JP4650550B2 - Optical pickup device - Google Patents

Description

  The present invention relates to an optical pickup device used when reading information from an optical recording medium or writing information on an optical recording medium. More specifically, the present invention relates to a technique suitable for an optical pickup device in which an objective lens that condenses light from a light source on an information recording surface of an optical recording medium is made of resin.

  Conventionally, reading of information recorded on an optical disc (optical recording medium) such as a Blu-ray disc (BD) and writing of information on the optical disc are performed using an optical pickup device. The optical pickup device is provided with an objective lens that condenses light from a light source on an information recording surface of an optical disc. Conventionally, for this objective lens, in order to reduce the cost of the optical pickup device, for example, a resin lens is sometimes used instead of a glass lens (see, for example, Patent Documents 1 and 2).

  By the way, the resin lens is easily affected by fluctuations in the environmental temperature, and if the objective lens included in the optical pickup device is a resin lens, the influence of spherical aberration that occurs with changes in the environmental temperature becomes a problem. As a countermeasure against spherical aberration caused by fluctuations in environmental temperature, for example, a diffraction groove is formed in the objective lens itself to suppress the spherical aberration.

However, in an objective lens having a high NA (for example, NA = 0.85) provided in an optical pickup device that can handle BD, it is not easy to suppress spherical aberration by providing a diffraction groove in the objective lens itself. .
Japanese Patent Laid-Open No. 10-40569 JP 2003-287675 A

  In view of the above, the present applicant has confirmed that a collimator lens (a lens that converts incident light into parallel light, which is conventionally provided in an optical pickup device, is disposed in an optical path between a light source and an objective lens. Is being movable in the direction of the optical axis, and a method of suppressing spherical aberration by moving the position of the collimating lens as the environmental temperature varies is being studied. When the collimating lens is moved in the optical axis direction, the convergence state or divergence state of the light incident on the objective lens changes. Then, by adjusting this convergence state or diverging state, it is possible to suppress spherical aberration that occurs in the objective lens.

  However, the applicant has found the following problems while studying such a method. FIG. 10 is a diagram illustrating a change in jitter characteristics of the optical pickup device with respect to a change in environmental temperature, where the horizontal axis represents the environmental temperature and the vertical axis represents the jitter value. In FIG. 10, white circles indicate the jitter characteristics when the setting of the optical pickup device is not adjusted at all (unadjusted) even when the environmental temperature varies. The white triangle marks indicate the jitter characteristics when the collimating lens position is adjusted in accordance with changes in the environmental temperature.

  In order to obtain the result of FIG. 10, the configuration of the optical pickup device was adjusted so that the best jitter characteristic value was obtained at 25 ° C. In addition, the position of the collimating lens at each temperature was examined at a position where the jitter characteristic was the best for each environmental temperature, and was arranged at such a position.

  According to FIG. 10, it can be seen that the jitter characteristic is improved (that is, the reproduction performance is improved) by changing the position of the collimating lens in accordance with the environmental temperature change in the configuration of the optical pickup device. However, it can be seen that the jitter characteristics are not very good even when the collimating lens position is adjusted, particularly on the low temperature side. In other words, it has been found that sufficient reproduction characteristics may not be obtained simply by moving the collimating lens position with temperature fluctuations so that spherical aberration generated in the objective lens due to fluctuations in environmental temperature can be corrected. .

  Accordingly, an object of the present invention is to provide an optical pickup device in which reproduction characteristics are not deteriorated even when an objective lens for condensing light from a light source on an information recording surface of an optical recording medium is a resin lens.

  In order to achieve the above object, an optical pickup device of the present invention includes a light source, an objective lens that focuses light emitted from the light source on an information recording layer of an optical recording medium, and a space between the light source and the objective lens. A movable lens that adjusts the convergence or divergence state of light that moves in the direction of the optical axis and reaches the objective lens, lens position adjusting means that adjusts the position of the movable lens, and the objective lens A tilt amount adjusting means for adjusting the tilt amount of the light source, and a temperature detecting means for detecting an environmental temperature, wherein the objective lens is disposed to be inclined with respect to an optical axis of light from the movable lens to the objective lens. When the change in the environmental temperature is detected, the position of the movable lens is changed and the tilt amount of the objective lens is changed.

  As described above, when the objective lens is a resin lens, it is necessary to correct the spherical aberration that occurs due to a change in environmental temperature. In this regard, according to this configuration, the spherical aberration can be corrected by moving the movable lens. On the other hand, in this configuration, in order to correct the influence of coma aberration of the objective lens at the time of manufacturing the optical pickup device, the objective lens is inclined with respect to the optical axis of light from the movable lens to the objective lens. To do. In such a configuration, coma aberration occurs when the position of the movable lens is moved for the purpose of correcting spherical aberration. Therefore, in this configuration, the position of the movable lens is changed in accordance with the change in the environmental temperature, and the tilt amount of the objective lens is also changed, so that the spherical aberration and the coma are corrected simultaneously. Therefore, according to this configuration, even when the objective lens is a resin lens, it is possible to appropriately suppress the influence of aberration due to temperature fluctuation.

  As a more specific configuration of the optical pickup device having the above-described configuration, the tilt amount adjusting unit adjusts the tilt amount by tilting the objective lens in a direction around a specific axis, and the objective lens is The direction tilted with respect to the optical axis of light from the movable lens to the objective lens may be a direction in which coma aberration can be corrected by tilting the objective lens by the tilt amount adjusting means. In this configuration, the specific axis is preferably an axis orthogonal to the focus direction and the track direction.

  In the optical pickup device having the above configuration, it is preferable that the tilt amount adjusting unit adjusts the tilt amount of the objective lens by tilting a lens holder that holds the objective lens. According to this configuration, it is possible to obtain the tilt amount adjusting means by simply changing the configuration of the objective lens actuator provided for moving the objective lens in the focus direction or the track direction.

  In the optical pickup device having the above-described configuration, the optical pickup device further includes a storage unit that stores in advance information on the position of the movable lens corresponding to the environmental temperature and the tilt amount, and when the change in the environmental temperature is detected, the storage unit The position of the movable lens and the tilt amount of the objective lens may be changed based on the stored information on the position of the movable lens and the tilt amount. According to this configuration, when the environmental temperature fluctuates, a setting that can appropriately suppress aberration can be quickly obtained.

  In the optical pickup device having the above-described configuration, the optical pickup apparatus further includes a storage unit that stores in advance information on the movable lens position corresponding to the environmental temperature, and the movable unit stored in the storage unit when a change in the environmental temperature is detected. The position of the movable lens may be changed based on the lens position information, and the optimum tilt amount may be determined while changing the tilt amount after the adjustment of the movable lens position.

  In the optical pickup device configured as described above, the movable lens is preferably a collimating lens. As a means for correcting spherical aberration by adjusting the convergence or divergence state of light reaching the objective lens, for example, there is a technique using a beam expander. A beam expander is usually provided with at least one movable lens. For this reason, the movable lens of the present invention can be a movable lens provided in a beam expander. However, it is preferable that the movable lens is a collimating lens as in this configuration because the number of components of the optical system provided in the optical pickup device can be reduced.

  According to the optical pickup device of the present invention, even when the objective lens that condenses the light from the light source on the information recording surface of the optical recording medium is a resin lens, the aberration is appropriately suppressed in response to the fluctuation of the environmental temperature. It is possible. That is, according to the present invention, it is possible to provide an optical pickup device in which reproduction characteristics are not deteriorated even when the objective lens is a resin lens.

  Hereinafter, embodiments of an optical pickup device of the present invention will be described with reference to the drawings.

(Configuration of optical pickup device)
First, the configuration of the optical pickup device of the present embodiment will be described with reference to FIGS. FIG. 1 is a schematic plan view showing the configuration of the optical pickup device of the present embodiment. FIG. 2 is a schematic diagram for explaining a configuration of an optical system provided in the optical pickup device of the present embodiment. FIG. 3 is a schematic plan view showing a configuration of a collimating lens position adjusting mechanism provided in the optical pickup device of the present embodiment. 4A and 4B are diagrams for explaining the configuration of the objective lens actuator provided in the optical pickup device of the present embodiment. FIG. 4A is a schematic perspective view showing the overall configuration of the objective lens actuator, and FIG. It is a schematic perspective view which shows the structure of the coil with which an objective lens actuator is provided.

  As shown in FIG. 1, the optical pickup device 1 of this embodiment includes a slide base 2. The slide base 2 is provided with two types of bearing portions 2a and 2b. Since the slide base 2 is slidably supported by the two guide shafts 71 extending in the radial direction using the bearing portions 2a and 2b, the optical pickup device 1 can move in the radial direction. The slide base 2 is moved by a known moving mechanism (not shown). As an example of a known moving mechanism, there is a configuration using a rack attached to the slide base 2 and a pinion rotated by a motor.

  An optical system as shown in FIG. 2 is mounted on the slide base 2. That is, on the slide base 2, the light source 11, the diffraction element 12, the polarization beam splitter 13, the ¼ wavelength plate 14, the collimator lens 15, the rising mirror 16, the objective lens 17, and the cylindrical lens. 18 and a photodetector 19 are mounted. The objective lens 17 is mounted on the slide base 2 while being mounted on the objective lens actuator 3.

  The light source 11 is composed of a semiconductor laser, and the optical pickup device 1 has a configuration corresponding to BD, and therefore emits a laser beam in the 405 nm band. The diffraction element 12 divides laser light emitted from the light source 11 into main light and two sub-lights. The reason why the light from the light source 11 is divided into three lights is to obtain a signal necessary for servo control.

  The polarization beam splitter 13 functions as an optical isolator in cooperation with the quarter wavelength plate 14. That is, the polarization beam splitter 13 reflects the laser light from the light source 11 and guides it to the optical disc 70 side, but transmits the return light reflected by the optical disc 70 and guides it to the photodetector 19 side.

  The collimating lens 15 is a lens that converts incident laser light into parallel light. However, in the optical pickup device 1, the collimating lens 15 is movable in the direction of the optical axis (the direction of the arrows pointing to the left and right in FIG. 2). For this reason, the laser light emitted from the light source 11 and emitted from the collimator lens 15 is not necessarily parallel light but may be convergent light or divergent light. The reason why the position of the collimating lens 15 can be adjusted in this way is to suppress the spherical aberration by adjusting the convergence state or divergence state of the laser light incident on the objective lens 17 by moving the position of the collimating lens 15. It is. The collimating lens 15 is an embodiment of the movable lens of the present invention.

  The means for adjusting the position of the collimating lens 15 is not particularly limited as long as the position of the collimating lens 15 in the optical axis direction can be adjusted. For example, the position of the collimating lens 15 can be adjusted using the collimating lens position adjusting mechanism 6 as shown in FIG. The collimating lens position adjusting mechanism 6 is disposed on the slide base 6. The collimating lens position adjusting mechanism 6 is an embodiment of the lens position adjusting means of the present invention.

  Referring to FIG. 3, collimator lens position adjustment mechanism 6 holds collimator lens 15, and a movable holder 61 provided so as to be movable, and two guides for guiding movable holder 61 to move in the optical axis direction. A shaft 62, a lead screw 64 that meshes with a lead nut 63 attached to the movable holder 61, and a stepping motor 65 that rotates the lead screw 64 are provided. Although not shown, a photo interrupter is also provided so that the reference position can be determined. With this configuration, the collimator lens 15 can be moved in the optical axis direction together with the movable holder 61 by rotating the lead screw 64 with the stepping motor 65. The position of the collimating lens 15 can be adjusted by the number of steps of the stepping motor 65.

  Returning to FIG. 2, the rising mirror 16 reflects the laser beam sent from the collimating lens 15. Thereby, the traveling direction of the laser light emitted from the light source 11 is bent, and becomes a light traveling in a direction orthogonal to the information recording surface 70 a of the optical disk 70.

  The objective lens 17 focuses the laser beam sent from the rising mirror 16 on the information recording surface 70 a of the optical disc 70. As described above, the objective lens 17 is mounted on the objective lens actuator 3. Then, the objective lens actuator 3 causes the objective lens 17 to move toward and away from the optical disc 70 (up and down direction in FIG. 2) and in a direction parallel to the radial direction of the optical disc 70 (in FIG. 2, with respect to the paper surface). In a direction perpendicular to the track direction). Further, the objective lens actuator 3 can tilt the objective lens 17 in the direction around the axis orthogonal to the focus direction and the track direction. That is, the tilt amount of the objective lens 17 can be adjusted by the objective lens actuator 3, and the objective lens actuator 3 is an embodiment of the tilt amount adjusting means of the present invention.

  With reference to FIG. 4, the structure of the objective lens actuator 3 with which the optical pick-up apparatus 1 is provided is demonstrated. The objective lens actuator 3 includes an act base 31 and a lens holder 32 that holds the objective lens 17. On the act base 31, a pair of permanent magnets 33 are erected so as to be symmetrically arranged with the lens holder 32 interposed therebetween.

  One end of each of the wires 34 is fixed to the lens holder 32, three wires on one side and six wires on both sides. The other end of each wire 34 is fixed to a circuit board 35 erected on the act base 31, so that the lens holder 32 is swingably supported by the wire 34.

  The lens holder 32 includes a focus coil 321 disposed so as to surround the optical axis of the objective lens 17 along the inner side wall of the lens holder 32, and an outer side wall of the lens holder 32 (a side wall facing the permanent magnet 33). The four track coils 322 that are each arranged at two symmetrical positions, and the two tilt coils 323 that are arranged symmetrically on the lower side of the focus coil 321 inside the lens holder 32 are attached. It has been. A current is supplied to these coils 321 to 323 via a wire 34.

  When a current flows through the focus coil 321, the objective lens 17 moves in the focus direction F together with the lens holder 32 according to the direction in which the current flows and the magnitude of the current due to the electromagnetic action with the magnetic field generated by the permanent magnet 33. To do. Similarly, when a current flows through the track coil 322, the objective lens 17 moves in the track direction T together with the lens holder 32 according to the direction and size.

  Further, when a current flows through the tilt coil 323, the objective lens 17 moves along an axis (indicated by a broken line in FIG. 3A) perpendicular to the focus direction and the tracking direction together with the lens holder 32 according to the direction and size. It rotates in the direction R around the axis. By this rotation, the objective lens 17 is tilted (tilted).

  Returning again to FIG. 2, the return light reflected by the information recording layer 70 a passes through the objective lens 17, the rising mirror 16, the collimating lens 15, the quarter wavelength plate 14, and the polarization beam splitter 13 in this order, and is cylindrical. It is sent to the lens 18. The cylindrical lens 18 gives astigmatism to the incident laser light. The astigmatism is given by the cylindrical lens 18 in order to obtain a signal necessary for performing the servo control.

  The laser beam given astigmatism by the cylindrical lens 18 is focused on the light receiving region of the photodetector 19. The photodetector 19 converts the optical signal received in the light receiving area into an electrical signal and outputs it. The electrical signal output from the photodetector 19 is processed by the signal processing unit 20 to generate a reproduction signal, a focus error signal, a track error signal, and the like.

  The control unit 21 receives the focus error signal and the track error signal from the signal processing unit 20, and controls the objective lens actuator 3 based on these signals to perform servo control such as focus control and track control. Here, the focus control is control performed so that the focal position of the objective lens 17 always matches the information recording surface 70a. The track control is control performed so that the light spot condensed by the objective lens 17 always follows the track formed on the optical disc 70.

  Further, the control unit 21 adjusts the position of the collimating lens 15 using the collimating lens position adjusting mechanism 6 and the objective lens using the objective lens actuator 3 based on the environmental temperature information from the thermistor 5 (see FIG. 1). 17 tilt amount adjustment is performed. The reason for performing such adjustment and the details of the operation will be described later. In order to appropriately correct (suppress) the aberration generated in the light spot condensed on the information recording surface 70a by the objective lens 17, these adjustments are performed. Done.

  The thermistor 5 is provided to detect the environmental temperature of the optical pickup device 1 and is mounted on a printed wiring board 4 (see FIG. 1) disposed on the slide base 2. The thermistor 5 is an embodiment of the temperature detecting means of the present invention, but the temperature detecting means of the present invention is not limited to the thermistor, and may be appropriately changed to other configurations such as a thermocouple. Moreover, it is preferable that the temperature detection means of the present invention can detect the environmental temperature in the vicinity of the objective lens 17, and is not limited to the position of the present embodiment, and may be changed as appropriate.

(Operations associated with environmental temperature fluctuations in optical pickup devices)
Hereinafter, the operation accompanying the environmental temperature fluctuation of the optical pickup device 1 of the present embodiment will be described. However, before explaining the details of the operation, the reason for performing aberration correction not only by adjusting the position of the collimating lens 15 but also by adjusting the tilt amount of the objective lens 17 as the environmental temperature varies will be described.

  The objective lens 17 of the optical pickup device 1 is a resin lens formed of resin. For this reason, it is necessary to suppress the spherical aberration caused by the fluctuation of the environmental temperature. Therefore, in the optical pickup device 1, the ambient temperature is detected by the thermistor 5, and when there is a temperature variation, the collimating lens position adjusting mechanism 6 adjusts the position of the collimating lens 15 to correct the spherical aberration. Yes. However, as described above, sufficient aberration correction cannot be performed by simply adjusting the position of the collimating lens 15 with the collimating lens position adjusting mechanism 6 (see FIG. 10). For this reason, the optical pickup device 1 is configured to adjust the tilt amount of the objective lens 17 when the temperature fluctuates.

  Hereinafter, the reason why the tilt amount adjustment of the objective lens 17 is also performed when the temperature fluctuates will be described.

  In the optical pickup device 1 of the present embodiment, the following manufacturing method is adopted in order to correct the coma aberration of the objective lens 17 at the time of manufacturing. First, the objective lens 17 is mounted on the objective lens actuator 3 so that the coma aberration direction of the objective lens 17 is directed in the radial direction (same as the track direction T). In addition, about the direction of the coma aberration of the objective lens 17, the mark is normally formed so that the direction can be known at the time of objective lens manufacture.

  Next, when the objective lens actuator 3 is mounted on the slide base 2, the objective lens actuator 3 (specifically, the act base 31) is tilted in a direction to cancel the coma aberration of the objective lens 17. Since the coma aberration direction of the objective lens 17 is adjusted to be the radial direction (the same as the track direction T) as described above, the direction in which the objective lens actuator 3 is tilted is the focus direction F and the track direction T. And the direction around the axis perpendicular to both.

  When the optical pickup device 1 is configured as described above, the optical axis of the objective lens 17 is inclined with respect to the optical axis of the light emitted from the collimating lens 15 and reflected by the rising mirror 16. Thus, when the position of the collimating lens 15 is moved when the objective lens 17 is tilted, coma aberration occurs in the radial direction. Therefore, the optical pickup device 1 is configured to adjust the tilt amount of the objective lens 17 using the objective lens actuator 3 in accordance with the adjustment of the collimating lens position when the temperature fluctuates.

  Next, the operation accompanying the environmental temperature fluctuation of the optical pickup device 1 will be described with reference to FIG. FIG. 5 is a flowchart showing an operation example according to the environmental temperature of the optical pickup device of the present embodiment. FIG. 5 shows an example of an operation (reproduction operation) when reading information recorded on the optical disc. The same applies to the operation (recording operation) for writing information on the optical disc.

  When starting reading of information using the optical pickup device 1, the temperature detected by the thermistor 5 is confirmed by the control unit 21 (step S1). Then, the position setting of the collimating lens 15 and the tilt setting of the objective lens 17 are performed based on the confirmed temperature (step S2). Specifically, the control unit 21 reads out the optimum position of the collimator lens 15 and the tilt amount of the objective lens 17 for each environmental temperature, which are stored in advance in a memory 22 (see FIG. 2) provided in the optical pickup device 1. . Then, the control unit 21 controls the collimating lens position adjusting mechanism 6 and the objective lens actuator 3 so that the read position and tilt amount are obtained.

  Here, the optimum position of the collimating lens 15 and the tilt amount of the objective lens 17 stored in advance in the memory 22 will be described in more detail.

  FIG. 6 is a graph showing the relationship between the environmental temperature and the collimating lens position where the jitter value is minimized. In FIG. 6, the horizontal axis represents the environmental temperature (° C.), and the vertical axis represents the number of steps of the stepping motor 65 (the motor provided in the collimating lens position adjusting mechanism 6; see FIG. 3) that minimizes the jitter value. Note that the number of steps of the stepping motor 65 in FIG. 6 is the number of steps from the reference position (position determined using a photo interrupter or the like as described above), and the number of steps and the position of the collimating lens 15 are one-to-one. There is a relationship. Therefore, it can be said that the vertical axis in FIG. 6 represents the position of the collimating lens 15.

  As shown in FIG. 6, the relationship between the environmental temperature and the collimating lens position where the jitter value is minimum is substantially linear, and this relationship is uniquely determined for each optical pickup device. In consideration of this point, in the optical pickup device 1, the position of the collimator lens 15 (specifically, the number of steps of the stepping motor 65) at which the jitter value is minimized for each environmental temperature is obtained in advance by experiments or the like. The optimum collimating lens position for each temperature is tabulated and stored in the memory 22. In this way, it is possible to read the optimum position of the collimating lens 15 from the memory 22 corresponding to the environmental temperature, and to place the collimating lens 15 at that position.

  The memory 22 does not store the table as described above, but a relational expression between the environmental temperature and the number of steps of the stepping motor 65 that minimizes the jitter value (for example, a linear function as shown in FIG. 6). But of course.

  FIG. 7 is a graph showing the relationship between the environmental temperature and the tilt amount of the objective lens that minimizes the jitter value after adjusting the position of the collimating lens. In FIG. 7, the horizontal axis represents the environmental temperature (° C.), and the vertical axis represents the tilt amount (minute) of the objective lens at which the jitter value becomes minimum after adjusting the position of the collimating lens.

  As shown in FIG. 7, the tilt amount of the objective lens that minimizes the jitter value after adjusting the position of the collimating lens is uniquely determined when the environmental temperature is determined, and the set value is unique to each optical pickup device. Determined. In consideration of this point, in the optical pickup device 1, after adjusting the position of the collimating lens 15, the tilt amount of the objective lens 17 that minimizes the jitter value for each environmental temperature (specifically, supplied to the tilt coil 323. (Current value) is obtained in advance by experiments or the like, and the optimum tilt amount of the objective lens 17 for each temperature is tabulated and stored in the memory 22. In this way, the optimum tilt amount of the objective lens 17 can be read from the memory 22 in accordance with the environmental temperature, and the objective lens 17 can be tilted so as to be the tilt amount.

  The memory 22 does not store the table as described above, but a relational expression (for example, as shown in FIG. 7) between the ambient temperature and the tilt amount of the objective lens that minimizes the jitter value after adjusting the position of the collimating lens. Of course, it may be a curve approximation formula.

  Returning to FIG. 5, when the position setting of the collimating lens 15 and the tilt setting of the objective lens 17 are performed, reading (reproduction) of information recorded on the optical disk 70 is started thereafter (step S3). When the reproduction of information is started, the control unit 21 monitors whether or not the environmental temperature has changed (step S4). Whether or not there is a change in the environmental temperature is, for example, larger than the threshold value set in advance, based on the temperature at the time when the position of the collimator lens 15 and the tilt of the objective lens 17 are set first. Judge by whether or not. For example, if the temperature change is smaller than a preset threshold value, it is determined that there is no change in the environmental temperature, and if it is equal to or greater than the threshold value, it is determined that there is a change in the environmental temperature.

  When it is determined that there is no fluctuation in the environmental temperature (Yes at Step S4), it is confirmed whether or not the reproduction is to be ended (Step S5). At this time, if the reproduction is finished, the aberration correction operation corresponding to the temperature fluctuation is finished. On the other hand, if it is not the end of the regeneration, the process returns to step S4 to continue monitoring whether there is a change in the environmental temperature.

  If it is determined that the environmental temperature has changed (No at step S4), the position of the collimator lens 15 and the tilt amount of the objective lens 17 are read from the memory 22 based on the temperature at that time, and the read setting is obtained. The setting is changed as follows (step S6). After changing the setting, it is confirmed whether or not to end the reproduction (same as step S5 described above). At this time, if the reproduction is finished, the aberration correction operation corresponding to the temperature fluctuation is finished. On the other hand, if it is not the end of the regeneration, the process returns to step S4 to continue monitoring whether there is a change in the environmental temperature.

  FIG. 8 is a graph showing the relationship between the environmental temperature and the jitter characteristics in the optical pickup device 1. In FIG. 8, the horizontal axis represents the environmental temperature (° C.), and the vertical axis represents the jitter value. In the optical pickup device 1 of the present embodiment, the collimating lens position is adjusted in accordance with the environmental temperature variation, and the tilt amount of the objective lens is also adjusted. With this configuration, as shown in FIG. 8, even if the environmental temperature changes, the jitter value can be reduced at any temperature (see the black squares in FIG. 8), and the reproduction performance is improved. I understand that I can do it. In FIG. 8, white circles and triangles are graphs shown as comparative examples, which are the same as the graph shown in FIG.

(Other)
The embodiment described above is an example of the present invention, and the present invention is not limited to the embodiment described above. That is, various modifications can be made without departing from the object of the present invention.

  For example, in the embodiment described above, information on the position of the collimating lens 15 corresponding to the environmental temperature and the tilt amount of the objective lens 17 is stored in the memory 22 in advance, and there is a temperature fluctuation based on this information. In this case, the position of the collimator lens 15 and the tilt amount of the objective lens 17 are changed. However, the present invention is not limited to this configuration. For example, it can also be configured as follows. That is, only the position of the collimating lens 15 corresponding to the environmental temperature is stored in the memory 22 in advance, and the position of the collimating lens 15 is changed when there is a temperature change based on this. Thereafter, the tilt amount of the objective lens 17 that can most appropriately suppress the aberration is searched, and the objective lens 17 is set to the tilt amount determined by the search. FIG. 9 shows an operation example according to the environmental temperature of the optical pickup device in such a configuration.

  Referring to FIG. 9, when reading of information using optical pickup device 1 is started, the temperature detected by thermistor 5 is confirmed by control unit 21 (step S11). And based on the confirmed temperature, the position of the optimal collimating lens 15 memorize | stored beforehand in the memory 22 is read, and the collimating lens 15 is set to the position (step S12).

  Next, for example, when the tilt value of the objective lens 17 is varied while monitoring the jitter value (or the amplitude value of the RF signal, etc.), and the jitter value becomes the minimum (in the case of the amplitude of the RF signal, the maximum). ) Is detected (step S13). Then, the objective lens actuator 3 is controlled to set the tilt of the objective lens 17 so that the detected optimum tilt amount is obtained (step S14).

  When the tilt setting of the objective lens 17 is performed, reading (reproduction) of information recorded on the optical disc 70 is then started (step S15). When the reproduction of information is started, the control unit 21 monitors whether or not there is a change in the environmental temperature (step S16). When it is determined that there is no change in the environmental temperature (Yes at Step S16), it is confirmed whether or not the regeneration is finished (Step S17). At this time, if the reproduction is finished, the aberration correction operation corresponding to the temperature fluctuation is finished. On the other hand, if the reproduction is not finished, the process returns to step S16 to continue monitoring whether there is a change in the environmental temperature.

  On the other hand, if it is determined that the environmental temperature has changed (No at Step S16), the position of the collimating lens 15 is read from the memory 22 based on the temperature at that time, and the setting is changed to the read setting. (Step S18). After changing the setting, for example, the tilt amount of the objective lens 17 is varied while monitoring the jitter value, and the case where the jitter value is minimized is detected (step S19). Then, the objective lens actuator 3 is controlled to set the tilt of the objective lens 17 so that the detected tilt amount is obtained (step S20). Thereafter, it is confirmed whether or not to end the reproduction (same as step S17 described above). At this time, if the reproduction is finished, the aberration correction operation corresponding to the temperature fluctuation is finished. On the other hand, if it is not the end of the regeneration, the process returns to step S4 to continue monitoring whether there is a change in the environmental temperature.

  In the embodiment described above, the temperature information from the thermistor 5 is output to one control unit 21, and the one control unit 21 allows the collimating lens position adjusting mechanism 6 and The objective lens actuator 3 is controlled. However, the present invention is not limited to this configuration. That is, for example, separate control units may be provided for the collimating lens position adjusting mechanism 6 and the objective lens actuator 3. In this case, the temperature information from the thermistor 5 may be output to these separate control units.

  In the embodiment described above, the objective lens actuator 3 is used as means for adjusting the tilt amount of the objective lens 17. However, the present invention is not limited to this configuration. For example, a unit that tilts the entire optical pickup device may be provided, and thereby the tilt amount of the objective lens 17 may be adjusted. Further, the direction in which the objective lens is tilted for adjusting the tilt amount is not limited to the direction of the present embodiment. In this case, at the time of manufacturing the optical pickup device 1, the coma aberration direction of the objective lens 17 and the direction in which the objective lens actuator 3 is tilted must be adjusted to a direction different from that in the present embodiment.

  Moreover, in embodiment shown above, the movable lens in this invention showed the structure which is a collimating lens. However, it is not limited to this configuration. For example, a configuration may be adopted in which, for example, a beam expander is used to correct spherical aberration that occurs due to a change in environmental temperature, and the movable lens in the present invention is a movable lens provided in the beam expander.

  In addition, the present invention can be suitably applied to an optical pickup apparatus whose information is read or written, but it goes without saying that the present invention can also be applied to optical pickup apparatuses compatible with other types of optical disks.

  The present invention can be suitably applied to an optical pickup device in which an objective lens that condenses light from a light source on an information recording surface of an optical recording medium is formed of a resin lens.

These are the schematic plan views which show the structure of the optical pick-up apparatus of this embodiment. These are the schematic diagrams for demonstrating the structure of the optical system with which the optical pick-up apparatus of this embodiment is provided. These are the schematic plan views which show the structure of the collimating lens position adjustment mechanism with which the optical pick-up apparatus of this embodiment is provided. These are the figures for demonstrating the structure of the objective lens actuator with which the optical pick-up apparatus of this embodiment is provided. These are the flowcharts which show the operation example according to the environmental temperature of the optical pick-up apparatus of this embodiment. These are graphs showing the relationship between the environmental temperature and the collimating lens position at which the jitter value is minimized. These are graphs showing the relationship between the environmental temperature and the tilt amount of the objective lens that minimizes the jitter value after adjusting the position of the collimating lens. These are graphs which show the relationship between environmental temperature and the jitter characteristic in an optical pick-up apparatus. These are the figures for demonstrating other embodiment of this invention. These are diagrams for explaining the problems of the conventional optical pickup device, and are diagrams showing changes in jitter characteristics of the optical pickup device with respect to changes in environmental temperature.

Explanation of symbols

1 Optical pickup device 3 Objective lens actuator (tilt adjustment means)
5 Thermistor (temperature detection means)
6 Collimating lens position adjustment mechanism (lens position adjustment means)
11 Light source 15 Collimating lens (movable lens)
17 Objective lens 22 Memory (memory means)
32 Lens holder 70 Optical disc (optical recording medium)
70a Information recording surface

Claims (5)

A light source;
An objective lens for condensing the light emitted from the light source on the information recording surface of the optical recording medium;
A movable lens that is disposed in an optical path between the light source and the objective lens, and is movable in the optical axis direction and adjusts the convergence or divergence state of the light reaching the objective lens;
Lens position adjusting means for adjusting the position of the movable lens;
A tilt amount adjusting means for adjusting the tilt amount of the objective lens;
Temperature detection means for detecting the environmental temperature;
Storage means for storing in advance information on the position of the movable lens corresponding to the environmental temperature;
With
The objective lens is disposed to be inclined with respect to the optical axis of light from the movable lens to the objective lens,
When the change in the environmental temperature is detected, the position of the movable lens is changed based on the information on the position of the movable lens stored in the storage unit ,
An optical pickup device characterized by determining an optimum tilt amount while changing the tilt amount after adjusting the movable lens position and changing the tilt amount of the objective lens. The tilt amount adjusting means adjusts the tilt amount by inclining the objective lens around a specific axis.
The direction in which the objective lens is inclined with respect to the optical axis of light from the movable lens to the objective lens is a direction in which coma aberration can be corrected by inclining the objective lens with the tilt amount adjusting means. The optical pickup device according to claim 1.   The optical pickup device according to claim 2, wherein the specific axis is an axis orthogonal to the focus direction and the track direction.   4. The optical pickup device according to claim 1, wherein the tilt amount adjusting unit adjusts a tilt amount of the objective lens by tilting a lens holder that holds the objective lens. 5. The optical pickup device according to claim 1, wherein the movable lens is a collimating lens.

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