JPS60117425A - Optical pickup - Google Patents

Abstract

PURPOSE:To form an optical pickup which can be used in a wide temperature range, by constituting the optical pickup so that it is difficult that heat from parts constituting the other opical systems such as a pickup base is transmitted to a semiconductor laser element. CONSTITUTION:A laser mount 3 is separated from a pickup base 1, and they are connected through a heat insulating spacer 8. That is, the heat insulating spacer 8 is constituted with materials having a low heat conductivity such as plastics or the like to prevent effectively heat conduction between the laser mount 3 and the pickup base 1. Thus, cooling of the semiconductor laser element having a problem with respect to high temperature operation especially in the optical pickup is accelerated effectively and surely to resolve an inconvenient feeling of an operator and a danger of the high temperature operation of the semiconductor laser element in the case where the optical pickup is used in an apparatus on a vehicle where the high temperature operation is a problem.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an improvement in the structure of an optical pickup used in, for example, a video disc player, a compact disc player, or an image file, and in particular takes heat radiation of a semiconductor laser element into consideration. The present invention relates to an optical pickup having a structure.

[Prior Art] Video disc players, compact disc players, image files, and the like have been put into practical use as devices using optical recording media.

Lasers are often used as light sources for reading or recording signals in this type of pupil wearing. Most laser light sources use semiconductor laser elements, and the current situation is that some devices using gas lasers are gradually being replaced with semiconductor laser elements.

Semiconductor lasers have the great advantage of being small and inexpensive compared to other laser devices, but on the other hand, they still have problems in terms of longevity and failure frequency when operating in high-temperature environments. Generally, in a semiconductor laser, if the temperature of the case rises by 10° C., the failure rate increases by about three times. Furthermore, low-temperature solder is often used when mounting laser element chips, etc., which is a disadvantage for operation in high-temperature environments.

Incidentally, the heat generated by the semiconductor laser element itself is usually several tens of milliwatts to several hundred milliwatts, except for particularly high-output ones. Therefore, by mounting the laser element on a small heat sink or a structure having an equivalent heat dissipation effect, the temperature rise due to the heat generated by the laser element itself can be suppressed to a sufficiently low level.

Therefore, the reality is that the temperature of the semiconductor laser element is almost determined not by the heat generated by the laser element itself, but by the temperature environment around the semiconductor laser element.

When using equipment that uses optical pickups in high-temperature environments for long periods of time, the only option is to suppress the temperature rise inside the equipment as much as possible and to improve the high-temperature resistance characteristics of the laser element itself. . However, for equipment used in spaces inhabited by humans, such as in-vehicle equipment placed inside the interior of a car, there is a natural limit to the environmental temperature, and the temperature will not rise that high, unless the equipment is exposed to direct sunlight. It's not a thing. Furthermore, even if a situation arises where the device is exposed to high temperatures for a long period of time, it may not necessarily be necessary for the device to perform its original operation under such a situation.

By the way, when it comes to in-vehicle equipment, if the car is left in direct sunlight, the temperature inside the car will drop to 60 to 70 degrees Celsius in the summer.
rises to. Furthermore, under weather conditions that are more severe than in Japan, such as in tropical regions, the temperature inside the vehicle becomes even higher. In such a situation, the equipment installed in the car will also be heated to this temperature. However, if you get back into the vehicle after leaving it for a long time, open the windows, or run a cooling device such as an air conditioner, the temperature inside the vehicle will drop to the outside temperature within a few minutes. The temperature can be lowered to:

Therefore, it may not be necessary for in-vehicle equipment to operate as intended at high temperatures.

However, the rate of decrease in temperature of in-vehicle equipment is extremely slow compared to the rate of decrease in atmospheric temperature inside the vehicle, and in most cases it takes several tens of minutes to reach the final steady humidity, depending on the structure of the device. be. In other words, if a person gets into a car that has been left unattended and has reached a high temperature, and then immediately attempts to operate the device, the device and its laser elements will be operated at extremely high temperatures for several tens of minutes. It turns out.

Moreover, the temperature rises rapidly due to heat generation inside the device.
The temperature conditions are even more severe for laser elements. Further, depending on the car, the repeated cycle of leaving the car and riding the car is complicated, and the riding time per cycle may not be very long.

In such a situation, equipment and laser elements are required to operate continuously at high temperatures for a long time.

By the way, in order to solve the above-mentioned problem, it is possible to provide a means to detect the temperature inside the device or the temperature around the laser element, and to prevent the device from operating when this temperature is high. In such a method, even if the laser element is perfectly protected, the operability of the device will be significantly reduced.

In other words, in the worst case scenario, people in the car will be unable to use the equipment for several tens of minutes, even though they feel that the atmospheric temperature has dropped sufficiently.

The above-mentioned problems are mainly based on the cooling speed of the equipment, but in order to speed up the cooling speed, providing ventilation holes in the equipment casing to promote internal heat dissipation has also been shown to be effective. However, in most cases, the essential problem lies in the structure and materials of the optical pickup. This problem will be explained in more detail below.

FIG. 1 is a schematic perspective view showing an example of a semiconductor laser device installed in a conventional optical pickup, and FIG. 2 is an example of an optical pickup incorporating the semiconductor laser device shown in FIG. It is a partially cutaway exploded perspective view shown in FIG. In Fig. 2, 1 indicates the pickup base;
Each component is precisely positioned and fixed on this, and in order to achieve this precise positioning and fixation, it is made of aluminum die-casting. 2 indicates a semiconductor laser element, 3 indicates a laser mount as a holding member,
This is a member that positions, fixes, and holds the semiconductor laser element 2. The laser element 2 is mounted and held on the laser mount 3 by a top plate 4 and a set screw 5. Note that 6 indicates a lens mount, and 7 indicates a prism, which are fixed on the pickup base 1. That is, the optical pickup shown in FIG. 2 includes a semiconductor laser element 2, a laser mount 3 as a holding member for holding the semiconductor laser element 2, and other components constituting an optical system.

Generally, in devices that apply laser coherency,
The optical system is constructed to maintain strict dimensional accuracy.

Therefore, not only optical components such as lenses, mirrors, and light sources, but also the base 1 for fixing these components must be made precisely.

In order to satisfy this requirement, the pickup base 1 is usually made of cut metal, especially die-cast metal. Therefore, there is a limit to the miniaturization and thinning of the base 1. Therefore, the heat capacity of the base 1 is by no means small, and is generally extremely large compared to the heat capacity of the laser element 2 including the sealing case 2a.

In order to suppress the temperature rise of the pickup due to heat generation of the laser element 2 itself, it is preferable that the base 1 has a large heat capacity. However, when the pickup base 1 is left in the above-mentioned high-temperature state, the amount of accumulated heat becomes extremely large. In addition, in the case of a device in which the information recording medium is in the shape of a disk and the entire optical pickup is moved in the radial direction, mutual heat is generated between the movable part including the optical pickup and the fixed part. It is extremely difficult to increase the conductivity, and it is extremely difficult to realize a configuration in which the heat of the optical pickup section is released to a fixed section with relatively excellent heat dissipation conditions.

Further, forced air cooling means such as fans are obviously highly effective, but needless to say, they lead to an increase in cost and an increase in the size of the equipment. Furthermore, if a heat radiator is provided for the entire optical pickup, there is also the problem that the heat radiator for producing such a heat radiation effect becomes quite large.

[Summary of the Invention] The present invention has been made with the aim of solving such problems, and focuses on the fact that it is not the entire optical pickup that needs to be cooled quickly, but the semiconductor laser element. By configuring the laser element so that heat from other components of the optical system, such as the pickup base, is difficult to transfer, the problem of high-temperature operation of the laser element is reliably resolved, making it an optical type that can be used over a wide range of temperatures. Pick-up is provided.

Other features of the invention will become clear from the following description of the embodiments.

[Embodiments of the Invention] As described above, in order to increase the cooling rate of a semiconductor laser device, (a) reducing the heat capacity of the structure around the semiconductor laser device and the semi-conductor laser device;
and (b) lowering the thermal resistance to the atmosphere, that is, increasing the heat dissipation rate.

As a concrete plan for this purpose, for (a), a structure that is thermally closely coupled to the semiconductor laser element, such as the laser mount 3 as a holding member shown in FIG.
After reducing the heat capacity of the other parts with large heat capacities (
For example, a configuration that is thermally insulated from the pickup base 1) in FIG. 2 can be considered. On the other hand, (b) is achieved by expanding the surface area of the semiconductor laser element itself or the structure including the semiconductor laser element, or by surface treatment with a high thermal emissivity, and is equivalent to installing a so-called heat sink. However, since this is different from the heat radiation of a heating element, if the heat radiator itself has a large heat capacity, condition (a) will be violated. Embodiments of the present invention will be described in more detail below with reference to the drawings.

FIGS. 3 to 6 show examples that satisfy the above-mentioned condition (b). In these embodiments, the same parts as those of the optical pickup shown in FIG. 2 are designated by corresponding reference numbers, and the explanation thereof will be omitted.

FIG. 3 is a schematic exploded perspective view of an embodiment using thermally insulating spacers. Here, the laser mount 3 is separated from the pickup base 1, and the two are newly coupled via a heat insulating spacer 8.

That is, by constructing the thermal insulating spacer 8 from a material with low thermal conductivity such as plastic, the flow of heat between the laser mount 3 and the pickup base 1 is effectively obstructed. It goes without saying that the heat insulating spacer 8 is not limited to the plate shape shown in the figure, but may be of various shapes, such as a film shape.

FIG. 4 is a schematic perspective view for explaining a second embodiment of the invention. Here, a cylindrical spacer 9 is attached around the semiconductor laser element 2. The cylindrical spacer 9 is made of a material with low thermal conductivity, such as plastic, like the thermally insulating spacer 8 described above, and therefore has the same function as the thermally insulating spacer 8. In this way, the cylindrical spacer 9 is attached to the semiconductor 1 nose rope 2.
By providing four parts, it is possible to effectively prevent heat from flowing to the semiconductor laser element 2 from other components having a large heat capacity, such as the pickup base 1.

FIG. 5 is a side view showing an embodiment in which the coupling structure between a semiconductor laser element and a laser mount serving as a holding member is improved. Unlike the embodiments shown in FIGS. 3 and 4, this embodiment does not use a material with excellent thermal insulation to prevent heat conduction.

By reducing the contact area between the semiconductor laser element 2 and the laser mount 3, mutual heat conduction is reduced.

That is, the semiconductor laser element 2 is supported by a plurality of thin protrusions 3a formed on the laser mount 3, thereby reducing the contact area between the two and effectively reducing heat conduction between them. has been done.

FIG. 6 is a cross-sectional view showing an embodiment in which the contact area between the laser mount as a holding member and the pickup base, which has an extremely large heat capacity among the components constituting the optical system 13, is reduced. The embodiment shown in FIG. 6 is similar to the embodiment shown in FIG. 5 in that the conduction of heat is not prevented by the material, but by the IN construction. That is, a plurality of thin protrusions 1a are formed on the pickup base 1, and these protrusions support the laser mount 3 as a holding member, thereby effectively conducting heat between the laser mount 3 and the pickup base 1. This will reduce the

As described above, in each of the examples shown in FIGS. 3 to 6, heat from the pickup base 1 having a large heat capacity is effectively prevented from being transmitted to the semiconductor laser element 2. Therefore, when mounted on a vehicle, for example, even if the entire device reaches a high temperature, it can be seen that the temperature of the semiconductor laser element 2 drops more quickly than that of the pickup base 1. Note that the configurations shown in FIGS. 3 to 6 above do not necessarily need to be used alone.
- Needless to say, it is possible to achieve even greater thermal insulation effects by appropriately combining them.

Next, an embodiment that satisfies the above-mentioned condition <a> will be described with reference to FIGS. 7 to 10. In addition, in FIGS. 7 to 11, the same parts as those shown in each of the above-mentioned figures are designated by corresponding reference numbers.
The explanation will be omitted.

FIG. 7 is a cross-sectional view showing an embodiment in which a radiator is further installed in the embodiment shown in FIG. As is clear from FIG. 7, here, the heat sink 10 is mounted so as to be in contact with the laser mount 3 which is thermally insulated from the pickup base 1 by the heat insulating spacer 8. Therefore, the thermal resistance of the laser mount 3 and the semiconductor laser element 2 to the atmosphere can be effectively lowered by the heat sink 10.

The same applies to the embodiments described below, but the radiator 10 is
It is preferable to use a thin plate of a material with excellent thermal conductivity, such as copper or aluminum, so as not to increase the heat capacity, and to perform surface treatment such as black alumite treatment to improve the thermal emissivity. Furthermore, it is also effective to use a filler such as silicone grease to enhance the thermal coupling between the heat radiator and the heat radiator 10.

FIG. 8 is a cross-sectional view showing an embodiment in which the laser mount itself as a holding member also serves as a heat sink. As is clear from FIG. 8, the laser mount 3 itself as a holding member here is formed into a thin fin shape, and also serves as a heat sink.

Therefore, the laser mount 3 is made of the same material as the heat sink 10 having the above-described structure.

FIG. 9 is a modification of the embodiment shown in FIG. 7, in which a heat sink is attached to the back side of the laser mount. That is, an opening is provided in the pickup base 1 and the heat insulating spacer 8, and the heat radiator 10 is extended from the back surface of the laser mount 3 to Th through this opening.

FIG. 10 is a schematic side view showing an embodiment in which a device is attached to the semiconductor laser element itself.

Here, a screw 10a is attached to the semiconductor laser element 2 itself, and a heat sink 10 is attached to the second screw 108.

By the way, in optical pickups, the problem is not only the dimensional accuracy inside the pink-up device (but also the mounting accuracy of the entire pickup). Therefore, most of the case is often made of metal such as die-casting.

The heat radiator 10 shown in FIGS. 7 to 10 exhibits its heat radiation effect when placed in a lower temperature atmosphere, and when placed in a closed space, the heat radiator 10 exhibits its heat radiation effect. Needless to say, it doesn't work. An example of a one-piece unit that solves this problem is the configuration shown in a schematic perspective view in FIG. 11. In FIG. 11, 11 is a case for an optical pickup, and is almost sealed except for an optical opening 12 through which an optical signal passes and a central opening 13 for preventing heat from escaping. There is. This thermal aperture 13 limits the heat capacity to a small value, and the laser mount 3 is thermally insulated such as the pickup base 1 and the case 11.
The heat sink 10 is attached to the laser mount 3 through this opening 13. Therefore, with this configuration, depending on the environment in which the optical pickup is used, it is possible to arbitrarily select whether or not to use the heat sink 10.

[Effects of the Invention] As described above, the present invention provides that the semiconductor laser element is attached to the parts that make up the optical system via a holding member so that heat from the parts that make up the optical system, such as the pickup base, is not easily transmitted. This makes it possible to effectively and reliably speed up the cooling of semiconductor laser elements in optical pickups, which have problems with high-temperature operation. When used in equipment, it is possible to eliminate the inconvenience to the operator and the danger of high temperature operation of the semiconductor laser element. Therefore, it becomes possible to realize an optical pickup that can be used over a wide range of operating temperatures.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view 18- showing an example of a semiconductor laser element used in a conventional optical pickup. FIG. 2 is a schematic exploded perspective view showing an example of a conventional optical pickup using the semiconductor laser device shown in FIG. 1. FIG. FIG. 3 is a partially cutaway exploded perspective view showing a first embodiment of the invention using a thermally insulating spacer. FIG. 4 is a perspective view for explaining a second embodiment of the invention. FIG. 5 is a side view for explaining a third embodiment of the invention. FIG. 6 is a cross-sectional view for explaining a fourth embodiment of the invention. FIG. 7 shows the fifth embodiment of this invention.
FIG. 3 is a partially cutaway sectional view showing an embodiment of the present invention, and shows a structure in which a heat radiator is attached. FIG. 8 is a partially cutaway sectional view showing a sixth embodiment of the present invention, in which the holding member has a structure that also serves as a radiator. FIG. 9 is a partially cutaway cross-sectional view showing a seventh embodiment of the invention. FIG. 10 is a partially cutaway side view for explaining the eighth embodiment of the present invention. Figure 11 shows
FIG. 7 is a partially cutaway exploded perspective view showing a ninth embodiment of the present invention. In the figure, 1 is a pickup base as a part constituting an optical system, 2 is a semiconductor laser element, 2a is a heat insulating spacer, 3 is a laser mount as a holding member, 3a is a long and narrow protrusion provided on the laser mount, 1a 8 is a long and narrow protrusion provided on the pickup base as a component of the optical system; 8 is a heat insulating spacer; 10 is a heat sink;
Reference numeral 11 indicates a case, and reference numeral 13 indicates an opening. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa

Claims (7)

[Claims] (1) An optical pickup that is used to read information from a recording medium and includes a semiconductor laser element as a light source, a holding member that holds the semiconductor laser element, and parts constituting an optical system, wherein the semiconductor An optical pickup characterized in that a laser element is connected to a component constituting the optical system via the holding member so that heat from the component constituting the optical system is not easily transmitted. (2) The holding member that holds the semiconductor laser element is
The optical pickup according to claim 1, wherein the optical pickup is connected to components constituting the optical system via a thermally insulating spacer. (3) The holding member that holds the semiconductor laser element is
The optical pickup according to claim 1, wherein the optical pickup is supported by a component constituting the optical system by a plurality of thin protrusions formed on the component constituting the optical system. (4) The optical pickup according to claim 1, wherein the semiconductor laser element is supported by a plurality of thin protrusions formed on the holding member. (5) The optical pickup according to any one of claims 1 to 4, wherein a radiator is attached to at least one of the semiconductor laser element and the holding member. (6) The optical pickup according to any one of claims 1 to 4, wherein the holding member also serves as a radiator. (7) The case further includes a case that houses the semiconductor laser element, the holding member, and parts constituting the optical system, and the case has at least a portion of at least one of the semiconductor laser element and the holding member exposed outside the case. The optical pickup according to any one of claims 1 to 6, wherein an opening is provided.