JPH0656665B2 - Focus control device - Google Patents

Description

The present invention relates to reproducing a signal recorded on a record carrier or irradiating a signal recorded on the record carrier by converging and irradiating a light beam generated from a light source on the record carrier. The present invention relates to an optical recording / reproducing apparatus for recording data, and more particularly to a focus control for controlling a converged state of a light beam irradiated on a record carrier in a predetermined state in the optical recording / reproducing apparatus. .

Structure of Conventional Example and Problems There are mainly two record carriers used in the optical recording / reproducing apparatus.
There are two main categories. One is a record carrier having a recording material layer and the other is a record carrier having no recording material layer. The former is one in which a recording material layer is formed on the surface of a base material having concave and convex groove tracks by means such as vapor deposition and a protective layer is provided on the recording material layer surface, and this type of record carrier newly records a signal. Although it is possible, it is very difficult to reproduce a large number of record carriers on which signals are recorded,
It has the disadvantage that the price of the record carrier is high when reproduced. The latter is one in which signals are recorded in the form of concavities and convexities, and although this type of record carrier cannot record new signals, it can be very easily duplicated by means of injection molding or the like. It has an advantage that the price of the carrier can be reduced.

There are various types of information, but for example, information used for personal computers and the like can be roughly classified into two. That is, one is information commonly used by the device, and the other one is information not commonly used by the device and recorded by a person who uses the device as needed. Since the former requires a large amount of the same material, a record carrier that can be easily duplicated and is suitable without a recording material layer is suitable for the latter, and the latter is required to record a signal. It must be a record carrier having a recording material layer.

However, the two types of record carriers described above are loaded in the same device to record or record a signal because the reflectivity of the record carrier surface is greatly different or the form of the track traced by the light beam is different. It was not possible to reproduce the existing signal. Further, in the case of a recordable record carrier, since the irradiation light amount greatly differs between recording and reproduction, the loop gain of the focus control system fluctuates greatly,
Stable recording and reproduction could not be performed.

OBJECT OF THE INVENTION The object of the invention is to eliminate the disadvantages of the above-mentioned conventional devices and to provide a signal which is loaded with a device which can be loaded with the two types of record carriers mentioned above, ie a record carrier having a recording material layer. It is an object of the present invention to provide an apparatus capable of recording or reproducing a recorded signal and reproducing the signal even when a record carrier having no recording material layer is loaded.

According to the present invention, there is provided a discriminating means for discriminating between a first record carrier having no recording material layer and a second record carrier having a recording material layer, and a circuit gain of a focus control system according to a signal of the discriminating means. Is configured so that focus control can be stably performed.

Further, the present invention provides a converging means for converging and irradiating a light beam generated from a light source onto a record carrier, a moving means for moving the converging means in a direction substantially perpendicular to a surface of the record carrier, and a reflecting means by the record carrier. The light amount detecting means for detecting the light amount of the reflected beam reflected, and the focus shift of the light beam on the record carrier is detected from the reflected beam reflected by the record carrier, and the moving means is driven based on the focus shift signal to record. In order to control so that the converged state of the light beam on the carrier is always in a predetermined state, the circuit is composed of focus control means in which the circuit gain changes in inverse proportion to the magnitude of the signal of the light amount detection means. Stable focus control is performed by switching the circuit gains of the light amount detecting means and the focus control means at almost the same time.

DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. The same numbers are used for the same numbers in the description of the drawings.

FIG. 1 shows an embodiment of the present invention.

A disk-shaped record carrier 1 having concentric tracks is attached to a rotation shaft of a disk motor 2 and is rotated at a predetermined rotation speed. The record carrier 1 is covered with a jacket 3 to protect it from dust and dirt.

The discriminator 4 for discriminating the record carrier 1 is composed of a light emitting diode and a light receiving element. The jacket 3 has different shapes depending on the type of the record carrier 1. When the jacket 3 containing the record carrier 1 is loaded, the light beam generated by the light emitting diode of the discriminator 4 is shielded by the jacket 3 and received. The element may not be irradiated with the light beam, or the light beam generated by the light emitting diode may not be shielded and may be irradiated onto the light receiving element. The signal of the light receiving element of the discriminator 4 is input to the processing circuit 5, and the processing circuit 5 outputs a signal according to the type of the record carrier 1.

Explaining the optical system, a light beam 7 generated from a light source 6 such as a semiconductor laser is converted into substantially parallel light by a coupling lens 8, and a polarization beam splitter 9 and a λ / 4 plate 10 (λ is a wavelength of the light beam 7). And is reflected by the reflecting mirror 11 and converged and irradiated on the record carrier 1 by the converging lens 12. The reflected light 13 of the light beam 7 reflected by the record carrier 1 again passes through the converging lens 12, the reflecting mirror 11, the λ / 4 plate 10, the polarizing beam splitter 9, and the convex lens 14. Further, the light passes through the cylindrical lens 15 and is irradiated onto the photodetector 16 having a four-division structure, which will be described in detail later.

The converging lens 12 is supported by rubber or the like, and when an electric current is passed through the focus element 17, the converging lens 12 moves in a direction substantially perpendicular to the surface of the record carrier 1 by an electromagnetic force,
When a current is applied to the tracking element 18, the converging lens 12 is configured to move in a direction substantially perpendicular to the track direction on the record carrier 1, that is, in the radial direction of the record carrier 1 by an electromagnetic force.

Light source 6, coupling lens 8, polarization beam splitter 9, λ / 4 plate 10, reflecting mirror 11, focus element 1
7, the tracking element 18, the convex lens 14, the cylindrical lens 15, and the photodetector 16 are attached to the transfer table 19, and are configured to move integrally in the radial direction of the record carrier 1 when the linear motor 20 is driven. Has been done.

The detection of the control signal will be described. The respective signals of the photodetector 16 are output through the lines 21, 22, 23 and 24. The synthesizing circuits 25, 26, 27, 28 and 29 are circuits for adding the input signals. Lines 21 and 22 are provided at the input end of the synthesizing circuit 25, and lines 23 and 24 are provided at the input end of the synthesizing circuit 26. However, lines 21 and 23 are connected to the input end of the synthesizing circuit 27, lines 22 and 24 are connected to the input end of the synthesizing circuit 28, and lines 21, 22, 23, and 24 are connected to the input end of the synthesizing circuit 29, respectively. ing. The signals of the combining circuits 27 and 28 are input to the differential amplifier 30, and the differential amplifier 30 outputs a difference signal between the signal of the combining circuit 27 and the signal of the combining circuit 28. As will be described later in detail, the differential amplifier 30 outputs a signal indicating the converged state of the light beam 7 on the record carrier 1, that is, a focus control signal. The signals of the combining circuits 25 and 26 are input to the differential amplifier 31, and the differential amplifier 31 outputs a difference signal between the signal of the combining circuit 25 and the signal of the combining circuit 26. As will be described later in detail, the differential amplifier 31 outputs a signal indicating the positional deviation between the light beam 7 focused on the record carrier 1 and the track, that is, a tracking control signal.

Focus control will be described. The signal of the differential amplifier 30 is composed of a divider 32, a gain switching circuit 33, a phase compensation circuit 34 for compensating the phase of the focus control system, a switch 35 for disabling the focus control, It is added to the focus element 17 via a drive circuit 36 for power amplification, and the focus element 17 is a differential amplifier 30.
The converging lens 12 is moved in a direction substantially perpendicular to the surface of the record carrier 1 in accordance with the signal of 1, and the light beam 7 on the record carrier 1 is controlled so as to be always in a constant converged state.

The tracking control will be described. The differential amplifier 31
The signal of is passed through a divider 37, a gain switching circuit 38, a phase compensation circuit 39 for compensating the phase of the tracking control system, a switch 40 for disabling tracking control, and a drive circuit 41 for power amplification. Are added to the tracking element 18, and the tracking element 18 moves the converging lens 12 in accordance with the signal from the differential amplifier 31.
By moving the light beam 7 on the record carrier 1 so that it is always on the track. In addition, the drive circuit 41
Is a drive circuit 4 for driving the linear motor 20.
2 is input to the linear motor 20 and the linear motor 20
The transfer table 19 is moved so that the output of the above is zero on average, in other words, the converging lens 12 moved by the tracking element 18 moves around the natural state.

If focus control and tracking control do not operate stably, high-quality recording and reproduction cannot be performed. In order to stably operate the focus control and tracking control, it is extremely important that the loop gain of the control system does not change. The dividers 32 and 37 and the gain switching circuits 33 and 38 are provided for this purpose.
These operations will be described below.

The synthesizing circuit 29 outputs a signal obtained by adding the four outputs of the photodetector 16 as described above, and this signal is input to the dividers 32 and 37 via the gain switching circuit 43. Divider 32, the output of the differential amplifier 30 X _1, the output of the gain switcher 43 outputs a signal corresponding to the value of When Y X ₁ / Y, divider 37 as well, the difference amplifier X ₂ output of 31
Then, the signal corresponding to the value of X ₂ / Y is output.

The signals of the processing circuit 5 are gain switching circuits 33, 38 and 43.
To the gain switching circuits 33 and 38, respectively.
And 43 switch the amplification factor according to the signal of the processing circuit 5. For example, the amplification factors of the gain switching circuits 33, 38 and 43 with the first record carrier loaded are G _1a , G _2a ,
G _3a, and the gains of the gain switching circuits 33, 38, and 43 loaded with the second record carrier are G _1b , G _2b , and G.
_{If 3b} , G _1b / G _1a = G _3b / G _3a = K (K is a positive real number) substantially holds, and as will be described later in detail, G _2b / G _2a <K.

The operation of preventing the focus control loop gain change will be further described.

Assuming that the reflectance of the first record carrier is K _R and the reflectance of the second record carrier is K _W and K _R / K _W = K, the output of the synthesizing circuit 29 when the first record carrier is loaded is When the second record carrier is loaded, the respective gains are K times, but since the amplification factor of the gain switching circuit 43 is 1 / K times, the output of the gain switching circuit 43 does not change. On the other hand, the output of the differential amplifier 30 with respect to the unit focus shift when the first record carrier is loaded is K times that when the second record carrier is loaded. Further, the output of the gain switching circuit 43 when the first record carrier is loaded is the same as that when the second record carrier is loaded. Therefore, the output of the divider 30 with respect to the unit defocus when the first record carrier is loaded is K times that when the second record carrier is loaded. However, since the amplification factor of the gain switching circuit 33 when the first record carrier is loaded is 1 / K of that when the second record carrier is loaded, the output of the gain switching circuit 33 changes with respect to the unit focus deviation. do not do. Therefore, although the first record carrier and the second record carrier have different reflectances, the focus control loop gain does not change.

As described above, the loop gain of the focus control does not change regardless of whether the first record carrier is loaded or the second record carrier is loaded. This is because it can be switched between the case of loading and the case of loading the second record carrier.

The operations of the divider 32 and the gain switching circuit 43 will be described.

There are various factors that change the loop gain of the focus control. For example, variations in the reflectance of the same type of record carrier 1 and the light beam 7 generated from the light source 6 are used.
Changes in the amount of light, the temperature characteristics of the photodetector 16, the reduction of the transmission efficiency of the light beam 7 due to dust, dust, and the like. All of these effects appear as changes in the output of the combining circuit 29. When the output of the combining circuit 29 becomes K _i times, the output of the differential amplifier 30 for the unit focus shift also becomes K _i times. As a matter of course, since the output of the gain switching circuit 43 also becomes K _i times, the output of the divider 32 with respect to the unit focus deviation is always constant, and the loop gain of the focus control does not change due to the above-mentioned factors.

In order to keep the loop gain of the focus control constant, unlike the embodiment of the present invention, the gain is not switched between the first record carrier and the second record carrier. For example, the gain switching circuit 33 is omitted, and the combining circuit 29 is used. It may be configured such that the signal of the above is input to the divider 32, but when configured in this way, the divider 32
And the divider 32 becomes expensive.

Explaining this further, for example, variations in the reflectance of the same type of record carrier 1, changes in the light amount of the light beam 7 generated from the light source 6, changes in the temperature of the photodetector 16, light beams caused by dust, dust, etc. The rate at which the output of the synthesizing circuit 29 changes due to a decrease in the transmission efficiency of 7, that is, the value of V _max / V _min when the minimum value of the output of the synthesizing circuit 29 is V _min and the maximum value V _max is four times, If the value of K is set to 5 times, the division range is required to be 20 times, but according to the embodiment of the present invention, the division range is 4 times and can be configured by a simple divider. .

The operation for preventing the loop gain change in tracking control will be described below.

_Letting K _{1T be} the output of the differential amplifier 31 with respect to a unit track deviation when the first record carrier is loaded and K _2T when the second record carrier is loaded, the value of K _1T / K _2T is K. Does not mean This will be described in detail later, but the detection sensitivity of the focus control signal is independent of the type of record carrier.
Although proportional to the reflectance of the record carrier, even if the reflectance of the first record carrier is K times the reflectance of the second record carrier, the detection sensitivity of the tracking control signal does not become K times. The value of K _1T / K _2T is K _c , the gain of the gain switching circuit 38 with the first record carrier loaded is G _2a , and the gain with the second record carrier loaded is G _2b. Then G _2b
It is configured such that / G _2a = K _c holds approximately.

The output of the differential amplifier 31 with respect to the unit track deviation when the first record carrier is loaded is K _c times that when it is loaded with the second record carrier. As described above, the output of the gain switching circuit 43 does not change when the first record carrier is loaded and when the second record carrier is loaded, so that the unit track deviation when the first record carrier is loaded Divider 37 against
Output is K _c times that when loaded with the second record carrier. However, since the amplification factor of the gain switching circuit 38 when the first record carrier is loaded is 1 / K _c of that when the second record carrier is loaded, the output of the gain switching circuit 38 with respect to the unit track deviation. Does not change. Therefore, although the detection sensitivity of the tracking control signal is different between the first record carrier and the second record carrier, the loop gain of tracking control does not change.

As a factor that changes the loop gain of the tracking control, a factor that changes the loop gain of the focus control described above can be considered. When the output of the synthesizing circuit 29 becomes K _i times due to these factors, the output of the differential amplifier 31 for the unit track deviation also becomes K _i times. Gain switching circuit 4
Since the output of 3 also becomes K _i times, the output of the divider 37 with respect to the unit track deviation is always constant, and the loop gain of tracking control is kept constant. It is needless to say that the divider 37 used for tracking control in the embodiment of the present invention can narrow the division range similarly to the divider 32 used for focus control described above.

Embodiments of the present invention include dividers 32 and 37 when loading a second record carrier having a recording material layer to record signals.
The division range of is narrowed. This will be described below.

When the light amount of the light beam 7 generated from the light source 6 is strongly modulated according to the signal to be recorded while the focus control and the tracking control are operating, the portion of the record carrier 1 irradiated with the strong light beam 7 Is physically changed by the heat of the light beam 7 and a signal is recorded. Light beam for recording 7
The amount of light is different depending on the location of the record carrier 1, but is about 7 to 10 times the amount of light of the light beam 7 during reproduction.

A recording period signal, that is, a signal representing a period during which the light amount of the light beam 7 is modulated in order to record the signal on the record carrier 1, is input to the input end 44. The signal at the input end 44 is transmitted to the gain switching circuits 33, 38 and 43, respectively, and when the recording period signal is input to the input end 44, the amplification factor of the gain switching 33, 38 and 43 is reduced to 1 / N. Is configured. N is a positive real number, the average light amount of the light beam 7 during recording is P _REC , and the light beam 7 during reproduction is
The light amount of P _PB is set so that N = P _REC / P _PB holds substantially.

_{Taking the} case of P _REC = N × P _PB as an example, the output of the synthesizing circuit 29 at the time of recording is N times that at the time of reproducing, but the amplification factor of the gain switching circuit 43 becomes 1 / N at the time of recording. Therefore, the output of the gain switching circuit 43 does not change between recording and reproducing. The output of the differential amplifier 30 with respect to the unit focus deviation during recording is N times that during reproduction. Since the output of the gain switching circuit 43 does not change between recording and reproduction,
The output of the divider 32 with respect to the unit focus deviation at the time of recording is also N times, but the amplification factor of the gain switching circuit 33 at the time of recording.
Since it is 1 / N, the output of the gain switching circuit 33 with respect to the unit focus deviation during recording does not change between recording and reproduction, and the loop gain of focus control is kept constant.

The light amount of the light beam 7 at the time of recording differs depending on the location of the record carrier 1, and is generally weak on the inner circumference of the record carrier 1 and strong on the outer circumference thereof. The change in the loop gain of the focus control system due to the change in the recording light amount depending on the position of the record carrier 1 is absorbed by the divider 32 and kept constant as described above.

The operation of the focus control circuit at the time of recording has been described above, but the operation of the tracking control circuit will be omitted because it can be easily understood from the above description.

FIG. 2 is an explanatory view of the first record carrier 1 having no recording material layer.

In FIG. 2A, a shaded area 51 indicates an area where a signal is recorded in the form of unevenness. FIG. 2B is an enlarged view of the area indicated by the broken line 52 in FIG. 1A, in which 53 is a pit having an uneven shape, and 54 is a track in which the pits 53 are arranged. FIG. 13C is a sectional view taken along the chain line 55 shown in FIG. 9B, where 56 is a base material, 57 is a metal layer such as aluminum, and 58 is a protective layer. 59 shows the depth of the pits 53, when the depth d ₁ of the pit _{53 d 1 = λ / (8} ×
n ₁ ). Where λ is the wavelength of the light beam 7, n ₁
Is the refractive index of the substrate 56.

FIG. 3 is an explanatory diagram of the second record carrier 1 having a recording material layer.

In FIG. 3D, the shaded area is an area where groove tracks are recorded in the form of depressions and projections, and is composed of a tracking track portion 61 and an address portion 62. FIG. 3E is an enlarged view of the area indicated by the broken line 63 in FIG. 3D, in which the track 64 is a groove-shaped tracking track 65 and the pits 6 having an uneven shape.
It is composed of 6. The tracks 64 are concentrically formed, and the pits 66 include address information for identifying the tracking tracks 65. Of course, the address information portion is only one minute of the track 64. 3F is a cross-sectional view taken along the alternate long and short dash line 67 shown in FIG. 3E, in which 68 is a base material, 69 is a recording material layer, and 70 is a protective layer. 71 is a pit 66 and a tracking track 65
Indicates the depth, when the depth and _{d 2, d 2 = λ /} (8 ·
n ₂ ).

However, n ₂ is the refractive index of the base material 68. Needless to say, the signal is recorded on the tracking track 65.

The detection of the focus control signal and the tracking control signal will be described with reference to FIG. FIG. 4 shows the photodetector 16
It is the figure which showed the beam spot shape of the upper reflected light 13. The photodetector 16 includes 16a, 16b, 16c and 16
d has four light receiving regions, and the light receiving regions 16a, 16b,
The signals of 16c and 16d are the lines 21 and 2 of FIG.
It is output through 2, 23, and 24. 13a, 13
b and 13c show the beam spot shape of the reflected light 13, the beam spot 13a has a regular distance between the record carrier 1 and the converging lens 12, and the converging point of the light beam 7 is on the record carrier 1. It shows a certain state. The beam spot 13b shows the reflected light 13 when the distance between the record carrier 1 and the converging lens 12 is too large, and the beam spot 13c shows the reflected light 13 when the distance between the record carrier 1 and the convergent lens 12 is too close. Shows. When the signals corresponding to the change in shape of the reflected light 13, that is, the outputs of the light receiving regions 16a, 16b, 16c, 16d are S ₁ , S ₂ , S ₃ , S ₄ , the differential amplifier 30 defines {(S ₁ + S ₃ )-(S ₂ + S ₄ )} corresponding signal is output. As a matter of course, when the focus control is operating, the reflected light 13 is reflected by the beam spot 13a.
It looks like.

The direction 81 indicates the track direction, that is, the longitudinal direction of the track. The differential amplifier 31 outputs a signal corresponding to {(S ₁ + S ₂ ) − (S ₃ + S ₄ )}. It is well known that the differential amplifier 31 outputs a signal representing the positional deviation between the light beam 7 focused on the record carrier 1 and the track, and it will not be described in detail.

The reflectance of the first record carrier is K of the reflectance of the second record carrier.
It will be described with reference to FIG. 5 that the detection sensitivity of the tracking control signal does not become K times, even if it is twice.

FIG. 5 shows S _T {(S ₁ + S ₂ ) − (S ₃ + S ₄ )} when the light beam 7 on the record carrier 1 crosses one track by folding the first record carrier 1. It is a representation. Note that the x-axis is the track deviation amount, y
The axis is shown as S _T. Pit 53 shown in FIG.
Only when the light beam 7 is scanning above, a signal (waveform 91) corresponding to the positional deviation between the light beam 7 on the record carrier 1 and the track 54 is output, and the light beam 7 scans between pits. It is not output when But pit 5
Since the length of 3 and the length between pits are very short, the light beam 7 on the record carrier 1 can scan over the track 54 when the tracking control is activated. For example, the response of tracking control is about 10 KHz, and the signal recorded on the record carrier 1 is several MHz. Therefore, in reality, the tracking control signal has a waveform 92 as if the waveform 91 was passed through a low pass filter, and the detection sensitivity of the tracking control signal is lowered.

Since the record carrier of FIG. 3 is a continuous track except the address part, the detection sensitivity does not decrease.

Therefore outputs K _1T of the differential amplifier 31 to a unit track shift when loaded with a first recording carrier, the value of it K _2T to the K _1T / K _2T when loaded with the second record carrier K However, K _1T <K × K _2T .

The present invention has been described in detail above, but the present invention is not limited to the above-described embodiments.

For example, the discrimination of the record carrier may be performed by detecting the difference in reflectance of the record carrier. More specifically, the size of the output of the combining circuit 29 can be used for the determination.

Also, various optical systems for detecting the focus control signal and the tracking control signal have been announced,
There is no problem with the present invention in any optical system.

EFFECTS OF THE INVENTION If the present invention is applied, the loop gain becomes constant because the circuit gain of the reflected light amount and the circuit gain of the focus control are switched at almost the same ratio during recording and during reproduction so that the loop gain becomes constant. Can be recorded and the signal can be reproduced with high reliability.

Further, since the loaded record carrier is discriminated and the focus control gain is switched according to the record carrier so that the loop gain becomes substantially constant, the focus control is extremely stable and the focus control circuit is simplified. Moreover, the price can be reduced, and the effect is extremely large.

[Brief description of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is an illustration of a first record carrier having no recording material layer, and FIG. 3 is an illustration of a second record carrier having a recording material layer. FIG. 4 shows the beam spot shape of the reflected light on the photodetector, and FIG. 5 shows the tracking control signal when the first record carrier is loaded. 1 ... record carrier, 3 ... jacket, 4 ... discriminator, 5
...... Processing circuit, 16 ...... Photodetector, 17 ...... Focus element, 27,28,29 ...... Combining circuit, 30 ...... Differential amplifier, 32 ...... Divider, 33 ...... Gain switching circuit, 34
...... Phase compensation circuit, 35 …… Switch, 36 …… Drive circuit.

Claims (3)

[Claims] 1. A device for loading different types of record carriers having different reflectances, the device comprising: a converging means for converging and irradiating a light beam generated from a light source onto the record carrier; and the converging means with respect to a record carrier surface. And a moving means for moving in a substantially vertical direction, and a focus shift of the light beam on the record carrier is detected from the reflected beam reflected by the record carrier, and the moving means is driven based on the focus shift signal to perform recording. Focus control means for controlling the converged state of the light beam on the carrier to be always in a predetermined state, and discrimination means for discriminating the type of the record carrier loaded in the apparatus are provided. The focus control device is characterized in that the circuit gain of the focus control means is switched. 2. The focus control means is provided with a light amount detecting means for detecting the light amount of the reflected beam reflected by the record carrier, and the circuit gain is changed in inverse proportion to the magnitude of the signal of the light amount detecting means. 2. The focus control device according to claim 1, wherein the circuit gains of the light amount detection means and the focus control means are switched at substantially the same ratio according to the signal of the discrimination means. 3. Converging means for converging and irradiating a light beam generated from a light source onto a record carrier, moving means for moving the converging means in a direction substantially perpendicular to the surface of the record carrier, and reflection by the record carrier. A light amount detecting means for detecting the light amount of the reflected beam, and a focus shift of the light beam on the record carrier from the reflected beam reflected by the record carrier are detected, and the moving means is driven based on the focus shift signal. Focus control means for changing the circuit gain in inverse proportion to the magnitude of the signal of the light amount detection means in order to control the converged state of the light beam on the record carrier to be always in a predetermined state. A focus control device characterized in that the circuit gains of the light amount detection means and the focus control means are switched at substantially the same ratio during the reproduction and during reproduction.