Optical system

The present application relates to an optical system (1) comprising a plurality of optical components, a pulse generating arrangement (3) configured to generate a treatment pulse along a treatment pulse optical path through said optical components, said pulse generating arrangement also being configured to generate a probe pulse along a probe pulse optical path extending through said optical components, a sensor (8) configured to generate information indicative of an optical characteristic of said probe pulse that has passed along said probe pulse optical path through said optical components, and a controller (5) configured to control said pulse generating apparatus (3) to selectively emit said treatment pulse along said treatment pulse optical path (2), in dependence on the information generated by the sensor (8).

This application is the U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2016/059120, filed on Apr. 25, 2016, which claims the benefit of International Application No. 15166752.4 filed on May 7, 2015. These applications are hereby incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to an optical system, in particular, an optical system having a probe pulse to determine the condition of an optical path. The present invention also relates to a laser treatment device comprising the optical system. The present invention further relates to a method for using the laser treatment device.

BACKGROUND OF THE INVENTION

Conventional technologies for the treatment of hair and skin include arrangements of mechanical blades and abrasives which are placed against and dragged across a skin surface to cut hair or remove dead skin, respectively. However, these conventional technologies are harsh on the skin surface and cause damage or irritation.

It is known to use a laser beam to sever hair or treat skin as an alternative to mechanical blades and abrasives. Laser beam treatments are preferred because they do not require moving cutting parts or abrasive surfaces to be placed against the skin or hair. Therefore, the problem of skin surface damage or irritation is reduced. Furthermore, the problem of cutting elements becoming blunt and abrasives becoming smooth is eliminated.

It is also known that laser beams can themselves cause damage and irritation if the high intensity portion contacts the skin surface. Traditional optical systems will deactivate the laser beam if the skin surface extends too close to the high intensity portion of the laser beam. However, optical systems can become contaminated and the trajectory of the laser beam altered from its intended path. This can result in the laser beam being directed onto the wrong areas of the skin surface and/or causing damage and irritation to the skin surface.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an optical system which substantially alleviates or overcomes the problems mentioned above.

According to the present invention, there is provided an optical system comprising a plurality of optical components, a pulse generating arrangement configured to generate a treatment pulse along a treatment pulse optical path through said optical components, said pulse generating arrangement also being configured to generate a probe pulse along a probe pulse optical path extending through said optical components, a sensor configured to generate information indicative of an optical characteristic of said probe pulse that has passed along said probe pulse optical path through said optical components, and a controller configured to control said pulse generating arrangement to selectively emit said treatment pulse along said treatment pulse optical path, in dependence on the information generated by said sensor.

Therefore, the optical system only emits a treatment pulse in dependence upon information generated by a sensor relating to a probe pulse.

The information generated by said at least one sensor may be indicative of any obstructions in said treatment pulse optical path.

The at least one sensor may be configured to generate information indicative of at least one characteristic of the probe pulse. The at least one characteristic may be, for example, but not limited to, the position of a taken altered probe pulse optical path through the optical system, the intensity, power, energy, spatial distribution or temporal distribution of the probe pulse. In some embodiments, if one or more of the sensed characteristics is not in accordance with a predetermined value or range of values, then the controller will not emit a treatment pulse.

Therefore, if the information, generated by the at least one sensor and indicative of the at least one probe pulse, indicates that the condition of the treatment pulse optical path is not satisfactory, i.e. the trajectory has been altered and the probe pulse contacts the skin surface, the treatment pulse will not be released. Consequently, the damage or irritation to the skin surface is reduced by the optical system.

The treatment pulse may be configured to treat skin and/or sever hair and has a pulse energy which may be greater than the pulse energy of said probe pulse.

Therefore, the optical system reduces any damage or irritation caused to the skin surface by ensuring that the lower intensity pulse is the only pulse which may contact the skin surface.

The pulse energy of said probe pulse may not be sufficient to harm a skin surface.

Therefore, the optical system may completely eliminate or at least significantly reduce the possibility of the skin surface being damaged or irritated.

The probe pulse optical path may be configured to coincide with at least part of said treatment pulse optical path. Alternatively, the probe pulse optical path can be a different optical path to the treatment pulse optical path. For example, the probe pulse optical path can extend substantially parallel to the treatment pulse optical path.

If the probe pulse and treatment pulse coincide, the probe pulse is able to verify the condition of the exact treatment pulse optical path taken by the treatment pulse. Because there is no difference in the optical path of the probe pulse and the treatment pulse the error in the determination of the condition of the treatment pulse's optical path may be eliminated or at least significantly reduced.

The probe pulse optical path may be substantially along the optical path or parallel to it to determine the condition of the optical path. Therefore, the probe pulse optical path may be shorter than the treatment pulse optical path. The probe pulse optical path may be arranged to focus on a specific portion of the treatment pulse optical path rather than the whole treatment pulse optical path.

The pulse generating arrangement may comprise a treatment pulse generator configured to generate said treatment pulse and a probe pulse generator configured to generate said probe pulse.

Therefore, the optical system requires fewer components and can help to minimise the size of devices in which it is used. It also makes it easier to ensure the probe pulse travels along the same optical path as the treatment pulse.

The pulse generator may be configured to generate the treatment pulse within 10 ms, or more preferably, less than 1 ms, of the probe pulse.

Therefore, the delay between the probe pulse and the treatment pulse is sufficiently small to guarantee that environmental influence on the treatment pulse optical path in between the pulses is negligible.

The pulse generator may be configured to generate successive probe pulses with a time gap of less than 10 ms.

Therefore, the optical system is able to provide at least 10 probe pulses per second along the probe pulse optical path. The greater number of probe pulses potentially leads to a greater number of treatment pulses being released which can help to reduce the time taken to perform a treatment. Furthermore, the greater number of probe pulses results in a quicker identification of an obstruction on the treatment pulse optical path.

The controller may be configured to compare the characteristic measured by the sensor to a predetermined value and to emit the treatment pulse if the sensed characteristic matches the predetermined value.

Therefore, analysis of the probe pulse can be performed quickly to ensure that the treatment pulse is only generated if the probe pulse verifies that the condition of the treatment pulse optical path, or optionally the probe pulse optical path indicative of the treatment pulse optical path, is completely uninterrupted or unaltered.

If the at least one determined characteristic of the probe pulse matches the intended value of the at least one characteristic then the controller activates the laser pulse generating arrangement to generate the treatment pulse. The at least one determined characteristic of the probe pulse will match the intended value if the optical path is not obstructed, interrupted or altered by an obstruction.

The controller can be configured to compare the characteristic measured by the sensor to a predetermined range and to emit the treatment pulse if the sensed characteristic falls within said predetermined range.

Therefore, the treatment pulse is only generated if the probe pulse verifies that the condition of the treatment pulse optical path, or optionally the probe pulse optical path indicative of the treatment pulse optical path, is within a defined range. This means that the treatment pulse may be released even if there is an insignificant alteration or interruption to the treatment pulse optical path. Therefore, minor alterations or interruptions in the treatment pulse optical path do not prevent the treatment pulse from being generated as long as the skin surface or other components of the optical system are not damaged or irritated.

The sensor may be at the end of said probe pulse optical path.

Therefore, the probe pulse is able to travel along the whole of the treatment pulse optical path, or optionally the probe pulse optical path indicative of the treatment pulse optical path. This ensures that the probe pulse verifies the condition of the entire length of the optical path of the treatment pulse, or optionally of the probe pulse indicative of the treatment pulse optical path, and ensures that there is no interruption or alteration along the entire treatment pulse optical path. This helps to reduce the likelihood of a treatment pulse damaging or irritating the skin surface or other components of the optical system.

According to another aspect of the present invention, there is provided a laser treatment device comprising said optical system according to an optical system of the present invention.

Therefore, the optical system can be used to cut hair or treat skin. The optical system may be programmed to know the difference between hair and/or skin and an obstruction. In shaving systems, the at least one sensor may be capable of generating information capable of identifying obstructions caused by hairs to be cut from other obstructions, such as skin surfaces or water droplets. For example, a multi-element imaging sensor may be able to identify hair and avoid false positives by comparing the cylindrical shape of a hair to the flat plane of a skin surface.

In an alternative example, the controller and an intensity sensor may know the intensity drop caused by a hair and will prevent the generation of the treatment pulse if the intensity drops below a predetermined level. In another alternative embodiment, the at least one sensor may measure the temporal profile of a characteristic. The temporal profile of hair will change quickly as the hair is cut, whilst skin or water droplet obstruction will remain in the probe pulse optical path for a longer amount of time. Therefore, the optical system may be able to distinguish hair from skin and/or obstructions.

In skin treatment systems, the at least one sensor may be a skin position sensor. The skin position sensor may be capable of generating information indicative of the skin surface's location and geometry. Variations in the skin surface's location and geometry occur in the order of milliseconds to seconds. The variations in spatial and temporal distributions may be used to distinguish the skin surface from hair and/or obstructions.

Furthermore, the at least one characteristic of the probe pulse may be determined before the section of the optical path in which hair and/or skin is placed. Therefore, a treatment pulse may be released to sever hair and/or treat skin.

However, the optical system is not limited to being used to cut hair and treat skin. Alternatively, the optical system may be used in any situation in which a probe pulse is emitted to check that there are no obstructions on the optical path before a hazardous treatment pulse is emitted along the optical path.

A part of said treatment pulse optical path may be across a recess in said laser treatment device, parallel to, and optionally spaced from, a plane that extends across said recess in which a skin engaging face lies.

Therefore, the probe and/or treatment pulses are at substantially the same distance from the skin surface as they travel across the recess. This means that they are not too close to the skin surface on one side of the recess and too far away on the other. This helps to reduce uneven performance by giving more uniform results.

According to another aspect of the present invention, there is provided a method for cutting hair using a laser shaving device, having a recess into which hair extends comprising, operating an optical system to direct a probe pulse along a probe pulse optical path extending through a plurality of optical components, generating information indicative of the condition of a treatment pulse optical path that also extends through said optical components by measuring a characteristic of said probe pulse using a sensor along said probe pulse optical path, comparing said information indicative of a characteristic of said probe pulse against a predetermined range, and emitting a treatment pulse along said treatment pulse optical path through said components to cut hair extending into said recess when said information indicative of the characteristic of said probe pulse falls within said predetermined range.

Therefore, the treatment pulse is not released if the condition of the treatment pulse optical path, or optionally the probe pulse optical path indicative of the treatment pulse optical path, is not satisfactory, i.e. the trajectory has been altered and the probe pulse contacts the skin surface. Consequently, the damage or irritation to the skin surface is reduced by the optical system.

According to another aspect of the present invention, there is provided a computer program comprising instructions which, when executed by at least one processor, cause the method according to the present invention to be performed.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring toFIG. 1, there is shown an optical system1. The optical system1is configured to guide a laser pulse along an intended optical path2. The intended optical path2is the route along which a laser pulse is intended to travel.

The optical system1comprises a laser pulse generating arrangement3. The laser pulse generating arrangement3is configured to generate a treatment pulse and a probe pulse. Therefore, the laser pulse generating arrangement3is at the beginning of the intended optical path2. The laser pulse generating arrangement3is configured to direct the laser pulses towards the rest of the optical system1. The laser pulse generating arrangement3may be, for example, but not limited to, a laser diode.

In the present embodiment, the laser pulse generating arrangement3is configured to generate two different laser pulses. The first laser pulse is the probe pulse. The second laser pulse is the treatment pulse. The laser pulse generating arrangement3generates the pulses in sequence. That is, the probe pulse is generated before the treatment pulse. The treatment pulse travels along a treatment pulse optical path2. The probe pulse travels along a probe pulse optical path (not shown). In the present embodiment, the probe pulse optical path is identical to and coincides with the treatment pulse optical path2. Therefore, if the treatment pulse optical path2is uninterrupted and/or undisturbed the probe pulse and the treatment pulse will both travel along it. However, if the treatment pulse optical path2is disturbed then the probe pulse will travel along an altered optical path4.

It will be understood that in an alternative embodiment, the laser pulse generating arrangement3of the optical system1may comprise individual laser pulse generators (not shown). In such an embodiment, the first laser pulse generator may generate the probe pulse and the second laser pulse generator may generate the treatment pulse. As the laser pulses originate from different sources, the probe pulse may only travel along an alternative probe pulse optical path (not shown). The alternative probe pulse optical path may be substantially the same as the treatment pulse optical path2of the treatment pulse. That is, the probe pulse may travel along the alternative probe pulse optical path, for example, but not limited to, parallel to and spaced from the treatment pulse optical path2. This alternative path is a predetermined different path (not shown) for the probe pulse to the probe pulse optical path that coincides with the treatment pulse optical path2.

The optical system1further comprises a controller5. The controller5is configured to control the operation of the laser pulse generating arrangement3. Therefore, the controller5controls the generation of the probe pulse and the treatment pulse. The controller5comprises a processor6. The controller5further comprises a memory7. The controller5is able to operate the optical system1.

The processor6may take any suitable form. For instance, the processor6may be or include a microcontroller, plural microcontrollers, circuitry, a single processor, or plural processors. The controller5may be formed of one or multiple modules.

The memory7may take any suitable form. The memory7may include a non-volatile memory and/or RAM. The non-volatile memory may include read only memory (ROM), a hard disk drive (HDD) or a solid state drive (SSD). The memory7stores, amongst other things, an operating system. The memory7may be disposed remotely. The RAM is used by the processor6for the temporary storage of data.

The operating system may contain code which, when executed by the controller5, controls the operation of the hardware components in the optical system1.

The optical system1further comprises at least one sensor8. In the present embodiment, the optical system comprises a single laser pulse sensor8. The laser pulse sensor8may be an electronic sensor. Alternatively, the laser pulse sensor8may be a photodiode array. In the present embodiment, the laser pulse sensor8is configured to generate information indicative of at least one of the optical characteristics of the probe pulse which has traveled along the probe pulse optical path which coincides with the treatment pulse optical path2.

In the present embodiment, one laser pulse sensor8is disposed at the end of the probe pulse optical path which coincides with the treatment pulse optical path2. In an alternative embodiment, the laser pulse sensor8may be positioned at a different position along the probe pulse optical path. The laser pulse sensor8intersects the probe pulse optical path. Therefore, the probe pulse has to travel along the whole of the treatment pulse optical path2or substantially along it to be sensed by the laser pulse sensor8. However, it will be understood that more than one laser pulse sensor8may be used.

The further along the probe pulse optical path the laser pulse sensor8is placed, the greater the proportion of the treatment pulse optical path2, or the alternative probe pulse optical path indicative of the treatment pulse optical path, can be declared safe for the treatment pulse. Therefore, the safety of the optical system1is increased and the likelihood of damage or injury is reduced.

The laser pulse sensor8is configured to generate information indicative of at least one characteristic of the probe pulse. The at least one characteristic may be, for example, but not limited to, the position of the taken altered optical path4through the optical system1, the intensity, power, energy, spatial distribution or temporal distribution of the probe pulse. The laser pulse sensor8is configured to communicate the information generated to the controller5. The controller5uses the information generated by the laser pulse sensor8to determine the at least one characteristic, for example, the taken altered optical path4and/or the intensity of the probe pulse.

The controller5then compares the at least one determined characteristic of the probe pulse to the intended value of the at least one characteristic of the probe pulse. By comparing the at least one determined characteristic of the probe pulse to the intended value of the at least one characteristic the controller5can determine the quality of the treatment pulse optical path2. If the at least one determined characteristic of the probe pulse matches the intended value of the at least one characteristic then the controller5activates the laser pulse generating arrangement3to generate the treatment pulse. The at least one determined characteristic of the probe pulse will match the intended value if the probe pulse optical path, which may coincide with the treatment pulse optical path2, is not obstructed, interrupted or altered by an obstruction9. The obstruction9may be a contaminant such as, for example, but not limited to detritus or the obstruction9may be a skin surface22, shown inFIG. 3. The contaminant may be, for example, but not limited to, detritus and a water or sweat droplet. The contaminant may be on any surface of the optical system1.

In the event that the at least one determined characteristic of the probe pulse does not match the intended values then the controller5does not activate the laser pulse generating arrangement3. Therefore, the treatment pulse is not generated and does not travel through the optical system1. The at least one determined characteristic of the probe pulse may not match the intended value if the treatment pulse optical path2, or alternative probe pulse optical path indicative of the treatment pulse optical path2, is contaminated by detritus or sweat(water) which refracts the probe pulse off course or is interrupted by detritus or a skin surface which blocks probe pulse.

In an alternative embodiment, the controller5may operate the laser pulse generating arrangement3to generate the treatment pulse if the at least one determined characteristic of the probe pulse is within a predetermined range of the intended values. The intended value may be a reference value that is programmed in the memory7of the controller5. Alternatively, the reference level or intended value may be measured or defined after manufacturing by sending a probe pulse along the uncontaminated probe pulse optical path, which may coincide with the treatment pulse optical path2. In another embodiment, the reference level or intended value may be set or updated by the user.

The predetermined range may be ±30%. That is, the at least one characteristic of the probe pulse may have to be within the range of up to ±30% of the intended value of said at least one characteristic of said probe pulse for the treatment pulse to be generated. More preferably, the predetermined range may be ±10%. Therefore, the at least one characteristic of the probe pulse may have to be within the range of up to ±10% of the intended value of said at least one characteristic of said probe pulse for the treatment pulse to be generated. Depending on the application of the optical system1, the predetermined range that the at least one characteristic of the probe pulse has to be within of the intended value may be as little as ±5%, or even ±1%.

In the present embodiment, the treatment pulse which is intended to travel along the treatment pulse optical path2through the optical system2has a pulse energy that is large enough to damage living tissue (not shown), and/or components of a device, an example of which can be seen inFIG. 2andFIG. 3, comprising the optical system1. Therefore, by preventing the generation and emission of the treatment pulse along the altered optical path4, which may direct the high intensity treatment pulse onto living tissue undesired damage or irritation can be avoided. The pulse energy of the treatment pulse may be between 0.1 and 1×103J. The intensity of the treatment pulse may be between 1×104and 1×1010W/m2.

The probe pulse which is emitted by the laser pulse generating arrangement3has a pulse energy which is less than the pulse energy of the treatment pulse. The pulse energy of the probe pulse may be between 1×10−1and 1 J. Therefore, even if the probe pulse optical path, which may coincide with the treatment pulse optical path2, is contaminated so that the probe pulse is deflected along the altered optical path4, the probe pulse will cause less damage or irritation to living tissue or components of a device comprising the optical system1. The intensity of the probe pulse is low enough that the probe pulse cannot cause damage or irritation to living tissue or components of a device comprising the optical system1. The intensity of the probe pulse may be between 1×10−5and 1×107W/m2. Therefore, no damage or irritation is caused by the optical system1when the probe pulse optical path and/or the treatment pulse optical path2is contaminated because the probe pulse is too weak and the treatment pulse is not generated and emitted.

The time delay between the release of the probe pulse and the subsequent treatment pulse, when the controller5determines that the condition of the treatment pulse optical path2is satisfactory, is less than 10 ms. More preferably, the time delay between the release of the probe pulse and the subsequent treatment pulse is less than 1 ms. Therefore, the time difference between analysing the condition of the treatment pulse optical path2and the emission of the treatment pulse is sufficiently small to ensure than environmental changes on the treatment optical path2, i.e. position of the contaminant9or location of new contaminants, is minimal. Hence, if the treatment pulse is emitted from the laser pulse generating arrangement3, it is more likely to successfully travel along the length of the treatment pulse optical path2.

Furthermore, the time gap between subsequent probe pulses is less than 10 ms. Therefore, the condition of the probe pulse optical path which coincides with the treatment pulse optical path2, or the alternative probe pulse optical path indicative of the treatment pulse optical path2, is evaluated frequently to ensure that any environmental change along the treatment pulse optical path2is measured. This helps to guarantee that the treatment pulse does not travel through the optical system1if it may cause damage. Furthermore, it means that more treatment pulses may be emitted by the laser pulse generating arrangement3which can increase the speed of a procedure or task being performed using the optical system1.

The optical system1may further comprise additional components configured to direct the laser pulses along the probe pulse optical path and/or the treatment pulse optical path2. In the present embodiment, shown inFIG. 1, for example, the optical system1further comprises a lens arrangement10. The lens arrangement10is configured to focus the laser pulses emitted from the laser pulse generating arrangement3. In the present embodiment, the lens arrangement10comprises a collimating lens11. The collimating lens11reduces or eliminates divergence of the laser pulses emitted from the laser pulse generating arrangement3towards the rest of the optical system1. The lens arrangement10further comprises at least one focus lens12. The present embodiment comprises two focus lenses12for converging and directing the collimated laser pulses.

The optical system1further comprises a first reflective element13and a second reflective element14. The first and second reflective elements13,14are configured to reflect an incident laser pulse along the probe pulse optical path and/or the treatment pulse optical path2. However, it will be understood that in an alternative embodiment the optical system1may have an alternative number of reflective elements. The first and second reflective elements13,14may comprises a mirror or prism or any other optically reflective surface.

The optical system1may further comprise an energy dissipater (not shown). The energy dissipater may be located at the laser pulse sensor8. Therefore, a treatment pulse travelling along the treatment pulse optical path2will not cause damage to any of the components of the optical system1. The optical system further comprises a detector lens15disposed on the probe pulse optical path and/or the treatment pulse optical path2prior to the laser pulse sensor8. The detector lens15is configured to adjust the dimensions of the laser pulse to suit the laser pulse sensor8. It will be understood that the detector lens15may be omitted.

In one embodiment, the optical system1may comprises an actuator (not shown) to adjust the probe pulse optical path and/or the treatment pulse optical path2. Therefore, a user may select the treatment pulse optical path2, which controls the degree of treatment, between the first and second reflective elements13,14using a user input (not shown).

As shown inFIG. 2andFIG. 3, a laser treatment device20comprises the optical system1. The laser treatment device20may be used to, for example, but not limited to, cut hair21extending from a skin surface22.

The laser treatment device20comprises a housing23. The housing23may comprise a guard24. The guard24may be a hair and skin manipulation module. The housing23has a skin engaging face25. The skin engaging face25is configured to be placed against the skin surface22. The skin surface22may be, for example, but not limited to, the face or leg of a user or person being treated.

The skin engaging face25comprises a recess26. The centre of the recess26is concentric with the centre of the skin engaging face25. The recess26is an oval slit. However, it will be understood that the shape of the cross-section of the recess26is not limited thereto. The recess26is greater than or equal to 0.3 mm and less than or equal to 1.5 mm wide in the direction of the shaving stroke. The recess width helps to control the doming of the skin surface22into the laser treatment device20. In the present embodiment, the width of the recess26is 0.8 mm. The skin engaging face25lies in a plane27that extends across the recess26.

The optical system1is located within the housing23of the laser treatment device20. The optical system1is located at least partially within the recess26. The recess26comprises a cutting zone28. When the skin engaging face25of the laser treatment device20is placed against the skin surface22and moved along it, the skin surface22and any hairs21on the skin surface may extend into the cutting zone28.

The optical system1directs the laser pulses across the recess26so that part of the treatment pulse optical path2is parallel and spaced from the plane27which extends across the skin engaging face25. The treatment pulse optical path2is proximate to the plane27which extends across the recess26. Therefore, when the skin engaging face25of the laser treatment device20is placed against the skin surface22, at least part of the treatment pulse optical path2is proximate the skin surface22. The treatment pulse, when emitted, may cut the hairs21extending from the skin surface22.

In the present embodiment, the probe pulse is emitted by the laser pulse generating arrangement3and is initially directed downwards towards the skin surface22. The laser pulse generating arrangement3directs the probe pulse to the collimating lens25which reduces the divergence of the probe pulse. The collimated probe pulse then passes through the focus lenses12which align the probe pulse so that it continues on the probe pulse optical path, which may coincide with the treatment pulse optical path2.

The first reflective element13, positioned on one side of the recess26, is configured to reflect the incident probe pulse across the cutting zone28of the recess26. That is, the first reflective element13is configured to reflect the incident probe pulse across the cutting zone28on the probe pulse optical path which is substantially parallel to and space from the plane27which extends across the recess26of the laser treatment device20. Therefore, the probe pulse optical path does coincide with the treatment pulse optical path2.

The second reflective element14, positioned on the opposite side of the recess26, is configured to reflect the probe pulse away from the cutting zone28. The second reflective element14is configured to reflect the probe pulse away from the skin surface22. The probe pulse is directed towards the detector lens15and laser pulse sensor8by the second reflective element14.

The laser pulse sensor8generates information indicative of the condition of the probe pulse optical path which coincides with the treatment pulse optical path2through the optical system1and communicates it to the controller5. The controller5determines the value for at least one of the optical characteristics of the probe pulse and compares it to the expected value.

If the treatment pulse optical path2is contaminated, i.e. a surface of one of the components of the optical system1has a contaminant on it that directs the probe pulse along an altered optical path4or an obstruction9such as the skin surface22blocks the probe pulse, then the determined value will not fall in the allowable range. Therefore, the controller5does not activate the laser pulse generating arrangement3to emit the treatment pulse to avoid causing damage or irritation.

If the treatment pulse optical path2is not contaminated or obstructed then the values will match and the controller5will activate the laser pulse generating arrangement3to emit the treatment pulse which will travel along the intended optical path2and cut the hairs21extending from the skin surface22.

The optical system1may be programmed to know the difference between hair and/or skin and an obstruction9. For example, the controller5may be able to determine the profile of hair and/or skin.

In shaving systems, the at least one sensor8may be capable of generating information capable of identifying obstructions caused by hairs21to be cut from other obstructions9, such as skin surfaces22or water droplets. For example, a multi-element imaging sensor may be able to identify hair21and avoid false positives by comparing the cylindrical shape of a hair21to the flat plane of a skin surface22.

In an alternative example, an intensity sensor may know the intensity drop caused by a hair21and will prevent the generation of the treatment pulse if the intensity drops below a predetermined level. In another alternative embodiment, the at least one sensor8may measure the temporal profile of a characteristic. The temporal profile of hair21will change quickly as the hair21is cut, whilst skin or water droplet obstruction9will remain in the probe pulse optical path for a longer amount of time. Therefore, the optical system1may be able to distinguish hair21from the skin surface22and/or obstructions9.

In skin treatment systems, the at least one sensor8may be a skin position sensor. The skin position sensor may be capable of generating information indicative of the skin surface's location and geometry. Variations in the skin surface's location and geometry occur in the order of milliseconds to seconds. The variations in spatial and temporal distributions may be used to distinguish the skin surface22from hair21and/or obstructions9.

In an alternative embodiment, the at least one characteristic of the probe pulse may be determined before the section of the optical path in which hair21and/or skin surface22is placed, for example, immediately before the probe pulse travels across the recess26parallel to the plane27that extends across the recess26. Therefore, a treatment probe may be released to sever hair when the hair21is the only “obstruction” on the optical path2.

However, the optical system1is not limited to being used to cut hair. Alternatively, the optical system1may be used in any situation in which a probe pulse is emitted to check that there are no obstructions9on the optical path before a hazardous treatment pulse is emitted along the optical path2.

Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel features or any novel combinations of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the parent invention. The applicants hereby give notice that new claims may be formulated to such features and/or combinations of features during the prosecution of the present application or of any further application derived therefrom.