JP2008010061A - Housing for optical head, optical head, its manufacturing method, and optical recording/reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce astigmatism caused by astigmatic difference of a semiconductor laser as well as astigmatism of a whole optical head. <P>SOLUTION: The housing for optical head houses an optical system including a collimator lens converting an optical beam emitted from a semiconductor laser and diffused to parallel light. In the housing of the optical head, a strut 22 by which the collimator lens is fixed is provided with side planes 22a and 22b. Also a strut 23 is provided with a side plane 23a. Thereby, the collimator lens can be fixed while tilting in the direction orthogonal to an optical axis of the optical system, in the radial direction, or in the tangential direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical head housing for recording or reproducing data on an optical recording medium such as an optical disk, an optical head including the housing, a method for manufacturing the optical head, and an optical recording / reproducing apparatus including the optical head.

  In general, a semiconductor laser used in an optical head has a rectangular shape with a slight thickness of an active layer that generates a light beam. For this reason, the apparent vertical focus position of the light beam and the horizontal focus position are slightly shifted in the optical axis direction. The distance between the vertical focal position and the horizontal focal position is called astigmatic difference.

  In general, an optical head emits a beam spot emitted from a semiconductor laser having the astigmatic difference, converts a diffused light beam into parallel light by a collimator lens, and then collects the light beam on an information recording surface of an optical recording medium by condensing it by an objective lens. Is forming. In this case, on the information recording surface of the optical recording medium, the beam waist is shifted between the radial direction of the beam spot (radial direction of the optical recording medium) and the tangential direction (circumferential direction of the optical recording medium), and the beam spot is elliptical. Exhibits shape and so on. Thus, the fact that the beam spot exhibits an elliptical shape or the like on the information recording surface of the optical recording medium is called astigmatism.

  In the optical recording / reproducing apparatus in which the astigmatism occurs, generally, the focal position where the level of the information reading signal is the best when reproducing the information recording surface of the optical recording medium, and the focal position where the level of the tracking error signal is the best. There will be a gap. As a result, such an optical recording / reproducing apparatus tends to have a low tolerance for defocusing.

  In the optical recording / reproducing apparatus, in particular, in order to stably perform tracking servo when accessing a desired track during reproduction, setting is made so that the focus servo is applied at the focal position where the level of the tracking error signal is the best. It is preferable. However, when such setting is performed by the optical recording / reproducing apparatus in which the astigmatism occurs, for example, the best jitter point where the jitter of the information reading signal is lowest is shifted from the focal position where the level of the tracking error signal is highest. As a result, there is a problem that the jitter margin becomes small (the error rate increases).

Thus, various methods for correcting astigmatism due to such astigmatism of the semiconductor laser have been proposed. For example, in a conventional optical head, the collimating lens is tilted by a predetermined angle with respect to a direction orthogonal to the optical axis so as to generate astigmatism whose sign is opposite to that of the astigmatic difference of the semiconductor laser. In some cases, the astigmatic difference of the semiconductor laser is corrected by arranging them (see, for example, Patent Document 1).
JP-A-8-147747 (Claim 1, [0015] to [0017], FIG. 2)

  The optical head has various astigmatisms caused by other optical elements as well as the astigmatism caused by the astigmatic difference of the semiconductor laser. However, the conventional optical head described above has a problem that various astigmatisms caused by other optical elements cannot be corrected.

  Further, when the optical element such as the collimating lens is inclined with respect to the direction orthogonal to the optical axis, it is necessary to prevent the principal point of the optical element from shifting in the optical axis direction. This is because when the principal point of the optical element is shifted in the optical axis direction, the parallel light becomes convergent light or divergent light, and spherical aberration occurs. In this regard, in [0020], [0021] and FIG. 4 of Patent Document 1 described above, a collimating lens whose outer peripheral surface is processed into a tapered shape having a predetermined angle with respect to the optical axis direction is fixed to the mounting surface. Are listed. In this description, in particular, FIG. 4B, it is shown that the principal point of the collimating lens is displaced in the optical axis direction.

  Therefore, it can be said that Patent Document 1 described above does not disclose or suggest any device for preventing the principal point of the collimating lens from deviating from the optical axis. For this reason, in the prior art described in the above-mentioned Patent Document 1, the above-described inconvenience that the parallel light becomes convergent light or divergent light and spherical aberration occurs cannot be solved.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an optical head housing, an optical head, a manufacturing method thereof, and an optical recording / reproducing apparatus that can solve the above-described problems. To do.

  In order to solve the above-mentioned problem, the optical head housing according to the first aspect of the present invention is a light in which an optical system including a collimator lens that is emitted from a semiconductor laser and converts a diffused light beam into parallel light is accommodated. The fixing member for fixing the collimating lens in the housing of the head is characterized in that the collimating lens can be fixed in a plurality of directions with respect to the optical axis of the optical system.

  According to a second aspect of the present invention, there is provided the optical head housing according to the first aspect, wherein the collimating lens is fixed to the fixing member by tilting the collimating lens in the plurality of directions. A plurality of surfaces corresponding to the plurality of directions with which the surfaces are in contact are provided.

  A third aspect of the present invention relates to the optical head housing according to the first or second aspect, wherein the fixing member is fixed even when the collimating lens is tilted and fixed in any of the plurality of directions. The distance from the emitting surface of the semiconductor laser to the principal point of the collimating lens is equal.

  According to a fourth aspect of the present invention, there is provided the optical head housing according to any one of the first to third aspects, wherein the plurality of directions include at least a direction orthogonal to an optical axis of the optical system, a radial direction, and It is characterized by a tangential direction.

  An optical head according to a fifth aspect of the present invention includes the optical head housing according to any one of the first to fourth aspects, wherein the collimating lens is formed on the entire optical head in the plurality of directions. The collimating lens is tilted in a direction in which astigmatism is generated so as to cancel astigmatism, and is fixed to the fixing member.

  According to a sixth aspect of the present invention, there is provided a method of manufacturing an optical head having a housing in which an optical system including a collimator lens that converts a diffused light beam emitted from a semiconductor laser into parallel light is accommodated. According to a method, a fixing member is formed in the housing so that the collimating lens can be fixed by being inclined in a plurality of directions with respect to the optical axis of the optical system, and the collimating lens is attached to the fixing member by the light of the optical system. A first step of tilting in a direction perpendicular to the axis and temporarily fixing, a second step of measuring astigmatism of the entire optical head, a measurement result of the second step, and characteristic data of the collimating lens The direction in which the collimating lens generates astigmatism so that the collimating lens cancels astigmatism of the entire optical head among the plurality of directions. It is characterized by having a third step of the fixed to the fixing member by tilting.

  According to a seventh aspect of the present invention, there is provided the optical head manufacturing method according to the first aspect, wherein the collimating lens is fixed to the fixing member by tilting the collimating lens in the plurality of directions. A plurality of surfaces corresponding to the plurality of directions with which the surface of the optical head is abutted, and in the third step, the surface of the collimating lens is made astigmatism of the entire optical head out of the plurality of directions. The collimating lens is fixed to the fixing member in contact with the surface of the fixing member corresponding to the direction in which the astigmatism is generated.

  The invention according to claim 8 relates to the method of manufacturing an optical head according to claim 6 or 7, wherein the fixing member is fixed by inclining the collimating lens in any of the plurality of directions. However, the distance from the emitting surface of the semiconductor laser to the principal point of the collimator lens is equal.

  A ninth aspect of the present invention relates to the method of manufacturing an optical head according to any of the fifth to eighth aspects, wherein the plurality of directions are at least a direction orthogonal to an optical axis of the optical system and a radial direction. And tangential direction.

  According to a tenth aspect of the present invention, an optical recording / reproducing apparatus includes the optical head according to the fifth aspect.

  According to the present invention, the optical head housing according to the first aspect of the present invention is an optical head housing in which an optical system including a collimating lens that converts a diffused light beam emitted from a semiconductor laser into parallel light is accommodated. Therefore, the fixing member to which the collimating lens is fixed is configured to be able to be fixed by inclining the collimating lens in a plurality of directions with respect to the optical axis of the optical system. Therefore, not only the astigmatism due to the astigmatism of the semiconductor laser but also the astigmatism of the entire optical head can be reduced. As a result, astigmatism can be reduced even when the astigmatism occurrence direction of the entire optical head is different. Furthermore, the angle adjustment of the collimating lens is easy, the number of parts does not increase, and the cost is not increased.

  An optical head according to a fifth aspect of the present invention includes the optical head housing according to any one of the first to fourth aspects, wherein the collimating lens is formed on the entire optical head in the plurality of directions. In order to cancel astigmatism, the collimating lens is tilted in a direction in which astigmatism occurs and is fixed to the fixing member. Accordingly, the focal position where the level of the information read signal when reproducing the information recording surface of the optical recording medium is best and the focal position where the level of the tracking error signal is optimal can be matched. Thereby, the tolerance with respect to a defocus can be made high.

  According to a sixth aspect of the present invention, there is provided a method of manufacturing an optical head having a housing in which an optical system including a collimator lens that converts a diffused light beam emitted from a semiconductor laser into parallel light is accommodated. According to a method, a fixing member is formed in the housing so that the collimating lens can be fixed by being inclined in a plurality of directions with respect to the optical axis of the optical system, and the collimating lens is attached to the fixing member by the light of the optical system. A first step of tilting in a direction perpendicular to the axis and temporarily fixing, a second step of measuring astigmatism of the entire optical head, a measurement result of the second step, and characteristic data of the collimating lens The direction in which the collimating lens generates astigmatism so that the collimating lens cancels astigmatism of the entire optical head among the plurality of directions. It tilted and has the third step of the fixed to the fixing member. Therefore, not only the astigmatism due to the astigmatism of the semiconductor laser but also the astigmatism of the entire optical head can be reduced. As a result, astigmatism can be reduced even when the astigmatism occurrence direction of the entire optical head is different. Further, the angle adjustment of the collimating lens is easy.

  An optical recording / reproducing apparatus according to a tenth aspect of the invention includes the optical head according to the fifth aspect. Therefore, the best jitter point where the jitter of the information reading signal is the lowest coincides with the focal position where the level of the tracking error signal is highest. As a result, the jitter margin increases (error rate decreases).

Embodiment 1 FIG.
FIG. 1 is a schematic diagram showing a configuration of an optical system of an optical head 1 according to Embodiment 1 of the present invention. As shown in FIG. 1, the optical head 1 has a semiconductor laser 3 as a light source for emitting a light beam. A diffraction grating 4 is disposed at a predetermined position on the light emitting side of the semiconductor laser 3. On one side of the diffraction grating 4, a light beam having a predetermined wavelength emitted from the semiconductor laser 3 is divided into three light beams (a zero-order main beam 14 and ± first-order sub beams 15a and 15b). A diffraction grating pattern is formed. That is, the diffraction grating 4 collects ± first-order sub-beams 15a and 15b at symmetrical positions on the information recording surface of the optical recording medium 2 with a predetermined distance in the track direction around the condensing position of the main beam 14. As described above, the light beam emitted from the semiconductor laser 3 is divided.

  On the light transmission side of the diffraction grating 4 as viewed from the semiconductor laser 3, a polarizing beam splitter 5, a quarter wave plate 6, a collimating lens 7 and an objective lens 8 are arranged in this order. In the polarization beam splitter 5, 90% or more of the P-polarized linearly polarized light components of the main beam 14 and the ± first-order sub-beams 15 a and 15 b from the diffraction grating 4 are transmitted to the quarter-wave plate 6. On the other hand, the remaining several percent of the linearly polarized light component of the P-polarized light is reflected by the polarization beam splitter 5 and enters the front monitor photodetector 9. In the polarization beam splitter 5, the S-polarized linearly polarized light component from the quarter-wave plate 6 is reflected almost 100% and enters a sensor lens 10 described later.

  The quarter-wave plate 6 converts the P-polarized linearly polarized component (hereinafter referred to as “outgoing light beam”) of the main beam 14 and the ± first-order sub beams 15a and 15b from the polarizing beam splitter 5 into a circularly polarized component. And the circularly polarized light component from the collimating lens 7 is converted into a linearly polarized light component in a direction orthogonal to the polarization direction of the forward light beam, that is, the linearly polarized light component of the S-polarized light.

  The collimating lens 7 converts the diffused light from the quarter-wave plate 6 into parallel light, and converts the parallel light from the objective lens 8 into focused light. The collimating lens 7 is optically recorded when its optical axis 26 (see FIG. 6) is orthogonal to the optical axis 16 of the entire optical system and a beam spot is formed on the information recording surface of the optical recording medium 2. The medium 2 is configured so as to be disposed at a predetermined angle θ with respect to a direction parallel to the radial direction of the medium 2 (hereinafter referred to as “radial direction”) (see FIGS. 1, 3, 4, and 6). . Further, the collimating lens 7 is optically recorded when its optical axis 26 (see FIG. 7) is orthogonal to the optical axis 16 of the entire optical system and a beam spot is formed on the information recording surface of the optical recording medium 2. The medium 2 is configured to be inclined by a predetermined angle φ with respect to a direction parallel to the circumferential direction of the medium 2 (hereinafter referred to as “tangential direction”) (see FIGS. 5 and 7).

  In FIG. 1, for simplicity of explanation, the collimating lens 7 has a flat surface (back surface) facing the quarter-wave plate 6 and a surface (front surface) facing the objective lens 8. It is shown that it is composed of one spherical lens that is a spherical surface. However, the actual collimating lens 7 is composed of, for example, 2 to 4 spherical lenses. Details of the configuration relating to the arrangement of the collimating lens 7 will be described later.

  The objective lens 8 condenses the parallel light from the collimating lens 7 on the information recording surface of the optical recording medium 2 and converts the reflected light from the optical recording medium 2 into parallel light. The front monitor photodetector 9 measures the light intensity of the light beam emitted from the semiconductor laser 3. Based on the output of the front monitor photodetector 9, the output of the semiconductor laser 3 is adjusted.

  On the other hand, the sensor lens 10, the cylindrical lens 11, and the light receiving elements 12, 13a, and 13b are arranged in this order on the light reflection side of the polarization beam splitter 5 when viewed from the quarter wavelength plate 6. The sensor lens 10 expands the main beam 14 and the ± first-order sub beams 15a and 15b reflected by the optical recording medium 2 at a predetermined optical system magnification. The sensor lens 10 is configured to be movable in the optical axis direction when the optical head 1 is assembled and adjusted. That is, by moving the sensor lens 10 in the optical axis direction, the main beam 14 reflected by the optical recording medium 2 and the ± first-order sub-beams 15a and 15b on the light receiving surfaces of the light receiving elements 12, 13a and 13b. The in-focus position can be optically adjusted.

  The cylindrical lens 11 gives the light beam from the sensor lens 10 astigmatism for detecting a defocus error, and changes the light beam only in the width direction (curvature direction) and in the length direction. Forms a linear beam without any change and forms images individually on the light receiving elements 12, 13a and 13b. The sensor lens 10 and the cylindrical lens 11 may be replaced with one anamorphic lens having both functions.

  The light receiving element 12 receives a main beam 14 reflected by the information recording surface of the optical recording medium 2 among light beams having a predetermined wavelength emitted from the light emitting region of the semiconductor laser 3. Similarly, the light receiving element 13 a receives the + 1st order sub beam 15 a reflected by the information recording surface of the optical recording medium 2 among light beams having a predetermined wavelength emitted from the light emitting region of the semiconductor laser 3. The light receiving element 13 b receives the −1st order sub beam 15 b reflected by the information recording surface of the optical recording medium 2 among the light beams having a predetermined wavelength emitted from the light emitting region of the semiconductor laser 3. The light receiving elements 12, 13a and 13b independently photoelectrically convert each received light beam in each divided light receiving region and output an electrical signal.

  In addition to the optical system shown in FIG. 1, the optical head 1 includes an objective lens driving device 17 that drives the objective lens 8 and a housing 18 as shown in FIG. 2. The housing 18 is made of, for example, a metal such as aluminum (Al), zinc (Zn), or magnesium (Mg), or a synthetic resin such as liquid crystal polymer (LCP).

  A laser holder 19 in which the semiconductor laser 3 is accommodated is inserted into an attachment hole (not shown) formed in the outer peripheral surface 18a of the housing 18, and is fixed by an adhesive or the like. Further, inside the housing 18, although not shown, the diffraction grating 4, the polarizing beam splitter 5, the quarter wavelength plate 6, the collimator lens 7, the front monitor photodetector 9, the sensor lens 10, The cylindrical lens 11 and the light receiving elements 12, 13a and 13b are accommodated.

  FIG. 3 is a perspective view showing a configuration of a main part to which the collimating lens 7 which is a feature of the present invention is attached, and FIG. 4 is a plan view of the main part of the housing shown in FIG. On the floor portion 21 of the housing 18, two support columns 22 and 23 are provided upright at positions substantially perpendicular to the optical axis 16 of the entire optical system. The columns 22 and 23 are formed integrally with the housing 18. The interval W2 between the columns 22 and 23 shown in FIGS. 3 and 4 is substantially equal to the width W1 of the collimating lens 7 shown in FIG.

  The column 22 has a side surface 22 a that is in contact with a reference line 24 that is orthogonal to the optical axis 16 of the entire optical system, and rises substantially perpendicular to the floor 21. Further, the support 22 is formed with a side surface 22b that extends to the top at an angle φ with respect to the vertical line, continuous to the side surface 22a that rises substantially perpendicular to the floor portion 21. This angle φ is an angle for inclining the collimating lens 7 in the tangential direction by bringing the back surface of the collimating lens 7 into contact with the side surface 22 b of the support column 22. 3 and 4, the reference line 25 is a virtual line that is parallel to the reference line 24 and passes through the principal point of the collimating lens 7. The height h of the side surface 22a is approximately half of the height H of the collimating lens 7. This is because the collimating lens 7 can be tilted with high accuracy even when the back surface of the collimating lens 7 is brought into contact with either the side surface 22a or the side surface 22b of the column 22.

  On the other hand, as shown in FIGS. 3 and 4, the column 23 rises with the side surface 23 a inclined at an angle θ with respect to the reference line 24 orthogonal to the optical axis 16 of the entire optical system. This angle θ is an angle for inclining the collimating lens 7 in the radial direction by contacting the back surface of the collimating lens 7.

  Next, a method of fixing the collimating lens 7 to the housing 18 of the optical head 1 having the above configuration will be described with reference to FIGS. As a premise, in the optical system shown in FIG. 1 provided inside the housing 18, the optical components other than the collimating lens 7 and the semiconductor laser 3 are already adjusted and fixed. Further, as shown in FIG. 5, the collimating lens 7 is temporarily fixed in a state where the back surface is in contact with the side surface 22 a (not shown) of the support column 22.

  In the state described above, the astigmatism of the entire optical head 1 having the above configuration is measured. Based on the measurement result and the characteristic data of the collimating lens 7, if the collimating lens 7 is permanently fixed in any of the following states (a), (b), or (c): It can be determined whether or not the astigmatism of the collimating lens 7 can be generated so as to cancel the astigmatism of the entire optical head 1 having the above configuration.

(A) A state in which the back surface of the collimating lens 7 is in contact with a side surface 22a (not shown) of the column 22 as shown in FIG. 5 (b) As shown in FIG. State in contact with side surface 23a (not shown) (c) State in which rear surface of collimating lens 7 is in contact with side surface 22b (not shown) of support 22 as shown in FIG.

  Therefore, the collimating lens 7 is permanently fixed in any one of the state (a), the state (b), or the state (c) based on the above measurement result. For example, when the collimating lens 7 having a focal length of 6 mm is tilted by 1 ° with respect to the radial direction, astigmatism of about 0.015 λrms can be corrected. λ represents the wavelength of the light beam emitted from the semiconductor laser.

  By the way, when a general collimating lens is tilted with respect to the optical axis, astigmatism and coma occur. However, the collimating lens 7 used in the optical head 1 satisfies the sine condition so that coma and spherical aberration can be removed simultaneously. For example, FIG. 8 shows an example of changes in astigmatism (curve a) and coma aberration (curve b) when the collimating lens 7 having a focal length of 26 mm is tilted with respect to the direction perpendicular to the optical axis. Yes. In FIG. 8, the unit λ on the vertical axis indicates the wavelength of the laser beam. From FIG. 8, it can be seen that the amount of increase in coma (curve b) is very small compared to the amount of increase in astigmatism (curve a). Therefore, even if the collimating lens 7 is tilted to correct the astigmatism of the entire optical head 1 having the above configuration, the coma aberration hardly increases, and the influence of the coma aberration can be ignored.

  Thus, according to the first embodiment of the present invention, the columns 22 and 23 for fixing the collimating lens 7 of the housing 18 in which the optical system of the optical head 1 is accommodated are provided. Side surfaces 22 a, 22 b, and 23 a are formed on these columns 22 and 23 in order to generate astigmatism in the collimating lens 7 so as to cancel the astigmatism of the entire optical head 1.

  (A) The side surface 22a is for making the back surface of the collimating lens 7 orthogonal to the optical axis 16 of the entire optical system. (B) The side surface 22b is for tilting the back surface of the collimating lens 7 by an angle θ in the radial direction with respect to the optical axis 16 of the entire optical system. (C) The side surface 23a is for inclining the back surface of the collimating lens 7 by an angle φ in the tangential direction with respect to the optical axis 16 of the entire optical system.

  Therefore, according to the first embodiment of the present invention, not only astigmatism due to the astigmatism of the semiconductor laser 3 but also astigmatism of the entire optical head 1 can be reduced. As a result, astigmatism can be reduced even when the astigmatism generation direction of the entire optical head 1 is different. For this reason, the focal position where the level of the information reading signal when the information recording surface of the optical recording medium 2 is reproduced can be matched with the focal position where the level of the tracking error signal is optimal. Thereby, the tolerance with respect to a defocus can be made high.

  In the optical recording / reproducing apparatus provided with the optical head 1 described above, the best jitter point where the jitter of the information read signal is lowest coincides with the focal position where the level of the tracking error signal is highest. As a result, the jitter margin increases (error rate decreases).

  Furthermore, according to the first embodiment of the present invention, as is apparent from FIGS. 5 to 7, the collimating lens 7 is in any of the above-described states (a), (b), and (c). Even so, the back surface of the collimating lens 7 hardly deviates from the reference line 24. That is, the principal point of the collimating lens 7 does not deviate from the optical axis 16 of the entire optical system. For this reason, since the collimating lens 7 can be tilted without changing the distance from the semiconductor laser 3 to the principal point of the collimating lens 7, the light emitted from the collimating lens 7 becomes convergent light or divergent light, and spherical aberration occurs. There is nothing.

  Further, according to the first embodiment of the present invention, the rear surface of the collimating lens 7 is brought into contact with the side surfaces 22a and 22b of the support column 22 or the side surface 23a of the support column 23, and then it is only fixed by an adhesive or the like. . Accordingly, the angle adjustment of the collimating lens 7 is easy. Furthermore, since it is only necessary to process the conventionally provided support columns, the number of parts does not increase and the cost does not increase.

Embodiment 2. FIG.
FIG. 9 is a schematic diagram showing a configuration of an optical recording / reproducing apparatus according to Embodiment 2 of the present invention. This optical recording / reproducing apparatus includes the optical head 1 according to the first embodiment, a spindle motor 31, a spindle motor drive circuit 32, a controller 33, a feed motor 34, a feed motor drive circuit 35, and a laser drive. The circuit 36 and the lens driving circuit 37 are roughly configured.

  The spindle motor drive circuit 32 rotates the optical recording medium 2 by driving the spindle motor 31 under the control of the controller 33. The controller 33 controls the spindle motor drive circuit 32, the feed motor drive circuit 35, the laser drive circuit 36 and the lens drive circuit 37 based on the photodetector detection signal supplied from the optical head 1.

  The feed motor drive circuit 35 drives the feed motor 34 under the control of the controller 33 to move the optical head 1 in the radial direction of the optical recording medium 2. The laser drive circuit 36 generates a laser drive signal for driving the semiconductor laser 3 (see FIG. 1) constituting the optical head 1 under the control of the controller 33 and supplies the laser drive signal to the optical head 1. The lens drive circuit 37 generates a lens drive signal for controlling the focusing, tracking, and tilt of the objective lens 8 constituting the optical head 1 under the control of the controller 33 and supplies the lens drive signal to the optical head 1.

  The controller 33 includes a focus servo tracking circuit 41, a tracking servo tracking circuit 42, a skew adjustment circuit 43, and a laser control circuit 43. The focus servo tracking circuit 41 is a focus for focusing the light beam emitted from the optical head 1 on the information recording surface of the rotating optical recording medium 2 based on the photodetector detection signal supplied from the optical head 1. A servo signal is generated and supplied to the lens driving circuit 37.

  The tracking servo tracking circuit 42 determines the beam spot of the light beam emitted from the optical head 1 with respect to the eccentric signal track of the optical recording medium 2 based on the photodetector detection signal supplied from the optical head 1. A tracking servo signal for tracking is generated and supplied to the lens driving circuit 37. The skew adjustment circuit 43 generates a skew adjustment signal for tilting the objective lens 8 (see FIG. 1) constituting the optical head 1 in the radial direction or the tangential direction based on the photodetector detection signal supplied from the optical head 1. Generated and supplied to the lens driving circuit 37. The laser control circuit 43 generates an appropriate laser drive signal based on the recording condition setting information recorded on the optical recording medium 2 extracted from the photodetector detection signal supplied from the optical head 1.

  The controller 33 may be configured by hardware such as a digital signal processor (DSP) and a sequencer, and the CPU (central processing unit) is configured by the focus servo tracking circuit 41, the tracking servo tracking circuit 42, the skew adjustment circuit 43, and the like. You may comprise so that the process which the said laser control circuit 43 performs may be performed based on a program.

  Thus, according to Embodiment 2 of the present invention, an optical recording / reproducing apparatus is configured using the optical head 1 according to Embodiment 1 described above. Therefore, the optical recording / reproducing apparatus matches the focal position where the level of the information read signal when reproducing the information recording surface of the optical recording medium 2 is the best with the focal position where the level of the tracking error signal is optimal. Can do. Thereby, the tolerance with respect to a defocus can be made high. In addition, the jitter best point at which the jitter of the information reading signal is lowest coincides with the focal position at which the level of the tracking error signal is highest. As a result, the jitter margin increases (error rate decreases).

Embodiment 3 FIG.
In the first and second embodiments described above, an example of an optical head provided with one semiconductor laser as a light source or an optical recording / reproducing apparatus provided with only one optical head has been described. However, the present invention is not limited to this. . The present invention can also be applied to an optical head provided with a plurality of light sources and an optical recording / reproducing apparatus provided with a plurality of optical heads. Such an optical head and an optical recording / reproducing apparatus are disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-295982.

As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to these embodiments, and the design can be changed without departing from the scope of the present invention. Is included in the present invention.
For example, in the first embodiment described above, the example in which the astigmatism is adjusted by tilting the collimating lens 7 in the radial direction or the tangential direction with respect to the optical axis of the entire optical system has been described, but the present invention is not limited thereto. For example, the astigmatism may be adjusted by tilting the collimating lens 7 in a direction rotated by 45 ° with respect to the optical axis of the entire optical system.

In Embodiment 1 described above, an example in which the collimating lens 7 is provided between the quarter-wave plate 6 and the objective lens 8 has been described, but the present invention is not limited to this. For example, the collimating lens 7 may be provided between the semiconductor laser 3 and the diffraction grating 4.
In the first embodiment described above, an example in which the collimating lens 7 is fixed to the columns 22 and 23 formed integrally with the housing has been described, but the present invention is not limited to this. The member for fixing the collimating lens 7 is not limited to the support columns 22 and 23, and may be any shape fixing member. After the collimating lens 7 is fixed to the floor 21 without being formed integrally with the housing, the collimating lens 7 is fixed. It may be configured as described above.

It is the schematic which shows the structure of the optical system of the optical head which concerns on Embodiment 1 of this invention. It is a perspective view which shows the external appearance structure of the optical head shown in FIG. It is a perspective view which shows the principal part structure of the housing which comprises the optical head shown in FIG. It is a top view of the housing principal part shown in FIG. It is a top view for demonstrating the method to fix a collimating lens to a housing. It is a top view for demonstrating the method to fix a collimating lens to a housing. It is a side view for demonstrating the method to fix a collimating lens to a housing. It is a figure which shows an example of the relationship of the astigmatism and coma aberration with respect to the inclination angle of a collimating lens. It is the schematic which shows the structure of the optical recording / reproducing apparatus which concerns on Embodiment 2 of this invention.

Explanation of symbols

1 Optical head
2 Optical recording media
3 Semiconductor laser
4 Diffraction grating
5 Polarizing beam splitter
6 quarter wave plate
7 Collimating lens
8 Objective lens
9 Light detector for front monitor
10 Sensor lens
11 Cylindrical lens
12, 13a, 13b Light receiving element
14 0th-order main beam
15a + 1st order secondary beam
15b-1st order secondary beam
16 Optical axis of the entire optical system
26 Optical axis of collimating lens 7
17 Objective lens drive
18 Housing
18a outer surface
19 Laser holder
21 Floor
22, 23 Prop (fixing member)
22a, 22b, 23a Side
24,25 Reference line
31 Spindle motor
32 Spindle motor drive circuit
33 controller
34 Feed motor
35 Feed motor drive circuit
36 Laser drive circuit
37 Lens drive circuit
41 Focus servo tracking circuit
42 Tracking servo tracking circuit
43 Skew adjustment circuit
44 Laser control circuit

Claims (10)

In a housing of an optical head in which an optical system including a collimating lens that converts a diffused light beam emitted from a semiconductor laser into parallel light is accommodated,
The fixing member to which the collimating lens is fixed is configured to be able to fix the collimating lens by tilting the collimating lens in a plurality of directions with respect to the optical axis of the optical system.   The fixing member is provided with a plurality of surfaces corresponding to the plurality of directions with which the surfaces of the collimating lens come into contact in order to incline and fix the collimating lens in the plurality of directions. The optical head housing according to claim 1.   The fixing member is provided so that the distance from the emission surface of the semiconductor laser to the principal point of the collimating lens is equal even when the collimating lens is tilted and fixed in any of the plurality of directions. The optical head housing according to claim 1, wherein the optical head housing is provided.   4. The optical head housing according to claim 1, wherein the plurality of directions are at least a direction perpendicular to an optical axis of the optical system, a radial direction, and a tangential direction.   5. The optical head housing according to claim 1, wherein the collimating lens is astigmatized so as to cancel astigmatism of the entire optical head among the plurality of directions. An optical head that is tilted in a direction in which aberrations occur and is fixed to the fixing member. In a method of manufacturing an optical head having a housing in which an optical system including a collimating lens that converts a light beam emitted from a semiconductor laser and diffusing into parallel light is accommodated,
In the housing, a fixing member is formed so that the collimator lens can be fixed by being inclined in a plurality of directions with respect to the optical axis of the optical system.
A first step of temporarily fixing the collimating lens to the fixing member by inclining in a direction perpendicular to the optical axis of the optical system;
A second step of measuring astigmatism of the entire optical head;
Based on the measurement result of the second step and the characteristic data of the collimating lens, the collimating lens is arranged so that the astigmatism of the entire optical head is canceled out of the plurality of directions. A method of manufacturing an optical head, comprising: a third step of inclining in a direction in which astigmatism is generated and permanently fixing to the fixing member. The fixing member is provided with a plurality of surfaces corresponding to the plurality of directions with which the surface of the collimating lens comes into contact in order to incline and fix the collimating lens in the plurality of directions.
In the third step, the surface of the collimating lens is fixed in correspondence with a direction in which the collimating lens generates astigmatism so as to cancel out astigmatism of the entire optical head among the plurality of directions. The method of manufacturing an optical head according to claim 1, wherein the optical head is fixed to the fixing member in contact with the surface of the member.   The fixing member is provided so that the distance from the emission surface of the semiconductor laser to the principal point of the collimating lens is equal even when the collimating lens is tilted and fixed in any of the plurality of directions. 8. The method of manufacturing an optical head according to claim 6, wherein the optical head is manufactured.   9. The method of manufacturing an optical head according to claim 5, wherein the plurality of directions are at least a direction orthogonal to an optical axis of the optical system, a radial direction, and a tangential direction.   An optical recording / reproducing apparatus comprising the optical head according to claim 5.

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