JPH0697506B2 - Auto tracking control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auto-tracking control device, and more particularly, to sensitivity switching control of detection means for detecting tracking abnormality.

[Prior Art] Conventionally, an optical head of an auto-tracking control device has a light source such as a laser, a collimator lens for collimating a light beam from this light source, and a light beam focused on a recording surface of an information medium as a minute light spot. It is composed of an optical system such as an objective lens for irradiating, and a photodetector for receiving the light flux reflected by the recording surface.

At the time of recording, the recording surface of the information medium is irradiated with a light beam which is modulated by predetermined information and focused by an objective lens, and information is recorded by causing a temperature rise or a chemical reaction on the recording surface. Also, during playback, it is reflected from the recording surface,
A light beam optically modulated by the recorded information is received by a photodetector, and the optical signal detected here is converted into an electric signal to obtain desired reproduction information.

Information media used for recording / reproducing such optical information include optical video discs, optical digital audio discs, optical cards, and the like. The information to be recorded is, for example, recorded on a concentric or spiral track in the case of a disk-shaped medium (hereinafter referred to as an optical disk) and in a plurality of tracks arranged in parallel in the case of a cart-shaped medium. It This information track is due to unevenness, presence / absence of bits, change in reflectance, change in magnetization direction, and the like.

In order to record information accurately without causing trouble such as crossing between information tracks, it is necessary to control the irradiation position of the light spot in a direction perpendicular to the scanning direction of the information tracks (auto tracking , Hereinafter referred to as "AT"). Further, in order to irradiate the light spot as a stable minute spot despite the bending and mechanical error of the optical card, it is necessary to control in the direction perpendicular to the recording surface (autofocusing, hereinafter referred to as “AF”). ). Also, the above-mentioned AT and AF are required even during reproduction.

FIG. 5 is a block diagram showing the configuration of an information recording / reproducing apparatus for an optical card.

In the figure, a system controller 20 controls motors 21 and 22, AT and AF control circuits 23 and 24 to control information recording / reproduction with respect to the optical card C.

The motor 21 reciprocates the optical card C in the direction of arrow a in the figure, whereby the optical head 25 emits a light spot along the information track of the optical card C. Motor 22
Is for controlling the movement of the optical head 25 in the vertical direction with respect to the information track on the optical card C.

The optical head 25 includes a light source 25a made of a semiconductor laser and a collimator lens 2 for collimating the light flux from the light source 25a.
It has 5b, a beam splitter 25c and an objective lens 25d, and irradiates the recording / reproducing light beam onto the recording surface of the optical card C.

Further, the optical head 25 has a beam splitter 25e, condenser lenses 25f and 25g, and photoelectric converters 25h and 25i, and converts the light beam reflected on the recording surface of the optical card C into the photoelectric converter 25h.
And 25i to convert into a tracking signal and a focusing signal, which are supplied to the AT control circuit 23 and the AF control circuit 24.

The AT control circuit 23 and the AF control circuit 24 move the objective lens 25d by moving a driving current to the tracking coil 25j and the focusing coil 25k of the optical head 25 to move the objective lens 25d.
Controls T and AF.

FIG. 6 is a block diagram showing the structure of the AT control circuit 23, and FIG. 7 is a waveform diagram for explaining the operation thereof.

In FIG. 6, the outputs Sa and Sb of the photoelectric conversion elements 1a and 1b of the photoelectric converter 25h are the tracking error amplifier 2
Then, the difference is amplified and extracted as a tracking error signal Sc. The tracking error signal Sc is appropriately phase-compensated by the phase compensation circuit 3 and input to the tracking servo circuit 4 to drive the tracking coil 25j.

The tracking error signal Sc is also input to the low pass filter (LPF) 5. LPF5 has an objective lens 25d
When the AT actuator deviates from the neutral point, the DC component Sd (Fig. 7A) of the tracking error signal Sc increases corresponding to the distance, so that only the DC component Sd is passed and the head-lube converter is passed. Enter in 6. The comparator 6 detects in which direction the AT actuator is displaced, and outputs a signal Se (FIG. 7B) or Sf (FIG. 7C) according to the displaced direction to the head move controller 7. It inputs and outputs the optical head drive signal Sg (FIG. 7D). The signal Se is also used as a head direction signal, and is output to the system controller 20 as a command signal for moving the optical head 25 in a predetermined direction together with the signal Sg.

The system controller 20 moves the optical head 25 in the tracking direction by driving the motor 22 described in FIG. 5 based on the optical head drive signal Sg and the signal Se. In other words, the two-stage actuator configuration of the AT actuator that drives the objective lens 25d and the motor 22 (optical head actuator) that drives the optical head 25 is adopted, and when the objective lens 25d deviates from the neutral point of the AT actuator, By driving the head 25, the objective lens 25d becomes AT
The actuator is controlled to return to the neutral point.

The outputs Sa and Sb of the photoelectric conversion elements 1a and 1b are added and amplified by the sum signal amplification circuit 8 and input to the comparator 9. The comparator 9 detects whether or not the light amount is within a predetermined range by comparing it with the comparison voltage Vr, and when the light amount decreases, that is, when the deviation amount of the light beam spot with respect to the information track is abnormal, tracking abnormality occurs. The detection signal Sn is output to the system controller 20 to report an abnormality. The system controller 20 prevents overwriting by issuing a command to immediately stop recording.

[Problems to be Solved by the Invention] In such a conventional example, the AT is always detected with the same AT abnormality detection sensitivity.
Since an abnormality is detected, the AT abnormality may be erroneously detected. That is, if the detection sensitivity is adjusted when the optical head is stationary, the vibration component due to the movement is added during the movement of the optical head, which may cause an erroneous detection of the AT abnormality. Also, if you match the detection sensitivity of the optical head while moving,
There was a problem that the AT was likely to come off when it was not moving, or the AT abnormality could not be detected when it came off.

In view of the above conventional problems, the present invention accurately detects an AT abnormality by reducing the abnormality detection sensitivity of the AT when the optical head is moving, regardless of whether the optical head is stationary or moving. It is an object of the present invention to provide an auto-tracking control device that can be used.

[Means for Solving the Problems] An object of the present invention is to provide an auto-tracking control device for performing tracking control of a light spot emitted from an optical head onto a recording medium with respect to a track on the recording medium. Tracking error signal generating means for detecting a deviation amount with respect to the track and generating a tracking error signal, a tracking actuator for moving the light spot in the tracking direction based on the tracking error signal, and a low frequency component of the tracking error signal. A low-frequency component extracting means for extracting the optical head, an optical head actuator for moving the optical head in the tracking direction based on the extracted low-frequency component, and a predetermined detection sensitivity for an abnormal amount of deviation of the light spot with respect to the track. Detection means to detect at With and
This is achieved by an auto-tracking control device characterized in that the detection means reduces the detection sensitivity when the optical head actuator is moving the optical head.

[Embodiment] Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an auto-tracking control device according to the present invention, and FIG. 2 is a waveform diagram for explaining its operation.

In FIG. 1, the same parts as those in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted here.

In this embodiment, instead of the comparator 9 shown in FIG.
The configuration is the same as that of FIG. 6 except that the AT abnormality detection circuit 10 and the sensitivity switching circuit 11 are provided.

In FIG. 1, the signal Sa + Sb additionally amplified by the sum signal amplifier circuit 8 is within a predetermined light amount fluctuation range within the AT accuracy range during tracking, but the tracking is caused by an external shock or a defect on the recording medium. When it is about to come off or comes off, it exceeds the predetermined fluctuation range of the light amount. The AT abnormality detection circuit 10 can monitor the output signal level of the sum signal amplification circuit 8 and can switch the AT abnormality detection sensitivity by the output signal of the sensitivity switching circuit 11 and set a predetermined level at each sensitivity. When a signal exceeding the limit is input, it is output to the system controller 20 as an AT abnormality detection signal Sn.

The input signal Si (FIG. 2B) of the sensitivity switching circuit 11 is formed based on the signal Sg (FIG. 2A) output from the head move controller 7 to the system controller 20.
The input signal Si is a signal output from the system controller 20 to the optical head drive system as an actual optical head drive signal, and is formed based on the signal Sg output from the head move controller 7 to the system controller 20. Sg
On the other hand, it has a slight delay time t ₁ and a delay time t ₂ required for the optical head drive system.

The sensitivity switching circuit 11 is composed of a one-shot circuit 12 and an OR circuit 13. Signal Si is input to the one-shot circuit 12.
Is input, and the one-shot signal Sj (FIG. 2C) that is triggered by the rising edge and becomes the “H” level only for the predetermined time T ₁ is output.

The OR circuit 13 takes the logical sum of the signal Si and the signal Sj and outputs the sensitivity switching signal Sk (FIG. 2D). AT error detection circuit 10
Is controlled so that the detection sensitivity decreases while the sensitivity switching signal Sk is at "H" level.

As described above, according to the present embodiment, by decreasing the AT abnormality detection sensitivity during the output of the optical head drive signal and during the predetermined time after the end of the signal, the vibration during the movement of the optical head is increased.
There is no erroneous detection of an AT abnormality (an abnormal signal is output although it is not an abnormality), and even if there is a discrepancy between the optical head drive signal and the actual drive system (mechanical delay, etc.), a predetermined time after completion By lowering the detection sensitivity, it is possible to prevent erroneous detection of AT abnormalities, and it is possible to detect AT abnormalities with high accuracy and without malfunction.

Next, FIG. 3 is a block diagram showing another embodiment of the automatic tracking control device according to the present invention, and FIG. 4 is a waveform diagram for explaining the operation thereof.

This embodiment has the same structure as that of FIG. 1 except that the structure of the sensitivity switching circuit 11 is different.

The sensitivity switching circuit 11 of this embodiment includes a series circuit of one-shot circuits 14 and 15, and one-shot circuits 14 and 15 of these series circuits.
And an AND circuit 16 which takes an AND condition for each output.

The one-shot circuit 14 is a signal which is triggered by the rising edge of the input signal Si (FIG. 4B) and is at the “L” level for a predetermined time T _2.
Outputs S ₁ (Fig. 4C), and also the one-shot circuit 15
Outputs a signal becomes the between the signal rising in triggered predetermined time S ₁ T ₃ "H" level Sj (Fig. 4 D). The signals S ₁ and Sj thus obtained are the AND circuit 16
Are ANDed and input to the AT abnormality detection circuit 10 as a switching signal Sk (FIG. 4E).

With this configuration, during the time T ₃ to the drive system after the time T ₂ of the up actual driving system optical head driving signal starts to output starts operation ends the operation, AT abnormality AT abnormality can be detected with high accuracy by lowering the detection sensitivity.

EFFECTS OF THE INVENTION As described above, according to the present invention, when the optical head is moving, the abnormality detection sensitivity of the AT is lowered so that the AT abnormality is erroneously detected by the vibration component generated during the movement of the optical head. The AT abnormality can be detected accurately and the AT abnormality detection sensitivity is higher when the optical head is stationary than when the optical head is moving. Therefore, the AT abnormality can be detected accurately, and the AT can be stopped while the optical head is moving. There is an effect that the abnormality of AT can be accurately detected regardless of the inside.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an auto-tracking control device according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, and FIG. 3 is an auto-tracking control according to the present invention. FIG. 4 is a block diagram showing another embodiment of the device, FIG. 4 is a waveform diagram for explaining the operation of FIG. 3, FIG. 5 is a block diagram of an information recording / reproducing device of an optical card, and FIG. FIG. 7 is a block diagram showing a conventional auto-tracking control device, and FIG. 7 is a waveform diagram for explaining the operation of FIG. 10 …… AT abnormality detection circuit 11 …… Sensitivity switching circuit 22 …… Motor 23 …… AT control circuit 25 …… Optical head 25h …… Photoelectric converter

Claims (1)

[Claims] 1. An automatic tracking control device for performing tracking control of a light spot emitted from an optical head onto a recording medium with respect to a track on the recording medium, wherein a tracking error is detected by detecting a deviation amount of the light spot with respect to the track. Tracking error signal generating means for generating a signal, a tracking actuator for moving the light spot in the tracking direction based on the tracking error signal, low frequency component extracting means for extracting a low frequency component of the tracking error signal,
An optical head actuator that moves the optical head in the tracking direction based on the extracted low frequency component, and a detection unit that detects an abnormality in the amount of deviation of the optical spot with respect to the track with a predetermined detection sensitivity, The auto-tracking control device, wherein the detection means lowers the detection sensitivity when the optical head actuator is moving the optical head.