JP2018094155A - Skin laser treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and inexpensive skin laser treatment device capable of reducing a risk of thermal damage to the skin in spite of its high output since it is possible to irradiate the skin with a burst pulse light formed by repeated emissions of a pulse laser beam having a short pulse width of picosecond order and high peak power to the skin.SOLUTION: A skin laser treatment device 1 includes an excitation light source 2, an optical fiber 3 for transmitting an excitation light discharged from the excitation light source 2, and a resonator 4 incorporating a microchip laser medium 5 and a saturable absorber 6 from which a laser beam is emitted when the transmitted excitation light is incident and excited. The pulse laser beam is emitted repeatedly and forms a burst pulse light, which is emitted to an affected part of the skin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a skin laser treatment device for treating a skin disease by irradiating an affected area of the skin with a laser, and more particularly, a burst pulse light formed by repeatedly emitting a pulse laser beam having a pulse width on the order of picoseconds. The present invention relates to a small and inexpensive skin laser treatment device.

Conventionally, for skin diseases such as aza, moles, and vascular lesions, treatment has been performed in which the affected area is irradiated with laser light having a wavelength, a pulse width, or the like corresponding to each disease.
As a treatment device used for such treatment, for example, a laser treatment apparatus using a Q-switched pulse laser has been used. As this laser treatment apparatus, for example, a solid laser medium in the lamp house, an excitation light source for exciting the laser medium, and a laser oscillator which is a Q switch laser, and a cooling water system for cooling the inside of the lamp house, , Generated in a laser medium or a resonator by cooling a cooling water system, a handpiece part for irradiating the affected part with pulsed laser light, an articulated light guide for guiding the pulsed laser light from the laser oscillator to the handpiece part, and There is a thing provided with the dew condensation prevention means for preventing dew condensation (patent documents 1).

  According to the laser treatment apparatus having such a configuration, even if the temperature of the laser medium is lowered by cooling the cooling water system, it is possible to prevent dew condensation occurring in the laser medium and the resonator. For this reason, it is possible to prevent the deterioration of the laser medium and the resonator and the decrease in the output of the laser. Further, by using a Q-switched laser as the laser oscillator, the pulse width of the laser light can be sufficiently short and the peak value can be increased. Therefore, for example, when treating aza, it is possible to destroy only cells having melanin pigment to a deeper level and not to destroy normal cells.

As other treatment devices, for example, handheld laser devices have been developed. The laser device includes a hand-held housing, a continuous wave laser member disposed in the housing and emitting an output beam, a power activation button for mounting the device, and a single first pulse of the output beam. A switch system is included that includes a power setting button for firing and, after interruption, subsequently firing a single second pulse of the output beam.
According to the laser device having such a configuration, the continuous laser is converted into the first and second pulses having a certain duration at a certain repetition rate. Since the first and second pulses successively strike a spot on the same specific skin, laser energy can be efficiently applied to this spot.

Further, similar to the laser apparatus described in Patent Document 2, a laser treatment apparatus capable of continuously emitting pulsed laser light has been developed. The laser treatment apparatus includes a laser and a control unit, and is a laser treatment apparatus that is a solid-state laser with a pump source. The control unit generates at least one first pulse of the laser in a first pulse operation. (Patent Document 3).
According to the laser treatment apparatus having such a configuration, a plurality of continuous first pulses are generated as shown in FIGS. The peak output of the first pulse is increased by more than 10 times the average output level of the conventional continuous laser by the high speed switch-on of the pump source. Therefore, it is possible to enable a treatment form that has been impossible due to insufficient output.

JP-A-8-266649 Special table 2014-522704 gazette Special table 2014-524286 gazette

However, the invention disclosed in Patent Document 1 has a disadvantage that the apparatus becomes complicated and large because it includes a cooling water system, an articulated light guide, and a dew condensation prevention means, and cannot be introduced at low cost.
Further, the laser device described in Patent Document 2 has an energy fluence range from 10 (ms) to 120 (ms) in pulse width and 0.5 (J / cm ² ) to 5 (J / cm ² ) in the output beam. This is a handy type device intended to treat wrinkles and hyperpigmentation by irradiating the skin with laser light having a wavelength of 1420 (nm) to 1470 (nm). In such a laser treatment device, although it is easy to handle, the peak power is very low and the wavelength is different from that of the Q-switched laser. Therefore, skin such as aza, mole, and vascular lesions, which are treatment targets of the present invention. There is a problem that it is difficult to use for treatment of diseases.
Furthermore, the laser treatment apparatus described in Patent Document 3 has an average output of 2 (W) obtained from a continuous wave (CW) laser, and a pulse peak output of about 35 (W) by switching on the pump source at high speed. Can be used for treatment methods such as “selective photothermal melting of the retina”, “photocoagulation method”, “thermotherapy”, and “vital stimulation method for eyes”. Therefore, the laser treatment apparatus described in Patent Document 3 is also a laser treatment apparatus that emits laser light having a very low peak power compared to the Q-switched laser, as in the laser apparatus described in Patent Document 2. There is a problem that it is difficult to use for skin diseases such as aza, mole, and vascular lesions, which are the treatment targets.

  The present invention has been made in response to such a conventional situation, and burst pulse light formed by repeatedly emitting a pulse laser beam having a short pulse width of a picosecond order and a high peak power is applied to the skin. Therefore, it is an object of the present invention to provide a skin laser treatment device that can reduce the risk of thermal damage to the skin while having high output, and that is small and inexpensive.

In order to achieve the above object, the first invention is a pulsed laser beam by exciting an excitation light source, an optical fiber that transmits the excitation light emitted from the excitation light source, and the transmitted excitation light being incident and excited. A microchip laser medium and a saturable absorber, and a pulse laser beam is repeatedly emitted to form burst pulse light, and this burst pulse light is applied to the affected area of the skin. It is characterized by irradiating.
In the invention having such a configuration, when the intensity of the laser beam resonance-amplified by the resonator exceeds a threshold value, the saturable absorber acts as a passive Q switch, and instantaneously has an energy Ep (mJ) and a peak power. And a short pulse laser beam having a short pulse width Wp (ps) are repeatedly emitted with a time interval.
A set of burst pulse light is formed from the pulse laser light emitted m times. When this set of burst pulse lights is formed n times with a time interval, the energy (mJ) of the n sets of burst pulse lights is the product of these, that is, [Ep · m · n].

Next, a second invention is characterized in that, in the first invention, the pulse laser beam has a pulse width of 1 to 700 ps.
In the invention having such a configuration, since the pulse width Wp is extremely short on the order of picoseconds, it is considerably shorter than the thermal relaxation time of the target substance. The target substance is, for example, a melanin pigment contained in the skin. The thermal relaxation time is the time when the target tissue reaches the maximum temperature by laser irradiation, and heat dissipation occurs due to the suspension of irradiation until it is cooled to 1 / e of the maximum temperature (about 37%, e is the base of natural logarithm). Time spent. The specific heat relaxation time is 50 to 280 (ns) for melanin pigments.

Further, according to a third invention, in the first or second invention, the pulse laser beam has a peak power density of 398 MW / cm ² and 199 MW / cm ² or more, respectively, when the wavelength is 1064 nm and 532 nm. It is characterized by.
In the invention of such a configuration, in addition to the operation of the first or second invention, an example of the peak power density of the laser light according to the prior art (133 (MW / cm ² ), peak power 67 (MW), Compared with the case of wavelength 1064 (nm) and spot diameter 8 (mm), the maximum peak power is about three times. Therefore, the deep penetration to the skin is improved. The peak power is a value represented by [energy of laser beam / pulse width].

According to a fourth aspect of the present invention, in any one of the first to third aspects of the invention, the second and subsequent pulse laser beams are emitted from the plurality of pulse laser beams, and the emission of the immediately preceding pulse laser beam is completed. It is characterized by starting with a first time interval.
In the invention with such a configuration, the first time interval changes depending on the energy Ep and pulse width Wp of the emitted pulsed laser light. Specifically, for example, in the case of pulse laser light having a pulse width of Wp100 (ps), the first time interval is 100 (μs). Further, the number of pulsed laser beams repeatedly emitted depends on the pulse width of the excitation light and the characteristics of the resonator.
In the invention with the above configuration, in addition to the action of any one of the first to third inventions, the burst pulse light is emitted with a plurality of pulse laser lights having a short pulse width with a first time interval. Therefore, heat accumulation in the skin is suppressed, and at the same time, the heat load in the resonator is suppressed.

In a fifth aspect based on any one of the first to fourth aspects, the excitation light is emitted at least once during a repetition period, and the burst pulse light is emitted along with the emitted excitation light. When a plurality of burst pulse lights are emitted, the second and subsequent burst pulse lights are emitted at a second time interval after the last emission of the excitation light is completed. Features.
In the invention having such a configuration, the second time interval depends on the excitation light period Te. For example, when the repetition frequency is 100 (Hz), the second time interval is 10 (ms).
In addition to the operation of any one of the first to fourth inventions, for example, when the excitation light is emitted once during the repetition period, the burst pulse light is also formed once at substantially the same timing. Further, when the excitation light is emitted five times during the repetition period, the burst pulse light is also formed five times at substantially the same timing. In other words, the second to fourth burst pulse lights are started with a second time interval from the end of the first to fourth excitation light emission. In addition, the period of excitation light is 10 (ms), for example.

  On the other hand, in the laser irradiation according to the prior art, for example, pulsed light having a pulse width of 6 (ns) is only formed once per 100 (ms). Accordingly, in the present invention, when one burst pulse light is formed by pulse laser light repeatedly emitted four times, the maximum energy [Ep (invention of the present invention) of the burst pulse light emitted during one repetition period. And energy of conventional laser irradiation emitted within the same time as the repetition cycle [Ec (energy of one pulse laser beam in the prior art) × 1] is equivalent, the burst pulse light is temporally dispersed and emitted during the repetition period, so that the thermal load on the skin and the resonator is smaller in the present invention than in the conventional laser irradiation. .

  According to the first invention, since the pulse laser beam having a high peak power and a short pulse width Wp (ps) is emitted instantaneously with the energy Ep (mJ), the thermal damage of the skin while having a high output. Can reduce the risk. Therefore, it is possible to improve the treatment results of skin diseases that have been insufficient due to insufficient output in the past and the removal results of tattoos composed of multiple types of pigments, and at the same time, it is possible to improve safety. .

  According to the second invention, in addition to the effects of the first invention, the pulse width Wp of the pulsed laser beam is considerably less than the thermal relaxation time of the target substance, so that heat dissipation to normal tissue around the affected area is suppressed. Can do. Therefore, side effects such as scarring due to skin damage due to heat diffusion can be prevented.

  According to the third invention, in addition to the effects of the first or second invention, the penetration of the pulsed laser light into the skin is improved, so that the pulsed laser light is emitted to the depth where the target substance exists in the affected area. It is possible to reach it sufficiently. Therefore, the thermal energy absorbed by the target substance can be increased and destroyed.

  According to the fourth invention, in addition to the effects of any one of the first to third inventions, heat accumulation in the skin is suppressed, and at the same time, the thermal load in the resonator is suppressed. The cooling means for cooling the skin and the resonator is unnecessary, or can be realized by a small cooling device. Therefore, since the configuration of the skin laser treatment device is simplified, the skin laser treatment device can be downsized, and the introduction cost can be reduced.

  According to the fifth invention, in addition to the effects of any one of the first to fourth inventions, the thermal load on the skin and the resonator is smaller in the present invention than in the conventional laser irradiation. Further, while maintaining this state, by selecting the type of the microchip laser medium and the saturable absorber, and realizing a short pulse width on the order of picoseconds, the peak of one pulse laser beam in the present invention is achieved. The power can be made larger than the peak power of one pulse laser beam in the prior art. In addition, the number of times the burst pulse light is emitted and the second time interval can be adjusted by adjusting the number and timing of the excitation light emitted during the repetition period. Therefore, according to the present invention, it is possible to freely adjust the maximum energy of the burst pulse light irradiated to the skin and the second time interval, so that optimum irradiation conditions can be set finely for various affected areas. can do.

It is a block diagram of the skin laser treatment apparatus which concerns on an Example. It is a block diagram of the resonator which comprises the skin laser treatment apparatus which concerns on an Example, and its periphery part. (A) And (b) is a conceptual diagram of the burst pulse light which the skin laser treatment apparatus concerning an Example radiate | emits, respectively, and the pulsed laser beam based on a prior art. (A) thru | or (e) is a conceptual diagram of the burst pulse light which the skin laser treatment apparatus concerning an Example each radiate | emits. It is the table | surface which compared the performance of the skin laser treatment apparatus which concerns on an Example, and the laser treatment apparatus which concerns on a prior art.

The skin laser treatment apparatus of the Example which concerns on embodiment of this invention is demonstrated in detail using FIG. 1 thru | or FIG. FIG. 1 is a configuration diagram of a skin laser treatment device according to an embodiment.
As shown in FIG. 1, a skin laser treatment device 1 according to the present embodiment includes an excitation light source 2, an optical fiber 3 that transmits excitation light Le emitted from the excitation light source 2, and a resonator 4. The resonator 4 includes a microchip laser medium 5 from which laser light is emitted when the transmitted excitation light Le is incident and excited, and a saturable light that generates pulsed laser light Lp from the emitted laser light L. And an absorber 6.
The resonator 4 is built in the head unit 9 together with the SHG (second harmonic generation module) 7 and the beam expander 8. Note that the non-contact sensor S is incorporated in the head unit 9 as detection means for stopping the irradiation of the laser beam when the head unit 9 is separated from the skin by a certain distance or more.
In such a skin laser treatment device 1, the pulse laser beam Lp is repeatedly emitted to form the burst pulse light Lb, and the burst pulse light Lb is emitted to the affected area of the skin a plurality of times during the repetition period Tr. .
In actual treatment, one shot of laser light for treatment is emitted every repetition period Tr. This one-shot therapeutic laser beam is a series of burst pulse laser beams Lb composed of a plurality of burst pulse laser beams Lb. Specifically, when the user sets the skin laser treatment device 1 in the Ready state and steps on the foot switch, for example, a series of burst pulse laser light Lb groups are automatically generated every repetition cycle Tr of 100 (ms). To exit. Then, the user irradiates a certain number of shots on the same treatment site, irradiates the treatment laser beam while shifting the site, and advances the treatment.

As the excitation light source 2, for example, a diode laser that generates 808.5 (nm), 880 (nm), or 885 (nm) excitation light Le if the microchip laser medium 5 is an Nd system is a Yb system. For example, a diode laser that generates excitation light Le of 940 (nm) or 970 (nm) is used.
The wavelength of the laser light L emitted from the resonator 4 is, for example, 1064 (nm). The laser beam L having this wavelength is a fundamental wave, and can be converted into a second harmonic having a wavelength of 532 (nm) by the SHG 7. Further, the fundamental wave and the second harmonic are switched manually.

Next, the resonator constituting the skin laser treatment device according to the embodiment and its peripheral portion will be described in more detail with reference to FIG. FIG. 2 is a configuration diagram of a resonator constituting the skin laser treatment device according to the embodiment and a peripheral portion thereof. In addition, about the component shown in FIG. 1, the same code | symbol is attached | subjected also in FIG. 2, and the description is abbreviate | omitted.
As shown in FIG. 2, between the optical fiber 3 and the resonator 4, a collimating lens 10 that adjusts the excitation light Le to parallel light and a condensing lens 11 that narrows down the parallel light that has passed through the collimating lens 10 are provided. . The excitation light Le narrowed down by the condenser lens 11 is incident on the excitation light antireflection film 12 constituting one end of the resonator 4.

The resonator 4 is resonantly amplified with the excitation light antireflection film 12, the total reflection mirror 13 that totally reflects light having a wavelength longer than the excitation light Le, the microchip laser medium 5, and the saturable absorber 6. And a partial reflection mirror 14 through which a part of the laser beam is transmitted. The length l along the long axis direction Y of the resonator 4 is the length l ₁ along the long axis direction Y of the microchip laser medium 5 and the long axis direction Y of the saturable absorber 6. This is the total value of the length l ₂ .

In the resonator 4, for example, an Nd: YAG (Yttrium Aluminum Garnet) crystal is used as the microchip laser medium 5. “Nd:” means a crystal doped with Nd (Neodymium). The same applies to “Cr ⁴⁺ :” described later.
The saturable absorber 6 works as an absorber having a large light loss for incident light having a low intensity, but the ability as an absorber is saturated for incident light having a high intensity, so that the light loss is reduced. It has the property of acting as a small transparent body. That is, the saturable absorber 6 has a threshold value for emitting laser light, and the intensity of the laser light resonantly amplified by the microchip laser medium 5, the total reflection mirror 13 and the partial reflection mirror 14 is the threshold value. If it exceeds, it will act as a passive Q (Quality factor) switch. As a result, high-energy pulsed laser light Lp is instantaneously transmitted through the partial reflection mirror 14 provided at the other end of the resonator 4 and emitted. As the saturable absorber 6, for example, Cr ⁴⁺ : YAG crystal is used.
As described above, the excitation light Le having a wavelength of 808.5 (nm) incident on the excitation light antireflection film 12 becomes the laser light L having a wavelength of 1064 (nm) by the microchip laser medium 5 and the like, and the saturable absorber 6 It is emitted as pulsed laser light Lp having a wavelength of 1064 (nm). The emitted pulse laser beam Lp is expanded by the beam expander 15 as desired.

Further, burst pulse light emitted from the skin laser treatment apparatus according to the embodiment will be described in more detail with reference to FIG. FIG. 3A and FIG. 3B are conceptual diagrams of burst pulse light emitted from the skin laser treatment apparatus according to the embodiment and pulse laser light according to the related art, respectively. 1 and 2 are denoted by the same reference numerals in FIG. 3 and description thereof is omitted.
FIG. 3A shows waveforms of the excitation light Le, the pulse laser light Lp, and the burst pulse light Lb when the horizontal axis is time t (ms) and the vertical axis is light energy E (mJ).
First, the waveform of the excitation light Le will be described. The excitation light Le is emitted, for example, five times during a repetition period Tr of 100 (ms). The pulse width We is 420 (μs), and the excitation light period Te is 10 (ms).

Next, with the emission of the excitation light Le, a plurality of pulse laser beams Lp are emitted through the resonator 4. Since each pulse laser beam Lp has a pulse width Wp that is directly proportional to the length l of the resonator 4, the pulse width Wp is set to 1 by designing the length l to be, for example, 0.1 to 70 (mm). It is possible to set to ~ 700 (ps). FIG. 3A shows a case where pulse laser light Lp having a pulse width Wp of 100 (ps) is emitted as an example. In this case, the length l is approximately 11 (mm). The range of the pulse width Wp that can be technically realized for the currently required output is, for example, 100 to 1000 (ps).
As shown in FIG. 3A, each of the plurality of burst pulse lights Lb is formed by repeatedly emitting the pulse laser light Lp four times. In each burst pulse light Lb, among the plurality of pulse laser lights Lp, the second and subsequent pulse laser lights Lp are emitted for the first time interval τ ₁ from the end of the emission of the immediately preceding pulse laser light Lp. Will be started. That is, the second to fourth pulse laser beams Lp are started with the same first time interval τ ₁ from the end of the emission of the first to third pulse laser beams Lp, respectively. Specifically, the first time interval τ ₁ is, for example, 100 (μs).

The burst pulse light Lb is emitted five times with the excitation light Le when the excitation light Le is emitted five times during the repetition period Tr.
In this case, the second burst pulse light Lb starts to be emitted after a second time interval τ ₂ from the end of the previous excitation light Le emission. That is, the second to fourth burst pulse lights Lb are started with the same second time interval τ ₂ from the end of the emission of the first to third excitation lights Le, respectively.
Specifically, the second time interval τ ₂ is approximately 10 (ms), for example. More precisely, the second time interval τ ₂ is a value obtained by subtracting the pulse width We (420 (μs)) of the excitation light Le from the excitation light period Te (10 (ms)).

  Further, when the wavelength of the pulse laser beam Lp is 1064 nm and 532 nm, the energy Ep is 20 (mJ) and 10 (mJ), respectively. Therefore, when the pulse width Wp is 100 (ps), the maximum peak power [Ep / Wp] of the pulse laser beam Lp is calculated as 200 (MW) and 100 (MW), respectively.

Next, the waveform of the pulsed light according to the prior art will be described with reference to FIG. FIG. 3B shows the waveform of the pulse laser beam according to the prior art when the horizontal axis represents time (ms) and the vertical axis represents light energy (mJ).
As shown in FIG. 3B, the pulsed laser light Lc according to the prior art is emitted once during a repetition period Tc of 100 (ms). The wavelengths are 1064 (nm) and 532 (nm), the pulse width Wc is 6 (ns) for all wavelengths, the energy [Ec] is 400 (mJ) and 160 (mJ), respectively, and the peak power [Ec / Wc] is 67 (MW) and 26 (MW), respectively. Note that the repetition period Tc of the pulse laser beam Lc is equal to the repetition period Tr of the excitation light Le.

Next, variations of the burst pulse light emitted from the skin laser treatment device according to the embodiment will be described in detail. FIGS. 4A to 4E are conceptual diagrams of burst pulse light emitted from the skin laser treatment apparatus according to the embodiment, respectively, showing burst pulse light emitted different times. .
4A to 4E show the waveforms of the pulse laser light Lp and the burst pulse light Lb, where the horizontal axis represents time t (ms) and the vertical axis represents light energy E (mJ). .
As shown in FIG. 4A, the burst pulse light Lb is also emitted five times with the excitation light Le emitted five times during the repetition period Tr.
Further, in FIGS. 4B to 4E, the burst pulse light Lb is emitted once every 4 times with the excitation light Le emitted once every 4 times during the repetition period Tr. Is shown.
Therefore, when the energy Ep of one pulsed laser beam Lp is 20 (mJ), the maximum energy Eb of the burst pulsed light Lb is between repetition periods Tr in FIGS. 4 (a) to 4 (e). , 400 (mJ), 320 (mJ), 240 (mJ), 160 (mJ), and 80 (mJ), respectively.

Next, the operation of the skin laser treatment device according to the embodiment will be described in more detail with reference to FIG. FIG. 5 is a table comparing the performance of the skin laser treatment device according to the example and the laser treatment device according to the prior art. This conventional laser treatment device (hereinafter referred to as a conventional device) is a Q-switched Nd: YAG laser treatment device.
As shown in FIG. 5, when the wavelength is 1064 (nm), the skin laser treatment device 1 and the conventional device have the same maximum energy 400 (mJ), but the peak powers are 200 (MW) and 67 (MW), respectively. The skin laser treatment device 1 has a value about three times that of the conventional device. This means that the energy 20 (mJ) per pulse laser beam Lp of the skin laser treatment device 1 is 1/20 of the energy 400 (mJ) per pulse laser beam Lc of the conventional device. Although it is small, this is because the pulse width Wp of the skin laser treatment device 1 is 100 / ps, which is 1/60, which is smaller than 6 (ns) of the pulse width Wc of the conventional device.
In this case, the energy density of the skin laser treatment device 1 and the conventional device are both equal to 12.7 (J / cm ² ). The peak power is an index indicating the depth of the skin where the laser beam reaches, and the energy density is an index indicating the degree of destruction of the melanin pigment or the like by the laser beam irradiation.

Here, the phenomenon in which melanin pigments and the like are destroyed will be described in more detail. When laser light is absorbed by a melanin pigment or the like, not only the photothermal effect but also adiabatic expansion occurs and thermoelastic waves (photoacoustic waves) are generated. That is, melanin pigments and the like are crushed by photoacoustic waves and removed by phagocytic cells, so that skin spots and aza are completely eliminated. It is considered that the stress of the photoacoustic wave that exhibits such a destructive effect is directly proportional to the energy density.
On the other hand, since the permeability of laser light into the skin increases according to the peak power, the skin laser treatment device 1 is more profound when the skin laser treatment device 1 and the conventional device have the same energy density. It can be said that the destructive effect on the pigment is strong.

Subsequently, focusing on the pulse width shown in FIG. 5, in the skin laser treatment device 1, the pulsed laser light Lp having a short pulse width Wp of 100 (ps) is generated in the first time interval during the excitation light period Te. When τ ₁ (100 (μs)) is emitted a plurality of times, the first time interval τ ₁ is 1 million times longer than the pulse width Wp of one burst pulse light Lb. That is, the time when the pulse laser beam Lp is not emitted is considerably longer than the time when it is emitted.
Furthermore, when the excitation light Le is emitted a plurality of times with a _second time interval τ ₂ during the repetition period Tr, the second time interval τ ₂ (about 10 (ms)) is one burst pulse. The length is 25 times the temporal width of the light Lb (about 400 (μs)). That is, even when a plurality of burst pulse lights Lb are emitted, the time during which the burst pulse light Lb is not emitted is longer than the time during which the burst pulse light Lb is emitted. In other words, each burst pulse light Lb is temporally dispersed and emitted during one repetition period Tr.
From the above, in the skin laser treatment device 1, the first time interval τ ₁ and the second time interval τ ₂ are secured, so that heat accumulation in the skin is suppressed, and at the same time, the resonator 4. The heat load at is suppressed.

In addition, in the skin laser treatment device 1, the pulse width Wp of the pulsed laser light Lp is on the order of picoseconds, which is much shorter than the pulse width Wc on the nanosecond order of the conventional device. Then, next, the advantage that the pulse width Wp is in the picosecond order will be described in detail based on the selective photothermal melting theory, which is the basic theory of skin disease treatment using laser light.
According to selective photothermal melting theory, in order to selectively destroy the target substance of the lesion (eg, melanin pigment, blood vessels) and minimize thermal damage to the surrounding normal tissue, laser light (1) A wavelength that is selectively absorbed by the target substance and reaches a depth at which the target substance exists, (2) has a pulse width shorter than the thermal relaxation time of the target substance, and (3) is irreversible to the target substance Three conditions of irradiation energy (energy density (J / cm ² )) sufficient to cause damage are necessary.

  First, considering the condition (2), the pulse width Wp of the pulse laser beam Lp is 1 to 700 (ps), and 1 / 50,000 to 1/70 of the shortest thermal relaxation time 50 (ns) in the melanin pigment. Has been shortened to be extremely short. Therefore, the skin laser treatment device 1 sufficiently satisfies the above condition (2). Further, since the pulse width Wp is shortened to 1/6000 to 1/9 of the pulse width Wc (6 (ns)) of the pulse laser beam Lc according to the conventional device, the pulse laser beam Lp is absorbed by the target substance. It is considered that the heat dissipation to the normal tissue that is caused by this is strongly suppressed as compared with the conventional device.

  Next, considering the condition (1), in the skin laser treatment device 1 of the present embodiment, the wavelengths of the pulsed laser light Lp are 1064 (nm) and 532 (nm). Among these, the wavelength of 1064 (nm) is selectively absorbed by the melanin pigment, and the wavelength of 532 (nm) has a property of being absorbed by pigments such as tattoo red and yellow in addition to the melanin pigment. Conventionally, it is known that these wavelengths have good reachability to the skin. Therefore, the skin laser treatment device 1 satisfies the above condition (1).

  Subsequently, regarding the condition (3), according to the maximum energy density of the plurality of burst pulse lights Lb described above with reference to FIG. 5, the melanin pigment or the like may be finely broken to cause irreversible damage. it can. Therefore, the skin laser treatment device 1 satisfies the above condition (3).

As described above, according to the skin laser treatment device 1 according to the present embodiment, the peak power per pulse laser beam Lp is as high as 200 (MW), and the pulse width Wp is on the order of picoseconds. Therefore, the photoacoustic effect can be generated up to the deep part of the skin.
Further, according to the pulse width Wp being in the picosecond order, for example, it is extremely shorter than the thermal relaxation time of the melanin pigment, so that thermal damage to the surrounding normal tissue can be minimized. Therefore, safety in skin treatment using laser light can be improved, and there is no need to provide skin cooling means.
Further, in the skin laser treatment device 1, pulsed laser light Lp having two types of wavelengths of 1064 (nm) and 532 (nm) is emitted by the SHG 7, so that tattoo removal including various skin diseases and multiple types of pigments is removed. It can be used to treat.

In addition, according to the skin laser treatment device 1, by adjusting the number and timing of the excitation light Le emitted during the repetition period Tr, the number of times the burst pulse light Lb is emitted and the second time interval τ. ₂ can also be adjusted. Therefore, according to the skin laser treatment device 1, since it is possible to freely adjust the maximum energy of the burst pulse light Lb irradiated to the skin and the second time interval τ ₂ , it is optimal for various affected parts. It is possible to set fine irradiation conditions in detail.

  Furthermore, according to the skin laser treatment device 1, in order to form the treatment laser light by emitting the burst pulse light Lb formed from a plurality of pulse laser lights Lp a plurality of times instead of a single pulse laser light, In the case of carrying out with a single pulse laser beam, the maximum energy of the laser emitted from the resonator 4 is required to be 400 (mJ), for example, but in the case of the skin laser treatment device 1, the laser 4 is emitted from the resonator 4. The maximum energy of the laser can be reduced to, for example, 20 (mJ). Therefore, the resonator 4 can be miniaturized and the thermal load can be suppressed. For this reason, the resonator 4 does not require a cooling means or can be realized by a small cooling device. In addition to this, the resonator 4 can be designed to have a length l of, for example, 0.1 to 100 (mm) and can be reduced in size. Can do. For this reason, it is possible to transmit from the excitation light source 2 to the resonator 4 through the optical fiber 3 and use the laser from the resonator 4 directly as the treatment light. Compared with the transmission method, it can be realized with a very simple structure. As a result, the skin laser treatment device 1 can be downsized (150H × 200W × 310D (150H × 200W × 310D) as compared with the dimensions (820H × 415W × 645D (mm)) and weight (about 100 (kg)) of the conventional device shown in FIG. mm)) and weight reduction (11 (kg)) can be realized. Therefore, the skin laser treatment device 1 can be easily handled and can be manufactured at low cost. Therefore, it can be expected that the introduction of the skin laser treatment device 1 becomes easy.

The structure of the skin laser treatment device 1 of the present invention is not limited to that shown in the examples. For example, Nd: YVO ₄ crystal, Nd: YLF crystal, or Yb: YAG crystal may be used as the microchip laser medium 5. Further, by adjusting the length l of the resonator 4, the pulsed laser light Lp having a pulse width Wp other than 100 (ps) may be emitted within a range of 1 to 1000 (ps).

  INDUSTRIAL APPLICABILITY The present invention can be used as a skin laser treatment device that treats skin diseases by irradiating the affected area of the skin with laser.

  DESCRIPTION OF SYMBOLS 1 ... Skin laser treatment device 2 ... Excitation light source 3 ... Optical fiber 4 ... Resonator 5 ... Microchip laser medium 6 ... Saturable absorber 7 ... SHG 8 ... Beam expander 9 ... Head part 10 ... Collimating lens 11 ... Condensing Lens 12 ... Excitation light antireflection film 13 ... Total reflection mirror 14 ... Partial reflection mirror 15 ... Beam expander S ... Non-contact sensor

Claims (5)

An excitation light source;
An optical fiber that transmits the excitation light emitted from the excitation light source;
A microchip laser medium and a saturable absorber in which a pulsed laser beam is emitted when the transmitted excitation light is incident and excited, and a resonator with a built-in resonator,
The pulse laser light is repeatedly emitted to form burst pulse light,
A skin laser treatment device characterized by irradiating the affected part of the skin with the burst pulse light.   The skin laser treatment device according to claim 1, wherein the pulse laser beam has a pulse width of 1 to 700 ps. 3. The skin laser according to claim 1, wherein the pulse laser beam has a peak power density of 398 MW / cm ² and 199 MW / cm ² or more when the wavelengths are 1064 nm and 532 nm, respectively. Treatment device.   Of the plurality of pulse laser beams, the second and subsequent pulse laser beams are emitted at a first time interval from the end of the previous emission of the pulse laser beam. The skin laser treatment device according to any one of claims 1 to 3. The excitation light is emitted at least once during a repetition period;
The burst pulse light is emitted along with the emitted excitation light,
When a plurality of burst pulse lights are emitted, the second and subsequent burst pulse lights are emitted with a second time interval from when the previous excitation light emission is completed. The skin laser treatment device according to any one of claims 1 to 4, wherein the device is a skin laser treatment device.

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