JP2000090563A - Optical disk player - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk player capable of maintaining a high transfer rate during playing while preventing an excessive increase in the temperature of an objective lens or a driving coil. SOLUTION: This optical disk reproducing device is adapted to reproduce information from an optical disk D to be controlled from a basic rotational speed to rotation higher in speed by (n) (integer) times by using an optical pickup 1 having a driving coil to perform focus control or tracking control for an objective lens. This device is provided with a temperature detecting means 22 for detecting the temperature of the driving coil, and the rotational speed of the optical disk D is controlled according to the detecting result of the temperature detecting means 22 to change a reading transfer rate. Thus, an excessive increase in the temperature of the objective lens or the driving coil is prevented, and a high transfer rate is maintained during reproducing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DVD (Digital Vers) which requires a digital signal having a high transfer rate.
The present invention relates to a playback device for an optical disc such as an optical disc (CD) or a CD-ROM. In particular, in order to read a signal on an optical disc that is rotating at high speed at n times the basic playback speed, the objective lens is driven and controlled by an actuator. The present invention relates to an optical disk reproducing apparatus for a servo control system.

[0002]

2. Description of the Related Art Generally, DVDs and CD-Rs are rotated at a high rotational speed.
In order to reproduce information from an optical disk such as an OM, it is necessary to control the objective lens of the optical pickup to follow the disk surface shake and eccentricity during high-speed rotation. In the disk standard, the magnitude of surface wobble and eccentricity is defined by the playback conditions for constant speed playback. According to this rule, the surface vibration of the basic rotation speed component per rotation is ± 0.5 mm in a CD-ROM, and the disk eccentricity is 70 μm.
This value is specified when the rotation speed of the disk is 1 × speed (basic rotation speed), and this standard is a specification in an initial shipping state of the disk. In principle, when the rotation speed of the disk is n times higher, the low-frequency displacement (DC (direct current) to the basic rotation speed component) does not change, the frequency axis changes n times, and the acceleration component in the high frequency becomes It increases in proportion to the square of the rotation speed. In this case, in order to perform a test of the drive reproduction tolerance, assuming the deformation of the disk after the disk is shipped, a change in the accuracy of the rotation mechanism of the drive, etc., an eccentricity limit test disk, a surface shake limit test disk Is used.

In a verification test of the reproduction characteristics of a drive assuming the worst case in actually reproducing such a disk, the surface deviation is ± 0.5 mm and the eccentricity is 70 to 280 μm. Then, in an actual reproducing apparatus, such a rotation fundamental frequency component is caused to follow the surface shake and eccentricity,
It is necessary to drive the objective lens two-dimensionally. A current of a magnitude corresponding to the objective lens displacement corresponding to the amount of surface shake and the amount of eccentricity is applied to the drive coil, tracking coil and focus coil of the actuator of the optical pickup. The power consumption determined by the current flowing through the drive coil and the coil resistance generates heat due to resistance loss, which raises the temperature of the drive coil and the lens holder. The objective lens is made of a plastic material such as PMMA (polymethyl methacrylate), PC (polycarbonate), ART.
ON, etc., heat deformation temperature is 100 ~ 1
At 60 ° C., the aberration change temperature is 75 to 120 ° C., the objective lens undergoes a shape deformation due to a thermal expansion coefficient due to a rise in temperature, and furthermore, when the temperature rise exceeds the thermal deformation temperature, the shape of the objective lens causes permanent deformation and breaks. . Therefore, in order to prevent destruction, it is necessary to suppress an extreme rise in temperature of the drive coil and the objective lens.

Here, the structure of a general optical pickup will be described. FIG. 9 is a perspective view showing an optical pickup, and FIG. 10 is a plan view of the optical pickup. In FIG. 9,
The yoke and the magnet are shown in a disassembled state for easy understanding of the structure. The optical pickup 1 has an objective lens 2 for focusing on an optical disk (not shown). The objective lens 2 is supported by a lens holder 3, and two kinds of coils, a focus coil 4 and a tracking coil 5, are wound around the lens holder 3. The coils 4 and 5 are wound with electric wires usually called magnet wires to convert electric energy and magnetic energy. Focus coil 4
Is wound on the side surface of the lens holder 3, and the tracking coil 5 is energized after being wound up in a ring shape using a self-fusing synthetic enameled wire (magnet wire).
The self-heating of the enamel wire itself melts the adhesive film around the winding wire to bond the enamel wires together, and is formed into a ring-shaped block by solidifying the winding. A total of four pairs are bonded on the focus coil 4 at both end surfaces of the pair. The lens holder 3 is connected to its side 4
The suspension wire 6 is supported by a suspension base 7.

[0005] A resilient member 8 is joined to the connection portion of each suspension wire 6 to the suspension base 7 so as to absorb unnecessary vibration of the wire 6. Further, on both sides of the lens holder 3, a relatively large rectangular yoke receiving hole 9 is provided, and a substantially U-shape is formed so as to connect the inside of the yoke receiving hole 9 and the outside of both ends of the lens holder 3. The completed yoke 10 is provided upright from a base (not shown) in a loosely fitted state.
Then, the yoke 1 facing the tracking coil 5
The magnet 11 is mounted on the opposite surface of the “0”. With this configuration, the objective lens 2 is driven two-dimensionally by the coils 4 and 5 in the focus control direction and the tracking control direction. This driving force is formed by an electromagnetic force generated between a magnetic field formed by the yoke 10 and the magnet 11 and a current supplied to the coils 4 and 5 placed thereon.

Here, when a current is applied to both coils 4 and 5,
Heat is generated in an amount corresponding to the resistance value or the current value. However, the upper limit of the temperature rise of the focus coil 4 is, in principle, heat generated because the coil is wound around the lens holder 3, and the insulation of the winding is deteriorated. Until you do. On the other hand, since the tracking coil 5 forms a block, the adhesive force of the adhesive is reduced due to heat generation, a force acts on the coil windings, and the adhesion between the windings is peeled off. The upper limit is a temperature state at which a force cannot be generated. As described above, since the coils 4, 5 and the objective lens 2 are destroyed due to the temperature rise, it is necessary to set an upper limit for the temperature rise generated by the reproduction of the limit disk, and to use the temperature below this temperature. Until now, objective lens 2, coil 4,
For the protection of No. 5, a measure has been taken in which the upper limit of the coil drive voltage is simply set and a circuit is provided so that a voltage higher than this voltage is not applied.

[0007]

However, in this method, since the dynamic range of the operating voltage is limited by the actuator drive circuit, a high-frequency noise component mixed into the servo error signal is limited by a limiter. There may be a problem that the operation of the system becomes nonlinear. In this way, the high-speed reproduction characteristic is maintained for as long as possible, and the temperature rise of the objective lens due to the heat generated by the coil is detected by some means to limit the temperature rise, thereby thermally destroying the objective lens and the coil. Is required for high-speed drive. The present invention has been made in view of the above problems, and has been conceived in order to effectively solve the problems. The purpose of the present invention is to prevent the objective lens and the drive coil from excessively rising while reproducing. It is an object of the present invention to provide an optical disk reproducing apparatus capable of maintaining a high transfer rate.

[0008]

According to a first aspect of the present invention, there is provided a focus control and tracking control for an objective lens from an optical disc which can be controlled from a basic rotational speed to a high speed of n (integer) times. An optical disc reproducing apparatus for reproducing information using an optical pickup having a drive coil for performing temperature information, comprising temperature detecting means for detecting the temperature of the drive coil, and rotating the optical disc in accordance with the detection result of the temperature detecting means. The transfer rate of reading is changed by controlling the number.
As described above, the temperature of the drive coil is detected by the temperature detecting means, and the number of revolutions of the optical disk is controlled in accordance with the detection result to change the transfer rate of reading.
It is possible to secure the maximum transfer rate within the allowable temperature range while preventing the drive coil and the objective lens from excessively rising in temperature.

In this case, the rotation of the optical disk is controlled stepwise between a basic rotational speed and an n-fold high-speed rotational speed. Further, as defined in claim 3, the temperature detecting means determines a temperature state of the drive coil based on a voltage drop amount of the drive coil, and a determination result of the temperature state determination section. And a rotation number determination unit that determines the rotation number of the optical disk based on

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an optical disk reproducing apparatus according to the present invention.
FIG. 1 is a block diagram showing a main part of an optical disk reproducing apparatus according to the present invention, and FIG. 2 is a block circuit diagram showing a temperature detecting means in FIG. As described above, when the objective lens is controlled and driven two-dimensionally in the focus direction and the tracking direction in a state where the optical disk with large surface shake and eccentricity is rotated at a high speed, the power consumption in the drive coil increases, and heat is generated due to heat dissipation. And the temperature of the lens holder rises,
As a result, the plastic objective lens is deformed, and in the worst case, permanently deformed. Therefore, it is an object of the present invention to prevent this. For this reason, in the present invention, the temperature rise of the objective lens is detected by measuring the resistance change of the drive coil, and when an excessive temperature rise of the lens holder is detected, control for reducing the number of rotations is performed.
Enhance system security.

As shown in FIG. 1, this reproducing device 15
A spindle motor 16 for rotating the optical disk D is provided.
Is controlled by The optical pickup 1 irradiates a laser beam onto the optical disc D and reads out information from the reflected light. The specific configuration has been described earlier with reference to FIGS. 9 and 10, and therefore the description thereof is omitted here. I do. The feed motor 18 controls the feed amount by moving the optical pickup 1 in the radial direction of the optical disc D, and controls the feed amount.
9.

The signal processing block 20 generates a reproduction signal, a servo signal, a speed signal for CLV or CAV control, and the like based on the information read from the optical pickup 1, and performs an error correction process on the reproduction signal. The pickup control block 21 outputs a focus control signal, a tracking control signal, and the like based on the servo signal obtained from the signal processing unit 20, and performs focus and tracking control of the optical pickup 1. The temperature detecting means 22, which is a feature of the present invention, indirectly determines the temperatures of the focus coil 4 and the tracking coil 5 (see FIG. 9) in the optical pickup 1 by electric means. The main control unit 23 includes, for example, a microprocessor or the like, and controls the operation of the entire device. still,
The playback device includes a decoder block for expanding compressed data, an A / V separation block for separating an audio signal from a video signal, and the like, in addition to the above-described blocks.

Next, the temperature detecting means 22 will be described with reference to FIG. The equivalent circuit of the drive coil is composed of the resistance and inductance of the winding made of copper wire and the back electromotive voltage when the objective lens (coil) moves. The drive voltage of the coil is composed of a surface shake and an eccentric component of the rotation frequency (AC component) and a DC component when the position is offset. In order to detect the change in resistance of the drive coil by a circuit, a method of detecting only a DC component and a method of detecting a frequency component including the number of rotations are considered. When detecting including the rotation speed component, it is necessary to accurately detect the back electromotive voltage having frequency characteristics, and it is possible in principle to obtain the voltage applied to the coil resistance by calculation, but resistance change due to temperature is not possible. It is difficult to perform highly accurate detection in a small number. Therefore, in the present invention, a circuit that detects only a DC component is configured. The DC component applied to the drive coil is an offset of the lens position or a DC deviation of the tracking control, and a constant value is not always added, but it is assumed that the DC component is generated within a certain time range.

As shown in FIG.
Is mainly composed of a track-side temperature detection circuit 25T, a track-side temperature state determination unit 26T, a focus-side temperature detection circuit 25F, a focus-side temperature state determination unit 26F, and a rotation speed determination unit 27. The focus-side temperature detection circuit 25F includes a focus coil 4 having a resistance value represented by Rf and a focus-side detection resistor 28F connected in series with the resistance value R1. Focus coil 4
The voltage drop at the focus coil 4 is obtained by inputting the voltage of the input side terminal of the focus detection resistor 28F to the focus side differential amplifier 31 via the low-pass filters 29 and 30. Further, the voltage drop amount of the focus side detection resistor 28F is obtained from the voltage of the input side terminal of the focus side detection resistor 28F.

The focus side temperature state determining section 26F determines the voltage drop amount of the focus side detection resistor 28F as K ₁ , K
three focus-side amplifiers 32A, 32B, and 32C that amplify based on three different gains of a and Kb; a subtractor 33 that subtracts the output of the focus-side amplifier 32A from the output of the focus-side differential amplifier 31F; Subtractor 3
3 and comparators 34 and 35 for comparing the outputs of the remaining amplifiers 32B and 32C. The track-side temperature detection circuit 25T has a resistance value of R
It comprises a tracking coil 5 represented by r and a track-side detection resistor 28T represented by a resistance value R2 connected in series with the tracking coil 5. Tracking coil 5 and track detection resistor 2
The voltage of each input terminal of 8T is converted to a low-pass filter 3
The voltage drop amount in the tracking coil 5 is obtained by inputting the signal to the track side differential amplifier 31T via the lines 6 and 37. Further, the voltage drop amount of the track side detection resistor 28T is obtained from the voltage of the input side terminal of the track side detection resistor 28T.

The track-side temperature state determination unit 26T determines the amount of voltage drop of the track-side detection resistor 28T as K ₂ , Kc, K
d, three track-side amplifiers 38A, 38B, and 38C that amplify based on three different gains; a subtractor 39 that subtracts the output of the track-side amplifier 38A from the output of the track-side differential amplifier 31T; It mainly comprises comparators 40 and 41 for comparing the output of 39 with the outputs of the remaining amplifiers 38B and 38C. Then, the state of the output signal of each of the comparators 34, 35, 40, 41, for example, 0,
The rotation speed determination unit 27 determines the rotation speed of the optical disk according to 1 (low, high) according to a table described later.

Next, the operation of the present embodiment configured as described above will be described. First, the rotation of the optical disc D can be controlled in a plurality of stages from a basic rotation speed (basic speed) to n times, for example, 32 times high speed (n times high speed double speed). Reading is performed at the corresponding transfer rate. First, the optical pickup 1
The information of the optical disc D read out is input to the signal processing block 20, where a reproduction signal and a servo signal which are AV signals are generated. Based on this servo signal, the disk rotation control block 17 controls the number of rotations of the optical disk D, and the pickup control block 21 performs focus control, tracking control, and the like on the objective lens 2 of the optical pickup 1. .

For efficient reproduction by shortening the reproduction time and the like, it is preferable to always read the information while maintaining the rotation of the optical disk D at the highest rotational speed of n times, which is the highest rotational speed. However, at this time, the focus control and the tracking control of the objective lens 2 are performed following the surface blur and the eccentricity. The larger the surface deviation or eccentricity, or the higher the speed of rotation of the disk, the more the above-mentioned control signal is supplied to the drive coil, so that the temperature rise is correspondingly large, and the objective lens and the drive coil are not thermally damaged. The chance of receiving it increases. However, in the present invention, the temperature rise is detected by the temperature detection means 22, and based on the detection result, for example, when the temperature of the drive coil is too high, the rotation speed of the optical disk is reduced, that is, the transfer rate is reduced. As a result, the value of the control current flowing through the drive coil is reduced, and as a result, the heat generation of the drive coil is suppressed, so that the objective lens and the drive coil can be prevented from being thermally damaged.

This will be described in more detail. FIG.
Shows the power loss characteristics of the drive coil at the time of high-speed rotation, FIG. 3A shows a graph of power consumption at the time of reproduction of the surface blur limit (± 0.5 mm), and FIG. (±
280 μm) is shown in a graph of power consumption during reproduction. Various types of drive coils A to F are studied. In general, when the relationship between power consumption when reproducing a surface fluctuation limit disk and an eccentric limit disk is determined from the specification data of a drive coil for high-speed reproduction, the drive voltage of the drive coil is represented by [DC resistance of drive coil × drive current]. It is equal to the value obtained by adding the back electromotive force when the coil moves to the obtained value. In this calculation, the back electromotive force is ignored because it is small.

For example, the power loss when the displacement の of the frequency f is generated by the drive coil shown in the specification of the voltage sensitivity of 200 Hz and the DC resistance is expressed by the following relational expression. ^{W = (△ × f 2/} 200) 2 / (K 2 × R) where, W [mW]: power loss, △ [μm]: wobbling or eccentricity, f [Hz]: rotational speed, K [ μm / V]: 2
00 Hz voltage sensitivity, R [Ω]: coil resistance. The power consumption is the surface deviation or the square of the eccentricity 、, and the rotation speed f
It increases in proportion to the power. The objective lens is ± 0.5mm
When the follow-up control is performed on the surface eccentric disk or the eccentric disk of ± 280 μm, the power consumption due to the voltage applied to generate the displacement of the basic rotational speed is calculated, and is shown in the graph of FIG. The horizontal axis is the speed of the CD-ROM and the vertical axis is the power consumption.

The temperature rise due to power consumption depends on the shape of the heat generating portion,
It is related to mass and heat dissipation. Lens holder is generally 4
When the surface area is about 600 mm ² and the thermal resistance is about 100 to 1000 mg, the thermal resistance is about 50 to 100 ° C./W, and the allowable power loss here is only about several hundred mW when the temperature rise is about 20 ° C. As shown in the graph, when the eccentric disk is continuously reproduced at a high speed of 32 times at a high speed of 32 times, the drive current becomes large, and the heat generation of the drive coil occurs. Increase. Therefore, when the control as in the present invention is not performed, it is assumed that it is extremely difficult to suppress the temperature rise of the lens holder to the extent that the objective lens and the drive coil are not damaged.

In the lens holder of the optical pickup, the drive coil serves as a heat source, and the heat is transmitted to the objective lens through the lens holder. The drive coil is a copper wire, which is metal and has high thermal conductivity. The lens holder is made of a thermoplastic resin material called a liquid crystal polymer and has a thermal conductivity of 0.25.
It is lower than metal at 0.3 Kcal / m · hr · ° C. The temporal change in temperature when a DC current is applied to the drive coil is different between the drive coil and the objective lens in terms of the heat source and heat receiver, and the metal and resin have different thermal conductivities, but the heat generator and heat receiver are on the lens holder. And a distance of 10 mm or less, and the measured results show that there is no difference between the temporal temperature change of the coil and the temporal temperature change of the objective lens. The temporal change in the temperature of the drive coil and the temperature of the objective lens can be approximated by an exponential function without any problem. The upper limit of the temperature is 100 to 120 ° C., at which no breakage occurs in the drive coil.

The objective lens is made of a plastic material, thermally expands with a rise in temperature, changes its shape, and changes its refractive index. As a result, the refraction angle of the incident light beam changes. Therefore, the temperature must be controlled to a temperature at which such thermal deformation does not occur (for example, 75 ° C. or less).
FIG. 4 shows the state of the temperature change between the objective lens and the drive coil. According to this graph, the temperature rise of the drive coil and the temperature rise of the objective lens are almost the same as the time-dependent temperature change according to the measured results. There is no problem to treat. FIG.
4A shows the temperature relationship between the objective lens and the focus coil, and FIG. 4B shows the temperature relationship between the objective lens and the tracking coil. In the graph, [calculation] is (1-exp
-(Τt / 1.3)) shows a curve calculated by the equation (τ: time constant, t: time), and the experimental data is the data until the convergence to 16 ° C after energization and the data after turning off the power from 16 ° C. Shows the data.

FIG. 5 shows the temperature rise characteristics of the drive coil and the objective lens when a current is applied to the drive coil.
5A shows the case of a tracking coil, and FIG. 5B shows the case of a focus coil. Measurement was performed at room temperature (25
(° C.) as a reference.
The power consumption is [square of current × resistance], and the temperature rise of the coil is proportional to the square of the current. Further, since the temperature of the objective lens passes from the coil of the heating element through the lens holder, the temperature rises due to the transmission of heat determined by the thermal resistance from the coil. In the actual measurement, since the focus coil 4 is close to the objective lens 3 (see FIG. 9), the temperature rise of the coil and the temperature rise of the objective lens are close values. On the other hand, since the tracking coil 5 is provided via the focus coil 4, only half of the temperature rise of the tracking coil 5 contributes to the temperature rise of the objective lens 2. Assuming that the temperatures of the two drive coils 4 and 5 are added, the following relational expression holds.

Tobj = 0.5 × Tr + 0.74 × Tf where Tobj is the temperature of the objective lens, Tr is the temperature of the tracking coil, and Tf is the temperature of the focus coil.
0.5 and 0.74 are heating contribution rates obtained from the graph shown in FIG. 5, and are defined by the temperature ratio between the objective lens and the coil. Here, it is assumed that the heat generated by the two drive coils by the temperature rise under the worst condition contributes to the lens temperature in the same manner. Then
The relationship of 0.5 × Tr = 0.75 × Tf = Tobj / 2 is established. Therefore, Tr = Tobj, Tf = 0.68 × Tobj
Becomes As a result, Tr <Tobj and Tf <0.68
If the temperature rise of each coil is suppressed within the range of × Tobj, the temperature rise of the objective lens can be limited. With respect to the limit test disk, only the surface deviation is the limit value and the eccentricity is small in the surface deviation limit disk, and only the eccentricity is the limit value in the eccentric limit disk and the surface deviation is small.
Therefore, since it is sufficient to raise the temperature of only one of the coils, the maximum temperature Tth of the tracking coil is expressed by the following equation, with the contribution on the focus side being zero. Tobj = 0.5 × Tr + 0 Here, if Tr is rewritten as Tth, Tth = 2 × Tobj
Becomes

Similarly, when the maximum temperature of the focus coil is Tfh, the following equation is obtained. Tobj = 0 + 0.75 × Tf Here, if Tf is rewritten as Tfh, Tfh = 1.35 ×
Tobj. Therefore, Tth <2 × Tobj and Tfh
The coil temperature may be controlled within a temperature range of <1.35 × Tobj. This is an area of M in the third quadrant as described later with reference to FIG. Now, the operation of the temperature detecting means of FIG. 2 which functions to suppress the coil temperature as described above will be described. This circuit configuration employs a method of detecting only a DC component in order to detect a change in resistance of a coil as described above. Since the tracking system and the focus system have the same circuit configuration, the tracking system will be described first as an example.

Considering only the DC component, the only component that contributes to heat generation is the resistance value, and the resistance value of this coil can be determined by the length and cross-sectional area of the copper wire. The resistance value when the temperature of the coil rises is determined by the temperature coefficient of resistance of the copper wire. Copper wire temperature t ° C
Resistance temperature coefficient α _t in is the following formula. α _t = 1 / (2
34.5 + t) Here, assuming that the resistance temperature coefficient at t = t ₀ is α ₀ , the coil resistance value Rt indicates the temperature change Δt =
If t−t ₀ is obtained, the following expression is obtained. Rt = R ₀ (1 + α ₀ × Δt) In order to detect the resistance value of the coil, a detection resistor 28T may be inserted in series with the drive coil 5. The driving coil 5 and the detection resistor 28T have different temperatures because the amounts of heat generated by the supplied current are different. The temperature rise of the drive coils 4 and 5 can be detected by comparing the resistance value of the detection resistor 28T with the corresponding coil resistance value. The temperature detecting means includes low-pass filters 36 and 37 for detecting a DC signal.

The tracking coils 5 (the resistance value: Rr) change of the resistance value due to the temperature change of the resistance 28T the resistance value of the detection resistor 28T inserted in series as R ₂ is extremely as compared to the change in the resistance of the coil And less. This is the same for the detection resistor 28F. _Assuming that the resistance value of the tracking coil 5 at the temperature t ° C. is R _rt , the temperature t ₀
Let R _{rt0 be} the resistance value at ° C, and set the tracking coil 5
From the voltage across, it was subtracted voltage of the detection resistor 28T voltage and V _rt. V _rt is represented by the following equation. _{V rt = (R rt -R 2} × K 2) × i r = (R rt0 (1 + α 0
_{× △ t) -R 2 × K} 2) × i r = R rt0 α 0 × △ t × i r where the _{R 2 × K 2 = R rt0} .

From the above equation, it can be seen that V _rt is proportional to the product of the temperature change and the current. It becomes the following equation to constitute the threshold voltage V _rth over coefficient K than the same current i _r. V _rth = K × i _r As is apparent from this equation, the threshold voltage V _rth also a current proportional. When these two voltages are compared by the comparators 40 and 41, the following equation is obtained. _{V rt -V rth = (R rt0} × α 0 × △ t-K) × i r Incidentally, prepared different threshold sets the gain K to Kc and Kd and Kd 'here, different temperatures, respectively Is to be detected. As is clear from this equation,
When V _rt changes in proportion, at a certain temperature, V _rt > V _rth
Here, it can be detected that the temperature of the tracking coil 5 has risen above the set temperature _Trth .

The above description also applies to the focus system. That is, the resistance value of the detection resistor 28F inserted in series with the focus coil 4 is R1.
From both ends of the focusing coil 4, the voltage V _ft obtained by subtracting the voltage of the detection resistor 28F is as following equation. V _ft = (R _ft −R ₁ × K ₁ ) × _if = (R _ft0 (1 + α
₀ × △ t) -R ₁ × K ₁ ) × _if = R _ft0 α ₀ × △ t × i
_f Note that R ₁ × K ₁ = R _ft0 . As is apparent from this equation, V _ft is proportional to the product of the temperature change and the current,
When the threshold voltage is formed from the same current _if as that of 8F, the following expression is obtained. V _fth = K × _if

The two voltages are compared by the comparators 34 and 35, and when V _ft > V _fth , it can be detected that the focus coil 4 has become higher than the set temperature T _fth . Also here, the gain K is set to Ka, Kb, and Kb 'to prepare different thresholds, and different temperatures are detected. Here, if a plurality of threshold voltages are set as described above, a plurality of temperature points can be detected.
In the present invention, the tracking coil 4 and the focus coil 5
Are detected at three points. One of the temperature detection points is an amplifier 32C and 38C for setting a threshold value.
Are switched to Kb and Kb 'and Kd and Kd', respectively. The detected temperature point is a temperature point obtained by dividing the coil allowable temperature rise range into four. This is called Tr1 to Tr3 and T
f1 to Tf3.

Here, each of the gains K ₁ , K ₂ , Ka to K
d has the following relationship. _{K 1 = R ft0 / R 1} K 2 = R ft0 / R 2 Ka = Rf × α 0 × Tf 2 Kb = Rf × α 0 × Tf 3 Kb = Rf × α 0 when the gain switching flag of Tr ₂ × Tf ₁ Kc = Rr × α ₀ × Tr ₂ Kd = Rr × α ₀ × Tr _{3 When the} gain is switched by the flag of Tf ₂ Kd = Rr × α ₀ × Tr ₁

In these settings, as shown in FIG. 6 to be described later, the coil temperature at which the temperature rise of the objective lens becomes 20 ° C. by each coil alone is set as the maximum temperature. Specifically, the temperature is 27 ° C. for the focus coil and 40 ° C. for the tracking coil. The temperatures Tf _{1 to} Tf ₃ and Tr _{1 to} Tr ₃ are four times the maximum temperature. And determining the coefficient at this temperature and resistance temperature coefficient alpha _1. FIG. 6 is a graph showing the relationship between the temperature rise of the tracking coil and the focus coil and the temperature rise of the objective lens. In this graph, in the second quadrant, the vertical axis indicates the temperature rise of the focus coil itself, and the horizontal direction to the left indicates the temperature rise of the objective lens caused by the focus coil. As described above, since the focus coil is close to the objective lens, the contribution to the temperature of the objective lens is high. On the other hand, since the tracking coil passes through the focus coil and the lens holder, the contribution to the temperature of the objective lens is low. Therefore, conversely, the temperature of the tracking coil increases.

The fourth quadrant shows the relationship between the temperature of the tracking coil itself and the temperature of the objective lens caused by the tracking coil. When the coordinate axes are determined in this manner, the X-direction and the Y-
The direction is the temperature rise of the objective lens by each coil. Assuming that this temperature is added, the temperature rise limit of the objective lens is set to 20 ° C. If the operating environment temperature is 40 ° C., the limit value of the maximum temperature of the objective lens is 60 ° C. This condition is that the temperature added value from each coil is 20 ° C
Therefore, the M region represented by Δ0AB is allowed as a stable region. Here, if the temperature detection is accurate, it is possible to perform control so as to accurately fill this area. However, in order to simplify the detection system, three points are set as described above.
Control within this range. Specifically, control is performed by approximating a stable area represented by Δ0AB with three rectangular areas (shown by oblique lines in the drawing). Although the operable stable region is slightly reduced due to the approximation, this is a safe direction control, so there is no problem. In order to divide the temperature range of each coil into four in accordance with the temperature of the objective lens, the three detected temperature points are set as described above.

Since Tr1 and Tf1 are necessary only when the temperature of the other coil rises, the gains of the amplifiers 32C and 38C, which form a threshold value based on the flag (the output of the comparators 34 and 40), as described above. Is formed by switching. The operation in this temperature range is shown in the operation table shown in FIG. In the table, the area indicated by ○ is a stable area, so that high-speed servo operation is allowed. Since the area X is at a dangerous temperature, it is an area where it is necessary to reduce the number of times of high-speed operation. First, when operating at 32 × speed, the heat generated by any of the coils causes X
Is detected, the rotation speed is reduced by, for example, 20%.
Since the heat generated by the coil becomes the fourth power of the number of revolutions as described above, the power consumption due to the number of revolutions is reduced by 60% to 40%.

If the temperature flag becomes a circle area in the table after the time of about the temperature time constant of the optical pickup elapses, the reproduction can be performed at the rotation speed or the original 32 times speed. However, if the temperature does not decrease, the number of revolutions is again reduced by, for example, 15% and the power consumption is further reduced by 50 (≒
0.85 ⁴ ) Perform control to decrease%. FIG. 8 shows how the power consumption is reduced when the rotation speed is reduced, and the temperature of the lens holder is reduced by an exponential function. Here, 32 times speed (× 3
2) and a state when 26 × speed (× 26) is controlled by the temperature flag. As shown in FIG.
It turns out that it can be stably controlled to be 0 ° C. or less. The above-described circuit configuration of the temperature detecting means, the gain of each amplifier, the number of double speeds, and the like are merely examples, and the present invention is not limited thereto.

[0037]

As described above, according to the optical disk reproducing apparatus of the present invention, the following excellent operational effects can be exhibited. Since the temperature of the drive coil is electrically detected to control the rotation speed of the optical disk,
The current flowing through the drive coil can be suppressed accordingly,
Therefore, it is possible to prevent the objective lens and the drive coil from being thermally damaged while maintaining the maximum transfer rate at that time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of an optical disk reproducing apparatus according to the present invention.

FIG. 2 is a block circuit diagram showing temperature detecting means in FIG.

FIG. 3 is a graph showing power consumption according to a voltage applied to generate a displacement amount of a basic rotation speed.

FIG. 4 is a diagram showing a state of a temperature change between an objective lens and a drive coil.

FIG. 5 is a diagram showing a temperature rise characteristic of a drive coil and an objective lens when a current is applied to the drive coil.

FIG. 6 is a graph showing a relationship between a temperature rise of a tracking coil and a focus coil and a temperature rise of an objective lens.

FIG. 7 is an operation table showing an operation in a predetermined temperature range.

FIG. 8 is a diagram illustrating a state in which the temperature of the lens holder decreases with an exponential function as the rotation speed decreases.

FIG. 9 is a perspective view showing an optical pickup.

FIG. 10 is a plan view showing an optical pickup.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical pickup, 2 ... Objective lens, 3 ... Lens holder, 4 ... Focus coil (drive coil), 5 ... Tracking coil (drive coil), 6 ... Suspension wire, 15 ... Reproduction device, 17 ... Disc rotation speed control block , 18: feed motor, 19: feed motor control block, 20: signal processing block, 21: pickup control block, 22: temperature detecting means, 23: main control unit, 25
T, 25F: temperature detection circuit, 26T, 26F: temperature state determination unit, 27: rotation speed determination unit, 28F, 28T: detection resistor, D: optical disk.

Claims (3)

[Claims] 1. An optical pickup having a drive coil for performing focus control and tracking control on an objective lens from an optical disk which can be controlled from a basic rotation speed to a high-speed rotation of n (integer) times using an optical pickup. An apparatus for reproducing an optical disk to be reproduced has a temperature detecting means for detecting a temperature of the drive coil, and controls a rotation speed of the optical disk in accordance with a detection result of the temperature detecting means to change a read transfer rate. An optical disk reproducing apparatus characterized in that: 2. The optical disk reproducing apparatus according to claim 1, wherein the rotation of the optical disk is controlled stepwise between a basic rotational speed and an n-fold high-speed rotational speed. 3. The temperature detecting means for judging a temperature state of the drive coil based on a voltage drop amount of the drive coil, and a temperature state judging section for judging a temperature of the optical disk based on a judgment result of the temperature state judging section. 3. The optical disk reproducing apparatus according to claim 1, further comprising: a rotation speed determining unit that determines a rotation speed.