JP2010054676A - Lens assembling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens assembling method for assembling a hemispherical lens including a first optical surface having a hemispherical projecting surface and a second optical surface having a radius of curvature larger than that of the first optical surface on a substrate by adjusting assembly so that light incident on the hemispherical lens may not be intercepted by adhesive. <P>SOLUTION: The hemispherical lens is incorporated in a lens barrel, and the adhesive is applied and hardened between the second optical surface and an inner surface of the lens barrel, and then the lens barrel is stuck to the substrate in air. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lens assembling method for assembling a lens used in an optical apparatus such as an optical disk.

  In the technical field of optical devices such as optical discs, lenses having unprecedented shapes have been developed with the progress of optical design technology and lens manufacturing technology. In particular, as the application of semiconductor lasers advances, the use of lenses with high NA is increasing. The high NA lens shape often has a hemispherical optical surface. Furthermore, with the increasing precision of optical devices, the size of lenses is becoming smaller, and there is an increasing number of cases where positioning adjustment is required when the lenses are incorporated into optical devices. In order to position and adjust such a small hemispherical lens and incorporate it into an optical device, the development of an advanced assembling technique has been a problem because it is small and hemispherical.

  In order to achieve the task of developing an advanced assembling technique, a method for assembling a lens in a V-groove positioning groove has been proposed (see Patent Document 1).

Regarding the position adjustment between the lens and the light source, the light source and the lens with respect to the V-groove shape are respectively positioned with high accuracy to ensure relative positional accuracy. Since the V-groove shape that can be produced by photolithography has high shape accuracy, difficult lens positioning can be performed with high accuracy.
JP 2004-354673 A

  The accuracy required for positioning of the hemispherical lens is increasing due to the higher accuracy of the optical device. If the light source cannot be positioned as designed as in the method disclosed in Patent Document 1, the light source The optical axis of the light beam emitted from the lens cannot be positioned with high accuracy on the optical axis of the lens. Therefore, there is a case where so-called aerial adhesion is adopted in which the hemispherical lens is positioned and adjusted in a state where it is floated with respect to the V-groove.

  When air bonding is performed, a space is generated between the V-groove and the hemispherical lens, and thus a large amount of adhesive is applied to fill the space. Then, since the adhesion surface of the V-groove and the hemispherical lens is a surface that is almost parallel, the adhesive extends in the optical axis direction of the hemispherical lens due to surface tension and blocks light passing through the hemispherical lens. Become.

  In view of the above problems, an object of the present invention is to provide a lens assembling method in which assembling is adjusted and adhered so that light incident on a hemispherical lens is not blocked by an adhesive.

  The above object is achieved by the invention described below.

1. A lens assembling method for assembling a lens having a convex first optical surface and a second optical surface having a radius of curvature larger than the radius of curvature of the first optical surface to a substrate,
Incorporating the lens into a lens barrel;
Applying a first adhesive between the second optical surface and the inner surface of the barrel;
Curing the first adhesive;
Applying a second adhesive to at least one of the adhesion surface of the substrate or the adhesion surface of the outer surface of the lens barrel in which the lens is incorporated;
The bonding surface of the substrate and the bonding surface of the outer surface of the lens barrel face each other without contacting each other, and the bonding surface of the substrate and the bonding surface of the outer surface of the lens tube are the first 2 a step of positioning and adjusting the lens barrel in which the lens is incorporated with respect to the substrate in a state of being connected via an adhesive;
Curing the second adhesive;
A lens assembling method.

  2. 2. The lens assembling method according to claim 1, wherein the first optical surface is hemispherical.

  ADVANTAGE OF THE INVENTION According to this invention, the method of attaching and adjusting can be provided so that the light which injects into a lens may not be interrupted | blocked by an adhesive agent.

  The lens assembling method and the embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiment.

  FIG. 1 shows variations in cross-sectional shape in a cross section parallel to the optical axis of the hemispherical lens L1. The hemispherical lens L1 to be assembled includes a first optical surface 3 having a hemispherical convex surface, and a second optical surface 4 having a convex surface, a flat surface, or a concave surface having a radius of curvature larger than that of the first optical surface. .

  1A to 1D, the first optical surface 3 is a convex hemisphere in common. FIG. 1A shows a case where the second optical surface 4 of the hemispherical lens L1 is a convex surface. The radius of curvature of the second optical surface 4 is larger than the radius of curvature of the first optical surface 3.

  FIG. 1B shows a case where the second optical surface 4 of the hemispherical lens L1 is a flat surface. The radius of curvature of the second optical surface is infinite, and the radius of curvature of the second optical surface 4 is larger than the radius of curvature of the first optical surface 3.

  FIG. 1C shows a case where the second optical surface 4 of the hemispherical lens L1 is a concave surface. The radius of curvature of the second optical surface 4 is larger than the radius of curvature of the first optical surface 3.

  FIG. 1D shows a case where the second optical surface 4 of the hemispherical lens L1 is a combination of a concave surface and a flat surface. In this case, as will be described later, the adhesive for bonding the semiconductor laser to the lens barrel is applied to the outer diameter portion of the first optical surface 3 and the second optical surface 4, so that the adhesive application surface is As in FIG. 1B, the adhesive is applied to the flat portion.

  The first optical surface 3 of the hemispherical lens L1 may have a radius of curvature larger than the radius of curvature in the case of a hemispherical shape, but the following is assumed to be hemispherical for convenience of explanation.

  FIG. 2 shows an optical module M to which the hemispherical lens L1 is assembled. The optical module M is provided with a light source LD that is a semiconductor laser, and an emitted light beam 21 from the light source LD generates a wavefront desired by the user. A wavefront is generated by the hemispherical lens L1 having a function. For example, a function of collimating light or condensing light to the diffraction limit is added.

  The hemispherical lens L1 is assembled to a cylindrical lens barrel 22, and is bonded and fixed on the substrate. The light source LD is bonded and fixed on the substrate via the stem 23 having high thermal conductivity. The adhesive between the light source LD and the stem 23 is made of a material having high thermal conductivity, and the heat generated by the light source LD is diffused to the substrate through the stem 23 to prevent the heat of the light source LD from rising. Assembly of the light source LD to the stem 23 is performed using a chip bonder (not shown). The light source LD is wired using a wire bonder (not shown) and emits light when supplied with power from a power source (not shown). The optical axis 24 of the emitted light beam 21 from the light source LD is set to be parallel to the substrate 26.

  In the optical axis adjustment in which the optical axis 24 of the light beam 21 emitted from the light source LD coincides with the optical axis 25 of the hemispherical lens L1, first, the height from the substrate bonding surface 27 of the light source LD is adjusted to a predetermined height. Next, the optical axis is adjusted by aligning the optical axis 25 of the hemispherical lens L1 with the optical axis 24 of the light source LD.

  The distance from the substrate 26 to the optical axis 24 of the emitted light beam 21 from the light source LD is set as designed by making the shape of the stem 23 into a desired size.

  Next, the optical axis adjustment of the optical axis 24 of the light beam emitted from the light source LD and the optical axis 25 of the hemispherical lens L1 is performed by the method described later.

  The lens barrel 22 to which the hemispherical lens L1 is assembled performs what is called air bonding in which the lens barrel 22 is fixed with an adhesive without contacting the substrate 26. An adhesive is filled and cured between a substrate bonding surface 27 that is a surface for applying an adhesive to the substrate 26 and a lens barrel bonding surface 28 that is a surface for applying an adhesive to the lens barrel 22.

  Next, an assembling apparatus 500 for assembling the lens barrel 22 incorporating the hemispherical lens L1 to the substrate 26 will be described with reference to FIG.

  The assembling apparatus 500 includes a CCD 31 that receives light emitted from the hemispherical lens L1, an actuator 32 that adjusts the position of the lens barrel 22, an image processing unit 33 that performs image processing on signals from the CCD 31, and a drive unit that drives the actuator 32. 35. Various arithmetic operations are performed on the signal from the image processing unit 33, the arithmetic processing unit 34 that transmits a driving signal to the driving unit 35, the calculation result of the arithmetic processing unit 34, the driving status of the actuator 32, and the like. It comprises a display unit 36 for displaying, an ultraviolet exposure device 37, and the like.

  As the type of the actuator 32, one having both fine adjustment and adjustment is suitable. First, the lens is moved quickly to a predetermined position, and then finely adjusted to position the lens with high accuracy. The actuator 32 is driven by power such as a servo motor (not shown), a pulse motor (not shown), or a piezo element. The actuator 32 is preferably one that can be driven three-dimensionally. The actuator 32 is provided with a holding portion 321 that holds the lens barrel 22. Since the hemispherical lens L1 is small and the lens barrel 22 is also small, for example, a vacuum suction method is suitable for the method of holding the lens barrel 22. That is, a minute hole that performs vacuum suction is formed at the tip of the holding part 321, air is sucked from the minute hole of the holding part 321 using a vacuum pump (not shown), and the minute hole is brought into contact with the lens barrel 22 to be in the lens barrel. 22 is held by suction.

  For example, when the actuator 32 is composed of a pulse motor, the drive unit 35 includes a circuit that generates an electric pulse that is a drive signal transmitted to the pulse motor. In the case of a servo motor, it has a servo circuit that applies servo so that it can be positioned at a predetermined target position. When the actuator 32 is a piezo element, it includes a booster for obtaining a voltage to be applied to the piezo element.

  The CCD 31 converts the image obtained on the image receiving surface into a video signal and sends it to the image processing unit 33. Based on the video signal, the image processing unit 33 gives “1” to pixels whose light intensity is equal to or higher than a predetermined threshold value, and gives “0” to pixels whose light intensity is lower than the predetermined threshold value. The intensity is binarized, and a signal having light intensity information given by the binary values “1” and “0” of each pixel is generated and given to the arithmetic processing unit 34.

  The arithmetic processing unit 34 has a function of comprehensively controlling each part of the assembling apparatus 500, and executes a calculation for calculating the center of gravity of the light intensity of the obtained image, an arithmetic program, a control program, data, and the like. ROM, a RAM used by the CPU as a work area, and the like.

  The calculation for calculating the center of gravity can be performed by a well-known method, for example, a weighting calculation of light intensity is performed on the pixel coordinates on the image receiving surface of the CCD 31. The display unit 36 represents the image of the image formed on the image receiving surface of the CCD 31 and the position of the center of gravity obtained by calculation.

  The display unit 36 includes, for example, a CRT (Cathode Ray Tube), an LCD (Liquid Crystal Display), and the like, and the image captured by the CCD 31 and the barycentric position of the image according to the instruction of the display signal sent from the arithmetic processing unit 34 Etc. are displayed.

  When obtaining the center of gravity, a PSD (Position Sensing Detector) may be used instead of the CCD 31. In that case, instead of the image processing unit 33, a signal processing unit that processes the output signal of the PSD is used.

  The ultraviolet exposure device 37 is a device that irradiates the ultraviolet adhesive with ultraviolet rays by using an ultrahigh pressure mercury lamp or an ultraviolet LED (Light Emitting Diode) as a light source. The ultraviolet exposure device 37 includes an irradiation probe 38 for guiding emitted light from a built-in ultra-high pressure mercury lamp or ultraviolet LED to an exposure target. The irradiation probe 38 is made of a quartz optical fiber having a high ultraviolet transmittance. The ultraviolet exposure device 37 includes an actuator (not shown), and when the adhesive is exposed to ultraviolet rays, the tip of the irradiation probe 38 is moved to the vicinity of the adhesive. After irradiation with ultraviolet rays, the irradiation probe 38 is configured to return to a predetermined position.

  Next, a flow of a method for incorporating the hemispherical lens L1 into the optical module M will be described with reference to FIG. First, in step S10, the hemispherical lens L1 is assembled into the cylindrical barrel 22 as shown in FIG. FIG. 5 (a) shows the type of hemispherical lens L1 shown in FIG. 1 (b), that is, the case where the first optical surface 3 is hemispherical and the second optical surface 4 is a flat lens. The hemispherical lens L1 may be assembled manually by an operator or may be mechanized and automated. When installing, be careful not to damage the optical surface of the light effective area centered on the optical axis. FIG. 5B shows a perspective view when the hemispherical lens L1 is incorporated in the lens barrel 22. As shown in FIG.

  As shown in FIG. 1, the hemispherical lens L1 is preferably provided with a cylindrical surface 6 on the outer shape. By providing the cylindrical surface 6, it can be incorporated along the cylindrical inner surface of the lens barrel 22 and can be held in the lens barrel 22 without play. The inner diameter of the lens barrel 22 is made slightly larger than the outer diameter of the cylindrical portion of the hemispherical lens L1.

  Next, in step S11, an adhesive is applied between the lens and the lens barrel 22 as shown in FIG. The adhesive is applied between the second optical surface 4 and the lens barrel 22. The first optical surface 3 and the second optical surface 4 differ in how the applied adhesive is stretched on the optical surface as shown in FIG. Since the first optical surface 3 is hemispherical, the first optical surface 3 and the lens barrel gradually become closer to the optical axis of the hemispherical lens L <b> 1 at the portion in contact with the inner surface of the lens barrel 22. The distance from the inner surface of 22 increases.

  Therefore, when the adhesive 51 is applied between the first optical surface 3 and the inner surface of the lens barrel 22, the surface of the first optical surface 3 extends in the optical axis direction due to surface tension. On the other hand, since the radius of curvature of the second optical surface 4 is larger than that of the first optical surface 3, the distance between the second optical surface 4 and the inner surface of the lens barrel 22 increases as it approaches the optical axis 25. Therefore, even if the adhesive 52 is applied between the second optical surface 4 and the inner surface of the lens barrel 22, the length of the adhesive extending on the second optical surface 4 by the surface tension is short. As described above, when the adhesive is applied to the first optical surface 3, the emitted light beam 21 from the light source LD is easily blocked, and the effective use range of light is reduced. Therefore, the adhesive is applied only to the second optical surface 4. .

  FIG. 5C shows a method for applying an adhesive between the second optical surface 4 and the inner surface of the lens barrel 22. As the adhesive, an ultraviolet curable adhesive is used, and the adhesive is applied using a syringe 40. The syringe 40 includes an adhesive tank 41 and an injection needle 42. The adhesive tank 41 is composed of a cylinder and a piston, and the piston is driven to increase the cylinder internal pressure by compressed air from a compressed air supply device (not shown), and the adhesive is discharged from the tip of the injection needle. As described above, the adhesive is build-up bonded between the second optical surface 4 and the inner surface of the lens barrel 22 as shown in FIG. Application is performed while the tip of the injection needle 42 is moved circumferentially along the inner surface of the barrel 22 and the second optical surface 4. FIG. 5D shows a cross section of the hemispherical lens L1 after the application is finished. Since the angle formed by the inner surface of the lens barrel 22 and the second optical surface 4 is large as described above, the adhesive does not extend along the second optical surface 4 due to surface tension.

  Next, in step S12, the adhesive is cured. The arithmetic processing unit 34 uses the actuator 32 (not shown) to bring the tip of the irradiation probe 38 closer to the hemispherical lens L1. Thereafter, the ultraviolet exposure device 37 is irradiated with ultraviolet rays. Specifically, when the ultraviolet exposure device 37 has a built-in ultrahigh pressure mercury lamp, a shutter provided between the irradiation probe 38 and the ultrahigh pressure mercury lamp is opened using a motor. The UV curable adhesive will be incompletely cured if the amount of irradiated UV light is small, and if the amount of UV light is large, a heat shock will be applied to the hemispherical lens L1 and its surroundings. And then irradiate. The amount of ultraviolet light is controlled by the time when the shutter is opened. In addition, after the ultraviolet irradiation is completed, the tip of the irradiation probe 38 is returned to the original position.

  Next, in step S13, the position of the center of gravity of the emitted light beam 21 from the light source LD (also referred to as the optical axis position) is obtained before mounting the lens in the assembling apparatus. In FIG. 3, the emitted light beam 21 from the light source LD is directly incident on the CCD 31 without the lens barrel 22 incorporating the hemispherical lens L <b> 1 being incorporated in the optical module M. The optical axis position of the light source LD is obtained as the coordinate value of the image receiving surface of the CCD 31. Specifically, as described above, the signal from the CCD 31 is received by the image processing unit 33 and the image I is displayed on the display unit 36, and at the same time, the arithmetic processing unit 34 obtains the center of gravity and coordinates 61 on the display unit 36. , And the center of gravity is projected as a cross-shaped mark C as shown in FIG. The coordinates 61 are stored in a storage unit such as a RAM (not shown) provided in the arithmetic processing unit 34, and can be continuously displayed on the display unit 36 as they are.

  Next, in step S14, in order to adjust and bond the lens barrel 22 incorporating the lens and the substrate 26 of the optical module M, an adhesive is applied to at least one of the bonding surfaces of the lens barrel 22 and the substrate 26. . It may be applied to both or may be applied to one.

  Next, in step S15, in order to position the lens barrel 22 with respect to the substrate 26, as shown in FIG. 3, the light beam emitted from the light source LD is held while the lens barrel 22 incorporating the lens is held by the holding portion 321. 21 is allowed to pass through the hemispherical lens L <b> 1, and the passed light is incident on the CCD 31. At this time, as shown in the figure, the applied adhesive before curing is passed between the lens barrel 22 and the substrate 26, and the amount of the adhesive is determined so that the lens barrel 22 and the substrate 26 are connected. It is preferable. This is for fixing the lens barrel 22 and the substrate 26 by irradiating ultraviolet rays after positioning to cure the adhesive.

  Next, in step S16, the optical axis is adjusted so that the position of the center of gravity of the light passing through the hemispherical lens L1 on the image receiving surface of the CCD 31 overlaps the position of the center of gravity of the emitted light beam 21 from the light source LD previously obtained. . The position of the center of gravity of the light passing through the hemispherical lens L1 can be obtained by the above method. The allowable value of the difference between the gravity center position of the emitted light beam 21 from the light source LD and the gravity center position of the light that has passed through the hemispherical lens L1 varies depending on the optical module M to be used, so that the allowable value is determined according to each optical module M. . The optical axis adjustment is performed using the actuator 32. Specifically, the calculation processing unit 34 compares the barycentric position of the light that has passed through the hemispherical lens L1 shown in the display unit 36 with the barycentric position of the emitted light beam 21 from the light source LD previously obtained. The distance between the centers of gravity is calculated, and an instruction for the amount of movement is sent to the drive unit 35 that drives the actuator 32 so as to be within an allowable value.

  Next, in step S17, the adhesive is cured by the same method as described above.

  Incidentally, the distance of the actuator 32 moved to move the hemispherical lens L1 may be different from the distance actually moved by the hemispherical lens L1. For example, this is a case where the actuator 32 that moves the hemispherical lens L1 has backlash or lost motion. For this reason, the movement of the hemispherical lens L1 only once may not be within the allowable value. In that case, the same process is repeated to adjust the tilt. If the amount of such backlash or lost motion is known in advance, if the hemispherical lens L1 is moved in consideration of these amounts, the inclination is adjusted within the allowable value by one movement. It is desirable to measure the amount of backlash and lost motion.

  As described above, according to the present embodiment, it is possible to provide a method for assembling and adhering light so that light incident on the hemispherical lens is not blocked by the adhesive.

It is a schematic block diagram which shows the variation of the cross-sectional shape in a cross section parallel to the optical axis of the hemispherical lens L1 in this embodiment. It is the schematic which shows the optical module M used as the object which attaches the hemispherical lens L1 in this embodiment. It is a conceptual diagram which shows the assembly | attachment apparatus 500 which assembles | attaches the lens barrel 22 incorporating hemispherical lens L1 in this embodiment to the board | substrate 26. FIG. It is a flowchart of the lens assembly method in this embodiment. It is a conceptual diagram showing the method of apply | coating an adhesive agent between hemispherical lens L1 and lens barrel 22 in this embodiment. It is a conceptual diagram showing a mode that the adhesive agent apply | coated between hemispherical lens L1 and the lens-barrel 22 in this embodiment extends with surface tension. It is the schematic of the image on the image receiving surface of CCD31 in this embodiment.

Explanation of symbols

L1 hemispherical lens LD light source M optical module 3 first optical surface 4 second optical surface 6 cylindrical surface 21 outgoing light beam 23 stem 24, 25 optical axis 26 substrate 27 substrate bonding surface 28 lens barrel bonding surface 31 CCD
32 Actuator 33 Image processing unit 34 Arithmetic processing unit 35 Drive unit 36 Display unit 37 UV exposure device 38 Irradiation probe 40 Syringe 41 Adhesive tank 42 Injection needle 51 Adhesive 61 Coordinate 321 Holding unit 500 Assembly device

Claims (2)

A lens assembling method for assembling a lens having a convex first optical surface and a second optical surface having a radius of curvature larger than the radius of curvature of the first optical surface to a substrate,
Incorporating the lens into a lens barrel;
Applying a first adhesive between the second optical surface and the inner surface of the barrel;
Curing the first adhesive;
Applying a second adhesive to at least one of the adhesion surface of the substrate or the adhesion surface of the outer surface of the lens barrel in which the lens is incorporated;
The bonding surface of the substrate and the bonding surface of the outer surface of the lens barrel face each other without contacting each other, and the bonding surface of the substrate and the bonding surface of the outer surface of the lens tube are the first 2 a step of positioning and adjusting the lens barrel in which the lens is incorporated with respect to the substrate in a state of being connected via an adhesive;
Curing the second adhesive;
A lens assembling method. The lens assembly method according to claim 1, wherein the first optical surface is hemispherical.

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