JPS62232732A - Optical information signal reproducing device - Google Patents

Abstract

PURPOSE:To obtain a reproducing signal without having a crosstalk from an adjacent recording trace and with a high modulation factor, and to miniaturize a control circuit, by performing an automatic control providing an inclination control system, a tracking control system, and a transfer motor control system. CONSTITUTION:The inclination control system which performs the inclination control of the lens axis of a condenser lens is constituted of a closed loop through the use of an optical detector 15, an inclination detection circuit, a low-pass filter LPF25, a tilt coil 26, a subtraction point SUB1, a subtraction point SUB2, a subtraction point SUB3, and a detector 15. Also, the tracking control system is constituted of the closed loop through the use of the detector 15, a tracking error detection circuit, a tracking coil 28, the subtraction point SUB3, and the detector 15. And the automatic control is performed so that the main plane of the condenser lens is put in parallel with the signal plane of the condenser lens by the control operation by means of those inclination control system, tracking control system, and transfer motor control system. In such a way, the reproducing signal without having the crosstalk from the adjacent recording trace and with the high modulation factor can be obtained, and also, a movable part is made small and lightened, and the control circuit can be miniaturized.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an optical information signal reproducing device.

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

Incidentally, 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.

1. The tracking error detection method used when performing racking 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. 19 is a schematic diagram showing the basic configuration of an optical information signal reproducing device to which the push-pull tracking error detection method described above is applied, in which 1 is a light source (for example, a laser light source); 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 a collimating lens 2, transmitted through a polarizing prism 3, then made into circularly polarized light by a λ/4 wavelength plate 4, and then condensed by a condensing lens 5 to be recorded. A light spot with a minute diameter is generated on the signal surface of the medium 6 (disc 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 becomes circularly polarized light in the opposite direction. The light passes through a condenser lens 5 and is applied to a λ/4 wavelength plate 4 .

In the λ/4 wavelength plate 4 described above, the reflected light is made into linearly polarized light having a plane of polarization perpendicular to the incident light, so the reflected light is reflected by the reflective surface 3a of the polarizing prism 3 and provided to the photodetector 7. It will be done.

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 the adder 8 and the subtractor f@9, and the reproduced signal is sent from the adder 8 to the output terminal 10.
Also, the tracking error signal from the subtracter 9 is output to the output terminal 1.
1. Q in FIG. 19 is a dividing line in the photodetector 7.

The optical information signal reproducing device shown in FIG.
A reproduced signal output is obtained by the sum of the output signals from a and 7b, and the two light receiving elements 7a in the photodetector 7
, 7b, the tracking error signal is obtained by the difference between the output signals from the optical information signal reproducing apparatus shown in FIG. An error signal is obtained only when the signal surface of the disk 6 is perpendicular to the optical axis of the projected light, as shown in FIG. 20(a), and the signal surface of the disk 6 is For example, in Figure 20 (
If the recording trace is inclined in the width direction as shown in b), the optical axis of the reflected light from the signal surface of the disk 6 is inclined, so that the optical axis of the reflected light is aligned with the 2nd direction on the photodetector 7. As a result, the difference signal between the output signals of the two light receiving elements 7d and 7b does not indicate correct tracking error information. Even if the signal surface of the disk 6 is perpendicular to the optical axis of the projected light as in a),
For example, the condensing lens 5 moves in the width direction of the recorded trace (Q
) has the serious drawback that a false tracking signal is generated even if there is a deviation of 2.

In order to solve the above-mentioned drawbacks of the push-pull type tracking error detection method, the applicant company has previously developed a method based on the arrangement of pits corresponding to the information signal, as disclosed in Japanese Patent Application Laid-Open No. 58-125242. A focused spot of light is projected onto the signal surface of a recording medium that has a signal surface on which a recording trace is formed, and its intensity is modulated by the pit. 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 the information is detected. In an optical information signal reproducing device that is capable of optically reproducing a signal, the modulated signal output from the photodetector is reproduced by a signal component that does not include tracking error information in the modulated signal output from the photodetector. Provided is a tracking error detection method for an optical signal information reproducing device in which a tracking error signal is obtained by a difference signal between the output signals from each of the two divided parts of the photodetector, and a tracking error detection method is provided, and a tracking error detection method is provided. Signal processing that removes false signals that occur in tracking error signals when the signal plane of the medium is tilted with respect to the optical axis of the laser beam projected onto the recording medium for reading information signals. By applying this to the tracking error signal, the conventional problems are satisfactorily solved.
In the existing proposal explained with reference to Fig. 20,
Even if the false (fi) signal in the tracking error signal is removed by the tilt information of the recording medium detected from the recording medium, the optical axis of the laser beam projected onto the recording medium for reading the information signal is Since the recording medium remains tilted relative to the signal surface of the recording medium, the light spot generated on the signal surface of the recording medium has comatic aberration, which causes the frequency characteristics of the reproduced signal to change. Undesirable phenomena occur such as deterioration of the record and crosstalk from adjacent records.

As mentioned above, when the optical axis of the laser beam projected onto the recording medium for reading the information signal is inclined with respect to the signal plane of the recording medium, Comatic aberration appears in the resulting light spot because the laser beam is projected onto the signal surface of the recording medium through the transparent medium of the recording medium in an inclined state.

Figure 2 shows the intensity distribution of the light spot when a laser beam with a wavelength of 78 on is focused on the signal surface of a so-called compact disc by a condensing lens with an NA of 0.45. FIG. 2(a) shows the light intensity distribution when the laser light is projected perpendicularly to the signal surface of the compact disc (light incident angle 0=00). FIG. 2(a) shows the intensity distribution of light when the laser beam is projected onto the signal surface of the compact disc at an incident angle of 1a (light incident angle θ=1°).

In the light intensity distribution curve shown in Figure 2(b), large side lobes occur, so when a laser beam tilted in this way is projected onto the signal surface of a recording medium, Crosstalk or digital signal jitter occurs in the reproduced signal.

In an LV player that plays video signals, the N of the condensing lens
Since -A is 0.5, the coma aberration due to the inclination of the laser beam becomes larger than in the case of the above-mentioned compact disc, and the deterioration of the MTF in the high range becomes significant. Also,
In optical discs or magneto-optical discs on which information signals are optically recorded or reproduced, the NA of the condensing lens is 0.
55 to 0.6, it is clear that the influence of the inclination of the laser beam in such a case is even greater.

Therefore, the applicant company has developed an optical information signal reproducing device capable of solving the above-mentioned problems using Japanese Patent Application Laid-Open No. 61-48138.
As disclosed in the publication, a light spot for reading signals from a light source is placed on the signal surface of a recording medium that has a signal surface on which a record trace is formed by optically recording an information signal. An optical information signal reproducing device that projects a reflected light whose intensity is modulated by an information signal in a recording trace and receives the reflected light with a photodetector to obtain a reproduced information signal from the photodetector. , an optical system in which the light source, a condensing lens for forming a light spot on the signal surface of the recording medium, a photodetector, etc. are fixed in a predetermined related arrangement in one housing; a driving device for an optical system that swings the optical axis so that the optical axis is moved directly in the direction of the optical axis of the optical system, and a spot of light is moved in a direction perpendicular to the optical axis; and a driving device for the optical system as described above, and a transporting device for transporting the optical system in the transverse direction of the recording trace of the recording medium, and a system 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 light spot to always track the recording trace, and also includes at least two
Recording in a direction perpendicular to the recording trace based on the difference in intensity of reflected light received by each light receiving surface separated by the dividing line in the photodetector having divided light receiving surfaces. means for obtaining inclination information between the signal plane of the medium and the optical axis;
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. proposed an optical information signal reproducing device comprising means for driving and controlling the above-mentioned transfer device.

(Problems to be Solved by the Invention) According to the above-mentioned new proposed device, the above-mentioned problems have been satisfactorily solved; however, in the above-mentioned new proposed device, (1) Since the configuration is such that the entire optical system is driven, power consumption is large. (2) The influence of vibration during driving of the optical system is large; (3) To make the optical system smaller and lighter.

The format of the optical system is limited to a simple format.

There are drawbacks such as the following, and especially regarding the point (3), since the use of optical discs and magneto-optical discs on which recording and reproduction are performed is prohibited, improvements have been sought.

(Means for Solving the Problems) The present invention projects a light spot for signal reading from a light source onto a signal surface of a recording medium having a signal surface on which a recording trace of an information signal is formed. Then, a photodetector receives the reflected light whose intensity is modulated by the information signal in the recording trace formed on the signal surface of the recording medium,
An optical information signal reproducing device configured to obtain a reproduced signal from the above-mentioned photodetector, wherein a condenser lens for forming a light spot on the signal surface of the above-mentioned recording medium has a direction of its lens axis. and the four linear movements in two directions perpendicular to the lens axis, and the four linear movements described above centering on the position of the focal point of the condensing lens on the light source side. A lens driving device configured to perform four operations, the above-mentioned light source, and a photodetector having a light-receiving element in each area divided into at least two by a line intersecting the optical axis are provided in a predetermined manner. an optical system fixed to a housing in a related arrangement manner, and a transfer device for transporting the housing of the optical system in a direction that traverses the recording trace formed on the signal surface of the recording medium; an automatic focusing control circuit that always causes a minute spot of light to be formed on the signal surface of the recording medium; an automatic tracking control circuit that always causes the spot of light to follow a recording trace; Based on the difference in the intensity of the reflected light received by the light-receiving elements provided in the two areas of the photodetector that receives the reflected light from the signal surface of the recording medium, the detection signal is detected perpendicular to the recording trace on the signal surface of the recording medium. Means for obtaining information on the inclination of the signal surface of a recording medium and the optical axis in a direction in which the signal surface of the recording medium and the optical axis are tilted in a direction orthogonal to the recording trace formed on the signal surface of the recording medium. Based on the output signal from the information obtaining means, drive control of a driving device that swings the lens axis of the condensing lens so that the lens axis of the condensing lens is perpendicular to the signal surface of the recording medium. and a spot of light from a light source for reading a signal on a signal surface of a recording medium having a signal surface on which a recording trace of an information signal is formed. is projected, and the reflected light whose intensity is modulated by the information signal in the recording trace formed on the signal surface of the recording medium is received by a photodetector to obtain a reproduced signal from the photodetector. In this optical information signal reproducing device, the condenser lens for forming a light spot on the signal surface of the recording medium has two directions: the direction of the lens axis and the direction perpendicular to the lens axis. 4 movements of the first oscillation in a plane including the above-mentioned two linear movements centered on the position of the focal point on the light source side of the condensing lens, and the above-mentioned two linear movements. The second in the plane that includes the lens axis among the planes perpendicular to the plane.
the above-mentioned light source, and the above-mentioned light detection device in which a light-receiving element is provided in each area divided into two by a line intersecting the optical axis; an optical system which is fixed to a housing in a predetermined related arrangement, and the housing of the optical system is moved in a direction that traverses the recording trace formed on the signal surface of the recording medium. A transport device, an automatic focus control circuit that always causes a minute spot of light to be formed on the signal surface of the recording medium, and an automatic tracking control circuit that always causes the spot of light to follow the recording trace. and a photodetector that receives the reflected light from the signal surface of the recording medium, provided in two areas separated by a first dividing line parallel to the recording trace formed on the signal surface of the recording medium. 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 formed on the signal surface of the recording medium based on the intensity difference of the reflected light received by the light receiving element; The lens axis of the condensing lens is determined based on the output signal from the means for obtaining the inclination information between the signal surface of the recording medium and the optical axis in the direction orthogonal to the recording trace formed on the signal surface of the recording medium. means for driving and controlling the drive device so as to be perpendicular to the signal surface of the recording medium by the first four oscillations; and a photodetector for receiving the reflected light from the signal surface of the recording medium. The first parallel to the recording trace formed on the signal surface
2 separated by a second dividing line perpendicular to the dividing line of
Information on the inclination of the signal surface of the recording medium and the optical axis in the direction in which the recording marks formed on the signal surface of the recording medium extend, based on the difference in the intensity of the reflected light received by the light receiving elements provided in the two areas. and the means for obtaining inclination information between the signal surface of the recording medium and the optical axis in the direction in which the recording trace formed on the signal surface of the recording medium extends. To provide an optical information signal reproducing device comprising means for driving and controlling a driving device so as to make the lens axis of a condensing lens perpendicular to the signal surface of a recording medium by the above-mentioned second four swing movements. It is.

(Example) Hereinafter, specific contents of the optical information signal reproducing device of the present invention will be explained in detail with reference to the accompanying drawings. FIG. 1 is a perspective view of an embodiment of the optical information signal reproducing device of the present invention. In FIG. 1, 11 is a light source (for example, a laser beam W), 12 is a collimator lens, 13 is a beam splitter, 14 is a condensing lens, 15 is a photodetector, 16 is a lens driving device, and 17 is an optical system housing, which includes the light source 11. Collimator lens 12. Beam splitter 13. The condenser lens 14, the photodetector 5, the lens driving device 16, and the like are each fixed to the optical system casing 17 in a predetermined related arrangement, thereby constituting the optical system LA as a whole.

Further, 18 is a motor that drives and rotates the disc 6 at a predetermined rotation speed, 19 is a transport motor that transports the optical system LA in the radial direction of the recording medium (disk 6), and 20 is a motor that drives and rotates the optical system LA at a predetermined rotation speed. The fixed rack 21 is a binion that meshes with the rack 20 described above, and this binion 2
1 is fixed to the rotating shaft of the above-mentioned transfer motor 19. The portion composed of the above-mentioned transport motor 19, rack and pinion 21, etc. transports the above-mentioned optical system housing 17 in a direction that traverses the recording trace formed on the signal surface of the recording medium 6. Transfer device that lets you do it! Functions as FA.

The light source 11 described above emits linearly polarized light from a minute light emitting section. The light emitted from the light source 11 is collimated by the collimating lens 12, reflected by the beam splitter 13, and incident on the condensing lens 14. 6)
A light spot with a minute diameter is generated on the signal surface of the

Since the signal surface of the disk 6 has a high reflectance, the light collected by the condenser lens 14 as described above is reflected by the signal surface of the disk 6 and passes through the condenser lens 14 again. The light then passes through a beam splitter 13 and is applied to a photodetector 15.

The photodetector 15 shown in FIG. The photodetector 15 has two light receiving elements 15a and 15b divided by
, 15b are output from the signal processing circuit in the form of various signals such as a reproduction signal, a tilt control signal, a tracking control signal, and a focus control signal through predetermined signal processing in the signal processing circuit.

Now, 1. The optical information signal reproducing device of the present invention includes a light source 11,
Also, a photodetector 15, etc., each having a light-receiving element in an area divided into at least two parts by a line intersecting the optical axis, is fixed to the housing 17 together with other optical members in a predetermined related arrangement. The optical system LA, the transport device FA that transports the optical system casing 17 in the direction Y that traverses the recording trace formed on the signal surface of the OIs body 6, and It is equipped with an automatic focusing control circuit that always forms a minute spot of light on the signal surface, and an automatic tracking control circuit that always makes the spot of light track the recording trace. The condenser lens 14 that forms a light spot on the signal plane of No. 6 is linearly operated in two directions: the direction Z of the lens axis of the condenser lens and the direction Y perpendicular to the lens axis. and oscillation 4 in the Y-Z plane including two directions in which the four linear movements described above are performed centering on the position of the focal point Fb (see FIG. 6) on the light source side of the condenser lens 14.
In addition, the photo detector 15 receives the reflected light from the signal surface of the recording medium 6, and the light receiving elements are provided in the two regions described above. means for obtaining inclination information between the signal surface of the recording medium 6 and the optical axis in the direction Y orthogonal to the recording trace on the signal surface of the recording medium 6 based on the intensity difference of the reflected light received by the recording medium 6; The lens axis of the condensing lens 14 is determined based on the output signal from the means for obtaining the inclination information between the signal surface of the recording medium 6 and the optical axis in the direction Y perpendicular to the recording trace formed on the signal surface of the recording medium 6. The above-mentioned condensing lens 14 is arranged perpendicularly to the signal plane of the recording medium 6.
an optical information signal reproducing device comprising: means for driving and controlling a driving device for swinging a lens axis; and a light source 11;
Also, an optical device in which a photodetector 15, etc., each having a light-receiving element provided in at least two areas divided by a line intersecting the optical axis, is fixed to the housing 17 together with other optical members in a predetermined related arrangement. system LA, and a transport device glFA that transports the casing 17 of the optical system in the direction Y that traverses the recording trace formed on the signal surface of the recording medium 6.

It is equipped with an automatic focus control circuit that always forms a minute spot of light on the signal surface of the recording medium 6, and an automatic tracking control circuit that always makes the spot of light track the recording trace. At the same time, with respect to the condensing lens 14 that forms a light spot on the signal surface of the disk 6, it is directed in two directions: the direction Z of the lens axis of the condensing lens, and the direction Y perpendicular to the lens axis. linear motion 4
and the focus Fb (sixth point) on the light source side in the condenser lens 14.
the first four oscillating movements in the Y-Z plane including two directions in which the four linear movements described above are performed centering on the position of (see figure);
x perpendicular to the Y-Z plane including the two translational directions mentioned above
-Second rocking 4 in a plane that includes the lens axis within the Z plane
In addition, a photodetector 15 that receives the reflected light from the signal surface of the recording medium 6 detects the recording formed on the signal surface of the recording medium. The direction perpendicular to the recording trace formed on the signal surface of the recording medium 6 is based on the difference in intensity of reflected light received by light receiving elements provided in two areas separated by a first dividing line parallel to the trace. means for obtaining inclination information between the signal surface of the recording medium 6 and the optical axis, and a means for obtaining inclination information between the signal surface of the recording medium 6 and the optical axis in a direction orthogonal to the recording trace formed on the signal surface of the recording medium 6. Based on the output signal from the means for obtaining tilt information, the lens axis of the condensing lens 14 is moved by the first four movements to move the recording medium 6.
means for driving and controlling the drive device so as to be perpendicular to the signal surface of the recording medium 6, and a photodetector 15 that receives the reflected light from the signal surface of the recording medium 6 at an angle of 6°. Based on the difference in intensity of the reflected light received by the light receiving element 15 provided in the two areas separated by the second dividing line perpendicular to the first dividing line parallel to the recording trace, the signal surface of the recording medium 6 is Means for obtaining inclination information between the signal surface of the recording medium 6 and the optical axis in the direction in which the formed recording trace extends; and the direction in which the recording trace formed on the signal surface of the recording medium 6 extends. Based on the output signal from the means for obtaining inclination information between the signal surface of the recording medium 6 and the optical axis, the lens axis of the condensing lens 4 is moved by the second rocking operation of the recording medium 6. In the optical information signal reproducing apparatus of the present invention, the optical information signal reproducing apparatus comprises means for driving and controlling the drive device so that the signal surface is perpendicular to the signal surface. As a driving device for the condensing lens 14 to form a light spot, the condensing lens 14 performs four linear movements in two directions: the direction Z of its lens axis and the direction Y perpendicular to the lens axis. In addition to the four driving operations to align the condenser lens 14 with the lens axis of the condenser lens 14, information on the inclination between the signal surface of the recording medium 6 and the optical axis obtained based on the output signal of the photodetector IS is used.
The direction of the arrow α shown in FIGS. 1 and 11, or the arrows α and β in FIGS. A condenser lens driving device 1 capable of performing four driving operations for performing four swing operations in the directions shown in
6 is used to perform tilt control on the condenser lens 14, thereby solving the drawbacks of the conventional optical information signal reproducing apparatus described above.

FIG. 4 is a plan view of a part of the signal surface of the disk 6,
In the fourth, Tl and T2 are pits p and p.

It is a record formed by the arrangement of P...
Further, 81 to S4 are light spots for signal reading projected on the signal surface of the disc 6, and in this FIG. An example is shown in which the relative positional relationships of the two are different.

In FIG. 4, light spots S1 and S4 are examples of light spots projected onto land portions of the signal surface, and light spots S2. S3 is an example of a light spot that partially or entirely overlaps the pit P portion.

The spot of light projected onto the signal surface of the disk 6 is the fourth
When the land is located on the signal surface as shown in the figure, Sl and S4, all the reflected light from the light spot generated on the signal surface passes through the condenser lens 14, so the photodetector 1
The output signal from 52.5 becomes maximum, and the spot of light projected onto the signal surface of the disk 6 becomes 52.5 in FIG. S
If it overlaps with the pit P on the signal surface as in 4,
Since the phase of the reflected light from the spora 1- of the light generated on the surface No. 48 is not uniform due to the pit, the reflected light is largely diffracted toward the outside of the aperture of the condenser lens 14. The amount of light that passes through and enters the photodetector 15 decreases, so that the output signal from the photodetector 15 has a reduced signal level.

Therefore, if the light spot moves in the order of S1→S2→S3→S4 with respect to the recording trace T1 in FIG.
A reproduced signal with a signal level corresponding to the presence or absence of the signal can be obtained. If the light spot is tracing the recording trace with the center of the light spot aligned with the center of the recording trace,
That is, when the reflected light generated on the signal surface corresponding to the light spots SL and S2 in FIG. The output signals have the same size as the solid curves shown in Fig. 5 (a) and (b), but the center of the light spot is off the center of the recording trace, and there are no pits. In a state in which a light spot is partially covered by a light spot, that is, when reflected light generated on the signal surface corresponding to the light spot S3 in FIG. The output signals outputted from the two light receiving elements 15a and 15b of 15 have different magnitudes as shown by the solid line curves in FIG. 5(c) and (d).

However, when the incident light is perpendicular to the recording medium 6, even if the light spot is correctly tracing the recording trace with its center aligned with the center of the recording trace, Alternatively, even when tracing a recording trace with the center of the light spot deviating from the center of the recording trace, the light reflected from the signal surface when the light spot is located on the land causes the photodetector 15 to be detected. Two light receivers 15a
.

The signal level of the output signal output from 15b is constant as indicated by A in FIG.

In addition, the output signal from the photodetector 15 when the center of the light spot is tracing the recording trace with the center of the recording trace being deviated from the center of the recording trace is the optical detection signal when the light spot is correctly tracing the recording trace. The reproduced signal has a modulation degree lower than that of the output signal from the device 15.

By the way, when the disk 6 is tilted as shown in FIG.
The amount of movement in this case is expressed by Δ=θ·f where θ is the inclination angle of the disk and f is the focal length of the condenser lens 14.

When the disk 6 is tilted as shown in FIG. 6(a), the peak value of the output signal of the light receiving element 15a of the photodetector 15 becomes larger. The curves indicated by broken lines in FIG. 5 indicate the output signals from the two light receiving elements 15a and 15b in the photodetector 15 in this state.

Therefore, the two light receiving elements 15a in the photodetector 15,
By detecting the difference between the output signals from the disc 15b and tilting the lens axis of the condenser lens 14 so that the difference signal becomes zero, the optical axis of the condenser lens 14 can be made perpendicular to the signal surface of the disk. can do.

When reproducing information signals from the disk 6, focus control is performed on the condenser lens 14 so that the signal surface of the disk 6 always becomes the focal plane of the condenser lens 14. The parallel light incident on the condenser lens 14 is focused by the condenser lens 14, and the reflected light from the light spot generated on the signal surface of the disk 6 located at the focal plane of the condenser lens 14 passes through the condenser lens 14 again. The condition that the light passes through the focal point on the light source side is that the signal surface of the disk 6 and the main surface of the condensing lens 14 are parallel, so that the condensing light passes through the focal point on the light source side as shown in FIG. 6(b). The condenser lens 14 is rotated around the focal point on the light source side of the lens 14, so that the intensity distribution of the five reflected lights becomes equal on the light receiving element of the photodetector. By controlling the axis inclination (tilt control), the main surface of the condensing lens 14 is always parallel to the signal surface of the disk 6, that is, the incident light on the signal surface of the disk 6 is kept parallel to the signal surface of the disk 6. can be controlled vertically.

FIG. 3 is a block diagram showing an example configuration of an optical information signal reproducing device equipped with a tilt control circuit for controlling the tilt of the lens axis of the condensing lens 14 as described above. The output signals from the two light receiving elements 15a in the photodetector 15 are supplied to the peak value detection circuit PDCa, and the output signals from the two light receiving elements 15b in the photodetector 15 are supplied to the peak value detection circuit PDCb. In both peak value detection circuits PDCa and PDCb, the two light receiving elements 15a and 1 in the photodetector 15 described above are
Each peak value in the output signal from 5b is detected and applied to the subtractor 24.

The output signals from the peak value detection circuits PDCa and PDCb described above are proportional to the light intensity distribution on the photodetector of the reflected light generated on the signal surface of the disk when the light spot is on the land on the signal surface of the disk 6. Therefore, the output signal from the subtracter 24 is the tilt information of the disk 6, as described above. The output signal from the subtracter 24 is passed through the low-pass filter 25 to the condensing lens 14.
The light is supplied to a tilt coil 26 provided at the focal plane position on the light source side.

Since the above-described tilt coil 26 is placed in a magnetic field as described below, the output of the subtracter 24 is caused by the electromagnetic force generated based on the magnetic field and the current flowing in the tilt coil 26. The condenser lens 14 is driven to tilt the lens axis of the condenser lens 14 in the direction where the signal becomes zero, and the condenser lens 14 is focused so that the lens axis of the condenser lens 14 is perpendicular to the signal surface of the disk 6. A tilt control operation is performed to tilt the lens axis of the optical lens 14 in the α direction.

The tilt control system for controlling the tilt of the lens axis of the condenser lens 14 as described above is shown in FIG. 9, which corresponds to the functional block diagram of the control system shown in FIG. 3 above. As shown, photodetector 15 → tilt detection circuit → low pass filter 25 → tilt coil 26 → subtraction point 5UBI
→ Subtraction point 5UB2 → Subtraction point 5UB3 → Photodetector 15 → It is constituted by a closed loop as follows. Note that the peak value detection circuits PDCa and PDcb in FIG.
The component consisting of the subtracter 24 and the subtracter 24 corresponds to the tilt detection circuit shown in FIG.

Then, by the operation of the tilt control system described above, the main surface of the condenser lens 14 is brought into a state parallel to the signal surface of the disk 6, and the comatic aberration of the light spot generated on the signal surface of the disk 6 is removed. This means that there is no crosstalk from the recorded history.

The subtracter 27 in FIG. 3 is a tracking error detection circuit using a so-called push-pull method, and when the output signal from the subtracter 27 is supplied to the tracking coil 28 via a compensation circuit (not shown), Since the tracking coil 28 is placed in a magnetic field as described below, the output signal of the subtracter 27 is changed by the electromagnetic force generated based on the magnetic field and the current flowing in the tracking coil 28. The condenser lens 14 is driven in the direction where the light spot becomes zero (the direction Y in which the light spot crosses the recording trace on the signal surface of the disk).
The tracking control system performs a tracking control operation on the object.

The tracking control system described above, as shown in FIG. 9, which corresponds to the functional block diagram of the control system shown in FIG. 3, includes the photodetector 15→tracking error detection circuit→ Tracking coil 28 → Subtraction point 5UB
3→photodetector 15→. Note that the tracking error detection circuit in FIG. 9 corresponds to the subtracter 27 in FIG.

If only the tilt control is performed on the condenser lens 14 as described above with reference to FIG. However, if a tracking control operation is also performed on the condenser lens 14 in addition to the above-mentioned tilt control operation, the position of the light spot will be changed by the above-mentioned tracking control operation. This is because the signal is kept on the record that is being played back.

In reality, no movement of the light spot occurs on the signal surface of the disk.If the cutoff frequency of the control loop of the tilt control system is set to about 1 decad lower than the cutoff frequency of the control loop of the tracking control system, Even when the above-mentioned tilt control operation is performed on the condenser lens 14, the light spot does not move away from the recording trace where the information signal is being reproduced. The low-pass filter 25 shown in FIG. 3 is used to set the cut-off frequency of the control loop of the above-mentioned slope control system to be lower than the cut-off frequency of the control loop of the tracking control system as required. It was established.

When the tracking control system is performing the tracking control operation on the condenser lens 14 as described above, the center of the condenser lens 14 is returned to the optical axis by the control operation by the tracking control system. In some cases, the center of rotation Fb for controlling the inclination of the condenser lens 14 is displaced by δ to the left of the optical axis, as shown in CQ) of Fig. 6. .

As mentioned above, in FIG. 9, the photodetector 15→tracking error detection circuit→tracking coil 28→subtraction point 5UB3
By the tracking control operation by the closed-loop tracking control system shown in the circuit of →photodetector 15→,
A DC component for displacing the center of rotation of the condenser lens 14 by δ is supplied to the tracking coil 28, but the DC component is supplied to the tracking coil 28 using a low-pass filter provided in the closed loop of the tilt control system. It is also supplied to the transport motor 19 via a low-pass filter 29 having a cut-off frequency approximately equal to the cut-off frequency of the filter 25 .

Accordingly, 9 is a photodetector 15 → tracking error detection circuit → low-pass filter 2
9 → Transfer motor 19 → Subtraction point 5UB2 → Subtraction point 5UB
By the automatic control operation of the closed-loop automatic control system shown in the circuit 3→photodetector 15→, the DC component rotates in the direction where the above-mentioned DC component becomes zero, and the optical axis of the incident light to the condenser lens 14 and the disk are rotated. In FIG. 6, the optical axis of the reflected light from the signal plane of FIG.
d). In the state shown in FIG. 6(d), the optical axis of the reflected light from the signal surface of the disk 6 coincides with the boundary II (dividing line) between the two areas on the photodetector 15. The condition is stable.

By the way, in the state shown in FIG. 6(d) described above, the center of the condenser lens 14 is shifted to the right with respect to the optical axis of the incident and reflected light.

The range through which the incident and reflected light passes is narrow as shown by the dotted line S in the figure. Therefore, at the aperture of the condensing lens, the range where the light returns is shown as the hatched area in (8) in Figure 6, but since the range where the light returns is symmetrical with respect to the optical axis, the light can be detected. Two light receiving elements 15 in the device 15
The amounts of incident light given to a and 15b are equal.

As already mentioned with reference to FIG. 6(b), the magnitude of δ=f・θ that occurs on the signal surface of the disk 6 when only the tilt control is performed on the condenser lens 14 can be expressed as follows: When the tilt control operation and the tracking control operation are performed on the condenser lens 14 at the same time, the light spot is moved by the distance δ. The above-mentioned light spot is prevented from moving on the signal surface of the disk 6 by maintaining it on the recorded trace being reproduced as shown in FIG. 6 (Q).

However, in the state shown in FIG. 6(c) described above, the disk 6
Since the optical axis of the reflected light from the signal plane is shifted to the left of the optical axis of the incident light, input to the tilt control system is generated again, and the lens axis of the condenser lens 14 is adjusted by the tilt control system described above. A tilt control operation is performed to further tilt the transfer motor 19, but the control operation for the transfer motor 19 by the transfer motor control system having a cutoff frequency approximately equal to the cutoff frequency of the control loop in the tilt control system is Since the control operation of the tilt control system is performed simultaneously with the control operation of the tilt control system that The transfer motor 19 is rotated by the control system of the transfer motor, so that the state shown in FIG. 6(d) is achieved.

That is, when the disk 6 is tilted as shown in FIG. By the tilt control operation by the tilt control system described above and the control operation by the transfer motor control system, stable operation as shown in (1) in FIG. As mentioned above, the closed loop cutoff frequency of the tilt control system and the closed loop cutoff frequency of the transfer motor control system are both higher than the closed loop cutoff frequency of the tracking control system. Since the surface control system is set to be about 1 decade lower, the control operation by the surface control system described above is started in about 0.1 seconds to 1 second.

By the way, the tilt control of the condensing lens 14 with respect to the lens axis that has been explained so far is related to the case where the disk 6 is tilted in the radial direction. 6 is shown in Figure 15 (
This occurs in correspondence with the case where the deformed shape is curved like a hat as illustrated in a). Since the inclination information obtained based on the radial inclination of the disk 6 in the deformed state as described above does not change rapidly on the time axis, Even if the control operation is started in about 0.1 seconds to 1 second, the above-mentioned tilt control operation is performed in a sufficiently good condition.

When the tracking error detection method is the push-pull method as described above, the signal surface of the disk 6 is
) When the optical axis of the reflected light from the optical surface of the disk 6 moves with an inclination as shown in FIG. Because there is a difference between the output signals from the two photodetectors,
A false tracking error signal appears. And if a false tracking error signal occurs as described above.

In the push-pull tracking error detection method, due to the deviation of the diffracted light caused by the center of the light spot shifting from the center of the pit, the seventh
As shown in the figure, since the center of the light spot is shifted by a small distance E from the center of the bit, the reproduced signal deteriorates even if no coma aberration occurs. This point has already been mentioned in the description of the prior art.

However, if the lens axis of the condensing lens 14 is controlled to tilt as in the present invention, false tracking error signals will not be generated even if the signal surface of the disk is tilted.
In order to eliminate the generation of a false tracking error signal during the time period of about 0.1 seconds to 1 second until the tilt control operation is started as described above, Japanese Patent Application Laid-Open No. 125242/1982, which is disclosed as a prior art, is used. By applying the means disclosed in the publication, for example, multipliers MULa, MULb are provided on the input side of the subtracter 27 in FIG.
Two light receiving elements 15a of the photodetector 15 by MULb,
15b output signal and the two light receiving elements 1 of the photodetector 15
The peak values of the output signals of 5a and 15b may be mutually multiplied. Alternatively, as a tracking error detection method, a tracking error detection method that is essentially not affected by the tilt of the disk, for example, the present applicant A tracking error detection method as disclosed in Japanese Patent Application No. 1517-1988 filed by the company may be adopted.

As is clear from the above description, in the optical information signal reproducing apparatus of the present invention, the disk 6 has a deformed shape that is curved like a hat, as illustrated in FIG. 15(a). Even if the disk 6 is tilted in the radial direction, the condenser lens 6 is
Since the main surface of the condensing lens 14 is automatically controlled to be parallel to the signal plane of the signal plane, coma aberration and tracking offset are eliminated, resulting in high modulation without crosstalk from adjacent recording traces. Thus, a reproduced signal of 100 degrees can be obtained.

In the embodiments described so far, the disk 6 is the 15th disk.
When the disc 6 is tilted in the radial direction, corresponding to the case where the disk 6 has a deformed shape curved like a hat, as illustrated in (a) of the figure, the tilt control system uses the tilt control system. The lens axis of the condenser lens 14 is automatically controlled to be perpendicular to the signal surface of the disk 6, and the main surface of the condenser lens 14 is made parallel to the signal surface of the disk 6. However, in addition to the manner of inclination of the signal surface of the disk 6 as exemplified in FIG. In some cases, the recording trace formed by the signal surface ring No. 6 is also inclined in the extending direction.

The absolute value of the slope occurring in the extending direction of the recording trace in the deformed disk as illustrated in FIG. 15(b) is the same as that in the radial direction of the disk as illustrated in FIG. 15(a). Although it is not as large as the resulting tilt, if comatic aberration occurs due to the tilt in the extending direction of the recording trace, it will significantly reduce the MTF (spatial frequency transmission capability of the lens) of the condenser lens 14, and the condensing PTF of optical lens 14
Since it degrades the phase transfer ability (phase transfer ability), it is not preferable when reproducing high frequency components of video signals or reproducing PCM signals.

Therefore, tangential tilt control is performed so that the lens axis of the condensing lens 14 follows the tilt in the extending direction of the recorded trace as described above.
Tilt control (tangential tilt control) for the condenser lens 14 is performed using a condenser lens driving device 16 that can perform four swing movements in the directions indicated by arrows β in FIG. ), the optical information signal reproducing device can be made to have even higher performance.

The frequency of the information signal to be reproduced on the disc 6 is usually several MHz or higher, which is sufficiently high compared to the several hundred hertz frequency that is considered to be the range of tangential tilt control, so it is not possible to record it on the signal surface of the disc. The change in the distribution of reflected and diffracted light on the time axis caused by the light spot passing through the bit array that is being The distribution of the reflected and diffracted light in the direction in which the recording traces extend is sufficiently averaged on the time axis, and is constant as long as there is no inclination on the disk in the direction in which the recording traces extend. Therefore, as shown in FIG. 16, for example, as shown in FIG. 16, a photodetector 30 configured to be divided into four parts by two orthogonal axes is used to obtain the difference in the light intensity distribution with respect to the Y axis. By doing so, it is possible to obtain information on the inclination in the extending direction of the recording trace on the disc.

In FIG. 16, the photodetector 30 is divided into four regions along the X-axis and the Y-axis, and each of the four regions is provided with light-receiving elements 30a, 30b, 30c, and 30d. The output signal from the light-receiving element 30a in the photodetector 30 described above is supplied as the subtracted signal of the subtractor 32, and the signal output from the light-receiving element 30a is supplied as the subtracted signal of the subtracter 32.
The output signal from the light-receiving element 30b is supplied to the subtractor 31 as a subtracted signal, and the output signal from the light-receiving element 30d is supplied to the subtractor 31 as a subtracted signal. is supplied.

The output signal from the subtracter 31 described above is supplied to the subtracter 33 as a minuend signal, and is also supplied to the adder 3
4 as one of its input signals.

Further, the output signal from the subtracter 32 described above is transmitted to the subtracter 33.
is supplied as a subtraction signal to the subtracter 33, and is also supplied as the other input signal to the adder 34.The output terminal 35 from the subtracter 33 has the following
The disc inclination information obtained as a result of calculating the difference in light distribution with respect to the X-axis described above, that is, the inclination information signal in the radial direction Y of the signal surface of the disc is output, and the signal is also output from the adder 34 described above. The output terminal 36 receives disc tilt information obtained as a result of calculating the difference in light distribution with respect to the Y-axis described above, that is, tilt information in the extending direction X of the recording trace formed on the signal surface of the disc. signal is output.

The output signal from the output terminal 35 described above causes the lens axis of the condensing lens 14 to swing in the direction α shown in FIGS. 1 and 11 about its rotation center Fb. The output signal from the output terminal 36 described above is shown in FIGS. 1 and 11 with the lens axis of the condensing lens 14 centered around its rotation center Fb. It is used to swing in the direction of β.

In FIG. 17, the photodetector 30 used in FIG. 16 is rotated by 45 degrees with respect to the This is an example of a simple circuit arrangement in which one device at a time can be made unusable. Even in the case of the circuit arrangement shown in FIG. 17, the output signal from the output terminal 35 is used to swing the lens axis of the lens in the direction α shown in FIGS. 1 and 11 about its rotation center Fb, and the output signal from the output terminal 36 is is used to swing the lens axis of the condenser lens 14 about its rotation center Fb in the direction β shown in FIGS. 1 and 11. Also the 18th
The figure shows a photodetector 37 divided into four parts, in which the arrangement of the light-receiving elements is different from that used in each of the light-receiving element arrangements shown in FIGS. 16 and 17. Even in the case of the light receiving element arrangement shown in FIG. It is used to swing the condenser lens 14 in the direction of α shown in FIGS. It is used to swing in the direction β shown in FIGS. 1 and 11 with Fb as the center.

Next, with reference to FIG. 3 and FIGS. 10 to 14, etc.,
A configuration example of a lens driving device configured to be able to drive the lens axis of the condensing lens 14 in a plurality of predetermined directions will be described. In FIG. 11, 43 is an upper lid of the lens driving device, and 44 is a lower lid of the lens driving device. Made of body material.

Pins 12a, 12b, and 12c are implanted at the four corners of the lower lid 44 of the lens driving device described above.

12d is for fixing the four arm parts 45a, 45b, 45c, and 45d provided on the suspension 45, and 44e is a protrusion on which the annular permanent magnet 46 is placed and fixed. Furthermore, 44f and 44g are boss portions provided with screw holes, and these boss portions 44f and 44g are provided with screw holes.
Holes 43a, 43 provided in the upper M43 in the screw hole g
By screwing in the screws 47a and 47b inserted into the upper cover 43 and the lower cover M44, the upper cover 43 and the lower cover M44 are fixed together.

The above-mentioned upper cover 43 and lower cover *44 are integrally connected and fixed as described above, and are thus integrated into a case of the lens driving device.

Further, 48 is a terminal board, to which the ends of the conductive wires of various coils constituting the coil assembly MCA to be described later are connected, and one end of the terminal board 48 is connected to the terminal board 48 for driving the lens. The driving power is supplied to the various coils constituting the coil assembly MCA from the portion that protrudes outside the case of the device.

The MCA is a coil assembly, and a condenser lens 14 is fitted and fixed in a center hole 49 of the MCA. The position where the condensing lens 14 described above is fixed to the coil assembly MCA is at the rear focal plane of the condensing lens 14. As described above, the condensing lens 14 is fixed to the coil assembly MCA and the two are integrated to constitute the movable part MA. The above-mentioned movable part M
The movable portion MA and the suspension 45 are integrally assembled by fitting and fixing the outer periphery of the coil assembly MCA in A into the annular portion 45s of the suspension 45 described above.

The suspension 45 is molded using a viscoelastic material such as silicone rubber, and
By fixing the arm portions 45a to 45d of the movable portion MA to the corresponding ones of the bins 44a to 44d of the lower lid 44 while being slightly stretched, the movable portion MA is supported at a predetermined spatial position. It will be done.

The movable part MA supported by the suspension 45 in the above state is moved to Z as shown in FIG.
4 linear motions in the axial direction and the Y@force direction, and 4 rotational motions in the α and β directions using the intersection of the rear focal plane of the condenser lens 14 and the optical axis as a rotational fulcrum. It has four degrees of freedom that allow it to do the following:

Next, a configuration example of the coil assembly MCA described above will be explained. In Fig. 10, 28 is a tracking coil;
Reference numeral 50 denotes a focus coil, each of which is composed of a sheet-shaped coil. In the illustrated example, the tracking coil 28 is a sheet-like coil 28al in which a spiral clockwise coil winding pattern is formed on a synthetic resin sheet using a conductive material.
, 28a2, and sheet coils 28bl and 28b2, each of which has a spiral counterclockwise coil winding pattern made of conductive material on a synthetic resin sheet. What is being said and what is being said. In each of the sheet-like coils described above, a thin insulating coating is applied to the conductor portion except for both ends of the coil winding pattern.

The four sheet-like coils described above are the sheet-like coil 28
al, sheet coil 28bl, sheet coil 28a
2. Sheet coils 28b2 are stacked in the order [1
As shown, the inner peripheral end of the coil winding pattern in the sheet-like coil 28a1 and the inner peripheral end of the coil winding pattern in the sheet-like coil 28bl are connected, and the inner peripheral end of the coil winding pattern in the sheet-like coil 28b1 is connected. The outer peripheral end and the outer peripheral end of the coil winding pattern in the sheet-like coil 28a2 are connected, and the sheet-like coil 2
The inner peripheral end of the coil winding pattern in 8a2 and the inner peripheral end of the coil winding pattern in sheet-like coil 28b2 are connected, and furthermore, the above-described sheet-like coil 2
It is constructed by connecting connections 11A51 and 52 to the outer peripheral end of the coil winding pattern in 8a1 and the outer peripheral end of the coil winding pattern in sheet-like coil 28b2, respectively.

1. For example, assuming that a current flows from the connection wire 52 of the tracking coil 28 to the connection wire 51, in this case, the current flows in each of the sheet coils in the clockwise direction. will flow. By the way, the coil assembly MCA in which this tracking coil 28 is incorporated is attached to the lower cover 4 shown in FIG.
Since the tracking coil 28 is supported by the suspension 45 in the magnetic field generated by the annular permanent magnet 46 fixed to the annular protrusion 44e provided on the annular projection 44e, the tracking coil 28 has a clockwise direction as described above. When a current is applied, it is displaced in the direction shown by the double arrow in FIG. 12(a). In FIG. 12, a single solid arrow indicates the direction of the magnetic field generated by the permanent magnet 46 described above.

That is, as shown in FIG. 11, each half of the annular permanent magnet 46 is magnetized with different magnetic poles, and one end is magnetized with a ferromagnetic material having high magnetic permeability. is fixed to the annular protrusion of the lower lid 44 made of body material,
In addition, since the other end thereof faces the upper cover 43 made of a ferromagnetic material having high magnetic permeability across the space where the coil assembly MCA in the movable part MA is located, the above-mentioned permanent The direction of the magnetic field generated by the magnet 46 is as indicated by the single solid line arrow in FIG.

Since the direction of the double arrow shown in FIG. 12(a) is the direction of the Y-axis shown in FIGS. 1 and 11, it is relative to the tracking coil 28. When a current is supplied, the movable part MA fixed to the coil assembly MCA in which the tracking coil 28 is incorporated moves linearly 4 in a direction that traverses the recording trace formed on the signal surface of the disk 6. The movable part MA can be driven and displaced so that the operation can be performed.

Therefore, when current is caused to flow in the tracking coil 28 from the connection wire 52 of the tracking coil 28 to the connection wire 51, and a current is caused to flow in the clockwise direction through each of the sheet-shaped coils described above. In this case, the movable part MA is driven and displaced in the direction of the double arrow Ft in FIG. Movable part M
A is driven and displaced in the opposite direction to the double arrow Ft in (a) of FIG.
4 is subject to tracking control.

In the illustrated example, the focus coil 50 shown in FIG. 4 with a winding pattern applied
Sheet coil 50al, 50a2.50bl,
50b2.

In each of the sheet-like coils described above, a thin insulating coating is applied to the conductor portion except for both ends of the coil winding pattern.

The sheet-like coils 50al and 50a2 described above have a clockwise spiral coil winding pattern applied to their right half, and a clockwise spiral coil winding pattern applied to their left half. The spiral coil winding pattern is counterclockwise. On the other hand, the sheet-like coils 50bl and 50b2 described above have a counterclockwise spiral coil winding pattern on their right half, and a counterclockwise pattern on their left half. The spiral coil winding pattern shown is clockwise.

The four sheet-like coils described above are the sheet-like coil 50.
al, sheet coil 50bl, sheet coil 50a
2. The sheet-like coils 50b2 are stacked in order, and as shown in the figure, each inner peripheral end of each coil winding pattern in the sheet-like coil 50al and each inner peripheral end of each corresponding coil winding pattern in the sheet-like coil 50bl. Also, each outer peripheral end of each coil winding pattern in the sheet-like coil 50bl is connected to each outer peripheral end of each corresponding coil winding pattern in the sheet-like coil 50a2, and further, the sheet-like coil 50a2 Each inner peripheral end of each coil winding lQ pattern and sheet-like coil 50b2 in
Connect each circumferential end of each corresponding coil winding pattern in the sheet-like coil 50al, and connect each outer circumferential end of each coil winding pattern in the sheet-like coil 50al! 53.
54, and also connect 1 to each outer peripheral end of each coil winding pattern in the sheet-like coil 50b2.
It is configured by connecting @55 and 56.

Now, for example, a current is made to flow from the connection wire 55 to the connection wire 53 in one of the two coils in the focus coil 50, and the two coils in the focus coil 5o Connect the connection wire 54 from the lX56 side to the other coil at
Assuming that the current flows in the direction of will flow, and a clockwise current will flow through the left half of the coil.

By the way, since this focus coil 50 is also placed in the magnetic field as clarified in the explanation about the tracking coil 28, the two coils of the focus coil 50 are placed in the above-mentioned direction as described above. When a current is applied, the focus coil 50 is displaced in the direction shown by the double arrow in FIG. 12(b).

Since the direction of the double arrow shown in FIG. 12(b) is the direction of the Z-axis shown in FIGS. 1 and 11, the direction of the double arrow shown in FIG. When a current is supplied, the movable part M fixed to the coil assembly MCA in which the focus coil 50 is incorporated
A can drive and displace the movable part MA so as to perform four linear movements in the direction perpendicular to the signal surface of the disk 6.

Therefore, for the focus coil 50, for example, in one of the two coils of the focus coil 50, current flows from the connection 11IA55 to the connection 49.53, and the focus coil 50
A connection wire 56 is connected to the other coil of the two coils.
When the current flows from the direction toward the connection wire 54, the movable part MA is driven and displaced in the direction of the double arrow Ff in FIG. 12(b), and each coil of the focus coil 50 When a current is passed in the opposite direction to that in the above case, the movable part MA moves as shown by the double arrow Ft in FIG. 12(b).
The condenser lens 14 is driven and displaced in the opposite direction, and the focus of the condensing lens 14 is controlled by supplying a focus control signal to the focus coil 50.

In the above description, the tracking coil 28 is a sheet-like coil 28al, 28a2, which is a synthetic resin sheet with a spiral clockwise coil winding pattern made of a conductive material.

It is constructed using two types of sheet-like coils: sheet-like coils 28bl and 28b2, which are formed by forming a spiral counterclockwise coil winding pattern on a synthetic resin sheet using a conductive material. However, the coil winding pattern in the sheet-shaped coils 28al and 28a2, in which a spiral clockwise coil winding pattern is applied to the synthetic resin sheet using a conductive material, and the synthetic resin sheet The coil winding patterns in the sheet coils 28bl and 28b2, on which a spiral counterclockwise coil winding pattern is applied using a conductive material, are in a reverse relationship with each other. It is only necessary to prepare one type of sheet-shaped coil to be used to configure the tracking coil 28.

In this respect, the sheet-shaped coils 50al, 50a2, 50b used to configure the focus coil 50 described above are
The same goes for lying on l, 50 b2. That is, the sheet-like coils 50al and 50a2 have a clockwise spiral coil winding pattern applied to their right half, and a spiral coil winding pattern applied to their left half. The spiral coil winding pattern is counterclockwise, whereas the sheet coil 5
0bl and 50b2 have a counterclockwise spiral coil winding pattern on their right half, and a spiral coil winding pattern on their left half. The winding pattern is clockwise, but the sheet-shaped coil 50a described above
Since the coil winding pattern in 1, 50a2 and the coil winding pattern in sheet coils 50bl and 50b2 are in a reverse relationship with each other, the sheet coil to be used to configure the focus coil 50 is Therefore, you only need to prepare one type.

Next, the tilt coil 26 provided in the coil assembly MCA described above. That is, the lens axis of the condensing lens 14 is located at the back focal point (focus on the light source side) of the condensing lens 14 at the position 1i'! F
An example of the configuration of the tilt coil 26 used for tilt control in the direction of arrow α in FIG. 11 or in the directions of arrows α and β in FIG. 11 with b as the rotation center will be described.

FIGS. 14A to 14C are diagrams showing different configuration examples of the tilt coil 26, respectively. First, the 14th
The tilt coil 26 exemplified in FIG. It is constructed as a sheet-like coil on which a winding pattern is applied, and in the configuration example shown in the figure, a spiral coil made of conductive material is formed on the outer periphery of the first synthetic resin sheet. A pattern of clockwise coil windings m26a is applied, and a spiral clockwise coil winding 26b made of conductive material is formed near the inner circumference of the pattern.
This is a sheet-like coil with a pattern of

Further, in the tilt coil 26 illustrated in FIG. 14(b), the pattern of the spiral coil winding 26c applied to the right half of the synthetic resin sheet is clockwise. Ori.

Further, the pattern of the spiral coil winding 26d applied to the left half of these sheets is a counterclockwise pattern. Compare the spiral coil winding pattern of the tilt coil 26 shown in FIG. 14(b) with the spiral coil winding pattern of the focus coil 50 already described with reference to FIG. As can be seen, the spiral coil winding patterns in both of the sheet-like coils described above are the same, so the tilt coil 26 to be provided in the coil assembly MCA is shown in FIG. 14(b). If such a configuration is used.

It can be seen that the tilt coil 26 and the focus coil 50 can be used together.

Incidentally, by using the tilt coil 26 having the configuration shown in FIG. 14(b), the tilt coil 26
When the focus coil 50 is also used, the 14th
The direction of the current to be supplied to the tilt coil 26 when controlling the tilt of the lens axis of the condensing lens 14 in a predetermined manner by the tilt coil 26 having the configuration shown in FIG. Needless to say, this is different from the direction of the current that should be supplied to the tilt coil 26 when the condenser lens 14 is directly controlled in the direction of the lens axis by the tilt coil 26 having the configuration shown in (b). , in this regard using a tilt coil 26 of the configuration shown in FIG. 14(b).

The description will be given later regarding the operation when controlling the tilt of the lens axis of the condenser lens 14, and the linear motion 4 of the condenser lens 14 in the lens axis direction by the focus coil 50 already described with reference to FIG. This can be easily understood by comparing it with the description of the work.

That is, when the tilt coil 26 having the configuration shown in FIG. 14(b) is used, the structure of the coil assembly is as shown in the exploded perspective view of FIG. In that case, the focus coil 50 in FIG. 10 may have a focus control current and a tilt so that the focus coil 50 in FIG. 10 is also used as the tilt coil 26. A combination of the above-mentioned surface control currents is supplied by an electric circuit so that the control current flows through the coil in a superimposed manner.

The condenser lens 14 is constructed using the tilt coil 26 having the configuration as shown in FIG. 14(a) or the tilt coil 26 having the configuration as shown in FIG. 14(b). What is the mode of tilt control when the tilt control of the lens axis cannot be performed?

As is clear from what will be described later with reference to FIG. 12(c), the direction of the arrow α shown in FIGS. 1, 11, and 13, that is, Y-Z In this plane, the lens axis of the condenser lens 14 is tilted around the focal point Fb of the condenser lens 14 near the light source.

The tilt coil 26 shown in FIG. 14(C) is tilted in two directions, the direction of the arrow α and the direction of the arrow β shown in FIG. 1 or FIG. 11, that is, the Y-Z plane. and x-
It is used when the lens axis of the condensing lens 14 is tilted in two planes with the Z plane, with the focal point Fb of the condensing lens 14 near the light source being the center of rotation. This is an example of a suitable tilt coil 26 configuration.

Tilt coil 26 illustrated in FIG. 14(c)
1 For example, a sheet of synthetic resin is divided into four parts by two orthogonal axes, the X axis and the Y, and a predetermined spiral coil winding 311 is applied to each part using a conductive material.
26e, 26f, 26g.

The coil is constructed as a sheet-like coil with a 26h pattern.6 In the configuration example shown in the figure, 1 is a spiral coil winding made of a conductive material provided on a synthetic resin sheet. In the pattern, the spiral coil windings 26e and 26f are made of a conductive material into a spiral clockwise coil winding pattern,
Further, the spiral coil windings 26g and 26h have a pattern of a spiral counterclockwise coil winding 26a.

Each of the sheet-shaped coils used as the tilt coil 26 shown in FIGS. 14(a) to 14(c) above has a thin insulating coating applied to the conductor portion excluding both ends of the coil winding pattern. There is.

The tilt coil 26 shown in FIG. 14(a), the tilt coil 26 shown in FIG. 14(b), or the tilt coil 26 shown in FIG. 14(0) described above. When any one of them is incorporated into the coil assembly MCA and used in a lens driving device, the used tilt coil 26 has the annular shape shown in FIGS. 11 and 13. The 14th r1!4 is placed in the magnetic field generated by the permanent magnet 46 of
For each coil winding 1 m 26 a to 26 h of each tilt coil 26 shown in (a) to (c) of FIG. Current Ia in the direction of the arrow as shown in FIG. If the tilt coil 2 shown in FIG. 14 (a) and (b) is supplied with
6 rotates as shown by the double arrow Ftt in FIG. 12(c), and the tilt coil 26 in FIG. 14(c) rotates as shown by the arrow β in FIG. 14(c). perform an action,
Coil 26a of tilt coil 26 in FIG. 14(c)
If a current in the same direction is supplied for ~26h, (Q) in Figure 14 is obtained.
12 (c)
The symbol H shown in FIGS. 13 and 14 (c) indicates the magnetic field H applied to the tilt coil 26.

The magnetic field H generated by the permanent magnet 46 in FIGS. 11 and 13 and applied to the tilt coil 26 is as already described with reference to FIG.

The various coils constituting the above-mentioned coil assembly MCA are sheet-like coils whose coil winding patterns are made by etching, for example, and can be made lightweight and highly rigid, so that they can be easily made into the movable part of the lens driving device. M.A.
It is lightweight and has excellent motion and vibration characteristics.

When it comes to farming, it is easy to automate winding and assembly, so products can be provided at low cost.

(Effects) As is clear from the above detailed explanation, the optical information signal reproducing device of the present invention is effective for the signal surface of a recording medium having a signal surface on which a recording trace of an information signal is formed. A light spot for signal reading is projected from a light source, and a photodetector receives reflected light whose intensity is modulated by the information signal in the recording trace formed on the signal surface of the recording medium. An optical information signal reproducing device configured to obtain a reproduced signal from a photodetector, the optical information signal reproducing device comprising:
The condensing lens that forms a light spot on the signal surface of the recording medium described above has four linear movements in two directions: the direction of the lens axis and the direction perpendicular to the lens axis, and the light source side of the light lens. A lens driving device configured to perform four oscillating movements in a plane including two directions in which the four linear movements described above are performed centering on the focal point position of the lens, the above-mentioned light source, and an optical axis. an optical system in which a photodetector is fixed to a housing in a predetermined related arrangement, and a photodetector is provided with a light receiving element in each area divided into at least two areas by a line that intersects with the signal plane of the recording medium; a transport device that transports the optical system casing in a direction across the recording trace formed on the recording medium; and an automatic focus control that constantly forms a minute spot of light on the signal surface of the recording medium. circuit and
an automatic tracking control circuit that always causes the spot of light to follow the recording trace; and a light receiving device provided in the two areas of the photodetector that receives the reflected light from the signal surface of the recording medium. Means for obtaining inclination information between a signal surface of a recording medium and an optical axis in a direction orthogonal to a recording trace on a signal surface of a recording medium based on a difference in intensity of reflected light received by an element, and a signal surface of the recording medium as described above. The lens axis of the condensing lens is aligned with the signal surface of the recording medium based on the output signal from the means for obtaining the inclination information between the signal surface of the recording medium and the optical axis in the direction orthogonal to the recording trace formed on the recording medium. an optical information signal reproducing device comprising means for driving and controlling a driving device for swinging the lens axis of the condensing lens so as to make it vertical; and a signal surface on which a recording trace of the information signal is formed. A light spot for signal reading from a light source is projected onto the signal surface of a recording medium having a recording medium, and the intensity is modulated by the information signal in the recording trace formed on the signal surface of the recording medium. An optical information signal reproducing device configured to receive reflected light with a photodetector and obtain a reproduced signal from the photodetector, which forms a light spot on the signal surface of the recording medium. The condensing lens has four linear motions in two directions: the direction of its lens axis and the direction perpendicular to the lens axis, and the two linear motion directions described above centering on the focal point on the light source side of the condensing lens. The first four rocking motions are performed within a plane containing the lens axis, and the second four rocking motions are performed within a plane containing the lens axis within a plane orthogonal to the plane containing the two linear motion directions. A driving device for a lens made of an optical system fixed to a housing; a transport device for transporting the housing of the optical system in a direction that traverses a recording trace formed on the signal surface of the recording medium; and a signal of the recording medium. An automatic focusing control circuit that always forms a minute spot of light on the surface, an automatic tracking control circuit that always causes the spot of light to follow the recording trace, and a signal surface of the recording medium. Difference in intensity of reflected light received by light receiving elements provided in two areas separated by a first dividing line parallel to the recording trace formed on the signal surface of the recording medium in a photodetector that receives reflected light of means for obtaining inclination information between a signal surface of a recording medium and an optical axis in a direction orthogonal to a recording trace formed on a signal surface of a recording medium based on the above-mentioned signal surface of a recording medium; Based on the output signal from the means for obtaining the inclination information between the signal surface of the recording medium and the optical axis in the direction orthogonal to the recording trace, the lens axis of the condensing lens is recorded by the first four movements of rocking. A means for controlling the driving device so as to be perpendicular to the signal surface of the medium, and a recording trace formed on the signal surface of the recording medium in the photodetector that receives the reflected light from the signal surface of the recording medium. Recording that is formed on the signal surface of a recording medium based on the difference in intensity of reflected light received by light receiving elements provided in two areas separated by a second dividing line perpendicular to a parallel first dividing line. Means for obtaining inclination information between a signal surface of a recording medium and an optical axis in a direction in which a trace extends; and a signal surface of a recording medium in a direction in which a recording trace formed on the signal surface of the recording medium extends; Based on the output signal from the means for obtaining information on the inclination with respect to the optical axis, the driving device is operated to make the lens axis of the condensing lens perpendicular to the signal plane of the recording medium by the second four movements of the condensing lens. Since the optical information signal reproducing apparatus of the present invention is equipped with drive control means, the optical information signal reproducing apparatus of the present invention is capable of preventing damage due to causes such as sagging of the peripheral part due to the weight of the disc or relaxation of disc molding stress. The occurrence of crosstalk from adjacent recording tracks caused by the presence of a tilt of about 1° at most in the radial direction of the disk can also be controlled by the tilt control system, the transport motor control system, and the tracking control system. The main surface of the condensing lens is automatically controlled to be parallel to the signal plane of the condensing lens, eliminating coma aberration and tracking offset, thereby eliminating crosstalk from adjacent recording traces. A reproduced signal with a high degree of modulation without any distortion can be obtained. When the above-mentioned tilt control is performed, the incident optical axis and the main surface of the condenser lens are not perpendicular to each other, but the condenser lens remains within a certain field of view as shown in Figure 8. The above point does not pose a practical problem because the wavefront aberration at
If it is 0.00 microns, the angle will be 1.49, but the wavefront aberration at this angle is sufficiently small, and the radial inclination of the disk is normal as described above, so there is no problem at all. be. Furthermore, by controlling the inclination in the extending direction of the recording trace on the signal surface of the disk, both the MTF and PTF of the condensing lens can be maintained at their best, and the frequency characteristics and phase characteristics of the reproduced signal can be optimized. Furthermore, since the condenser lens is a movable part consisting of a lightweight yet highly rigid coil assembly and is driven by a lens drive device, the optical axis of the condenser lens can be tilted perpendicular to the signal surface of the disk. An optimal tilt control loop can be constructed by rapidly performing control operations such as this, and by setting the cutoff frequencies in the tilt control system, transfer motor control system, tracking control system, etc. in a predetermined manner. In addition, since the movable part is small and lightweight as described above, the lens driving device can be driven with small driving power, so that various advantages can be obtained, such as the control circuit can be miniaturized.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a part of an embodiment of the optical information signal reproducing device of the present invention, FIGS. 2, 5, and 8 are explanatory characteristic example diagrams, and FIGS. 3 and 9. 16 to 18 are block diagrams of an embodiment of the optical information signal reproducing device of the present invention, FIG. 4 is a plan view of a part of the signal surface of the disk, and FIGS. 6 and 20 are explanations of the operation. Side view of the optical system for
Figure 7 is a side view of a part of the disk, Figures 10 and 14.
The figures are plan views of various sheet-like coils, FIG. 11 is an exploded perspective view of a coil drive device, FIG. 12 is a perspective view for explaining the coil drive mode, and 1311! 15 is a sectional view and a plan view of a coil driving device, FIG. 15 is an oblique view of a disk, and FIG. 19 is a block diagram showing an example of a conventional device. 6... Disk, 11... Light source, 12... Collimating lens, 13... Beam splitter, 14...
Condensing lens, 7, 15, 30, 37... Photodetector, 1
6... Lens drive device, 18... Disc drive motor, 19... Transfer motor, 20... Rack,
21... Binion, 24.27.31-33,38,
39, 41.42... Subtraction base, 5UBI to 5UB3.
...Subtraction points. 25.29...Low pass filter, 26...Dil 1
- Coil, 28... Tracking coil, 33...
Adder, 43... Upper cover, 44... Lower cover, 45...
Suspension, 46... Permanent magnet, 50... Focus coil, MCA... Coil assembly, MA...
Movable body, PDCa. PDCb...Peak value detection circuit, P...Pit. Sl-S4-... Spot of light, MULa, MULb-
- Multiplier, FA...Transfer mechanism, LA...Optical system. Patent applicant Victor Japan Co., Ltd. Horse 3m 9th grade Pechu V (q) (b) Fake 51mm father-in-law

Claims (1)

[Claims] 1. A spot of light for signal reading from a light source is projected onto the signal surface of a recording medium having a signal surface on which a recording trace of an information signal is formed, and the aforementioned recording medium An optical information signal that is configured to receive a reflected light whose intensity is modulated by the information signal in the recording trace formed on the signal surface of the optical detector, and to obtain a reproduced signal from the aforementioned optical detector. The reproducing apparatus includes a condensing lens that forms a light spot on the signal surface of the recording medium, and a condensing lens that performs linear motion in two directions, that is, the direction of the lens axis and the direction perpendicular to the lens axis, and condenses the condensing lens. A lens driving device configured to perform rocking movement in a plane including two directions in which the above-described linear movement is performed centered on the focal point position on the light source side of the optical lens;
and an optical system in which the above-mentioned light source and a photodetector each having a light-receiving element provided in at least two areas divided by a line intersecting the optical axis are fixed to a housing in a predetermined related arrangement. system, a transport device that transports the casing of the optical system in a direction that traverses the recording trace formed on the signal surface of the recording medium, and a transport device that transports the casing of the optical system in a direction that traverses the recording trace formed on the signal surface of the recording medium, and an automatic focus control circuit that causes a spot to be formed; an automatic tracking control circuit that causes the spot of light to constantly track the recording trace; and a light detection circuit that receives reflected light from the signal surface of the recording medium. The inclination of the signal surface of the recording medium and the optical axis in the direction orthogonal to the recording trace on the signal surface of the recording medium is determined based on the difference in intensity of the reflected light received by the light receiving elements provided in the two areas described above in the device. Based on output signals from the means for obtaining information and 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 formed on the signal surface of the recording medium, An optical information signal reproducing device 2 comprising means for driving and controlling a driving device that swings the lens axis of the condensing lens so as to make the lens axis of the condensing lens perpendicular to the signal plane of the recording medium. , for a transport device that transports an optical system casing in a direction that traverses a recording trace formed on a signal surface of a recording medium,
The optical information signal reproducing device 3 according to claim 1, wherein the tracking control signal output from the automatic tracking control circuit is supplied through a low-pass filter, and a recording trace is formed by the information signal. A light spot for signal reading from a light source is projected onto the signal surface of a recording medium having a signal surface, and the information signal in the recording trace formed on the signal surface of the recording medium is An optical information signal reproducing device configured to receive intensity-modulated reflected light with a photodetector and obtain a reproduced signal from the photodetector, wherein the optical information signal is A condensing lens that forms a spot is subjected to linear movement in two directions: the direction of its lens axis and the direction orthogonal to the lens axis, and the above-mentioned 2 movements centering on the position of the focal point on the light source side of the condensing lens. A first oscillating motion within a plane including the two axial directions, and a second oscillating motion within a plane including the lens axis within a plane perpendicular to the plane including the two axial directions. A lens driving device configured to perform the above operations, the above-mentioned light source, and the above-mentioned photodetector each having a light receiving element provided in an area divided into two by a line intersecting the optical axis, are operated in a predetermined manner. Related arrangements include an optical system fixed to a housing, a transport device for transporting the housing of the optical system in a direction that traverses the recording trace formed on the signal surface of the recording medium, and the recording medium as described above. an automatic focusing control circuit that always forms a minute spot of light on the signal surface of the medium; an automatic tracking control circuit that always causes the spot of light to follow a recording trace; Reflected light received by light receiving elements provided in two areas separated by a first dividing line parallel to the recording trace formed on the signal surface of the recording medium in a photodetector that receives reflected light from the signal surface. Based on the strength difference of
means for obtaining inclination information between a signal surface of a recording medium and an optical axis in a direction orthogonal to a recording trace formed on a signal surface of a recording medium; Based on the output signal from the means for obtaining the inclination information between the signal surface of the recording medium and the optical axis in the direction in which the signal surface of the recording medium is means for controlling the driving device so as to be perpendicular to the signal surface of the recording medium; The extension of the recording trace formed on the signal surface of the recording medium based on the intensity difference of the reflected light received by the light receiving element provided in the two areas separated by the second dividing line perpendicular to the dividing line. means for obtaining inclination information between the signal surface of the recording medium and the optical axis in the direction in which the signal surface of the recording medium and the optical axis extend in the direction in which recording traces formed on the signal surface of the recording medium extend; Means for driving and controlling the driving device so as to make the lens axis of the condensing lens perpendicular to the signal plane of the recording medium by the second rocking motion based on the output signal from the means for obtaining tilt information. an optical information signal reproducing device 4 comprising:
The optical information signal reproducing device according to claim 3, wherein the tracking control signal output from the automatic tracking control circuit is supplied via a low-pass filter.