WO2004072698A1

WO2004072698A1 - Microlens array integrated lens

Info

Publication number: WO2004072698A1
Application number: PCT/JP2004/001697
Authority: WO
Inventors: Junichi Kubo; Kouei Hatade; Masayoshi Yamada
Original assignee: Nalux Co., Ltd.
Priority date: 2003-02-17
Filing date: 2004-02-17
Publication date: 2004-08-26
Also published as: JPWO2004072698A1

Abstract

An optical element for forming microlenses, each provided with a beam shaping function, into an array, realizing the high-efficiency coupling of a semiconductor laser, and condensing a laser beam after shaping into a sufficiently small spot diameter by a lens. A microlens array in which micolenses are arranged for shaping beams from individual laser diodes is provided on one surface and a shape is provided on the other surface for condensing shaped beams. In one embodiment, the plane of a microlens is non-circular at any in-plane section including the optical axis. In another embodiment, the optical axis agrees with Z-axis in a 3-axis orthogonal XYZ coordinates system and a microlens plane is represented by a numerical expression including a term representing a non-rotary-symmetric non-spherical surface profile and at least one correction term.

Description

Microphone with lens array integrated lens

The present invention relates to a lens having an integrated lens array with a micro aperture for condensing a beam from a light source such as a semiconductor laser array. The lens with an integrated microphone aperture lens array of the present invention can be used for a laser processing head or the like.

Light

Background art

Drilling and cutting in the manufacturing industry have an extremely strong demand for ultra-fine writing, but conventional machining has the following processing limits.

In printed circuit board through-hole processing, mechanical punching cannot be less than 0.8 mm and drilling cannot be less than 0.2 mm.

Drilling and thinning of thin metal plates In drilling, it is impossible to make a diameter of 0.2 mm or less by drilling. 、 Etching requires a mask, and it is difficult to machine straight holes and slits. It is.

In label processing, complicated fine cutting cannot be performed. The conventional processing method does not allow a tool with a line width of 200 m or less.

Therefore, expensive YAG laser processing machines are used for fine drilling and cutting force below these limits. Conventionally, a Xe lamp-pumped YAG laser has been used, but in recent years, a semiconductor diode-pumped YAG with high energy conversion efficiency has been used. However, it is expensive and the equipment size is large, so there is a sense of stagnation in its spread.

If the high-power semiconductor laser array itself developed for pumping YAG lasers can be directly used as the light source for laser processing, energy-saving, inexpensive, compact, and high-performance laser processing machines, and the currently widely used A compact laser-processed head that can be mounted on a center can be developed. Furthermore, it can be used in the market for single excitation of YAG laser in the future.

However, a high-power semiconductor laser array has a power capability of several 10 W class, but its output beam spreads to several 10 degrees, so it is necessary to focus on a small spot with high energy required for processing. Was extremely difficult. Also, a power supply for laser processing using a microlens array has been proposed, but a type in which a condensing lens is separately provided (see, for example, Japanese Patent Application Laid-Open No. 2002-264652, 26 paragraphs, Fig. 8, etc.)). Disclosure of the invention

The present invention has been made in view of the above situation. In other words, an array of microlenses with a beam shaping function is realized to realize high-efficiency coupling of a semiconductor laser, and to provide an optical element that focuses the shaped laser beam to a sufficiently small spot diameter by a lens. Aim. Here, the micro lens does not specify an absolute size, but means that the micro lens is relatively small as compared with the lens on the light-collecting surface.

The lens with integrated microphone aperture lens array according to the present invention includes a microlens array in which microlenses for receiving beams from individual light sources are arranged on one surface, and the shaped beam is condensed or parallelized on the other surface. It has a shape to be converted. Therefore, highly efficient coupling of the semiconductor laser can be realized, and the laser beam can be focused to a sufficiently small spot diameter by the lens.

According to one embodiment of the present invention, the surface of the microlens is non-circular in any in-plane cross-section including the optical axis.

According to one embodiment of the present invention, the surface of the microlens is represented by a mathematical expression including a term representing a non-rotationally symmetric aspherical aperture file.

Therefore, the laser beam shape can be shaped mainly by the non-rotationally symmetric aspherical profile, and the aberrations can be minimized by the collection term.

According to one embodiment of the present invention, the optical axis of the micro lens coincides with the Z axis of a three-axis orthogonal XYZ coordinate system, c _x is the curvature of the center of the curve of the XZ cut surface, _{C y} is YZ switching Kx and ky are coefficients representing the shape of the curve, and AR, BR, CR, DR, AP, BP, CP and DP are correction coefficients (constants). The lens surface is

+ BR [(l-BP) x ² + (1 + BP) y ² f + CR [(1-CP) x ² + (1 + CP) y ² f + DR [(l-DP) x ² + ( 1 + DP) y ² ] Is represented by Therefore, it is possible to mainly c _x, 0 ₇ Oyopi 1 ?: shapes the record one The one beam shape by ky, to as small to so that possible aberrations by further correction term.

According to one embodiment of the present invention, coincides with the Z-axis optical axis of a three-axis orthogonal XY Z coordinate system of microlenses, c _x is the curvature of the center of the curve of the XZ cut surface, c _y is YZ Kx, ky are coefficients representing the shape of the curve, and assuming that the correction coefficients A i and B; are constants,

Is represented by Therefore, mainly c _x, c _y and kx, shapes the record one The one beam shape by ky, can be further only small to so that possible aberrations by the correction term. In addition, the degree of freedom of correction is improved by independently operating the correction term relating to X and the correction term relating to y.

According to one embodiment of the present invention, when the optical axis of the microlens coincides with the Z axis of the three-axis orthogonal XYZ coordinate system, k is a constant that determines the shape of the quadratic curve, c is the central curvature, A Is the correction coefficient.

C ⁼ R

Is represented by

According to one embodiment of the present invention, the other surface is represented by an aspherical surface. According to one embodiment of the present invention, the other surface has an optical axis that is orthogonal to three axes. Where k is a constant that determines the shape of the quadratic curve, c is the central curvature, and A is the correction coefficient.

c =

R

ch "

z = ■ + 2i

1 + l- (1 + k) c 2 h 2 it - is represented by.

Therefore, the shaped laser beam can be focused to a sufficiently small spot diameter by the lens.

According to one embodiment of the present invention, the other surface forms a cylindrical lens for condensing or collimating a beam. Therefore, the crystal rod can be irradiated with the excitation light to extract the stimulated emission light. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows an embodiment of a microlens array integrated lens according to the present invention.

FIG. 2 is a diagram showing a beam shaping optical element.

FIG. 3 is a diagram showing a curved surface of the beam shaping optical element.

FIG. 4 is a diagram showing an optical path of a beam shaping optical element.

FIG. 5 is a diagram showing a shunt switching basic circuit.

FIG. 6 shows the shape of a microlens array-integrated lens including an emission surface.

FIG. 7 is a view showing a method of defining a light beam of the microlens array integrated lens of the present invention.

FIG. 8 is a diagram showing an embodiment of a lens with an integrated microphone aperture lens array of the present invention.

FIG. 9 is a diagram showing a relationship between a semiconductor laser and a microlens array. FIG. 10 is a diagram showing a YZ section of a type 1 optical path.

FIG. 11 is a diagram showing an XZ cross section of a type 1 optical path.

FIG. 12 is a three-dimensional view of a type 1 optical path.

FIG. 13 is a diagram showing a cross section of a spot including a type 1 peak in the Y and X directions.

FIG. 14 is a diagram showing a YZ section of a type 2 optical path. FIG. 15 is a diagram showing an XZ cross section of a type 2 optical path.

FIG. 16 is a three-dimensional view of a type 2 optical path.

FIG. 17 is a diagram showing a spot cross section in the Y direction and the X direction including a type 2 peak.

FIG. 18 is a diagram showing a YZ section of a type 3 optical path.

FIG. 19 is a diagram showing an XZ cross section of a type 3 optical path.

FIG. 20 is a three-dimensional view of a type 3 optical path.

FIG. 21 is a diagram showing a spot cross section in the Y direction and the X direction including a type 3 peak.

FIG. 22 is a diagram showing a YZ section of a type 4 optical path.

FIG. 23 is a diagram showing an XZ section of a type 4 optical path.

FIG. 24 is a three-dimensional view of a type 4 optical path.

FIG. 25 is a diagram showing a cross section of a spot including a type 4 peak in the Y direction and the X direction.

FIG. 26 is a diagram showing solid-state laser oscillation due to bombing of a semiconductor laser array. BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 and FIG. 8 show the configuration of a lens with an integrated microphone aperture lens array according to the present invention. On the entrance surface of the lens with integrated microphone aperture lens array, an array with microlenses with a beam shaping function is provided for each laser of the laser diode array. The exit surface of the microlens array integrated lens is designed to focus the shaped beam.

The laser diode array is connected to an ultrashort pulse generation circuit. The ultrashort pulse generation circuit uses the energy efficient shunt switching circuit shown in Fig.5. That is, by switching the current i flowing through the inductance L by the power M0SFET, a large current is instantaneously passed through the semiconductor laser LD, and the short pulse compression operation is performed electrically.

The surface of the microlens is determined based on the following equation with the optical axis as the Z axis. c _x x + c _v y

Z + AR [(1-AP) x ² + (1 + AP) y ²

1 + 1— (1 + k _x c _x x ^) — (1 + (c)

+ BR [(l-BP) x ² + fl + BP) y ² + CR [(1-CP) x ² + (1 + CP) y ² ] ⁴ + DR [(l-DP) x ² + (1 + DP) y ² ]

(1) Here, c _x is the curvature of the center of the curve of the XZ cut _{surface, c x = l / Rx,} c y is the center of curvature of the curve of YZ cut surface is a c _y = lZRy. kx and ky are coefficients representing the shape of the curved line. The second and subsequent terms are correction terms representing deviations from the curved surface. AR, BR, CR, DR, AP, BP, CP and DP are correction factors (constants). ■ Alternatively, it is determined by the following equation.

Here, c _x and c _y are the curvature of the X-axis and Y-axis direction of the surface, respectively, k _x Contact and k _y and the correction coefficients A i and B i are constants.

In the above equation (1) or (2), by adjusting the coefficient of the term representing the aspherical profile of the first term, a function such as changing the beam shape can be mainly achieved. Here, changing the beam shape means changing a beam emitted from a semiconductor laser having an elliptical energy distribution into a beam having an approximately circular energy distribution. Further, by manipulating the coefficients of the X and Y correction terms, functions such as minimizing wavefront aberration can be achieved.

The use of super-resolution in a microlens can reduce the beam spot diameter and increase the depth of focus.

FIG. 2 is a diagram illustrating an example of a beam shaping optical element. FIG. 3 is a diagram illustrating an example of a curved surface of the beam shaping optical element. FIG. 4 is a diagram illustrating an example of an optical path of a beam shaping optical element.

If 0.07 wavefront aberration can be obtained in the design, a spot diameter of 20 μm or less can be obtained as shown in the bottom row of Table 1. Table 1 shows the general relationship between the lens diameter, the focal length, and the lZe ² spot diameter. In Table 1, bre and re indicate intermediate parameters. From Table 1, although depending on the lens diameter and the focal length, spot diameters less than 10 μπι are also sufficiently possible. table 1

Next, the shape of the exit surface (S2 surface) of the microlens array integrated lens of the present invention will be described. Figure 6 shows the shape of the microlens array-integrated lens including the exit surface. The S 2 plane is, for example, an optical axis symmetric rotation plane obtained by rotating the following quadratic curve around the optical axis. Here, the optical axis is represented by _Z , and the coordinates of a plane perpendicular to the optical axis are represented by xy. k is a constant that determines the shape of the quadratic curve, and c is the central curvature. A is a correction coefficient. h = 2 +

For example, a coefficient up to the fourth order is used as the correction coefficient A. Table 2 shows the design specifications of the optical system in Fig. 6. The circled numbers in the table correspond to those in Figure 6. In Table 2, LD represents a laser diode as a light source. Table 2

• Optical design specifications

Fig. 7 explains the method of defining light rays. The S2 surface is decentered, and the principal ray position (condensing position) on the image plane is changed by the same amount as the S2 surface is decentered. Table 3 shows the resulting relationship between the surface eccentricity and the focusing position. Table 3

Principal ray passing position on image plane

In addition to the embodiment shown in FIG. 1 in which the laser diode array is provided near the microphone lens array, an embodiment in which a laser beam is supplied to the micro lens array via an optical fiber is also conceivable.

As another embodiment of the present invention, as shown in FIG. 26, a system that irradiates a crystal aperture with reflected light to extract stimulated emission light can be considered. In this case, a cylindrical lens is arranged on the other surface of the lens array surface, and a focused or collimated light beam is made incident on the crystal aperture. Design example 1

In this design example, an array of 25 semiconductor lasers (LDs) shown in Table 4 is used. The light emitted from the semiconductor laser is assumed to have a Gaussian distribution, and the numerical aperture 規定 is specified so as to capture the ideal effective Gaussian energy of 86.5%. Table 4

Using the semiconductor lasers shown in Table 4, a coordinate system is created as shown in FIG. 9, and a lens array element is provided on the surface on the semiconductor laser side so as to correspond to each semiconductor laser arranged in an array. The optical system is designed so that the chief rays emitted from each semiconductor laser with the numerical aperture NA shown in Table 1 converge at one point on the image plane, and the wavefront aberration is minimized. Design is performed using optical design software.

Intensity magnification is defined as a lens evaluation index. Emitting from a semiconductor laser The light beam is captured with an ideal effective Gaussian energy of 86.5%, and the intensity magnification when condensed by an ideal lens without wavefront aberration is 1. Therefore, the effective Gaussian energy (%) is Divide by 86.5 (%) and multiply by the Strehl ratio to obtain the intensity magnification, where the Strehl ratio is the ratio of the intensity resulting from the wavefront aberration to the intensity of the ideal lens. .

By the way, when light from different light sources is superimposed, no interference is observed under normal conditions, and the total intensity is equal to the sum of the individual light fluxes at any location (see “Principles of Optics II” Tokai University Press, pp. 421). Therefore, the intensity distribution of each semiconductor laser is calculated separately, and the total intensity distribution is calculated by calculating the sum. Thus, the maximum intensity magnification when using 25 semiconductor lasers is 25.

Spot diameter is defined as another evaluation index. In the image plane intensity distribution, the spot diameter in the X direction and the Y direction is calculated with a range of the intensity of 13.5% (1 / e ² ) or more relative to the peak intensity as a spot. The smaller the spot diameter, the easier the microfabrication becomes. Furthermore, a side lobe is defined as another evaluation index. In the image plane intensity distribution, the ratio (%) of the intensity of the place that can be regarded as the second peak to the peak intensity is supported. And a drip rope.

Table 5 shows the lens specifications of Design Example 1 and the above evaluation indices. In Table 5, type 1 defines the surface of the microlens by equation (2), and the image-side condensing surface (S2 plane) by equation (3). In Table 5, for Type 2, the condensing surface (S2 surface) on the near image side of the microlens surface is defined by equation (3). In Table 5, the 0-31 plane distance represents the distance between the semiconductor laser and the corresponding microlens plane. BF represents pack focus. The free form of the surface definition represents the surface defined by equation (2), and the aspherical surface represents the surface defined by equation (3). It should be noted that design can be performed in the same manner by using equation (1) instead of equation (2). Table 5

In Table 5, Type 1 is superior to Type 2 in all of the evaluation indexes for strength magnification, spot diameter, and side lobe. In fact, Type 1 wavefront aberrations are much smaller than Type 2 wavefront aberrations. Thus, the wavefront aberration can be made extremely small by defining the surface of the microlens by equation (2). Wear.

Table 6 shows the coefficients for Type 1 and Type 2. The optical path diagram of type 1 is shown in Figs. 10 to 12, and the spot cross section including the peak is shown in Fig. 13. The optical path diagrams of type 2 are shown in FIGS. 14 to 16, and the spot cross section including the peak is shown in FIG. Table 6

Design example 2

In this design example, an array of 46 semiconductor lasers (LD) as shown in Table 7 is used. Table 7 also shows the array of Design Example 1. Table 7

The difference between the semiconductor lasers in Design Example 1 and Design Example 2 is the XY ratio of the emission angle to the emission angle. Although the number of semiconductor lasers is increasing, the pitch of the semiconductor laser array Is smaller, so the maximum object height is smaller, making it easier to design. Table 8 shows the lens specifications and evaluation indices of Design Example 2. Table 8 also shows the lens specifications and evaluation indices of Design Example 1. In Table 8, for types 3 and 4, the condensing surface (S2 surface) on the surface and image side of the microlens is defined by equation (3). Type 3 has a pack focus of 45 mm, and type 4 has a back focus of 3 O mm. Table 8

In the case of design example 2, a good evaluation index can be obtained even when both the microlens surface and the light-collecting surface are defined by the equation (3). In the case of Design Example 2, although the number of semiconductor lasers is larger than in the case of Design Example 1, the object height is reduced due to the small pitch. , Design becomes easier. For this reason, there is no need to specify the equation (2).

Table 9 shows type 3 and type 4 coefficients. The optical path diagram of type 3 is shown in Figs. 18 to 20, and the cross-sectional view of the spot including the peak is shown in Fig. 21. The optical path diagrams of type 4 are shown in FIGS. 22 to 24, and the spot cross-sectional view including the peak is shown in FIG. Table 9

Type3 Type4

Array surface S2 surface Array surface S2 surface

Definition Aspheric surface Aspheric surface Aspheric surface Aspheric surface

C 3.916815121 -0.04351724 3.916818208 -15.322196

K -2.28196922 0.0-2.28196645 0

A4 0 2.33E-05 0 7.82E-05

A6 0 0 0 0

A8 0 0 0 0

A10 0 0 0 0

Claims

The scope of the claims

1. A microlens array-integrated lens that has a microlens array in which microphone aperture lenses that receive beams from individual light sources are arranged on one surface and condenses or collimates the beam on the other surface. .

2. The microlens array-integrated lens according to claim 1, wherein the surface of the microlens is non-circular in any in-plane cross section including the optical axis.

3. The microlens array-integrated lens according to claim 1, wherein the surface of the microlens is represented by a mathematical expression including a term representing a non-rotationally symmetric aspherical profile.

4. Consistent with the Z-axis optical axis of a three-axis orthogonal XYZ coordinate system of microlenses, c _x is the curvature of the center of the curve of the XZ cut surface, c _y is the center curvature der curves YZ cut surface Where kx and ky are coefficients representing the shape of the curve, and AR, BR, CR, DR, AP, BP, CP and DP are correction coefficients (constants).

Z = ——. + AR [(1-AP) x ² + (1 + AP) y ² f

1 + ^ - (1 + k x) (c x 2 x 2) - (l + k y) (V)

+ BR [(l-BP) x ^l + (1 + BP) y ² † + CR [(1-CP) x ^z + (1 + CP) y ² ] ⁴ + DR [(1-DP) x ² + 4. The lens integrated with a microphone opening lens array according to claim 3, represented by (1 + DP) y ² ].

5. the optical axis of the micro lens coincides with the Z axis of a three-axis orthogonal XYZ coordinate system, c _x is the curvature of the center of the curve of the XZ cut surface, c _y is the center curvature der curves YZ cut surface Ri, k X, ky is a coefficient representing the shape of the curve, the correction coefficient a ₅ and _B; a is a constant, the surface of the microlens, wherein z _y ²ⁱ

4. The microlens array-integrated lens according to claim 3, represented by:

6. When the optical axis of the micro lens coincides with the Z axis of the three-axis orthogonal XYZ coordinate system, k is a constant that determines the shape of the quadratic curve, c is the center curvature, and A is the correction coefficient. The lens surface is

The microlens array-integrated lens according to claim 1, represented by:

7. The lens with an integrated microphone aperture lens array according to claim 1, wherein the other surface is represented by an aspherical surface.

8. When the other surface coincides with the Z-axis of the three-axis orthogonal XYZ coordinate system, k is a constant that determines the shape of the quadratic curve, c is the center curvature, and A is the correction coefficient. H = y [x ² + y ² 1 r 2 m

Ch \ 9;

= ——, = + ∑Αφ

1 + + k) c ² h ²

The microphone lens body type lens according to any one of claims 1 to 6, represented by:

9. The lens integrated with a microphone opening lens array according to any one of claims 1 to 8, wherein super resolution is used for the micro lens.

10. The microphone-integrated lens array lens according to claim 1, wherein the other surface forms a cylindrical lens that focuses or collimates a beam.