JP2011150747A - Laser unit adjusting device, optical pickup device equipped with the same, and laser unit adjusting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser unit adjusting device which attains precise positional adjustment and miniaturization of a plurality of semiconductor lasers provided for a laser unit. <P>SOLUTION: The laser unit adjusting device is provided with: a collimator lens 32 which nearly collimates outgoing light outgoing from a two-wavelength semiconductor laser 1 and a blue semiconductor laser 2; a half mirror 33 having a mirror surface perpendicular to the optical axis of the collimator lens 32; a moving means which moves the two-wavelength semiconductor laser 1 and the blue semiconductor laser 2; and a control means for controlling the moving means. The control means moves the moving means and controls the moving means to move the semiconductor lasers to the position where the relative increase of the light output intensity of the semiconductor lasers with respect to the current injected to the semiconductor lasers or the relative decrease of the current injected to the semiconductors with respect to the light output intensity of the semiconductor lasers is detected. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an adjustment device and a laser unit adjustment method for adjusting a laser unit that includes a plurality of semiconductor lasers and is mounted on an optical pickup device. More specifically, the present invention relates to a technique for adjusting a light emitting point position of laser light emitted from each of a plurality of semiconductor lasers in a laser unit.

  2. Description of the Related Art Conventionally, optical pickup devices used for recording and reproduction of BD (Blu-ray Disc), DVD (Digital Versatile Disc), CD (Compact Disc) and the like have been widely developed. Among them, an optical pickup device that includes a plurality of semiconductor lasers and that records and reproduces three types of optical discs of BD, DVD, and CD is drawing attention.

  As an example, a conventional optical pickup device according to Patent Document 1 is shown in FIG. FIG. 6 is a cross-sectional view schematically showing the optical pickup device 130 of Patent Document 1. As shown in FIG. The optical pickup device 130 includes a first semiconductor laser 51 that emits laser light having a wavelength of 405 nm, and a second semiconductor laser 52 that emits laser light having a wavelength of 650 nm and 780 nm, and the dichroic beam splitter 53 emits laser light of each wavelength. Combine. The dichroic beam splitter 53 has a function of reflecting laser light having a wavelength near 405 nm and transmitting laser light having wavelengths near 650 nm and 780 nm, and includes a first semiconductor laser 51 and a second light source that are first light sources. The laser light emitted from the second semiconductor laser 52 is guided to substantially the same optical path.

  Next, the laser light is guided to the objective lens through the PBS (polarizing beam splitter) 54, the collimating lens 55, the quarter wavelength plate 57, and the prism. The PBS 54 transmits P-polarized laser light, and reflects S-polarized laser light in which the laser light and the polarization direction are orthogonal to each other. The quarter-wave plate 57 performs mutual exchange between linearly polarized light and circularly polarized light. The quarter-wave plate 57 rotates the polarization direction of the laser light between the forward and backward paths by 90 degrees, so that the PBS 54 separates the laser light in the forward and backward paths.

  The aberration correction mechanism that corrects the aberration of the laser light includes a collimating lens 55 that converts the laser light emitted from the semiconductor laser into parallel light and a lens driving mechanism 56. Further, spherical aberration due to the thickness error of the protective layer of the optical disk is corrected by driving the collimating lens 55 in the optical axis direction.

  The first reflecting surface 58 of the prism reflects laser light having a wavelength of about 405 nm and guides it to the first objective lens 60, and the second reflecting surface 59 reflects laser light having a wavelength of about 650 nm and a wavelength of about 780 nm to reflect the second objective lens. Lead to 61. The first objective lens 60 and the second objective lens 61 are mounted on an objective lens actuator 62, and are movable in the optical axis direction and a direction orthogonal thereto. The first objective lens 60 condenses the incident laser light on the BD disc 63, and the second objective lens 61 condenses the incident laser light on the DVD / CD disc 64.

  The return light from the BD disc 63 or the DVD / CD disc 64 passes through the first objective lens 60 or 61, the quarter wavelength plate 57 and the collimator lens 55, is reflected by the PBS 54, and receives the hologram element 65, the detection lens 66, and the light reception. The light is guided to a signal detection optical system including the element 67, and an RF signal and various servo signals are detected by the light receiving element 67. The signal detection optical system is shared by three wavelengths.

  In such an optical pickup device, although a plurality of light sources are provided, the signal detection optical system is integrated into one system, and the number of parts is small. Therefore, the structure is advantageous for downsizing and cost reduction of the device. It has become. When manufacturing such an optical pickup device, generally, a method is adopted in which the components are positioned and fixed in the order of the first light source, the signal detection optical system, and the second light source.

JP 2008-146684 A (published on June 26, 2008)

  However, the conventional optical pickup device 130 has a problem that it is difficult to precisely fix the position of the second light source.

  This will be specifically described below. In the production of a multi-wavelength optical pickup device equipped with at least two semiconductor lasers for recording / reproducing BD / DVD / CD, the positions of the first semiconductor laser, the photodetector, and the second semiconductor laser are adjusted in this order. When fixing, triaxial adjustment may be required to adjust and fix each optical element.

  Referring to FIG. 6, first, the first semiconductor laser 51 is adjusted and fixed in a plane orthogonal to the optical axis in accordance with the optical axis of the collimating lens 55, and then the light receiving element 67 and the detection lens 66 are adjusted and fixed. To do. At this time, the light receiving element 67 is adjusted in a plane orthogonal to the optical axis, the position of the detection lens 66 is adjusted in the optical axis direction, and the adjustment is fixed while confirming the RF signal, the focus error signal, the tracking error signal, and the like.

  Finally, the second semiconductor laser 52 is adjusted and fixed. At this time, it is necessary to adjust and fix the light emitting point of the second semiconductor laser 52 at a position conjugate with the light receiving element 67. Adjustment of the two semiconductor lasers 52 in three directions is required. In order to enable adjustment in three directions, the second semiconductor laser 52 is spatially adjusted and then fixed after covering the periphery with an adhesive.

  When adjusting only one direction with respect to the adjustment of the semiconductor laser, for example, when adjusting only the Y-axis direction, the adjustment in the Y-axis direction can be performed with the semiconductor laser fixed in the Z-axis direction. However, when performing adjustment in three directions, it is necessary to adjust the space of the semiconductor laser in a state where none of the three directions is fixed. After adjusting the space of the semiconductor laser, the semiconductor laser is fixed with an adhesive. However, since none of the three directions is fixed, the position of the semiconductor laser tends to shift when the adhesive expands or contracts or expands. When a large shift occurs in the fixed position due to such factors, specifically, when the fixed position shifts by 10 μm, there is a problem that the control of the tracking control becomes impossible or the tracking error signal leaks into the focus error signal. Problems such as enlargement may occur.

  The present application has been made in view of the circumstances described above, and an object of the present application is to provide a laser unit adjustment device that realizes precise position adjustment and miniaturization of a plurality of semiconductor lasers included in the laser unit, and an optical pickup including the same. An apparatus and a laser unit adjusting method are provided.

  In order to solve the above problems, a laser unit adjusting apparatus according to the present invention is a laser that adjusts the relative positions of a plurality of semiconductor lasers included in a laser unit that combines and emits light emitted from a plurality of semiconductor lasers. A unit adjusting device, a collimating lens for making the emitted light emitted from the semiconductor laser substantially parallel, a plane mirror having a mirror surface perpendicular to the optical axis of the collimating lens, and a movement for moving the semiconductor laser And a control means for controlling the moving means, and the control means moves the moving means to increase the light output intensity of the semiconductor laser relative to the injection current of the semiconductor laser, or the semiconductor laser. The relative decrease in the injection current of the semiconductor laser with respect to the light output intensity is determined, and the relative increase or decrease is detected. To move said semiconductor laser, and wherein said control means controls the moving means.

  When the outgoing light emitted from the semiconductor laser and collimated by the collimator lens and the return light reflected by the collimating lens and the plane mirror and returning to the semiconductor laser are substantially parallel, Since the light emission point and the focal point of the return light coincide with each other, the self-coupling effect causes a relative increase in the light output intensity of the semiconductor laser with respect to the semiconductor laser injection current, or the semiconductor laser injection current with respect to the light output intensity of the semiconductor laser. A relative decrease occurs.

  According to the present invention, the moving means is controlled by the control means, and the position where the relative increase or decrease is detected based on the self-coupling effect, that is, the position where the emitted light and the return light are substantially parallel. Since the semiconductor laser is moved to a precise position, precise position adjustment is possible. Furthermore, the present invention is used for adjusting a laser unit including a plurality of semiconductor lasers. Since the laser unit combines and emits light emitted from a plurality of semiconductor lasers, it is possible to reduce the size of the laser unit.

  The laser unit adjusting apparatus of the present invention further includes a wavefront sensor that detects wavefront information of the emitted light emitted from the semiconductor laser and transmitted through the collimating lens, and the control means emits the emitted light detected by the wavefront sensor. Based on the wavefront information, the moving means is preferably controlled so that the position of the semiconductor laser is changed to a position where the incident light on the wavefront sensor becomes parallel light with respect to the collimating lens.

  According to the wavefront sensor, it is possible to detect how much the incident wavefront to the wavefront sensor is deviated from the parallel light wave. For this reason, before the semiconductor laser position is adjusted, coarse adjustment can be performed using the wavefront sensor, and the semiconductor laser position can be quickly adjusted.

  In the laser unit adjusting apparatus of the present invention, the control means fixes one of the injection current and the optical output intensity of the semiconductor laser to a constant value, and relates to the other of the injection current and the optical output intensity of the semiconductor laser. The moving means is controlled to move the semiconductor laser to the position where the maximum value is determined, and the maximum value regarding the semiconductor laser injection current is a relative decrease of the semiconductor laser injection current with respect to the light output intensity of the semiconductor laser. The maximum value and the maximum value related to the optical output intensity of the semiconductor laser is preferably the maximum value of the relative increase in the optical output intensity of the semiconductor laser with respect to the injection current of the semiconductor laser.

  By fixing one of the injection current and optical output intensity of the semiconductor laser to a constant value by the control means, it is easy to determine an increase / decrease value for the other of the injection current and optical output intensity of the semiconductor laser. Further, when the maximum value of the relative increase / decrease or decrease is determined, the emission point of the emitted light from the semiconductor laser and the convergence point of the return light substantially coincide. Therefore, since the semiconductor laser can be moved to a position where the emission point of the emitted light and the convergence point of the return light substantially coincide with each other, it is possible to adjust the position very precisely.

  In order to solve the above problems, the laser unit adjustment method of the present invention is a laser that adjusts the relative positions of a plurality of semiconductor lasers included in a laser unit that multiplexes and emits light emitted from a plurality of semiconductor lasers. A unit adjustment method comprising: a collimating lens for collimating outgoing light emitted from the semiconductor laser; a plane mirror having a mirror surface perpendicular to the optical axis of the collimating lens; and a movement for moving the semiconductor laser A laser unit adjustment apparatus comprising: a laser unit adjustment apparatus comprising: means for adjusting a position of the plurality of semiconductor lasers so that a focal position of the collimating lens and a light emitting point of the plurality of semiconductor lasers coincide with each other Including an adjustment step, and in the adjustment step, the moving means is moved to inject a semiconductor laser injection current. The relative increase of the light output intensity of the semiconductor laser against, or relative decrease of the injection current of the semiconductor laser is characterized by moving the semiconductor laser to the sensed position relative to the light output intensity of the semiconductor laser.

  When the outgoing light emitted from the semiconductor laser and collimated by the collimator lens and the return light reflected by the collimating lens and the plane mirror and returning to the semiconductor laser are substantially parallel, Since the light emission point and the focal point of the return light coincide with each other, the self-coupling effect causes a relative increase in the light output intensity of the semiconductor laser with respect to the semiconductor laser injection current, or the semiconductor laser injection current with respect to the light output intensity of the semiconductor laser. A relative decrease occurs.

  According to the present invention, based on the self-coupling effect, the semiconductor laser is moved to the position where the relative increase or decrease is detected, that is, the position where the emitted light and the return light are substantially parallel. Position adjustment is possible. Furthermore, the present invention is used for adjusting a laser unit including a plurality of semiconductor lasers. Since the laser unit combines and emits light emitted from a plurality of semiconductor lasers, it is possible to reduce the size of the laser unit.

  Further, in the laser unit adjustment method of the present invention, the laser unit adjustment device includes a wavefront sensor that detects wavefront information of the emitted light emitted from the semiconductor laser and transmitted through the collimator lens, and before the adjustment step, Based on the wavefront information of the emitted light detected by the wavefront sensor, a preparatory step for controlling the moving means so as to adjust the position of the semiconductor laser to a position where the incident light on the wavefront sensor becomes parallel light to the collimating lens. It is preferable to include.

  According to the wavefront sensor, it is possible to detect how much the incident wavefront to the wavefront sensor is deviated from the parallel light wave. For this reason, before the adjustment process for adjusting the semiconductor laser position, a preparation process for coarse adjustment using the wavefront sensor can be performed, and the semiconductor laser position can be adjusted quickly.

  In the laser unit adjustment method of the present invention, in the adjustment step, one of the injection current and the optical output intensity of the semiconductor laser is fixed to a constant value, and the other of the injection current and the optical output intensity of the semiconductor laser is related to the other. The moving means is controlled to move the semiconductor laser to the position where the maximum value is determined, and the maximum value regarding the semiconductor laser injection current is a relative decrease of the semiconductor laser injection current with respect to the light output intensity of the semiconductor laser. The maximum value and the maximum value related to the optical output intensity of the semiconductor laser is preferably the maximum value of the relative increase in the optical output intensity of the semiconductor laser with respect to the injection current of the semiconductor laser.

  By fixing one of the injection current and optical output intensity of the semiconductor laser to a constant value, it is easy to determine the increase / decrease value for the other of the injection current and optical output intensity of the semiconductor laser. Further, when the maximum value of the relative increase / decrease or decrease is determined, the light emitted from the semiconductor laser and the return light are almost completely parallel. Therefore, since the semiconductor laser can be moved to a position where the emitted light and the return light are almost completely parallel, it is possible to adjust the position very precisely.

  As described above, in the laser unit adjusting apparatus of the present invention, the control means moves the moving means to increase the light output intensity of the semiconductor laser relative to the injection current of the semiconductor laser, or the light output of the semiconductor laser. The control means controls the moving means so as to determine a relative decrease in the injection current of the semiconductor laser with respect to the intensity and move the semiconductor laser to a position where the relative increase or decrease is detected. .

  Further, the laser unit adjustment method of the present invention includes an adjustment step of adjusting the positions of the plurality of semiconductor lasers so that the focal position of the collimating lens and the light emitting points of the plurality of semiconductor lasers coincide with each other. The moving means is moved to a position where a relative increase in the light output intensity of the semiconductor laser with respect to the injection current of the semiconductor laser or a decrease in the injection current of the semiconductor laser with respect to the light output intensity of the semiconductor laser is detected. This is a method of moving the semiconductor laser.

  Therefore, according to the present invention, the semiconductor laser is moved to the position where the relative increase or decrease is detected based on the self-coupling effect, that is, the position where the emitted light and the return light are substantially parallel. Therefore, precise position adjustment becomes possible. Furthermore, the present invention is used for adjusting a laser unit including a plurality of semiconductor lasers. Since the laser unit combines and emits light emitted from a plurality of semiconductor lasers, the laser unit can be reduced in size.

It is a schematic sectional drawing which shows the structural example of the optical pick-up apparatus which mounts the laser unit manufactured by the adjustment process of this invention. (A) is a figure for demonstrating a self-coupling effect, (b) is a graph which shows the relationship between the laser injection current when a self-coupling effect arises, and a laser beam output. It is sectional drawing which shows the laser unit adjustment apparatus and laser unit adjustment apparatus which concern on this Embodiment. It is a figure explaining the adjustment procedure regarding the adjustment fixation of a semiconductor laser unit. It is a flowchart which shows the laser unit adjustment method which concerns on this Embodiment. It is sectional drawing which shows the conventional optical pick-up apparatus.

  One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic cross-sectional view showing a configuration example of a three-wavelength optical pickup device 30 equipped with a laser unit adjusted and fixed by applying the present invention. A three-wavelength optical pickup apparatus to which the present invention is applied performs recording and reproduction of BD, DVD, and CD-type discs. When roughly classified, the optical pickup device 30 includes a laser unit 25 and various lenses provided in the main housing 22.

  The laser unit 25 includes a two-wavelength semiconductor laser 1, a blue semiconductor laser 2, a dichroic beam splitter 3, a diffraction element 4 and a monitor PD (monitoring light receiving means) 5. Each member will be described below.

  The two-wavelength semiconductor laser 1 emits laser light having a wavelength of 650 nm band and 780 nm band. Recording / reproduction of a CD disk is performed using a laser beam of 780 nm band of both laser beams, and recording / reproduction of a DVD disk is performed using a laser beam of 650 nm band. The blue semiconductor laser 2 emits laser light having a wavelength of 405 nm, and recording / reproduction of the BD disc is performed using the laser light of 405 nm.

  The diffractive element 4 divides the laser light emitted from the light source into three light spots of zero order light and ± first order light. The provision of the diffraction element 4 makes it possible to detect a tracking error signal using a three-beam method, a DPP (Differential Push-Pull) method, or the like.

  The dichroic beam splitter 3 reflects laser light having a wavelength near 405 nm, while transmitting laser light having wavelengths near 650 nm and 780 nm, and is emitted from the two-wavelength semiconductor laser 1 and the blue semiconductor laser 2. 7 and 8 are guided to substantially the same optical path. That is, it plays a role of combining and emitting light beams emitted from a plurality of semiconductor lasers.

  The monitor PD 5 detects the light output intensity of the two-wavelength semiconductor laser 1 and the blue semiconductor laser 2. Using the detection signal of the monitor PD5, the laser injection current is controlled so that the light output intensities of the two-wavelength semiconductor laser 1 and the blue semiconductor laser 2 are constant.

  The above-described optical components are housed in a laser unit housing 6 and form a laser unit 25 as a whole. The laser unit 25 is attached to the main housing 22.

  In the main housing 22, a blue rising mirror 15, a blue objective lens 17, a two-wavelength rising mirror 14, a two-wavelength objective lens 16, a broadband quarter-wave plate 13, a collimating lens 12, a collimating lens driving unit 21, a polarization A beam splitter 11, a hologram element 18, a sensor lens 19, and a light receiving element (OPIC) 20 are accommodated. The blue objective lens 17 and the two-wavelength objective lens 16 are mounted on an actuator (not shown) and can be driven in an optical axis direction and a direction orthogonal to the optical axis.

  The polarization beam splitter 11 changes the direction of the laser light 9 by reflecting the laser light 9 emitted from the laser unit. The laser light 7 or 8 emitted from the laser unit 25 is linearly polarized light, and the polarization beam splitter 11 is designed to reflect the laser light emitted from the light source and transmit linearly polarized light orthogonal to the polarization direction. Yes. As will be described later, the laser light emitted from the light source and the reflected light from the optical disc have polarization directions different from each other by about 90 °, and the polarization beam splitter 11 is designed to reflect the forward light and transmit the backward light. Has been.

  The collimating lens 12 makes the laser beam reflected by the polarization beam splitter 11 substantially parallel light. Note that substantially parallel light includes perfect parallel light. The collimating lens 12 is mounted on the collimating lens driving unit 21 and is movable in the optical axis direction. In the recording / reproduction of a BD disc, since the numerical aperture is high, the influence of spherical aberration due to the thickness error of the protective layer of the optical disc becomes large. This spherical aberration is corrected by driving the collimating lens 12.

  The broadband quarter-wave plate 13 converts linearly polarized light having a wavelength of 405 to 780 nm into circularly polarized light, and conversely converts circularly polarized light into linearly polarized light. As the linearly polarized light travels back and forth through the broadband quarter-wave plate 13, the polarization direction of the linearly polarized light is rotated by 90 degrees.

  The two-wavelength raising mirror 14 reflects the laser light of the wavelength 650 nm band and the 780 nm band and transmits the laser light of the wavelength 405 nm band. The reflected laser light is guided to the two-wavelength objective lens 16. The blue rising mirror 15 reflects laser light having a wavelength of 405 nm, and the reflected laser light is guided to the blue objective lens 17.

  The two-wavelength objective lens 16 condenses incident laser light on a CD disk and DVD disk to form a light spot on the optical information recording layer. The blue objective lens 17 condenses the incident laser beam on the BD disc to form a light spot on the optical information recording layer.

  The hologram element 18 has a function of diffracting return light from the optical disk and dividing it into a plurality of diffracted light beams. For example, 80% of the laser light incident on the hologram element is transmitted as it is as zero-order light, and the remaining 20% is divided into two as ± first-order light and emitted.

  The sensor lens 19 is a lens having a cylindrical surface. The sensor lens 19 gives astigmatism to the reflected light from the optical disk, and by inserting this lens, a focus error signal can be detected by the astigmatism method.

  The light receiving element 20 receives the reflected light from the sensor lens 19 and converts it into various servo signals.

  The operation of the three-wavelength optical pickup device 30 will be described below. The first laser beam 7 having a wavelength of 650 nm band emitted from the two-wavelength semiconductor laser 1 is transmitted through the dichroic beam splitter 3, reflected by the polarization beam splitter 11, changed in direction by 90 °, and parallel by the collimating lens 12. It is lighted.

  The collimated first laser light passes through the broadband quarter-wave plate 13 and becomes circularly polarized light, and is reflected by the two-wavelength rising mirror 14 to rise in the direction of the optical disk (the optical disk The direction is changed to a direction) and the light is condensed on the recording / reproducing surface of the optical disk by the two-wavelength objective lens 16. The light reflected by the recording / reproducing surface of the optical disc is guided to the collimating lens 12 and the polarization beam splitter 11 along the path opposite to the forward path. That is, it passes through the two-wavelength objective lens 16, the two-wavelength rising mirror 14, and the broadband quarter-wave plate 13, and becomes linearly polarized light orthogonal to the forward light, and is guided to the collimating lens 12 and the polarization beam splitter 11. . The light passes through the polarization beam splitter 11 and is guided to the signal detection optical system through a path of the hologram element 18, sensor lens 19, and light receiving element 20.

  On the other hand, the second laser light 8 having a wavelength of 405 nm band emitted from the blue semiconductor laser 2 is incident on the dichroic beam splitter 3, reflected, reflected by the polarization beam splitter 11, and collimated by the collimating lens 12. The collimated laser light passes through the broadband quarter-wave plate 13 to become circularly polarized light, passes through the two-wavelength rising mirror 14, is reflected by the blue rising mirror 15, and is raised in the direction of the optical disk. The light is focused on the recording / reproducing surface of the optical disk by the blue objective lens 17. The reflected light from the optical disk follows the path opposite to the forward path and is guided to the collimating lens 12. That is, the light is guided to the collimating lens 12 through the blue objective lens 17, the blue rising mirror 15, and the two-wavelength rising mirror 14, and is guided to the signal detection optical system through the path of the hologram element 18, sensor lens 19, and light receiving element 20. It is burned.

  In this optical system, the optical system from the broadband quarter-wave plate 13 to the light receiving element 20 is an optical system common to the BD, DVD, and CD for the return side optical system. A common light receiving element 20 detects a track error signal, a focus error signal, and a reproduction signal for BD, DVD, and CD. Further, in order to simplify the adjustment, the BD and DVD reproduction signal detection light receiving portions are made the same. As described above, in the optical pickup device 30 according to the present embodiment, a plurality of light sources are provided, but the signal detection optical system is integrated into one system, and the number of parts is small. It is a structure that is advantageous for the reduction of.

  In the optical pickup device 30, if the positional deviation between the BD light source and the DVD light source occurs, the optical axis and the central axis of the reproduction signal detecting light receiving unit are shifted for either one of the laser beams. The signal cannot be detected accurately. For example, when the positions of the blue semiconductor laser and the two-wavelength semiconductor laser are shifted by several tens of μm along the optical axis direction, an offset always occurs in one focus error signal, and accurate focus control cannot be performed. In addition, when the deviation is 10 μm along the in-plane direction, an offset always occurs in one tracking error signal and accurate tracking control cannot be performed, or the leakage of the tracking error signal into the focus error signal becomes large, and the focus error signal increases. Control may become unstable. In order to avoid these problems, it is necessary to adjust the positions of the two light sources on the order of microns.

  In the present embodiment, the self-coupling effect of the semiconductor laser is used to adjust the positions of the two-wavelength semiconductor laser 1 and the blue semiconductor laser 2 that are the two light sources. The self-coupling effect will be described with reference to FIG. FIG. 2A is a diagram for explaining the self-coupling effect, and FIG. 2B is a graph showing the relationship between the laser injection current and the laser light output when the self-coupling effect occurs.

  The optical system shown in FIG. 2A includes a semiconductor laser 31, a collimating lens 32, a half mirror (planar mirror) 33, and a photodetector 34. The semiconductor laser 31 is connected to an injection current detection means 37 and a drive circuit 38. As the injection current detecting means 37, a known injection current detector may be used. The drive circuit 38 drives the semiconductor laser 31 by outputting to the semiconductor laser 31 a drive signal input from a control means described later.

  Here, when the emitted light emitted from the semiconductor laser 31 is converted into parallel light by the collimator lens 32, reflected by the half mirror 33, and returned to the semiconductor laser 31 again, the threshold current of the injection current is the intensity of the return light. A phenomenon that decreases in proportion to is shown. This phenomenon is called the self-coupling effect. FIG. 2B shows the injection current-light output characteristics when the self-coupling effect occurs. The broken line is the injection current-light output characteristic in the normal oscillation state, and the solid line is the injection current-light output characteristic when the self-coupling effect occurs. As shown in FIG. 2B, when the self-coupling effect occurs, the threshold current of the injected current is lowered.

  From the result showing the self-coupling effect, it can be determined that the emission point of the emitted light from the semiconductor laser 31 coincides with the focal point of the return light, so that the semiconductor laser 31 is located at a position where the semiconductor laser 31 shows the self-coupling effect. By arranging 31, precise position adjustment can be realized.

  The following method is mentioned as a specific method for confirming the expression of the self-binding effect. For example, if the injection current to the semiconductor laser 31 is kept constant, the light output intensity of the light emitted from the collimating lens 32 becomes smaller than that in a state where the light is completely parallel light. Therefore, by detecting the output of the monitor light receiving means (not shown), it is possible to appropriately adjust whether or not the light emitted from the collimating lens 32 is in a parallel light state.

  As another method, if a current is injected into the semiconductor laser 31 so that the output of the light receiving means for monitoring is constant, the injection current increases when the light emitted from the collimating lens 32 deviates from the parallel light state. Therefore, it is possible to appropriately adjust whether or not the light emitted from the collimating lens 32 is in the parallel light state by detecting the change in the injected current by the injected current detecting means. The self-coupling effect is also disclosed in JP-A-2002-373449.

  That is, a position where a relative increase in the light output intensity of the semiconductor laser with respect to the injection current of the semiconductor laser or a relative decrease in the injection current of the semiconductor laser with respect to the light output intensity of the semiconductor laser is detected (the relative decrease is It is determined that the self-binding effect was developed at the observed position).

  Further, if the light beam traveling from the collimating lens 32 to the half mirror 33 is completely parallel light, and its optical axis is parallel to the normal line of the half mirror 33, the return light returns directly to the light emitting point of the semiconductor laser 31, and self The coupling effect is maximized and the change in the threshold of the injected current is maximized. When the self-coupling effect is maximized, the emission point of the emitted light coincides with the focus point of the return light, which is very preferable because the semiconductor laser can be fixed precisely.

  Whether or not the self-coupling effect is maximized can be confirmed in advance by the following method. First, one of the injection current and the optical output intensity of the semiconductor laser is fixed to a constant value, and the position of the semiconductor laser is finely adjusted in various directions. Thereafter, the moving means is controlled to move the semiconductor laser to a position where the maximum value related to the other of the injection current and the optical output intensity of the semiconductor laser is determined. The maximum value related to the semiconductor laser injection current is the maximum value of the relative decrease in the semiconductor laser injection current relative to the semiconductor laser light output intensity. The maximum value related to the semiconductor laser light output intensity is the semiconductor laser injection current. Is the maximum value of the relative increase in the light output intensity of the semiconductor laser. It is determined that the self-coupling effect is maximized at the position where the maximum value is determined. As described above, the other change amount of the injection current or the optical output intensity of the semiconductor laser that is not fixed shows the maximum value, so that the maximum value can be determined in advance.

  When the normal line of the half mirror 33 is adjusted in advance so as to be completely parallel to the optical axis of the collimating lens 32, the semiconductor laser 31 is in the case where the focal point of the collimating lens 32 and the light emitting point of the semiconductor laser 31 are matched. The self-bonding effect is maximized. In this case, by monitoring the output of the monitoring light receiving means or the output of the injection current detecting means, it becomes possible to accurately align the light emitting point of the semiconductor laser 31 with respect to the focal point of the collimating lens 32. .

  If the light emitted from the collimator lens 32 is deviated from the parallel light or the optical axis is deviated, the return light does not return to the light emitting point or becomes a large point. In this case, no self-bonding effect is shown.

  In addition, even when a plurality of semiconductor lasers are provided and the respective emitted lights are combined by a dichroic beam splitter, the light emitting point position adjusting method using the self-coupling effect described above for each semiconductor laser Using this, it becomes possible to align the focal point of the collimating lens.

  A method for adjusting the light emitting point positions of a plurality of lasers using the self-coupling effect will be specifically described. In the present embodiment, adjustment is performed using an adjustment optical system. FIG. 3 is a cross-sectional view showing the adjusting optical system of the laser unit adjusting apparatus according to the present embodiment.

  The adjusting optical system of the laser unit adjusting device is configured by a collimating lens 32, a half mirror 33, and a wavefront sensor. The collimating lens 32 is corrected for chromatic aberration, and is adjusted and fixed so that the mirror surface of the half mirror 33 is perpendicular to the optical axis of the collimating lens 32. Further, the center axis of the wavefront sensor 36 is also adjusted in advance so as to coincide with the optical axis of the collimating lens 32.

  As the wavefront sensor 36, a Shack-Hartmann sensor, an interferometer, or the like can be used. In particular, the Shack-Hartmann sensor is preferable because it can detect wavefront information in real time and is advantageous in reducing the tact time. The adjustment optical system 40 is an optical system that is freely movable in the X, Y, and Z directions.

  The laser unit adjusting apparatus 50 includes moving means 1a and 2a, a power meter (monitor PD 35) 35, an injection current detecting means 37, a drive circuit 38, and a control means 39. The light output intensity of the semiconductor laser is detected by a power meter 35. As shown in the figure, the power meter 35 may be incorporated on the laser unit adjusting device 50 side, or the monitor PD 5 mounted on the optical pickup device 30 in FIG. You may utilize for the detection of the optical output intensity of the wavelength semiconductor laser 1 and the blue semiconductor laser 2. FIG. The injection current detector 37 adjusts the injection currents of the two-wavelength semiconductor laser 1 and the blue semiconductor laser 2 based on the output signal amplified by the drive circuit 38 and detects the injection current.

  The control means 39 is mainly composed of a CPU (Central Processing Unit) and controls the power meter 35, the injection current detection means 37, and the drive circuit 38. Specifically, a control signal is transmitted to the drive circuit 38, the injection current of the semiconductor laser is adjusted via the injection current detection means 37, and each output is made constant so that the output in the power meter 35 is constant. Control is performed to inject current into the semiconductor laser.

  Further, the control means 39 can be configured to be connected to the wavefront sensor 36. In this case, based on the wavefront information of the emitted light detected by the wavefront sensor 36, the position of the two-wavelength semiconductor laser 1 or the blue semiconductor laser 2 is changed to a position where the incident light on the wavefront sensor 36 becomes parallel light to the collimating lens. Thus, each of the moving means 1a and 2a is controlled.

  The control means 39 also determines whether or not the self-coupling effect has been shown based on the injection current detected by the injection current detection means 37. Further, the control means 39 is connected to moving means 1a and 2a provided in the two-wavelength semiconductor laser 1 and the blue semiconductor laser 2, respectively.

  The moving means 1a and 2a are members for moving the two-wavelength semiconductor laser 1 and the blue semiconductor laser 2, respectively, and are controlled by a control signal from the control means 39. Specifically, the moving means 1a and 2a can be configured by an actuator or the like. As shown in FIG. 3, the two-wavelength semiconductor laser 1 can be adjusted in the X direction and the Z direction. On the other hand, the blue semiconductor laser 2 can be adjusted in the Y direction.

  In FIG. 3, when the light emitting point of the semiconductor laser coincides with the focal point of the collimating lens 32 of the adjusting optical system 40, the laser light emitted toward the collimating lens 32 is collimated by the collimating lens 32 and the half mirror 33. The light is partially reflected by the collimating lens 32 and returned to the position of the light emitting point of the original semiconductor laser to show a self-coupling effect. Confirmation of the self-coupling effect is confirmed by setting the laser injection current in the vicinity of the threshold current in the normal oscillation state, monitoring the light output intensity with the power meter 35, and checking the light output intensity with the injection current detecting means 37. This can be done by confirming that it has increased.

  Alternatively, the self-coupling effect can be confirmed by automatically controlling the injection current of the semiconductor laser so that the light output intensity becomes constant and checking the amount of decrease of the injection current. By confirming this self-coupling effect, the coincidence between the focal point of the collimating lens 32 and the emission point of the semiconductor laser is determined.

  This self-coupling effect is extremely accurate, and it is possible to detect misalignment in the order of microns in the thickness direction of the semiconductor laser active layer and in the direction perpendicular to the thickness direction, and in the order of 5 microns for positional changes in the optical axis direction. is there. Therefore, if the position of one semiconductor laser is adjusted at the focal point of the collimator lens 32 and then the position of the other semiconductor laser is adjusted in the same manner, the relative positional deviation between the two lasers is ± 10 in the optical axis direction. Adjustments can be made with an accuracy of ± 5 microns or less in the direction perpendicular to the optical axis.

  Next, a specific adjustment procedure will be described with reference to FIG. FIG. 4 is a diagram for explaining an adjustment procedure for adjustment and fixing of the semiconductor laser unit. For simplification of the drawing, the configuration of the laser unit adjustment device 50 other than the adjustment optical system 40 and the power meter 35 is not shown. FIG. 5 is a flowchart showing a laser unit adjustment method according to the present embodiment.

  First, as shown in FIG. 4A, the position of the adjustment optical system 40 is adjusted with respect to the emission point of the two-wavelength semiconductor laser 1 (S1 in FIG. 5 (S indicates a step)). First, the two-wavelength semiconductor laser 1 is finely adjusted by the control means 39 via the moving means 1a, and the wavefront sensor 36 detects how much the incident wavefront is deviated from the parallel light wave. If the position of the light emitting point of the two-wavelength semiconductor laser 1 and the position of the focal point of the collimating lens 32 are shifted in the Z direction, the value of the defocus term of the wavefront sensor 36 is increased. If the position of the light emitting point of the two-wavelength semiconductor laser 1 and the position of the focal point of the collimator lens 32 are shifted in the X direction or the Y direction, the value of the tilt term of the wavefront sensor 36 is increased. The control means 39 adjusts the position of the adjustment optical system 40 in the three directions so that the respective values become smaller.

  Next, as shown in FIG. 4B, the blue semiconductor laser 2 is adjusted (S2 in FIG. 5, preparation step). Specifically, the blue semiconductor laser 2 is caused to emit light, the output of the wavefront sensor 36 is monitored, the blue semiconductor laser 2 is changed in the Y direction, and the position of the adjustment optical system 40 is changed in the X and Z directions. The input wavefront to the wavefront sensor 36 is adjusted to be a parallel wavefront. Further, fine adjustment is performed until the self-coupling effect is shown (adjustment process).

  Whether or not the self-coupling effect has been shown is determined by the control means 39 (S3 in FIG. 5). When the self-coupling effect is not shown (NO), the process returns to S2 again and the blue semiconductor laser 2 is adjusted. On the other hand, when the self-coupling effect is indicated (YES), it is determined whether or not the self-coupling effect is maximized (S4 in FIG. 5). The S4 is very effective for making the emitted light from the blue semiconductor laser 2 completely parallel light. However, S4 may be omitted if very precise adjustment is not required. In this case, the adjustment time can be shortened although the accuracy of the adjustment is reduced. When the self-coupling effect is not the maximum (NO), the process returns to S2 again and the blue semiconductor laser 2 is adjusted. On the other hand, when it is determined that the self-coupling effect is the maximum (YES), the process proceeds to the adjustment of the two-wavelength semiconductor laser 1.

  That is, first, as shown in FIG. 4C, the two-wavelength semiconductor laser 1 is adjusted (S5 in FIG. 5, preparation step). Similarly to S2, the two-wavelength semiconductor laser 1 is caused to emit light, the output of the wavefront sensor 36 is monitored, and the two-wavelength semiconductor laser 1 is moved in the X and Z directions so that the input wavefront to the wavefront sensor 36 becomes a parallel wavefront. adjust. The adjustment is made by the control means 39 controlling the moving means 1a.

  Further, the fine adjustment is repeated, and similarly to S3 and S4, it is determined by the control means 39 whether or not the self-coupling effect is shown (S6 in FIG. 5, adjustment step). It is determined (S7 in FIG. 5). Similar to S4, S7 may be omitted.

  After confirming that the self-coupling effect was shown with respect to the two-wavelength semiconductor laser 1 and the blue semiconductor laser 2 with the position of the adjustment optical system 40 fixed (YES), the two-wavelength semiconductor laser 1 and the blue semiconductor laser 2. Adhesive fixation of 2 is performed.

  As described above, the laser unit adjusting device 50 adjusts the laser unit by adjusting the two-wavelength semiconductor laser 1 in the X direction and the Z direction and adjusting the blue semiconductor laser 2 in the Y direction. Thus, each laser need not be adjusted in the three directions of the X direction, the Y direction, and the Z direction. That is, the two-wavelength semiconductor laser 1 can be adjusted in a state fixed in the Y-axis direction, and the blue semiconductor laser 2 can be adjusted in a state fixed in the X direction and the Z direction. Thus, the semiconductor laser can be bonded and fixed. For this reason, even if the adhesive expands and contracts, since at least one direction of the semiconductor laser is fixed, the positional deviation of the semiconductor laser due to the expansion and contraction of the adhesive can be suppressed.

  Further, as in Patent Document 1, when adjusting a semiconductor laser, it is not necessary to perform spatial adjustment in three directions, and adjustment and fixing can be performed more easily. More specifically, in the laser unit adjusting method, the direction along the traveling direction of the parallel light passing through the collimating lens is the Z direction, and the directions perpendicular to the Z direction and orthogonal to each other are the X direction and the Y direction. These semiconductor lasers are a first semiconductor laser and a second semiconductor laser, the moving means is controlled so as to move the position of the second semiconductor laser in the Y direction, and the position of the first semiconductor laser is changed to the X direction and Z It can be said that this is a method of controlling the moving means so as to change the direction.

  Further, by using the laser unit adjusting device 50, it is possible to measure the misalignment of the two-wavelength semiconductor laser 1 and the blue semiconductor laser 2 after bonding and fixing by determining the self-bonding effect, and to detect imperfect bonding. It is possible to use in.

  As described above, the laser unit adjustment device and the laser unit adjustment process of the present invention enable a laser unit equipped with a plurality of semiconductor lasers to be manufactured accurately and inexpensively, and the cost of a multi-wavelength optical pickup equipped with the laser unit can be reduced. It is effective for improving productivity.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the technical means disclosed in different embodiments can be appropriately combined. Such embodiments are also included in the technical scope of the present invention.

  The laser unit adjustment device and the laser unit adjustment method of the present invention are useful for improving the productivity of a multi-wavelength optical pickup device.

1 Dual wavelength semiconductor laser 2 Blue semiconductor laser 3 Dichroic beam splitter 4 Diffraction element 5 Monitor PD
DESCRIPTION OF SYMBOLS 11 Polarizing beam splitter 12 Collimating lens 13 Broadband quarter wave plate 14 Two-wavelength raising mirror 15 Blue raising mirror 16 Two-wavelength objective lens 17 Blue objective lens 18 Hologram element 19 Sensor lens 20 Light receiving element 21 Collimating lens drive unit 25 Laser Unit 32 Collimating lens 33 Half mirror 34 Photo detector 35 Power meter 36 Wavefront sensor 39 Control means 40 Adjustment optical system 50 Laser unit adjustment device

Claims (5)

A laser unit adjustment device that adjusts the relative positions of a plurality of semiconductor lasers included in a laser unit that combines and emits light emitted from a plurality of semiconductor lasers,
A collimating lens for collimating the emitted light emitted from the semiconductor laser, a plane mirror having a mirror surface perpendicular to the optical axis of the collimating lens, a moving means for moving the semiconductor laser, and the moving means. Control means for controlling,
The control means moves the moving means to determine a relative increase in the semiconductor laser light output intensity with respect to the semiconductor laser injection current, or a relative decrease in the semiconductor laser injection current with respect to the semiconductor laser light output intensity. And
The laser unit adjusting apparatus, wherein the control means controls the moving means so as to move the semiconductor laser to a position where the relative increase or decrease is detected. A wavefront sensor that detects wavefront information of the emitted light emitted from the semiconductor laser and transmitted through the collimator lens;
The control means changes the moving means so as to change the position of the semiconductor laser to a position where the incident light on the wavefront sensor becomes parallel light with respect to the collimating lens based on the wavefront information of the emitted light detected by the wavefront sensor. The laser unit adjusting device according to claim 1, wherein the laser unit adjusting device is controlled. The control means fixes one of the injection current and optical output intensity of the semiconductor laser to a constant value,
Controlling the moving means to move the semiconductor laser to a position where the maximum value related to the other of the injection current and the optical output intensity of the semiconductor laser is determined;
The maximum value for the semiconductor laser injection current is the maximum relative decrease in the semiconductor laser injection current with respect to the semiconductor laser optical output intensity, and the maximum value for the semiconductor laser optical output intensity is relative to the semiconductor laser injection current. 3. The laser unit adjusting apparatus according to claim 1, wherein the laser unit adjusting apparatus is a maximum value of a relative increase in light output intensity of the semiconductor laser. A laser unit adjustment method for adjusting the relative positions of a plurality of semiconductor lasers included in a laser unit that multiplexes and emits light emitted from a plurality of semiconductor lasers,
Laser unit adjustment comprising: a collimating lens for collimating outgoing light emitted from the semiconductor laser; a plane mirror having a mirror surface perpendicular to the optical axis of the collimating lens; and a moving means for moving the semiconductor laser A laser unit adjustment method using the apparatus as an adjustment member,
An adjustment step of adjusting the positions of the plurality of semiconductor lasers so that the focal positions of the collimating lenses and the emission points of the plurality of semiconductor lasers coincide with each other;
In the adjustment step, the moving means is moved to increase the light output intensity of the semiconductor laser relative to the injection current of the semiconductor laser, or to decrease the injection current of the semiconductor laser relative to the light output intensity of the semiconductor laser. A laser unit adjustment method, wherein the semiconductor laser is moved to a detected position. The laser unit adjustment device includes a wavefront sensor that detects wavefront information of emitted light that is emitted from the semiconductor laser and transmitted through a collimator lens,
Prior to the adjustment step, based on the wavefront information of the emitted light detected by the wavefront sensor, the movement of the semiconductor laser is adjusted so that the incident light on the wavefront sensor becomes parallel light with respect to the collimating lens. 5. The laser unit adjustment method according to claim 4, further comprising a preparation step for controlling the means.

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