JPS6138711B2 - - Google Patents

Description

[Detailed description of the invention]

(1) Technical Field of the Invention The present invention relates to a laser device, and more particularly to a laser device capable of outputting laser light such that the intensity distribution of the irradiated laser light on an irradiated object is uniform. (2) Prior Art Currently, there has been remarkable progress in laser technology, and its application is being attempted in various fields. One of them is birthmarks on the surface of living organisms (e.g. birthmarks,
A method of using a laser device to treat dark spots, freckles, etc. has been proposed and is being carried out on a trial basis.
Its effectiveness has been reported. By the way, conventional treatments for birthmarks include baking with electric drying, cell destruction using dry ice, etc.
Alternatively, there are many treatment methods such as excision, thinning, and skin grafting, but all of them are highly invasive, painful, require long treatment periods, and have poor effects. There are drawbacks,
In some cases, hospitalization was necessary. On the other hand, the method of burning the affected area with laser light has the advantage of being less invasive and therefore less painful, but the light intensity distribution in the cross section perpendicular to the direction of travel of the laser beam is limited by the resonator inside the laser oscillation source. The laser beam has a distribution determined by the unique characteristics of the excitation source, and is generally not uniform.Furthermore, due to the light intensity distribution characteristics of the light guide system that guides the laser light from the laser oscillation source, the laser beam is irradiated onto the biological surface. In some cases, it was difficult to obtain the expected treatment results due to uneven irradiation. In other words, there are currently two main methods of laser therapy: one is to directly irradiate the affected area with laser light, and the other is to guide the laser light through a light guide such as an optical fiber and irradiate it to the affected area. The laser beam has a light intensity distribution that is strong near the center and weaker toward the outer periphery, exhibiting a convex shape distribution. In addition, in the latter method, the laser light emitted from the output end face of the fiber has a far-field pattern determined by the characteristics of the fiber, and the shape of the light intensity distribution of the emitted laser light is determined by the distance between the fiber output end face and the affected area. changes in a complicated manner, making it impossible to obtain laser light with a uniform distribution. Therefore, both methods have fundamental causes of uneven irradiation. Therefore, the kaleidoscope described below was developed to solve these drawbacks.
The method using a kaleidoscope has the characteristics that the laser beam can be irradiated with a nearly uniform light intensity distribution within the irradiation field, and the shape of the irradiation field can be arbitrarily selected. The light emitted from the end surface spreads rapidly in free space, and the output per unit area also rapidly attenuates.Moreover, the output light loses coherence, so if it accidentally hits the body, especially the eyes. It is an ideal method for treating bruises, etc., as it has the advantage of being highly safe. A kaleidoscope is a transparent rod-shaped light transmitter made of acrylic or optical glass. Both end faces are flat and the periphery is smooth. It is a type of light guide that randomizes light during the light guide process. It is. By passing through this kaleidoscope, the light intensity distribution of the laser light is made uniform, and the field of the emitted light has the shape of the light emitting end face of the kaleidoscope, so that the desired field shape and uniform light intensity distribution are achieved. can irradiate with laser light. (3) Problems with the conventional technology However, since the kaleidoscope is made of a column made of optical glass, the material is fragile, so even if a slight impact is applied to the corners or sides, those parts may break. , easy to damage such as cracks. The light that passes through a kaleidoscope is randomized and made uniform during the process of passing through the inside of the kaleidoscope, and as mentioned above, if it is damaged, the light intensity distribution will change due to diffuse reflection occurring at that part. will occur. Furthermore, if this damage occurs, new chips or cracks will occur in this area, and the product will eventually become unusable. (4) Purpose of the Invention The present invention has been made in view of the above circumstances, and has an object to form a kaleidoscope into a shape that is less susceptible to such damage, and to make it possible to make the light intensity distribution uniform. An object of the present invention is to provide a laser device having a kaleidoscope. (5) Summary of the invention Specifically, the sides of the kaleidoscope are slightly chamfered to eliminate sharp edges that are likely to break, thereby eliminating damage caused by impact during handling. . (6) Structure of the Invention Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing the overall configuration of the device of the present invention, in which 1 is a power source, and 2 is a laser oscillation source that receives power from the power source 1 via a cable 1a to excite laser light. . Reference numeral 3 denotes an optical fiber for leading out laser light, which is connected to the output end of the laser oscillation source 2 via a connector 4, and the laser light excited by the laser oscillation source 2 is transmitted through the optical fiber 3 to other sources. led to the edge. Reference numeral 5 denotes an operating tool incorporating a polygonal prism-shaped kaleidoscope. The incoming laser light enters the kaleidoscope in the operating tool 5, and after the light intensity distribution is made uniform, it is emitted from the output end 5a. FIG. 2 is a sectional view showing the structure of the operating tool 5, in which 7 is a cylindrical housing and 5a is the output end. Reference numeral 8 denotes a polygonal, for example, rectangular columnar kaleidoscope provided within the housing 7. The casing 7 has a threaded portion 7a on the laser beam incident side, into which the connector 6 of the optical fiber 3 is screwed, and the axes of the kaleidoscope 8 and the optical fiber 3 are aligned with each other so that the light is transmitted. The connector 6 of the fiber 3 is screwed on. As a result, the laser beam emitted from the optical fiber 3 is transmitted to the kaleidoscope 8.
The light is transmitted into the kaleidoscope 8 from the entrance end face 8a of the light. In this device having such a configuration, the operating tool 5 is held in the hand, and after the light intensity distribution is made uniform by the kaleidoscope 8 inside the operating tool 5 guided by the optical fiber 3, the light is emitted from the output end 5a. Treatment is performed by irradiating the emitted laser light onto the affected area. Since the operating tool 5 is pen-shaped and the optical fiber 3 is highly flexible,
The operator can aim the laser beam at a desired location. The present invention is characterized in that, in such a laser device for treatment, the kaleidoscope 8 is formed so that damage such as chipping or cracking is less likely to occur in the kaleidoscope 8, and this will be explained below. In other words, in a polygonal columnar kaleidoscope, if an impact is applied to the sharp angle part during handling, it will easily chip or crack, which will impair the uniformity of the light intensity distribution or cause the damage to progress, making it unusable. I am worried that it will become. Therefore, in order to prevent this cracking and chipping, the sides and corners of the kaleidoscope 8 are chamfered to eliminate sharp corners that are easily damaged. However, since the method of chamfering has a considerable effect on the light intensity distribution, the chamfering process must be performed in a manner that causes no practical problems. The optimum chamfering process will be described below. First, the chamfering of each side around the laser beam output end face will be explained. FIG. 3 shows the ideal shape of a rectangular columnar kaleidoscope. That is, in a kaleidoscope with a regular square cross section, where the axis length is B and the cross section is represented by the side length a (however, in the figure, the length in the X-axis direction is shown as a and the length in the Y-axis direction is shown as b, but a = b). ,B/a,
When B/b is constant, optical transmission exhibits the lowest loss and highest uniformity. That is, in Fig. 3, if the length in the Y-axis direction is y and the length in the X-axis direction is x when viewed from the axis O of the kaleidoscope, then x, X, y, and Y are -b/2<x< b/2 ………………………(1) −a/2<y<a/2 …………………(2) X=±mb+x (however, m=0, 1, 2…)
...(3) Y=±na+y (however, n=0, 1, 2...)
...(4) Here, when the profile of the light incident on the kaleidoscope is approximated by exp (exponential), the light intensity distribution σ _xy on the xy plane is expressed by the following equation. where K is the reflectance of the kaleidoscope, W _p is the total optical energy, ω is the angular frequency, = d/tan, d is the diameter of the optical fiber, is the spread angle of the laser beam emitted from the optical fiber, θ _n , _o is the phase difference of the laser beam that occurs when propagating through the kaleidoscope. On the other hand, if the sides of the exit end face of the kaleidoscope are chamfered as shown in Fig. 4a, and each of the chamfered portions t has a width of Z ₀ as shown in Fig. 4b, then the kaleidoscope The light intensity σ _xy on the exit end face of the scope is expressed by the following equation.

[Table] When calculating the above equation (6), the larger Z ₀ is, the more
It can be seen that the light intensity fluctuation (fractuation) on the output end face of the kaleidoscope worsens near the four sides, that is, from the periphery of the output end face of the kaleidoscope toward the center. On the other hand, to prevent cracking and chipping on the four sides and increase mechanical strength, make Z ₀ as large as possible.
It is necessary to take at least about 50 μm. Therefore, regarding the case where BK-7, which is one of the optical glasses, is used as the kaleidoscope material, Z ₀
When the chamfer width U ₀ of the exit end face side of the kaleidoscope is determined by setting the value of U as a variable so that the fracture does not worsen, that is, keeping it constant, the following conditional expression holds true. U ₀ ≒Z ₀ ……………(7) However, here it is assumed that the reflection is total reflection due to air and BK-7, and Z ₀ refers to the width of the side chamfer of the kaleidoscope. In general, a kaleidoscope has the function of uniformizing the light distribution even when total reflection occurs with an optical material other than air, but in this case, chamfering according to the following formula is preferable. U ₀ < Z ₀ ……………(8) On the other hand, if U ₀ is set large, cracking and chipping due to impact can be greatly prevented and mechanical strength can be improved, but the kaleidoscope output When the light output obtained on the end face decreases and Z ₀ is set to 0.2 mm or less under the conditions shown by the above equation (7), the deterioration in light output efficiency due to chamfering can be approximated by equation (9). η=1−(1/a+1/b)U ₀ ……………(9) where η is the rate of light output efficiency deterioration due to chamfering around the output end face. For this reason, in a rectangular columnar kaleidoscope, a = 10 mm, b = 10 mm, B = 100 mm,
The kaleidoscope material is BK-7, and U ₀ =
Figure ₅ shows a graph of the relationship between the chamfer width U ₀ , Z ₀ and the fracture, and the relationship between the chamfer width U ₀ , Z ₀ and the efficiency deterioration η when the periphery of the light emitting end face is chamfered as Z 0 . It will look like this. The figure also shows the results of investigating the frequency of cracking and chipping when used in actual use with chamfer widths U ₀ and Z ₀ . As can be seen from FIG. 5, the deterioration of efficiency shows a gradual decreasing tendency, and the fractionation increases rapidly above 200 μm. On the other hand, it can be seen that the frequency of occurrence of cracks and chips shows a tendency to rapidly decrease after 100 μm. For this reason, in order to obtain sufficient mechanical strength without deteriorating fracturing in the above material and shape, it is necessary to chamfer with a width of 100 μm to 200 μm. Next, a case where the side portions of the peripheral surface along the axial direction of the kaleidoscope (excluding the portions corresponding to the four sides of the light emitting end face) are chamfered as shown by the hatched portion t in FIG. 6a will be described. In this case, the light intensity distribution σ _xy on the light output end face of the kaleidoscope is given by equation (10).

【table】

【table】 however

【table】

[Table] K _XU {x<|b/2−Δb|}=K ₁ K _XU {x−b/2+Δb}=K _XU {b/2 −Δbx}=K _{2 K} 2- _Δb |}=K ₁ K _{XD =} {x- _b /2 ₊ Δb}= _X y−a/2+Δa}=K _YU {a/2−Δay}=K ₂ K _YD {y<|a/2−Δa|}=K ₁ K _YD {y−a/2+Δa}=K _YD {a/ 2 -Δay}=K ₂ Note that Res is the remainder, mod is the modulus and represents n-ary, K is the reflection coefficient, and n and m are the number of reflections. At this time, the above a, b, and B are a=10 mm, b=10
mm, B = 100 mm, and if the chamfer width Δa on one surface and the chamfer width Δb on the other surface are each 50 μm as shown in Figure 6b, the light on the light output end face of the kaleidoscope will be The intensity distribution draws an X-shaped pattern, and if the E part in the figure is used as a reference, the output will decrease by 10% in the F part, and 20% in the center G part, and the fracture at this time will be about 20%. It will also happen. For this reason, chamfering the sides along the axis of the kaleidoscope improves the mechanical strength of this part against cracks and chips, but the ability to equalize the light intensity distribution of the kaleidoscope is significantly degraded, and the original characteristics This results in the loss of information. Therefore, it is desirable to avoid chamfering the sides of the kaleidoscope as much as possible, so the circumferential surface along the axis of the kaleidoscope that can be covered should be covered with a cover (housing) to protect against shocks, etc.
Cover the area with a cover etc. to avoid chamfering this part, and only the edges of the light input/output end face or the light output end face that cannot be covered with a cover etc.
Perform chamfering in μm. This makes it possible to increase the mechanical strength of the parts that are susceptible to mechanical shock and make them less susceptible to damage, and also to extend the life of the kaleidoscope without impairing the light intensity distribution uniformity function. In addition, in order to minimize light attenuation,
As shown in FIG. 8, the light incident end face of the kaleidoscope has a concave curved surface 81 formed at its center. As a result, a concave lens effect can be obtained, a lens system can be omitted, and the axial length B of the kaleidoscope can be shortened. That is, since the laser light emitted from the optical fiber spreads at an angle determined by the numerical aperture unique to the optical fiber, it is not necessarily necessary to use a lens system at the light entrance end face of the kaleidoscope to spread the laser light, but it is common to The output light of the optical fiber is about 1/3 to 2/3 of the divergence angle required for the kaleidoscope, and the kaleidoscope length B required to obtain the same fractionation must be longer. . In other words, in order to make the light intensity distribution uniform at the light emitting end face of the kaleidoscope, the laser light must spread over the entire cross section perpendicular to the optical axis of the kaleidoscope. Due to structural constraints, the spread of the laser light that reaches the light incident end face of the kaleidoscope is 1/3 to 2/3 of the cross section perpendicular to the optical axis of the kaleidoscope.
Since only a certain extent can be obtained, it is necessary to either expand it within a kaleidoscope or expand it through a lens system. However, since there is laser light attenuation within the lens system, the only way to avoid this is to use a kaleidoscope to diffuse the light.In that case, the axial length of the kaleidoscope is sufficient. It becomes necessary. For example, the divergence angle of the laser beam emitted from the optical fiber is
Assuming that the material of the kaleidoscope is BK-7, the maximum angle of incidence on the light incident end face of the kaleidoscope determined by the total reflection of BK-7 and air is
When the angle is set at 45°, the axial length of the kaleidoscope required to obtain the same fracturing is 50% different when the light entrance end face of the kaleidoscope is flat and concave. By making the kaleidoscope more effective, the shaft length can be halved, which saves on expensive kaleidoscope material, and the operating tool 5, which is the manual operation part that houses the kaleidoscope, can be made smaller. It is possible to make the size easy to operate. Furthermore, by forming the concave surface as described above, it is possible to obtain a more excellent light intensity distribution uniformity function compared to a planar case even with the same kaleidoscope axis length. (7) Effects of the Invention As detailed above, the present invention allows laser light guided by an optical fiber from a laser light source to be incident on an operating tool having a built-in transparent columnar kaleidoscope, and the kaleidoscope measures the light intensity. In a laser device that emits light with a uniform distribution and uses the emitted light for treatment, the kaleidoscope is chamfered by 100 to 200 μm on the side of the laser light emitting end to prevent mechanical shock and strain. By increasing the strength of the edges of the kaleidoscope against cracks and chips caused by such causes, damage to the light emitting end face, where it is difficult to install a protective cover and is susceptible to external shocks, can be greatly suppressed. Therefore, it is possible to prevent the decline in the light intensity distribution uniformity function of the kaleidoscope caused by cracks and chips, and the structure is resistant to damage, so the kaleidoscope does not develop damage due to scratches and has a long service life. Accordingly, it is possible to provide a laser device equipped with a kaleidoscope that has a good function of uniformizing the light intensity distribution.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the overall configuration of the device of the present invention, FIG. 2 is a side sectional view showing the configuration of the operating tool, FIG. 3 is a diagram for explaining the kaleidoscope, and FIG. 4 , FIG. 6 is a diagram showing a kaleidoscope that has been chamfered according to the present invention, FIG. 5 is a diagram for explaining various characteristics of a kaleidoscope that has been chamfered, and FIG. FIG. 8 is a diagram for explaining the light intensity distribution on the light output end surface of the kaleidoscope shown in the figure, and FIG. 8 is a diagram showing a kaleidoscope in which a concave curved surface portion is provided on the light input end surface. 1... Power supply, 2... Laser oscillation source, 3... Optical fiber, 4, 6... Connector, 5... Operation tool, 5
a... Output end, 7... Housing, 8... Kaleidoscope, t... Chamfered portion.

Claims (1)

[Scope of Claims] 1 Laser light guided from a laser light source by a flexible light guide is made incident on an operating tool having a built-in transparent columnar kaleidoscope, and the kaleidoscope uniformizes the light intensity distribution. The laser device is characterized in that the kaleidoscope has a chamfered edge on the side of the light emitting end face of the laser beam. laser equipment. 2 The kaleidoscope has the chamfering process
2. The laser device according to claim 1, wherein a laser device having a width of 100 μm to 200 μm is used.