KR20090029565A - Laser module having aspheric collimate lens - Google Patents

Abstract

A laser module comprising a collimated lens is disclosed. According to one embodiment of the present invention, a light exit surface of an aspherical surface having a first basic curvature r1 and a light incident surface of an aspherical surface having a second basic curvature r2 are provided on both sides and have a predetermined thickness. Mate lenses; And a laser window spaced apart from the light incident surface of the lens by a walking distance (WD). According to the present invention, the laser module can be miniaturized and applied to a miniaturized device, and there is an effect of having more excellent optical performance (MTF characteristics, optical trajectory, spherical aberration, etc.).

Description

Laser module having aspherical collimate lens

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a collimated lens used in a laser package / module, and more particularly, to a collimated lens that emits light incident from a light source in parallel while having a high numerical aperture (NA) and a short focal length (f). It is about.

Aspheric lenses can simply control the light emitted from the laser with a single lens. In addition, in the case of semiconductor lasers used in laser packages / modules, the amount of light emitted is large, and in order to control the amount of light emitted, it is necessary to parallel or focus the emitted light. In the case of semiconductor lasers, aspheric collimating lenses are used to control the degree of light emission.

In the case of the collimated lens used in the optical device including the semiconductor laser, a high numerical aperture and a constant working distance are required. Numerical Aperture (NA) is a number that determines resolution in an optical device. The larger the numerical aperture, the more luminous flux is used, the brighter the image, and the higher the resolution for identifying two adjacent points, so that even small objects can be seen. The working distance (WD) must be sufficiently separated by the distance between the light exiting surface of the lens and the lens window to fully function the laser package / module. However, when the working distance WD is sufficiently secured, the curvature of the lens is increased and the eccentricity capacity of the lens is reduced, thereby reducing productivity. Therefore, it is required to maintain the working distance WD appropriately.

In addition, the conventional collimated lens has a problem that the focal length f is rather long and cannot be used for miniaturized electronic products.

Accordingly, the present invention relates to a collimated lens capable of increasing the numerical aperture and ensuring sufficient walking distance.

In addition, the present invention enables miniaturization of electronic products in which a laser package / module is used through a collimated lens having a short focal length.

The present invention also provides a collimated lens having better optical performance (spherical aberration, optical trajectory, MTF characteristics, etc.).

According to one aspect of the invention, according to one aspect of the invention, the light exit surface of the aspherical surface having the first basic curvature r1 and the light incident surface of the aspherical surface having the second basic curvature r2 are on both sides A collimated lens provided and having a predetermined thickness; And a laser window spaced apart from the light incident surface of the lens by a walking distance (WD). In this case, the first basic curvature r1 of the collimated lens may have the same absolute value as that of the second basic curvature r2 and may have the opposite sign, and the working distance WD and the focal length f of the collimated lens may be different. The relationship with may be WD> (f / 1.2-1).

In addition, the refractive index (Nd) of the collimated lens can satisfy the relationship of 1.4 <Nd <2, the Abbe number (Vd) of the collimated lens can satisfy the relationship of 20 <Vd <90, and the center thickness ( The relationship between CT) and the edge thickness ET can satisfy the relationship of ET / CT> 0.4.

In addition, the wavelength λ incident on the collimating lens may be in the range of 350 nm ≦ λ ≦ 1600 nm, and the numerical aperture NA of the collimating lens may be in the range of 0 <NA <0.6.

In addition, the relationship between the focal length f and the outer diameter OD of the collimated lens may satisfy a relationship of f / OD <0.6.

In the case of the collimated lens included in the laser module according to the present invention, the numerical aperture can be increased and sufficient walking distance can be ensured.

In addition, by providing a collimated lens having a short focal length, it is possible to miniaturize electronic products in which the collimated lens is used.

In addition, it is possible to provide a collimated lens having excellent optical performance (light trajectory, spherical aberration, MTF characteristics, etc.).

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms including ordinal numbers such as first and second may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is said to be "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but other components may be present in the middle. It should be understood. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and in describing the present invention with reference to the accompanying drawings, the same or corresponding components are given the same reference numerals regardless of the reference numerals. Duplicate explanations will be omitted.

Hereinafter, a schematic configuration of a laser module using a collimated lens according to an embodiment of the present invention will be described with reference to FIG. 1. 1 is a block diagram of a laser module including a collimating lens according to an embodiment of the present invention.

The laser module according to an embodiment includes a combined laser light source. The multiplexing laser light source is a collimating lens 111, 112, 113 provided opposite to each of the semiconductor lasers LD1, LD2, LD3, LD4, LD5, LD6 and LD7 arrayed and fixed on the heat block 100 and the laser. , 114, 115, 116 and 117 are present. The outgoing light incident on the collimated lenses 111, 112, 113, 114, 115, 116 and 117 and exited in parallel passes through the condenser lens 120 and proceeds to the optical modulator according to an embodiment of the present invention. do. The condenser lens 120 is an aspherical lens and is formed in an elongate shape in the arrangement direction of the collimating lenses 111 to 117. In this way, the collimated lenses 111 to 117 serve to make the light beam incident from the light source into parallel light. Therefore, the collimated lens 111 to 117 is an optical device that can be applied to the laser module / package that needs to emit the incident light in parallel-for example, display device, bar code scanner, laser diode coupler, optical disk, printer , Medical lasers, and the like.

Hereinafter, a collimating lens according to an embodiment of the present invention will be described with reference to FIG. 2. 2 is an exemplary view showing an embodiment using a collimated lens according to an embodiment of the present invention. For convenience of illustration, only the projection examples of the two incident rays are shown.

The collimated lens 210 emits the light emitted from the light source 260 as parallel light. Light emitted from the light source 260 passes through the cover glass 230 and the laser window 220 before being incident on the collimated lens 210. Then, the light penetrating the cover glass 230 and the laser window 220 and incident on the collimated lens 210 is emitted through the aperture 240. The diaphragm is a mechanism for adjusting the amount of light, and according to an embodiment of the present invention, serves to adjust the amount of light transmitted through the collimating lens 210.

The collimated lens 210 according to the embodiment of the present invention is an aspherical lens. Aspherical lenses are lenses for solving spherical aberration, and are referred to as lenses whose surfaces are aspherical rather than spherical in plan. The edge thickness ET 290 refers to the thinnest thickness at the tip of the lens as shown in the figure. The median thickness CT 294 of the collimated lens 210 is the thickness of the most central portion, that is, the thickest portion of the collimated lens 210. And the diameter of the edge of the lens is called the outer diameter (OD, 291) and the range of light emitted by the aperture 240 is limited to the clear aperture (CA, 292).

The distance from the collimated lens 210 to the laser window 220 is called working distance (WD) 293, and the working distance 293 must be sufficiently secured to fully function the optical device including the collimated lens 210. Can be exercised.

In order to fabricate the collimated lens 210 having a high numerical aperture (NA), a suitable working distance (WD) 293, and a short focal length (f, 295) according to an embodiment of the present invention, the following relationship must be satisfied. do. In order to keep the numerical aperture high while shortening the focal length f and 295 and implementing the collimated lens 210 having an appropriate walking distance, the three elements must be balanced.

According to an embodiment of the present invention, the numerical aperture NA of the collimated lens 210 may be 0 <NA <0.6, wherein the radius r1 of the first surface 270 of the collimated lens 210 and the first Radius r2 of the two surfaces 280 may have a relationship in which the absolute values are the same and opposite in sign, that is, r1 = -r2. This is because the radius has a negative sign because it is convex in the opposite direction. In addition, the collimated lens 210 shown in FIG. 2 has a positive refractive power.

And the ratio of the edge thickness (ET, 290) and the center thickness (CT, 294) may be a relationship of ET / CT> 0.4, the outer diameter (OD, 291) and the focal length (f, 295) is f / OD < May be 0.6. In this case, the wavelength λ of the light incident on the collimated lens 210 should satisfy a predetermined range, which may be 350 nm ≦ λ ≦ 1600 nm.

In addition, the refractive index (Nd) of the collimated lens 210 may be 1.4 <Nd <2 and the Abbe number (Vd) may be 20 <Vd <90. At this time, Abbe's number (Vd) is an amount that defines the property of light dispersion of the optical glass, the larger the Abbe's number, the smaller the dispersion, and is a value normally used for calculation of chromatic aberration correction such as a lens or a prism.

As described above, according to the laser module of the present invention, it is possible to provide a collimated lens having excellent optical characteristics (spherical aberration, optical trajectory, etc.) while being able to be used in a miniaturized device due to a short focal length. This can be clarified from the detailed description with reference to FIGS. 3A to 7C below.

Hereinafter, the actual implementation data of the collimated lens according to an embodiment of the present invention will be described with reference to FIGS. 3A, 3B, and 3C. 3A, 3B and 3C are tables of actual implementation data of a collimated lens according to an embodiment of the present invention.

Here, 'RDY' of the table is data representing the radius of curvature corresponding to each part of the collimated lens of the present invention, and 'THIGLAS' is a reference to the thickness or optical axis of each part of the collimated lens of the present invention. Data representing the distance to each part. 'Nd' is data representing the refractive coefficients of the collimated lens and the cover glass of the present invention, and 'Vd' is data representing the Abbe's number of the collimated lens and the cover glass of the present invention.

In addition, 'OBJ' of the table means an optical modulator according to an embodiment of the present invention, and 'STO' means the aperture 240. In addition, "IMG" means a light source.

An example of the implementation data for each part of the collimated lens of the present invention will be described with reference to FIG. 3A.

First, the numerical aperture (NA) of the collimated lens 210 according to the embodiment of the present invention is 0.475, the focal lengths f and 295 are 2.405 mm, the outer diameter OD and 291 are 4 mm, and the working distance WD 293) is 1.005 mm. In addition, the edge thicknesses ET and 290 of the collimated lens 210 are 1 mm, the center thicknesses CT and 294 are 1.75 mm, and the wavelength? Of light incident on the lens is 445 nm. The clear aperture (CA) 292 is 2.6 mm.

Next, in the case of the radius of curvature for each part of the projection lens of the present invention, light incident on the light modulator ('OBJ' of the table), the aperture 240 ('STO' of the table), and the collimated lens will be emitted. The radius of curvature of the light source ('IMA' of the table) is infinity (ie flat with no curvature), the radius of curvature r1 of the first surface 270 of the collimated lens 210 is 4.214839, The radius of curvature r2 of the second surface 280 is -4.214839, and the radius of curvature of the laser window 220 and the radius of curvature of the front and rear surfaces of the cover glass 230 are infinity (that is, flat without curvature). Is designed. This satisfies the condition of r1 = -r2.

Next, in the case of the thickness of the collimated lens of the present invention or the distance to each part, it is assumed that the object is infinity and the thickness of the aperture 240 is 0 mm. In addition, the center thickness CT of the collimated lens 294, that is, the distance d1 between the first surface 270 and the second surface 280 of the collimated lens 210 is 1.75 mm. The distance d2 between the second surface 280 of the collimated lens 210 and the laser window 220 is 1.005 mm, and the distance d3 between the cover glass 230 at the laser window 220 is 0.5 mm. The thickness d4 of the cover glass 230 is 0.25 mm, and the distance d5 from the cover glass 230 to the light source 260 is 0.25 mm.

At this time, in the collimated lens of the present invention, since the working distances WD and d2 are 1005 mm and the focal lengths f and 295 are 2.405 mm, the relationship of WD> (f / 1.2-1) is satisfied. In addition, the edge thickness (ET) of the collimated lens 210 is 1mm and the center thickness (CT, d1) is 1.75mm, which satisfies ET / CT> 0.4 and the wavelength of light incident on the collimated lens 210 ( lambda) satisfies 350 nm ≦ λ ≦ 1600 nm at 445 nm.

Next, in the collimation lens and the Abbe's number of the collimated lens of the present invention, the refractive index of the collimate lens 210 is 1.922859 and the Abbe's number is 20.8835. In addition, the cover glass 230 has a refractive index of 1.516798 and an Abbe number of 64.1983. This satisfies the condition that the refractive index Nd is 1.4 <Nd <2 and the Abbe's number Vd is 20 <Vd <90.

3B and 3C can be interpreted in a similar manner to the above-described case of FIG. 3A, and main data among other examples of implementation data for each part in the collimated lens of the present invention of FIGS. 3B and 3C Looking at it as follows.

In the implementation data of FIG. 3B, the working distance (WD, d2) is 2.046799 mm and the focal length f is 3.612 mm, satisfying the condition of WD> (f / 1.2-1), and the edge thickness of the collimated lens 210. (ET) is 1.03mm and center thicknesses (CT, d1) are 1.9mm, satisfying the relationship of ET / CT> 0.4. In addition, the refractive indexes of the collimated lens and the cover glass were 1.605004 and 1.516798, respectively, and the conditions of the refractive index Nd of 1.4 <Nd <2 were satisfied. Finally, Abbe's (Vd) also satisfies 20 <Vd <90 with a collimated lens 50.4193 and a cover glass 64.1983.

Finally, in the implementation data of FIG. 3C, the working distance (WD, d2) is 2.438983 mm and the focal length f is 3.957 mm, satisfying the condition of WD> (f / 1.2-1), and the collimated lens 210 is used. The edge thickness (ET) of is 0.78mm and the center thickness (CT, d1) is 1.75mm, which satisfies the relationship of ET / CT> 0.4. In addition, the refractive indexes of the collimated lens and the cover glass are 1.53116 and 1.516798, respectively, and the refractive index (Nd) satisfies the condition of 1.4 <Nd <2. Finally, Abbe's (Vd) also satisfies 20 <Vd <90 with a collimated lens 56.04138 and a cover glass 64.1983.

Hereinafter, excellent optical properties of the collimated lens used in the laser package according to an embodiment of the present invention will be described with reference to FIGS. 4 to 7C.

4 is an exemplary view showing a traveling path of light incident by a collimating lens according to an embodiment of the present invention.

Light is incident from the light source 410 into the collimated lens 420. The light incident on the collimated lens 420 is emitted in parallel while passing through the optical axis 430 of the lens. The light passing through the collimated lens 420 is emitted in parallel to form a wavefront. In the case of the wavefront by the ideal collimated lens 420, it should be formed in a straight line parallel to the vertical direction of the collimated lens 420, such as the wavefront 440 shown in dashed lines in FIG. However, in the case of the actual collimated lens 420, unlike the ideal wavefront 440 shown by the dotted line, the actual wavefront 450 is slightly deviated from the straight line. In this case, in FIG. 4, the actual wavefront 450 is exaggerated for clarity.

The distance in the direction of light travel between the ideal wavefront 440 and the actual wavefront 450 is referred to as the light traveling vehicle 460. Therefore, the smaller the optical trajectory 460, the better the optical performance of the collimated lens 420. In general, when the wavelength of light incident on the collimated lens 420 is λ, the optical performance of the collimated lens 420 is excellent, that is, the ability to output incident light in parallel when the optical trajectory 460 is less than 0.07λ. see.

Hereinafter, the graph of FIGS. 5A to 5C will be analyzed based on the above-described bar. 5A to 5C are graphs showing the light traveling 460 by the collimated lens 420 according to an embodiment of the present invention. The optical trajectory graph corresponding to the implementation data of FIG. 3A is FIG. 5A, and the optical trajectory graph corresponding to the implementation data of FIG. 3B is FIG. 5B, and the optical trajectory graph corresponding to the implementation data of FIG. 3C is FIG. 5C.

First, referring to FIG. 5A, the x-axis represents a distance away from the center axis of the collimating lens 420 in the vertical direction at the 'PY' axis, and the y-axis represents the light traveling 460 at the 'W' axis.

When the wavelength λ is 445 nm, since the maximum scale of the graph becomes 0.05 λ, the optical trajectory 460 is 0.07 λ or less, and thus the optical performance of the collimated lens 420 according to the exemplary embodiment of the present invention is excellent.

5B and 5C, the optical trajectory 460 also exhibits a value of 0.07λ or less at a maximum of 0.02λ and 0.02λ, respectively, indicating that the optical performance of the collimated lens 420 is excellent.

Hereinafter, the MTF (Modulation Transfer Function) characteristics of the collimated lens according to an embodiment of the present invention will be described with reference to FIGS. 6A to 6C.

FIG. 6A is a diagram illustrating MTF characteristics of a collimated lens according to actual implementation data of FIG. 3A, and FIG. 6B is a diagram illustrating MTF characteristics of a collimated lens according to actual implementation data of FIG. 3B, and FIG. 6C is a diagram of FIG. MTF characteristics of the collimated lens according to the actual implementation data of 3c.

Here, in the MTF charts of FIGS. 6A to 6C, the x-axis represents a spatial frequency and the y-axis represents contrast. The unit of spatial frequency is lp / mm (line pair / mm), which means the number of line pairs (consisting of pairs of white and black lines) included per 1 mm of the optical modulator or screen. For example, the spatial frequency is 5 lp / mm when there are five pairs of lines (one white line and one black line) within 200 mm intervals within 1 mm of the screen. Contrast in these MTF charts decreases with increasing spatial frequency, which clearly identifies lines within 1 mm on the screen through the human eye as the number of included line pairs per 1 mm on the light modulator or screen increases. It's harder to do it. That is, the MTF chart indicates the degree to which a person can clearly recognize (divided) through the eye the image projected on the screen through the projection lens of the present invention. However, the MTF charts of FIGS. 6A-6C show MTF characteristics on an optical modulator rather than on the screen.

Therefore, referring to the MTF charts of FIGS. 6A to 6C, respectively, a space of modulated light on an optical modulator is assumed to be about 0.3 (the maximum contrast is 1). It can be seen that the frequency is about 1005 lp / mm in FIG. 6A, about 544 lp / mm in FIG. 6B, and 373 lp / mm in FIG. 6C. Therefore, assuming that the magnification of the collimated lens of the present invention is 20 times, the spatial frequency of the projected image on the screen having a contrast of about 0.3 is about 50 lp / mm (= 1005 lp / mm in the case of FIG. 6A). ㅧ (1/20)), about 27 lp / mm (= 544 lp / mm ㅧ (1/20)) for FIG. 6B, about 13 lp / mm (= 373 lp / mm ㅧ (1/20) for FIG. 6C 20)), becomes In other words, this means that the degree to which humans can clearly distinguish from the image of the collimated lens according to the present invention is 50, 27, and 13 line pairs per 1 mm, respectively, and thus, the optical of the collimated lens of the present invention. It can be seen that the performance is quite good.

Hereinafter, spherical aberration according to a collimated lens according to an embodiment of the present invention will be described with reference to FIGS. 7A to 7C. 7A to 7C are graphs of spherical aberration according to an embodiment of the present invention. Each graph shows the spherical aberration of the collimated lens according to the implementation data according to FIGS. 3A-3C.

Spherical aberration is an aberration that occurs because a shop made from a point on the optical axis depends on which part of the lens the beam passes through. The y-axis of the graph, i.e., the value of the x-coordinate, is 0 when the image is formed at the ideal focus by the collimated lens. Therefore, the further away from the y-axis, the greater the spherical aberration.

The maximum scale of FIG. 7A is 0.01 mm, but the aberration is much smaller than that, and the maximum scale is 0.002 mm in FIG. 7B and the maximum scale is 0.005 mm in FIG. 7C, so that all spherical aberration values exist within the maximum scale range. It can be seen that the spherical aberration value is small. That is, according to the collimated lens according to the embodiment of the present invention, the spherical aberration value is small.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below It will be appreciated that modifications and variations can be made.

1 is a block diagram of a laser module including a collimating lens according to an embodiment of the present invention.

Figure 2 is an exemplary view showing an embodiment using a collimated lens according to an embodiment of the present invention.

3A, 3B and 3C are tables of actual implementation data of a collimated lens in accordance with one embodiment of the present invention.

4 is an exemplary view showing a propagation path of light incident by a collimating lens according to an embodiment of the present invention.

5A to 5C are graphs showing light travel by the collimated lens 420 according to an embodiment of the present invention.

6A to 6C are graphs illustrating Modulation Transfer Function (MTF) characteristics of a collimated lens according to an embodiment of the present invention.

7A to 7C are graphs of horizontal axis aberration among spherical aberrations according to an embodiment of the present invention.

Claims (9)

A collimated lens having a light exit surface of an aspherical surface having a first basic curvature r1 and a light incident surface of an aspherical surface having a second basic curvature r2 provided at both sides and having a predetermined thickness; And And a laser window spaced apart from the light incident surface of the lens by a working distance (WD). The method of claim 1, And the first basic curvature r1 of the collimated lens has the same absolute value as that of the second basic curvature r2 and has the opposite sign. The method of claim 1, The relationship between the working distance WD and the focal length f of the collimated lens is A laser module characterized by satisfying a relationship of WD> (f / 1.2-1). The method of claim 1, The refractive index (Nd) of the collimated lens Laser module characterized by satisfying the relationship of 1.4 <Nd <2. The method of claim 1, Abbe number (Vd) of the collimated lens is A laser module characterized by satisfying a relationship of 20 <Vd <90. The method of claim 1, The relationship between the center thickness CT and the edge thickness ET of the collimated lens is A laser module that satisfies the relationship of ET / CT> 0.4. The method of claim 1, The range of the wavelength λ incident on the collimated lens is A laser module, which satisfies the range of 350 nm ≦ λ ≦ 1600 nm. The method of claim 1, The numerical aperture (NA) of the collimated lens is A laser module satisfying the range of 0 <NA <0.6. The method of claim 1, The relationship between the focal length (f) outer diameter (OD) of the collimated lens A laser module characterized by satisfying a relationship of f / OD <0.6.

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