[Object] To freely set a target region while ensuring a necessary speckle diameter, in speckle image capturing that uses coherent light. [Solution] Provided is an optical unit that radiates a coherent light such that the coherent light is incident in a target region of speckle image capturing in accordance with a pattern that includes a bright region and a dark region located uniformly in at least one direction in the target region. Provided is a measurement system including: an optical unit that radiates a coherent light such that the coherent light is incident in a target region in accordance with a pattern that includes a bright region and a dark region located uniformly in at least one direction in the target region； a light reception unit that receives a reflected light of the coherent light in the target region； and an imaging unit that captures an image of a speckle included in the reflected light.
