JPH0490136A - Information recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent the focusing position of a light beam from deviating from an information recording surface by providing a control means for controlling a light beam converging means to be held in its position during a period of detecting a defect on an information recording medium. CONSTITUTION:At a defective spot such as a flaw and dust, etc., on an optical card 8, a focus sum signal S6 that is outputted by an adder 16 is lowered below a reference voltage, and an output signal S7 at a high level is outputted by a voltage comparator 17. A switch 23 of a lens driving signal output means 9 is turned off by a CPU 21 to stop the supply of a lens driving signal S4 which is an output of a servo circuit 13, and also a D/A converter 22 is controlled to hold a lens driving signal S4'. Consequently, a constant driving signal is supplied from a power amplifier circuit 15 to a driving coil 6, and the focus position of an objective lens 5 is held in a position immediately before a defect is detected. By this method, the focus of the light beam is never deviated from the information recording surface, and hence the recording/reproducing of information are accurately performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an information recording and reproducing method in which information is recorded/reproduced by focusing a light beam on the surface of a recording medium, typified by an optical card information recording/reproducing device. Regarding a playback device.

[Conventional technology]

Conventionally, in this type of device, the shift in the focus position of the information recording surface corresponding to the warping or bending of the optical card, which is the recording medium, is detected as the amount of focus error, and the objective lens is adjusted in accordance with this amount of focus error. It is driven vertically with respect to the information recording surface so that the focus position is always on the information recording surface.

[Problem to be solved by the invention]

However, in the above-mentioned conventional optical card information recording/reproducing device, if the optical card has scratches or dust, for example, the projected light beam is temporarily blocked, and the focus error signal is interrupted, making it impossible to detect the amount of focus error. In view of these conventional problems, the object of the present invention is to remove the focus of the light beam from the information recording surface of the optical card when the information is recorded or reproduced. To provide an information recording/reproducing device which prevents the focal position of a light beam from deviating from the information recording surface of an optical card even if there are defects such as scratches or dust.

[Means to solve the problem]

The present invention provides an information recording and reproducing apparatus having a light beam focusing means for focusing a light beam on an information recording surface of an information recording medium and a light detection means for detecting a light beam reflected from the information recording surface of the information recording medium. , a defect detection means for detecting a defect on the information recording medium based on the output from the light detection means, a focus error signal detected based on the output of the light detection means, and a light beam focusing means based on the focus error signal. and control means for controlling the light beam focusing means to maintain the position of the light beam focusing means during a period in which the defect detection means detects a defect on the information recording medium based on the output from the defect detection means. It is characterized by having the following.

[Effect]

In the information recording/reproducing apparatus having the above configuration, the light beam focusing means focuses the light beam onto the information recording surface of the information recording medium such as an optical card. What is the light detection means?

A light beam reflected from the information recording surface of the optical card is detected, and an output (focus signal) is sent to the control means and defect detection means. The control means detects a focus error signal based on the output from the light detection means, controls the light beam focusing means based on this focus error signal, and focuses the light beam on the information recording surface of the optical card. On the other hand, defect detection means.

When a defect on the optical card is detected based on the output from the optical detection means, the detection output is sent to the control means.

The control means, based on the output from the defect detection means,
While the defect detection means detects defects on the optical card,
The light beam focusing means is controlled to maintain the focused position of the light beam.

Therefore, while the defect detection means detects defects such as scratches and dust on the optical card, the control means cannot detect the focus error signal, and even if the focus error amount cannot be detected, the focus position by the light beam focusing means Since the light beam is held at a position immediately before a defect is detected, the focus of the light beam does not deviate from the information recording surface of the optical card.

In addition, even if there are defects such as scratches or dust on the optical card, the light beam will not be defocused from the information recording surface of the optical card, so even if it becomes necessary to refocus, it will take a long time to refocus. can be shortened.

〔Example〕

Next, embodiments of the present invention will be described using the drawings.

FIG. 1 is a diagram illustrating an embodiment of an optical card information recording/reproducing apparatus to which the information recording/reproducing apparatus of the present invention is applied.

In the figure, an optical head 1 includes a light emitting diode 2 as a light source, a collimator lens 3, and a beam splitter 4.
, an objective lens 5 as a light beam focusing means of the present invention that focuses the light beam on the optical card 8, a drive coil 6 that drives the objective lens 5 in the focus direction, and a light beam at the focus position of the objective lens 5. It is comprised of a photodetector 7 as a photodetection means of the present invention which outputs the deviation of the card 8 from the information recording surface as a focus signal S1.

The focus signal S1 consists of two signals, and each signal is supplied to the lens drive signal output means 9 and the lens drive signal waveform storage means 10 via separate signal lines. Although not shown here, the photodetector 7
The playback signal is extracted from the output from.

The lens drive signal output means 9 includes a differential amplifier 11 that differentially amplifies the focus signal S1 and outputs the output signal as a focus error signal S2, and a preset setting signal S3 and a switch 23 from the differential amplifier 11. a subtraction circuit 12 that calculates a difference between the focus error signal S2 supplied through the subtraction circuit 12 and outputs the difference; and a servo circuit 13 that outputs a lens drive signal S4 in response to the difference from the subtraction circuit 12.
and a lens drive signal S4, which is the output of the servo circuit 13, and a lens drive signal S4' from a digital/analog converter (hereinafter abbreviated as a D/A converter) 22, which will be described later, and outputs the sum. 14 and the lens drive signal S5, which is the output of the adder circuit 14, is power amplified and sent to the drive coil 6.
The power amplifier circuit 15 that outputs the output to the subtraction circuit 12 and the supply of the focus error signal S2 from the differential amplifier 11 to the subtraction circuit 12 are turned on/off under the control of a central processing unit (hereinafter abbreviated as CPU) 21, which will be described later. It is composed of a switch 23 that is turned off. This switch 23 is controlled by the CPU 21 so that it is turned off while a voltage comparator 17 (described later) detects a defect such as a scratch or dust on the optical card 8, and is turned on otherwise.

On the other hand, the lens drive signal waveform storage means 10 stores the optical card 8
The waveform of the lens drive signal S5 obtained by one reciprocating movement is stored, and the signal corresponding to the stored waveform is set as the lens drive signal S4' by the addition circuit 14 of the lens drive signal output means 9. Drive coil 6 via power amplification circuit 15
This is what is output to. The lens drive signal waveform storage means 10 includes a current detection circuit 18 that detects the current of the lens drive signal S5 from the power amplification circuit 15, and a low-pass filter to which the output from the current detection circuit 18 is supplied.
(abbreviated as LPF) 19 and this low-pass filter 1
Analog/digital converter (hereinafter abbreviated as A/D converter) 20 that converts the output of 9 into analog/digital.
and an adder 16 which adds the focus signal S1 from the photodetector 7 and outputs a focus sum signal S6, which inputs this focus sum signal S6, compares the focus sum signal S6 with a reference voltage, and outputs a focus sum signal S6. A voltage comparator 17 that detects fluctuations in the focus sum signal S6 caused by scratches or dust on the top, and an output of the A/D converter 20 and the voltage comparator 17.
A CPU 21 is supplied with the output of the switch 23 and controls the on/off of the switch 23, and a D/D converter that converts the lens drive signal (digital signal) from the CPU 21 into an analog signal and outputs it to the adder circuit 14 as a lens drive signal 84'. A converter 22.

Here, the adder 16 and the voltage comparator 17 constitute defect detection means of the present invention. Further, the drive coil 6, the lens drive signal output means 9, the current detection circuit 18, the low-pass filter 19, the A/D converter 2o, the CPU 21, and the D/A converter 22 constitute the control means of the present invention.

Next, the operation will be explained with reference to FIG. 2, focusing on the lens drive signal waveform storage means 1o. In addition, Figure 2 shows
FIG. 2 is a diagram for explaining the operation of FIG. 1;

First, in the optical card information recording/reproducing device, the optical card 8
is transported back and forth within the monitor section of FIG. In this case, when the optical card 8 is tilted in the focus direction (optical axis direction), the differential amplifier 11 generates a focus error signal S2 as shown in FIG. is output to the subtraction circuit 12 via the switch 23. The subtraction circuit 12 takes the difference between the setting signal S3 and the focus error signal S2, and sends the difference to the servo circuit 13.
Output to. The servo circuit 13 sends a lens drive signal S4 as shown in FIG.
Output to 5. The lens drive signal S5, which is the output of the power amplification circuit 15, is output to the drive coil 6, thereby adjusting the position of the objective lens 5 in the focus direction. Further, the lens drive signal S5, which is the output of the power amplification circuit 15, is transmitted to the current detection circuit 18 of the lens drive signal waveform storage means 10.
supplied to This lens drive signal S5 is detected by the current detection circuit 18, and the low-frequency component corresponding to the change thereof is extracted by the low-pass filter 19, and transmitted to the CP via the D/A converter 20.
It is supplied to U21.

The CPU 21 stores the waveform of the lens drive signal S5 within the monitor section in FIG. 2 from the current value converted from analog to digital by the A/D converter 20.

The stored signal corresponding to the waveform is sent to the D/A converter 2.
2 as a lens drive signal S4' as shown in FIG.
The signal is outputted to the adding circuit 14 of the lens drive signal output means 9 according to the movement position of the lens drive signal.

The adder circuit 14 adds the lens drive signal S4' to the lens drive signal S4 from the servo circuit 13 and outputs the result to the power amplifier circuit 15. A lens drive signal S5, which is the output of the power amplification circuit 15, is supplied to the drive coil 6. In this way, the drive coil 6.

A predetermined bias current (
Since the lens drive signal 84') is supplied, the focus error signal s2 within the operation period has waveform portions a and b within the first monitor period, as shown in section C shown in FIG.
As shown in FIG.

Therefore, even if the optical card 8 being transported is tilted in the focus direction, the objective lens 5 is simultaneously driven to follow the change in tilt so that the focus position is on the information recording surface of the optical card 8. Therefore, accurate recording/reproduction of information on the information recording surface of the optical card 8 becomes possible.

Next, there are defects such as scratches and dust on the optical card 8 during the operation period for the optical card 8.

The operation will be described with reference to FIG. 3 in the case where the focused light by the objective lens 5 is blocked and the focus signal Sl and focus error signal S2 become zero. In addition, the third
The figure is an explanatory diagram of the operation of FIG. 1 when there is a defect such as a scratch or a dust on the optical card.

There are defects such as scratches and dust on the optical card 8.

At the defective location, the focus error signal S2 does not become like the part C in FIG. 2, but as shown in FIG. 3(a).
At the front and rear ends of the defect, pseudo pulses PL and P
2.

Here, if the switch 23 is not turned off, the lens drive signal output means 9 outputs a focus error signal S2 as shown in FIG.
3.

Then, the servo circuit 13 outputs a noise drive signal S4 corresponding to this pseudo pulse P1°P2 to the addition circuit 14.

The output of the adder circuit 14 is supplied to the drive coil 6 via the power amplifier circuit 15. The objective lens 5 is driven based on a lens drive signal S5 corresponding to the pseudo pulse, and the focus of the light beam will be deviated from the information recording surface of the optical card 8, and in the worst case, the focus servo will be deviated. .

However, in the present invention, the above problem is prevented from occurring in the following manner.

That is, the adder 16 inputs the focus signal (consisting of two signals) from the photodetector 7 and generates the focus sum signal S.
6 to the voltage comparator 17. The voltage comparator 17 compares the focus sum signal s6 with a predetermined reference voltage set in advance, and outputs an output signal S7 corresponding to the comparison result to the CPU.
Output to 21. In this case, at locations on the optical card 8 where there are no defects such as scratches or dust, the output of the adder 16 is higher than the reference voltage, and therefore the output of the voltage comparator 17 remains at a low level. Therefore, in areas where there is no defect on the optical card 8, the CPU 21 does not perform any special operation based on the output of the voltage comparator 17. However, where there are defects such as scratches or dust on the optical card 8, the focus sum signal S6 output from the adder 16 becomes lower than the reference voltage, as shown in FIG. 3(b). As a result, the voltage comparator 17 sends a high level output signal s7 to the CPU as shown in FIG. 3(c).
Output to 21. This output signal S7 is a pseudo pulse P generated due to a defect in the focus error signal S2 mentioned above.
□, has a faster rise than P2. The CPU 21 turns off the switch 23 of the lens drive signal output means 9 during the period when this output signal S7 is input (the period from the front end to the rear end of the defect), and outputs the lens drive signal output from the servo circuit 13. At the same time as stopping the supply of signal S4,
The lens drive signal S4' which is the output of the A converter 22 is the third
The D/A converter 22 is controlled so as to be held as shown in Figure (d). As a result, the lens drive signal S4' from the D/A converter 22 is held as shown in FIG. 3(d). Therefore, the lens drive signal S5 input to the power amplification circuit 15 is the held lens drive signal S4'
A constant lens drive signal is supplied from the power amplification circuit 15 to the drive coil 6, and the objective lens 5 is held so as not to deviate significantly from the focus position.

As can be seen from the above description, in the present invention, even if the optical card 8 is tilted in the focus direction and there are defects such as scratches or dust on the optical card 8, the voltage During the period when the comparator 17 is detecting a defect such as a scratch or dust on the optical card 8, the focus position of the objective lens 5 is held at the position immediately before the defect occurs under the control of the CPU 21. card 8
The focus position shift will not occur due to pseudo pulses generated in the focus error signal S2 at the defective location of the focus error signal S2.
The objective lens 5 is driven to the focus position substantially parallel to the inclination of the optical card 8. Therefore, the focus of the light beam does not deviate from the information recording surface of the optical card 8. Therefore, it is resistant to defects such as scratches and dust on the optical card 8 during recording/reproduction, and is expected to improve data reliability.

In addition, even if there are defects such as scratches or dust on the optical card,
Since the focus of the light beam does not deviate from the information recording surface of the optical card, the time required for refocusing can be shortened even if refocusing is required thereafter.

In this embodiment, a case has been described in which the optical card 8 is tilted in the focus direction with respect to the transport direction, and there are also defects such as scratches and dust on the optical card 8. Without limitation, the present invention is similarly applied even when the optical card 8 has no inclination toward the focus direction (perpendicular to the focus direction) and there are defects such as scratches or dust on the optical card 8.

The present invention is not limited to the examples, and various applications and modifications can be made without departing from the gist of the present invention. Furthermore, the present invention can also be applied to recording and reproducing devices for information recording media other than optical cards.

〔Effect of the invention〕

As described above, by using the information recording/reproducing apparatus according to the present invention, the following various effects can be obtained.

(1) While the defect detection means is detecting defects such as scratches or dust on the optical card, the control means maintains the position (focus position) of the light beam focusing means at the position immediately before the defect is detected. As a result, the focus of the light beam does not deviate from the information recording surface.

Therefore, information can be recorded/reproduced accurately.

(2) According to (1) above, even if there are defects such as scratches or dust on the information recording medium, the focus of the light beam will not be removed from the information recording surface, so if it becomes necessary to refocus after that, The time required to re-focus can be shortened.

(3) It is resistant to defects such as scratches and dust on the information recording medium during recording/reproduction, and is expected to improve data reliability.

[Brief explanation of the drawing]

FIG. 1 is a main part configuration diagram showing an embodiment of an optical card information recording and reproducing device to which the information recording and reproducing device of the present invention is applied, and FIGS. 2 and 3 respectively explain the operation of the embodiment of FIG. 1. This is a time chart for. DESCRIPTION OF SYMBOLS 1... Optical head, 5... Objective lens, 6... Drive coil, 7... Photodetector, 9... Lens drive signal output means, 10... Lens drive signal waveform storage means, 11
... Differential amplifier, 12 ... Subtraction circuit, 13 ... Servo circuit, 14 ... Addition circuit, 16 ... Adder, 1
7...Voltage comparator. 18... Current detection circuit, 21... CPU, 23...
·switch.

Claims (1)

[Claims] An information recording and reproducing apparatus comprising: a light beam focusing means for focusing a light beam on an information recording surface of an information recording medium; and a light detection means for detecting a light beam reflected from the information recording surface of the information recording medium. a defect detection means for detecting a defect on the information recording medium based on the output from the detection means; and a focus error signal for detecting a focus error signal based on the output of the light detection means, and the light beam focusing means based on the focus error signal. Based on the output from the defect detection means, during the period when the defect detection means is detecting a defect on the information recording medium, the light beam focusing is controlled to maintain the position of the light beam focusing means. 1. An information recording and reproducing apparatus comprising: a control means for controlling the means.