JPH05166218A - Optical pickup device - Google Patents

Abstract

PURPOSE:To perform stable recording and reproduction by eliminating the error of a track control signal. CONSTITUTION:An outgoing light from a semiconductor laser element 1 is converted to a parallel luminous flux by a coupling lens 2, a luminous flux in the center part of the parallel luminous flux is condensed by an objective lens 5 and a minute light spot having a diameter of about 1mum is formed on the recording layer of the optical disk 6 and the information is recorded and reproduced. A ring-shaped bisected photodetector 12 is disposed between the coupling lens 2 and the objective lens 5 so as to a luminous flux out of the luminous flux reaching the objective lens 5 is received and the deviation of the outgoing light angle from the semiconductor laser element 1 is adjusted by the difference signal of the output from light receiving faces 12a and 12b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device for recording, reproducing or erasing information by irradiating an optical information recording medium with light emitted from a semiconductor laser element as a minute spot light.

[0002]

2. Description of the Related Art Generally, in an optical pickup device of this type, reflected light from an optical information recording medium such as an optical disc is separated from incident light and guided to a split light receiving element so that spot light and track position are separated from each other. It is output as a track error signal indicating the deviation.

FIG. 6 shows an optical system of a general optical pickup device. Light emitted from a semiconductor laser device 1 is collimated by a coupling lens 2, and a beam splitter 3 and a quarter wave plate 4 are provided. Through the objective lens 5 to form a minute spot light having a diameter of about 1 μm on the recording layer of the optical disk 6.

The reflected light from the optical disk 6 is collimated by the objective lens 5, transmitted through the quarter-wave plate 4, reflected at a right angle by the beam splitter 3 and separated from the incident light, and then the condenser lens. 7, the half of the convergent light beam 10 is received by the first two-divided light receiving element 8 and is output as a track error signal, and the remaining light beam is the second two-divided light receiving element arranged at the converging point. The light is received at 9 and is output as a focus signal. FIG. 7 shows light receiving portions 8a ', 8b' which are received by the light receiving surfaces 8a, 8b of the first two-divided light receiving element 8 by the above-mentioned convergent light beam 10.

FIG. 8 shows the position of the spot light formed on the recording layer of the optical disk 6 and the light of the light receiving portion formed on the light receiving surfaces 8a and 8b of the first two-divided light receiving element 8 corresponding thereto. The intensity distribution is shown, and the track error signal can be obtained from the difference signal between the outputs A and B from the light receiving surfaces 8a and 8b.

Now, in the state shown in FIG. 8A in which the spot light focused by the objective lens 5 is accurately formed on the information track 11 of the recording layer of the optical disk 6,
The light intensity distribution received by the light receiving surfaces 8a and 8b is symmetrical with respect to the dividing line 8c parallel to the information track 11, and the respective light receiving amounts A and B at that time are A = B.

In FIG. 8B, the position of the spot light formed on the recording layer of the optical disc 6 is displaced from the information track 11, and the light intensity received by the light receiving surfaces 8a and 8b is the dividing line 8.
The state is asymmetric with respect to c and A> B.

FIG. 9 shows the state of the track error signal when the spot light crosses the information track 11. The normal track error signal shows a sin curve which is vertically symmetrical about the 0V level, as shown in FIG. FIG. 2B shows a state where the semiconductor laser element 1 is tilted from the normal state and the center of the intensity of the parallel light flux transmitted through the coupling lens 2 and the center of the objective lens 5 do not coincide with each other. In some cases, an offset x occurs and an error occurs in the track error signal, making it impossible to perform normal tracking.

The cause of the offset in the track error signal due to the inclination of the semiconductor laser device 1 is considered as follows. That is, in general, the intensity peak P of the semiconductor laser light has a maximum deviation of 3 ° from the reference mounting position of the semiconductor laser element 1 as shown in FIG. Now, when the intensity peak of the semiconductor laser light deviates from the reference mounting position by an angle θ,
As shown in, the shift amount Δ of the light intensity peak P of the parallel light from the optical axis L can be expressed by the following equation, where f is the focal length of the coupling lens 2. Δ = f × sin θ

Here, if θ = 3 ° and f = 15 mm,
Δ = 15 × sin3 ° = 0.785 mm, that is, the deviation amount of the parallel light intensity peak P from the optical axis L is 785 μm.

Conventionally, as a method of adjusting the two-divided light receiving element 8 for detecting a track error in the assembling of the optical pickup device, as shown in FIG. 12, the light receiving surfaces 8a and 8b from the portion where the information track of the optical disk 6 does not exist. The mounting position of the two-divided light receiving element 8 is adjusted so that the intensity distributions of the reflected light received by are equal, that is, the outputs A and B of the light receiving surfaces 8a and 8b are A = B.

[0012]

However, in such a conventional optical pickup device, when the above adjustment is performed, the intensity peak P of the parallel light is the optical axis of the objective lens 5 as shown in FIG. When it is deviated from L, the dividing line 8c of the two-divided light receiving element 8 is deviated from a predetermined position as shown in FIG. 12 even if the outputs of both light receiving surfaces are A = B. is there.

Therefore, when the spot light from the objective lens 5 is formed on the information track by using the optical pickup device adjusted as described above, A> B as shown in FIG. 13 even if there is no track error. Conversely, even when there is a track error, A = B and an error occurs in the track error signal.

FIG. 14 shows the relationship between the inclination of the semiconductor laser device 1 and the track control signal error. It can be seen that a 1 ° inclination of the semiconductor laser device 1 causes a track control signal error of 0.03 μm. Generally, the error of the track control signal is required to be 0.01 μm or less, and therefore the inclination between the optical axis L of the optical system in the optical pickup device and the light emission direction from the semiconductor laser device 1 must be adjusted to 20 ′ or less. I won't.

The present invention has been made in view of the above points, and an object thereof is to provide an optical pickup device capable of performing stable recording, reproduction or erasing by eliminating an error of a track control signal. To do.

[0016]

In order to achieve the above object, the present invention allows light emitted from a semiconductor laser device to be transmitted through a beam splitter as a parallel light beam by a coupling lens and then condensed by an objective lens to record optical information. In an optical pickup device for recording, reproducing or erasing information by forming a minute spot light on a medium, light emitted from the semiconductor laser element is received by a split light receiving element having a plurality of light receiving surfaces, and its output Based on the above, there is provided an optical pickup device provided with adjusting means for adjusting the inclination of the semiconductor laser device.

Further, in the above optical pickup device, there is also provided an optical pickup device provided with control means for controlling the output of the semiconductor laser element based on the output from the divided light receiving element.

Furthermore, it is preferable that the split light receiving element receives a light beam outside the light beam incident on the coupling lens, and may also receive the reflected light from the mirror provided on the outer peripheral portion of the coupling lens. It is possible. Further, it is preferable that the mirror is a molded product integrally molded with the coupling lens.

[0019]

By configuring the optical pickup device according to the present invention as described above, the deviation of the emission angle of the semiconductor laser element can be detected by the difference signal of the divided light receiving elements, and the track error can be adjusted by adjusting the deviation. It becomes possible to eliminate signal errors.

Then, if the output of the semiconductor laser element is also controlled based on the output of the divided light receiving element,
It is not necessary to separately provide a light receiving element for monitoring. Further, if the split light receiving element receives a light beam outside the light beam incident on the coupling lens, all the emitted light from the semiconductor laser device can be effectively used.

When the light receiving element receives the reflected light from the mirror provided on the outer peripheral portion of the coupling, an inexpensive light receiving element which is usually used can be used.
Furthermore, if the mirror is formed integrally with the coupling lens, the productivity is good and the optical pickup device can be supplied at a low cost.

[0022]

Embodiments of the present invention will be specifically described below with reference to the drawings. Since the entire optical system has the same structure as that shown in FIG. Only the system is shown. FIG. 1 is a configuration and circuit diagram showing a main part optical system of an embodiment of the present invention, and FIG. 2 is a diagram showing a light intensity distribution of emitted light from a semiconductor laser device 1.

In this embodiment, a ring-shaped two-divided light receiving element 1 with the optical axis L as the center in the parallel light flux from the coupling lens 2 to the objective lens 5 as shown in FIG.
2 is provided, and the light receiving surface thereof is divided into two substantially equal parts by a dividing line 12c to form a pair of light receiving surfaces 12a and 12b. A tubular light beam outside the light beam entering the objective lens 5 is received by the light receiving surfaces 12a and 12b. So that it receives light.

The light emitted from the semiconductor laser device 1 is collimated by the coupling lens 2 and the light flux at the center thereof is condensed by the objective lens 5 to form a minute spot light on the recording layer of the optical disc 6. Then, the light flux outside thereof is received by the light receiving surfaces 12a and 12b of the two-divided light receiving element 12. The light beams received by the light receiving surfaces 12a and 12b correspond to the shaded portions 1a and 1b of the light intensity distribution curve shown in FIG. 2, the portion 1a being the light receiving surface 12a and the portion 1b being the light receiving surface 12b. Received light.

When the direction of the light emitted from the semiconductor laser device 1 is parallel to the optical axis L, the outputs S12a and S12b from the light receiving surfaces 12a and 12b are equal. Here, when the tilt signal of the emitted light of the semiconductor laser device 1 is T, T = S12
a-S12b = 0. If the emitted light of the semiconductor laser device 1 is inclined, the areas of the portions projected onto the light receiving surfaces 12a and 12b are different, and the outputs S12a ≠ S12b and T ≠ 0. Therefore, the tilt of the semiconductor laser device 1 may be adjusted by a known tilt adjusting means (not shown) so that the tilt signal T becomes zero.

The two-divided light receiving element 12 is not limited to a ring shape as long as it is a light receiving element having a plurality of light receiving surfaces and can receive a light beam outside the objective lens light beam. It may have any shape, and its position can be provided at any position between the coupling lens 2 and the objective lens 5.

Next, FIG. 3 shows another embodiment of the present invention, in which the ring-shaped two-divided light receiving element 13 is connected to the coupling lens 2 between the semiconductor laser element 1 and the coupling lens 2. Is provided at a position capable of receiving a light flux outside the light flux of, and the light-receiving surface is divided into two equal parts by a dividing line 13c passing through the center as shown in FIG.
3b is formed. The light fluxes received by the light receiving surfaces 13a and 13b are shaded portions 1c and 1d of the light intensity distribution curve shown in FIG. 4, and the light receiving surfaces 13a and 13b.
Let S13a and S13b be the outputs output from S, and T be the tilt signal of the emitted light, the tilt signal T is T = S13a-S1.
3b can be obtained.

According to this embodiment, as is clear from a comparison between FIG. 4 and FIG. 2, a larger amount of received light can be obtained than in the previous embodiment, and the detection sensitivity of the tilt signal T can be increased. At the same time, the diameter of the coupling lens 2 can be reduced.

FIG. 5 shows still another embodiment of the present invention, in which a ring-shaped collar portion 14 is integrally molded on the outer peripheral portion of the coupling lens 2 as shown in FIG. The flange portion 14 is formed by molding or the like, and a spherical or aspherical reflecting surface 14 is formed on the surface of the collar portion 14 facing the semiconductor laser device 1.
c and 14d are formed respectively, and a pair of light receiving elements 15 and 16 are formed to reflect the outer light rays of the light emitted from the semiconductor laser element 1 by the reflecting surfaces 14c and 14d and apply the divided light receiving elements.
To receive light respectively. Also in this case, if the outputs from the light receiving elements 15 and 16 are S15 and S16, the tilt signal T can be obtained by T = S15-S16. The collar portion 14 may be provided on the lens barrel portion of the coupling lens 2 instead of being integrated with the coupling lens 2.

According to this embodiment, the light receiving element does not need to have a special shape as in the above-described embodiments, so that an ordinary inexpensive one can be used. In addition, the collar 14
If is formed integrally with the coupling lens 2,
The productivity is improved and it can be supplied at a lower cost.

Further, in each of the above-mentioned embodiments, a control means for controlling the output of the semiconductor laser element 1 using the sum signal of the light-receiving elements 12, 13, 15, 16 is provided, and each of the above-mentioned light-receiving elements is used as a semiconductor laser element It is also possible to use it as a monitor light receiving element.

[0032]

As described above, in the optical pickup device according to the present invention, the light emitted from the semiconductor laser element is received by the divided light receiving elements having a plurality of light receiving surfaces, and the inclination of the semiconductor light receiving element is determined based on the output thereof. Since it was adjusted, the error of the track error signal is eliminated and stable recording is performed.
Playback is possible.

If the output of the semiconductor laser element is also controlled based on the output from the above-mentioned divided light receiving element, it is not necessary to separately provide a light receiving element for monitoring the semiconductor laser element, and the optical pickup device can be provided. It can be supplied at low cost.

If the split light receiving element receives a light beam outside the light beam incident on the coupling lens, all the light emitted from the semiconductor laser device can be effectively used, and the light beam outside the light beam can be effectively used. If the light receiving element that receives the light receives the reflected light from the mirror provided on the outer peripheral portion of the coupling lens, it is possible to use an inexpensive light receiving element that is widely and generally used.

Further, when the above-mentioned mirror is a molded product integrally molded with the coupling lens, it is possible to achieve a lower cost and higher accuracy than the case where the mirror is formed as a single body and attached to the outer peripheral portion of the coupling lens.

[Brief description of drawings]

FIG. 1 is a configuration and circuit diagram showing a main part optical system of an embodiment of the present invention.

FIG. 2 is a diagram showing a light intensity distribution of emitted light of the same semiconductor laser device.

FIG. 3 is a configuration and a circuit diagram showing an essential part optical system of another embodiment of the present invention.

FIG. 4 is a diagram showing a light intensity distribution of emitted light of the same semiconductor laser device.

FIG. 5 is a configuration and circuit diagram showing a main part optical system of still another embodiment of the present invention.

FIG. 6 is a configuration and circuit diagram showing an optical system of a general optical pickup device.

FIG. 7 is an explanatory view showing a light receiving portion of the two-divided light receiving element.

FIG. 8 is an explanatory view showing the principle of detecting the track error signal.

FIG. 9 is a waveform diagram of the same track signal.

FIG. 10 is a diagrammatic view showing the relationship between the emission angle and the light intensity of the semiconductor laser device.

FIG. 11 is an optical path diagram when the emission angle of the semiconductor laser device is tilted.

FIG. 12 is an explanatory diagram showing an adjustment state at the time of assembling when the two-divided light receiving element is displaced.

FIG. 13 is an explanatory diagram showing a detection state of the track error signal of the same.

FIG. 14 is a diagram showing the relationship between the tilt of the semiconductor laser device and the error of the track control signal.

[Description of Reference Signs] 1 semiconductor laser element 2 coupling lens 3 beam splitter 4 1/4 wavelength plate 5 objective lens 6 optical disk (optical information recording medium) 7 condensing lens 8 first split light receiving element 9 second 2 Split light receiving element 10 Convergent light flux 11 Information track 12, 13 2 Split light receiving element 14 Collar portion 14c, 14d
Mirror 15,16 Light receiving element

Claims (5)

[Claims] 1. Recording of information by emitting light emitted from a semiconductor laser element as a parallel light flux through a coupling lens and passing through a beam splitter and condensing by an objective lens to form a minute spot light on an optical information recording medium. In an optical pickup device for reproducing or erasing, an adjusting means for receiving the emitted light from the semiconductor laser element by a divided light receiving element having a plurality of light receiving surfaces and adjusting the inclination of the semiconductor laser element based on the output thereof is provided. An optical pickup device characterized by being provided. 2. The optical pickup device according to claim 1, further comprising control means for controlling an output of the semiconductor laser element based on an output from the divided light receiving element. 3. The optical pickup device according to claim 1, wherein the split light receiving element is adapted to receive a light beam outside the light beam incident on the coupling lens. 4. The optical pickup device according to claim 1, wherein the split light receiving element is adapted to receive the reflected light from the mirror provided on the outer peripheral portion of the coupling lens. 5. The optical pickup lens according to claim 4, wherein the mirror is a molded product integrally molded with the coupling lens.