Beam splitter using multi-refractive index layer and defective element detecting device comprising same

A beam splitter using a multiple refractive index layer, the beam splitter comprising:

• a multiple refractive index layer configured to reflect first light and transmit second light having a wavelength longer than a wavelength of the first light;
• and
• a base layer provided on one side of the multiple refractive index layer and configured to transmit the second light transmitted through the multiple refractive index layer,
• wherein the multiple refractive index layer comprises:
• a first multiple refractive index layer comprising a first refractive index layer having a first refractive index and a second refractive index layer having a second refractive index less than the first refractive index, the first refractive index layer and the second refractive index layer being alternately and repeatedly arranged, the first multiple refractive index layer being configured to reflect an area including a first center wavelength from among reflection areas of the first light;
• and
• a second multiple refractive index layer comprising a third refractive index layer having a third refractive index and a fourth refractive index layer having a fourth refractive index less than the third refractive index, the third refractive index layer and the fourth refractive index layer being alternately and repeatedly arranged, the second multiple refractive index layer being configured to reflect an area including a second center wavelength that is different from the first center wavelength from among the reflection areas of the first light, and
• the wavelength of the second light is 10 times or more than the wavelength of the first light.