a light source, the light source generating an incident light field;

a light intensity modulator, according to at least one modulation pattern generated by a controlling signal, the light intensity modulator modulating the incident light field into a detection light field, the at least one modulation pattern having a varied optical amplitude gradient along a radial direction;

a condenser, the condenser positioned at one side of the light intensity modulator, the light intensity modulator positioned on a Fourier plane of the condenser, the condenser receiving the detection light field and refracting the detection light field to generate an off-axis light field to project to an object for generating an object light field, the off-axis light field projecting beyond a first axial direction;

an objective lens positioned at one side of the condenser and the object positioned on a focal length of the objective lens, the object located between the condenser and the objective lens, and the objective lens receiving the object light field; and

an image capturing module, the image capturing module coupled to the objective lens, wherein the image capturing module receives the object light field and generates an optical image corresponding to the varied optical amplitude gradient;

wherein the light intensity modulator is a liquid crystal module (TFT shield) for controlling a light penetration intensity or a liquid crystal on silicon (LCoS), the light intensity modulator comprises a liquid crystal unit for changing an amount of light penetration and colors of the light penetration according to the controlling signal.