JPH0682468B2 - Optical information recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention records information on an optical information recording medium, reproduces the information recorded on the medium, and / or records the information on the medium. The present invention relates to an optical information recording / reproducing apparatus capable of erasing information, and more particularly to an autofocus and / or autotracking pull-in circuit.

[Prior Art] Conventionally, various types of media such as a disc, a card, and a tape are known as forms of a medium for recording information using light and reading the recorded information. Among these, a card-shaped optical information recording medium (hereinafter referred to as an "optical card") is expected to be in great demand as a medium having a large recording capacity that is small and lightweight and convenient to carry.

FIG. 4 is a schematic plan view of such an optical card 101.
02 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.

The optical card 101, by scanning with a light beam that is modulated according to the recording information and is focused on a minute spot,
Information is recorded as a record bit string (information track) so as to be optically detectable. At this time, in order to record information accurately without causing trouble such as crossing of information tracks, the irradiation position of the light beam spot is controlled in the direction perpendicular to the scanning direction within the optical card surface (auto tracking , Hereinafter referred to as "AT"). Also, in order to irradiate the light beam as a minute spot of a stable size despite the bending and mechanical error of the optical card, control is performed in the direction perpendicular to the optical card surface (autofocusing, hereinafter referred to as "AF"). There is a need. Also, the above-mentioned AT and AF are required even during reproduction.

FIG. 5 shows a block diagram of an apparatus for recording and reproducing information on and from an optical card. 106 is a motor for driving the optical card 101 in the direction of the arrow in the figure, and 107 is a semiconductor laser or the like. A light source, 108 is a collimator lens for collimating the light from the light source 107, 109 is a beam splitter, 110 is an objective lens,
Reference numeral 111 is a tracking coil, 112 is a focusing coil, 113 and 114 are condenser lenses, 115 and 116 are photoelectric conversion elements, 117 is a tracking control circuit, and 118 is a focusing control circuit. Based on the tracking signal and the focusing signal detected by the photoelectric conversion elements 115 and 116, a command is issued from the control circuits 117 and 118, and current is passed through the tracking coil 111 and the focusing coil 112, respectively, to move the objective lens 110 and perform AT and AF. . 119 is a system controller for controlling the recording / reproducing apparatus, and 120 is a group of various control signals output from the controller. From the controller 119, 120
Other signals are also output, but not shown here.
Reference numeral 121 denotes an optical head, and 122 is a drive motor for moving the optical head in the u direction in FIG.

The light from the light source 107 is collimated by a collimator lens,
After passing through the beam splitter 109, by the objective lens 110,
It is focused on the recording track of the optical card 101. The light reflected by the recording track is transmitted through the beam splitter 109 this time, and is divided into two by the beam splitter 109. The condenser lenses 113 and 114 respectively focus the light on the tracking signal detecting photoelectric conversion element 115 and the focusing signal detecting photoelectric conversion element 116. Focused on top. The signals obtained by the photoelectric conversion elements 115 and 116 are used as a tracking error signal and a focusing error signal by a tracking control circuit 117 and a focusing control circuit 118, respectively, and a current is passed through the tracking coil 111 and the focusing coil 112 to cause the objective lens 110 to move. Move and do AT and AF.

FIG. 6 is a detailed diagram of an example of the focusing control circuit 118.

In the figure, 201 is an amplifier for amplifying the electric focusing signal from the photoelectric conversion element 116 to an appropriate voltage, and 202 is a phase compensation circuit for stabilizing the focusing servo control. Reference numeral 203 denotes an analog switch, the output of the amplifier 201 is input to one input terminal of the signal from the phase compensation circuit 202 via point B, and the output of the triangular wave generation circuit 206 is input to the other input terminal via point C. Is entered. Reference numeral 204 denotes a driver for receiving a signal from the analog switch 203 and passing a drive signal current through the focusing coil 112. 205 is a focusing control circuit that receives the signal 120 from the system controller 119.
A focusing controller that controls the entire 118. The focusing controller is shown in FIG.
Although it is shown that a signal is input from 205 to only the analog switch 203, in reality, the focusing controller 205 also outputs other signals (not shown).

Figures 7 (a) and (b) and Figures 8 (a) and (b) show the sixth.
In the focusing control circuit shown in the figure, time changes of signal outputs at points C and A are shown. The horizontal axis represents time and the vertical axis represents output.

A focusing servo pull-in method will be described below with reference to FIGS. 6, 7, and 8.

First, referring to FIG. 6, the focusing controller 20
The signal D from 5 causes the analog switch 203 to be in a state where the point B side is open and the point C side is closed. As a result, the objective lens 110 is driven by the output C of the triangular wave generating circuit 206 (see FIG. 7A). Then, in the vicinity of the focus of the objective lens 110 on the optical card, the voltage at the point A changes into an S shape (so-called S curve) (see FIG. 7 (b)). Next, when pulling in the focus servo,
At time t0 in FIG. 8B, the focusing controller 205 detects that the point A becomes OV, sends a signal D to the analog switch 203, closes the point B side, and opens the point C side. This makes it possible to pull in the focusing servo.

[Problems to be Solved by the Invention] However, in the above-described conventional example, if the process from the start of focus search to the end of focus pull-in is performed in a short time in order to speed up the processing of the apparatus, the objective lens moves at high speed. I will let you. Therefore, the frequency of the S-shaped curve that appears also becomes high, and it becomes necessary to detect the OV at point A at a high speed, and a circuit that can handle the speed must be built, resulting in an expensive device. It has the drawback of being lost. Similarly, since the momentum of the objective lens is large when the focusing servo is pulled in, the overshoot voltage Vover after that also becomes large as shown in FIG. 8 (b), and sometimes the servo pull-in fails. In some cases, there is a disadvantage that the device becomes unstable in operation.

The occurrence of such a problem also occurs in servo pull-in in AT.

[Means for Solving Problems] An object of the present invention is to provide an optical information recording / reproducing apparatus capable of realizing stable operation without increasing the cost of the apparatus in view of the problems of the above-mentioned conventional techniques.

The above-mentioned object is to provide an optical system for irradiating the information track of the optical information recording medium with a light spot, and drive means for moving the light spot in the optical axis direction of the optical system or in the direction orthogonal to the information track. A signal supply means for supplying to the drive means a drive signal for moving the light spot so as to pass through a retracted position of auto-focusing or auto-tracking; and a detection circuit for detecting the focusing or tracking error signal of the light spot, A position detection circuit for detecting the pull-in position by comparing the error signal with a reference value, and stopping the supply of the drive signal to the drive means at the pull-in position so that the error signal is input to the drive means. And a switch circuit for switching, and at least recording and reproducing information by the light spot. In the optical information recording and reproducing apparatus for performing one, a drive signal for initially moving at a high speed light spot over a wide range is supplied to the driving means from said signal supply means,
During this high-speed movement, the pull-in position is detected by the position detection circuit, and a drive signal for moving the light spot at a low speed in a narrow range near the detected pull-in position is supplied from the signal supply means to the drive means, This is achieved by an optical information recording / reproducing apparatus characterized in that when the pull-in position is detected by the position detection circuit during the low speed movement, the switch circuit is switched to pull in auto-focusing or auto-tracking. It

[Operation] According to the present invention, since the servo search is divided into coarse detection and fine detection and performed stepwise, the speed of the light beam spot at the time of finally pulling in the servo can be reduced. , OV detection circuit can be low speed and cheap. Further, since the speed of the light beam spot when the servo is pulled in is small, the overshoot voltage Vover thereafter is also small, and the device can be stabilized. Further, since the rough detection allows the approximate position of the servo pull-in to be known, there is an advantage that the time can be shortened as compared with searching the position in a wide range by the fine detection.

[Embodiment] An optical information recording / reproducing apparatus of the present invention will be described in detail below with reference to the drawings.

The idea of the present invention can be applied not only to AF but also to AT, but in the following embodiments, a focusing control circuit will be described as an example.

FIG. 1 is a detailed diagram of a focusing control circuit according to the present invention. The members (circuits) having the same functions as those in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted. A triangular wave generation circuit 306 can change the frequency of the triangular wave and the DC component of the triangular wave by a signal E from the focusing controller 307. That is, the triangular wave generation circuit 306
The focusing controller 307 (or, if necessary, the system controller 308 is also involved in the processing) are configured to perform the operations described below.

2 (a) and 2 (b) are C of the embodiment of FIG. 1, respectively.
The voltage changes at points A and A are shown.

When the focusing servo is pulled in, first, the objective lens is moved at a high speed in a large range for the time I shown in FIG. 2 (b), and the in-focus position is roughly detected at t1. For that purpose, the triangular wave generated by the triangular wave generating circuit 306 is set to the waveform 30 having a large inclination (see FIG. 2A). next,
After moving the objective lens to the vicinity of the in-focus position obtained by I by the signal E at t2 at the time of II, the objective lens is moved to I
Then, the focus controller 307 accurately detects the OV at the point A by moving it at a speed lower than that at the time. As the triangular wave at that time, a waveform 31 having a small inclination is used. Then, at time t3, the focusing servo is pulled in. Thus, by dividing the servo search into coarse detection and fine detection and performing them stepwise, the focusing data obtained by rough detection can be utilized for the subsequent fine detection operation, and the above-mentioned problems can be solved. it can.

FIG. 3 is a flow chart showing the pull-in operation of the focusing servo according to this embodiment.

That is, coarse detection is performed over a wide range and at high speed (step S
1), roughly know the in-focus position (step S2). Next, a high speed movement is performed near the focus (step S3), a dense detection is performed at a low speed (step S4), and the focus servo is pulled in (step S5).

Next, another embodiment according to the present invention will be described.

FIG. 9 is a diagram showing an embodiment of the present invention. In the figure, 201 is an amplifier for amplifying the signal from the photoelectric conversion element 116 to an appropriate voltage, 203 is an analog switch, and 202 is a phase compensation circuit for stabilizing the focusing servo. Reference numeral 204 denotes a driver that receives a signal from the phase compensation circuit 202 and causes a current to flow through the focusing coil 112. Reference numeral 212 denotes a microprocessor, which is a signal group 120 from the system controller 119.
In response to this, the entire focusing controller 118 is controlled. 209 is an objective lens position sensor, and objective lens 1
The output voltage changes depending on the position of 10 in the focus direction. Reference numerals 207 and 211 denote DA converters that receive a digital signal from the microprocessor 212 and output an analog signal. 208 is an AD converter,
It receives an analog signal and outputs a digital signal to the microprocessor 212. 206 and 210 are subtraction circuits, respectively. Further, the subtraction circuit 206 has an amplification factor of 8 times.

In FIG. 9, the signal H causes the phase compensation circuit 203 to
The signal K is input. As a result, the objective lens position servo operation including the objective lens position sensor 209 in the loop is performed. In this state, the microprocessor 212 to D
It sends a digital signal to the A converter 207 or 211 and outputs an analog signal as the signal J or the signal F. Then, as the signal J or the signal F is gradually changed, the objective lens moves accordingly. Thereby, the objective lens can be moved to the in-focus position.

Also, when actually pulling in the focusing servo, the objective lens is moved to a large range to roughly detect the in-focus position,
Next, the objective lens is moved to a small range in the vicinity of the focus position, the focus position is accurately detected, and the focusing servo is pulled in.

FIG. 10 is a timing chart of signals at points A, G, F, and J of the circuit shown in FIG.

Next, referring to FIGS. 9 and 10, the AF pull-in operation in this embodiment will be described.

The moving range of the objective lens 110 is set to 2 mm, and the DA converter 207
If the resolution is 8 bits (2 to the 8th power = 256), the resolution per bit is 2 mm / 256 = 7.8 µm, and the focusing servo pull-in range is 30 µm.
Then, it is not a fine value. Therefore, there is no problem during the rough detection operation of the in-focus position, but since the resolution of the signal J is 7.8 μm when the next in-focus position is accurately detected, the in-focus position is accurately fixed. Can not do it.
Therefore, when switching to the focusing servo, the focusing servo may be dislocated. Therefore, the subtraction circuit 210 is provided in the subsequent stage of the subtraction circuit 206 having a gain of 8 times, and the signal F is injected. This signal F
The resolution of is 7.8 μm ÷ 8 = 1.0 μm per bit.

FIG. 10 is a timing chart of signals of various parts. First, the signal K is connected to the phase compensation circuit 202 by the signal H, and the objective lens position servo is operated. Here, the signal F is kept constant, the signal J is changed, the objective lens is moved in a large range, and the focus position is roughly detected at time t0. Next, the signal J is kept constant and the signal F is changed.
At this time, since the resolution of the signal F is 1.0 μm, the signal F
Even if is changed at the same time as the signal J, the amount of movement of the objective lens,
Also, the moving speed is 1/8 of that when the signal J is changed. Therefore, the objective lens can be moved at a low speed in a small range. In this way, the focus position is finely detected at the time t1, the signal A is connected to the phase compensation circuit 203 by the signal H, and the AF servo is pulled in. As a result, the error is 1.0 when accurately detecting the in-focus position.
Since it becomes μm, the focusing servo can be stably pulled in. Further, since the DA converter 207 and the DA converter 211 can use the same output voltage variable width and the same resolution, the device can be made inexpensive and simple as compared with the case where different DA converters are used.
That is, according to this embodiment, a position servo loop different from the focusing servo and the tracking servo is provided, and the voltage applied to the first portion in the position servo loop is changed to change the target position of the focusing or tracking servo. The target position of focusing or tracking servo can be accurately detected by performing detection and then changing the voltage applied to the second portion having a small transfer gain up to the amount of movement of the objective lens.

Although the embodiment has been described with respect to the AF servo, it is obvious that the same can be applied to the AT servo.

According to the embodiment shown in FIG. 9, by operating the position servo loop different from the focusing servo and the tracking servo, it becomes resistant to external vibration and stable pull-in of the servo becomes possible.

In other words, the voltage of the first variable voltage generator is applied to the first portion in the position servo loop other than the focusing and tracking servo, and the transfer gain up to the objective lens movement amount is the first portion. Second to smaller second part
Voltage of the variable voltage generator is first applied to change the voltage of the first variable voltage generator to roughly detect the pull-in position of the focusing or tracking servo, and then to the second variable voltage generator. The objective lens can be accurately positioned by changing the voltage of (1) and detecting the pull-in position of the focusing or tracking servo, so that the focusing servo and the tracking servo can be pulled in stably.

[Effects of the Invention] As described above, according to the optical information recording / reproducing apparatus of the present invention, the target position is roughly detected during the pre-search, and then the vicinity of the target position is searched at a low speed, By pulling in the servo, the speed of the light beam spot at the time of pulling in the servo can be reduced, so that the OV detection circuit can be made slow and inexpensive. And,
Since the momentum of the movable object (objective lens in the embodiment) when the servo is pulled in is small, the subsequent overshoot is also small, and stable operation of the device can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram of a focusing control circuit according to the present invention. 2 (a) and 2 (b) are timing charts of the signals in FIG. FIG. 3 is a diagram showing a flowchart according to this embodiment. FIG. 4 is a schematic plan view of the optical card. FIG. 5 is a block diagram of an optical information recording / reproducing apparatus. FIG. 6 is a detailed diagram of a conventional focusing control circuit. FIGS. 7 and 8 are timing charts of signals in the focusing control circuit shown in FIG. FIG. 9 is a block diagram of a focusing control circuit according to another embodiment of the present invention. FIG. 10 is a timing chart of the signals in FIG. 306: triangular wave generation circuit, 307: focusing controller, 308: system controller, 110: objective lens, 11
1: tracking coil, 112: focusing coil, 113 and 114: condenser lens, 115 and 116: photoelectric conversion element, 117: tracking control circuit, 118: focusing control circuit, 201: amplifier, 202: phase compensation circuit, 203: Analog switch.

Claims (1)

[Claims] 1. An optical system for irradiating a light spot on an information track of an optical information recording medium, a drive means for moving the light spot in the optical axis direction of the optical system or in a direction orthogonal to the information track, and the light. A signal supply means for supplying a drive signal to the drive means for moving the spot so as to pass through a retracted position of auto-focusing or auto-tracking; a detection circuit for detecting a focusing or tracking error signal of the light spot; A position detection circuit for detecting the pull-in position by comparing a signal with a reference value, and a switch for stopping the supply of the drive signal to the drive means at the pull-in position and switching to input the error signal to the drive means. And a circuit for recording and / or reproducing information by the light spot. In the optical information recording / reproducing apparatus, first, a drive signal for moving a light spot at a high speed in a wide range is supplied from the signal supply means to the drive means, and a pull-in position is detected by a position detection circuit during the high speed movement, Next, a drive signal for moving the light spot at a low speed in a narrow range near the detected pull-in position is supplied from the signal supply means to the drive means, and the pull-in position is detected by the position detection circuit during the low speed movement. The optical information recording / reproducing apparatus is characterized in that the switch circuit is switched at any time to pull in auto-focusing or auto-tracking.