JP2654045B2 - Information recording and playback method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical recording medium on which information is recorded by irradiating a light beam and in which the information thus recorded can be optically reproduced. Recording and reproducing method.

[Prior Art] In recent years, commercialization and research of optical information recording / reproducing devices such as an electronic file system using a compact disk or a write-once disk, or an optical disk system using an erasable magneto-optical material or a phase change material have been conducted. Development is active. Furthermore,
As a new type of optical information recording medium, a card type (a size called a wallet size) has appeared. This card (hereinafter referred to as an optical card) is characterized in that it can be easily carried in its form and has a large information capacity (2 MByte or more) for its area, and its commercialization is expected.

[Problems to be Solved by the Invention] The present invention solves the problem of reproduction light deterioration (optical change of the medium's reflectivity and the like due to information reproduction light) occurring in an optically recordable / reproducible (green reusable) medium. It was devised to do so.

Usually, the optical recording medium is irradiated with light energy necessary for forming a hole due to a change in reflectance and melting, and information is recorded. Information reproduction from the optical recording medium is performed by tracing the information recording section with light energy that does not change the optical recording medium, and photoelectrically detecting a change in the amount of reflected or transmitted light. For this reason, the optical recording medium is required to have clear threshold characteristics as shown by the solid line in FIG. However, a general dye-based recording medium having a high durability especially against temperature and humidity does not satisfy this requirement as shown by the broken line in FIG. FIG. 4 shows a characteristic curve of the optical recording medium. The horizontal axis represents irradiation energy, and the vertical axis represents a change in reflectance or the degree of hole formation. That is, in a recording medium having characteristics as indicated by a broken line, the irradiation light energy at the time of reproducing information must be extremely small.

The limitation is that the amount of light incident on the photodetector that detects a change in the amount of light is extremely small, and the error signal for auto-focusing (hereinafter referred to as AF signal), the error signal for auto-tracking (hereinafter referred to as AT signal), and the information reproduction signal This means that detection becomes difficult.

In the case of an optical disc, generally, the loop pull-in of AF and AT, the selection (access) of an information track, etc. are performed on an information medium,
That is, the operation is performed while the disk is rotating. Therefore, the light energy of the portion where the medium is effectively irradiated is reduced (because the light energy density of the irradiated part is smaller than that in the stationary state when the medium is moving even when the medium is irradiated with the same amount of light). Therefore, in the optical disk system, the light irradiation amount of the medium can be increased, and as a result, the light amount incident on the photodetector can be obtained as required. That is, in the optical disc, the problem of the reproduction light deterioration is solved or deteriorated by the rotation of the recording medium, and the balance between the deterioration and the quality of the detection signal (S / N ratio) is closed.

However, in the case of an optical recording medium in the form of a card,
If the optical card is stationary while the pull-in and access operations of the AF and the AT are performed, the reliability of the device is improved. Hereinafter, an optical card and an optical card recording / reproducing apparatus will be described to help understand the explanation of the reason.

One example of an optical card is shown in FIGS. FIG. 5 is a plan view of the optical card. The optical card 200 is provided with a recording area 201, and this area is coated with an optical recording medium by coating or vapor deposition means. Further, the tracking track 202 is preformatted with irregularities or a reflectance different from the surrounding reflectance. Note that another preformat signal (for example, a track number clock signal) is provided as needed. The size of the optical card is typically about 85.6 mm x 54 mm.

FIG. 6 is an example of a sectional configuration of the optical card 200. The recording medium 204 is coated on the preformat side of the transparent substrate 203 on which the preformat pattern is provided with irregularities. Further, the adhesive 205 is used to protect the recording medium.
The support substrate 206 is adhered via. The light is collected by the lens 33, and the optical card 200 is transmitted from the transparent substrate 203 side.
To create a spot of several μm on the recording medium 204 surface.
Re-record information.

FIG. 7 shows an example of the configuration of an optical head used for recording and reproducing information on the optical card 200. The light is converted into a parallel light by the light condenser lens 28 emitted from the semiconductor laser 27 or the like. The cross-sectional shape of the light beam at this time has an elliptical distribution when a semiconductor laser is used as a light source. For this reason, a circular cross section is formed by utilizing the refraction effect of the prism 29.
The light beam is split into three light beams of 0th order and ± 1st order by the grating 30, and after passing through the beam splitter 31, the direction is changed by the prism mirror 32. It is collected. Optical card 2
The light beam reflected at 00 passes through the objective lens 33 and the prism mirror 32 again, and is separated from the incident light beam by the beam splitter 31. The reflected light flux passes through, for example, an anamorphic optical system including a circular lens 34 and a cylindrical lens 35 and enters a photodetector 36. In this optical head, the AF signal is obtained by a well-known astigmatism method (Japanese Patent Publication No. 57-12188).
The AT signal can be obtained according to the following principle.

As shown in FIG. 8, the three divided light beams 37, 38, and 39 are condensed by an objective lens, and at least three different pre-formatted tracking tracks 202 and at least three of them having a size of several μm are interposed therebetween. A spot is formed. The tracking tracks 202 are parallel to each other, so that the photodetectors 36b and 36c detect the information of the spots 37 and 38.
The difference of the electric signal from FIG. 7 is the AT signal. Normally, the spots 37 and 38 are 20% or less of the light amount of the spot 39.

The spot 39 condensed between the tracking tracks 202 plays a role in recording and reproducing information. Therefore, the information track exists at a part between the tracking tracks.

FIG. 9 shows an example of an optical card recording / reproducing apparatus. Optical card 20
0 is a card holder 41 called a shuttle from the insertion slot 40
To be loaded. The optical head shown in FIG. 7 is shown at 42, and moves in the direction perpendicular to the track of the card by driving the pulse motor 45 along guides 43 and 44. The shuttle 41 reciprocates in the AB direction via the belt 47 by the drive of the motor 46.

The example of the optical card and the recording / reproducing apparatus of the optical card has been schematically described above.

Next, the positions of the optical card and the optical head are shown in FIG. In the case of an optical card, when loading the card 200, first,
The optical head is on standby at the home position 48, and the AF control is first performed at that position. Next, the optical head is moved to the area where the tracking track exists by the pulse motor, and the AT signal control is performed. The reason why the AF pull-in is not performed in the area where the track exists is that the track information does not affect the AF signal and the AF control is reliably performed. Next, move the optical head to the desired track position.
The optical head is moved to 50, that is, the optical head is moved along the chain line in FIG. 10 (the chain line indicates the head of the information section of each track). After that, for the first time, the optical card is reciprocated to record and reproduce information. Thus, in the optical card recording / reproducing operation, there is a state where the card is stationary. For this reason, the influence of reproduction deterioration is an important problem in the case of an optical card system. In this specification, the state in which the recording medium is stationary includes a low-speed movement that substantially causes a problem of deterioration of the reproduction light.

The state at the time of AF pull-in will be described with reference to FIG. Twelfth
The figure shows the AF error signal during pull-in. The objective lens 33 is moved in a direction perpendicular to the card by moving means called an actuator. Now, when the lens approaches the card from a position far from the card, the AF error signal becomes S-shaped near the surface of the optical card, and then becomes S-shaped near the surface of the recording medium.
It becomes letter-shaped. Point B in FIG. 12 indicates focus on the card surface, and point A indicates focus on the recording medium surface. Since the AF control needs to be performed in the vicinity of the point A, it is necessary to distinguish the S character on the card surface from the S character on the medium surface. This distinction is made based on whether or not the level of the error signal is equal to or higher than V _O , as shown by the dashed line in FIG. Usually, the reflectance on the surface of the card is 5% or less, and the reflectance on the recording medium surface is 10% or more. However, when the reflectance of the medium changes due to the reproduction light deterioration and the amount of light entering the photodetector decreases,
An error signal as shown by a dotted line is generated, and it becomes impossible to distinguish between the card surface and the medium surface, so that the AF pull-in cannot be performed.

Furthermore, it is A
After the F and AT have been pulled in, this is the waiting time until a track selection is performed and an information recording / reproduction command is received.

In the time until this command comes, the characteristics of the medium change and the amount of reflected light decreases, so that the servo gain decreases. Because of this,
It becomes weak to external vibrations, etc., and the AF is likely to come off. In the example shown in FIG. 7, since the tracking spot has a smaller light amount ratio than the AF spot, the AF control loop is affected first during this waiting time.

One solution to the problem of reproduction light degradation is to lower the output of the semiconductor laser.However, taking into account the stable oscillation of the semiconductor laser, the light amount on the medium surface should be 0.1 mW or more. Since the amount of reflection and the amount of reflected light themselves change, a decrease in servo gain cannot be avoided, and it is difficult to realize.

FIG. 11 shows the state of reproduction light deterioration of the dye-based recording medium by a solid line. The dyes shown in FIG. 11 are polymethine dyes, but the same applies to cyanine dyes. Eleventh
In the figure, the horizontal axis represents time, and the vertical axis represents changes in the amount of light received by the photodetector. The measured conditions were as follows: the card was stationary,
The spot diameter is φ3 μm, and the light amount is 0.2 mW. Further, it has been experimentally confirmed that this characteristic change changes with the integration of the illumination time even if the light blinks intermittently.

[Means for Solving the Problems] As described above, measures for preventing the reproduction light from deteriorating are indispensable for putting the optical card system into practical use.

The present applicant has already proposed in Japanese Patent Application No. 62-25975 a method for solving this problem of reproduction light deterioration in an AF control loop.

An object of the present invention is to provide a method for solving the above-mentioned problem of reproduction light deterioration in an AT control loop (AT irradiation spot).

According to the present invention, in order to achieve the above object, while irradiating a light spot on an optical information recording medium while performing auto tracking, execution of relative movement of the light spot and the recording medium in the track direction and An information recording / reproducing method for recording / reproducing information on / from the recording medium while performing the stop, wherein the light spot is moved in a tracking direction with respect to the recording medium when the relative movement is stopped. And an information recording / reproducing method.

For example, according to one embodiment of the present invention (see FIG. 3),
The photodetector divided into a plurality of portions (in a so-called push-pull method, which is often used, the light receiving portion of the photodetector is 2
Photodetectors 14a and 14b divided into two
), A switch is provided in the detection circuit, and when the recording medium is at rest, the switch can be turned off alternately at 19a and 19b to move the objective lens in the AT direction, thereby recording. The position of the irradiation spot on the medium surface can be changed. As a result, the problem of reproduction light deterioration can be solved.

[Operation] If the light energy density of the light spot does not change by frequently moving the position of the light spot that irradiates the recording medium surface as described above, for example, light irradiation to one location on the recording medium surface When the time becomes 1/4, the amount of deterioration of the reproduction light becomes 1/4
Thus, the problem of reproduction light deterioration can be largely solved, and according to this method, the total amount of light incident on the photodetector does not decrease, so that the gain of the servo loop does not change.

In fact, when the light irradiation time to one place on the recording medium surface was reduced to 1/4, a great improvement was observed as shown by the broken line in FIG.

[Examples] Hereinafter, the recording / reproducing method of the present invention will be described in detail based on specific examples.

FIG. 1 is a signal processing block diagram of an optical card recording / reproducing apparatus to which the recording / reproducing method of the present invention can be applied, and FIG. 2 shows an example of a control flowchart thereof.

In FIG. 1, 1 is an optical card, 2 is a photocoupler for determining whether the optical card is at a predetermined position,
Is a pulse generator which receives a signal from the photocoupler 2 and sends a pulse signal to the system controller 4; 4 is a system controller for controlling the entire optical recording / reproducing apparatus; 5 is an optical head as shown in FIG. 7; An actuator for driving the head in a focus direction and a tracking direction; a photodetector for receiving reflected light from the optical card to obtain an AF signal and an AT signal; and an actuator for detecting an AF signal and an AT signal based on a signal from the photodetector. , A head feed mechanism, 10 a head feed driver, 11 a card feed mechanism, and 12 a card feed driver.

FIG. 3 is a diagram schematically showing the photodetector 7 and the servo circuit 8 shown in FIG.

In FIG. 3, reference numeral 13 denotes an AF photodetector having a four-divided light receiving surface by an astigmatism method, 15 denotes an AF differential amplifier that obtains an autofocus error signal by taking a difference between the light receiving surfaces, 16 denotes an amplifier, 23 Is a voltage circuit for applying the voltage V1 to the amplifiers 16 and 18, 21 is a phase compensation circuit, 22 is an actuator driver, and 6 is an actuator. 14 is 14a, 14b
AT photodetector consisting of two light receiving surfaces:
AT differential amplifier that obtains an auto-tracking error signal by taking the difference between the outputs of a and 14b, 18 is an amplifier, and 19a and 19b are light-receiving surfaces 14a,
A switch for opening or shorting a signal line from 14b to the AT differential amplifier 17.

Next, the operation of the apparatus of FIG. 1 and the recording / reproducing method of the present invention will be described with reference to the flowchart of FIG.

First, the outline of the operation will be described based on the flowchart of FIG. First, the optical card 1 is loaded into the device (step S1 in FIG. 2), and the AF is performed (step S1).
S2). To prevent the reflection characteristics of the recording medium from deteriorating due to the light spot on the card when AF is pulled in, switch
19a and 19b are turned ON and OFF alternately (step S3). afterwards,
Move to seek operation (step S4). At this time, switch
After turning on 19, it may shift to seek operation (step
S3 '). When the optical head comes to a predetermined position for recording or reproduction (step S5), a recording or reproduction operation is normally performed (step S6). When performing the operation of step S3 ', the switches 19a and 19b are alternately turned on and off, and then the process proceeds to step S5 (step S4').

Next, the operation will be described in detail with reference to FIG. 1 and FIG.

In FIG. 1, the loading of the card 1 is detected by, for example, a photocoupler 2 and its output is sent to a pulse generator 3 (binarization circuit), and a pulse signal of loading completion is sent to a system controller 4.

In response to this, the system controller sends a signal for moving the actuator 6 of the optical head 5 to the servo circuit 8 to perform the AF operation.
A pull-in operation is performed. The third showing the outline of the servo circuit
In the figure, the output from each detection element (light receiving surface) 13a, 13b, 13c, 13d of the photodetector 13 is the difference between the output of 13a and the output of 13d, the output of 13b and the output of 13c, Input to the dynamic amplifier 15. From the differential amplifier 15, an output signal (a so-called S-shaped curve) of (13a + 13d)-(13b + 13c) is obtained at a predetermined amplification factor.

This signal is further amplified by the next amplifier 16 at a predetermined amplification factor.

In FIG. 3, the S-curve signal thus obtained is differentiated so that servo control can be performed at a potential of 0 so that the light spot is focused on the recording medium surface.

Next, in order to control the tracking direction, control is performed so that the difference between the outputs from the two light receiving surfaces 14a and 14b of the AT photodetector 14 becomes the potential 0. Normally, when the irradiation spots 37 and 38 are on the track as shown in FIG.
Servo control is performed so that (14a-14b) becomes zero even when there is no track at all.

When the recording medium is stationary, the switches 19a and 19b are turned ON and OFF alternately. Normally, a certain amount of force is applied when performing servo control in the AT direction of the actuator,
When the switch is turned off, the balance is lost and the light receiving surface 14
The objective lens is moved in the AT direction so that the difference between 14a and 14b becomes zero. And further switches 19a and 19b
In order to turn ON and OFF alternately, the objective lens vibrates in the AT direction. Therefore, the light from the light source stays at a fixed position on the recording medium for a short time.

The output from the amplifier 18 is processed by the phase compensation circuit 21 and the actuator driver circuit 22 and applied to the actuator 6. After that, a command from the system controller 4 is sent to the head feed driver to select a track, and when the optical head 5 moves, the optical head 5 is moved as it is or once the switch 19 is turned on and moved in a normal state. The former is a so-called open-loop head seek mode, and the latter is a seek mode in which the number of track crossings is counted.
When the track selection is completed, the switch 19 is turned ON when recording or reproducing information, because the spot is continuously reversed in the AT direction. At the same time, the system controller 4 sends a signal to the card feed driver to reciprocate, and performs recording or reproduction by modulating or emitting a constant light amount of the semiconductor laser.

With the above operation, it is possible to solve the problem of the reproduction light deterioration in the stationary state of the light spot in the standby state after the AF pull-in and until the recording / reproduction.

The present invention is not limited to the above embodiment, and various modifications and applications are possible.

In the above embodiment, the light spot is moved in the tracking direction with respect to the recording medium by alternately supplying the outputs of the two light receiving surfaces that take the difference to the actuator. A second signal composed of a first signal obtained by performing a process of periodically increasing or decreasing the output of one of the two light receiving surfaces in the tracking direction movement and the other output of the two light receiving surfaces. By taking the difference with the signal of

FIG. 13 is a diagram schematically showing a servo circuit having such a configuration. In the figure, when the recording medium is stationary, it is connected to the x terminal side by the switch 19C. Then, the output from the light receiving surface 14a is input to the AT differential amplifier 17 through an amplifier or a water reducer 70 to which an oscillator 71 is added, so that the output of the amplifier 17 changes periodically. Thereby, the light spot on the recording medium can be periodically moved in the AT direction.

Also, regardless of the embodiment shown in FIG. 13, appropriate processing is performed on the output of each light receiving surface, and the output signal obtained by inputting the processed signal to the AT differential amplifier 17 periodically changes. It is obvious that the present invention can be constituted regardless of the method.

Until now, the description has been made on the assumption that the push-pull method having a two-divided light receiving surface is adopted as the tracking method. However, the change is captured by a pair of diagonal lines of the four-divided light receiving surface, and the phase difference is detected. It is apparent that the idea of the present invention can be similarly applied to the case where the heterodyne method for performing the above is adopted.

Further, in the above-described embodiment, the description has been given of the case where the reproduction light deterioration reduces the amount of reflected light. However, in the case of a multilayer structure including a dye layer and a metal layer, the reproduction light deterioration phenomenon increases the light amount. In this case, there is no disadvantage that it is difficult to distinguish from the surface, but there is a problem in that the servo gain changes. Therefore, this method is also effective in this case.

As described above, reproduction light deterioration is a particular problem when an optical card-shaped recording medium is used. However, the same applies to a reciprocating recording medium such as an optical tape. It is apparent that the technical idea of the present invention can be applied even when a recording medium having a high intensity is used.

[Effects of the Invention] As described above, according to the recording / reproducing method of the present invention, the recording / reproducing method of the present invention is currently used by the device of operating the optical head without using means such as improvement of the recording medium. The problem of reproduction light deterioration can be solved with an optical recording medium, and the practical advantage is extremely large. Further, by performing the method of the present invention, the problem of reproduction light deterioration has been solved, and it has become possible to make the optical card system function in a desired sequence.

[Brief description of the drawings]

FIG. 1 is a signal processing block diagram of an example of the recording / reproducing method of the present invention. FIG. 2 is an example of a flowchart of the apparatus shown in FIG. FIG. 3 is a diagram schematically showing a servo circuit. FIG. 4 is a sensitivity characteristic curve of the recording medium. FIG. 5 is a plan view of the optical card. FIG. 6 is a sectional view of the optical card. FIG. 7 shows an example of the optical head. FIG. 8 is a diagram for explaining the function of the light spot on the card surface. FIG. 9 shows an example of an optical card recording / reproducing apparatus. FIG. 10 is a diagram for explaining a desirable sequence of the optical card system. FIG. 11 shows the characteristics of reproduction light deterioration. FIG. 12 is a view showing the influence of the AF pull-in when there is reproduction light deterioration. FIG. 13 is a diagram schematically showing a servo circuit according to another embodiment of the present invention. 1: optical card, 2: photo coupler, 3: pulse generator, 4:
System controller, 5: Optical head, 6: Actuator, 7: Optical detector, 8: Servo circuit, 9: Optical head feed mechanism,
10: Head feed driver, 11: Optical card feed mechanism, 12:
Card feed driver, 13: AF photodetector, 14a, 14b: AT
Detector, 15: AF differential amplifier, 16: AF amplifier, 17, 18:
AT amplifier, 19a, 19b, 19c: switch, 20: switch switching processor, 21 phase compensation circuit, 22: actuator driver, 23: voltage circuit, 70: amplifier or attenuator, 71:
Oscillator.

Claims (4)

(57) [Claims] 1. A method for irradiating a light spot onto an optical information recording medium while performing auto-tracking, and performing and stopping relative movement of the light spot and the recording medium in a direction along a track. An information recording / reproducing method for recording / reproducing information on / from a recording medium, wherein, when the relative movement is stopped, the light spot is vibrated relative to the recording medium in a direction perpendicular to a track. Recording and playback method. 2. The auto-tracking device according to claim 1, wherein light from the light spot on the recording medium is detected by a photodetector having two light receiving surfaces, and a tracking actuator is detected based on a difference between outputs from the two light receiving surfaces. The information recording / reproducing method according to claim 1, wherein the method is performed by driving. 3. The information recording / reproducing method according to claim 2, wherein the vibration of the light spot is performed by alternately supplying outputs of the two light receiving surfaces to the actuator. 4. The method according to claim 1, wherein the vibration of the light spot is a first signal obtained by performing a process of periodically increasing or decreasing the output of one of the two light receiving surfaces and a signal of the two light receiving surfaces. 3. The information recording / reproducing method according to claim 2, wherein the method is performed by taking a difference from a second signal composed of the other output.