JPH077526B2 - Optical recording / reproducing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical recording / reproducing apparatus for optically recording / reproducing information such as an optical disk.

Conventional Technology It is said that the present age is the information age, and technological development of high-density and large-capacity memory, which is the core of it, is being actively conducted. As the capacity required for memory, in addition to the above-mentioned high density and large capacity,
High reliability, high speed access, etc. are mentioned, and the optical disk memory has been receiving the most attention as satisfying all of them. The optical disk memory is for optically recording / reproducing information on / from a recording medium, and recently, many studies have been conducted on a magneto-optical disk capable of erasing recorded information. Since the optical disk memory is a non-contact recording / reproducing system, it has a great feature that it does not damage the information recording medium.Therefore, in the optical recording / reproducing apparatus, an optical head forms a minute light spot on the information recording medium. ing.

The optical head includes a collimator lens that converts the divergent light of the semiconductor laser into parallel light, an objective lens that forms a minute light spot on the information recording medium, an information detection function, a focus error between the information recording medium and the objective lens, and a tracking error. Function to detect, focus servo by driving the objective lens
An objective lens actuator for performing tracking servo is required.

This optical head, when the external environment changes (temperature change, humidity change, mechanical vibration or shock, etc.), causes the optical axis of parallel light to be tilted or the parallel state to change.
Large errors will occur in information detection, focus and tracking error detection. Especially, it is sensitive to temperature changes.

Hereinafter, the conventional optical head described above will be described with reference to the drawings.

FIG. 2 is a schematic configuration diagram of a conventional optical head.

In FIG. 2, 1 is an optical block made of aluminum, 2
Is a semiconductor laser, 3 is a collimator lens, 4 is a half mirror, 5 is an objective lens, 6 is an information recording medium, 7 is a mirror, 8 is detection means, and 9 is a photodetector.

The operation of the conventional optical head configured as described above will be described below.

The divergent light from the semiconductor laser 2 is converted into parallel light by the collimator lens 3, enters the objective lens 5 through the half mirror 4, and forms a minute light spot on the information recording medium 6. The reflected light from the information recording medium 6 passes through the objective lens 5, is reflected by the half mirror 4 and the mirror 7, and enters the photodetector 9 through the detecting means 8.

The detection means 8 is a detection means that also performs signal detection, focus error detection, and tracking error detection.

In general, the optical block 1 is made of aluminum, and the holder for fixing the semiconductor laser 2, the collimating lens 3, the information detecting means 8, the photodetector 9 and the like to the optical block 1 is also made of aluminum. Has been formed.

Here, as described above, the semiconductor laser, the collimator lens holder, the detecting means holder, and the photodetector holder fixed on the optical block 1 made of aluminum are the same material as the optical block made of aluminum. The same thermal expansion / contraction occurs in the plane perpendicular to the optical axis with respect to the temperature change in the outside world, and no distortion / displacement in the in-plane direction of the optical axis occurs between the optical axes.

Therefore, the parallel tilt / deviation from the collimator lens 3 and the tilt / deviation of the light beam incident on the photodetector 9 do not occur due to the distortion / deviation of the optical axis.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, although there is no distortion or deviation in the in-plane direction of each optical axis due to temperature changes in the external environment, the value of the linear expansion coefficient α of the aluminum optical block 1 is relatively large. Yes (in the case of aluminum, α = 25 × 10 ⁻⁶ / ° C.), the distance a between the semiconductor laser 2 and the collimating lens 3 and the distance b between the detecting means 8 and the photodetector 9 are heat due to temperature changes in the external environment. Influenced by expansion / contraction (for example, a = 10 mm, b = 30 mm, the expansion / contraction amount is Δa =
(10 μm, Δb = 30 μm) The values of a and b change, and relative positional deviation occurs in the distance of the light flux in the optical axis direction. For this reason, the state of the parallel light flux by the collimator lens 3 changes, a light spot cannot be stably obtained on the information recording medium 6, and the light flux entering the photodetector 9 from the detection means 8 defocuses.
There is a problem that detection cannot be stably obtained.

The present invention has been made in view of the above problems, and the relative position in the optical axis direction of the light beam between the semiconductor laser that is the light source and the collimating lens that is the parallel light converting means and the detecting means even if the temperature changes in the external environment. This makes it possible to prevent the relative position of the light beam between the optical detector and the photodetector in the optical axis direction from changing more than the allowable value and causing neither inclination nor deviation of each optical axis. Therefore, it is an object of the present invention to provide an optical recording / reproducing apparatus capable of stably detecting a light spot on an information recording medium and a signal by a photodetector.

Means for Solving the Problems In order to achieve the above object, the optical block of the optical recording / reproducing apparatus of the present invention is provided only in the optical axis direction of the luminous flux emitted from the semiconductor laser or in the luminous flux emitted from the semiconductor laser. The linear expansion coefficient is substantially zero in the optical axis direction and in the optical axis direction of the light beam incident on the detector from the detecting means with the optical axis parallel to the optical axis of the semiconductor laser, and the plane perpendicular to these optical axes. In the inside, the semiconductor laser, the collimator lens, the detecting means, the photodetector, etc. are made of resin having a characteristic substantially equal to the linear expansion coefficient of the material of the fixing member for fixing the optical block.

It is also possible to make the material of each fixing member the same as the resin forming the optical block.

Action The present invention has the above-described configuration, and first, the distance a between the semiconductor laser and the collimating lens and the distance b between the detecting means and the photodetector.
Since the coefficient of linear expansion of the optical block itself becomes substantially zero in the optical axis direction of the light flux, even if there is a temperature change in the external environment, relative displacement of the distance in each optical axis direction does not occur.

The semiconductor laser fixing holder, the collimating lens fixing holder, the detecting means fixing holder, and the photodetector fixing holder as fixing members are made of aluminum. The linear expansion coefficient of the material of the optical block is the vertical plane of the optical axis of the light beam. Since it is made of a resin that is substantially equal to the linear expansion coefficient of aluminum in the inward direction, substantially the same expansion / contraction occurs in the in-plane direction perpendicular to the optical axis of the light beam, and no tilt or shift occurs.

Regarding the expansion / contraction of the light flux of each holder itself in the optical axis direction, the holder itself is small compared to the values of the distance a between the semiconductor laser and the collimator lens and the distance b between the detection means and the photodetector, and the expansion / contraction is small. It is within the range of allowable values, and also within the allowable range of changes in focal length and working distance due to thermal expansion / contraction of the semiconductor laser, collimating lens, detecting means, photodetector and the like.

Furthermore, if each holder is made of resin with the above characteristics, the expansion and contraction of each holder in the optical axis direction will be almost zero,
The stability becomes more predominant because the linear expansion coefficients are exactly the same in the in-plane direction perpendicular to the optical axis.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an optical recording / reproducing apparatus in an embodiment of the present invention.

In FIG. 1, 2 is a semiconductor laser, 3 is a collimator lens, 4 is a half mirror, 5 is an objective lens, 6 is an information recording medium, 7 is a mirror, 8 is a detection means, 9 is a photodetector, and 10
Is an optical block made of resin.

Incidentally, 2 semiconductor lasers excluding 10 resin optical blocks, 3 collimating lenses, 4 half mirrors, 5 objective lenses, 6 information recording media, 7 mirrors, 8 detecting means, 9 light The detector has the same structure as the conventional example.

Regarding the optical recording / reproducing apparatus configured as described above,
The operation will be described below.

First, the divergent light emitted from the semiconductor laser 2 is converted into parallel light by the collimator lens 3, then enters the objective lens 5 through the half mirror 4, and forms a minute light spot on the information recording medium 6. The reflected light from the information recording medium 6 passes through the objective lens 5, is reflected by the half mirror 4 and the mirror 7, and enters the photodetector 9 through the detecting means 8.

Here, the detection means 8 detects the signal, the focus error,
It shall also be used for tracking error detection.

As described above, according to the present embodiment, the linear expansion coefficient β ₁ = 3 × 10 ⁻⁶ / ° C. in the flow direction of a resin having a directional linear expansion coefficient, for example, polyphenylene sulfite resin, The linear expansion coefficient α of aluminum is α = 25 × 10 ^{-6 when} compared with the linear expansion coefficient α of aluminum used in conventional optical heads and holders at a linear expansion coefficient β _{2 of} 30 × 10 ^-6 / ° C. / ° C, the linear expansion coefficient β _{2 in the in-} plane direction perpendicular to the flow direction of polyphenylene sulfite
And the linear expansion coefficient β ₁ in the flow direction is about 1/10 of the linear expansion coefficient α of aluminum, and β ₁ can be assumed to be substantially zero.

Therefore, by forming the optical block by aligning the resin flow direction with the optical axis direction of the light flux, the linear expansion coefficient of the optical axis in the light flux direction becomes substantially zero for the above reason, and the in-plane direction perpendicular to the optical axis direction of the light flux. Then, the coefficient of linear expansion of aluminum forming the fixing members such as the semiconductor laser fixing holder and the collimating lens fixing holder is substantially equal to that of aluminum.

As a result, relative positional deviations due to temperature changes in the external environment do not occur in the distance a between the semiconductor laser and the collimator lens and the distance b between the detection means and the photodetector. And since the linear expansion coefficient of the material of the optical block is formed of a resin that is substantially equal to the linear expansion coefficient of aluminum in the plane perpendicular to the optical axis of the light flux, the same expansion / contraction occurs in the optical axis direction of the light flux, No tilting or misalignment occurs.

For example, if the distance a between the semiconductor laser and the collimating lens is a = 10 mm when the outside temperature rises by 40 ° C., the extension Δa of the optical block made of the above resin is Δa = 1.2 μm, which is larger than that of the conventional example Δa = 10 μm. It will be about 1/10.

Further, each fixed holder is also formed of polyphenylene sulphite having the above linear expansion coefficient, so that each relative positional deviation in the optical axis direction and inclination in the in-plane direction perpendicular to the optical axis direction, deviation, etc. can be further suppressed, As compared with the case where only the optical block is formed of polyphenylene sulfite, a stable light spot on the information recording medium and a detection signal at the photodetector can be obtained.

Here, the holders for fixing the semiconductor laser 2, the collimating lens 3, the detecting means 8, and the photodetector 9 to the optical block are not shown.

As described above, the present invention provides an optical block of an optical recording / reproducing apparatus in which only the optical axis direction of a luminous flux emitted from a semiconductor laser, or the optical axis direction of a luminous flux emitted from a semiconductor laser, and The linear expansion coefficient is substantially zero in the direction of the optical axis of the light beam incident on the detector from the detection means with the optical axis parallel to the light beam optical axis emitted from the semiconductor laser, and the plane perpendicular to these light beam optical axes. In the inside, a holder for fixing the semiconductor laser to the optical block, and a resin having a characteristic substantially equal to the linear expansion coefficient of the material of the fixing member such as the holder for fixing the photodetector to the optical block,
Even if the ambient temperature changes, the relative position of the semiconductor laser, which is the light source, and the collimator lens, and the relative position of the detection means and the photodetector do not change more than the permissible value, and neither tilt nor shift of each optical axis occurs. Therefore, the light spot on the information recording medium and the detection signal by the photodetector can be stably obtained.

Further, if the fixing member such as the semiconductor laser is also formed of the resin forming the optical block, the relative positional deviation in the optical axis direction and the inclination and deviation in the in-plane direction perpendicular to the optical axis direction have a greater effect. Can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an optical recording / reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a conventional optical recording / reproducing apparatus. 1 ... Aluminum optical block, 2 ... Semiconductor laser, 3 ... Collimating lens, 4 ... Half mirror, 5
…… Objective lens, 6 …… Information recording medium, 7 …… Mirror,
8 ... Detection means, 9 ... Photodetector, 10 ... Resin optical block.

Claims (4)

[Claims] 1. A semiconductor laser that is a light source, a collimator lens that converts divergent light from the semiconductor laser into parallel light, and parallel light obtained by the collimator lens is condensed on an information recording medium to form a small light spot. And an objective lens for forming an optical disc, a means for detecting an information signal by reflected light from the information recording medium, a means for detecting a focus error signal, and a means for detecting a tracking error signal, and all the objective lenses except the objective lens. An optical block having built-in constituent elements, wherein the optical block is provided only in the optical axis direction of the luminous flux emitted from the semiconductor laser, or in the optical axis direction of the luminous flux emitted from the semiconductor laser, and in the detecting means. A surface having a linear expansion coefficient of substantially zero in the optical axis direction of the light beam incident on at least one of the detection means, and a plane perpendicular to the optical axis of each of the light beams. The linear expansion coefficient in the direction is formed of a resin having a characteristic that is substantially equal to the linear expansion coefficient of a fixing member for fixing the component such as the semiconductor laser to the optical block in the direction perpendicular to the optical axis of each light beam. An optical recording / reproducing device characterized in that 2. A fixing member for fixing a component such as a semiconductor laser to an optical block is formed of the same resin as the resin forming the optical block.
The optical recording / reproducing apparatus described. 3. A resin forming an optical block, wherein the linear expansion coefficient in the flow direction is approximately 3 × 10 ⁻⁶ / ° C. and the linear expansion coefficient perpendicular to the flow direction is approximately 30 × 10 ⁻⁶ / ° C. The optical recording / reproducing apparatus according to claim 1, wherein the optical recording / reproducing apparatus is formed of polyphenylene sulfite having characteristics. 4. An optical recording / reproducing apparatus according to claim 3, wherein a fixing member for fixing a component such as a semiconductor laser to the optical block is made of polyphenylene sulfite.