Spectral response of the human eye
The traditional radiometric concept (such as "power", the unit is "watt") can objectively describe "energy", but when it is used to describe "light", it is not suitable because: the human eye has different wavelengths. The light feels different. For example, the human eye can only perceive light with a wavelength of about 380~780nm, and has almost no perception of light with other wavelengths; the green LED and blue LED with the same radiation power, the visual brightness and darkness brought to the human eye are also different. completely different. In order to fully describe people's perception of light and darkness, the concept of photometry was introduced.
However, "brightness" and "darkness" are subjective feelings after all, and they are also related to the environment where the eyes are located and the personality of the person. The human eye's sense of brightness comes from countless light-sensitive cells on the retina, which are divided into two types: rod cells and cone cells. Rod cells can sense strong light, but with low sensitivity; cone cells can sense weak light, but with high sensitivity. If the light-sensitive cells are compared to a ruler for measuring brightness, the former (rod cells) have a large range, but a lower resolution, and the latter (cone cells) have a small range, but can measure small changes—two The use of the ruler together makes people sigh the subtlety of the creator.
In a brightly lit environment, mainly rod-shaped cells work, causing "photopic vision"; in a dimly lit environment, mainly cone cells work, causing "scotopic vision" (scotopic vision). ". Through a large number of experiments, the relative sensitivity of two types of cells to different wavelengths of light was measured:
For rod cells (corresponding to photopic vision), the most sensitive wavelength of the human eye is 555 nm, and the color is green-yellow; for cone cells (corresponding to scotopic vision), the most sensitive wavelength of the human eye is 507 nm, and the color is blue-green ( blue.
