JPH06243471A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To maintain test reliability by switching over the write power between a synchronizing pattern section and other than the synchronizing pattern section in the data section of each sector and writing. CONSTITUTION:When a write pulse S10 is outputted, a read current iR and a normal write current iN flow through a semiconductor laser LD and the laser is driven by a current (iR+iN) and emits light. When the write pulse S10 is not outputted, only the read current iR flows through the semiconductor LD. Thus, at each sector, the read current iR and the normal write current iN flow through the semiconductor LD by a normal write power instruction signal S15 in a synchronizing pattern section. In other data sections such as a user data area DATA and an ECC area section, the read current iR and a write current iW flow. Therefore, a necessary synchronizing pattern is surely detected at the time of reading the data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control circuit for a light source such as a semiconductor laser (laser diode) suitable for use in an optical information recording / reproducing apparatus using an optical disk, an optical card, etc. Even in the test area recorded with a low output write power during the condition test, only the synchronization information necessary for reading the data is written with the normal emission power that allows the synchronization pattern to be extracted completely, The present invention relates to an optical information recording / reproducing device with improved reliability.

[0002]

2. Description of the Related Art In recent years, an optical disk device for optically recording / reproducing information using light emitted from a light source such as a semiconductor laser has been put into practical use and widely used as a large-capacity information recording device. There is. This optical disk device collects light emitted from a light source such as a semiconductor laser provided inside the device on an optical disk and records information by changing the optical characteristics of the light condensing point. Information is reproduced by detecting the change state of the dynamic characteristics.

By the way, in this optical disk device, the recording sensitivity varies depending on the disk or the recording position of the disk, the fluctuation of the beam intensity of the element itself constituting the light source such as a semiconductor laser, and the recording due to the ambient temperature. There is a problem that the recording conditions change due to changes in sensitivity. Therefore, the pit length of the recording pit, the C / N, the jitter, and the like vary, so that the reliability of the reproduced signal cannot be stably ensured.

In order to eliminate the influence of such fluctuations in the recording conditions, for example, a method of obtaining the optimum write power by a test has been proposed (Japanese Patent Laid-Open No. 4-21251, "Optical Disk Recording / Reproducing Apparatus"). With this method,
Prior to the actual information recording operation, the test pulse is recorded by sequentially changing the beam intensity (write power) of the laser light, and then the recorded area is reproduced to reproduce the pulse width of the reproduction signal. (That is, the pit length) is detected, and the write power for obtaining the optimum pit length is obtained.

As described above, if the test pulse recording and the reproduction thereof are tested prior to the actual recording of the information, the optimum write power can be obtained, so that the recording condition varies. It is possible to avoid the effect.
Although a detailed explanation is omitted, in this way, before the actual recording operation, while changing the write power, the optimum recording condition (and thus the optimum reproduction condition) is obtained, and thereafter, by this test, Various other test methods have been proposed as the test method for recording information with the optimum write power in accordance with the obtained conditions.

That is, the test method for obtaining this optimum recording condition is already known per se, and has been generally carried out in recent years in order to eliminate the fluctuation of the recording condition.
Next, an optical disk device having such a recording condition test function will be described with reference to the drawings.

FIG. 5 is a functional block diagram showing an example of the main configuration of an optical disk device having a conventional recording condition test function. In the figure, 1 is an optical head,
LD is its semiconductor laser, 1a is an objective lens, 1b is a photodetector, 2 is a first stage amplifier, 3 is a binarization circuit, 4
Is a sync extraction circuit, 5 is an error corrector, 6 is a data buffer, 7 is a sector detector, 8 is a write timing control circuit, 9 is a semiconductor laser drive circuit (LD drive circuit), 10 is a D / A converter, and 11 is CPU, 12 are disks, S1 is a light reception output detection signal, S2 is an analog reproduction signal, S3 is a digital reproduction signal, S4 is MO read data, S5 is corrected read data, S6 is write data, and S7 is RF read data. , S8 is RF / MO
Switching signal, S9 ID detection signal, S10 write pulse, S11 write power data, S12 write gate signal, S13 write power control signal, S14 LD
Indicates drive current.

First, the configuration of the conventional optical disk device,
The basic operation will be described, and then the test operation for obtaining the optimum recording condition will be described. In the optical disk device of FIG. 5, the light emitted from the semiconductor laser LD (laser diode) provided in the optical head 1 is focused on the disk 12, and the reflected light is detected by the photodetector 1b.

Therefore, from the photo detector 1b,
A detection signal proportional to the reflected light is output as the light reception output detection signal S1. The received light output detection signal S1 is amplified by the first-stage amplifier 2 to become an analog reproduction signal S2, which is input to the next binarization circuit 3 to select the reproduction system.

That is, the binarizing circuit 3 selectively outputs an RF / MO switching signal S8 for instructing whether to reproduce the RF signal in the pre-formatted area or the MO signal in the data area. Thus, the reproduction system is selected and the binarized digital reproduction signal S3 is output to the sync extraction circuit 4. The sync extraction circuit 4 synchronizes the input digital reproduction signal S3 and outputs the RF read data S7 to the sector detector 7 and the MO read data S4 to the error corrector 5, respectively.

The sector detector 7 has a function of detecting which position of the sector the laser focusing point scans on the basis of the RF read data S7. As a real-time timing detection signal, The RF / MO switching signal S8 and the ID detection signal S9 are output. On the other hand, the corrected read data S5 whose error has been corrected by the error corrector 5 is sent to the data buffer 6.

The data buffer 6 exchanges recording / reproducing data with the outside of the apparatus via an external interface (not shown). Now, at the time of data writing, the write data S6 is sent from the data buffer 6 to the write timing control circuit 8.

The write timing control circuit 8 processes the supplied write data S6 in accordance with the timing of the ID detection signal S9, generates a write pulse S10, and outputs it to the semiconductor laser drive circuit 9. In this case, the light emission power when writing data, that is,
The write power of the semiconductor laser LD in the optical head 1 is
It can be set by the CPU 11.

Specifically, according to the write power data S11 given from the CPU 11 to the D / A converter 10, the write power data S from the D / A converter 10 is given.
A write power control signal S13 proportional to 11 is generated and output to the semiconductor laser drive circuit 9. At the same time, the write pulse S from the write timing control circuit 8
10 is logically ANDed by the write gate signal S12 from the CPU 11 and given to the semiconductor laser drive circuit 9.

Therefore, the semiconductor laser drive circuit 9 outputs a pulsed LD drive current S14 obtained by ANDing the write gate signal S12 to drive the semiconductor laser LD in the optical head 1. .
The above is the configuration of the conventional optical disk device and the basic operation.

In this optical disk device, in order to obtain the optimum write power, the CPU 11 changes the write power data S11 to perform the write operation in the above-mentioned test, and checks and executes the reproduction state. ing. Here, the detailed configuration of the conventional semiconductor laser drive circuit 9 shown in FIG. 5 will be described.

FIG. 6 is a block diagram showing an example of a detailed circuit configuration of the conventional semiconductor laser drive circuit 9. In the figure, LD is a semiconductor laser, TR1 and TR2 are transistors, U11 is an AND gate circuit, U
21 is an inverter, WPS is a write power constant current source, R
PS is a read power constant current source, R1 is a resistor, i
W indicates a write current and iR indicates a read current. The input signal is the same as that in FIG. 5, S10 is a write pulse,
S12 is a write gate signal, and S13 is a write power control signal.

In the drive circuit 9 shown in FIG. 6,
The write pulse S10 and the write gate signal S12 are input to the AND gate circuit U11 and subjected to logical product processing. When the result is "1", the transistor TR1 is driven. In addition, via the D / A converter 10 shown in FIG.
The write power control signal S13 (write power control voltage set by the CPU 11) is supplied, and the write power constant current source WPS outputs the write current iW.

This write current iW is transferred to the transistor TR.
1 to the semiconductor laser LD. This semiconductor laser LD always has a read power constant current source RPS.
Since the read current iR from the above is supplied, both of these currents are added during the write operation, and the current (iW +
iR).

On the other hand, when the result of the logical product by the AND gate circuit U11 is "0", the transistor TR2 is driven and the write current iW flows to the dummy resistor R1. Therefore, only the read current iR is supplied to the semiconductor laser LD. Flows. The control operations of the write power and the read power in the conventional optical disk device having the write power test function and the semiconductor laser drive circuit are as described above.

However, the conventional optical disk device has the following problems when the above-mentioned recording condition test is executed in order to obtain the optimum write power.
In such a test, the test data is recorded while changing the write power of the semiconductor laser LD.

At the time of reproduction, the write data portion is read, and various synchronization patterns for obtaining the synchronization information of the reproduction signal are inserted in the data portion. That is, the sector format of an optical information recording medium such as a magneto-optical disk is defined by the ISO standard, the Japanese Industrial Standard, or the like.

For example, "ID" is an address and "GAP"
Is a gap with no data, "VFO3" is a continuous data pattern for PLL lock, "SB" (SYNC BYT
E) is a sync signal of the data part, "DATA" is a user data area, "RS" (RESSYNC) is a special code for synchronization, and the like. Thus, in each sector,
In addition to "DATA" and "ECC", a "VFO3" pattern, an "SB" pattern, an "RS" pattern, etc. are inserted (see FIG. 3 below).

At the time of data reading, the synchronization of the read data is realized by extracting the synchronization information from the respective synchronization patterns of "VFO3", "SB" and "RS". In this case, if these pieces of synchronization information are lost, the synchronization information cannot be obtained, so that it is practically impossible to execute the data read.

For example, in the test under the optimum recording condition, in the test area where the write power is set to low output, the sync patterns of "VFO3", "SB" and "RS" are necessarily low output. Will be recorded. as a result,
In this test area, the extraction of the synchronization pattern is incomplete, and satisfactory data reading cannot be performed.

As described above, in the data write in such a test area and the test of the recording condition by the read, there is a problem in the extraction of the synchronization pattern in the case of the data recorded with the low output write power. Therefore, in the conventional test of the recording condition, there is a problem that the reliability of the result may be questioned and the meaning of the test itself may be lost.

[0027]

SUMMARY OF THE INVENTION According to the present invention, in the conventional optical information recording / reproducing apparatus, such inconvenience that occurs during the test of the optimum recording condition is solved, and the test of the data recorded with the low output write power is performed. Even in the area, only the synchronization information necessary for reading data can be recorded with normal write power, and the synchronization pattern can be extracted completely, thereby improving the reliability of test results. And

[0028]

According to the present invention, firstly,
In an optical information recording / reproducing apparatus having a recording condition test function of writing data while changing the write power of a light source such as a semiconductor laser and reading the data to measure the reproduction state, the data portion of each sector at the time of data writing And a portion other than the synchronization pattern, which is provided with a means for switching the write power between the synchronization pattern portion and the portion other than the synchronization pattern. With, the write power is switched to write data.

Secondly, in an optical information recording / reproducing apparatus having a test function of writing data while changing the write power of a light source such as a semiconductor laser and reading the data, the sector data is read. In the synchronization pattern section in the section, a write timing control circuit for outputting a normal write power instruction signal, a write current supply means for supplying at least two different write currents to a light source such as a semiconductor laser, and a write current supply means The light current supplied to the light source such as the semiconductor laser is
And a means for switching according to the normal write power instruction signal.

Thirdly, in the second optical information recording / reproducing apparatus, a logical product calculating means for taking a logical product of all the signals controlling the write current supplying means and the write gate signal instructing the data write. It is a configuration provided with.

[0031]

According to the present invention, in order to ensure the reliability of the test, even in the test area recorded with the write power in the low output state, only the synchronization information necessary for the data read is written with the normal laser emission amount. By controlling so that the sync pattern can be extracted completely. That is, in the conventional device, during the write operation,
Both the read current iR and the write current iW are added and supplied, and only the read current iR is supplied to the semiconductor laser LD during the read operation, but when the write current iW is low output, all tests are performed. As a result of recording the data at a low output, the synchronization information detected at the time of reading becomes small.

According to the present invention, only the synchronization information required for data read is directly related to the level of the write current iW.
In order to perform recording with a write current of a predetermined level, the sync pattern portion in the data portion of each sector is detected during the test, and control is performed so that the normal write current is output at that timing (claims 1 and 2). Invention). Also,
In order to reduce power consumption, all signals controlling the write current supply means are ANDed with the write gate signal instructing the data write, so that the semiconductor laser, the dummy resistor, etc. Also, the current is not supplied (the invention of claim 3).

[0033]

Embodiment 1 Next, an optical information recording / reproducing apparatus of the present invention will be described in detail with reference to the drawings. This embodiment mainly corresponds to the inventions of claims 1 and 2, but the basic operation of the test of the optimum recording condition is also related to the invention of claim 3.

FIG. 1 is a functional block diagram showing an embodiment of the main configuration of the optical information recording / reproducing apparatus of the present invention. Reference numerals in the figure are the same as those in FIG.
Reference numeral 15 indicates a normal write power instruction signal.

In FIG. 1, only the changed parts of FIG. 5 are shown so that the characteristic points of the present invention can be easily understood. As shown in FIG. 1, the write timing control circuit 8 is configured to newly generate the normal write power instruction signal S15 together with the write pulse S10 of FIG. 5 and output it to the semiconductor laser drive circuit 9. There is.

In this case, the write timing control circuit 8
, The ID detection signal S9 from the sector detector 7,
That is, since the real timing information indicating where in the sector the converging point of the semiconductor laser LD is scanning is input, the current position of the sector can be detected based on the ID detection signal S9. . The write timing control circuit 8 basically has the same function as that of FIG. 5 described as a conventional example.

In the present invention, the write timing control circuit 8 is provided with the function of generating the normal write power instruction signal S15 in synchronization with the ID detection signal S9 from the sector detector 7. That is, by the control operation in the write timing control circuit 8, with respect to the sector of the data section,
The normal write power instruction signal S15 is output only at the timing of the position where the synchronization patterns of "VFO3", "SB", and "RS" are recorded.

As described above, in the optical information recording / reproducing apparatus of the present invention, when the write power of the semiconductor laser LD is controlled by using the normal write power instruction signal S15 and the data of the synchronous pattern portion is written, Instead of the conventional write current (iR + iW), only the synchronization information necessary for the data read is the write current (iR + iN) of the predetermined level.
The feature is that it is recorded at. Other configurations and operations are basically the same as those in FIG. 5 described above as a conventional example.

In FIG. 1 described above, the main points of the optical information recording / reproducing apparatus of the present invention have been described. Next, a specific configuration of the semiconductor laser drive circuit will be described. here,
Description will be made in correspondence with FIG. 6 showing a conventional example.

FIG. 2 is a block diagram showing an embodiment of the detailed circuit configuration of the semiconductor laser drive circuit in the optical information recording / reproducing apparatus of the present invention. Reference numerals in the figure are the same as those in FIGS. 6 and 1, TR3 and TR4 are transistors, U12 and U13 are AND gate circuits, U22 and U23 are inverters, NWPS is a normal write power constant current source, R2 is a resistor, iN usually indicates a write current.

The semiconductor laser drive circuit shown in FIG.
As is clear from a comparison with the conventional drive circuit shown in FIG. 6, the circuit shown in FIG. 2 is provided with the normal write power constant current source NWPS and is supplied with the normal write current iN. The points are clearly different. In the circuit of FIG. 2, when the normal write power instruction signal S15 is given from the write timing control circuit 8 in the write operation during the test for obtaining the optimum write power, the normal write current iN is output together with the read current iR. ,
Both currents are added and supplied to the semiconductor laser LD.

FIG. 3 is a time chart for explaining the operation of the semiconductor laser drive circuit shown in FIGS. 1 and 2 during data writing. The symbols attached to the waveforms correspond to the symbol positions in FIGS. 1 and 2, and the sector format is an example of the Japanese Industrial Standard.

The time chart of FIG. 3 shows the case of writing data of 2 sectors. At the time of this write operation, the write gate signal S12 is output at "H", and the sector detector 7 of FIG.
9 is output at "H", the write timing control circuit 8 shown in FIG.
15 is generated and becomes “H”.

From the write timing control circuit 8,
The write pulse S10 similar to the conventional one is output. Therefore, in the semiconductor laser drive circuit of FIG. 2, the write pulse S10 and the normal write power instruction signal S15 are
Input from the write timing control circuit 8 and CP
A write power control signal S13 is input from U11 via the D / A converter 10, and a write gate signal S12 is further input from the CPU 11.

In FIG. 2, the write power control signal S13 is sent from the CPU 11 to the D /
It is set via the A converter 10 and controls the write current iW from the write power constant current source WPS. On the other hand, the newly provided normal write power instruction signal S15 is a signal output only in the sync pattern part of "VFO3", "SB", "RS" of the data part in each sector which executes data write. .

The write gate signal S12 is also a signal output from the CPU 11 in FIG. 5, and the write gate signal S12 is a signal for roughly instructing the data write operation and emits light from the semiconductor laser LD. The write timing control circuit 8 is controlled to output a pulse signal for this purpose. In FIG. 2, the read current iR from the read power constant current source RPS is constantly supplied to the semiconductor laser LD.

At the time of the test, the write current iW for performing the write operation, which is variably controlled by the instruction from the CPU 11, is supplied from the write power constant current source WPS. In this case, in FIG. 2, the AND gate circuit U1
The following operation is performed by the logic circuit including 1 to U13 and the inverters U21 to U23.

First, when the normal write power instruction signal S15 is not output, that is, the emitted light from the semiconductor laser LD is in a position such as the user area of the data section or the ECC area section, and the write pulse S10. Is output, the write current iW is supplied to the semiconductor laser LD via the transistor TR1 as in the conventional case. Therefore, in this state, the semiconductor laser LD
Read current iR and write current iW flow to
It is driven by a current of "+ iW" to emit light.

When the write pulse S10 is not output, the write current iW flows from the transistor TR2 to the dummy resistor R1. Therefore, only the read current iR flows in the semiconductor laser LD. On the other hand, when the normal write power instruction signal S15 is output, the following operation is performed.

First, when the write pulse S10 is being output, the normal write current iN supplied from the normal write power constant current source NWPS flows from the transistor TR3 to the semiconductor laser LD.
The read current iR and the normal write current iN flow, and "iR
It is driven by a current of "+ iN" to emit light. On the other hand, when the write pulse S10 is not output, this normal write current iN is transmitted from the transistor TR4 to the dummy resistor R2.
To the semiconductor laser LD, the read current iR
Only flows.

As described above, at the time of data writing in the test of the optimum recording condition, in each sector of the data part,
In the sync pattern portion, the normal write power instruction signal S15
As a result, the read current iR and the normal write current iN flow to the semiconductor laser LD, and the read current iR and the read data i in the user data area DATA and ECC area of the other data section.
Since R and the write current iW flow, it is possible to reliably detect a necessary synchronization pattern when reading data. Therefore, the reliability of the test under the optimum recording condition can be improved.

[0052]

Second Embodiment Next, a second embodiment of the present invention will be described. This embodiment mainly corresponds to the invention of claim 3, but is also related to the inventions of claim 1 and claim 2.

In the first embodiment described above, as described with reference to FIG. 2, two types of write currents iW and iW are used during the test write.
Although data writing is performed by switching N and N, when the write gate signal S12 is not output, it is not necessary to supply current to the transistors TR1 to TR4. Therefore, the second embodiment is characterized in that such waste is eliminated and power consumption is reduced.

FIG. 4 is a block diagram showing a second embodiment of the detailed circuit configuration of the semiconductor laser drive circuit in the optical information recording / reproducing apparatus of the present invention. Reference numerals in the figure are the same as those in FIG. 2, and U14 to U17
Is an AND gate circuit, and U24 and U25 are inverters.

Also in the second embodiment shown in FIG. 4, the operation timing of each signal is the same as that in FIG. 3 described above, and therefore detailed description thereof will be omitted. In the circuit of FIG. 4, since all the transistors TR1 to TR4 are gated by the write gate signal S12, the drive current (write current iW or normal write current iN) flows into the dummy resistors R1 and R2. Only when the gate signal S12 is output.

When the write gate signal S12 is not output, that is, when the data write is not performed, the semiconductor laser LD and the dummy resistors R1 and R2 are used.
No current is supplied to either. Therefore, it is possible to prevent useless current from being generated in the non-write state,
In addition to the same effect as the first embodiment, the unique effect that the consumption current can be saved can be obtained.

As described above, in the optical information recording / reproducing apparatus of the present invention, in order to detect the optimum write power, the data write operation is performed while changing the write power, and the data is read and reproduced. In the test of the recording condition for checking the recording pattern, even in the test area written with the low output write power, the "V
Only the sync patterns such as FO3 "," SB "," RS ", etc. are written with the normal write power.Therefore, when the test area is read, the sync pattern can be detected stably. Data can be read while maintaining the synchronized state.

As a result, the reliability of the test for obtaining the optimum write power of the semiconductor laser LD can be maintained. In the above embodiments, the case of the optical disk device was mainly described, but a magneto-optical disk device,
It is obvious that the write-once type optical disk device, the optical card, and the like can be similarly implemented, and the present invention is not limited to the case of the embodiment.

[0059]

According to the optical information recording / reproducing apparatus of the first aspect of the present invention, in order to obtain the optimum write power, a test of recording conditions, that is, data write / write while varying the write power is performed.
Even when the test area recorded in the state where the write power is low is read, the "VFO" is read.
Only sync patterns such as 3 "," SB ", and" RS "are written (recorded) with normal write power. Therefore, when such a test area is read (reproduced), it is stable. Data can be read in the synchronized state, and the reliability of the test is maintained.

In the optical information recording / reproducing apparatus of the second aspect, in order to maintain the reliability of the test by the optical information recording / reproducing apparatus of the first aspect, the write pulse output is performed by the normal write power instruction signal from the write timing control circuit. At the same time, the write current supplied to the light source such as a semiconductor laser is controlled so as to be switched between the synchronization pattern section, the user data and the ECC section. Therefore, the same effect as that of the optical information recording / reproducing apparatus of the first aspect can be obtained.

In the optical information recording / reproducing apparatus of the third aspect, the signal for driving each transistor is generated by the logical product with the write gate signal in the control circuit of the light source such as the semiconductor laser. Therefore, in the state where the write gate signal is not output, all the transistors are turned off, so that useless current is prevented from flowing, and in addition to the effect of the optical information recording / reproducing apparatus according to claim 2, Power saving is realized.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of the main configuration of an optical information recording / reproducing apparatus of the present invention.

FIG. 2 is a block diagram showing an example of a detailed circuit configuration of a semiconductor laser drive circuit in the optical information recording / reproducing apparatus of the present invention.

FIG. 3 is a time chart for explaining an operation at the time of writing data in the semiconductor laser drive circuit shown in FIGS. 1 and 2.

FIG. 4 is a block diagram showing a second embodiment of the detailed circuit configuration of the semiconductor laser drive circuit in the optical information recording / reproducing apparatus of the present invention.

FIG. 5 is a functional block diagram showing an example of a main part configuration of an optical disc device having a conventional recording condition test function.

FIG. 6 shows a conventional semiconductor laser drive circuit 9,
It is a block diagram showing an example of the detailed circuit configuration.

[Explanation of symbols]

 1 Optical Head LD Semiconductor Laser 1a Objective Lens 1b Photodetector 2 First Stage Amplifier 3 Binarization Circuit 4 Sync Extraction Circuit 5 Error Corrector 6 Data Buffer 7 Sector Detector 8 Write Timing Control Circuit 9 Semiconductor Laser Drive Circuit 10 D / A Converter 11 CPU

Claims (3)

[Claims] 1. An optical information recording / reproducing apparatus having a recording condition test function of writing data while changing the write power of a light source such as a semiconductor laser and reading the data to measure a reproduction state, at the time of data writing. A means for switching the write power between the sync pattern part in the data part of each sector and the part other than the sync pattern is provided, and when executing the test of the recording condition, at the time of data write,
An optical information recording / reproducing apparatus, characterized in that the write power is switched between the sync pattern part in the data part of each sector and the part other than the sync pattern to write data. 2. An optical information recording / reproducing apparatus having a test function of writing data while changing the write power of a light source such as a semiconductor laser, reading the data, and measuring a reproduction state, in a data section of a sector. A write timing control circuit that outputs a normal write power instruction signal in the synchronization pattern section, a write current supply unit that supplies at least two different write currents to a light source such as a semiconductor laser, and the semiconductor device from the write current supply unit. An optical information recording / reproducing apparatus comprising: means for switching a write current supplied to a light source such as a laser according to the normal write power instruction signal. 3. The optical information recording / reproducing apparatus according to claim 2, further comprising a logical product calculating means for calculating a logical product of all signals controlling the write current supplying means and a write gate signal for instructing data writing. An optical information recording / reproducing apparatus characterized in that