JPH0815087A - Instrument and method for measuring characteristics of optical pickup - Google Patents

Abstract

PURPOSE:To absorb the peculiar fluctuation of a tracking coil so as to improve the reliability of measuring the visual field of an optical pickup by storing a steep digital value at the point of time the steep digital value becomes coincident with a preset digital value and driving the tracking coil based on the steep digital value. CONSTITUTION:The principal part of an instrument for measuring characteristics of optical pickup is constituted of a moving amount detecting section 2 which detects the moving amount of signals by inputting electric signals from a light receiving section 1, control section 3 which outputs the control signal corresponding to the moving amount after comparison, and change-over switch SW1 which switches a steep signal to a tracking error signal or a tracking error signal to a steep signal. The output signal of the switch SW1 controls the drive of a tracking coil 6 through a driving amplifier 5. At the time of measuring the visual field of the optical pickup, the influence of the fluctuation of the coil 6 on the measurement is eliminated by controlling a memory 7 which stores the steep digital value at the point of time the value becomes coincident with a preset digital value, switch SW2 which selects the moving direction of the optical pickup, and polarity inverting circuit 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup characteristic measuring apparatus and method for measuring the optical characteristic of an optical pickup, for example, for measuring the optical characteristic such as a visual field measurement.

[0002]

2. Description of the Related Art At present, a recording and / or reproducing apparatus using an optical disk capable of holding a large amount of data as a recording medium is supplied to the market. The writing of data to the optical disc and the reading of data from the optical disc are performed by moving an optical pickup incorporated in the apparatus within a recordable range. At this time, the recording and / or reproducing device supplies servo control to the tracking coil to perform servo control so that the optical pickup can follow the track of the optical disk.

[0003]

By the way, the operating characteristics of the optical pickup, which is delicately moved along with the operation of the tracking coil during manufacturing, becomes an important factor in recording and reproduction. Therefore, an item called visual field measurement is provided during the measurement of the characteristics of the optical pickup. In this field-of-view measurement, conventionally, the measurement was performed by applying a constant voltage.

However, when the field of view is measured, the moving distance of the tracking coil may not be within the specified range even if a driving current is supplied to the tracking coil due to the application of a constant voltage. As described above, it is known that the tracking coil has inherent variations in operation. Since this variation is not absorbed, there are cases where the optical pickup cannot be moved from the measurement start position to a predetermined track. In such a case,
The visual field could not be measured accurately.

Therefore, the present invention has been made in view of the above-mentioned circumstances, and an optical pickup characteristic measuring device and an optical pickup capable of controlling the operation of the optical pickup by absorbing variations inherent in the coil. The purpose is to provide a characteristic measuring method.

[0006]

In order to solve the above-mentioned problems, the optical pickup characteristic measuring apparatus according to the present invention moves the objective lens of the optical pickup to a predetermined track position by using a tracking coil, and moves the objective lens to a predetermined track position. In the optical pickup characteristic measuring device for measuring the optical characteristic of the optical pickup at the track position of the optical pickup, the objective lens of A movement amount detection unit that detects a movement amount, a control unit that outputs a control signal by comparing the output from the movement amount detection unit with a preset value, and converts the supplied sweep value into an analog signal D / A converter output and tracking error signal according to the output signal from the control unit It is characterized by having a changeover switch for switching.

Here, the optical measurement is a visual field measurement for measuring the level and the balance of the tracking error signal at a predetermined measurement position. A memory is provided for storing a value supplied according to a control signal from the control unit when the output of the D / A converter is stopped, that is, a value of a sweep digital signal for generating a tracking coil voltage, for example. .

Further, when the objective lens is moved from the current position to the other direction by the tracking coil, for example, to a predetermined position where the inner circumference side of the optical disk is the negative side, the sweep value supplied and the value read from the memory. And a polarity inversion circuit that inverts the polarity of the output signal from the D / A converter with respect to the output of the signal selection switch. The operations of the memory, the signal selection switch, and the polarity inversion circuit are controlled according to the control signal supplied from the CPU, for example. Further, the changeover switch is also changed over, for example, in response to a changeover signal from the CPU.

In order to solve the above-mentioned problems, the optical pickup characteristic measuring method according to the present invention moves the objective lens of the optical pickup to a predetermined track position by using a tracking coil, and the optical pickup at the predetermined track position. In the optical pickup characteristic measuring method for measuring the optical characteristics of the optical pickup, a rotation stopping step of stopping the rotation of the optical disc, that is, a rotation of the spindle motor, a focus on step of operating the focus servo of the optical pickup, and a driving of the tracking coil. A counting step of counting the number of tracks accompanying the movement of the optical pickup while applying the voltage required for the, a comparing step of comparing the count value in the counting step with a preset count value, and a predetermined step after this comparing step. Move the distance It is characterized by having an optical measuring step of optical measurement by the optical pickup.

In the optical measuring step, a visual field measurement for measuring the level and the balance of the tracking error signal at a predetermined measuring position is performed.

[0011]

In the optical pickup characteristic measuring apparatus according to the present invention, the output of the movement amount detecting unit detecting the amount of movement of the coil in one direction from the current position is supplied to the control unit. The control unit outputs a control signal, which compares the detected output and a preset value, to the changeover switch. Also, the D / A converter is
The supplied sweep digital value is converted into an analog signal and supplied to the changeover switch. The selector switch switches between the analog signal and the tracking error signal and outputs it. Thereby, for example, the tracking coil that causes the optical pickup to follow the track absorbs the variation of the tracking coil itself and reliably moves the optical pickup to a predetermined track position.

By storing the value of the sweep digital signal for generating the tracking coil voltage in the memory, the optical measurement corresponding to each unique tracking coil can be repeated.

Further, by providing a signal selection switch and a polarity reversing circuit for reversing the polarity of the output signal via the D / A converter with respect to the output of the signal selection switch, control of the reverse polarity to the tracking coil is also performed. Can be done accurately.

In the optical pickup characteristic measuring method according to the present invention, for example, the rotation of the spindle motor is stopped in the rotation stop step to remove the influence of the eccentricity of the optical disk, and the focus servo of the optical pickup is turned on in the focus on step. In the counting step, the number of tracks of the optical pickup crossed is counted, and when this count value and the preset count value are compared in the comparison step and they match, for example, the operation of the D / A converter is stopped, and the optical measurement step is performed. By measuring the level and balance of the tracking error signal by the optical pickup at the movement end position, the optical pickup is accurately moved to a desired position while avoiding the influence of eccentricity, for example, visual field measurement is performed.

[0015]

Embodiments of an optical pickup characteristic measuring device and an optical pickup characteristic measuring method according to the present invention will be described below with reference to the drawings.

In the optical pickup characteristic measuring apparatus of the present invention, for example, as shown in FIG. 1, the detection output from the light receiving elements A, B, C and D divided into four in the "rice field" shape of the light receiving section 1 is used. On the other hand, although not shown, a current / voltage conversion process has been performed 4
A movement amount detection unit 2 that inputs two electric signals a, b, c, d to detect the movement amount, a control unit 3 that outputs a control signal corresponding to the movement amount by comparison, and a D / A converter 4. , And a changeover switch SW1 for switching between a sweep signal for moving the optical pickup and a tracking error signal to be supplied.

The circuits in each block will be briefly described.

The movement amount detection unit 2 detects a movement amount of a track based on the detection output from the light receiving unit 1 in order to detect the movement amount to the + side, and a zero cross comparison circuit 2a from the zero cross comparison circuit 2a. It has a count circuit 2b for counting the outputs.

The zero-cross comparison circuit 2a detects from the detection output of the light-receiving section 1 of the optical pickup whether or not it crosses the track of the optical disc by the zero-cross of the waveform. This detection is performed as a count pulse by the count circuit 2b.
Is supplied to.

The control section 3 includes a digital value setting circuit 3a for setting a digital value in advance, a comparison circuit 3b for comparing the output from the count circuit 2b with the output from the digital value setting circuit 3a, and the comparison circuit 3b. And a CPU 3c that outputs various control signals based on the comparison result and the like.

The D / A converter 4 converts the tracking coil drive sweep digital signal supplied through the input terminal 10 into an analog signal. D / A converter 4
Uses a characteristic that the relationship between the track coil control voltage and the track-cut count value can be kept linear.

The output signal from the changeover switch SW1 is supplied to the drive amplifier 5 as a drive voltage to be supplied to the tracking coil 6. The drive amplifier 5 supplies a drive current to the tracking coil 6 to drive and control the operation of the tracking coil 6.

Generally, in the normal tracking control, the tracking coil 6 is controlled based on the tracking error signal supplied through the input terminal 9 while rotating the optical disk according to the rotation of the spindle motor. . At this time, the changeover switch SW1 is turned to the terminal b side by the changeover control signal from the CPU 3c.

Further, with the above-mentioned configuration, when the outer side of the diameter of the optical disc is set to the + side from the current position, the configuration is such that it is moved in the-direction, that is, the inner side of the diameter.

In this case, the optical pickup characteristic measuring apparatus selects the memory 7 for storing the sweep digital value at the time when it coincides with the preset digital value, and the output signal concerning the movement to the + side and the movement to the-side. It has a signal selection switch SW2 for switching and a polarity inverting circuit 8 for inverting the polarity of the output signal from the D / A converter 4. A control signal from the CPU 3c is supplied to the memory 7 as a write signal W and a read signal R. Of these, the read signal R is also used as an enable signal for the polarity inverting circuit 8. The CPU 3c uses the signal selection switch SW2
The switching operation of is also controlled.

Next, the case of performing the visual field measurement, which is one of the optical characteristic measurement of the optical pickup, will be described with reference to the flowchart of FIG. 2 and the timing chart of FIG.

Here, the visual field measurement is the measurement of the level and balance of the tracking error signal when the tracking coil 6 is 0.4 mm. If the track pitch of the optical disc is 1.6 μm, the optical pickup is 0.4 mm.
By moving it, the counting circuit 2b
It is known from the calculation in advance that 250 is counted. The value of 250 is set in the digital value setting circuit 3a of the control unit 3. The count circuit 2b uses, for example, a 12-bit count circuit with a margin in the count value.

The visual field measurement is started. In step S10, the rotation of the spindle motor that rotates the optical disk is stopped (the spindle motor is turned off in the level "H" state of FIG. 3 (e)). By this processing, the influence of the eccentricity of the optical disc which appears when the optical disc is rotating is prevented from appearing and the process proceeds to the next step S11.

In step S11, the focus servo of the optical pickup is turned on. In this way, the light received by the light receiving section 1 is normally performed by the reflected light from the optical disk.

Next, in step S12, the movement of the optical disc in the outward direction is regarded as the movement in the + direction, and this +
Start preparation for voltage setting to move to the side. CPU
3c supplies a control signal so as to incline to the terminal b side of the signal selection switch SW2.

Further, the user can select the digital value setting circuit 3
For example, a count value of 250 is set in a, and a sweep digital signal for driving the tracking coil is supplied via the input terminal 10. The sweep digital signal for driving the tracking coil may be generated by a method in which the voltage is changed within a certain time with a certain voltage width and the voltage is passed through an A / D converter.

Next, in step S13, the counting circuit 2
The counting of b is started and the process proceeds to step S14.

In step S14, a wait process is performed as a setup time, that is, a waiting time until the operation of the tracking coil 6 is stabilized.

Next, in step S15, the count circuit 2b is supplied with a clear signal for clearing the count value from the CPU 3c, for example. After that, the CPU 3c supplies a count enable signal to the count circuit 2b and causes the D / A converter 4 to perform conversion, as shown in FIG. 3B, for example. This count enable signal is D /
After being supplied to the A converter 4, the output signal from the D / A converter 4 in this case passes through the polarity reversing circuit 8 and is supplied to the drive amplifier 5 via the changeover switch SW1. Thus, for example, as shown in FIG. 3A, the drive control voltage to the tracking coil 6 is gradually increased. The tracking coil 6 moves the objective lens of the optical pickup to the + side in accordance with the drive current supplied from the drive amplifier 5 to the tracking coil 6. When the tracking coil 6 moves the objective lens of the optical pickup, the count detected by the movement amount detector 2 increases (see FIG. 3C).

In step S16, it is determined whether the output signal from the D / A converter 4 is maximum and the count value is less than 250. In step S16, a voltage higher than a predetermined voltage is applied to prevent the tracking coil 6 from being broken by being applied. In step S16, when the count value is smaller than 250 (Yes) even though the maximum value defined for the D / A converter 4 is still reached, it is determined that the characteristic of the tracking coil 6 is bad, and S
Go to 18. In other cases, for example, D
When the / A converter 4 has not reached the maximum output (No), the process proceeds to step S17.

Next, in step S17, the count value in the count circuit 2b and the count value set by the digital value setting circuit 3a are compared in the comparison circuit 3b. In the comparison circuit 3b, the count result is set to, for example, 2 as a specified value.
When it is not equal to 50 (No), the process returns to step S16 again. If the count value becomes equal to 250 (Yes), the process proceeds to step S19.

When the count value reaches 8 to 9 tracks before 250, for example, as shown in FIG. 3D, a count-up flag CUF is set up for a period of about 40 ms and an operation is performed based on this flag CUF. May be controlled.

In step S18, the count enable signal is set to level "L" to stop the counting of the counting circuit 2b, and the process returns to step S12 to repeat the above-mentioned routine. If the condition of step S17 is not satisfied even if this routine is repeated N times, a message indicating that the tracking coil is defective may be displayed and the routine may be ended.

In step S19, the CPU 3c outputs the control signal to the D / A converter 4 according to the output from the comparison circuit 3b.
Supply to. At this time, the D / A converter 4 stops the output according to the control signal and proceeds to step S20. For example, the count enable signal in FIG. 3B has a level "L".
Then, the operation of the counting circuit 2b is stopped.

In step S20, the sweep digital value when the output of the D / A converter 4 is stopped is calculated by the CPU 3c.
Is written in the memory 7 in accordance with the control signal from, that is, the write signal W.

Next, in step S21, it is determined that the objective lens of the optical pickup has reached the target position, and the operation of the spindle motor is turned on. At this time,
The CPU 3c tilts the changeover switch SW1 toward the terminal b to supply the tracking error signal to the tracking coil 6.

After reaching the target position in this way, the optical pickup measures the level and balance of the tracking error signal received through the objective lens in step S22. By absorbing the peculiar variation of the tracking coil 6 as compared with the conventional case, the optical pickup can be accurately moved to the target position, so that the reliability of the visual field measurement can be further enhanced.

Next, the inner side of the diameter from the current position of the optical disk is treated as the-direction, and the operation of the tracking coil 6 is confirmed. In step S22, preparation for setting the voltage on the negative side is performed. In this case, the value of the sweep digital signal to the + side is stored in the memory 7. In the opposite direction −
When moving in the direction, the value stored in the memory 7 is used to reliably move the optical pickup in the opposite direction. The memory 7 is supplied with the read signal R from the CPU 3c. The read signal R is, for example, the polarity inverting circuit 8
Is also supplied. The memory 7 reads the data from the address storing the previous data by supplying the read signal R. Also, in this preparation, the CPU 3c
Controls the changeover switch SW1 to the terminal a side, and supplies a count enable signal to the count circuit 2b.

This data is supplied to the terminal a side of the signal selection switch SW2. At this time, the signal selection switch SW
2 is switched to a contact on the terminal a side by a control signal from the CPU 3c. The output signal from the signal selection switch SW2 is supplied to the D / A converter 4.

Next, in step S25, the analog signal converted by the D / A converter 4 is supplied to the polarity inverting circuit 8. The polarity reversing circuit 8 activates the original operation of the circuit from the state in which the circuit is through, for example, according to the control signal from the CPU 3c. That is, the polarity inverting circuit 8 inverts the polarity of the supplied analog signal and outputs it to the terminal a side of the changeover switch SW1 (FIG. 3).
(See (a)). A negative signal is supplied to the tracking coil 6 via the changeover switch SW1 and the drive amplifier 5.

Next, in step S26, a wait process is performed in which the time until the operation of the tracking coil 6 stabilizes is treated as a waiting time also in this case. Also when the movement to the negative side is performed, the operation of the tracking coil 6 may be confirmed by outputting the count-up flag CUF described above. After the optical pickup is moved to the target position in this way, the spindle motor is turned on in step S27 as shown in FIG. 3 (e) (level "L" state in FIG. 3 (e)).

Next, in step S28, visual field measurement is performed. That is, the level and balance of the tracking error signal are measured in the same manner as in step S22. After performing the visual field measurement in this way, the visual field measurement routine is ended.

By the way, it is generally known from experience so far that when the movement to the + side is accurately performed, the movement to the-side is also accurately performed. For this reason, when the movement to the + side is accurately performed, it is possible to omit the routine part for performing the movement to the − side and measuring the visual field, and to terminate the routine immediately after step S22, for example. As a result, the time required for this visual field measurement routine work may be shortened.

With the above-described structure, the conventional visual field measurement, which is a measurement of optical characteristics, has poor reliability with respect to the measurement results. Since the optical pickup can be moved accurately while avoiding the influence of the inherent variation of the coil, the reliability can be made sufficiently higher than the conventional one.

By reading the data from which the optical pickup could be moved accurately when it was moved in one direction, and moving it in the opposite direction based on this data,
It is possible to repeatedly perform an accurate operation.

Further, the memory 7 and the signal selection switch SW2
Further, by providing the polarity reversing circuit 8, it is possible to accurately move in the opposite direction to the one direction, and it is possible to improve the reliability of the visual field measurement of the optical pickup.

By performing the optical pickup characteristic measuring method according to the above-described procedure, the optical pickup can be moved accurately while avoiding the influence of the inherent variation of each tracking coil, and therefore the reliability is higher than that of the conventional one. Can be high enough.

In the embodiment of the present invention, the visual field measurement has been described as an example of the measurement of the optical characteristics of the optical pickup, but the invention is not limited to the measurement of the visual field characteristics, and for example, a groove is formed. It can also be applied to the case where the number of so-called grooves is counted and the surface is optically measured by a predetermined measurement.

[0054]

In the optical pickup characteristic measuring apparatus according to the present invention, although the reliability of the measured result is poor in the conventional optical measurement, one method of evaluating the characteristic of the optical pickup is, for example, visual field measurement is performed for individual tracking. Since the optical pickup can be moved accurately while avoiding the influence of the inherent variation of the coil, the reliability can be made sufficiently higher than the conventional one.

By reading the data from which the optical pickup could be moved accurately when moving in one direction, from the storage means and moving it in the opposite direction based on this data,
It is possible to repeatedly perform an accurate operation.

By providing the storage means, the signal selection means, and the polarity reversal means, the movement in the opposite direction to the one direction can be accurately performed, and the reliability of the visual field measurement of the optical pickup can be improved.

Further, in the optical pickup characteristic measuring method according to the present invention, since the measurement of the optical characteristic can avoid the influence of the inherent variation of each tracking coil, the optical pickup can be moved accurately.
The reliability can be made sufficiently higher than in the past.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an optical pickup characteristic measuring device according to the present invention.

FIG. 2 is a flowchart illustrating an operation procedure of the optical pickup characteristic measuring device.

FIG. 3 is a timing chart for explaining operation timing of the optical pickup characteristic measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light receiving part 2 Moving amount detection part 3 Control part 4 D / A converter 5 Driving amplifier 6 Tracking coil SW1 changeover switch SW2 Signal selection switch 2a Zero cross comparison circuit 2b Count circuit 3a Digital value setting circuit 3b Comparison circuit 3c CPU

Claims (6)

[Claims] 1. An objective lens of an optical pickup is moved to a predetermined track position by using a tracking coil,
In an optical pickup characteristic measuring device for measuring the optical characteristic of an optical pickup at a predetermined track position, the movement amount of the objective lens when moving from the current position of the tracking coil to the position where the optical measurement is performed in one direction is detected. Moving amount detecting means, control means for outputting a control signal by comparing an output from the moving amount detecting means with a preset value, and signal converting means for converting the supplied sweep value into an analog signal An optical pickup characteristic measuring device comprising: switching means for switching between an output of the signal converting means and a tracking error signal according to an output signal from the control means. 2. An optical pickup characteristic measuring device, wherein the optical measurement is a visual field measurement for measuring a level and a balance of a tracking error signal at a predetermined measurement position. 3. A storage means for storing a sweep value supplied in response to a control signal from the control means when the output of the signal conversion means is stopped. 1. The optical pickup characteristic measuring device described in 1. 4. A signal selection means for switching between the supplied sweep value and the value read from the storage means when the objective lens is moved from the current position to a predetermined position in the other direction by the tracking coil. 4. The optical pickup characteristic measuring device according to claim 3, further comprising: polarity inverting means for inverting the polarity of the output signal from the signal converting means with respect to the output of the signal selecting means. 5. An objective lens of an optical pickup is moved to a predetermined track position by using a tracking coil,
In the optical pickup characteristic measuring method for measuring the optical characteristic of the optical pickup at the predetermined track position, a rotation stopping step of stopping the rotation of the optical recording medium, a focus on step of operating a focus servo of the optical pickup, and a tracking step of A counting step of counting the number of tracks accompanying the movement of the objective lens of the optical pickup while applying the voltage required for driving the coil, and a comparison step of comparing the count value in the counting step with a preset count value. And an optical measurement step of performing optical measurement with an optical pickup moved by a predetermined distance after the comparison step. 6. The optical pickup characteristic measuring method according to claim 5, wherein in the optical measuring step, a visual field measurement for measuring the level and the balance of the tracking error signal at a predetermined measurement position is performed.