JP6097164B2 - Optical pickup control device and optical disk device - Google Patents

Description

  The present invention relates to an optical pickup control device and an optical disk device.

2. Description of the Related Art A disk device that reproduces a disk-type recording medium (optical disk) such as a CD (Compact Disc) or a DVD (Digital Versatile Disk) includes an optical pickup that irradiates the optical disk through an objective lens and receives the reflected light. ing.
The optical pickup includes a drive unit for performing tracking control and focusing control for adjusting the position of the objective lens in order to read data on the recording surface of the disk. In this type of disk device, a collision prevention mechanism is provided or special control is performed so that the objective lens does not collide with the disk (for example, Patent Documents 1 and 2).

JP 2012-94199 A JP 2004-303329 A

  However, in the above configuration, it is necessary to provide a collision prevention mechanism or the like, which complicates the configuration. In addition, the sensitivity of the optical pickup (that is, the sensitivity of the operating unit that performs focusing control. For example, it is represented by the movement amount of the objective lens / control voltage and the unit is represented by [mm / V]). is there. For this reason, even if driving with the same control voltage, the position of the objective lens changes due to individual differences, and it is difficult to accurately control the distance between the optical disk and the objective lens with the control voltage.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup control device and an optical disc apparatus that can reduce the collision prevention mechanism and can accurately control the distance between the optical disc and the objective lens.

In order to achieve the above object, the present invention includes an objective lens that is movable in a focus direction with respect to an optical disk, and an actuator that moves the objective lens in the focus direction, and light is applied to the optical disk via the objective lens. In the control device of the optical pickup that receives the reflected light, the amount of movement of the objective lens and the control value of the actuator when the actuator focuses on a plurality of predetermined reference positions of the optical disc, Based on the above, a change characteristic of the actuator sensitivity is obtained, and based on the change characteristic, a control unit for controlling a distance between the optical disk and the objective lens, and a change in sensitivity of the actuator of the same type as the actuator A storage unit that stores a plurality of characteristics, and the control unit is connected to the actuator. The sensitivity is calculated based on the amount of movement of the objective lens and the control value of the actuator when focused on two predetermined reference positions of the optical disc, and a plurality of values stored in the storage unit are stored. The change characteristic of the sensitivity is specified based on the change characteristic having the same or close sensitivity as the sensitivity under the same condition, and the optical disc and the objective lens are determined based on the specified change characteristic. The distance is controlled .

In the above configuration, the control unit may specify the change characteristic of the sensitivity based on a ratio between the measured sensitivity and the sensitivity under the same condition in the change characteristic stored in the storage unit. .
In the above configuration, the sensitivity change characteristic may be a non-linear characteristic. In the above structure, the change characteristic of the sensitivity, a Gaussian function, or even so as to be approximated by a tertiary or more functions not good.

Further, the configuration smell Te, a control device of an optical pickup noted above, may be to provide an optical disc apparatus for reproducing an optical disc using the optical pickup.

  According to the present invention, the collision prevention mechanism can be reduced, and the distance between the optical disk and the objective lens can be controlled with high accuracy.

1 is a block diagram showing a configuration of an optical disc apparatus according to a first embodiment of the present invention. It is the figure which showed the relationship of the focusing position of CD and DVD. It is the figure which showed the structure of the drive part for a focus, and the relationship between Lorentz force. It is a flowchart which shows a dynamic characteristic learning process. It is a figure where it uses for description of the measurement of a dynamic characteristic learning process. It is a flowchart which shows the disk discrimination | determination process in automatic adjustment. It is the figure which showed the change characteristic of the sensitivity memorize | stored in a memory | storage part. It is a flowchart which shows a dynamic characteristic learning process.

Embodiments of the present invention will be described below with reference to the drawings.
<First Embodiment>
FIG. 1 is a block diagram showing the configuration of the optical disc apparatus according to the first embodiment of the present invention. FIG. 1 mainly shows a configuration related to the control of the optical pickup.
The optical disk apparatus 10 is an in-vehicle optical disk apparatus that is mounted on a vehicle and reproduces a disk type recording medium (hereinafter referred to as an optical disk 11) such as a CD or a DVD.
The optical disk device 10 includes an optical pickup 21 that reproduces information recorded on the optical disk 11. Although not shown, the optical disc apparatus 10 includes a stepping motor that rotationally drives the optical disc 11, a sled motor that moves the optical pickup 21 in the radial direction of the optical disc 11, and the like.

The optical pickup 21 includes a laser irradiation unit 22, a light receiving unit 23, an optical system 25 such as an objective lens 24, and a lens driving actuator 26. The laser irradiation unit 22 is a light source that emits laser light that is applied to the optical disc 11. The light receiving unit 23 receives the laser beam reflected by the optical disc 11 and outputs the light reception result to a servo control unit 31 and the like which will be described later. The objective lens 24 is a lens that condenses laser light on the recording surface of the optical disk 11.
Components constituting the optical system 25 other than the objective lens 24 are mirrors, lens components, and the like. In FIG. 1, the reflection mirror 27 that reflects the emitted light (laser light) of the laser irradiation unit 22, the light from the reflection mirror 27 is reflected toward the optical disk 11, and the reflected light of the optical disk 11 is directed toward the light receiving unit 23. The beam splitter 28 is shown.

The objective lens 24 is supported so as to be movable in the focus direction and the tracking direction with respect to the optical disc 11 and is a component closest to the optical disc 11.
The lens driving actuator 26 is a biaxial actuator that drives the objective lens 24 in a focus direction and a tracking direction by a control voltage. The lens driving actuator 26 uses a coil (FIG. 3 to be described later) and a magnet (FIG. 3 to be described later) to generate an electromagnetic force by causing a current corresponding to a control voltage to flow through the coil. Thus, the electromagnetic lens is configured to move the objective lens 24 in the focus direction and the tracking direction.

For example, the lens driving actuator 26 includes a focus coil wound so as to be parallel to the optical axis direction of the objective lens 24, and a tracking coil wound so as to be orthogonal to the optical axis of the objective lens 24. Each of the focus coil and the tracking coil includes a permanent magnet that is attached to the yoke so that the magnetic flux of the permanent magnet is linked. A wide variety of known structures can be applied to the lens driving actuator 26.
Hereinafter, for easy understanding, the actuator part that drives the objective lens 24 in the focus direction is referred to as a focus drive part 26A, and the actuator part that drives the objective lens 24 in the tracking direction is referred to as a tracking drive part 26B.

The servo control unit 31 outputs control voltages VF and VT to the focus drive unit 26A and the tracking drive unit 26B. More specifically, the servo control unit 31 varies the control voltage VF of the focus driving unit 26A based on the light reception result of the light receiving unit 23, thereby changing the distance between the objective lens 24 and the recording surface of the optical disc 11. Control to keep constant (focusing control).
Further, the servo control unit 31 varies the control voltage VT of the tracking drive unit 26B based on the light reception result of the light receiving unit 23, thereby performing control to position the laser beam on a predetermined track of the optical disc 11 ( Tracking control).
It should be noted that known control can be widely applied to the focusing control and tracking control.

The system control unit 32 centrally controls each unit of the optical disc apparatus 10 and includes an arithmetic processing unit (for example, CPU) having a program execution function and an arithmetic processing function. The storage unit 33 stores data such as a control program executed by the system control unit 32 and various data used by the system control unit 32.
The limit control unit 35 electrically restricts the rise of the objective lens 24 by limiting the control voltage VF to the focus driving unit 26A to a preset clip voltage (limit value) C.
Thus, even when the recording surface cannot be detected when focusing on the recording surface of the optical disc 11 and the objective lens 24 continues to rise, the objective lens 24 rises when the control voltage VF reaches the clip voltage C. Stopped.

FIG. 2 shows the relationship between the in-focus positions of the CD and the DVD.
The specifications of the optical disk 11 such as CD and DVD are determined by the standard, and when the CD and DVD disk surfaces are aligned, the DVD recording surface is provided closer to the disk surface than the CD recording surface. Yes.
The spatial distance between the disc surface and the DVD recording surface (first layer DVD recording surface) is 600 μm, and the optical distance is 387 (= 600 × refractive index of optical disc 11 (1.55)) μm. The optical distance between the DVD recording surface and the CD recording surface is also 387 μm.
In the example of FIG. 2, the control voltage VF is −100 mV when the objective lens 24 is at the in-focus position on the disc surface, and the control voltage VF is −50 mV at the in-focus position on the DVD recording surface. Show. Further, when the objective lens 24 is at the in-focus position on the CD recording surface, the control voltage VF is 2 mV.

By the way, the sensitivity of the operating unit that performs the focus control of the optical pickup 21, that is, the sensitivity of the focus drive unit 26A (for example, expressed by the movement amount of the objective lens 24 / control voltage VF, the unit is [mm / V]). There are individual differences. For this reason, even if driven by the same control voltage VF, the position of the objective lens 24 is different, and it is desirable to set the clip voltage C of the limit control unit 35 for each optical pickup 21.
As a method for setting the clip voltage C for each optical pickup 21, a method is conceivable in which the actuator sensitivity S is obtained by a linear expression shown in the following equation (1) and the clip voltage C is set based on the sensitivity S.
S = (movement amount between two points) / (difference in control voltage VF between two points) (1)

Here, an example of calculating the sensitivity S using a DVD is shown below.
In the case of FIG. 2, the movement distance (387 μm) between the disk surface and the DVD recording surface is substituted as (the amount of movement between the two points), and the difference between the disk surface and the control voltage VF between the two points is calculated. The difference (50 mV) of the control voltage VF from the DVD recording surface is substituted. Thereby, the sensitivity S is obtained.
S = 387/50 = 7.74 [mm / V] (2)

Based on this sensitivity S, as shown in the following formula (3), the objective lens 24 does not collide with the disk surface and can be focused on the CD recording surface (for example, 600 μm from the focused position on the CD recording surface). ) To set the clip voltage C.
C = (control voltage VF at the in-focus position on the CD recording surface) +600 μm / sensitivity S
= 2mV + (600 / 7.74) mV
= 80 mV ... Formula (3)

The above method assumes that the sensitivity S is constant.
However, since the focus drive unit 26A has an electromagnetic drive structure, the sensitivity S actually changes according to the positional relationship between the coil (electricity) and the magnet. Hereinafter, the change in sensitivity S will be described.
FIG. 3 shows the relationship between the structure of the focus driving unit 26A and the Lorentz force.
As shown in FIG. 3, when the objective lens 24 is at the control voltage VF = 0 position (self-weight position), the Lorentz force (sensitivity S) increases because the center of magnetism and the direction of electricity intersect perpendicularly. On the other hand, when the objective lens 24 moves upward (on the optical disc 11 side), the Lorentz force (sensitivity S) decreases because the magnetic center and the direction of electricity are in a twisted positional relationship.

  For this reason, if the sensitivity S is calculated at a position away from its own weight position, the sensitivity becomes lower than the original sensitivity. In this case, since the clip voltage C is set higher, the upper limit position of the objective lens 24 is increased accordingly. In this case, since the objective lens 24 approaches the optical disc 11, there is a possibility that a sufficient gap cannot be secured due to the warp of the optical disc 11 or the like. In particular, the in-vehicle optical disc apparatus 10 is affected by external vibrations, and therefore it is highly necessary to ensure a gap between the objective lens 24 and the optical disc 11 with high accuracy.

  Therefore, in the present embodiment, a dynamic characteristic learning process for calculating a sensitivity change characteristic of the focus driving unit 26A (also referred to as a dynamic characteristic of the focus driving unit 26A) is performed. Then, by setting the clip voltage C based on this calculation result, the upper limit position of the objective lens 24 can be set with high accuracy.

FIG. 4 is a flowchart showing the dynamic characteristic learning process. This dynamic characteristic learning process is a process performed in the production process of the optical disc apparatus 10.
In order to execute the dynamic characteristic learning process, first, an optical disk for inspection (referred to as an inspection disk) 11A is inserted into the optical disk apparatus 10, and the start of the dynamic characteristic learning process is instructed from the outside. In response to this instruction, the system control unit 32 reads a control program for dynamic characteristic learning processing from the storage unit 33 and executes the control program.
FIG. 5 is a diagram for explaining the measurement of the dynamic characteristic learning process. As shown in FIG. 5, an optical disc 11 having a DVD recording surface and a CD recording surface is used as the inspection disc 11A.

  Returning to FIG. 4, first, the system control unit 32 turns on the laser beam (DVD laser beam), and moves the objective lens 24 up and down by the focus drive unit 26A. Then, as shown in FIG. 5, the system control unit 32 causes the disk surface of the inspection disk 11A to be focused on (the objective lens 24 is focused) (step S11). Thereafter, the system control unit 32 measures the control voltage VF (-200 mV in FIG. 5) when the disk surface is focused on, and temporarily stores it in the storage unit 33 (step S12).

  Next, the system control unit 32 moves the objective lens 24 up and down by the focus driving unit 26A to focus on the DVD recording surface of the inspection disk 11A (step S13). Then, the system control unit 32 measures the control voltage VF (−45 mV in FIG. 5) when the DVD recording surface is focused on, and temporarily stores it in the storage unit 33 (step S14).

  Next, the system control unit 32 moves the objective lens 24 up and down by the focus drive unit 26A to focus on the CD recording surface of the inspection disc 11A (step S15). Then, the system control unit 32 measures the control voltage VF (100 mV in FIG. 5) when the DVD recording surface is focused on, and temporarily stores it in the storage unit 33 (step S16).

Subsequently, based on the measured three data (control voltage VF), the system control unit 32 calculates an approximate expression that approximates the dynamic characteristic of the sensitivity S, as will be described later (step S17), and the storage unit 33. Remember me. The above is the flow of the dynamic characteristic learning process.
As described above, in the dynamic characteristic learning process, the control voltage VF is measured when each of the three reference positions including the disk surface, the DVD recording surface, and the CD recording surface is focused on, and approximated based on these measurement data. Calculate the formula.

Next, the calculation process in step S17 will be described.
The dynamic characteristic of the sensitivity S changes depending on the structure of the focus driving unit 26A. As a result of studies by the inventors, it has been found that in the case of the electromagnetically driven focus drive unit 26A, the Gaussian function can approximate the dynamic characteristic of the sensitivity S satisfactorily. Therefore, in step S17, an approximate expression is calculated using a Gaussian function expressed by the following expression (4).
S = a × exp (−b × E ² ) [mm / V] (4)
The value E is the control voltage VF, and the values a and b are constants.

As described above, the measured control voltage VF is the disc surface: -200 mV, the DVD recording surface: -45 mV, and the CD recording surface: 100 mV.
When the movement distance is Y, the following formula (5) is established.
Y = ΣS = Σ (a × exp (−b × E ² )) = aΣexp (−b × E ² ) (5)

By using this equation (5), the following equations (6) and (7) are obtained.
Disc surface to DVD recording surface: 0.387 mm = aΣ (exp (−b × (−200) ² ) + (exp (−b × (−199) ² )) + to + (exp (−b × (−45 ² )) ... Formula (6)
DVD surface to CD recording surface: 0.387 mm = aΣ (exp (−b × (−45) ² ) + (exp (−b × (−44) ² )) + to + (exp (−b × (100) ² )) ... Formula (7)

From the equations (6) and (7), the following equation (8) is obtained.
0.387 mm / a = Σ (exp (−b × (−200) ² ) + (exp (−b × (−199) ² )) + ˜ + (exp (−b × (−45) ² ))) = Σ (exp (−b × (−45) ² ) + (exp (−b × (−44) ² )) + ˜ + (exp (−b × (100) ² ))) Equation (8)

By expanding the equation (8), b = 4655.2 × 10 ⁽⁻⁹⁾ is obtained, and a = 0.00268890902615806 is also obtained.
Since the resolution is [mm / V], when the unit is [μm / V],
a = 2.6819, b = 4655.2 × 10 ⁽⁻⁹⁾ .
Thereby, the following formula (9) is obtained.
S = 2.6819 × exp (−4655.2 × 10 ⁽⁻⁹⁾ × E ² ) [mm / V] (9)

In the case of DVD, the clip voltage C is set to 1000 μm from the DVD recording surface. In this case, the clip voltage C = 429 mV can be obtained by using Expression (9).
Further, when processing is performed by the CPU, it takes time to calculate exp (exponential function), but if the value n is large according to the following formulas (10) and (11), it converges to the relational formula of formula (12). To do.
exp (−b × E ² ) = exp (−b × A) = exp (A) ^(−b) = (exp (A / n) ⁿ ) ^(−b) Expression (10)
(Exp (A / n) = (1 + x / n + (x / n) 2/2! + (X / n) 2/3! + ···) ··· (11)
exp (A) = (exp ( A / n) n = (1 + x / n + (x / n) 2/2! + ···) n ≒ (1 + x / n) n ··· (12)

If n = 2 ⁴ , according to equation (12),
exp (A) = ((((1 + x / (2 ⁴ )) ² ) ² ) ² ) ² , and calculation is possible by repeating simple four-rule operations. Also, accuracy is ensured by increasing the value of n. The above is the calculation process in step S17.
The stored dynamic characteristics of the sensitivity S are used for automatic adjustment and operation during reproduction.

FIG. 6 is a flowchart showing a disc discrimination process during automatic adjustment.
This process is performed when the system control unit 32 reads a predetermined control program from the storage unit 33 and executes it when the optical disc 11 is inserted.
First, the system control unit 32 acquires the dynamic characteristic of the sensitivity S stored in the storage unit 33, and sets the clip voltage C (429 mV in the present embodiment) (step S21).
Next, the system control unit 32 starts the rotation of the optical disc 11 (step S22), and causes the laser irradiation unit 22 to turn on the CD laser light (step S23). Next, the system control unit 32 considers surface blurring caused by warpage of the optical disc 11 and the like, and moves the objective lens 24 further down to 400 μm below the recording surface with the lowest focus position by the focus driving unit 26A (step) S24).

Subsequently, the system control unit 32 drives the focus driving unit 26A from the position lowered in step S24 to the clip voltage C, and measures the maximum amplitude of the focus signal (step S25).
Next, the system control unit 32 turns on the DVD laser beam instead of the CD laser beam by the laser irradiation unit 22 (step S26). Next, the system control unit 32 moves the objective lens 24 further to 400 μm below the recording surface with the lowest focus position by the focus driving unit 26A (step S27).
Subsequently, the system control unit 32 drives the focus driving unit 26A from the position lowered in step S27 to the clip voltage C, measures the maximum amplitude of the focus signal, and obtains the maximum amplitude of the focus signal acquired in step S25. Compare (step S28).

And it discriminate | determines that it is the optical disk 11 with the larger amplitude of a focus error signal (step S29, 30).
As described above, in this embodiment, the dynamic characteristic of the sensitivity S is obtained, and the clip voltage C is set based on the dynamic characteristic. Therefore, the upper limit position of the objective lens 24 can be set with high accuracy. Therefore, since the optical disc 11 is discriminated by moving the objective lens 24 up and down after setting the clip voltage C, disc discrimination can be performed while avoiding the collision between the optical disc 11 and the objective lens 24. .

  As described above, the system control unit 32 of the present embodiment controls and controls the amount of movement of the objective lens 24 when the focus driving unit (actuator) 26A focuses on a plurality of predetermined reference positions on the optical disc 11. Based on the voltage (control value) VF, the change characteristic of the sensitivity S of the focus drive unit 26A is obtained. Then, the system control unit 32 controls the distance between the optical disc 11 and the objective lens 24 by setting the clip voltage C based on the obtained change characteristic. Thereby, the collision prevention mechanism for preventing the collision of the objective lens 24 can be reduced, and the distance between the optical disk 11 and the objective lens 24 can be accurately controlled.

  In addition, in the present embodiment, the movement amount of the objective lens 24 and the control voltage VF when the objective lens 24 is moved by the focus driving unit 26A and focused on three or more predetermined reference positions on the optical disc 11 are set. Since the approximate expression that approximates the change characteristic of the sensitivity S is calculated based on the above, the change characteristic of the sensitivity S can be calculated with high accuracy.

  Further, since the focus driving unit 26A is of an electromagnetic drive type, the change characteristic of the sensitivity S is a non-linear characteristic. In this configuration, since the change characteristic of the nonlinear sensitivity S is obtained based on the movement amount of the objective lens 24 and the control voltage VF when the focus is turned on at a plurality of reference positions, it can be obtained with high accuracy. Thus, the objective lens 24 can be accurately controlled by the electromagnetically driven focus drive unit 26A.

At this time, since the change characteristic of the sensitivity S is approximated by a Gaussian function, the sensitivity of the electromagnetically driven focus drive unit 26A can be obtained with high accuracy, and the objective lens 24 can be controlled with higher accuracy. Become.
In the present embodiment, the case of approximating with a Gaussian function has been described, but the present invention is not limited to this. For example, a cubic or higher function such as a cubic function may be used. In this embodiment, three points of measurement are performed in order to calculate two unknown constants of the Gaussian function. However, there are no unknown constants, or two points may be measured in the case of one. In short, the number of measurements may be set appropriately according to the approximate expression.

Second Embodiment
In the first embodiment, since a Gaussian function is used, measurement at three points is necessary, and the amount of calculation for specifying an unknown constant is relatively large.
On the other hand, in the second embodiment, a plurality of sensitivity change characteristics of an actuator of the same type as the focus drive unit 26A are stored, and the sensitivity at one point is measured. Then, by comparing the sensitivity at one point with the stored change characteristic, the actual change characteristic of the sensitivity of the focus driving unit 26A is specified.

More specifically, the storage unit 33 stores a plurality of sensitivity change characteristics for the electromagnetically driven focus drive unit 26A that is an actuator of the same type.
Here, FIG. 7 shows a change characteristic of sensitivity stored in the storage unit 33. In addition, the vertical axis | shaft of FIG. 7 is the sensitivity S, and a horizontal axis is the control voltage VF.
As shown in FIG. 7, the storage unit 33 has an upper limit characteristic S1, an average characteristic S2, and a lower limit characteristic based on the results obtained by measuring a large number of electromagnetically driven focus drive units 26A. Three types of S3 are stored. Each characteristic S1 to S3 is stored as table data describing a coordinate value group of the horizontal axis and the vertical axis.

  FIG. 8 is a flowchart showing the dynamic characteristic learning process. This dynamic characteristic learning process is also performed in the production process of the optical disc apparatus 10 as in the first embodiment. In addition, the same processes as those in the first embodiment are denoted by the same numbers, and redundant description is omitted. However, in the second embodiment, it is not necessary to use the same inspection disk 11A as in the first embodiment, and a general DVD optical disk 11 having a DVD recording layer may be used.

As shown in FIG. 8, in the second embodiment, it is only necessary to measure the control voltage VF when the focus is turned on at two reference positions each consisting of the disk surface and the DVD recording surface (steps S11 to S14).
In step S15A, the sensitivity SX between the disc surface and the DVD recording surface is obtained by calculation. In this case, for example, the sensitivity SX may be obtained using the above-described equation (2). Next, as shown in FIG. 7, the change characteristic having the same or close sensitivity as the sensitivity under the same condition as the sensitivity SX, that is, the sensitivity between the disc surface and the DVD recording surface is the same or close to the sensitivity SX. The change characteristics S1 and S2 are specified.

Subsequently, based on the ratio between the measured sensitivity SX and the stored sensitivities S1X and S2X of the change characteristics S1 and S2, a characteristic that passes between the change characteristics S1 and S2 is determined as a focus drive in the optical disc apparatus 10. It is calculated as a change characteristic of sensitivity of the part 26A (characteristic SS indicated by a two-dot chain line in FIG. 7).
In the example of FIG. 7, when the distance between the sensitivity SX and the sensitivity S1X is a value α, and the distance between the sensitivity SX and the sensitivity S2X is a value β, α: β = 1: 1. Therefore, based on the ratio of α and β, the characteristic SS is calculated to be an intermediate characteristic between the change characteristics S1 and S2. In this case, it is only necessary to obtain each value of the intermediate characteristic using the table data of the change characteristics S1 and S2, and thus the calculation is extremely easy.

If any of the characteristics S1 to S3 has a change characteristic having the same sensitivity as the measured sensitivity SX, the change characteristic is used as the characteristic of the focus drive unit 26A. In this case, calculation of the ratio is unnecessary.
In addition, the inventors have confirmed that the sensitivity change characteristics of the same type of electromagnetic drive type focus drive unit are correlated, and the sensitivity (characteristics) is determined by the method based on the above ratio. SS) could be obtained with high accuracy.

As described above, also in this embodiment, the system control unit 32 moves the control amount of the movement amount of the objective lens 24 and the control voltage (when the focus driving unit 26A focuses on a plurality of predetermined reference positions of the optical disc 11). Based on the control value (VF), the change characteristic of the sensitivity S of the focus drive unit 26A is obtained. Then, the system control unit 32 controls the distance between the optical disc 11 and the objective lens 24 by setting the clip voltage C based on the obtained change characteristic.
As a result, as in the first embodiment, the collision prevention mechanism for preventing the collision of the objective lens 24 can be reduced, and the distance between the optical disc 11 and the objective lens 24 can be accurately controlled. It has various effects such as

  In addition, in the present embodiment, the storage unit 33 stores a plurality of sensitivity change characteristics of the focus drive unit 26A of the same type as the focus drive unit 26A. Then, the system control unit 32 is based on the amount of movement of the objective lens 24 and the control voltage VF (control value) when the focus driving unit 26A focuses on two predetermined reference positions of the optical disc 11. The sensitivity SX is calculated. Thereafter, the system control unit 32 obtains the change characteristics of the sensitivity based on the change characteristics S1 and S2 having the same or similar sensitivity S1X and S2X as the sensitivity SX among the plurality of change characteristics stored in the storage unit 33. Identify. As a result, it is possible to obtain the change characteristic of the sensitivity S only by measurement at two locations.

At this time, the system control unit 32 specifies the change characteristic of the sensitivity S based on the ratio between the measured sensitivity SX and the change characteristics S1 and S2 stored in the storage unit 33. Therefore, the sensitivity S can be obtained by simple calculation. Can be obtained.
In the present embodiment, the case of storing the three types of the upper limit characteristic S1, the average characteristic S2, and the lower limit characteristic S3 has been described. However, three or more types of characteristics may be stored.

Each embodiment mentioned above is only one aspect of the present invention, and can be arbitrarily changed within the scope of the present invention. For example, in each of the above-described embodiments, the case where the control voltage VF of the focus driving unit 26A is used has been described, but the current value supplied to the coil of the focus driving unit 26A may be used instead of the control voltage VF. good. When using a current, a clip current (limit value) may be used instead of the clip voltage C.
In each of the above-described embodiments, the case where the clip voltage C that restricts the upper limit position of the objective lens 24 is set based on the obtained change characteristics has been described. However, even when the clip voltage C that restricts the lower limit position is set. good.

In each of the above-described embodiments, the present invention is applied to the case where the change characteristic of the sensitivity S of the electromagnetically driven focus drive unit 26A is obtained. However, the present invention is not limited to this, and focus drive of other drive methods is used. The present invention can also be applied to the case where the change characteristic of the sensitivity S of the unit 26A is obtained.
In each of the above-described embodiments, the case where a control program for performing the above-described control is stored in the optical disc apparatus 10 in advance has been described. Not limited to this, the control program is stored in a computer-readable recording medium such as a magnetic recording medium, an optical recording medium, or a semiconductor recording medium, and the computer reads the control program from the recording medium and executes it. Also good. The control program may be downloaded from a distribution server or the like via a communication network (electric communication line).

  In each of the above-described embodiments, the case where the present invention is applied to the control device for the optical pickup 21 for in-vehicle use for reproducing a CD or DVD and the optical disc apparatus 10 has been described. Further, the present invention may be applied to a control device for an optical pickup that reproduces another optical disc such as a BD or an optical disc device.

DESCRIPTION OF SYMBOLS 10 Optical disk apparatus 11 Optical disk 21 Optical pick-up 22 Laser irradiation part 23 Light receiving part 24 Objective lens 25 Optical system 26 Lens drive actuator 26A Focus drive part (actuator)
26B Tracking drive unit 31 Servo control unit 32 System control unit (control unit)
33 storage unit 35 limit control unit VF control voltage (control value)
C Clip voltage (limit value)

Claims (6)

An optical pickup that includes an objective lens that can move in the focus direction with respect to the optical disc, and an actuator that moves the objective lens in the focus direction, and irradiates the optical disc with light through the objective lens and receives the reflected light In the control device of
Based on the amount of movement of the objective lens and the control value of the actuator when the actuator is focused on a plurality of predetermined reference positions of the optical disc, a change characteristic of the sensitivity of the actuator is obtained, and the change characteristic A control unit for controlling a distance between the optical disc and the objective lens ,
A storage unit that stores a plurality of sensitivity change characteristics of the actuator of the same type as the actuator;
The control unit calculates the sensitivity based on a movement amount of the objective lens and a control value of the actuator when the actuator focuses on two predetermined reference positions of the optical disc, Among the plurality of change characteristics stored in the storage unit, the change characteristic of the sensitivity is specified based on the change characteristic having the same or close sensitivity as the sensitivity under the same condition, and the optical disc is determined based on the specified change characteristic. And a control device for the optical pickup, wherein the distance between the objective lens and the objective lens is controlled. The said control part specifies the change characteristic of the said sensitivity based on the ratio of the measured said sensitivity and the sensitivity in the same condition in the change characteristic memorize | stored in the said memory | storage part. The optical pickup control device described. 3. The optical pickup control apparatus according to claim 1, wherein the sensitivity change characteristic is a non-linear characteristic. 4. The optical pickup control apparatus according to claim 3, wherein the sensitivity change characteristic is approximated by a Gaussian function or a function of third order or higher. 5. The optical pickup according to claim 1, wherein the control unit sets a limit value of the actuator when performing focusing control of the objective lens based on the change characteristic. 6. Control device. An optical disc apparatus comprising the optical pickup control device according to claim 1 and reproducing the optical disc using the optical pickup.

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