Light emitting apparatus, light emitting method, light detection apparatus and spectrum detection method

A spectrum detection method, comprising steps sequentially executed as follows:

• providing a plurality of light emitting units, wherein the light emitting units emit light with different a light emission peak wavelengths and wavelength ranges, and each of the light emitting units is controlled to discontinuously emit the light with a lighting frequency;
• providing current densities respectively to the light emitting units, so that the light emitted by each of the light emitting unit has a light intensity, wherein the current densities provided to the light emitting units are the same;
• measuring an initial spectrum energy distribution curve of each of the light emitting units;
• selecting the lighting emitting unit corresponding to the light intensity of a specific value among the light intensities, increasing or decreasing the current density corresponding to the non-selected light emitting unit, so to make the light intensity corresponding to the non-selected light emitting unit similar or approximate to the light intensity corresponding to the selected light emitting unit, so that signal to noise ratios (SNRs) of the wavelength ranges corresponding to the non-selected light emitting units are increased, and SNRs of the wavelength ranges corresponding to all of the light emitting units are similar to each other;
• receiving a spectrum signal of an object under test and a background noise, during a light emitting unit turned-on time interval of the lighting frequency, wherein a received signal is a composite signal of a background noise and the spectrum signal of an object under test, the received signal during a light emitting unit turned-off time interval of the lighting frequency is the background noise, and the spectrum signal of the object under test and the background noise forms a time-domain signal of the object under test;
• performing a mathematical transformation on the time-domain signal of the object under test to obtain a frequency-domain signal of the object under test, wherein the frequency-domain signal of the object under test comprises a frequency-domain signal of the spectrum signal of the object under test and a frequency-domain signal of the background noise;
• and
• filtering out the frequency-domain signal of the background noise and reserving the frequency-domain signal of the spectrum signal of the object under test, so as to increase a SNR of an overall spectrum of the object under test.