# Research on the Application of the Dynamic Assisted Sleep Light to Smart Mobile Devices
## 1 Introduction  
Sleep is the most basic need of human beings every day. Sleep allows the brain to rest and carry out the learning work of memory reorganization, storage, body relaxation, etc. Most human beings gain external experience and knowledge through vision, as an important way of obtaining external information. In the process of visual access to external information, it is necessary to rely on the interaction between light and objects in the physical world, light which then reaches the retina through the refraction and reflection effects of light. Then, the information is stored and transmitted to the brain by neurons in the retina [1]. However, there are many regions and neurons in the human brain which process information related to vision, analyzing the optical information obtained by vision and converting it into neural signals that the brain can understand, and then storing that information in the memory through sleep. However, the optical information that human vision can detect is only a small part of the light spectrum, and the wavelength ranges from 380-780 nm. It was previously understood that the photoreceptor cells in people's eyes were composed of rod cells and cone cells, which, respectively, controlled the storage and analysis of external light intensity and color texture changes. In 2002, however, with the continuous progress of medical and scientific technology, scientists in the United States discovered a third kind of special photosensitive cell [2; 3; 4]: intrinsically photosensitive retinal ganglion cells (ipRGC). These ipRGC do not rely on cone-shaped and rod-shaped cells for sensitization, but rather melanopsin, thus breaking with the traditional concept of visual photosensitive organs. As a result, the discovery of ipRGC changed the long-termunderstanding of photobiology, and at the same time, it was known that illumination would have other effects on the human body. In the discovery of the third kind of intrinsically photosensitive retinal ganglion cells (ipRGC), it was revealed that this cell receives light through melanopsin and then influences various physiological adjustments and reactions, such as melatonin secretion, circadian rhythm phase shift, sleep time, etc. [5; 6]. In 2005, [PERSON] et al. used light sources with different color temperatures to study sleep, and conducted sleep experiments at 3000 K, 5000 K and 6700 K with illumination of less than 10 lx. The experimental results show that the total sleep time at 6700 K is less than that at 3000 K [7]. The research results of [PERSON] et al. in 2013 also showed that melatonin was obviously inhibited at the color temperature of 6500 K two hours before going to bed under the illumination of a light source with a color temperature of 3000 K and illumination of 40 lx at 6500 K; meanwhile, alertness increased, happiness increased, and visual comfort increased, but slow wave sleep without rapid eye movement decreased in the first sleep cycle [8]. In 2017, the research of [PERSON] et al. also found that in people who were deprived of sleep at night, after being stimulated by 2700 K, 500 lx illumination and 6000 K, 500 lx light, all the subject's showed emotions of high excitement and alertness at 6000 K color temperature [9]. For the dynamic color temperature, in the research of [PERSON], [PERSON], et al. in 2013, physiological experiments were conducted by means of dynamic illumination, and [PERSON] et al. conducted experiments for female employees who worked shifts. Because the shift workers' sleep quality, mood, and stress are worse than those of people with normal daily routines and rest, in order to adjust the circadian rhythm of the workers, the dynamic changes of the light source in the working environment are used in the experiment. The experimental results show that the workers who use the dynamic light source at work see a significant improvement in mood and sleep quality compared with those who use the general lighting.