JP2017152677A - Light source unit, light source module, and laser ignition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source unit which inhibits deterioration of accuracy even in a location where an environmental temperature is high.SOLUTION: A light source unit 10 includes: a lens array 23 in which multiple lenses 25 are two-dimensionally arranged; and an element substrate part 22 supporting light emission parts 21. The lens array 23 has a lens substrate part 26 which holds the lenses 25. The lens substrate part 26 has a linear expansion coefficient that is substantially the same as that of the element substrate part 22.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a light source unit, a light source module, and a laser ignition device.

When using an optical element that receives or emits light, a light source unit in which a plurality of lenses are arranged to face the optical element is known in order to improve the efficiency of using light to the optical element (for example, (See Patent Documents 1 and 2).
In the lens array used in such a light source unit, if the position of the optical element and the lens constituting the lens array shifts, the light use efficiency deteriorates. Therefore, particularly in a place where the temperature is high due to heat from the outside. Not suitable for use.

  An object of this invention is to provide the light source unit which suppresses a fall of precision also in the place where environmental temperature is high.

  As a means for solving the above problems, a light source unit of the present invention is a light source unit including a lens array in which a plurality of lenses are two-dimensionally arranged and an element substrate portion that supports the plurality of light emitting portions. The lens array includes a lens substrate portion that holds the lens, and the lens substrate portion has a linear expansion coefficient substantially the same as that of the element substrate portion.

  According to the present invention, a decrease in accuracy is suppressed even in a place where the environmental temperature is high.

It is a figure which shows an example of the whole structure of the laser ignition system concerning embodiment of this invention. It is an enlarged view which shows an example of a structure of the laser ignition device in this invention. It is a top view which shows an example of a structure of the micro lens unit shown in FIG. FIG. 2 is a plan view illustrating an example of a configuration of an optical transmission line illustrated in FIG. 1. FIG. 2 is a plan view illustrating an example of a configuration of an optical amplifying unit illustrated in FIG. 1. It is the figure which showed typically about an example of the formation process of a micro lens. It is a figure which shows an example of the manufacturing method of a micro lens. It is a top view which shows the prior art example of a micro lens unit. It is a top view which shows the influence by the thermal expansion of the prior art example shown in FIG. It is a figure which shows the shift | offset | difference of the focus at the time of thermal expansion shown in FIG. It is a figure which shows typically the other modification of a structure of a micro lens.

As a first embodiment according to the present invention, FIGS. 1A and 1B show a laser ignition system 500 using a laser ignition plug 100 as a laser ignition device.
The laser ignition system 500 includes a laser spark plug 100 that ignites the laser beam L by condensing the laser beam L toward the combustion chamber 700, a drive device 400 that drives the laser spark plug 100, and a drive device 400. And a control device 300 for controlling.
The laser ignition system 500 includes a piston 701 that periodically changes the volume of the combustion chamber 700 by vertical movement in FIG. 1, a cylinder 703 that constitutes the combustion chamber 700 in contact with the piston 701 via the piston ring 702, have.
Laser ignition system 500 includes an intake valve and an intake port for supplying fuel to combustion chamber 700, and an exhaust valve and an exhaust port for discharging fuel after combustion from combustion chamber 700.
The combustion chamber 700 is a combustion chamber of an internal combustion engine such as an engine as an example. In addition, description is abbreviate | omitted about a structure known as an internal combustion engine among this structure.

As shown in FIG. 1B, the laser spark plug 100 includes a laser light source unit 10 that is a light source unit for emitting laser light L, and a condensing optical system 20 that condenses the laser light L emitted from the laser light source unit 10. And an optical transmission line 30 and an optical amplifying unit 40.
The laser spark plug 100 includes a condensing lens 50 for condensing the laser light L amplified by the optical amplifying unit 40 at a condensing position P in the combustion chamber 700, and between the condensing lens 50 and the combustion chamber 700. And an emission window 60 provided in the window.
The laser spark plug 100 has a function as a light source module including an optical system for condensing the laser light L emitted from the light source at the condensing position P.

  The driving device 400 is an LD driver for driving the laser light source unit 10 in the present embodiment, and drives the laser light source unit 10 based on an instruction from the control device 300 to emit laser light L.

As shown in FIG. 2, the laser light source unit 10 is an element substrate portion in which a light emitting portion 21 as a single element that emits laser light L in the Z direction and a plurality of light emitting portions 21 are arranged integrally on a plane. And a laser substrate portion 22. The laser substrate portion 22 and the light emitting portion 21 are integrally formed to constitute a VCSEL element, in other words, a surface emitting laser element, and have a function as a light source.
The laser light source unit 10 includes a lens array 23 that is disposed so as to face the laser substrate portion 22 and that is bound by the laser substrate portion 22 and the fixing portion 24.
That is, the laser light source unit 10 is a light source unit including a surface emitting laser element and a microlens array in the present embodiment.
In the following description, the direction in which the laser beam L is emitted is the Z direction, and among the directions perpendicular to the Z direction, the direction perpendicular to the paper surface of FIG. 2 is the Y direction, and the direction perpendicular to the Z direction and the Y direction. Is the X direction.

The lens array 23 includes a lens 25 provided to face the light emitting unit 21 on a one-to-one basis, and a lens substrate unit 26 provided to hold the lens 25.
The lens array 23 includes a first antireflection layer 27 formed on the outermost surface of the lens 25, that is, a surface on the −Z direction side, and a second antireflection layer 28 formed between the lens 25 and the lens substrate portion 26. And a third antireflection layer 29 formed on the exit side surface of the lens substrate portion 26.
In the present embodiment, a configuration including the first antireflection layer 27, the second antireflection layer 28, and the third antireflection layer 29 will be described, but the configuration is not limited thereto. The first antireflection layer 27, the second antireflection layer 28, and the third antireflection layer 29 do not need to form all three, and any one or two of them may be formed, or none. Good.

The light emitting unit 21 is integrally provided on the surface on the + Z side of the φ9 GaAs laser substrate unit 22 and constitutes a vertical cavity surface emitting laser (VCSEL).
The laser substrate portion 22 is a GaAs substrate having a linear expansion coefficient of 6.86 × 10 ⁻⁶ / K at an absolute temperature of 300 K (about 27 ° C.).

The lens substrate unit 26 is a glass lens substrate that transmits the laser light L.
The lens substrate unit 26 has an average thermal linear expansion coefficient in a temperature range of −30 ° C. to + 70 ° C., which is an environmental temperature in which the laser light source unit 10 is used, so as to match the linear expansion coefficient of the laser substrate unit 22. That is, it is desirable to be in the range of 6.8 to 6.9 × 10 ⁻⁶ / K.
Examples of glass materials satisfying such a linear expansion coefficient include N-BAF52 (manufactured by SCHOTT), S-BAH11, S-BAH32, S-NBH53 (all manufactured by OHARA), BACD18, TAFD30, TAFD33, TAFD37, LAC7, M -LAC130 (all are made by HOYA).

In this embodiment, the lens 25 is a lens made of synthetic quartz glass that is convex in the −Z direction and has positive power. Such synthetic quartz glass has a linear expansion coefficient of 0.47 × 10 ⁻⁶ / K.
In addition to the synthetic quartz glass, the lens 25 may be made of a glass material such as borosilicate glass such as Neoceram N-0 (manufactured by JEOL Glass) or TEMPAX Florat (registered trademark, manufactured by SCHOTT). good.
Further, the lenses 25 adjacent to each other are arranged apart by a minute distance d. That is, the plurality of lenses 25 are arranged in a manner separated from each other.

Lens 25, the lens optical axis O of the lens 25 is disposed so as to coincide with the optical axis of the emitted laser beam of the opposing light emitting portion 21 (particularly in Figure 2 denoted as laser beam L _1). Further, the focal point of the lens 25 is arranged by adjusting the inter-substrate distance z ₁ so as to match the light emitting point of the surface emitting laser 21.
That is, the lens 25 is disposed so as to face the optical axis of the light source.
Lens array 23, by such a configuration, emits a laser beam L ₁ emitted from the opposite light emitting section 21 as parallel light.

  The fixing portion 24 is an ultraviolet curable resin for binding the lens substrate portion 26 and the laser substrate portion 22.

The first antireflection layer 27 is an antireflection film for suppressing surface reflection light when the laser light L enters the lens 25. The first antireflection layer 27 may be a multilayer film formed by overlapping a plurality of layers. Examples of such an antireflection film include a dielectric multilayer film and an MgF ₂ thin film.

The effect of such an antireflection film will be described in more detail.
At the interface between two materials having different refractive indexes, a part of the transmitted light is reflected. In general, it is known that the amount of reflected light tends to increase as the difference in refractive index between two substances increases.
Here, when the laser light L incident on the lens 25 is reflected, the amount of light transmitted through the lens array 23 naturally decreases according to the amount of reflection, resulting in an increase in power consumption and a decrease in the life of the light emitting unit 21.
Further, if the reflected light is incident on the light emitting unit 21 again, there is a problem that the laser oscillation becomes unstable and the output from the laser light source unit 10 is not stable.

Therefore, in this embodiment, the refractive index of air (about 1.0) and the refractive index of the synthetic quartz glass constituting the lens 25 (about 1.5 depending on the wavelength) are formed on the surface of the lens 25 on the −Z side. The first antireflection layer 27 having an intermediate refractive index is formed.
With this configuration, the lens array 23 suppresses the incident laser light L from being reflected to the light emitting unit 21 and improves the light utilization efficiency. Here, the reflected light is suppressed by adjusting the refractive index of the first antireflection layer 27. However, for the purpose of suppressing the reflected light, the material of the first antireflection layer 27 is not particularly limited. Absent.

The second antireflection layer 28 is an antireflection film for suppressing reflected light at the interface between the lens 25 and the lens array 23. For the second antireflection layer 28, it is desirable to use aluminum oxide (Al ₂ O ₃ ) having a refractive index intermediate between the material constituting the lens 25 and the material constituting the lens substrate portion 26. The materials mentioned in the prevention layer 27 may be used.
Further, the film formation method of the first antireflection layer 27 and the second antireflection layer 28 is not particularly limited, but electron beam evaporation or the like is used.
With this configuration, the lens array 23 further suppresses the incident laser light L from being reflected to the light emitting unit 21.
Note that the configuration of the third antireflection layer 29 is the same as that of the first antireflection layer 27 and the second antireflection layer 28, and thus description thereof is omitted.

  The condensing optical system 20 is a condensing lens that condenses the light emitted from the laser light source unit 10 and emits it toward the optical transmission path 30. The condensing optical system 20 may be a condensing optical system formed using at least one lens, and its configuration is not particularly limited.

As shown in FIG. 3, the optical transmission path 30 includes an optical fiber 31 that transmits light incident on the incident port 30a to the output port 30b, and a collimator lens 32 that changes the light from the output port 30b into parallel light. ,have. The optical transmission line 30 includes a condensing lens 33 that condenses the laser light L that has been converted into parallel light by the collimator lens 32 and enters the light amplification unit 40.
In the present embodiment, the optical transmission path 30 is an optical system configured by combining an optical fiber, a collimating lens, and a condensing lens. However, the laser light L from the condensing optical system 20 is converted into an optical amplifying unit. What is necessary is just to make it enter into 40.

The optical amplifying unit 40 receives the laser light L as excitation light, so that the internal laser medium 41 and the saturable absorber 42 act as a Q-switch laser oscillator and emit a pulse laser L ′ having a large gain. It is a laser resonator.
As shown in FIG. 4, the optical amplifying unit 40 is formed at the laser medium 41, the saturable absorber 42, the first dielectric multilayer film 43 formed at the −Z direction end, and the + Z direction end. And a second dielectric multilayer film 44.
The optical amplifying unit 40 is a composite crystal integrally formed by joining a laser medium 41 and a saturable absorber 42, and the laser medium 41 is arranged on the incident side and the saturable absorber 42 is arranged on the outgoing side. Has been.
The incident side of the laser medium 41, that is, the end on the −Z direction side in FIG. 4 and the end on the + Z direction side of the saturable absorber 42 are optically polished, and further, the first dielectric multilayer film 43 and the second A dielectric multilayer film 44 is formed.
With this configuration, both end portions in the ± Z direction of the optical amplifying unit 40 have a function as mirror surfaces that reflect the pulse laser L ′ that is pumped inside in an opposing manner.

The laser medium 41 is an Nd: YAG crystal doped with 1.1% Nd.
The saturable absorber 42 is a Cr: YAG crystal, and the initial transmittance is about 30%.
The first dielectric multilayer film 43 is a coating that exhibits high transparency with respect to the wavelength of the laser beam L and exhibits high reflectance with respect to the wavelength 1064 nm of the pulse laser L ′ emitted from the laser medium 41.
The second dielectric multilayer film 44 is a coating that exhibits a reflectance of 30 to 80% with respect to a pulse laser L ′ having a wavelength of 1064 nm.
As described above, the configuration in which different dielectric multilayer films are formed at both ends in the ± Z directions causes the optical amplifying unit 40 to more efficiently oppose and reflect the pulse laser L ′ excited inside.

The laser light L enters the laser medium 41 and is excited to create an inverted state.
The saturable absorber 42 has a function as a passive Q switch. That is, when the light amount of the pulse laser L ′ is less than a predetermined value, it acts as an absorber, and when it exceeds the predetermined value, the pulse laser L ′ is transmitted as emitted light.
With this configuration, the laser beam L incident into the optical amplifier 40 is emitted as a pulsed laser L ′ amplified by resonance.

  The pulse laser L ′ emitted from the optical amplification unit 40 is condensed toward the irradiation position P by the condenser lens 50 and ignites the air-fuel mixture inside the combustion chamber 700.

Incidentally, in such a laser spark plug 100, in order to efficiently ignite the air-fuel mixture, an improvement in output per light emitting portion 21 is required.
However, the improvement in the output of the light emitting unit 21 has a problem that the heat generated from the laser light source unit 10 is increased.
Further, as in the present embodiment, the laser spark plug 100 is often disposed in the vicinity of the combustion chamber 700 of the internal combustion engine, and the environmental temperature changes greatly due to heat from the outside.

As a conventional example, a configuration in which a lens array 73 and a lens 75 are integrally formed as in a laser light source 70 shown in FIG. 7 is considered.
When the laser light source 70 having such a configuration is used in a state where the ambient temperature is high, the lens optical axis O of the lens 75 and the lens array 73 and the laser substrate 72 are different from each other by the difference in linear expansion coefficient between the lens array 73 and the laser substrate 72 as shown in FIG. , there is a possibility that deviation occurs between the optical axis of the laser beam L _1.
Specifically, assuming that the size and shape of the laser substrate 72, which is a GaAs substrate, is a circle having a diameter of 9 mm and the environmental temperature has changed from 20 ° C. to 50 ° C., the displacement amount ΔL ₇₂ at the outer peripheral portion in the + X direction of the laser substrate ₇₂ is Ask. In the following description, for the sake of simplicity, particularly when the displacement amount ΔL of a member is indicated, the number of the member is numbered with a subscript.

Similarly, since the linear expansion coefficient of synthetic quartz glass is 4 × 10 ⁻⁷ (/ K), the amount of thermal expansion displacement ΔL ₇₃ of the lens array ₇₃ is expressed by Equation 2.

Thus, when the environmental temperature rises by 30 ° C., a deviation of about 0.9 μm occurs between the surface emitting laser element 71 and the lens array 73 in the outer peripheral portion.
When the center of the optical axis of the lens optical axis and the laser beam L ₁ in the lens 75 by such deviation will not match, as shown schematically by the dashed line in FIG. 8, not to maintain the collimation by the lens 75 A part of the laser light L collected at the focal point of the condensing optical system 20 diverges.
An example of such a deviation of the condensing point is shown exaggerated so as to be easily understood by the solid line and the broken line in FIG. As described above, the laser light L is not easily condensed at the focal point of the condensing optical system 20 due to the deviation between the lens optical axis and the light emitting point.
In other words, the utilization efficiency of the laser light L emitted from the laser light source 70 is reduced. In other words, such a decrease in utilization efficiency leads to a decrease in the amount of excitation light in the optical amplifying unit 40, making it difficult to stably emit the pulse laser L ′.

  Further, if the lens array 73 is simply made of a material that matches the linear expansion coefficient of the laser substrate 72, the refractive index of the lens array 73 that can be selected is limited. There is a problem that becomes a restriction. Furthermore, many glass materials used for optical applications with a good refractive index have poor processability by dry etching, and it is difficult to produce microlenses with high accuracy.

Therefore, in the present embodiment, the lens array 23 has a lens substrate 26 that holds the lens 25 and has substantially the same linear expansion coefficient as the laser substrate portion 22.
Here, the “linear expansion coefficient” is “substantially the same” means that the difference between the displacement amount ΔL ₂₃ and the displacement amount ΔL ₂₂ that can be caused by thermal expansion is within the range of the environmental temperature in which the lens array 23 is used. It is said that it is the same as it can be said that it is small enough compared with an effective diameter. With such a configuration, a deviation between the lens optical axis O of the lens 25 and the optical axis center of the light emitting unit 21 is suppressed, and the collimated state of the laser light L is maintained.
With this configuration, the laser light source unit 10 suppresses a decrease in light use efficiency even in a place where the environmental temperature is high, so that a decrease in accuracy is suppressed.

Specifically, the linear expansion coefficient of the lens substrate unit 26 is α _lens , the linear expansion coefficient α _base of the laser substrate unit 22, the distance L between the center C of the lens substrate unit 26 and the lens 25 farthest from the center C, and the environment When the temperature difference ΔT of the temperature and the tolerance Δd of the optical axis deviation of the lens 25 are set, Expression (1) is satisfied.
For example, when designing L = 4.5 [mm], ΔT = 30 [K], and Δd = 0.1 [μm], if the laser substrate 22 is a GaAs substrate, α _base = 6.86 × 10 ^{Since it is −6} [/ K], it is desirable that it falls within the range of 6.12 ≦ α _lens ≦ 7.60 [× 10 ⁻⁶ / K].
The range of values that the linear expansion coefficient α _lens can take increases as the tolerance Δd of the optical axis deviation increases. When Δd = 0.5 μm, 3.16 ≦ α _lens ≦ 10.56 [× 10 ⁻⁶ / K], Δd = 0.93 ≦ α _lens ≦ 12.78 [× 10 ⁻⁶ / K] when = 0.8 μm.

On the other hand, the linear expansion coefficient α _lens has a narrower range of values as the temperature difference ΔT of the ambient temperature used increases, and when ΔT = 50 [K], 6.42 ≦ α _lens ≦ 7.30 [× 10]. ⁻⁶ / K]. Similarly, when ΔT = 100 [K], 6.64 ≦ α _lens ≦ 7.08 [× 10 ⁻⁶ / K]. The distance L is determined depending on the size of the VCSEL element. When L = 9 mm, 6.49 ≦ α _lens ≦ 7.23 [× 10 ⁻⁶ / K], and when L = 18 mm, 6.67. ≦ α _lens ≦ 7.05 [× 10 ⁻⁶ / K] The width of the selectable linear expansion coefficient becomes narrower as the size of the laser substrate portion 22 becomes larger.

Further, in the configuration in which the GaAs substrate is removed from the laser substrate and is pasted on a metal or ceramic substrate having a good thermal conductivity to form the laser substrate portion 22, the linear expansion coefficient of the metal or ceramic is used as α _base to form a lens substrate. What is necessary is just to determine the linear expansion coefficient of the part 26. FIG.
For example, when bonded to an aluminum nitride substrate, α _base = 4.6 [× 10 ⁻⁶ / K], and when bonded to a copper substrate, α _base = 16.8 [× 10 ⁻⁶ / K]. ]
In this case, in the configuration of L = 4.5 [mm], ΔT = 30 [K], and Δd = 0.1 [μm] described above, α _base = 4.6 [× 10 ⁻⁶ / K]. In some cases, it is desirable that the range is 3.86 ≦ α _lens ≦ 5.34 [× 10 ⁻⁶ / K]. Similarly, when α _base = 16.8 [× 10 ⁻⁶ / K], the range of 16.1 ≦ α _lens ≦ 17.5 [× 10 ⁻⁶ / K] is desirable.

By the way, as shown in FIG. 10, even if the lens array 73 includes the lens 75 and the glass substrate portion 76, when the lens 75 is provided adjacent to each other, the line between the lens 75 and the glass substrate portion 76 is obtained. When the difference in expansion coefficient is large, there is a risk of warping or cracking.
In order to prevent such a problem, when the difference in deformation amount z2 caused by the change in the environmental temperature due to the difference in linear expansion coefficient is sufficiently large with respect to the thickness of the lens substrate portion, the adjacent lenses are separated from each other by a minute distance d. It is desirable to arrange them.
The portion separated by the minute interval d is a boundary region where the plurality of lenses 25 are separated by the minute interval d in the lens substrate portion 26.
In other words, the boundary region indicates a region between the inflection points R of the lenses 25 adjacent to each other, and indicates a region having no curvature in the lens array 23.
By providing such a boundary region, the displacement of the lens array 23 does not depend on the material of the lens 25, and a decrease in light use efficiency in a place where the environmental temperature is high is suppressed.

In the present embodiment, the lenses 25 are held by the lens array 23 in a manner spaced from each other.
With this configuration, the amount of displacement caused by the thermal expansion of the lens array 23 does not depend on the material of the lens 25, so that the light use efficiency in a place with a high environmental temperature is reduced while the material used for the lens 25 is freely selected. And the deterioration of accuracy is suppressed.

In the present embodiment, the lens array 23 includes the lens substrate portion 26 having a linear expansion coefficient different from that of the lens 25.
With this configuration, the material used for the lens 25 can be freely selected, and the decrease in light use efficiency in a place with a high environmental temperature is suppressed.

In this embodiment, the lens array 23 includes the first antireflection layer 27 formed on the outermost surface of the lens 25 on the −Z direction side.
With this configuration, the incident laser light L is prevented from being reflected to the light emitting unit 21, and the light utilization efficiency is improved.
In the present embodiment, the second antireflection layer 28 is formed between the lens 25 and the lens substrate portion 26.
With this configuration, the incident laser light L is further prevented from being reflected to the light emitting unit 21, and the light use efficiency is improved.

A method for manufacturing the lens array 23 will be described.
As shown in FIG. 5A, first, the second antireflection layer 28 and the synthetic quartz glass 88 are formed in layers on a substrate 86 made of N-BAF52, which is a material constituting the lens substrate portion 26 (FIG. 6). Step S101).
On the synthetic quartz glass 88, a pattern of a circular or polygonal photosensitive resin 89 is formed by photolithography (step S102).
When the photosensitive resin 89 formed on the surface is heated, the photosensitive resin 89 is deformed by heat as shown in FIG. 5B, and is a hemispherical surface or a curved surface convex toward the −Z direction side according to the surface tension. Is formed (step S103).
Step S103 is a mask forming process for forming a mask pattern with the photosensitive resin 89. In the mask formation step, a microlens pattern is formed on the surface of the synthetic quartz glass 88 simulating the shape of the lens 25 manufactured by the photosensitive resin 89.
In this mask formation step, the height from the lower end to the upper end of the lens shape formed by the photosensitive resin 89, in other words, the layer thickness of the photosensitive resin 89 is approximately the same as the thickness of the layer of the synthetic quartz glass 88. It is desirable to be.

Next, an etching process such as ECR plasma etching or RIE etching is performed using an etching gas obtained by mixing an oxygen gas for etching the photosensitive resin and a chlorofluorocarbon-based gas for etching the synthetic quartz glass (step S104).
In the etching process of step S104, as shown in FIG. 5C, the photosensitive resin 89 and the synthetic quartz glass 88 are etched in a state where the shape of the photosensitive resin 89 is transferred onto the synthetic quartz glass 88. .

When the etching process is advanced until the photosensitive resin 89 runs out, the shape of the photosensitive resin 89 is transferred to the synthetic quartz glass 88, and the lens 25 is formed as shown in FIG.
In this embodiment, the layer thickness of the photosensitive resin 89 and the layer thickness of the synthetic quartz glass 88 are approximately the same, and the etching rate is also approximately the same. Therefore, when the photosensitive resin 89 is used up, the synthetic quartz glass is removed. 88 forms the lens 25 of the aspect spaced apart from each other. Further, the second antireflection layer 28 may be formed so as to fill between the lenses 25.
At this time, if the material of the substrate 86 that is not etched or hardly etched by the etching gas is selected, even if the layer thickness of the photosensitive resin 89 is different from the layer thickness of the synthetic quartz glass 88, the lens 25 are formed in a manner spaced from each other.
Similarly, the etching rate may be controlled in accordance with the layer thickness by a method such as changing the mixing ratio of the etching gas.

  After the etching is completed and the lens array 23 having the lens 25 formed of the synthetic quartz glass 88 and the lens substrate portion 26 formed of the substrate 86 is formed, a method such as vacuum film formation is used as necessary. The first antireflection layer 27 is formed (step S105).

The lens array 23 is attached to the laser substrate unit 22 by the fixing unit 24 so that the lens 25 faces the light emitting unit 21 (step S106).
Step S106 is a coupling step for coupling and fixing the lens array 23 and the laser substrate unit 22.
In the present embodiment, the fixing portion 24 is an ultraviolet curable resin and has some flexibility even after fixing.
In the present embodiment, the fixing portion 24 is made of an ultraviolet curable resin. However, the fixing portion 24 in step S106 may be soldered and heated to 300 ° C. and then cooled and fixed.
In the joining process, in the configuration as in the conventional example already described in FIG. 8, there is a possibility that the lens array 23 may be thermally expanded or damaged by thermal stress due to heating and cooling.
However, in the present embodiment, the lens array 23 holds the lens 25 and has the lens substrate portion 26 having substantially the same linear expansion coefficient as that of the laser substrate portion 22, so that the difference in thermal deformation is small and the coupling step. In the case where the heat treatment is included, the damage due to the thermal stress is prevented.

In the present embodiment, the laser spark plug 100 has an optical amplifying unit 40 that amplifies the laser light L emitted from the laser element 21 and a condensing light for condensing the laser light L to the entrance of the optical amplifying unit 40. And an optical system 20.
With this configuration, it is possible to suppress a decrease in light use efficiency even in a place where the environmental temperature is high.

  As mentioned above, although embodiment of this invention was described, embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms.

  For example, in the present embodiment, three antireflection layers are provided, but such an antireflection layer may not be used, or an arbitrary number of antireflection layers may be provided.

10 Light source unit (laser light source unit)
21 Single element (light emitting part)
22 Element substrate (laser substrate)
23 Lens array 25 Lens 26 Lens substrate unit 30 Optical transmission path 40 Optical amplification unit 100 Laser ignition device (laser ignition plug)
203 Optical element (TFT element)
205 Optical element substrate (glass substrate)
500 Laser ignition system 700 Combustion chamber L Laser light O Lens optical axis Z ₁ Distance between substrates

JP 2014-192166 A Japanese Patent No. 3617846

Claims (14)

A light source unit including a lens array in which a plurality of lenses are two-dimensionally arranged and an element substrate portion that supports a plurality of light emitting portions,
The lens array has a lens substrate portion that holds the lens,
The lens substrate unit is a light source unit having a linear expansion coefficient substantially the same as the element substrate unit. The light source unit according to claim 1,
The light source unit, wherein a linear expansion coefficient of the lens and a linear expansion coefficient of the lens substrate portion are different. The lens array according to claim 1 or 2,
The light source unit, wherein the plurality of lenses have boundary regions separated from each other by a minute interval and are held on the lens substrate. The light source unit according to any one of claims 1 to 3,
The light source unit, wherein the light emitting unit of the light source and the plurality of lenses are arranged to face each other on a one-to-one basis. The light source unit according to any one of claims 1 to 4,
A light source unit comprising the plurality of lenses so as to coincide with optical axes of the plurality of light emitting units. The light source unit according to any one of claims 1 to 5,
The product of the difference between the linear expansion coefficient of the element substrate portion and the linear expansion coefficient of the lens substrate portion, the distance from the center of the lens array to the center of the lens farthest from the center, and the temperature difference of the ambient temperature. A light source unit characterized by being less than or equal to a lens optical axis deviation tolerance. The light source unit according to any one of claims 1 to 6,
A light source unit comprising a first antireflection film formed on the outermost surface of the lens. The light source unit according to any one of claims 1 to 7,
A light source unit comprising a second antireflection film formed between the lens and the lens substrate. The light source unit according to any one of claims 1 to 8,
A light source comprising a single element disposed opposite to the lens and an element substrate unit integrally including the single element;
A light source unit comprising: a fixing portion for fixing the lens substrate portion and the element substrate portion to each other. The light source unit according to any one of claims 1 to 9,
The light source unit, wherein the lens is arranged in a convex shape so as to face the plurality of light sources. The light source unit according to claim 9 or 10,
And a condensing lens that condenses the excitation light from the light source unit. A light source module according to any one of claims 8 to 10,
A laser ignition device comprising a laser resonator that absorbs excitation light emitted from the light source unit. The laser ignition device according to claim 12,
A laser ignition device, comprising: an optical transmission path that is disposed between the light source module and the laser resonator and transmits the excitation light. The laser ignition device according to claim 12 or 13,
A laser ignition device having a condensing optical system for condensing the excitation light to an entrance of the laser resonator.

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