Patent ID: 7910876

Claim:
A plant sensor, comprising: a light source section, including: a first light emitter configured to periodically emit first measuring light whose peak wavelength of emission intensity is a first wavelength, and to irradiate the first measuring light toward an object to be measured; a second light emitter configured to periodically emit second measuring light whose peak wavelength of emission intensity is a second wavelength, and to irradiate the second measuring light toward the object to be measured; and a light receiver configured to receive reflected light of each of the first measuring light and the second measuring light from the object to be measured, and output light-receiving signals; a controller configured to control emission of the first light emitter and emission of the second light emitter at different timings; an integrator configured to integrate the light-receiving signals by performing a first integration step comprising integration of the light-receiving signals including a component of the reflected light of each of the measuring light from the object to be measured in synchronization with lighting of each of the light emitters and outputting a first integration signal, and by performing a second integration step comprising integration of the light-receiving signals without having the component of the reflected light of each of the measuring light from the object to be measured in synchronization with lighting-off of the each of the light emitters and outputting a second integration signal; and a calculator configured to calculate, according to the first integration signal and the second integration signal from the integrator, a reflection rate as a ratio of light intensity of the reflected light of the first measuring light from the object to be measured to light intensity of the first measuring light, and a reflection rate as a ratio of light intensity of the reflected light of the second measuring light from the object to be measured to light intensity of the second measuring light, to obtain information regarding a growing condition of the object to be measured, and to reduce the first integration signal obtained by the first integration step by the second integration signal obtained by the second integration step.