Circadian Light Meter

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About this app

Light is important in our daily life. Besides helping us with visual acuity and perceiving color, it also plays a role in the non-visual functions of the human body.

During daytime, sunlight plays the most important part in regulating the Circadian Rhythm. Nowadays, people are spending more and more time indoors during the day, and thus the time of the eyes being exposed to blue-enriched sunlight is reduced. Eye exposure to appropriate amounts of blue light during the daytime is healthful, and it helps cognitive function, elevates moods and synchronizes body-clock.

Medical studies have shown that blue light in the nighttime disrupts people’s natural sleep-wake cycles by suppressing the production and release of Melatonin (a.k.a. Sleep Hormone). So, we should avoid our eyes exposed to bright blue-enriched artificial lighting and electronics screen before going to bed. Disruption of natural sleep-wake cycles may be linked to depression, diabetes and obesity.

Blue light within the visible light spectrum consists of two components, i.e., blue-violet light (415 - 455 nanometers) and blue-turquoise light (456 - 490 nanometers). Blue-turquoise light is preferred to blue-violet light because of the following two benefits,

1) More efficient to regulate the Circadian Rhythm.
2) Medical researches show that blue-turquoise light may be less damaging than blue-violet light, which can bring on AMD (Age-related macular degeneration) and digital eye strain.

Circadian Light Meter (CLM) app is to assess the Circadian Entrainment and Blue Light Content of your lighting environment by measuring the amount of light entering the cornea at a vertical pane, which is called vertical illuminance (Ev) in Lux unit. After obtaining the Ev value, CLM then calculates the Circadian Entrainment according to two different metrics, namely, Equivalent Melanopic Lux (EML) and Circadian Stimulus (CS). Those two metrics are adopted by WELL Building Standard v2 under Feature 54 Circadian Lighting Design.

CLM also evaluates the blue light content emitted by the lighting fixtures, which consists of two components. The first component is the percentage of blue light out of the total spectral power of the visible light spectrum, and the second component is the relative percentage of blue-turquoise light and blue-violet light within the blue light content.
Different make of Smartphones may show different Lux reading due to its own light sensor performance. CLM offers the following two ways to overcome this setback,

1) Adjust the Smartphone's light sensor reading against a Lux meter by inputting a calibration ratio into the CLM. Then this calibration ratio will be used in future display.
2) Directly input the vertical illuminance (Ev) value into CLM for calculation of Circadian entrainment and Blue Light Content.
Updated on
Oct 19, 2019

Data safety

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What's new

This is the first release of Circadian Light Meter