Illuminator for plant growth

An illumination method for plant growth, comprising steps of:

• providing a light source composed of a semiconductor optical device;
• modulating light generated by the light source with a rhythm signal extracted from a musical composition produced artificially, and
• illuminating a plant to be illuminated with the modulated light;
• wherein said rhythm signal produced artificially indicates sound length, pitch or stress according to a certain musical time or rule;
• wherein the light source is comprised in an illuminator composed of a semiconductor optical device, and which comprises a control unit for outputting a turn-on timing signal for the light source, a rhythm signal detecting unit for taking in an input rhythm signal, a timing signal modulating unit for modulating said turn-on timing signal with the output signal from the rhythm signal detecting unit, and a pulse drive unit for pulse-modulating a power signal with the modulated turn-on timing signal outputted from the timing signal modulating unit and supplying the pulse-modulated power signal to said light source, whereby the plant to be illuminated is pulse-illuminated while changing a light quantity of the light source in synchronization with said input rhythm signal;
• wherein said timing signal modulating unit multiplies the output signal from said rhythm signal detecting unit by the turn-on timing signal generated by said control unit to generate a signal synchronized with an amplitude of the rhythm signal, and sums the signal and said turn-on timing signal to modulate said turn-on timing signal.