JP6097584B2 - Laser oscillation device and manufacturing method thereof - Google Patents

Description

  The present invention condenses coherent excitation light emitted from an excitation light source such as a semiconductor laser and transmitted through an optical fiber by an excitation light condensing means (collimating lens), and a laser medium and a saturable absorber. In particular, the present invention relates to a laser oscillation apparatus that irradiates a Q-switch type resonator combining the above and amplifies the inside of the resonator to oscillate a pulse laser having a high energy density, and a manufacturing method thereof. A laser ignition device that focuses and ignites a high-density pulse laser, a laser welding device that focuses a high energy density pulse laser on a workpiece and welds the workpiece, and a workpiece cut It is suitable for a laser processing apparatus that performs processing.

  In recent years, a Q-switch type pumping light oscillated from a pumping light source such as a flash lamp or a semiconductor laser is used to ignite a non-ignitable internal combustion engine such as a high-supercharged engine, a high-compression engine, or a natural gas engine having a large cylinder inner diameter. Irradiate the laser resonator containing the laser medium, oscillate it as a pulsed laser that concentrates and emits energy with a short pulse width, and condenses the pulsed laser in the mixture using optical elements such as a condenser lens. Various laser ignition devices that ignite an internal combustion engine by generating flame nuclei with high energy density have been proposed.

For example, Patent Document 1 discloses an internal combustion engine equipped with a laser ignition device (see Patent Document 1 FIGS. 1a and 1b).
Further, in Patent Document 1, a coupling device having a predetermined cross section used for coupling a laser beam emitted from a diode laser used in such a laser ignition device or the like to an optical fiber with a low loss is used. A method for efficiently and integrally forming a fiber is disclosed.

However, there are inevitably individual differences in the characteristics of the laser diode that oscillates the excitation light, the polished shape of the end portion of the optical fiber, the loss during input coupling, and the light is necessarily emitted from the end portion of the optical fiber. Individual differences occur in the radiation angle and energy density of the excitation light.
The radiation angle of the excitation light varies depending on the mounting angle of the excitation laser, the alignment of an optical system such as a condensing lens and a prism, the diameter of the optical fiber, the curvature of the end face of the optical fiber end portion, and the like. For this reason, in order to make excitation light enter the resonator with a predetermined beam diameter, an input coupling device as in Patent Document 1 is used in a state where the distance between the optical fiber and the excitation light condensing lens is constant. Even if the pumping light emitted from the laser diode can be coupled to the optical fiber with low loss, the radiation angle and beam diameter of the pumping light finally incident on the resonator change, so that the beam in the resonator It was found that individual differences were also generated in the profiles, and as a result, it was difficult to keep the quality of the pulsed light emitted from the resonator constant.
Such variations in the quality of the pulsed light make the ignitability of the laser igniter unstable and make the processing speed and processing accuracy of the laser welding machine and laser cutting machine unstable.

  Therefore, the present invention has been made in view of such circumstances, and even if there is an individual difference in the excitation light incident on the resonator, the beam profile in the resonator is brought into a state close to a Gaussian function shape, and light emitted from the resonator is emitted. By adjusting the distance between the end of the optical fiber and the condensing lens while monitoring the output from the resonator so that the emitted pulsed light has high quality and high output, it is possible to reduce the individual differences. It is an object of the present invention to provide a high laser oscillation device and a manufacturing method thereof.

In the present invention (6, 6a, 6b, 6c, 6d, 6e, 6f), the excitation light source (3) that emits coherent excitation light (LSR _PMP ) and the excitation light that collects the excitation light (LSR _PMP ) Condensing means (10), a resonator (11) that oscillates as a pulse light (LSR _PLS ) with high energy density by resonance amplification of the condensed pumping light (LSR _PMP ), and the pulsed light (LSR _PLS ) An expanding means (13) for expanding the light, a pulsed light condensing means (14) for condensing the expanded pulsed light (LSR _PLS ), and a protective cover (15) are disposed coaxially to form a cylindrical shape. The output unit (1) integrally accommodated in the housing (16, 16a, 16b, 16c, 17 , 18), and the excitation unit provided between the excitation light source (3) and the output unit (1) Excitation to transmit light (LSR _PMP ) A laser oscillation device comprising an electromotive transmission unit (2),
The excitation light transmission unit (2) includes an optical fiber (20), a cylindrical fixing member (22) into which the optical fiber (20) covered with a protective coating (21 ) is press-fitted, and the fixing member ( 22) a flexible protective tube (24) fixed to the base end side (224) of the optical fiber (20) and protecting the outer periphery of the optical fiber (20) ,
The distance from the end surface (200) of the optical fiber (20) that coincides with the tip of the fixing member (22) to the excitation light condensing means (10) is defined as an excitation light incident distance (L), and the fixing member (22) as a distance adjusting means for adjusting the excitation light incident distance (L), a fixing portion holding means (221) for facilitating movement of the fixing member (22) in both directions of pushing back; An elastic member (23, 23a, 23b, 23c) that presses the fixing member (22) in the return direction, and the fixing member (22) and the above-mentioned in order to fix the excitation light incident distance (L) at a predetermined position A fixing means (25, 25a, 25c) for fixing the output section (1) ;
In the fixing member (22), a fitting portion (223) on the distal end side is press-fitted into the housing (16, 16a, 16b, 16c), and the fixing portion (22) is fixed on the proximal end side of the fitting portion (223). The elastic member (23, 23a, 23b, 23c) is accommodated in a space defined between the outer peripheral surface of the member (22) and the inner peripheral surface of the housing (16, 16a, 16b, 16c). .

  At least the optical fiber (20) covered with the protective coating (21) is press-fitted into the cylindrical fixing member (22) while being inserted into the flexible protective tube (24), and the optical fiber (20). The terminal surface (200) of the fixing member (22) is pulled out until it coincides with the distal end of the fixing member (22), and the flexible protective tube (24) is fixed to the base end side (224) of the fixing member (22) to excite light. Excitation light transmission part forming step for forming the transmission part (2), the elastic holding member (12), the resonator (11), and the excitation light condensing means (10) in the substantially cylindrical second housing (17). And a substantially cylindrical first housing (16) and the second housing (17) are screwed through an elastic seal ring (190) to form a resonator assembly (W). The pump assembly (2) through the resonator assembly forming step and the elastic member (23). , By the method for producing a laser oscillation apparatus comprising: a transmission portion fixing step of assembling the said resonator assembly (W), the laser ignition device of the present invention can be realized.

  In particular, in the transmission unit fixing step, the pumping light (LSRPMP) is introduced into the resonator (11), and the output is maximized while monitoring the beam profile in the resonator (11). By fixing the pumping light transmission part (2) and the resonator assembly (W), the radiation angle of the pumping light (LSRPMP) emitted from the terminal part (200) of the optical fiber (20) can be increased. Even if there is a difference, the excitation light incident distance (L) is fixed after confirming the position where the pulsed light oscillated from the resonator (11) has the highest quality and high output. The power consumption in the excitation light source (3) is reduced, and the tone system for wavelength stabilization can be reduced in size and cost.

The laser oscillation device (6, 6a, 6b, 6c, 6d, 6e, 6f) is arranged and fixed as desired in the combustion chamber (530) of the internal combustion engine (5). When used as a laser ignition device, it is possible to stably realize ignition of a highly ignitable engine such as a high-supercharged, high-compression automobile engine, an engine with a large cylinder bore diameter, and a power generation engine using natural gas.
Further, when the laser oscillation device (6, 6a, 6b, 6c, 6d, 6e, 6f) of the present invention is used as a laser welding device or a laser processing device, the processing speed is increased or the processing accuracy is improved. It becomes possible to do.

Sectional drawing which shows the principal part of the laser ignition device in the 1st Embodiment of this invention. 1 is a cross-sectional view showing an overall outline of a laser ignition device according to a first embodiment of the present invention. The expanded view for demonstrating the outline | summary of the excitation light transmission means manufacturing process and ignition part manufacturing process in the manufacturing method of the laser ignition device of this invention. The block diagram which shows the outline | summary of the assembly | attachment process of the ignition part which is the principal part of the manufacturing method of the laser ignition apparatus of this invention, and an excitation light transmission part. The energy density analysis figure which shows the test result of the comparative example 1 performed in order to confirm the effect of this invention. The energy density analysis figure which shows the test result of Example 1 performed in order to confirm the effect of this invention. The energy density analysis figure which shows the test result of the comparative example 2 performed in order to confirm the effect of this invention. The characteristic view which shows the energy density distribution of the comparative example 1. FIG. 3 is a characteristic diagram showing an energy density distribution of Example 1. The characteristic view which shows the energy density distribution of the comparative example 2. The characteristic view which shows the change of pulsed light energy with respect to the change of the distance from an optical fiber end surface to a condensing lens. The principal part sectional drawing which shows the outline | summary of the output part (ignition part) 1a in the 2nd Embodiment of this invention. The principal part sectional drawing which shows the outline | summary of the output part (ignition part) 1b in the 3rd Embodiment of this invention. The principal part sectional drawing which shows the outline | summary of the output part (ignition part) 1c in the 4th Embodiment of this invention. The principal part sectional drawing which shows the example of the excitation light source used for this invention, and an input coupling part. The principal part perspective view which shows the modification of the excitation light source used for this invention, and an input coupling part. The principal part perspective view which shows the other modification of the excitation light source used for this invention, and an input coupling part.

The outline of the laser oscillation apparatus according to the first embodiment of the present invention will be described with reference to FIGS. 1A, 1B, and 2A.
The present invention includes an excitation light source 3 that emits coherent excitation light _{LSR PMP,} the excitation light and the pumping light condensing means 10 for condensing the _{LSR PMP,} the energy density of the focused excitation light _{LSR PMP} resonating amplified coaxial resonator 11 which oscillates as a high pulse light _{LSR PLS,} and expansion means 13 for expanding the pulse light _{LSR PLS,} the pulsed light condensing means 14 for condensing the expanded pulsed light _{LSR PLS,} and a protective cover 15 An output unit 1 disposed on the housing 16, 17, and 18 and integrally disposed in the housings 16, 17, 18; a pumping light transmission unit 2 provided between the pumping light source 3 and the output unit 1 for transmitting the pumping light LSR _PMP ; The present invention relates to a laser oscillation device 6 comprising:

The pumping light transmission unit 2 includes an optical fiber 20, a protective coating 21, a fixing member 22, and a flexible protective tube 24.
In the present embodiment, the distance from the end surface 200 of the optical fiber 20 to the excitation light condensing means 10 is the excitation light incident distance L, and the fixing member 22 adjusts the distance for adjusting the light incident incident distance L. As means, a fixing portion holding means 221 that makes it easy to move the fixing member 22 in both directions of pushing back, an elastic member 23 that presses the fixing member 22 in the returning direction, and an excitation light incident distance L are fixed at predetermined positions. Therefore, it is characterized by including a fixing means 25 for fixing the fixing member 22 and the output unit 1.

Hereinafter, a case where the output unit 1 is provided in the internal combustion engine 5 and used as a laser ignition unit used for ignition of the fuel-air mixed gas introduced into the combustion chamber 530 will be described in detail.
The laser ignition device 6 is provided in an internal combustion engine 5 that is not described in detail, and includes an engine control device 4 (hereinafter referred to as ECU 4), an excitation light source 3, an excitation light transmission unit 2, and an output unit (ignition unit) 1. And is composed of.

The ECU 4 outputs an ignition signal IGt according to the operating condition of the internal combustion engine 5.
In accordance with the ignition signal IGt, the supply of the drive voltage to the excitation light source 3 is stopped.
The pumping light source 3 can be a known pumping light source such as a flash lamp or a semiconductor laser. The pumping light source 3 converts the energy supplied from the power source into high frequency pumping light LSR _PMP and outputs it via the pumping light transmission unit 2. Excitation light LSR _PMP is incident on the part (ignition part) 1.

The pumping light transmission unit 2 includes an optical fiber 20, a protective coating 21, a fixing member 22, an elastic member 23, and a flexible metal protective tube 24.
The fixing member 22 which is a main part of the present invention is made of, for example, a metal such as copper, stainless steel, iron, or nickel in a substantially cylindrical shape.
The fixing member 22 has a flange portion 221 in which a part of the outer periphery of the cylindrical base body 220 is protruded in a hook shape toward the outer diameter direction, and a fixing member side diameter changing portion 222 whose outer diameter is reduced stepwise. And a fitting portion 223 for fitting with the output portion (ignition portion) 1, a base end portion 224 for fitting with the flexible protective tube 24, and a through hole 225 for inserting the optical fiber 20. Is formed.
The optical fiber 20 is fixed to the first housing 16 (hereinafter simply referred to as the housing 16) while being held by the fixing member 22 via the protective coating 21.
The fixing member side diameter changing portion 222 divides a space for housing the elastic member 23 between the fixing member side diameter changing portion 222 and a housing side diameter changing portion 162 described later.

The fitting portion 223 in the present embodiment is provided with a taper that is slightly tapered with respect to the axial direction so as to be fitted to the inner peripheral surface 161 of the housing 16 when press-fitted into the housing 16.
The optical fiber 20 covered with the protective coating 21 is inserted and held in a through hole 225 provided inside the fixing member 22.
A metal flexible protective tube 24 is fitted to the base end portion 224 and is fixed by laser welding or the like to protect the optical fiber 20 and prevent moisture from entering from the outside.
As the optical fiber 20, for example, a known optical fiber having NA <0.09 (NA is a numerical aperture, numerical aperture) and a core diameter of 600 μm can be used.
A known flexible member such as a fluorine resin or a silicone resin is used for the protective coating 21 and covers the optical fiber 20.

For example, the housing 16 is formed of a metal such as stainless steel, iron, or nickel in a substantially cylindrical shape.
The housing 16 includes a housing base 160, an inner peripheral surface 161, a housing side diameter changing portion 162, a base end portion 163, a screw portion 163, a distal end portion 165, and a screw tightening portion 167.
A fitting portion 223 provided on the distal end side of the fixing member 22 is press-fitted into the inner peripheral surface 161 of the housing 16. Since the inner peripheral surface 161 of the housing 16 is tapered, when the fitting portion 223 of the fixing member 22 is inserted, the inner peripheral surface 161 extends from the inner peripheral surface 161 to the outer peripheral surface of the optical fiber 20 via the fitting portion 223. The surface pressure is applied, and the force for holding the optical fiber 20 is increased.
The housing-side diameter changing portion 162 and the fixed member-side diameter changing portion 222 define an elastic member accommodation space, and the substantially ring-shaped elastic member 23 is accommodated.
As the elastic member 23 in the present embodiment, for example, a seal ring made of a known elastic member such as urethane rubber, fluorine rubber, or silicone rubber is used.
The elastic member 23 is pressed from above and below in the axial direction by the housing side diameter changing portion 162 and the fixing member side diameter changing portion 222, and the reaction force causes the fixing member 22 to move toward the base end side, that is, toward the return direction. Pressing.

The distance from the end portion 201 of the optical fiber 20 to the surface of the excitation light condensing means 10 described later so that the energy density PD of the pulsed light LSR _PLS oscillated from the resonator 11 is maximized by the manufacturing method described later. (Hereinafter referred to as excitation light incident distance.) With the L adjusted, the fixing member 22 is welded and fixed at the housing base end 163 by forming a laser welding portion 25 as fixing means.
The flange portion 221 is used for facilitating movement of the fixing member 22 in the housing 16 in the push-back direction when adjusting the excitation light incident distance L as shown in a manufacturing method described later. Not only the shape but also a hollow shape in which a part of the outer peripheral surface of the fixing member 22 is recessed may be used.
In the present invention, the distance from the terminal portion 201 of the optical fiber 20 to the surface of the pumping light collecting means 10 is defined as the pumping light incident distance L. Define the distance to some standard position, such as the center of the condensing means 10, the focal point of the excitation light condensing lens 100, the end face of the lens holder 101, and set the position of the terminal portion 20 of the optical fiber 20 based on this distance. I can do it.

The output unit (ignition unit) 1 includes an excitation light condensing unit 10, a resonator 11, an elastic holding member 12, a pulse light expanding unit 13, a pulse light condensing unit 14, and a protective cover 15 arranged on one axis. The first housing 16, the second housing 17 (hereinafter referred to as “housing 17”), and the third housing 18 (hereinafter referred to as “housing 18”) are accommodated and fixed in a substantially cylindrical shape.
The output unit (ignition unit) 1 is housed and fixed in the plug hole 501 of the internal combustion engine 5 and is exposed in the combustion chamber 530 through a protective cover 15 disposed at the tip.
The excitation light condensing means 10 includes an excitation light condensing lens 100 and a lens holder 101.

The excitation light condensing lens 100 is made of a known optical element material such as optical glass, heat-resistant glass, quartz glass, or sapphire glass. The incident surface is concaved toward the tip side, and the exit surface is on the tip side. Aspherical lenses that bulge toward a convex surface and have different radii of curvature are formed integrally.
The entrance surface and the exit surface of the excitation light collecting lens 100 are each provided with a known AR coating such as magnesium fluoride in order to suppress reflection of the excitation light LSR _PMP .

The excitation light condensing means 10 includes a condensing lens 100 having a predetermined refractive index and a lens holder 101 that accommodates the condensing lens 100. The excitation light LSR _PMP radiated from the terminal surface 200 of the optical fiber 20 is converted into a predetermined beam diameter. The light is condensed and incident on the resonator 11.
When the bottom surface of the lens holder 101 and the top surface of the resonator 11 come into contact with each other, the bottom surface of the lens holder 101 has a function of maintaining a constant distance between the excitation light collecting lens 100 and the resonator 11. Processed with high accuracy.

The laser resonator 11 is provided with a laser medium 110 and an AR coating 111 that suppresses reflection of the excitation light LSR _PMP on one end surface thereof, and transmits the excitation light LSR _{PMP having} a short wavelength (for example, wavelength λ _IN = 808 nm). When the reflected light having a long wavelength (for example, the wavelength λ _OUT = 1064 nm) is totally reflected and the other end face is disposed, and the light in the laser medium 110 is not more than a predetermined Q value, The saturable absorber 113 constituting the passive Q switch that totally reflects and transmits when the Q value is exceeded, and the partial reflection film 114 are integrally formed.
As the laser medium 110, for example, a known laser medium such as Nd: YAG in which a YAG single crystal is doped with Nd is used.
As the saturable absorber 113, a known passive Q switch such as Cr: YAG in which Y4 single crystal is doped with Cr4 + is used.

The resonator 11 resonates and amplifies the excitation light LSR _PMP introduced into the resonator 11 and emits it as pulsed light LSR _PLS having a high energy density.
The pulsed light LSP _PLS emitted from the resonator 11 is, for example, parallel light having a high light collecting property of M ² = 1.2 to 1.4 and a beam diameter of about φ1.2 mm.
The resonator 11 is not limited to the above-described configuration. As the laser medium 110, known Nd: YVO, Nd: GVO, Nd: GGG, Nd: SUAP, Yb: YAG, YB; LUAG, passive Q switch For 112, Cr: GGG, V: YAG, Co: spinel, or the like can be appropriately employed.

The housing 17 has a substantially cylindrical shape, and on the inner side, a screw portion 174 that is screwed with the housing 16, a condensing means accommodating space 173 that accommodates the excitation light condensing means 10, the resonator 11, and the elastic member 12. A resonator accommodating space 172 to be accommodated and a through hole 171 through which the pulsed light LSR _PLS emitted from the resonator 11 passes are formed, and a screw fastening portion 177 is formed on the outer periphery.
The step portion 176 between the light condensing means accommodation space 173 and the resonator accommodation space 172 supports the bottom surface of the light condensing means 11 and constitutes the first reference plane S1.
A step portion 175 between the resonator accommodating space 172 and the through hole 171 locks the elastic holding member 12.

The elastic holding member 12 is made of an elastic member such as a coiled spring, and elastically presses the resonator 11 accommodated in the housing 17 toward the base end side, and the upper surface of the resonator 11 and the bottom surface of the lens holder 101. Is maintained so that the distance between the excitation light condensing means 10 and the resonator 11 is constant.
After housing the elastic holding member 12, the resonator 11, and the excitation light condensing means 10 in this order in the housing 17, the screw portion 194 of the housing 16 and the screw portion 174 of the housing 17 are screwed together to collect the excitation light. The optical means 10 and the resonator 11 are in a state in which the bottom surface of the lens holder 101 is in close contact with the first reference plane S1 and is elastically held in the housing 17.
The elastic seal member 190 exhibits a buffering effect so that the distal end surface 165 of the housing 16 does not excessively press the excitation light collecting means 10 when the housing 16 and the housing 17 are screwed together. The housing 17 is brought into close contact with each other to prevent water droplets or the like from entering the resonator accommodating space.

For the expansion lens 130, a known optical element material such as optical glass, heat-resistant glass, quartz glass, sapphire glass, or the like is used.
Each of the entrance surface and the exit surface of the extension lens 130 is provided with an AR coating that suppresses reflection of the pulsed light LSR _PLP .
The extended lens 130 is an integral aspherical lens having different radii of curvature on the entrance surface and the exit surface.

For the condenser lens 14, a known optical element material such as optical glass, heat-resistant glass, quartz glass, sapphire glass, or the like is used.
Each of the incident surface and the exit surface of the condenser lens 14 is provided with an AR coating that suppresses reflection of the pulsed light LSR _PLP .
The condensing lens 140 is an integral aspheric lens having different radii of curvature on the entrance surface and the exit surface.

The protective glass 150 faces the inside of the combustion chamber 530 and protects the condenser lens 14 from contamination caused by heat, pressure, fuel, soot and the like in the combustion chamber 530.
For the protective glass 15, a known optical element material such as optical glass, heat-resistant glass, quartz glass, sapphire glass or the like is used.
An AR coating that suppresses reflection of the pulsed light LSR _PLS emitted from the condenser lens 14 is applied to the incident surface of the protective glass 15.

A heat resistant metal such as SUS is used for the housing 18.
The housing 18 has a substantially cylindrical shape, and accommodates and holds the pulsed light expanding means 13 (beam expander), the pulsed light condensing means 14 and the protective cover 16 inside.
The housing 18 accommodates the substantially cylindrical housing base 180, the condensing lens housing space 181 that houses the pulse condensing lens 14, the spacer 192, and the protective cover 15 provided inside the housing base 180, and the pulse light expanding means 13. The internal combustion engine 5 includes an expansion lens housing space 182, a screw portion 183 for screwing the housing 17, through holes 184 and 185 for passing the pulsed light LSR _PLS, and a housing 18 provided in a part of the outer peripheral surface. A screw portion 187 for fixing to the cylinder head 50, a hexagonal portion 188 for tightening the screw portion 187, the pulse condensing lens 14 accommodated in the condensing lens accommodating space 181, the spacer 192, and the protective cover 15 And a caulking portion 186 for integrally caulking and fixing.
A step portion between the extended lens housing space 182 and the through hole 184 becomes a second reference surface S2, and the bottom surface of the lens holder 131 of the pulsed light expanding means 13 housed in the extended lens housing space 182 contacts.

When the threaded portion 178 of the housing 17 and the threaded portion 183 of the housing 18 are screwed together with the elastic seal member 191 interposed, the front end surface 179 of the housing 17 comes into contact with the upper surface of the lens holder 131, and the lens holder The bottom surface of 131 is elastically pressed against the second reference surface S2.
At this time, the elastic seal member 191 suppresses the lens holder 131 from being excessively pressed.

The step portion between the through hole 185 and the condensing lens housing space 181 becomes the third reference surface S3, and when the condensing lens 14, the spacer 192, and the protective cover 15 are housed, the lens holder 141 of the condensing means 14 is used. The upper surface of the abuts.
The distance between the second reference surface S2 and the third reference surface S3 is processed with high accuracy, and the distance between the expansion lens 130 and the condenser lens 140 is constant.

The pulsed light LSR _PLS emitted from the resonator 11 is substantially parallel light, and the extended lens 130 and the condenser lens 140 are arranged at a certain distance, and thus the pulse expanded by the extended lens 130. When the light LSR _PLS is condensed by the condenser lens 140, the light LSR _PLS is always condensed at a predetermined condensing point FP.
At this time, in the present invention, even if there is an individual difference in the emission angle of the pumping light LSR _PMP emitted from the terminal surface 200 of the optical fiber 20, the quality and output of the pulsed light LSR _PMP emitted from the resonator 11 are high. Since the excitation light incident distance L is adjusted so as to be as high as possible, the stable quality pulse light LSLPLS is condensed at a certain position, so that stable ignition can be realized.

2A and 2B, in order to output high-quality pulsed light LSR _PMP , which is a main part of the present invention, the output unit 1 and the pumping light transmission unit 2 are adjusted while adjusting the pumping light incident distance L. Will be described.
In the method of manufacturing the laser oscillation device of the present invention, at least the optical fiber 20 covered with the protective coating 21 is pressed into the cylindrical fixing member 22 while being inserted into the flexible protective tube 24, and the optical fiber 20 is inserted. A pumping light transmission part forming step in which the pumping light transmission part 2 is formed by pulling out the terminal surface 200 of the fixing member 22 until it coincides with the distal end of the fixing member 22 and fixing the flexible protective tube 24 to the proximal end side 224 of the fixing member 22; The elastic holding member 12, the resonator 11, and the excitation light condensing means 10 are accommodated in the substantially cylindrical second housing 17, and the substantially cylindrical first housing 16 is interposed via the elastic seal ring 190. A resonator assembly forming step of forming a resonator assembly W by screwing the second housing 17, and a transmission for assembling the pumping light transmission unit 2 and the resonator assembly W via the elastic member 23. Part fixing step.

Hereinafter, each step and steps necessary until the completion of the laser oscillation device of the present invention will be described in detail.
As shown in FIG. 2A, the optical fiber 20 covered with the protective coating 21 is inserted into the cylindrical fixing member 22 while being inserted into the flexible protective tube 24, and the end surface 200 of the optical fiber 20 is inserted. Is pulled out until it coincides with the distal end of the fixing member 22, and the flexible protective tube 24 is welded and fixed to the proximal end side of the fixing member 22 to complete the excitation light transmission unit 2.
At this time, since the resin protective coating 21 has elasticity, it slides inside the fixing member 22 while being elastically deformed. However, when the distal end portion 200 of the optical fiber 20 is disposed at a predetermined position and becomes stationary, The restoring force of the protective coating 21 acts on the inner peripheral surface of the fixing member 22 and the optical fiber 20, and the optical fiber 20 does not move in the fixing member 22 due to frictional force. Note that an adhesive may be filled between the optical fiber 20 and the fixing member 22, or a fixing ring may be press-fitted.

Next, the elastic holding member 12, the resonator 11, and the excitation light collecting means 10 are accommodated in the housing 17, and are screwed to the housing 16 and the housing 17 via the elastic seal ring 190.
Further, the pumping light transmission unit 2, the elastic holding member 12, the resonator 11, and the pumping light condensing means 10 are accommodated therein, and the housings 16 and 17 are integrated (hereinafter referred to as a resonator assembly W). And the elastic member 23 are assembled by an assembling apparatus ASM as shown in FIG. 2B.

Together with an example of the assembling apparatus ASM, an excitation light incident distance adjusting step that is a main part of the present invention will be described.
The assembly device ASM drives and controls the transmission unit holding clamp CLP1, the work clamps CLP2 and CLP3, the transmission unit fixing position adjusting means SVO, the pulsed light monitor MON, the laser welding machine WLD provided as a fixing device. It is comprised by the control apparatus CNT.
The work clamps CLP2 and CLP3 provided as assembly holding means are driven to open and close by the postnatal device CNT, and hold and fix the resonator assembly W.
At this time, you may utilize the screw fastening part 167,177 provided in the outer periphery of the housings 16,17.

The transmission part holding clamp CLP1 provided as the transmission part holding means holds the flange part 221 provided on the fixing member 22 of the excitation light transmission part 2.
The transmission portion holding clamp CLP1 is driven by the transmission portion fixing position adjusting means SVO so that the fitting portion 223 provided at the tip of the fixing member 22 slides on the inner peripheral surface 161 of the housing 16 of the resonator assembly W. Move.
The transmission unit fixed position adjusting means SVO can adjust the excitation light incident distance L with an adjustment width of 30 μm to 300 μm.

The pulsed light monitor MON monitors the beam profile in the resonator 11 when the pumping light LSR _PMP is introduced from the pumping light source 3 into the resonator assembly W using the pumping light transmission unit 2, and the output is monitored. The position of the terminal surface 200 of the optical fiber 20 that is maximum is detected.
Specifically, as the excitation light monitor MON for detecting the beam profile, a known image sensor type laser beam profiler, a scanning type laser beam profiler, or the like can be used.
In the present invention, since the relative result only needs to be known, the temperature distribution on the output side surface of the resonator 11 may be measured as a substitute characteristic of the energy density.
The control device CNT determines the position where the beam profile in the resonator 11 detected by the excitation light monitor MON is optimal while driving the transmission unit fixed position adjusting means SVO and changing the excitation light incident distance L. Then, the transmission portion fixing position adjusting means SVO is stopped at the excitation light incident distance L when the laser quality is the highest and the output is stable, and the laser welding machine WLD is driven to fix the fixing member 22 and the base end of the housing 16. By fixing the part 163 by laser welding, the assembly of the resonator assembly W and the pumping light transmission unit 2 is completed.

The transmission unit fixed position adjusting means SVO is a combination of a driving means such as a servo motor, a solenoid actuator, an air cylinder, a moving direction converting means such as a ball screw or a linear guide, and a speed change gear. Any mechanism may be used as long as the pressing back of the fixing member 22 can be freely controlled in the range of 30 μm to 300 μm by forward and reverse rotation.
In addition, the inner peripheral surface 161 of the housing 16 is slightly inclined so that the diameter decreases toward the tip, and when the fixing member 22 is press-fitted, the housing 16 is fixed between the fixing member 22 and the inner surface 161. A surface pressure acts on the optical fiber 20 so that the optical fiber 20 disposed in the fixing member 22 does not move in the fixing member 22.

Further, the elastic member 23 urges the fixing member 22 in the anti-insertion direction while the transmission unit fixing position adjusting unit SVO is moved, so that the fixing member 22 is suddenly moved into the housing by the transmission unit fixing position unit SVO. 16 can be suppressed.
In addition, after the assembly of the fixing member 22 and the housing 16 is completed, the airtightness between the housing 16 and the fixing member 22 is ensured, and the seal member functions as a seal member that prevents intrusion of water droplets or the like inside.
The pulsed light LSR _PLS emitted from the resonator 11 is input to the pulsed light monitor MON by changing the emission direction to a specific direction by using the total reflection mirror ML, and the resonator 11 and the like by return light. The damage may be prevented.

A test conducted to confirm the effect of the present invention will be described with reference to FIGS. 3A, 3B, 3C, 4A, 4B, 4C, and 5. FIG.
Resonance when the distance L from the end surface 200 of the optical fiber 20 to the surface of the excitation light condensing means 10 is changed from 3.0 mm to 3.6 mm based on the same principle as the assembling apparatus ASM shown in FIG. 2B. The output of the vessel 11 was monitored.

When the excitation light incident distance L is changed, the position where the output is highest (L = 3.3 mm) is taken as Example 1, and when the excitation light incident distance L is made shorter than in Example 1 (L = 3.0 mm) is Comparative Example 1, and when the excitation light incident distance L is longer than that of Example 1 (L = 3.6 mm) is Comparative Example 2.
As shown in FIGS. 3A and 4A, in Comparative Example 1, the output beam diameter is small and the energy density is low.
As shown in FIGS. 3C and 4C, in Comparative Example 2, the output beam diameter is increased, but the energy density in the central portion is averaged, and the output intensity is decreased.
As shown in FIG. 3B, FIG. 4B, and FIG. 5, the excitation light incident distance L has an optimum value that maximizes the output intensity of the pulsed light LSR _PLS .
In particular, as the energy distribution in the laser medium 110 becomes closer to a Gaussian function as shown in FIG. 4B, the output quality is improved.

On the other hand, the optimum value of the pumping light input distance L depends on the quality of the semiconductor laser used for the pumping light source 2, the loss at the time of input coupling to the optical fiber 20, the end face shape of the end face 200 of the optical fiber 20, etc. There is an individual difference in the radiation angle of the emitted excitation light LSR _PMP .
However, according to the present invention, even if there is such individual difference, the pumping light LSR _PMP is incident on the resonator assembly W, and the pumping light incident light distance L is adjusted while monitoring the output of the pulsed light LSR _PLS. By doing so, the output can be optimized.

With reference to FIG. 6, the output part 1a and the excitation light transmission part 2a which are the principal parts of the laser oscillation apparatus 6a in the 2nd Embodiment of this invention are demonstrated.
In this embodiment, based on the same configuration as that of the above-described embodiment, the adjusting means for adjusting the excitation light incident distance L, the fixing member 22a and the housing after determining the optimum excitation light incident distance L The fixing means 25a for fixing 16a is different.
For this reason, the same reference numerals are given to the same configurations as those in the above-described embodiment, and the characteristic portions in the present embodiment are indicated with alphabetical branch numbers, so only the characteristic portions will be described. In FIG. 6, the protective coating 21 covering the optical fiber 20 is not shown . The same applies to the following embodiments.

  In the above embodiment, in order to adjust the excitation light incident distance L, the flange 221 is held by the clamp CLP1, the fixing member 22 is moved back and forth by the fixing position adjusting device SVO, and the fixing member is fixed by the laser welding unit 25. In the present embodiment, a nut portion 250a that is screwed into a tip portion 163a provided with a screw portion of the housing 16a and a lock that fixes the nut portion 250a are shown. The member 251a is provided, and the elastic member 23a has a tapered shape with a tapered surface that reduces the diameter toward the distal side, and a tapered surface is also provided on a part of the housing side diameter changing portion 162a of the housing 16a. To do.

In this embodiment, when the nut portion 250a is tightened, the flange portion 221 is pushed in, the excitation light incident distance L is shortened, and when the nut portion 250a is loosened, the fixing portion side diameter changes due to the restoring force of the elastic member 23a. The portion 222 is pushed back to the base end side, and the excitation light incident distance L is increased.
In the above-described embodiment, in the above-described assembly device ASM, the fixing member 22 is pushed back by holding the flange portion 221 by the transfer portion holding clamp CLP1, but in this embodiment, the nut portion 250a is tightened and loosened. By configuring the fixed position adjusting device SVO as described above, the excitation light incident distance L can be adjusted.

In the present embodiment, in addition to the same effects as in the previous embodiment, when the nut portion 250a is pressed by the elastic member 23a, the tapered surface provided on the tip side is pushed into the tapered surface of the housing side diameter changing portion 162a. As a result, an elastic pressure in the radial direction is generated, and the fixing member 22a is firmly held.
The lock member 251a fixes the nut portion 250a at a position where the beam profile in the resonator 11 is optimal as in the above embodiment.
In the present embodiment, the specific fixing method of the lock member 251a is not particularly limited. For example, the annular member is press-fitted from the base end side of the fixing member base 220, or the base member side of the fixing member 22 is screwed. This can be realized by forming a portion and tightening the nut portion 250a with a lock nut or by fixing the nut portion 250a and the fixing member base 220 by welding.

With reference to FIG. 7, the output part 1b and the excitation light transmission part 2b which are the principal parts of the laser oscillation apparatus 6b in the 3rd Embodiment of this invention are demonstrated.
The present embodiment is different from the second embodiment in that a coiled spring member is used as the elastic member 23b in place of the elastic member 23a.
In the present embodiment, after the excitation light incident distance L is optimized by the same method as in the second embodiment, the fixing member 22b can be held at a predetermined position with respect to the housing 16b.
In this embodiment, unlike the second embodiment, the pressure of the elastic member 23a cannot be used for the holding force in the radial direction, but at least the same effect as that of the first embodiment can be exhibited.

With reference to FIG. 8, the output part 1c and the excitation light transmission part 2c which are the principal parts of the laser oscillation apparatus 6c in the 4th Embodiment of this invention are demonstrated.
In the embodiment, the elastic members 23, 23a, 23b are accommodated in a space defined by the fixing member side diameter changing portion 222 of the fixing members 22, 22a, 22b and the housing side diameter changing portions 162, 162a. However, in this embodiment, the space is not used as a housing space for the elastic member 23c, but is used as a space for filling the lock member 251c such as epoxy resin or adhesive as the fixing means 25c. The difference is that the elastic member 23c is housed in a space formed between the upper surface of the base end portion 163c of the housing 16c and the flange portion 221 and the nut portion 250a.

In the present embodiment, a through hole 162c is provided in the base end portion 163c to communicate with a space formed between the fixing member 22c and the housing base end portion 162c, and the lock member 251c is poured from the through hole 162c to be solidified. Thus, the fixing member 22c can be fixed at a predetermined position.
Also in this embodiment, the same effect as the first and third embodiments is exhibited.

With reference to FIG. 9, a description will be given of a modification 3d of the excitation light source applicable to the laser oscillation apparatus of the present invention and an input coupling means to the excitation light transmission unit 2. FIG.
In the above embodiment, a known pumping light source 3 is used, and the output unit 1 is configured to receive pumping light LSR _PMP oscillated from one semiconductor laser built in the pumping light source 3. In the present embodiment, the excitation light source 3d collects the plurality of semiconductor lasers 30, the condensing lens 31 that collects the excitation light LSR _PMP emitted from each semiconductor laser 30, and the plurality of excitation lights LSR _PMP. The difference is that the condensing unit 32 that condenses and the reflecting mirror 33 that changes the incident angle of the excitation light LSR _PMP that has passed through the condensing unit 32 into the optical fiber 20 are different.
In the present embodiment, the light incident side terminal surface of the optical fiber 20 is changed by changing the zero incident angle of the pumping light LSR _PMP that is coupled to the light incident side terminal surface 203 from the pumping light source 3d to the optical fiber 20. The radiation angle θ of the excitation light LSR _PMP emitted from 200 is stabilized.

In the excitation light source 3d, a plurality of semiconductor lasers 30 are arranged on a spherical surface or a curved surface in the housing 34.
A cylindrical lens 31 having a predetermined refractive index is disposed in the light output direction of each semiconductor laser 30.
The plurality of excitation lights LSR _PMP collected through the cylindrical lens 31 are collected through the condenser means 32 including the condenser lens 320 and the lens holder 321, and the reflecting mirror 33 having a substantially mortar-like mirror surface. And is inputted into the optical fiber 20 from the incident side terminal portion 203 of the optical fiber 20.

The inside of the optical fiber 20 is constituted by a core 201 having a high refractive index and a clad 202 having a relatively low refractive index. In the optical fiber 20, the pumping light LSR _{PMP that} has entered the core 201, the clad 201, It is transmitted while repeating reflection at the boundary.
At this time, since the pumping light LSR _PMP emitted from the plurality of semiconductor lasers 30 is input into the optical fiber 20 at different incident angles as in the present embodiment, there are a plurality of transmission modes in the core 201. As a result, the secondary refraction is promoted in the core 201, and the radiation angle θ of the excitation light LSR _PMP emitted from the terminal surface 200 on the emission side becomes constant due to the formation of the composite wave.

With reference to FIGS. 10 and 11, laser devices 6e and 6f including modifications 3e and 3f of the excitation light source and the input coupling unit used in the present invention will be described.
In the configuration shown in FIG. 9, an example in which the semiconductor laser 30 is disposed on a spherical surface and the reflecting mirror 33 is formed so that the reflecting surface has a substantially conical surface shape is shown. However, in the modified example 3e shown in FIG. An excitation light source 3e is constituted by a laser diode array (also called a laser bar) 30e in which semiconductor lasers are arranged in a flat plate shape and a lens array 31e in which a plurality of condensing lenses are arranged on the optical axis of each semiconductor laser. In addition, a curved reflecting surface whose radius of curvature gradually increases toward the connection side with the optical fiber 20 and protrudes toward the light source side with respect to the optical axis is provided at the input coupling portion with the optical fiber 20. A reflecting mirror 33e is used.
Further, in the modified example 33f shown in FIG. 11, a surface emitting laser 30f in which a plurality of semiconductor lasers are arranged in a planar shape, and a lens in which a plurality of condenser lenses are arranged on the optical axis of each semiconductor laser. The excitation light source 3f is constituted by the array 31f, and the radius of curvature gradually increases toward the connection side with the optical fiber 20 at the input coupling portion with the optical fiber 20, and protrudes toward the light source side with respect to the optical axis. A reflecting mirror 33f having a curved reflecting surface is used.
With such a configuration, the excitation light LSR _PMP radiated from the excitation light sources 3 and 3e is coupled to the further optical fiber 20 by suppressing the generation of return light returning to the excitation light source side by the reflecting mirrors 33e and 33f. It is also possible to improve the light collection efficiency of the excitation light LSRPMP.
In addition, this modification can be suitably employed for any of the laser devices in the above embodiment.

In the above embodiment, the case where the laser oscillation device of the present invention is used as an ignition device for an internal combustion engine has been described as an example. However, the laser oscillation device of the present invention is not limited to an application as an ignition device. Also, it can be appropriately employed for applications such as laser welding machines, laser cutting machines, and laser processing machines.
Also in this case, since the pulse laser is efficiently oscillated, the heat generation of the resonator is suppressed, and the processing speed can be improved.
Also, the resonator cooling system can be reduced in size and cost.

1 Output part (ignition part)
DESCRIPTION OF SYMBOLS 10 Excitation light condensing means 11 Resonator 12 Elastic holding member 13 Pulse light expansion means 14 Pulse light condensing means 15 Protective covers 16, 17, 18 Housing 2 Excitation light transmission part 20 Optical fiber 21 Protective coating 22 Fixing member 220 Fixing part Base body 221 Distance adjusting means (buttock)
222 fixing member side diameter changing portion 223 fitting portion 224 base end portion 225 optical fiber insertion hole 3 excitation light source 4 electronic control unit (ECU)
5 Internal combustion engine 6 Laser oscillation device (laser ignition device)

Special table 2010-539530 gazette

Claims (12)

An excitation light source (3) that emits coherent excitation light (LSR _PMP );
Resonance for oscillating said excitation light _{(LSR PMP)} the focused excitation light condensing means (10), focused excitation light _{(LSR PMP)} and resonates amplified energy dense pulse light as _{(LSR PLS)} a vessel (11), the pulsed light and _{(LSR PLS)} expansion means for expanding (13), and extended pulsed light _{(LSR PLS)} pulsed light condensing means for condensing the (14), a protective cover (15 And an output portion (1) integrally disposed in a cylindrical housing (16, 16a, 16b, 16c, 17, 18),
A laser oscillation device comprising: an excitation light transmission unit (2) that is provided between the excitation light source (3) and the output unit (1) and transmits the excitation light (LSR _PMP );
The excitation light transmission unit (2) includes an optical fiber (20), a cylindrical fixing member (22) into which the optical fiber (20) covered with a protective coating (21) is press-fitted, and the fixing member ( 22) a flexible protective tube (24) fixed to the base end side (224) of the optical fiber (20) and protecting the outer periphery of the optical fiber (20) exposed to the base end side (224),
The distance from the end surface (200) of the optical fiber (20) that coincides with the tip of the fixing member (22) to the excitation light condensing means (10) is defined as an excitation light incident distance (L),
As the distance adjusting means for adjusting the excitation light incident distance (L), the fixing member (22) makes it easy to move the fixing member (22) in both directions of pushing back. And the elastic member (23, 23a, 23b, 23c) for pressing the fixing member (22) in the return direction, and the fixing member (22) to fix the excitation light incident distance (L) at a predetermined position. And fixing means (25, 25a, 25c) for fixing the output section (1),
A fitting portion (223) provided on the distal end side of the fixing member (22) is press-fitted into the cylinder of the housing (16, 16a, 16b, 16c), and on the proximal side from the fitting portion (223). The elastic member (23, 23a, 23b, 23c) is accommodated in a space defined between the outer peripheral surface of the fixing member (22) and the housing (16, 16a, 16b, 16c). Laser oscillation device characterized by (6, 6a, 6b, 6c, 6d, 6e, 6f)   The elastic member (23, 23a) is a seal member accommodated in a space defined between an inner peripheral surface of the housing (16, 16a) and an outer peripheral surface of the fixing member (22, 22a). 1 (6, 6a, 6d, 6e, 6f)   The laser oscillation device (6, 6d, 6e) according to claim 1, wherein the fixing means is a welded portion (25) in which the fixing member (22) is fixed by welding at a base end portion (163) of the housing (16). 6f) A nut portion (250a) for fastening the fixing member (22a, 22b) by fastening the fixing means (25a) to a screw portion provided at a base end portion (163a) of the housing (16a, 16b); ,
The laser oscillation device (6a, 6b, 6d, 6e, 6f) according to claim 1, which is a lock member (251a) for fixing the nut portion (250a). A nut portion (250c) in which the fixing means (25c) is screwed into a screw portion provided on a base end portion (163c) of the housing (16c) to fasten and fix the fixing member (22c);
The laser oscillation according to claim 1, which is a lock member (251c) filled and solidified in a space defined between an outer peripheral surface of the fixing member (22c) and an inner peripheral surface of the housing (16c). Device (6c, 6d, 6e, 6f) The excitation light source (3d) includes a plurality of semiconductor lasers (30), a condensing lens (31) that collects excitation light (LSR _PMP ) emitted from each semiconductor laser (30), and a plurality of excitation lights. and _{(LSR PMP)} collectively condensed to the condensing means (32), reflection of changing the light incident angle to the optical fiber (20) of the excitation light that has passed through the light-concentrating means (32) _{(LSR PMP)} The laser oscillation device (6d) according to any one of claims 1 to 5, further comprising a mirror (33). The excitation light source (3d) includes a plurality of semiconductor lasers (30), a condensing lens (31) that collects excitation light (LSR _PMP ) emitted from each semiconductor laser (30), and a plurality of excitation lights. and _{(LSR PMP)} collectively condensed to the condensing means (32), reflection of changing the light incident angle to the optical fiber (20) of the excitation light that has passed through the light-concentrating means (32) _{(LSR PMP)} The laser oscillation according to any one of claims 1 to 5, further comprising a mirror (33), wherein the reflecting surface of the reflecting mirror (33) has a curved surface that is convex toward the light source with respect to the optical axis. Device (6e, 6f)   The output part (1, 1a, 1b, 1c, 1d) is a laser ignition part provided in the internal combustion engine (5) and used for ignition of a fuel-air mixed gas introduced into the combustion chamber (530). 6. The laser oscillation device according to any one of 6 (6, 6a, 6b, 6c, 6d, 6e, 6f) At least the optical fiber (20) covered with the protective coating (21) is press-fitted into the cylindrical fixing member (22) while being inserted into the flexible protective tube (24), and the optical fiber (20). The terminal surface (200) of the fixing member (22) is pulled out until it coincides with the distal end of the fixing member (22), the flexible protective tube (24) is fixed to the base end side (224) of the fixing member (22) The fitting portion (223) provided on the distal end side of the fixing member (22) is press-fitted into the cylindrical first housing (16), and the fixing member is disposed on the proximal end side of the fitting portion (223). the space defined between the inner circumferential surface of the outer peripheral surface of the (22) first housing (16), to form the excitation light transmitting portion to accommodate the elastic member (23) (2) excitation An optical transmission part forming step;
The elastic holding member (12), the resonator (11), and the excitation light condensing means (10) are accommodated in the substantially cylindrical second housing (17), and are substantially interposed via the elastic seal ring (190). A resonator assembly forming step of forming a resonator assembly (W) by screwing a cylindrical first housing (16) and the second housing (17);
A transmission unit fixing step for assembling the excitation light transmission unit (2) and the resonator assembly (W) through the elastic member (23) ;
Excitation light incident distance (L) from the end face (200) of the optical fiber (20) to the excitation light condensing means (10) in the state where the transmission unit fixing step is via the elastic member (23). And a pumping light incident distance adjusting step for adjusting the excitation light incident distance adjusting step. The transmission unit fixing step introduces the pumping light (LSR _PMP ) into the resonator (11), adjusts the pumping light incident distance (L), and a beam profile in the resonator (11). at a position where the output is maximized while monitoring the manufacturing method of the excitation light transmitting portion (2) and the resonator assembly (W) and a laser oscillating apparatus of Ru solid Teisu claim 9, wherein The transmission unit fixing step includes
Assembly solid holding means (CLP2, CLP3) for holding and fixing the resonator assembly (W);
Transmission unit holding means (CLP1) for holding the pumping light transmission unit (2), and transmission unit fixed position adjusting unit (SVO) for driving the transmission unit holding unit (CLP1) and driving the transmission unit (2) back. )When,
An excitation light monitor (MON) that introduces excitation light (LSR _PMP ) into the assembly (W) via the excitation light transmission unit (2) and detects a beam profile in the resonator (11);
A fixing device (WLD) for fixing the pumping light transmission unit (2) and the resonator assembly;
An assembly device (ASM) configured by a control device (CNT) for driving and controlling the transmission unit fixed position adjusting means (SVO), the excitation light monitor (MON), and the fixing device (WLD);
In the output from the beam profile detected by the excitation light monitor (MON) is the maximum position while before Ki励 vary the force light incident distance (L) by driving the transmission portion securing position adjustment means (SVO), Stop the transmission unit fixed position adjusting means (SVO),
The method of manufacturing a laser oscillation device according to claim 9 or 10, wherein the fixing device (WLD) is driven to fix the pumping light transmission unit (2) and the resonator assembly (W).   The method for manufacturing a laser oscillation device according to claim 11, wherein an adjustment width of the excitation light incident distance (L) is 30 µm or more and 300 µm or less.