Patent Application
20120283801
The present invention relates to apparatus for detecting the presence of skin, typically for use as a safety device to ensure that light therapy devices are not used where there is no target area of skin present. The invention also encompasses a method for detecting of the presence of skin suitable for use in controlling operation of such light therapy devices, both for therapeutic purposes and for cosmetic purposes).
Various types of light therapy are known. For example, intense-pulsed-light (IPL) is used for local treatment of various skin conditions and to influence non-desired hair growth.
It is important to ensure that the light is directed at the area of skin to be treated, and not for example, at more delicate body parts (such as the eyes) and not used where skin is not detected.
US2004/0167502 A1 discloses a device and method for sensing the presence of human skin by evaluating the spectral remittance of electromagnetic radiation from the surface in question. Such a device requires complicated circuitry and optical control, separate from the optical control needed in apparatus for dermatological treatment. It is an object of the invention to provide simplified apparatus for this purpose.
According to a first aspect of the invention, there is provided apparatus for detecting the presence of skin, which apparatus comprises
a) a set of probes each having tips arranged to simultaneously touch the skin and define a predetermined pattern on the skin, at least one of said probes (hereinafter referred to as a transmitter probe) being arranged to transmit a pulsed electrical signal and at least one of said probes (hereinafter referred to as a receiver probe) being arranged to receive said transmitted electrical signal;
b) signal detector means for detecting the or each received electrical signal;
c) means for comparing a numerical value obtained from at least one detected signal from said signal detector means with at least one predetermined numerical value; and
d) means for providing an output when said value obtained from the detected signal differs from said predetermined numerical value by more than a predetermined amount.
The receiver probe may be the same as the transmitter probe, or it may be different thereto. If the receiver probe and transmitter probe are the same, the apparatus may take measurements based on capacitance (such as elapsed time to reach a predetermined voltage). In this embodiment, it is preferred that all of the set of probes are both transmitter probes and receiver probes.
If the transmitter probe and receiver probe are different probes, it is preferred to provide a single transmitter probe, with the remainder of the probes being receiver probes.
In an advantageous embodiment of the invention, the tips of the probes are fixed to a support, such that the tips together define a two dimensional pattern, such as a rectangle, in which all the tips are intended to be in contact with the skin. This pattern preferably defines the perimeter of an area that is slightly larger than the area of an aperture of an intense-pulsed-light device, such as a discharge lamp, which is to be contacted with the skin. Such a pattern is typically a rectangle measuring about 10 to 15 mm×20 to 30 mm. An arrangement of the nature just described ensures that the aperture is not obscured by the probes.
The probes themselves are preferably elongate pins, typically having a diameter of about 2 to 3 mm.
Because dry skin, oily skin and gel-covered skin all have different electrical properties, including conductance and capacitance, it is preferred that the predetermined amount is sufficiently distinct from the predetermined value in order to provide a margin of error. For example, if the predetermined value is voltage, it is preferred that the minimum of the range be above the minimum known for skin. If the predetermined value relates to capacitance, the predetermined value is preferably based on elapsed time to reach a threshold voltage which, in turn will depend on the capacitance of the skin contacted by the probe.
The apparatus according to the invention may be used for the detection of the presence of skin in an automated decision stage of a microprocessor to activate an intense-pulsed-light unit when pre-determined input conditions are fulfilled (that is when skin having parameters within a predetermined range is detected).
An advantageous use of the apparatus is to automatically determine whether the parameters measured indicate that a gel-like substance has been applied to the skin. In this case, the firing of the intense-pulsed-light is only permitted when such gel-coated skin is detected.
The output provided when the values are outside a predetermined range may comprise an alarm, which can typically be one or more of an audio signal, a visible signal or a movement signal (such as a vibration or other movement of the apparatus). Alternatively, the output may be a feedback signal arranged to cause an intense-pulsed-light source to cut out when values outside the predetermined range are detected.
According to a further aspect of the invention, there is provided a method for controlling the operation of an intense-pulsed-light source, which method comprises applying a set of probes each having tips simultaneously touching a test surface so as to define a predetermined pattern on the test surface,
transmitting a pulsed electrical signal from at least one of the probes;
receiving the signal by at least one of the probes (which may be the same as, or different to, the probe which transmits the signal),
providing connection of each of the probes receiving the transmitted pulsed electrical signal to a respective individual signal detector,
comparing a value of the detected signals from the or each signal detector with at least one predetermined value; and
providing an output when the compared value is outside a predetermined range, which output either prevents or permits the operation of the light source.
Preferred embodiments of the present invention will be further described, by way of example only, with reference to the accompanying drawings, in which
According to a first embodiment of the invention as shown in
A storage device 10 connected to the microprocessor contains reference data such as the conductance and capacitance of various skin types, such as dry skin and oily skin. The storage device 10 further comprises reference data for the various skin types under different conditions, for example with and without the presence of a coupling gel. In addition, the storage device 10 further comprises a table that correlates skin type and condition, with the dosage of intense-pulsed-light that is required to treat the skin type. This means that the microprocessor 9 is able to provide a dosage that will be tolerated by the skin under its actual conditions, while obtaining the end result desired.
Referring to
Exemplary control circuitry, which controls the firing of the tube (not shown) in accordance with a second embodiment of the invention, is shown in
The control circuit 14 shown in
The voltage input to each comparator 18 is governed by a pair of resistors 19 each typically being about 100 kΩ, arranged in a series configuration with the respective comparator 18. Each of the four probes 13a to 13d is separately connected to a respective circuit path 17a to 17d at a position intermediate the respective pairs of series resistors 19. The probes 13a to 13d in the embodiment of
The distal end of each probe 13a to 13d may be initially located in free space (in contact with air) and will thus generate a small capacitance. Accordingly, the application of a voltage pulse to the power rail 16 will cause the voltage input to the respective comparator 18 to increase to the threshold voltage over a time interval t1. If the probes 13a to 13d are all in contact with skin, then this will act to increase the effective capacitance of the probes 13a to 13d thereby causing an increase in the interval t1.
In use, a periodic train of voltage pulses, each of magnitude approximately 5V and duration up to 100 μs is continuously applied to the power rail 16. At a time corresponding to the leading edge of each voltage pulse on the power rail 16, the voltage input to each comparator 18 will begin to increase. The rate of increase of the voltage input to each comparator 18 will depend upon whether the respective probe 13a to 13d is in free space or coupled to skin. In the latter case, the rate of increase of the voltage input to each comparator 18 will further depend on the condition of the skin and on whether a coupling gel has been applied to the skin.
Probes 13a to 13d will, when coupled to the skin, cause the voltage input to the respective comparator 18 to increase more slowly than for those comparators for which the probes are arranged in free space. Moreover, it is found that the application of a coupling gel to the skin further reduces the rate of voltage rise input to the respective comparator 18.
The processing unit 15 only outputs a signal to cause the discharge lamp (not shown) to generate a pulse of intense light when it is determined that all four probes 13a to 13d are in contact with skin. Accordingly, the time for the comparators 18 to change output state is monitored and only if the time taken for each comparator 18 to change output state is above a threshold time, as determined from the leading edge of a selected voltage pulse on the power rail 16, will the processing unit 15 instruct the firing of the discharge lamp (not shown). In this respect, it is not necessary for each comparator 18 to change output state. If the output from each and every comparator 18 does not change state due to an excessively long rise time, then this is further taken to indicate that the respective probe(s) 13a to 13d is/are in contact with the skin.
The continuous application of voltage pulses to the power rail 16 thus provides for a continuous verification of whether the probes 13a to 13d are in contact with skin, and thus the circuit 14 will inhibit the firing of the discharge lamp (not shown) if at least one of the probes 13a to 13d breaks or loses contact with the skin.
Referring to
Block A represents the first step, namely the application of gel to the skin. Block B represents the second step, namely the application of an array of probes 2 to or 13a to 13d, to the skin.
A pulsed electrical signal is sent through the probes 2 to 5, or 13a to 13d in step C and the time to reach the threshold voltage for each probe 2 to 5, or 13a to 13d is assessed in step D. The time is compared to a stored threshold value in step E; when the time is found to be greater than the stored threshold value in step F, the processing unit 10 or 15 outputs a control signal to permit a discharge lamp (not shown) to fire. Conversely, when the time is determined to be less that the stored threshold value in step F, the firing of the discharge lamp (not shown) is inhibited.
The stored threshold value chosen will depend to some extent on the frequency of the applied voltage pulse. Accordingly, it is preferably to normalise the time. Normalised time values of about 5.1 were obtained using apparatus according to the second embodiment of the invention (with the probes 13a to 13d being both transmitters and receivers) with oily skin; about 5.4 with degreased skin; about 6.3 for sweaty skin and over 7.0 for gel-coated skin—depending on the nature of the skin to which the gel was applied.
The stored time, below which firing is not permitted, may therefore be based on the above values, such as about 4. In that case, the firing will be permitted even when the probes 13a to 13d are not in contact with gel-coated skin. Alternatively, the stored output time below which firing is not permitted, may be set at about 7; in which case the firing will only be permitted when the probes 13a to 13d are in contact with gel-coated skin.
If the normalised time is less than a first threshold (column Y), this is taken to be indicative of the absence of skin, whereas if it exceeds a second threshold this is taken to be indicative of the presence of gel-coated skin (column Z). An intermediate value corresponds to a value measured for oily skin. If the detected value is below the first threshold, an alarm is triggered or a feedback signal is provided to prevent inadvertent operation of an intense-pulsed-light source.
From the foregoing therefore, it is evident that the apparatus and method of the present invention can prevent inadvertent operation of an intense-pulsed-light source when, for example one or more of the tips of the probes fail to contact skin, or for example when they contact another part of a body, such as an eye or mucous membrane.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200700581 | Apr 2007 | DK | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB08/50278 | 4/21/2008 | WO | 00 | 9/15/2011 |
