OPT4001 spectral response closely matches that of the human eye. If the ambient light sensor measurement is used to help create a good human experience, or create optical conditions that are good for humans, then the sensor must measure the same spectrum of light that a human sees.

OPT4001 also has excellent infrared light (IR) rejection. This IR rejection is especially important because many real-world lighting sources have significant infrared content that humans do not see. If the sensor measures infrared light that the human eye does not see, then a true human experience is not accurately represented.

If the application demands hiding OPT4001 underneath dark window (such that the end-product user cannot see the sensor) the infrared rejection of the OPT4001 becomes significantly more important because many dark windows attenuate visible light but transmit infrared light. This attenuation of visible light and lack of attenuation of IR light amplifies the ratio of the infrared light to visible light that illuminates the sensor. Results can still be well matched to the human eye under this condition because of the high infrared rejection of the OPT4001.