JP5093141B2 - Optical pickup device and optical disk drive - Google Patents

Description

  The present invention relates to an optical pickup device corresponding to a plurality of types of optical discs such as a Blu-ray disc (BD), a DVD, and a CD, and an optical disc drive including the same.

  As an optical pickup device corresponding to a plurality of types of optical disks having different recording densities, there is one disclosed in Patent Document 1. In the technique disclosed in this document, for example, two types of objective lenses corresponding to optical disks of high recording density and low recording density are provided in a lens unit (movable body), and this lens unit is operated for focusing by a plurality of focus coils. On the other hand, a tracking operation is performed by a plurality of track coils.

  In general, the higher the recording density of the optical disc, the smaller the track pitch and the smaller the focal depth. For this reason, when the lens unit is servo-controlled with respect to a high recording density optical disk, it is required to perform the focusing operation and the tracking operation with high accuracy, that is, to increase the acceleration resolution during the operation. On the other hand, when servo-controlling the lens unit for an optical disk with a low recording density, the amount of disturbance such as surface deflection and eccentricity increases, and the range of motion for focusing and tracking operations increases. It is required to increase acceleration.

JP 2006-309911 A

  However, the conventional optical pickup device technology cannot change the electrical characteristics of the focus coil and the track coil for any of the optical disks having a high recording density and a low recording density. In other words, even when the optical disk is switched from a high recording density to a low recording density, or from a low recording density to a high recording density, the acceleration resolution and the maximum generated acceleration of the lens unit are not changed. For this reason, the focusing operation and tracking operation accompanying the servo control of the lens unit have room for optimization according to the type of the optical disk.

  The present invention has been conceived under the circumstances described above, and includes an optical pickup device capable of optimizing the operation by servo control in accordance with the type of optical disc, and such an optical pickup device. The problem is to provide an optical disk drive.

  In order to solve the above problems, the present invention takes the following technical means.

  According to the present invention, there is provided an optical pickup device including a lens unit corresponding to a plurality of types of optical discs and a plurality of focus coils for causing the lens unit to perform a focusing operation. Focus coil connection mode switching means for switching to either serial connection or parallel connection, optical disc discrimination means for discriminating the type of the optical disc, and focus coil connection according to the type of the optical disc discriminated by the optical disc discrimination means There is provided an optical pickup device comprising a connection mode switching control unit for controlling the mode switching unit.

  According to the technology disclosed by the present invention, for example, the connection form of a plurality of focus coils can be switched from serial connection to parallel connection, or from parallel connection to series connection. Thereby, the electrical characteristics of the plurality of focus coils are changed, and accordingly, the acceleration resolution and the maximum generated acceleration of the lens unit are also changed. Therefore, the focusing operation associated with the servo control of the lens unit can be optimized by changing the electrical characteristics of the focus coil in accordance with the type of the optical disk.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

1 is a perspective view showing an embodiment of an optical pickup device to which the present invention is applied. It is the perspective view which showed the positional relationship of the coil and magnet in the optical pick-up apparatus of FIG. It is a schematic diagram which shows the optical disk drive provided with the optical pick-up apparatus of FIG. It is explanatory drawing for demonstrating the connection form of the coil in the optical pick-up apparatus of FIG. It is explanatory drawing for demonstrating other embodiment of an optical pick-up apparatus.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  1 to 4 show an embodiment of an optical pickup device to which the present invention is applied. As shown in FIG. 3, the optical pickup apparatus A according to the present embodiment is used for a plurality of types of optical discs D (three types of Blu-ray disc (hereinafter abbreviated as “BD”), DVD, and CD as examples) having different recording densities. A corresponding optical unit 1 and control unit 2 are provided. The optical unit 1 and the control unit 2 are built in an optical disk drive B in which the optical disk D can be replaced. A lens unit 100 is mounted on the optical unit 1. This optical disk drive B has a spindle motor M for rotating an optical disk D of a replaceable medium inserted at a predetermined position. The optical unit 1 is capable of seeking and moving in the disk radial direction while facing the recording surface of the optical disk D.

  As shown in FIGS. 1 to 3, the lens unit 100 includes a lens holder 10, a blue laser objective lens 11, a red laser objective lens 12, two focus coils 13A and 13B, and four track coils 14A and 14B. It has two permanent magnets 15, a focus coil switching circuit SW1, and a track coil switching circuit SW2. In addition to the lens unit 100, the optical unit 1 includes a blue laser diode 16, a red laser diode 17, and a photodetector 18. The control unit 2 includes a signal computing unit 20, a servo controller 21, an optical disc determination unit 22, a switching control unit 23, and an LD light emission control unit 24.

  The lens holder 10 is supported by the fixing member 3 through a plurality of elongated wires W so as to be swingable in the focusing direction f (thickness direction of the optical disc D) and the tracking direction t (disc radial direction of the optical disc D). Yes. The lens holder 10 is provided with two objective lenses 11 and 12 so as to face the recording surface of the optical disc D.

  Blue laser light from the blue laser diode 16 is guided to the blue laser objective lens 11. The blue laser light is irradiated onto the recording surface of the optical disc D through the objective lens 11, reflected by the recording surface, and then guided to the photodetector 18. Such blue laser light is applied to a BD having a high recording density.

  Red laser light from the red laser diode 17 is guided to the objective lens 12 for red laser. The red laser light is irradiated onto the recording surface of the optical disc D through the objective lens 12, reflected by the recording surface, and then guided to the photodetector 18. Such a red laser beam is applied to a DVD or CD having a low recording density.

  The focus coils 13A and 13B are provided on the lens holder 10 so that the coil axis coincides with the focusing direction f. A part of each of the focus coils 13A and 13B is disposed so as to face the permanent magnet 15, and when a current flows through this part, an electromagnetic force (Lorentz force) in the focusing direction f is generated. When the focus coils 13A and 13B are driven and controlled by the servo controller 21, the lens holder 10 is swung in the focusing direction f as a focusing operation.

  The track coils 14 </ b> A and 14 </ b> B are provided at four locations on the lens holder 10, and two sets of the same sign that are diagonally opposite each other form a set. These track coils 14A and 14B are arranged so that the coil axis coincides with the direction perpendicular to the focusing direction f and the tracking direction t, and a part of each is opposed to the permanent magnet 15, and current flows through these parts. When flowing, an electromagnetic force (Lorentz force) in the tracking direction t is generated. When the track coils 14A and 14B are driven and controlled by the servo controller 21, the lens holder 10 is swung in the tracking direction t as a tracking operation.

  The permanent magnet 15 is for generating an electromagnetic force as a Lorentz force in the focus coils 13A and 13B and the track coils 14A and 14B, and in a direction perpendicular to the focusing direction f and the tracking direction t with respect to the lens holder 10. It is fixedly installed near the lens holder 10 so as to face each other.

  The focus coil switching circuit SW1 is for switching the connection form of the focus coils 13A and 13B to either one of series connection or parallel connection. When the focus coils 13A and 13B are connected in series by the switching circuit SW1, the signal line from the servo controller 21 is formed so as to be grounded from one focus coil 13A through the other focus coil 13B. . When the focus coils 13A and 13B are connected in parallel, the signal line from the servo controller 21 branches so as to lead to the respective focus coils 13A and 13B, and these focus coils 13A and 13B are individually grounded. Formed as follows. The switching operation of the switching circuit SW1 is controlled by the switching control unit 23. When the connection form of the focus coils 13A and 13B is switched to the series connection or the parallel connection, the electrical characteristics of the focus coils 13A and 13B as a whole change.

  The track coil switching circuit SW2 is for switching the connection form of the track coils 14A and 14B to either one of serial connection and parallel connection. When the track coils 14A and 14B are connected in series by the switching circuit SW2, the signal line from the servo controller 21 is formed to be grounded from one track coil 14A through the other track coil 14B. . When the track coils 14A and 14B are connected in parallel, the signal line from the servo controller 21 branches so as to lead to the respective track coils 14A and 14B, and these track coils 14A and 14B are individually grounded. Formed as follows. The switching operation of the switching circuit SW2 is controlled by the switching control unit 23 in the same manner as the switching circuit SW1 described above. When the connection form of the track coils 14A and 14B is switched to the series connection or the parallel connection, the electrical characteristics of the track coils 14A and 14B as a whole change. Note that the switching circuit for the focus coil and the track coil may be moved from the lens unit to the optical unit or the control unit.

  The blue laser diode 16 emits blue laser light suitable for BD, for example, about 400 to 450 nm. The blue laser diode 16 is controlled to be turned on by the LD light emission control unit 24.

  The red laser diode 17 emits red laser light suitable for DVD and CD, for example, about 650 nm. The red laser diode 17 is controlled to be turned on by the LD light emission control unit 24 in the same manner as the blue laser diode 16 described above.

  The photodetector 18 is composed of a plurality of photosensors that can receive reflected light from the optical disk D, for example. The received light signal from the photodetector 18 is taken into the signal calculator 20.

  The signal computing unit 20 generates a focusing error signal, a tracking error signal, and further a reproduction signal based on the light reception signal from the photodetector 18. The focusing error signal and the tracking error signal are transmitted to the servo controller 21, and the reproduction signal is transmitted to the optical disc determination unit 22.

  The optical disc discriminating unit 22 discriminates the type of the optical disc D such as BD, DVD, CD based on the reproduction signal from the signal calculator 20. The disc discrimination signal from the optical disc discriminating unit 22 is output to the servo controller 21, the switching control unit 23, and the LD light emission control unit 24.

  The servo controller 21 controls the lens unit 100 while optimizing the servo control, specifically, the focusing operation and the tracking operation according to the type of the optical disc D. The AD converter 210, the phase compensation filter 220, the filter coefficient A memory 230 and a DA converter 240 are included.

  The focusing error signal and tracking error signal from the signal calculator 20 are input to the phase compensation filter 220 via the AD converter 210. The phase compensation filter 220 is composed of, for example, a digital signal processor. Based on the disc discrimination signal from the optical disc discriminating unit 22, the phase compensation filter 220 takes in the filter coefficient optimum for the type of the target optical disc D from the filter coefficient memory 230, and the filter. A predetermined phase compensation process is performed on the focusing error signal and the tracking error signal using the coefficients. As a result, the phase compensation filter 220 outputs the focus coil drive signal and the track coil drive signal. The focus coil drive signal and the track coil drive signal are converted to analog via the DA converter 240, further amplified by the power amplifiers 31 and 32, and then input to the focus coil 13A and the track coil 14A.

  Specifically, when the focus coils 13A and 13B and the track coils 14A and 14B are connected in series, the focus coil drive signal and the track coil drive signal are the preceding coils 13A and 14A, the switching circuits SW1 and SW2, and the subsequent coil 13B. , 14B in this order. When the focus coils 13A and 13B and the track coils 14A and 14B are connected in parallel, the focus coil drive signal and the track coil drive signal are transmitted to the preceding coils 13A and 14A, and the subsequent coils via the switching circuits SW1 and SW2. Simultaneously transmitted to the coils 13B and 14B. When the focus coils 13A and 13B and the track coils 14A and 14B are driven by such focus coil drive signals and track coil drive signals, the focusing operation and the tracking operation of the lens unit 100 are realized.

  The switching control unit 23 controls the switching circuits SW1 and SW2 based on the disc discrimination signal from the optical disc discrimination unit 22 so that the coil connection form is optimal for the type of the optical disc D that is the current target. For example, in the case of a BD, the switching circuits SW1 and SW2 are controlled so that the connection forms of the focus coils 13A and 13B and the track coils 14A and 14B are connected in series. In the case of DVD or CD, the connection form is a parallel connection. Thus, the switching circuits SW1 and SW2 are controlled.

  The LD light emission control unit 24 controls lighting of the blue laser diode 16 and the red laser diode 17 based on the disc discrimination signal from the optical disc discrimination unit 22 so that the laser light according to the type of the optical disc D that is the current target is emitted. To do. For example, when the optical disk D is inserted at a predetermined position, the LD light emission control unit 24 alternately controls the blue laser diode 16 and the red laser diode 17 until the optical disk determination unit 22 generates a correct disk determination signal. When a correct reproduction signal is obtained on the basis of the reflected light from the optical disk D during the irradiation of one of the blue laser light and the red laser light, a correct disk discrimination signal indicating the type of the optical disk D is obtained. When this disc discrimination signal is transmitted from the optical disc discrimination unit 22 to the LD light emission control unit 24, either the blue laser diode 16 or the red laser diode 17 is emitted so that a laser beam corresponding to the type is emitted until the optical disc D is replaced. One of them is controlled to be lit.

  Next, the operation of the optical pickup device A will be described.

  For example, for the three types of BD, DVD, and CD as the interchangeable optical disc D, the specification conditions shown in Table 1 below are generally required with respect to the depth of focus and the track pitch.

  In the servo control of the lens unit 100 according to the specification conditions shown in Table 1, it is necessary to perform the focusing operation and the tracking operation with higher accuracy as the optical disc D has a higher recording density. On the other hand, when the optical disc D has a low recording density, the tracking accuracy of the focusing operation and the tracking operation is relaxed, but since the amount of disturbance such as surface runout and eccentricity becomes larger than that of the high recording density, a larger output acceleration. Will be required. That is, in the servo control for the low recording density optical disc D, it is desirable that the maximum generated acceleration during operation is larger than that in the case of the high recording density optical disc D, whereas in the servo control for the high recording density optical disc D, the low recording density is low. It is desirable that the acceleration resolution be higher than in the case of a high density optical disc D. Based on these, in the optical pickup device A of the present embodiment, the electrical characteristics of the coils 13A, 13B, 14A, and 14B can be changed by automatically switching the connection form of the focus coils 13A and 13B and the track coils 14A and 14B. By changing, the optimum focusing operation and tracking operation are performed according to the type of the optical disc D.

  For example, if the characteristics of the electrical components are shown in the following formula 1, and when connected in series as shown in FIG. 4, the maximum generated acceleration Gmax, the acceleration slight change amount ΔG, the servo as shown in the following formula 2 The motor efficiency Mw. The minute acceleration change ΔG is an index representing acceleration resolution, and the smaller the ΔG, the higher the acceleration resolution.

  On the other hand, in the case of parallel connection as shown in FIG. 4, the maximum generated acceleration Gmax, the minute acceleration change ΔG, and the servo motor efficiency Mw as shown in the following Equation 3 are obtained.

  For example, when the acceleration sensitivity Km1 and Km2 of the coils m1 and m2 is 10 G / v, and the resistance values Km1 and Km2 are 5Ω, the maximum generated acceleration Gmax, the minute acceleration change ΔG, and the servo motor efficiency when connected in series and parallel As Mw, it becomes like the following numerical formula 4.

  That is, when the coils m1 and m2 are the focus coils 13A and 13B and the track coils 14A and 14B, and the connection form of the coils is connected in series to perform servo control for the BD, the maximum generated acceleration Gmax is reduced and the acceleration is small. The amount of change ΔG is also reduced, and the acceleration resolution is relatively high. On the other hand, when servo control is performed on a DVD or CD with the coil connection form being connected in parallel, the maximum generated acceleration Gmax is relatively large and the minute acceleration change ΔG is also large, resulting in relatively low acceleration resolution. . As the focus coils 13A and 13B and the track coils 14A and 14B, coils having the same electrical characteristics are generally applied. Therefore, the servo motor efficiency Mw can be set to either a series connection or a parallel connection. But it doesn't change theoretically.

  Therefore, according to the optical pickup apparatus A of the present embodiment, the focusing coil 13A and the tracking coils 14A and 14B are connected in series for the focusing operation and the tracking operation associated with the servo control in the case of the servo control for the BD having a high recording density. As a connection, the acceleration resolution can be made relatively high. On the other hand, in the case of servo control for a low recording density DVD or CD, the maximum generated acceleration Gmax can be made relatively large by connecting the focus coils 13A and 13B and the track coils 14A and 14B in parallel. Thereby, the focusing operation and the tracking operation of the lens unit 100 can be optimized according to the type of the optical disc D.

  FIG. 5 shows another embodiment of the optical pickup device. Note that the same or similar components as those of the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.

  The optical pickup device shown in FIG. 5 differs in the configuration of the switching circuits SW1 and SW2 for the focus coil and the track coil.

  The switching circuits SW1 and SW2 include a resistance element Rs. The switching circuits SW1 and SW2 can switch the connection form of the coils m1 and m2 (focus coils 13A13B and track coils 14A and 14B) to a parallel connection and a series connection. It is possible to selectively switch between the resistance relay connection and the simple short-circuit series connection without the resistance element Rs. In the case of short-circuited series connection or parallel connection, it is the same as that according to the above-described embodiment. In the case of the resistance relay connection, the signal line from the DA converter 240 is formed so as to be connected to the ground from one coil m1 through the resistance element Rs and further through the coil m2. The switching circuit may be provided in any of the lens unit, the optical unit, and the control unit.

  In such a switching circuit SW1, SW2, for example, in the case of a BD having the highest recording density, the coils m1, m2 are controlled to be connected to a resistance relay, and in the case of a DVD having an intermediate recording density, the coils m1, m2 are In the case of a CD having the lowest recording density, the coils m1 and m2 are controlled so as to be connected in parallel.

  For example, as the characteristics of the electrical components, the resistance value r (Ω) of the resistance element Rs is considered in addition to the one shown in the above mathematical formula 1. As shown in FIG. 5, in the case of the resistance relay connection, the maximum generated acceleration Gmax, the acceleration slight change amount ΔG, and the servo motor efficiency Mw as shown in the following formula 5 are obtained. Further, the ratio T of the electrical time constant in the case of the resistance relay connection and the short-circuit series connection is always smaller than 1 as shown in Equation 5. The smaller the electrical time constant of the lens unit, the easier it is to increase the servo band and the better the servo control response.

  For example, when the acceleration sensitivities Km1 and Km2 of the coils m1 and m2 are 10 G / v and the resistance values Km1, Km2 and r are 5Ω, the maximum generated acceleration Gmax, the minute acceleration change ΔG, and the servo motor efficiency Mw when the resistance relay is connected. As shown in Equation 6 below. In the case of short-circuited series connection or parallel connection, it is as shown in Equation 4 above.

  That is, when the coils m1 and m2 are the focus coils 13A and 13B and the track coils 14A and 14B and the connection form of the coils is a resistance relay connection and servo control is performed on a high recording density BD, the maximum generated acceleration Gmax Becomes the smallest, and the minute acceleration change ΔG also becomes smaller and the acceleration resolution becomes the highest. When servo control is performed on a CD having a low recording density with the coil connection form connected in parallel, the maximum generated acceleration Gmax becomes the largest and the minute acceleration change ΔG also becomes the largest, resulting in the lowest acceleration resolution. . When servo control is performed on a medium-recording density DVD with the coil connection form short-circuited in series, the maximum generated acceleration Gmax and the minute acceleration change ΔG are intermediate level values, and the acceleration resolution is also intermediate level.

  Therefore, according to the optical pickup apparatus having the configuration shown in FIG. 5, the focusing and tracking operations associated with servo control are the focus coils 13A and 13B and the track coil 14A in the case of servo control for the BD having the highest recording density. , 14B can be connected to resistance relays to achieve the highest acceleration resolution. In the case of servo control for a medium recording density DVD, the focus coils 13A and 13B and the track coils 14A and 14B are short-circuited in series so that the maximum generated acceleration Gmax and acceleration resolution can be set to an intermediate level. In the case of servo control for CD, the maximum generated acceleration Gmax can be maximized by connecting the focus coils 13A and 13B and the track coils 14A and 14B in parallel. Thereby, the focusing operation and the tracking operation of the lens unit 100 can be more finely optimized according to the type of the optical disc D, and in particular, the servo control response to a high recording density BD can be further improved.

  The present invention is not limited to the above embodiments.

  The configuration shown in the above embodiment is merely an example, and the design can be changed as appropriate according to the specification.

  For example, the switching circuit may be provided in one of the focus coil and the track coil, and only one of the focusing operation and the tracking operation may be optimized according to the type of the optical disc.

  The number of coils connected via the switching circuit may be three or more.

  There may be four or more types of corresponding optical disks.

  The present invention can be used for an optical disc drive capable of reading and writing on a plurality of types of optical discs such as a Blu-ray disc, a DVD, and a CD.

A optical pickup device D optical disk 1 optical unit 13A, 13B focus coil 14A, 14B track coil SW1 switching circuit for focus coil (focus coil connection mode switching means)
SW2 Switching circuit for track coil (track coil connection mode switching means)
2 Control unit 22 Optical disc discriminating unit (optical disc discriminating means)
23. Switching control unit (connection mode switching control means)
100 lens unit

Claims (6)

An optical pickup device comprising a lens unit corresponding to a plurality of types of optical discs and a plurality of focus coils for causing the lens unit to perform a focusing operation,
Focus coil connection form switching means for switching the connection form of the plurality of focus coils to either one of serial connection and parallel connection;
Optical disc discrimination means for discriminating the type of the optical disc;
A connection mode switching control unit that controls the focus coil connection mode switching unit according to the type of the optical disc determined by the optical disc determination unit;
An optical pickup device comprising: An optical pickup device comprising a lens unit corresponding to a plurality of types of optical disks, and a plurality of track coils for causing the lens unit to perform a tracking operation,
Track coil connection mode switching means for switching the connection mode of the plurality of track coils to either one of serial connection and parallel connection;
Optical disc discrimination means for discriminating the type of the optical disc;
A connection mode switching control unit for controlling the track coil connection mode switching unit according to the type of the optical disc determined by the optical disc determination unit;
An optical pickup device comprising: An optical pickup device comprising a lens unit corresponding to a plurality of types of optical discs, a plurality of focus coils for causing the lens unit to perform a focusing operation, and a plurality of track coils for causing the lens unit to perform a tracking operation,
Focus coil connection form switching means for switching the connection form of the plurality of focus coils to either one of serial connection and parallel connection;
Track coil connection mode switching means for switching the connection mode of the plurality of track coils to either one of serial connection and parallel connection;
Optical disc discrimination means for discriminating the type of the optical disc;
A connection mode switching control unit for controlling the focus coil connection mode switching unit and the track coil connection mode switching unit according to the type of the optical disc determined by the optical disc determination unit;
An optical pickup device comprising: The types of optical discs are divided into two types: high recording density discs and low recording density discs,
The connection mode switching control unit controls the focus coil connection mode switching unit and the track coil connection mode switching unit so that the connection mode is the series connection when it is determined as a high recording density disk, The optical pickup device according to claim 3, wherein when the disc is determined to be a low recording density disc, the connection form is controlled to be the parallel connection. The types of optical discs are divided into three types: high recording density discs, medium recording density discs, and low recording density discs,
The focus coil connection mode switching unit and the track coil connection mode switching unit can selectively switch, as the series connection, a resistance relay connection via a predetermined resistance element and a short-circuit series connection without such a resistance element. And
The connection mode switching control unit controls the focus coil connection mode switching unit and the track coil connection mode switching unit so that the connection mode is the resistance relay connection when it is determined as a high recording density disk. When the disc is determined to be a medium recording density disc, the connection mode is controlled to be the short-circuited serial connection, and when the disc is determined to be a low recording density disc, the connection mode is controlled to be the parallel connection. The optical pickup device according to claim 3.   An optical disc drive comprising the optical pickup device according to claim 1.

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