JPH058503B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical information reproducing device for optically reading information from a disk-shaped record carrier, and in particular to a VHD
Like a disk, next to the video and audio signal track,
The present invention relates to an optical information reproducing apparatus for optically reproducing a disc on which a guiding pilot signal is recorded.

Configuration of conventional examples and their problems Optical information reproducing devices that optically read information from a disc-shaped record carrier (hereinafter referred to as a "disk") that stores video and audio information and pilot information for guidance have been proposed in the past. This conventional optical information reproducing device will be explained with reference to FIG. Disc 1 is held by turntable 2,
It is rotated by a motor 3 at a constant rotation speed (for example, 900 rpm in the case of the NTSC system). For example, He
A light beam _A1 emitted from a radiation source 4, such as a -Ne laser, passes through a lens 5, a polarizing beam splitter 6, a λ/4 plate 7, a mirror 8, and an objective lens 9, and reaches a point a on the disk 1. Condensed light is irradiated.
The reflected light from point a passes through an objective lens 9, a mirror 8, a λ/4 plate 7, a polarizing beam splitter 6, and a cylindrical lens 12, and then reaches an optical detector 1.
3. The distance between the objective lens 9 and the disk surface changes depending on the inclination of the disk 1, warpage, and unevenness of the disk surface, and the light beam is always directed to the disk surface.
A ₁ cannot be focused and irradiated. This requires an automatic focus control device. When the reflected light from the surface of the disk 1 is incident on the optical detector 13, it changes as shown in FIG. 2 depending on the distance between the objective lens 9 and the disk surface. The optical detector 13 is a four-part detector as shown in FIG. Optical detector 1
3A and 13C to the positive terminal of the differential amplifier 14,
Further, the optical detectors 13B and 13D are added to the negative terminal of the differential amplifier 14. Differential amplifier 1
The output of No. 4 is applied to the linear motor 10 through the control circuit 15. This linear motor 10 vibrates the objective lens 9 up and down to focus it on the disk surface. As shown in FIG. 3, on the disk 1, a video/audio information signal (hereinafter referred to as "information signal") and a pilot signal for tracking are alternately recorded. Disc 1 bias and disc 1
Due to the undulations of the above information track and pilot signal track, the light beam _A1 does not always illuminate the information track. Therefore, a control system is required to always irradiate the light beam _A1 onto the information track. The outputs of the optical detector 13 are added by an adder circuit 16 and applied to a signal separation circuit 17. The information signal separated by the signal separation circuit 17 is applied to a demodulator 18, and the pilot signals _fp1 , _fp2 , _fp3 are applied to bandpass filters 19-21. The bandpass filter 19 extracts the pilot signal fp ₁ (≈511KHz), the bandpass filter 20 extracts the pilot signal fp ₂ (≈711KHz), and the bandpass filter 21 extracts the pilot signal fp ₃ (≈275KHz).
It is configured to extract. The outputs of the bandpass filters 19 to 21 are applied to envelope detection circuits 22 to 24.
The outputs of 2 and 23 are operated by amplifier 2 with different polarity.
Added to 5,26. The outputs of the operational amplifiers 25 and 26 are applied to a switch circuit 27. The signal detected by the envelope detection circuit 24 is 1/
The frequency is divided by the frequency divider circuit 28 and applied to the switch circuit 27. In response to this signal, the switch circuit 27 switches the outputs of the differential amplifiers 25 and 26 and supplies an error signal to the control circuit 29. The output of the control circuit 29 is applied to the motor 11, and the output of the control circuit 29 is applied to the motor 11.
1 swings the mirror 8 as shown by the arrow in Figure 1 and moves the light beam A ₁ in the radial direction on the disk surface, thereby controlling the tracking so that the light beam A ₁ always runs along the information track. There is. The output of the control circuit 29 is also applied to a feed motor control circuit 30 to drive a feed motor 33. The entire optical pickup 31 can be moved in the radial direction by means of a feed mechanism 32 and a feed motor 33. Note that this is a monitor TV.

However, in such a conventional device, as shown in FIG. 3, the information signal and the pilot signal _fp3 are recorded on the same track, and the pilot signal
Since the fp ₃ frequency is approximately 275KHz and the information signal has a high basic component of 6MHz to 8MHz, it is difficult to stably read out both signals with the same beam.
There was a problem that the unstable reading of the pilot signal _FP3 affected the tracking control, making it impossible to obtain a stable screen.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and an object of the present invention is to provide an optical information reproducing device that can stably read a pilot signal and obtain stable tracking servo.

Structure of the Invention In order to achieve the above object, an optical information reproducing apparatus of the present invention rotates an optical information recording carrier, on which three types of pilot signals are recorded on both sides of an information signal and superimposed on the information signal, at a predetermined number of rotations. a radiation source; a radiation source; a radiation source; and a radiation source that guides an emitted light beam from the radiation source onto the optical information recording carrier and irradiates it with focused light using an objective lens to convert the reflected light from the optical information recording carrier into a first one. A first optical means for guiding the light beam to the optical detector, an automatic focus control means for controlling the objective lens so that it is always focused on the optical information recording carrier, and the three types of pilot signals are used to control the light beam. a tracking control means for controlling the optical information recording carrier to track the information signal; and a tracking control means for controlling the optical information recording carrier to track the optical information on the optical information recording carrier. a second optical means for directing light onto the optical information record carrier and for directing reflected light from the optical information record carrier to a second optical detector, the pilot signal being superimposed on the information signal of the optical information record carrier is transmitted to the second optical detector; The configuration is such that detection is performed from the output of an optical detector.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a block diagram of an optical information reproducing apparatus according to the first embodiment of the present invention, in which the same components as those shown in FIG. 1 are given the same reference numerals and their explanations will be omitted. In FIG. 4, 34 is a polarizing beam splitter, 35 is a mirror, 36 is a lens, 3
7 is a mirror, 38 is a mirror, 39 is an optical detector, and 40 is a preamplifier.

The emitted light beam A from the radiation source 4 is split into light beams A ₁ and A ₂ by a polarizing beam splitter 34 . Light beam A ₂ passes through mirror 35 and lens 3
6, a mirror 37, a polarizing beam splitter 6, a λ/4 plate 7, a mirror 8, and an objective lens 9. At this time, the light beam _A2 on the disk surface is several tens of times larger than the spot size of the light beam _A1 . The reflected light _A2 from the disk surface is reflected by the objective lens 9, mirror 8, and λ/4
The light passes through the plate 7, the polarizing beam splitter 6, and the mirror 38 and enters the optical detector 39. The output of the optical detector 39 is supplied to the bandpass filter 21 through a preamplifier 40. By being able to stably detect the pilot signal _fp3 using the light beam _A2 , stable reproduction can be obtained.

FIG. 5 is a configuration diagram of an optical information reproducing apparatus according to a second embodiment of the present invention, in which 41 is an optical detector;
42 is a differential amplifier, 43 is an adder circuit, and 44 is a preamplifier.

The reflected light beam A ₁ from the disk surface passes through the objective lens 9, the mirror 8, the λ/4 plate 7, and the polarizing beam splitter 6, and enters the optical detector 13'. The output of the optical detector 13' is applied to the signal separation circuit 17 via a preamplifier 44.
At this time, unlike the first embodiment, since there is no cylindrical lens 12, the focus control method is performed as follows. The light beam A from the radiation source 4 is split by a polarizing beam splitter 34 into light beams A ₁ and A ₂ . The light beam A ₂ then passes through the mirror 3
5, lens 36, mirror 37, polarizing beam splitter 6, λ/4 plate 7, mirror 8, and objective lens 9
The light enters the disk surface through the The reflected beam from the disk surface passes through the objective lens 9, the mirror 8, the λ/4 plate 7, the polarizing beam splitter 6, and the mirror 38, and enters the optical detector 41.
The movement of the light beam _A2 on the optical detector 41 is as shown in FIG. 6, and as it moves like this,
Lens 36, objective lens 9, mirrors 35, 37,
38 etc. are arranged. 2-split detector 4
The outputs of 1A and 41B are applied to a differential amplifier 42 to detect a focus error signal and applied to the control circuit 15. The output of the control circuit 15 is the linear motor 10
In addition, the focal position is controlled by moving the objective lens 9 up and down. On the other hand, the outputs of the detectors 41A and 41B are also applied to an adder circuit 43, and the output of the adder circuit 43 is applied to the bandpass filter 21. Pilot signal like this
By creating a light beam for _fp3 detection, stable tracking control can be configured. Furthermore, since the disk 1 has an arrangement pattern as shown in FIG. 3, it is not necessary to irradiate the same place, and the irradiation position may be slightly shifted in the radial direction.

Effects of the Invention As explained above, according to the present invention, the optimum beam spot size for detecting the pilot signal _fp3 can be arbitrarily selected. Therefore, stable detection can be performed regardless of the inner or outer circumference of the disk, and as a result, stable tracking control can be obtained.
Furthermore, the light beam for detecting the pilot signal _fp3 can also be used for detecting focus errors, making it possible to simultaneously obtain a focus servo with a wide pull-in range and a stable tracking servo.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional optical information reproducing device, Fig. 2 is an explanatory diagram of a focus error detection method in the same optical information reproducing device, Fig. 3 is an explanatory diagram of a signal arrangement pattern on a disk, and Fig. 4 is an explanatory diagram of a focus error detection method in the optical information reproducing device. FIG. 5 is a block diagram of an optical information reproducing apparatus according to a first embodiment of the present invention, FIG. 5 is a block diagram of an optical information reproducing apparatus according to a second embodiment of the present invention, and FIG. 6 is an optical detector in the optical information reproducing apparatus. It is an explanatory view of movement of a light beam above. 1...disc, 2...turntable, 3...
...Motor, 4...Radiation source, 5...Lens, 6...
...Polarizing beam splitter, 7...4/λ plate, 8
... Mirror, 9 ... Objective lens, 10 ... Linear motor, 11 ... Motor, 12 ... Cylindrical lens, 13, 13' ... Optical detector, 1
4... Differential amplifier, 15... Control circuit, 16...
Addition circuit, 17... Signal separation circuit, 18... Demodulator, 19-21... Bandpass filter, 22
~24... Envelope detection circuit, 25, 26...
... Differential amplifier, 27 ... Switch circuit, 28 ...
1/2 frequency divider circuit, 29...control circuit, 30...feed motor control circuit, 31...optical pickup, 3
2...Feed mechanism, 33...Feed motor, 34...
Polarizing beam splitter, 35...Mirror, 36...
... Lens, 37, 38 ... Mirror, 39 ... Optical detector, 40 ... Preamplifier, 41 ... Optical detector, 42 ... Differential amplifier, 43 ... Addition circuit, 44 ... Preamplifier.

Claims (1)

[Scope of Claims] 1. A rotation control means for rotating an optical information record carrier on which three types of pilot signals are recorded on both sides of an information signal and superimposed on the information signal at a predetermined number of rotations, a radiation source, and a radiation source; a first optical means for directing an emitted light beam from a source onto the optical information record carrier and irradiating it with focused light through an objective lens and directing the reflected light from the optical information record carrier to a first optical detector; automatic focus control means for controlling the objective lens so that it is always focused on the optical information recording carrier; and a light beam tracking the information signal on the optical information recording carrier using the three types of pilot signals. tracking control means for controlling the first
A light beam having a spot size larger than the light beam of the optical means is directed onto the optical information record carrier and the reflected light from this optical information record carrier is directed to the second optical information record carrier.
an optical information reproducing apparatus, comprising a second optical means for guiding the optical information to an optical detector, and detecting a pilot signal superimposed on the information signal of the optical information recording carrier from the output of the second optical detector. 2 The second optical detector is a two-split detector, and has a differential amplifier that detects a focal shift from the output signal of the two-split detector, and an adder circuit that adds the outputs of each of the two-split detectors. The optical information reproducing apparatus according to claim 1, wherein the optical information reproducing apparatus is configured to detect a pilot signal from the addition output of the addition circuit.