JP2006351076A - Optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve JITT (Just In Time Training) characteristics with respect to various kinds of optical disks by suppressing distortion of a half mirror at the low temperature operation of an optical pickup. <P>SOLUTION: An outgoing light beam of a light emitting element 32 is guided to a recording medium D, and the half mirror 4 for guiding a return light beam reflected by the recording medium D to a light receiving element 33 is joined to a base 1 at two points by adhesives 61, 62. For the two points of joining places, a first position 51 at a middle part in the thickness direction on one corner (a) among four corners (a), (b), (c), (d) of the rectangular half mirror 4 and a second position 52 on a projecting corner part at a light entering surface side on another one corner (c) in the diagonal direction with respect to the corner (a) are selected, and an adhesive having Young's modulus smaller than that of the adhesive 61 of the first position 51 is used for the adhesive 62 of the second position 52. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical pickup, and more specifically, a half mirror that guides light emitted from a light emitting element to a recording medium (optical disk) and guides return light reflected by the recording medium to a light receiving element at two points to the base with an adhesive. Related to an optical pickup.

  Conventionally, a triangular glass mirror, which is an example of an optical component of an optical pickup, and an aluminum alloy housing (base) are bonded to each other using a non-flexible adhesive and a flexible adhesive. The mirror is fixed at two points in one plane, and the mirror is restrained by an adhesive that is not flexible to prevent the mirror from being displaced or tilted. When the ambient temperature changes, the mirror and the base A technique has been proposed in which the stress caused by the difference in linear expansion coefficient is absorbed by an adhesive having flexibility (see, for example, Patent Document 1). Further, Patent Document 1 describes that it is considered to use a two-component mixed epoxy adhesive as a non-flexible adhesive and a flexible adhesive.

  In addition, a technique (for example, refer to Patent Document 2) that prevents the problem of misalignment that can occur when the half mirror is bonded at three points, or the epoxy system of a flat half mirror is used. There has also been proposed a technique (see, for example, Patent Document 3) in which a thermosetting adhesive is joined at two points and mounted on an apparatus frame. Furthermore, a technique for joining the diffraction grating of the optical head with an adhesive without positional deviation has been proposed (see, for example, Patent Document 4).

  On the other hand, in an optical pickup that is used in an optical disk device such as a DVD drive and scans a recording surface of a disk as a recording medium, as shown in a schematic plan view in FIG. In addition to the formation of a certain light passage hole 2, the light emitting element (not shown) attachment location A, the half mirror (not shown) attachment location B, the reflector (not shown) (Shown) and the mounting location D of the light receiving element (not shown) are determined. Then, as shown in the optical system configuration diagram of FIG. 4, the light emitted from the light emitting element 32 formed of a laser diode is guided to the collimator lens 35 by the Her mirror 4 to become a parallel light beam, and further passes through the objective lens 31 to be recorded on the recording medium. The return light irradiated to the optical disk D and reflected by the optical disk is guided to the light receiving element 33 through the objective lens 31, the collimator lens 35, and the half mirror 4. Then, in order to correct a change in the positional relationship between the optical disk D and the objective lens 31 due to warpage or eccentricity of the optical disk D, the lens holder 3 is controlled to be displaced in the focus direction and the tracking direction with respect to the optical disk D by the action of the drive unit 36. To be done.

  By the way, the inventor of the present application, in the optical pickup having the configuration described with reference to FIG. 3 or FIG. 4, has four corners a and b of the rectangular half mirror 4 having the constant thickness illustrated in FIG. 5. , C and d, the first position 51 of the middle portion in the thickness direction in one upper corner a, and the light incident surface side output corner in the other one lower corner c diagonally to the corner a. The second position 52 of the portion and the third position 53 of the middle portion in the thickness direction in the other one upper corner d are selected, and the three points of the respective positions 51, 52, 53 are set as the bonding positions by the adhesive. After preparing and fixing an adhesive to the base 1 (see FIG. 3), various optical disks were tested at room temperature at 25 ° C. and at a low temperature of −5 ° C. to perform JITT characteristics ( Jit characteristics) were investigated. As a result of this investigation, it has been found that the digit characteristics of most optical discs are lowered at a lower temperature than at a normal temperature. In addition, one of the causes of deterioration of JITT characteristics in a low temperature operation test at −5 ° C. is the distortion of the half mirror 4 at a low temperature. The shrinkage of the adhesive, the shrinkage of the adhesive bonding the half mirror 4 to the base, and the shrinkage of the half mirror 4 itself were considered.

  On the other hand, in the above-mentioned Patent Document 1, a triangular glass mirror is formed by using a non-flexible adhesive and a flexible adhesive at two points in one plane of the mirror. Although it is said that the stress caused by the difference in linear expansion coefficient between the mirror and the base when the ambient temperature changes can be absorbed by the flexible adhesive, this patent document No. 1 does not show a measure for suppressing the deterioration of the Jit characteristic in the low-temperature operation test for the rectangular half mirror, and Patent Document 1 does not suggest such a measure.

The technique proposed by Patent Document 2 is a technique useful for solving the problem of misalignment when the half mirror is fixed to the base. The technique proposed by Patent Document 3 is also a half mirror. This technique is useful for fixing to the base, and the technique proposed by Patent Document 4 is a technique for bonding the diffraction grating of the optical head with an adhesive without positional deviation. Therefore, these techniques cannot improve the jit characteristics during the low-temperature operation of the rectangular half mirror.
JP-A 63-269323 JP 2002-342946 A JP 2005-44398 A JP 2003-141748 A

  The present invention has been made under the above circumstances, and by devising the type of adhesive and the bonding position by the adhesive, the distortion that occurs in the half mirror during low temperature operation of the optical pickup can be suppressed and various types can be achieved. An object of the present invention is to provide an optical pickup capable of improving the JIT characteristic for an optical disc.

  An optical pickup according to the present invention is an optical pickup in which a half mirror that guides outgoing light of a light emitting element to a recording medium and guides return light reflected by the recording medium to a light receiving element is bonded to the base at two points with an adhesive. In the above two points, the first position of the intermediate portion in the thickness direction in one corner of the four corners of the rectangular half mirror and the other one in the diagonal direction with respect to the corner The second position of the light incident surface side corner at the corner is selected, and the adhesive at the first position and the adhesive at the second position have different Young's moduli.

  By adopting this configuration, the adhesive with a large Young's modulus is mainly useful for fixing the half mirror to the base, and the adhesive with a small Young's modulus prevents the distortion of the base from reaching the half mirror and distorting the half mirror. Mainly helps to do. And this and the selection of the first position and the second position described above as the two joints are synergistic, and the low-temperature jitter characteristics are not so much lower than the normal-temperature jitter characteristics. I was able to confirm that.

  In the present invention, when the Young's modulus of the adhesive at the first position is different from the Young's modulus of the adhesive at the second position, the Young's modulus of the adhesive at the second position is higher than the Young's modulus of the adhesive at the first position. It is desirable to reduce this, and by doing so, as will be described in the embodiments described later, the jit characteristics during low-temperature operation are reliably improved.

  An optical pickup according to the present invention is an optical pickup in which a half mirror that guides outgoing light of a light emitting element to a recording medium and guides return light reflected by the recording medium to a light receiving element is bonded to the base at two points with an adhesive. In the above two points, the first position of the intermediate portion in the thickness direction in one corner of the four corners of the rectangular half mirror and the other one in the diagonal direction with respect to the corner A second position of the light incident surface side corner at the corner is selected, and an adhesive having a smaller Young's modulus than the adhesive at the first position is used as the adhesive at the second position. It is made more concrete by adopting the configuration that is relaxed.

  As described above, according to the present invention, it is possible to suppress the distortion generated in the half mirror during the low temperature operation of the optical pickup by simply devising the type of the adhesive and the bonding position by the adhesive, and the JIT characteristic for various optical disks. It becomes possible to provide an improved optical pickup. In other words, it provides an optical pickup that is stable in read / write performance with respect to an optical disc not only when used in a non-cold region but also when used in a cold region, and in which the stability of the read / write performance with respect to the optical disc is less likely to be impaired by changes in the use environment temperature. It becomes possible.

  FIG. 1 is an explanatory diagram showing the number of joints and the number of half mirror adhesives in an optical pickup according to the present invention, and FIG. 2 is a drawing substitute showing an operation test result for explaining the effect of the present invention. It is a table.

  The overall configuration of this optical pickup is the same as that described with reference to FIG. 3 or FIG. In this optical pickup, as shown in FIG. 1, among the four corners a, b, c, and d of the rectangular half mirror, as the joining portion of the half mirror 4 with the adhesive to the base 1 (see FIG. 3). Incident light in the middle portion in the thickness direction of one upper corner a, more specifically, the first position 51 in the middle portion in the thickness direction, and light incident in the other lower corner c diagonally with respect to the corner a. Two points with the second position 52 of the surface-side corner are selected. The adhesive 61 at the first position 51 and the adhesive 62 at the second position have different Young's moduli. Specifically, the stress at the second position 52 is relaxed by using an adhesive 62 having a Young's modulus smaller than that of the adhesive 61 at the first position 51 as the adhesive 62 at the second position 52.

  Using the optical pickup (invention product) in which the half mirror 4 is bonded to the base 1 (see FIG. 3) at two points in the above-described form, the distortion rate and the low temperature of the various optical disks at normal temperature (25 ° C.). A test to investigate the distortion factor of the half mirror at the time (−5 ° C.) was conducted, and the result was compared with the optical pickup (reference example) having the half mirror 4 bonded to the base in the form described in FIG. did. The result is shown in FIG. In FIG. 2, the types of optical disks used in the tests are indicated by A to I, and these are generally commercially available optical disks.

  According to FIG. 2, in the reference example, the distortion factor of the half mirror is larger at the lower temperature than at the normal temperature for all except the optical disk H, whereas in the inventive product, the distortion factor of the half mirror is the optical disk A. Although -E is larger at a lower temperature than at normal temperature, the other optical discs F-I are smaller at a lower temperature than at normal temperature. In other words, the optical characteristics of the optical disks F to I are improved at a lower temperature than at a normal temperature. In addition, when the amount of change in distortion at normal temperature and low temperature is compared between the inventive product and the reference example, the inventive product is smaller than the reference example for all except the optical disc C. As a result, the inventive product has improved JIT characteristics compared to the reference example. When used in a non-cold area, the read / write performance of the optical disc is stable and the use environment temperature changes. Therefore, it can be said that the stability of the read / write performance with respect to the optical disk is hardly impaired.

  In the present invention, the type of adhesive is not particularly limited, and an epoxy or acrylic adhesive can be appropriately selected and used. If the Young's modulus is different, the same type of adhesive can be used. It can be used at two joints.

It is explanatory drawing which showed the joining location etc. by the adhesive agent of the half mirror in the optical pick-up which concerns on this invention. It is the table | surface for drawing substitution which showed the operation test result for demonstrating the effect of this invention. It is a schematic plan view of the base of an optical pickup. It is an optical system block diagram of an optical pick-up. It is explanatory drawing which showed the joining location etc. by the adhesive agent of the half mirror employ | adopted as the reference example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base 4 Half mirror 32 Light emitting element 33 Light receiving element 51 1st position 52 2nd position 61,62 Adhesives a, b, c, d Four corners of half mirror D Optical disk (recording medium)

Claims (3)

In an optical pickup in which a half mirror that guides outgoing light of a light emitting element to a recording medium and guides return light reflected by the recording medium to a light receiving element is bonded to the base with an adhesive at two points.
As the joining point of the two points, the first position of the middle portion in the thickness direction in one corner of the four corners of the rectangular half mirror, and the other corner in the diagonal direction with respect to the corner The second position of the light incident surface side corner is selected, and the adhesive at the second position is reduced by using an adhesive having a Young's modulus smaller than that of the adhesive at the first position. An optical pickup characterized by that. In an optical pickup in which a half mirror that guides outgoing light of a light emitting element to a recording medium and guides return light reflected by the recording medium to a light receiving element is bonded to the base with an adhesive at two points.
As the joining point of the two points, the first position of the middle portion in the thickness direction in one corner of the four corners of the rectangular half mirror, and the other corner in the diagonal direction with respect to the corner An optical pickup characterized in that the second position of the light incident surface side corner is selected, and the adhesive at the first position and the adhesive at the second position have different Young's moduli. The optical pickup according to claim 2, wherein the Young's modulus of the adhesive at the second position is smaller than the Young's modulus of the adhesive at the first position.

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