JP2875618B2 - Mirror detection circuit of optical disk player - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mirror detecting circuit used for detecting the number of traversing tracks in an optical disc player.

[Conventional technology]

An optical disc player such as a compact disc player is usually provided with a mirror section detecting circuit for detecting a mirror section which is a mirror-like section between tracks formed by a pit row on an optical disc. This mirror section detection circuit is used to determine the number of mirror sections to be passed when the optical head jumps a predetermined number of tracks, such as 10 tracks or 1 track, for the purpose of making the optical head access a desired track. Detecting is used to detect the number of tracks traversed.

 FIG. 10 shows a conventional mirror section detection circuit.

The current output from the two light receiving sections 1a and 1c in the four-division light receiving element that receives the return light from the optical disk is RFI
-V amplifier circuit 2 and the other two light receiving sections 1b and 1d
Are output to the RFI-V amplifier circuit 3 and converted into voltages. RFI-V amplifier circuit 2
The sum of the output voltages of (3) is amplified by the RF amplifier circuit 4, and the RF amplifier circuit 4 outputs an EFM-modulated RF signal (pit reproduction signal on the optical disc) as shown in FIG. 7 (a). You.

Here, as shown by an arrow M in FIG. 7A, the lower envelope of the RF signal, that is, the portion where the bottom level becomes higher is the mirror portion. FIG. 7 (b) is the same as FIG. 7 (a).
Is a waveform observed by an oscilloscope by extending the time axis of the signal, and is also called an eye pattern, and is a collection of EFM waveforms reproduced from pits having various pit lengths.

The output of the RF amplifier 4 is input to a peak hold circuit (PH circuit) 5 for holding the peak value and a bottom hold circuit (BH circuit) 6 for holding the bottom value.
Then, a peak hold signal is output from the PH circuit 5 as indicated by I in FIG. 11 (a), while a bottom hold signal is output from the BH circuit 6 as indicated by II in FIG. 11 (a). Is done.

The bottom hold signal is input to the non-inverting input terminal of the comparator 7. On the other hand, the constant voltage source 8
Of the comparator 7 (see III in FIG. 11A) obtained by adding a constant voltage supplied from the comparator 7 (the constant voltage is a negative voltage, and therefore, is substantially subtracted). Input to the inverted input terminal. As a result, a mirror section detection signal as shown in FIG. 11 (b) is output from the comparator 7. The high-level section in the mirror section detection signal indicates a mirror section, and the low-level section indicates a track by a pit train.

[Problems to be solved by the invention]

Meanwhile, when an optical disk such as a compact disk is formed of, for example, resin, the thickness of the optical disk, the depth of pits, the reflectance of the mirror portion, and the like tend to vary. In this case, as shown by an arrow M 'in FIG. 8A, in the RF signal output from the RF amplifier circuit 4, the bottom level in the mirror section decreases, or M "in FIG. As shown, variations occur such as an increase in the bottom level in the mirror portion, etc. Note that FIGS.8 (b) and 9 (b) show the signals of FIGS.8 (a) and 9 (a), respectively. 4 is a waveform observed by an oscilloscope with the time axis of FIG.

As described above, since the level of the RF signal differs for each optical disc, the output of the BH circuit 6 is connected to the PH circuit 5 as described above.
When the binarization is performed by the slice level obtained by subtracting the constant voltage from the output of FIG. 8, for example, when the bottom hold signal in the mirror section is small as shown by II in FIG. In (correspondence), a high-level section (corresponding to the mirror portion) in the mirror portion detection signal is shortened as shown in FIG.

On the other hand, when the bottom hold signal in the mirror section is large as shown at II in FIG. 13 (a) (corresponding to FIG. 9 (a)), the high level in the mirror section detection signal as shown in FIG. 13 (b) is obtained. The section of the level becomes longer. If the bottom hold signal is extremely small, a high level may not be output in the mirror section detection signal when the signal passes through the mirror section.

[Means for solving the problem]

In order to solve the above-described problems, a mirror unit detection circuit of an optical disc player according to the present invention includes an RF amplifier circuit that amplifies an RF signal reproduced from an optical disc, and a peak value that holds a peak value of an output of the RF amplifier circuit. A peak hold circuit that outputs a hold signal, a bottom hold circuit that holds the bottom value of the output of the RF amplifier circuit and outputs a bottom hold signal, and a slice based on the AC component of the peak hold signal and the output of the RF amplifier circuit. A means for generating a level signal; and a comparator for binarizing the bottom hold signal with the slice level signal to generate a mirror section detection signal, and the means for generating the slice level signal includes an RF amplifier circuit. Means for extracting the AC component of the output, and the extracted AC component is below the reference level. Integrating means for calculating the difference between the area of the region and the area of the region above the reference level, obtaining a voltage having a polarity corresponding to the level of the RF signal from the output of the integrating means, and converting the voltage to a peak hold signal. , To generate a slice level signal.

[Action]

According to the above configuration, when generating the slice level signal, instead of subtracting a constant voltage from the peak hold signal, the AC component of the output of the RF amplifier circuit is extracted, and the extracted AC component is compared with the reference level. The difference between the area of the lower region and the area of the region above the reference level was obtained, a voltage having a polarity corresponding to the level of the RF signal was obtained from this difference, and the voltage was subtracted from the peak hold signal. Therefore, the length of the high-level section when the bottom hold signal is binarized by the slice level signal is substantially constant for each optical disc. Thereby, the detection of the mirror portion can be performed reliably.

〔Example〕

One embodiment of the present invention will be described below with reference to FIGS. 1 to 9.

As shown in FIG. 1, currents output from two light receiving portions 11a and 11c in a four-division light receiving element for receiving return light from an optical disk are input to an RFI-V amplifier circuit 12,
The current output from the other two light receiving units 11b and 11d is RFI-
The signals are input to the V amplifier circuit 13 and converted into voltages. The sum of the output voltages of the RFI-V amplifier circuits 12 and 13 is amplified by the RF amplifier circuit 14, and is output from the RF amplifier circuit 14 as shown in FIG.
As shown in FIG. 7, an EFM-modulated RF signal (a pit reproduction signal on an optical disk) is output.

The output of the RF amplifier circuit 14 includes a peak hold circuit (PH circuit) 15 for holding the peak value (see I in FIG. 2A) and a bottom value (see II in FIG. 2A). It is input to the bottom hold circuit (BH circuit) 16 for holding. The bottom hold signal output from the BH circuit 16 is input to the non-inverting input terminal of the comparator 17.

On the other hand, a slice level signal (see III in FIG. 2A) obtained by adding the voltage supplied by the constant voltage source 18 and the subtraction voltage adjusting circuit 20 to the output of the PH circuit 15 is inverted by the comparator 17. Input to the input terminal. Since a constant negative voltage is supplied from the constant voltage source 18, in practice
Subtraction is performed from the output of the PH circuit 15. This subtraction amount is adjusted by the subtraction voltage adjustment circuit 20 according to the output level of the RF amplifier circuit 14, as described later.

The comparator 17 binarizes the output of the BH circuit 16 based on the slice level signal to generate a mirror detection signal (see FIG. 2B). The high-level section in the mirror section detection signal indicates a mirror section, and the low-level section indicates a track by a pit string.

The subtraction voltage adjustment circuit 20 includes a capacitor 21 connected to the output terminal of the RF amplifier circuit 14 and a pair of inverters 22 and 23.
And an integrating circuit 26 consisting of a resistor 24 and a capacitor 25 for integrating the output of the inverter 22, an integrating circuit 29 consisting of a resistor 27 and a capacitor 28 for integrating the output of the inverter 23, and an output of the integrating circuit 26 And a differential amplifier 31 to which the output of the integrating circuit 29 is input to the non-inverting input terminal. The output terminal of the differential amplifier 31 is a comparator
Connected to 17 inverting input terminals.

The subtraction voltage adjustment circuit 20 outputs a positive, 0 [V] or negative voltage according to the level of the RF signal output from the RF amplifier circuit 14. That is, when the level of the RF signal output from the RF amplifier circuit 14 is a standard level as shown in FIGS. 7A and 5B and FIG. A ₁ · A ₃ … (fifth
(Shown by hatching in FIG. 7A) and the reference level B
The areas of the lower regions A ₂ , A _4, ...

On the other hand, as shown in FIGS. 8 (a) and (b) and FIG. 5 (b), when the level of the RF signal is lower than the standard level, the area A _{2. 4} are larger than the areas of the regions A ₁ , A _3, ... Above the reference level B.

On the other hand, as shown in FIGS. 9A and 9B and FIG. 5C, when the level of the RF signal is higher than the standard level,
Upper area A ₁ · A ₃ ... area of the reference level B is greater than the area A ₂ · A ₄ ... area of the lower side of the reference level B.

Therefore, the subtraction voltage adjusting circuit 20 sets the reference level B to 0 [V] by extracting the AC component of the output of the RF lamp circuit 14 by the capacitor 21, and the output of the inverter 22 is integrated by the integrating circuit 26. By integrating, the value obtained by subtracting the area of the area A ₁ · A ₃ ··· above the reference level B (positive side) from the area of the area A ₂ · A ₄ ··· below the negative level (negative side) is obtained. On the other hand, the output of the inverter 23 is
Above, the upper side (positive side) of the reference level B
Region A ₁ · A ₃ ... finding the value obtained by subtracting the area A ₂ · A ₄ ... area of (lower than the reference level B) negative from the area of. Then, the outputs of both integrating circuits 26 and 29 are input to the differential amplifier 31,
The differential amplifier 31 outputs a voltage having a polarity corresponding to the level of the RF signal.

That is, when the level of the RF signal is the standard level as shown in FIG.
[V]. On the other hand, as shown in FIG.
If the signal level is lower than the standard level,
31 outputs a negative voltage. On the other hand, when the level of the RF signal is higher than the standard level as shown in FIG. 5C, a positive voltage is output from the differential amplifier 31.

FIG. 6 shows a slice level signal input to the inverting input terminal of the comparator 17. Assuming that the slice level signal takes the value indicated by the straight line C in FIG. 6 when the level of the RF signal output from the RF amplifier circuit 14 is the standard level, the level of the RF signal is clear as described above. Is low, the slice level signal is as shown in D in FIG.
The level of the RF signal is lower than when it is at the standard level.

Therefore, when binarizing this low-level RF signal (the peak hold signal becomes like I in FIG. 3 (a) and the bottle hold signal becomes like II in FIG. 3 (a)), As shown by III in FIG. 2A, the slice level signal is smaller than the standard time (see III in FIG. 2A).
The high level section of the quantified mirror section detection signal (FIG. 3 (b)) is substantially equal to the level when the RF signal level is the standard level (see FIG. 2 (b)).

On the other hand, when the level of the RF signal output from the RF amplifier circuit 14 is higher than the standard level, the slice level signal is higher than when the level of the RF signal is the standard level as shown in E in FIG.

Therefore, when binarizing this high-level RF signal (the peak hold signal becomes like I in FIG. 4 (a) and the bottle hold signal becomes like II in FIG. 4 (a)), As shown by III in FIG. 2A, the slice level signal becomes larger than when the RF signal is at the standard level (see III in FIG. 2A). The high-level section in FIG. 4 (b) is almost equal to when the level of the RF signal is the standard level (see FIG. 2 (b)).

As described above, according to the present invention, since the slice level signal for binarizing the bottom hold signal is changed according to the level of the RF signal output from the RF amplifier circuit 14, the binarization is performed. The length of the high-level section (corresponding to the mirror section) in the mirror section detection signal obtained is substantially constant regardless of the level of the RF signal. As a result, an accurate mirror section detection signal is obtained, so that the number of tracks traversed by the optical head can be accurately detected.

〔The invention's effect〕

As described above, the mirror section detection circuit of the optical disc player according to the present invention is configured such that the slice level signal for generating the mirror section detection signal by binarizing the bottom hold signal of the output of the RF amplifier circuit is output from the RF amplifier circuit. The AC component of the output is extracted, and for the extracted AC component, the difference between the area of the region below the reference level and the area of the region above the reference level is obtained by the integration means. In this configuration, a voltage having a polarity corresponding to the level of the RF signal is obtained, and the voltage is subtracted from the peak hold signal.

As a result, when generating a slice level signal, instead of subtracting a constant voltage from the peak hold signal, a voltage determined according to the output level of the RF amplifier circuit is subtracted. The length of the high-level section when the bottom hold signal is binarized by the level signal is substantially constant for each optical disc, so that the mirror section can be reliably detected.

[Brief description of the drawings]

1 to 9 show an embodiment of the present invention. FIG. 1 is a circuit diagram showing a mirror section detection circuit. FIGS. 2 (a) and 2 (b) are explanatory diagrams showing the binarization of the RF signal when the level of the RF signal is a standard level. FIGS. 3 (a) and 3 (b) are illustrations showing how the RF signal is binarized when the level of the RF signal is low. FIGS. 4 (a) and 4 (b) are explanatory diagrams showing the binarization of the RF signal when the level of the RF signal is high. FIGS. 5 (a) to 5 (c) are explanatory diagrams showing variations in the level of the RF signal. FIG. 6 is an explanatory diagram showing a change in the slice level signal accompanying a change in the level of the RF signal. FIG. 7 (a) is an explanatory diagram showing a standard level RF signal when a track is traversed. FIG. 2B is an explanatory diagram showing a waveform obtained by expanding the time axis of FIG. FIG. 8 (a) is an explanatory diagram showing a low-level RF signal when crossing a track. FIG. 2B is an explanatory diagram showing a waveform obtained by expanding the time axis of FIG. FIG. 9A is an explanatory diagram showing a high-level RF signal when crossing a track. FIG. 2B is an explanatory diagram showing a waveform obtained by expanding the time axis of FIG. 10 to 13 show a conventional example. FIG. 10 is a circuit diagram showing a mirror section detection circuit. FIGS. 11 (a) and 11 (b) are illustrations showing how the RF signal is binarized when the level of the RF signal is a standard level. FIGS. 12 (a) and 12 (b) are explanatory diagrams showing the binarization of the RF signal when the level of the RF signal is low. FIGS. 13 (a) and 13 (b) are explanatory diagrams showing the state of binarization of the RF signal when the level of the RF signal is high. 14 is an RF amplifier circuit, 15 is a peak hold circuit, 16 is a bottom hold circuit, 17 is a comparator, and 20 is a subtraction voltage adjustment circuit.

Claims (1)

(57) [Claims] 1. An RF amplifier circuit for amplifying an RF signal reproduced from an optical disk, a peak hold circuit for holding a peak value output from the RF amplifier circuit and outputting a peak hold signal, and a bottom value of an output of the RF amplifier circuit. And a bottom hold circuit that outputs a bottom hold signal and
Means for generating a slice level signal based on the AC component of the peak hold signal and the output of the RF amplifier circuit;
A means for generating a mirror section detection signal by converting the value into a value, and a means for generating the slice level signal includes: a means for extracting an AC component of an output of the RF amplifier circuit; and for the extracted AC component, Integrating means for calculating the difference between the area of the region below the reference level and the area of the region above the reference level, and obtaining a voltage having a polarity corresponding to the level of the RF signal from the output of the integrating means, A mirror detection circuit for an optical disk player, wherein a slice level signal is generated by subtracting the voltage from a peak hold signal.