There is provided a vision system for assessing defects on biochips and a corresponding method. The vision system comprises an imaging region in which a biochip sheet including at least one biochip is locatable in use: an imager arranged in use to image at least a portion of the imaging region, wherein, when the biochip sheet is located in the imaging region. the portion includes at least a face of the biochip sheet: and an illumination source arranged in use to direct illumination on to the face the biochip sheet. thereby illuminating defects on the at least one biochip when a mask material layer is present on the at least one biochip and when a mask material is absent and allowing the defects to be included in the imaged at least a portion of the imaging region.