JPH0628701A - Disk reproduction device - Google Patents

Abstract

PURPOSE:To protect a laser diode and to shorten a wait time until the reproduction is made available by controlling lighting/extinction of a laser in response to a temperature of the laser diode itself or its ambient temperature. CONSTITUTION:A temperature sensor 41 detects a temperature of a pickup or its ambient temperature and outputs a signal to a temperature discrimination circuit 42. The temperature discrimination circuit 42 receives the temperature signal sensed by the temperature sensor 41 and compares the temperature with a preset temperature. A CPU 43 receives power supply through a power switch 44 of the player, a stabilizing power supply 45 and a diode 46 to control the operation of the temperature discrimination circuit 42. A backup capacitor 47 acts like a power supply for the CPU when the power switch 44 is turned off and the diode 46 prevents reverse flowing of the charge in the backup capacitor 47. A CPU operation stop circuit 48 detects it that the player power supply is turned off to send an instruction used to allow the CPU 43 to preserve its internal state with minimum power consumption.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to the protection of semiconductor laser diodes.

[0002]

2. Description of the Related Art Generally, a compact disc is assumed to have an optimum wavelength of 780 nm (10 ^-9 m) as a wavelength of a light source for reading the recorded information. The wavelength was already achievable with semiconductor laser diodes. In fact, semiconductor laser diodes are mostly used in compact disc players (hereinafter referred to as players) announced by respective manufacturers.

The laser diode has features of (1) small size and (2) low power consumption as compared with other laser generating means, which enables downsizing of a player and a disc. Since it is possible to miniaturize a so-called optical pickup that is a single unit that includes a lens, a prism, and other optical components required for reading information from the device, or a focus adjustment mechanism, a tracking adjustment mechanism, etc. is doing. But,
At present, laser diodes are not sufficient in terms of operational reliability in high temperature environments. The laser diode has the same temperature range as general silicon semiconductor devices such as transistors and ICs in the non-operating storage temperature rating, and if the failure rate during operation is below room temperature, it becomes a general silicon semiconductor device. It is also a little inferior. However, laser operating at high temperature such as ambient temperature exceeding 60 ℃
In most cases, the failure rate of a diode is several hundred to several thousand times worse than that of a general silicon semiconductor element. The cause is that the increase rate of the failure rate with respect to the rise of the ambient temperature in the laser diode is large.

As described above, in the use of a laser diode having a high failure rate against high-temperature operation, measures are taken to improve reliability. For example, (1) the laser diode envelope is coupled to a heat sink. To prevent temperature rise due to self-heating, (2) forced air cooling with a fan, etc., and (3) forced cooling using a Peltier element. Out of these (2)
, (3) requires a considerable cost, and the ambient temperature for use in ordinary households is usually up to 40 ° C. Therefore, for so-called household players, the measures in (1) above should be taken. We have ensured practical reliability by taking measures such as suppressing the temperature rise in the.

[0005]

However, in a so-called portable compact disc player (hereinafter referred to as a portable player) or an in-vehicle compact disc player (hereinafter referred to as an in-vehicle player) used outdoors, direct sunlight irradiation and the player are performed. Due to the greenhouse effect of the housing, the air temperature inside the housing easily rises to about 70-90 ℃. Lighting the laser diode for a long time at such a high temperature significantly accelerates the deterioration of the laser element, and the desired life cannot be satisfied. Therefore, use the above-mentioned forced air cooling or forced cooling means, or
There was a problem that problems would occur in practical use unless the characteristics of the diode itself were improved.

The present invention has been made in view of the above-mentioned problems of the prior art, and detects the temperature of the laser diode itself or its surroundings, and controls the turning on / off of the laser based on the result. Protects the laser diode, and the ambient temperature of the player changes from a temperature that cannot operate continuously to a temperature that allows operation to prevent the temperature gradient of each part of the player housing or the temperature of a specific part within a certain time. It is an object of the present invention to provide a disc reproducing apparatus capable of shortening the waiting time until the reproducing operation becomes possible by predicting by detecting the change and controlling the turning on / off of the laser based on the prediction.

[0007]

DISCLOSURE OF THE INVENTION A disk reproducing apparatus according to the present invention is a disk reproducing apparatus having a pickup for reading information, and a temperature detector for detecting the temperature of the pickup or its surroundings and a temperature detector for detecting the temperature. The temperature determination means for comparing and comparing the temperature with a predetermined temperature set in advance, the temperature detected by the temperature detector using the determination result of the temperature determination means measures the duration of time in a state higher than the predetermined temperature, Continuation temperature state determination means for determining whether or not this duration is a predetermined time interval or more,
And a reproduction operation control means for stopping the operation of the pickup when the continuous temperature state determination means determines that it is longer than a predetermined time.

[0008]

According to the disk reproducing apparatus of the present invention, even if the temperature detected by the temperature detector is equal to or higher than the temperature at which the laser diode can be protected, if the temperature is lower than the predetermined time, the laser diode is turned on for the predetermined time or longer. If it is, turn it off.

[0009]

【Example】

Example 1. Examples of the present invention will be described below. First, an example that is a premise for reaching the present invention will be described. In the present invention, it is fundamental to determine the turning on / off of the laser by knowing the temperature of the laser diode itself or the ambient temperature, and first, a temperature detecting means is required. This temperature detection method is basically a method of detecting various characteristics that change depending on the temperature of the laser diode itself, a resistance change of the positive / negative polarity thermistor, a semiconductor P
Anything can be used as long as it can detect a voltage change of the N-junction. What is used as a so-called temperature sensor may be used.

FIG. 1 is a schematic perspective view of a disk reproducing apparatus which is a premise of the present invention. In this figure, a positive polarity thermistor is used for the above temperature sensor. In the figure, 1 is an optical pickup housing, which is a laser
The diode 2 and other optical components such as lenses and mirrors (not shown), focus and tracking adjustment mechanism, etc. are built in, and the emitted light Y of the laser diode 2 is emitted from the optical opening 3 by the above optical components. A light beam X for signal reading is obtained. A laser holder 4 positions the laser diode 2 and fixes it with a fixing plate 5 and a set screw 6. The laser holding portion 4 is made of a metal having a high thermal conductivity, for example, aluminum die casting, in order to release self-heating of the laser diode 2,
Heat is radiated from the surface of the optical pickup housing 1 integrated with this. Reference numeral 7 denotes a temperature detecting thermistor, which is provided on the outer wall of the optical pickup housing 1 and is thermally coupled to the optical pickup housing 1 with an adhesive. As is apparent from the figure, the laser diode 2 and the optical pickup housing 1 are thermally and tightly coupled, and the temperature of the envelope of the laser diode 2 can be detected almost accurately even at the mounting portion of the thermistor 7. . That is, a temperature change can be detected as a resistance value change.

As the temperature detection, the temperature of the case surface of the optical pickup housing 1 is not detected, but the air temperature inside the closed space of the optical pickup housing 1 is detected, or inside the laser diode enclosure. It is also conceivable to fix a temperature sensor such as a thermistor or a semiconductor chip, and take out the lead of the temperature sensor outside the envelope to detect the temperature.

A method of controlling the turning on / off of the laser diode, that is, the start, continuation and stop of the reproducing operation of the player by using such temperature detecting means will be described below.

In this method, as a result of temperature detection, the current temperature of the laser diode portion is continuously operated (continuous lighting).
Configured to get higher or lower than possible temperature limit,
It is a method of directly turning on / off the laser from the result. FIG. 2 is used in the above-described example in which the temperature detection method applying the thermistor as shown in FIG. 1 determines the magnitude of the detected temperature (hereinafter referred to as T) with respect to the continuous operable limit temperature (hereinafter referred to as Tmax). The temperature determination circuit 18 is shown in the figure. In the figure, 7 is a thermistor, 12 is a resistor, which constitutes a bridge together with the thermistor 7,
The comparator 13 obtains the bridge balance as a binary output. 14 is a power source for the bridge.

In this configuration, the thermistor 7 at Tmax
Resistance to balance the bridge against the resistance value of
It is sufficient to determine each of the 12 values. That is, for example, taking a case where a controller such as a microprocessor, which is a reproduction operation control means, controls the player operation, the temperature detection result is input to the controller at appropriate time intervals, and if T> Tmax. The player's playback operation is stopped and the laser is turned off. Alternatively, when T> Tmax, the temperature detection result is input as an interrupt to the controller to stop the player and turn off the laser, whereby the laser diode can be protected.

As described above, the method of directly determining whether to turn on or off the laser diode based on the magnitude relationship between the detected temperature T at this time and the continuous operation limit temperature Tmax is simple, and in terms of protection of the laser diode. It is effective. However, the instantaneous temperature T fluctuates slightly due to heat generation inside the player, temperature change around the set, self-heating of the laser diode, etc. Even if this is detected, the player can operate at short time intervals. Since it is not preferable that it becomes impossible, it is conceivable to add a hysteresis in the temperature detection as a countermeasure.

FIG. 3 shows an example of the construction of such a temperature determination circuit 19, and in the figure, the same symbols as those in FIG. 2 indicate the same or corresponding parts. In this circuit 19, the output of the comparator 13 in FIG. 2 is positively fed back to the input by the feedback resistor 15, and thereby the output has hysteresis.
At this time, needless to say, the hysteresis width is determined by the amount of positive feedback.

However, the above-mentioned example has various problems when it is used in a severe temperature environment such as a vehicle. Before describing this problem, the temperature environment in which the in-vehicle player is placed will be described. Vehicles have extremely high indoor temperatures due to high outside temperature, strong sunlight, and greenhouse effect in a closed state. It is unacceptable from the reliability point of view that the laser diode continuously lights for a long time in such a state. On the other hand, as a general rule, the player's reproduction is for listening to a person in the same room, and the room temperature when the player is used from this point can be said to be a temperature at which a person can live and is not so high. It will be. Indoor air that has risen to an extremely high temperature when left unattended by a car is cooled to a sufficiently low temperature of 40 ° C or lower in a few minutes to 10 minutes by running in a window or using a cooler. If the laser diode whose temperature has risen changes at the same speed as the change in the room air temperature, the player can be reproduced even after a short waiting time even with the first method. However, in an actual player, the temperature of the laser diode or its surroundings changes very slowly compared to the temperature of the room air. This is because (1) an optical pickup is generally configured to move in the radial direction of a compact disc, and it is difficult to dissipate heat through a good conductor of heat such as metal (the majority of heat dissipation is heat radiation). (2) In the optical pickup, dust is mixed inside and adheres to the surface of the optical parts, which causes a defect.On the other hand, there is a lot of dust inside the vehicle, so a large-area ventilation hole is opened in the player's housing. Not possible (air circulation is bad). (3) Optical pickups often use materials with good workability and dimensional stability, such as aluminum die-casting, to precisely position and fix various optical components including laser diodes. For this reason, the heat dissipation effect for the self-heating of the laser diode is sufficient, but the heat capacity tends to be large (the heat capacity is large). Etc. is the cause.

Therefore, under such a circumstance, even if the temperature of the indoor atmosphere is rapidly lowered, the waiting time until the player's operation is performed becomes extremely long, which is inconvenient. The following method is to balance the inconvenience reduction for the operator and the protection purpose of the laser diode.
If T <Tmax after a short time even for x,
It aims to eliminate or shorten the waiting time by turning on the laser diode. As a method of embodying this idea, first, there is a method of providing a temperature sensor in a portion which responds to the atmospheric temperature around the player earlier than in the laser diode portion, so that the temperature change of the laser diode is preempted.

FIG. 5 is a schematic view for explaining an example using this method. In the figure, 21 is an optical pickup, which has a laser diode (not shown) built therein and is inside a player housing 22. Reference numeral 23 is a vent hole provided in the player housing 22, and 24 is a temperature sensor provided in the player housing 22, for example, a thermistor. Reference numeral 25 denotes a temperature determination circuit, which determines from the output of the temperature sensor 24 whether the current temperature is higher than or lower than a certain reference temperature, that is, the continuous operation limit temperature. Note that the temperature sensor
If 24 is a thermistor, the temperature determination circuit used in this example 25
The circuits 18 and 19 shown in FIG. 2 or 3 correspond to this.

FIG. 4 shows the difference in temperature change between each part of the structure shown in FIG. 5 and the optical pickup part. This figure shows that the temperature (A) of the atmosphere inside the vehicle, the temperature (B) of the optical pickup section, and the temperature (C) of the temperature sensor section, which have been heated under direct sunlight, are lowered by opening a window or operating a cooler at time t = t _0. It shows the change as it goes. As shown in the figure, the temperature of the optical pickup (B) is the temperature of the atmosphere (A).
Is much slower than the decreasing speed of the temperature sensor (C)
Will be between them. Since the temperature of each part normally converges to almost the same temperature, it can be seen that the temperature sensor 24 in FIG. 5 preempts the temperature of the optical pickup 21. That is, the reference temperature of the temperature determination circuit 25 is set to Tma
If x is set and the laser diode can be turned on when the temperature of the temperature sensor 24 becomes equal to or lower than Tmax, the first method does not turn on the laser until t ₃ in FIG. 4, whereas the second method does. The laser is turned on at t ₂ , and the waiting time until the player operation starts is shortened.

However, the temperature of the optical pickup 21 apparently exceeds Tmax between t ₂ and t ₃ , which is not preferable in terms of protection of the laser diode, but this time does not exceed a certain value. When the temperature inside the vehicle rises again and exceeds Tmax, the controller turns off the laser diode.

The present invention is a further development of this idea and will be described in detail below. First, the gist of the present invention is to eliminate the waiting time by allowing the ignition of the laser diode within a certain time even if the current temperature is above the limit temperature, while the laser
The diode is turned off to protect it. In this case, it is not necessary to consider the temperature detection point. Now, attach a temperature sensor (thermistor) to the optical pickup section as shown in FIG. 1, and combine the first and second temperature determination circuits 18 and 19 as shown in FIG. 2 or FIG.
A case will be described in which the output of the determination circuit is input to a controller composed of a CPU which is a reproduction operation control means to perform processing. FIG. 6 shows a processing flow chart of the controller for explaining this method.

In FIG. 6, the current temperature T detected by the temperature sensor is first input (step 31), and the temperature judgment circuit judges the magnitude of T and Tmax (limit temperature at which continuous operation is possible) (step 32). If T> Tmax, then T
The time during which the following states continue is measured by the counter by the software of the CPU, and the CPU already has T> Tmax.
Whether the state has not continued for more than the allowable time,
That is, the continuous temperature state is determined (step 33). The counter for counting the permissible time is a temperature detection loop that is repeated at substantially constant time intervals and integrates the number of times T> Tmax is detected, and obtains a continuous time in the state of T> Tmax. It is a thing. And the above N
> Nmax? When the result of the determination is NO, that is, step 33
If the count value N is less than or equal to Nmax, the counter value is incremented (added by 1) (step 34) and set to 1
End the cycle. On the other hand, when the determination result is YES, that is, when N> Nmax, it means that the high temperature state continues for a certain period of time or more, so the laser diode is turned off including the stop of the reproducing operation of the player (step 35).
In order to get out of this extinguished state, T <Tma
It is when x is detected, and at this time, the diode outputs that the laser diode can be turned on (step 36).
(Or, the reproduction operation may be started immediately), and the counter is reset (step 37).

The concept of the present invention described above can be applied to the above-mentioned method, and the waiting time significantly shortened by the above-mentioned method can be brought closer to zero.

The above-described method according to the present invention is a laser
It shows almost sufficient effect as high temperature protection of diode,
Since the time when the high temperature state (T> Tmax) continues is measured by the counter by the software of the CPU, if the player's power is repeatedly turned on / off within a specific time interval in the high temperature state, the power is not turned on. Always laser
The diode will continue to light up. As a method of eliminating such a risk, it is effective to retain the value of the counter, that is, the duration information of the output state of the temperature determination circuit even when the power of the player is turned off. FIG. 7 is a block diagram of a player configured such that the power of the CPU having the counter function in FIG. 6 is backed up even when the power of the player is turned off.

In FIG. 7, reference numeral 41 is a thermistor attached to the temperature sensor, and 42 is a temperature determination circuit, which is shown in FIGS. 2 and 3, for example. Reference numeral 43 denotes a CPU which controls the above count, and the CPU 43 is supplied with power through a power switch 44, a stabilizing power supply 45 and a diode 46 of the player. Reference numeral 47 is a backup capacitor, which serves as a power source for the CPU 43 when the power switch 44 is OFF, and at that time, the diode 46 is a backup capacitor.
It prevents the backflow of 47 charges. Reference numeral 48 denotes a CPU operation stop circuit, which detects that the player power has been turned off, and issues an instruction for switching the CPU 43 to an internal state or a state in which the internal memory can be saved and power consumption is minimized. To do.

CP formed by recent CMOS process
In U, it is possible to back up for a considerable time with a capacitor having a large capacity as shown in FIG. However, as a matter of course, a primary battery or a secondary battery may be used for backup, and in the case of vehicle-mounted use, a lead storage battery mounted on the vehicle itself may be used as a backup power source. Since these specific circuits are common to those skilled in the art, the description thereof will be omitted.

[0028]

As described above, according to the present invention, the temperature is at the temperature detected by the temperature sensor provided in the optical pickup or its surroundings, and even if the temperature is higher than the temperature at which the laser diode can be protected, the temperature is predetermined. The laser diode is turned on if it is less than the time interval and turned off if it is more than the predetermined time interval. There is an effect that protection can also be performed.

[Brief description of drawings]

FIG. 1 is a perspective view of a disc reproducing apparatus which is a premise of the present invention.

FIG. 2 is a circuit diagram showing an example of a temperature determination circuit which is a premise of the present invention.

FIG. 3 is a circuit diagram showing another example of a temperature determination circuit which is a premise of the present invention.

FIG. 4 is a diagram showing a temperature change of each part of the disc reproducing apparatus which is a premise of the present invention.

FIG. 5 is a diagram in which a temperature detector, which is a premise of the present invention, is arranged near a ventilation hole.

FIG. 6 is a flowchart showing a temperature control method for a disc reproducing apparatus according to the present invention.

FIG. 7 is a block diagram showing a control circuit for temperature determination according to the present invention.

[Explanation of symbols]

 2 Semiconductor laser diode 7 Temperature sensor (temperature detector) 18 Temperature judgment circuit 19 Temperature judgment circuit 22 Enclosure 23 Vent 24 Temperature detector 25 Temperature judgment circuit 41 Temperature detector 42 Temperature judgment circuit 43 CPU 44 Power switch 45 Stabilization Power supply 46 Diode 47 Backup capacitor 48 CPU operation stop circuit

Claims (2)

[Claims] 1. A disc reproducing apparatus having a pickup for reading information, wherein a temperature detector for detecting the temperature of the pickup or its surroundings and a temperature for comparing and judging the temperature detected by the temperature detector with a predetermined temperature set in advance. The duration of time when the temperature detected by the temperature detector is higher than the predetermined temperature is measured using the determination means and the determination result of the temperature determination means, and whether the duration is a predetermined time interval or more is determined. A disc reproducing apparatus comprising: a continuous temperature state determining means for determining; and a reproduction operation control means for stopping the operation of the pickup when the continuous temperature state determining means determines that the predetermined temperature is longer than a predetermined time. . 2. The continuous temperature state determination means has a storage means for storing the duration information indicating that the temperature detected by the temperature detector is higher than the predetermined temperature even when the power of the disc reproducing apparatus is turned off. The disk reproducing device according to claim 1.