Whether the circadian rhythm of Blu ray will replace the standard blue purple LED LED?

The light has effect on our health and sleep cycle, which is recognized. In modern society, artificial light can be everywhere, like the sun as the impact of the diurnal cycle. For solid state lighting (SSL) industry is an exciting opportunity, but also a potential concern. In this paper, will discuss about the light of non visual knowledge, and how to develop the LED light source for the benefit of human health and well-being.

In early twenty-first Century, the groundbreaking research on light and sleep on, researchers discovered the unknown cells in our retina: ipRGCs. These cells are sensitive to light, these cells can receive optical signals, and directly connected to our brain that regulates sleep patterns, effects of circadian rhythm.

These cells are the most important is that they are very sensitive to blue light, their peak sensitivity at a wavelength of about 450-480nm. When light stimulation, they emit a wake-up signal. The signal can be observed in various physiological reactions; for example, it can prevent our body to release melatonin, melatonin and circadian cycle is closely related to our. The maximum sensitivity to blue light and natural light: blue light radiation is more common in the morning the day, night; therefore, our body will it as a biological clock synchronization prompt.

Opportunities and challenges

On the one hand, can provide additional light, help those under natural conditions is not enough light person. For example, a small blue morning can help those living in less sunny areas, or that the circadian cycle is not so regular people, such as teenagers and the elderly. On the morning we are particularly sensitive to blue light in the head up to two hours after.

On the other hand, exposure to light can cause unwanted effects at night. Research shows that common indoor lighting conditions (100 LX and above) can affect the circadian cycle significantly. This effect lasted for several hours in the light off, it will delay sleep. From the mobile phone and tablet computer light is another issue of concern. With the popularity of LED lighting, this fear becomes more serious, especially the use of strong blue light LED.

For the regulation of circadian rhythms spectrum

The total proportion of circadian rhythms and blue light. The amount of blue light is a product of two factors: one is the total amount of light; the other is a relative amount in the spectrum of Blu ray radiation. In order to influence the circadian cycle, can change the light level and spectrum.

At present, have proposed various metrics to quantify the amount of blue light but the spectrum at 450-480nm with peak sensitivity. Therefore, provide the greatest opportunity to modify the spectra in this range.

LED technology can according to need to form a spectrum, especially the re organization of spectrum to increase or eliminate blue radiation, but must also maintain other important characteristics of light. A key aspect is the color light itself, should be white. If you simply remove all blue light from the white light source (for example, with the blue light inhibition filter), is produced by the light yellow green, not suitable for practical use. Therefore, to reduce the circadian rhythm of light stimuli cannot be simplified to simply remove blue radiation.

Morning and evening demand

The white light is characterized by its correlated color temperature (CCT). High temperature and light, such as sunlight, contain more short wavelength radiation, low temperature and light contains more red radiation (Figure 1). In this way, the circadian rhythm can be adjusted by the CCT and to modulate the intensity of the light source, high and low at night morning. The human visual system by color adaptation process to adapt naturally to different CCT light, so the extensive CCTs is acceptable for general lighting.

Figure 1. depicts the different shades of light. Black White said black locus. Remove from incandescent blue radiation will make it become yellow green. Although technically classified as white candle, but the candle has obvious yellow hue.

This method can increase the circadian rhythm very well in the morning, CCT to 4000-5000K, and the light intensity increased to more than 1000lx. Medical research has demonstrated that the rich blue and high CCT light can help synchronize the sleep time, especially for the need to change the medical conditions of the circadian cycle population. Therefore, the lighting industry has embraced the concept, and launched a number of blue radiation products.

On the other hand, produce a physiological stimulation of low light at night is more challenging. In order to reduce the total amount of blue, must adjust light and spectrum. The light intensity can be slightly lower, from the typical 100-300 LX to 30-50 LX, but for family use, it's too dull. In order to obtain the blue spectral radiation very little time, there will be more serious challenge, because the lower temperature reached the limit. If the CCT is far lower than that of 2700K, the equivalent of an incandescent bulb temperature, then it is not so perfect. In spite of the technology on the performance of white light, but the light is yellow. One example is the candle light produced; CCT 2000K, in a particular case may be pleasant, but for most family activities, this looks too yellow.

Today, all the "sleep friendly" type light bulbs are using this method at low temperature (the temperature range from 2000-2300K), so the color is not natural. Because of this problem, the color quality of the light bulb manufacturers recommend, some can only be used for lighting, for example, bedlight. It is worth noting that, so far, the efficacy of these products have not been clinical research