JPS6334529B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for obtaining an optimal focus state of a recording light beam in an optical information recording apparatus that records signals on a recording medium with a light beam.

When recording by projecting a modulated laser beam onto a recording medium on which a reflective metal layer is formed by vapor deposition on a glass substrate, focus control is performed using a condensing lens, that is, an objective lens. If the position of the converter changes due to temperature or the like, the target focus state cannot be obtained even if the focus control system is operating normally.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for obtaining an optimum focus state of a recording light beam, which enables optical recording by accurately performing focus control.

To achieve the above object, the present invention includes a focus control circuit that controls a condenser lens disposed in the optical path of a recording light beam to maintain a constant position with respect to a recording medium prior to main recording. A focus adjustment signal is supplied from the outside while changing with time, and the focus state of the recording light beam is changed with time based on the change in the focus adjustment signal, and the focus state of the recording light beam changes with time. recording a certain optimal focus state determining signal on the recording medium; reproducing the recording of the optimal focus state determining signal with a reproducing light beam passing through the condensing lens; determining an optimal focus adjustment signal corresponding to the optimal reproduction output based on a change in the reproduction output corresponding to the change; and controlling the main recording signal with the focus control by the focus control circuit corrected by the optimal focus adjustment signal The present invention relates to a method for obtaining an optimal focus state of a recording light beam in an information recording apparatus, which comprises recording on the recording medium with the recording light beam.

According to the present invention, optical recording is performed while changing the focus state over time, and when this is reproduced, the playback output becomes the optimum value at the optimum focus state, that is, at the optimum recording state, and the true optimum focus state is known. I can do it. Then, if the focus control circuit is corrected using a focus adjustment signal that can obtain this optimal focus state, the focus control circuit will be able to control to obtain the true optimal focus state, and will be able to correct focus deviations due to temperature changes, etc. I can do it.

Embodiments of the present invention will be described below with reference to the drawings.

In the optical recording system according to the embodiment of the present invention shown in FIG.
and a monitor reproduction light beam 3 at the same time, and in order to generate a relative scanning movement between the recording medium 1 and the two light beams 2 and 3, a disk rotation drive device 4 and a feeder are used. It has a drive device 5. A recording light beam sending unit 6 for projecting the recording light beam 2 includes a recording light source 7 made of an Ar laser that generates a laser beam with a first wavelength λ ₁ ;
It also includes an optical modulator 8 for modulating the unmodulated optical beam 2a sent out from the light source 7 with an electrical signal. The recording light beam 2 sent out from the light beam sending unit 6 is projected onto the recording medium 1 via an optical path integrator 9 and a condenser lens 10 that reflect the recording light beam 2 but transmit the reproduction light beam 3. . Further, a reproducing unit 11 that projects an unmodulated reproducing light beam 3 immediately after the recording light beam 2 and reads the recording using the modulated transmitted light 3a sends out a laser beam of a second wavelength λ ₂ . A reproducing light source 12 consisting of a HeNe laser
It consists of a condensing lens 10a for the transmitted light 3a, a beam splitter 13 that extracts only the transmitted light 3a of the reproduction light beam by using the difference in wavelength, and a photoelectric converter 14 that detects the transmitted light 3a.

15 is a focus detection beam, and the beam emitted from the reproduction light source 12 is passed through a half mirror 16.
obtained by dividing the reflecting mirror 1
7, 18, and 19 are projected obliquely onto the recording medium 1. The reflected light of this focus detection beam 15 is guided to a two-part photodetector 20.
The two-segment photodetector 20 detects beam 1 at optimum focus at standard temperature and standard mounting conditions.
The photoelectric conversion elements A and B are attached so that the center thereof coincides with the dividing line between the two photoelectric conversion elements A and B. recording light beam sending section 6, reproducing section 11, condensing lens 10,
10a, half mirror 16, reflective mirror 17, 1
8, 19, a photodetector 20, etc. are mounted on a common board to constitute a recording/reproducing head 21, and this head 2
1 is coupled to a feed drive 5 for providing radial feed of the recording medium 1 .

The optical modulator 8 includes an electro-optic crystal and an analyzer,
The light beam is interrupted in response to an electric signal applied from the drive amplifier 22 to the electrodes of the electro-optic crystal. This optical modulator 8 receives the frequency modulation signal of the line 23, that is, the main recording signal, from the contact a of the switch 24.
In addition to being provided via the drive amplifier 22,
The reference frequency signal generated from the 8MHz oscillator 25, that is, the recording signal for determining the optimum focus, is transmitted to the switch 24.
is applied via contact b of .

An amplifier 26 and an envelope detection circuit 27 are provided on the output line of the photoelectric converter 14.
The envelope detection circuit 27 is a circuit that detects a signal indicating a change in the amplitude of the AC component, that is, a change in the reproduced output voltage. A/
D, that is, the analog-to-digital converter 28 converts the reproduced output obtained from the detection circuit 27 into a digital value and supplies it to the control circuit 29. As explained in FIG.
1, a second memory 32 consisting of RAM, and a start switch 33, which determines the optimum focus based on the playback output data supplied from the A/D converter 28, and in order to obtain the optimum focus. The adjustment signal is held in the memory 32, and the optimal focus adjustment signal held during main recording is sent out. A digital focus adjustment signal outputted from the control circuit 29 is converted into an analog focus adjustment signal by a D/A, ie, digital-to-analog converter 34.

The focus control circuit 35 has a first input terminal connected to the element A of the photodetector 20 via an adjustment resistor 36, and a second input terminal connected to the element B via a correction circuit 37. , an error amplifier 38 that generates a voltage corresponding to the difference in voltage between both input terminals;
A driving amplifier 39 is included to control a known moving coil 40 coupled to the condenser lens 10 in the form of a speaker voice coil. If the focus control system is set so that the beam is incident on the dividing line of the photodetector 20 at the time of optimum focus, accurate focus control is theoretically possible. However, if it becomes impossible to satisfy the above conditions due to temperature changes, aging, etc., even if the focus control system appears to be in an optimal focus state, it will actually not be in an optimal focus state. Therefore, a focus correction circuit 37 consisting of a multiplier is provided, to which the output of the D/A converter 34 is supplied via an amplifier 41. That is, the closed loop control system is corrected by a focus adjustment signal from the outside.

Next, a method and operation for recording a signal on the recording medium 1 using the apparatus shown in FIG. 1 will be described. As the recording medium 1, for example, an unrecorded medium 1 having a reflective metal layer 43 deposited on the entire surface of a glass substrate 42 as shown in FIG. The feed drive device 5 is driven so that the recording light beam 2 is projected onto the innermost peripheral region _P1 of the disk, and the monitor reproduction light beam 3 following this and the focus detection beam 15 are projected onto the non-recording region. Next, the start switch 33 of the control circuit 29
When turned on, beams are emitted from the recording light source 7 and the reproducing light source 12. In addition, the changeover switch 24 is turned on to contact b for a certain period of time, and an 8MHz optimum focus determination signal is supplied to the optical modulator 8, and a light beam modulated by this signal is projected onto the recording medium 1 as the recording light beam 2. be done. Further, a focus correction program is read from the first memory 31 in the control circuit 29, and based on this program, a focus adjustment signal for determining the optimum focus for changing the focus of the recording light beam 2 over time is sent out. be done. That is, the focus adjustment signal is supplied to the correction circuit 37 so that the error amplifier 38 receives an input equivalent to that the output of the element B gradually changes from the minimum value to the maximum value or from the maximum value to the minimum value. Since such an adjustment signal for determining the optimum focus is written in the second memory 32 in advance, it can be obtained simply by reading the data from the memory 32 according to a program. However, it is of course possible to form this adjustment signal for determining the optimum focus inside or outside the control circuit 29 by controlling a counter or the like. The output of the error amplifier 38 changes in response to the adjustment signal for determining the optimal focus state, and when the lens 10 is displaced together with the moving coil 40, the focus state changes.

As described above, when a constant frequency signal is recorded on the recording medium 1 by changing only the focus with the modulated light beam 2, a recording pattern is formed in area _P1 of the recording medium 1 in FIG. 3 as shown in the enlarged view in FIG. 4. be done.
That is, recording is performed such that the pattern of the metal-removed recording portion 44 changes in response to changes in the tracks T ₁ , T ₂ , and T ₃ . The optimal pattern of the recording portion 44, which has a similar shape to the optical pits of a video disc, is determined in relation to the reproducing light beam 3.
The pattern of T ₂ is the optimal pattern. A determination as to whether or not the focus state is optimal is made based on the output of monitor playback. Figure 6 shows the A/D converter 28
This shows the relationship between the monitor playback output voltage input to the monitor playback output voltage and the focus adjustment signal, that is, the focus state, and shows that the maximum playback output E _M is obtained when the focus adjustment signal has a value indicated by J. In order to find the point of maximum reproduction output E _M shown in FIG. 6, in this method, the reproduction light beam 3 is immediately followed by the recording light beam 2
is projected and the recorded portion 44 is read substantially simultaneously. The reproduction output corresponding to the change in the focus state is input to the control circuit 29, and the maximum value E _M of the reproduction output is detected by a calculation that compares the magnitude of the previous data and the next data. Then, the focus adjustment signal sent from the control circuit 29 to obtain the focus state corresponding to the maximum value E _M is written into the memory 32 as the optimum focus adjustment signal.

Once the optimum focus adjustment signal, that is, the focus correction signal is determined using the partial area _P1 of the recording medium 1, in addition to storing this in the memory 32,
It is also stored in the recording medium 1. That is, with the focus control circuit 35 controlled by the optimal focus adjustment signal, a reference recording portion 44 is formed in an area _P2 of approximately 1 mm width on the recording medium 1 in correspondence with an 8MHz reference signal, as shown in an enlarged view in FIG. do. That is, an optimal recording pattern is formed in an optimal focus state and an optimal light amount state.

When the recording for determining the optimum focus is completed as described above, the main recording is then started. In this embodiment, since the optimal focus adjustment signal is written in the memory 32 and the optimal recording pattern is also written in the recording medium 1, main recording can be started in two ways. If there is a small time difference and a small temperature difference between the time when the optimal focus adjustment signal is determined based on the recording of area P ₁ and the time of main recording, the main recording is started immediately using the optimal focus adjustment signal in the memory 32. . That is, the optimum focus adjustment signal held in the memory 32 is applied to the correction circuit 37 to correct the focus control system so as to obtain the optimum focus state, thereby performing main recording. When performing main recording, the changeover switch 24 is turned on to contact a, a modulated electrical signal such as a video signal on the line 23 is supplied to the optical modulator 8, and a modulated light beam 2 corresponding to the electrical signal is sent to the recording medium. Project to 1.

On the other hand, after a considerable amount of time has passed since the recording of area P ₁ or P ₂ and there has been a change in temperature, the area
If it is desired to perform main recording in P _o , there is no problem in performing recording and reproducing with optimum focus state determination similar to that performed in area P ₁ using the head portion of area P _o . However, the utilization rate of the recording medium decreases. Therefore, the reproduction light beam 3 and the focus detection beam 1
Only 5 is the optimum recording pattern forming area of recording medium 1.
_P2 , the focus state is changed in the same way as when recording the area _P1 , and a focus adjustment signal that provides the maximum reproduction output is written in the memory 32 as an optimal focus adjustment signal. That is, when the start switch 33 is turned on and the focus adjustment signal that changes over time is read out from the memory 32 to change the focus state, and the optimum recording pattern shown in FIG. 5 is read with the reproduction light beam 3, the same as shown in FIG. Changes in playback output can be obtained, and an optimal focus state is achieved at maximum playback output. Therefore, the focus adjustment signal supplied to obtain the maximum reproduction output is written into the memory 32, and this focus adjustment signal is read out during main recording to perform focus correction.

As is clear from the above, in this embodiment, focus control is performed by correcting the focus control system to achieve the optimum focus state, so even if a shift occurs in the focus control system due to changes in temperature, etc., this can be compensated for. Main recording can be performed using

In addition, the optimal recording pattern is recorded in the specific area _P2 of the recording medium 1, and this is used to determine the optimal focus state, so when multiple recordings are made on a single recording medium under different conditions. In addition, the optimum focus can be determined without performing recording for determining the optimum focus state prior to main recording.

Furthermore, since the recording light beam 2 and the reproduction light beam 3 are arranged close to each other, the optimum light amount determination control signal at the time when the reproduction light beam 3 reaches its maximum is written into the memory 31 as an optimum focus adjustment signal.
Even if it is used for subsequent control of main recording, almost no error occurs. Therefore, the optimum focus adjustment signal can be easily obtained.

Also, record for optimal focus.
Since it is performed using a constant frequency signal of 8MHz, it is possible to accurately determine the optimal focus.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto and can be further modified. For example, as shown in FIG. 7, in place of the control circuit 29 in FIG. First, contact b of the switch 48 is turned on to supply a signal from the variable adjustment signal generation circuit 47 to the correction circuit 37 shown in FIG. 1 for recording, and the output of the photoelectric converter 14 shown in FIG. The optimum focus determination circuit 45 determines the optimum focus based on the optimum focus, and the corresponding optimum focus adjustment signal is held in the memory 46. When performing main recording, contact a of the switch 48 is turned on, and the optimum focus adjustment signal is stored in the memory 46. The focus adjustment signal may be read out and supplied to the correction circuit 37.

Furthermore, the present invention is not limited to forming records for reproduction using a transmission method, but can also be applied to recording on a disc for reproduction using a reflection method. It is also applicable to a system in which records are formed by an array of optical pits, such as a flip-flop video disc. In the case of the reflection method, after the modulated reflected light of the reproduction light beam 3 passes through the condenser lens 10, it is separated from the recording light beam 2 and its reflected light by a beam splitter, and is then separated from the recording light beam 2 and its reflected light by a photoelectric converter. All you have to do is detect it.

Furthermore, the present invention is not limited to the recording medium 1 shown in FIG. 2, and can also be applied to cases where a magneto-optical recording medium or the like is used. Further, the tracks may be either concentric or spiral. It is also applicable to a method in which the recording medium 1 is moved in the radial direction. It is also applicable to a case where a recording format is taken from the outer circumference to the inner circumference of the recording medium 1.

Further, the light beams 2 and 3 may be either visible light or non-visible light. Further, the correction circuit 37 may be provided at the output stage of the error amplifier 38. In addition, without projecting the focus light beam 15, a photoelectric conversion element is arranged in the path of the transmitted or reflected light of the reproduction light beam 3, and optimum focus detection is performed based on the change in the spot of the transmitted or reflected light. It is also applicable to a control method.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a recording method according to an embodiment of the present invention, FIG. 2 is a partially enlarged sectional view of a recording medium, FIG. 3 is a plan view of the recording medium, and FIGS.
The figure is a partially enlarged plan view of the recording medium, Figure 6 is a characteristic diagram showing the relationship between focus state and reproduction output, and Figure 7 is a characteristic diagram showing the relationship between focus state and reproduction output.
The figure is a block diagram showing a modification of the control circuit. In the symbols used in the drawings, 1 is a recording medium, 2 is a recording light beam, 3 is a reproduction light beam, 10 is a condensing lens, 29 is a control circuit, 31 is a memory, and 35 is a focus control. The circuit 37 is a correction circuit.

Claims (1)

[Claims] 1. Prior to main recording, a focus control circuit that controls a condensing lens disposed in the optical path of the recording light beam to maintain a constant position with respect to the recording medium,
A focus adjustment signal is supplied from the outside while changing with time, and the focus state of the recording light beam is changed with time based on the change in the focus adjustment signal, and the focus state of the recording light beam changes with time. recording a certain optimal focus state determining signal on the recording medium; reproducing the recording of the optimal focus state determining signal with a reproducing light beam passing through the condensing lens; determining an optimal focus adjustment signal corresponding to the optimal reproduction output based on a change in reproduction output corresponding to the change; A method for obtaining an optimum focus state of a recording light beam in an optical information recording apparatus, comprising correcting focus control by the focus control circuit according to the method.