JPS63244322A - Optical head controlling method - Google Patents

Abstract

PURPOSE:To prevent the generation of the deterioration of are produced light by driving an optical head as specifying time S to irradiate one spot of a recording medium. CONSTITUTION:When an irradiation time, during which the characteristic of the recording medium is changed by the light irradiation to the recording medium, and an AF control loop comes impossible to be drawn in the optical head because of the change of the quantity of light, incident to a photodetector, is assumed to be T, and the number of times that the said recording medium is expected to be used, is assumed as N, the optical head is driven so that the time S, for which one spot of the recording medium is irradiated, comes to be S<(T/N). In concrete terms, a system controller sends a timer ON signal to a timer circuit 9 at a drawing finish signal, and makes it count the prescribed time. when the count of the prescribed time is finished, a finish signal is sent to the system controller 4, and the system controller 4 sends the signal for driving the optical head 5 or a card to the respective drivers 10, 11. Thus, the AF can be surely drawn in without receiving the influence of the reproduced light deterioration.

Description

[Detailed Description of the Invention] [Fields of Application on Beams] The present invention is characterized in that information is recorded by irradiation with a light beam,
In addition, the recording and reproducing method of optical recording media that can optically reproduce the information recorded in this way %] In recent years, electronic file systems using compact discs and write-once discs, or erasable optical Commercialization and research and development of optical information recording and reproducing devices such as optical disk systems using magnetic materials and phase transition materials are active. Furthermore, a new optical information recording medium in the form of a card (of a size called wallet size) has appeared.

This card (hereinafter referred to as an optical card) is easy to carry due to its form, and has a large information capacity considering its area (2
MByte or larger), and its commercialization is expected.

[Problems to be Solved by the Invention] The present invention solves the problem of reproduction light deterioration (optical changes such as reflectance of the medium due to information reproduction light) that occurs in optically recordable and reproducible (recordable and reproducible) media. It was designed to do.

Normally, information is recorded on an optical recording medium by irradiating it with light energy necessary to change its reflectance and form holes through dissolution. To reproduce information from an optical recording medium, the information recording section is traced with light energy that does not change the optical recording medium.
This is done by photoelectrically detecting changes 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 Figure i4. However, general dye-based recording media, which have particularly high durability against temperature and humidity, do not meet this requirement, as shown by the broken line in Figure 4. Furthermore, Figure 4 shows the characteristic curve of optical recording media. The horizontal axis shows the irradiation energy, and the vertical axis shows the change in reflectance or the degree of hole formation.In other words, for a recording medium with the characteristics shown by the broken line, the irradiation light energy when reproducing information must be extremely small. .

This limitation means that the amount of light incident on the photodetector that detects changes in light amount becomes extremely small, resulting in an error signal for auto-focusing (hereinafter referred to as AF signal) and an error signal for auto-tracking (hereinafter referred to as AT multiplied signal).

This means that it becomes difficult to detect the information reproduction signal.

In the case of an optical disc, generally, AF, AT loop pull-in, information track selection (access), etc. are performed while the information medium, that is, the disc, is rotating. Therefore, the effective light energy of the area where the medium is irradiated decreases (even if the medium is irradiated with the same amount of light, the light energy density of the irradiated area is lower when the medium is moving than when it is stationary). In disk systems.

The amount of light irradiated onto the medium can be increased, and as a result, the amount of light incident on the photodetector can be as much as necessary. That is, in optical discs, the problem of reproduction light deterioration is solved by rotating the recording medium, or a balance is maintained between the deterioration and the quality W (S/N ratio) of the detection signal.

However, in the case of an optical recording medium in the form of a card, A
The reliability of the device is improved if the F, AT pull-in and access operations are performed with the optical card stationary. To help explain the reason for this, an optical card and a recording/reproducing device for the optical card will be described below.

An example of an optical card is shown in FIGS. 5 and 6. FIG. 5 is a plan view of the optical card. The optical card 20 is provided with a recording area 21, and this area is coated with an optical recording medium. It is coated by vapor deposition means, etc. Further, the tracking track 22 is preformatted with irregularities or with a reflectance different from that of the surrounding area. Note that other preformat signals (eg, track number clock signal, etc.) are provided as necessary. The standard size of an optical card is approximately 85.8 m layers x 54 layers.

FIG. 6 is an example of a cross-sectional configuration of the optical card 20. As shown in FIG. A recording medium 24 is coated on the preformat side of a transparent substrate 23 on which a preformat pattern is provided with unevenness. Furthermore, an adhesive 25 is added for the purpose of protecting the recording medium.
A support substrate 26 is attached via. The light is focused by the lens 33, enters the optical card 20 from the transparent substrate 23 side, creates a spot of several pm on the surface of the recording medium 24, and records and reproduces information.

FIG. 7 shows an example of the configuration of an optical head used for recording and reproducing information on the optical card 20. The light beam emitted from the semiconductor laser 27 or the like becomes a parallel light beam by the condenser m-lens 28. 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 purpose, the refraction effect of the prism 29 is utilized to form the cross section into a circular shape. The light beam is split into three beams of 0th and 11th order by a grating 30, passes through a beam splitter 31, changes direction by a prism mirror 32, and is focused onto an optical card 20 into a spot of several JLm by an objective lens 33. be illuminated. The light beam reflected by the optical card 20 passes through the objective lens 33 and the prism mirror 32 again, and the reflected light beam, which is separated from the incident light beam by the beam splitter 31, is separated from the incident light beam by the beam splitter 31. The light passes through the optical system and enters the photodetector 36.

In this optical head, the AF signal is obtained by the well-known astigmatism method (Japanese Patent Publication No. 57-12188). Further, the AT multiplication signal can be obtained using the following principle.

As shown in Fig. 8, the luminous flux is divided into three parts 37, 38, 39
is condensed by an objective lens, and spots of at least three colors m in size are formed between different preformatted tracking fist tracks 22-1 and 22-2. Tracking - Tracks 22-1, 22-2 are parallel to each other, so spot 37 and spot 3
Photodetectors 36b and 36c for detecting information No. 8 (Fig. 7)
The difference between the electric signals from the AT signal is 0. Normally, the spots 37 and 38 are 20% or less compared to the photo sulfur of the spot 39.

Note that the spot 39 that is focused between the tracking tracks 22 is responsible for recording and reproducing information, so the information track exists in a part between the tracking tracks.

FIG. 9 shows an example of an optical card recording/reproducing device. optical card 20
A card holding stand 41 called a shuttle is inserted from the insertion slot 40.
is loaded. The optical head shown in Fig. 7 is 42
, and is moved along guides 43, 44 in a direction perpendicular to the tracks of the card by the drive of a pulse motor 45. The shuttle 41 is driven by a motor 46 and reciprocates in the →AB direction via a belt 47.

An example of an optical card and a recording/playback device for the optical card has been briefly described above.

From the above explanation, it can be understood that the optical card basically moves back and forth to perform recording and playback. The biggest drawback resulting from this reciprocating motion is that vibrations are likely to occur when the motion is reflected.

Because of this vibration, there is a drawback that when the AT and AP control is pulled in, it is difficult to perform the pull-in operation if the card is moving. Furthermore, during track selection, ie, access operation, if the optical head is moved while the card is being moved, the access time becomes longer.

In order to suppress the vibration during reciprocating interlocking to a practical level, the moving speed must be at most several hundred μm/sec.
When the speed is high, the acceleration generated during deceleration and acceleration during reversal becomes large, and therefore vibration becomes large. In contrast, in the case of an optical disk, the disk travels smoothly due to its rotational motion, and the linear velocity is usually on the order of several m/secC.

Therefore, even if a track is selected by moving the optical head while rotating the disk, the beginning of the information track will be directly below the optical head in a short time. Therefore, in the case of an optical disk, the access time is dominated by the movement time of the head.

On the other hand, with an optical card, it takes time to bring the beginning of the information track directly below the optical head, resulting in a longer access time. Therefore, it is advantageous to select an information track while keeping the card in place.

FIG. 10 summarizes and explains the above.

In the case of an optical card, when the second card 20 is loaded, first, the optical head is waiting at the home position 48, and at that point, AF surface control is first performed. Move to the area where the truck is and perform AT sub control pull-in, A
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 ensures reliable AF.
In order to perform surface control, the optical radar is moved to a desired track position 50, that is, one point tl in FIG.
The optical head is moved along the J line (one point lK4 line indicates the beginning of the information section of each track). Thereafter, the optical card is reciprocated for the first time to record and reproduce information. In other words, during the recording and reproducing operation of the optical card, the card may be in a stationary state. Therefore, the influence of reproduction deterioration becomes an important problem in the case of optical card systems.

The state at the time of AF pull-in will be explained using FIG. 12. FIG. 12 shows the AF error signal at the time of pull-in. The objective lens 33 is moved perpendicularly to the card using a moving means called a 7-cut unit. When the lens approaches the card from a far position, the AF error signal becomes S-shaped near the surface of the optical card, and then , it becomes S-shaped near the surface of the recording medium. Point B in the tjS12 diagram indicates focus on the card surface, and point A indicates focus on the recording medium surface.Since AF surface control needs to be performed near point A, 5 points on the card surface
It is necessary to distinguish between the characters and the five characters on the surface of the medium. This distinction is made based on whether the C level of the error signal is greater than or equal to Vo as shown by the dashed line in Figure 12.0 Normally, the reflectance on the card surface is less than 5%, and the reflectance on the recording medium surface is 103 Because of the above, it is possible to differentiate using the above method. However, when the reflectance of the medium changes due to deterioration of the reproduction light and the amount of light entering the photodetector decreases, an error signal as shown by the dotted line is generated, making it impossible to distinguish between the card surface and the medium surface, and AF pull-in becomes impossible. .

FIG. 11 shows the state of reproduction light deterioration of dye-based recording media. The dye shown in FIG. 11 is a polymethine-based dye, but the same was true for cyanine-based dyes.

In FIG. 11, the horizontal axis represents time, and the vertical axis represents changes in the amount of light received by the photodetector. The measurement conditions were that the card was stationary, the spot diameter was φ37tm, and the light intensity was 0.2mW. Furthermore, this characteristic change shows that even if the light is flickered intermittently, the illumination time is t! It has also been experimentally confirmed that it changes with one calculation.

[Means for Solving the Problems] As described above, countermeasures against the deterioration of the reproduced light are essential in order to put the optical card system into practical use.

An object of the present invention is to provide a method for solving the above problem of reproduction light deterioration.

The object of the present invention is to provide a method for controlling an optical head in which a photodetector receives light from the surface of a recording medium and performs autofocusing (AF) control.

By irradiating the recording medium with light, the characteristics of the recording medium change and the amount of light incident on the photodetector changes, so that the AFi! An optical head control method characterized by the time S for irradiating one point on the recording medium, where T is the irradiation time at which the J control loop cannot be pulled in, and N is the expected number of times the recording medium will be used. This is achieved by

For example, if the present invention is applied to a certain optical recording material, the light spot will be at one point on the recording medium when the amount of reflected light decreases before it adversely affects the AF control loop, and the expected number of times the optical card will be used is N. The irradiation time S will be .

The optical head may be driven by moving the optical head, the optical recording medium, or both after the AF control is pulled in at the time S.

The method of the present invention will be specifically explained below.

When a dye-based recording medium is used with the configuration shown in Figure 6,
The reflectance on the surface of the recording medium is usually about 10% to 30%. In particular, the refractive index is 1.8 to 2. O1 absorption coefficient 0.8-1.0
Media film thickness 800A to 150A using polymethine dye
At 0A, the reflectance is 10% to 15%.

Further, there are conditions under which 25 to 30% of the cyanine-based Niff 1 dye can be obtained. If the reflectance of the medium when no light is irradiated is RO, and the reflectance on the card surface is R1, then AF
The rate of reflectance reduction allowed for control pull-in is R1/
Becomes an RO.

For example, when R1 = 5% and RO = 12%, the permissible rate of decrease in reflectance is approximately 42%, and with the characteristics shown in Figure 11, an irradiation time of approximately 5 hours is permitted. Normally, this permissible time is 0.5 time m
1 or more can be used for practical purposes.

Therefore, if the number of times the card is used is 5000, it is 3.6
A time S for irradiating one point on the second card is allowed. Generally, the number of uses is expected to be 3,000 to 10,000 times. That is, if the head is moved or the card is moved after 3.6 seconds, reliable AF pull-in is possible without being affected by reproduction light deterioration.

[Example] Hereinafter, a method for controlling an optical head of the present invention will be described in detail based on a specific example.

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

In FIG. 1, l is an optical card, 2 is a photocoupler for determining whether the optical card is in a predetermined position, and 3 is a pulse generator that receives a signal from the photocoupler 2 and sends a pulse signal to the system controller 4. 4 is a system controller that controls the entire optical recording and reproducing device, 5 is an optical head as shown in FIG. 8, 6 is an actuator that drives the optical head in the focusing direction and the tracking direction, and 7 is a reflection from the optical card. a photodetector for receiving light and obtaining an AF signal and an AT double signal; 8, a servo circuit for controlling the actuator 6 based on the signal from the photodetector; 9;
11 is an optical head feeding mechanism; 10 is a head feeding driver; 13 is a card feeding mechanism; and 12 is a card feeding driver.

Next, the operation of the apparatus shown in FIG. 1 and the method of controlling the optical head according to the present invention will be explained with reference to the flowchart shown in FIG.

First, an outline of the operation will be explained based on the flowchart shown in FIG.

When the optical card is loaded into the device (step 31 in Figure 2), the AF retraction operation is started (step S2), and when the retraction is completed (step S3), the timer is immediately turned on and the irradiation time is set. Start measuring (
Step S4) When a predetermined set time has elapsed (Step S5), the optical head or card is simultaneously moved (Step S6) to reduce the time at which the recording medium is irradiated to less than the irradiation time at which the aforementioned control loop cannot be drawn in. suppress.

Next, a method for controlling an optical head according to the present invention will be explained in detail based on FIG.

In FIG. 1, loading of the card I is detected by, for example, a photocoupler 2, its output is sent to a pulse generator (binarization circuit), and a pulse signal indicating the end of loading is sent to the system controller 4. In response to this, the system controller causes the servo circuit 8 to
Sends a signal to move the cutter 6. Light detection! An AF error signal is detected from I7, the control loop is closed by the function of the servo circuit 8, and at the same time a pull-in completion signal is sent to the system controller 4. With this signal, the system controller sends a timer ON signal to the timer circuit 9 to count a predetermined time (for example, 3.8 seconds as in the above example). When the measurement of the predetermined time is completed, a termination signal is sent to the system controller 4, and the system controller 4 sends a signal to drive the optical radar 5 or the card to the respective drivers 10 and 11.

With the above-described operation, AF pull-in can be performed without the influence of reproduction light deterioration, and after AF pull-in, tracking pull-in in the track area can be performed by moving the optical head, and a standby state for information recording/reproduction can be established.

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

In the above embodiments, reproduction light degradation refers to a decrease in the amount of reflected light, but in the case of a multilayer structure such as a dye layer and a metal layer,
The phenomenon of reproduction light deterioration results in an increase in the amount of light. In this case, there is no disadvantage that it becomes difficult to distinguish from the surface, but there is a problem in that the servo gain changes. Therefore, this method is effective in this case as well.

It is clear that the irradiation time T depends on the reproduction light deterioration characteristics of the recording medium, but it also depends on the ability of the control loop circuit of the optical head used (the ability to determine the amount of light necessary for AF control). It is clear that it will change depending on the

[Effects of the Invention 1] As explained above, according to the optical head control method of the present invention, the method of controlling the optical head of the present invention can be achieved by using the aesthetic ingenuity of operating the optical head without using any means such as improving the recording medium. It is possible to solve the problem of reproduction light deterioration in optical recording media, which has extremely great practical advantages.In addition, by implementing the method of the present invention, it is possible to solve the problem of reproduction light deterioration and improve optical card systems. It became possible to function in the desired sequence.

[Brief explanation of drawings]

FIG. 1 is a signal processing block diagram of an example of the optical head control method according to the present invention. FIG. 2 is an example of a flowchart of the apparatus shown in FIG. FIG. 3 is a signal processing block diagram of a device that provides further effects. 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 an optical head. FIG. 8 is a diagram illustrating the function of the light spot on the card surface. FIG. 9 shows an example of an optical card recording/reproducing device. FIG. 10 is a diagram illustrating a desirable sequence of the optical card system. The t511 diagram shows the characteristics of reproduction light deterioration. FIG. 12 is a diagram showing the influence of AF pull-in when there is reproduction light deterioration. l: Optical card 2: Photo coupler 3: Pulse generator 4 System controller 5: Optical head 6: Actuator tough: Photodetector 8: Servo circuit 9: Timer 10: Head feed driver ll: Card feed driver 12 :Host Computer Agent Patent Attorney Johei YamashitaFigure 1Figure 3Figure 4Figure 5Figure 6Figure 7Figure 8Figure 9Figure 10HayashiFigure 11 Irradiation timeFigure 12AF error episode 4 A lot

Claims (3)

[Claims] (1) A photodetector receives the light from the surface of the recording medium, and
A method of controlling an optical head that performs focusing (AF) control, wherein the characteristics of the recording medium are changed by irradiating the recording medium with light, and the amount of light incident on the photodetector is changed, so that the AF in the optical head is controlled. Let T be the irradiation time at which the control loop cannot be pulled in, and N be the number of times the recording medium is expected to be used, then set the time S for irradiating one point on the recording medium so that S<T/N. A method for controlling an optical head, the method comprising driving an optical head. (2) The method for controlling an optical head according to claim 1, wherein the driving of the optical head is to move the optical head or an optical recording medium, or both after AF control pull-in. . (3) The method for controlling an optical head according to claim 1, wherein an optical recording medium is used in which N is 3,000 to 10,000 times and T is 0.5 hours or more.