JP4622697B2 - Optical disk device - Google Patents

Description

The present invention relates to an optical disc apparatus that reproduces information recorded on an optical disc, and more particularly to control of a focus speed during a focus search in an optical pickup.

In an optical disk device that records information on or reproduces information from an optical disk, the objective lens of the optical pickup is focused in a direction perpendicular to the recording surface of the optical disk, that is, the objective lens is focused by a focus actuator, before the focus servo is pulled in. Focus search operation to search the focal position (focusing point) of the objective lens by moving in the direction (when the optical pickup is located below the optical disc, the objective lens is shaken from the bottom toward the recording surface of the optical disc. Operation). In this case, the objective lens should be mounted so that the focal position of the objective lens can be detected even if the distance from the center position of the objective lens to the focal point varies due to the warp or surface deflection of the optical disk, the accuracy of mounting the focus actuator or spindle motor, etc. The focus search operation is performed by moving the head in the focus direction with a constant amplitude.

Note that the type of the optical disk loaded in the optical disk device at the time of focus search is determined as follows:
Based on the level of the focus error signal (FE) at the time of the focus search and the order of level change of the focus error signal, whether the objective lens is closer to the recording surface of the optical disc than the focal point or away from it This is well known by measuring the level of the area determination signal (AS) indicating

FIG. 4 is a circuit block diagram of a focus drive circuit and its peripheral circuits provided in a conventional optical disc apparatus. In FIG. 4, the focus drive circuit 1 includes a resistor 2 and a resistor 3
, An operational amplifier 4 constituting an inverting amplifier circuit, and a positive / negative drive voltage separation circuit 5. The CPU 6 is a signal processing circuit that includes an A / D converter 61 that converts an analog signal into a digital signal and a D / A converter 62 that converts a digital signal into an analog signal, and generates and outputs a focus drive signal. The RAM 7 is a random access memory that temporarily stores data necessary for the CPU 6 arithmetic processing, and the ROM 8 is a read-only memory that stores programs and data necessary for the CPU 6 arithmetic processing.

In the focus drive circuit 1, the non-inverting input terminal + of the operational amplifier 4 is grounded, and the inverting input terminal − is connected to the output terminal of the operational amplifier 4 through the resistor 3 and to one end of the resistor 2. The output terminal of the operational amplifier 4 is connected to the input terminal of the positive / negative drive voltage separation circuit 5. The output terminals of the D / A converter 62 in the CPU 6 are a resistor 9 and a resistor 1
It is connected to the other end of the resistor 2 via 0. A connection point between the resistor 10 and the resistor 2 is grounded via a capacitor 11. The output line L1 of the plus driving voltage FS + for focus is
The output line L2 of the focus minus drive voltage FS− is connected to the minus drive voltage input terminal of the focus actuator 19 and connected to the plus drive voltage input terminal of the focus actuator 19 in the optical pickup 20.

The focus actuator 19 finely moves an objective lens (not shown) in the optical pickup 20 in a direction perpendicular to the recording surface of the optical disk. When a focus plus drive voltage FS + is applied to a coil (not shown), the objective lens is moved. When moving in the direction approaching the recording surface of the optical disk and applying a minus driving voltage FS− for focusing to the coil,
The structure is such that the objective lens is moved away from the recording surface of the optical disk.
JP 2004-273023 A JP 2002-203323 A JP 2002-170250 A JP-A-10-55546

In such a conventional optical disc apparatus, an IC (
The voltage of the output stage of the focus drive circuit 1 varies due to variations in the integrated circuit). Characteristics (gain) of IC manufacturers and operational amplifiers 4 in the focus drive circuit 1
For example, the output stage voltage of the focus drive circuit 1 may vary by about 4 dB. If the speed of the focus search is too slow, the surface shake speed of the optical disc with the surface shake may be lost, and the S-shaped focus error signal may not be measured.

FIG. 5 is a waveform diagram showing the relationship between the focus search drive voltage (FD) and the focus error signal (FE) when focus search is performed at a predetermined target speed. FIG.
) Indicates a focus search drive voltage (FD) applied to the coil of the focus actuator when focus search is performed at a predetermined target speed. In FIG. 5A, when the horizontal axis is the time and the vertical axis is the position of the objective lens of the optical pickup relative to the optical disk (the position closer to the optical disk as it goes up), the focus search drive voltage (FD )
This line 51 can also be viewed as the movement locus of the objective lens.

The focus search drive voltage (FD) changes stepwise with time, and the lower the voltage for each step, the lower the focus search drive voltage (FD) per unit time. Change becomes smaller and the focus search speed becomes slower. Conversely, the higher the voltage for each step, the greater the change in the focus search drive voltage (FD) per unit time, and the faster the focus search speed.

FIG. 5 (2) shows a normal focus error signal (FE) obtained when the objective lens is moved in accordance with the focus search drive voltage (FD) indicated by the line 51 in the case of reproducing an optical disk having no runout. Indicates. FIG. 5 (3) shows a focus error signal at the time of surface shake obtained when the objective lens is moved in accordance with the focus search drive voltage (FD) indicated by the line 51 in the case of reproducing an optical disc having surface shake. FE).

FIG. 6 is a waveform diagram showing the relationship between the focus search drive voltage (FD) and the focus error signal (FE) when focus search is performed at a speed slower than a predetermined target speed. FIG. 6A shows a focus search drive voltage (FD) applied to the focus actuator coil when focus search is performed at a speed slower than a predetermined target speed. Also in FIG. 6A, when the horizontal axis is the time and the vertical axis is the position of the objective lens of the optical pickup relative to the optical disk (the position closer to the optical disk as it goes upward), the focus search drive voltage ( The line 61 of (FD) can also be viewed as the movement locus of the objective lens.

FIG. 6 (2) is obtained when an optical disk without surface shake is reproduced, and is obtained when the objective lens moves in accordance with the focus search drive voltage (FD) indicated by the line 61, and when the focus search speed is low. A focus error signal (FE) is shown. FIG. 6 (3) shows a case where an optical disk with surface wobbling is reproduced, and the focus search drive voltage (F
D) Focus error signal (FE) at the time of surface shake obtained when the objective lens moves according to D)
).

The focus error signal (FE) shown in FIG. 6 (3) is not S-shaped and is in a state where it cannot be measured. As mentioned above, if the focus search speed is too slow,
This is the reason why the S-shape of the focus error signal (FE) cannot be measured due to the loss of the surface shake speed of the optical disc having the surface shake.

FIG. 7 is a waveform diagram showing the relationship between the focus search drive voltage (FD) and the focus error signal (FE) when focus search is performed at a speed faster than a predetermined target speed. FIG. 7A shows the focus search drive voltage (FD) applied to the coil of the focus actuator when focus search is performed at a speed faster than a predetermined target speed. Also in FIG. 7A, when the horizontal axis is the time and the vertical axis is the position of the objective lens of the optical pickup relative to the optical disk (the position closer to the optical disk as it goes up), the focus search drive voltage ( The line 71 of (FD) can also be viewed as the movement locus of the objective lens.

FIG. 7 (2) is obtained when an optical disk without surface shake is reproduced, and is obtained when the objective lens is moved according to the focus search drive voltage (FD) indicated by the line 71, and when the focus search speed is high. A focus error signal (FE) is shown. FIG. 7 (3) shows a case where an optical disk with surface wobbling is reproduced, and the focus search drive voltage (F
D) Focus error signal (FE) at the time of surface shake obtained when the objective lens moves according to D)
). As described above, the focus error signal (FE) as shown in FIG. 7 (2) or FIG. 7 (3) has a too high focus search speed, so the sampling becomes rough, and the accurate level of the S-shape can be measured. The reason is that there is a possibility that it will not be possible.

The prior art in Patent Document 1 is configured so that the focus search operation can be performed with the minimum necessary amplitude around the focal point by moving the objective lens of the optical pickup in a direction perpendicular to the disk surface. However, it does not suppress variations in the gain of the focus driver circuit, and does not relate to the focus search speed.

The prior art of Patent Document 2 is an interlayer jump for applying focus control to each recording layer of a disc having a plurality of recording layers, without being affected by disturbances or changes in the moving speed of the objective lens.
Although it can be performed stably in a short time, this prior art also does not suppress variations in the gain of the focus driver circuit, and does not relate to the focus search speed.

The prior art of Patent Document 3 is performed by changing the fluctuation range of the focus search driving voltage of the focus actuator that moves the focusing means according to the position of the optical pickup in the radial direction of the optical disc. This prior art also does not suppress variation in the gain of the focus driver circuit, and does not relate to the focus search speed.

The prior art of Patent Document 4 shortens the time from loading to reproduction by shortening the time of focus search, and can perform focus control stably without being affected by scratches or vibration of the optical disk. However, this prior art also does not suppress the variation in the gain of the focus driver circuit, and does not relate to the focus search speed.

The present invention has been made to solve the above-described problems, and an optical disc having a focus drive circuit capable of absorbing a variation in search speed during a focus search in an optical pickup and making the search speed constant. An object is to provide an apparatus.

In order to achieve the above object, the invention of claim 1 includes an optical pickup that optically reads information recorded on an optical disc, a signal processing circuit that generates and outputs a focus drive signal,
In an optical disk apparatus having a focus drive circuit that inputs a focus drive signal from the signal processing circuit and supplies a focus plus drive voltage and a focus minus drive voltage to a focus actuator in the optical pickup, an output from the focus drive circuit A difference voltage output circuit that outputs a difference voltage between the focus plus drive voltage and the focus minus drive voltage, and the voltage of the output stage of the focus drive circuit is supplied via the difference voltage output circuit when the power is turned on. The control is performed so as to suppress the gain variation of the focus drive circuit by feeding back to the signal processing circuit, and a voltage of 0 V is output from the D / A converter in the signal processing circuit to / D converter for electricity Offset storage means for storing in memory the voltage value as an offset voltage value by measuring the value, the outputs a positive voltage from the D / A converter A
A positive voltage measurement storage means for measuring the voltage value with the / D converter and storing the voltage value in the memory as a positive measurement value; and outputting the negative voltage from the D / A converter to the A
A negative voltage measurement storage means for measuring the voltage value with the / D converter and storing the voltage value in the memory as a negative measurement value, and a positive correction value based on the positive measurement value and the target voltage value And a correction value calculation means for calculating a negative correction value based on the negative measurement value and the target voltage value, and a positive search speed that is actually output during a focus search. And a search speed calculation means for calculating a negative search speed that is actually output during a focus search based on the negative correction value and the target speed set value and calculating based on the target speed set value. In preparation for
The positive voltage measurement storage means performs a calculation of positive measurement value = measurement value of A / D converter at the time of positive output−offset voltage value, and the negative voltage measurement storage means
The minus side measurement value = calculation value of the A / D converter at the minus side output−the offset voltage value is calculated, and the correction value calculation means is the plus side correction value = the plus side measurement value ÷ the target voltage value. The calculation and the calculation of minus correction value = minus measurement value / target voltage value are performed, and the search speed calculating means outputs the actually output plus search speed = plus correction value × target speed setting value, An optical disc apparatus is provided that performs an operation of a negative search speed to be actually output = a correction value on the negative side × a target speed set value.

In this configuration, the offset measurement storage means first outputs a 0V voltage from the D / A converter, and when the 0V voltage is measured by the A / D converter, the offset voltage at that time is generated as a digital value. Save the voltage value in memory.

Next, the positive voltage measurement storage means outputs a + voltage from the D / A converter, and when this + voltage is measured by the A / D converter, the + voltage at that time is generated as a digital value. The + voltage value is stored in the memory as the measured value on the plus side. The plus side voltage measurement storage means performs a calculation of plus side measured value = measured value of A / D converter at plus side output−offset voltage value.

Thereafter, the negative voltage measurement storage means outputs a negative voltage from the D / A converter,
When the negative voltage is measured by the A / D converter, the negative voltage at that time is generated as a digital value, and the negative voltage value is stored in the memory as a negative measured value. The minus side voltage measurement storage means performs a calculation of minus side measurement value = A / D converter measurement value at minus side output−offset voltage value.

Since the target voltage value is derived from the measurement value (voltage value measured by the A / D converter), in order to match the focus search drive voltage at the target search speed with the target voltage value, The correction value calculation means calculates a correction value. That is, the correction value calculation means performs a calculation of plus correction value = plus measurement value / target voltage value and minus correction value = minus measurement value / target voltage value.

When the correction value is calculated in this way, the focus search drive voltage that can be actually output can be obtained. Therefore, the search speed calculation means actually outputs the focus search based on the correction value and the target speed setting value. Calculate the search speed. That is, the search speed calculation means calculates the actual output plus side search speed = plus correction value × target speed setting value and the actual output minus side search speed = minus side correction value × target speed setting value. I do.

According to this configuration, when the power is turned on, the focus search drive voltage at the output stage of the focus drive circuit is fed back to the signal processing circuit via the differential voltage output circuit, thereby suppressing variations in the gain of the focus drive circuit. As a result, variations in the search speed during focus search in the optical pickup can be absorbed, and the search speed can be made constant. Therefore, the focus search can be accurately performed even on an optical disc having surface wobbling. It becomes possible.

According to a second aspect of the present invention, there is provided an optical pickup that optically reads information recorded on an optical disc, a signal processing circuit that generates and outputs a focus driving signal, and a focus driving signal from the signal processing circuit. In an optical disc apparatus having a focus drive circuit that supplies a focus plus drive voltage and a focus minus drive voltage to a focus actuator in an optical pickup, a focus plus drive voltage and a focus minus drive voltage output from the focus drive circuit, A difference voltage output circuit for outputting a difference voltage of the focus drive circuit, and a voltage of an output stage of the focus drive circuit is fed back to the signal processing circuit via the difference voltage output circuit when the power is turned on to Suppress variation in To provide an optical disk apparatus characterized in that a configuration of controlling the so that.

In this configuration, when the power is turned on, the voltage at the output stage of the focus drive circuit is fed back to the signal processing circuit via the differential voltage output circuit, thereby suppressing variations in the gain of the focus drive circuit.

According to this configuration, when the power is turned on, the focus search drive voltage at the output stage of the focus drive circuit is fed back to the signal processing circuit via the differential voltage output circuit, thereby suppressing variations in the gain of the focus drive circuit. As a result, variations in the search speed during focus search in the optical pickup can be absorbed, and the search speed can be made constant. Therefore, the focus search can be accurately performed even on an optical disc having surface wobbling. It becomes possible.

According to a third aspect of the present invention, in the second aspect of the present invention, the signal processing circuit outputs a voltage of 0 V from a D / A converter inside the signal processing circuit and outputs a voltage at the A / D converter inside the signal processing circuit. Offset measurement storage means for measuring the value and storing the voltage value in the memory as an offset voltage value; outputting a positive voltage from the D / A converter and measuring the voltage value by the A / D converter; Plus-side voltage measurement storage means for storing in the memory as a plus-side measured value, and a negative voltage is output from the D / A converter, the voltage value is measured by the A / D converter, and the voltage value is Negative voltage measurement storage means for storing in the memory as a measured value, and a positive correction value is calculated based on the positive measured value and the target voltage value, and the negative voltage is calculated. Correction value calculating means for calculating a negative correction value based on the measured value and the target voltage value, and the positive search speed actually output during the focus search based on the positive correction value and the target speed setting value. And a search speed calculation means for calculating a negative search speed that is actually output during the focus search based on the negative correction value and the target speed setting value.

Therefore, the signal processing circuit obtains the search speed that is actually output by calculating the offset voltage value, the positive measurement value, the negative measurement value, the positive correction value, and the negative correction value. Can do.

In the invention of claim 4, in the invention of claim 3, the plus side voltage measurement storage means performs a calculation of a plus side measurement value = a measurement value of the A / D converter at the plus side output−an offset voltage value, The minus side voltage measurement storage means performs a calculation of minus side measurement value = A / D converter measurement value at minus side output−offset voltage value, and the correction value calculation means has a plus side correction value = plus. Side search value ÷ target voltage value and minus side correction value = minus side measurement value ÷ target voltage value. The search speed calculation means calculates the actual search output plus side search speed = plus side. Correction value × target speed set value and the actual output minus side search speed = minus side correction value × target speed set value.

Therefore, the measured value on the plus side, the measured value on the minus side, the corrected value on the plus side, the corrected value on the minus side, the plus side search speed that is actually output, and the minus side search speed that is actually output are specifically calculated. It becomes possible to calculate.

As described above, according to the present invention, an optical pickup that optically reads information recorded on an optical disc, a signal processing circuit that generates and outputs a focus drive signal, and a focus drive signal from the signal processing circuit are input. In the optical disk apparatus having a focus drive circuit for supplying a focus plus drive voltage and a focus minus drive voltage to the focus actuator in the optical pickup, the focus plus drive voltage and the focus minus output from the focus drive circuit A differential voltage output circuit for outputting a differential voltage with respect to the drive voltage, and the voltage of the output stage of the focus drive circuit is fed back to the signal processing circuit via the differential voltage output circuit when the power is turned on, and the focus drive If the gain of the circuit It is configured to control the delay, and a voltage of 0 V is output from the D / A converter in the signal processing circuit, and the voltage value is measured by the A / D converter in the signal processing circuit to offset the voltage value. Offset storage means for storing the voltage value in the memory, outputting a positive voltage from the D / A converter, measuring the voltage value by the A / D converter, and storing the voltage value in the memory as a measured value on the positive side Plus-side voltage measurement storing means, minus-side voltage measurement for outputting a minus voltage from the D / A converter, measuring the voltage value by the A / D converter, and storing the voltage value in the memory as a minus-side measured value A positive correction value is calculated based on the storage means, the positive measurement value and the target voltage value, and based on the negative measurement value and the target voltage value. Correction value calculation means for calculating a negative correction value, and a positive search speed actually output during focus search is calculated based on the positive correction value and target speed set value, and is actually calculated during focus search. The signal processing circuit includes search speed calculation means for calculating a negative search speed to be output based on the negative correction value and the target speed setting value, and the positive voltage measurement storage means includes a positive measurement Value = measurement value of A / D converter at plus side output−offset voltage value, and minus voltage measurement storage means has minus side measurement value = measurement value of A / D converter at minus side output. A calculation called an offset voltage value, and the correction value calculating means calculates a correction value on the plus side = a measured value on the plus side ÷ target voltage value; And the correction value on the minus side = the measured value on the minus side / the target voltage value, and the search speed calculation means calculates the actual output plus side search speed = the correction value on the plus side × the target speed set value and the actual value. The negative search speed to be output to the negative side = the correction value on the negative side x the target speed set value is calculated, so that variation in the gain of the focus drive circuit can be suppressed. Variations in the search speed can be absorbed, and the search speed can be made constant. Therefore, it is possible to perform a focus search with high precision even for an optical disc having surface wobbling.

According to the present invention, an optical pickup that optically reads information recorded on an optical disc, a signal processing circuit that generates and outputs a focus drive signal, and a focus drive signal from the signal processing circuit are input. A focus plus drive voltage and a focus minus drive voltage output from the focus drive circuit in an optical disc apparatus having a focus drive circuit for supplying a focus plus drive voltage and a focus minus drive voltage to a focus actuator in the optical pickup. A voltage output circuit for outputting a voltage difference between the output of the focus drive circuit and the feedback signal from the output stage of the focus drive circuit to the signal processing circuit via the difference voltage output circuit when the power is turned on. Gain variation Since the control is configured to suppress the variation in the gain of the focus drive circuit, the variation in the search speed during the focus search in the optical pickup can be absorbed, and the search speed can be made constant. Therefore, it is possible to perform a focus search with high accuracy even for an optical disc having surface wobbling.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a circuit block diagram of a focus drive circuit and its peripheral circuits provided in an optical disc apparatus according to an embodiment of the present invention.

In FIG. 1, the focus drive circuit 1 includes a resistor 2, a resistor 3, an operational amplifier 4 that constitutes an inverting amplifier circuit, and a positive / negative drive voltage separation circuit 5. The CPU 6 is a signal processing circuit that includes an A / D converter 61 that converts an analog signal into a digital signal and a D / A converter 62 that converts a digital signal into an analog signal, and generates and outputs a focus drive signal. The RAM 7 is a random access memory that temporarily stores data necessary for the CPU 6 arithmetic processing, and the ROM 8 is a read-only memory that stores programs and data necessary for the CPU 6 arithmetic processing.

In the focus drive circuit 1, the non-inverting input terminal + of the operational amplifier 4 is grounded, and the inverting input terminal − is connected to the output terminal of the operational amplifier 4 through the resistor 3 and to one end of the resistor 2. The output terminal of the operational amplifier 4 is connected to the input terminal of the positive / negative drive voltage separation circuit 5. The output terminals of the D / A converter 62 in the CPU 6 are a resistor 9 and a resistor 1
It is connected to the other end of the resistor 2 via 0. A connection point between the resistor 10 and the resistor 2 is grounded via a capacitor 11.

The differential voltage output circuit 18 includes a resistor 12, a resistor 13, a resistor 14, an operational amplifier 15 that constitutes a differential amplifier circuit (1 × amplification), a resistor 16, and a capacitor 17. In the differential voltage output circuit 18, the non-inverting input terminal + of the operational amplifier 15 is grounded via the resistor 14, and the inverting input terminal − is connected to one end of the resistor 16 and one end of the capacitor 17. The other end of the resistor 16 and the other end of the capacitor 17 are connected to the output terminal of the operational amplifier 15 and the CP.
It is connected to the input terminal of the A / D converter 61 in U6.

The non-inverting input terminal + of the operational amplifier 15 is connected to the output line L1 of the focus plus drive voltage FS + of the positive / negative drive voltage separation circuit 5 of the focus drive circuit 5 via the resistor 13. The inverting input terminal − of the operational amplifier 15 is connected to the output line L 2 of the focus negative drive voltage FS− of the positive / negative drive voltage separation circuit 5 of the focus drive circuit 5 via the resistor 12.
It is connected to the. The focus positive drive voltage FS + output line L1 is connected to the positive drive voltage input terminal of the focus actuator 19 in the optical pickup 20, and the focus negative drive voltage FS− output line L2 is the negative drive voltage of the focus actuator 19. Connected to the input terminal.

The focus actuator 19 finely moves an objective lens (not shown) in the optical pickup 20 in a direction perpendicular to the recording surface of the optical disk. When a focus plus drive voltage FS + is applied to a coil (not shown), the objective lens is moved. When moving in the direction approaching the recording surface of the optical disk and applying a minus driving voltage FS− for focusing to the coil,
The structure is such that the objective lens is moved away from the recording surface of the optical disk.

The CPU 6 outputs a voltage of 0 V from the D / A converter 62, measures the voltage value by the A / D converter 61, and stores the voltage value in the RAM 7 as an offset voltage value, and the D / A The A / D converter 61 outputs a positive voltage from the converter 62.
The positive voltage measurement storage means 64 that measures the voltage value and stores the voltage value in the RAM 7 as a positive measurement value, and outputs a negative voltage from the D / A converter 62, and the A / D converter 61 outputs the voltage value. And a negative voltage measurement storage means 65 for storing the voltage value in the RAM 7 as a negative measurement value, and calculating a positive correction value based on the positive measurement value and the target voltage value. Correction value calculation means 66 for calculating a negative correction value based on a negative measurement value and a target voltage value, and a positive search speed that is actually output during a focus search is set to the positive correction value and target speed setting. The negative search speed that is calculated based on the value and actually output during the focus search is calculated based on the negative correction value and the target speed setting value. And a search speed calculation means 67 for calculating.

The positive side voltage measurement storage unit 64 performs a calculation of the positive side measurement value = the measurement value of the A / D converter at the time of the positive side output−the offset voltage value, and the negative side voltage measurement storage unit 65 performs the calculation of the negative side measurement value. = Calculation of measured value of A / D converter at minus side output-offset voltage value. The correction value calculation means 66 performs a calculation of plus correction value = plus measurement value ÷ target voltage value and minus correction value = minus measurement value ÷ target voltage value, and search speed calculation means. 67 calculates the actual output positive side search speed = positive side correction value × target speed setting value and the actual output negative side search speed = negative side correction value × target speed setting value.

FIG. 2 is a signal waveform diagram for explaining the operations of the CPU 6, the focus drive circuit 1 and the differential voltage output circuit 18 shown in FIG. 2A is a focus drive signal output from the CPU 6, FIG. 2B is a focus search drive voltage output from the operational amplifier 4 of the focus drive circuit 1 based on the focus drive signal, and FIG. Is a focus positive drive voltage FS + output from the output line L1 of the positive / negative drive voltage separation circuit 5 based on the focus search drive voltage, and FIG. 2 (4) is a positive / negative drive voltage separation based on the focus search drive voltage. Focusing minus driving voltage FS output from the output line L2 of the circuit 5
FIG. 2 (5) shows the differential voltage as a feedback signal output from the differential voltage output circuit 18.

FIG. 3 is a flowchart for explaining processing until calculation of a search speed that is actually output in the focus search in the present embodiment. With reference to this flowchart and FIG. 1, processing until calculation of the search speed that is actually output during the focus search will be described.

First, a 0V voltage is output from the D / A converter 62 of the CPU 6 (step S1), and when this 0V voltage is measured by the A / D converter 61 of the CPU 6 (step S2), the offset voltage at that time is generated as a digital value. Therefore, this offset voltage value is stored in the RAM 7 (step S3). The processes in steps S1 to S3 are performed by the offset measurement storage unit 63 of the CPU 6.

Next, when a + voltage is output from the D / A converter 62 (step S4) and this + voltage is measured by the A / D converter 61 (step S5), the + voltage at that time is generated as a digital value. The + voltage value is stored in the RAM 7 as a positive measured value (step S6). The processes in steps S4 to S6 are performed by the plus-side voltage measurement storage unit 64 of the CPU 6. The plus side voltage measurement storage means 64 performs a calculation of plus side measurement value = A / D converter measurement value at plus side output−offset voltage value.

Thereafter, a negative voltage is output from the D / A converter 62 (step S7), and when the negative voltage is measured by the A / D converter 61 (step S8), the negative voltage at that time is generated as a digital value. The negative voltage value is stored in the RAM 7 as a negative measurement value (step S9). The processes in steps S7 to S9 are performed by the minus side voltage measurement storage unit 65 of the CPU 6. The minus side voltage measurement storage means 65 performs a calculation of minus side measurement value = A / D converter measurement value at minus side output−offset voltage value.

Since the target voltage value is derived from the measured value (voltage value measured by the A / D converter), the CPU 1 is set so that the focus search drive voltage at the target search speed is matched with the target voltage value. The correction value calculation means 66 calculates a correction value (step S10).
That is, the correction value calculation means 66 performs a calculation of plus correction value = plus measurement value ÷ target voltage value and minus correction value = minus measurement value ÷ target voltage value.
The target voltage value referred to here is, when the gain of the focus drive circuit 1 is in a typical state, for example, if the gain varies between 18 dB and 22 dB, it is an intermediate value of 20
It means a voltage value measured by the A / D converter 61 in the state of dB.

When the correction value is calculated in this way, the focus search drive voltage that can be actually output can be obtained. Therefore, the search speed calculation means 76 of the CPU 6 performs the focus search based on the correction value and the target speed setting value. The search speed to be actually output is calculated (step S11).
That is, the search speed calculation means 76 is that the positive search speed that is actually output = the correction value on the positive side × the target speed setting value and the negative output speed that is actually output = the correction value on the negative side × the target speed setting value. Perform the operation.

As described above, according to the present embodiment, the focus search drive voltage at the output stage of the focus drive circuit 1 is fed back to the CPU 6 via the differential voltage output circuit 18 when the power is turned on. Variation in gain can be suppressed, and as a result, variation in search speed at the time of focus search in the optical pickup 20 can be absorbed, and the search speed can be made constant. Focus search can be performed with high accuracy.

1 is a circuit block diagram of a focus drive circuit and its peripheral circuits provided in an optical disc apparatus according to an embodiment of the present invention. FIG. 2 is a signal waveform diagram for explaining operations of a CPU, a focus drive circuit, and a differential voltage output circuit shown in FIG. 1. 5 is a flowchart for explaining processing until calculation of a search speed that is actually output in the focus search in the embodiment. It is a circuit block diagram of a focus drive circuit and its peripheral circuit provided in a conventional optical disc apparatus. FIG. 6 is a waveform diagram showing a relationship between a focus search drive voltage and a focus error signal when a focus search is performed at a predetermined target speed. FIG. 6 is a waveform diagram showing a relationship between a focus search drive voltage and a focus error signal when focus search is performed at a speed slower than a predetermined target speed. FIG. 6 is a waveform diagram showing a relationship between a focus search drive voltage and a focus error signal when focus search is performed at a speed faster than a predetermined target speed.

Explanation of symbols

1 Focus drive circuit 6 CPU (signal processing circuit)
7 RAM (memory)
DESCRIPTION OF SYMBOLS 18 Differential voltage output circuit 19 Force actuator 20 Optical pick-up 61 A / D converter 62 D / A converter 63 Offset measurement preservation | save means 64 Plus side voltage measurement preservation | save means 65 Negative side voltage measurement preservation | save means 66 Correction value calculation means 67 Search speed calculation means

Claims (3)

An optical pickup that optically reads information recorded on an optical disc, a signal processing circuit that generates and outputs a focus drive signal, and a focus drive signal from the signal processing circuit is input to focus on a focus actuator in the optical pickup In an optical disc apparatus having a focus drive circuit for supplying a positive drive voltage for focus and a negative drive voltage for focus,
A differential voltage output circuit for outputting a differential voltage between a focus positive drive voltage and a focus negative drive voltage output from the focus drive circuit, and the voltage of the output stage of the focus drive circuit is set to the difference voltage when the power is turned on; It is fed back to the signal processing circuit via an output circuit, and is configured to control so as to suppress variation in gain of the focus drive circuit,
Offset measurement storage that outputs a voltage of 0 V from the D / A converter in the signal processing circuit, measures the voltage value by the A / D converter in the signal processing circuit, and stores the voltage value in the memory as an offset voltage value And a positive-side voltage measurement storage unit that outputs a positive voltage from the D / A converter, measures a voltage value by the A / D converter, and stores the voltage value in a memory as a positive-side measurement value; Negative voltage measurement storage means for outputting a negative voltage from the D / A converter, measuring the voltage value with the A / D converter, and storing the voltage value in a memory as a negative measurement value, and the positive measurement The correction value on the plus side is calculated based on the value and the target voltage value, and the correction value on the minus side is calculated based on the measured value on the minus side and the target voltage value. The value calculating means calculates the positive search speed that is actually output during the focus search based on the positive correction value and the target speed setting value, and the negative search speed that is actually output during the focus search. A search speed calculation means for calculating based on a correction value on the side and a target speed set value in the signal processing circuit,
The positive voltage measurement storage means performs a calculation of positive measurement value = A / D converter measurement value at the time of positive output−offset voltage value, and the negative voltage measurement storage means is a negative measurement value. = A / D converter measured value at minus side output-offset voltage value is calculated, and the correction value calculating means calculates plus side correction value = plus side measured value ÷ target voltage value and minus side Correction value = minus side measured value / target voltage value is calculated, and the search speed calculation means actually outputs plus side search speed = plus side correction value × target speed set value and actually outputs There line calculation of negative search speed = minus side of the correction value × target speed setting value,
The optical disc apparatus , wherein the signal processing circuit generates the focus drive signal based on a calculation result of the search speed calculation means . An optical pickup that optically reads information recorded on an optical disc, a signal processing circuit that generates and outputs a focus drive signal, and a focus drive signal from the signal processing circuit is input to focus on a focus actuator in the optical pickup In an optical disc apparatus having a focus drive circuit for supplying a positive drive voltage for focus and a negative drive voltage for focus,
A differential voltage output circuit for outputting a differential voltage between a focus positive drive voltage and a focus negative drive voltage output from the focus drive circuit, and the voltage of the output stage of the focus drive circuit is set to the difference voltage when the power is turned on; It is fed back to the signal processing circuit via an output circuit, and is configured to control so as to suppress variation in gain of the focus drive circuit ,
The signal processing circuit outputs a voltage of 0 V from a D / A converter inside the signal processing circuit, measures a voltage value with the A / D converter inside the signal processing circuit, and stores the voltage value as an offset voltage value Offset measurement storage means for storing the positive voltage, and a positive voltage that outputs a positive voltage from the D / A converter, measures the voltage value by the A / D converter, and stores the voltage value in the memory as a positive measurement value Measurement storage means, negative voltage measurement storage means for outputting a negative voltage from the D / A converter, measuring a voltage value with the A / D converter, and storing the voltage value in a memory as a negative measurement value; The correction value on the plus side is calculated based on the measured value and the target voltage value on the plus side, and the minus side is calculated on the basis of the measured value and the target voltage value on the minus side. Correction value calculation means for calculating a correction value, and a positive side search speed that is actually output during the focus search is calculated based on the positive side correction value and the target speed setting value, and a negative side that is actually output during the focus search. Search speed calculating means for calculating the search speed based on the negative correction value and the target speed setting value,
The optical disc apparatus , wherein the signal processing circuit generates the focus drive signal based on a calculation result of the search speed calculation means . The positive voltage measurement storage means performs a calculation of positive measurement value = A / D converter measurement value at the time of positive output−offset voltage value, and the negative voltage measurement storage means is a negative measurement value. = A / D converter measured value at minus side output-offset voltage value is calculated, and the correction value calculating means calculates plus side correction value = plus side measured value ÷ target voltage value and minus side Correction value = minus side measured value / target voltage value is calculated, and the search speed calculation means actually outputs plus side search speed = plus side correction value × target speed set value and actually outputs 3. The optical disc apparatus according to claim 2 , wherein the calculation is performed as: minus side search speed = minus side correction value × target speed set value.

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