JP2014225312A - Optical disk player and semiconductor laser deterioration detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to detect deterioration of a semiconductor laser in a short time with high accuracy without adding a circuit unit for measurement to an optical disk player and without being influenced by irregularities and environmental temperatures of optical pickups and optical disks.SOLUTION: An optical disk player includes a laser controller that can control an output light quantity of a semiconductor laser by an APC reference voltage, measures amplitudes FEL1, FEL2, and FEL3 as output light quantities of the semiconductor laser in respective stages by changing the APC reference voltage to a plurality of stages of APC reference voltages REF1, REF2, and REF3, determines efficiency that is a ratio of the APC reference voltage to the output light quantity in each stage, further determines an efficiency rate that is a rate of efficiency in the plurality of stages, and compares the efficiency rate with a predetermined value, thereby detecting whether the semiconductor laser deteriorates.

Description

  The present invention relates to an optical disc player and a semiconductor laser deterioration detection method.

The optical disc player is equipped with an optical pickup for reproducing the signal of the optical disc, and the optical pickup is equipped with a semiconductor laser as a light source. Since semiconductor lasers are easily deteriorated by overcurrent and static electricity, attention is paid to their handling and usage, but it is not easy to eliminate the generation of deteriorated products. Further, the semiconductor laser gradually deteriorates when it is operated, and the lifetime becomes shorter as the ambient temperature becomes higher. However, the lifetime of the laser diode deteriorated due to overcurrent or static electricity becomes shorter than that of a normal product. Therefore, detecting the deterioration of the semiconductor laser and removing the deteriorated product is an important inspection for improving the reliability of the product. For example, the laser current value in the reproduction operation state is measured in the production process of the optical disc player. Then, an inspection for detecting a deteriorated product is performed by comparison with a specified value. Various methods for detecting deterioration have been proposed (see, for example, Patent Documents 1 and 2).
Patent Document 1 relates to an optical recording / reproducing apparatus, and is an invention in which deterioration is determined when the magnitude of a reproduction signal in a reproduction operation state does not reach a specified value in a configuration circuit normally provided in an optical disc player. . Patent Document 2 is an invention in which a ratio between a laser current value difference and a light emission amount difference between a plurality of operating points of a light output control circuit is obtained, and this is compared with a value between other operating points to detect deterioration. .

Japanese Patent Laid-Open No. 3-205625 JP 61-216141 A

However, when the laser current is measured in the playback state of the optical disc player as in the conventional case, an external measurement circuit needs to be connected because the circuit portion inside the product does not have a laser current measurement unit. For this reason, detection is performed in an intermediate process in which an external circuit can be connected, and cannot be detected in a finished product. Further, the laser current value in the reproducing operation state varies among optical pickups, and varies greatly depending on the environmental temperature. Therefore, it is difficult to reliably detect a deteriorated product by comparison with a certain specified value.
In the method of Patent Document 1, degradation can be determined by using a circuit that an optical disc player normally has, but the reproduction signal changes individually depending on the signal characteristics of the optical pickup and the optical disc, their situation, and the environmental temperature, so a prescribed value is set. It is not easy to do, and it is difficult to detect anything that is clearly degraded. In addition, since an operation for detection is performed after the actual reproduction operation state is set, a corresponding time is required until the determination. In the method of Patent Document 2, if the operating point is appropriately selected, slight deterioration can be detected without being affected by variations in the optical pickup or the optical disk or the environmental temperature. It is necessary to measure a laser current value that is not present, and it is necessary to provide a circuit portion for this purpose.

  The present invention has been made in view of the above-described circumstances, and without adding a circuit unit for measurement to an optical disc player, a semiconductor laser with high accuracy without being affected by variations of an optical pickup or an optical disc and environmental temperature. The purpose is to make it possible to detect the deterioration of the ink in a short time.

  In order to achieve the above object, the present invention includes a laser control unit capable of controlling the amount of light output from a semiconductor laser using an APC reference voltage, and changing the APC reference voltage in a plurality of stages to change the output of the semiconductor laser in each stage. The output light quantity is measured, the efficiency that is the ratio of the APC reference voltage and the output light quantity at each stage is obtained, the efficiency ratio that is the ratio of the efficiency of the plurality of stages is obtained, and the efficiency ratio and a predetermined value are obtained. In comparison, deterioration of the semiconductor laser is detected.

  According to the present invention, the APC reference voltage is changed in three steps in order of increasing voltage, and is a ratio of a difference between the APC reference voltage and a difference in the output light amount in the second step and the first step. An efficiency and a second efficiency which is a ratio of the difference between the APC reference voltage and the difference in the output light amount in the third stage and the second stage, and a ratio between the second efficiency and the first efficiency. Thus, the efficiency ratio is obtained.

Further, the invention is characterized in that the output light amount of the semiconductor laser is measured from the amplitude of a focus error signal.
Furthermore, the present invention is characterized in that the output light amount of the semiconductor laser is measured from an output of a monitor light receiving element.
The optical disk that reflects the laser is stopped when measuring the output light amount of the semiconductor laser.

  In the optical disk player and the semiconductor laser degradation detection method according to the present invention, the semiconductor laser is accurately detected without being affected by variations in the optical pickup and the optical disk and the environmental temperature without adding a circuit unit for measurement to the optical disk player. Degradation can be detected in a short time.

1 is a diagram showing a configuration of an optical disc player according to a first embodiment of the present invention. It is a figure which shows the structure of an optical pick-up, (a) shows the whole structure, (b) shows a light receiving element. It is a figure which shows the structure of a laser control part and a semiconductor laser apparatus. It is a figure which shows the relationship of the output light quantity with respect to the laser current of a semiconductor laser element. It is a figure which shows the relationship between an APC reference voltage and output light quantity. It is a figure which shows the relationship between the APC reference voltage obtained by the semiconductor laser element which has not deteriorated, and a focus error signal amplitude. It is a figure which shows the relationship between an APC reference voltage, an output light quantity, a focus rocking | fluctuation waveform, and a focus error signal. It is a figure which shows the relationship between the APC reference voltage obtained by the deteriorated semiconductor laser element, and a focus error signal amplitude. It is a flowchart of a laser degradation detection operation. It is a figure which shows the structure of the laser control part and semiconductor laser apparatus in 2nd Embodiment. It is a flowchart of the laser degradation detection operation | movement in 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a diagram showing a configuration of an optical disc player according to the first embodiment of the present invention. Here, in FIG. 1, portions not related to the present invention are omitted.
The optical disc player 50 (optical disc playback apparatus) includes a spindle motor 2, and the disc 1 is rotatably supported by the spindle motor 2 via a turntable (not shown). The disc 1 is an optical disc such as a CD or a DVD.

  The optical disk player 50 includes an optical pickup 3 that reads information on the disk 1, a laser control unit 6 that controls a semiconductor laser of the optical pickup 3, a focus drive unit 5 that drives a focus operation of the optical pickup 3, and a focus swing waveform. A search waveform generation unit 8 that generates and sends the signal to the focus drive unit 5, a signal amplification unit 4 that amplifies a signal read by the optical pickup 3, a focus error signal generation unit 7 that generates a focus adjustment signal, A signal level measurement unit 9, a system control unit 10 that controls each unit of the optical disc player 50, and a display unit 11 are provided.

  The system control unit 10 causes the search waveform generation unit 8 to generate a focus swing waveform (see FIG. 7C), drives the focus drive unit 5 by the focus drive unit 5, and drives the optical pickup 3 by the laser control unit 6. The semiconductor laser is turned on. The four signal outputs A, B, C, and D from the optical pickup 3 are respectively output from the A signal amplification unit 4a, the B signal amplification unit 4b, the C signal amplification unit 4c, and the D signal amplification unit 4d of the signal amplification unit 4. Amplified and sent to the focus error signal generator 7. The focus error signal generation unit 7 generates a focus error signal shown in FIG. 7 (d). The amplitude of the focus error signal is measured by the signal level measurement unit 9, and this amplitude value is read by the system control unit 10. It is done. The signal level measuring unit 9 is a measuring unit that measures the output light amount of the laser light.

2A and 2B are diagrams showing the configuration of the optical pickup 3, wherein FIG. 2A shows the overall configuration, and FIG. 2B shows the light receiving element.
The optical pickup 3 includes a semiconductor laser device 23 that emits laser light, a diffraction grating 32 that splits the laser light into a main beam and a sub beam, a half mirror 33, an objective lens 34, and a focus coil that drives the objective lens 34. 39 and a light receiving element 35 formed of a photodiode. The optical pickup 3 is moved in the radial direction of the disk 1 by a traverse mechanism (not shown) controlled by the system control unit 10.
The optical disc player 50 focuses the laser beam on the signal surface of the disc 1 with the focus drive unit 5, rotates the disc 1 with the spindle motor 2, and moves the optical pickup 3 in the radial direction of the disc 1 with the traverse mechanism. As a result, the information recorded on the disc 1 is read, and the information on the disc 1 is reproduced.

  The laser light emitted from the semiconductor laser device 23 is divided into a main beam and a pair of sub beams by the diffraction grating 32, and the main beam and the sub beams pass through the half mirror 33 and reach the objective lens 34. It is condensed on the signal surface. The laser light reflected from the signal surface of the disk 1 passes through the objective lens 34, is reflected by the half mirror 33, and is received by the light receiving element 35. The laser beam received by the light receiving element 35 is converted into an electric signal, and information on the disk 1 is read as an electric signal.

The light receiving element 35 includes a main detector 37 for detecting the main beam and a pair of sub detectors 36 and 38 for detecting the sub beams, respectively.
The main detector 37 has light receiving portions 37a, 37b, 37c, and 37d divided into four, and generates a focus error signal. Specifically, the signal outputs A, B, C, and D (FIG. 1) are received by the light receiving units 37a, 37b, 37c, and 37d, respectively, and the focus error signal is obtained by a generation formula of (A + D) − (B + C). It is done. In this generation formula, A, B, C, and D are the amounts of light received by the light receiving portions 37a, 37b, 37c, and 37d.

  In the optical disc player 50, the focus of the objective lens 34 is adjusted by the astigmatism method. Specifically, the system control unit 10 changes the focus error signal by driving the focus coil 39 and reciprocatingly moving the objective lens 34 in the focus direction, and the light reception amounts of the light receiving units 37a, 37b, 37c, and 37d are changed. The focus coil 39 is servo-driven so as to be equal, that is, so that the focus error signal becomes 0, so that the laser beam is accurately focused on the signal surface of the disk 1.

  The sub detectors 36 and 38 are used for generating a track error signal. The track error signal is obtained from the difference in the amount of light received by the sub-detectors 36 and 38. The system control unit 10 detects the position shift of the main beam using the track error signal and drives the traverse mechanism to accurately control the radial position of the optical pickup 3 in the disk 1.

FIG. 3 is a diagram showing the configuration of the laser controller 6 and the semiconductor laser device 23.
The semiconductor laser device 23 includes a semiconductor laser element 21 that generates laser light and a monitor light receiving element 22. The monitor light receiving element 22 is disposed on the side opposite to the direction in which the laser beam for reading the disk 1 is emitted, and is integrated into the semiconductor laser device 23.
When driven by the laser controller 6, the semiconductor laser element 21 generates output light L 1 emitted to the outside of the semiconductor laser device 23 and monitor output light L 2 emitted to the monitor light receiving element 22.
The output light L1 is light for reading the disk 1, and is reflected by the disk 1 and received by the light receiving element 35 as described above.
The monitor output light L2 is received by the monitor light receiving element 22 in the semiconductor laser device 23 and used for measuring the output light amount of the semiconductor laser element 21. The monitor light receiving element 22 converts the received light into a current and outputs it to the laser controller 6.

The laser control unit 6 detects the light output of the semiconductor laser element 21 by the monitor light receiving element 22 and controls the drive current of the semiconductor laser element 21 to keep the output of the laser light of the semiconductor laser element 21 constant. A drive circuit that performs laser light amount control of a semiconductor laser having such a feedback mechanism is called an APC (Auto Power Control) circuit (automatic light output control circuit).
Since the optical output characteristics of semiconductor lasers are sensitive to changes in the ambient temperature, the optical output varies greatly due to ambient temperature changes or self-heating even when driven at a constant current. Use an APC circuit. Thus, it can cope with the temperature dependence of the optical output.

  The laser control unit 6 includes a monitor current measuring unit 25 that measures a current output from the monitor light receiving element 22, a laser driving unit 24 that drives the semiconductor laser element 21, and a reference voltage of the APC circuit (hereinafter referred to as an APC reference voltage). .), And a voltage comparison unit 26 that compares the output of the monitor current measurement unit 25 with the output of the reference voltage generation unit 27 and outputs the difference.

The output current (monitor current) of the monitor light receiving element 22 is proportional to the output light amount of the semiconductor laser element 21. The monitor current measurement unit 25 converts the monitor current into a voltage (monitor voltage) having a magnitude proportional to the monitor current, and this monitor voltage becomes one input voltage VM of the voltage comparison unit 26.
The reference voltage generator 27 generates an APC reference voltage under the control of the system controller 10. The APC reference voltage is the other input voltage REF of the voltage comparison unit 26.
The voltage comparison unit 26 outputs a voltage difference between one input voltage VM and the other input voltage REF to the laser driving unit 24.

The laser driver 24 outputs a laser current according to the output of the voltage comparator 26 to drive the semiconductor laser element 21.
When the monitor voltage (one input voltage VM) is smaller than the APC reference voltage (the other input voltage REF), the voltage comparison unit 26 increases the output light amount of the semiconductor laser element 21. It is comprised so that it may become a side. Further, the voltage comparison unit 26 reduces the output light amount of the semiconductor laser element 21 when the monitor voltage (one input voltage VM) is larger than the APC reference voltage (the other input voltage REF). It is comprised so that it may become the side to make.

The monitor voltage is proportional to the monitor current of the monitor light receiving element 22, and the monitor current is proportional to the output light amount of the semiconductor laser element 21. That is, the output light amount of the semiconductor laser element 21 is controlled to a constant value based on the voltage fed back as the monitor voltage so that the light amount corresponds to the APC reference voltage.
Moreover, the output light quantity of the semiconductor laser element 21 changes by changing the APC reference voltage. The system control unit 10 sets the output light quantity of the semiconductor laser element 21 by designating the APC reference voltage output from the reference voltage generation unit 27 to various values.

FIG. 4 is a diagram showing the relationship of the output light quantity with respect to the laser current of the semiconductor laser element 21.
The semiconductor laser element 21 does not start laser oscillation until the laser current reaches the threshold current Ith, and the amount of output light is very small.
When the laser current exceeds the threshold current Ith, the semiconductor laser element 21 outputs light by laser oscillation, and the output light amount is proportional to the laser current. The ratio of the output light quantity to the laser current in the region where the laser current is equal to or greater than the threshold current Ith is defined as the light emission efficiency η (not shown).
In the normal semiconductor laser element 21, the light emission efficiency η is constant regardless of the laser current, and the relationship between the laser current and the output light quantity is a straight line like the line N. On the other hand, in the deteriorated semiconductor laser element, the light emission efficiency η decreases as the laser current increases, and the relationship between the laser current and the output light amount becomes a curve like the line F.

The output light quantity of the semiconductor laser element 21 is P, the photodetection sensitivity of the monitor light receiving element 22 and the monitor current measuring unit 25 is K, the monitor voltage output from the monitor current measuring unit 25 is VM, and the APC reference is output from the reference voltage generating unit 27. The voltage is REF, the error output that is the difference between the APC reference voltage REF and the monitor voltage VM is D, the amplification factor including the current conversion rate of the laser driver 24 is G, and the laser current that is the output current of the laser driver 24 is I. If the threshold current is Ith,
D = REF-VM (Formula 1)
I = G · D (Formula 2)
P = η (I−Ith) (Formula 3)
VM = K · P (Formula 4)
Holds.
From Equation 1, Equation 2, Equation 3, and Equation 4,
P = G · η · K / (1 + G · η · K) · REF / K−η · Ith / (1 + G · η · K) (Formula 5)
It becomes.

The output light quantity P is determined by a first term proportional to the APC reference voltage REF and a second term that is an influence of the threshold current Ith.
Both the first term and the second term are affected by the luminous efficiency η.
From Equation 1, Equation 2, Equation 3, and Equation 4,
D = 1 / (1 + G · η · K) · REF + 1 / (1 + G · η · K) · η · K · Ith (Expression 6)
It becomes.
The error output D is also determined by a first term proportional to the APC reference voltage REF and a second term that is an influence of the threshold current Ith. Both the first term and the second term are affected by the light emission efficiency η, and the error output D increases as the light emission efficiency η decreases. This error output D becomes a steady deviation of a normal feedback control system.

FIG. 5 is a diagram illustrating a relationship between the APC reference voltage REF and the output light amount.
If the laser control unit 6 performs an ideal operation without a steady deviation, the output light amount becomes a straight line proportional to the APC reference voltage REF as shown by the line X. Thus, the line X is a straight line having a slightly different inclination. Further, when the semiconductor laser element 21 is deteriorated and the light emission efficiency η decreases as the output light quantity increases, the steady deviation increases as the output light quantity increases. Therefore, the APC reference voltage REF and the output light quantity are increased. Is a curve like the line Z.

FIG. 6 is a diagram showing the relationship between the APC reference voltage obtained by a non-degraded semiconductor laser element and the focus error signal amplitude. FIG. 7 is a diagram illustrating a relationship among the APC reference voltage, the output light amount, the focus swing waveform, and the focus error signal. In FIG. 6, APC reference voltage REF1 (first stage), APC reference voltage REF2 (second stage), and APC reference voltage REF3 (third stage) are shown in three stages in ascending order of voltage.
When a focus sway waveform (see FIG. 7C) is applied to the focus coil 39, the objective lens 34 reciprocates in the focus direction, thereby generating an amplitude in the focus error signal. Since the amplitude of the focus error signal (see FIG. 7D) is proportional to the output light amount of the semiconductor laser element 21, if the relationship between the APC reference voltage REF and the output light amount is a straight line such as the line Y in FIG. Similarly, the relationship between the APC reference voltage REF and the amplitude of the focus error signal is also a straight line. In the state shown in FIG. 6, the slope of the line H1 between the points of the APC reference voltage REF1, the APC reference voltage REF2, and the APC reference voltage REF3 is the same, and the difference in the focus error signal amplitude between the points and the APC The ratio of reference voltage differences is constant.

FIG. 8 is a diagram showing the relationship between the APC reference voltage obtained by the deteriorated semiconductor laser element and the focus error signal amplitude. In FIG. 8, APC reference voltage REF1 (first stage), APC reference voltage REF2 (second stage), and APC reference voltage REF3 (third stage) are shown in three stages in ascending order of voltage.
In the deteriorated semiconductor laser element, the relationship between the APC reference voltage REF and the output light quantity is a curve as shown by the line Z in FIG. 5, and therefore the line H2 indicating the relationship between the APC reference voltage and the focus error signal amplitude is also a curve. , The slope of the line H2 between the points of the APC reference voltage REF1, the APC reference voltage REF2, and the APC reference voltage REF3 is different from each other, and the ratio of the difference in focus error signal amplitude between the points and the difference in APC reference voltage Are not equal.

FIG. 9 is a flowchart of the laser deterioration detection operation.
In the optical disk player 50 of FIG. 1, the disk 1 is mounted on the spindle motor 2. The system controller 10 causes the search waveform generator 8 to generate a focus wobbling waveform (see FIG. 7C), and drives the focus coil 39 of the optical pickup 3 by the focus driver 5 (step S1). The spindle motor 2 is not rotated and the disk 1 is stopped.

When a focus sway waveform is applied to the focus coil 39, the objective lens 34 reciprocates in the focus direction, thereby generating an amplitude in the focus error signal.
Next, the system control unit 10 sets the APC reference voltage REF1 for the laser control unit 6 (step S2), and causes the semiconductor laser element 21 to emit light. Here, the APC reference voltage REF1 is a value corresponding to a laser current larger than the threshold current Ith, and is a voltage in an initial region where light emission of the semiconductor laser element 21 starts to rise.
The laser beam emitted from the objective lens 34 is reflected by the disk 1 and enters the light receiving element 35.

Signal outputs A, B, C, and D from the optical pickup 3 are amplified by an A signal amplification unit 4a, a B signal amplification unit 4b, a C signal amplification unit 4c, and a D signal amplification unit 4d, respectively, to generate a focus error signal. The unit 7 generates a focus error signal shown in FIG. 7D from these signals (step S3). Using the signal outputs A, B, C, and D output from the main detector 37 of the light receiving element 35, a focus error signal is obtained by a generation formula of (A + D)-(B + C).
The focus error signal is measured for amplitude FEL1 (FIG. 7 (d)) by the signal level measurement unit 9, and the measured amplitude FEL1 is read by the system control unit 10 (step S3).

Next, the system control unit 10 sets the APC reference voltage REF2 in which the output light amount of the semiconductor laser element 21 is larger than the APC reference voltage REF1 in the laser control unit 6 (step S4). Here, the APC reference voltage REF2 is a voltage having a magnitude that causes the semiconductor laser element 21 to generate a normal amount of light used when the disk 1 is reproduced.
When the APC reference voltage REF2 is set, the amplitude of the focus error signal becomes an amplitude FEL2 (FIG. 7 (d)) larger than the amplitude FEL1, and the amplitude FEL2 measured by the signal level measuring unit 9 is the system control unit 10. (Step S5).

Next, the system control unit 10 calculates the signal efficiency E1 (first efficiency) from the amplitude FEL1, the amplitude FEL2, the APC reference voltage REF1, and the APC reference voltage REF2 by the following expression (Step S6). In Equation 7, only a symbol is shown for simplification.
E1 = (FEL2-FEL1) / (REF2-REF1) (Expression 7)

Next, the system control unit 10 sets the APC reference voltage REF3 in which the output light amount is larger than the APC reference voltage REF2 to the laser control unit 6 (step S7). Here, the APC reference voltage REF3 is a voltage higher than the voltage used during normal reproduction of the disk 1, but is set to a large value within a range in which the semiconductor laser element 21 does not deteriorate due to excessive light emission.
When the APC reference voltage REF3 is set, the amplitude of the focus error signal becomes an amplitude FEL3 (FIG. 7 (d)) larger than the amplitude FEL2, and the amplitude FEL3 measured by the signal level measuring unit 9 is the system control unit 10. (Step S8).

The system control unit 10 calculates the signal efficiency E2 (second efficiency) from the amplitude FEL2, the amplitude FEL3, the APC reference voltage REF2, and the APC reference voltage REF3 by Expression 8 (Step S9). In Formula 8, only a sign is shown for simplification.
E2 = (FEL3-FEL2) / (REF3-REF2) (Equation 8)
Next, the system control unit 10 calculates the efficiency ratio ΔE from the signal efficiencies E1 and E2 by Equation 9 (step S10). The system control unit 10 includes a calculation unit 10a that calculates the signal efficiencies E1 and E2 and the efficiency ratio ΔE.
ΔE = E2 / E1 (Equation 9)
Next, the system control unit 10 compares the efficiency ratio ΔE with the predetermined value EL using Expression 10 and determines whether or not the efficiency ratio ΔE is smaller than the predetermined value EL (step S11). Here, the predetermined value EL is an efficiency ratio of the semiconductor laser element 21 in a state that can be regarded as deterioration of the semiconductor laser element 21, and is determined in advance by an experiment or the like. The system control unit 10 includes a comparison unit 10b that compares efficiency ratios.
ΔE <EL (Formula 10)
When it is determined that Expression 10 is established and the efficiency ratio ΔE is smaller than the predetermined value EL (step S11: YES), the system control unit 10 determines that the semiconductor laser element 21 has deteriorated, and determines that the laser has deteriorated. The display is performed on the display unit 11 to notify the deterioration (step S12). If the system control unit 10 determines that Equation 10 is not satisfied and the efficiency ratio ΔE is larger than the predetermined value EL (step S11: NO), the system control unit 10 determines that the semiconductor laser element 21 has not deteriorated, and No display indicating deterioration.

As described above, the efficiency ratio ΔE is obtained by using the focus error signal that is normally used by the optical disc player 50 to adjust the focus of the laser beam, and the efficiency ratio ΔE is compared with the predetermined value EL, thereby degrading the semiconductor laser element 21. Therefore, it is not necessary to provide a dedicated circuit for detecting the deterioration of the semiconductor laser element 21, and the deterioration can be detected with a simple configuration. In addition, since the efficiency ratio ΔE is obtained from the signal efficiencies E1 and E2 measured under substantially the same conditions, individual differences of the optical pickup 3 and the influence of the ambient temperature can be eliminated, and deterioration of the semiconductor laser element 21 can be detected with high accuracy. it can. The above laser degradation detection operation can be performed on the production line, but it can be performed at the stage before the regeneration operation to detect degradation regardless of whether it is in the finished product state or on the production line. Yes, detection in a short time is possible.
In addition to the focus error signal, other signals obtained during the normal reproduction operation of the disk 1 may be used for detection of deterioration as long as the output light amount of the semiconductor laser element 21 is used. However, in this case, it takes time until the reproduction state is set, and the output light amount of the semiconductor laser element 21 can be changed only within a range where the stable servo operation of the focus coil 39 is possible. The amount of change in a narrower range than the focus error signal obtained before setting the state is used, and the measurement accuracy is inferior.

  As described above, according to the first embodiment to which the present invention is applied, the laser control unit 6 that can control the output light amount of the semiconductor laser element 21 by the APC reference voltage REF is provided, and the APC reference voltage REF is The amplitude of the focus error signal is measured as the output light quantity of the semiconductor laser at each stage by changing to a plurality of stages, and the signal efficiencies E1 and E2 which are the ratios of the APC reference voltage REF and the output light quantity at each stage are obtained. Further, an efficiency ratio ΔE, which is a ratio of the efficiencies E1 and E2, is further obtained, and the deterioration of the semiconductor laser element 21 is detected by comparing the efficiency ratio ΔE with a predetermined value EL. Thereby, the deterioration of the semiconductor laser element 21 can be detected by using the output light amount of the semiconductor laser element 21 of the optical disc player 50, and it is not necessary to add a dedicated circuit unit for measurement to the optical disc player 50. Degradation can be detected by structure. Further, since the deterioration of the semiconductor laser element 21 can be detected by the ratio of the signal efficiencies E1 and E2 at each stage, the deterioration can be detected accurately without being affected by variations in the optical pickup 3 and the disk 1 and the environmental temperature. Furthermore, the deterioration of the semiconductor laser element 21 can be detected without bringing the optical disc player 50 into the reproduction state, and the deterioration can be detected in a short time.

  In addition, the APC reference voltage REF is changed in three stages of APC reference voltage REF1, APC reference voltage REF2, and APC reference voltage REF3 in order of increasing voltage, and the APC reference voltages REF2 and REF1 in the second stage and the first stage. Signal efficiency E1 which is the ratio of the difference between the amplitudes FEL2 and FEL1, and the signal efficiency E2 which is the ratio of the difference between the APC reference voltages REF3 and REF2 and the difference between the amplitudes FEL3 and FEL2 in the third and second stages. And the efficiency ratio ΔE is obtained by the ratio of the signal efficiency E2 and the signal efficiency E1. As a result, the efficiency ratio ΔE can be obtained by measuring the amplitude of the focus error signal as the output light quantity with respect to a wide range of APC reference voltages with a small number of measurement steps, so that the semiconductor laser element 21 can be obtained with high accuracy and in a short time. Can be detected.

Further, since the output light quantity of the semiconductor laser element 21 is measured from the amplitude of the focus error signal, there is no need for a dedicated circuit for measuring the output light quantity, and the deterioration of the semiconductor laser element 21 can be detected with a simple structure. .
Further, when measuring the output light amount of the semiconductor laser element 21, the disk 1 that reflects the laser light is stopped, so that the operation of rotating the disk 1 is not required, and the deterioration of the semiconductor laser element 21 can be detected in a short time. In addition, it is possible to detect deterioration with high accuracy by reducing the influence of variation.

In addition, the said 1st Embodiment shows the one aspect | mode which applied this invention, Comprising: This invention is not limited to the said 1st Embodiment.
In the first embodiment, the APC reference voltage REF is set in three stages. However, the present invention is not limited to this and may be set in a plurality of stages including four or more stages. Even in this case, the signal efficiency at each stage is obtained, the efficiency ratio ΔE is obtained by comparing at least two signal efficiencies, and the deterioration of the semiconductor laser element 21 can be detected.

[Second Embodiment]
Hereinafter, a second embodiment to which the present invention is applied will be described with reference to FIGS. 10 and 11. In the second embodiment, parts that are configured in the same manner as in the first embodiment are given the same reference numerals, and descriptions thereof are omitted.
In the first embodiment, the output light amount of the semiconductor laser element 21 is described as being measured from the amplitude of the focus error signal. However, in the second embodiment, the output light amount of the semiconductor laser element 21 is The point measured from the output of the monitor light receiving element 22 is different from that of the first embodiment.

FIG. 10 is a diagram illustrating a configuration of the laser control unit 106 and the semiconductor laser device 23 in the second embodiment.
The laser control unit 106 includes a monitor current measurement unit 25, a laser drive unit 24, a voltage comparison unit 26, and a reference voltage generation unit 27, and is configured in substantially the same manner as the laser control unit 6 of the first embodiment. However, the monitor current measurement unit 25 is connected not only to the voltage comparison unit 26 but also to the system control unit 10. The system control unit 10 includes a voltage measurement unit 10 c that measures the voltage output from the monitor current measurement unit 25.

The output current (monitor current) of the monitor light receiving element 22 is proportional to the output light amount of the semiconductor laser element 21. The monitor current measurement unit 25 converts the monitor current into a voltage (monitor voltage) having a magnitude proportional to the monitor current, and this monitor voltage becomes one input voltage VM of the voltage comparison unit 26. The input voltage VM (hereinafter sometimes referred to as the monitor voltage VM) is also input to the system control unit 10.
The reference voltage generator 27 generates an APC reference voltage under the control of the system controller 10. The APC reference voltage is the other input voltage REF of the voltage comparison unit 26.

The voltage comparison unit 26 outputs a voltage difference between one input voltage VM and the other input voltage REF to the laser driving unit 24.
As in the first embodiment, the output light amount of the semiconductor laser element 21 is controlled to a constant value so that the light amount corresponds to the APC reference voltage based on the voltage fed back as the monitor voltage.
The system control unit 10 sets the output light amount of the semiconductor laser element 21 by designating the APC reference voltage output from the reference voltage generation unit 27, and measures the actual output light amount of the semiconductor laser element 21 using the monitor voltage. .

FIG. 11 is a flowchart of the laser deterioration detection operation in the second embodiment.
First, the system control unit 10 sets the APC reference voltage REF1 (first stage) to the reference voltage generation unit 27 of the laser control unit 106, and causes the semiconductor laser element 21 to emit light (step S21). Here, the disk 1 is not set on the spindle motor 2.
The monitor output light L2 of the semiconductor laser element 21 is received by the monitor light receiving element 22 to become a monitor current corresponding to the magnitude of the APC reference voltage REF1, converted into the monitor voltage VM1 by the monitor current measuring unit 25, and the monitor voltage VM1. Is read by the system controller 10 (step S22).

Next, the system control unit 10 sets the APC reference voltage REF2 (second stage) in which the output light amount is larger than the APC reference voltage REF1 to the reference voltage generation unit 27, and causes the semiconductor laser element 21 to emit light (see FIG. Step S23). The monitor output light L2 of the semiconductor laser element 21 is received by the monitor light receiving element 22 to become a monitor current corresponding to the magnitude of the APC reference voltage REF2, converted into the monitor voltage VM2 by the monitor current measuring unit 25, and the monitor voltage VM2 Is read by the system control unit 10 (step S24).
The system control unit 10 calculates the signal efficiency E1 (first efficiency) from the monitor voltages VM1 and VM2 and the APC reference voltages REF1 and REF2 using Equation 11 (step S25). In Formula 11, for simplification, it shows only with a code | symbol.
E1 = (VM2-VM1) / (REF2-REF1) (Equation 11)

Next, the system control unit 10 sets the APC reference voltage REF3 (third stage) in which the output light amount is larger than the APC reference voltage REF2 to the reference voltage generation unit 27, and causes the semiconductor laser device 21 to emit light (see FIG. Step S26). The monitor output light L2 of the semiconductor laser element 21 is received by the monitor light receiving element 22 to become a monitor current corresponding to the magnitude of the APC reference voltage REF3, converted into the monitor voltage VM3 by the monitor current measuring unit 25, and the monitor voltage VM3. Is read by the system control unit 10 (step S27).
The system control unit 10 calculates the signal efficiency E2 (second efficiency) from the monitor voltages VM2 and VM3 and the APC reference voltages REF2 and REF3 according to Equation 12 (step S28). In Formula 12, for simplification, only the symbol is shown.
E2 = (VM3-VM2) / (REF3-REF2) (Equation 12)
Next, the system control unit 10 calculates the efficiency ratio ΔE from the signal efficiencies E1 and E2 by Expression 13 (step S29).
ΔE = E2 / E1 (Formula 13)
Next, the system control unit 10 compares the efficiency ratio ΔE with the predetermined value EL using Expression 14, and determines whether or not the efficiency ratio ΔE is smaller than the predetermined value EL (step S30). Here, the predetermined value EL is an efficiency ratio of the semiconductor laser element 21 in a state that can be regarded as deterioration of the semiconductor laser element 21, and is determined in advance by an experiment or the like.
ΔE <EL (Formula 14)
When the system control unit 10 determines that Expression 14 is satisfied and the efficiency ratio ΔE is smaller than the predetermined value EL (step S30: YES), the system control unit 10 determines that the semiconductor laser element 21 has deteriorated, and causes the laser to deteriorate. The display is displayed on the display unit 11 to notify the deterioration (step S31). If the system control unit 10 determines that Equation 14 is not satisfied and the efficiency ratio ΔE is larger than the predetermined value EL (step S30: NO), the system control unit 10 determines that the semiconductor laser element 21 has not deteriorated, and No display indicating deterioration.

As described above, according to the second embodiment to which the present invention is applied, the output light amount of the semiconductor laser element 21 is the monitor for the APC circuit provided to keep the output light amount of the semiconductor laser element 21 constant. Since the measurement is performed from the output of the light receiving element 22, a dedicated circuit or the like for measuring the output light amount is not required, and the deterioration of the semiconductor laser element 21 can be detected with a simple structure.
Further, since the deterioration of the semiconductor laser element 21 can be detected by the ratio of the signal efficiencies E1 and E2 at each stage, the deterioration can be detected accurately without being affected by variations in the optical pickup 3 and the environmental temperature.
Furthermore, since the monitor output light L2 is received by the monitor light receiving element 22 and used for determination of deterioration, it is not necessary to set the disk 1 in order to detect the deterioration of the semiconductor laser element 21. For this reason, deterioration of the semiconductor laser element 21 can be detected in a short time.

1 disc (optical disc)
6,106 Laser controller 21 Semiconductor laser element (semiconductor laser)
22 Monitor light receiving element 50 Optical disc player E1 Signal efficiency (efficiency, first efficiency)
E2 Signal efficiency (efficiency, second efficiency)
EL Predetermined value REF APC reference voltage ΔE Efficiency ratio

Claims (6)

  A laser control unit capable of controlling an output light amount of the semiconductor laser by an APC reference voltage; measuring the output light amount of the semiconductor laser at each step by changing the APC reference voltage in a plurality of steps; The efficiency, which is the ratio between the reference voltage and the output light quantity, is obtained, the efficiency ratio, which is the efficiency ratio of the plurality of stages, is obtained, and the degradation of the semiconductor laser is detected by comparing the efficiency ratio with a predetermined value. An optical disc player characterized by the above.   The APC reference voltage is changed in three steps in ascending order of voltage, and a first efficiency which is a ratio of a difference between the APC reference voltage and a difference in output light amount in the second step and the first step, and a third step. And a second efficiency which is a ratio of the difference between the APC reference voltage and the output light quantity in the second stage, and the efficiency ratio is obtained by a ratio between the second efficiency and the first efficiency. The optical disc player according to claim 1, wherein the optical disc player is provided.   3. The optical disc player according to claim 1, wherein the output light amount of the semiconductor laser is measured from an amplitude of a focus error signal.   3. The optical disk player according to claim 1, wherein the output light amount of the semiconductor laser is measured from an output of a monitor light receiving element.   4. The optical disk player according to claim 1, wherein the optical disk that reflects the laser is stopped when measuring the output light amount of the semiconductor laser.   The APC reference voltage of the laser control unit that can control the output light amount of the semiconductor laser is changed in a plurality of steps to measure the output light amount of the semiconductor laser at each step, and the APC reference voltage and the output light amount at each step are measured. An efficiency ratio that is a ratio of the plurality of stages, an efficiency ratio that is a ratio of the efficiency of the plurality of stages, and a comparison between the efficiency ratio and a predetermined value to detect deterioration of the semiconductor laser. Degradation detection method.

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