Spectral confocal measurement utilizes the physical phenomenon that optical materials have different refractive indices for different monochromatic wavelengths. By using specially designed lenses, it extends the focal spot distances of different wavelengths, creating a controlled axial chromatic aberration. This ensures that, depending on the distance from the target object to the lens, a specific wavelength of light is precisely focused onto the target. By measuring the wavelength of the reflected light, the precise distance from the target object to the lens can be determined.