Abstract: The present invention relates to a hair-detection device (100), with a source (80) of electromagnetic radiation and an imaging sensor (74), and with radiation selection means (83, 48). During use of the device, the selection means improve a ratio between the part of the emitted radiation that is coupled into a skin (8), homogenized via multiple scattering without much absorption in the skin, reaches the sensor (74) and thus provides an image of the skin, and the part that reaches the sensor via other ways, such as reflection at the skin surface. The radiation preferably has a wavelength between about 700 nm and 1100 nm. The radiation selection means may e.g. comprise a separate wall (83) around at least one of the source (80) and the sensor (74) and the sensor (74), crossed polarizers, etc. By means of this selection, the contrast of the image may be improved, and may be made less dependent on skin color and skin artifacts, thus enabling easier detection of e.g. white hairs on a fair skin.

Abstract: The invention relates to a device (1) for treating human skin by means of radiation. The device has a housing (5) with a radiation exit opening (13), a radiation source (9) which is accommodated in the housing, and a radiation path (15) between the radiation source and the radiation exit opening. A radiation filter (17) is provided in the radiation path. According to the invention the radiation filter (17) comprises water (23) which is in solid state at least during an initial phase of operation of the device (1). The water in solid state has an optical transmission spectrum which corresponds to the optical transmission spectrum of water in liquid state as present in the skin. As a result the water in solid state acts as an ideal filter for the IR light and near IR light, which would otherwise be absorbed by the water in the skin and cause unwanted heating of the skin.