LED light blue | expert interpretation

Light enters the human eye with two visual channels, one for the imaging visual channel (solid line in Figure 1) and the other for the non-imaged channel of the circadian clock and hour (the dotted line in Figure 1). On the imaging vision channel, the blue light of the LED luminaire may create a visual hazard to the retina. On non-imaging channels, the blue light of an LED luminaire may have an effect on the circadian rhythm.

Figure 1 Imaging vision channel and non-imaging vision channel for human eyes receiving light

The wavelength of the blue LED is around 450 nm, which is exactly the same as the human body's circadian rhythm/biological clock rhythm. It has a strong ability to secrete melatonin inhibitors. The reduction in melatonin makes people excited and does not sleep. Longer this will affect people's immune mechanisms.

Figure 2 is a typical 5500K blue-rich LED white light emission spectrum, with a thick line depicting the maximum spectral energy wavelength in the 460nm region, which coincides with the human body's spectral curve for the secretion of melatonin inhibitors. As a result, long-term companionship will affect The circadian rhythm of the human body's normal sunrise and sunset, so it is very important to limit the blue light energy below 500nm and reduce the influence on human circadian rhythm.

In order to avoid the possible adverse effects on the human health caused by the use of rich blue LED lamps, the color temperature of indoor LED lamps should not exceed 4000K.

The influence of blue light on the circadian rhythm of LED lamps is usually included in the performance indicators of the product standard.

Fig.2 Spectral sensitivity curve of blue LED white light spectrum curve and melatonin inhibitor

The coincidence indicates that the blue LED white light at night is unfavorable.

How is the blue light of LED lamps formed?

In order to obtain stable, reliable and simple white light, the most common method currently used is to excite yellow phosphors with blue-emitting LED chips. The LED emits blue light with a wavelength of about 450 nm. The blue light is divided into two parts in this process. A part of the blue light excitation phosphor emits yellow-green light with a wavelength of about 570 nm, and the other part of the blue light is transmitted and mixed with the yellow-green light generated by the excitation phosphor to produce white light. As shown in Figure 3.

Figure 3 blue LED chip plus phosphor to produce white light

Color temperature is the most common indicator of the spectral quality of the source. According to the proportion and composition of the phosphor, the white LED can provide a full range of color temperature range of cool white, neutral and warm white with a color temperature between 2700 and 6500K.