Skin treatment device

A skin treatment device comprising:

• a treatment light source;
• a light emission window comprising a window element arranged for getting into skin contact during operation;
• a first sensor arranged for providing a first sensor signal indicative of an amount of hemoglobin in a skin area underneath the light emission window;
• and
• a processor coupled with the first sensor for communicating the first sensor signal in a user-perceptible manner by means of an indicator or for controlling a function of the skin treatment device in dependence on the first sensor signal;
• the first sensor comprises a first light source, a second light source and at least a first light-sensitive detector,
• wherein the first light source is a narrow-band light source or a monochromatic light source emitting light in a first wavelength range from about 300 nm to about 620 nm and the second light source is a narrow-band light source or a monochromatic light source emitting light in a second wavelength range from about 620 nm to about 1200 nm;
• and
• wherein the first light-sensitive detector is arranged to measure a first light intensity of light originating from the skin in the first wavelength range and a second light intensity of light originating from the skin in the second wavelength range.

A method of applying light to skin for achieving a cosmetic effect, the method comprising the steps of:

• pushing a light emission window of a skin treatment device against the skin, the light emission window comprising a window element;
• irradiating the skin with light in a first wavelength range from about 300 nm to about 620 nm;
• measuring a first light intensity of light originating from the skin in the first wavelength range;
• irradiating the skin with light in a second wavelength range from about 620 nm to about 1200 nm;
• measuring a second light intensity of light originating from the skin in the second wavelength range;
• determining a first sensor signal indicative of an amount of hemoglobin present in at least a portion of the skin underneath the light emission window based on at least the first light intensity and the second light intensity;
• and
• indicating the determined first sensor signal in a user-perceptible manner;
• or
• controlling a function of the skin treatment device in dependence on the determined first sensor signal.