JPH0589506A - Optical recorder - Google Patents

Abstract

(57) [Abstract] [Purpose] The power of the laser beam of the magneto-optical disk recording / reproducing apparatus is optimally controlled according to the ambient temperature and the recording pattern. [Composition] Upper and lower limits of the output power level of the laser beam in a range in which a part of the emitted light of the laser beam is sampled at the first timing and the second timing and the output power linearly changes with respect to the drive current. Are held in the sample hold circuits 3a and 3B.
The full scale of the D / A converter 9 is set so that the laser beam is controlled within the range of the upper limit and the lower limit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording device used for controlling the laser power of a magneto-optical disk, and more particularly to an optical recording device capable of controlling the laser power according to a mark pattern to be recorded. ..

[0002]

2. Description of the Related Art In a magneto-optical disk recording apparatus, a laser beam is irradiated at the time of recording to raise the temperature of the portion above a Curie temperature and an external magnetic field is applied to mark a mark in the direction of magnetization of a perpendicular magnetic film. Forming and recording data. Conventionally, in such a magneto-optical recording device, an AP is used so that the laser beam power during recording becomes constant.
A C loop is provided.

That is, FIG. 8 shows an example of a conventional magneto-optical recording apparatus. In FIG. 8, 201 is a magneto-optical disk, and this magneto-optical disk 201 is driven by a spindle motor 202 at a constant angular velocity or linear velocity. An optical pickup 210 and a magnetic head 211 are provided facing the magneto-optical disk 201. The optical pickup 210 includes a laser diode 209 and a photodiode 212.

At the time of recording, a laser beam is emitted from the laser diode 209. The perpendicularly magnetized film of the magneto-optical disk 201 at the portion irradiated with this laser beam is heated. When the temperature of this heated portion reaches near the Curie temperature, the direction of the perpendicular magnetization film of that portion is determined according to the direction of the external magnetic field applied from the magnetic head 211.

Digital data to be recorded on the magneto-optical disk 201 is supplied from an input terminal 220 to an encoder 221. The encoder 221 encodes the recording data in a predetermined format. The output of the encoder 221 is supplied to the light intensity modulation circuit 222, and the output of this modulation circuit 222 is supplied to the laser diode 209 via the drive circuit 223.

A part of the laser beam emitted from the laser diode 209 is reflected by the prism mirror and supplied to the photodiode 212 for detecting the laser beam power. The output of the photodiode 212 is the amplifier 2
It is supplied to the comparator 225 via 24. Comparator 225
Is supplied with a reference level from the reference signal setting circuit 226. In the comparator 225, the detected value of the laser power passed through the amplifier 224 is compared with the reference signal from the reference setting circuit 26, and this comparison output is fed back to the light intensity modulation circuit 22. Thereby, the laser diode 21
The laser power of 0 is controlled to a constant value.

[0007]

In the conventional magneto-optical disk recording apparatus, the laser power is controlled to be constant by such an APC loop. However, the optimum laser power during recording depends on the ambient temperature. For example, in the case of a pattern in which "1" s are continuous, since the ambient temperature has already risen, a large laser power is not required to record "1" next time. On the other hand, in the case of a pattern for recording "0" to "1", a larger laser power is required.

If the relationship between the current passed through the laser diode and the power of the laser beam is linear, it is easy to control the power of the laser beam according to the pattern to be recorded. Since the relationship with the power of the laser beam is non-linear, it is difficult to control the power of the laser beam according to the recording pattern in the related art.

Therefore, an object of the present invention is to provide an optical recording apparatus capable of easily controlling the power of a laser bee according to the pattern of recorded data and the temperature.

[0010]

According to the present invention, there is provided a detection means for receiving a part of light emitted from a laser light source, and a first detection result obtained by sampling a detection output from the detection means at a first timing. The upper and lower limits of the power level of the output of the laser light source are set based on the output and the second output obtained by sampling the detection output from the detection means at the second timing, and the first output and the above An optical recording device comprising: a control signal generating unit that generates a control signal that controls the emission power of a laser light source within the upper and lower limits based on the second output.

[0011]

The laser beam power can be controlled according to the recording pattern by controlling the laser beam by using the portion in which the relation between the current flowing in the laser beam and the power of the laser beam can be linearly approximated.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The present invention is used to construct an APC loop that controls the laser beam of a magneto-optical disk.

FIG. 1 shows a first embodiment of the present invention. In FIG. 1, the output power of the laser beam that irradiates the magneto-optical disk with the laser beam is detected by a photodiode (not shown), and this detection output V _FAC is supplied to the input terminal 1. Signal V _FAC from input terminal 1
Is supplied to the sample hold circuits 3A and 3B via the low pass filter 2. Sample and hold circuit 3A
Timing pulses are applied to terminals 3 and 3B from terminals 4A and 4B, respectively. Due to this timing pulse, the output signal of the low pass filter 2 is changed to the sample hold circuit 3
A and 3B are sample-held.

The outputs of the sample and hold circuits 3A and 3B are supplied to integrators 5A and 5B, respectively. The integrators 5A and 5B have a set voltage V ₁ from terminals 6A and 6B, respectively.
And V ₂ are given. The relationship between the set voltages V ₁ and V ₂ is (V ₁ <V ₂ ). Setting voltage V ₁ and V
₂ is set corresponding to the part where the relationship between the current flowing through the laser diode and its output is linear.

The integrators 3A and 3B integrate the difference voltage between the input signal voltage held by the sample and hold circuits 3A and 3B and the set voltages V ₁ and V ₂ , respectively. The outputs of the integrators 5A and 5B are the terminals 7A and 7B of the switch 7.
To the subtracter 8. The output of the subtractor 8 is supplied to the reference terminal of the D / A converter 9. The full scale of the D / A converter 9 is set by the input of this reference terminal.

Write data is supplied from the input terminal 11 to the shift register 13, and a write clock is supplied from the clock input terminal 12 to the clock input terminal of the shift register 13. The shift register 13 serially / parallel converts this input write data. The output of the shift register 13 is supplied to the logic circuit 14. The logic circuit 14 is provided with a table for setting the laser power according to the mark pattern of the input write data. The output of the logic circuit 14 is supplied to the data input terminal of the D / A converter 9.

The output of the logic circuit 14 is D / A converted by the D / A converter 9. The output of the D / A converter 9 is
It changes according to the mark pattern of the write data.
The output of the D / A converter 9 is supplied to one input terminal of the adder 10. The output of the integrator 5A is supplied to the other input terminal of the adder 10. The output of the adder 10 is supplied to the terminal 7C of the switch 7. The output of the switch 7 is output from the output terminal 15. The output V _APC from the output terminal 15 controls the power of the laser beam during recording.

The magneto-optical disk is provided with a servo area in which wobble pits for tracking are arranged at predetermined angular intervals, and a so-called sample servo for performing tracking control using the reproduction output of the wobble pits in this servo area. The system type is used. In the recording format of the magneto-optical disk of such a sample servo system,
As shown in FIG. 2, gray code pits P1 and P2 for track access, wobble pits P3 and P4 for tracking, and a pit P5 for clock reproduction are arranged in the servo area. Then, in the data area of the segment of the header, the sector mark indicating the beginning of the sector and the track address are recorded. Then, the succeeding areas T ₁ and T ₂ of the track address are areas for laser power detection, as will be described later.

FIG. 3 shows the relationship between the current supplied to the laser diode and the laser power. In FIG. 3, the horizontal axis represents the current passed through the laser diode and the vertical axis represents the power of the laser diode. The relationship between the current passed through the laser diode and the output laser power is non-linear as shown in FIG. Therefore, it is difficult to control the power of the laser beam to be optimum according to the pattern of the mark to be recorded.

Therefore, in one embodiment of the present invention, the laser beam can be controlled by using a portion in which the relationship between the current passed through the laser diode and the output laser power can be approximated linearly. As described above, by using the portion in which the relationship between the current passed through the laser diode and the output laser power can be linearly approximated, the power of the laser beam can be controlled to be optimized according to the pattern of the mark to be recorded.

That is, first, in the initial state, the D / A converter 9 is set to 0 and the switch 7 is set to the terminal 7A side. At this time, the set voltage V ₁ is output from the output terminal 15 via the path PH1, and the current corresponding to the set voltage V ₁ is passed through the laser diode. The detection signal of the power of the laser beam at this time is input from the input terminal 1. Then, at the timing of T ₁ shown in FIG. 2, the level from the input terminal 1 through the low pass filter 2 is sampled and held by the sample and hold circuit 3A. Assuming that a current corresponding to the current I ₁ in FIG. 2 is applied to the laser diode at the set voltage V ₁ , the sample-hold circuit 3A has a laser power Q at this current I _1.
The detection level q ₁ corresponding to ₁ is held (see FIG. 3).

Next, the switch 7 is set to the terminal 7B side. At this time, the set voltage V ₂ is output from the output terminal 15 via the path PH2, and the current corresponding to the set voltage V ₂ is passed through the laser diode. The detection signal of the power of the laser beam at this time is input from the input terminal 1.
Then, at the timing of T ₂ shown in FIG. 2, the level from the input terminal 1 through the low pass filter 2 is sampled and held by the sample and hold circuit 3B. Set voltage V
_{At 2,} it is assumed that a current corresponding to the current I ₂ in FIG. 3 is passed through the laser diode, and the sample-hold circuit 3B holds the detection level q ₂ corresponding to the laser power Q ₂ at this current I _2. become.

[0023] Integrator output and the output of the integrator 5B of 5A is supplied to the subtracter 8, the detection level q ₂ corresponding to the laser power Q ₂ in the subtracter 8, the detection level q ₁ corresponding to the laser power Q ₁ Is subtracted. As a result, FIG.
Level corresponding to (Q ₂ -Q ₁₎ in is obtained.
The level corresponding to the (Q ₂ -Q _1), the full scale of the D / A converter 9 is set.

In the steady state, the switch 7 is, for example, the terminal 7
It is set on the C side. Therefore, in the adder 10, the integrator 5
The output of A and the output of the D / A converter 9 are added, and the output of the adder 10 is output from the output terminal 15.

The output of the D / A converter 9 changes according to the pattern of recording data. For example, if the data input given to the D / A converter 9 has a minimum value of 0, the output of the path PH1 appears from the output terminal 15, so the output of the output terminal 15 becomes q ₁ + 0 = q ₁ . Therefore, the power of the laser diode is
It is set to Q ₁ in FIG.

If the D / A converter 9 is 8 bits and the data input given to the D / A converter 9 is the maximum value FF (hexadecimal number), the output of the D / A converter 9 is (q ₂₋ q ₁ ), the output from the output terminal 15 is q ₁ + (q ₂ −q ₁ ) = q ₂ .

As described above, when the D / A converter 9 changes from the minimum value to the maximum value, the output signal from the output terminal 15 changes from q _{1 to} q ₂ and the laser power changes linearly in the range Q _1. ~ Changes within Q ₂ .

FIG. 4 shows a second embodiment of the present invention. In the above-mentioned first embodiment, the switch 7 must be set in three stages. On the other hand, in this embodiment, it can be controlled by one two-stage switch 27.

In FIG. 4, the signal V from the input terminal 21
_{The FAC} is supplied to the sample hold circuits 23A and 23B via the low pass filter 22. The sample and hold circuits 23A and 23B have terminals 24A and 2 respectively.
Timing pulse is given from 4B. The timing signal causes the output signal of the low-pass filter 22 to be sampled and held in the sample and hold circuits 23A and 23B.

The outputs of the sample hold circuits 23A and 23B are supplied to integrators 25A and 25B, respectively. The integrators 25A and 25B have terminals 26A and 26B, respectively.
Are applied with set voltages V ₁₁ and V ₁₂ (V ₁₁ <V ₁₂ ). The outputs of the integrators 25A and 25B are supplied to the terminals 27A and 27B of the switch 27, respectively, and the subtracter 2
8 are supplied. The output of the subtractor 28 is supplied to the reference terminal of the D / A converter 29. The full scale of the D / A converter 29 is set by the input of this reference terminal.

Write data is supplied from the input terminal 31 to the shift register 33, and a write clock is supplied from the clock input terminal 32 to the clock input terminal of the shift register 33. The shift register 33 serially / parallel converts this input write data. The output of the shift register 33 is supplied to the logic circuit 34. The logic circuit 34 is provided with a table for setting the laser power according to the mark pattern of the input write data. The output of the logic circuit 34 is supplied to the data input terminal of the D / A converter 29.

The output of the logic circuit 24 is D / A converted by the D / A converter 29. The output of the D / A converter 29 changes according to the mark pattern of the write data. The output of the D / A converter 29 is supplied to one input terminal of the adder 30. The output of the switch 27 is supplied to the other input terminal of the adder 30. The output of the adder 30 is output from the output terminal 35 as the APC voltage V _APC . The output V _APC from the output terminal 35 controls the power of the laser beam during recording.

First, in the initial state, the D / A converter 2
The output of 9 is set to 0. Then, the switch 27 is set to the terminal 27A side. At this time, the set voltage V ₁₁ is output from the output terminal 15. A current corresponding to the set voltage V ₁₁ is passed through the laser diode, and a signal corresponding to the output of the laser beam at this time is input from the input terminal 21. At timing T ₁ , the photodiode output signal V
_{The FAC} is sampled and held by the sample and hold circuit 23A. From the value q ₁₁ sampled and held by the sample and hold circuit 23A, the value corresponding to the laser power Q ₁ at the starting point I ₁ where the relation between the current flowing through the laser diode and the output laser power becomes linear in FIG. To be held.

Next, the switch 27 is set to the terminal 27B side. At this time, the set voltage V ₁₂ is output from the output terminal 35. A current corresponding to the set voltage V ₁₂ is passed through the laser diode, and a signal corresponding to the output of the laser beam at this time is input from the input terminal 21. At timing T ₂ , the input signal V _FAC at this time is sampled and held by the sample and hold circuit 23B. A value corresponding to the laser power Q ₂ at I ₂ in FIG. 3 is held from the value q ₁₂ sampled and held by the sample hold circuit 23B.

The output of the sample hold circuit 23A and the output of the sample hold circuit 23B are respectively integrator 25.
Is supplied to the subtractor 28 via A and 25B, and the subtractor 2
At 8, the output of integrator 25A is subtracted from the output of integrator 25B. The output held in the sample hold circuit 23A corresponds to the laser power Q ₁ in FIG.
Since the output held in the sample hold circuit 3B corresponds to the laser power Q ₂ in FIG. 3,
In the subtractor 28, the value (q ₁₂ −) corresponding to (Q ₂ −Q ₁ )
q ₁₁ ) is required. The output of the subtractor 28 is supplied to the D / A converter 29, so that the output of the subtractor 28 corresponding to this (Q ₂ −Q ₁ ) becomes full scale.
The A converter 29 is set.

In the steady state, the switch 27 has the terminal 27A.
Switched to the side. The output of the switch 27 is the adder 30.
Is supplied to. Further, the output of the D / A converter 29 is supplied to the adder 30. For example, when the output of the D / A converter 29 is 8 bits, the output of the D / A converter 29 changes from 00 to FF (hexadecimal number). Assuming that the data input given to the D / A converter 29 is 0, the output from the output terminal 35 is q ₁₁ + 0 = q ₁₁ . Then, if the data input given to the D / A converter 29 is FF, the output from the output terminal 15 is q ₁₁ + (q ₁₂ −q ₁₁ ) = q ₁₂ . Thus, the AP output from the output terminal 35
The C signal changes in a section where the relationship between the current flowing through the laser diode and the output laser power is linear.

FIG. 5 shows a third embodiment of the present invention. In the first and second embodiments described above, control of the switch is necessary, but in this embodiment, control of the switch is unnecessary.

In FIG. 5, the output signal V _{FAC of the} photodiode for detecting the output power of the laser beam with which the optical disk is irradiated is supplied to the input terminal 41. The output signal V _FAC of this photodiode is the low-pass filter 42.
Is supplied to the sample and hold circuits 43A and 43B via. Timing pulses are applied to the sample hold circuits 43A and 43B from terminals 44A and 44B, respectively, and the output signals of the low-pass filter 42 are sample-held in the sample hold circuits 43A and 43B by these timing pulses.

The outputs of the sample hold circuits 43A and 43B are supplied to integrators 45A and 45B, respectively. The integrators 45A and 45B have terminals 46A and 46B, respectively.
Are applied with set voltages V ₃₁ and V ₃₂ (V ₃₁ <V ₃₂ ). The output of the integrator 45A is supplied to the adder 48. The output of the integrator 45B is supplied to the reference terminal of the D / A converter 47. The full scale of the D / A converter 47 is set by the input of this reference terminal.

Write data is supplied from the input terminal 51 to the shift register 53. The write clock is supplied from the clock input terminal 52 to the clock input terminal of the shift register 53. The input write data is serial / parallel converted by the shift register 53. The output of the shift register 53 is supplied to the logic circuit 54. Logic circuit 5
A table is provided in 4 for setting the laser power according to the mark pattern of the input write data. The output of the logic circuit 54 is supplied to the data input terminal of the D / A converter 47.

The output of the logic circuit 54 is D / A converted by the D / A converter 47. The output of the D / A converter 47 is supplied to the adder 48. The output of the adder 48 is APC
The voltage V _APC is output from the output terminal 49. This A
The power of the laser beam is controlled by the PC voltage V _APC .

The data given to the D / A converter is 0.
At the time of, the output of the integrator 45A is output from the output terminal 49 via the adder 48, so the output from the output terminal 49 is q ₃₁ . This corresponds to Q ₁ in FIG. When the data supplied to the D / A converter is FF, the output of the D / A converter 47 is q ₃₂ , and the output from the output terminal 49 is (q ₃₁ + q ₃₂ ). If the output level q ₃₁ is made to correspond to Q ₁ in FIG. 2 and the output level (q ₃₁ + q ₃₂ ) is made to correspond to Q ₂ in FIG. 2, the APC signal output from the output terminal 49 is converted into the current flowing through the laser diode. The output laser power can be changed in a linear section.

In the above-described embodiment, the laser beam can be controlled within the range of Q _{1 to} Q ₂ with reference to Q ₁ in FIG. 3, but with reference to Q ₂ , Q ₁ to The laser beam may be controlled within the range of Q ₂ . In this case, adders 10, 30, 48
Is a subtractor configuration.

FIG. 6 shows a fourth embodiment of the present invention. In the above-mentioned first to third embodiments, the current flowing through the laser diode is changed to control the power of the laser diode. In this embodiment, however, the laser diode is pulse-driven and the duty ratio of this pulse signal is changed. I am trying to change.

In FIG. 6, the detection output V _FAC of the output power of the laser beam is supplied to the input terminal 61. The signal V _FAC from the input terminal 61 is supplied to the sample hold circuits 63A and 63B via the low pass filter 62. Timing pulses are applied to the sample hold circuits 63A and 63B from terminals 64A and 64B, respectively. With this timing pulse, the output signal of the low-pass filter 62 is changed to the sample hold circuits 63A and 6A.
3B is sample-held.

The outputs of the sample hold circuits 63A and 63B are supplied to integrators 65A and 65B, respectively. The integrators 65A and 65B have terminals 66A and 66B, respectively.
Are applied with set voltages V ₄₁ and V ₄₂ . Set voltage V ₄₁
And V _{42 have} a relationship of (V ₄₁ <V ₄₂ ). Integrator 6
The outputs of 5A and 65B are supplied to the terminals 77A and 77B of the switch 77, respectively. The output of the switch 77 is output from the output terminal 84. At the same time, the output of the integrator 65A is supplied to the A / D converter 78, and the output of the integrator 65B is supplied to the reference input terminal of the A / D converter 78. The full scale of the A / D converter 78 is
It is set by the input of this reference terminal. A / D
The output of the converter 78 is supplied to the logic circuit 79.

Write data is supplied from the input terminal 81 to the shift register 83, and a write clock is supplied from the clock input terminal 82 to the clock input terminal of the shift register 83. The shift register 83 serially / parallel converts this input write data. The output of the shift register 83 is supplied to the logic circuit 79. The logic circuit 79 is provided with a table for setting the laser power according to the mark pattern of the input write data. The output of the logic circuit 79 is supplied to the pulse width control circuit 80. The pulse width control circuit 80 sets the pulse width of the laser pulse according to the output of the logic circuit 79.
The output of the pulse width control circuit 80 is output from the output terminal 85.

First, the switch 77 is set to the terminal 77B side. At this time, a current corresponding to the higher set voltage V ₄₂ is passed through the laser diode, a signal corresponding to the output of the laser beam at this time is input from the input terminal 61, and is sample-held by the sample-hold circuit 63B. A value corresponding to the laser power Q ₂ at I ₂ in FIG. 3 is held from the value sampled and held by the sample hold circuit 63B. With this value, A /
The full power of the D converter 78 is set. In the steady state, the switch 77 is set to the terminal 77A side.

FIG. 7 shows a fifth embodiment of the present invention. Also in this embodiment, the laser diode is pulse-driven to change the duty ratio of the pulse signal.

In FIG. 7, the detection output V _FAC of the output power of the laser beam is supplied to the input terminal 91. The signal V _FAC from the input terminal 91 is supplied to the sample hold circuits 93A and 93B via the low pass filter 92. Timing pulses are applied to the sample hold circuits 93A and 93B from terminals 94A and 94B, respectively. Due to this timing pulse, the output signal of the low-pass filter 92 is changed to the sample hold circuits 93A and 9A.
3B is sample-held.

The outputs of the sample hold circuits 93A and 93B are supplied to integrators 95A and 95B, respectively. The integrators 95A and 95B have terminals 96A and 96B, respectively.
Are applied with set voltages V ₅₁ and V ₅₂ . Set voltage V ₅₁
And V ₅₂ is (V ₅₁ <V ₅₂ ). Integrator 9
The output of 5 A is supplied to the subtractor 107 via the switch 98 and the A / D converter 97. The output of the integrator 95B is supplied to the subtractor 107, and
It is supplied to the reference input terminal of the A / D converter 97. The full scale of the A / D converter 97 is set by the input of this reference terminal. The output of the A / D converter 78 is supplied to the logic circuit 79. Subtractor 9
The output of 6 is output from the output terminal 105.

From input terminal 101 to shift register 103
Write data is supplied to the clock input terminal 102.
From, the write clock is supplied to the clock input terminal of the shift register 103. The shift register 103 serially / parallel converts this input write data. The output of the shift register 103 is supplied to the logic circuit 99. The logic circuit 99 is provided with a table for setting the laser power according to the mark pattern of the input write data. The output of the logic circuit 99 is supplied to the pulse width control circuit 100. Pulse width control circuit 100
Then, the pulse width of the laser pulse is set according to the output of the logic circuit 99. The output of the pulse width control circuit 100 is output from the output terminal 104.

First, the switch 78 is turned off. At this time, a current corresponding to the higher set voltage V ₅₂ is passed through the laser diode, and a signal corresponding to the output of the laser beam at this time is input from the input terminal 91 and sample-held by the sample-hold circuit 93B. From the value sampled and held by the sample hold circuit 93B, the value corresponding to the laser power Q ₂ at I ₂ in FIG. 3 is held. With this value, the full power of the A / D converter 78 is set. In the steady state, the switch 98 is turned on.

[0054]

According to the present invention, the laser beam is controlled by using the portion in which the relation between the current flowing in the laser beam and the power of the laser beam can be approximated linearly. Therefore, the power of the laser beam can be easily and optimally controlled according to the ambient temperature such as the recording pattern.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram used for explaining a recording format of a magneto-optical disk.

FIG. 3 is a graph showing an example of characteristics of a laser diode.

FIG. 4 is a block diagram of a second embodiment of the present invention.

FIG. 5 is a block diagram of a third embodiment of the present invention.

FIG. 6 is a block diagram of a fourth embodiment of the present invention.

FIG. 7 is a block diagram of a fifth embodiment of the present invention.

FIG. 8 is a block diagram used to describe a conventional magneto-optical disk recording device.

[Explanation of symbols]

1, 21, 41, 61, 91 Input terminals 3A, 3B, 23A, 23B, 43A, 43B, 63
A, 63B, 93A, 93B Sample and hold circuit 9, 29, 47 D / A converter

Claims (1)

[Claims] 1. A detection means for receiving a part of light emitted from a laser light source, a first output obtained by sampling a detection output from the detection means at a first timing, and a detection output from the detection means. The upper limit and the lower limit of the power level of the output of the laser light source are set based on the second output obtained by sampling the detection output at the second timing, and the first output and the second output are set to the first output and the second output. An optical recording device comprising: a control signal generation unit that generates a control signal that controls the emission power of the laser light source based on the upper limit and the lower limit.