Multiple incident angles and wavelengths identifiable proximity optical communication scheme utilizing the Talbot effect and deep neural network

A lensless light field image sensor configuration is presented to realize a proximity light communication system from multi-light-emitting diode (LED) clusters with different incident angles. The light field image sensor is fabricated on a standard complementary metal–oxide–semiconductor (CMOS) process and utilizes the Talbot effect. Two metal layers are stacked above the photodiode acting as diffraction gratings at the top and a masking layer at the bottom placed at Talbot depth to either pass or block the incident light. In particular, we introduce a proximity optical communication scheme to achieve dual light communication from different incident angles with various wavelengths. To simplify the classification between different combinations of incident angles and wavelengths, a deep neural network (DNN) is utilized. We reduced the number of light field image sensors by 50% and increased the transmission data bits per clock by 114% compared with our previous work. A test environment for deciphering three incident angles and three types of wavelength combinations is devised. For each incident angle, three LEDs, which are red, green, and blue (RGB), are located at precomputed locations. A 3 × 3 chip LED array consisting of three sets of RGB LEDs is used to transmit signals, and a light field image sensor chip acts as a receiver 3.5 cm away. A range of 46 different types of blink combinations are tested from this single LED array considering up to dual lights communication. The light field image sensor chip consists of six photodiodes with different grating pairs. In particular, three types of grating layer combinations with the photodiodes can detect nine different single blinks and 36 different dual blink combinations, thus totaling 46 types of spatial signals. We achieved a maximum data rate of 251 kbit / s with the proposed prototype at a 45.5-kHz sample rate. The proposed proximity optical communication scheme had power dissipations of 30.6 mW on a 1.8-V power supply for the sensor chip and 27.5 mW on a 3.3-V power supply for the LED array. This can be applied in the low-power data input/output communication between a compact cluster of chips.