Analysis of the visual brightness of LED light source and the error of luminaire measurement

With the development of LED chip packaging technology, high-power white LED lighting technology has become increasingly mature, and entered the lighting practice with the development scale of acceleration. The principle of illumination of LED light sources is very different from that of traditional light sources. The white light is our first impression of this kind of light source, but what about the advantages and disadvantages of this light and traditional light? Below I will carry out an analysis from the perspective of spectroscopy, hoping to play a role in attracting jade.

1. Light is a form of electromagnetic wave

Under the same illumination, the LED light source illumination environment is much brighter than the traditional light source illumination environment. Why is this happening? This has to start from the spectral energy distribution of different light sources.

Light is a form of electromagnetic wave, electromagnetic radiation with a wavelength between 380 nm and 760 nm, located between a small fraction of the ultraviolet and infrared spectrum.

Light of different wavelengths visually form different colors. The light emitted by a general light source is often composed of electromagnetic waves of different wavelengths. Such light is called polychromatic light; light of a single wavelength is called monochromatic light. Most of the light sources in nature are multi-color light, laser.

The light emitted by different light source bodies has different spectral characteristics (ie, electromagnetic spectrum). For example, the sodium lamp spectrum is distributed more in the long-wave region, while the fluorescent light wave is more distributed in the short-wave region, and the spectral distribution of the LED light source is mainly in the human eye energy response. The best 550nm wavelength adjacent area, LED light source is the best source of human eye vision response.

The diagram below shows the spectral characteristics of several different sources.

2. How the human eye feels about light waves

Different wavelengths of light enter the human eye, stimulating the photoreceptor cells in the eye, and enter the brain through the optic nerve to form a visual image.

There are two types of photoreceptors in the eye: one is a cone-shaped cell that can sense color, and the cone-shaped cell is most sensitive to light with a wavelength of 550 nm. The usual required brightness is at least a few candelas per square meter, so it is often referred to as bright vision.

The other is rod-shaped cells that are indistinguishable from color. Rod cells are most sensitive to light with a wavelength of 510 nm. The required brightness is generally less than a few candelas per square meter, so it is often called dark vision.

The intermediate vision is between the above two kinds of vision.