JPH05189771A - Information recording and reproducing method and device and recording medium used therein - Google Patents

Abstract

PURPOSE:To miniaturize the information recording and reproducing device and to improve its reliability by controlling the plural reproduced signals of the information recording and reproducing device for two beams which checks the recording state of the information by irradiation with reproducing spots right after recording of the information. CONSTITUTION:Plural detection signals are inputted to a reproducing means and contact points 12a, 12b are reproduced by selecting any of the plural detection signals at the time of irradiating the surface of a recording medium 30 with the plural light spots 21, 22 and reproducing the plural detection signals obtd. according to the respective light spots. The control to switch the plural inputted detection signals and the control of the outputs of the light sources 1, 2 for irradiation with the light spots are executed in the reproducing means. Then, the information recording and reproducing device which can reproduce the information with the reproducing means fewer than the number of the detection signals without providing the reproducing means for each of the plural detection signals is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing method for recording or reproducing information on a recording medium, and particularly to an information recording / reproducing method suitable for controlling a reproduction signal and an information recording using the same. The present invention relates to a reproducing device and a recording medium suitable for use in the reproducing device.

[0002]

2. Description of the Related Art For example, in Japanese Patent Laid-Open No. 58-146039, in order to detect a defect on a recording medium at an early stage, the recorded information is reproduced immediately after the information is recorded on the recording medium. There is disclosed an optical head for confirming that the data has been recorded. The structure is shown in FIG. The optical head of the apparatus shown in FIG. 7 includes a light source 60 for recording and a reproduction light source 68 for confirming recording.
Have. When recording information, a light beam 74 from the recording light source 60 forms a recording spot with the objective lens 63 and irradiates the medium 64. The luminous flux 75 from the light source 68 also forms a reproduction spot for confirmation by the objective lens 63 and forms the medium 64.
Irradiate on top. The confirmation reproducing spot is located behind the recording spot with respect to the traveling direction. That is, the information recorded by the recording spot is confirmed by guiding the reflected light from the confirmation reproducing spot to the signal detector 73 and reproducing it.

However, although the above-mentioned prior art discloses the structure of the recording / reproducing optical head, the structure for converting the signal obtained by the signal detector 73 into information, the signal processing method, and the recording / reproducing method. Nothing is disclosed regarding the positional deviation of the reproducing light spot.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to control a plurality of reproduction signals in a two-beam information recording / reproducing apparatus which irradiates a reproduction spot immediately after recording information to confirm the recording state of information. The object is to reduce the size and reliability of the information recording / reproducing apparatus.

Another object of the present invention is to provide an inexpensive information recording / reproducing apparatus while improving the information transfer speed.

[0006]

In order to achieve the above object, an apparatus for irradiating a plurality of light spots on a recording medium to record or reproduce information, wherein the light for forming the plurality of light spots is used. A head and a reproducing means for inputting a plurality of detection signals obtained corresponding to each of the plurality of light spots, selecting one of the detection signals, and reproducing information, are provided. By arranging them adjacent to each other in the front-rear direction with respect to the traveling direction of the recording medium, the recorded information is reproduced and the information recording is confirmed immediately after recording on the recording medium. The reproducing means has a selecting means for selecting any one of the plurality of input detection signals, and when the information is recorded in the recording area on the recording medium using one light spot, the information is recorded. Immediately after the recording, the reproduction for confirming the recording of the information is performed almost at the same time as the recording based on the detection signal obtained by irradiating the other light spot with the above information. In this way, less than a plurality of recording and reproducing means,
It realizes a processing system for converting into information.

Further, in order to realize the reproduction of information by the signal reproducing means, which is smaller in number than the above-mentioned plurality of light spots, the judgment for selecting the signal to be reproduced is selected from the plurality of detection signals. And a means for reproducing information by selecting one of a plurality of detection signals according to the judgment. Further, in order to efficiently perform various operations such as a recording operation, a reproducing operation, and a standby operation (an operation in which information is not recorded or reproduced, and other operations can be quickly realized), a plurality of light spots are used. Means for forming and outputting a plurality of detection signals, means for converting the plurality of detection signals into information, means for making a judgment for selecting one of the plurality of detection signals, and the judgment. And a control signal for controlling the means for forming the plurality of light spots and the means for selecting any one of the detection signals. is there.

[0008]

In the recording operation, it is confirmed that the information has been recorded after the operation of recording the information on the recording medium.
This confirmation is performed by reproducing the recorded information. With respect to the traveling direction of the recording spot for recording information,
The confirmation reproduction spot for confirming the recording is arranged at the rear. It is confirmed that the information is recorded based on the reproduction signal obtained from the reflected light of the reproduction spot. In the recording operation, two signals are obtained, a signal based on the reflected light of the recording spot and a signal based on the confirmation reproducing spot for confirming that the information has been recorded. It is not necessary to provide a means for processing the signals for each of the two signals. The two signals are input to one signal processing means to process one of the signals. As a result, it is not necessary to provide a processing system for converting a signal obtained based on the reflected light from the recording medium into information for each signal, and it is possible to reproduce the information by the processing system that is smaller than the conventional device. ..

In the reproducing operation, since the data recorded in advance on the recording medium is sequentially reproduced as information, the information is reproduced by using the reflected light from the recording spot or the reproducing spot described above. Information can also be reproduced by alternately using signals corresponding to recording spots or reproduction spots.

In the standby operation, the two light spots are controlled so as to be accurately arranged on the recording medium. For example, it may be operated in the same manner as the signal control during the reproducing operation. In addition, if there is a difference in physical wear, wear, and performance deterioration of the components used during recording or during playback including confirmation operation, recording should be performed to reduce the burden on the components that are rapidly deteriorated. Alternatively, it is possible to control the operation of reproduction.

[0011]

EXAMPLES The present invention will be described below with reference to examples. FIG. 1 is an example of a device configuration diagram of the present invention.

The recording medium 30 includes at least a substrate 31 and a recording film.
It consists of 32 and. Grooves 33 and land portions 34 between the grooves are provided on the recording film 32, and in this embodiment, recording pits are recorded in the land portions 34.

A recording medium 30 is recorded on the recording medium 30 by the optical head 20.
Illuminates two light spots. One light spot is the first light spot 21 for mainly recording the information on the recording medium 30 by changing the physical characteristics of the recording film 32. The other light spot is the second light spot adjacent to the first light spot. The second light spot 22 is always located behind the first light spot 21 on the moving recording medium 30. The laser beam emitted from the first laser provided in the optical head 20 is applied to the recording medium 30 as the first light spot 21, and the reflected light thereof is received by the first light receiver 3.
It is converted into an electrical signal. Further, the laser beam emitted from the second laser 2 provided in the optical head 20 is applied to the recording medium as the second light spot 22, and the reflected light is reflected by the second light spot 22.
The light is received by the light receiver 4 and converted into an electric signal.

The electric signal converted by the first light receiver 3 is input to the reproduction amplifier 10, and the electric signal converted by the second light receiver 4 is input to the reproduction amplifier 11. The outputs of the reproduction amplifiers 10 and 11 are the terminals 1 of the input switching device 12.
2a and 12b, respectively. Input switch 12
Selects a signal from either the terminal 12a or 12b and outputs it to the signal processing system. First, the output of the input switch 12 is input to the waveform equalizer 13. The output of the waveform equalizer 13 is converted into a pulse signal indicating the presence or absence of a signal by the shaper 14. In this embodiment, the reproduction amplifier 10 or 1
The electric signal from 1 is selected by the input switch 12 and input to the waveform equalizer 13.
3 may be provided between the reproduction amplifier 10 and the input switch 12, and between the reproduction amplifier 11 and the input switch 12, respectively. In particular, when the wavelengths of the first laser 1 and the second laser 2 are different, the reproduction amplifiers 10 and 11 and the input switch 12
It is better to provide the waveform equalizer 13 between and.

The pulse signal output by the shaper 14 is input to the discriminator 16 and the PLL 15. Further, the discriminator 16 also receives a synchronization signal output from the PLL 15 (a signal synchronized with the basic cycle of the pulse signal). The discriminator 16 generates a detection code string using the pulse signal and the synchronization signal. The detected code string is input to the decoder 17, and the data bit string (information) is output. The data bit string is also output to the address discriminator 18.
A control signal 19 is also input to the address discriminator 18. The address discriminator 18 uses the data bit string and the control signal 19 to generate an input switching signal indicating which of the electrical signal from the first photoreceiver 3 and the electrical signal from the second photoreceiver 4 is selected. Output to 12.

The first laser 1 is an input data bit string (information)
Driven according to. The input data bit string is converted into a recording code string by the encoder 7. The recording code string and the control signal 19 are input to the APC 6 that controls the laser driving amplifier 5 that drives the first laser 1. The control signal 19 is also input to the APC 9 that controls the laser drive amplifier 8 that drives the second laser 2. Therefore, the optical output of each of the first laser 1 and the second laser 2 can be changed according to the control signal 19.

FIG. 2 shows a specific structural example of the optical head 20. The optical head 20 has a function of narrowing the light emitted from the first laser 1 and the second laser 2 onto the recording medium 30. That is, as shown in FIG. 2, the first laser 1 made of a semiconductor laser is caused to emit light, which is collimated by the collimator lens 36, is made to be parallel light, is transmitted through the prism 40, and is made incident on the objective lens 43 to be recorded on the recording medium 30. First
A light spot 21 is formed. Next, the second laser 2 is caused to emit light, which is collimated by the collimator lens 37 to be incident on the prism 40. In the prism 40, the second laser 2
Is reflected and guided to the objective lens 43, and the second light spot 22 is formed on the recording medium 30. And
The first light spot 1 and the second light spot 2 irradiated on the recording medium are reflected from the recording medium 30 and become parallel light by the objective lens 43, respectively, and the reflected light of the first light spot 1 is reflected by the prism 40 and the wavelength. Reflected by the separation filter 42,
The first optical receiver 3 that passes through the lens 38 and is polarized (not shown) by a beam splitter or the like to detect a light spot control signal such as a focus shift signal or a track shift signal and an information signal such as an address information or a recording information signal. It is composed by. On the other hand, the reflected light of the second light spot 22 is reflected by the prism 40.
Is reflected by the laser beam, passes through the wavelength separation filter 42, is reflected by the prism 41, passes through the lens 39, is polarized by a beam splitter, etc., and detects various signals in the same manner as in the case of the first light spot 21. The second light receiver 4 is used.

Next, the input switching operation of the reproduction signal from the reproduction amplifier 10 or 11 in the input switch 12 will be described. FIG. 3 shows an example of the recording medium 30, and FIG. 4 shows the sector format structure of the recording medium 30 and the input switch 1.
The relationship of the input switching operation in 2 is shown. Recording medium 30
Have a disk shape having concentric or spiral recording tracks. The recording medium 30 also has a groove for track positioning of a light spot from the light source.
The group 33 is closer to the entrance surface 25, and the land 3 is farther away.
Call it 4.

On the recording medium 30 having such a structure, a recording track is a 360 ° path on which information is recorded on the circumference.

The recording track is radially divided into a plurality of sectors. Each sector has the sector format structure shown in FIG.

Information is recorded by tracking the track by a groove for track positioning, and the land 34 or the group 33 is recorded.
Are recorded in the form of holes, for example.

FIG. 4 shows three kinds of control signals 19 for instructing the input switching operation. The control means 23 controls the control signal 19-1 at the time of recording or erasing (state 1), the control signal 19-2 at the time of reproducing (state 2), and the standby time (state 3).
In, the control signal 19-3 is output. Below, the selection processing of the reproduction signal obtained from the optical head 20 will be described in correspondence with the sector format structure of the medium 30.

In the state 1, according to the control signal 19-1,
After the information is recorded or erased by the first laser 1, the recorded or erased portion is reproduced to confirm the recorded or erased state. Therefore, the second light spot 22 located behind the first light spot 21 with respect to the traveling direction of the recording medium.
The reproduction signal based on the above is introduced to the reproduction signal processing system. Therefore, the input switching unit 12 is switched. As shown in the upper part of FIG. 4, the sectors constituting the track include a prerecorded address portion 50, a data portion 52 in which the user records information, and a flag portion located behind the address portion 50.
It is composed of a buffer 53 located behind the data section 52. State 1 means confirmation after recording information in the data section 52. The confirmation is an operation of reproducing the information on the recording or erasing state of the information. Further, it is assumed that the recording operation corresponds to the first laser 1 and the reproducing operation corresponds to the second laser 2.

When reproducing the address section 50, the control signal 19-1 is used to control the output of the first laser 1 for recording operation by the APC 6, and the electric power obtained from the reflected light of the first laser 1 is used. The first light receiver side contact 12a is selected to reproduce the signal. Here, the reason for selecting the contact 12a is that the address portion 50 of the recording area is firstly recorded.
This is because the recording operation is performed in the data section 52 following the address section 50 after the confirmation by the laser 1.

Next, in the area of the flag portion 51, the contact is switched to the second photodetector side contact 12b. FIG. 5 shows an example in which a region necessary for switching the contacts (12a, 12b) is newly added in the flag unit 51. The flag unit 51 uses the FLG 511.
And a switching unit 512. The FLG 511 indicates information such as whether this sector is already written block, defective block, or already deleted block. The switching unit 512 irradiates the recording medium with 2
This is a region where selection of processing of two electric signals obtained from one light spot is performed. That is, in the switching unit 512, the input switching operation of the input switching unit 12 that receives the electric output based on the two light spots is performed. During the input switching operation, information is not reproduced including the confirmation operation. Therefore,
The length of the switching unit 512 is equal to or longer than the light spot distance between the first light spot 21 and the second light spot 22. Therefore, the switching unit 512 may have a length equal to or greater than the light spot interval.
Even if information is erroneously recorded in the switching unit 512, the information will not be read. That is, the switching unit 5
Reference numeral 12 is an area in which information is not reproduced, although it does not matter whether information is recorded or not. In order to provide such a region, assuming that the two light spot intervals are several tens of μm and the bit pitch is 0.5 μm / bit, the above-mentioned light spot interval switching unit 512 may be newly provided in the flag unit 51. Since the capacity loss is about several tens of bytes or less, there is no problem. (The capacity loss due to the switching unit 532 in the buffer 53 described later is also taken into consideration).

In the data section 52, the first laser 1 performs the recording operation, and the reproduction operation for confirmation is performed from the reflected light from the second laser 2. In the data section 52, the first
Since the information is recorded by the laser 1, the first
This is because it is very difficult to reproduce the information from the reflected light from the laser 1.

After the recording or erasing operation in the data section 52, the two light spots illuminate the buffer 53. The buffer 53 includes an area buffer unit 531 for absorbing the rotation fluctuation and a switching unit 532. The role of the switching unit 532 is the same as the role of the switching unit 512 in the flag unit 51, and performs the input switching operation of the input switching unit 12 that inputs the electric output based on the two light spots. Therefore, the switching unit 532 also moves the first light spot 21 and the second light spot 21 in the traveling direction.
The length of the light spot 22 is equal to or longer than the light spot interval. Then, the switching unit 532, like the switching unit 512,
The structure does not matter. Thus, in the buffer 53, the first light-receiver-side contact 12a obtained from the first laser 1 performing the recording operation is selected, and the address section 50 is reproduced.

As described above, in order to confirm the recording state or the erasing state of information, two signals are switched and input to the signal processing system for reproducing the information. Immediately after that, reproduction for confirmation can be performed. Further, since the information can be recorded after confirming the position of the recording spot, it is possible to reliably prevent the data destruction of the other data portion due to the recording.

In the state 2, in order to reproduce the already recorded information, the contacts (12a, 12b) of the input switching section 12 are switched according to the control signal 19-2. That is, in the input switching unit 12, the first light receiver side contact 12
Input is not switched until a is selected and the operating state changes.

The state 3 is a standby state for shifting to the next operation (recording operation, erasing operation, reproducing operation), and the control signal 19-
3, the contacts (12a, 12b) of the input switching unit 12
Is switched. For example, the first light receiver side contact 12a and the second light receiver side contact 12b are alternately switched for each sector. This is suitable for extending the life of the apparatus and the medium and reducing the power consumption when the standby operation is continued for a long time.

The sector format structure on the recording medium will be partially described. The address section 50 represents the physical address of the sector on the disc, and the SM 501 and ID 5
It consists of 02. SM501 indicates that it is the beginning of the sector format, and track number and sector number are written in ID502. The data section 52 is an area for writing data required by the user, and has a VFO 521 having a continuous repetitive data pattern for surely reproducing the data even if the rotation of the disk fluctuates, and the data. SYNC 522, which is the synchronization signal of the unit 52, DATA, which is an area where the user writes data, and when there is a defect in the originally written sector, write it in another sector (replacement sector) (defect processing).
Control, ECC or CRC that is a redundant word for error correction detection, and RESYNC having a synchronization code pattern for preventing a large spread of data errors.
523 consisting of C [DATA / ECC / RESYNC /
CONTROL / CRC].

Next, an embodiment of a laser driving method for extending the life of the apparatus and the medium and reducing the power consumption will be described. FIG. 6 shows the relationship between the operation control signal and the laser driving.

The operation states (states 1 to 3) in the upper part of FIG.
This is the same as the operation state (states 1 to 3) described in FIG.
The driving states of the first laser 1 and the second laser 2 are shown corresponding to changes in the operating state. Control signal 19- in state 3
In 3, the first laser 1 is driven and the second laser 2 is stopped. (The first laser 1 and the second laser 2 may be alternately turned on / off.) In this case, the operation of the input switching device 12 performs the input switching described by the control signal 19-2 in FIG.

Next, when the state 3 is changed to the state 1,
Both the first laser 1 and the second laser 2 are driven. The operation of the input switching device 12 in this case is the input switching described in the state 1 of FIG. If you change from state 1 to state 2,
The first laser 1 is stopped and the second laser 2 is driven as it is. (The first laser 1 may be driven and the second laser 2 may be stopped).

When the state 2 is changed to the state 3, the first laser 1 and the second laser 2 are alternately driven and stopped. The operation of the input switching device 12 in this case is performed in substantially the same manner as the input switching described in the state 3 of FIG. Further, the input switching is performed in synchronization with the alternate driving of the lasers. As a result, the first light spot 21 and the second light spot 22 can alternately reproduce the address portion, so that the positional relationship between the first light spot 21 and the second light spot 22 can be recognized. The positional relationship of the light spot can be eliminated by feeding back this positional relationship to the light spot control system by some means. Further, as in the case of the state 3 described above, either one of the lasers may be driven.

For example, even when a large number of light spots are arranged on the recording medium and a large number of electric signals corresponding to the reflected light can be obtained, the same functions and effects as described above can be obtained.

[0037]

According to the present invention, since it is possible to realize a processing system for converting information, which is smaller than a plurality of recording / reproducing means, there is an effect that the information recording / reproducing apparatus can be downsized.

Since a plurality of recording / reproducing means can be alternately driven and stopped, there is an effect that power consumption can be reduced.

Further, since the positional deviation of the light spot can be eliminated, the reliability in information recording / reproducing can be ensured.

[Brief description of drawings]

FIG. 1 is a device configuration diagram for explaining an embodiment of the present invention.

FIG. 2 is a partial configuration diagram of the present invention.

FIG. 3 is an overall view of a recording medium.

FIG. 4 is a conceptual diagram showing an input switching operation of a reproduction processing signal according to an operation control signal in the present invention.

FIG. 5 is a configuration diagram showing a sector format of a recording medium used in the present invention.

FIG. 6 is a time chart diagram showing an example of the relationship between an operation control signal and laser driving according to the present invention.

FIG. 7 is a block diagram of a conventional recording / reproducing apparatus.

[Explanation of symbols]

1 ... 1st laser, 2 ... 2nd laser, 3 ... 1st light receiver, 4
… Second receiver, 5,8… Laser drive amplifier, 6,9… A
PC (auto power controller), 7 ... encoder, 1
0, 11 ... Reproduction amplifier, 12 ... Input switcher, 12a ... First light receiver side contact, 12a ... Second light receiver side contact, 13 ... Waveform equalizer, 14 ... Shaper, 15 ... PLL (phase locked loop) , 16 ... Discriminator, 17 ... Decoder, 18 ... Address discriminator, 19 ... Control signal, 20 ... Optical head, 21
... first light spot, 22 ... second light spot, 23 ... control means, 25 ... incident surface, 30 ... recording medium, 31 ... substrate, 3
2 ... Recording film, 33 ... Group, 34 ... Land portion, 36,
37, 38, 39 ... Condensing lens, 40, 41 ... Prism, 42 ... Wavelength separation filter, 43 ... Objective lens, 50
... address part, 51 ... flag part, 52 ... data part, 53
…buffer.

Claims (17)

[Claims] 1. A light source, an optical system for shaping a light beam emitted from the light source to irradiate a plurality of light spots on a recording medium, and detecting an electric signal corresponding to each of the plurality of light spots. An optical head composed of a plurality of detectors for outputting and outputting the plurality of electric signals, a means for reproducing and outputting a smaller number of electric signals than the plurality of electric signals, the optical head and the electric signals An information recording / reproducing apparatus, comprising: a control unit that is connected to a unit that reproduces and outputs the signal and that includes a signal reproducing unit that outputs a control signal to each unit. 2. The information recording / reproducing apparatus according to claim 1, wherein said signal reproducing means has a selecting means for selecting said plurality of electric signals. 3. The control signal is a signal for controlling the light source of the optical head via a means for controlling the output of the light source and for controlling the selecting means. Information recording / reproducing apparatus. 4. The recording medium has at least 2 in one sector.
4. The information recording / reproducing apparatus according to claim 1, wherein the information recording / reproducing apparatus has one switching unit, and a length of each of the switching units in a moving direction has at least an interval of the plurality of light spots. .. 5. The information recording / reproducing apparatus according to claim 4, wherein the selection unit is switched when the plurality of light spots are illuminating the switching unit. 6. A light source, an optical system for shaping a light beam emitted from the light source to illuminate a plurality of light spots on a recording medium, and means for outputting a plurality of electric signals corresponding to the plurality of light spots. Connected to the optical head and the signal reproducing means, which inputs the plurality of electric signals and reproduces and outputs a smaller number of electric signals than the plurality of optical spots. , And an information recording / reproducing apparatus having control means for outputting a control signal to each. 7. The signal reproducing means has a selecting means for selecting the plurality of electric signals.
The information recording / reproducing apparatus described in. 8. The control signal is a signal for controlling the light source of the optical head through a means for controlling the output of the light source and for controlling the selecting means. Information recording / reproducing apparatus. 9. The recording medium has at least two in one sector.
9. The information recording / reproducing apparatus according to claim 6, wherein the information recording / reproducing apparatus has one switching unit, and a length of each of the switching units in a moving direction has at least an interval between the plurality of light spots. .. 10. The information recording / reproducing apparatus according to claim 9, wherein the selection unit is switched when the plurality of light spots are illuminating the switching unit. 11. A light beam emitted from a light source is shaped to irradiate a plurality of light spots on a recording medium, and a plurality of electric signals corresponding to each of the plurality of light spots are output to output the plurality of electric signals. An information recording / reproducing method characterized by inputting a signal, reproducing and outputting a smaller number of electric signals than the plurality of electric signals, and using a control signal when controlling the output of the light source and controlling the reproduction. .. 12. The information recording / reproducing method according to claim 11, wherein among the plurality of electric signals, an electric signal reproduced and output is selected by the control signal. 13. The control signal according to claim 12, wherein the control signal is a signal for controlling the light source of the optical head through a means for controlling the output of the light source and for controlling the selecting means. Information recording and reproducing method. 14. The recording medium has at least two switching portions in one sector, and the length of each switching portion in the moving direction has at least the interval of the plurality of light spots. The information recording / reproducing method according to any one of claims 11 to 14. 15. The information recording / reproducing method according to claim 14, wherein the output signal is selected when the plurality of light spots are illuminating the switching unit. 16. A recording area on a recording medium is irradiated with a first optical spot by a first optical head to record information, and a first detection signal based on the first optical spot is obtained, The second optical head irradiates a second light spot to obtain a second detection signal based on the second light spot, and selects either the first detection signal or the second detection signal. A recording medium for use in a recording / reproducing apparatus for reproducing by using a sector format having a switching unit having a length at least equal to or longer than an arrangement interval of the first light spot and the second light spot. And the selection is performed when the first light spot and the second light spot are illuminating the switching unit. 17. A recording area on a recording medium is irradiated with a first light spot and a second light spot by an optical head, and a second light spot based on the first light spot and the second light spot is irradiated. A recording medium used in a recording / reproducing apparatus for obtaining a detection signal and selecting and reproducing either the first detection signal or the second detection signal, wherein the first light spot and the second light are used. When a sector format having a switching unit having a length at least equal to or longer than the arrangement interval of spots is provided and the first light spot and the second light spot illuminate the switching unit, A recording medium characterized in that the above selection is performed.