JPS58161156A - Optical disck device - Google Patents

Abstract

PURPOSE:To prevent a recording error, by detecting a fact that an optical output of a laser exceeds a proper range, at each time of write and read. CONSTITUTION:An abnormal state detecting circuit 6 detects a fact that laser power is shifted from a proper range at each time of read and write, and applies a signal 60 to a protecting circuit 5 in case of an abnormal state. The protecting circuit 5 lowers resistance between its 2 terminals, makes a current 30 bypass to a protecting circuit side 50, and eliminates the current flowing to a laser 1 or makes it low enough, by which occurrence of a recording error is prevented. Also, a power monitoring circuit 7 outputs an output 70 corresponding to monitor light 10. Subsequently, shift from a proper range, of read and write power is detected by comparing circuits 65, 64 through a mean value circuit 68. This output is inputted to a flip-flop 63, and the control signal 60 to the protecting element 5 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical disc device, and more particularly to a recording protection device in an optical disc device that additionally records information.

In an optical disk device capable of recording and reproducing, both recording and reproduction are performed using the same optical head. A semiconductor laser is suitable as a light source because it is easy to modulate and has a small and light lid.

In recording mode, does the laser output correspond to the recording information? Recording is performed by applying a pulsed power of Pw to the recording film on the disk (optical slit) which is finely narrowed down by an optical head, and changing the optical properties of the recording film in the aperture area where it hits. . On the other hand, in playback mode, the laser power is set to a constant value P.
The read power Pa, denoted by i, is controlled to an energy of approximately frXA when the above-mentioned change in the recording film occurs due to the traveling light spot. In other words, note 2.・The difference in reproduction is simply the difference in the magnitude of the laser power. Therefore, if the laser power becomes excessive compared to the normal read power due to some reason such as a failure or malfunction of the logic circuit or element in the playback mode, erroneous recording may occur or information that has already been recorded may be lost. There is a possibility that it may be misleading. Therefore, in the reproduction mode, it is necessary to limit the laser power so that it does not increase beyond a constant 1-speed, and in the recording mode, it is necessary to control the range of the main recording power to a predetermined value.

On the other hand, recordable/reproducible optical disk devices are not provided with conventional protection means. In addition, in the case of a source disk device exclusively used for starting out, the above-mentioned problem cannot occur. Furthermore, the same applies to other devices using semiconductor lasers. Therefore, the above-mentioned problem can be said to be a new problem unique to optical disk devices for recording and reproducing.

SUMMARY OF THE INVENTION According to the present invention, it is an object of the present invention to obtain a protection device that prevents erroneous recording due to the optical output of a laser exceeding an appropriate range during each of recording (writing) and reproducing (reading).
purpose.

Figure 1 shows the laser power X on the recording film surface and the deformation i of the recording film.
It is an explanatory diagram of the relationship of iY. The power on the membrane surface is Xr, and the l-value power is During reading, deformation of the film surface must not occur, so in order to ensure that X t and for normal read signal processing, it must be maintained within an appropriate range a X 1 <: X < Although it is sometimes necessary that XT<X, the amount of deformation of the film surface must be within an appropriate range in order to read the recorded information correctly.
Although recording is possible with a power slightly higher than XT, the re-correction signal is so small that it is affected by noise and the like, making it impossible to reproduce information correctly. On the other hand, if the deformation sensitivity is too high (1), there will be problems such as deterioration of resolution with adjacent information.

Therefore, the light power must be kept within the range of XS <X < X4.

Erroneous recording of a musical composition refers to a case in which the above-mentioned ranges are exceeded in each of reading and writing. Therefore, the present invention detects all cases in which the above-mentioned ranges are exceeded, and performs a protective operation to prevent erroneous recording. That's true.

Figure 2 shows the semiconductor laser current ■ and the laser output power P(2
) shows the % gender summary. When the current I exceeds the threshold I t+y l", the laser output increases in proportion to the exceeded current. The laser output is narrowed down to a minute spot on the recording film through the optical system 4. Lead 9 in FIG. In order to maintain the appropriate power for each light, the current to the laser must be controlled.

Here, the characteristics of the laser fluctuate depending on temperature and other factors, as shown in the straight lines shown in FIGS. 2(a) and 2(b), so it is necessary to always keep the power at an appropriate level, including these fluctuations. By the way, the power at the time of reading is a continuous constant value, but at the time of writing, the power is controlled to a recording appropriate value in a pulse manner only when recording information. FIG. 3 is an explanatory diagram thereof. That is, the power is controlled to an appropriate value for writing in a pulse manner at the location where the information bit is formed. Third
In the figure, Pm indicates a read power value and Pw indicates a write power value. A VCVi information focus is formed on the recording film in response to the write pulse. This situation is shown in FIG. 3 [F]).

FIG. 4 shows the basic configuration of the present invention. In Figure 4, 1 is the semiconductor laser, 2 is the write drive control circuit, and 3j-j is the current to the laser? 4 is a current detection circuit, 5 is a protection circuit, 6 is an abnormality detection circuit, and 7 is a laser power monitor circuit. In normal operation, the current 30 from the current #i3 is applied to the laser 1, and during reading, a constant current corresponding to the read power Pm1C is applied to the laser 1, and during writing, the pulse signal 1511 corresponding to the write power Pw is applied to the two terminals of the protection circuit 5. The resistance is very high, and the current 50 to the protection circuit is zero. Therefore, a portion of the output of the laser 1 is guided to a 10t power monitor circuit 7, and the power is controlled to an appropriate level by a monitor output cuff 0. The current source 3 also includes the control function described above.

The current detection circuit 4 simply detects the current 40 and performs a current limiting function to prevent the power control circuit from running out of control for some reason and causing an overcurrent to flow to the laser.

An abnormality detection circuit 6 detects when the laser power deviates from the appropriate range for reading and writing, and provides a signal 60 to the protection circuit 5 when an abnormality occurs. Given the signal 60,
The protection circuit 5 lowers the resistance between its two terminals and reduces the current 3 (
l The protection circuit 5 is connected in parallel with the laser 1 and the current to the laser 1 is bypassed to make the current to the laser 1 zero or sufficiently low to prevent erroneous recording. However, it is easy to think that the protective function can be achieved by inserting a protective element in series with the laser circuit and increasing the resistance of that element in the event of an abnormality. However, the over-I current limiter by the current detector 4 and the current source 3 in Fig. 4 is different from the above-mentioned series type protection function in principle because it can achieve the fik function of the line. It is easy to design such a device.The present invention is to provide a capture means in a different manner in parallel with the laser, even though the above machine ttgt current source 3 has. It is possible to obtain a highly reliable device that prevents fatal false charges.In addition, when the protection function is activated, it has a means to notify the outside of the activation, and the cause of the activation is investigated. A more reliable device can be realized by providing logic that returns to normal operation only after the confirmation signal is confirmed.The above confirmation signal can be achieved by providing the confirmation signal as a signal 61 to the abnormality detection circuit 6.Signal 61 is given manually or from a higher level normality confirmation means.

This will be explained in detail below using examples. FIG. 5 shows a functional configuration diagram of the abnormality detection circuit. The power monitor circuit 7 is a circuit consisting of a photodetection diode D1, a load resistor R1, and an amplifier 5A, and is an output circuit corresponding to the monitor light 10.

Output as . The 700 waveform is a constant cough corresponding to the read power when reading, but is a pulsed write power waveform when writing. 68#i is an average value circuit, and outputs the average value of the monitor waveform with a time constant that is sufficiently long compared to the write pulse period. Reference numerals 65 and 64 are comparison circuits for detecting the deviation t of the read and write powers from the appropriate ranges, respectively. 69 is a reference signal indicating an appropriate value of write power, and 67 is a reference signal indicating an appropriate value of read power. Is 62 in read or write state? This signal indicates the read power reference signal 67? during writing. Can be corrected. Comparator 64.65
The output of the flip-flop 630 is led to the set input of the flip-flop 630, and when either output becomes 11", the 7 flip-flop 63 is set. The comparator circuits 64 and 65
It has input/output characteristics as shown in the figure. In other words, it is "O" in the range of 7 + ΔX for standard human power x6, and '1' when this range is exceeded.
This characteristic is usually called a window comparator. Figure 7 shows two comparators C
An example using 1,,C:l- is shown. In addition, in Fig. 7, E+ and El are X(, +ΔX and xo−Δ
Power supply indicating the reference value of the size of X, AND circuit at A, IA
and 0. , , Fi are an input terminal and an output terminal, respectively. Note that for the sake of simplification, it is often effective as a protection function even if only one side of the XO+Δχ side is used. In the write power comparison circuit 64, the value corresponding to xo in FIG. 6 is the appropriate write power value PW, and XQ-.DELTA.x and x6+.DELTA.X correspond to Xs and X4 in FIG. 1, respectively. In addition, in the read power comparison circuit 65, Xo is the appropriate value Pa of the read power, and
Q - ΔX, X (1+ΔX are X+ in Figure 1, respectively
Corresponds to X2.

Next, we will explain the operation of the comparison circuit on the read side during writing. Figure 8 shows the power waveform when moving from reading to writing. From time 1, a write pulse is given according to the write information. Assuming that the power level when there is no write pulse is the same as the level when reading, the average power value increases by ΔP. Read and write power ((Pm + Pws If the duty ratio of the write pulse is ΔP = P n, that is, when writing The average power is about twice as much as when reading.Also, the duty D of the write pulse varies depending on the write information slam, so the abnormality detection circuit on the read side is corrected by taking these factors into consideration.In other words, when writing, the abnormality detection circuit on the read side is corrected. The detection threshold value is increased by an amount corresponding to ΔP. The control signal for this purpose is 62 in FIG. 5, and the means for adding ΔPm is 66. In FIG. An example is shown below.

The voltage of the power supply 660 is divided by a circuit consisting of resistors 661, 662, and 663, and the reference voltage is 670? It is applied to the comparison circuit 65. Here, this is achieved by turning on and off the resistor 663 and the switch 620 according to the light information 62. Further, if a write pulse signal is used as the light 1 blue@62 and the time constant of 2 from the capacitor 664, resistor 661, etc. is selected to be equal to that of the average value circuit 68 in FIG. 5, more precise control is possible.

In the above explanation, is the error detection circuit on the read side also during writing? The reason for setting it in the operating state is as follows. That is, in order to record proper information (P), not only the amplitude of the write pulse but also the pulse width must be controlled within a certain range.
The write-side comparison circuit 64 shown in the figure cannot detect width information. On the other hand, is the average value manipulated on the lead side? Therefore, the pulse width is reflected in the average value output. This is F'! , # is clear from the fact that ΔP is proportional to the duty DK of the pulse. This can also prevent errors caused by the pulse width becoming excessive for some reason.

Various types can be used as long as they have the ability to bypass. For example, an SCR or other semiconductor switching element can be used.

Note: It is also actually effective to use only either read or write circuits as an abnormality detection circuit. In particular, when only the read side is used, as mentioned above, ΔP includes information r about the amplitude and width of the write pulse, so although the response time for average value processing is longer, it is also possible to detect abnormalities during writing, which is particularly useful in practice. It is valid. FIG. 10 is an embodiment in which only the HIJ side is used and the @ housing detection is also simplified.

Is the resistor 11 connected in series with the laser 1 a bypass effect due to the protection element 5? This is to make it more reliable. The protection element 5 is an SCR whose anode and cando terminals are connected in parallel with the laser circuit. When the current of 80R5 is applied, 5CRa turns on, bypassing the current of V-the. In the gate circuit of the SCR, a monitor output cuff o from the power monitor 7 functions as a voltage source 660 in FIG. 9, and a gate current supply circuit consisting of a resistor 665, a transistor 666, and a resistor 667 is formed. When the output 670 of the circuit corresponding to FIG. 9 exceeds a certain threshold, activating transistor 666, and exceeding the SCR gate current threshold, the SCR
turns off. Therefore, in this example, the reference interval (#
LFi is the operating threshold of the above transistor and SCR. The parameters of the circuit are set so that this value corresponds to a predetermined power threshold.

In Figure 10, 3-1 and 3-2 are read and write driver circuits, respectively? Constituent transistors, 4-1
and 4-2Fi are also resistive elements, and these driver circuits supply predetermined currents from the power supplies ER and Ew, respectively.

Q: According to the above explanation, does the present invention cause errors such as erroneous recording during reading for some reason, or recording too many or too few information bits during writing, making it impossible to reproduce correctly? It can be prevented. In an apparatus in which read and write operations are distinguished depending on the magnitude of the laser power impinging on the recording film, the problems posed by the present invention cannot be avoided, so the protection function of the present invention is indispensable. In addition to the above, if reading and writing are performed using the same laser beam, separate slots are required for reading and writing.
The same applies to devices using f, as well as devices using the head of l't IJ-driver circuit.
Everything about them is valid.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the relationship between the laser power applied to the recording film and the recording film changing device, Fig. 2 is a diagram showing the characteristics of the semiconductor laser current and laser output power, and Fig. 3 is a diagram showing the relationship between the write pulse and the recording pitch. 4 is a diagram showing the basic configuration of the present invention, Figure 5 is a diagram showing the configuration of an embodiment of the present invention, and Figure 6 is a diagram showing the structure of an embodiment of the present invention.
i An explanatory diagram showing an example of the characteristics of the comparison circuit in FIG. 5,
Is Fig. 7 an example of realizing the characteristics shown in Fig. 6? 8 is an explanatory diagram showing the write pulse and average power during writing, and FIG. 9 is a circuit diagram showing an embodiment for obtaining a reference signal corresponding to fluctuations in average power due to the write pulse. Figure 10 shows the lead side detection circuit.

Claims (1)

[Claims] In an optical disk device that uses a semiconductor laser as a light source and performs recording and reproduction depending on the optical output of the laser, a monitor signal r corresponding to the optical output of the semiconductor laser is used.
an abnormality detection means for detecting that the monitor signal exceeds a predetermined value; and a protection means having a characteristic ft such that an output of the abnormality detection means causes a short-circuit state between two terminals. A configuration connected in parallel to the laser circuit? An optical disk device with TW characteristics.