Optical convolutional neural network based on an amplitude modulation SLM and a 4-level phase plate

In this paper, we propose a method to realize complex amplitude modulation with a 4-level phase plate and an amplitude-modulated SLM. We implement this complex amplitude modulator system in classical 4f system and use this system to realize highly precise convolution to verify its feasibility. The optical convolution accuracy is higher than the phase-only modulator or the amplitude-only modulator method. We then incorporate this system with a one-layer CNN as its convolutional layer to accomplish a handwriting recognition inference, the image classification accuracy is also comparable to all-electrical result with the same framework.