Multi-color pulse-amplitude modulated handheld fluorescence imager

A portable device operable to identify photosynthetic activity and contents of compounds in a plant part, the portable device comprises:

• a light source comprising light-emitting diodes operable to irradiate the plant part with light comprising more than one wavelength;
• a control module operable to (i) have the light-emitting diodes emit the light as pulse signals and (ii) modulate amplitude and width of the pulse signals, which involve:
• the control module operable to have the light-emitting diodes irradiate red light on the plant part to induce a first far-red fluorescence intensity signal from the plant part, and then irradiate ultraviolet light on the plant part to induce a second far-red fluorescence intensity signal from the plant part;
• a focus-adjustable lens and a filter optically coupled to the light source, wherein the adjustable lens and the filter are co-operable to consolidate light reflected from the plant part which is irradiated by light from the light-emitting diodes;
• and
• a detector optically positioned to receive from the focus-adjustable lens and the filter the light reflected from the plant part, wherein the light reflected from the plant part corresponds to the photosynthetic activity and contents of compounds in the plant part, and the light reflected is transmitted as fluorescence,
• wherein, from the control module, a numerical value is rendered by dividing the first far-red fluorescence intensity signal by the second far-red fluorescence intensity signal;
• and
• having a flavonol content in the plant part identified by taking a logarithm of the numerical value.