Some of HW-Security’s cameras are using IR lens. Ordinary camera using non-IR lens could get a clear image at the daytime but an unclear and out of focus image in the nighttime.  HW-Security’s IR lens can avoid focus shift when IR LED starts working at night.
         The spectrum of regular visible light is 380nm--780nm, while the spectrum of infrared light is 830--950nm. Normal glass has different refraction for different wavelength of light. Nowadays, normal glass lens can focus light of wavelength varies from 430--650nm or 650--900nm. That is why the ordinary glass lens cannot focus both visible and infrared light onto a same focal plane.
         But HW-Security’s IR lens corrects the problem: