JPH01285025A - Optical signal reproducing circuit for optical disk device - Google Patents

Abstract

PURPOSE:To improve an S/N by setting a first reference voltage at a voltage lower by the degree of a prescribed voltage than the output voltage of a current- voltage converter obtained at the time of irradiating an area, in which the information of an optical disk is not recorded at all, with a light beam. CONSTITUTION:A first switching circuit 6 is provided which inputs the output voltage from a current-voltage converter 2 through an inverting amplifier 4 to a following stage amplifier 3 when the output voltage from the current- voltage converter 2 is smaller than the first reference voltage and which inputs the output voltage from the current-voltage converter 2 directly or through a buffer 5 to the following stage amplifier 3 when the former is larger than the latter to the contrary. The first reference voltage is set at the voltage lower by the degree of the prescribed voltage than the output voltage of the current-voltage converter 2 obtained at the time of irradiating the area, in which the information of the optical disk is not recorded at all, by means of the light beam by referring to a comparison result with a first comparator 7. Thus, the information to be reproduced can be correctly detected, the quantizing accuracy cannot be deteriorated, and the S/N in the current-voltage converter can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical disc device that records and reproduces information by irradiating an optical disc with a light beam, and particularly relates to an optical disc device that records and reproduces information by irradiating an optical disc with a light beam. This invention relates to an optical signal regeneration circuit that detects and regenerates a signal.

[Conventional technology]

In a conventional optical signal reproducing circuit in an optical disc device, a light beam reflected from an optical disc is detected by a photodetector, and all output current is input to a current-voltage converter to convert it into a voltage signal and output it. ing.

FIG. 9 is a circuit diagram showing a conventional optical signal regeneration circuit.

In Fig. 9, l is a photodetector, 2 is a current-voltage converter, 3 is a post-stage amplifier, OPI and OF2 are operational amplifiers, R1, R2, R3, and R4 are resistors, D is a diode, and VCC is a bias. The voltage, V, is the output voltage.

That is, a light beam (not shown) reflected from an optical disk (not shown) is detected by a photodetector 1 shown in FIG. 9, and its output current is converted into a voltage signal by a current-voltage converter 2. Thereafter, it is input to the rear-stage amplifier 3 via the resistor R2 and amplified, resulting in an output voltage ■. Bind and output.

In addition, related circuits of this type include Japanese Patent Application Laid-open No. 59
Examples include those described in JP-A-186143.

[Problem to be solved by the invention]

Fig. 10<a) is an explanatory diagram for explaining the format of an optical disk in the boat fishing sampling servo method, and Fig. 10(b) is an explanatory diagram specifically showing the servo field of Fig. 10(a). , is.

In FIG. 10, X represents the circumferential direction of the optical disc, and y represents the radial direction of the optical disc. Further, in FIG. 10(b), 31 to 34 are wobbling marks, 35 and 36 are embedded clocks, and the dashed-dotted line represents the center line of the virtual track.

Note that 1 byte is 15 channel bits.

In the optical disc using the sampling servo method, along the circumferential direction X, as shown in FIG. exist alternately.

As shown in FIG. 10(b), the servo field is provided in advance with wobbling marks 31 to 34 and embedded clocks 35 and 36 as pre-pits for performing tracking control, as well as wobbling marks 35 and 36 for performing focusing control. A unique distance section is provided.

Here, it is determined by standard that prepits are formed in any optical disc so that the reflectance (reflectance of the light beam) of the pre-pits is lower than the reflectance of the mirror surface of the optical disc. Note that the mirror surface of the optical disc referred to herein refers to a surface on which no information is written, such as the above-mentioned unique distance section.

Furthermore, when information is written to the data field of an optical disk using a light beam, the information is recorded as recording bits, but the recording bits are recorded depending on the optical disk, with a reflectance lower than that of the mirror surface. In some cases, it is formed so that the reflectance is higher than that of the mirror surface.

Now, in this way, optical disks using the sampling servo method are formed such that the reflectance of the recording bit part is lower than the reflectance of the mirror surface, and the other optical disk is formed so that the reflectance of the recording bit part is lower than the reflectance of the mirror surface. There are optical discs that are formed so that the height is higher than that of the optical disc, and it is desirable for an optical disc device to be able to record and reproduce information not only on one optical disc but also on both optical discs. .

However, when using a conventional optical signal reproducing circuit as shown in Figure 9 in an optical disc device that records and reproduces information on both optical discs, the following problems arise. was there.

FIG. 11(a) is a waveform diagram showing the waveform of the output current of the photodetector 1 in FIG. 9 separately during writing and reading of information, and FIG. 11(b) is a waveform diagram showing the waveform of the output current of the photodetector 1 in FIG. 9 separately. FIG. 2 is a waveform diagram showing the waveform of the output voltage of the current-voltage converter 2, divided into the time of writing and the time of reading information.

In Fig. 11, 41 is the peak due to the return light of the light beam, 42.45 is the peak due to prepits, and 43.44 is the peak due to the return light of the light beam.
is the peak due to recorded bits. Note that the data field period refers to the period during which the light beam irradiates the data field of the optical disk, and the servo field period refers to the period during which the servo field is irradiated.

First, the first problem will be explained.

During writing, when a light beam (specifically, a laser beam) is irradiating the data field of an optical disk to record information, the power of that light beam is high, so the return light of that light beam is used for photodetection. When detected by the current-voltage converter 1, a large peak 41 as shown in FIG. 11(b) appears in the output voltage of the current-voltage converter 2. On the other hand, when the light beam is irradiating the servo field of the optical disk, a peak 42 due to pre-pits appears in the output voltage of the current-voltage converter 2.

Here, the output voltage of the current-voltage converter 2 is input to the downstream amplifier 3 via the resistor R2, but when a large peak 41 appears due to the return light of the light beam as described above, it causes When the rear-stage amplifier 3 becomes saturated and ringing occurs in its output voltage o, and a peak 42 due to pre-pits appears immediately thereafter, the peak 42 due to pre-pits is hidden by the ringing, resulting in normal tracking. The problem was that it could not be controlled.

Therefore, in order to solve this problem, in the conventional example shown in FIG.
The signal is limited by the limiter level shown in FIG. 3(b) and input to the subsequent amplifier 3.

On the other hand, during reading, when a light beam illuminates the data field of the optical disk to reproduce information, the target optical disk is formed so that the reflectance of the recording pit portion is lower than the reflectance of the mirror surface. In the case of an optical disc in which the data is recorded, a peak 43 as shown by a solid line in FIG. 11(b) appears in the output voltage of the current-voltage converter 2 as a peak due to the recording bit.

However, if the target optical disk is an optical disk formed such that the reflectance of the recording pit portion is higher than the reflectance of the mirror surface, the current-voltage converter 2
The output voltage has the first peak due to the recording bit.
A peak 44 as shown by the broken line in FIG. 1(b) will appear, and at this time, if the level of this peak 44 exceeds the limiter level set by the diode D of the post-stage amplifier 3 mentioned above, There is a problem in that the level of the peak 44 is limited, making it impossible to detect the peak, and thus making it impossible to correctly detect the reproduced information.

The above is the first problem.

As mentioned above, the reflectance of the pre-pit part' in the servo field is formed to be lower than the reflectance of the mirror surface of any optical disk according to the standard, so that when reading, the light beam When irradiating the target optical disc, the output voltage of the current-voltage converter 2 will have a peak such as the one shown in FIG. 45 will appear.

Next, the second problem will be explained.

When the optical signal reproducing circuit shown in FIG. 9 is applied only to an optical disc formed so that the reflectance of the recording pit portion is lower than that of the mirror surface, the dynamic As a microwave, ■8
However, in order to be compatible with optical disks formed so that the reflectance of the recording pit portion is lower than that of the mirror surface, and optical disks formed so that the reflectance of the recording pit portion is higher than that of the mirror surface, it is necessary to It is necessary to have a dynamic range of V and +VP. Here, ■N is the first
As shown in FIG. 1(b), the maximum level value (■) of the peak 43 appearing in the output voltage of the current-voltage converter 2 is also the maximum level value of the peak 44. Note that both V and V are values based on the signal level (2) on the mirror surface.

Therefore, in the above two cases, the output voltage of the rear stage amplifier 3 is, respectively. When considering quantizing with n bits, the quantization accuracy is lower in the latter case than in the former case. That is, in the former case, the output voltage proportional to ■8 will be quantized with n bits, and in the latter case, the output voltage proportional to V N +V P will be quantized with n bits. For example, V
s ”V P, then (VN/2''')/((VN+VP)/2')=(V
Therefore, there is a problem in that the quantization accuracy in the latter case is 1/2 times worse than in the former case.

The above is the second problem.

Next, the third problem will be explained.

One possible way to avoid the first problem mentioned above is to eliminate the diode D as a limiter in the optical signal regeneration circuit shown in FIG. 9.

However, when doing so, when writing,
In order to prevent the subsequent stage amplifier 3 from becoming saturated as described above, the value of the resistor R1 of the current-voltage converter 2 must be made small.

However, if the value of the resistor R1 of the current-voltage converter 2 is reduced, as shown in FIG. 12, the current noise iR due to the resistor R1 will increase. That is, the current noise 1R (pA/J) due to the resistor R1 is as follows, assuming that the noise of the resistor R1 is eR.

Here, k: Boltzmann constant (1,38X 10-”) (W
-s/K)T: Absolute temperature (K) Δr: Equivalent noise bandwidth [Se].

Therefore, if the output current (signal component) of the photodetector 1 is i, the S/N in the current-voltage converter 2 is eR =:;- 1,l, and when the value of the resistor R1 is decreased, the current - There was a problem that the S/N ratio in the voltage converter 2 deteriorated.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an optical disc that is formed such that the reflectance of the recording pit portion is lower than the reflectance of the mirror surface. Even if the optical disc is formed to have a high height, it is possible to correctly detect the reproduced information during reading, and the quantization accuracy will not deteriorate when the output voltage of the downstream amplifier is quantized. Na(
Another object of the present invention is to provide an optical signal regeneration circuit that can improve the S/N ratio in a current-voltage converter.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention provides an optical disc device that records and reproduces information by irradiating an optical disc with a light beam, and an optical signal reproducing circuit that receives the irradiated light beam from the optical disc. a photodetector that detects reflected light and outputs a current according to the reflected light, a current-voltage converter that inputs the output current from the photodetector, converts it into a voltage, and outputs the voltage; - A first comparator that inputs the output voltage from the voltage converter and a first reference voltage and compares the magnitude of both voltages, and a first comparator that inputs the output voltage from the voltage converter and a first reference voltage, and an inverting amplifier that inverts and outputs the input voltage, a post-stage amplifier that amplifies and outputs the input voltage, and a comparison result by the first comparator to determine whether the output voltage from the current-voltage converter is is the first
When the output voltage from the current-voltage converter is smaller than the reference voltage, the output voltage from the current-voltage converter is inputted to the latter stage amplifier via the inverting amplifier, and when the output voltage from the current-voltage converter is larger, the current-voltage a first switch circuit that inputs the output voltage from the converter directly or via a buffer to the post-stage amplifier; The voltage is set to be a predetermined voltage lower than the output voltage of the current-voltage converter obtained when irradiating areas that are not exposed.

Further, a second comparator inputs the output voltage from the current-voltage converter and a third reference voltage and compares the magnitude of the two voltages; and a certain fourth reference voltage, and with reference to the comparison result by the second comparator, if the output voltage from the current-voltage converter is greater than the third reference voltage, further comprising a second switch circuit that outputs the output voltage from the current-voltage converter and outputs the fourth reference voltage when the output voltage from the current-voltage converter is smaller; The third reference voltage is set to be lower than the minimum value of the output voltage of the current-voltage converter obtained when reproducing information from the optical disc, and when recording information to the optical disc The output voltage of the current-voltage converter is set to a higher voltage than the output voltage of the current-voltage converter obtained when the current-voltage converter is in use. When the output voltage from the current-to-voltage converter is smaller than the first reference voltage, the output voltage from the second switch circuit is inputted to the second stage amplifier via the inverting amplifier, and the output voltage from the current-voltage converter is When the output voltage is higher, the output voltage from the second switch circuit may be input to the latter stage amplifier directly or via a buffer.

[Effect]

In the present invention, for example, if the target optical disk (sampling servo type optical disk) is an optical disk formed so that the reflectance of the recording pit portion is lower than the reflectance of the mirror surface, the data field at the time of reading During the period (the period during which the light beam is irradiating the data field of the optical disc), the current -
Since the peak caused by the recording pit appearing in the output voltage of the voltage converter takes a value larger than the first reference voltage, the first switch circuit converts the output voltage from the current-voltage converter directly or through a buffer. The signal is inputted to the post-stage amplifier via the signal. Also, during the servo field period (the period during which the light beam is irradiating the servo field of the optical disk) during reading, the peak due to prepits appearing in the output voltage of the current-voltage converter is lower than the first reference voltage. Since the output voltage also takes a large value, the first switch circuit inputs the output voltage from the current-voltage converter to the second-stage amplifier directly or via a buffer.

On the other hand, if the target optical disc is an optical disc formed such that the reflectance of the recording pit portion is higher than the reflectance of the mirror surface, the current-voltage converter is Since the peak caused by the recording pit appearing in the output voltage takes a value smaller than the first reference voltage, the first switch circuit converts the output voltage from the current-voltage converter through the inverting amplifier. The signal is input to the post-stage amplifier. In addition, during the servo field period during readout, as in the case of the optical disk formed so that the reflectance is lower than the reflectance of the mirror surface, the peak due to the pre-pits that appears in the output voltage of the current-voltage converter is Since it takes a value larger than the first reference voltage, the first switch circuit inputs the output voltage from the current-voltage converter to the second-stage amplifier directly or via a buffer.

As described above, according to the present invention, at the time of reading,
Even when the target optical disc is an optical disc formed such that the reflectance of the recorded bit portion is higher than the reflectance of the mirror surface, the output voltage of the current-voltage converter is equal to the first reference voltage. When the output voltage from the current-to-voltage converter is inverted and input to the second stage amplifier, the level of the input voltage input to the second stage amplifier is set to the second stage amplifier. without being limited by a built-in limiter and always
The reproduced information can be detected correctly.

Furthermore, since there is no need to increase the dynamic range of the post-stage amplifier, the quantization accuracy does not deteriorate when the output voltage of the post-stage amplifier is quantized.

In addition, the saturation of the post-stage amplifier that occurs during writing is
This can be prevented by a limiter provided in the latter stage amplifier, so the value of the resistance in the current-voltage converter can be reduced (
Therefore, the S/N ratio in the current-voltage converter can be improved.

Further, when the second comparator and the second switch circuit are further provided, a large peak due to the return light of the light beam appears in the output voltage of the current-voltage converter during writing. In this case, the large peak is the third peak.
Since the second switch circuit outputs the fourth reference voltage, the second switch circuit outputs the fourth reference voltage. Therefore,
For example, the fourth reference voltage may be set to a voltage approximately equal to the output voltage of the current-voltage converter obtained when the light beam is irradiating a tilted wall of the optical disc on which no information is recorded. By doing this, a large peak due to the return light of the light beam is cut off by the second switch circuit and is never input to the post-stage amplifier.

'In this way, when the second comparator and the second switch circuit are further provided, the large peak due to the return light of the light beam is cut off at the time of writing, so that it is not input to the subsequent stage amplifier. Therefore, there is no need to provide a limiter in the latter stage amplifier. Moreover, it is not necessary to reduce the value of the resistance in the current-voltage converter, and therefore the S/N in the current-voltage converter can be improved.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

In FIG. 1, the same components as those in FIG. 9 described above are given the same reference numerals.

In addition, 4 is an inverting amplifier, 5 is a buffer, 6 is a switch circuit, 7 is a comparator, 8 is a switch control circuit, 9 is a processing circuit, OF2 is an operational amplifier, R5 is a resistor, V rafl+
Vref! are the reference voltages, respectively. Here, as shown in FIG. 11(b), the reference voltage V refl is set to a level slightly lower than the signal level (2) on the mirror surface obtained as the output voltage of the current-voltage converter 2. , and the reference voltage ■0. is set to exactly the same level as the signal level (2) on the mirror surface.

Now, the operation of this embodiment will be explained.

A light beam (not shown) reflected from an optical disk (not shown) is detected by a photodetector l shown in FIG. 1, and its output current is converted into a voltage by a current-voltage converter 2 for comparison. The signal is input to the non-inverting input terminal of the device 7 and the switch circuit 6, respectively.

At this time, the reference voltage V re is applied to the inverting input terminal of the comparator 7.
Since fl is input, the comparator 7 outputs the output voltage of the current-voltage converter 2 and this reference voltage ■.

As a result, when the output voltage of the current-voltage converter 2 is larger, a positive value is output as the output voltage, and when it is smaller, a negative value is output.

On the other hand, the processing circuit 9 is a circuit that controls the entire optical disc device, and during the period in which the light beam is irradiating the servo field of the optical disc (i.e., the servo field period), it outputs a positive value as its output voltage and irradiates the data field. During this period (ie, data field period), a negative value is output.

The switch control circuit 8 inputs the output voltage from the comparator 7 and the output voltage from the processing circuit 9, and outputs a positive value as the output voltage only when both are negative values, and otherwise outputs a positive value. In this case, a negative value is output.

The switch circuit 6 connects the switch to the a side when the output voltage from the switch control circuit 8 has a positive value, and connects it to the b side when the output voltage has a negative value. Therefore, the switch circuit 6
When the switch is connected to the b side, the output voltage of the current-voltage converter 2 is input to the subsequent amplifier 3 as it is via the buffer 5, but when it is connected to the a side, the current-voltage The output voltage of the converter 2 is inverted by an inverting amplifier 4 and then input to a subsequent amplifier 3.

The latter stage amplifier 3 amplifies the input voltage to produce an output voltage ■. Bind and output.

FIG. 2 is a waveform diagram showing signal waveforms at various parts in FIG. 1.

In FIG. 2, (a) shows the waveform of the output voltage of the processing circuit 9, (b) shows the waveform of the output voltage of the comparator 7, and (C) shows the waveform of the output voltage of the switch control circuit. There is. In addition, A represents the waveform when the target optical disc is an optical disc formed such that the reflectance of the recorded bit portion is lower than the reflectance of the mirror surface, and B, B'
1 and 2 respectively show waveforms in the case of an optical disc formed so that the reflectance is higher than the reflectance of the mirror surface.

Therefore, for example, if the target optical disc is an optical disc that is formed so that the reflectance of the recording bit portion is lower than the reflectance of the mirror surface, the current In the output voltage of the voltage converter 2, a peak 43 as shown by the solid line in FIG. 11(b) appears as a peak due to the recording bit, but at this time, the peak 43 is the reference voltage . , l, the output voltage of the comparator 7 is a positive value as shown in FIG. 2(b)A, and the output voltage of the processing circuit 9 is a negative value as shown in FIG. 2(a). Therefore, the output voltage of the switch control circuit 8 becomes a negative value as shown in FIG. 2(c)A, and as a result, the switch of the switch circuit 6 is connected to the b side. The output voltage of No. 2 is input to the subsequent stage amplifier 3 via the buffer 5 as is.

Also, in the servo field period during readout,
In the output voltage of the current-voltage converter 2, a peak 45 as shown in FIG. 11(b) appears as a peak due to pre-pits, but at this time, the peak 45 is equal to the reference voltage V raft
Therefore, the output voltage of comparator 7 is as shown in FIG. 2(b)A.
Since the output voltage of the processing circuit 9 is a positive value as shown in FIG. 2(a), the output voltage of the switch control circuit 8 is as shown in FIG. 2(c)A. As a result, the switch of the switch circuit 6 is connected to the b side. Therefore, the output voltage of the current-voltage converter 2 is input to the subsequent stage amplifier 3 via the buffer 5 as it is.

On the other hand, if the target optical disc is an optical disc that is formed so that the reflectance of the recording bit portion is higher than the reflectance of the mirror surface, the current - Voltage converter 2
In the output voltage of the 11th peak due to the recording pit,
A peak 44 as shown by a broken line appears in FIG. 4(b). In this case, since the peak 44 takes a value smaller than the reference voltage Vr*r+, the output voltage of the comparator 7 takes a negative value as shown in FIG. 2(b)B. Furthermore, since the output voltage of the processing circuit 9 is a negative value as shown in FIG. 2(a), the output voltage of the switch control circuit 8 is a positive value as shown in FIG. 2(c)B. , the switch of the switch circuit 6 is connected to the a side. Therefore, the output voltage of the current-voltage converter 2 is inverted by the inverting amplifier 4 and then input to the subsequent stage amplifier 3. Here, the reference voltage ■, at the inverting amplifier 4. , 2 is the signal level ■ on the mirror surface.

Therefore, the output voltage of the current-voltage converter 2 is inverted in the inverting amplifier 4 around the signal level 2 on the mirror surface.

Also, in the servo field period during readout,
Since the output voltage of the comparator 7 is a positive value as shown in FIG. 2(b)B, and the output voltage of the processing circuit 9 is a positive value as shown in FIG. 2(a), the switch control circuit The output voltage of the switch 8 becomes a negative value as shown in FIG. 2(c)B, and as a result, the switch of the switch circuit 6 is connected to the b side. Therefore, the output voltage of the current-voltage converter 2 is input to the subsequent stage amplifier 3 via the buffer 5 as it is.

In this embodiment, since the switch circuit 6 generates noise every time the switch is changed, the value of the output voltage of the switch control circuit 8 changes from the data field as shown in FIG. 2(c)B. If it changes frequently during the period and the switch circuit 6 is constantly switched, the generation of the above-mentioned noise will increase. Therefore, as shown in FIG. 2(c)B', the switch control circuit 8 is configured so that once the output voltage reaches a positive value, it holds that value during the data field period. It is possible to reduce the noise generated by switching the switch.

Also, during writing, by always connecting the switch of the switch circuit 6 to the b side, the output voltage of the current-voltage converter 2 has a peak due to the return light of the light beam during the data field period. Figure 11 (b
Even if a large peak 41 as shown in FIG. ), the level of the peak 41 can be correctly limited by the limiter level.

As explained above, according to this embodiment, even when the target optical disk is an optical disk formed such that the reflectance of the recording pit portion is higher than the reflectance of the mirror surface during reading, , the level of the input voltage input to the rear stage amplifier 3 falls between the signal level ■1 and the maximum level ■8 on the mirror surface shown in FIG. 11(b), so the diode D of the rear stage amplifier 3
The level will not be limited beyond the limiter level set by , and reproduced information can always be detected correctly.

Also, as the dynamic range of the rear amplifier 3, ■
Since we only need to have 9, the output voltage of the second stage amplifier 3 ■.

When quantizing , the quantization accuracy does not deteriorate.

Further, saturation of the rear stage amplifier 3 that occurs during writing can be prevented by the diode D provided as a limiter in the rear stage amplifier 3, so there is no need to reduce the value of the resistor R1 in the current-voltage converter 2, and therefore, The S/N ratio in the current-voltage converter 2 does not deteriorate.

Next, FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

In FIG. 3, the same components as those in FIG. 1 described above are given the same reference numerals.

Additionally, 10 is external input means.

This embodiment differs from the embodiment shown in FIG. 1 in that an external input means 10 is provided in place of the comparator 7.

Now, the operation of this embodiment will be explained.

The user of an optical disc device (not shown)
When loading an optical disc (not shown) into an optical disc device, check whether the optical disc is an optical disc that is formed so that the reflectance of the recording pit portion is lower than the reflectance of the mirror surface (not shown).
Alternatively, whether the optical disc is formed so that the reflectance is higher than the reflectance of the mirror surface is input into the optical disc apparatus by external input means 10 shown in FIG.

When the loaded optical disc is input as an optical disc formed such that the reflectance of the recording pit portion is lower than the reflectance of the mirror surface, the external input means 10 outputs a positive value as its output voltage. However, if it is input as an optical disc formed to have a reflectance higher than the reflectance of the mirror surface, a negative value is output.

Therefore, the output voltage of the switch control circuit 8 is determined when the mounted optical disc (that is, the target optical disc) is formed such that the reflectance of the recording pit portion is higher than the reflectance of the mirror surface. , Moreover, it becomes a positive value only during the data field period at the time of reading, and becomes a negative value in all other cases.

Note that other operations are the same as those in the embodiment shown in FIG. 1, so their explanation will be omitted.

Therefore, in this embodiment as well, the same effects as in the embodiment shown in FIG. 1 can be obtained. Furthermore, in this embodiment, it is necessary to determine whether the target optical disk is an optical disk formed such that the reflectance of the recording pit portion is lower than the reflectance of the mirror surface, or Since information indicating whether the optical disc is formed in such a manner as to be
There is no need to provide the comparator 7 as shown in FIG. 1, so the circuit configuration becomes simple.

Next, FIG. 4 is a circuit diagram showing a third embodiment of the present invention.

In FIG. 4, the same components as those in FIG. 1 described above are given the same reference numerals.

Additionally, 6' is a switch circuit.

This embodiment differs from the embodiment shown in FIG. 1 described above in that the switch control circuit 8 is omitted.

As mentioned above (according to the standard, the reflectance of the pre-pit portion in the servo field is lower than the reflectance of the mirror surface in any optical disc, so during the servo field period during readout, the current-voltage converter 2, there is always a peak 4 as shown in Figure 11(b) as a peak due to pre-pits.
5 appears, and its peak 45 is the reference voltage V rl! Since it is larger than fl, the output voltage of comparator 7 always takes a positive value.

Therefore, the output voltage of the comparator 7 takes a negative value when the target optical disc is an optical disc that is formed so that the reflectance of the recording pit portion is higher than the reflectance of the mirror surface. In addition, since it is limited only to the data field period at the time of reading, the switching circuit can be controlled only by the output voltage from the comparator 7, without having to obtain information indicating whether it is a data field period or a servo field period from the processing circuit 9. can be switched correctly.

Now, the operation of this embodiment will be explained.

The switch circuit 6° shown in FIG. 4 connects the switch to the b side when the output voltage from the comparator 7 is a positive value,
If the value is negative, connect to the a side.

Therefore, for example, if the target optical disk is an optical disk formed such that the reflectance of the recording pit portion is lower than the reflectance of the mirror surface, the output voltage of the comparator 7 during the data field period during reading becomes a positive value, and as a result, the switch of the switch circuit 6' becomes b
connected to the side.

Therefore, the output voltage of the current-voltage converter 2 is input to the subsequent stage amplifier 3 via the buffer 5 as is.

Next, in the servo field period during readout,
As described above, the output voltage of the comparator 7 becomes a positive value, and as a result, the switch of the switch circuit 6 is connected to the b side. Therefore, similarly, the output voltage of the current-voltage converter 2 is 5, the signal is input to the subsequent stage amplifier 3 as it is.

On the other hand, if the target optical disc is an optical disc that is formed so that the reflectance of the recording pit portion is higher than the reflectance of the mirror surface, the comparator is The output voltage of circuit 7 has a negative value, and the switch of switch circuit 6'' is connected to the a side.

Therefore, the output voltage of the current-voltage converter 2 is inverted by the inverting amplifier 4 and then input to the subsequent stage amplifier 3.

Also, in the servo field period during readout,
As in the case of an optical disk formed with a reflectance lower than that of the mirror surface, the output voltage of the comparator 7 is a positive value, and the switch of the switch circuit 6° is connected to the b side. The output voltage of the current-voltage converter 2 is transferred to the buffer 5.
The signal is input as is to the subsequent stage amplifier 3 via the .

As described above, the same effects as in the embodiment shown in FIG. 1 can be obtained in this embodiment as well. Furthermore, in this embodiment, since the switch control circuit 8 is removed,
The circuit configuration becomes simpler.

Next, FIG. 5 is a circuit diagram showing a fourth embodiment of the present invention.

In FIG. 5, the same components as those in FIG. 4 described above are given the same reference numerals.

This embodiment differs from the embodiment shown in FIG. 4 described above in that the buffer 5 is deleted.

The buffer 5 is not necessarily indispensable in the configuration (when the switch of the switch circuit 6'' is connected to the b side, the output voltage of the current-voltage converter 2 is directly connected to the The signal may also be input to the downstream amplifier 3.

Next, FIG. 6 is a circuit diagram showing a fifth embodiment of the present invention.

In FIG. 6, the same components as those in FIG. 1 described above are given the same reference numerals.

In an optical disc device (not shown), when an astigmatism method is used as a method for detecting a focusing error signal, the photodetector 1 is divided into four parts. Therefore, the configuration of the optical signal regeneration circuit in such a case is to provide a signal processing system for each of the four divided photodetectors 1, so that a total of four
It must consist of two signal processing systems.

Therefore, in this embodiment, as shown in FIG. 6, there are four signal processing systems (each signal processing system includes a photodetector 1.
Current-voltage converter2. Switch circuit 6, inverting amplifier 4.
From the rear stage amplifier 3. ), a comparator 7 and a switch control circuit 8 are provided for one signal processing system, and the output voltage from the comparator 7 and the output voltage from the processing circuit 9 are input to the switch control circuit 8. , by its output voltage,
Not only the switch circuit 6 of the signal processing system but also the switching of the other three switch circuits 6 of the signal processing system are controlled.

In this embodiment, the switch control circuit 8 may be provided independently for each of the four signal processing systems.

Note that other operations are the same as those of the embodiment shown in FIG. 1 described above, so a description thereof will be omitted.

As described above, according to this embodiment, even when the astigmatism method is used as the method for detecting the focusing error signal, the same effects as in the embodiment shown in FIG. 1 described above can be obtained.

Next, FIG. 7 is a circuit diagram showing a sixth embodiment of the present invention.

In FIG. 7, the same components as those in FIG. 5 described above are given the same reference numerals.

Additionally, 11 is a switch circuit.

This embodiment is different from the embodiment shown in FIG. 11 was provided.

Now, the operation of this embodiment will be explained.

As described above, the processing circuit 9 is a circuit that controls the entire optical disc device, and outputs a positive value as its output voltage during the servo field period and a negative value during the data field period.

On the other hand, the switch circuit 11 connects the switch to the a side when the output voltage from the processing circuit 9 has a positive value, and connects it to the b side when the output voltage has a negative value. Therefore, the switch circuit 8
When the switch is connected to the a side, the output voltage of the current-voltage converter 2 is input to the switch circuit 6', but when the switch b
When connected to the side, the reference voltage Vr*f□ is input to the switch circuit 6'.

By the way, in each of the above-mentioned embodiments, during writing, by always connecting the switch of the switch circuit 6.6° to the b side, the level of the input voltage input to the rear-stage amplifier 3 can be changed to the rear-stage amplifier 3. The provided diode D is used to properly restrict the beam so that a large beam 41 due to the return light of the light beam as shown in FIG. 11(b) does not enter the rear stage amplifier 3 and saturate the latter stage amplifier 3.

However, during writing, a large peak 41 due to the return light of the light beam as shown in FIG. 11(b) appears in the output voltage of the current-voltage converter 2 only during the data field period. Therefore, in this example,
Only during the data field period during writing, the current is −
Instead of the output voltage of the voltage converter 2, the reference voltage is used.

is input to the switch circuit 6' to prevent a large peak due to the return light of the light beam from being input to the subsequent stage amplifier 3. .

That is, in the servo field period during writing,
Since the peak 42 caused by prepits as shown in FIG. 11(b) is necessary for tracking control, the switch circuit 11 is connected to the a side by the output voltage of the processing circuit 9, and the switch In circuit 6',
The output voltage from the current-voltage converter 2 is input. Further, during the servo field period during writing, the switch circuit 11 is connected to the b side by the output voltage of the processing circuit 9, and the reference voltages 2, . . . f2 are input to the switch circuit 6''. Here, the reference voltage V r
As mentioned above, af□ is set to exactly the same level as the signal level ■1 on the mirror surface, so the large peak 41 due to the return light of the light beam as shown in FIG. 11(b) is caused by this. It is cut by the switch circuit 11 and is never input to the subsequent stage amplifier 3.

Further, in this embodiment, the read operation is exactly the same as that of the embodiment shown in FIG. 5 described above by always connecting the switch of the switch circuit 11 to the a side.

As explained above, according to this embodiment, it is possible to cut off the large peak due to the return light of the light beam during writing and prevent it from being input to the downstream amplifier 3. There is no need to provide a diode D as a function. Furthermore, there is no need to reduce the value of the resistor R1 in the current-voltage converter 2, and therefore the S/N ratio in the current-voltage converter 2 does not deteriorate.

Also, when reading, the target optical disc is
Even in the case of an optical disc formed so that the reflectance of the recording pit portion is higher than that of the mirror surface, the level of the input voltage input to the rear stage amplifier 3 is set at the first level.
Since the signal level falls between the signal level ■ and the maximum level ■ on the mirror surface shown in Figure 1 (b), for example,
To always correctly detect reproduced information without limiting the level beyond the limiter level set by the diode D even if a diode D as a limiter is provided in a rear stage amplifier 3. I can do it.

Also, as the dynamic range of the rear amplifier 3, ■
Since it is sufficient to have 8, the output voltage of the rear stage amplifier 3■.

When quantizing , the quantization accuracy does not deteriorate.

Next, FIG. 8 is a circuit diagram showing a seventh embodiment of the present invention.

In FIG. 8, the same components as those in FIG. 7 described above are given the same reference numerals.

In addition, 12 is a comparator, and Vrar3 is a reference voltage. Here, the reference voltage V rats is as shown in Fig. 1L (b)
As shown in , when the target optical disc is an optical disc formed such that the reflectance of the recording pit portion is higher than the reflectance of the mirror surface, the output voltage of the current-voltage converter 2 is The level is set to be lower than the peak value of the peak 44 that appears as a peak due to pits.

This embodiment is different from the embodiment shown in FIG.
The point is that control is performed using the output voltage of a newly provided comparator 12 instead of the output voltage of the comparator 12.

Now, the operation of this embodiment will be explained.

The comparator 12 shown in FIG. 8 inputs the output voltage from the current-voltage converter 2 to its non-inverting input terminal, inputs the reference voltage Vr*f3 to its inverting input terminal, and inputs both of them. As a result of comparison, when the output voltage of the current-voltage converter 2 is larger, a positive value is outputted as the output voltage, and when it is smaller, a negative value is outputted.

Therefore, in the servo field period during writing, as described above, a peak 42 as shown in FIG. 11(b) appears in the output voltage of the current-voltage converter 2 as a peak due to prepits, but at that time, The peak 42 is the reference voltage ■. 2. Therefore, the output voltage of the comparator 12 becomes a positive value, and the output voltage of the current-voltage converter 2 is inputted to the switch circuit 6. Therefore, the peak 42 due to prepits necessary for tracking control is input to the subsequent amplifier 3 in its original state.

On the other hand, in the data field period when writing,
As mentioned above, the output voltage of the current-voltage converter 2 is
A large peak 41 appears due to the return light of the light beam as shown in FIG. The switch circuit 6 receives the reference voltage (2) instead of the output voltage of the current-voltage converter 2. f2 will be input. Therefore, the large peak 41 due to the return light of the light beam is cut off by the switch circuit 11 and is never input to the subsequent stage amplifier 3.

In addition, in this embodiment, the reference voltages {circle over (2)}, ..., f3 are set to a value lower than the peak value of the peak 44 shown in FIG. 11(b) as described above. Switch No. 11 will always be connected to the a side, so the operation at that time will be the same as the switch No. 5 described above.
The operation is exactly the same as the embodiment shown in the figure.

As explained above, according to this embodiment, the same effect as the embodiment of FIG. 7 described above can be obtained without using the information from the processing circuit 9 indicating whether it is a data field period or a servo field period. I can do it.

Although each of the above embodiments has been described assuming that the target optical disc is an optical disc using a sampling servo system, the present invention can also be applied to a case where the target optical disc is an optical disc using a general continuous groove system. .

〔Effect of the invention〕

As explained above, according to the present invention, even if the target optical disk is formed such that the reflectance of the recording pit portion is lower than the reflectance of the mirror surface, the Even if the optical disc is formed to can be detected.

In addition, since there is no need to increase the dynamic range of the post-stage amplifier, when quantizing the output voltage of the post-stage amplifier,
The quantization accuracy does not deteriorate.

In addition, the saturation of the post-stage amplifier that occurs during writing can be prevented by the limiter installed in the post-stage amplifier.
There is no need to reduce the value of the resistance in the current-voltage converter, and therefore the S/N in the current-voltage converter can be improved.

Furthermore, in some cases, during writing, it is possible to cut off a large peak due to the return light of the light beam and prevent it from being input to the downstream amplifier, so it is possible to install a limiter in the downstream amplifier, or use a current-to-voltage converter. There is no need to reduce the value of the resistance at.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, FIG. 2 is a waveform diagram showing signal waveforms of each part in FIG. 1, and FIG. 3 is a circuit diagram showing a second embodiment of the present invention. FIG. 4 is a circuit diagram showing a third embodiment of the invention, FIG. 5 is a circuit diagram showing a fourth embodiment of the invention, and FIG. 6 is a circuit diagram showing a fifth embodiment of the invention. , FIG. 7 is a circuit diagram showing a sixth embodiment of the present invention, FIG. 8 is a circuit diagram showing a seventh embodiment of the present invention, and FIG. 9 is a circuit diagram showing a conventional optical signal regeneration circuit. Figure 10(a) is an explanatory diagram for explaining the format of an optical disc in a general sampling servo system, and Figure 10(b) is an explanatory diagram for explaining the format of an optical disc in a general sampling servo system.
FIG. 11(a) is an explanatory diagram specifically showing the servo field in FIG. FIG. 11(b) is a waveform diagram showing the waveform of the output voltage of the current-voltage converter 2 in FIG. 9 separately for when writing and reading information, and FIG. is a characteristic diagram showing the relationship between the value of the resistor R1 of the current-voltage converter 2 and the current noise caused by the resistor R1 in FIG. 9,
It is. Explanation of symbols 1... Photodetector, 2... Current-voltage converter, 3...
- Post-stage amplifier, 4... Inverting amplifier, 5... Buffer, 6゜6'', 11... Switch circuit, 7, 12...
Comparator, 8... switch control circuit, 9... processing circuit, 10... external input means. Agent Patent Attorney Akio Namiki Figure 2 Figure 3 Figure 5 Figure 9 Figure 6 Figure 7

Claims (1)

[Claims] 1. In an optical signal reproducing circuit of an optical disc device that records and reproduces information by irradiating a light beam onto an optical disc, detecting reflected light from the optical disc of the irradiated light beam. , a photodetector that outputs a current according to the reflected light, a current-voltage converter that inputs the output current from the photodetector, converts it into a voltage, and outputs it, and a current-voltage converter that outputs the output current from the current-voltage converter. A comparator that inputs an output voltage and a first reference voltage and compares the magnitude of both voltages; and an inverting amplifier that inverts the input voltage around a certain second reference voltage and outputs the inverted voltage. , a post-stage amplifier that amplifies and outputs the input voltage;
Referring to the comparison result by the comparator, when the output voltage from the current-voltage converter is smaller than the first reference voltage, the output voltage from the current-voltage converter is outputted via the inverting amplifier. a switch circuit that inputs the output voltage from the current-to-voltage converter to the second-stage amplifier, and inputs the output voltage from the current-to-voltage converter to the second-stage amplifier directly or via a buffer when the output voltage from the current-to-voltage converter is larger; The first reference voltage is a voltage lower by a predetermined voltage than the output voltage of the current-voltage converter obtained when the light beam illuminates an area of the optical disc where no information is recorded. An optical signal reproducing circuit for an optical disc device, characterized in that the circuit is set to: 2. In the optical signal reproducing circuit according to claim 1, when the optical disc is a sampling servo type optical disc, it is determined whether the light beam illuminates the data field or the servo field of the optical disc. from a processing circuit that controls the operation of the optical disc device, and the switch circuit also refers to the first information obtained from the processing circuit in addition to the comparison result by the comparator. and when the light beam illuminates the data field and the output voltage from the current-to-voltage converter is smaller than the first reference voltage, the output voltage from the current-to-voltage converter is An optical signal reproducing circuit for an optical disc device, characterized in that the optical signal is input to the post-stage amplifier via the inverting amplifier. 3. In the optical signal regeneration circuit according to claim 2, an external input means is provided in place of the comparator, and the switch circuit receives information from the outside via the external input means in place of the comparison result by the comparator. using second information indicating whether the optical disc belongs to the first type or the second type, which is inputted by With reference to the first information, the output voltage from the current-voltage converter is input to the post-stage amplifier via the inverting amplifier, or the output voltage from the current-voltage converter is input directly or An optical signal reproducing circuit for an optical disc device, characterized in that an optical signal reproducing circuit for an optical disc device is configured to select whether to input the signal to the subsequent stage amplifier via a buffer. 4. In an optical signal reproducing circuit of an optical disc device that records and reproduces information by irradiating a light beam onto an optical disc, detecting the reflected light from the optical disc of the irradiated light beam, and detecting the reflected light from the optical disc and responding to the reflected light. a photodetector that outputs a current output from the photodetector, a current-voltage converter that inputs the output current from the photodetector, converts it into a voltage, and outputs it; a first comparator that inputs a reference voltage and compares the magnitude of both voltages; and a first comparator that inputs the output voltage from the current-voltage converter and a certain second reference voltage, When the output voltage from the current-voltage converter is larger than the first reference voltage, the output voltage from the current-voltage converter is output, and the current - a first switch circuit that outputs the second reference voltage when the output voltage from the voltage converter is smaller; inputs the output voltage from the current-voltage converter and a third reference voltage; A second comparator that compares the magnitude of both voltages, an inverting amplifier that inverts the input voltage around a certain fourth reference voltage and outputs it, and amplifies the input voltage and outputs it. When the output voltage from the current-voltage converter is smaller than the third reference voltage, the output voltage from the first switch circuit is The output voltage is inputted to the second stage amplifier via the inverting amplifier, and when the output voltage from the current-voltage converter is larger, the output voltage from the first switch circuit is inputted to the second stage amplifier directly or through a buffer. a second switch circuit for inputting the input to the amplifier, and the first reference voltage is lower than the minimum value of the output voltage of the current-voltage converter obtained when reproducing information from the optical disc. is also low, and the current obtained when recording information on the optical disk -
The third reference voltage is set to a voltage higher than the output voltage of the voltage converter, and the third reference voltage is set to a voltage higher than the output voltage of the voltage converter. - An optical signal reproducing circuit for an optical disc device, characterized in that the voltage is set to a predetermined voltage lower than the output voltage of a voltage converter. 5. In the optical signal reproducing circuit according to claim 4, when the optical disk is a sampling servo type optical disk, it is determined whether the light beam illuminates the data field or the servo field of the optical disk. from a processing circuit that controls the operation of the optical disc device, and the first switch circuit refers to the information obtained from the processing circuit as a substitute for the comparison result by the first comparator. and outputting the output voltage from the current-to-voltage converter when the light beam is irradiating the servo field of the optical disk, and outputting the second reference voltage when the light beam is irradiating the data field of the optical disk. An optical signal reproducing circuit for an optical disc device, characterized in that the optical signal reproducing circuit outputs an optical signal.