JPH0546616B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention records information on an optical information recording medium, reproduces the information recorded on the medium, and/or reproduces the information recorded on the medium. The present invention relates to an optical information recording/reproducing device capable of erasing information. Such an information recording/reproducing apparatus is suitably applied, for example, as an information recording/reproducing apparatus using a card-shaped information recording medium in which a plurality of linear information tracks are arranged in parallel.

[Prior Art] Conventionally, the media used to record information using light and read out the recorded information have been disc-shaped,
Various types such as card-shaped, tape-shaped, etc. are known. Among these, optical information recording media formed in the shape of a card (hereinafter referred to as "optical card") are:
It is expected to be in great demand as a medium with a large storage capacity that is small, lightweight, and convenient to carry.

FIG. 4 is a schematic plan view of such an optical card 101, in which 102 is an information recording area, 103 is an information track, 104 and 104' are track selection areas, and 105 is a home position of a light beam spot.

Information is recorded on the optical card as an optically detectable recording bit string (information track) by scanning with a light beam that is modulated according to the recorded information and focused on a minute spot. On this occasion,
In order to accurately record information without causing problems such as crossing of information tracks, it is necessary to control the irradiation position of the light beam spot in the direction perpendicular to the scanning direction within the surface of the optical card (hereinafter referred to as auto tracking). (referred to as "AT"). In addition, in order to irradiate the light beam as a stable minute spot despite the bending and mechanical errors of the optical card, it is necessary to control the light beam in a direction perpendicular to the optical card surface (auto focusing, hereinafter referred to as "AF"). There is. Also, the above AT and AF are required during playback.

FIG. 5 shows a configuration diagram of a device for recording and reproducing information on an optical card, in which 106 is a motor for driving the optical card 101 in the direction of the arrow in the figure, and 107 is a light source such as a semiconductor laser. , 108 is a collimator lens, 109 is a beam splitter,
110 is an objective lens, 111 is a tracking coil, 112 is a focusing coil, 113
114 is a condenser lens, 115 and 116 are photoelectric conversion elements, 117 is a tracking control circuit, 1
18 is a focusing control circuit. The objective lens 110 is moved by passing current through the tracking coil 111 and the focusing coil 112 in response to commands from the control circuits 117 and 118 based on tracking signals and focusing signals detected by the photoelectric conversion elements 115 and 116. Perform AT and AF. Further, 119 is a system controller that controls the recording/reproducing device, and 120 is a group of various control signals output from the controller. Note that signals other than 120 are also output from the controller 119, but are not shown here. Reference numeral 121 indicates an optical head, and reference numeral 122 indicates a drive motor for moving the optical head in the u direction in FIG.

FIG. 6 is a detailed diagram of the tracking control circuit 117. In this figure, 201 is an amplifier that amplifies the electrical tracking signal from the photoelectric conversion element 115 to an appropriate voltage, and 202 is a phase compensation circuit for stabilizing tracking servo control. Reference numeral 203 designates an analog switch, to one input terminal of which a signal is input from the output of the amplifier 201 from the phase compensation circuit 202 via point B, and to the other input terminal a ground potential is input via point C. A driver 204 receives a signal from the analog switch 203 and causes a drive signal current to flow through the tracking coil 111. 205 is the system controller 11
This is a tracking controller that receives a signal 120 from 9 and controls the entire tracking control circuit 117. In addition, in FIG. 6, signals are shown to be inputted from the tracking controller only to the analog switch 203. but,
The tracking controller 205 also outputs other signals (not shown).

FIG. 7 shows A of the phase compensation circuit 202 in FIG.
This shows the frequency characteristics of the gain from point to point B. As shown in Figure 7, in order to increase the gain in the low frequency region, from DC to _L , for example,
It is a constant value of 20dB, and -20dB/from _L to _H.
It decreases by dec, and is 0dB above _H. here,
_L and _H are usually several Hz to several tens of Hz.

Next, a method of recording and reproducing information will be explained with reference to FIGS. 4, 5, and 6. Initially, the light beam spot is at home position 105. next,
The light beam spot moves in the direction u in the figure in the track selection area 104, finds the track N to be recorded or reproduced, operates AT and AF there, scans the track N in the r direction, and records or reproduces the track. . When the light beam spot enters the track selection area 104', a large current is momentarily passed through the tracking coil 111 shown in FIG. 5, thereby causing the light beam spot to be directed to the track (N+1). Therefore, the direction is changed to the l direction and track (N+1) is scanned and recorded or reproduced.
Then, depending on the amount of information, the scanning of the information track 103 by the light beam spot and the kicking operation of the light beam spot in the track selection areas 104, 104' are repeated several times in the same manner.

Here, we will explain the operation of operating the AT servo system to perform AT retraction and auto-tracking to a target track.

First, a signal from the tracking controller 205 causes the analog switch 203 to open the point B side and close the point C side.

8A and 8B are time charts showing the voltage at point A and the voltage at point B in FIG. 6, respectively. When the light beam spot is moved in the u direction in Fig. 4,
The light beam spots traverse the information track 103 one after another. At this time, the voltage changes at points A and B become as shown in Figure 8, and when the light beam spot is applied to a part other than the information track (hereinafter referred to as "solid part"), points A and B are The voltage of is 0V, and when the light beam spot is applied to the track, A
The voltages at point and point B change in an S-time pattern (so-called S-curve). Note that the frequency of the S-curve portion is normally set to a higher value than _H. This is because the moving speed of the light beam spot is increased in order to complete access to the information track in a short time. The times when the center of the light beam spot is on the track center are t _3S1 and t _3S2 . AT pull-in time
If it is performed outside of t ₃₁ and t ₃₂ , the servo system will receive positive feedback and the objective lens 110 will swing greatly in the u direction, so generally a detection circuit (not shown) will set the voltage of the S-curve to 0V. This is done by detecting the point in time and sending a signal from the tracking controller 205 to the analog switch 203 to open the point C side and close the point B side.This closes the tracking servo system, and the AT
Retraction is complete.

[Problems to be solved by the invention] However, in reality, as shown in FIG. 8 above, the voltage of the solid portion is rarely 0V;
The voltages at point A and point B become as shown in FIGS. 9 and 10. That is, for example, manufacturing errors in each part of the optical head 121 and non-parallelism between the optical head and the surface of the optical card (an optical card inherently has some degree of warpage, and there is also warpage due to deformation due to pressure during installation). Therefore, depending on the position of the light beam spot in the u direction, the voltage at point A becomes v _A2 and v _A3 even in a solid area, as shown in FIGS. 9A and 10A.
It will look like this.

Since the gain from point A to point B has a frequency characteristic as shown in Figure 7, in the case of the voltage at point A as shown in Figure 9 A, the voltage at point B has a portion corresponding to the solid area. It is amplified with a low frequency gain of 20 dB to become 10 V _A2 , and the S-curve portion corresponding to the information track is amplified with a high frequency gain of 0 dB and becomes 10 V _A2 . Note that the signs are reversed at point A and point B, as in the case of FIG. 1st
Similarly, in the case of the voltage at point A as shown in Figure A, the voltage at point B is such that the part corresponding to the solid area is 10v _A3 , and the part corresponding to the information track is amplified by 0dB and superimposed on the 10v _A3 . becomes. Therefore, the above 8th
As explained in relation to the figure, when AT is pulled in at the time points t _4S1 , t _4S2 , t _5S1 , t _5S2 when the voltage at point A becomes 0V, as shown in Figures 9B and 10B, the AT pull-in occurs. At this point, the voltage at point B is not 0V,
v _4C and v _5C . As a result, the voltages v _4C and v _5C are input to the driver 204 at the moment the servo is closed, and as a result, a large current flows through the coil 111, causing the objective lens 110 to swing significantly in the u direction.
to a different track that is significantly different from the desired track.
AT may become blurred, or in the worst case, vignetting of the optical system may occur, reducing the amount of light reaching the photoelectric conversion elements 115 and 116, resulting in both AT and AF becoming out of alignment.

As described above, in the conditions shown in FIGS. 9 and 10, it is difficult to accurately and quickly access the target information track, and it is difficult to access the target information track again by slowing down the moving speed of the light beam spot. There was a problem that it took a considerable amount of time to access the site. Furthermore, in order to always obtain the state shown in Fig. 8, it is necessary to manufacture the optical head, the optical card, and the mounting means for the optical card with high precision, which is said to be a factor in increasing costs. There was a problem.

[Means for Solving the Problems] According to the present invention, in order to solve the problems of the prior art as described above, one of the plurality of tracks arranged in parallel on an optical information recording medium is an optical system that performs at least one of recording and reproduction by irradiating a beam spot; a tracking drive means that moves the light beam spot in a direction across a track; a detection means that detects a tracking signal; an amplifier for amplifying a tracking signal, a servo circuit for performing tracking servo by inputting the output of the amplifier to the tracking drive means, a switch for opening and closing the servo circuit, and a switch for opening and closing the servo circuit; An optical information recording and reproducing apparatus comprising: a controller that controls the switch to access a desired track with a light beam spot while monitoring a tracking signal, and close the servo circuit at the timing when the tracking signal becomes zero; An optical information recording and reproducing device, characterized in that it is provided with a gain control means that lowers the gain of the amplifier at the time when the servo circuit is closed during access, and increases the gain of the amplifier after a predetermined time after closing the servo circuit, is provided.

[Example] Hereinafter, specific examples of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a tracking control circuit section of an optical card recording/reproducing apparatus which is an optical information recording/reproducing apparatus according to the present invention, and shows the same portion as FIG. 6 above. Incidentally, in this figure, members having the same functions as in FIGS. 5 and 6 are given the same reference numerals, and explanations thereof will be omitted here.

In FIG. 1, 17 represents a tracking control circuit, and 5 represents a tracking controller.
Moreover, 3 is an analog switch, and this switch is for controlling the short circuit of both ends of the capacitor|condenser C1. The tracking controller 5 receives a signal 120 from the system controller.
In response to this, signals are output for controlling the states of analog switches 3 and 203, respectively.

In this embodiment, the frequency characteristics of the gain from point A to point B are as shown in FIG. That is, when the analog switch 3 is open, as shown in a of FIG. 2, the characteristics are the same as those of FIG. 6 (FIG. 7), and when the analog switch 3 is closed, As shown in Figure 2b, it is 0 dB over all frequencies.

Next, the AT pull-in operation of this embodiment will be explained.

First, a signal from the tracking controller 5 causes the analog switch 203 to open the point B side and close the point C side, while the analog switch 3 closes and closes the capacitor C.
Both ends of 1 are shorted.

Next, the light beam spot is moved in the u direction in FIG. As a result, voltages as shown in FIG. 3A and B appear at points A and B, respectively. That is, when the analog switch 3 is closed, the frequency characteristic of the gain from point A to point B becomes as shown by b in Fig. 2, so the voltage at point A of the solid part voltage V _A0 as shown in Fig. 3 A is As shown in FIG. 3B, a voltage at point B appears with only the sign reversed.

Therefore, the points t _S1 and t _S2 at which the voltage at point A becomes 0 are detected, and the tracking controller 5 sends a signal to the analog switch 203 to open the point C side and close the B point side. This closes the tracking servo system. At this point, the voltage at point B is always 0V
Therefore, the voltage input to the driver 204 is
0V, so no current flows through the coil 111. As a result, when retracting AT, objective lens 1
10 is not swayed greatly and the desired track can be accessed well.

After that, it takes time for AT to stabilize (usually several ms to several tens of ms).
ms), the tracking controller 5 sends a signal to the analog switch 3, which opens the switch and opens both ends of the capacitor C1.
As a result, the frequency characteristic of the gain from point A to point B becomes as shown in a of FIG. 2, and tracking servo is performed with the normal gain characteristic enhanced in the low frequency region.

In the above embodiment, an example is shown in which the frequency characteristics of the gain are changed during and after the AT is pulled in, but in the present invention, it is not necessarily necessary to change the frequency characteristics of the gain.
It is also possible to use a gain obtained by lowering the characteristic shown by a in FIG. 2 by a certain percentage (for example, 1/2) as a whole at the time of AT pull-in, and to obtain a gain as shown in a in FIG. 2 after AT pull-in. According to this, although the voltage at point A at the time of AT pull-in does not become 0V, it can be made sufficiently low, so that substantially good AT pull-in is possible.

[Effects of the Invention] According to the present invention as described above, the servo circuit is closed at the timing when the tracking signal becomes zero, and the AT
Lower the servo gain when retracting and AT
By increasing the servo gain after pulling in,
It is possible to perform AT retraction without increasing the precision of the optical head, the optical information recording medium, and the means for mounting the medium, thus achieving high precision and speed of access at low cost, and reliability. improvement is realized.

[Brief explanation of the drawing]

1 and 6 are configuration diagrams of a tracking control circuit of an optical card recording/reproducing device. FIGS. 2 and 7 are graphs showing frequency characteristics of AT servo gain. Figures 3, 8, 9 and 10
The figure is a time chart of signals at points A and B. FIG. 4 is a plan view of the optical card. FIG. 5 is a block diagram of the optical card recording/reproducing device. 3,203...Analog switch, 5,205
...Tracking controller, 17,117...
...tracking control circuit, 118 ... focusing control circuit, 119 ... system controller, 201 ... amplifier, 202 ... phase compensation circuit, 204 ... driver.

Claims (1)

[Claims] 1. An optical system that performs at least one of recording and reproduction by irradiating a light beam spot onto one of a plurality of tracks arranged in parallel on an optical information recording medium; a tracking drive means for moving in the direction;
a detection means for detecting a tracking signal, an amplifier for amplifying the detected tracking signal, a servo circuit for performing tracking servo by inputting the output of the amplifier to the tracking drive means, and opening/closing of the servo circuit. a controller that controls the switch so that the optical beam spot accesses a desired track while monitoring a tracking signal with the servo circuit open, and closes the servo circuit at the timing when the tracking signal becomes zero. In the optical information recording/reproducing device, the gain control means lowers the gain of the amplifier at the time when the servo circuit is closed during the track access, and increases the gain of the amplifier after a predetermined time after closing the servo circuit. An optical information recording/reproducing device characterized by: