JPS6148138A - Optical information signal reproducing device - Google Patents

Abstract

PURPOSE:To improve high-frequency characteristics by extracting slope information comporising a low-frequency component separated in terms of frequency from a tracking error signal and a jitter correction signal from a disc with a simple means and applying automatic control to the optical system so that the optical axis of a condenser lens is made vertical to the signal face of the disc depending thereupon. CONSTITUTION:When a recording medium (disc 6) is tilted by an angle theta, a shaking fulcrum Q of an optical system P existing at a distance L from the signal face of the recording medium 6 is shaken by Xa=Ltantheta to make the optical axis of the incident light to the recording medium 6 vertical to the signal face of the recording medium 6 based on the slope information detected by a proper means. Then no comatic aberration is caused to the lightsot formed onto the recording medium 6 by the condenser lens 5 of the optical system. Then a focus error signal Sf is obtained by a signal difference between the output signals from photodetectors 27a, 27c placed diagonally in the photodetector 27 and the photodetectors 27b, 27d.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention projects a minute spot of strange light onto the signal surface of a recording medium that has a signal surface on which an information signal is recorded. , information based on the reflected light from the signal surface (
The present invention relates to a tracking error detection method for an optical information signal reproducing device adapted to reproduce No. 3.

(Prior art and problems) A spot of light with a minute diameter is projected onto the signal surface of a recording medium that has a signal surface on which information signals are recorded, and information is detected based on the light reflected from the signal surface. It is well known that various types of optical information signal reproducing devices for reproducing signals have been proposed.

By the way, in an optical information signal reproducing device that reproduces information signals from a recording medium on which information signals are recorded at high density, the reproduction of information signals from the recording medium is performed under tracking control. Various types of tracking control systems for optical information signal reproducing devices are also known.

The tracking error detection method used when performing tracking control uses the fact that the intensity distribution of the reflected light from the recording medium is biased due to the tracking error to detect the tracking error. A so-called push-pull tracking error detection method is widely used because the optical system has a simple configuration and is advantageous in terms of cost.

FIG. 1 is a schematic diagram showing the basic configuration of an optical information signal reproducing apparatus to which the push-pull tracking error detection method described above is applied.

1 is a light source (for example, a laser light source), and the light source 1 emits linearly polarized light from a minute light emitting part.

The light emitted from the light source 1 is made into parallel light by the collimating lens 2, and then transmitted through the polarizing prism 3, and then made into circularly polarized light by the λ74 wavelength plate 4, and then condensed by the condensing lens 5 to be sent to the recording medium 6. A light spot with a minute diameter is generated on the signal surface of the disk 6.

Since the signal surface of the disk 6 has a high reflectance, the light focused by the condenser lens 5 as described above is reflected from the signal surface of the disk 6 and travels in a circle in the opposite direction. It becomes polarized light and passes through the condensing lens 5 again with λ/4 wavelength @4
given to.

In the above-mentioned λC wave plate 4, the reflected light is made into linearly polarized light having a plane of polarization perpendicular to the incident light, so that one reflected light is reflected by the reflective surface 3a of the polarizing prism 3 and given to the photodetector 7. .

The photodetector 7 described above has two light receiving elements 7 divided by a plane including the extending direction of the recording trace on the signal surface of the disk 6 and the optical axis of the light projected onto the signal surface of the disk 6.
a, 7b, and the two light receiving elements 7a, 7
The output signal from b is given to an adder 8 and a subtracter 9,
The adder 8 sends a reproduced signal to the output terminal 10, and also subtracts! From 119, a tracking error signal is sent to output terminal 11. Ω in Figure 1 is photodetection 977,
This is the dividing line.

In the optical information signal reproducing device shown in FIG. 1, as described above, the two light receiving elements 7a17b in the photodetector 7
The output of the reproduced signal is obtained by the sum of the output signals from the
Further, since a tracking error signal is obtained by the difference between the output signals from the two light receiving elements 7a and 7b in the photodetector 7, the device has a feature that the configuration is simple. What are the conditions under which an accurate tracking error signal can be obtained in an information signal reproducing device?

This is true only when the signal surface of the disk 6 is perpendicular to the optical axis of the projected light, as in (a) of the second @, and the signal surface of the disk 6 is as shown in (b) of FIG. As in, the width direction of the record trace is the first; if it is slanted.

The optical axis of the reflected light from the signal surface of the disk 6 is tilted, and as a result, the optical axis of the reflected light moves by y from the position of the dividing line between the two light receiving elements 7a and 7b in the photodetector 4117. The difference signal between the output signals of the light receiving elements 7a and 7b does not indicate correct tracking error information, and the signal surface of the disk 6 is not aligned with the optical axis of the projected light as shown in FIG. 2(a). Even if they are perpendicular to each other, the condensing lens 5 is in the 2nd B! (c) of l
It has a serious drawback that a false tracking signal is generated even if there is a deviation of 2 as shown in FIG.

In order to solve the above-mentioned drawbacks of the push-pull tracking error detection method, the applicant company has previously developed a recording method using an array of pits corresponding to information signals, as described in Japanese Patent Application Laid-Open No. 58-125242. A spot of focused light is projected onto the signal surface of a recording medium that has a signal surface on which traces are formed so that the diameter is approximately the same as that in the recording trace, and the intensity is modulated by the pits. The reflected light is received by a photodetector that is divided into two by a plane that includes the extending direction of the recording trace on the signal surface of the recording medium and the optical axis of the light projected onto the signal surface of the recording medium, and detects the information signal. In an optical information signal reproducing device that is capable of optically reproducing information, the modulated signal output from the photodetector is corrected by a signal component that does not include tracking error information in the modulated signal output from the photodetector. The present invention provides a tracking error detection method for an optical information signal reproducing device in which a j tracking error signal is obtained by a difference signal between output signals from each of the two divided parts of the photodetector. Good results have been achieved.

However, the tracking error detection method of the previously proposed optical information signal reproducing device cannot be applied to a recording medium in which land portions and pit portions are arranged in the extending direction of the recording trace in correspondence with the information signal. The desired effect is achieved, but the structure is similar to so-called rewritable optical discs, which have recently come into practical use, in which a groove of a certain depth is provided in one direction of the recording trace. The problem was that it could not be applied to recording media.

In order to solve the above-mentioned problems, the applicant company has previously proposed, in accordance with Japanese Patent Application No. 59-914, a signal surface having a green color on which information signals are optically recorded. A spot of light for signal reading is projected onto the signal surface of the recording medium, and the reflected light, whose intensity is modulated by the information signal in the recording trace, is detected in the direction in which the recording trace extends on the signal surface of the recording medium. The light is received by a photodetector divided into two by a plane including the optical axis of the light projected onto the signal surface of the medium, and the difference signal between the output signals output from each of the two divided parts of the photodetector is detected. In an optical information signal reproducing apparatus equipped with a subtraction means for obtaining a recording medium, as the spot of light projected onto the signal surface of a recording medium shifts from the center position of the recording trace on the signal surface in the width direction of the recording trace, Tracking is performed based on the amount of deviation between the axis of symmetry in the form of change in signal amplitude that occurs in the reproduced signal in response to the reflected light whose intensity is modulated by the information signal in the trace and the point at which the output signal from the subtraction means described above becomes zero. A tracking error detection method of an optical information signal reproducing device configured to detect the offset of output signal.

a means for holding a reproduced signal generated based on reflected light whose intensity is modulated by an information signal in a recording trace when the value becomes a predetermined positive or negative value; A tracking error detection method for an optical information signal reproducing device comprising means for obtaining a difference signal, and a difference signal between output signals respectively output from two divided parts of the photodetector described above an optical system comprising: means for multiplying the reflected light whose intensity is modulated by the information signal in the recording trace by a reproduction signal generated correspondingly; and means for integrating the output (No. 1) from the multiplication means. The above-mentioned problems have been solved by providing a tracking error detection method for a digital information signal reproducing device.

The tracking error detection method of the optical information signal reproducing device proposed by the applicant company in Japanese Patent Application No. 59-914 will be explained as follows with reference to FIGS. 3 and 4. be.

In FIG. 3, components corresponding to those in the tracking error detection method of the optical information signal reproducing device shown in FIG. 1 already described are given the same drawing symbols as those used in FIG. It is used. In Figure 3, 1 is light -
The light emitted from the light 117 The light is condensed by the condenser lens 5 to form a light spot with a minute diameter on the signal surface of the recording medium 6 (disc 6).

The light condensed by the condensing lens 5 as described above is reflected by the signal surface of the disk 6, becomes circularly polarized light in the opposite direction, passes through the condensing lens 5 again, is applied to the λ/4 wavelength plate 4, and is given to the λ/4 wavelength plate 4 as described above. In the λ/4 wavelength plate 4, the reflected light is converted into linearly polarized light having a plane of polarization perpendicular to the incident light, and the reflected light is reflected by the reflective surface 3a of the polarizing prism 3 and provided to the light emitter 7.

The photodetector 7 described above includes two light-receiving elements 7a that are divided by a plane that includes the extending direction of the recording trace on the signal surface of the disk 6, the signal surface of the disk 6, and the optical axis of the projected light. 7b (2 is a dividing line in the photodetector 7), and when the output signals from the two light receiving elements 7a+7b are given to the subtraction circuit 19, the subtraction circuit 1
From 9, a tracking error signal is sent to an output terminal 11. Terminal 20 in subtraction circuit 19 is an offset adjustment terminal.

In the apparatus shown in FIG. 3, the output signals from the two light receiving elements 7a and 7b in the photodetector 7
The sum signal added by is output to the output terminal 10 as the output of the reproduction (No. 6).

The reproduced signal output from the adder 8 is sent to an envelope detector 14.
After being detected, the signal is supplied to gate circuits 15 and 16. Output signals from the two light receiving elements 7a+7b in the photodetector 7 are subtracted from one by the other in a subtracting circuit 19, and a tracking error signal is sent to the output terminal 1.
1 is output. The tracking error signal output from the subtraction circuit 19 to the output terminal 11 is applied to a comparator 12.13. Among the comparators 12 and 13 described above, one of the comparators 12 generates a gate signal and controls it when a tracking error signal higher than a predetermined positive voltage +Vo is supplied to the comparator s12. The other comparator 13 generates a gate signal and gates it when a tracking error signal higher than a predetermined negative voltage -Vo is supplied to the comparator 13. to the circuit 16.

The output signals from the gate circuits 15 and 16 described above are as follows.

Holding circuit (hold circuit) Given to 17.18.

A subtracter 21 subtracts one of the output signals of the holding circuits 17 and 18 from the other.

The output signal of the subtractor 21 is supplied to an amplifier 23 via a low-pass filter 22, where it is amplified and then offset by 20! in the subtractor circuit 19! 1lIlIa terminal 20, the circuit arrangement shown in the third diagram is as follows.
The offset in the tracking error signal is removed by the operation described below with reference to FIG.

FIG. 4(a) is a relationship diagram between tracking error X and tracking error voltage V, with 1-racking error oo' is an offset corresponding to the tracking error. Further, (b) in FIG. 4 is the detected signal output of the reproduced signal, which is the maximum output at the true tracking point 0.

As mentioned above, from the subtraction circuit 19 to the comparator 1 in FIG.
2. When the tracking error signal applied to 13 exceeds +Vo with a positive voltage, the gate circuit 15 is opened by the gate signal generated from the comparator 12, and the signal shown in FIG. 4(a)
The voltage v1 is sent to the holding circuit 17 and held there.

Furthermore, when the tracking error signal applied from the subtraction circuit 19 to the comparator 12.13 in FIG. , Voltage ■2 in (a) of Figure 4
is sent to the holding circuit 18 and held there.

The output signals from the holding circuits 17 and 18 are supplied to a subtracter 21, and the voltages Mvt and vz mentioned above are subtracted by the subtracter 21, and the output signal of (Vl-V2) from the subtracter 21 is large. The signal is applied to a low-pass filter 22 having a time constant and integrated. In the example being described now, the output signal (Vl-V2) from the subtracter 21 becomes a negative voltage, and this voltage is passed through the amplification @23 to the subtracter 1'81.
G offset l! 11! 20, the subtraction circuit 19 performs an offset adjustment in the positive direction, raising the Qn point in (a) of FIG. 1 in the positive direction, and The 0'' point and the 0 point in FIG. 4(b) are matched, so that false tracking signals due to optical offset are eliminated.

It is preferable that the tracking errors Xi and X2 corresponding to +Vo and -Vo described above are set to a tracking error level that normally occurs, for example, about 20% of the recording trace interval.

As is clear from the above explanation, when the signal surface of the recording medium is tilted with respect to the optical axis of the laser beam projected onto the recording medium for reading the information signal, the tracking error signal is When information signals are recorded on a recording medium by arranging land portions and pits, removal of false signals occurring in
By the technical means disclosed in Publication No. 125242,
Furthermore, if the recording of the information signal on the recording medium is carried out on a continuous groove-like part or a continuous protrusion-like part, then the The technical means disclosed in No. 914 detects the tilt information of each recording medium and body, and adds a signal to the tracking error signal so that the above-mentioned false tracking error signal is removed based on the detected tilt information. However, in the existing proposals explained with reference to Figs. 1 and 3, the problems detected in the recording medium are Even if the false signal in the tracking error signal is removed by the tilt information of the recording medium, the optical axis of the laser beam projected onto the recording medium to read the information signal is not relative to the signal plane of the recording medium. Since the recording medium is left tilted, the light spot generated on the signal surface of the recording medium has comatic aberration, which may deteriorate the frequency characteristics of the reproduced signal or interfere with adjacent signals. Since various undesirable phenomena such as crosstalk from recorded traces occur, improvements have been sought.

(Means for Solving the Problems) The present invention provides a method for reading signals from a light source on a signal surface of a recording medium having a signal surface on which a record is formed by optically recording an information signal. A light spot is projected, and a photodetector receives the reflected light, whose intensity is modulated by the information signal in the recorded trace.

An optical information signal reproducing device configured to obtain a reproduced information signal from the above-mentioned photodetector, which includes the above-mentioned light source, a focusing lens that forms a light spot on the signal surface of the recording medium, a photodetector, etc. are arranged in a predetermined related arrangement in one housing, the above-mentioned optical system is moved directly in the direction of its optical axis, and the light spot is moved in a direction perpendicular to the above-mentioned optical axis. a driving device for an optical system that swings the optical axis so that it can be moved; and a transporting device that transports the optical system and the driving device for the optical system in a direction transverse to a recording trace of a recording medium. an automatic focus control circuit that automatically forms a tiny spot of light on the signal surface of the recording medium, and an automatic focus control circuit that always makes the spot of light track the recording trace. The reflected light received by each light-receiving surface separated by the dividing line in the photodetector, which is equipped with a tracking control circuit and has a light-receiving surface divided into at least two parts on the optical axis. means for obtaining inclination information between the signal surface of the recording medium and the optical axis in the direction orthogonal to the recorded trace based on the difference in strength of the recorded trace; and means for driving and controlling the above-mentioned 19 transport device so as to make the optical axis of the above-mentioned optical system perpendicular to the signal surface of the recording medium based on an output signal from the means for obtaining tilt information. an optical system including an information signal reproducing device, a light source, a condensing lens for forming a light spot on the signal surface of a recording medium, a photodetector, etc. fixed in a predetermined related arrangement in one housing; an optical system driving device that swings the optical axis so that the optical system can be moved directly in the direction of its optical axis and the spot of light can be moved in a direction perpendicular to the optical axis; It is equipped with the above-mentioned optical system and a drive device for the above-mentioned optical system, and a transport device that moves the above-mentioned optical system in the transverse direction of the recording trace of the recording medium, and also automatically and constantly places a minute spot of light on the signal surface of the recording medium. It is equipped with an automatic focusing control circuit that causes the spot of light to be formed on the recording trace, and an automatic tracking control circuit that causes the spot of light to always track the recording trace. Based on the difference in intensity of reflected light received by each light receiving surface separated by the first dividing line in the photodetector having a light receiving surface divided into two by the first dividing line, means for obtaining inclination information between the signal surface of the recording medium and the optical axis in the direction of the recording medium;
The optical axis of the optical system is made perpendicular to the signal surface of the recording medium based on the output signal from the means for obtaining inclination information between the signal surface of the recording medium and the optical axis in the direction orthogonal to the recording trace. means for driving and controlling the above-mentioned transfer device;
The signal surface of the recording medium and the light in the extending direction of the recording trace according to the output difference signal from the light receiving surface of the photodetector separated by the second dividing line perpendicular to the first dividing line. The optical axis of the optical system is set to the recording medium based on the output signals from the means for obtaining inclination information with respect to the optical axis and the means for obtaining inclination information between the signal surface of the recording medium and the optical axis in the extending direction of the recording trace. The present invention provides an optical information signal reproducing device comprising means for driving and controlling a device for moving a light spot relative to a recording medium so as to make the light spot perpendicular to the signal plane of the recording medium.

(Example) Hereinafter, specific contents of the optical information signal reproduction IATct of the present invention will be explained in detail with reference to the accompanying drawings.

First, 5th c! 1 is a diagram illustrating an outline of the operation mode of the optical information signal reproducing apparatus of the present invention, and FIG. 5(a) shows that when the recording medium (disk 6) is tilted by an angle θ,
The reflected light 24r of the incident light 24 on the disk 6 is the incident light 24.
It has an angle of 20 with respect to 4, and the reflected light 24
This figure shows the same situation as described in FIG. 2(b), in which the optical axis of r is separated by y from the optical axis of the incident light 24.

Further, (b) in FIG. 5 shows the optical information signal reproduction according to the present invention in a state where the recording medium (disk 6) is tilted by an angle of 0, as in the case of (, a) in FIG. 5 described above. 5 is a diagram illustrating and explaining what state the optical system P is in with respect to the recording medium 6 in the apparatus. In the optical information signal reproducing apparatus of the present invention, (a
) and (b), when the recording medium (disc 6) is tilted by an angle of 0, the signal surface of the recording medium 6 is determined based on the tilt information detected by an appropriate means. The swing fulcrum Q of the optical system P, which is located at a distance from This prevents comatic aberration from occurring in the spot of light that is imaged on the recording medium 6 by the condensing lens 5 in the optical system described above. In addition,
In FIG. 5, 68 is a pit.

FIG. 6 is a block diagram of an embodiment of the optical information signal reproducing apparatus of the present invention. In FIG.
turntable TT rotated at a predetermined number of rotations by d
It is driven and rotated at a predetermined rotational speed by being fixed to.

PR is a reproducing element, and this reproducing element PH is an optical system P.
and four coils 30 and 31 fixed to the optical system P.
, 32, 33, and a yoke 34, 3'4.
and a permanent magnet 35.35, and a rubber retainer 36.36 which flexibly connects the movable part and the magnetic circuit member.

40 is a carriage, and this carriage 40 is guided by guide rails 41m and 41b to transport the above-mentioned reproducing element PR in the radial direction of the recording medium 6,
Drive for transporting the carriage 40 in the radial direction of the recording medium 6 is performed by the feed motor 42 via a wire 44 wound around a pulley 43 fixed to the rotating shaft of the feed motor 42.

FIG. 7 illustrates a specific example of the configuration of the optical system P. In FIG. 7, 1 is a semiconductor laser, and 2 is a semiconductor laser.
is a collimating lens, 3 is a polarizing prism, 4 is a 174 wavelength plate, 5 is a condensing lens, 26 is a cylindrical lens, and 27 is a photodetector (a photodetector consisting of four light receiving elements). On the optical axis, there are a quarter wavelength plate 4, a collimating lens 2, a polarizing prism 3. Each component such as the semiconductor laser 1 is fixed to the housing 29 of the optical system P in an aligned state, and the cylindrical lens 26 and the photodetector 27 arranged on the side of the polarizing filter 3 are also attached to the optical system. It is fixed to the housing 29 of P.

The laser beam emitted from the semiconductor laser 21 in the optical system P is transmitted through the polarizing prism 3 → collimating lens 2 → 1/4
A minute spot of light is imaged on the signal surface of the recording medium 6 via the wavelength plate 4 → the condensing lens 5, and the reflected light from the signal surface is transmitted through the condensing lens 5 → the 1/4 wavelength plate. 4 → Collimating lens → Polarizing filter 3 → Cylindrical lens 26 → Photodetector 2
The light is supplied to a photodetector 27 (see FIG. 6) having four light receiving elements 27a to 27d through a path 7.

The four light receiving elements 27a, 27b, 27c, 27 described above
d is.

The photodetector 27 is the first. It is divided into four by second dividing lines QL and Q2, and in the following description, the output signal from the light receiving element 27a in the photodetector 27 is tE.
a, the output signal from the light-receiving element 27b is Hb, the output signal from the light-receiving element 27c is Ec, and the output signal from the light-receiving element 27d is 1Ed.
It is expressed as.

The information signal reproduced from the recording medium 6 is the sum of output signals (E
a+Hb+Ec+Ed), which is obtained by the circuit arrangement of adders 45, 46, and 49 in the optical information signal reproducing apparatus shown in FIG. The reproduction information signal 1 described above undergoes necessary signal processing by the reproduction signal processing circuit 51 and is outputted from the output terminal 0 as the reproduction signal Sr.

The reproduced signal processing circuit 51 also generates a time axis error signal (jitter correction signal) Sj by a well-known means and supplies it to the arithmetic circuit 50.

Next, the focus error signal Sf is detected by means conventionally known as the A-Tingmart method, that is, by means of four light-receiving elements 27a to 27d in the photodetector 27.
Two light receiving elements 27a located diagonally in
, 27c and the sum of the output signals from the light-receiving elements 27b and 27d. In the optical information signal reproducing apparatus shown in FIG. is supplied to circuit 50.

In FIG. 6, the coordinate axis A signal obtained by subtracting the sum of the output signals of the two light receiving elements 2b and 27c arranged below with respect to the dividing line Q1 from the sum of the output signals of the two light receiving elements 27a and 27d. .

That is, (27a+27d)+(27b+27c
) is used as the tracking error signal SL, and the above-mentioned tracking error signal St is used in the optical information signal reproducing apparatus shown in FIG.

Adders 45, 46. The tracking error signal St obtained by the circuit arrangement including the subtracter 28 and the like and obtained as described above is supplied from the subtracter 28 to the arithmetic unit 50.

The arithmetic circuit 50 described above includes adders 50a to 50d and subtracters 50e to 50g, for example, as shown in FIG.
This arithmetic circuit 50 outputs a focus error signal Sf and tracking error signals S7 and S1.
When the time axis error signal Sj is calculated as required and the output signal is supplied to the four coils 30 to 33 of the movable part in the reproducing element PIE described above, the optical system P moves in the optical axis direction. Drive control is performed in a state in which four direct motion operations, a tracking control operation, and a jitter correction control operation are performed simultaneously (for the configuration of the arithmetic circuit 50 and the four drive operations of the optical system, , special public official 1977-260
Please refer to Publication No. 87).

In the circuit arrangement shown in FIG. 8, when the focus error signal Sf is passed counterclockwise to all the coils 30 to 33, the optical system P is displaced upward (perpendicular to the plane of the paper). . In addition, the tracking error (ff) is caused by the arrow T in FIG. The lens 5 in the optical system is displaced and driven to the left (toward the outer circumferential side in the radial direction of the disk) by generating a torque in the direction.

When the jitter correction signal Sj is passed clockwise through the coils 30 and 31, and counterclockwise between the coils 32, 33, the jitter correction signal Sj changes in the direction of the arrow in FIG. A torque is generated, and the lens 5 in the optical system is displaced upward. When the disk 6 is rotating counterclockwise as indicated by the arrow R in FIG. 6, the relative speed between the lens 5 and the disk 6 decreases due to the displacement drive of the lens 5 described above.

In FIG. 6, 52 and 53 are peak value holding circuits, the peak value holding circuit 52 is given the output signal of the adder 45, and the peak value holding circuit 53 is fed with the output signal of the adder 46.
The output signal of is given. FIG. 9 shows a specific example of the configuration of the peak value holding circuits 52 and 53 described above. The peak value holding circuit shown in FIG. 9 is composed of a diode D1, a capacitor C1, and a resistor R1. has been done.

In the peak value holding circuit 52, the output signal of the adder 45, that is, the output signal E of the light receiving element 27a in the photodetector 27 and the output signal @Ed of the light receiving element 27d) knee (D sum (1
) The peak value of the sum signal (Eb+Hc) is held.

Then, as shown in FIG. 10, the disk 6 is
When the recording trace is composed of an array of pits, the peak value of the signal held by the peak value holding circuits 52 and 53 is the state in which the light spot is placed on the land. This was obtained in response to

That is, the light spot deviates from the position of the pit 6a of the disc, for example 55a in FIG.

Since there is no polarization of the diffracted light in the reflected light from the spot when the spot is located on a land as shown in 55b, the signal obtained corresponding to the spot 1 will be the peak value of the signal. be.

The output difference from the two peak value holding circuits 52 and 53 described above is proportional to the radial inclination of the disk, and the output difference from the two peak value holding circuits 52 and 53 described above is proportional to the radial inclination of the disk. The output signal from the subtracter 54, which generates a difference signal between the output signals from the two peak value holding circuits 52 and 53, indicates the radial tilt information of the disk. It has become.

The above points will be explained in more detail as follows. As shown in Figure 1O, the state of the information signal reproduced based on the arrangement of pits 6 (L, 6 (L...) forming the recording trace of the disc 6 is as shown in Figure 10. A light spot exists at the position 9, for example, 55c, 55d
As shown in the waveform shown by the dotted line in FIG. 11, the signal is small in the state of , and becomes large in the state where the spot of light is on the land.
The signal changes in size depending on the presence or absence of pits.

The peak value detection circuit 5 to which such a signal is applied
3. The output signal from 54 increases or decreases only around the maximum value of the signal added to it, as shown by the solid line in Figure 11, so the above-mentioned peak value holding circuit The output signal from 53 and 54 does not include information from the pit IC in the recording trace.

It contains only information near the land portion of the recording trace, and therefore the output signal from the subtracter 54 indicates the tilt information on the disk 6.

Therefore, the state in which the output signal from the subtracter 54 is zero is a state in which the disk 6 is not tilted, that is, a state in which the optical axis of the condenser lens 5 in the optical system P is perpendicular to the signal surface of the disk 6. It shows.

When the tracking control operation is being performed, the light spot on the signal surface of the disk 6 is always tracing a recording trace consisting of an array of pits. The entire optical system P is connected to X in FIG. 5 so that the output signal from the
If the optical system P is automatically controlled to move by a, the optical axis of the condensing lens 5 in the optical system P will always be aligned with the disk 6.
The information signal is read from the disk 6 while being held perpendicular to the signal surface of the disk 6. To achieve this, the carriage is moved in the direction in which the output signal from the subtracter 54 becomes smaller. 40 may be automatically controlled to be transferred by the feed motor 42.

FIG. 12 is a block diagram showing another example of a tilt information generation circuit for a disk in which recording traces are formed by an array of pits on a flat surface. Adders 45, 46, and 49 are.

This shows the adders 45, 46, and 49 used in the optical fishing axis m-signal reproducing device already described with reference to FIG. The feed motor 42 and calculation circuit 1'850 used in the optical information signal reproducing apparatus described above are shown respectively, and 28 is used in the optical information signal reproducing apparatus described with reference to FIG. This shows the subtractor used inside. In FIG. 12, 56 is a high-pass filter;
57 is a comparator, 58 and 59 are gate circuits, and 60 is a polarity inverter.6Adder 49 shown in FIG.
The reproduction information signal sent from the adder 49 in FIG. 12, which corresponds to However, the high-pass filter 56 to which the reproduced information signal in such a signal form is supplied removes the DC component in the reproduced information signal and outputs only the exchange signal.

The comparator 57 to which only the exchange of the reproduced information signal is supplied from the above-mentioned high-pass filter 56 receives the signal (shown in FIG. 13) corresponding to the positive part of the AC signal input thereto.
An output signal as shown in b) is generated and applied to the polarity inverter 60 and also to the gate circuit 58 as a gate signal. Further, the output signal as shown in FIG. 13(c) generated by the polarity inverter 60 described above is given to the gate circuit 59 as a gate signal.

The gate circuits 58 and 59 described above include the subtracter 28 shown in FIG. 6 and the corresponding subtracter 2 in FIG.
The tracking control signal St sent out from the gate circuit 58 is supplied, but the output signal from the gate circuit 58 described above is supplied with a gate signal as shown in FIG. 13(b). The feed motor 42 is controlled by the output signal from the gate circuit 58, since this is an information signal in the state where the spot is located on the land, that is, a signal containing only information on the inclination of the disk 6.

As described with reference to FIG. 6, the optical axis of the condenser lens 5 in the optical T1P is always maintained perpendicular to the signal surface of the disk 6, and information signals from the disk 6 are read. The optical system P is automatically controlled according to the state.

I soaked it up. The output signal from the gate circuit 59 described above to which the gate signal shown in FIG. 13(c) is given is:
The output signal from the gate circuit 59 is an information signal in a state where the light spot is located on the east side of the pit 6, that is, a signal that includes only the polarization of the diffracted light due to the six peaks of the pits on the disk 6. By supplying the tracking coil to the tracking coil via the arithmetic circuit 50, even better tracking control operation can be performed.

The description so far has been made regarding the case where the present invention is implemented in an optical information signal reproducing apparatus configured to reproduce information signals from a disk in which recording traces are formed by an array of pits on a flat surface. Regarding the embodiment, firstly, a continuous groove-like portion (or groove) having a constant depth in the extending direction of the recorded trace.

An optical optical system adapted to reproduce information signals from a disk (a partial cross-section of the disk is shown in FIG. An embodiment in which the present invention is applied to an information signal reproducing device will be described.

Means for detecting disk inclination information in a disk configured such that a continuous groove-like portion of a certain depth (or a continuous protrusion-like portion of a certain height) is provided in the extending direction of a recording trace. As for the above-mentioned patent application proposed in 1982-9,
Technical measures such as those presented in No. 14 can be adopted.

FIG. 15 shows a disk in a disk 6 having a configuration in which a continuous groove-like portion of a certain depth (or a continuous protrusion-like portion of a certain height) is provided in the extending direction of the recording trace. detects the inclination rI information of the disc, and supplies the detected disc inclination information to the feed motor 42 so that the optical axis of the condensing lens 5 of the optical system P is always perpendicular to the signal surface of the disc 6. 1 is a block diagram of a part of an optical information signal reproducing device in which the system is controlled; FIG.

In FIG. 15, 45, 46, and 49 are adders, and 28 is a subtracter. Adders 45, 46, 49 and subtracter 28 used in the optical information signal reproducing device described above are shown, and 42.50 is the same as that already described with reference to FIG. A feed motor 42 and arithmetic circuit 50 used in an optical information signal reproducing device are shown. In FIG. 15, 61 is an envelope detector, 62 is a multiplier, and 63 is a low-pass filter.

The first one corresponding to the adder 49 shown in FIG.
The reproduced information signal sent from the adder 49 in FIG.

Reduced s! 1. The tracking error signal St output from the circuit 28 is supplied to the multiplication circuit 62 and the arithmetic circuit 50 described above. The output signal of the multiplication circuit 62 described above is supplied to the feed motor 42 via a low-pass filter 63.

Next, the above-mentioned circuit layout W-CD operation will be explained with reference to FIG. 16.

FIG. 16(a) shows the detected signal output of the reproduced information signal, which is the maximum output when the light spot position is at the true tracking point 0 and the disc tilt is zero. . FIG. 16(b) is a relationship diagram between tracking error X and tracking error voltage V, with tracking error X plotted on the horizontal axis and tracking error voltage V plotted on the vertical axis.

In the figure, o-o' is an offset corresponding to the tracking error. The tracking error shown in Figure 16 (b) becomes 0 when the light spot is at the center of the groove (or protrusion) if the disk is not tilted. However, when the disk is tilted, and the light spot is at 0'', off the center of the groove (or protrusion), the polarization of the reflected light due to the disk tilt is replaced by the polarization of the diffracted light. Because the compensation error signal becomes 0.

In this case, the position deviates from the maximum value of the reproduced information signal.

FIG. 16C is a diagram showing the distribution of the number of occurrences of tracking error, and the occurrence of tracking error is maximum at the origin 0' of the error signal.

By the multiplication performed in the multiplication circuit 62 in the circuit arrangement shown in FIG. 15, (the value shown in (a) in FIG. 16) and (
A signal having an instantaneous value represented by the product of (the value shown in (b) in FIG. 16) is obtained as the output signal of the multiplier circuit 62. When integrated through the low-pass filter 63, the error signal becomes distributed as shown in FIG.
a)) X ((b) in Figure 16) X (((b) in Figure 16)
C)), that is, as shown in FIG. 16(d).

When the tracking error X is O, the total product is 0,
Furthermore, when the tracking error X is to the left of θ', the 16th
As shown in (a) of the figure, the size of the reproduction information signal is large, so in the example being explained now, the first
As shown in Figure 6 (d), the distribution on the left side of 0'' is large, so this is a low-pass filter 0 with a large (long) time constant.
When integrated by , the 161i-th (d) waveform is smoothed and a negative voltage is generated.

In this way, in the circuit arrangement shown in fE15, the output signal of the multiplier 62 becomes asymmetrical depending on the position of the point θ' at which the tracking error signal is set to 0, as shown in FIG. 16(d). , Due to the integration effect of the low-pass filter 63, a DC signal indicating the inclination information of the disk 6 is obtained as the output signal from the low-pass filter 63.
The output signal of the multiplication circuit 62 described above is passed through a low-pass filter 63.
By supplying the feed motor 42 through the feed motor 42, the optical axis of the condensing lens 5 in the optical system P is always maintained perpendicular to the signal surface of the disk 6, as described with reference to FIG. The optical system P is automatically controlled to a state in which the information signal is read from the disk 6.

The explanation of the embodiments that have been made so far involves detecting inclination information regarding the radial inclination, which tends to appear largely among the inclinations of the disk, and using that inclination information to determine the optical axis of the condenser lens 5 in the optical system. The system was designed to automatically control the direction perpendicular to the signal surface of the disc, but next, the tilt information in the extending direction of the recording trace on the disc is detected, and the tilt information is used to control the optical system. A purchasing example in which the optical axis of the condensing lens 5 is automatically controlled to be perpendicular to the signal surface of the disk will be described with reference to FIG.

In FIG. 6, four light-receiving elements 27a to 27d in the photodetector 27 are divided into two by a dividing line a2, resulting in a set of light-receiving elements 27a and 27b and a set of light-receiving elements 27c and 27d. The outputs of the two sets of light receiving elements (No. 1 are added by adders 47 and 48, respectively, and the output signal (I!a+Eb) from the adder 47 is supplied to the subtracter 64 as a subtraction signal, and , adder 4
8, the output signal (Ec+Ed) is supplied to the subtractor 64 as a minuend signal.

In the subtracter 64 described above, (Ec+Ed) −(Ea+
Eb) is calculated and the output signal is supplied to the low-pass filter 65. The output from the low-pass filter 65 (It number is No. 43 indicating the inclination information in the extending direction of the recording trace on the disk 6, and the signal indicating the inclination information in the extending direction of the recording trace on the disk 6 is variable. It is supplied as a control signal to the delay circuit 66. In the variable delay circuit 66, the phase of the color subcarrier given thereto from the reproduced signal processing circuit 51 is the output signal of the low-pass filter 65, that is, the disc A signal that is varied in accordance with the signal indicating the inclination information in the extending direction of the recording trace No. 6 is applied as a comparison signal to the phase comparator 68.A reference signal is applied to the phase comparator 68 from the reference oscillator G7. Therefore, the phase comparator 68 outputs an error signal corresponding to the tilt information in the extending direction of the recording trace on the disk 6 and supplies it to the arithmetic circuit 50, and the error signal is passed to the low-pass filter 69. It is supplied to the drive motor Md via.

In an optical information signal reproducing device, its jitter correction operation is performed so that the relative velocity between the disk and the light spot is constant so that there is no time axis variation in the reproduced information signal due to eccentricity or distortion of the recording trace. This is done by driving the optical system P in the direction in which the recording trace extends. and,
Although the drive motor Md described above is driven so that the period of the synchronization signal in the reproduction signal is constant, the DC position of the light spot in the direction of extension of the recording trace on the disk remains unchanged. .

Therefore, the rotational phase of the drive motor Md is changed by supplying the error signal corresponding to the inclination information in the extension direction of the recording trace of the disk 6 outputted from the phase comparator G8 to the drive motor Md. The optical system is automatically controlled to displace the position of the light spot in the extending direction of the recording trace on the disc 6 so that the optical axis of the condensing lens 5 in the optical system becomes perpendicular to the signal surface of the disc.

The optical system detects tilt information in the extending direction of the recording trace on the disc, and uses the tilt information to automatically control the optical axis of the condenser lens 5 in the optical system to be perpendicular to the signal surface of the disc. The above-mentioned optical information signal reproducing apparatus is configured to reproduce the optical information signal as described above for a disc used for reproducing information signals, on which recording traces are formed by an array of pits on a flat surface. Not only the playback device but also the disk used to play back the information signal has a continuous groove of a certain depth (or a continuous protrusion of a certain height) in the direction of the recording trace. A disk (14th
The same means as described above can be applied to an optical information signal reproducing device that reproduces information signals from a disk (partial cross section of a disk is shown in the figure). It goes without saying that an automatic control system for the optical system can be constructed to displace the position of the light spot in the extending direction of the recording trace on the disc 6 so that the optical axis of the lens 5 is perpendicular to the signal surface of the disc.

(Effects of the Invention) The optical information signal reproducing device of the present invention has a recording medium having a signal surface on which a recording trace is formed by optically recording an information signal. Projects a spot of light for signal reading.

An optical information signal reproducing device configured to receive reflected light whose intensity is modulated by an information signal in a recording trace with a photodetector and obtain a reproduced information signal from the photodetector, the device comprising the light source as described above. and an optical system in which a condenser lens, a photodetector, etc. that form a light spot on the signal surface of a recording medium are fixed in a predetermined related arrangement in one housing, and the optical system is arranged in the direction of its optical axis. a drive device for an optical system that swings an optical axis so that the optical axis is moved in a direction perpendicular to the optical axis, and a spot of light is moved in a direction perpendicular to the optical axis; It is equipped with a system drive device and a transport device that moves the system in the transverse direction of the recording trace of the recording medium, and an automatic focusing system that automatically forms a minute spot of light on the signal surface of the recording medium at all times. It is equipped with a control circuit and an automatic tracking control circuit that causes the spot of light to constantly track the recording trace,
Further, based on the difference in intensity of reflected light received by each light receiving surface separated by the dividing line in the photodetector having a light receiving surface divided into two on the optical axis,
means for obtaining inclination information between the signal surface of the recording medium and the optical axis in a direction orthogonal to the recording trace; and means for obtaining inclination information between the signal surface of the recording medium and the optical axis in the direction orthogonal to the recording trace; An optical information signal reproducing device comprising means for driving and controlling the above-mentioned transfer device so as to make the optical axis of the above-mentioned optical system perpendicular to the signal surface of the recording medium based on an output signal, and a light source and a recording medium. An optical system includes a condensing lens that forms a light spot on a signal surface, a photodetector, etc., fixed in a predetermined related arrangement in one housing, and the above-mentioned optical system is moved directly in the direction of its optical axis. a driving device for an optical system that swings an optical axis so that the optical system can be moved in a state in which the light spot is moved in a direction perpendicular to the optical axis; an automatic focus control circuit that automatically forms a minute spot of light on the signal surface of the recording medium at all times; and an automatic tracking control circuit that causes the spot of light to always track the recording trace, and also has a light receiving surface divided into at least two parts on the optical axis by a first dividing line. Based on the difference in the intensity of the reflected light received by each light receiving surface separated by the first fraction 1sIIA in the photodetector, the signal surface of the recording medium and the optical axis in the direction orthogonal to the recording trace are determined. The optical axis of the optical system is recorded based on output signals from the means for obtaining inclination information of the recording medium and the inclination information of the optical axis and the signal surface of the recording medium in the direction orthogonal to the recording trace. A means for driving and controlling the transfer device so as to be perpendicular to the signal plane of the medium, and an output from the light receiving surface of the photodetector separated by a second dividing line perpendicular to the first dividing line. means for obtaining inclination information between the signal surface of the recording medium and the optical axis in the extending direction of the recording trace according to the difference signal;
The optical axis of the optical system is made perpendicular to the signal surface of the recording medium based on the output signal from the means for obtaining inclination information between the signal surface of the recording medium and the optical axis in the extending direction of the recording trace. Since the optical information signal reproducing apparatus of the present invention comprises means for driving and controlling a relative movement device between a light spot and a recording medium, the optical information signal reproducing apparatus of the present invention eliminates the tracking error from the disk. Signals and jitter correction signals are obtained by simply extracting tilt information consisting of low-frequency components that can be separated in frequency, and then aligning the optical axis of the condensing lens of the optical system with the signal surface of the disk based on the extracted tilt information. Since the optical system is automatically controlled so that the optical system is vertical, coma aberration does not occur, and therefore, there is no deterioration of the frequency characteristics of the reproduced signal or crosstalk from adjacent recording traces. For example, an optical information signal reproducing device with excellent high-frequency characteristics can be easily provided, and the problems of the prior art described above can be satisfactorily solved. Furthermore, in the optical information signal reproducing apparatus of the present invention, the optical system is automatically adjusted so that the optical axis of the condensing lens of the optical system is perpendicular to the signal surface of the disk, as described above. Strict precision is not required for vertical adjustment of the reproduction element,
The production of optical information signal reproducing devices becomes easier, and
Since no equipment dedicated to optical axis adjustment is used as the optical axis automatic adjustment device, there is an advantage that it can be manufactured at low cost.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional example of a tracking error detection method for an optical information signal reproducing device, Figures 2 and 5 are side views of the vicinity of the recording medium to explain the problems, and Figure 3 is an existing proposal. - optical information (a block diagram of the tracking error detection method of the f1 reproduction device, FIGS. 4 and 16 are curve diagrams for explaining the operation, and FIG. 6 is a block diagram of the optical information signal reproduction device of the present invention) Fig. 7 is a tilted diagram showing an example of the configuration of the optical system, Fig. 8 is a block diagram of an example of the configuration of the drive section of the optical system, Fig. 9 is a circuit diagram of the peak value holding circuit, and Figs. 10 and 14. 11 and 13 are explanatory waveform diagrams, and FIGS. 12 and 15 are block diagrams of parts of other embodiments. 1... Light source; 5... Condensing lens, 6... Recording medium, 7° 7a, 7b = Light receiving element, 8, 37, 38, 4
5, 46, 47, 48° 49.50a, 50b, 50e
, 50d...-Adder, 9, 19, 21, 28, 39
゜50a, 50f, 50B, 54.61...Subtractor, 0
．． 10. LL...output terminal, L2,1:l...comparator, 14.61...envelope detector, 15,1 detector,
27a, 27b, 27c, 27d-light receiving element, 29--housing, 30.31, 32.33--coil, 34--yoke, 35--permanent magnet, 36--
・Flexible suspension, 40... Carriage, 4
1a, 42b=guide rod, 42...feed motor, 43...pulley, 44...wire, 50...arithmetic circuit, 51...reproduction signal processing circuit, 62...multiplier ( Multiplier circuit) 1Md...drive motor, 66...
Delay circuit, 67... Reference signal oscillator, 68... Phase comparator, TT... Turntable, P... Optical system, PE... Reproduction element,

Claims (1)

[Claims] 1. Projecting a light spot for signal reading from a light source onto the signal surface of a recording medium that has a signal surface on which a record trace formed by optically recording an information signal is formed. and an optical information signal reproducing device configured to receive reflected light intensity-modulated by an information signal in a recording trace with a photodetector and obtain a reproduced information signal from the photodetector, the optical information signal reproducing device comprising: An optical system includes a light source, a condensing lens for forming a light spot on the signal surface of a recording medium, a photodetector, etc. fixed in a predetermined related arrangement in one housing, and the optical system a driving device for an optical system that swings the optical axis so that the optical axis can be moved directly in the axial direction and the light spot can be moved in a direction perpendicular to the optical axis;
It is equipped with the above-mentioned optical system and a drive device for the above-mentioned optical system, and a transport device that moves the above-mentioned optical system in the transverse direction of the recording trace of the recording medium, and also automatically and constantly places a minute spot of light on the signal surface of the recording medium. and an automatic tracking control circuit that causes the light spot to always follow the recording trace, and a light receiving surface that is divided into at least two parts on the optical axis. Based on the difference in intensity of reflected light received on each light receiving surface separated by the dividing line in the photodetector having a The optical axis of the optical system is determined based on the output signals from the means for obtaining information on the inclination with the optical axis and the means for obtaining the information on the inclination between the signal surface of the recording medium and the optical axis in the direction orthogonal to the recording trace. An optical information signal reproducing device 2 comprising means for driving and controlling the above-mentioned transfer device so that the information signal is perpendicular to the signal surface of the recording medium, and a recording trace where the information signal is optically recorded is composed of an array of pits. In addition, a photodetector is used in which the dividing line is parallel to the recording trace, and the light spot is located on a flat area between the pits that make up the recording trace. The optical transfer device according to claim 1, wherein the transfer device is driven and controlled in a direction in which a difference in output from both light-receiving surfaces separated by the dividing line in the photodetector is reduced. In the information signal reproducing device 3, the recording trace formed by optically recording the information signal is configured as a continuous groove-like portion or a continuous protrusion-like portion, and the dividing line is formed on the recording trace. The parallel photodetectors are used, and the peak value of the reproduced information signal is maximized when the output difference from the two light-receiving surfaces of the photodetector separated by the dividing line becomes zero. The optical information signal reproducing device 4 according to claim 1, wherein the transfer device is drive-controlled, and the optical information signal reproducing device 4 has a signal surface on which a recording trace is formed by optically recording the information signal. A light spot for signal reading from a light source is projected onto the signal surface of the recording medium, and a photodetector receives the reflected light whose intensity is modulated by the information signal in the recording trace. An optical information signal reproducing device configured to obtain a reproduced information signal, wherein the light source, a condensing lens for forming a light spot on a signal surface of a recording medium, a photodetector, etc. are housed in one housing. The optical system is fixed in a predetermined related arrangement, and the optical system can be moved directly in the direction of its optical axis, and the spot of light can be moved in a direction perpendicular to the optical axis. An optical system drive device that swings the optical axis as shown in FIG.
It is equipped with the above-mentioned optical system and a drive device for the above-mentioned optical system, and a transport device that moves the above-mentioned optical system in the transverse direction of the recording trace of the recording medium, and also automatically and constantly places a minute spot of light on the signal surface of the recording medium. and an automatic tracking control circuit that causes the spot of light to always track the recording trace, and also includes an automatic focusing control circuit that causes the spot of light to always follow the recording trace, and also includes an automatic focusing control circuit that causes the spot of light to always track the recording trace, and also includes an automatic focusing control circuit that causes the spot of light to always follow the recording trace, and also includes an automatic focusing control circuit that causes the spot of light to always follow the recording trace, and also includes an automatic focusing control circuit that causes the spot of light to always follow the recording trace. Based on the difference in intensity of reflected light received by each light receiving surface separated by the first dividing line in the photodetector having a light receiving surface divided into two, means for obtaining inclination information between the signal surface of the recording medium and the optical axis in the direction of
The optical axis of the optical system is made perpendicular to the signal surface of the recording medium based on the output signal from the means for obtaining inclination information between the signal surface of the recording medium and the optical axis in the direction orthogonal to the recording trace. means for driving and controlling the transfer device described above; A means for obtaining inclination information between the signal surface of the recording medium and the optical axis in the extending direction of the recording trace, and an output signal from the means for obtaining inclination information between the signal surface of the recording medium and the optical axis in the extending direction of the recording trace. Based on The information signal reproducing device 5 is an optical detection device in which the recording trace formed by optically recording the information signal is composed of an array of pits, and the first dividing line is parallel to the recording trace. Further, when the light spot is on the flat part between the pits constituting the recording trace, from both light-receiving surfaces separated by the first dividing line in the light detection ring. The optical information signal reproducing device 6 according to claim 4, wherein the transfer device is drive-controlled in a direction in which the output difference between , a photodetector configured as a continuous groove-like portion or a continuous protrusion-like portion, and in which the first dividing line is parallel to the recording trace; A patent claim in which the transfer device is drive-controlled so that the peak value of the reproduced information signal becomes maximum when the output difference from both light receiving surfaces separated by the first dividing line becomes zero. The optical information signal reproducing device according to item 4 of the scope of