JPS63113948A - Optical head device for optical pickup - Google Patents

Abstract

PURPOSE:To obtain a simple optical head to which the position of a photodetector light receiving position does not require any adjustment by providing a laser diode light source, a flat plate optical element reflecting its emitting luminous flux on the front and rear face and emitting the flux and a photodetector light receiving section receiving the emitting light on one and same block while sealing hermetically them in a package. CONSTITUTION:The laser diode 1, the beam splitter (BS) 4, the photodetector light receiving section 10 and a photodetector light receiving section 10' for monitor are positioned in a block 18 and they are sealed hermetically in one package together with an emitting window 17. The optical head unit 13 is fitted to a barrel including a converging optical element (e.g., objective lens) 5. Then the light emitted from the laser diode 1 is reflected in the surface 4a of the BS 4 and collected to the surface of a sample 19 having unevenness on its surface and moved in the direction A though the window 17 and the objective lens 5. The reflected light goes backward and is reflected in the rear face 4b of the BS 4 and made incident on the light receiving section 10.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to an optical pickup optical head device used for recording/reproducing information on an optical information recording medium, and particularly relates to a light emitting head device that can be used as a non-contact position sensor. - This relates to an optical pickup optical head device that also serves as a light receiver.

[Prior Art] An optical pickup optical system in a recording device converges a laser beam emitted from a laser diode light source onto an information recording medium through a convergent optical element such as an objective lens, and focuses the laser beam on the surface of the information recording medium. Read information stored in
Alternatively, it is known as a device for writing and storing information on the surface of the information recording medium. Whether optically reading or writing information, the laser beam must be accurately focused onto the surface of the information recording medium by a converging optical element such as an objective lens.

Therefore, there is a need for an optical pickup optical head device that operates while detecting whether or not the laser beam is converged onto the surface of the information recording medium using a convergent optical element such as an objective lens.

FIGS. 5A and 5B are configuration diagrams showing the layout of a conventional pickup optical head device. In the figure, (1) indicates a laser diode that serves as a light source,
(2) is a laser beam flux emitted from the laser diode (1).

(4) is a parallel plate beam splitter that splits the laser beam, (5) is a light converging lens element such as a condensing lens that converges these beams, and (6) is an optical card, optical tape, or circular plate. It is an optical information recording medium such as a plate-shaped optical disk, and (7) is an information track formed on the information recording surface of the information recording medium (6), and (10) is a laser reflection from the optical information recording medium (6). This is a photodetector light receiving section that receives light (2').

Next, the operation will be explained. The diverging luminous flux (2) emitted from the LD (1) is directed to the surface of the flat beam splitter (4) (
After being reflected by 4a), the light is focused onto an optical information recording medium (6) by a converging light converging lens element (5). The reflected light beam (2') reflected from the optical information recording medium (6) is reflected by the back surface (4b) of the flat plate beam splitter (4), is slightly shifted from the output light beam (2), and travels in the opposite direction of travel. The light is received by the photodetector light receiving section (10). Optical information recording medium (6)
In order to obtain the information correctly, the light converging spot (3) must be illuminated precisely onto the information track (7) surface. Since the reflected light beam (2') is a convergent light beam, astigmatism occurs as is well known when it travels from the flat plate beam splitter (4) to the photodetector light receiving section (10).

Now, the flat plate beam splitter (4) is a parallel plate, whose thickness is t1 whose refractive index is 01 and whose angle of incidence on the surface (4a) is θ[r
ad], the astigmatism difference Δ is given by the following equation.

The reflected light beam (2') from the beam splitter (4) given the astigmatism is the output light beam (2') of the LD (1).
) and is shown by a dashed line in the figure, is 2t-tanθ'・cosθ
The light is incident on the photodetector (10) with a deviation of . here,
The above θ' satisfies n sin θ−=sin θ.

In such an optical head device, when the photodetector light receiving section (10) is in a focused state on the light convergence spot on the optical disk (6), the light beam reflected from the information recording medium disk is detected as shown in FIG. As shown in b), the circle of least confusion (
11) at a position in the optical axis direction. As shown in the figure, this photodetector light receiving section (10) is divided into four detecting elements (10a), (10b), (10c), and (10d), and each of these detecting sections has an amount of incident light flux. Detect.

As is well known, the output of each of these detection sections is diagonally opposed to each other, because if a defocus occurs, the light convergence spot on the light receiving section (1o) of the photodetector becomes a distorted spot (12). The defocus of the light beam can be detected by calculating the sum of the photoelectric conversion outputs of the detection elements and calculating the difference output between the pair of opposing detection units.

That is, the left output of the sum output bear of the opposing sensing element section is f
(10a) +(10c)l −f(10b)+(10
d)l, this calculation output signal is output as a focus error signal, and a focus actuator (not shown) corrects the focal shift of the light convergence spot on the optical information recording medium.

On the other hand, tracking is performed as an adjustment means in the in-plane direction in order to correctly irradiate the light convergence point (3) on the optical information recording medium (6) onto the information track. Although not specifically explained here, twin spot method, push-pull method, etc. can be applied to this conventional device.

[Problems to be Solved by the Invention] Since the conventional optical head device was configured as described above, the following problems occurred.

As mentioned earlier, the light emitting point of the laser diode (1) and the light convergence spot (11) of the photodetector light receiving part (10) are δ=2・t・sinθ・tan (
θ′). For example, θ-45', t-
If it is considered as 1 square, it is less than δ-0.75 city and 1 m+++. Also, at this time, the amount of deviation in the optical axis direction (x) is as short as 1 mrx or less.

Therefore, there is a problem in that it is very difficult to separately arrange the laser diode (1) and the photodetector light receiving section (10) as shown in the figure. Further, as mentioned above, the photodetector light receiving section (10) must be placed at a position where the circle of least confusion (11) is irradiated, and has an adjustment means. However, as mentioned above, since it is adjacent to the laser diode (1), there is a problem that the configuration and arrangement of the adjusting means is extremely difficult.

To solve this problem, a laser diode (1
) and the light convergence spot (11) are adjacent to each other by 1 mm or less in the optical axis and the direction perpendicular to the optical axis to form the laser diode chip and the photodetector element on the same substrate. can also be considered.

The light emitting point of the laser diode (1) and the light convergence spot (1)
1) is in a conjugate relationship, so as long as the relative positional accuracy and parallelism of the flat beam splitter (4) can be ensured, the photodetector light receiving part can be positioned at the relative position from the laser diode (1) determined by calculation. This means that it is only necessary to set it, and it is possible to eliminate the need for adjusting the detector.

Relative position accuracy is relatively easy if the pixel elements are formed on the same substrate, but the permissible range of parallelism of the flat beam splitter (4) is strict. For example, in Fig. 5, the distance from the laser diode (1) to the flat beam splitter is 15 mu + (4a) of the parallel beam splitter (4).
To set the permissible displacement of the light convergence spot (11) with respect to the light receiving part (]0) of the photodetector to be ±10 μm, assuming that the Merchant angle of incidence is 45″, n-1,5, t = 1 mm, and parallelism a [deg]. α-0,010'(-0,8-) is required.

In this way, the photodetector light receiving part (10) and the laser diode (
In order to integrate 1) without adjustment, it is necessary to maintain parallelism with a high precision of 1° or less in the parallel beam splitter (4), and the required effective area of the flat beam splitter is also smaller than the laser beam in the above example. When the numerical aperture NA of the diode's luminous flux is 0.1, it becomes a circle with a diameter of approximately 5 mm, and high precision flatness is required over a wide area. There is a problem in that the cost is high due to the risk of man-hours, skill, and low yield.

The present invention has been made to solve the above-mentioned problems, and aims to eliminate the need for adjusting the position of the light receiving part of a photodetector, and to provide an inexpensive and simple optical pickup optical head device. It is something to do.

[Means for Solving the Problems] The optical pickup optical system head device according to the present invention combines a light source such as a laser and a beam splitter photodetector light receiving section into one.
This is achieved by means of matching the relative positional accuracy between each element to a high-precision state.

[Function] The optical pickup optical head device according to the present invention can easily constitute an optical pickup optical system head device by combining and packaging a light converging lens and an actuator for controlling its position.
This has the effect of allowing signals and light convergence point position information to be obtained without adjusting the dimensions and positions of other important optical elements of the light receiving section of the photodetector.

[Embodiment] Hereinafter, the configuration of an optical pickup optical system according to an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, a laser diode (1), a beam splitter (4), and a photodetector light receiving section (10) have the same functions as the respective elements of the conventional example. The laser diode (1) is P
A semiconductor chip consisting of an N junction is used, and (10') is a light receiving part of a photodetector for monitoring the output of the laser diode. Further, (17) shows the exit window of the laser beam from the present optical pickup optical system.

Here is the laser diode (1) beam splitter (4)
, the photodetector light receiving part (10) is formed while being positioned with respect to the block (18).
8) also serves as a means for dissipating heat from the laser diode.

Each important optical element in these optical pickup optical devices is constructed and sealed in one package as shown in the figure, and the relative position of each optical element is set with high precision.

In the case of this embodiment, for example, 1-1 mm, similar to the conventional example,
Assuming that the numerical aperture is NA -0.1, the relative positional accuracy of the laser diode (1) and the light receiving part of the photodetector with respect to other important optical elements in the system is ±25 μm in the optical axis direction, and in the direction perpendicular to the optical axis. It is adjusted to ±5 μm. The overall shape of the package that determines the relative positions of such important optical elements is preferably cylindrical, with an outer diameter of at most 10 mm or less. Although it is theoretically and practically difficult to create a circular tube package with a diameter that is too small, it is theoretically possible to create an optical pickup optical unit (13) having a package with a diameter of 5 mm.

In the optical pickup optical system head unit (13) according to the embodiment of the present invention, the distance l between the laser diode (1) and the beam splitter (4) is set to be very short. It is sufficient that the parallelism of the splitter (4) is about 3' at worst, and adjustment of the photodetector light receiving section (10) is not necessary.

Also, regarding detailed illustrated embodiments of the invention, please refer to
Since the effective area of the musburitter (4) can also be reduced, it is advantageous in terms of maintaining surface accuracy, which is an important element, and can contribute to an inexpensive beam splitter. and,
What is the relative positional relationship? and the thickness t1 of the flat plate beam splitter
This is a value that is automatically determined once the slope -θ is determined.

FIGS. 2A, 2B, and 2C show other embodiments in which the optical pickup optical unit (13) of the present invention is used as a more specific optical head device.

In FIGS. 2A, 2B, and 2C, (14) is an optical lens barrel, and (15) is an actuator related to focusing and tracking that performs feedback drive control of the light converging lens element.

The operation of the optical pickup optical head unit (13) of the embodiment of the present invention is basically the same as the operation of the conventional example, or the optical pickup optical head unit (13) and the objective lens are connected to the optical lens barrel (14). Convergent optical elements such as (5
), it is possible to catch the signal and convergent light spot position information of the information recording medium disk (6) from the optical pickup optical head unit (13). Further, there is an effect that no adjustment work of the photodetector light receiving section or the like is required during assembly.

By using this optical pickup optical device, even more diverse optical head devices can be configured. Therefore, one example of such an optical head device is shown in FIG. 2B. (16) is a reflecting mirror, and since the reflecting mirror (16) bends the optical path and then enters a converging optical element such as an objective lens, it usually compresses a large volume and the occupied optical path space. By doing so, it is possible to easily provide a thinner optical head device.

In FIGS. 2A and 2B, the optical pickup optical head unit (13) of the present invention is constructed such that the central axis of the package and the optical axis of the emitted light coincide with each other as described above. As shown, the package center axis line and the emitted light optical axis line do not overlap, and a thinner optical head can be obtained.

Although the tracking method was not particularly mentioned in the explanation of the conventional example, the beam splitter (4) in the optical element (13)
) By forming a diffraction grating on the surface (4a), tracking using the twin spot method can be performed without adding new optical components. Since the twin spot method itself is well known, explanation thereof will be omitted. When the twin spot method is adopted, the focal point of the three beams emitted from the surface (4a) on the optical disk (6) is set on the information track (7) with reference to the θ-order light convergence point (3). It may be necessary to adjust the rotation of the diffraction grating so that it is slightly tilted. In Figure 3 (3a).

If (3b) is the ±1st order light, the track pitch is P1±I order light, and the Oth order light interval is d, the largest tracking signal can be obtained when θ is rotationally adjusted so that it becomes d-1.

In this case, the optical pickup optical head unit (13)
It is advantageous that the center of the package and the optical axis of the emitted light coincide with each other, and the entire optical pickup optical head unit (13) can be rotated and adjusted using the attachment part of the optical lens barrel (14). Since the optical axis does not shift even when rotated, good light convergence characteristics can be maintained without causing an image height for the convergent optical element (5) such as the objective lens. Also, at this time, it is clear that the focus signal is not affected at all, so there is no need to adjust the photodetector.

However, the photodetector light-receiving section (10) requires at least a six-divided detection section.

In the above embodiment, the optical unit (13) has a cylindrical external shape, but it is also possible to use a square package, for example, and the external shape can be selected as appropriate for each usage.

Further, the optical unit (13) of the present invention is not only applicable to the optical head device as described above, but also used for various purposes such as a position sensor as a light emitting and light receiving element.

This will be explained with reference to FIG. 4 as an example. (19) is a sample, and an optical unit (13) of the present invention and an objective lens (5) are fixed to a lens barrel (14). At this time, if the sample (19) is placed near the focusing position, the focus error signal is zero when the sample surface is focused, but when the sample (19) is moved in the direction of A, there are irregularities on the surface. If there is, the focus error signal changes. By calibrating the amount of unevenness and the focus error signal, the surface shape can also be investigated.

By selecting the light convergence numerical aperture NA of the convergence optical element such as the objective lens, the position from the convergence optical element such as the objective lens to the surface of the light convergence spot can be changed over a wide range of measurement accuracy and measurement range. It can function as a sensor to detect.

[Effects of the Invention] As described above, according to the present invention, since the laser diode, beam splitter, and photodetector are configured in one package, there is no need to adjust the light receiving section of the photodetector, and an inexpensive beam A single stable optical pickup optical head device can be provided using a splitter. By applying it as a part of such an optical head device, not only can an inexpensive optical head device with a very simple configuration be obtained, but also the thinness of the optical head device itself,
Miniaturization can be achieved.

[Brief Description of the Drawings] Fig. 1 is a configuration diagram of an optical pickup optical unit according to an embodiment of the present invention, and Figs. 2A, 2B, and 2C are optical pickup optical units to which the optical pickup optical unit of the embodiment of the present invention is applied. A configuration diagram of the head device, FIG. 3 is an explanatory diagram of an adjustment method using the twin spot method according to an embodiment of the present invention, FIG. 4 is a configuration diagram showing a modified example of the position sensor of the embodiment of the present invention, and FIGS. 5A and 5B. The figure is a configuration diagram showing a conventional optical pickup optical head device. In the figure, (1) is a laser diode, (4) is a flat beam splitter, (10) is a photodetector light receiving part, and (13) is a flat beam splitter.
) is an optical pickup optical unit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent: Patent attorney Masuo Oiwa (and 2 others) Figure 1, Figure 2A, Figure 2B, Figure 1') Figure 2C, Figure 5A, Figure 5B, 0C Procedural amendment. Name of the invention: Optical head unit 3, Relationship to the case of the person making the amendment Patent applicant address: 2-2-3 Marunouchi, Chiyoda-ku, Tokyo. Name (601) Mitsubishi Electric Corporation Representative Moriya Shiki 4, Agent address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Specification 1 Name of the invention Optical head unit 2 Scope of claims (1) ) A laser diode light source, a flat plate optical element that reflects the emitted light beam from the laser diode light source on a first surface, which is a front surface, and emits it, and incident light that returns through the same optical path as the emitted light of the flat plate optical element. a photodetector light-receiving section that receives a beam that is reflected by a second surface that is the back side of the flat optical element and converges at a position adjacent to the laser diode light source, the laser diode light source, the flat optical element An optical head unit characterized in that the photodetector light receiving section is formed on the same block and sealed in a predetermined package. (2) The light-receiving section of the photodetector has at least one four-division detection light-receiving element, and has means for outputting light collection spot position information of the emitted light beam. optical head unit. (3) The optical head unit according to claim 1 or 2, wherein a diffraction grating is arranged on the first surface of the flat optical element. (4) Claims 1 to 3, characterized in that the package for sealing has a cylindrical shape, and the center line of the cylindrical package coincides with the optical axis of the emitted light beam. The optical head unit according to any one of the preceding items. 3. Detailed Description of the Invention [Industrial Application Field] The present invention relates to an optical head device used for recording/reproducing information on an optical information recording medium, and in particular has a light emitting/light receiving function that can be applied as a non-contact position sensor. The present invention relates to an optical head unit equipped with the following. [Prior Art] An optical system in a recording/reproducing device converges a laser beam emitted from a laser diode light source onto an information recording medium through a converging optical element such as an objective lens, and focuses the laser beam on the surface of the information recording medium. It is known as a device that reads information stored on an information recording medium or writes and stores information on the surface of the information recording medium. Whether optically reading or writing information, the laser beam must be accurately focused onto the surface of the information recording medium by a converging optical element such as an objective lens. Therefore, there is a need for an optical head device that operates while detecting whether or not the laser beam is converged onto the surface of the information recording medium using a converging optical element such as an objective lens. FIGS. 5A and 5B are configuration diagrams showing the layout of an optical head device related to a conventional example. In the figure, (1)
indicates a laser diode serving as a light source, and (2) indicates a laser beam flux emitted from the laser diode (1). (4) is a parallel plate beam splitter that splits the laser beam, (5) is a light collecting lens element such as a condensing lens that converges these beams, and (6) is an optical card, optical tape, or circular plate. It is an optical information recording medium such as a plate-shaped optical disk, and (7) is an information track formed on the information recording surface of the information recording medium (6), and (10) is a laser reflection from the optical information recording medium (6). This is a photodetector light receiving section that receives light (2'). Next, the operation will be explained. The diverging beam (2) emitted from the laser diode (1) is sent to the flat beam splitter (4).
) is reflected by the surface (4a) of the light beam, and is focused onto the optical information recording medium (6) by the condensing light collection lens element (5). Reflected light flux (2゛) reflected from the optical information recording medium (6)
is reflected by the back surface (4b) of the flat beam splitter (4), is slightly shifted from the output beam (2), travels in the opposite direction of travel, and is received by the photodetector light receiving section (10). In order to correctly obtain the information of the optical information recording medium (6), the light collecting spot (3) must be illuminated precisely onto the information track (7) surface. Since the reflected light beam (2') is a convergent light beam, it is transmitted from the flat beam splitter (4) to the photodetector light receiving section (
10), astigmatism occurs as is well known. Now, the flat plate beam splitter (4) is a parallel plate, and assuming that the thickness is t1, the refractive index is n, and the angle of incidence on the surface (4a) is θ [rad], the astigmatism difference Δ is given by the following equation. The reflected light beam (2') from the beam splitter (4) given the astigmatism is the output light beam (2') of the LD (1).
), and is shown by a dashed line in the figure, is 2t-tanθ-・cosθ
...With the deviation of (2), the photodetector (1
0). Here, the θ゛ is n sin θ
In such an optical head device, the photodetector light receiving section (10) detects the light reflected from the information recording medium disk when the light collection spot on the optical disk (6) is in focus. As shown in Fig. 5(b), the luminous flux obtained by
11) at a position in the optical axis direction. The photodetector light receiving section (10) has detection elements (10a), (10b), (10c), (10
d), and each of these detection sections detects the amount of incident light flux. As is well known, the output of each of these detection sections is distorted in the diagonal direction because the light collecting spot on the light receiving section (10) of the photodetector becomes a distorted spora I- (12) when a defocus occurs. The defocus of the luminous flux can be detected by summing the photoelectric conversion outputs of the opposing detection elements and calculating the difference output between the pair of opposing detection units. In other words, the left output of the sum output bare of the opposing sensing element section is
1(10a)+(10c)l-f(10b)+(1
0cl)l, and this calculation output signal is output as a focus error signal, and a focus actuator (not shown) corrects the focal shift of the light collecting spot on the optical information recording medium. On the other hand, tracking is performed as an adjustment means in the in-plane direction in order to correctly irradiate the light convergence point (3) of the optical information recording medium (6)-1 onto the information track. Although not specifically explained here, twin spot method, push-pull method, etc. can be applied to this conventional device. [Problems to be Solved by the Invention] Since the conventional optical head device was configured as described above, the following problems occurred. As mentioned earlier, the light emitting point of the laser diode (1) and the light collection spot (11) of the photodetector light receiving part (10) are δ-2・t・sinθ・tan (
It is shifted by θ゛). For example, θ=45°, t-
If it is 1 mm, then δ-0.75 mm, which is less than 1 mm. Further, at this time, the amount of deviation in the optical axis direction (x) is also as short as 1 mm or less. Therefore, there is a problem in that it is very difficult to separately arrange the laser diode (1) and the photodetector light receiving section (10) as shown in the figure. Further, as mentioned above, the photodetector light receiving section (10) must be placed at a position where the circle of least confusion (11) is irradiated, and has an adjustment means. However, as mentioned above, since it is adjacent to the laser diode (1), there is a problem that the configuration and arrangement of the adjusting means is extremely difficult. To solve this problem, a laser diode (1
) and the light convergence spot (11) are adjacent to each other by one angle or less in the optical axis and the direction perpendicular to the optical axis to form the laser diode chip and the photodetector element on the same substrate. can also be considered. The light emitting point of the laser diode (1) and the light convergence spot (1)
1) is in a conjugate relationship, so as long as the relative positional accuracy and parallelism of the flat beam splitter (4) can be ensured, the photodetector light receiving part can be positioned at the relative position from the laser diode (1) determined by calculation. This means that it is only necessary to set it, and it is possible to eliminate the need for adjusting the detector. Relative position accuracy is relatively easy if the pixel elements are formed on the same substrate, but the permissible range of parallelism of the flat beam splitter (4) is strict. For example, in FIG. 5, the laser diode (1) has a distance K to the flat beam splitter.
Jl of 15 mms flat plate beam splitter (4)
a) Incident angle 45°, n-1,5, t = '1 mm
The parallelism is a [deg], and the allowable displacement of the light convergence spot (11) with respect to the photodetector light receiving part (10) is ±10μ.
To make m, α-o, oto. (-0,6").In this way, in order to integrate the photodetector light receiving part (10) and the laser diode (1) without adjustment, the parallel beam splitter (4) must have a diameter of 1" or less. It is necessary to maintain parallelism with high precision, and the required effective area of the flat plate beam splitter is a circle with a diameter of approximately 5 mm when the numerical aperture NA of the laser diode beam is 0.1 in the above example, which is a large area. Since flatness is required with high accuracy over a wide area, there is a problem in that the cost is high to maintain these flatness over a wide area.The present invention was made to solve the above problems. It is an object of the present invention to provide an inexpensive and simple optical head device that eliminates the need to adjust the position of the light receiving part of a photodetector. The pickup optical system head device includes a light source such as a laser, a beam splitter, and a light receiving section of a photodetector in one package, and uses means for matching the relative positional accuracy between each element to a high precision state. [Function] The optical head device of the present invention can be easily constructed by combining and packaging a light converging lens and an actuator for controlling its position. This has the effect of being able to obtain signals and light convergence point position information without having to adjust the dimensions and positions of other important optical elements in the optical head. The t7a configuration of the unit will be explained with reference to the figure. In Figure 1, the laser diode (1), beam splitter (4), and photodetector light receiving section (10) have the same functions as each element of the conventional example. .The laser diode (1) is P
A semiconductor chip consisting of an N junction is used, and (1 (I) is a photodetector light receiving part for monitoring the output of the laser diode. (17) is an output window for the laser beam from the present optical head device. Shown here: laser diode (1) beam splitter (4)
, the photodetector light receiving part (10) is formed while being positioned with respect to the block (18).
8) also serves as a means for dissipating heat from the laser diode. Each important optical element in these optical head units is constructed and sealed in one package as shown in the figure, and the relative position of each optical element is set with high precision. In the case of this embodiment, as in the conventional example, for example, t-1mm5
Assuming that the numerical aperture is NA-0.1, the relative positional accuracy of the laser diode (1) and the light receiving part of the photodetector with respect to other important optical elements in the system is ±25 μm in the optical axis direction1 in the direction perpendicular to the optical axis. Adjust to ±5 μm. The overall shape of the package that determines the relative positions of such important optical elements is preferably cylindrical, and the outer diameter is preferably at most lOn+m. Although it is theoretically and practically difficult to create a circular tube package with a very small diameter, it is theoretically possible to create an optical head unit with a 5 mm diameter package (
13) is also possible. In the optical head unit (13) according to the embodiment of the present invention, the distance #E between the laser diode (1) and the beam splitter (4) is set to be very short, so that, for example, j! -3nun, beam splitter (4)
It is sufficient that the parallelism is about 3-3 at worst, and adjustment of the photodetector light receiving section (10) is not necessary. Furthermore, in the detailed embodiment of the present invention, the effective area of the beam splitter (4) can be made small, so that the surface accuracy, which is an important element, can be maintained. It is also advantageous from the point of view of the beam splitter, and can contribute to an inexpensive beam splitter. The relative positional relationship is l and the thickness t of the flat beam splitter.
If 1 slope 10 is determined, this is a value automatically determined by equation (2). Specifically, in order to ensure the above-mentioned relative distance and assemble the optical unit, the block (18) must be equipped with a laser diode (1) and a light detection:! If you create a mark, such as a groove, for positioning W (10), it will be possible to achieve ± with mechanical accuracy.
Sufficient positioning can be achieved with a positional accuracy of 5 μm. FIG. 2A, FIG. 2B, and FIG. 2C show an embodiment in which the optical head device f(13) of the present invention is applied to an optical head device. In FIGS. 2A, 2B, and 2C, (14) is an optical lens barrel, and (15) is an actuator related to focus and tracking that performs feedback drive control of the light converging lens element. The operation of the optical head unit 1-(13) according to the embodiment of the present invention is basically the same as that of the conventional example, but the optical head unit (13) and objective lens are mounted on the optical barrel (14). The optical head unit 1-(1
3) It is possible to catch the signal of the information recording medium disk (6) and the convergent light spot position information. Further, there is an effect that no adjustment work of the photodetector light receiving section or the like is required during assembly. By using this optical device, even more diverse optical head devices can be constructed. Therefore, one example of such an optical head device is shown in FIG. 2B. (16) is a reflective mirror, and since the reflective mirror (16) is configured to bend the optical path and then enter a converging optical element such as an objective lens, it usually requires a large volume and optical path space. By compressing, it is easy to install a thinner optical head L'2 (t
c. In FIGS. 2A and 2B, the optical head unit (13) of the present invention is constructed so that the central axis of the package and the optical axis of the emitted light coincide with each other, or as shown in FIG. 2C. Furthermore, the package center axis and the emitted light optical axis do not overlap, and a thinner optical head can be achieved. Although the tracking method was not particularly mentioned in the explanation of the conventional example, by forming a diffraction grating on the surface (4a) of the beam splitter (4) in the optical head unit (13), it is possible to avoid adding new optical components. Tracking using the twin spot method can be performed. Since the twin spot method itself is well known, explanation thereof will be omitted. When using the twin spot method, the information track is set on /i based on the focal point of the three beams emitted from the surface (4a) on the optical disk (6) or the zero-order beam convergence point (3). It may be necessary to adjust the rotation of the diffraction lever so that it is slightly tilted with respect to (7). In Figure 3, (3a), (3b
) is the ±1st order light, the track pitch is P1, and the interval between the θth order light and the θ order light is d. When θ is rotationally adjusted so that d=-, the tracking signal becomes 1 at its maximum. In this case, if the package center of the optical head unit (13) and the optical axis of the output light are aligned, it is only necessary to rotate and adjust the entire optical head unit (13) using the mounting part of the optical lens barrel (14). . Since the optical axis does not shift even when rotated, good light convergence characteristics can be maintained without creating an image height for the convergent optical element (5) such as the objective lens. Also, at this time, it is clear that the focus signal is not affected at all, so there is no need to adjust the photodetector. However, the photodetector light-receiving section (10) requires at least a six-divided detection section. In the above embodiment, the external shape of the optical head unit 1-(13) is shown to be cylindrical, but it is also possible to form a square package, for example, and the external shape can be selected as appropriate for each usage. Further, the optical head unit (13) of the present invention is not only applicable to the optical head device as described above, but also used for various purposes such as a position sensor as a light emitting and light receiving element. This will be explained with reference to FIG. 4 as an example. (19) is a sample, and an optical head unit (13) of the present invention and an objective lens (5) are fixed to a VT fishing rod (14). At this time, if the sample (19) is placed near the focusing position, the focus error signal is zero when the sample surface is focused, but the sample (19) is
19) in the direction of A, the focus error signal changes if there are irregularities on the surface. By calibrating the amount of unevenness and the focus error signal, the surface shape can also be investigated. By selecting the light convergence numerical aperture NA of the convergence optical element such as the objective lens, the position from the convergence optical element such as the objective lens to the surface of the light convergence spot can be changed over a wide range of measurement accuracy and measurement range. It can function as a sensor to detect. [Effects of the Invention] As described above, according to the present invention, the laser diode, the beam splitter, and the photodetector are configured in one package, so that the number of photodetectors and photodetectors can be reduced to 5! ! This eliminates the need for alignment, and it is possible to provide one stable optical head unit using an inexpensive beam splitter. By applying it as a part of an optical head device, it is possible to obtain an inexpensive optical head device with a very simple configuration, and also to realize reductions in thickness and size of the optical head device itself. 4. Brief description of the drawings Figure 1 is a configuration diagram of an optical head unit according to an embodiment of the present invention, and Figures 2A, 2B, and 2C are configurations of an optical head device to which the optical head unit of an embodiment of the present invention is applied. FIG. 3 is based on the twin spot method relating to the embodiment of the present invention. ? ! FIG. 4 is a configuration diagram showing a modified embodiment of the position sensor according to the embodiment of the present invention, and FIGS. 5A and 5B are configuration diagrams showing an optical head device related to a conventional example. In the figure, (1) is a laser diode, (4) is a flat beam splitter, (10) is a photodetector light receiving part, and (13) is a flat beam splitter.
) is an optical head unit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent: Masuo Oiwa, patent attorney (and 2 others)

Claims (4)

[Claims] (1) A laser diode light source, a flat plate optical element that reflects the emitted light beam from the laser diode light source on a first surface that is the front side and emits it, and the light returns through the same optical path as the emitted light of the flat plate optical element. The laser diode light source is composed of a photodetector light receiving section that receives a beam that is reflected by the flat plate optical device and a second surface that is the back side of the element, and that is converged at a position adjacent to the laser diode light source. An optical pickup optical head device characterized in that a flat plate optical element and a photodetector light receiving section are constructed on the same block and sealed in a predetermined package. (2) The light-receiving section of the photodetector has at least one four-division detection light-receiving element, and has means for outputting light convergence spot position information of the emitted light beam. optical pickup optical head device. (3) The optical pickup optical device according to claim 1 or 2, characterized in that a diffraction grating is arranged on the first surface of the flat optical element. (4) Claims 1 to 3, characterized in that the package for sealing has a cylindrical shape, and the center line of the cylindrical package coincides with the optical axis of the emitted light beam. The optical pickup optical head device according to any one of the preceding items.