Optical measurement system and optical measurement method

An optical measurement method using an optical system comprising a beam splitter that divides light from a light source into first light and second light, the optical measurement method comprising:

• recording with an image sensor, a first hologram resulting from modulation with the second light, of light obtained by illumination of a sample with the first light, the second light being diverging light;
• recording with the image sensor, a second hologram resulting from modulation of the first light with the second light while there is no sample, the second light being diverging light;
• and
• calculating a geometry of the sample based on the first hologram and the second hologram, wherein
• spread of the light obtained by illumination of the sample with the first light is restricted to be kept within a predetermined range,
• a size of the predetermined range is determined such that, in a spatial frequency domain of a hologram recorded with the image sensor, a component resulting from the modulation of the first light by the second light is not superimposed on another component, and
• an opening pattern corresponding to the predetermined range is formed in a shielding member.