JPH0453029A - Optical information recording and/or reproducing device - Google Patents

Abstract

PURPOSE:To detect an accurate on-track/off-track signal by setting Bh lower than a peak value, where convergent values of bottom and peak value hold means are denoted as Ph and Bh, and Ph which is in specific proportion to the peak value further lower than Bh in level. CONSTITUTION:A sum total signal 1 of a photosensor is peak-held by a differential amplifier 2, and a peak holding signal of the output of a differential amplifier 4 is attenuated by a time constant of C1 and R1 to be converged to the ground level. On the other hand, an input signal of a differential amplifer 3 is bottom-held, and a bottom hold signal of the output of a differential amplifier 5 is converged to a convergent value set with R7 and R8 by a time constant C2 and R2. An intermediate value is calculated by R3 and R4 from the outputs of the amplifiers 4 and 5, and this value is always the intermediate value of the sum total signal of the photosensor even when an offset of the sum total signal of the photosensor and a degree of modulation are changed. By this method, the signal 1 and the intermediate value are compared with each other, and the accurate on-track/off-track signal 7 is always outputted from a comparator 6.

Description

Detailed Description of the Invention [Field of Application of Togami] The present invention relates to a device for recording and/or reproducing information on an optical recording medium by irradiation with a light beam, and in particular, on-track recording from reflected or transmitted light of the light beam. The present invention relates to an optical information recording and/or reproducing device equipped with means for obtaining an off-track signal (track count signal).

[Prior Art] FIG. 3 is a schematic diagram showing an example of the configuration of a conventional optical information recording/reproducing device. In the figure, numeral 10 indicates an optical disk, on which a plurality of tracks are arranged in parallel in a spiral or concentric manner. This optical disc 10 is rotationally driven by a spindle motor 11, and information is recorded or reproduced by irradiating a light beam from an optical head 21. Here, the optical head 21 has a built-in semiconductor laser 12 serving as a light source. The light beam emitted from this semiconductor laser 12 passes through a collimator lens 13, a beam splitter 14, and an objective lens 15, and is focused onto the optical disk IO. Further, the light reflected by the optical disk 1O passes through the objective lens 15 again, is separated from the incident light beam by the beam splitter 14, and is detected by the photodetector 18 via the sensor lens 17. This photodetector 18 is divided into a plurality of areas on its light receiving surface, and based on the output of each area, an auto tracking (AT)/auto focusing (AF) control circuit 19 performs an astigmatism correction method. , a push-pull method, etc., are used to detect the focus and tracking signals. These detected control signals are fed back to the lens actuator 16 to move the objective lens 15 in the direction of the optical axis and in the direction perpendicular to the optical axis and across the track.
-Perform AF.

In the above-mentioned apparatus, in order to access a desired track with a light beam, the entire optical head 21 is moved by the linear motor 22 in the radial direction of the disk, that is, in the direction across the track, or the lens actuator 16 is used to perform a track jump. Input a signal to move the objective lens across the track. At this time, an on-track/off-track signal is used to determine the position and moving direction of the light beam. This on-track/off-track signal is obtained by processing the sum signal of the outputs of all areas of the photodetector 18 using the on-track/off-track detection circuit 20.

FIG. 4 is a schematic diagram showing an example of a conventional on-track/off-track detection circuit as described above. Here, the output of the photodetector (
The sum signal) 1 is compared with a constant reference value C output from the constant voltage source 8 and set near the average value of the output 1 by the comparator 6. Then, an on-track/off-track signal 7 as shown in FIG. 5(b) is output.

When the light beam crosses the track with the focus servo turned on, the sum signal of the optical sensor becomes a signal that has an offset with respect to the ground level G and is modulated by the track. Then, the offset and modulation degree change depending on changes in the reflectance of the disk or changes in laser power. Therefore, in the conventional device, when such offset changes and modulation degree changes are large, the on-track/off-track signal that is the output cannot be obtained with sufficient accuracy because the comparison voltage is a constant voltage.

On the other hand, optical information recording and/or
Alternatively, a playback device is proposed in Japanese Patent Laid-Open No. 2-101637. An example of an on-track/off-track detection circuit used in this device is shown in FIG.

In FIG. 6, 1 is the sum signal of the optical sensor, 2 and 4 are the diode DI, capacitor C1, resistor R1,
a differential amplifier that constitutes a peak hold circuit together with R5;
3 and 5 are a diode D2, a capacitor C2,
A differential amplifier constitutes a bottom hold circuit together with resistors R2 and R6, R3 and R4 are resistors that create an intermediate value between the peak hold value and the bottom hold value, 6 is the intermediate value between the peak hold value and the bottom hold value, Optical sensor sum signal 1
A comparator 8 is a constant voltage that is a convergence value of the hold circuit.

The sum signal 1 from the optical sensor is input to a differential amplifier 2.3, where it is peak-held and bottom-held. The peak held voltage is determined by the time constant determined by CI and R1, and the bottom held voltage is determined by C2 and R2.
It moves toward a constant voltage 8 with a time constant determined by the voltage. The peak-held and bottom-held voltages further pass through buffers of differential amplifiers 4 and 5, respectively, and are determined to be reference voltages by R3 and R4. This voltage always becomes the intermediate value of the optical sensor's total signal (modulated signal by the track) even if the offset or modulation degree of the optical sensor's total signal changes. This situation is shown in FIG. 7(a).

Here, S represents the waveform of the summation signal, RH represents the peak hold signal, BH represents the bottom hold signal, M represents the calculated intermediate value, and G represents the ground level.

Therefore, by comparing the sum signal 1 and the intermediate value M, the comparator 6 always outputs an accurate on-track/off-track signal 7, as shown in FIG. 7(b).

[Problem to be solved by the invention] In normal conditions, the detection circuit shown in FIG. 6 can detect on-track/off-track with high accuracy. Since the level is set to the average level of the total signal of

For example, if the detection signal does not reach its peak value or convergence value due to a decrease in the amount of light detected by the optical sensor, the peak hold signal PH will not change at all and the intermediate value M
is derived to be considerably larger than the average level of the detection signal S. Therefore, the on-track/off-track detection signal S output from the comparator 6. is not accurate as shown in FIG. 8(b). When the amount of detected light further decreases, the detection signal S no longer reaches the peak or the intermediate value M as shown in FIG. 9(a), and as shown in FIG. 9(b),
On-track off-track detection signal cannot be obtained at all.

Furthermore, in the circuit of FIG. 6, the peak hold signal PH,
Since the settling point (convergence value) of the bottom hold signal BH is the same, there is a possibility that tracking pull-in may be adversely affected.

For example, as shown in FIG. 1O(a), when the track is pulled in at the time point A, the intermediate value M is the detection signal S.
approaching the level of And an on-track off-track detection signal S.

In this case, signal disturbances as shown in FIG. 10(b) occur.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide optical information recording and/or recording that can accurately detect on-track and off-track signals even when the amount of light received by an optical sensor decreases.
Or to provide playback equipment.

[Means for Solving the Problems] The above object of the present invention is to provide a means for irradiating a light beam onto an optical recording medium arranged in parallel with a track, and a means for relatively moving the light beam in a direction across the track. and means for detecting reflected or transmitted light of the light beam modulated by crossing the track, and converging the peak value of the signal detected by the detecting means toward a convergence value at a predetermined time constant. means for holding the bottom value of this detection signal while converging it toward a convergence value for a predetermined time constant, and deriving an intermediate value between the held peak value and bottom value. and means for comparing the derived intermediate value with the detection signal to obtain an on-track-off-track signal, wherein the convergence value of the bottom value holding means is set to the peak value. by setting the convergence value of the peak value holding means to a level lower than the convergence value of the bottom value holding means, and by setting the convergence value of the peak value holding means to a level lower than the convergence value of the bottom value holding means achieved.

[Example code] Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of an on-track/off-track detection circuit used in the apparatus of the present invention. The device of the present invention is constructed in the same manner as shown in FIG. 3 except for this circuit. In Figure 1, 1 is the sum signal of the optical sensor, 2, 4
are tie auto D1, capacitor ci, and resistor R1, respectively.
,, A differential amplifier that constitutes a peak hold circuit together with R5, 3.5 is a diode D2 and a capacitor 02, respectively.
, a differential amplifier that together with resistors R2 and R6 constitute the circuit from Hole 1 to Hole 1, R3, R, and 4 are resistors that create an intermediate value between the peak bold value and the bottom hold value, and 6 is the value to the peak hole 1. This is a comparator for comparing the intermediate value of the bottom hold value and the sum signal 1 of the optical sensor to obtain a double-converted on-track off-track signal 7. Further, R7, R, and 8 are resistors for dividing the peak hold voltage 1 and setting a redundant convergence value for the volume hole l signal.

The total signal l of the optical sensor is inputted to the differential amplifier 2 as Dl.
, CI, and R1, and the differential amplifier 4
The output is passed through the buffer. This peak hold signal is CI.

It attenuates with a time constant determined by R1 and converges to the ground level. On the other hand, the signals input to the differential amplifier 3 are D2. C
2, R2, and is output through the differential amplifier I5. This bottom hold signal has a time constant determined by C2, R2, and a convergence value set by R7 and R8. It converges towards ゛C.

, 1-, an intermediate value is calculated from the output of the differential amplifier 4.5 using R3°R4. This value varies depending on the offset and modulation degree of the optical sensor's total signal, 'ζ't+, and is always an intermediate value of the optical sensor's total signal (modulated signal by the track). This kind of cool figure 2 (a) is a little clever. Here, S is the waveform of the summation signal, RH is the signal to beak hole 1, BH is the bottom hold signal, M is the calculated intermediate value, and G is the ground level.

Therefore, by comparing the sum signal 1 and the intermediate value M, the comparator 6 always outputs a reliable on-track/off-track signal @7 as shown in FIG. 2(b).

Further, in the present invention, the peak hold signal is divided into voltages by the resistors R7 and R8, and this divided voltage value is used as the destination (convergence value) of the bottom hold signal. This convergence value is
The voltage changes depending on the peak hold value, and is always lower than the peak hold value. Therefore, for example, even if the level of the total signal of the optical sensor decreases due to dirt on the objective lens, the intermediate value M, as shown in FIG. 2(a),
Located between the peak hold value and the bottom hold value,
On-track and off-track signals can be detected accurately. Furthermore, since the peak hold value, bottom hold value, and intermediate A1 do not coincide, there is no adverse effect on tracking pull-in. For example, even if the tracking is pulled in at point A in FIG. 2(a), the on-track/off-track detection signal S is generated as shown in FIG. 2(b). There will be no disturbance. Therefore, even after tracking is pulled in, it is possible to accurately determine whether the light beam is on the track or between the tracks.

The present invention can be applied in various ways in addition to the embodiments described above. For example, although the embodiment is configured to detect light reflected by a medium, if the medium is a transmission type, the configuration is configured to detect transmitted light. Further, the shape of the medium is not limited to a disk shape, but may be any shape such as a cart shape or a tape shape.

[Effects of the Invention] As explained above, the present invention provides an optical information recording and/or reproducing apparatus that detects an on-track and off-track signal by using a peak value hold means and a bottom value hold means. The convergence value of the means is set to a level lower than the peak value and at a predetermined ratio to the peak value, and the convergence value of the peak value hold means is set to
By setting the level lower than the convergence value of the bottom value holding means, it is possible to accurately detect the track off track signal even when the amount of light received by the optical sensor decreases or after tracking pull-in is performed. The following effects were obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of an on-track and off-track signal detection circuit used in the optical information recording and/or reproducing apparatus of the present invention, FIG. 2 is a diagram showing signal waveforms of various parts in the circuit shown in FIG. 1, FIG. 3 is a schematic diagram showing an example of the configuration of an optical information recording and/or reproducing device to which the present invention can be applied, FIG. 4 is a diagram showing an example of a conventional on-track/off-track signal detection circuit, and FIG. 4 is a diagram showing signal waveforms of various parts in the circuit shown in FIG. 6. FIG. 6 is a diagram showing another example of a conventional on-track/off-track signal detection circuit. The sio diagram is a diagram showing signal waveforms at various parts in the circuit shown in FIG. 1... Optical sensor total signal 2.3, 4.5... Differential amplifier 6... Comparator 7... On-track off-track signal DI, D2...
・Diode CI, C2...Capacitor R1-R8...Resistor No. 1 Figure 2 q Punishment □・5°C To J 6th connection 7th

Claims (1)

[Claims] (1) means for irradiating a light beam onto an optical recording medium on which tracks are arranged in parallel; means for relatively moving the light beam in a direction across the tracks; means for detecting reflected or transmitted light of the light beam; means for holding the peak value of the signal detected by the detection means while converging it toward a convergence value with a predetermined time constant;
Similarly, means for holding the bottom value of this detection signal while converging it toward a convergence value with a predetermined time constant, means for deriving an intermediate value thereof from the held peak value and bottom value, and a derived intermediate value. and means for comparing a value with the detection signal to obtain an on-track-off-track signal, the convergence value of the bottom value holding means being lower than the peak value, and Set the level at a predetermined ratio to the peak value, and set the convergence value of the peak value holding means to
An optical information recording and/or reproducing device characterized in that the bottom value holding means is set at a level lower than the convergence value.