JPH0754586B2 - Recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an apparatus for recording on a master by at least two laser beams, and more particularly, to a relative position of the two laser beams with high accuracy. The present invention relates to a recording device having a holding unit.

(Prior Art) A technology for recording information on a disc by a laser beam is a master cutting device for manufacturing a read-only disc such as a VHD (AHD) system or a laser system video disc, or a writable optical disc. It has been put to practical use as a device and the like.

In such a recording device, for example, when recording is performed on a VHD type master disc for a video disc, 2
Information signals and tracking signals are recorded on different tracks by using one laser beam. In this case, the track pitch of the information signal and the tracking signal is, for example, 1.35 μm.
Therefore, it is necessary to accurately maintain the distance between the tracking signal recording laser beam and the information signal recording laser beam on the disk at 1/2 of the track pitch, that is, 0.675 μm.

Conventionally, the positions of two laser beams for recording an information signal and for recording a tracking signal are respectively detected by a two-division photodetector, and each optical axis is individually controlled based on the detected positions. However, in this method, if there is a positional shift of the photodetector, it immediately causes a laser beam position detection error, resulting in a change in the distance between the two beams on the disk. Therefore, it is required that the position accuracy of the photodetector be extremely high, and that the optical system be complicatedly adjusted every time the laser device or the like is replaced. This problem becomes more serious when the track pitch is narrowed to increase the recording capacity of the disc.

(Problems to be Solved by the Invention) As described above, the conventional technique has a problem in that it is difficult to maintain the distance between the two laser beams on the master with high accuracy.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a recording apparatus which can maintain the distance between two laser beams on a master disc with high accuracy and which does not require complicated adjustment when exchanging a laser device or the like.

[Structure of the Invention] (Means for Solving the Problems) The present invention detects an error in the relative position of two laser beams, and based on an error signal obtained thereby, one of the optical axes of the two laser beams is detected. It is characterized by controlling.

Here, the error detecting means for detecting an error in the relative position of the two laser beams includes a beam spot interval detecting means for detecting an interval between two beam spots formed on the master by the two laser beams, and this means. And a means for obtaining a difference between the detected beam spot distance and a predetermined reference distance as an error between relative positions of the two laser beams.

Further, the beam spot interval detecting means detects the interval between the two beam spots in the horizontal scanning direction from the television signal obtained by imaging the two beam spots formed on the master, for example.

(Operation) In the present invention, the optical axis of one laser beam is controlled so that the error between the relative positions of the two laser beams is minimized. As a result, the relative positions of the two laser beams are maintained with extremely high precision, and The distance between the two upper beams is kept constant with high precision.

(Example) Hereinafter, the Example of this invention is described. FIG. 1 is a block diagram showing a schematic configuration of the entire recording apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing a detailed configuration from an Ar ⁺ laser device to a recording optical system in FIG.

In FIG. 1, a disk 1 is, for example, a glass master used for manufacturing a VHD type video disk, and is rotated by a rotary motor (a DC motor in this example) 3 connected via an air spindle 2. The rotary motor 3 is controlled by the rotary servo system 4.

The air slider 5 provided on the disk 1 is driven by a feed motor 6 controlled by a feed servo system 7 and moves in the radial direction of the disk 1. Air slider 5
An objective lens 8 and a moving optical system 9 are attached to. The moving optical system 9 includes a mirror 10 for guiding information signal and tracking signal beams introduced from a recording optical system described later to the objective lens 8, and a He-Ne for focusing.
A laser device 11, mirrors 12 and 13, a quarter-wave plate 14, a polarization beam splitter 16, a photodetector 16 and the like are provided. The output signal of the photodetector 16 is guided to the focus servo system 17 and the defect detector 18. The laser beam irradiation position on the disk 1, that is, the recording position is detected by the recording position detector 19, and the horizontal position of the air slider 5 is detected by the laser interferometer 20. Output signals of the defect detector 18 and the laser interferometer 20 are supplied to an external CPU (not shown).

Referring to FIG. 2, the laser beam (wavelength 4579Å) emitted from the Ar ⁺ laser device 21 is guided by the mirror 23, and then, the two servo mirrors 24 and 25 constituting the optical correction unit 22 in FIG. To correct the optical axis. Servo mirrors 24 and 25 are optical axis correction servo system 2
Controlled by 6. The laser beam reflected by the servo mirror 25 is split by the beam splitter 27 into an information signal recording beam and a tracking signal recording beam.

The information signal recording beam divided by the beam splitter 7 is guided to the optical modulator 28a, and light intensity modulation based on the information signal and light amount control are performed in accordance with signals from the optical modulator servo system 29 and the light amount servo system 30. Then, it is guided to the recording optical system 31.

The information signal recording beam from the optical modulator 28a introduced into the recording optical system 31 is transmitted through the mirrors 32 and 33 to the two convex lenses 3
First collimator optical system 37 consisting of 4,35 and pinhole 36
And the beam diameter is expanded, and then the beam is incident on the mirror 38. The beam reflected by the mirror 38 is incident on the half mirror 39. For example, 96% of the light amount is transmitted and the beam combiner 40
The remaining amount of light of 4% is reflected and guided to the two-part photodetector 42 via the convex lens 41. Using the output signal of the photodetector 42 as a control signal, the first convex lens 34 of the first collimator system 37 is driven by a lens drive motor (not shown), thereby minimizing the optical axis fluctuation of the information signal recording beam. To be

On the other hand, the tracking signal recording beam split by the beam splitter 27 is incident on the half mirror 42, where most of the light amount is further transmitted to the mirror 46, and the remaining light amount is used as a control beam for the half mirror. It is incident on 43. The beam transmitted through the half mirror 43 and the beam reflected by the half mirror 43 are respectively photodetectors in the optical axis correction servo system 26.
Guided by 44,45. The output signals of the photodetectors 44 and 55 are used to control the servo mirrors 24 and 25 in the optical axis correction unit 22, respectively.

The tracking signal recording beam reflected by the mirror 46 is guided to the optical modulator 28b, and the light intensity modulation based on the tracking signal and the light amount control are performed according to the signals from the optical modulator servo system 29 and the light amount servo system 30. After that, it is guided to the recording optical system 31. Optical modulator introduced in recording optical system 31
The tracking signal recording beam from 28b is reflected by the mirror 47, and the polarization direction is converted from the direction perpendicular to the platen surface to the horizontal direction by the half-wave plate 48, and then the two convex lenses 50, 50 through the mirror 49. The beam diameter is expanded by being guided to the second collimator system 53 composed of 52 and the pinhole 51. The tracking signal recording beam emitted from the second collimator system 53 is incident on the half mirror 55 via the mirror 54. For example, the beam of 96% light amount that has passed through the half mirror 55 is
When the beam is incident on the beam combiner 40 via the mirror 56, the beam is combined with the information signal recording beam. Also,
The remaining amount of light reflected by the half mirror 55 is the convex lens 58.
The light is incident on the two-divided photodetector 59 via. This photo detector
The second collimator system 53 uses the output signal of 59 as a control signal.
The first convex lens 50 is driven by a lens driving motor (not shown), so that the fluctuation of the optical axis of the tracking signal recording beam can be minimized.

The information signal recording beam and the tracking signal recording beam combined by the beam combiner 40 are incident on the half mirror 61 via the mirror 60, and this half mirror 61
For example, 96% of the amount of light passes through and is guided to the moving optical system 9 via the mirror 69 as shown in FIG. As a result, the information signal and the tracking signal are recorded on the disc 1.

The beam of the remaining light amount reflected by the half mirror 61 is totally reflected by the mirror 62 and is incident on the focusing lens 63. The shape of the beam narrowed down by the focusing lens 63 is as follows: objective lens 64, mirror 65, half mirror (light amount division ratio 50%: 5
0%) 66 and an eyepiece 67. The beam spot of the laser beam formed on the half mirror 66 is picked up by the ITV camera 68, and the spot shapes and intervals of the two beams for information signal recording and tracking signal recording and the reflected light from the disc 1 are recorded. The beam shape, etc. are observed. The output signal of the ITV camera 68 is the beam position servo system in FIG.
Entered in 70.

The beam position servo system 70 uses the ITV camera 68 as described later.
Error of the relative positions of the two beams is detected based on the output signal of the first convex lens 34, 50 in the first and second collimator systems 37, 53, for example, an information signal recording beam. The convex lens 34, which passes through, is moved in a predetermined direction orthogonal to the optical axis via the lens drive motor. In that case, a convex lens based on the output signal of the photodetector 42
The driving of 34 is unnecessary, and the half mirror 39, the convex lens 41, and the photodetector 42 are omitted. Further, when the beam position servo system 70 moves the convex lens 50 through which the tracking signal recording beam passes in a predetermined direction orthogonal to the optical axis, it is not necessary to drive the convex lens 50 based on the output signal of the photodetector 59. , Half mirror 55, mirror 57, convex lens 58, photodetector 59
Is omitted. By such movement control of the convex lens 34 or 50, the relative positions of both the information signal recording beam and the tracking signal recording beam are controlled.

The system controller 71 in FIG.
Controls various servo systems based on commands from the CPU. The CRT display 72 is the operation of various servo systems in this device,
It is for monitoring various data.

Next, the beam position servo system 70 according to the gist of the present invention will be described with reference to FIGS.

In FIG. 3, the television signal processing circuit 81 has a second
A television signal 80 as shown in FIG. 5 (a) obtained by the ITV camera 68 in the figure is input, and a video signal component 82 and horizontal and vertical synchronizing pulses HD, VD are extracted by this circuit 81. Sync pulse HD and VD are gate pulse generator 8
It is input to 3 and two gate pulses T ₁ and T ₂ shown in FIGS. 5C and 5D are generated. Gate pulses T ₁ and T ₂ are adders
The addition is performed at 84, and the output of the adder 84 is further added at the adder 85 with the video component 82. The output of adder 85 is provided to the luminance input of CRT display 72 in FIG.

FIG. 4 shows a display example on the CRT display 72 corresponding to the signal from the amplifier 86, and P ₁ and P ₂ represent the beam spots of the laser beams for recording the information signal and the tracking signal. The bright lines in the horizontal direction H indicated by H ₁ and H ₂ are displays corresponding to the gate pulses T ₁ and T ₂ (hereinafter, this display is referred to as a marker). Gate pulse H ₁ , H ₂
The timing of occurrence of T can be arbitrarily set by the operator, and while watching the display on the CRT display 72, the operator can set the marker T ₁ and H ₂ so that they pass substantially the centers of the spots P ₁ and P ₂ , respectively. Adjust the generation timing of ₁ and T ₂ .

The video signal component 82 separated by the television signal processing circuit 81 is also input to the comparator 87 and compared with an appropriate reference voltage Δv. At the output CP of the comparator 87, as shown in FIG. 5 (b), when the level of the video signal component 82 exceeds the reference voltage Δv, that is, when the laser beam spots P ₁ and P ₂ are detected. Pulses CP ₁ and CP ₂ are obtained. The output CP of the comparator 87 is input to the monostable vibrators 88 and 89, and thin pulses corresponding to the rising and falling of each pulse in the output CP are created. The outputs of the monostable vibrators 88 and 89 are supplied to one input terminal of the AND gates 90a and 90c and one input terminal of the AND gates 90b and 90d. The gate pulse T ₁ is applied to the other input ends of the AND gates 90a and 90b, and the gate pulse T ₂ is applied to the other input ends of the AND gates 90c and 90d.

The outputs of the AND gates 90a and 90b correspond to the rising and falling edges of the virtual pulse waveform T ₁ * CP ₁ (* represents the logical product) shown in FIG.
The outputs of 90c and 90d correspond to the rising and falling of the virtual pulse waveform T ₂ * CP ₂ shown in FIG. 6 (c). The pulse waveforms in FIGS. 6D and 6C correspond to the beam spots P ₁ and P ₂ , respectively. The sample hold circuits 91a to 91d are supplied with the outputs of the AND gates 90a to 90d as sampling pulses, and are driven by the horizontal synchronizing pulse HD shown in FIG. 6 (a). The sampled and held sawtooth wave having the horizontal scanning period shown in FIG.

The output voltage of the sample-and-hold circuit _{91a~91d V 1, V 2, V} 3, V
₄ , the adders 94 and 95 and the subtractor 96 have V (Δl) =
The operation of (V ₄ + V ₃ ) / 2− (V ₂ + V ₁ ) / 2 is performed. The calculation result V (Δl) corresponds to the time from the center of the pulse waveform of FIG. 6 (c) to the center of the pulse waveform of (d), that is, the center interval Δl of the beam spots P ₁ and P ₂ in the horizontal scanning direction. is doing. This calculation result V (Δl) and the reference interval Δ
The difference from the voltage corresponding to l ₀ , that is, the error signal 98 of the relative position of the two laser beams is obtained by the differential amplifier 97.
The error signal 98 is supplied to, for example, a lens drive motor (not shown) that drives the convex lens 34 shown in FIG. 2 to correct the error in the relative position of the two laser beams. That is, when viewed on the display screen shown in FIG.
When l produces an error, the convex lens 34 is driven to move the laser spot P ₁ of the information recording laser beam in the horizontal scanning direction so that the error becomes zero.

Thus, the error in the relative position of the two laser beams for recording the information signal and for recording the tracking signal is detected,
By correcting the optical axis of either one of the laser beams on the basis of this error signal, the distance between the two beams on the disk 1 can be kept constant with high precision.

In particular, in the above embodiment, the moving direction of the laser beam is made to coincide with the horizontal scanning direction of the television and the distance between the beam spots of the two laser beams in the horizontal scanning direction is detected to obtain the error in the relative position of the two beams. Therefore, the error can be detected with higher accuracy. That is, if an attempt is made to detect the distance between the beam spots of two laser beams in the vertical scanning direction, the accuracy will decrease due to the existence of many horizontal blanking periods. In the above embodiment, the interval between the two beam spots can be detected with high accuracy without being affected by the horizontal blanking period.

In the above embodiment, the case where the information signal is recorded by one of the two laser beams and the tracking signal is recorded by the other beam has been described, but the present invention is not limited to this. For example, in a writable optical disc device, a guide groove for tracking and sector information are recorded on the disc in advance. In this case, conventionally, the sector information is recorded in the guide groove after the guide groove is formed in advance. However, according to the present invention, the interval between the two laser beams can be controlled with high accuracy. It is possible to form a guide groove and record sector information so that it is positioned between the guide grooves with the other laser beam. In short, the present invention can be applied to all devices that record on different tracks on a disc by using at least two laser beams.

EFFECTS OF THE INVENTION According to the present invention, the distance between two laser beams can be maintained on the disc with extremely high accuracy, and the error in the relative position between the two beams is caused even when the position of the photodetector is displaced. Is corrected, there is an advantage that no complicated adjustment of the optical system is required when replacing the laser device or the like.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing the overall configuration of a recording apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view showing in detail the configuration from the laser device to the recording optical system in FIG. FIG. 3 and FIG. 3 are circuit diagrams showing a concrete structure of the error detecting means of the beam position servo system in the embodiment, and FIG. 4 is a CR.
Figures, 5 and 6 showing examples of display on the T display
The figure is a signal waveform diagram for explaining the operation of FIG. 1 ... Disk, 13 ... Moving optical system, 21 ... Laser beam device, 31 ... Recording optical system, 68 ... ITV camera (imaging means), 70 ... Beam position servo system, 80 ... Television signal , 97 …… Differential amplifier, 98 …… Error signal.

Claims (2)

[Claims] 1. A recording apparatus for irradiating two laser beams onto a rotating master disk for recording, and an error detection means for detecting an error in relative position of the two laser beams, and an error signal obtained by this means. And a means for controlling one optical axis of the two laser beams based on the above, the error detecting means is a beam for detecting an interval between two beam spots formed on the master by the two laser beams. And a means for determining a difference between the distance between the two beam spots detected by the means and a predetermined reference distance as an error in the relative position of the two laser beams. Recording device. 2. The beam spot interval detecting means detects an interval between two beam spots in a horizontal scanning direction from a television signal obtained by imaging the two beam spots formed on the master. The recording apparatus according to claim 1, wherein