(1) Field of the Invention
The present invention relates to a camcorder; and, more particularly, to control of a laser diode for writing information to an optical disk device used in a camcorder.
(2) Description of the Related Art
It has been long since a video camera using an optical disk device as a recording medium was produced. The optical disk device itself is now expanding its application from CD (Compact Disc) and DVD (Digital Versatile Disc) towards a next generation DVD such as HD DVD (High Definition DVD) and Blu-ray Disc (BD). The next generation DVD has a recording capacity three to five times greater than traditional DVDs, and recent advances in PDP (Plasma Display Panel) and increasing demand for high definition image has aroused a lot of interest in it as a recording medium to cope with an increase in data rate along with the high definition image.
In the optical disk device, an increase in recording capacity per unit area is one of factors of increasing the recording capacity. To accomplish this, it is necessary to make laser light irradiated onto an optical disk to record or read data smaller in diameter. The diameter of laser light can be reduced simply by using a shorter wavelength laser light for reading.
Among laser diode (LD) light sources, a blue-violet laser diode is known to output the light with the shortest wavelength. Examples of products that have an optical disk device using the blue-violet laser diode include PC (Personal Computer), game device, video recorder, and so on.
A laser beam image forming apparatus is another one that uses a laser diode. In such a device, however, if temperature of a laser diode is lower than ambient temperature, dews are sometimes formed on the output side of the laser diode and energy of the laser beam is converted into heat energy by the waterdrops, possibly breaking a lens. To prevent this, Japanese Patent Application Laid-Open Publication No. 2000-040850 or Japanese Patent Application Laid-Open Publication No. 2000-027905 suggests that if dew condensation takes place or LD temperature is lower than a preset temperature, laser beam should not be outputted until dew condensation is eliminated by feeding an offset current lower than a threshold level.
In addition, Japanese Patent Application Laid-Open Publication No. 2004-171655 describes that photographing operation of an optical disk device used for a camcorder can be assured by lowering false detection of dew condensation on a laser diode of the optical disk device.
However, a blue-violet LD has a narrower operation guarantee temperature range than LDs of different colors, and does not operate at a low temperature. Also, a low temperature kink phenomenon may occur. The low temperature kink phenomenon is observed when current-laser power linearity breaks down, given that current (horizontal axis) fed to a LD and laser light output (vertical axis) characteristics are plotted with temperature as a parameter.
These problems rarely occur when camcorders or portable BD players are used indoor, but recording (write) or reading information may not be possible if they are used in cold outdoor areas.
In
Temperature characteristics of an LD will now be described with reference to
As shown in
Meanwhile, when LD temperature is at 0° C., linearity disappears in mid course. The phenomenon of losing linearity at a low temperature is called a low-temperature kink. Since linearity is not present at a temperature where the low-temperature kink is observed, the temperature is outside the operation guarantee temperature range. Typically, LD would not operate at temperature outside the operation guarantee temperature range, it is impossible to perform a write (record) operation onto an optical disk device.
Japanese Patent Application Laid-Open Publication No. 2000-040850 and Japanese Patent Application Laid-Open Publication No. 2000-027905 as related art technologies concerning a laser diode drive controller provided with a cooler are to prevent an LD from being cooled to extremely low temperatures even if the LD may have become very hot by laser light output. In particular, Japanese Patent Application Laid-Open Publication No. 2000-040850 is about how to eliminate trouble in a laser drive controller caused by dew condensation, and Japanese Patent Application Laid-Open Publication No. 2000-027905 discloses a technique for driving a disk within a reference temperature range by feeding current lower than a threshold value since the temperature control is not possible at a low temperature where a cooler does not operate, thereby changing output of laser light.
According to Japanese Patent Application Laid-Open Publication No. 2004-171655, dew condensation is observed when an optical disk device built in a camcorder is cooled so that an LD therein itself becomes cooled to a temperature even lower than the ambient temperature, causing moisture in ambient atmosphere stuck to the LD. In other words, when LD temperature is higher than the operation guarantee temperature of the LD, a cooling operation is carried out compulsively. This makes only the LD temperature lower than the ambient temperature such that dew condensation problems are accompanied inevitably. This dew condensation phenomenon of Japanese Patent Application Laid-Open Publication No. 2004-171655 is also found in Japanese Patent Application Laid-Open Publication No. 2000-040850 concerning the countermeasure of dew condensation and in Japanese Patent Application Laid-Open Publication No. 2000-027905 concerning a laser diode drive controller with a cooler.
At any rate, problems in related art techniques illustrated in Japanese Patent Application Laid-Open Publications No. 2000-040850, 2000-027905, and 2004-171655 is not the same as the low-temperature kink phenomenon, i.e. a problem at a dew condensation temperature of LD or lower.
In view of the foregoing problems mentioned above, it is therefore an object of the present invention to provide a control method and device of a laser diode used for a write operation of an optical disk device employed in an apparatus, in case the laser diode is used at such a low temperature that a low temperature kink phenomenon may occur (that is, the laser diode is used for an apparatus like a camcorder and outdoors) or a surrounding temperature is lower than the operation guarantee temperature range of the laser diode, and a camcorder.
To achieve the above object, there is provided a laser diode control method, laser diode control device, and a camcorder, wherein initial current-laser power characteristics of individual laser diode are acquired before shipping at a factory, with a predetermined temperature as a parameter, and the characteristics are stored in a memory of a camcorder or the like. Further, threshold current values at different temperatures are stored, and the laser diode temperature is monitored by the temperature sensor. Therefore, if the laser diode temperature is low, the user may issue a command to set the low-temperature write mode. In such case, a current equal to or below the threshold value at a given temperature is applied to the laser diode. During the current supply, the laser diode temperature detected by the temperature sensor is continuously monitored such that the laser diode is controlled to be supplied with a threshold current value corresponding to its present temperature.
Preferably, a threshold current value increases in accompany with an increase in temperature.
Moreover, a current value outputting a predetermined maximum power and a threshold value change over a period of years. When training mode is selected (or when power is inputted), the initial state characteristics are shifted to new ones under control.
That is, one aspect of the present invention provides a laser diode control method of a laser diode control device including a laser diode, a drive device for driving the laser diode by supplying current for laser light output, and a temperature sensor for detecting temperature around the laser diode, wherein, if temperature detected by the temperature sensor is equal to or below a predetermined value of the laser diode, current equivalent to a threshold current value of the laser diode is supplied to the laser diode, and laser light is outputted after a predetermined amount of time lapses.
Another aspect of the present invention provides a laser diode control device comprising: a laser diode; a drive device for driving the laser diode by supplying current for laser light output, the laser diode control device; a temperature sensor for detecting temperature around the laser diode; a memory for recording a threshold current value of the laser diode; and control means for supplying a threshold current corresponding to temperature to the laser diode on the basis of a temperature detected by the temperature sensor, and supplying a current for laser beam output to the laser diode after verifying that the temperature detected by the temperature sensor reached an operation guarantee temperature of the laser diode.
Preferably, the control means updates a current to be supplied to the laser diode at a predetermined interval, depending on temperature provided by the temperature sensor.
Yet another aspect of the present invention provides a camcorder, including a laser diode control device having a laser diode and a drive device for driving the laser diode by supplying current for laser light output, so as to record acquired video data onto a recording medium through the laser diode control device, the camcorder further includes: a temperature sensor for detecting temperature around the laser diode; a memory for recording a threshold current value of the laser diode; and control means for supplying a threshold current corresponding to temperature to the laser diode on the basis of the temperature detected by the temperature sensor, and supplying a current for laser beam output to the laser diode after verifying that the temperature detected by the temperature sensor reached an operation guarantee temperature of the laser diode.
Preferably, the control means of the camcorder updates a current to be supplied to the laser diode at a predetermined interval, depending on temperature provided by the temperature sensor.
The present invention makes it possible to perform a proper operation of information recording.
The camcorder includes an optical (pickup) head 1, an optical disk 2, a laser diode (LD) 3, a temperature sensor 4, a collimating lens 5, a beam splitter 6, a tracking actuator 7, a focus actuator 8, an objective lens 9, a condenser lens 10, a photodiode (PD) to convert light from the objective lens 10 into an electrical signal, a camera block 11, an audio input block 12, a video/audio encoder 13, a compression/expansion processing block 14, a random access memory (RAM) 15, a DVD signal processor 16, a playback RAM 17, a recording RAM 18, a control microcomputer 19, an analog front end 20, a motor AMP 21, a spindle motor 22, a seek motor 24, a multiplexer 31, a video processor 32, and an audio processor 33.
An optical disk device in the camcorder in
Similarly, the optical disk device, the laser diode control device, or the camcorder has a unit that operates in response to a clock signal. Thus, measurement of a temporal element or decision means (to be described) will not necessarily be dealt with here.
Going back to
The video processor 32 converts an input image into a digital image signal and outputs the signal to the multiplexer 31 and the video/audio encoder 13, respectively. The audio processor 33 converts inputted sound into a digital image signal to output it to the multiplexer 31 and the video/audio encoder 13. The video/audio encoder 13 outputs input video and audio data, under the control of the microcomputer.
The multiplexer 31 multiplexes the input video data and audio data and outputs it to the DVD signal processor 16.
The DVD signal processor 16 temporarily stores the compressed video and audio data inputted from the multiplexer 31 in the recording RAM 18 and outputs a DVD recording stream to the analog front end 20. At the same time, the DVD signal processor 16 outputs a servo system signal (this is used for playback as well) to the motor AMP 21 to control a write operation on the optical disk 2. The playback RAM 17 is used for temporarily storing video and audio data that are read from the optical disk 2 and outputted from the analog front end 20 in form of a DVD playback stream during playback, and outputting the data to the multiplexer 31.
The analog front end 20 converts the DVD recording stream supplied from the DVD signal processor 16 to a current pulse and supplies it to the laser diode 3 of the optical head 1.
The laser diode 3 outputs laser light with a power level corresponding to the current value of the supplied current. The output laser light is radiated onto a recording layer of the optical disk 2 through the collimating lens 5, the beam splitter 6, and the objective lens 9 to perform a record (write) operation. At this time, the laser light emitted from the laser diode 3 is split in part by the beam splitter 6 and enters the photo diode 25 through the condenser lens 10. The photo diode 25 detects intensity of the incoming light and outputs the detected intensity data to the analog front end 20. The analog front end 20 then decides whether a current laser light power is suitable, based on the light intensity data being inputted. If so, the analog front end 20 supplies current as it is set at present. If not, however, the analog front end 20 changes a conversion rate for converting the DVD recording data stream that has been supplied from the DVD signal processor 16 to a current pulse and supplies current. Here, the analog front end 20 and the control microcomputer 19 always access data with each other and continuously update the setup conditions according to given circumstances.
The motor AMP 21 receives a servo system signal from the analog front end 20, outputs, based on the received servo system signal, a spindle control signal to the spindle motor 22; a focus control signal to the focus actuator 8; a tracking control signal to the tracking actuator 7; and a seek control signal to the seek motor 24. And the spindle motor 22 rotates the optical disk 2 in response to the spindle control signal, the tracking actuator 7 calibrates a, minute position misalignment in a radius direction (normal direction), e.g., a horizontal dithering during the rotation of the disc, in response to the tracking control signal, the focus actuator 8 adjusts the objective lens 9 in response to the focus control signal and changes a focus position of the laser light radiated onto the optical disk 2 in response to the focus tracking control signal, and the seek motor 24 changes the radiation position of the laser light to a predetermined position of the optical disk 2 in response to the seek control signal.
The temperature sensor 4 is installed in the vicinity of the laser diode 3 to detect temperature of the laser diode 3 or temperature information, and outputs the detected temperature or the temperature information to the control microcomputer 19. The control microcomputer 19 realizes or learns temperature of the laser diode 3 out of the detected temperature or the temperature information provided from the temperature sensor 4, and accesses, if necessary, to the analog front end 20 to change the conversion rate of current value to be fed to the laser diode 3 or controls the supply startup or stop.
In addition, the control microcomputer 19 not only accesses between the analog front ends 20, but also between components of the camcorder in general such that the camcorder can be kept in proper operating state.
The optical disk device 41 is so constructed that it accepts a removable medium, such as, an optical disk (e.g., DVD-RAM), from an outside, in a detachable manner, and therefore it is susceptible to an outside atmosphere, in particular, temperature thereof.
For subsequent operations, the control microcomputer 19 accesses all necessary components inside the camcorder according to an operational program of the camcorder (e.g., taking information and executing a control). In addition, data that are required to decide, calculate or refer to an operational program are preserved in advance in a memory (not shown) in the control microcomputer 19 for example, such that the control microcomputer 19 may withdraw the data, and contents of the data are also updated according to needs. Also, the temperature sensor 4 detects temperature of the laser diode 3 at a preset time intervals that would not impede the processing operations of the control microcomputer 19 and outputs it to the control microcomputer 19. The photodiode and other detection components operate in a similar manner.
Referring to
First of all, in step S501, the control microcomputer 19 decides whether temperature of the laser diode 3 detected by the temperature sensor 4 is equal to or below the predetermined temperature. If the temperature of the laser diode 3 is equal to or below the predetermined temperature, the control microcomputer proceeds to step S502; otherwise, it proceeds to step S508.
In step S508, laser light is emitted and the typical operation where the user can write (record) to or from the camcorder or the optical disk is carried out. That is, the camcorder executes writing (recording) a photographed image onto or from a disk, e.g., DVD-RAM, which is set to the optical disk device, and ends the operation after the writing (recording) operation is performed.
In step S502, the control microcomputer 19 calculates a temperature difference between the current laser diode temperature and the predetermined temperature as a temperature rise.
In step S503, the control microcomputer 19 acquires a maximum current value where no laser light is outputted at the present temperature (i.e. a threshold current value Ith at the detected temperature) by referring to I-L characteristic data (shown in
In step S504, the analog front end 20 provides the current of the current value which the control microcomputer 19 has commanded to the laser diode 3 (the laser diode 3 is preheating).
In step S505, the control microcomputer 19 decides whether the calculated amount of time has elapsed. If no, it proceeds to step S506; otherwise, it stops the current supply and proceeds to step S508.
The current supply may be continued until the operation in step S508 starts.
Instead of calculating time, it is also possible to issue a command again after a preset amount of time has lapsed, by recalculating a value of the temperature sensor for a start-up.
In step S506, the control microcomputer 19 receives from the analog front end 20 a detection result of an incoming light intensity provided by the photodiode 25. If light is detected (“Yes”—whether photosensitivity is available), it proceeds to step S507; otherwise, it proceeds to step S504.
In step S507, the control microcomputer 19 issues a command for the analog front end 20 to lower the value of supplied current by a predetermined value from the present value of supplied current. And after the front end 20 lowered current value, the control microcomputer 19 proceeds to step S504.
As has been explained so far, according to the embodiment in
Next, the following will now describe another embodiment (Mode II) of the operation of the present invention optical disk device, with reference to
For subsequent operations, the control microcomputer 19, as is done in
Referring to
First of all, in step S501, the control microcomputer 19 decides whether temperature of the laser diode 3 detected by the temperature sensor 4 is equal to or below the predetermined temperature. If the temperature of the laser diode 3 is equal to or below the predetermined temperature, the control microcomputer proceeds to step S603; otherwise, it proceeds to step S508.
In step S508, the typical operation of laser light output is carried out. That is, the camcorder executes recording of a photographed image onto a disk, e.g., DVD-RAM, which is set to the optical disk device, and ends the operation after the writing (recording) operation is performed.
In step S603, as is done in the step S502 of
In step S604, the analog front end 20 provides the current of the current value which the control microcomputer 19 has commanded to the laser diode 3 (the laser diode 3 is preheating). After a preset amount of time being commanded lapses, the control microcomputer 19 stops the current supply and proceeds to step S508.
The current supply may be continued until the operation in step S508 starts.
As has been explained so far, even at a low temperature outside the operation guarantee temperature range incapable of outputting laser light, a current equal to or below the threshold current value may be supplied to the laser diode to increase its temperature without outputting laser light. In so doing, the laser diode temperature gets into the operation guarantee temperature range and starts outputting laser light, such that a normal writing operation can be performed.
The following will now explain a table or an equation required for the processing operation in
Temperature characteristics of a laser diode used for a camcorder, an optical disk device, or a laser diode itself are acquired respectively at the time of shipping, and data on the acquired temperature characteristics are stored in a memory (e.g., a non-volatile memory built in the control microcomputer 19) inside a camcorder.
In step S503 of
For example, in the graph of
Step S603 in
Going back to
Δt=Q/Tc Equation (1)
Heat quantity Q and power P (unit:[W]) satisfy a relationship expressed in Equation (2):
Q=P×t=(Id×Vd×t) Equation (2)
where, t is time (unit:[s]), Id is a supply current (unit:[A]), and Vd is a supply voltage (unit:[V]).
Substituting the Equation (1) to the Equation (2), we obtain Equation (3):
Δt=(Id×Vd×t)/Tc Equation (3)
If the supply current Id and the supply voltage Vd are constant, power P becomes constant as well. In such case, since a constant heat quantity Q is given all the time, the temperature rise At is increased proportionally to the elapsed time t (FIG. 7[d]). In reality, however, heat goes off from the junction, heat quantity Qo=a x(Tj−T0) escapes. Here, “a” is a thermal conductivity, Tj is the temperature at an junction (unit:[° C.]), and T0 is an ambient temperature (unit:[° C.]). Since heat quantity Qo being escaped is increased as the temperature at an junction is higher, a saturated state is resulted as shown in FIG. 7[c]. Also, since it takes longer time to the saturated state if a threshold current value is larger (e.g., an elapsed time D at the temperature rise [b] in
Therefore, when operations are carried out as in Mode III of FIG. 8 by modifying the sequence of operations in the flow chart of Mode I shown in
For subsequent operations, the control microcomputer 19 accesses all necessary components inside the camcorder according to an operational program of the camcorder (e.g., taking information and executing a control). In addition, data that are required to decide, calculate or refer to an operational program are preserved in advance in a memory (not shown) in the control microcomputer 19 for example, such that the control microcomputer 19 may obtain the data, and contents of the data are also updated according to needs. Also, the temperature sensor 4 detects temperature of the laser diode 3 at a preset time intervals that would not trouble the processing operations of the control microcomputer 19 and outputs it to the control microcomputer 19. The photodiode and other detection components operate in a similar manner.
Referring to
First of all, in step S501, the control microcomputer 19 decides whether temperature of the laser diode 3 detected by the temperature sensor 4 is equal to or below the predetermined temperature. If the temperature of the laser diode 3 is equal to or below the predetermined temperature, the control microcomputer proceeds to step S803; otherwise, it proceeds to step S508.
In step S508, laser light is emitted and the typical operation where the user can write (record) or read (playback) to or from the camcorder or the optical disk is carried out. That is, the camcorder records a photographed image onto a disk, e.g., DVD-RAM, which is set to the optical disk device, and ends the operation after the writing (recording) operation is performed.
In step S803, the microcomputer 19 calculates a maximum current value where no laser light is outputted at the present temperature (i.e. a threshold current value Ith at the detected temperature) by referring to I-L characteristic data (shown in
In step S804, the analog front end 20 provides the current of the current value which the control microcomputer 19 has commanded to the laser diode 3 (the laser diode 3 is preheating), and the control microcomputer 19 proceeds to step S506.
In step S506, the control microcomputer 19 receives from the analog front end 20 a detection result on the intensity of an incident light to the photodiode 25 through a condenser lens 10. If light is detected (“Yes”—whether photosensitivity is available), it proceeds to step S507; otherwise, it proceeds to step S805.
In step S507, the control microcomputer 19 issues a command for the analog front end 20 to lower the value of supplied current by a predetermined value from the present value of supplied current. And after the front end 20 lowered current value, returns to step S504.
In step S805, the control microcomputer 19 monitors whether a preheating time passed a preset amount of time. If the preset amount of time has not yet lapsed, it continues monitoring; otherwise, it returns to step S501.
In step S501, the control microcomputer 19 checks temperature of the laser diode again, which the temperature has been increased by preheating. If the laser diode temperature exceeds the predetermined temperature, the control microcomputer 19 proceeds to step S508; otherwise, it proceeds to step S803 and further, and supplies a current of a maximum current value where no laser light is outputted at the present temperature (i.e. a threshold current value Ith at the detected temperature) to the laser diode.
As such, the embodiment of
The predetermined cycle or time interval may vary according to a temperature range. For instance, a long cycle may be set if the laser diode temperature is low, while a short cycle may be set if the laser diode temperature is high. Also, if the laser diode temperature is within a high temperature range, it is possible to reduce the cycle gradually by setting the temperature range small.
As has been explained so far, even at a low temperature outside the operation guarantee temperature range incapable of outputting laser light, a current equal to or below the threshold current value may be impressed to the laser diode to increase its temperature. In so doing, the laser diode temperature gets into the operation guarantee temperature range and starts outputting laser light, such that a normal writing operation can be performed.
Still another embodiment (Mode IV) will now be described with reference to
In
First of all, in step S501, the control microcomputer 19 decides whether temperature of the laser diode 3 detected by the temperature sensor 4 is equal to or below the predetermined temperature. If the temperature of the laser diode 3 is equal to or below the predetermined temperature, the control microcomputer proceeds to step S903; otherwise, it proceeds to step S508.
In step S508, the typical operation of laser light output is carried out. That is, the camcorder executes recording of a photographed image onto a disk, e.g., DVD-RAM, which is set to the optical disk device, and ends the operation after the writing (recording) operation is performed.
In step S903, the microcomputer 19 calculates a maximum current value where no laser light is outputted at the present temperature (i.e. a threshold current value Ith at the detected temperature) by referring to I-L characteristic data (shown in
In step S904, the analog front end 20 provides the current of the current value which the control microcomputer 19 has commanded to the laser diode 3 (the laser diode 3 is preheating), and the control microcomputer 19 proceeds to step S508.
In case of the embodiment of
As has been explained so far, even at a low temperature outside the operation guarantee temperature range incapable of outputting laser light, a current equal to or below the threshold current value may be impressed to the laser diode to increase its temperature. In so doing, the laser diode temperature gets into the operation guarantee temperature range and starts outputting laser light, such that a normal writing operation can be performed.
Still another embodiment of the present invention will now be described with reference to
In particular, the low-temperature standby mode is advantageous for preventing dew condensation on a laser diode. For example, when a user exchanges a removable medium in an optical disk device, an opening/closing cover for the optical disk device is opened and closed, making a laser diode therein susceptible to dew condensation. At this time, by turning off the low-temperature standby mode, dews are not formed on the laser diode and a decrease in life span of the laser diode due to damages for example can be prevented.
Another way is to set the low-temperature standby mode to be turned off automatically for a certain period of time whenever the cover of the optical disk device is either opened or closed, and let a finder to show a warning of that intention.
Referring to the embodiment of
In step S1001, the control microcomputer 19 decides whether the user has set the low-temperature standby mode of a camcorder or an optical disk device to ON. If the low-temperature standby mode is set to ON, the control microcomputer 19 proceeds to step S1002. If the low-temperature standby mode is set to OFF, however, the control microcomputer 19 executes a writing (recording) operation in step S508 discussed earlier with referred to
In step S1002, a preheating operation is carried out as is done in the embodiments of
As has been explained so far, even at a low temperature outside the operation guarantee temperature range incapable of outputting laser light, a current equal to or below the threshold current value may be impressed to the laser diode to increase its temperature. In so doing, the laser diode temperature gets into the operation guarantee temperature range and starts outputting laser light, such that a normal writing operation can be performed.
Referring to
Under limited space of the drawing in
In step S1101, the control microcomputer 19 decides whether a simple mode (automatic mode) is set by a user. If the simple mode is set, it proceeds to step SI 102; otherwise, it proceeds to step S1103.
In step S1102, the control microcomputer 19 decides whether Mode II (shown in
In step S1103, the control microcomputer 19 decides whether Mode I (shown in
In step S1104, the sequence of operations for Mode II (shown in
In step S1105, the sequence of operations for Mode IV (shown in
In step S1106, the sequence of operations for Mode I (shown in
In step S1107, the sequence of operations for Mode III (shown in
As has been explained so far, even at a low temperature outside the operation guarantee temperature range incapable of outputting laser light, a current equal to or below the threshold current value may be impressed to the laser diode to increase its temperature. In so doing, the laser diode temperature gets into the operation guarantee temperature range and starts outputting laser light, such that a normal writing operation can be performed.
The following will now describe still another embodiment of the present invention with reference to
Therefore, at the time of shipment or adjustment at a factory, initial I-L characteristics of each laser diode are first measured at every predetermined temperature and at every predetermined sampling (at every predetermined current value) to collect data, and the data are stored in a memory that is built in a camcorder or an optical disk device, or in a memory that is accessible to either one in form of a table or a equation. Moreover, laser power or intensity of laser light is measured and detected with a photodiode or the like as shown in the schematic block diagram of
As to the changes over a period of years, the control microcomputer 19 measures a current value Imax outputting a maximum power rate HI being set and a threshold current value Ith based on temperature of a laser diode provided by the temperature sensor when a camcorder or an optical disk is running, and substitutes the preserved data with the measured data for shift. Even though temperature setting is not mentioned here, the laser diode may be preheated up to a predetermined temperature range as in embodiments of the present invention.
The embodiment described above has explained a camcorder combined with an optical disk device. However, the present invention is not limited to, but can be applicable to a separate video camera (including a digital camera) and an optical disk device only. Further, the optical disk device of the present invention is not limited to a camera such as a camcorder, but can be applied to an electronic machine, particularly a portable electronic machine, loaded with an optical disk device as an information recording device.
For instance, the optical disk device can be incorporated into PDA, cell phones, etc.
The present invention relates to a laser diode used for writing (recording) or reading data to or from an optical disk device as a recording medium. It is not necessarily to use a CD, DVD, next-generation DVD, etc., as long as laser light is used to perform a writing operation. For instance, a magneto-optic type recording medium using magnetism for a reading operation, e.g., Magneto-Optical Disc (Mo) or Mini Disc (MD) may be used as well. Therefore, as MD has been mentioned, any recording purposes or objects can be acceptable.
Moreover, the present invention is not limited to a laser diode only, but can be applied to LEDs with the same properties. For example, it can be used advantageously for signal lights, outdoor lamps, advertisement displays such as electric signs, traffic signs, TV sets and so on.
Even though the temperature sensor detected temperature directly, the controller like the control microcomputer may detect data in a separate physical unit like thermocouple and convert it to temperature. Also, the table or the equation does not have to be expressed in terms of temperature but as data in physical unit that the temperature sensor detects.
According to the embodiments explained so far, even at a low temperature outside the operation guarantee temperature range incapable of outputting laser light, a current equal to or below the threshold current value may be impressed to the laser diode to increase its temperature. In so doing, the laser diode temperature gets into the operation guarantee temperature range and starts outputting laser light, such that a normal writing operation can be performed.
Number | Date | Country | Kind |
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2007-155120 | Jun 2007 | JP | national |