The invention relates to an automatic recognizing method and device for
nitrogen phosphorus and
potassium stress of protected tomatoes. The automatic recognizing device consists of a CCD (
charge coupled device), a
spectrograph, an optical
system, a
light source, a displacement platform, a controller, a PC (
personal computer), a display and a light box. The method comprises the following steps of: firstly, performing
system experiment calibration on the automatic recognizing device by a calibrating sample; then sampling a
model sample during a whole growth period at
equal time intervals, and collecting the reflection intensity, the polarization distribution and hyper spectrum image information of visible light-near
infrared of inverted-7-shaped leaves of the tomatoes; analyzing and acquiring a main ingredient image of a
nutrition stress sample according to main ingredients by combining with a measured value of chemical
nitrogen phosphorus and
potassium analysis and a
micro structure scanning electron microscope test of the
model sample, thus determining the characteristic
wavelength of
nitrogen phosphorus and
potassium; and classifying
nutrition stress characteristics into three types including a polarization characteristic, an intensity characteristic and an image characteristic, establishing the
characteristic space of the
nutrition stress characteristics, and establishing an automatic recognizing and comprehensive evaluation model for
nitrogen phosphorus and potassium of the tomatoes according to a D-S (Dempster / Shafer) criterion theory, thus automatically recognizing and diagnosing the
nitrogen phosphorus and potassium stress types of the protected tomatoes.