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EP-4531731-B1 - A LIGHT TREATMENT DEVICE

EP4531731B1EP 4531731 B1EP4531731 B1EP 4531731B1EP-4531731-B1

Inventors

  • VAN ABEELEN, FRANK ANTON
  • VERHAGEN, RIEKO
  • BOAMFA, MARIUS IOSIF
  • THUMMA, KIRAN KUMAR
  • NUIJS, ANTONIUS MAARTEN

Dates

Publication Date
20260506
Application Date
20230518

Claims (13)

  1. A treatment device (2; 30; 60; 130) for performing a light-based treatment operation on or to a subject, the treatment device (2; 30; 60; 130) comprising: a light source (12) for generating light for performing the treatment operation; a dichroic filter (34; 64; 104; 134) arranged at a first angle with respect to incident light such that the incident light is separated into a transmitted light component and a reflected light component according to a cut-off wavelength of the dichroic filter (34; 64; 104; 134), wherein the transmitted light component is transmitted through the dichroic filter (34; 64; 104; 134) and the reflected light component is reflected by the dichroic filter (34; 64; 104; 134); a light exit window (10) arranged with respect to the dichroic filter (34; 64; 104; 134) such that one of the transmitted light component and the reflected light component is emitted from the treatment device (2; 30; 60; 130) via the light exit window (10); a beam dump (44; 74; 140) configured and arranged with respect to the dichroic filter (34; 64; 104; 134) such that the other one of the transmitted light component and reflected light component is incident on the beam dump (44; 74; 140) and absorbed by the beam dump (44; 74; 140); and a heat sink (46; 76; 142) coupled to the beam dump (44; 74; 140) to dissipate heat from the beam dump (44; 74; 140); characterized in that the dichroic filter (34; 64; 104; 134) is provided on a first surface of a solid dichroic prism (38; 68) or an internal surface in a solid dichroic cuboid.
  2. The treatment device (2; 30; 60; 130) of claim 1, further comprising an absorption filter arranged with respect to the dichroic filter (34; 64; 104; 134) and the light exit window (10) such that the one of the transmitted light component and the reflected light component that is emitted from the treatment device (2; 30; 60; 130) via the light exit window (10) passes through the absorption filter.
  3. The treatment device (2; 30; 60; 130) of claim 2, wherein the absorption filter (48; 78; 144) is configured to absorb light having wavelengths corresponding to the wavelengths of the other one of the transmitted light component and the reflected light component.
  4. The treatment device (2; 30; 60; 130) of claim 2 or 3, wherein the absorption filter (48; 78; 144) is combined with the dichroic filter (34; 64; 104; 134).
  5. The treatment device (2; 30; 60; 130) of any of claims 1-4, further comprising, when the dichroic filter (34; 64; 104; 134) is provided on a first surface of a solid dichroic prism (38; 68), a second prism (39; 69) arranged in contact with the first surface of the solid dichroic prism (38; 68) such that the light component transmitted by the dichroic filter (34; 64; 104; 134) passes through the second prism (39; 69).
  6. The treatment device (2; 30; 60; 130) of claim 5, wherein a low refractive index boundary is provided at a second surface of the dichroic prism (38; 68) through which the reflected light component is to exit the dichroic prism (38; 68), wherein the low refractive index boundary has a lower refractive index than the dichroic prism (38; 68).
  7. The treatment device (2; 30; 60; 130) of any of claims 1-4, wherein, when the dichroic filter (34; 64; 104; 134) is provided on an internal surface in a solid dichroic cuboid, a low refractive index boundary is provided at a first surface of the dichroic cuboid through which the reflected light component is to exit the dichroic cuboid, wherein the low refractive index boundary has a lower refractive index than the dichroic cuboid.
  8. The treatment device (2; 30; 60; 130) of any of claims 1-7, wherein the dichroic filter (34; 64; 104; 134), light exit window (10) and beam dump (44; 74; 140) are configured with respect to each other such that the transmitted light component is emitted from the treatment device (2; 30; 60; 130) via the light exit window (10) and the reflected light component is incident on the beam dump (44; 74; 140).
  9. The treatment device (2; 30; 60; 130) of claim 8, wherein the dichroic filter (34; 64; 104; 134) is configured such that the transmitted light component comprises light having wavelengths above the cut-off wavelength, and the reflected light component comprises light having wavelengths below the cut-off wavelength.
  10. The treatment device (2; 30; 60; 130) of any of claims 1-7, wherein the dichroic filter (34; 64; 104; 134), light exit window (10) and beam dump (44; 74; 140) are configured with respect to each other such that the reflected light component is emitted from the treatment device (2; 30; 60; 130) via the light exit window (10) and the transmitted light component is incident on the beam dump (44; 74; 140).
  11. The treatment device (2; 30; 60; 130) of claim 10, wherein the dichroic filter (34; 64; 104; 134) is configured such that the transmitted light component comprises light having wavelengths below the cut-off wavelength, and the reflected light component comprises light having wavelengths above the cut-off wavelength.
  12. The treatment device (2; 30; 60; 130) of claim 10 or 11, wherein the treatment device (2; 30; 60; 130) comprises a diverging cavity section (152) and a converging cavity section (156), wherein the light source (12) is arranged towards a first end of the diverging cavity section (152), the light exit window (10) is arranged at an end of the converging cavity section (156), and the dichroic filter (34; 64; 104; 134) is arranged between the diverging cavity section (152) and the converging cavity section (156).
  13. The treatment device (2; 30; 60; 130) of claim 12, wherein the converging cavity section (156) and diverging cavity section (152) are configured such that light entering the converging cavity section (156) without reflecting from the dichroic filter (34; 64; 104; 134) is reflected by the converging cavity section (156) away from the light exit window (10) and towards the diverging cavity section (152).

Description

FIELD OF THE INVENTION This disclosure relates to a treatment device for performing light-based treatment operations on or to a subject. BACKGROUND OF THE INVENTION Techniques for the removal of unwanted hairs include shaving, electrolysis, plucking, laser and light therapies (known as photoepilation) and injection of therapeutic anti-androgens. Light-based technologies are also used in other types of dermatological treatments, including skin rejuvenation and treating acne. Light-based hair treatments inhibit the growth of hair by exposing the skin to bright flashes or pulses of light (in case of non-coherent sources), known as intense pulsed light (IPL). Through the use of an appropriate configuration of the light energy, i.e. in terms of wavelength, intensity and/or pulse duration (if the light is to be pulsed), selective heating of the hair root and subsequent temporary or permanent damage to the hair follicle can be achieved. The IPL may be generated by a high intensity light source such as a gas discharge lamp (e.g., a Xenon flash lamp). The light penetrates the skin and is absorbed, among other places, in the root of the hair by the pigment melanin. This causes an increase in the temperature of the root of the hair and subsequently the temperature of the surrounding tissue. The generated heat damages the hair follicles, and the growth of the hair is inhibited if the temperature rise is sufficient. This process is known as photothermolysis. When the treatment is repeated in intervals of 2 to 4 weeks, a long-lasting hair reduction is achieved. The main optical components of the light arrangement in a typical IPL device are a light source such as a flash lamp, a concave back reflector, side reflectors and an absorption filter. The flash lamp emits light in all directions. The back reflector and side reflectors form a reflective cavity around the lamp that directs the light towards the skin (i.e. the reflective cavity can collimate the light emitted by the lamp). A Xenon flash lamp can be used. As these lamps have a broad emission spectrum, the IPL device can comprise a long-pass absorption filter with a cut-off between 500 and 600 nanometres (nm) to prevent shorter wavelengths of light from reaching the skin. These shorter wavelengths are typically absorbed by haemoglobin in the blood and would otherwise cause discomfort and side effects to the subject, whereas the longer wavelengths of light are passed by the filter and are incident on the subject to perform the photothermolysis process on the skin/hairs. Due to the absorption of the unwanted light (the shorter wavelengths of light), the absorption filter gets hot. When flashing an IPL device for a prolonged period at high repetition rate, the absorption filter gradually increases in temperature and may reach temperatures in excess of 200°C. This high temperature is perceived as unpleasant by the subject or device user through the radiative heat passing through the aperture (light exit window) to the skin as well as from the aperture materials themselves becoming too hot to touch. In addition, the filter may exceed safe touching temperatures. This may be a problem because the filter can be exposed to the user when an attachment is exchanged or cleaned. Furthermore, the cut-off wavelength may shift as a function of the filter temperature. As an alternative to the use of an absorption filter to separate the light into the treatment light (i.e. the light that is to effect the hair removal operation) and the unwanted light (e.g. shorter wavelengths of light), the absorption filter may be replaced by a dichroic filter, such as a long-pass dichroic reflectance filter or a short-pass dichroic filter reflectance filter. However, in this case the unwanted light is still present in the treatment device and can 'reflect around' the interior of the treatment device, potentially damaging components, and also exit the treatment device through the light exit window. In these arrangements, while the dichroic filter acts as the primary separator for the generated light into the treatment light and the unwanted light, an absorption filter can be provided at or near the light exit window to absorb any 'stray' unwanted light that would otherwise exit the treatment device. However, where much of the unwanted light separated by the dichroic filter reflects around the interior of the treatment device, the absorption filter will absorb a lot of light, leading to the heating problems outlined above. For example, a large fraction of the light reflected by the dichroic filter can find its way back to the absorption filter via multiple reflections in the reflective cavity surrounding the lamp, until it is incident on the dichroic filter at a large angle. At large angles, the dichroic filter will inevitably have a leak and transmit that component of light to the absorption filter. Through this recycling process, a significant part of the energy at the shorter wavelength end of the