JPS6124029A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To apply tracking control stably with high accuracy by increasing the gain of a tracking control while a signal is detected from a pre-format part of a recording medum. CONSTITUTION:A detection signal of photodetectors 13A, 13B is given to an adding amplifier 20 and a subtration amplifier 21. A signal from the substraction amplifier 21 is formed into a track control signal by a low pass filter 22, and an output signal (a) of the addition amplifier 20 is subject to cut off of a fluctuation component at a band pass amplifier 23, and an effective value detection circuit 16 detects a data recording part. The track control signal from the low pass filter 22 is controlled for the gain by using an output signal (c) of the effective value detection circuit 16 at a varible gain circuit 17 and when the signal (c) is increased, the gain is increased. Thus, the stable tracking control gain is ensured to an information bit 6, a pre-format part 1 and an unrecorded part and the stable tracking control with high accuracy is sttained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an optical information recording/reproducing apparatus having a tracking control system.

(Prior Art) In high-density, large-capacity optical information recording and reproducing devices such as optical disk devices, information signals are processed as shown in FIGS. 6 and 7 in order to access information signals recorded on a recording medium at high speed. is divided into units of a certain number of bits, which are called sectors),
A preformat section 1 having a predetermined concavo-convex pattern containing address information, etc. for recording and reproducing information signals in sector units and a guide groove 2 for tracking are placed in advance at the recording trunk forming position on the substrate 4 of the recording medium 3. An effective method is to form it in advance. The concavo-convex pattern of the preformat section 1 is formed so that the depth of the concave portion is the same as the depth of the guide groove 2, in order to simplify the production of the master of the substrate 4, that is, it is formed by intermittent formation of the guide groove. . The information signal is formed as information pits 6 in the guide groove 2 by melting and removing the recording layer 5 with a strong laser beam, and is reproduced with a weak laser beam.

FIG. 3 shows an example of an optical pickup optical system in an optical information recording/reproducing apparatus.

The semiconductor laser 7 emits a strong beam of light in accordance with the information signal during recording, and emits a weak beam of light during reproduction.

This light beam is made into parallel light by a coupling lens 8, and is converted into a parallel beam by a polarizing beam splitter 9. λ/4 plate 10. The light is focused onto the recording medium 3 through the objective lens 11 as a spot with a diameter of about 1.6 μm. The light beam reflected from this recording medium 30 is reflected by the objective lens 1.
1. λ/4 plate゛10. Focus detection light detection in which the light passes through the polarization beam splinter 9 and is focused by the condenser lens 12, a part of the light is received by the track detection photodetector 13, and the remaining part is placed at the convergence point of the reflected light beam. The light is received by vessels 14 and 15.

The light receiving state of the photodetectors 14 and 15 is as shown in Fig. 4 (a) when in focus.
4(b) and 4(c) when the recording medium 3 moves away or approaches. The focus adjusting device shown in the drawings adjusts the focus by driving the objective lens 11 back and forth based on the difference between the output signals of the photodetectors 14 and 15. As shown in FIG. 6, the guide groove 2 is formed spirally or concentrically on the substrate 4, and the track detection photodetectors 13 are arranged symmetrically with respect to the optical axis in a direction (radial direction) across the guide groove 2. It consists of a pair of photodetectors 13A and 13B. Track detection is performed by detecting the symmetry of the far-field image F of the reflected light with respect to the center of the guide groove based on the phase difference of the reflected light due to the optical distance between the guide groove 2 and the portion between each guide groove, as shown in FIG. I'll do my best. In other words, when the laser beam is incident on the edge of the guide groove 2 with the above spot shifted from the center of the guide groove 2 and has a phase difference of about V2 with respect to the part between the guide grooves, the far field image F of the reflected light is shown in FIG. (
a) As shown in (e), the areas with high light intensity shift in the direction in which the spot is shifted. Therefore, this change in light intensity is detected by the photodetectors 13A and 13B, and both photodetectors 13A and 1
A track signal is obtained by detecting the difference in the current flowing through 3B, and this trunk signal is passed through a low-pass filter to become a tracking control signal. direction, the spot tracks the guide groove 2. Recording and reproduction of information signals are performed while applying tracking control in this manner. Further, by adding the output signals of the photodetectors 13A and 13B, an information signal is reproduced, and this information signal becomes as shown in FIG. The depth of the guide groove 2 is λ/8 (λ
: the wavelength of the laser beam), the reproduced information signal is at level t with respect to the convex portion of the preformat section 1, and the amount of reflected light is reduced by approximately 30 degrees with respect to the concave portion due to diffraction. The light level decreases to a sea level t2, and the amount of reflected light from the pit 6 further decreases to a sea level t3. Since the convex portion of the preformat section 1 has virtually no guide groove, the track signal is always zero even if the laser beam shifts to the left or right as shown in FIG. 5(d). Therefore, as shown in Figure 9, spora)
When S crosses the preformat section 1 in the direction of 0/o, the track signal is interrupted by the uneven pattern of the preformat section 1, as shown by the solid line in Fig. 10. Since the frequency of the signal is higher than the band of variation of the track signal, the track signal passes through the bandpass filter as shown by the dotted line in Figure 10, and tracking control is applied by this signal. Therefore, the gain of tracking control is reduced in the preformat section 1 compared to the unrecorded guide groove 2, and tracking becomes unstable.

Even in the information pit 6, there is a problem that the gain of the tracking control decreases due to the decrease in the amount of reflected light.As a countermeasure, the value of D is defined from the amount of light entering the photodetectors 13A and '13B, and the value of D is There is a method of using it as a tracking error signal (13th Image Engineering Conference "Small three-dimensional drive optical head for recording and reproduction" 9-11). However, this method has the opposite effect in that the gain of the tracking control described above decreases in the preformat section 1 compared to the unrecorded guide groove 2, making tracking unstable, and on the contrary, it causes the unrecorded guide groove 2 to decrease. Preformat section 1
This increases fluctuations in the tracking control gain.

(Objective) An object of the present invention is to provide an optical information recording/reproducing device that can perform tracking control stably with high precision.

(Structure) In order to achieve the above object, the present invention is configured to increase the gain of the trunking control during the period when a signal is detected from the preformat section.

FIG. 1 shows a circuit section in one embodiment of the present invention;
The figure shows the signal waveforms of each part.

In this embodiment, an effective value detection circuit 16 and a variable gain circuit 17 are provided in the optical information recording/reproducing apparatus described above. The photocurrents detected by the photodetectors 13A and 13B are converted into voltages by preamplifiers 18 and 19, respectively, and then added by a summing amplifier 20, and a subtracting amplifier 21.
Subtracted by The track signal from the subtractive amplifier 21 passes through the low-pass filter 22 and becomes a track control signal as shown by the dotted line in FIG. components and high frequency noise are cut out, resulting in the result as shown in Figure 2. This signal is sent to a waveform shaping circuit and binarized to reproduce the information signal. The output signal of the band amplifier 23 is still detected as an effective value by an effective value detection circuit 16 such as a rectifier circuit, as shown in FIG. 2C. The output signal of the band amplifier is preformatted by 1. Regardless of the information pit 6, since AC output is generated for the part where data is recorded, its effective value is much smaller than the unrecorded part, and the effective value detection circuit 16 detects the part where data is recorded. will be detected. The gain of the track control signal from the low-pass filter 22 is adjusted by the variable gain circuit 17 according to the output signal C of the effective value detection circuit 16. If the signal C is zero, it remains unchanged; If it increases, the profit will increase. As a result, a stable tracking control gain can be ensured in each part of the information bit 6, preformat part 1 degree unrecorded part, and highly accurate and stable tracking control can be performed. The track control signal from the variable gain circuit 17 is applied to a drive circuit 25 via a phase compensation circuit 24, and this drive circuit 25 drives a motor 26, which drives the optical system in the radial direction of the recording medium 3. The spot traces the guide groove 2.

In the above embodiment, an envelope detection circuit may be used in place of the effective value detection circuit 16. In this case, the envelope detection circuit detects the envelope of the output signal d of the band amplifier 23 as shown in FIG. 11, and outputs the detection signal d to the variable gain circuit 17. Further, although the track detection photodetectors 13A and 13B detect the reflected light from the recording medium 3 in the above embodiment, they may also detect the transmitted diffracted light from the recording medium 3.

(Effects) As described above, according to the present invention, the gain of tracking control is increased during the period when a signal is detected from the print-out section of the recording medium, so tracking control can be performed with high accuracy and stability. I can do it.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a circuit section of an embodiment of the present invention, Fig. 2 is a waveform diagram showing signal waveforms of each part of the embodiment, and Fig. 3 is an example of an optical information recording/reproducing device. A side view showing the optical system, FIGS. 4(a) to (O) are side views showing each focal state of the optical system, and FIGS. 5(a) to (d) explain tracking control of the optical system. FIG. 6 is a plan view showing a part of an example of a recording medium, FIG. 7 is a perspective view showing a part of the same recording medium, and FIG. 8 is a diagram showing the same recording medium and a reproduced information signal. , FIGS. 9 and 10 are perspective views and waveform diagrams showing an example of the locus of a spot on a recording medium and a track signal, and FIGS.
The figure is a waveform diagram showing signal waveforms of various parts in another embodiment of the present invention. 16... Effective value detection circuit, 17... Variable gain circuit. Figure 1 side Figure 2 Figure 5 Figure 4 Rira Ra Figure (0) (ka) tc > td) side Figure 6
7 side figure 6 downward view figure 悌 (1 figure d.

Claims (1)

[Claims] A laser beam is irradiated onto a recording medium in which a guide groove for tracking is formed at the recording track formation position, a part of this guide groove is a non-guide groove part, and a preformat part is formed as a convex-concave pattern, and the laser beam is reflected. Optical information that detects light or transmitted diffracted light with a photodetector, detects a track signal from the output signal of this photodetector, and records and reproduces an information signal in the guide groove of the recording medium while applying tracking control. An optical information recording and reproducing apparatus, characterized in that the gain of the tracking control is increased during a period when a signal is detected from the preformat section.