Illumination method and light-emitting device

摘要

To provide an illumination method and a light-emitting device which are capable of achieving, under an indoor illumination environment where illuminance is around 5000 lx or lower when performing detailed work and generally around 1500 lx or lower, a color appearance or an object appearance as perceived by a person, will be as natural, vivid, highly visible, and comfortable as though perceived outdoors in a high-illuminance environment, regardless of scores of various color rendition metric. Light emitted from the light-emitting device illuminates an object such that light measured at a position of the object satisfies specific requirements. A feature of the light-emitting device is that light emitted by the light-emitting device in a main radiant direction satisfies specific requirements.

主权项

1. A light-emitting device comprising at least a semiconductor light-emitting element as a light-emitting element, wherein
light emitted from the light-emitting device includes, in a main radiant direction thereof, light whose distance DuvSSL from a black-body radiation locus as defined by ANSI C78.377 satisfies −0.0350≦DuvSSL<0, and if a spectral power distribution of light emitted from the light-emitting device in the radiant direction is denoted by φSSL (λ), a spectral power distribution of a reference light that is selected according to a correlated color temperature TSSL (K) of the light emitted from the light-emitting device in the radiant direction is denoted by φref (λ), tristimulus values of the light emitted from the light-emitting device in the radiant direction are denoted by (XSSL, YSSL, ZSSL), and tristimulus values of the reference light that is selected according to the correlated color temperature TSSL (K) of the light emitted from the light-emitting device in the radiant direction are denoted by (Xref, Yref, Zref), and if a normalized spectral power distribution SSSL (λ) of light emitted from the light-emitting device in the radiant direction, a normalized spectral power distribution Sref (λ) of a reference light that is selected according to the correlated color temperature TSSL (K) of the light emitted from the light-emitting device in the radiant direction, and a difference ΔS (λ) between these normalized spectral power distributions are respectively defined as
SSSL (λ)=φSSL (λ)/YSSL,Sref (λ)=φref (λ)/Yref andΔS (λ)=Sref (λ)−SSSL (λ) and a wavelength that produces a longest wavelength local maximum value of SSSL (λ) in a wavelength range of 380 nm to 780 nm is denoted by λR (nm), then a wavelength Λ4 that assumes SSSL (λR)/2 exists on a longer wavelength-side of λR, and an index Acg represented by formula (3) below satisfies −360≦Acg≦−10[Expression 6]
Acg=∫380495ΔS(λ)dλ+∫495590(−ΔS(λ))dλ+∫590Λ4ΔS(λ)dλ  (3).