Evaluating Human Factors of Desktop Light Therapy Lamps
Under the guidance of current Lighting Research Center (LRC) director
Dr. Mariana Figueiro, I completed a Master's thesis design & research project aiming to debunk myths surrounding traditional light therapy boxes and present a methodology for designers to build light boxes that are both efficient and ergonomically friendly.
Introduction
The Dilemma With Traditional Light Boxes
Dating back to the early 1980's, traditional light boxes have been prescribed by licensed doctors to provide relief from ailments such as sleep disorders, jet lag, and depression. These light boxes classically entail a rectangular box placed on a table spewing bright white light at the user. The prescription: sit with face at least one foot away from the box and stare into the box for 1-2 hours every morning until symptoms recede. This prescription is based off of research done in the early 80s by a group of scientists at the National Institute of Mental Health (NIMH) seeking to provide remedies for sleep disturbances and depression in their patients. Their discoveries regarding light and its effect on the biological regulating hormone Melatonin led them to experiment on their patients using large light boxes with several fluorescent lamps inside spewing roughly 20% of the light levels received by the Sun. Although their work was groundbreaking, it lacked important scientific analysis of the biological mechanisms that make us sensitive to light, the characteristics of that light, and the human experience with these lights.
Research
How Science Can Inform Design
What the NIMH did have right was that internal human biological rhythms [aka Circadian Rhythms] that occur roughly every 24 hours [ i.e. eating, sleeping, urinating etc.] are regulated by exposure to light. This relationship is best measured in the presence of the melatonin and serotonin which are hormones that regulate our rest and activity cycles respectively. The NIMH understood that light regulated the behavior of these hormones however, they had not discovered that light sensitive cells in our eyes called IPRGC's are sensitive to short wavelength light. When the eyes receive this type of light, they send signal to the Hypothalamus of the brain which controls hormonal release through the pineal gland. Circadian rhythms need to be in sync with the external light/dark cycle or hours of day/night time to maintain a happy and healthy body. As a result, disruptions in this cycle lead to ailments such as sleep disorders, depression, and jet lag. The NIMH researcher's saw success in placing their patients in front of these light boxes because they received the short wavelength light. However, the amount of light was way over saturation leading to discomfort from eye strain or worsened symptoms do to too much light. This research garnered a design research problem statement:
How can we design a light therapy device that ergonomically friendly and energy efficient?
analysis
Bridging the gap between science and design
Further research regarding the human biological response to light, and conversely, methods of measuring subjective responses to light stimuli garnered the following insights to be tested in the field:
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IPRGC's are specifically sensitive to 470-80nm wavelength light
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Although the visual and circadian system are both sensitive to short wavelength light, the circadian system is not concerned with image formation and is rendered blind to wavelengths longer than 600nm
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the LRC produced a metric known as Circadian Stimulus (CS) which provides a way to measure the light from a light source and equivocate it to the amount of melatonin it will suppress.
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the CS metric is helpful to ensure the effectivity of a light source as light therapy
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LRC Researcher's produced two formulas incorporating various factors of light surrounding the light source to predict subjective comfort when using light source.
implementation
Putting Research Into Practice
For my thesis, I used the LRC's Circadian Stimulus (CS) as a standard for measuring the efficiency of a desktop light therapy lamp. Given that a CS over .3 or 30% is a threshold for effectively suppressing melatonin [ the basis behind light therapy lamps], i sought to determine the following:
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Do traditional light therapy lamps actually provide a CS of > .3 ? and if so, is this provided at a reasonable comfort level to the user?
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Along with the CS metric, can formulas incorporating factors such as the spectral power distribution of a light source and surrounding light levels help designers predict subjective comfort levels when using the lamp?
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Are various factors of subject identity such as age or visual impairment levels correlated with light source type and orientation preference?
Calculation
Formulas used for predicting subjective comfort when using light therapy lamps
Spectral Sensitivity Function
DeBoer Scale Predictions
In order to test how spectral light distribution effects sensitivity to discomfort glare, I used the following formula created by LRC Researcher John Bullough in 2009:
In a series of experiments, Bullough derived this formula after finding that discomfort glare ratings decrease following a logarithmic function as wavelength decreased. This suggested that the short wavelength S-cone plays a significant role in discomfort glare. As a result, the function derived differs from traditional photopic functions by incorporating the the scone sensitivity as well in order to predict discomfort glare levels.
The De Boer Scale--introduced in 1967--provides a comprehensive way for subjects to subjectively communicate comfort when exposed to glare sources. A scale from 1-9 shows (1) being unbearable, (5) being just acceptable, (7) being satisfactory, and (9) being just acceptable. Hence, a rating over 7 is best case scenario.
In 2008, LRC researchers John Bullough, Mark Rae, and Jennifer Brons performed a series of experiments deriving the following formula:
This function pre-determines discomfort glare (DG) levels from a light source by incorporating:
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Light Source Illuminance ( El ) : vertical illuminance from light source at the eye using a baffle that blocks light surrounding the light source from reaching the eye
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Light Source Luminance ( L l ): measured at distance where the luminance meter aperture covers as much of light source as possible without producing dark areas
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Ambient Illuminance ( Ea ): measured vertically at the eye with light source turned off
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Surround Illuminance ( Es ): estimated by measuring total vertical illuminance at the eye with light source on and subtracting (Ea) from that value.
After finding the aforementioned measurements, they are plugged into the (DG) formula and converted into De Boer Scale predictions.
Experiment Set-up
Experiment Apparatus
To test how light source type or spectral power distribution effects comfort levels, I built a desktop light therapy lamp modeled off of those used in LRC experiments to derive and verify the CS metric. The light source housing featured a simple LED strip covered by translucent material to emit diffuse light. The light source was mounted on a metal mount for both structure and heat control. Since the research showed that short wavelength light is most efficient at suppressing melatonin, I built two separate light source housings. One with 6500k LEDs and one with a 460nm LED.
The light source was placed right above eye level behind a monitor in a room/setup meant to mimic regular office conditions. Three measurement points [ at eye level, just below the monitor, and on the keyboard ] were determined to ensure that CS levels were met in the various positions one would move their head while working. It was key to measure points vertically at eye level as direct light to the eyes is used to determine CS levels. Subjects were asked to sit approx. 20" away from the monitor and perform a typing task on the computer for one minute. After each session, the experiment proctor showed them the De Boer scale and recorded their responses. Subjects were then given 30 seconds to recover from previous light exposure with eyes closed while the proctor changed the light level and. or light source type.
I also incorporated a traditional light box as the third test condition to provide a point of reference to compare the built light source results to. The type of light box also served as a way to determine how lamp orientation effects comfort as well.
Experiment Procedures
Subject recruitment and experiment procedures
Three light source levels A, B, and C were determined based on the light levels correlated with a CS level above .3 [melatonin suppression threshold] and below .7 [melatonin suppression saturation. These measurements were plugged into the aforementioned DB scale prediction formula to determine the DB Scale predictions shown above. Similarly, a glare illuminance level in lux was determined using the SPDs found at the highest light levels (A) and plugging them into the aforementioned spectral discomfort glare function. The results showed the white source being slightly more comfortable than the blue.
Subject Recruitment
Each built light source [blue and white] was shown to subjects three times [low, medium, and high light levels] as well as the traditional light therapy lamp for a total of 7 experiment conditions. Their subjective De Boer Scale preferences were recorded and compared to those found through the aforementioned calculations. This was a within subject experiment. There were a total of 12 subjects, 6 females, and 6 males. 7 of the subject wore glasses, one wore contacts, and all had sufficient vision for legal driving. 6 subjects were 22-30 yrs old , 4 subjects were 30-50 yrs old, and 2 were 50+. Each subject saw each condition for one minute followed by 30 seconds of recovery while light levels were changed. Each subject saw each light source in random order. Follow up interviews were conducted afterwords to determine orientation and color preferences.
Experiment Results
Results and Insights
The results of average De Boer Scale ratings for each light source and light level compared to predicted measurements are graphed above. Here, it can be seen that the formulas quite accurately predicted the real world results and most notably, the traditional light box was rated far below the CS tuned fixtures. The light box was rated unacceptable while the CS tune figured averaged at least satisfactory.
Similarly, as predicted, the white CS tuned fixture was rated slightly above the blue light source however the difference was statistically insignificant (p-.14). Conversely, the light box was rated significantly lower than the CS effective light fixtures (p-.03)
With regard to age, subjects over 50+ actually rated the blue light source significantly higher (p-.001) than the white light source. However, all subjects rated the traditional light box higher than the CS effective fixtures. No correlation was found with regard to wearing glasses or not.
Notable Insights
Taken together, the results show that functions such as the De Boer scale prediction and Spectral Sensitivity to discomfort glare functions are useful for predicting comfort with desktop light therapy fixtures. They also clearly show, that without a threshold for referencing light source levels, light therapy lamps can easily negate their actual purpose with being uncomfortable to use.. Several insights should be evaluated with regard to the discrepancies within the results. Most of this comes from the way the light was delivered in the experiment. For example, the traditional light box had a smaller aperture or surface area and was displayed below and to the side of the subjects' eye level. During interviews, most subjects stated they preferred the light source more in light with their line of sight. Also, the therapy lamp featuring a smaller aperture may make the light seem more harsh especially since it did not have a diffusing lens like the CS effective fixtures. These results reinforce the importance for light therapy designers to take knowledge of the biological response to light as well as surrounding light levels and ratios to make their lamps more ergonomic and efficient.
Download my full thesis report here:
How Can We Make The Public More Conscious of Their Waste Habits?
As part of a design studio course taught by human-centered designer
Emily Pilloton, I created an interactive exhibit with a group of UC Davis students intended to help the public become more aware of their waste habits.
Project completed with: Kari Kiyono + Jenny Ruedy
Inspiration
Waste habits around the world
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Every 2 hours we create enough waste to fill the world's largest container ship with trash, 12 container ships a day and 4380 container ships a year.
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Every bag of household waste has produced approximately 70 bags of waste upstream.
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Over 4 billion aluminum cans dumped are annually in the US, enough for 25,000 jetliners
What is found in landfills
Where waste goes
Insights
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Some of the largest cities, such as San Francisco are built on top of landfills
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Landfill sites appear stable, but especially in earthquakes, the ground can turn into quicksand in seconds.
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The world's waste habits are potentially catapulted by essentially and literally sweeping it under the ground.
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Bringing the risk more visually clear and close to home may increase awareness and improve behavior.
Ideation
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The interview we conducted revealed that the general public would be more willing to change their behavior if they could visibly see the damage it does to the environment.
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This insight yielded to a concept of an interactive trash can that allows users to literally see the effects of their waste filling the cities. This is emphasized by the clear container and the grass cover which directly represents the ground we walk on.
Implementation
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I created a scaled city line modeled off of the San Francisco skyline given that the project was done in Northern California and the site being one of the largest landfills in the world.
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I scaled the model using 3D software to make sure real world measurements were realistic
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We used mattboard covered with cement textured spray paint for the buildings, imitation grass for the foundation, and an used aquarium for the can itself.
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Holes were created in the foundation that matched opening atop a few of the buildings to emphasize the message of throwing trash into our cities
The final product incorporated billboards with facts about landfills to further educate and drive the point home. The exhibit was met with positive reviews with many pointing to the fact that it was an actual trash at life size that made it memorable.
How Might We Involve the Public in the Process of Healing For Domestic Violence Victims
As part of a design studio course taught by human-centered designer
Emily Pilloton, I created an interactive exhibit with fellow UC Davis student Eigi Nigoshi intented to help victims of domestic violence heal and provide awareness.
Inspiration
Problem Statement Phase #1: How might we help victims heal in the wake of domestic violence?
We started with conducting interviews with victims and abuse shelter/programs . From this we derived the following insights:
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Domestic violence is a complex problem with a broader scope than meets the eye.
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There seems a common theme of neglect and invalidation resulting in the victim struggling to regulate emotions and create a sense of self.
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Most victims endure abuse without knowledge and/or in denial of being mistreated.
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Domestic violence centers stress pamphlets and infomercials being helpful for victims identifying the problem.
We conducted further research to learn more about the psychology behind victims of abuse and gleaned the following insights:
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Research further confirmed that healing starts with victims acknowledging mistreatment as bad behavior.
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Recovery is dependent on a victims ability to create a sense of self and identity apart from the abuser.
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Having the ability to share their stories and connect with other victims is helpful.
These insights helped determine the audience for our project to expand beyond victims to public who is uncomfortable or ignorant about the topic.
Ideation
Problem Statement Phase #2: How might we give victims a platform to voice their self-worth?
During the ideation phase we began focusing on a product, a tool kit to connect victims of domestic violence together and guide them through a 5 step program or a product to help facilitate communicating difficult emotions when victims share their story . The problem statement changed to giving victims a platform to voice their self worth. However, the product felt too narrow and wasn’t accessible to the public. Also, follow up feedback from other victims advised us not to place too much focus on a personal product for victims as this can pressure them but placing even more responsibility on them. As a result, we changed the project scope to thinking of space where this information could be obtained and shared with the public.
We began playing with forms and thinking about how people interact with spaces and images. Our statement evolved again to include the larger context of the community of students we were surrounded by. Two profile pictures facing each other in a V shape gave way to ideas on how to place viewers in the middle of pertinent questions to domestic violence. What it is , what it causes, and what someone can do about it. We continued to find inspiration in the form of typographic installations and it seemed to fit well with the fact that words played a huge part what composed communication in the first place. It had universal appeal, with no specific connotation to a culture. The shape created easy to set up displays in the form of a v shape and went along with the idea of opening something.
Implementation
Problem Statement Final Phase: How might we involve the public in the process of healing victims of domestic violence?
We created a concept of a life-size exhibit where both victims and the public can learn about domestic violence. We incorporated a color pallet associated with healing and communication. Intended as a pop up installation, the site features life size pages covering some of the most misunderstood topics under domestic violence. It also offers tips for being an ally as well as support for victims.
OPEN DOMESTIC VIOLENCE
Education. Validation. Compassion
We named the final procect
The final form was named "Open Domestic Violence." This was meant to emphasize the need for healing to start with open communication provided through education and done with compassion. Validation is found through human beings interacting with each other and public becoming more aware of the victims struggle a swell as the victim identifying that they are worthy and not alone. The exhibit resembles a large open book with each page providing education and/or resources for education and help. The center of the piece has a large hole intended the drive the point of open communication home while providing a physical way for visitors to simultaneously see their peers while they experience a different page. This is intended to further communication and comfortability with communication. Similarly, images of togetherness and faces facing each-other further drive the point home.
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