Researchers developed a method called phase lock-in amplification to detect weak signals accurately in the presence of background noise. By using a special amplifier and filter, they were able to isolate and analyze weak signals even when surrounded by high levels of noise. The system they created using FPGA technology showed high precision in detecting weak photoelectric signals, with a minimum detection accuracy of 0.02pA even at a signal-to-noise ratio of -26dB. This method has broad applications in various scientific and engineering fields.