Switched lasers for dermal treatment

Abstract

An applicator comprising multiple laser assemblies connected to a power supply and a controller that switches each pulse to a different one of the laser assemblies. Each laser assembly deposits a laser spot on the skin and the result is to produce a large ‘aggregate’ spot without requiring extra power or extra lasers. In one embodiment, each pulse serves as a trigger to switch the next pulse to the next laser assembly.

Claims

1. A device for applying laser energy to human or other mammalian skin, the device comprising: at least one applicator, each applicator comprising two or more laser assemblies, each laser assembly configured to receive an electrical pulse and convert it into laser energy incident on a spot of the skin; a controller configured to switch an electrical pulse or a group of electrical pulses to each laser assembly in sequence; wherein the controller comprises a counter incremented by an internal trigger, wherein the internal trigger detects an event selected from the group consisting of a change in pulse voltage, a change in pulse current, a change in laser energy intensity, and combinations thereof.

2. The device of claim 1 wherein the laser assemblies are arranged so that the distribution of their respective deposited spots is selected from at least one of the group consisting of adjoining, overlapping in full and not adjoining.

3. The device of claim 1 wherein the controller is configured to switch multiple pulses to each laser assembly in sequence.

4. The device of claim 1 wherein the controller is configured to repeat the switching multiple times.

5. The device of claim 1 wherein the counter comprises outputs, each output connected to the gate of a transistor, each transistor connected to a laser assembly, wherein activation of the output puts the connected transistor into an ‘on’ state, switching the next pulse to the connected laser assembly.

6. The device of claim 1 wherein the laser assembly comprises a semiconductor laser.

7. The device of claim 6 wherein the semiconductor laser comprises a stack of bars of laser diodes.

8. The device of claim 7 wherein each laser assembly is associated with at least one from the group consisting of a cylindrical lens and a light guide.

9. The device of claim 1 wherein at least some laser assemblies are of different wavelengths from one another.

10. The device of claim 1 wherein the wavelength of the laser energy produced by the laser assembly is between 755 nm +/−20% and 1064 nm +/−20%.

11. The device of claim 1 further comprising a cooled window.

12. The device of claim 1 wherein the counter comprises outputs, each output connected to the gate of a transistor, each transistor connected to a laser assembly, wherein activation of the output puts the connected transistor into an ‘on’ state, switching the next pulse to the connected laser assembly.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates results of applying a prior art laser applicator to an area of a subject's skin

(2) FIG. 2 illustrates results produced by a laser applicator constructed in accordance with the present invention to an area of a subject's skin comparable to that in FIG. 1.

(3) FIG. 3 is a view of components of a laser applicator constructed in accordance with the present invention.

(4) FIG. 4 is a view of a treatment of window of the applicator of FIG. 3.

(5) FIG. 5 is a view of parts of a laser assembly in the applicator of FIG. 3.

(6) FIG. 6 is a view of lenses of a laser assembly in the applicator of FIG. 3.

(7) FIG. 7 is a view of other parts of a laser assembly in the applicator of FIG. 3.

(8) FIG. 8 is a block diagram and simplified circuit diagram of a laser applicator constructed in accordance with the present invention.

DETAILED DESCRIPTION

(9) The present invention is directed to switching pulsed power between multiple laser assemblies to treat a subject's skin. In this manner a single power supply can supply all the laser assemblies, by supplying one at a time.

(10) The subject can be a human or other mammal. The application can be medical or cosmetic.

(11) In some embodiments, the laser assemblies are arranged so that the individual laser spots produced on the skin by their incident beams adjoin one another to form a relatively large aggregate laser spot. In other embodiments, the laser assemblies are arranged so that the individual laser spots uniformly overlap (i.e., are coincident) in part or in full. In other embodiments, the laser assemblies are arranged so that the individual laser spots are spaced apart by regular regions of skin that remain untreated.

(12) FIG. 1 illustrates results of a prior art device used to treat a skin surface area 50 measuring about 3.2 cm by 16 cm, or about 51 square cm. The spot size of the prior art device is about 0.8 cm by 1.6 cm, or 1.28 square cm, so 40 steps are required to cover the target skin area.

(13) FIG. 2 illustrates results obtained on the same skin area by an embodiment of the invention comprising four laser assemblies. Each laser assembly has a spot size like that of the prior art device, about 0.8 cm by 1.6 cm, or 1.28 square cm. After each step (advance) of the applicator, power is switched sequentially to each of the four laser assemblies, to produce a set of adjoining spots (labeled A, B, C, and D) forming an ‘aggregate spot’ of 4×1.28 square cm, or 5.12 square cm. In ten steps, labeled 1 to 10, the target area is covered. The switching sequence can hardwired or set by the operator, for example through a graphical user interface. The switching sequence can be any number of activations of a given laser assembly, any order in which the laser assemblies are activated, and any number of repetitions of the switching sequence. Some examples: one activation of the laser assembly incident on spot A, then the one of the laser assembly incident on spot B, then one of the assembly incident on spot C, and then one of the assembly incident on spot D. Or multiple activations of each laser assembly before switching to the next laser assembly. Or different numbers of activations depending on the laser assembly. Or a round of single or multiple activations of each laser assembly followed by more rounds.

(14) In the example, the invention requires 75% less steps than the prior art. Treatment is accordingly much faster with less operator effort and less risk of faulty alignment.

(15) FIG. 3 depicts a laser treatment applicator 20 in accordance with an embodiment of the invention. The applicator shown is handheld with the outer shell removed. Automated embodiments are also possible. Pulses from a diode driver (not shown) are supplied through an umbilical cord (not shown) and routed sequentially by controller 34 through switches 36 to laser assemblies 22. In some embodiments, applicator 20 is a standalone device, for example in home use formats.

(16) FIGS. 4 to 7 show components of laser assembly 22. There are at least two laser assemblies 22, each comprising a laser diode stack 24. Laser diode stack 24 is optically associated with a plano concave cylinder lens 28, which is optically associated with a light guide 30. Light guides 30 are optically associated with a cooling window 32.

(17) In use, pulses from the diode driver are switched sequentially to laser diode stacks 24 where they are converted into laser output beams that are widened along their slow axis by lens 24, then are channeled and shaped by light guide 30, and then pass through laser-transparent window 32, which is in contact with the subject's skin, to deposit a spot of laser energy on the skin. Window 32 is chilled by a thermoelectric cooler and so cools the skin surface by conduction. Laser assembly 22 is radiatively cooled by a circulating coolant.

(18) In some embodiments the spot size produced is about 16 mm by 8 mm. However other common sizes may be used.

(19) There are many ways to switch the pulses between the diode laser stacks 22. FIG. 8 shows an embodiment with automatic switching to route a pulse sequentially to each diode stack 24.

(20) Each activation of trigger 40 increments counter 42, activating a different output, which puts a signal on the gate of an associated transistor 44, which acts as a low side switch, opening the path between the drain and the source for a pulse to reach the associated diode laser array 24.

(21) An internal trigger detects the event. For example, the trigger might be detection of the change in pulse voltage or current or it might be detection of the laser light. The trigger detection is performed off-line (not under load) for increased reliability and decreased switching losses in the circuit.

(22) In some embodiments, the controller can be an external component, such as a microcontroller. In such cases, the controller can be programmed to switch on the transistor for a number of pulses or it can be programmed to repeat the switching sequence a number of times.

(23) The embodiment shown in FIGS. 3 to 7 comprises two laser assemblies 22. Alternatively, there can be 3, 4, 5, 6, 7, 8, 9, 10 or even more laser assemblies within practical limits, such as weight limitations. Similarly, each diode laser stack 24 can comprise any practical number of diode laser bars 26. In some embodiments, there may be more than one diode laser stack 24 per diode laser assembly 22.

(24) Laser diode stacks 24 may be all of a single wavelength or some or all of them may be of different wavelengths. The laser diode bars 26 of a laser diode stack 24 may be all of a single wavelength or some or all may be of different wavelengths.

(25) The arrangement of the laser assemblies 22 in applicator 20 depends on the desired spot pattern. In some embodiments, the laser assemblies 22 are arranged so that the spots produced at least substantially adjoin one another to form an aggregate spot of maximum size.

(26) In some other embodiments, at least some laser assemblies 22 may be arranged so that the spots produced overlap in whole (i.e., cover the same specific area) or in part. For example, laser assemblies of different wavelengths could be arranged to treat the same spot. While the aggregate spot size would be smaller, there is the benefit of applying multiple wavelengths at full fluence without having to move the applicator.

(27) In some embodiments, at least some laser assemblies 22 may be arranged with a gaps between them, for example to create lines of undamaged skin to accelerate post-treatment recovery from thermal damage to the treated parts of the skin surface.

(28) In some embodiments, applicator 20 is a stationary device. In some embodiments, there are multiple instances of applicator 20. For example, a number of applicators 20 may be positioned at different locations on the target skin area and applied concurrently.