, when a difficult task had been sufficiently practiced.

Architectural Science Review, 2010

The integration of daylighting and electric lighting systems within buildings (also designated as... more The integration of daylighting and electric lighting systems within buildings (also designated as ‘green lighting’) is a recent issue for the lighting research community: it allows achieving better lighting conditions for building occupants, in particular within office rooms. Besides the substitution of electric light, daylighting can contribute in a significant way to improve the users&amp;amp;amp;amp;amp;amp;#39; visual comfort and performance, with

Suboptimal light distribution in a room can cause visual discomfort and glare. Next to rods and c... more Suboptimal light distribution in a room can cause visual discomfort and glare. Next to rods and cones, perception of light is also governed by a third class of photoreceptors, important for circadian rhythm regulation and non-visual functions such as alertness, mood and hormonal secretion. These receptors show greatest sensitivity in the blue part of the visible light spectrum. In order to assess light distribution with respect to non-visual sensitivity functions, we aimed at validating a new device to create light distribution maps with a circadian weighted radiance (Lec) which accounts for this difference in sensitivity. We utilized a camera-like light sensor (CLLS) to assess the distribution of Lec. For this purpose, we equipped the device with customized filters to adapt the camera’s spectral sensitivity to circadian sensitivity, similarly, as we had previously reported for the photometric calibration with the same device [1]. After spectral calibration and circadian weighted ra...

Lighting Research & Technology, 2014

Lighting conditions in workplaces contribute to a variety of factors related to work satisfaction... more Lighting conditions in workplaces contribute to a variety of factors related to work satisfaction, productivity and well-being. We tested whether different photometric variables also influence visual perception and the comfort of the lighting, as well as subjective non-visual variables such as mood, alertness and well-being. Twenty-five young subjects spent two afternoons either under electric light or daylighting conditions (without view from the window). Subjects overall preferred the daylighting for visual acceptance and glare. Changes of photometric variables modulated changes in visual light perception, alertness and mood in the course of the afternoon. Finally, we found several associations of visual and non-visual functions, indicating a potential relationship of visual comfort with other circadian and wake-dependent functions in humans, which consequently could impact office lighting scenarios in the future.

Solar Energy, 2016

We previously developed a Camera-Like Light Sensor (CLLS) to record images using a novel High Dyn... more We previously developed a Camera-Like Light Sensor (CLLS) to record images using a novel High Dynamic Range (HDR) imaging vision sensor. The device was equipped with customized filters for adapting the camera's spectral sensitivity to both photopic and circadian sensitivities. Here, we aim at investigating photometric and circadian metrics to assess and simulate the potential of light on non-visual functions. The CLLS was used to monitor luminance and circadian weighted radiance (L ec) over time in two test rooms, equipped with different daylight redirecting devices: venetian blinds (VB) and optical louver systems (OLS). Additionally, a computer simulation was performed for the two test rooms using the software RADIANCE: false colour images were used to demonstrate distribution of luminance and absolute values of L ec. Circadian weighted irradiance (E ec) was also computed at different positions corresponding to the gaze directions of a seated office worker. From our results, the VB provided overall higher illuminance compared to the OLS, but when a virtually seated observer was facing desk, the OLS provided larger circadian weighted irradiance in the afternoon. Our results illustrate the use of simulations for circadian metrics, which will be applicable in the future to predict the potential impact of light on non-visual functions for daylighting optimization in buildings.

Proceedings of Clima Conference, 2013

Proceedings of Cisbat 2013 Cleantech For Smart Cities and Buildings, 2013

Suboptimal light distribution in a room can cause visual discomfort and glare. Next to rods and c... more Suboptimal light distribution in a room can cause visual discomfort and glare. Next to rods and cones, perception of light is also governed by a third class of photoreceptors, important for circadian rhythm regulation and non-visual functions such as alertness, mood and hormonal secretion. These receptors show greatest sensitivity in the blue part of the visible light spectrum. In order to assess light distribution with respect to non-visual sensitivity functions, we aimed at validating a new device to create light distribution maps with a circadian weighted radiance (L ec) which accounts for this difference in sensitivity. We utilized a camera-like light sensor (CLLS) to assess the distribution of L ec. For this purpose, we equipped the device with customized filters to adapt the camera's spectral sensitivity to circadian sensitivity, similarly, as we had previously reported for the photometric calibration with the same device [1]. After spectral calibration and circadian weighted radiance calibration, we validated the CLLS in real scenes. The results showed that circadian luminance maps of a room can be efficiently assessed in a very short time (i.e. within 100 ms) under electric lighting as well as under daylighting conditions. We also used the CLLS to compare the L ec values between two rooms, equipped with different daylighting systems such as LightLouver TM and standard venetian blinds. Our results showed different dynamics of luminance and L ec in the course of the day with highest values at noon. We also found higher luminance and L ec values in the test room with the venetian blinds, when compared to the room equipped with LightLouvers TM. Taken together, the validation of circadian luminance maps under real dynamic lighting conditions offers new possibilities to integrate the CLLS into advanced (day-) light sensors systems. This would allow to instantly adapting ambient lighting conditions with respect to tailored biological user needs.

Visual comfort at workplaces has often been considered in terms of discomfort glare, luminance di... more Visual comfort at workplaces has often been considered in terms of discomfort glare, luminance distribution and task visibility. Besides visual effects, the lighting environment has also impact on human physiology and behaviour. These effects of light are transmitted via a novel class of photoreceptors in the mammalian retina, which was discovered only a decade ago. Since then, it has become evident that light also plays an important role in regulating Non-Image Forming (NIF) functions such as circadian rhythms, alertness, well-being and mood. In lighting design it is accordingly necessary to take into account not only luminous intensity, but also light's spectral composition, since the novel class of photoreceptors is more maximally sensitive to different luminous wavelengths than the classical photoreceptors (e.g. rods and cones). The main focus of this doctoral thesis is on visual comfort assessment at workplaces. It was hypothesized that the impact of light on visual comfort comprises not only luminance distribution and/or luminous intensity, but also other qualitative aspects of the lighting environment. Office lighting influences building occupants in terms of visual task performance, alertness, health and well-being. The aim of this thesis was to assess the impact of office lighting on visual comfort including NIF effects. Firstly, in order to monitor the luminance distribution within a scene, a new photometric device based on a high dynamic range logarithmic visual sensor (IcyCAM TM) was set up. After calibrations and validations, the photometric device was used to assess luminance distribution of office spaces in a very efficient way. Secondly, two experimental studies were performed with human subjects, aiming to test the acute effects of light on visual comfort variables, subjective alertness, mood and well-being. Lastly, the novel device was also used during one of the studies to monitor the impacts of luminous distribution over time and under various lighting conditions. The novel photometric device enables to assess luminous distribution also in circadian metrics with respect to NIF effects of light. The results from the two studies showed the effects of office lighting including different sky conditions and time-of-day changes on visual comfort and NIF functions. Inter-individual differences, as assessed in extreme chronotypes, also had an influence on visual comfort. Interestingly, luminance distribution was not only found to impact on visual comfort but also on subjective alertness, mood and well-being. To conclude, the results obtained with the new device provide a more comprehensive scientific framework and practical basis for indoor lighting design at workplaces.