On 4th December 1925, Poul Henningsen with his manufacturer Louis Poulsen applied under Danish law for the patent titled ‘Reflector for Incandescent Lamp’. The patent was granted on 19th May 1928 with the Danish patent number 38897, and later by the USA patent office 6th May 1930. The specifics of the patent included a technical drawing and stated the characteristics of the invention: ‘A reflector for diffusing the light of incandescent lamps comprising a plurality of concentric downwardly concave shades disposed above and below the plane of the source of light, the inner surfaces of said shades being directed toward the source of light, the surfaces of said shades making at all points angles less than 45 with a line to the source of light, the inner surfaces of the shades being dulled.’

Regarding Henningsen’s reliance upon patent law and copyright law, Stina Teilmann-Lock writes: ‘the lamp has been defined, respectively, as both ‘industrial property’ and ‘artistic property’, as an invention and as a work of art’. Prior to the patent being granted, Henningsen was awarded by the jury of the 1925 World’s Fair in Paris, L’Exposition Internationale des Arts Décoratifs et Industriels Modernes, a gold medal and Louis Poulsen silver for their lighting. Henningsen developed his ‘system of shades’ into types, which ranged from smallest to largest, and were available in different types of glass. Painted copper shades were then applied to various lighting formats. More than ninety years after L’Exposition Internationale des Arts Décoratifs et Industriels Modernes, Henningsen’s work still resonates, and the ‘PH lamp’ continues to be ‘an exceedingly beautiful light’ (Poul Henningsen, LP Nyt, December 1941).