JPH01236459A - Double record preventing method for optical recording medium - Google Patents

Abstract

PURPOSE:To prevent the double recording of information into a space where the information is already recorded by stopping temporarily the operations of a beam tracking function and a writing function in case the electric signal obtained from detection of a reflected beam exceeds the reference level of a comparator. CONSTITUTION:When it is detected that a main beam reached a defect position on the surface of a carrier at recording of information, the output higher than the reference set value of a comparator COMP is defined as a pulse signal G. Then the recording job is stopped when the pulse of the signal G lasts longer than a certain time. In case an information pit that is already recorded is detected when a pickup moves to a track where the information is already recorded, said information pit is regarded as a defect position on the carrier surface and a writing action is stopped. Thus the continuous recording actions are prevented to the adjacent tracks even in case a tracking servo function is sampled and held for a long period of time. In such a way, the unreasonable reduction of a recording space is avoided.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention is applicable to optical recording media such as optical cards (carriers) due to defects such as dirt and scratches that adhere to the top surface of the carrier during recording and reproduction, especially when information is written. This method is suitable for use in a laser card reader/writer, and relates to a method for preventing the pickup from moving to an adjacent track and duplicating already recorded information when the track 77 function is held. .

"Prior Art" A beam emitted from a laser light source is focused by an optical system, and an optical spot is used to arrange and record bit-shaped information between guide tracks on a thin carrier, which is a recording medium. The basic configuration of a laser card reader/writer that focuses on and reads (plays)
Normally, the laser beam emitted by a laser light source is divided into three by a diffraction grating, and the central main beam is used to focus the optical spot through an objective lens and to record and reproduce information.
The main beam is placed on the adjacent guide track with two side spots from the sub beams on both sides, and the light reflected on the carrier is focused by the objective lens and imaged on the photoreceptor, that is, the photodetector. The beam transmits a signal for information, and the sub beam is controlled so that the main spot of the main beam is located in the center between the guide tracks, so that the two light receiving elements have equal amounts of light.

In other words, when a light beam of the same illuminance enters, the error signal becomes zero, and if the guide track is unevenly distributed, the amount of light incident on the detector becomes unbalanced, and the servo system is corrected based on this. I'm letting you do it.

By the way, when recording information, the laser output is increased more than during reproduction to burn into pits. Therefore, once recorded information cannot be erased.

Currently, when there is a defect such as dirt or scratches on the carrier surface, the focused main beam spot detects when the defect has arrived at that area and holds the tracking function. The above-mentioned hold time, that is, the open loop period is extended, the pickup moves to the next adjacent track, and the recording operation proceeds on the skipped track.

The cause of the above-mentioned ambush recording is the tracking hold caused by the defect on the carrier surface and the mechanical vibration in the board, which also causes tracking loss. Heavy writing could not be avoided.

``Problem to be Solved by the Invention'' However, the present invention makes effective use of recording space by preventing redundant recording in the space where information has already been recorded even when tracking loss occurs due to defects on the carrier surface. The purpose is to measure the

``Means for solving the problem'' When recording information, the main beam reaches the defect position on the carrier surface by using a pulse signal that is equal to or higher than the standard setting value of the comparator, and exceeding the time of the pulse. When the pickup moves to a track where information has already been recorded, if there are already recorded information bits, those bits are considered to be defective parts on the carrier surface. This problem is solved by providing a double recording prevention response circuit that stops the write operation and follows instructions from the CPU.

"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 showing the double recording prevention response circuit, where T is the detection signal A+H of the main beam's two-split light receiving element.
The input terminal C8 is a filter that removes high frequency components in the main beam detection signal, and SW is a switch that momentarily opens and then closes by manually applying a delayed signal to terminal T2 in order to suppress high output voltage during recording. , a capacitor and a resistor with a time constant of C2, buffer amplifiers B and AMP constitute a Tana/full hold circuit. R and C are filters for absorbing spike noise generated by the opening and closing of the SW, R and C are filters for removing DC components included in the main beam detection signal, and R and C are one-shot pulse generators. Time constant element for RTOMB, R,, R8,, R
.

is a level setting resistor for one terminal of the reference level of the comparator COMF, and the ORgate which receives two signals from the input/output terminal of the one-shot bus generator and sends a 1" or "0" signal to the CPU is Connected to the final stage.

The waveforms of each part of the double recording prevention response circuit during the period when the beam is placed on the carrier defect site are shown in FIG. 2, with the horizontal axis corresponding to the time axis. First (5) is the waveform of the amplifier AMP output of the main beam signal A and B detected by dividing into two, (q is the buffer amplifier B via the switch SW,
Waveform at point C on the output side of AMP, (D) is comparator COMP
(C) is the output waveform of the comparator, (G) is the one-shot pulse generator RT
Waveform of output terminal F point of OMB, (q is C of ORgate
This is the waveform at the signal sending point G to the PU.

During tracking hold, the pickup moves to an adjacent track due to mechanical vibration, etc., and when you try to write to a track that has already been recorded, there is an information pit on the carrier surface, causing the pickup to move to an adjacent track. The waveform at the point is as shown in FIG. 2 (c).

Since the one-shot pulse generator RTOMB in the double recording prevention response circuit has an IJ) trigger function, points B, F, and G in Fig.
.

(Corresponding to q, σ9■ in the same figure, rl to a waveform like H.
Ru.

In the present invention, when the spot of the light beam falls on a defective area during writing of information onto a carrier, the level of the two-split light reception detection signal from the main beam inputted to the input terminal T and JC in FIG. Since the signal level is much higher than the signal level output when the beam moves to the adjacent track, it is impossible to determine whether the beam has moved to the adjacent track or not. Therefore, it is determined whether writing is prohibited based on the sending time of the output pulse at point G.

The above time determination is normal if the pickup does not move to the adjacent track even if the tracking servo is held while detecting a defective signal, and if for some reason double writing is performed on an already recorded track. In order to avoid a bad record, it is necessary to satisfy the condition that the demodulating function can be fully utilized even if the part where the double writing is omitted is not possible.

Thus, according to the double recording prevention method of the present invention, if the surface of the carrier, which is an information recording medium, has defects due to dirt or scratches, the beam passes through a wide range of defective areas, causing the sampling hold of the tracking servo function to take a long time. Even if the data is overwritten, it is possible to prevent the continuation of recording to neighboring tracks.
It is possible to prevent the recording space from being reduced unconsciously, and it is extremely useful in practice as it eliminates the trouble of losing information data that has already been recorded due to double recording.

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram of a double recording prevention response circuit for carrying out the double recording prevention method of the present invention, and FIG. 2 shows each point A, C, D, E, F, and G in FIG. 1. This is a waveform graph at . T,...input terminal, AMP,...amplifier, SW...
・Switch B, AMP...Buffer amplifier, COMP
...Comparator, RTOMB...One-shot pulse generator.

Claims (1)

[Claims] To write information to a thin carrier and read recorded information from the carrier, a beam emitted from a laser light source is focused on the information bits arranged on the carrier through the medium of an optical system, and the beam is directed along a track. In the recording and reproducing method for an optical recording medium, the beam scans the carrier, the period from the moment the beam comes into contact with a defective part such as dirt or scratches attached to the carrier surface during recording of information to the carrier until the beam leaves the carrier; When the electrical signal based on the detection of the reflected light of the beam exceeds the reference level of the comparator, the tracking function of the beam is temporarily stopped and the writing function is also stopped, so that when the track moves to the adjacent track, there is no record on the carrier. A method for preventing double recording on an optical recording medium, characterized in that the writing is continued by detecting this, but the writing function is stopped when there is a record.