Although smart phone usage has increased dramatically, many users are unaware of the proximity sensors used in their devices. The proximity sensor (infrared hole) is one of many possible biosensors and is usually identifiable as a black round hole located at the top of the mobile phone screen. These biosensors control mobile phone screens by sensing infrared changes occurring in the human body, making them more useful to consumers. To achieve such screen control, the IR hole on the mobile phone has to selectively pass infrared rays, while blocking ultraviolet rays and visible light. This application note describes how PerkinElmer LAMBDA 1050+ UV/Vis/NIR Spectrophotometer with Integrating Sphere can be used for transmittance test of infrared proximity sensors.