PROBLEM TO BE SOLVED To accurately measure the amount of moisture contained in a plant which is an indicator of the health of plants.SOLUTION: A first projection light source of a plant detection camera 1 irradiates near infrared light (reference light) of a first wavelength (905 nm) having a characteristic hard to be absorbed by moisture to a leaf PT 3 of a plant PT . The second projection light source of the plant detection camera 1 irradiates leaves of the plant PT with near infrared light (measurement light) of a second wavelength (1550 nm) having characteristics that it is easily absorbed by moisture by optical scanning. Based on the reflected light of 905 nm reflected at all the irradiation positions of the leaves and the reflected light of 1550 nm reflected at all irradiation positions of the leaves, the threshold value setting / moisture index detection processing section calculates the sum total Ln of the reflection intensity ratios of one leaf (I905/ I1550) Is calculated.BACKGROUND OF THE INVENTION【課題】植物の健全度の指標となる植物に含まれる水分量を正確に測定する。【解決手段】植物検出カメラ1の第1の投射光源は、光学走査により、水分に吸収され難い特性を有する第1波長(905nm)の近赤外光(参照光)を植物PTの葉PT3に向けて照射する。植物検出カメラ1の第2の投射光源は、光学走査により、水分に吸収され易い特性を有する第2波長(1550nm)の近赤外光(測定光)を植物PTの葉に向けて照射する。閾値設定/水分指数検出処理部は、葉の全照射位置において反射した905nmの反射光と葉の全照射位置において反射した1550nmの反射光とを元に、葉1枚の反射強度比の総和ΣLn(I905/I1550)である水分指数を算出する。【選択図】図1
