JP2627529B2 - Double recording prevention method for optical recording media - Google Patents

Description

The present invention relates to an optical recording medium (carrier) such as an optical card for recording / reproducing, particularly, for writing information, because of defects such as dirt and scratches attached to the upper surface of the carrier. The present invention relates to a method for preventing a pickup from moving to an adjacent track and double-recording information already recorded when the tracking function is held, which is suitable for use in a laser card reader / writer.

"Prior art" An optical spot formed by focusing a beam emitted from a laser light source by an optical system is used to record and record pit-like information between guide tracks on a thin-plate carrier as a recording medium, or to record recorded pits. In a basic configuration of a laser card reader / writer which reads (reproduces) an image by focusing on a laser beam, a laser beam emitted from a laser light source is usually divided into three by a diffraction grating, and a central main beam is passed through an objective lens. Are used for focusing and recording and reproduction of information, and are arranged so as to be placed on an adjacent guide track with two side spots formed by sub beams on both sides, and the reflected light on the carrier is objectively reflected. Condensed by a lens and focused on a photoreceptor, that is, a photodetector, a signal for information from the main beam, and a main spot by the main beam for the sub beam In order to position them at the center between the tracks, the two light receiving elements are controlled so that their light amounts are equal.
That is, when a light beam of the same illuminance is incident, the error signal becomes zero, and if it is unevenly distributed on one of the guide tracks, the incident light amount of the detector will be unbalanced, and the servo system will be corrected based on this. ing.

By the way, at the time of recording information, the laser output is burned in a pit shape by enhancing the laser output more than at the time of reproduction. Therefore, once recorded information cannot be erased.

Now, if there is a defect such as dirt or scratch on the surface of the carrier, it is detected that the focused main beam spot has arrived at the site, and measures are taken to hold the tracking function.
As the defect area becomes wider, the hold time, that is, the period of the open loop is extended, and the pickup moves to the next adjacent track, and the recording operation proceeds with the skipped track.

The cause of the above-described alternate recording is a tracking hold due to the defect on the surface of the carrier and a mechanical vibration during the hold, which causes a tracking deviation, so long as the control method based on the servo system is employed, the information is duplicated. Writing cannot be avoided.

"Problems to be solved by the invention" The present invention is intended to prevent duplicate recording in a space in which information has already been recorded even when a tracking error occurs due to a defect on a carrier surface, and effectively utilize the recording space. Is to measure.

"Means to solve the problem" A device that records information on a carrier with a laser beam that scans along the track of a thin carrier is used to record information at a defective portion such as dirt or scratches attached to the carrier surface. Signal level obtained by detecting the reflected light of the laser beam during the recording of the information on the carrier in order to prevent the double recording of the information at the location where the information is already recorded and the predetermined level. A comparison is made with a reference level, and when the signal level exceeds the reference level for more than a prescribed time, the tracking function is stopped and the recording of information is stopped.

"Example" An example of implementing the method of the present invention will be described below with reference to the drawings.

Figure 1 is a system configuration diagram representing the double recording prevention responsive circuit, the detection signal A + B of the light receiving element of the T ₁ is the main beam
Input terminal, C ₁ R ₁ is the main beam filter for removing high-frequency components in the detection signals, SW'm connexion instantly between open to the input of the delay signal to the terminal T ₂ in order to suppress the high output voltage at the time of recording of A switch that closes afterwards constitutes a sample-and-hold circuit including a capacitor and a resistor having a time constant of R ₂ C ₂ and a buffer amplifier B.AMP. R ₃ C ₃ is a filter for absorbing spike noise generated by opening and closing the above SW, R ₄ C ₄ is a filter for removing a DC component included in the detection signal of the main beam,
R ₅ C ₅ is constant elements time for one to bract pulse generator RTOMB, the reference level of R _7, R _8, R ₉ is a comparator COMP (-) is a resistor for level setting of the terminal, the one-to bracts pulse generator Receives two signals from input / output terminals of the unit and sends them to the CPU as “1” or “0”
An ORgate for transmitting a signal is connected to the last stage.

FIG. 2 shows the waveforms of the respective portions of the double recording prevention response circuit during the period when the beam is mounted on the carrier defect portion, with the horizontal axis corresponding to the time axis. First (A) is 2
The waveform of the amplifier AMP output of the main beam signal A + B detected by splitting, (C) is a buffer amplifier B.AM through a switch SW.
The waveform at point C on the output side of P, (D) is the waveform applied to one (+) input terminal of the comparator COMP, (E) is the output waveform of the comparator, and (F) is the output of the one-shot pulse generator RTOMB. Waveform at terminal F, (G) shows signal transmission point G to ORgate CPU.
It is a waveform at.

When the pickup is moved to an adjacent track due to mechanical vibration or the like at the time of the tracking hold, and an attempt is made to write on the already recorded track, there is an information pit on the carrier surface, so that the information pickup shown in FIG. The waveform at point D is as shown in FIG.

Since the one-shot pulse generator RTOMB in the double-recording prevention response circuit has a retrigger function, points E, F, and G in FIG. 1 are respectively linked to (E), (F), and (G) in FIG. Correspondingly, the waveforms are as shown in (J), (K), and (M) in FIG.

In the present invention, when the Supotsuto light beam is at a defect site at the time of writing information onto the carrier, the level of the light receiving detection signal from the main beam to be input to the input terminal T ₁ of the first diagram adjacent track Since the signal level is much larger than the signal level output when the beam has moved, it cannot be determined whether the beam has moved to an adjacent track. Accordingly, the prohibition of writing is determined based on the output pulse transmission time at point G.

The above determination of the time is normal if the pickup does not move to the adjacent track even if the tracking servo is held during the detection of the defect signal, and if the track already recorded is double-written for some reason. In order to prevent a bad recording, it is necessary to satisfy the condition that the demodulation function can be sufficiently exhibited even if the double-written portion is omitted.

Therefore, the period during which the main beam is placed on the defective portion or pit row on the carrier is converted into a pulse signal, and when the signal exceeds a specified time, a write-protection command is issued from the CPU to stop the recording function. .

[Effect] According to the double recording prevention method of the present invention, the surface of the information recording medium, such as the carrier, is contaminated or flawed by a flaw, and the beam passes through a wide area of the defect area, so that the tracking servo function is not provided. Even if the sampling hold is applied for a long time, it is possible to prevent continuation of recording in the neighboring track, so that it is possible to prevent the recording space from being lost unnecessarily, and when the information data already recorded due to double recording is lost. The harmful effects are eliminated and it is very useful in practice.

[Brief description of the drawings]

FIG. 1 is a connection diagram of a double recording prevention response circuit for implementing the double recording prevention method of the present invention, and FIG. 2 is a circuit diagram of FIG.
It is a waveform graph in each point of A, C, D, E, F, and G. T ₁ …… Input terminal, AMP …… Amplifier, SW… Stitch, B.
AMP: Buffer amplifier, COMP: Comparator, RTOMB: One-shot pulse generator.

Claims (1)

(57) [Claims] An apparatus for recording information on a carrier with a laser beam scanning along a track of a thin carrier prevents recording of information on a defective portion such as dirt or a flaw adhering to the surface of the carrier. In order to prevent double recording of information at a location where information is recorded, a signal level obtained by detecting reflected light of the laser beam during recording of information on the carrier is compared with a predetermined reference level. A double recording prevention method for an optical recording medium, wherein the tracking function is stopped and the recording of information is stopped when the signal level exceeds the reference level for a predetermined time.