JPS60246027A - Focus controller - Google Patents

Abstract

PURPOSE:To attain the stable focus control by discriminating a recording carrier set into a focus controller and switching the gain of a focus control system so as to secure the stable focusing state for the light beam on the recording carrier in response to the discriminating signal. CONSTITUTION:A discoid recording carrier 1 is attached to the rotary shaft of a disk motor 2 and revolved in a prescribed number of revolutions. A jacket 3 covers the carrier 1 for protection. A discriminator 4 consists of a light emitting diode and a photodetecting diode. The type of the carrier 1 is discriminated by detecting the form or the reflection factor of the jacket 3. A processing circuit 6 supplies the output of the discriminator 4 and delivers the signal corresponding to the type of the carrier 1. A synthesizing circuit 29 delivers the signal obtained by adding four outputs of a photodetector 16 and supplies it to dividers 32 and 37 via a gain switching circuit 43. The signal of a circuit 5 is supplied to gain switching circuits 33, 38 and 43, and these switching circuits change the amplification factor in response to the signal of the circuit 5. In such a way, the stable focus control is secured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention converges and irradiates a light beam generated from a light source onto a record carrier to reproduce a signal recorded on the record carrier or reproduce a signal recorded on the record carrier. The present invention relates to an optical recording/reproducing device for recording, and in particular, to focus control for controlling the convergence state of a light beam irradiated onto a record carrier to a predetermined state in an optical recording/reproducing device. .

Conventional structure and problems The record carriers used in optical recording and reproducing devices are mainly two types.
It can be roughly divided into One is a record carrier with a recording material layer and the other is a record carrier without recording material N. The former is one in which a recording material layer is formed by means such as vapor deposition on the surface of a base material having uneven groove tracks, and a protective layer is provided on the surface of the recording material layer. However, it is very difficult to reproduce large quantities of the record carrier on which the signal is recorded.
Duplication has the disadvantage that the cost of the record carrier becomes high. In the latter, signals are recorded in the form of concave and convex shapes, and although it is not possible to record new signals on this type of record carrier, it is very easy to copy by means such as injection molding, and recording It has the advantage that the cost of the carrier is low.

There are various types of information, but information used in personal computers and the like can be broadly classified into two types. That is, one is information that is commonly used for all devices, and the other is information that is not common to all devices and is recorded by the person using the device as needed. The former requires a large amount of the same material, so a record carrier without a recording material layer that can be easily duplicated is suitable, and the latter requires a record carrier that can record signals. It must be a record carrier with a layer of material.

However, the two types of record carriers mentioned above are loaded into the same device to record signals or not to record signals because the reflectance of the record carrier surface is significantly different or the shape of the track tracked by the light beam is different. It was not possible to reproduce the signal that was present.

OBJECTS OF THE INVENTION The object of the present invention is to eliminate the drawbacks of the above-mentioned conventional devices and to provide a device which can be loaded with two types of record carriers as mentioned above, i.e. when a record carrier with a layer of recording material is loaded, the signal cannot be transmitted. It is an object of the present invention to provide a device which is capable of recording or reproducing recorded signals, and which is also capable of reproducing signals when a record carrier without a recording material layer is loaded.

Structure of the Invention The present invention provides discrimination means for distinguishing between a first record carrier having no recording material layer and a second record carrier having a recording material layer, and performs gloss control in accordance with a signal from the discrimination means. This system is configured to switch the loop gain of the system to ensure stable focus control.

Description of examples The present invention will be described in detail below with reference to the drawings.

Note that the same numbers are used to describe the same parts in the drawings.

FIG. 1 shows one embodiment of the invention.

A disk-shaped record carrier 1 having concentric tracks is attached to a rotating shaft of a disk motor 2 and rotated at a predetermined number of rotations. The record carrier 1 is covered with a jack 3 to protect it from dirt, dust, and the like.

A discriminator 4 for discriminating the record carrier 1 is composed of a light emitting diode and a light receiving element. The shell 3 has different shapes depending on the type of record carrier 1 9. When the jacket 3 containing the record carrier 1 is loaded, a light beam generated from the light emitting diode of the discriminator 4 is directed through the jacket 3. The light beam may not be irradiated onto the light-receiving element due to the shielding, or the light beam generated by the light-emitting diode may not be shielded and may be irradiated onto the light-receiving element. A signal from the light receiving element of the discriminator 4 is input to the processing circuit 5.
outputs a signal depending on the type of record carrier 1.

To explain the optical system, a light beam 7 generated by a light source 6 such as a semiconductor laser is made into approximately parallel light by a coupling lens 8, and a polarizing beam sinter 9 and a λ/4 plate 10 (λ is the light beam 7 wavelength), is reflected by the reflecting mirror 11, and is focused and irradiated onto the record carrier 1 by the converging lens 12. The light beam 70 reflected by the record carrier 1 passes through the converging lens 12 again, is reflected by the reflecting mirror 11, passes through the λ/4 plate 1o,
It is reflected by the polarizing beam splitter 9, and the convex lens 1
4 and a cylindrical/vertical lens 15, and is irradiated onto a 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 a current is applied to the focusing element 17, the converging lens 12 moves in a direction substantially perpendicular to the surface of the recording carrier 1 due to electromagnetic force.
When a current is applied to the tracking element 18, the converging lens 12 is moved by electromagnetic force in a direction substantially perpendicular to the track direction on the record carrier 1, that is, in a radial direction of the record carrier 1.

Light source 6. Coupling lens 8. Polarizing beam splitter 9, λ/4 plate 10. Anti-falsification 11. Focus element 17
．． Tracking element 18. The convex lens 14, the cylindrical lens 16, and the photodetector 6 are attached to a transfer stage 19, and are configured to move together in the radial direction of the record carrier 1 when the linear motor 2o is driven.

Detection of control signals will be explained. The respective signals of the photodetectors 16 are output through lines 21, 22, 23 and 24. The combining circuits 26, 26, 27, 28 and 29 are circuits that increase the input signals, and the input terminal of the combining circuit 26 has lines 21 and 22, and the input terminal of the combining circuit 26 has lines 23 and 22. Lines 21 and 23 are connected to the input end of the combining circuit 27, lines 22 and 24 are connected to the input end of the combining circuit 28, and lines 21, 22, 23 and 24 are connected to the input end of the combining circuit 29, respectively. It's because of that. 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 in detail later, the differential amplifier 3° outputs a signal representing the convergence state of the original 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 26 and the signal of the combining circuit 26.

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, ie, a tracking control signal, which will be described in detail later.

Regarding focus control, the signal from the differential amplifier 30 is sent to the divider 32. Gain switching circuit 33. Phase compensation circuit 34 for compensating the phase of the focus control system. Switch 36 to disable focus control. The power is applied to the focus element 17 via a drive circuit 36 for power amplification, and the focus element 17 is connected to a differential amplifier 3o.
The converging lens 12 is moved in a direction substantially perpendicular to the surface of the record carrier 1 in response to the signal, and the light beam 7 on the record carrier 1 is controlled to always be in a constant convergence state.

To explain the tracking control, the differential amplifier 31
The signal is sent to the divider 37. Gain switching circuit 38. Phase compensation circuit for compensating the phase of the tracking control system 9. Switch 40 for disabling tracking control. The tracking element 18 is connected to the tracking element 18 via a drive circuit 41 for power amplification, and the tracking element 18 moves the converging lens 12 in the radial direction of the record carrier 1 according to the signal from the differential amplifier 31. The upper light beam 7 is controlled so that it is always on the track. Further, the signal of the drive circuit 41 is transmitted to the drive circuit 42 which drives the near motor 20.
The linear motor 20 moves the transfer stage so that the output of the drive circuit 41 becomes zero on average, in other words, so that the converging lens 12 moved by the tracking element 18 moves around its natural state. Move 19.

Unless focus control and tracking control operate stably, high-quality recording and reproduction cannot be performed. In order to operate focus control and tracking control stably, it is extremely important to prevent the loop gain of the control system from changing. The divider 32.37 and the gain switching circuit 33.38 are of this type,
These operations will be explained below.

As described above, the combining circuit 29 outputs a signal obtained by adding the four outputs of the photodetector 16, and this signal is input to the dividers 32 and 37 via the gain switching circuit 43.

The divider 32 outputs a signal corresponding to the value x1/Y, where the output of the differential amplifier 30 is Xl and the output of the gain switching circuit 43 is Y. Similarly, the divider 32 outputs a signal corresponding to the value x1/Y. Letting the output of 31 be x2, it outputs a signal corresponding to the value of x2//Y.

The signal of the processing circuit 5 is transmitted to the gain switching circuits 33, 38 and 4.
3, respectively, and the gain switching circuit 33.3
8 and 43 switch the amplification factor according to the signal from the processing circuit 6. For example, the amplification factors of the gain switching circuits 33, 38 and 43 when the first record carrier is loaded are set to Gla,
G2a and G3a, and the amplification factors of the gain switching circuits 33, 38 and 43 when the second record carrier is loaded are G.
1 b l ci2b.

If G3b, then G1b/G1a-G3b/G3a-K (K is a positive real number)
As will be explained in detail later, G2b/G2a<K is established.

The operation of preventing loop gain change in focus control will be further explained.

If the reflectance of the first record carrier is KR2 and the reflectance of the second record carrier is Kw, Kn/KW=, then the output of the combining circuit 29 when the first record carrier is loaded is the second nine Although it is twice that when a carrier is loaded, the gain switching circuit 4
Since the amplification factor of 3 is doubled to 1/, the gain switching circuit 43
The output of does not change. On the other hand, the output of the differential amplifier 3o for a unit focus shift when the first record carrier is loaded is twice that when the second record carrier is loaded. The output of the gain switching circuit 43 when the shredded first record carrier is loaded is the same as the output when the second record carrier is loaded. Therefore, the output of the divider 3o for a unit focus shift when the first record carrier is loaded is twice 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 for a unit focus shift changes. Quiet. Therefore, although the first record carrier and the second record carrier have different reflectances, the loop gain of the focus control does not change.

As explained above, the reason why the focus control loop gain does not change whether the first record carrier is loaded or the second record carrier is loaded is that the amplification factor of the gain switching circuit 33 This is because switching is possible between when the recording carrier is loaded and when the second record carrier is loaded.

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

There are various factors that change the loop gain of focus control.
These include fluctuations in the reflectance of the light beam, changes in the light intensity of the light beam 7 emitted from the light source 6, temperature characteristics of the photodetector 16, or a decrease in the transmission efficiency of the light beam 7 due to dirt, dust, etc. appears as a change in the output of the combining circuit 29. When the output of the combining circuit 29 increases by 1, the output of the differential amplifier 30 for a unit focus shift also increases by Ki times. Naturally, the output of the gain switching circuit 43 Since both are multiplied by 9, the output of the divider 32 for a unit focus shift is always constant9, and the loop gain of focus control does not change due to the above-mentioned factors.

In order to keep the loop gain of 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 is used. However, it may be configured such that the signal of 29 is being input to the divider 32.

If configured in this way, the division range of the divider 32 will be widened, making the divider 32 expensive.

To explain this further, for example, variations in the reflectance of the same type of record carrier 1, changes in the light intensity of the light beam 7 generated from the light source 6, changes in the temperature of the photodetector 16, or light beams due to dirt, dust, etc. The rate at which the output of the combining circuit 29 changes due to a decrease in the transfer efficiency of No. 7, etc., that is, the minimum value of the output of the combining circuit 29 is v, and the maximum value of No. 4 is vm.
If the value of Vtmax/vmio when aX and mzn+ is 4 times, and the above-mentioned value of K is 5 times, then the division range needs to be 20 times, but according to the embodiment of the present invention, the division range is 4 times. It can be configured with a simple divider.

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

If the output of the differential amplifier 31 for a unit track deviation when the first record carrier is loaded is 1T, and when the second record carrier is loaded is 2T, then K1T/2
The value of T is not equal to K. This will be explained in detail later, but the detection sensitivity of the focus control signal is proportional to the reflectance of the record carrier, regardless of the type of record carrier.
Even if the reflectance of the first record carrier is twice that of the second record carrier, the detection sensitivity of the tracking control signal is not doubled. K is the value of 2T in K1T/. , if the amplification factor of the gain switching circuit 38 in the state where the first record carrier is loaded is G2a and that in the state where the second record carrier is loaded is "2b," then G2ゎ/G2a=Kc is approximately It is structured in such a way that it works.

The output of the differential amplifier 31 for a unit track deviation while loading the first record carrier is twice that when loading the second record carrier. As mentioned above, since 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, the unit track deviation when the first record carrier is loaded is divider 32 for
The output is close to 0 times that when the second record carrier is loaded. However, since the amplification factor of the gain switching circuit 38 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 38 for a unit track deviation is It does not change. Therefore, although the detection sensitivity of the tracking control signal differs between the first record carrier and the second record carrier, the loop gain of the tracking control does not change.

Possible factors that change the loop gain of tracking control include the aforementioned factors that change the loop gain of focus control. When the output of the combining circuit 29 increases by a factor of Ki due to these factors, the output of the differential amplifier 31 for a unit track deviation also increases by a factor of 0. Since the output of the gain switching circuit 43 is also multiplied by 0, the output of the divider 37 for a unit trunk shift is always constant, and the loop gain of tracking control is kept constant. Incidentally, in the embodiment of the present invention, the divider 37 used for tracking control is the same as the divider 3 used for focus control described above.
As with 2, it is no secret that the division range can be narrowed.

Embodiments of the invention provide that the dividers 32 and 37
is configured so that the division range of is narrowed. This will be explained below.

When the light intensity of the original beam 7 generated from the light source 6 is modulated to be strong or weak according to the signal to be recorded while the focus control and tracking control are operating, the portion of the record carrier 1 that is irradiated with the strong light beam 7 is is physically changed by the heat of the light beam 7, and a signal is recorded. Light beam 7 during recording
Although the amount of light differs depending on the location on the record carrier 1, it 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 intensity of the light beam 7 is modulated in order to record a signal on the record carrier 1 is inputted to the input terminal 44 . The signal at the input terminal 44 is transmitted to the gain switching circuits 33, 38, and 43, respectively, and when the recording period signal is input to the input terminal 44, the amplification factors of the gain switching circuits 33, 38, and 43 are reduced to 1/N. is configured to do so. N is a positive real number, and if the average light intensity of the light beam 7 during recording is PREC, and the light intensity of the light beam 7 during playback is ``PB'', then ``T=PREC/
It is set so that PPB substantially holds true.

P HB; (2=iJ Since it becomes 1A, the gain switching circuit 43
The output does not change between recording and playback. The output of the differential amplifier 3o for a unit focus shift during recording is N times that during reproduction. Since the output of the gain switching circuit 43 does not change during recording and playback, the output of the divider 32 for a unit focus shift during recording is also multiplied by N, but the amplification factor of the gain switching circuit 33 during recording is 1/N. Therefore, the gain switching circuit 33 for unit focus shift during recording
The output does not change between recording and playback, and the focus control loop gain is kept constant.

The light intensity of the light beam 7 during recording varies depending on the location on the record carrier 1, and is generally weaker at the inner circumference of the record carrier 1 and stronger at the outer circumference. Changes in the loop gain of the focus control system due to changes in the amount of recording light depending on the location of the record carrier 1 are absorbed by the divider 32 and kept constant as described above.

Although the operation of the focus control circuit during recording has been described, the operation of the tracking control circuit will be omitted since it can be easily understood from the above explanation.

FIG. 2 is an explanatory diagram of the first record carrier 1 without a recording material layer.

In FIG. 2A, a shaded area 51 indicates an area where signals are recorded in the form of unevenness. Figure B is an enlarged view of the area indicated by the broken line 62 in Figure A, where 53 is an uneven pit and 64 is a track on which pits 63 are lined up. Figure C is a sectional view taken along the dotted line shown in Figure B, where 66 is a base material, 67 is a metal layer such as aluminum, and 68 is a protective layer. 59 indicates the depth of the pit 63, and if the depth of the pit 63 is dl and 1-, then dl-
λ/(8×n1). However, λ is the wavelength of the light beam 70+n1 is the refractive index of the base material 56.

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

In the third diagram, the shaded area is an area where groove tracks are recorded in the form of unevenness, and is composed of a tracking trunk part 61 and an address part 62.

FIG. 3E is an enlarged view of the region indicated by the broken line in the figure, and the track 64 is composed of a groove-like tracking track 66 and a pit 66 in the form of unevenness. track 64
are formed in concentric circles, and the pits 66 contain address information for identifying the tracking track 66. As a matter of course, the address information portion occupies only a small portion of the track 64. FIG. 3F is a sectional view taken along the dashed 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. Reference numeral 71 indicates the depth of the pit 66 and the tracking track 66, and when the depth is d2, it is d2-λ/(8·n2).

However, n2 is the refractive index of the base material 68. Needless to say, the signal is recorded on the tracking track 66.

Detection of the focus control signal and the tracking control signal will be explained with reference to FIG. 4. Figure 4 shows the photodetector 16
It is a figure which shows the beam spot shape of the upper reflected light 13. The photodetector 16 is 16a.

It has four light receiving areas 16b, 16c, and 16d, and the signals of the light receiving areas 16a, 16b, 16c, and 16d correspond to lines 21, 22, 23, . and 24. 13a, 13b and 13C show the beam spot shapes of the reflected light 13;
3a shows a state in which the distance between the record carrier 1 and the converging lens 12 is normal, and the convergence point of the light beam 7 is on the record carrier 1. The beam spot 13b is the reflected light 13 when the distance between the record carrier 1 and the converging lens 12 is too far.
The beam spot 13C shows the reflected light 13 when the distance between the recording horse body 1 and the converging lens 12 is too close. The differential amplifier 30 generates a signal corresponding to the shape change of the reflected light 13, that is, the light receiving areas 16a, 16b,
The outputs of 16G and 16d are connected to Sl, S2. S3. If it is S4, a signal corresponding to ((S1,083)-(S2,084)) is output. Naturally, when the focus control is in operation, the reflected light 13 has a beam spot 13a.

Direction 81 indicates the track direction, that is, the longitudinal direction of the track. The differential amplifier 31 is ((S1+82)-(
Outputs a signal corresponding to S3,84)). It is readily known that the differential amplifier 31 outputs a signal representative of the positional deviation of the light beam 7 focused on the record carrier 1 and the track, and will not be described in detail.

It will be explained with reference to FIG. 5 that even if the reflectance of the first record carrier is twice that of the second record carrier, the detection sensitivity of the tracking control signal will not be doubled.

Figure 6 shows the state in which the first record carrier 1 is loaded and the light beam 7 of the record carrier 1'' crosses one trunk.
1+82)-(S3+84)).

Note that the X-axis represents the amount of track deviation, and the y-axis represents ST. Only when the light beam 7 is scanning the focus 53 shown in FIG. 2, a signal (waveform 91) corresponding to the positional deviation between the original beam 7 and the track 64 on the record carrier 1 is output, No output is made when the light beam 7 is scanning between the two. However, the length of the bits 53 and the length between the bits are so short that the light beam 7 of the record carrier 1'' can be scanned over the track 54 when the tracking control is activated.

For example, the responsiveness of the tracking control is about 10 KHz, and the signal recorded on the record carrier 1 is several ν5 Hz. Therefore, in reality, the tracking control signal becomes a waveform 92 that is obtained by passing the waveform 91 through a low-pass filter, and the detection sensitivity of the dragging control signal decreases.

Since the second record carrier has continuous tracks except for the address area, the detection sensitivity is not reduced.

Therefore, the output of the differential amplifier 31 for a unit track deviation when the first record carrier is loaded is 1T.

The value of 2T is not K, and the value of 2T is 2T when a record carrier of 2 is loaded.
becomes.

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

For example, the record carrier may be identified by detecting a difference in reflectance of the record carrier. More specifically, it can be determined by dl and the magnitude of the output of the combining circuit 29.

In addition, various optical systems for detecting focus control signals and tracking control signals have been announced.
Regarding the present invention, there is no problem with any optical system. ” Effects of the Invention By applying the present invention, the loaded record carrier is determined and the focus control gain is switched depending on the record carrier, so that the loop gain is kept approximately constant, so the focus control can be improved. In addition to being extremely stable, the on-ocus control circuit can be simplified and lowered in cost, and its effects are extremely large.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of a first record carrier without a recording material layer, and FIG. 3 is an explanatory diagram of a second record carrier with a recording material layer. , FIG. 4 shows the beam spot shape of the reflected light on the photodetector, and FIG. 6 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--Focusing element, 28.29--Synthesizing circuit, 30--Differential amplifier, 32--Divider, 33 gain switching circuit,
34... Phase compensation circuit, 36... Switch, 36... Drive circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 f −,111′ 2 , q8 f+ 1 71 1 ! 4 4ρ + // 1.3 ' 11ρ # 1 A1 ff /6 -ter- 2, 2,, 39 '' 2224 $ I'4 31 21 $ each 7 7 3/ Journey l Figure 2 Figure 3 2 6'J /2 f,?

Claims (3)

[Claims] (1) 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 approximately perpendicular to the surface of the record carrier; a convergence state detection means for detecting a convergence state of the light beam irradiated onto the carrier; and a convergence state detection means for driving the moving means in accordance with a signal from the convergence state detection means to detect the convergence state of the light beam on the record carrier. A focus control means for always controlling to a predetermined state, a discrimination means for discriminating the record carrier loaded in the apparatus, and a gain of the control system of the focus control means according to No. 3 of the discrimination means. 1. A focus control device comprising: gain switching means for switching. (2) The focus control device according to claim 1, wherein the discrimination means is configured to discriminate the record carrier by detecting the shape of a jacket protecting the record carrier. (3) The focus control device according to claim 1, wherein the discriminating means is configured to discriminate between record carriers by detecting a difference in reflectance of the record carriers.