Investigation of suitable lighting conditions on emotions and perception models for beauty aromatherapy application

Human-centric lighting considers all aspects of the relationship between people and light. By appropriately controlling lighting, it aims to enhance human health and well-being in the environment while meeting emotional needs. However, the effect of lighting design on beauty aromatherapy still needs to be investigated. This research study reports the results of a psychophysical experiment exploring the subjective emotional perception of the observers, including distressed, hostile, alert, ashamed, inspired, nervous, determined, attentive, afraid and active emotions, under white light sources with different luminance (i.e. 300 cd m −2 , 150 cd m −2 and 37.5 cd m −2 ), correlated colour temperature (CCT; i.e. 3000 K and 5000 K) and distance to the blackbody locus (i.e. −0.02, 0 and +0.02) and chromatic light sources composed of varying lightness (i.e. 100, 50, 12.5), chroma (i.e. 20 and 50) and hue angles (i.e. 0°, 30°, 60°, 120°, 240° and 270°) with five essential oils (i.e. lavender, tea tree, geranium, peppermint and sweet orange). The experiment results indicate that white light sources of varying luminance and chromatic light sources with changes in lightness significantly impact all emotional perceptions. The blackbody locus, CCT, hue, chroma and essential oils also notably influence certain emotions. A third-order polynomial regression is adopted to build an aromatherapy lighting perception model, which can accurately predict the perceptual items from different lighting configurations. The experimental results and the derived model can provide the ideal lighting design for beauty aromatherapy applications and be regarded as a reference for developing the standards by the international lighting organization.