A projector for image projection, includes: an optical element included by an optical system to project an image; a tripod that supports the projector; and a tripod-fixing part that is connected with the optical element and fixes the tripod, wherein the tripod and tripod-fixing part are each constituted by a heat-conductive member. The measurement device includes an illumination unit which directs individual measuring light beams towards the areas on the optical surface. A management system based on the real-time analysis is designed that computes the amount of water and fertilizer needed every day to the plants.