Culture-medium-monitoring apparatus

A culture-medium-monitoring apparatus comprising:

• an optical measurement unit that includes:
• an illuminating portion that is configured to radiate an illumination light beam onto a culture medium in a closed-bottom cylindrical vessel as a bioreactor;
• a stirrer disposed in the vessel and configured to rotate around a center axis of the vessel to stir the culture medium in the vessel;
• a retroreflective member that has an array in which a plurality of micro-reflective elements are arrayed, that is disposed so as to sandwich the vessel between the illuminating portion and the retroreflective member, and that is configured to reflect the illumination light beam that has passed through the culture medium in the vessel;
• and
• a light-detecting portion that is configured to detect an intensity of the illumination light beam that has passed through the culture medium in the vessel after being reflected by the retroreflective member;
• and
• a control portion that is configured to cause the intensity of the illumination light beam to be repeatedly detected at a prescribed timing by controlling the optical measurement unit, and to determine a state of the culture medium based on a change over time in the intensity of the illumination light beam,
• wherein:
• the illuminating portion is configured to enter the illumination light beam into the vessel along a direction intersecting a height direction of the vessel, and
• the illumination portion, the retroreflective member, and the stirrer are disposed at positions at which the illumination light beam traveling inside the vessel does not interfere with the stirrer.