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|1. (WO2017038766) DEVICE PROVIDED WITH OPTICAL UNIT|
|Title:||DEVICE PROVIDED WITH OPTICAL UNIT|
The purpose of the present invention is to provide a device provided with a compact and highly accurate optical unit which, while capturing an image of a granular material or the like, which is the subject, at close range, is capable of capturing an entire image thereof. If, for example, an offset parabolic concave mirror is used as a concave curved mirror provided in the optical unit, when a condensing optical system having an entrance pupil is disposed at the geometric focal position of the offset parabolic concave mirror, a group of light rays which enter parallel to the optical axis of the offset parabolic concave mirror becomes a telecentric principal ray with respect to the object surface which is orthogonal to the optical axis of the offset parabolic concave mirror, and thus it is possible to detect divergent light from each object point on the target object surface without a blind spot on a secondary image plane made by the condensing optical system which is at the focal position of the offset parabolic concave mirror. Since an image of the target object is further detected after a light beam, which has been reflected by the offset parabolic concave mirror, is caused to enter the condensed optical system after being bent with a reflecting mirror, making the device remarkably compact and achieving a low price has been made possible.