Study on Measurement Error Reduction Using the Internal Interference Light Reduction Structure of a Time-of-Flight Sensor

In recent years, the demand for the installation of Time-of-Flight (ToF) sensors in mobile phones and other devices to send and receive distance information has increased. A ToF sensor is a system that measures the distance to an object by calculating the elapsed time of an infrared (IR) light emitted from a vertical-cavity surface-emitting laser to the moment it returns to the single-photon avalanche diode after being reflected by the object. In this study, we analyzed the IR optical path of a ToF sensor structure using optical simulation. In addition, we analyzed the field of view, amount of light source, and intensity of the internal interference light. Moreover, the internal structure of the ToF sensor, which can minimize the intensity of interference light, was optimized and designed. Consequently, the internal interference light intensity decreased by 84% compared to the structure designed using conventional method. Furthermore, a structure was optimized using a polarizing film and quarter-wave plate, the internal interference light intensity of this structure reduced by 88% compared to that of the conventional method, and the distance measurement error of the ToF sensor decreased significantly.