JP2005331739A - Grin lens and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a GRIN lens and a manufacturing method therefor capable of manufacturing a polymer-made GRIN lens at a low cost, which is used as a lens for conversion etc. of beam state according to the connection between different optical systems in the field of optics. <P>SOLUTION: The GRIN lens 4 is provided with a cylindrical mold part 1, which is transparent with respect to at least ultraviolet rays and is cylindrical and a lens part 2 which is filled inside the cylindrical part 1 and has at least a part having a refractive index of decreasing as the part leaves from the optical axis in the vertical direction, with respect to the optical axis passing the open end part of one side and the open end part of the other side of the cylindrical mold part 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a GRIN lens and a manufacturing method thereof. For example, the present invention relates to a cylindrical GRIN lens whose refractive index decreases in a parabolic manner according to the distance from the optical axis, and a manufacturing method thereof.

  In the optical field, a lens is used to convert a beam state for coupling of different optical systems such as between waveguides or between a light source and a waveguide. This lens has a convex (concave) lens that uses refraction at the air interface between the entrance end and the exit end of the lens, and a flat column shape on at least one of the input and output end faces, and is a distance from the optical axis. A GRIN lens whose refractive index decreases (or rises) in a parabolic manner can be used, but it is easier to assemble a GRIN lens that can control the lens effect with the refractive index distribution shape and the optical axis adjustment with the lens shape. Can reduce costs.

  The conventional GRIN lens refracts according to the distance from the surface by diffusing the monomer to be copolymerized from the surface of the synthetic resin in the case of synthetic resin, and ion-exchange diffusion of the glass modified oxide from the surface of the glass in the case of glass. The rate has been increased (see, for example, Patent Document 1).

  Further, from the surface of the base material having self-supporting formation that is incompletely polymerized, a monomer that forms a polymer having a refractive index different from that of the base material is diffused and polymerized. Some control the refractive index distribution with high accuracy by controlling the polymerization rate (see, for example, Patent Document 2).

In addition, the laser beam is condensed from the periphery with a YAG laser at the center of the thermoplastic resin core wire manufactured by continuous extrusion method, and refracted from the center to the periphery according to the maximum power distribution at the center. Some manufacture a core wire (optical fiber) having a refractive index distribution with a decreasing rate (see, for example, Patent Document 3).
JP 57-53702 (FIG. 1) JP-A-60-73502 (FIG. 1) JP 63-33705 A (FIG. 1)

  However, in the production methods of Patent Document 1 and Patent Document 2, a monomer (monomer) that generates a polymer having a refractive index different from that of the base material is physically formed in the base material of the incomplete polymer (polymer). It moves from the surface to the inside (diffusion), and the diffused monomer is polymerized and mixed with the polymer that forms the base material to form a refractive index distribution. There was a problem of requiring a long time. In addition, since the polymer is simply a mixed pair of polymers having different refractive indexes, there is a drawback that secular change occurs due to a temperature change or the like. Furthermore, since it is common to use a fluororesin as the resin material, there is a problem that the material itself becomes expensive.

  On the other hand, since the manufacturing method of Patent Document 3 forms a refractive index distribution by providing a power distribution by laser irradiation in a thermoplastic resin, an expensive high power laser is necessary, and the same material is altered. Therefore, there is a problem that a large refractive index difference cannot be expected.

The present invention solves the above-mentioned conventional problems, and can be manufactured at a low cost by a simple process.
An object of the present invention is to provide a GRIN lens and a manufacturing method thereof.

In order to solve the above-described problem, the first aspect of the present invention provides:
A cylindrical mold part that is transparent to at least ultraviolet rays and has a cylindrical shape;
The refractive index decreases with increasing distance from the optical axis with respect to the optical axis filled in the cylindrical mold part and passing through one open end and the other open end of the cylindrical mold part. A GRIN lens having at least a portion and a lens portion.

The second aspect of the present invention
The lens part is a resin whose refractive index changes due to an oxidation reaction,
The refractive index distribution is the GRIN lens according to the first aspect of the present invention, which is controlled by an oxygen concentration distribution when the resin is irradiated with ultraviolet rays while being heated.

The third aspect of the present invention provides
The resin is a resin having a polysilane structure,
The GRIN lens according to the second aspect of the present invention, wherein the refractive index distribution is formed by a distribution of the polysilane structure and a siloxane structure formed by chemically changing the polysilane structure.

The fourth invention relates to
The refractive index distribution of the lens portion is approximately the same as the refractive index n (r) with respect to the distance r from the refractive index maximum portion (refractive index maximum value: n ₁ ) on a concentric circle centered on the optical axis. The GRIN lens according to any one of the first to third aspects of the present invention decreases along a quadratic function of (Equation 1).

第５の本発明は、
少なくとも紫外線に対して透明で、筒形状をした筒状型部の内部に、酸素雰囲気中で加熱されながら紫外線が照射されることにより化学変化を生じて屈折率が変化する樹脂を充填する第１の工程と、
前記樹脂を充填した前記筒状型部の周囲から、酸素雰囲気中で加熱しながら紫外線を実質上均質に照射する第２の工程とを備えた、ＧＲＩＮレンズの製造方法である。

The fifth aspect of the present invention relates to
First, a cylindrical mold part that is transparent to at least ultraviolet rays and filled with a resin whose refractive index changes due to a chemical change caused by irradiation with ultraviolet rays while being heated in an oxygen atmosphere. And the process of
And a second step of substantially uniformly irradiating ultraviolet rays while heating in an oxygen atmosphere from the periphery of the cylindrical mold portion filled with the resin.

The sixth invention relates to
The resin is a resin having a polysilane structure,
When the resin is cured in the second step, a part of the resin is changed from the polysilane structure to the siloxane structure.

The seventh invention relates to
In the second step, two open end surfaces of the cylindrical mold part are moved by moving an irradiation device that irradiates a part of the cylindrical mold part with respect to the cylindrical mold part. In the manufacturing method of the GRIN lens of the fifth aspect of the present invention, ultraviolet rays are irradiated substantially uniformly in the height direction connecting the two.

The eighth invention relates to
In the first step, after inserting one open end of the cylindrical mold part into the resin stored in the container, the capillary process is used, or the atmospheric pressure in the cylindrical mold part is reduced in the container. The GRIN lens manufacturing method according to the fifth aspect of the present invention is configured to guide the resin to the other open end of the cylindrical mold portion by lowering the pressure below the atmospheric pressure.

The ninth invention relates to
After curing the resin filled in the cylindrical mold part in the second step,
Further, the cylindrical mold is combined with the resin filled therein so that the length of the cylindrical mold portion after cutting is an integral multiple of π / 2 g (g is a refractive index distribution constant). It is a manufacturing method of the GRIN lens of 5th this invention provided with the 3rd process cut | disconnected in parallel with the open end surface of the said cylindrical mold part.

The tenth aspect of the present invention is
After the second step, the thickness of the cylindrical mold part is changed by changing the length in the height direction connecting the two open end faces of the cylindrical mold part in which the cured resin is inherent. Then, the third step is performed, and the manufacturing method of the GRIN lens of the ninth aspect of the present invention is performed.

  According to the present invention, it is possible to provide a GRIN lens and a manufacturing method thereof that can be manufactured at low cost by a simple process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of a polysilane-made GRIN lens according to Embodiment 1 of the present invention.

  The GRIN lens 4 with a cylindrical mold according to the first embodiment includes a cylindrical part 1 that is transparent to at least ultraviolet rays, and a GRIN lens part 2 that is filled inside the transparent cylindrical part 1. The GRIN lens portion 2 has a polysilane structure having a refractive index distribution 3 in a direction perpendicular to the optical axis, the refractive index of which decreases substantially parabolically according to the distance from the optical axis.

  Next, a method for manufacturing the polysilane cylindrical GRIN lens 4 according to the first embodiment will be described with reference to FIGS.

  FIG. 2 is a process schematic diagram of the manufacturing method of the cylindrical-type GRIN lens 4 made of polysilane according to the first embodiment.

  As shown in FIG. 2A, the manufacturing method of the GRIN lens 4 with a cylindrical mold is as follows. First, one end of a transparent cylindrical mold 5 having a sufficient length that is transparent to at least ultraviolet rays such as a glass tube or a resin tube is used. The resin is immersed in a resin (pre-curing polysilane) 6 having a polysilane structure stored in a container, and the pre-curing polysilane 6 is guided to the other end of the transparent cylindrical mold 5 by using a capillary phenomenon. 6 is filled. The transparent cylindrical mold 5 is an example of a cylindrical mold part of the present invention.

  Next, as shown in FIG. 2 (b), the length in the longitudinal direction from the periphery of the transparent cylindrical mold 5 filled with the pre-curing polysilane 6 using a ring-shaped ring-type ultraviolet irradiation device 8 while being heated. In contrast, ultraviolet rays are uniformly irradiated in a strip shape having a short width. At the same time, at least one of the transparent cylindrical mold 5 and the ring-type ultraviolet irradiation exposure 8 is moved in the longitudinal direction of the transparent cylindrical mold 5, that is, the transparent cylindrical mold 5 is relative to the ring-type ultraviolet irradiation exposure 8 relative to the moving direction 9. The ultraviolet rays are uniformly irradiated also in the longitudinal direction of the transparent cylindrical mold 5. Here, the ring-type ultraviolet irradiation device 8 is an ultraviolet irradiation device that can uniformly irradiate ultraviolet rays around a part of the width of the transparent cylindrical mold 5 in the longitudinal direction, and is an example of the irradiation device of the present invention.

  By irradiating ultraviolet rays while heating, the pre-curing polysilane 6 filled in the transparent cylindrical mold 5 becomes a polysilane 7 after curing by an oxidation reaction, and a refractive index distribution in which the refractive index decreases from the center toward the periphery is formed. The By performing this ultraviolet irradiation over the entire length of the transparent cylindrical mold 5 in the longitudinal direction, the GI waveguide 10 with a cylindrical mold is produced.

  Finally, as shown in FIG. 2 (c), this cylindrically attached GI-type waveguide 10 is cut perpendicularly to the optical axis so as to have a length required for the lens. The GRIN lens 4 is completed.

  2A, 2B, and 2C are examples of the first step, the second step, and the third step of the present invention, respectively.

  FIG. 3 shows changes due to the chemical reaction of the polysilane base material in the manufacturing process shown in FIG. 2B of the cylindrical GRIN lens 4 according to the first embodiment.

  FIG. 4 shows the mechanism by which the refractive index distribution is formed in the polysilane base material in the manufacturing process shown in FIG. 2B of the cylindrical GRIN lens 4 according to the first embodiment. In addition, the same code | symbol is used about the same component as FIG.

  In general, when the polysilane structure is irradiated with ultraviolet rays and cured while being heated in an oxygen atmosphere, the polysilane structure 15 undergoes an oxidation reaction by irradiation with ultraviolet rays as shown in FIG. To change. That is, the post-curing polysilane 7 shown in FIG. 2B has a polysilane structure and a siloxane structure.

  Therefore, as shown in FIG. 4, a resin (pre-curing polysilane) 6 having a polysilane structure in which an oxygen atom is diffused in advance by diffusing an oxide or the like is filled into a transparent cylindrical mold 5 to form a cylindrical shape. When the ultraviolet rays are uniformly irradiated from the circumferential direction, the oxidation reaction of the polysilane structure occurs more actively as the surroundings are irradiated by the ultraviolet rays from the surroundings. As a result, the oxygen consumption decreases from the surroundings toward the inside, so that the distribution of the siloxane structure having a relatively low refractive index becomes smaller toward the inside.

  FIG. 4 shows, in order from the top, the state of the transparent cylindrical mold 5 before irradiating the ultraviolet rays 12, the state during the irradiation with the ultraviolet rays 12, and the state after the irradiation with the ultraviolet rays 12. By irradiating ultraviolet rays 12 from the periphery of the transparent cylindrical mold 5, a polysilane structure multi-part 13 remains in the vicinity of the optical axis 11 with a large amount of polysilane structure. As the distance from the optical axis 11 increases, the polysilane structure has more siloxane structures by oxidation reaction. The siloxane structure multi-part 14 is obtained. Therefore, a refractive index distribution is formed in which the refractive index of the optical axis 11 portion is the largest and the refractive index decreases as the distance from the optical axis 11 increases. Further, since the oxidation reaction of the polysilane structure occurs more actively as the distance from the optical axis 11 increases, the oxygen consumption increases as the distance from the optical axis 11 increases.

  As shown in FIG. 1, the GRIN lens portion 2 of the cylindrical GRIN lens 4 thus manufactured has a parabolic refractive index distribution 3 in which the optical axis portion is maximal and the refractive index decreases as the distance from the optical axis increases. Is formed.

That is, the refractive index distribution of the GRIN lens portion 2 is such that the refractive index n (r) with respect to the distance r from the refractive index maximum portion (refractive index maximum value: n ₁ ) on a concentric circle centered on the optical axis is the refractive index. When the distribution constant is g, the distribution approximately decreases along the quadratic function of the following equation (1).

   In the first embodiment, the method of filling the pre-curing polysilane 6 into the transparent cylindrical mold 5 is a method using the capillary phenomenon, but it may be filled by other methods. For example, the pressure in the transparent cylindrical mold 5 is made lower than the pressure in the container in which the pre-curing polysilane 6 is stored, so that the pre-curing polysilane 6 is filled to the other end of the transparent cylindrical mold 5. May be.

  Further, by adjusting the intensity of the ultraviolet rays irradiated in the step shown in FIG. 2B of the first embodiment so as not to reach the specific range around the optical axis, the specific range is maximized with the same refractive index. Can be part. Since the pre-curing polysilane in the specific range around the optical axis does not change to the siloxane structure and remains in the polysilane structure, the specific range has a refractive index distribution with the same refractive index. In the portion around the specific range, as the distance from the optical axis increases, the polysilane structure changes to a siloxane structure by an oxidation reaction, so that a refractive index distribution is formed in which the refractive index decreases as the distance from the optical axis increases.

  FIG. 5 is a schematic diagram of the configuration of the cylindrical GRIN lens 24 produced when the intensity of ultraviolet rays is adjusted and irradiated as described above. In the GRIN lens 24 with a cylindrical mold manufactured in this way, a GRIN lens portion 22 having a refractive index distribution as shown in FIG. 5 is formed inside the transparent cylindrical portion 21. The refractive index distribution of the GRIN lens portion 22 is a constant refractive index portion 25 in a range where the ultraviolet rays around the optical axis have not reached, and the refractive index distribution around the refractive index distribution decreases as the distance from the optical axis increases. A parabolic refractive index distribution 23 is obtained. Here, since the constant refractive index portion 25 is a portion that remains in the polysilane structure without causing an oxidation reaction, it becomes the maximum refractive index portion of the GRIN lens portion 22.

(Embodiment 2)
FIG. 6 is a process schematic diagram of a method for manufacturing a polysilane GRIN lens according to Embodiment 2 of the present invention. A method for manufacturing the GRIN lens according to the second embodiment will be described with reference to FIGS. In FIG. 6, the same reference numerals are used for the same components as in FIG.

  The method of manufacturing the GRIN lens of the first embodiment is different from the method of irradiating ultraviolet rays, and the method of manufacturing the GRIN lens of the second embodiment differs from the step (b) in FIG. To do.

  In the first embodiment, as shown in FIG. 2B, ultraviolet rays are irradiated in a band shape using the ring-type ultraviolet irradiation device 8, but in the second embodiment, the partial ultraviolet irradiator 17 is used to emit ultraviolet rays. Is irradiated in a strip shape.

  Two partial ultraviolet irradiators 17 are arranged in two ultraviolet irradiation regions divided in the circumferential direction of the transparent cylindrical type. Then, at least one of the transparent cylindrical type and the two partial ultraviolet irradiators 17 is moved around the optical axis of the transparent cylindrical type, that is, the two partial ultraviolet irradiators 17 are relatively rotated with respect to the transparent cylindrical type. It moves so that it may rotate relatively in the direction, and uniformly irradiates ultraviolet rays around a part of the strip-like portion in the longitudinal direction of the transparent cylindrical mold.

  In this way, while uniformly irradiating ultraviolet rays to a part of the strip in the longitudinal direction of the transparent cylindrical mold, the transparent cylindrical mold is relatively moved in the relative movement direction 9 with respect to the two partial ultraviolet irradiators 17. By moving it, it is possible to uniformly irradiate ultraviolet rays in the longitudinal direction of the transparent cylindrical type.

  In the second embodiment, the peripheral ultraviolet irradiation region of the transparent cylindrical type is divided into two and two partial ultraviolet irradiation units 17 are provided. However, the transparent ultraviolet irradiation region of the transparent cylindrical type is provided. The division is not limited to two, and may be divided into at least one or more. The number of partial ultraviolet irradiators and the positions where they are arranged are not particularly limited, and are provided in accordance with the divided ultraviolet irradiation regions, and the ultraviolet rays are uniformly applied to the belt-like portion around a part of the longitudinal direction of the transparent cylindrical type. Any structure can be used as long as it can be irradiated.

(Embodiment 3)
FIG. 7 is a process schematic diagram of a method for manufacturing a polysilane GRIN lens and a GI waveguide according to Embodiment 3 of the present invention.

  The GRIN lens and the GI type waveguide according to the third embodiment of the present invention are manufactured by processing the GI type waveguide with a cylindrical shape 10 shown in FIG. 2B manufactured in the first embodiment.

  First, the cylindrically attached GI waveguide 30 is manufactured by the manufacturing method of the first embodiment. The GI-type waveguide 30 with a cylindrical shape is the GI-type waveguide 10 with a cylindrical shape manufactured in the process of FIG.

  Next, when a pulling force is applied in the optical axis direction while heating the GI waveguide 30 with a cylindrical shape produced by curing a resin having a polysilane structure, the diameter is smaller than that of the GI waveguide 30 with a cylindrical shape. A cylindrically attached GI-type waveguide 31 is obtained.

  Then, the cylindrical GRIN lens 32 can be manufactured by cutting the cylindrically attached GI waveguide 31 into an appropriate length. By adjusting the pulling force applied to the GI waveguide 30 with cylinder when the GI waveguide 31 with cylinder is manufactured, the GI waveguide 31 with any diameter can be obtained. Can be produced.

  Further, it is possible to use the GI type waveguide 31 with a cylindrical shape as it is like a GI type optical fiber without cutting it into an appropriate length.

  In addition, a tensile force is applied in the optical axis direction while heating the plurality of GI type waveguides 30 with a cylindrical shape, and at that time, the side walls of the plurality of GI type waveguides 30 with a cylindrical type are fused. It is also possible to produce a cylindrical waveguide 33 with a long length.

  In each embodiment, the transparent cylindrical shape may be removed after the polysilane is cured when a GRIN lens or a GI-type waveguide is manufactured.

  In each embodiment, the GRIN lens length is set to a length that is an integral multiple of π / 2g (g is a refractive index distribution constant) in which the condensed light and the parallel light can be freely combined at the input and output ends. Most effective.

  In addition, as described in each embodiment, it is desirable to use a transparent cylindrical type made of a material having a refractive index smaller than that of the polysilane structure, but the diameter of the transparent cylindrical type is sufficiently larger than the power distribution of the ultraviolet beam. If it is large, there is substantially no problem even if a transparent cylindrical type made of a material having a refractive index larger than that of the polysilane structure is used.

  As described above, by irradiating ultraviolet rays from the surface of a polymer base material having a polysilane structure held in a cylindrical shape with a transparent cylindrical shape in a heated state, the polymer base material is directed from the periphery toward the center. Since the siloxane structure changes to a relatively low refractive index according to the oxidation reaction of the polysilane structure that becomes smaller, the refractive index distribution in which the refractive index decreases on the parabola from the optical axis to the periphery on the cylindrical polymer matrix. It can be formed.

  By using the GRIN lens manufacturing method of the present invention, a conventional polymer GRIN lens that requires an expensive device can be easily obtained by using an inexpensive polysilane resin, a commercially available transparent cylindrical pipe, and an ultraviolet irradiator. Can be manufactured inexpensively by a simple process.

  The manufacturing method of the GRIN lens of the present invention is useful as a method for reducing the cost of the GRIN lens.

1 is a schematic configuration diagram of a polysilane GRIN lens according to a first embodiment of the present invention. (A)-(c) Process outline | summary figure of the manufacturing method of the GRIN lens made from polysilane of Embodiment 1 of this invention The figure which shows the chemical reaction in the base material made from polysilane of Embodiment 1 of this invention The figure explaining the mechanism in which the base material made from polysilane of Embodiment 1 of this invention forms refractive index distribution Configuration schematic diagram of a polysilane GRIN lens having another refractive index profile of Embodiment 1 of the present invention Schematic diagram of ultraviolet irradiation method for scanning in the rotation direction and the longitudinal direction with the partial irradiation ultraviolet according to Embodiment 2 of the present invention Process outline | summary which shows the manufacturing method of the GRIN lens and GI type | mold waveguide of Embodiment 3 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,21 Transparent cylindrical part 2,22 GRIN lens part 3,23 Parabolic refractive index distribution 4,24 GRIN lens with cylindrical type 5 Transparent cylindrical type 6 Pre-curing polysilane (resin having polysilane structure)
7 Polysilane after curing (resin having polysilane structure and siloxane structure)
DESCRIPTION OF SYMBOLS 8 Ring type ultraviolet irradiation device 9 Relative moving direction 10 GI type waveguide with cylindrical type 11 Optical axis 12 Ultraviolet ray 13 Polysilane structure multi-part 14 Siloxane structure multi-part 15 Polysilane structure 16 Siloxane structure 17 Partial UV irradiator 18 Relative rotation 25 Refractive index constant part 30, 31, 33 GI type guide path with cylindrical type 32 GRIN lens with cylindrical type

Claims (10)

A cylindrical mold part that is transparent to at least ultraviolet rays and has a cylindrical shape;
The refractive index decreases with increasing distance from the optical axis with respect to the optical axis filled in the cylindrical mold part and passing through one open end and the other open end of the cylindrical mold part. A GRIN lens having at least a portion and a lens portion. The lens part is a resin whose refractive index changes due to an oxidation reaction,
The GRIN lens according to claim 1, wherein the refractive index distribution is controlled by an oxygen concentration distribution when the resin is irradiated with ultraviolet rays while being heated. The resin is a resin having a polysilane structure,
The GRIN lens according to claim 2, wherein the refractive index distribution is formed by a distribution of the polysilane structure and a siloxane structure formed by chemically changing the polysilane structure. The refractive index distribution of the lens portion is approximately the same as the refractive index n (r) with respect to the distance r from the refractive index maximum portion (refractive index maximum value: n ₁ ) on a concentric circle centered on the optical axis. The GRIN lens according to claim 1, which decreases along a quadratic function of (Equation 1).

First, a cylindrical mold part that is transparent to at least ultraviolet rays and filled with a resin whose refractive index changes due to a chemical change caused by irradiation with ultraviolet rays while being heated in an oxygen atmosphere. And the process of
And a second step of substantially uniformly irradiating ultraviolet rays while heating in an oxygen atmosphere from the periphery of the cylindrical mold portion filled with the resin. The resin is a resin having a polysilane structure,
The method for manufacturing a GRIN lens according to claim 5, wherein when the resin is cured in the second step, a part of the resin changes from the polysilane structure to a siloxane structure.   In the second step, two open end surfaces of the cylindrical mold part are moved by moving an irradiation device that irradiates a part of the cylindrical mold part with respect to the cylindrical mold part. The manufacturing method of the GRIN lens of Claim 5 which irradiates an ultraviolet-ray substantially uniformly about the height direction which ties.   In the first step, after inserting one open end of the cylindrical mold part into the resin stored in the container, the capillary process is used, or the atmospheric pressure in the cylindrical mold part is reduced in the container. The manufacturing method of the GRIN lens of Claim 5 which guide | induces the said resin to the other open end part of the said cylindrical type | mold part by making it lower than this atmospheric pressure. After curing the resin filled in the cylindrical mold part in the second step,
Further, the cylindrical mold is combined with the resin filled therein so that the length of the cylindrical mold portion after cutting is an integral multiple of π / 2 g (g is a refractive index distribution constant). The manufacturing method of the GRIN lens of Claim 5 provided with the 3rd process cut | disconnected in parallel with the open end surface of the said cylindrical mold part. After the second step, the thickness of the cylindrical mold part is changed by changing the length in the height direction connecting the two open end faces of the cylindrical mold part in which the cured resin is inherent. The method of manufacturing a GRIN lens according to claim 9, wherein a third step is performed after the step.

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