Skin treatment apparatus and methods of operation of the same

Abstract

Aspects of the present invention relates to a skin treatment device, preferably an Intense Pulsed Light (IPL) hair removal device for generation of high intensity pulses of broadband light The skin treatment device in one aspect comprises a cooling arrangement housed by the body, the cooling arrangement comprising a heat sink configured to cool the solid material; with a primary air flow pathway through at least a portion of the body with the heat sink in the primary air flow pathway, and a secondary air flow pathway through at least a portion of the body with the light source in the secondary air flow pathway, the device further comprising an air moving arrangement for causing air flow through the primary and secondary air flow pathways.

Description

[0001] TITLE

[0002] Skin Treatment Apparatus and Methods of Operation of the Same

[0003] BACKGROUND

[0004] The present invention relates to a skin treatment device, preferably an Intense Pulsed Light (IPL) hair removal device for generation of high intensity pulses of broadband light.

[0005] The light pulses are typically generated by discharging the electrical energy stored in a charge storage device through a xenon flashlamp delivering light energy in the form of pulses. The light from the lamp is passed through a filter to remove potentially harmful wavelengths in the ultraviolet and blue region. The light is then directed onto an area of skin for treatment. In IPL treatment the light energy intensity and pulse duration is optimised to safely target heating of the hair root to cause the hair root to die.

[0006] A typical skin treatment device comprises a handheld housing connected to a Power Supply Unit (PSU). The energy pulses pass from the light source, along a light transmission pathway and out of a transmission window in the housing and onto the skin of a user.

[0007] It is known in some skin treatment devices that the heads of the devices for contacting the skin are interchangeable or replaceable. There can be many reasons for this such as:

[0008] The desire to treat larger or smaller skin areas which could be for example easier and more difficult treatment areas (leg compared to lip for example) through the provision of different area output windows;

[0009] The desire to utilise different light filters that enable passing of different spectrum ranges to the skin;

[0010] The desire to provide different skin sensor capabilities. For example in some circumstances it is beneficial to allow:

[0011] o skin tone sensing to ensure appropriate energy is delivered for the specific user’s skin tone; and / or

[0012] o multi point skin contact sensing to ensure the device cannot emit an energy pulse unless appropriately oriented;

[0013] The desire to emit different fluence ranges.

[0014] P393888.WO.01Accordingly multiple interchangeable heads can be provided in order to achieve the desired functionality for the user.

[0015] It is further desirable in skin treatment devices where energy is delivered to the skin that the device includes functionality that enables cooling of the skin. This enables safer treatment as reduces the possibility of burning the skin.

[0016] An option to achieve this cooling effect is to utilise a cooling system comprising an actively cooled glass or sapphire block at the front of the device through which light energy is transmitted. The block is cooled below skin temperature providing a cooling and soothing effect to the skin. Accordingly, a suitable cooling system in either case may comprise:

[0017] - A skin contacting cooling element - sapphire block or metal plate

[0018] A Peltier / thermoelectric cooling element

[0019] A heat sink / radiator to remove the heat from the Peltier element

[0020] - A fan to force air over the radiator element and remove the heat from the device.

[0021] Interchangeable heads can be used as an attachment in a supplementary form to skin treatment devices that utilise an integrated cooling system. In this way for example a different size output window can be achieved. The head may attach to the front or leading end of the device effectively extending the length of the device. The head therefore covers the cooled metal plate or sapphire block, and spaces the metal plate or sapphire block from the skin. Accordingly, the device can be operated in two distinct modes with either the head attached or the head removed. When the head is attached, little or no cooling effect is provided by the metal plate or sapphire block due to the separation from the skin. With the head removed, the metal plate or sapphire block contacts the skin and direct cooling of the skin can be achieved.

[0022] Aspects of the present invention aim to provide improvements to skin treatment devices or at least provide a useful alternative. Some aspects aim to address problems associated with such a device that utilises skin cooling and removable head functionality or provide a useful alternative.

[0023] P393888.WO.01SUMMARY

[0024] Aspects of the present disclosure are set out in the accompanying independent and dependent claims. Combinations of features from the dependent claims may be combined with features of the independent claims as appropriate and not merely as explicitly set out in the claims.

[0025] First Aspect

[0026] According to an aspect of the present disclosure, there is provided a skin treatment device for delivery of light energy to skin of a subject, the skin treatment device comprising:

[0027] o a body having a transmission window;

[0028] o a light source housed within the body for emitting light energy along a light energy emission pathway through the transmission window;

[0029] o a solid material disposed in the light emission pathway through which light energy from the light source is transmitted;

[0030] o a cooling arrangement housed by the body, the cooling arrangement comprising a heat sink configured to cool the solid material;

[0031] the skin treatment device further comprising a primary air flow pathway through at least a portion of the body with the heat sink in the primary air flow pathway, and a secondary air flow pathway through at least a portion of the body with the light source in the secondary air flow pathway, the device further comprising an air moving arrangement for causing air flow through the primary and secondary air flow pathways.

[0032] The air moving arrangement may comprise a fan or a blower. The heat sink may also be termed a radiator.

[0033] The solid material temperature is increased by the heat generated by the light source (conduction, convection and direct radiation absorption). Therefore, the higher the power through the light source (energy per flash / time between flashes), then the higher the heat generated by the light source, and consequently the higher the heat input to the solid material. Therefore, the higher the cooling power and effectiveness of the solid material cooling arrangement, the higher the power that can be put through the light source whilst keeping the solid material below an effective or safe temperature. The first aspect therefore provides for improved cooling capability increasing the power that can be put through the light source P393888.WO.01thereby improving usability of the device (faster operation) whilst maintaining safety of the device for the user.

[0034] The primary air flow pathway may extend between an inlet and an outlet in the body.

[0035] The secondary air flow pathway may fork from the primary air flow pathway intermediate the inlet and the outlet.

[0036] The secondary air flow pathway may fork from the primary air flow pathway after the heat sink.

[0037] The secondary air flow pathway may rejoin the primary air flow pathway before the outlet.

[0038] The light source may be disposed in a chamber, and the chamber may be in the secondary air flow pathway.

[0039] The secondary airflow pathway may be at least partially intermediate the solid material and the light source.

[0040] The chamber is defined by a chamber wall, and a portion of the chamber wall either comprises or is in direct physical communication with the solid material. A rearward surface of the solid material may comprise a coating such as a dichroic filter, and the dichroic filter may form a portion of the chamber wall. This means that at least a part of the secondary air flow pathway is intermediate the solid material and the light source. This effectively partially insulates the light source from the solid material. A further part of the chamber wall is defined by a reflector for reflecting light energy towards the solid material. The light reflector effectively defines a part of the light guide.

[0041] A labyrinth region may be provided downstream of the chamber for restricting light energy transmission from the chamber. Such a labyrinth region may be specifically designed to limit light reflection further downstream through the provision of reduced cross-sectional area and / or multiple direction changes in the secondary air flow pathway.

[0042] P393888.WO.01The cooling arrangement may comprise a Thermoelectric Cooling System. The cooling arrangement may further comprise a Peltier in physical contact with the solid material and the heat sink.

[0043] The Peltier and solid material may comprise a thermal pad therebetween. The thermal pad beneficially improves the thermal bond between the Peltier and solid material. The cooling arrangement may further comprise a heat pipe extending between the Peltier and the heat sink.

[0044] The solid material may comprise a block. The solid material may comprise a sapphire block. The solid material may comprise a skin contact surface. The skin contact surface is therefore in contact with the skin in operation. The solid material is a light transparent material.

[0045] The fan arrangement may be downstream of the heat sink. This means that the fan arrangement draws air through the inlet and subsequently through the heat sink.

[0046] The device may comprise a reflector for reflecting light energy emitted by the light source towards the solid material. The light source may be disposed forwardly of the reflector. The reflector is beneficially curved, and the light source is positioned within the curve of the reflector. The reflector may be parabolic in cross section.

[0047] A second heat sink may be provided in the primary air flow pathway in communication with the light reflector. Accordingly, the primary air flow through the primary air flow pathway is used to remove significant heat energy from the reflector by virtue of the heat sink.

[0048] The average cross-sectional area of the primary air flow pathway is greater than the average cross sectional area of the secondary air flow pathway. This is beneficial to ensure fast air flow through the primary airflow pathway to optimise cooling of the heat sink and thereby optimise the power through the device through cooling of the solid material (as discussed above) improving for example pulse repetition rate. The primary air flow pathway is beneficially configured to enable faster air flow therethrough. This may be achieved by cross sectional area and / or less resistance to air flow such as by providing disruptions to the air flow pathway.

[0049] P393888.WO.01The skin treatment device may comprise a control system for controlling delivery of light energy pulses from the light source, where the control system is at least partially disposed on a printed circuit board (PCB), and where the light source is mounted to the PCB by a mounting bracket, the skin treatment device further comprise a third air flow pathway through at least a portion of the body with the mounting bracket in the secondary air flow pathway, the fan arrangement arranged to further effect air flow through the third air flow pathway.

[0050] The third air flow pathway may branch from the primary air flow pathway (preferably downstream of the fan arrangement). The third air flow pathway may rejoin the primary air flow pathway.

[0051] The solid material may have a forward surface defining a skin contact surface and a rearward surface facing the light source, with a dichroic filter coating provided directly on the rearward surface. The provision of the secondary air flow pathway enables cooling of the solid material and therefore it has been found it is not essential to thermally isolate a wavelength filter (glass sheet with a dichroic coating) from the solid material.

[0052] Second Aspect

[0053] Many skin treatment devices such as those used in IPL utilise a flash lamp as a light source with a capacitor discharging over the light source to cause emission of a pulse of light energy. A charge control system is used to charge this capacitor in such devices and is designed to convert a relatively low voltage (from the mains supply or battery) to the higher voltage required in the main capacitor (normally in the range 250v to 450v).

[0054] Known charge circuitry in the charge control system is of a fairly simple design that is either on or off. When the capacitor is at the required voltage, the charger is off (not supplying energy), and when the capacitor is at a lower than required voltage (e.g. after a flash), then the charger is switched on to charge the capacitor. The 'speed' (time taken) at which the charger can charge the main capacitor (from a given low voltage to a given high voltage) is a fixed and constant quantity that is inherent in the design. This also means that the 'power' drawn by the charger is constant (on average over a charge cycle). The charge control system is designed to charge at the speed needed to meet the requirement for minimum time between flashes.

[0055] P393888.WO.01However, it is also typical that the time between flashes of an IPL device increases as the device heats up. That is, when the device is cold, it will flash at a first short time between flashes. As the device becomes hot, the time between flashes is increased in order to reduce the rate of heat generation and give the device more time to cool down. To achieve the longer time between flashes, a pause is often introduced after the main capacitor is charged.

[0056] In addition to the electrical energy used by the charger to charge the main capacitor, an IPL device also needs electrical energy to run other systems, including:

[0057] ■ Microprocessor, sensors, user interface etc.

[0058] ■ Cooling fan

[0059] ■ Peltier (TEC) module (optional) for a contact cooling system.

[0060] The power source has a finite power output meaning that the power drawn is highly variable leading to sudden peaks and troughs which results in various issues associated with heating effects and stress on components.

[0061] An improvement has been devised.

[0062] A skin treatment device for delivery of light energy pulses to a subject’s skin, the skin treatment device comprising:

[0063] a body having a transmission window;

[0064] a light source housed within the body for discharging light energy through the transmission window;

[0065] a capacitor for discharge over the light source;

[0066] a charge control system for controlling charging of the capacitor;

[0067] wherein the charge control system charges the capacitor at a charging speed dependent upon operation of the device.

[0068] This means that the different charge speeds (time to charge from a given first voltage to a given second voltage) can be utilised. The instantaneous power drawn from the charging system can be increased or decreased.

[0069] P393888.WO.01There are significant benefits associated with this aspect. Power drawn from the mains or battery power supply is better managed. This means that power drawn is less variable and peaks are lower. This averages out heating effects, reduces peak stress and other issues associated with high power draw.

[0070] Operation of the device may be dependent on internal operating parameters of the device. This could for example be that temperature of the device may increase because of multiple consecutive light energy pulses being emitted requiring additional fan speed in which case the speed of charging the device is reduced meaning fan speed can be increased. Another example could be if the device can provide additional treatment capability or effect such as skin cooling or alternative energy mode of energy emission (eg emit radiofrequency or light from LEDs) then input energy from the power source may be directed towards the features requiring energy input in partial or complete preference to charging of the capacitor. Another example may be that the user requires a different effect (such as increased skin cooling) and selects an appropriate user input for this effect, meaning the charge control system charges the capacitor at a decreased charging speed such that power may be diverted to achieve the cooling effect.

[0071] The speed of charging of the capacitor is therefore adapted to be optimised to the operation of the device.

[0072] The charge control system may charge the capacitor at a charging speed selected from a plurality of different charging speeds dependent upon operation of the device.

[0073] The device may comprise one or more sensors (such as a temperature sensor) and the charge control system may select a charging speed to charge the capacitor dependent upon one or more sensor inputs from the one or more sensors. The charging speed is therefore controlled dependent upon operation of the device which is sensed by the sensor.

[0074] The device may comprise a user input for a user to select an operating parameter of the device, where the control system may select a charging speed to charge the capacitor dependent upon the selected input.

[0075] P393888.WO.01The input may be used to select parameters individual to that user, so for example if a user preferred additional cooling the charging speed of the capacitor may be reduced whilst the power to a cooling system may be increased. The speed of charging is therefore adapted to be optimised to the desired operation.

[0076] The device may be further arranged such that the light source emits light energy along a light emission pathway and out of the body; the device further comprising:

[0077] a solid material disposed in the light emission pathway through which light energy from the light source is transmitted, the solid material defining a first skin contact surface for providing contact with a subject’s skin;

[0078] a cooling arrangement housed by the body configured to cool the solid material; a head arranged to be mountable and demountable to the body, the head comprising a rearward end for releasably mounting to the body and extending to a forward end comprising a second skin contact surface, the head defining an extension of the light emission pathway from the first contact surface to the second contact surface;

[0079] the device being operable in a first configuration with the head demounted from the body and a second configuration where the head is mounted to the body such that in the second configuration the first skin contact surface is spaced apart from the subject’s skin and the light energy pulses pass through both the solid material of the first lightguide and the extension of the light emission pathway; wherein in the first configuration the charge control system is arranged to control charging of the capacitor at a first speed and in the second configuration the charge control system is arranged to control charging of the capacitor at a second speed different to the first speed.

[0080] The second speed may be greater than the first speed. Accordingly, without the head attached the optical power output is relatively low and this means that the time between emission of energy pulses is relatively long. Further the cooling system requires additional power to maintain the solid material (and thus the skin) cool. Accordingly, the speed of charging of the capacitor can be reduced, and additional power supplied to the cooling system. With the head attached, the solid material is spaced apart from the skin and it is less important to maintain cool meaning the optical power can be higher and the power supplied to the cooling system relatively lower. Accordingly with the head attached flash rate can be maximised.

[0081] P393888.WO.01The cooling system may comprise a Thermoelectric Cooling (TEC) system, preferably a Peltier and a heat sink. The Peltier may be in direct physical communication with the solid material. The cooling system is beneficially as described with respect to other aspects of the invention.

[0082] The light emission pathway between the first and second skin contact surfaces may comprise an airgap. The second skin contact surface may define an opening to the extension of the light emission pathway.

[0083] The charger is designed to charge at the speed needed to meet the requirement for minimum time between flashes.

[0084] Third Aspect

[0085] It is necessary to restrict the wavelength ranges of light emitting devices that emit light energy to the skin to ensure that harmful wavelengths such as those in the ultraviolet and blue regions do not contact the skin. For this reason, dichroic filters are utilised to restrict wavelengths to those that provide a benefit and remove those that are harmful. These filters are typically manufactured of glass into a relatively thin (i.e. less than 2mm) sheet onto one side of which is applied the dichroic coating. The coated glass sheet is then positioned into a slot or similar in the body of the device at a location that is spaced apart (e.g. by around 0.5mm) from a cooled solid block which is designed to provide cooling to a user when the device is in operation.

[0086] Such a configuration is adopted for multiple reasons in addition to the requirement to enable wavelength filtering. A first reason for the provision of a filter in the form of a coated glass sheet is the area of the front and rear faces of the sheet can be larger than the adjacent face of the solid material. This increases the creepage distance between the high voltage reflector that partially surrounds the lamp and any electronics that may be forwardly of the glass sheet such as a Peltier element in communication with the solid material or contact sensors at the forward edge of the device for determining contact with a user’s skin to allow discharge of light energy pulses. A second reason is that the coated glass sheet can isolate the solid material from high components and air near to the lamp.

[0087] P393888.WO.01It is desirable to improve the light energy transmission efficiency of existing devices which is reduced by virtue of the glass sheet and air space between the glass sheet and the solid material.

[0088] According to an aspect of the present disclosure, there is provided a skin treatment device for delivery of light energy to skin of a subject, the skin treatment device comprising:

[0089] o a body;

[0090] o a light source housed within the body for emitting light energy along a light emission pathway through a transmission window;

[0091] o a solid material disposed in the light emission pathway through which light energy from the light source is transmitted, the solid material for providing a cooling effect to skin of a subject, the solid material having a forward surface defining a skin contact surface and a rearward surface facing the light source; o a dichroic filter coating provided directly on at least one of the skin contact surface and the rearward surface.

[0092] The dichroic filter coating is a coating on the skin contact and / or rearward surface meaning it is in direct contact with the respective surface. The coating is therefore not a separate and distinct item to the solid material. The coating is deposited on the respective surface during manufacture. The solid material is arranged to be cooled during operation by a cooling arrangement such as a Thermoelectric Cooling system (TEC) thereby applying a cooling effect to a user’s skin. The provision of the coating directly applied to the solid material means that light transmission efficiency is significantly increased (in the order of greater than 10%).

[0093] The dichroic filter coating may be provided directly on the rearward surface. This is beneficial as the coating is then protected from damage and contaminants. Further it is possible that a surface contaminant such as oil may affect the performance of the coating.

[0094] The dichroic filter coating may have a cut-on value of between 500 and 600nm.

[0095] The solid material may be sapphire.

[0096] P393888.WO.01The forward and / or rearward surfaces of the solid material may comprise an anti reflective coating thereon. An antireflective coating improves transmission of light into the solid material by reducing the refractive index. The anti-reflective coating can be applied to the same surface as the dichroic coating.

[0097] The skin treatment device may further comprise a cooling arrangement housed by the body for cooling the solid material, the cooling arrangement comprising a heat sink configured to cool the solid material.

[0098] The cooling arrangement may comprise a Thermoelectric Cooling (TEC) system.

[0099] The cooling arrangement may comprise a Peltier for transferring heat energy away from the solid material to the heat sink.

[0100] The device may comprise a reflector for reflecting light energy emitted by the light source towards the solid material. The light source is disposed forwardly of the reflector. The reflector is beneficially curved, and the light source is positioned within the curve of the reflector. The reflector may be parabolic in cross section.

[0101] There may be an electrical isolator between the Peltier and the reflector and light source in order to electrically isolate the Peltier from both of the light source and the reflector. The electric isolator may take various forms, such as potting the Peltier, providing an insulating seal or extending the length of a thermal pad intermediate the Peltier and the solid material. Other conductive or electronic components should also be electrically isolated, for example the TEC further comprises one or more heat pipes for transferring heat away from the Peltier and the one or more heat pipes are also beneficially electrically isolated, as are any other electronic components in the vicinity.

[0102] Fourth Aspect

[0103] Some known skin treatment devices in IPL utilise a solid material such as a sapphire block in the light energy transmission pathway from the light source and skin of a user. The sapphire block is cooled below skin temperature (typically) by a TEC system comprising a Peltier mounted to the surface of the sapphire block. The heat from the Peltier is removed by a heat sink (radiator) where airflow over the radiator is generated by a fan inside the device which P393888.WO.01draws cool air from outside the device into the device, and then back out of the device once it has absorbed heat from the radiator.

[0104] Existing skin treatment devices using a Peltier leave the control of the Peltier 'open loop'. This means that the Peltier is powered by a fixed current / voltage supply and is continuously powered whilst the device is on. The temperature of the sapphire is therefore uncontrolled.

[0105] If the device is not flashing thereby emitting light energy pulses, the heat input to the sapphire is relatively low, and the sapphire temperature will drop until equilibrium is reached between the Peltier 'cooling power', the heat conduction from surroundings into the sapphire, and the heat transfer out of the Peltier into the heat transmission element and ultimately into the air flow. This can be as low as -5degC. One problem with this low temperature is that condensation can occur on the sapphire, and even ice can form. This reduces the efficiency of light transmission. Additionally, very cold temperatures are uncomfortable to the user.

[0106] If the device is flashing and therefore emitting light energy pulses, then the heat input to the sapphire is significantly increased (from light absorption, heat conduction from the surroundings and also heat absorption from the skin). The temperature of the sapphire will increase, again until equilibrium is reached between the Peltier power, heat input and heat output to the air flow. Depending on the situation, the sapphire temperature can increase until it is above the skin temperature. In this case, the sapphire is no longer providing cooling to the skin but instead heating the skin. This can be a potential hazard, particularly in combination with the heat supplied by a flash.

[0107] This aspect aims to address the above mentioned deficiencies or at least provide a useful alternative.

[0108] According to an aspect of the present disclosure, there is provided a skin treatment device for delivery of light energy to skin of a subject, the skin treatment device comprising:

[0109] o a body having a transmission window;

[0110] o a light source housed within the body for emitting light energy along a light energy emission pathway through the transmission window;

[0111] o a solid material disposed in the light emission pathway through which light energy from the light source is transmitted;

[0112] P393888.WO.01o a temperature sensor configured to sense temperature of the solid material and output temperature information;

[0113] o a control system for controlling operation of the device;

[0114] the temperature sensor and control system being in operable communication such that the control system receives the temperature information and controls operation of the device using the temperature information.

[0115] The control system may control delivery of light energy as light energy pulses delivered at a pulse repetition frequency, where the control system may control operation of the device by modifying the pulse repetition frequency dependent upon the temperature information. As an example, if the solid material becomes too hot, then the flash rate may be slowed down, or even stopped to reduce the heat input to the solid material, so that the temperature stops rising or the temperature decreases to an acceptable level. Once this level is achieved then the flash rate can again increase.

[0116] The control system may control delivery of the light energy as delivery of light energy pulses, and wherein the control system may control operation of the device by controlling the fluence of the light energy pulses dependent upon the temperature information. For example, the fluence may be reduced if the temperature of the solid material is too high to thereby have the effect of reducing the overall temperature rise of the skin. Alternatively, reducing the fluence at a fixed flash rate will reduce the heat energy input to the solid material stopping the temperature rise or reducing the temperature of the Sapphire.

[0117] The device may comprise a cooling arrangement housed by the body, the cooling arrangement comprising a Thermoelectric Cooling (TEC) system for cooling the solid material, the TEC comprising a Peltier in communication with a heat sink, wherein the control system may be configured to modify power supplied to the Peltier dependent upon the temperature information.

[0118] The device may further comprise a temperature sensor mounted to the TEC system for measuring the temperature on an opposite side of the Peltier to the solid material and output secondary temperature information, and wherein the control system is arranged to determine a temperature differential between the temperature information comprising primary

[0119] P393888.WO.01temperature information and the secondary temperature information, and wherein the control system is arranged to control operation of the device based on the temperature differential.

[0120] There are benefits associated with the ability to calculate a value for or infer the temperature differential. A first benefit is in damage protection. There is a maximum allowable temperature difference across a Peltier before it will be damaged. If the measured temperature across the Peltier is too high, then the power supplied to the Peltier could be reduced or switched off.

[0121] Another benefit of determining or inferring a temperature differential is optimisation of Coefficient of Performance (COP). The COP of a Peltier is related to the power provided to the Peltier and also the temperature difference across the Peltier. Therefore, in order to optimise the performance during operation, the power provided could be modified dependant on the temperature differential.

[0122] The control system may control delivery of light energy as light energy pulses, and the control system may be configured to prevent emission of light energy pulses if the sensed temperature of the solid material exceeds a predetermined value.

[0123] The device may comprise a visual indication of the temperature of the solid material.

[0124] The temperature sensor may be an Infrared (IR) temperature sensor.

[0125] A clamp may be provided arranged to clamp the temperature sensor to the solid material. This is advantageous to ensure a good thermal bond between the temperature sensor and the solid material by providing pressure from the sensor onto the solid material.

[0126] Fifth Aspect

[0127] Many skin treatment devices such as IPL devices that comprise a capacitor discharging over a flashlamp utilise the concept of providing interchangeable heads. These may provide different functionality for a user to allow treatment with a smaller output window for example allowing treatment of bony or sensitive treatment areas. Other functionality that could be modified is for example the ability to have different filters in different heads thereby allowing different light wavelengths to be pass through and onto the skin. In another example, the P393888.WO.01device may comprise a solid material with a cooling system to cool the solid material in the light emission pathway. The solid material has a skin contact surface which provides a cooling effect to the skin whilst being treated. Such a device may then have a supplementary head that can be attached that spaces the skin contact surface from the skin and may be operated in this operable configuration with the head attached.

[0128] Accordingly, in any of these examples, output parameters of the device must be modified depending on whether the head is attached or detached from the body of the device. Such parameters may comprise as examples only pulse duration, fluence and capacitor voltage. When a head is attached, the control system of the device interrogates the head for an identifier. The control system then looks up the parameters associated with that identifier in the control system memory, and the device is then operated accordingly. For example, when a head is attached, the requirement is for a lower fluence for a specific skin tone as it is deemed that the device is being used for more sensitive body areas plus the output window is smaller meaning the fluence on skin (for the same skin tone) must be reduced. Accordingly, the capacitor voltage can be reduced, or discharge of the capacitor over the flashlamp can be terminated earlier.

[0129] Whilst such a set up will mean that light emission parameters are modified according to the attached head, the present invention provides an improved arrangement or at least a useful alternative.

[0130] According to an aspect there is a skin treatment device for delivery of light energy to skin of a subject, the skin treatment device comprising:

[0131] a body having a transmission window;

[0132] a light source housed within the body for emitting light energy pulses along a light energy emission pathway and through the transmission window;

[0133] a control system for controlling delivery of the light energy pulses having light energy pulse parameters from the light source by controlling light source drive parameters to the light source;

[0134] - the device being operable in a first configuration where light energy pulses are emitted along the light energy emission pathway and through the transmission window;

[0135] P393888.WO.01a head arranged to be mountable and demountable to the body, the head comprising a rearward end for releasably mounting to the body and extending to a forward end, such that when the head is mounted to the body the head defines an extension of the light emission pathway to a secondary transmission window at the forward end, the head further comprising a memory having stored light source drive parameters to deliver corresponding light energy pulse parameters; - the device being operable in a second configuration with the head mounted to the body, wherein the control system is arranged to identify operational engagement between the head and the body, and further read the stored light source drive parameters and apply the light source drive parameters to cause delivery of light energy pulses from the light energy source through the extended light emission pathway and from the secondary transmission window.

[0136] The device is beneficially configured to detect whether the head is mounted or demounted from the housing.

[0137] The head can therefore be mounted without the control system of the device already having stored operating information regarding the head. Instead, the head can be mounted and the operating information stored on the head, which is the light source drive parameters to cause the desired associated effect on the light energy pulse, is interrogated by the control system of the device and the appropriate control can therefore be given applicable to that specific head. Accordingly, new heads with different operating requirements can be readily introduced without requiring the device to be appropriately programmed.

[0138] The light source drive parameters may comprise one or more of duration of energy delivered to the light source for controlling light energy pulse duration, time period between consecutive deliveries of energy to the light source to control light energy pulse rate and quantity of energy delivered to the light source per pulse. It will be appreciated that there are many potential drive parameters that the head may store. The head may store one or more of intended fluence to be delivered to skin for each skin tone and setting, treatment area of the head, optical power output table (dependant on handset temperature) which is used to calculate the flash rate at a given fluence and capacitor charge voltage per mode. The head may also store a head efficiency value equal to the energy out of head divided by the energy into head because of energy losses in the head.

[0139] P393888.WO.01Other drive parameters that could be stored energy per flash, treatable skin tones, skin sensor operation parameters (skin tone or skin contact), Peltier cooling parameters such as on / off / power etc, throttling parameters relating to how fast to flash at various measured temperatures.

[0140] The device may comprise a capacitor for discharge over the light source (preferably a flashlamp) for delivery of the light energy pulses, wherein the light source drive information may comprise one or more capacitor voltage values.

[0141] The head may comprise one or more sensors for measuring a skin property, and the head may be configured to determine contact with the skin from the measured property, and wherein the head may be configured to transmit information regarding skin contact to the control system, where the control system is further arranged to control delivery of light energy pulses dependent the information received. For example, the head comprises electronics configured to utilise the measured property, and based on this measured property determine whether there is contact with the skin. A signal can then be transmitted to the control system to control delivery of light energy pulses. This may be to prevent light energy pulses being emitted if there is no signal sent indicative of skin contact. This may also or alternatively be a skin tone measurement taken by one or more sensors, and the corresponding light source drive parameter(s) may be transmitted to the control system derived from the skin tone measurement.

[0142] Sixth Aspect

[0143] IPL skin treatment devices typically utilise a flashlamp and a capacitor that discharges over the flashlamp and thereby causes the flashlamp to emit a light energy pulse. There are three voltages required to successfully trigger emission of a light energy pulse from a flashlamp. They are as follows:

[0144] a) The voltage of the capacitor storage capacitor, which supplies the flash energy. This is typically around 300 to 400V in a home use IPL device but this may be lower in some operational circumstances where for example a lower fluence on the skin is required. This main capacitor is typically charged from the mains power supply (or a battery) by an electronic charger circuit which stops charging once the desired main capacitor voltage is reached.

[0145] P393888.WO.01b) A higher 'boost voltage' applied across the flashlamp anode and cathode at the point of triggering that helps drive lamp ionisation. This typically needs to be around 800V for a 30mm arc length quartz, xenon flashlamp in a home use device. However, it is dependent on the exact lamp properties. This high voltage is typically generated using an electronic doubler or tripler circuit from the main capacitor voltage.

[0146] c) A low energy oscillating trigger voltage applied externally to the flashlamp to initiate ionisation. This is typically around 8Kv and is applied to the lamp reflector or sometimes a trigger wire wrapped around the lamp. This voltage is also typically generated from the voltage in the main capacitor which is transformed up to the high voltage via a 'trigger coif.

[0147] A common problem with the typical method of boost voltage and trigger voltage generation is that it is dependent on the voltage of the main capacitor. In some operational circumstances, for example when it is desirable to provide a lower fluence on the user’s skin, the main capacitor must be charged to a lower voltage to achieve the required fluence. If the main capacitor is charged to a lower voltage e.g. 200V, then the dependent voltages would also be much lower, which may result in a failure to trigger the lamp.

[0148] This aspect of the invention aims to address this problem or at least provide a useful alternative.

[0149] According to an aspect there is a method of delivering light energy pulses from an Intense Pulsed Light (IPL) device, the IPL device comprising a body having a transmission window, a flashlamp housed within the body for emitting light energy pulses along a light energy emission pathway and through the transmission window; a primary charge storage element for discharging over the flashlamp to cause emission of a light energy pulse and a secondary charge storage element for discharging over the flashlamp to effect ionisation of the flashlamp; and a charge circuit for enabling charging of the primary and secondary charge storage elements from a power source;

[0150] the method comprising the steps of:

[0151] A) charging the primary and secondary charge storage elements from the power source; B) disconnecting the primary charge storage element from the power source;

[0152] C) further charging the secondary charge storage element while the first charge storage element is disconnected from the power source; and

[0153] P393888.WO.01D) discharging the secondary charge storage element to effect ionisation of the flashlamp such that the primary charge storage element discharges over the flashlamp to cause emission of a light energy pulse.

[0154] Accordingly, by disconnecting the primary charge storage element from the power source after charging to the required voltage, the secondary charge storage element can be charged to the higher necessary voltage independently of charging of the primary charge storage element.

[0155] It will be understood that there may be a single power source for charging the primary charge storage element and the secondary charge storage element. Accordingly, a single circuit can be utilised for charging the primary charge storage element and secondary charge storage element.

[0156] The primary and optionally the secondary (and optionally tertiary) charge storage elements each comprise a capacitor.

[0157] It will be appreciated that steps A-D of the method are performed in sequence.

[0158] The primary and secondary charge storage elements may be charged to a first voltage, and the step of charging the secondary charge storage element while the first charge storage element is disconnected from the power source is to a second voltage greater than the first voltage.

[0159] The primary and secondary charge storage elements may be charged simultaneously (in step A).

[0160] It will be appreciated that the primary charge storage element discharges over the flashlamp while the primary charge storage device is disconnected from the power source.

[0161] The primary charge storage element may be charged by closing a switching arrangement in the charge circuit and may be disconnected from the power source by opening the switching arrangement.

[0162] P393888.WO.01The switching arrangement may comprise a first switch. The first switch may be arranged to automatically open upon the voltage on the capacitor reaching a predetermined voltage. Such a type of switch may be controlled by a charge controller to move from the open to the closed configuration. However, it may be further configured such that when current stops flowing through the switch (because a predetermined voltage is reached) then it is automatically opened.

[0163] There is beneficially a tertiary charge storage element for discharging a trigger voltage to the flashlamp for initiating ionisation of the flashlamp, where the charge circuit is further arranged for charging the tertiary charge storage element from the power source; and where the method further comprises charging the tertiary charge storage element while the first charge storage element is disconnected from the power source and discharging the tertiary charge storage element over the flashlamp to initiate ionisation of the flashlamp.

[0164] The tertiary charge storage element may be discharged to the flashlamp reflector (that reflects the light from the flashlamp in the required direction) or to a trigger wire wrapped around the lamp.

[0165] As described above a single circuit can be utilised for charging the primary charge storage element and secondary charge storage element, and the same single circuit can also be utilised for charging the tertiary charge storage element.

[0166] The secondary charge storage device may be charged to the predetermined voltage concurrently with charging the capacitor to the predetermined voltage. This effectively means that a boost voltage is applied to the second charge storage device after charging to the predetermined voltage.

[0167] The tertiary capacitor may be discharged while the first charge storage element is disconnected from the power source.

[0168] In step C the secondary charge storage device may be charged to a higher voltage than the voltage of the primary charge storage device.

[0169] P393888.WO.01The tertiary charge storage device may be charged to a higher voltage than the secondary charge storage device.

[0170] There may be provided a voltage boost circuit comprising the secondary charge storage element, and there may be a trigger circuit comprising the tertiary charge storage element for applying the trigger voltage to the flashlamp.

[0171] The method may further comprise repeating steps A-D.

[0172] According to a further aspect there is an Intense Pulsed Light (IPL) device, the IPL device comprising a body having a transmission window, a flashlamp housed within the body for emitting light energy pulses along a light energy emission pathway and through the transmission window; a primary charge storage element for discharging over the flashlamp to cause emission of a light energy pulse and a secondary charge storage element for discharging over the flashlamp to effect ionisation of the flashlamp; and a charge circuit for charging the primary and secondary charge storage elements from a power source;

[0173] the device further comprising a switching arrangement configured to enable the charge circuit to charge the primary and secondary charge storage elements from the power source; disconnect the primary charge storage device from the power source; and further charge the secondary charge storage element while the first charge storage element is disconnected from the power source.

[0174] General Statements

[0175] In any of the aspects the skin treatment device has common preferred features. The skin treatment device may comprise an Intense Pulsed Light (IPL) device. Such an IPL device is for removal of unwanted hair. The skin treatment device comprises a capacitor arranged to discharge over a flashlamp, preferably a xenon flashlamp. A control system is arranged to control charging and discharging of the capacitor. The control system is arranged to control delivery of the light energy pulses. The light energy pulses may be delivered at a pulse repetition frequency, which may be predetermined or modified during operation by the control system dependent on one or more of sensor inputs from the device and / or user input. Fluence on skin may also be controlled. Typical values of pulse rate frequency are between 3 Hz and 0.3Hz. Typical values of fluence onto the skin range between 2J / cm2and 7J / cm2per pulse depending on numerous factors such as skin tone, pulse repetition frequency etc.

[0176] P393888.WO.01The solid material may be a sapphire block. The cooling system for cooling the solid material may comprise a Thermoelectric Cooling (TEC) system. The device may comprise a head arranged to be mountable and demountable to the body, the head comprising a rearward end for releasably mounting to the body and extending to a forward end comprising a second skin contact surface, the head defining an extension of a light emission pathway. The device is then operable in a first configuration with the head demounted from the body and a second configuration where the head is mounted to the body. A control system is configured to control delivery of multiple light energy pulses and to control delivery of an optical power output, the control system being further configured to cause modification to the optical power output dependent upon whether the head is mounted or demounted from the housing, where the optical power output is defined as light output energy per pulse emitted from the device divided by the time between consecutive pulses. The optical power output is greater when the head is mounted to the body.

[0177] BRIEF DESCRIPTION OF THE DRAWINGS

[0178] Embodiments of this disclosure will be described hereinafter, by way of example only, with reference to the accompanying drawings in which like reference signs relate to like elements and in which:

[0179] Figure 1 shows a schematic perspective view showing the skin treatment device in two different operable configurations with a removable head attached to the device body (Figure la) and without a removable head attached to the device body (Figure lb) according to an embodiment of this disclosure;

[0180] Figure 2 is a schematic cross sectional representation in two different operable configurations with a removable head attached to the device body (Figure 2a) and without a removable head attached to the device body (Figure 2b) according to an embodiment of this disclosure;

[0181] Figure 3a is a schematic representation of the device according to an embodiment of the disclosure with various components missing to better show the cooling system, and Figure 3b is the cooling system in isolation according to an embodiment of this disclosure;

[0182] P393888.WO.01Figure 4a-d are schematic representations of a device according to an embodiment of this disclosure showing in particular different air flow pathways through the device;

[0183] Figures 5a-c are partial schematic cross sectional representations of a device according to an embodiment of this disclosure;

[0184] Figure 6 is a schematic cross sectional representation of a device according to an embodiment of this disclosure;

[0185] Figure 7 is a schematic plan view of a part of a device according to an embodiment of this disclosure;

[0186] Figure 8 is a front perspective view of a device according to an embodiment of this disclosure with a front body portion shown see through in order to show the underlying components;

[0187] Figures 9a-c are schematic representations of part of a device according to an embodiment of this disclosure;

[0188] Figure 10 is a schematic representation of charging circuitry according to an embodiment of this disclosure;

[0189] Figure 11 is a schematic representation of charging circuitry according to an embodiment of this disclosure;

[0190] Figure 12 is a schematic representation of charging circuitry according to an embodiment of this disclosure.

[0191] P393888.WO.01DETAILED DESCRIPTION

[0192] Embodiments of this disclosure are described in the following with reference to the accompanying drawings.

[0193] Referring to Figure la there is a schematic perspective representation of an illustrative embodiment of the present invention. Presented is an IPL device 2 comprising a housing / body 4 arranged to be received in the hand of a user. The device may connect to a mains power source via a cord or comprise a rechargeable battery and further comprises a user operated trigger in the form of a push button 8 for causing operation. This discharges a capacitor (not shown) over a light source (not shown) in the form of a flashlamp. A light energy dose is therefore emitted.

[0194] An outlet or vent 10 is provided in the housing for exhausting hot air. At a forward end 11 of the housing 4 a head 12 is shown mounted relative to the housing 4. The head comprises a rearward end 14a arranged to mount and demount relative to the housing 4 and a forward end 14b defining a (second) skin contact surface 16 in the form of a peripheral rim surrounding an output window 18 through which light energy pulses are transmitted. A portion of the rim is defined by opposing first and second shoulders 17 that are pivotally mounted relative to the head to allow displacement against the user’s skin to thereby accommodate different body geometries and reduce the possibility of stray light escaping whilst also achieving increased usability. The output window 18 is an opening into the head 12, specifically into a lightguide 20 typically in the form of a channel comprising aluminium channel walls for directing the light energy pulses through the output window 18 and onto the skin of a user. The channel may comprise a through-bore extending through the entirety of the head from the forward to a rearward ends 14b, 14a. One or more sensors are provided in the skin contact surface 16 for determining contact with the skin of a user, from which an output is transmitted to the control system for controlling operation of the device 2. With the head 12 mounted to the housing 4, the device is operable in a configuration where there is no physical contact of the leading end of the body 4 with the user’s skin, rather it is the peripheral rim of the head that contacts the skin.

[0195] Referring now to Figure lb, the head 12 is demounted from the body 4 which can equally be termed a housing 4. The device 2 is therefore operable in a first configuration without the P393888.WO.01presence of the head 12. The forward end of the housing 4 is shaped to receive the head 12 and comprises a further lightguide 24 comprising a solid material 26 having a first skin contact surface 28. In operation, the first skin contact surface 28 of the material 26 communicates with the skin and provides a cooling effect as described further with respect to subsequent Figures.

[0196] Referring now to Figure 2 a cross sectional view of the forward end of an illustrative embodiment of the present invention is presented with the head 12 in communication with the housing 4 (Figure 2a) and with the head 12 removed from the housing 4 (Figure 2b). The device comprises a charge storage device (not shown) in the form of a capacitor and a control system 32 for controlling operation of the device including discharge of the capacitor over the flashlamp 34. Further provided is a fan arrangement 36 for directing cooling air across the flashlamp 34 and out of the outlet / vent 10. A primary lightguide extends between the flashlamp 34 and the first skin contact surface 28. The primary lightguide comprises the solid material 26 typically comprising glass or sapphire having at a trailing edge a filter 38 which may be a coating applied directly onto the material 26 for filtering most harmful wavelengths of light in the UV and blue wavelength ranges that are inherently emitted by the flashlamp 34. A further coating material may comprise an anti-reflective material to assist with light transmission into the solid material 26. The primary lightguide comprises a light reflective wall defining a channel 39 in which is positioned the solid material 26. The solid material 26 abuts against the wall meaning light energy pulses must travel through the solid material.

[0197] During operation of the device in a first operable configuration with the head 12 demounted from the housing 4 the solid material 26 will heat up due to transmission losses and conduction during the emission of each energy pulse from the flashlamp 34. Without cooling the material 26 it is likely that the material may reach a temperature painful or harmful to the skin. The device 2 therefore further comprises a cooling arrangement for cooling the material 26 in the form of a Thermoelectric Cooling System (TEC) comprising a thermoelectric cooler such as a Peltier 40, heat pipes 42 and heat sink or radiator 44. The fan 36 drives air across the heat sink 44. In the embodiment shown the fan is downstream of the heat sink meaning the fan draws air across the heat sink from the air inlet 46. The air inlet 46 is provided in the housing for enabling passage of cooling air over the heat sink 44. A significant benefit of utilising a solid material 26 is that it may be cooled to a temperature below normal skin

[0198] P393888.WO.011

[0199] temperature which means the skin contact surface 28 of the material 26 cools the skin which is particularly beneficial for sensitive treatment areas such as underarm and bikini areas.

[0200] The rearward end 14a of the head 12 is arranged to be mounted to the leading portion of the housing 4 through a connector 50. In the illustrative embodiment the connector 50 extends outwardly from the rearward end 14a of the head 12 and seats into a corresponding opening in the forward end of the housing 4. Engagement between the connector 50 and the housing couples the head 12 to the housing 4. Additional or alternative connections may be provided for enabling engagement such as mechanical or magnetic attachment mechanisms. Electronics present in the head (as described further below) are coupled to the control system with the head mounted by the connector 50.

[0201] The device can determine that the head is mounted to the body and / or that the head is detached from the body and operation of the device is modified. This may be achieved for example by a sensor output or the detection of an electrical connection between electronics provided in the head. The operative parameter is typically power, and the control system enables a higher output power output with the head mounted compared to the optical power output with the head demounted. In the first configuration with the head detached, as an example the optical power is at a reduced value of 6W. To produce this power the optical power may be output at 18J and 3 seconds between flashes, where 18J may be 6J / cm2for a 3cm2treatment area. The TEC is operational at a suitable power to control the temperature of the solid material 26 such that the skin contact surface 28 cools the skin. In the second operative configuration with the head mounted to the housing, a relatively high optical power can be output. For example, 20W may be produced by 18J and 0.9 seconds between flashes, where 18J may again be 6J / cm2for a 3cm2treatment area. In this second operational configuration, the TEC may be switched off or operated at reduced power (compared to the optical power) due to the spacing of the first skin contact surface 28 from the skin.

[0202] When the head 12 is attached to the body 4, as described above control of the operation of the device is modified. This means that one or more parameters of delivery of energy to the light source are modified, such as energy delivery value, energy delivery timing and energy delivery discharge profile (i.e. whether it is modulated from the capacitor for example). It is beneficial that the head has a memory for storing information relating to the light source drive parameters relevant to that particular head. When attached to a body, the control system P393888.WO.01of the device can operate the device to deliver the profile of the energy appropriate to the head that is attached. So, with the head attached, the delivery profile might be such that the pulse repetition frequency is increased. Furthermore, the head comprises one or more sensors and a processor in the head determines (by known means of look up tables) as to whether for example a capacitive touch sensor is in sufficient contact with the user’s skin to allow emission of an energy pulse. An output signal is then sent to the control system as to whether the device can emit an energy pulse. Furthermore, the head processor may receive sensor inputs from skin tone sensors in the head and based on this determine the appropriate fluence on skin required for that skin tone. The head can then also output a signal to the control system to ensure that the appropriate energy is delivered from the capacitor to the light source to achieve the desired effect. Signals can be sent from the head to the control system at a frequency suitable to maintain the primary function of the sensors, so for example skin tone sensor signals can be communicated at least once every flash period, and signals representing contact with the skin can be sent at least once every 100msec.

[0203] With further reference to Figure 2a and b, there is provided a charge control system. The charge control system is arranged to adapt the charging speed of the capacitor depending on certain factors relating to operation of the device. These operational features may be automated (for example such as when the head is attached or detached, or when a sensor sense a specific predetermined input such as a predetermined temperature is exceeded) or alternatively when a user inputs a user selection to modify the treatment protocol by for example selecting multiple different functionalities. This may be for example a device that both outputs light energy pulses from a flashlamp and also outputs other energy types such as RF to provide alternative functionality.

[0204] Utilising mains input for example in normal device operation there is a total available 75W of power. This must be split between the necessary power drains, so the majority initially is used for charging the capacitor, whist some power is used to power the cooling system, sensors (such as skin contact and tone sensors), fan, processor etc. In the illustrative embodiment, reference is made to the modification of speed of charging dependent upon whether the head 12 is attached as shown in Figure 2a or detached as shown in Figure 2b. This means that when the device is in cooling mode without the head attached and with the solid material in contact with and cooling the skin, the optical power is relatively low and the charging power can be reduced (on average), resulting in more power being given to the P393888.WO.01Peltier. When the device is in non-cooling mode with the head attached and thus the solid material being separated from the skin, the charging power can be increased to maximise the flash rate, and the power given to the Peltier can be lower. Overall, the benefit is that the power drawn from the mains supply (or battery) is better managed in that it is less variable and the peaks are lower. This averages out heating effects, reduces peak stress on components and other issues with high peak power draw. It is noted that whenever reference is made to optical power output, this term can be defined as light output energy per pulse emitted from the device divided by the time between consecutive pulses. Accordingly, the optical power output is greater when the head is mounted to the body.

[0205] Referring back to Figure 2a, the head 12 defines a head skin contact surface 16 which sits against the skin in use. A portion of the lightguide is defined between the first skin contact surface 28 and the second skin contact surface 16. The secondary lightguide comprises a reflective wall 52 defining a channel or pathway for the light energy pulses. The channel is an airgap, and the secondary lightguide may be termed a light pipe. Typical lightguides comprise a reflective aluminium wall defining the channel, with no solid medium that can contact the skin. The second skin contact surface is the peripheral rim of the leading end of the head 12.

[0206] Referring to both Figures 2a and b, the flashlamp 34 is shown provided in a chamber 54 with a leading end of the chamber 54 defined by a dichroic filter 56 coating the rearward face of solid material 26, i.e. the face that faces the light source. The chamber is further defined by a reflector 58, where the reflector forms a first portion of the lightguide and directs light energy towards the filter 56 and solid material 26. The reflector 58 is parabolic to maximise reflection of light energy forwardly toward a forward end of the device, and out onto the skin of a user. The solid material then defines a further portion of the lightguide defining the first skin contact surface 28 without the head 12 attached as shown in Figure 2b.

[0207] The TEC system has been briefly described above, and is presented in more detail in Figures 3a and b. It may take various forms where a heat input element such as a heat plate 41 is in thermal contact with the hot side of the Peltier 40 (often with a thermal grease applied to decrease thermal resistance). A heat transmission element 42 is used to transfer the heat to the heat sink. The heat sink 44 may also be termed a radiator. The heat transmission element 42 should be thermally conductive and may comprise:

[0208] P393888.WO.01- A suitable highly conductive solid material such as aluminium or copper.

[0209] - A heat pipe(s) 42 - a heat transfer component utilising a pipe filled with a phase changing liquid.

[0210] - A vapour chamber - similar to a heat pipe but constructed from sheet material.

[0211] In the illustrative embodiment of Figure 3 the heat transmission element is a heat pipe having a flattened area connected to the heat plate 41 which then extends and is connected to the heat sink 44 to transfer heat to a passing airflow.

[0212] Referring now to Figure 4a, the air flow pathways through the body 4 of the device are more clearly shown in an illustrative embodiment. The primary air flow pathway 60 (represented by arrows 60) is firstly through the inlet 46 and through the heat exchanger 44 of the thermoelectric cooling system. The fan arrangement 36 is downstream of the heat exchanger 44 in this illustrative embodiment and therefore draws air through the inlet 46 and heat exchanger 44. It will be appreciated that this order could be reversed depending on device configuration desired. The primary air flow pathway then extends towards the outlet vent 10 passing by a heat sink 62 positioned rearwardly of the reflector 58 and designed to conduct heat generated by emission of light energy from the flashlamp away from the flashlamp and solid material 26. The flashlamp is intermediate the solid material and the heat sink 62.

[0213] The primary air flow pathway 60 is designed as a high by-pass system, meaning that the majority of the air flow generated by operation of the fan arrangement 36 is relatively unimpeded through the body thereby maximising air flow rate. Accordingly, the heat exchanger impedes flow or air while heating the air flow, the rate of flow remains high, and the temperature of the air flow does not increase significantly. Air downstream of the heat exchanger can be used to further assist in cooling of the heat sink 62. The heat sink 62 is designed with a low number of ribs to minimise resistance to air flow. Following this, the air then exists through the outlet / vent 10. The air flow pathway is between a first side of the body and a second opposing side.

[0214] There is a secondary air flow pathway 66 (represented by arrows 66) that branches from the primary air flow pathway. In the embodiment presented the branch is after the fan arrangement 36. The secondary air flow pathway extends through an inlet into the chamber 54 which houses the flashlamp 34. The secondary air flow pathway then passes through an outlet in the chamber 54, through a labyrinth pathway (to prevent light energy escaping) and P393888.WO.01merges with the primary air flow pathway before the outlet 10. By providing a secondary air flow pathway through the chamber in which the flashlamp is located improves the ability to cool the flashlamp, which in turns enables the device to operate at higher pulse repetition rates without overheating providing increased useability without affecting safety.

[0215] As will be apparent from Figure 4a, the secondary air flow pathway passes through the chamber 54 which is has a chamber wall in physical communication with the solid material 26. The filter 56 is positioned in contact with the secondary air flow pathway, however the thickness of such a filter is minimal and accordingly heat is conducted away from the rearward surface of the solid material. This air flow is beneficial as provides an insulating effect between the heat generated by emission of light energy pulses by the flashlamp and the solid material.

[0216] As described above, the secondary air flow pathway 66 further comprises a labyrinth pathway region 68 to prevent light energy leaking from the body and is preferentially black to reduce internal reflection. The secondary air flow pathway then merges with the primary air flow pathway before the outlet 10 and because of the airflow restrictions in the labyrinth the airflow travels slower in the secondary air flow pathway than in the primary air flow pathway. Accordingly, when the airflow pathways merge, air is drawn from the secondary airflow pathway by virtue of the Bernoulli effect.

[0217] Referring to Figure 4b, the body 4 has been removed to show the internal fan arrangement 36, lamp 34 and air duct components. Visible is the vent 10 and the main PCB 31 including the control system 32. Further shown is a bracket 69 that connects the lamp to the PCB 31. A lesser volume of small amount of air through the device also branches from the primary air flow pathway 60, passes over the lamp brackets before re-joining the majority flow of the primary air flow pathway 60. This air flow pathway is a third air flow pathway 73 through the device. This air flow exists the device through the vent 10 at the respective ends as shown by arrows 75. For additional explanation, further sectional views of the device are presented in Figures 4c and 4d. In Figure 4c, the branch from the fan arrangement of the third airflow pathway 73 is shown passing across the lamp bracket 69 by virtue of a cross sectional plan view, and in Figure 4d another cross sectional view is presented showing the third airflow pathway 73 from bottom to top of the device as the air flow passes across the lamp brackets

[0218] P393888.WO.0169 to assist cooling of the lamp 34. Also visible in Figure 4d are baffles 77 provided to shield light from escaping from the device through the third airflow pathway 73.

[0219] As described above it is beneficial for improvement in optical efficiency that the dichroic filter is a coating that is applied directly to a rearward face (the face that opposes the light source). This creates a potential problem. As the reflector 58 and flashlamp 34 are high voltage components they can reach as high as 9KV whilst the flashlamp is triggered to emit a light energy pulse. It is therefore essential for any conductive elements in the vicinity of the flashlamp 34 to have sufficient creepage and isolation distances from the reflector to prevent arcing / breakdown. With the provision of a Peltier 40 mounted to the solid material 26 the Peltier is relatively close to the forward edge of the reflector 58. Insulation between the Peltier 40 and the reflector 58 is therefore required.

[0220] Referring to Figure 5a, a first option is to utilise a Peltier that is potted. For example, the Peltier can be potted in a silicon adhesive. The potted Peltier is represented by reference numeral 40a. As shown in Figure 5b, alternatively or preferably in addition, an insulating seal 72 may be achieved by bonding the plastic body / housing 4 to the solid material between the Peltier 40 and reflector 58 to create an insulating seal. A further option as presented in Figure 5c is to extend the length of a thermal pad 70 mounted between the Peltier and solid material to act as electrical isolation. A thermal pad 70 is typically necessary to improve the thermal bond between the Peltier and solid material (typically sapphire) and is shown in each of Figures 5a-c. The thermal pad 70 should be a non-metallic, electrically insulating compliant material with a relatively high thermal conductivity. A further option to be used in addition to one of the options presented (such as potting the Peltier) is to bond an insulating and isolating shield to the Peltier intermediate the reflector 58 and Peltier 40. This shield may be applied to the rearward edge of the Peltier 40. This isolating shield may comprise for example polycarbonate or similar and be bonded to the Peltier.

[0221] Referring to Figure 6, there is a schematic cross-sectional representation of a device according to an illustrative embodiment. It will be appreciated that although the device is described without attachment of the detachable head, it will be appreciated that this is a feature that may be used with this device as described.

[0222] P393888.WO.01The device comprises a body 4 having a transmission window through which light energy pulses from the flashlamp 34 along a light emission pathway are emitted under the control of control system 32. Disposed in the light transmission pathway is a solid light transmissive material such as a sapphire block 26 to provide a cooling effect to the skin of the user in operation. Further provided is a temperature sensor 80 which may take different forms such as being an infrared temperature sensor configured to sense temperature of the solid material and output temperature information to the control system. The control system can then in turn control operation of the device using the temperature information.

[0223] Using the temperature information the power to the Peltier 40 can be controlled, so the power can be increased, decreased or switched off. Alternatively, the flash rate can be changed. This means that:

[0224] • A minimum temperature can be set. For example, if a minimum of 15°C is set, then when the temperature sensor 80 detects that this temperature has been reached, the power supplied to the Peltier 40 can be reduced or switched off, until an increase in the sapphire block 26 temperature is detected. This would also minimise wasted energy cooling the sapphire block when it is not needed.

[0225] • A maximum temperature can be set. For example, if a maximum sapphire block temperature of 33°C is set, then if the sapphire block 26 reaches that temperature, the flash rate can be reduced (time between flashes increased) to reduce the heat input to the sapphire block 26 and prevent any further increase in sapphire block temperature. Additionally, if the temperature limit is exceeded, then the control system can prevent the device from emitting a light energy pulse. As an alternative to decreasing the flash rate, the fluence per flash could also be reduced to reduce the heat input.

[0226] • The power provided to the Peltier 40 may be set proportional to the temperature of the sapphire block 26. For example, the colder the sapphire block 26 the lower the Peltier 40 power, and the higher the sapphire block 26 temperature the higher the power.

[0227] A further feature may be to include a temperature sensor 82 on the hot side of the Peltier e.g. mounted on the heat pipe 42. This would allow the temperature difference across the Peltier

[0228] P393888.WO.01to be known (or inferred) by the control system based on the two sensor 80,82 inputs. Knowing the temperature difference across the Peltier could enable:

[0229] • Damage protection - there is a maximum allowable temperature difference across a Peltier 40 before it will be damaged. If the measured temperature across the Peltier is too high, then the power supplied to the Peltier could be reduced or switched off.

[0230] • Optimisation of Co-efficient of Performance (COP). The COP of a Peltier is related to the power provided to the Peltier and also the temperature difference across the Peltier. Therefore, to optimise the performance during operation, the power provided could be modified dependant on the temperature of the sapphire block 26 and the temperature difference across the Peltier 40.

[0231] A common problem with applying temperature sensors is that a good thermal bond must be maintained between the temperature sensor and the sapphire block 26. Accordingly, it is beneficial to ensure a good long-lasting contact. This can be achieved through a double-sided adhesive tape with high low thermal resistance between the sapphire block 26 and temperature sensor 80. Alternatively, a thermal adhesive, thermal grease or thermal pad could also be used along with another method holding the temperature sensor in place such as a small clamp arranged to apply a pressure pressing the temperature sensor 80 onto the sapphire block. An alternative may be utilise a non-contact sensor such as am Infrared sensor.

[0232] Referring to Figure 7, there is a display arrangement 84 that provides information to the user about the temperature status of the sapphire block 26 meaning there is a quick and easy to interpret cooling indicator of the sapphire block 26. The display arrangement is arranged to change colour in operation. As an example, the colour changes sequentially between multiple different colours, such as transforming from blue, to blue / green, to white at a maximum temperature where the device remains operable. Beyond a white colour, the display arrangement turns red, and emission of energy pulses are prevented until the sapphire block cools sufficiently, at which point the display arrangement will revert back initially to white, then blue / green and ultimately blue.

[0233] As has been described elsewhere in the specification, an embodiment of the invention utilises the provision of a head detachable with respect to the body where in the detached configuration the solid material contacts the user’s skin to provide a cooling effect and with P393888.WO.01the head attached the solid material is spaced apart from the user’s skin meaning the solid material does not provide a significant cooling effect to the skin. In the configuration when the head is attached, it is not necessary to try and keep the solid material temperature below the skin temperature, because in this configuration, the solid material does not touch the skin. Accordingly, the solid material needs only to stay below safe momentary touch temperatures. For example, a safe touch temperature is defined in IEC 60601-1, table 24. That is, for a glass like material with a touch time <lmin, the maximum allowable (safe) temperature is 56°C. To achieve this, the Peltier can be run at lower power (e.g. 30% max) until the temperature of the solid material approaches the temperature limit (e.g. 56°C). At this time, the Peltier can be run at full power, at which, it can maintain the solid material below the temperature limit even at the higher Optical Power (19W).

[0234] To achieve the cooling capacity required to keep the solid material below skin temperature at an optical power of 8W, a relatively large blower / fan with high flow rate is required. It is typical that a fan or blower of this type is relatively noisy, often around 65dB. This can be annoying to the consumer if it runs continuously. To minimise this issue, the device may comprise fan speed control. This can be implemented so that the blower / fan runs at low speed when first switched on (soft start) and cooling from the fan is not needed. The blower / fan speed is increased when device gets hot and cooling is needed. The blower / fan is slowed down again if the device temperature drops sufficiently.

[0235] Reference is now made to Figures 7 to 9. IPL devices designed for home use typically include capacitive skin contact sensors to detect the presence of skin around the treatment area, and inhibit flashing if skin is not detected. It is beneficial if these sensors are equally spaced around the treatment area and are positioned such that in use they are located very close to the skin surface with the distance ideally being around 1mm or less. The further the plates of the sensors are from the skin contact surface of the device, the less accurate and sensitive is the skin contact measurement.

[0236] Capacitive contact sensors require metallic (or conductive) plates 200 mounted parallel to the contact surface (either of the body 4 or the forward end of the head 12), connected to an electronic circuit that can detect a change in 'capacitance' due to a body in close proximity to the plates. However, since the capacitive plates 200 required are part of an electronic circuit, consideration must be made for electronic safety in the event of an electronic fault. This P393888.WO.01generally means ensuring suitable electrical creepage and clearances are provided between the metal plates and the skin. Due to the high voltages used in an IPL device, a suitable creepage and clearance is often >4mm. This causes design issues as 4mm is a relatively large distance in such a small place.

[0237] Referring to Figure 8, the forward end of the device without the presence of the head is shown, however it will be appreciated that the head also has the characteristics as further described in the following paragraphs with respect to the sensor configuration and mounting. Figure 8 shows the forward end of the device with the forward portion of the body transparent. In this way the capacitive sensor plates 200 are visible. Also shown is a skin tone sensor (STS) 202 in the form of a proximity sensor on the basis of which skin tone and accordingly energy to be delivered can be determined. This sensor requires a transparent light guide passing through the Front housing to receive reflectance from the skin.

[0238] Referring to Figure 9a, there is an internal view of the front of the body showing the window through which the light energy pulses are transmitted. Figures 9b and c show cross sectional views taken in the planes shown in Figure 9a. Viewing Figure 9a and looking into the front body portion, the rear contact plates 204 that connect to the capacitive sensor circuitry. The capacitive sensor plates 200 and the STS sensor 202 are not visible as they are encapsulated by an overmoulded plastic covering 206. If the correct plastic and overmould settings are used, the bond between the moulding plastic material and the inside of the forward part of the body 5 (or head 12) is good enough to electrically isolate the plates allowing the plates to be much closer to the front surface. Referring now to Figure 9b, the capacitive sensor plates 200 are encapsulated by the plastic covering 206, and a seal 208 is formed to ensure there is no creepage pathway to the front of the device and therefore the skin of the user. Referring to Figure 9c, the rear contact plates 204 are shown and the creepage and clearance distance from the front of the device to this exposed metal is sufficient. The seal 210 between the capacitive sensor plates 200 and the body / head 4,12 is shown.

[0239] Capacitive sensor plate 200 encapsulation and skin tone sensor encapsulation is therefore achieved in a single overmould operation with the process of overmoulding a plastic covering 206. Furthermore, the STS 202 is bonded to the forward end of the body 4 or head 12 as this prevents any ingress of liquids or dust.

[0240] P393888.WO.01Referring now to Figures 10-12, in each of these Figures common features have been identified with the same reference numerals. Each Figure shows a schematic representation of charge circuitry in illustrative embodiments to enable triggering of a flashlamp 102 to cause discharge of a capacitor 104 over the flashlamp 102.

[0241] Referring to each of Figures 10-12, the charger circuit 106 controls an output voltage sufficient to charge the capacitor 104 from a power source such as mains or battery power 108 This charge circuit 106 may contain additional features to control, isolate and provide safety to the capacitor voltage. The main capacitor 104 is the primary store of the energy used in the flash discharge of the lamp. Typically, this is of the aluminium electrolytic type. The voltage range is typically 300V to 450V, but not restricted to this range. Energy stored is typically 50J-100J.

[0242] Further provided is an anode boost circuit 110 including a secondary capacitor which is used to apply an increased voltage (2-3 times greater than the voltage across the lamp provided by the capacitor) across the anode and cathode of the flashlamp and at the time of triggering aids in creation of a plasma stream between the electrodes inside the lamp 102. Once established, the plasma stream allows the flow of electrons from the main capacitor 104 and the flash discharge of light begins. The potential difference across the lamp is typically 2 or 3 times the main capacitor voltage, less the loss in the generation process. The energy stored in the anode boost output is typically in the millijoule range, thousands of times less than in the main capacitor 102.

[0243] Further provided is a trigger circuit 112 including a tertiary capacitor that generates a high voltage needed to ionise the gas inside the lamp to aid electron flow of the anode boost potential. The voltage is typically 6Kv to 12kV and the energy is very low, typically around 10-15mJ. The high voltage exists only for around 50ps and is typically generated by discharging the tertiary capacitor (not shown) through one transformer coil whilst the other is connected to the lamp.

[0244] Also shown as an optional feature is the provision of discharge control functionality 114, where discharge of the main capacitor 104 can be used as a low side switch to be able to end the discharge at a chosen point. This is not required in a device using the entire of the light pulse in the treatment.

[0245] P393888.WO.01Importantly, and with reference to Figure 10, a beneficial feature is the provision of a switching arrangement in the form of a switch 116 that disconnects the main capacitor 104 from the anode boost 110 and trigger 112 circuits. This allows those circuits to be charged to a higher potential, increasing the output of each circuit, and allowing the main capacitor 104 to be operated at voltages lower than would be possible if that voltage was also used for anode boost and trigger circuits. As presented in Figure 10, the switch can be a single switch to disconnect the main capacitor 104 from the anode boost and trigger circuits.

[0246] Referring to Figures 11 and 12, two variations can be used where in Figure Il a two pole switch directs the output from the power supply to either branch of the main capacitor or the anode boost and trigger circuits. In Figure 12, two switches 116a,b are provided and used to disconnect the main capacitor 104 from the anode boost 110 and trigger circuits 112 again ensuring that the capacitor is only charged to a predetermined lower voltage.

[0247] Control of the charger and the switch(es) may be from an embedded controller. The switch(es) 116 may be reliant on the charger control. Accordingly, the switch cannot be switched from a closed to an open configuration unless the power is removed. The benefit of this is the use of a simpler, cheaper switching and control method.

[0248] Although particular embodiments of this disclosure have been described, it will be appreciated that many modifications / additions and / or substitutions may be made within the scope of the claims.

[0249] P393888.WO.01

Claims

39CLAIMS1. A skin treatment device for delivery of light energy to skin of a subject, the skin treatment device comprising:o a body having a transmission window;o a light source housed within the body for emitting light energy along a light energy emission pathway through the transmission window;o a solid material disposed in the light emission pathway through which light energy from the light source is transmitted;o a cooling arrangement housed by the body, the cooling arrangement comprising a heat sink configured to cool the solid material;the skin treatment device further comprising a primary air flow pathway through at least a portion of the body with the heat sink in the primary air flow pathway, and a secondary air flow pathway through at least a portion of the body with the light source in the secondary air flow pathway, the device further comprising an air moving arrangement for causing air flow through the primary and secondary air flow pathways.

2. A skin treatment device according to claim 1 wherein the primary air flow pathway extends between an inlet and an outlet in the body.

3. A skin treatment device according to claim 2 wherein the secondary air flow pathway forks from the primary air flow pathway intermediate the inlet and the outlet.

4. A skin treatment device according to claim 3 wherein the secondary air flow pathway forks from the primary air flow pathway after the heat sink.

5. A skin treatment device according to any of claims 3-4 wherein the secondary air flow pathway rejoins the primary air flow pathway before the outlet.

6. A skin treatment device according to any preceding claim wherein the light source is disposed in a chamber, and the chamber may be in the secondary air flow pathway.P393888.WO.01407. A skin treatment device according to any preceding claim wherein the secondary airflow pathway is at least partially intermediate the solid material and the light source.

8. A skin treatment device according to claim 6 comprising a labyrinth region provided downstream of the chamber for restricting light energy transmission from the chamber.

9. A skin treatment device according to any preceding claim wherein the cooling arrangement may comprise a Thermoelectric Cooling System.

10. A skin treatment device according to claim 9 wherein cooling arrangement comprises a Peltier in physical contact with the solid material and the heat sink.

11. A skin treatment device according to any of claims 9-10 wherein the fan arrangement is downstream of the heat sink.

12. A skin treatment device according to any preceding claim comprising a reflector for reflecting light energy emitted by the light source towards the solid material, the device further comprising a second heat sink in the primary air flow pathway in communication with the light reflector13. A skin treatment device according to any preceding claim wherein the average cross- sectional area of the primary air flow pathway is greater than the average cross sectional area of the secondary air flow pathway.

14. A skin treatment device according to any preceding claim further comprising a control system for controlling delivery of light energy pulses from the light source, where the control system is at least partially disposed on a printed circuit board (PCB), and where the light source is mounted to the PCB by a mounting bracket, the skin treatment device further comprise a third air flow pathway through at least a portion of the body with the mounting bracket in the secondary air flow pathway, the fan arrangement arranged to further effect air flow through the third air flow pathway.P393888.WO.014115. A skin treatment device according to any preceding claim wherein the solid material comprises a forward surface defining a skin contact surface and a rearward surface facing the light source, with a dichroic filter coating provided directly on the rearward surface.

16. A skin treatment device for delivery of light energy pulses to a subject’s skin, the skin treatment device comprising:a body having a transmission window;a light source housed within the body for discharging light energy through the transmission window;a capacitor for discharge over the light source;a charge control system for controlling charging of the capacitor;wherein the charge control system charges the capacitor at a charging speed dependent upon operation of the device.

17. A skin treatment device according to claim 16 wherein the charge control system is arranged to charge the capacitor at a charging speed selected from a plurality of different charging speeds dependent upon operation of the device.

18. A skin treatment device according to any of claims 16-17 comprising one or more sensors and the charge control system is arranged to select a charging speed to charge the capacitor dependent upon one or more sensor inputs from the one or more sensors.

19. A skin treatment device according to any of claims 16-18 wherein the device comprises a user input for a user to select an operating parameter of the device, where the control system is arranged to select a charging speed to charge the capacitor dependent upon the selected input.

20. A skin treatment device according to any of claims 16-19 wherein the device is further arranged such that the light source emits light energy along a light emission pathway and out of the body; the device further comprising:a solid material disposed in the light emission pathway through which light energy from the light source is transmitted, the solid material defining a first skin contact surface for providing contact with a subject’s skin;P393888.WO.01a cooling arrangement housed by the body configured to cool the solid material;a head arranged to be mountable and demountable to the body, the head comprising a rearward end for releasably mounting to the body and extending to a forward end comprising a second skin contact surface, the head defining an extension of the light emission pathway from the first contact surface to the second contact surface;the device being operable in a first configuration with the head demounted from the body and a second configuration where the head is mounted to the body such that in the second configuration the first skin contact surface is spaced apart from the subject’s skin and the light energy pulses pass through both the solid material of the first lightguide and the extension of the light emission pathway; wherein in the first configuration the charge control system is arranged to control charging of the capacitor at a first speed and in the second configuration the charge control system is arranged to control charging of the capacitor at a second speed different to the first speed.

21. A skin treatment device according to claim 20 wherein the second speed is greater than the first speed.

22. A skin treatment device according to any of claims 16-21 wherein the cooling system comprises a Thermoelectric Cooling (TEC) system, preferably a Peltier and a heat sink.

23. A skin treatment device for delivery of light energy to skin of a subject, the skin treatment device comprising:o a body;o a light source housed within the body for emitting light energy along a light emission pathway through a transmission window;o a solid material disposed in the light emission pathway through which light energy from the light source is transmitted, the solid material for providing a cooling effect to skin of a subject, the solid material having a forward surface defining a skin contact surface and a rearward surface facing the light source;P393888.WO.01O a dichroic filter coating provided directly on at least one of the skin contact surface and the rearward surface.

24. A skin treatment device according to claim 23 wherein the dichroic filter coating has a cut-on value of between 500 and 600nm.

25. A skin treatment device according to any of claims 23-24 wherein the solid material comprises sapphire.

26. A skin treatment device according to any of claims 23-25 wherein the forward and / or rearward surfaces of the solid material comprise an anti-reflective coating thereon.

27. A skin treatment device according to any of claims 23-26 further comprising a cooling arrangement housed by the body for cooling the solid material, the cooling arrangement comprising a heat sink configured to cool the solid material.

28. A skin treatment device according to claim 27 comprising a Peltier for transferring heat energy away from the solid material to the heat sink.

29. A skin treatment device according to any of claims 23-28 further comprising a reflector for reflecting light energy emitted by the light source towards the solid material.

30. A skin treatment device according to claims 27-29 further comprising an electrical isolator between the Peltier and the reflector and light source in order to electrically isolate the Peltier from both of the light source and the reflector.

31. A skin treatment device for delivery of light energy to skin of a subj ect, the skin treatment device comprising:o a body having a transmission window;o a light source housed within the body for emitting light energy along a light energy emission pathway through the transmission window;o a solid material disposed in the light emission pathway through which light energy from the light source is transmitted;P393888.WO.0144o a temperature sensor configured to sense temperature of the solid material and output temperature information;o a control system for controlling operation of the device;the temperature sensor and control system being in operable communication such that the control system receives the temperature information and controls operation of the device using the temperature information.

32. A device according to claim 31 wherein the control system is arranged to control delivery of light energy as light energy pulses delivered at a pulse repetition frequency, where the control system controls operation of the device by modifying the pulse repetition frequency dependent upon the temperature information.

33. A device according to any of claims 31-32 wherein the control system is arranged to control delivery of the light energy as delivery of light energy pulses, and wherein the control system control operation of the device by controlling the fluence of the light energy pulses dependent upon the temperature information.

34. A device according to any of claims 31-33 further comprising a cooling arrangement housed by the body, the cooling arrangement comprising a Thermoelectric Cooling (TEC) system for cooling the solid material, the TEC comprising a Peltier in communication with a heat sink, wherein the control system is configured to modify power supplied to the Peltier dependent upon the temperature information.

35. A device according to claim 34 further comprising a temperature sensor mounted to the TEC system for measuring the temperature on an opposite side of the Peltier to the solid material and output secondary temperature information, and wherein the control system is arranged to determine a temperature differential between the temperature information comprising primary temperature information and the secondary temperature information, and wherein the control system is arranged to control operation of the device based on the temperature differential.

36. A device according to any of claims 31-35 wherein the control system is arranged to control delivery of the light energy as light energy pulses, and the control system isP393888.WO.0145further configured to prevent emission of light energy pulses if the sensed temperature of the solid material exceeds a predetermined value.

37. A device according to any of claims 31-36 further comprising a visual indication of the temperature of the solid material.

38. A device according to any of claims 31-37 wherein the temperature sensor comprises an Infrared (IR) temperature sensor.

39. A device according to any of claims 31-38 further comprising a clamp arranged to clamp the temperature sensor to the solid material.

40. A skin treatment device for delivery of light energy to skin of a subject, the skin treatment device comprising:a body having a transmission window;a light source housed within the body for emitting light energy pulses along a light energy emission pathway and through the transmission window;a control system for controlling delivery of the light energy pulses having light energy pulse parameters from the light source by controlling light source drive parameters to the light source;the device being operable in a first configuration where light energy pulses are emitted along the light energy emission pathway and through the transmission window;a head arranged to be mountable and demountable to the body, the head comprising a rearward end for releasably mounting to the body and extending to a forward end, such that when the head is mounted to the body the head defines an extension of the light emission pathway to a secondary transmission window at the forward end, the head further comprising a memory having stored light source drive parameters to deliver corresponding light energy pulse parameters;the device being operable in a second configuration with the head mounted to the body, wherein the control system is arranged to identify operational engagement between the head and the body, and further read the stored light source drive parameters and apply the light source drive parameters to cause P393888.WO.0146delivery of light energy pulses from the light energy source through the extended light emission pathway and from the secondary transmission window.

41. A device according to claim 40 wherein the light source drive parameters comprise one or more of duration of energy delivered to the light source for controlling light energy pulse duration, time period between consecutive deliveries of energy to the light source to control light energy pulse rate and quantity of energy delivered to the light source per pulse.

42. A device according to any of claims 40-41 comprising a capacitor for discharge over the light source (preferably a flashlamp) for delivery of the light energy pulses, wherein the light source drive information may comprise one or more capacitor voltage values.

43. A device according to any of claims 40-42 wherein the head comprises one or more sensors for measuring a skin property, and the head may be configured to determine contact with the skin from the measured property, and wherein the head may be configured to transmit information regarding skin contact to the control system, where the control system is further arranged to control delivery of light energy pulses dependent the information received.

44. A method of delivering light energy pulses from an Intense Pulsed Light (IPL) device, the IPL device comprising a body having a transmission window, a flashlamp housed within the body for emitting light energy pulses along a light energy emission pathway and through the transmission window; a primary charge storage element for discharging over the flashlamp to cause emission of a light energy pulse and a secondary charge storage element for discharging over the flashlamp to effect ionisation of the flashlamp; and a charge circuit for enabling charging of the primary and secondary charge storage elements from a power source;the method comprising the steps of:A) charging the primary and secondary charge storage elements from the power source;P393888.WO.0147B) disconnecting the primary charge storage element from the power source;C) further charging the secondary charge storage element while the first charge storage element is disconnected from the power source; andD) discharging the secondary charge storage element to effect ionisation of the flashlamp such that the primary charge storage element discharges over the flashlamp to cause emission of a light energy pulse.

45. A method according to claim 44 wherein the primary and optionally the secondary charge storage elements each comprise a capacitor.

46. A method according to any of claims 44-45 wherein steps A-D of the method are performed in sequence.

47. A method according to any of claims 44-46 wherein the primary and secondary charge storage elements are charged to a first voltage, and the step of charging the secondary charge storage element while the first charge storage element is disconnected from the power source is to a second voltage greater than the first voltage.

48. A method according to any of claims 44-47 wherein the primary and secondary charge storage elements are charged simultaneously in Step A.

49. A method according to any of claims 44-48 wherein the primary charge storage element is charged by closing a switching arrangement in the charge circuit and is disconnected from the power source by opening the switching arrangement.

50. A method according to claim 49 wherein the switching arrangement comprises a first switch arranged to automatically open upon the voltage on the first charge storage element reaching a predetermined voltage.

51. A method according to any of claims 44-50 wherein the device further comprises a tertiary charge storage element for discharging a trigger voltage to the flashlamp for initiating ionisation of the flashlamp, where the charge circuit is further arranged for P393888.WO.0148charging the tertiary charge storage element from the power source; and where the method further comprises charging the tertiary charge storage element while the first charge storage element is disconnected from the power source and discharging the tertiary charge storage element over the flashlamp to initiate ionisation of the flashlamp.

52. A method according to any of claims 44-51 comprising charging the secondary charge storage device to the predetermined voltage concurrently with charging the capacitor to the predetermined voltage.

53. A method according to claim 51 wherein the tertiary charge storage device is charged to a higher voltage than the secondary charge storage device.

54. A method according to any of claims 44-53 wherein in step C charging the secondary charge storage device to a higher voltage than the voltage of the primary charge storage device.

55. A method according to any of claims 44-54 comprising repeating steps A-D.

56. An Intense Pulsed Light (IPL) device, the IPL device comprising a body having a transmission window, a flashlamp housed within the body for emitting light energy pulses along a light energy emission pathway and through the transmission window; a primary charge storage element for discharging over the flashlamp to cause emission of a light energy pulse and a secondary charge storage element for discharging over the flashlamp to effect ionisation of the flashlamp; and a charge circuit for charging the primary and secondary charge storage elements from a power source;the device further comprising a switching arrangement configured to: enable the charge circuit to charge the primary and secondary charge storage elements from the power source; disconnect the primary charge storage device from the power source; and further charge the secondary charge storage element while the first charge storage element is disconnected from the power source.P393888.WO.01

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