JP2008181579A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately write or read data by correcting the effects of a light reflectance from each layer of an optical disk, fluctuation of a tracking error signal, and positional shifting of a photodetector to carry out stable focus control. <P>SOLUTION: Signals are generated at focus error signal generation units 42a and 42b via A/D converters 41a and 41b. An all summation correction coefficient AS_ATT for correcting the amplitude of an all summation signal to a prescribed value is obtained. A focus error correction coefficient FE_ATT is set as a value equal to that of the coefficient AS_ATT in an attenuator 46a. 3AS/FE is calculated by a calculation unit 45, where FE is amplitude of a focus error signal before focus is turned ON, and AS is amplitude of an all summation signal after focus is turned ON. When 3AS/FE>1.4(3 dB) is satisfied, the set focus error correction coefficient is multiplied by an adjust value calculated based on 3AS/FE. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus that performs focus control when data is written to or read from an optical disc, and more particularly to amplitude adjustment of a focus error signal applied to the control.

  In general, in an optical disc apparatus, a laser beam is applied to a disc (hereinafter abbreviated as an optical disc) on which information is optically recorded / reproduced using an optical pickup including a laser semiconductor, an objective lens, a photodetector, an actuator, and the like. Is recorded, and information recorded is reproduced by utilizing the difference in the amount of reflected light of the laser beam. At this time, based on a focus error signal generated by a known astigmatism method or the like and a tracking error signal generated by a known push-pull method or the like, the objective lens is moved and the laser beam irradiated by the semiconductor laser is Focus control and tracking control for adjusting the condensing position are performed.

  By the way, in a disc in which recording / reproducing films are multilayered due to an increase in the capacity of the optical disc, the light reflectance from each layer is different, resulting in fluctuations in the light reception level by the photodetector. As a result, the focus error signal and tracking error signal Variations in amplitude occur. In addition, the amplitude of the focus error signal is affected by fluctuations in the tracking error signal and a positional deviation of the photodetector incorporated in the light receiving part of the photodetector, and the fluctuation occurs. Therefore, in focus control and tracking control, the amplitude of the above signal is set in advance in order to prevent the feedback gain used for the servo from fluctuating and making it impossible to finely adjust the focusing position of the laser beam. It is adjusted so that it becomes the specified value.

For example, in Patent Document 1, an all-sum signal, which is the sum of electrical signals output from a photodetector, is generated, and the correction is performed so that the amplitudes of the focus error signal and tracking error signal are set to predetermined values. An optical disc apparatus is disclosed in which a value is calculated and the amplitude is adjusted by an attenuator based on the correction value. Further, in Patent Document 2, when generating a focus error signal by the astigmatism method, a correction value for correcting the fluctuation of the tracking error signal is set, thereby adjusting the amplitude of the focus error signal and the position of the photodetector. An optical disc apparatus provided with a focus error signal amplitude calculation method capable of increasing a tolerance for deviation is disclosed.
Japanese Patent Laid-Open No. 2002-092907 Japanese Patent Laid-Open No. 2002-074696

  However, in the optical disk apparatus as described above, the amplitude of the focus error signal is adjusted to a specified value with respect to all the effects of the light reflectance from each layer of the optical disk, the fluctuation of the tracking error signal, and the positional deviation of the photodetector. It was not possible to perform stable focus control.

The present invention has been made to solve the above problem, and in the amplitude adjustment of the focus error signal, corrects the influence of the light reflectance from each layer of the optical disc, the fluctuation of the tracking error signal, and the positional deviation of the photodetector, An object of the present invention is to provide an optical disc apparatus capable of appropriately writing or reading data by performing stable focus control.

  In order to achieve the above object, a first aspect of the present invention is a semiconductor laser that irradiates an optical disc with laser light, and an objective lens that condenses the laser light emitted from the semiconductor laser onto the optical disc on an optical disc surface. And a photodetector for detecting reflected light from the optical disk surface with respect to the laser light irradiated on the optical disk surface through the objective lens, and the light receiving portion of the photodetector is divided into four regions. An optical pickup composed of a photodetector; and a control means for performing focus control and tracking control for adjusting a condensing position of laser light irradiated by the semiconductor laser by moving the objective lens, and the control means The focal point of the laser beam irradiated onto the optical disk surface through the objective lens based on the electrical signal output from the photodetector A focus error signal that is a signal corresponding to a deviation amount with respect to the optical disc surface and a tracking that is a signal corresponding to a deviation amount from a track on the optical disc surface of a condensing point of laser light irradiated onto the optical disc surface through the objective lens A signal generation means for generating an error signal and an all-sum signal that is a sum of the divided electric signals; and measuring a peak level and a bottom level in each of the focus error signal, the tracking error signal, and the all-sum signal; Amplitude adjustment means for adjusting the amplitude of each signal so that the difference between the peak level and the bottom level at each becomes a predetermined value set in advance, and the focus error signal adjusted by the amplitude adjustment means; Control based on the tracking error signal In the optical disk reproducing apparatus using the astigmatism method when generating the focus error signal, the signal generating means is a correction coefficient for correcting the amplitude of each signal to the specified value. Of the correction coefficients, the focus error correction coefficient for correcting the amplitude of the focus error signal is set as the same value as the all-sum correction coefficient for correcting the amplitude of the all-sum signal, and the focus before the focus is turned on. When the amplitude of the error signal is FE and the amplitude of the all-sum signal after the focus is turned on is AS, and 3AS / FE> 1.4, the set focus error correction coefficient is 3AS / FE. What adjusts the amplitude of the focus error signal by using a value obtained by multiplying the calculated adjustment value as a new correction coefficient A.

  The invention of claim 2 includes an irradiating means for irradiating the optical disk with light, and a light detecting means for detecting reflected light from the optical disk surface with respect to the light irradiated to the optical disk from the irradiating means, Corresponds to the amount of deviation of the condensing point of the light irradiating the optical disc surface with respect to the optical disc surface based on the reading means in which the light receiving portion of the photo detection means is divided into a plurality of regions and the electrical signal output from the photo detection means A sum of a focus error signal that is a signal to be recorded, a tracking error signal that is a signal corresponding to a shift amount of a light condensing point of light irradiated on the optical disc surface from a track on the optical disc surface, and the divided electric signal. Signal processing means for generating an all-sum signal, and each of the focus error signal, the tracking error signal, and the all-sum signal And the amplitude adjustment means for adjusting the amplitude of each of the signals so that the difference between the peak level and the bottom level is a preset specified value. A control means for performing focus control and tracking control for adjusting a condensing position of light applied to the optical disk based on the focus error signal and the tracking error signal, The amplitude adjusting means multiplies the amplitude of each signal by a correction coefficient for correcting the value to the specified value. The amplitude of the all-sum signal after the focus is turned on is the amplitude of the focus error signal before the focus is turned on. When the divided value becomes larger than a preset threshold value, the correction coefficient among the correction coefficients is The focus error correction coefficient for correcting the amplitude of Suera signal, and adjusts the amplitude of the focus error signal is multiplied by the adjustment value proportional to the value.

  According to a third aspect of the present invention, in the second aspect of the present invention, the light receiving portion of the light detecting means is divided into four regions, and the signal processing means generates a focus error signal by an astigmatism method. .

  According to the first aspect of the present invention, when 3AS / FE> 1.4, a value obtained by multiplying the set focus error correction coefficient by the adjustment value calculated by 3AS / FE is used as a new correction coefficient. As a result, fluctuations in the amplitude of the focus error signal due to the position shift of the photo detector can be corrected within the specs corresponding to the preset specified values, so there is no need to maintain the photo detector mounting accuracy with high accuracy. Is easy to handle and stable focus control can be performed. The focus error correction coefficient for correcting the amplitude of the focus error signal is set as the same value as the all-sum correction coefficient for correcting the amplitude of the all-sum signal. Even when the focus is turned on, the amplitude of the focus error signal can be adjusted to a predetermined value set in advance. Furthermore, it is possible to eliminate fluctuations in the amplitude of the focus error signal with respect to fluctuations in the received light level and fluctuations in the tracking error signal due to the influence of disturbances such as temperature rise.

  According to the invention of claim 2, when the value obtained by dividing the amplitude of the all-sum signal after the focus on by the amplitude of the focus error signal before the focus on becomes larger than a preset threshold, the amplitude of the focus error signal By adjusting the focus error signal by multiplying the adjustment value proportional to the value to the focus error correction coefficient to correct the focus error signal, fluctuations in the focus error signal due to the photodetector misalignment can be corrected. It is not necessary to maintain the photo detector mounting accuracy with high accuracy, and the apparatus main body is easy to handle, and stable focus control can be performed.

  According to the invention of claim 3, it is not necessary to maintain the mounting accuracy of the photodetector with high accuracy, and it is easy to handle and an optical disc apparatus capable of performing stable focus control is obtained.

  An optical disc apparatus according to the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an optical disc apparatus. The optical disc apparatus 1 includes a spindle motor 2 for rotationally driving a loaded optical disc 10, an optical pickup 3 for writing or reading data on the rotating optical disc 10, and an electric signal output from the optical pickup 3. And a control unit 4 for controlling the spindle motor 2, the optical pickup 3 and the like, and reads the video, audio and the like recorded on the optical disc 10 and reproduces them.

  The optical pickup 3 includes a semiconductor laser 31 that irradiates the optical disc 10 with laser light, an objective lens 32 that condenses the laser light emitted from the semiconductor laser 31 onto the optical disc 10 on the surface of the optical disc 10, and the objective. A beam splitter 33 that divides the optical path of the reflected light from the optical disk 10 surface with respect to the laser light irradiated on the optical disk 10 surface via the lens 32, and a collimator lens that causes astigmatism in the reflected light that has passed through the beam splitter 33. 34, a photodetector 35 that detects the reflected light that has passed through the collimator lens 34, and an actuator 36 that moves the objective lens 32 in the optical axis direction and the radial direction of the optical disc 10 according to a signal from the control unit 4. . The light receiving unit of the photodetector 35 is constituted by a divided photodetector (not shown) divided into four regions.

  The control unit 4 generates a focus error signal, a tracking error signal, and an all-sum signal from the electric signal photoelectrically converted by the divided photodetector. Here, the focus error signal is a signal corresponding to the amount of deviation of the condensing point of the laser light with respect to the optical disc 10 surface, and the tracking error signal is the condensing point of the light irradiated on the optical disc 10 surface through the objective lens 32. The all-sum signal is a sum signal of the divided electrical signals. Thereafter, the peak level and the bottom level in each of the signals are measured, and the amplitude of the signals is adjusted so that the difference between the peak level and the bottom level in each signal becomes a preset specified value. Based on the adjusted focus error signal and tracking error signal, the objective lens 32 is moved by the actuator 36 to perform focus control and tracking control for adjusting the condensing position of the laser light emitted from the semiconductor laser 31. The control unit 4 also controls the spindle motor 2 and a feed motor (not shown) for feed driving the optical pickup 3.

  Next, the amplitude adjustment of the focus error signal will be specifically described. FIG. 2 shows an amplitude adjustment circuit for the amplitude of the focus error signal in the control unit 4. First, a focus search operation is started, the objective lens 32 is driven in the optical axis direction to change the distance from the optical disc 10, and an electric signal is output by the divided photodetector. This electrical signal is converted into a digital signal by the A / D converter 41a, and based on this electrical signal, the focus error signal generation unit 42a provided in the control unit 4 generates a focus error signal by the astigmatism method. .

  Next, the peak detection circuit 43a and the bottom detection circuit 44a provided at the subsequent stage of the focus error signal generation unit 42a detect the peak level of the signal by the peak detection circuit 43a, and the bottom level of the signal is detected by the bottom detection circuit 44a. To do. The calculation unit 45 calculates the amplitude of the focus error signal based on the detected peak level and bottom level by calculating the amplitude of the focus error signal = peak level−bottom level.

  Similarly, an all-sum signal generation unit 42b provided in the control unit 4 takes the sum of the electric signals based on the electric signal output from the divided photodetector and converted into a digital signal by the A / D converter 41b. By doing so, the all-sum signal is generated. The peak detection circuit 43b and the bottom detection circuit 44b provided at the subsequent stage of the all-sum signal generation unit 42b detect the peak level of the signal with the peak detection circuit 43b, and the bottom level of the signal with the bottom detection circuit 44b. Based on the detected peak level and bottom level, the calculation unit 45 calculates the amplitude of the focus error signal by calculating the amplitude of the all-sum signal = peak level−bottom level.

  Next, adjustment is made so that the amplitude of the all-sum signal becomes a preset specified value. The all-sum correction coefficient AS_ATT for correcting the amplitude of the all-sum signal is obtained by calculating the all-sum correction coefficient AS_ATT = specified value / the amplitude of the all-sum signal. The calculated all-sum correction coefficient AS_ATT is set in the attenuator 46b, and the amplitude of the all-sum signal is adjusted by multiplying the amplitude of the all-sum signal by the all-sum correction coefficient AS_ATT.

  On the other hand, when the amplitude of the focus error signal before the focus is turned on is FE and the amplitude of the all-sum signal after the focus is turned on is AS, the ratio of FE and AS is substantially constant (3: 1). Thus, the focus error correction coefficient FE_ATT for correcting the amplitude of the focus error signal is set in the attenuator 46a as the same value as the calculated all-sum correction coefficient AS_ATT. Then, the amplitude of the focus error signal is adjusted by multiplying the amplitude of the focus error signal by the focus error correction coefficient FE_ATT. As a result, in a multi-layer disc in which recording / reproducing films having different reflectivities are multilayered, the focus error signal amplitude is set in advance even when the focus is turned on to a layer different from the layer measured before the focus is turned on. It can be adjusted to be a value. Furthermore, fluctuations in the received light level due to the influence of disturbances such as temperature rise and fluctuations in the amplitude of the focus error signal with respect to fluctuations in the tracking error signal can be eliminated, so that stable servo can be applied.

  Here, since the optical detector 35 is mechanically attached in the optical pickup 3, if the position of the photodetector is shifted due to this, the correlation between the ratio of FE and AS is caused by the fluctuation of the amplitude of the focus error signal. I can't take it. Therefore, in the present invention, the focus error correction coefficient FE_ATT is adjusted. FIG. 3 shows a flowchart of the adjustment process. When 3AS / FE is calculated by the calculation unit 45 and 3AS / FE> 1.4 (3 dB), the set focus error correction coefficient FE_ATT is multiplied by the adjustment value calculated by 3AS / FE, Do not multiply in other cases. As a result, even if the position error of the photodetector occurs and the amplitude of the focus error signal fluctuates, and the correlation between the ratio of FE and AS cannot be obtained, the correction is made within the specification corresponding to the preset specified value. Therefore, it is not necessary to maintain the mounting accuracy of the photodetector with high accuracy, the apparatus main body is easy to handle, and focus control capable of applying a stable servo can be performed.

  In addition, this invention is not restricted to the structure of the said various embodiment, A various deformation | transformation is possible in the range which does not change the meaning of invention. For example, the condition for adjusting the focus error correction coefficient FE_ATT is set to 3AS / FE> 1.4 (3 dB). However, even if the condition can be changed according to the specification corresponding to the preset specified value. Good. Moreover, although the example in case the light-receiving part of the photodetector 35 is comprised by the division | segmentation photodetector divided | segmented into four area | regions was shown, this light-receiving part should just be divided | segmented into the several area | region. Further, the case where the A / D converters 41a and 41b are arranged before the focus error signal generation unit 42a and the all-sum signal generation unit 42b is shown, but the A / D converter is arranged after the attenuators 46a and 46b. There may be.

1 is a block configuration diagram of an optical disc apparatus according to an embodiment of the present invention. The amplitude adjustment circuit diagram of the amplitude of the focus error signal in the control unit of the disk device. 10 is a flowchart showing adjustment processing of a focus error correction coefficient FE_ATT.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 2 Spindle motor 3 Optical pick-up 4 Control part 10 Optical disk 31 Semiconductor laser 32 Objective lens 33 Beam splitter 34 Collimator lens 35 Photo detector 36 Actuator 41a, 41b A / D converter 42a Focus error signal generation part 42b All-sum signal generation part 43a, 43b Peak detection circuit 44a, 44b Bottom detection circuit 45 Arithmetic unit 46a, 46b Attenuator

Claims (3)

A semiconductor laser for irradiating the optical disk with laser light, an objective lens for condensing the laser light emitted from the semiconductor laser onto the optical disk onto the optical disk surface, and the optical disk surface via this objective lens. An optical pickup comprising a photodetector for detecting reflected light from the optical disk surface with respect to the laser light, and a light receiving portion of the photodetector being divided into four regions;
Control means for performing focus control and tracking control for adjusting the condensing position of the laser light irradiated by the semiconductor laser by moving the objective lens,
The control means is a focus error which is a signal corresponding to a deviation amount of a condensing point of a laser beam irradiated to the optical disk surface via the objective lens with respect to the optical disk surface based on an electric signal output from the photodetector. Signal, a tracking error signal that is a signal corresponding to the amount of deviation from the track on the optical disk surface of the condensing point of the laser beam irradiated onto the optical disk surface through the objective lens, and the sum of the divided electric signals Signal generating means for generating an all-sum signal;
Measure the peak level and bottom level in each of the focus error signal, the tracking error signal and the all-sum signal, and the difference between the peak level and the bottom level in each is set to a preset specified value. Amplitude adjusting means for adjusting the amplitude, and performing control based on the focus error signal and the tracking error signal adjusted by the amplitude adjusting means,
In the optical disk reproducing apparatus using the astigmatism method when generating the focus error signal, the signal generating means,
The amplitude adjusting means multiplies the amplitude of each signal by a correction coefficient for correcting the value to the specified value,
Among the correction coefficients, the focus error correction coefficient for correcting the amplitude of the focus error signal is set as the same value as the all-sum correction coefficient for correcting the amplitude of the all-sum signal,
When the amplitude of the focus error signal before focus on is FE and the amplitude of the all-sum signal after focus on is AS, and 3AS / FE> 1.4, the set focus error is set. An optical disc apparatus, wherein the amplitude of the focus error signal is adjusted by using a value obtained by multiplying a correction coefficient by an adjustment value calculated by 3AS / FE as a new correction coefficient. An irradiating means for irradiating the optical disc with light; and a light detecting means for detecting reflected light from the optical disc surface with respect to the light emitted from the irradiating means to the optical disc. Reading means divided into a plurality of regions;
Based on the electrical signal output from the light detection means, a focus error signal, which is a signal corresponding to the amount of deviation of the condensing point of the light irradiating the optical disc surface with respect to the optical disc surface, and condensing the light irradiating the optical disc surface A signal processing means for generating a tracking error signal that is a signal corresponding to a deviation amount from a track on the optical disc surface of the point, and an all-sum signal that is a sum of the divided electric signals;
Measure the peak level and bottom level in each of the focus error signal, the tracking error signal and the all-sum signal, and the difference between the peak level and the bottom level in each is set to a preset specified value. Amplitude adjusting means for adjusting the amplitude;
Control means for performing focus control and tracking control for adjusting a condensing position of light irradiated on the optical disk based on the focus error signal and the tracking error signal adjusted by the amplitude adjusting means. In the optical disc playback apparatus,
The amplitude adjusting means multiplies the amplitude of each signal by a correction coefficient for correcting the value to the specified value,
When the value obtained by dividing the amplitude of the all-sum signal after the focus on by the amplitude of the focus error signal before the focus on becomes larger than a preset threshold value, the amplitude of the focus error signal is corrected among the correction coefficients. An optical disc apparatus characterized in that the focus error correction coefficient is adjusted by an adjustment value proportional to the value to adjust the amplitude of the focus error signal. The light receiving part of the light detection means is divided into four regions,
3. The optical disc apparatus according to claim 2, wherein the signal processing means generates a focus error signal by an astigmatism method.

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