WO2013046086A1

WO2013046086A1 - Skin treatment device with radiation emission protection

Info

Publication number: WO2013046086A1
Application number: PCT/IB2012/054803
Authority: WO
Inventors: Guofu Zhuo; Jorgen Meeusen
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2011-09-26
Filing date: 2012-09-14
Publication date: 2013-04-04

Abstract

A light emitting device for application near mammal tissue is disclosed. The device includes at least one light source for emitting light towards a light emitting surface and at least one tissue sensor for detecting the presence of mammal tissue facing said light emitting surface. The device further includes a controller for controlling the at least one light source as a function of a value received from the at least one tissue sensor, wherein the at least one tissue sensor is a temperature sensor.

Description

Skin treatment device with radiation emission protection

FIELD OF THE INVENTION

The present invention relates to a skin treatment device for treating skin by means of radiation. More specifically, the present invention relates to a skin treatment device and a method of skin treatment which prevents undesired emission of radiation when the skin treatment device it is not in a position for skin treatment.

BACKGROUND OF THE INVENTION

It is well known that the application of light and/or heat to mammal tissue may achieve a therapeutic or healing effect, not only in the superficial skin layers (epidermis) but also in deeper layers (subcutaneous layer, fatty tissue, muscles, etc.). In all applications of light and/or heat to mammal tissue, safety is a primordial concern.

WO 2006/038168 Al discloses a skin treatment device comprising a radiation source mounted in a housing, such that radiation can be emitted through an exit opening in the housing. The device further comprises at least one skin presence sensor capable of measuring the presence of skin in a number of respective positions, and a control unit which is constructed to determine a covered portion of the exit opening from a measurement signal of the skin presence sensor and to restrict emission of the radiation to the covered portion of the exit opening. Disclosed skin presence sensors may include a physical pressure sensor, a gas flow sensor, an electrical impedance sensor (pair of electrodes), a light

reflection/scattering sensor, or a heat conductivity sensor.

SUMMARY OF THE INVENTION

It would be advantageous to have a light and/or heat emitting device for application near mammal tissue that is safe to operate at minimal additional cost.

To better address this concerns, in a first aspect of the invention a light emitting device for application near mammal tissue is presented that comprises at least one light source for emitting light towards a light emitting surface and at least one tissue sensor for detecting the presence of mammal tissue in front of said light emitting surface. A controller is provided for controlling the at least one light source as a function of a value received from the at least one tissue sensor, wherein said at least one tissue sensor is a temperature sensor. The light emitting device may be controlled to switch on only upon detection of mammal tissue in front of the light emitting surface. An advantage of the invention is the fact that light emitting devices used in for example skin treatment often already have a temperature sensor build in for shutting off the device when the skin temperature increases to dangerous levels with substantial risk of overheating or burns. The invention thus further increases the safety of the device at no additional cost.

The temperature sensor may be a contactless sensor such as an IR temperature sensor or a contact sensor such as a thermocouple. Both types of sensor are relatively small and can be easily integrated in a light emitting device.

In a preferred embodiment, the controller may be arranged for controlling the light source at a reduced light intensity or disable the light source when the tissue sensor value is indicative for the absence of mammal tissue. The advantage of controlling the light source at reduced light intensity when the device is not applied near the tissue is that it is possible to inspect the light source, while operating at a safe intensity level, before the device is applied near or to the mammal tissue. The detection whether mammal tissue is absent in front of the light emitting surface may be based on the detection of a temperature value lower than the ambient skin temperature, which is approximately 33°C, or a temperature value representative for ambient temperature. Ambient skin temperature is defined as the skin temperature under normal conditions. Ambient temperature may for example refer to room temperature.

In a further embodiment, the controller may be arranged for controlling the light source according to a light protocol suitable for light and/or heat treatment of mammal tissue, only when the tissue sensor value is indicative for the presence of mammal tissue. The detection of mammal tissue in front of the device is a good and reliable indication that the device is applied near or to the tissue and that the risk of the user looking into the light has disappeared. Hence, the device can be operated at full functionality, at whatever light intensity needed for the light and/or heat treatment. Detection of the presence of mammal tissue may be based on a temperature value reading higher than the ambient skin temperature, which is approximately 33°C (i.e. normal human skin temperature). In a further embodiment, a temperature value reading above approximately 43°C may be indicative for potential danger of burns or overheating of the tissue and the controller may be arranged to switch off the light source or drive the light source at reduced intensity so as to protect the mammal tissue and further allow the user to safely remove the device from the tissue. A skin temperature of approximately 43°C is considered the maximum allowable safe skin temperature.

In another preferred embodiment, the light emitting device may comprise a plurality of light sources for creating a larger light emitting surface and thus irradiating a larger area of mammal tissue at once. The temperature sensor may then provide input to the controller for controlling the plurality of light sources together.

The safety of the light emitting device may be further increased by providing a plurality of tissue sensors for detecting the presence of mammal tissue at a plurality of locations across or surrounding the light emitting surface. The controller may then be arranged for controlling the light source or the plurality of light source as a function of a value received from at least one tissue sensors. The plurality of tissue sensors may be used to create redundancy in the device and to make sure at least one sensor is always available for detection or plurality of tissue sensors may be used to have multiple sensor values combined into a more reliable detection. The plurality of tissue sensors may also be used to create a contact map, i.e. a map of locations where the light emitting device is properly contacting or facing the tissue. The controller may use this information to generate a corresponding light map and control the light source or the plurality of light sources to emit light only at those locations where mammal tissue is detected in front of the device. For this purpose, it is advantageous that the plurality of tissue sensors are located in between the plurality of light sources, which may be realized by having an array of sensors mixed or interwoven with an array of light sources. Alternatively the plurality of tissue sensors may be position at the periphery of the light emitting surface and surround the light sources.

In a specific embodiment of a light emitting device suitable for pain relief of human skin, the one or more light source are light emitting diodes (LEDs) emitting light in a wavelength range 410-480 nm. A safe operating level to avoid blue-light hazard when looking into blue light, with a high photon energy content, is thought to correspond to a power density lower than 5 mW/cm2 emitted from the light emitting surface. As tissue sensors, contactless IR sensors may be used. Both the LEDs and IR sensors may be arranged and mixed on a single substrate such as for example a flexible PCB or electronic textile.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects, as well as additional objects, features and advantages of the present invention, will be more fully appreciated by reference to the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, when taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a cross section of an embodiment of the invention.

Fig. 2 is a block diagram of a software program that may be executed by a controller of a light emitting device according to an embodiment of the invention.

DETAILED DESCRIPTION

Fig. 1 illustrates a blue light-emitting device with an integrated infra-red temperature sensor. The temperature sensor 2 is arranged on the same substrate 1 , on the same side and oriented in the same direction as the light sources (LEDs) 3. The temperature sensor is used to detect the presence of skin 4. A temperature is measured and compared with the ambient human skin temperature, i.e. the temperature of human skin in normal condition (not being treated). When the detected temperature is below the ambient human skin temperature, e.g. 33°C, the device will emit light at the lowest intensity or is fully disabled. The device will switch to the desired treatment optical intensity only when the detected temperature is equal to or above the ambient human skin temperature. The temperature sensor will prevent the human eye from (accidentally) looking direct into the light source when it is driven at the full light intensity.

Fig. 2 shows example of a block diagram for a controlling algorithm according an embodiment of the invention. When a user tries to switch on the device, the temperature sensor will measuring the skin temperature and compare the measurement with the ambient human skin temperature value, which may for example be preset to e.g. 33C°. If the detected temperature is below this skin temperature reference value, the device will be disabled or switch on only at low intensity. If the detected temperature is equal to or above the skin temperature reference value, the device is enabled and will apply a desired, possibly time varying, skin irradiance level according to a treatment program. During skin irradiation, the temperature sensor may be continuously, periodically or via interrupt read and compared with the ambient skin temperature reference value. If the detected temperature is below this reference value, this is indicative for a detachment of the device from the skin and the device will be immediately switched off or switch to low intensity. Otherwise, light irradiation will continue until a full treatment program is completed.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. For example, it is possible to operate the invention in an embodiment wherein some light sensors are added to the system to identify the presence of mammal tissue with alternative measurement techniques based on for example reflection or scattering of light from mammal tissue.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A light emitting device for application near mammal tissue, comprising:

an application surface for positioning near and facing mammal tissue, the application surface comprising a light emitting surface;

at least one light source for emitting light towards said light emitting surface; - at least one tissue sensor for detecting the presence of mammal tissue facing said application surface, and;

a controller for controlling said at least one light source as a function of a value received from said at least one tissue sensor,

wherein said at least one tissue sensor is a temperature sensor.

2. The light emitting device according to claim 1 wherein said tissue sensor is a contactless sensor, preferably a IR temperature sensor.

3. The light emitting device according to claim 1 wherein said tissue sensor is a contact sensor, preferably a thermocouple.

4. The light emitting device according to claim 1 wherein said controller is arranged for controlling said at least one light source at a reduced light intensity or disable said at least one light source when said tissue sensor value is indicative for the absence of mammal tissue.

5. The light emitting device according to claim 4 wherein the absence of mammal tissue is based on a temperature value lower than the ambient skin temperature, which is approximately 33°C or a temperature value representative for ambient temperature.

6. The light emitting device according to claim 1 wherein said controller is arranged for controlling said at least one light source according to a light protocol suitable for light and/or heat treatment of said mammal tissue when said tissue sensor value is indicative for the presence of mammal tissue.

7. The light emitting device according to claim 6 wherein the presence of mammal tissue is based on a temperature value higher than the ambient skin temperature, which is approximately 33°C (normal human skin temperature) and lower than

approximately 43°C (maximum allowable skin temperature).

8. The light emitting device according to claim 1 comprising a plurality of tissue sensors for detecting the presence of mammal tissue facing a plurality of locations across said application surface and wherein said controller is arranged for controlling said at least one light source as a function of at least one value received from at least one of said plurality of tissue sensors.

9. The light emitting device according to claim 8 comprising a plurality of light sources for emitting light towards a plurality of locations across said light emitting surface and wherein said controller is arranged for controlling said plurality of light sources as a function of at least one value received from at least one of said plurality of tissue sensors.

10. The light emitting device according to claim 1 wherein said at least one light source is an LED for emitting light in a wavelength range 410-480 nm and wherein said reduced light intensity is lower than 5 mW/cm2 emitted from said light emitting surface.

11. A method of irradiating mammal tissue using a light emitting device, comprising the steps of:

- detecting the presence of mammal tissue in front of said light emitting device by means of a temperature sensor;

operating a light source for irradiating said mammal tissue based on the detection of said mammal tissue in front of said device.