JP2004272951A - Optical head and optical recording/reproducing device using optical head, adjusting and manufacturing method of optical head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultra small optical head of an integrated optical system which includes the objective lens, its effective adjusting method and a manufacturing method, relating to an optical head which records and reproduces information on an optical recording medium, an optical recording/reproducing device which uses this head and the adjusting and manufacturing method of this optical head. <P>SOLUTION: This optical head comprises an objective lens 18 to focus a beam from an semiconductor laser 13 on the information recording surface of an optical recording medium, a hologram element 16 to diffract the light reflected on the information recording surface, a pair of light receiving elements 14, 14' to receive the light diffracted by the hologram element 16, a case 11 to enclose them, and a reflector plate 11e which forms a part of the case 11 and reflects the diffracted light to input to the light receiving element 14'. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical head that records information on an optical recording medium or reproduces the recorded information, an optical recording / reproducing apparatus using the same, and a method of adjusting and manufacturing an optical head.
[0002]
[Prior art]
The optical recording / reproducing apparatus records information in a predetermined area of a plurality of tracks formed in a circumferential direction of a disk-shaped optical recording medium (optical disk) and formed in a plurality of radial directions of the optical recording medium. An optical head for reproducing information recorded in a predetermined area of the track is provided. Optical heads include a recording-only type that is used only for recording information on an optical recording medium, a reproduction-only type that is used only for reproducing information, and a recording / reproduction type that can be used for both recording and reproduction. is there. Therefore, the devices equipped with these are an optical recording device, an optical reproducing device, and an optical recording / reproducing device, respectively. In the present application, hereinafter, all of them are collectively referred to as an optical recording / reproducing device. The optical recording / reproducing apparatus has the advantage that the optical recording medium can be easily replaced at a low cost as compared with the magnetic recording apparatus typified by a hard disk apparatus, and the information reproducing capability even if the optical head or the surface of the optical recording medium is damaged to some extent. Has high reliability that can be maintained. For this reason, optical recording / reproducing devices are widely used as external storage devices for various electronic information devices including computers.
[0003]
On the other hand, since the optical head of the optical recording / reproducing apparatus is larger and heavier than the magnetic head of the magnetic recording apparatus, it has a disadvantage that the access speed when moving the optical head to a desired track position on the optical recording medium is slow. ing. In order to overcome this drawback, many developments have been made to reduce the weight of the optical head and improve the performance of its driving mechanism.
[0004]
For example, Patent Document 1 discloses an optical head in which a lens holder and light emitting / receiving means are integrated with each other for the purpose of providing a miniaturized optical head capable of high-speed access. Patent Document 2 discloses an ultra-thin optical pickup device in which an allowable relative displacement between a light-emitting element, a light-receiving element, and a beam splitter in the optical pickup apparatus is greatly reduced. Further, in the example of Patent Document 3, the size of the optical head is reduced by an optical path that makes effective use of the reflection at the optical member. Patent Document 4 discloses an optical head having a structure in which a light source and a light receiving element can move independently on a surface of an optical member which is horizontal and transparent to an optical system.
[0005]
[Patent Document 1]
JP-A-07-114743
[Patent Document 2]
JP 05-28517 A
[Patent Document 3]
JP 05-203824 A
[Patent Document 4]
JP-A-07-021581
[0006]
[Problems to be solved by the invention]
However, although the optical path of an optical system for integrating a plurality of components of an optical head is specified in Patent Literature 1, the structure of a portion including a light source and a light receiving element, and the optical axis between each optical element are described. There is no specific method for adjusting the value. Also in Patent Document 2, although the optical path including the light source and the light receiving element is specified, the accuracy of the optical axis shift and the method of adjusting the optical axis shift required for realizing the phase difference detection method for obtaining the focus error signal are described. Is not described.
[0007]
Further, in the example of Patent Document 3, in order to adjust the optical axis of the return path system, it is necessary to move the light receiving element provided with the electrode in close contact with the inclined surface of the transparent substrate, and the adjustment work is extremely difficult. There is a problem that it becomes complicated. Further, the structure of the adjusting device becomes complicated, and a measure for maintaining the strength of the lead wire is required so that the lead wire drawn from the electrode of the light receiving element is not cut during the optical axis adjustment.
[0008]
Further, in the optical head disclosed in Patent Document 4, the adjustment of the optical axis of the return path system is relatively easy, but the optical path lengths of the forward path and the return path are determined by the dimensions of the transparent optical member occupying the main part. However, there is a disadvantage that there is no effective means for finely adjusting the difference between the optical path lengths of the forward path and the return path. Such a deviation from the design value of the optical path length of the forward path and the multiple path appears as a deviation (offset) of the optimum pull-in voltage when the focus servo is applied to the optical recording medium. Normally, this offset component can be corrected by changing the pull-in voltage itself during focus servo (that is, by electrical adjustment), but if the amount of deviation is large, it will hinder focus servo performance. It is necessary to keep it within a certain range. Specifically, the center voltage of a focus error signal called an S-shaped curve is usually set to the optimum pull-in voltage, but the allowable focus deviation amount of the allowable voltage optimum value is usually equal to the S-shaped curve in the optical head. Is specified within ± 10% to ± 20% of the amplitude (assumed to be ± 50%). If the amplitude exceeds this value, the operation of the focus servo becomes unstable and the system may not operate normally. There is a problem that.
[0009]
An object of the present invention is to provide an ultra-small optical head in which an optical system including an objective lens is integrated, an optical recording / reproducing apparatus using the same, and a method for effectively adjusting and manufacturing the optical head. It is in.
[0010]
[Means for Solving the Problems]
The object is to provide a light source for emitting light for irradiating an information recording surface of an optical recording medium, an objective lens for condensing light emitted from the light source on the information recording surface, and an emission lens for emitting the emitted light on the information recording surface. A diffractive element for diffracting the reflected light, a set of light receiving elements for receiving the diffracted light diffracted by the diffractive element, a light source, an objective lens, a diffractive element, and a housing for accommodating the light receiving element; And a reflector that partially forms the light and reflects the diffracted light and makes the light incident on one of the pair of light receiving elements.
[0011]
In the optical head of the present invention, the height and inclination of the reflection plate with respect to a reference plane are variable when adjusting the optical path and the optical path length of the diffracted light.
[0012]
In the optical head of the present invention, the diffraction element is movable by a predetermined amount in a direction parallel to the optical path of the reflected light when adjusting the optical path and the optical path length of the diffracted light.
In the optical head of the present invention, the optical head further includes an optical path changing element disposed in front of the objective lens on an optical path of the emitted light, wherein the diffraction element is disposed between the light source and the optical path changing element. It is characterized by having.
[0013]
As the diffraction element in the optical head of the present invention, for example, a polarizing diffraction grating having a different diffraction efficiency depending on the polarization component of incident light can be used. At this time, it is preferable that the polarizing diffraction element has a quarter-wave plate disposed between the diffraction element and the objective lens. In the optical head of the present invention, it is preferable that the diffraction element has a function of a quarter-wave plate.
[0014]
Further, the above object is an optical recording / reproducing apparatus equipped with an optical head mounted at the tip and having a swing arm movable in a radial direction of a disk-shaped optical recording medium, wherein the optical head is the optical recording medium according to the present invention. This is achieved by an optical recording / reproducing device, which is an optical head.
[0015]
Further, the object is to irradiate the information recording surface of the optical recording medium with light, make the light reflected on the information recording surface incident on a diffraction element and diffract it, and reflect the diffracted light diffracted by the diffraction element with a reflection plate. After that, the light is incident on the light receiving element, and the height and the inclination of the reflection plate from the reference plane are changed based on the output of the light receiving element to adjust the optical path and the optical path length of the diffracted light. This is achieved by an optical head adjustment method.
[0016]
In the above-described method for adjusting an optical head according to the present invention, the diffraction element is further moved in a direction parallel to an optical path of the reflected light to adjust an optical path and an optical path length of the diffracted light.
[0017]
Still further, the object is to provide a light source for emitting light for irradiating an information recording surface of an optical recording medium, an objective lens for condensing light emitted from the light source on the information recording surface, and the information recording of the emitted light. A method for manufacturing an optical head in which a diffraction element that diffracts light reflected by a surface and a set of light receiving elements that receive the diffracted light diffracted by the diffraction element are housed in a housing, wherein a part of the housing is provided. A reflecting plate that reflects the diffracted light and makes it incident on one of the pair of light receiving elements, reflects the diffracted light diffracted by the diffractive element and then makes the light incident on the light receiving element, and outputs the light from the light receiving element. The height and the inclination of the reflection plate from the reference plane are changed based on the above, thereby adjusting the optical path and the optical path length of the diffracted light.
[0018]
In the method of manufacturing an optical head according to the present invention, the diffractive element may be moved in a direction parallel to the optical path of the reflected light to adjust the optical path and the optical path length of the diffracted light.
The method for adjusting the optical path and optical path length of the diffracted light in the method for manufacturing an optical head of the present invention can be appropriately selected. For example, a focus error signal (referred to as an S-shaped signal) obtained from a rotating disk that intentionally oscillates during rotation by processing into a turntable is adjusted so as to have a good waveform. The optical path and the optical path length can be adjusted by a method of adjusting the amplitude of the information signal (referred to as an RF signal) to be maximized. In this case, by using an adjustment objective lens mounted on an actuator that can apply focus servo and tracking servo, the optimum point can be determined while directly observing not only the quality of the signal waveform but also the jitter value of the RF signal. It is very preferable because it can be obtained and adjusted.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
An optical head according to an embodiment of the present invention, an optical recording / reproducing apparatus using the same, and an effective adjusting method and a manufacturing method of the optical head will be described with reference to FIGS. First, a schematic configuration of the optical head according to the present embodiment will be described with reference to FIGS. 1 to 3 together with a light traveling path (optical path). The optical head according to the present embodiment is a microminiature optical head in which a light source, a diffraction element, an optical path changing element, an objective lens, and a light receiving element are integrally housed in a housing.
[0020]
FIG. 1 shows a state in which the optical head according to the present embodiment is seen transparently from the plane direction thereof. FIG. 2 shows a cross section taken along line AA in FIG. 1 and a region including the vicinity thereof. FIG. 3 is an exploded perspective view showing main members constituting the optical head according to the present embodiment, and shows an assembly procedure thereof. As shown in FIGS. 1 to 3, the optical head 10 has a housing 11. The housing 11 has a rectangular plate-shaped substrate portion 11a, and two side wall portions 11b, 11b vertically rising from two opposing sides of the substrate portion 11a in the same direction and formed at substantially the same height. I have. Two openings 11c, 11c opening at a predetermined width d are formed at the same position facing one end of the two side walls 11b, 11b.
[0021]
The other end of the side walls 11b, 11b is formed obliquely, and the slider 11d is fixed to the oblique side. On an upper surface between the openings 11c, 11c of the side walls 11b, 11b and the slider 11d, a reflecting plate 11e for adjusting an optical path of light traveling in the optical head 10 is fixed by an adhesive or the like. The substrate 11a side of the reflection plate 11e is a light reflection surface. FIG. 1 shows the inside of the optical head 10, in which the slider 11d and the reflection plate 11e are detached, which are indicated by dashed virtual lines.
[0022]
The slider 11d and the reflection plate 11e form an opposing surface that opposes the surface of the optical recording medium with an objective lens support 11f described later. The slider 11d is disposed so as to be an inflow side end of an airflow generated between the slider 11d and the rotating optical recording medium. When the optical recording medium rotates, a lift is generated in the housing 11 in a direction away from the optical recording medium due to an airflow flowing from the slider 11 d side and passing between the optical recording medium and the housing 11. The housing 11 is configured to maintain a certain distance from the optical recording medium at a predetermined distance from the optical recording medium by the lift and an external force such as an actuator.
[0023]
On the substrate portion 11a, a substrate 12 having a base layer formed of silicon (Si) or the like and on which various components and optical systems are mounted is mounted. On the substrate 12, a semiconductor laser 13 as a light source for emitting light for irradiating the optical recording medium, two light receiving elements 14, 14 ', a front monitor photodetector 15, and a hologram element (diffraction element) 16 And a start-up mirror 17 are provided.
[0024]
The semiconductor laser 13 is attached to an upper surface of a mounting table 26 formed at a predetermined height from the surface of the substrate 12. The light emission side of the semiconductor laser 13 faces the diffraction grating surface of the hologram element 16 held by the holding plate 24 sandwiched between the openings 11c, 11c of the housing 11, and has an axis substantially parallel to the surface of the substrate 12. When the diverging light beam is emitted from the semiconductor laser 13, a sufficient amount of light enters the hologram element 16.
[0025]
The hologram element 16 has a function as a transmission type diffraction grating. The hologram element 16 may be formed substantially at the center of the rectangular plate-shaped holding plate 24. Alternatively, it may be held on the holding plate 24 as a separate component. Both ends of the holding plate 24 are formed to be thinner than the opening width d of the openings 11c, 11c, and are adhesively fixed in the openings 11c, 11c. Therefore, the holding plate 24 can be moved in the openings 11c and 11c until the holding plate 24 is fixed with the adhesive, whereby the diffraction grating surface of the hologram element 16 is moved from the information recording surface of the optical recording medium. Can be adjusted to move by a predetermined amount in a direction parallel to the optical path (return path) of the reflected light.
[0026]
A rising mirror (optical path changing element) 17 is fixed on the substrate 12 opposite to the semiconductor laser 13 with respect to the hologram element 16. The reflecting surface of the rising mirror 17 is arranged at an angle of approximately 45 ° with respect to the surface of the substrate 12. Light emitted from the semiconductor laser 13 and transmitted through the hologram element 16 is bent by the rising mirror 17 and travels toward the objective lens 18.
[0027]
The objective lens 18 is attached to and supported by an opening that is opened substantially at the center of the objective lens support 11f. The objective lens support 11f is fixed between one ends of the side walls 11b, 11b and the openings 11c, 11c. Of the light transmitted through the hologram element 16, the zero-order light traveling straight is bent by the rising mirror 17 and enters the objective lens 18. The light incident on the objective lens 18 is converged light and is irradiated on the optical recording medium. The light incident on the optical recording medium is reflected by the information recording surface below the protective layer on the surface of the optical recording medium and returns to the objective lens 18.
[0028]
The return light from the optical recording medium passes through the objective lens 18, is bent by the rising mirror 17, and enters the hologram element 16. FIG. 4 shows an overview of the hologram element 16 as viewed from the semiconductor laser 13 side. As can be seen from FIG. 4, the hologram element 16 is formed with a linear transmission diffraction grating in which the grid lines are inclined at a predetermined angle in the counterclockwise direction with respect to the substrate surface of the substrate 12 and the grid pitch is equally spaced. The ± 1st-order diffracted lights emitted from the hologram element 16 are respectively incident on the light receiving elements 14 and 14 ′ as focused light fluxes.
[0029]
The light receiving element 14 has two divided light receiving sections 14a and 14b. Further, the light receiving element 14 'has two divided light receiving sections 14c and 14d. The light receiving sections 14a to 14d are formed of, for example, photodiodes.
[0030]
In addition, the dividing line of the two-divided light receiving portions 14a and 14b of the light receiving element 14 is adjusted so as to be parallel to, for example, the axis of the converged light beam of the + 1st-order diffracted light, and the two divided light receiving portions 14c and 14d of the light receiving element 14 'are divided. The lines are adjusted to be parallel to the axis of the focused ray bundle of the -1st order diffracted light. As a result, the dividing lines of the two-divided light receiving portions 14a and 14b and the dividing lines of the two-divided light receiving portions 14c and 14d are substantially parallel to the tangential direction (tangential direction) of the track formed on the optical recording medium.
[0031]
The + 1st-order diffracted light emitted from the hologram element 16 becomes a converged light beam and directly enters the light receiving sections 14a and 14b of the light receiving element 14. At this time, the position of the hologram element 16 and the position of the light receiving element 14 are adjusted so that the light receiving surface of the light receiving element 14 is located closer to the focus position of the converged light beam of the + 1st-order diffracted light.
[0032]
On the other hand, the -1st-order diffracted light emitted from the hologram element 16 becomes a converged light beam, is reflected by the reflection surface of the reflection plate 11e, and is incident on the light receiving sections 14c and 14d of the light receiving element 14 '. At this time, the positions of the hologram element 16, the reflection plate 11e, and the light receiving element 14 'are adjusted such that the light receiving surface of the light receiving element 14' is farther from the converging position of the converged light beam of the first-order diffracted light. Therefore, the -1st-order diffracted light that has become a divergent light beam enters the light receiving surface of the light receiving element 14 '.
[0033]
In the present embodiment, a linear transmission diffraction grating is used as shown in FIG. 4, but the diffraction grating is formed into a curved shape having a predetermined curvature and the grating pitch is gradually changed, so that the hologram element 16 is formed. As a matter of course, the + 1st-order diffracted light and the -1st-order diffracted light may have converging properties.
Further, if the hologram element 16 is designed to be a polarizing hologram element in which the amount of diffracted light varies depending on the plane of polarization of the incident light, and the element itself has the function of a 波長 wavelength plate, the semiconductor laser 13 Most of the light emitted from the optical recording medium is transmitted as the 0th-order light, and most of the reflected light from the optical recording medium can be diffracted as ± 1st-order light. It is possible to manufacture the optical head 10 with high efficiency.
[0034]
The front monitor photodetector 15 is arranged at a position for receiving a part of the light emitted from the semiconductor laser 13. The output signal of the front monitor photodetector 15 is used for automatically adjusting the amount of light emitted from the semiconductor laser 13. In this example, as shown in FIG. 1, the front monitor photodetector 15 is disposed on the substrate 12 near the midpoint of the openings 11c, 11c of the side walls 11b, 11b of the housing 11. In the present embodiment, the semiconductor laser 13, the two light receiving elements 14, 14 ', the front monitor photodetector 15, and the mounting table 26 are attached and arranged on the substrate 12, so-called a hybrid type. A monolithic type may be formed integrally on the substrate 12 by a photolithography process.
[0035]
Wiring (not shown) for supplying power to the semiconductor laser 13, the light receiving elements 14 and 14 ′, and the photodetector 15 for front monitoring and extracting signals is formed on the substrate 12. These wirings are connected to a plurality of pads 21 formed on one end of the substrate 12. Each pad 21 is connected to a plurality of wiring terminals (not shown) provided at one end of the flexible printed board 20. Since one end of the flexible printed board 20 is directly fixed to the board 12 on which the wiring layer (not shown) is formed, the optical head 10 and the flexible printed board 20 can be connected with sufficient mechanical strength. The other end of the flexible printed circuit board 20 is connected to each connection terminal of an electronic circuit in an optical recording / reproducing device (not shown). 2 and 3, the illustration of the flexible printed circuit board 20 is omitted.
[0036]
Next, a method of detecting a focus error signal, a tracking error signal, and an information reproduction signal according to the present embodiment will be described with reference to FIGS. 5A to 7, (a) shows the light receiving sections 14 a and 14 b of the light receiving element 14, and (b) shows the light receiving sections 14 c and 14 d of the light receiving element 14 ′. In each of the drawings, the dividing line between the light receiving units 14a and 14b and the dividing line between the light receiving units 14c and 14d are illustrated in parallel for easy explanation.
[0037]
FIG. 5 shows the light receiving surfaces of the light receiving elements 14 and 14 ′ in a state where the light emitted from the objective lens 18 to the optical recording medium has the smallest diameter on the information recording surface of the optical recording medium (hereinafter referred to as a focused state). + 1S and -1S. In the focused state, the light spot of the + 1st-order diffracted light beam at the light receiving surfaces of the light receiving sections 14a and 14b of the light receiving element 14 plus the spot diameter of 1S (see FIG. 5A) and the light reception of the light receiving element 14 '. Arrangement of the hologram element 16 and the reflector 11e so that the spot diameter of the light spot-1S of the divergent light beam of the -1st-order diffracted light on the light receiving surfaces of the portions 14c and 14d is equal (see FIG. 5B). Has been adjusted.
[0038]
FIG. 6 shows the light spots + 1S and -1S on the light receiving surfaces of the light receiving elements 14 and 14 'when the distance between the objective lens 18 and the optical recording medium is shorter than in the focused state. In this state, the spot diameter of the light spot + 1S of the converged light beam of the + 1st-order diffracted light on the light receiving surfaces of the light receiving portions 14a and 14b of the light receiving element 14 (see FIG. 6A) is in the focused state (FIG. 5A). (See FIG. 6 (a)), while the spot diameter of the light spot-1S of the divergent light beam of the −1st-order diffracted light on the light receiving surfaces of the light receiving portions 14c and 14d of the light receiving element 14 ′ (see FIG. 6 (b)). ) Is smaller than in the focused state (see FIG. 5B).
[0039]
FIG. 7 shows light spots + 1S, -1S on the light receiving surfaces of the light receiving elements 14, 14 'when the distance between the objective lens 18 and the optical recording medium is longer than in the focused state. In this state, the spot diameter of the light spot + 1S of the converged light beam of the + 1st-order diffracted light on the light receiving surfaces of the light receiving portions 14a and 14b of the light receiving element 14 (see FIG. 7A) is in the focused state (FIG. 5A). (See FIG. 7 (a)). On the other hand, the spot diameter of the light spot-1S of the divergent light beam of the −1st-order diffracted light on the light receiving surfaces of the light receiving portions 14c and 14d of the light receiving element 14 ′ (see FIG. 7 (b)) ) Is larger than in the focused state (see FIG. 5B).
[0040]
When the light emitted from the objective lens 18 onto the optical recording medium accurately follows the track of the optical recording medium, the axes of the two diffracted light beams incident on the light receiving elements 14 and 14 'are the light receiving sections 14a and 14a. It is located on the dividing line between 14b and the dividing line between the light receiving units 14c and 14d, and there is no difference in the intensity distribution between the light beams on both sides of each dividing line. However, if the focused light emitted from the objective lens 18 is relatively displaced in one radial direction (radial direction) of the optical recording medium, the intensity distribution of the two diffracted light beams incident on the light receiving elements 14 and 14 ′ changes. However, the amount of light incident on the light receiving units 14a and 14d is smaller than the amount of light incident on the light receiving units 14b and 14c. When the light emitted from the objective lens 18 onto the optical recording medium is relatively displaced in the opposite direction to the above-described one direction, the intensity distribution of the two diffracted light beams incident on the light receiving elements 14 and 14 'similarly changes, and The amount of light incident on the units 14b and 14c is smaller than the amount of light incident on the light receiving units 14a and 14d.
[0041]
Therefore, assuming that the outputs of the light receiving sections 14a, 14b, 14c and 14d are A, B, C and D, respectively, the focus error signal FES, tracking error signal RES and information reproduction signal RF can be obtained by the following equations. it can.
[0042]
FES = (A + B)-(C + D)
RES = (A + D)-(B + C)
RF = A + B + C + D
[0043]
Next, an adjustment method and a manufacturing method of the optical head according to the present embodiment will be described mainly along an assembly procedure shown in FIG. Note that the assembling procedures (1) to (7) shown in FIG. 3 are merely examples, and the order of the procedures (1) to (7) can be changed as appropriate.
[0044]
First, a substrate 12 for mounting an electronic circuit and an optical system, at least a base layer of which is formed of silicon or the like, is formed in a predetermined rectangular shape, and then a plane portion on which a semiconductor laser 13 is mounted is positioned at a predetermined height. The mounting table 26 is formed (procedure (1)). Next, the semiconductor laser 13 is mounted on the mounting table 26. Further, light receiving elements 14 and 14 ′ for detecting return light from the optical recording medium are mounted at predetermined positions on the same plane on the substrate 12. With this configuration, the height of the entire optical head 10 can be reduced. Also, the dividing line between the light receiving sections 14a and 14b of the light receiving element 14 is attached so as to be substantially parallel to the axis of the converging light beam of the + 1st-order diffracted light from the hologram element 16 after assembly, and , 14d are attached so as to be substantially parallel to the axis of the convergent ray bundle of the -1st-order diffracted light. Accordingly, even if the oscillation wavelength of the semiconductor laser 13 fluctuates during the subsequent adjustment operation of the optical system, the axis of the ± 1st-order diffracted light from the hologram element 16 can be hardly shifted from the division line.
[0045]
Further, the front monitor photodetector 15 is mounted at a predetermined position on the surface of the substrate 12 at a position where a part of the light emitted from the semiconductor laser 13 can be directly received. In this example, the front monitor photodetector 15 is mounted on the substrate 12 near the midpoint connecting the openings 11c so that the laser light amount can be detected without being affected by the reflected light from the optical recording medium. ing.
[0046]
The semiconductor laser 13, the light receiving elements 14, 14 ', and the front monitor photodetector 15 may be formed on the substrate 12 by using photolithography. Furthermore, an electronic circuit for converting a current output from the semiconductor laser 13, the light receiving elements 14, 14 ', and the front monitor photodetector 15 into a voltage or the like may be simultaneously formed on the substrate 12 by photolithography. Good. By doing so, not only the accuracy of the arrangement position of each element can be improved, but also the quality of the photoelectric conversion signal can be improved.
[0047]
Next, the plurality of pads 21 formed on one end of the substrate 12 and the plurality of wiring terminals provided on one end of the flexible printed board 20 (not shown in FIG. 3) are connected. Next, the substrate 12 on which the light source and the light receiving system are formed is placed on the substrate 11a of the housing 11, and the other end of the flexible printed circuit board 20 is connected to a circuit in the optical recording / reproducing apparatus. The above is the assembling operation of the procedure (2).
[0048]
Next, both ends of the holding plate 24 on which the hologram element 16 is formed are inserted into the openings 11c, 11c, and are temporarily arranged on the substrate 12 (procedure (3)). At this stage, the lattice plane of the hologram element 16 is located only perpendicular to the surface of the substrate 12 and can move in the openings 11c, 11c almost in parallel with the optical path of the light emitted from the semiconductor laser 13. I have. Since the hologram element 16 is disposed in front of the rising mirror 17, not only the height of the optical head 10 can be kept low, but also the position of the hologram element 16 can be easily adjusted.
[0049]
Next, a rising mirror 17 that is located on the opposite side of the semiconductor laser 13 with respect to the hologram element 16 and folds the light transmitted through the hologram element 16 substantially perpendicularly to the surface of the substrate 12 is mounted on the substrate 12 (procedure). (4)).
[0050]
Next, before the objective lens 18 is attached, an objective lens (not shown) mounted on an adjustment actuator (hereinafter, referred to as an adjustment objective lens) is installed above the installation position of the objective lens 18. Next, the semiconductor laser 13 is driven to emit light, and an optical recording medium for adjustment (not shown) (or an alternative reflector for adjustment) is provided above the objective lens for adjustment.
[0051]
Next, a reflector 11e for adjusting the optical axis and the optical path length of the reflected light from the optical recording medium for adjustment in the optical path (return path) is held on the upper portion of the housing 11 by an adjustment jig (not shown). The adjustment jig can finely adjust the height and inclination of the reflection plate 11e with the substrate 12 as a reference plane. First, the adjusting jig positions the reflecting surface of the reflecting plate 11e above the light receiving elements 14 and 14 'and the semiconductor laser 13, and brings both ends of the reflecting plate 11e close to the side walls 11b and 11b of the housing 11. The reflector 11e is held substantially parallel to the surface of the substrate 12.
[0052]
In this state, the light emitted from the semiconductor laser 13 passes through the hologram element 16, the optical path is bent by the rising mirror 17, enters the adjustment objective lens, is collected, and is reflected by the adjustment optical recording medium. The reflected light reaches the hologram element 16 through the adjusting objective lens and the rising mirror 17, and is diffracted to extract the diffracted light of the ± 1st order focused light beam.
[0053]
At this time, the + 1st-order diffracted light is directly incident on the light receiving surfaces of the light receiving portions 14a and 14b of the light receiving element 14 on the front side of the focusing position, while the light receiving surfaces of the light receiving portions 14c and 14d of the light receiving element 14 ' , The -1st-order diffracted light reflected once by the reflection surface of the reflection plate 11e is incident on the front side of the convergence position. Here, the holding plate 24 for holding the hologram element 16 is formed with the width of the openings 11c and 11c so that a sufficient amount of light is obtained in the light receiving sections 14a and 14b of the light receiving element 14 and the light receiving sections 14c and 14d of the light receiving element 14 '. Within d, the light is moved in parallel with the optical path of the reflected light from the optical recording medium for adjustment, and the height and inclination of the reflector 11e are adjusted.
[0054]
When a sufficient amount of light can be adjusted to be incident on the light receiving element 14 and the light receiving element 14 ', the respective light amounts of the two-divided light receiving portions 14a and 14b of the light receiving element 14 on which the + 1st-order diffracted light is directly incident are compared by an electric signal. Then, the position of the hologram element 16 is adjusted by moving the hologram element 16 again in parallel with the optical path of the reflected light from the adjustment optical recording medium so that the respective light amounts of the light receiving sections 14a and 14b become substantially equal.
[0055]
Then, by rotating the optical recording medium for adjustment (optical disk) or, in the case of an adjusting reflector, changing the distance of the reflecting surface or changing the direction of the reflecting surface with respect to the adjusting objective lens, the S-shaped curve is obtained. And observe the focus error signal FE. The inclination of the reflector 11e is adjusted so that the amplitude of the S-shaped curve of the focus error signal FE is obtained substantially symmetrically with respect to the reference level.
[0056]
Next, focus servo is applied to the adjustment objective lens based on the obtained focus error signal FE. In this case, the adjustment objective lens is mounted on an actuator that can apply focus servo and tracking servo. Then, the servo pull-in voltage is set to a design center value (for example, 0 V). In this state, a position where a high spatial frequency signal (RF signal or track cross signal) engraved on the optical recording medium can be obtained with the best quality. The height of the reflection plate 11e is adjusted so as to satisfy (Step (5)). After the height adjustment of the reflector 11e is completed, if necessary, the operation of adjusting the position of the hologram element 16 and the operation of adjusting the inclination and height of the reflector 11e are repeated.
[0057]
The holding plate 24 and the reflection plate 11e of the hologram element 16 for which the position adjustment has been completed are fixed to the housing 11 with an adhesive or the like. As a result, the reflection plate 11e becomes a part of the components of the housing 11. Next, the objective lens supporting portion 11f supporting the objective lens 18 is fixed on the upper part of the rising mirror 17, and is integrated with the housing 11 (procedure (6)). Next, the slider 11d is attached. As a result, the entire optical head 10 has the same slider shape as the magnetic head used in the hard disk device (procedure (7)).
[0058]
FIG. 8 shows an optical head device 1 on which the optical head 10 manufactured according to the above procedure is mounted. The optical head device 1 has a structure in which the optical head 10 is mounted on the distal end of the swing arm 30 so that the optical recording medium 100 can be moved in the radial direction, and a coil or a magnet is provided in a part of the optical head device. The actuator structure is such that it can move in a direction perpendicular to the information recording surface of the optical recording medium 100. Thus, the entire light head 10 is driven to perform focus control and tracking control.
[0059]
As described above, according to the present embodiment, the adjustment of the optical axis to the light receiving elements 14 and 14 ′, the adjustment of the symmetry in the focus servo signal, and the adjustment of the conjugate position between the light source and the light receiving element are easily and independently performed. You can do it. Further, by using the optical head structure of the present embodiment, it is possible to achieve a reduction in size and weight, and an improvement in performance by mounting and controlling the entire optical head on an actuator.
[0060]
FIG. 9 shows a schematic configuration of an optical recording / reproducing apparatus 50 equipped with the optical head 10 according to the present embodiment. The optical recording / reproducing apparatus 50 includes a spindle motor 52 for rotating the optical recording medium 100 as shown in FIG. 9, an optical head 10 for irradiating the optical recording medium 100 with a laser beam and receiving reflected light thereof, It includes a controller 54 for controlling the operation of the motor 52 and the optical head 10, a laser drive circuit 55 for supplying a laser drive signal to the optical head 10, and a lens drive circuit 56 for supplying a lens drive signal to the optical head 10. .
[0061]
The controller 54 includes a focus servo tracking circuit 57, a tracking servo tracking circuit 58, and a laser control circuit 59. When the focus servo tracking circuit 57 operates, the information recording surface of the rotating optical recording medium 100 is in focus, and when the tracking servo tracking circuit 58 operates, the eccentric signal track of the optical recording medium 100 , The spot of the laser beam enters an automatic following state. The focus servo tracking circuit 57 and the tracking servo tracking circuit 58 have an auto gain control function for automatically adjusting the focus gain and an auto gain control function for automatically adjusting the tracking gain. The laser control circuit 59 is a circuit that generates a laser drive signal supplied by the laser drive circuit 55, and generates an appropriate laser drive signal based on the recording condition setting information recorded on the optical recording medium 100. I do.
[0062]
The focus servo tracking circuit 57, the tracking servo tracking circuit 58, and the laser control circuit 59 need not be circuits incorporated in the controller 54, and may be separate components from the controller 54. Furthermore, these need not be physical circuits, but may be software executed in the controller 54.
[0063]
The present invention is not limited to the above embodiment, and various modifications are possible.
For example, in the above embodiment, the reference surface is the substrate 12 surface, but the present invention is not limited to this. For example, the optical system may be arranged with a plane inclined with respect to the substrate 12 as a reference plane. In this case, the mirror surface of the rising mirror or the like, which is an optical path changing element, need not necessarily be 45 ° with respect to the reference plane.
Further, in the above embodiment, the rising mirror is used as the optical path changing element, but the present invention is not limited to this, and it is of course possible to use a prism element or the like.
[0064]
【The invention's effect】
As described above, according to the present invention, an ultra-small optical head in which an optical system including an objective lens is integrated and an optical recording / reproducing apparatus using the same can be realized, and an effective adjusting method and manufacturing of the optical head can be realized. The method can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram showing a state in which an optical head according to an embodiment of the present invention is seen transparently from a plane direction thereof.
FIG. 2 is a diagram showing a cross section taken along line AA in FIG. 1 and a region including the vicinity thereof.
FIG. 3 is an exploded perspective view showing main members constituting the optical head according to the embodiment of the present invention, and a view showing an assembling procedure thereof.
FIG. 4 is a diagram showing an overview of the hologram element 16 as viewed from the semiconductor laser 13 side of the optical head according to one embodiment of the present invention.
FIG. 5 is a diagram illustrating a method of detecting a focus error signal, a tracking error signal, and an information reproduction signal in the optical head according to one embodiment of the present invention.
FIG. 6 is a diagram illustrating a method for detecting a focus error signal, a tracking error signal, and an information reproduction signal in the optical head according to one embodiment of the present invention.
FIG. 7 is a diagram illustrating a method for detecting a focus error signal, a tracking error signal, and an information reproduction signal in the optical head according to one embodiment of the present invention.
8 is a diagram showing an optical head device 1 on which the optical head 10 manufactured according to the procedure shown in FIG. 3 is mounted.
FIG. 9 is a diagram showing a schematic configuration of an optical recording / reproducing apparatus equipped with an optical head according to an embodiment of the present invention.
[Explanation of symbols]
1 Optical head device
10 Optical head
11 Case
11a Substrate
11b Side wall
11c opening
11d slider
11e Reflector
11f Objective lens support
12 Substrate
13 Semiconductor laser
14, 14 'light receiving element
15 Front monitor photodetector
16 Hologram element
17 Start-up mirror
18 Objective lens
20 Flexible printed circuit board
21 pads
24 Holding plate
26 Mounting table
50 Optical recording / reproducing device
52 spindle motor
54 Controller
55 Laser drive circuit
56 Lens drive circuit
57 Focus servo tracking circuit
58 Tracking servo tracking circuit
59 Laser control circuit
100 Optical recording medium

Claims (12)

A light source for emitting light for irradiating the information recording surface of the optical recording medium,
An objective lens for condensing the light emitted from the light source on the information recording surface,
A diffraction element that diffracts the reflected light of the emission light on the information recording surface,
A set of light receiving elements for receiving the diffracted light diffracted by the diffraction element,
A housing for housing the light source, the objective lens, the diffraction element, and the light receiving element,
An optical head comprising: a part of the housing; and a reflector that reflects the diffracted light and makes it incident on one of the set of light receiving elements. The optical head according to claim 1,
An optical head, wherein the reflector has a variable height and inclination with respect to a reference plane when adjusting the optical path and the optical path length of the diffracted light. The optical head according to claim 1, wherein
An optical head, wherein the diffraction element is movable by a predetermined amount in a direction parallel to the optical path of the reflected light when adjusting the optical path and the optical path length of the diffracted light. The optical head according to any one of claims 1 to 3,
Further comprising an optical path changing element disposed in front of the objective lens on the optical path of the emitted light,
The optical head, wherein the diffraction element is arranged between the light source and the optical path changing element. The optical head according to any one of claims 1 to 4,
The diffraction element is a polarizing diffraction grating having a different diffraction efficiency depending on a polarization component of incident light,
An optical head, wherein a quarter-wave plate is disposed between the diffraction element and the objective lens. The optical head according to any one of claims 1 to 4,
An optical head, wherein the diffraction element has a function of a quarter-wave plate. An optical recording / reproducing apparatus equipped with an optical head at a tip and a swing arm movable in a radial direction of a disk-shaped optical recording medium,
An optical recording / reproducing apparatus, wherein the optical head is the optical head according to any one of claims 1 to 6. Irradiating the information recording surface of the optical recording medium with light,
The reflected light on the information recording surface is diffracted by being incident on a diffraction element,
The reflected light diffracted by the diffractive element is reflected by a reflector and then incident on a light receiving element,
A method for adjusting an optical head, comprising: changing a height and an inclination of the reflection plate from a reference plane based on an output of the light receiving element to adjust an optical path and an optical path length of the diffracted light. The method for adjusting an optical head according to claim 8,
The method of adjusting an optical head, further comprising: moving the diffractive element in a direction parallel to an optical path of the reflected light to adjust an optical path and an optical path length of the diffracted light. A light source for emitting light for irradiating the information recording surface of the optical recording medium, an objective lens for condensing the emitted light from the light source on the information recording surface, and diffracting the reflected light of the emitted light on the information recording surface. A method for manufacturing an optical head in which a diffractive element and a set of light receiving elements that receive diffracted light diffracted by the diffractive element are housed in a housing.
Forming a part of the housing, by a reflecting plate that reflects the diffracted light and makes it incident on one of the set of light receiving elements, reflects the diffracted light diffracted by the diffraction element, and then makes the light incident on the light receiving element. ,
A method for manufacturing an optical head, comprising: changing a height and an inclination of the reflection plate from a reference plane based on an output of the light receiving element to adjust an optical path and an optical path length of the diffracted light. The method for manufacturing an optical head according to claim 10,
Further, a method of manufacturing an optical head, wherein the diffraction element is moved in a direction parallel to an optical path of the reflected light to adjust an optical path and an optical path length of the diffracted light. The method for manufacturing an optical head according to claim 10,
Adjustment of the optical path and the optical path length of the diffracted light,
A method for manufacturing an optical head, wherein the method is performed using an adjustment objective lens mounted on an actuator capable of applying focus servo and tracking servo.

Images