Illumination apparatuses including semiconductor light-emitting devices such as laser emitting diodes (LED) as light sources, instead of fluorescent or incandescent lamps, have been used indoors, or used in buildings or in houses. For example, an illumination apparatus including a light-emitting device is used as a light source for indoor visual inspection of painted surfaces of products, such as home electric appliances and automobiles.
A semiconductor light-emitting device emits light with a narrow region of wavelengths, and may only emit monochromatic light. To produce white light as illumination light, a plurality of semiconductor light-emitting devices that emit light with different wavelength regions are prepared, and a plurality of light beams with different colors emitted from such semiconductor light-emitting devices are combined to produce white light. A plurality of phosphors that emit light with different wavelength regions using excitation light with the same wavelength are prepared, and a plurality of fluorescence beams with different colors are combined into white light.
This method of combining colors allows a light source to produce white light and also light with other spectra for intended use.
The light-emitting apparatus described in Japanese Unexamined Patent Application Publication No. 2015-126160 includes two blue light-emitting devices with different peak wavelengths, a green phosphor that is excited by light emitted from the blue light-emitting device to emit green light, and a red phosphor that emits red light to improve color rendering.