A high-efficiency acquisition method of LED multispectral images using Gray code based square wave frequency division modulation

LED illumination-based multispectral imaging (LEDMSI) is a fast, convenient, and effective multispectral image acquisition technique. The square wave frequency division modulation (SFDM) and the integral sampling of the camera can build an efficient match pattern. With regards to image quality decline problems due to the ringing effect caused by the drive module while square wave high-low level conversion in the SFDM-LEDMS system. This paper proposes a multispectral image acquisition method combining Gray code and square wave frequency modulation. The micro control unit was used to generate a series of frequency division square waves in Gray code mode followed by LEDs of different wavelengths modulated by SFDM-square waves as a light source. Subsequently, the camera was used to simultaneously collect a sequence of multi-spectral images followed by single-wavelength images using differential accumulation demodulation. Finally, the no-reference image quality assessment (NR-IQA) was used to evaluate the quality of each single-wavelength image obtained by Binary code and Gray code. We deployed five wavelengths as examples to verify the effectiveness of the proposed method. The accumulated results indicated an improvement of the image quality in terms of information and gradient using Gray code. In conclusion, the present study can provide an effective image acquisition alternative for household medical equipment.