This lensless imaging system comprises a receiving support configured to receive a sample, a light source configured to emit a light beam illuminating the sample in an illumination direction, the light source including a diode and a diaphragm, the diaphragm being positioned between the diode and the receiving support in the lighting direction, and a matrix photodetector configured to acquire at least one image of the sample, each image being formed by radiation emitted by the illuminated sample and including at least one elementary diffraction pattern, the receiving support being positioned between the light source and the matrix photodetector in the illumination direction.The system further comprises a light diffuser positioned between the diode and the diaphragm.