JPH0536103A - Position detector of objective lens - Google Patents

Abstract

PURPOSE:To reduce the size and weight of a moving part including an objective lens and to improve the driving sensitivity of the moving part by providing notches in both side parts in the direction parallel with the tangent direction of the tracks provided on an information recording medium. CONSTITUTION:An incident pupil 6 is nearly circular in shape and is provided with square notches on both side in a direction Y. The light beam which is made incident on an optical disk 8 and is reflected and diffracted by the recording pits formed in the tracks of the optical disk 8 passes the objective lens 4 again and is made incident on a half mirror 3 through the incident pupil 6. The beam past the half mirror 3 is made incident on a photodetector 9 and forms a light spot 10. The notches provided in the incident pupil 6 in such a manner are formed in the positions where the influence of the + or -1st order diffracted light of the reflected beam is most hardly received and, therefore, there are substantially no errors in the moving quantity of the objective lens 4, i.e., the correction value of push-pull signals.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens position detecting device, and particularly to an objective lens effectively applicable to an optical pickup device for recording / reproducing optical information on / from an optical information recording medium. The present invention relates to a position detection device.

[0002]

2. Description of the Related Art An optical pickup device detects a positional deviation between a light beam spot and a track, that is, a tracking error, in order to accurately follow the light beam spot on a desired track on an information recording medium. Based on the detected value, the objective lens is moved in the direction (tracking direction) orthogonal to the track direction to correct the tracking error.

The push-pull method is well known as one of methods for detecting such a tracking error. This method uses the fact that when a single light beam is applied to a track formed on an information recording medium such as an optical disk, the light diffraction pattern becomes asymmetrical depending on the deviation of the light beam spot in the tracking direction from the track. Then, the reflected light beam from the information recording medium is detected by a photodetector divided in two in a direction parallel to the tangential direction of the track on the information recording medium, and the differential output of two light receiving regions of this photodetector is detected. Is obtained to obtain a tracking error signal.

In this push-pull method, when the objective lens itself moves in the tracking direction, or when the optical disc is tilted and the optical axis is deviated, the spot on the photodetector also becomes the dividing line of the photodetector. There is a drawback that the tracking error signal is offset in parallel due to the parallel movement in the orthogonal direction.

Various proposals have been made to overcome such drawbacks. For example, in Japanese Unexamined Patent Publication No. 3-66032, as shown in FIGS. 12 and 13, the center of a photodetector 50 for detecting a reflected light beam from the optical disc 44 is parallel to the direction of a track provided on the optical disc. The photodetector 50 is provided in which three dividing lines 50p, 50q, 50r are provided in different directions, and the light receiving region is divided into four regions 50a, 50b, 50c, 50d from the left. In this case, in these light receiving regions defined by the dividing lines 50p, 50q, 50r, when the objective lens 43 is at the substantially central position of the track, the light spot 47 is at a position substantially symmetrical with respect to the central dividing line 50q. Is formed. In this example, the light receiving area 50
a and 50c are connected to obtain the sum of the electric signals of these regions, while the light receiving regions 50b and 50d are connected to obtain the sum of the electric signals of these regions. The tracking error signal is obtained by taking the difference.

FIGS. 13A and 13B show a photodetector 50.
FIG. 3 is an enlarged view showing a light spot 47 formed on this photodetector. The optical spot 47 is the optical disc 44.
It is reflected and diffracted by the upper track, and the 0th-order diffracted light 47a, ± 1
It is composed of the next-order diffracted light 47b. Also, reference numeral 47
x indicates the center position of the light spot 47.

FIG. 13 (a) shows the position of the light spot 47 on the photodetector 50 when the objective lens 43 is located substantially in the center of the track on the optical disc 44. In this case, the center 47x of the light spot 47 is located on the dividing line 50q at the center, and the 0th order diffracted light is mainly in the light receiving regions 50b and 50c, and the ± 1st order diffracted light is mainly emitted in the light receiving regions 50a and 50d. To receive. The output of the differential amplifier 46 at this time, that is, the tracking error signal is a signal without offset.

In FIG. 13B, the objective lens 43 is shown in FIG.
The position of the light spot 47 on the photodetector 50 when moved in the + direction shown in FIG. In this state, the center 47x of the light spot 47 having the highest light intensity is located at the light receiving region 5
Move to be located at 0c. Therefore, while the light amount increases in the light receiving regions 50c and 50d, the light receiving region 50c
In a and 50b, the light quantity is reduced. Therefore, by appropriately setting the distance between the dividing lines 50p and 50r with respect to the dividing line 50q, it is possible to make the amount of increase or decrease in the light amount in each light receiving region substantially the same. Therefore, the light receiving regions 50b and 50d are connected to obtain the sum of electric signals generated in these regions, and the light receiving region 5
The offset of the tracking error signal can be suppressed by connecting 0a and 50c, taking the sum of the electric signals generated in these regions, and taking the difference of these sums by the differential amplifier 46.

Another method for reducing the offset of the tracking error signal is disclosed in Japanese Patent Application Laid-Open No. 62-102433. This is shown in FIGS.
As shown in, a support frame 64 for supporting the objective lens 63
, A pair of photodetectors 61a and 61b (FIG. 14) are provided so as to be located on both sides of the objective lens, or a pair of reflecting mirrors 62a and 62b are provided, and further on the optical path of the light reflected by the reflecting mirrors. Photodetectors 61a and 61b are provided (FIG. 15) so that a part of the incident light beam is emitted from these photodetectors 6
The position of the objective lens in the tracking direction is detected by detecting with 1a and 61b and taking the differential output.

[0010]

However, in the device disclosed in Japanese Patent Laid-Open No. 3-66032, the photodetector 50 is used.
The light intensity distribution of the light spot in the direction orthogonal to the upper dividing line is maximum in the center and flat. Therefore, even if the light spot moves on the photodetector 50 in the direction orthogonal to the dividing line, the change in the amount of light in the vicinity of the center of the photodetector 50 is small, and therefore the correction sensitivity of the offset of the tracking error is low. Will end up.

Further, in this apparatus, the optical disc 4
The focus state of the light spots on the four surfaces changes,
When the diameter of the light spot on the photodetector 50 changes, the ratio of the central light receiving regions 50b and 50c to the size of the light spot 47 also changes, which causes a problem that the correction value of the tracking error signal deviates. is there.

In the apparatus disclosed in Japanese Patent Laid-Open No. 62-102433, the moving amount of the light spot formed on the photodetector (not shown) for tracking error detection is not directly measured, and the objective lens is not used. This is because the photodetectors 61a and 61b separately provided on the lens holder 64 of 63 detect the position of the objective lens 63 by receiving a part of the incident light beam. Therefore, when the emitted light from the laser light source (not shown) is tilted or the like, the position detection of the objective lens 63 is deviated, and this deviation also deviates the correction value of the tracking error signal. is there.

Further, in this apparatus, since the photodetectors 61a and 61b for detecting the position of the objective lens 63 or the reflection mirrors 62a and 62b are formed integrally with the objective lens 63, a focusing error or a tracking error is generated. When driving the objective lens 63 for correction, these photodetectors 61a and 61b and the reflection mirror 6 are used.
2a and 62b move in the focus direction or the tracking direction together with the objective lens 63. For this reason, there is a drawback that the mass and size of the movable portion become large and the driving sensitivity of the objective lens 63 is lowered. Further, in this device, since the photodetectors 61a and 61b and the reflection mirrors 62a and 62b are formed integrally with the objective lens 63, the driving device for the objective lens 63 cannot be downsized.

Further, when the objective lens 63 is moved in the focus direction or the tracking direction in order to correct the focusing error or the tracking error, for example, the mounting error of the support spring supporting the objective lens or this support spring is used. The objective lens 63 itself may be tilted due to the resonance or the like, but in this apparatus, the differential output of the two photodetectors 61a and 61b changes due to the tilt of the objective lens 63, There is also a drawback that an error occurs in the correction value.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a novel and useful objective lens position detecting device. By applying the device according to the present invention to an optical pickup device, the amount of movement of the objective lens in the tracking direction is detected and the offset of the tracking error signal is corrected more appropriately without obstructing downsizing of the drive device of the objective lens. can do. Further, the position detecting device of the objective lens of the present invention can be used for a two-step servo of the objective lens or the like.

[Means and Actions for Solving the Problems]

In order to solve the above-mentioned problems, the position detecting device for an objective lens of the first invention of the present application includes at least a light source, an objective lens for projecting a light beam emitted from the light source as an optical spot on an information recording medium, and Of the reflected light beam reflected from the information recording medium and transmitted through the objective lens, a photodetector that does not include a central portion and receives a light beam that is not affected by diffraction in the information recording medium, The position of the objective lens is detected based on the output of the photodetector.

The objective lens position detecting device according to the second aspect of the present invention includes at least a light source, an objective lens that projects a light beam emitted from the light source as a light spot on an information recording medium, and moves integrally with the objective lens. And a photodetector for receiving the light beam that has passed through the light transmitting portion that projects the light beam onto the information recording medium, and detecting the position of the objective lens based on the output of the photodetector. It is a feature.

As described above, in the position detecting device for the objective lens of the first invention of the present application, the central part of the reflected light beam reflected by the information recording medium and transmitted through the objective lens is not included, and the position of the information recording medium is reduced. A photodetector that receives a light beam that is not affected by diffraction is provided, and the position of the objective lens is detected based on the amount of movement of this light beam on the photodetector. In the objective lens position detecting device according to the second aspect of the present invention, the objective lens position detecting device detects the light beam that moves integrally with the objective lens and transmits the light beam that transmits the light beam onto the information recording medium. I am trying to detect the position. Therefore, the apparatus of the present invention can accurately detect the position of the objective lens, and
When the device of the present invention is applied to an optical pickup device or the like,
The offset value of the focus error signal or tracking error signal can be corrected with good sensitivity. Further, since the position of the objective lens is detected by using the reflected light from the information recording medium and the photodetector for detecting the signal, a photodetector dedicated to detecting the position of the objective lens is not required. The size and weight of can be reduced. Also,
Even if there is a tilt of the light emitted from the laser light source, a tilt of the objective lens itself, and the like, the position of the objective lens can be accurately detected, and the correction value does not shift due to these.

[0019]

1 is a diagram showing the overall construction of a first embodiment of an objective lens position detecting device of the present invention. The laser beam emitted from the laser light source 1 is collimated by the collimator lens 2
Then, it becomes a parallel beam, enters the half mirror 3, and the optical path can be bent by 90 °. This laser beam is further focused by the objective lens 4 supported by the lens holder 5 and is incident on the optical disc 8 which is an information recording medium to form a light spot. In the following figures, the X direction is the direction orthogonal to the tangential direction of the track on the optical disk 8, and the Y direction is the tangential direction of the track.

An entrance pupil 6 is formed in the lens holder 5, and the shape of the entrance pupil 6 is shown in FIG. As is clear from FIG. 2, the entrance pupil 6 has a substantially circular shape, and square notches 7a and 7b are provided on both sides in the Y direction. The light beam that is incident on the optical disk 8 and is reflected and diffracted by the recording pits formed on the track of the optical disk 8 passes through the objective lens 4 again, enters the half mirror 3 through the entrance pupil 6, and then passes through the half mirror 3. The light beam passes through the light detector 9 and forms a light spot 10. The shape of the light spot 10 is shown in the plan view of the photodetector 9 shown in FIG. The rectangular notches 10a and 10b formed on both sides of the light spot 10 in the Y direction correspond to the notches 7a and 7b provided in the entrance pupil 6, respectively.

The photodetector 9 is divided into two in the Y direction by a dividing line 9g. The dividing line 9g is divided into three parts so that the center is slightly shortened, and the photodetector 9 is directed toward this dividing point. Further dividing lines 9h, 9i, 9j, 9k from the respective corners of
Is provided, and is divided into 6 as a whole by these dividing lines 9g to 9k. The position of the light spot 10 on the disk 8 when the light spot is in the on-track state is shown by a solid line in FIG. The broken line shows the state in which the objective lens 4 moves in the X direction and the light spot 10 on the photodetector 9 moves in the X direction along with this movement.

Each light receiving area 9a, 9b, 9 of the photodetector 9
A push-pull signal = [9a-9b] is obtained from the outputs of c, 9d, 9e, and 9f, and the amount of movement of the light spot 10 in the X direction when the objective lens 4 moves in the X direction, that is, a push-pull signal The correction signal of is obtained from the correction signal = [9c + 9e] − [9d + 9f]. Therefore, the corrected push-pull signal in which the amount of movement of the objective lens 4 in the X direction is corrected can be obtained by calculating the corrected push-pull signal = [push-pull signal] −k [correction signal]. Here, k is a coefficient for optimally correcting the push-pull signal. It should be noted that the correction signal can be normalized by dividing the value of the correction signal by the total light amount of the photodetector 9 so that the correction signal can be obtained regardless of the total fluctuation of the light amount incident on the photodetector 9. Further, the coefficient k can be set to 1 by determining the dividing line of the photodetector 9 so that the change amount of the push-pull signal and the change amount of the correction signal are the same.

As described above, in the first embodiment of the present invention, the notches 7a and 7b provided in the entrance pupil 6 are formed at the positions where they are least susceptible to the ± first-order diffracted light of the reflected beam. An error does not easily occur in the movement amount of the objective lens 4, that is, the correction value of the push-pull signal. Since the notches 7a and 7b are formed on both sides of the entrance pupil 6 in the Y direction, the correction signal is less affected by the movement of the light spot on the photodetector 9 in the Y direction.

3 and 4 are views showing a second embodiment of the present invention. The overall structure is similar to that of the first embodiment shown in FIGS. 1 and 2, but the shape of the entrance pupil 30 is such that a light transmitting portion remains at the center of both ends in the Y direction of the lens holder 5, as shown in FIG. In this way, the convex portions 30a, 30b, 30c, 30d are provided,
Recesses (light transmitting portions) are formed on both ends as a whole. Further, the photodetector 31 is divided into two in the X direction by the dividing line 31g, further divided into three in the Y direction by the dividing lines 31h and 31i, and is divided into six as a whole.

The push-pull signal is obtained from [push-pull signal] = [31a + 31b + 31c]-[31d + 31e + 31f], and the movement amount of the light spot 32 in the X direction is obtained from [X-direction movement amount] = [31a + 31c]-[31d + 31f]. be able to. In this embodiment, the error detection in the focus direction is performed by using the so-called beam size method, and therefore the focus error signal can be obtained from [focus error signal] = [31b + 31e] − [31a + 31c + 31d + 31f].

FIG. 5 shows the movement amount of the light spot 32 in the X direction on the photodetector 31 by simulating the second embodiment, and the movement amount and the light spot of the objective lens 4 in the X direction at this time. 9 is a graph showing the relationship between 32 and the amount of movement in the X direction. However, the movement amount of the light spot on the photodetector 31 is normalized by calculating {[31a + 31c] − [31d + 31f]} / [31a + 31c + 31d + 31f]. From this graph, it can be seen that the position of the objective lens 4 can be obtained from a signal with good linearity and sensitivity. The light that passes through the cutout portion of the entrance pupil 6 and enters the photodetector is closer to the center of the light spot in the X direction as compared with the first embodiment, so the amount of incident light is large, and this light is The sensitivity is improved because it is hardly affected by diffraction. Further, since the division of the photodetector for focus detection and tracking error detection is used, no extra division or preamplifier is required. Further, in this embodiment, the convex portions are provided on both sides of the lens holder 5 in the Y direction, but only one side 30a, 30b may be provided. Even in this case, the light spot 32 similar to that shown in FIG. 4 is formed in the light spot 32, and in this case, there is an effect that the light amount loss due to the convex portion 30 of the emitted light of the objective lens 4 becomes half of that in the second embodiment. is there.

6 and 7 are views showing the shape of the entrance pupil 6 and the shape of the light spot 12 formed on the photodetector 9 according to the third embodiment of the present invention. Since the configuration other than the shape of the light spot generated on the photodetector 9 and the shape of the entrance pupil 6 is the same as that of the first embodiment, the drawings and the description thereof are omitted.

In the third embodiment, the shape of the entrance pupil 6 is as shown in FIG. That is, on both sides of the entrance pupil 6 provided in the lens holder 5 in the Y direction, the convex portions 11a,
11b is formed. Therefore, in the light spot 12 formed on the photodetector 9, the defective portions 12a and 12b are generated on the dividing line in the Y direction. The dividing lines 9g to 9k of the photodetector 9 are constructed in the same manner as in the first embodiment, and the push-pull correction signal can be obtained in the same manner as in the first embodiment described above.

8 and 9 are views showing a fourth embodiment of the present invention. FIG. 8 is a diagram showing an outline of the entire optical pickup device, and FIG. 9 is a diagram showing the shape of the entrance pupil 6 provided in the lens holder 5 of the objective lens 4. Since the configuration other than the shapes of the lens holder 5, the entrance pupil 6 and the photodetector 16 is the same as that of the first embodiment, the description thereof will be omitted.

As shown in FIG. 8, a circular entrance pupil 6 is formed in the lens holder 5, and openings 15a, 1 are formed on both sides of the entrance pupil 6 in the Y direction at positions apart from the entrance pupil 6.
5b is formed. The incident light beam reflected by the half mirror 3 enters the objective lens 4 through the entrance pupil 6, is reflected and diffracted by the optical disc 8, and is again objective lens 4.
The photodetector 1 passes through the half mirror 3 via the entrance pupil 6.
The light spot 17 is made incident upon the light beam 6 to form a light spot 17. On the other hand, a part of the incident light beam passes through the openings 15a and 15b and directly passes through the optical disk 8 without passing through the objective lens 4.
The light beam that is incident on and reflected by the aperture 15a,
After passing through 15b again, it is incident on the photodetection regions, which will be described later, provided on both sides of the photodetector 16 in the Y direction through the half mirror 3 to form light spots 18a and 18b.

The photodetector 16 comprises a first light receiving area 16a and a second light receiving area 16b for receiving the light spot 17.
Light receiving area and two four-divided light receiving areas 16c, 16d, 16e.
The second light receiving region is composed of 16f, 16g, 16h, 16i, and 16j, and is divided into 10 as a whole. The amount of movement of the light spots 18a and 18b is the same as the amount of movement of the light spot 17.

In the fourth embodiment, the push-pull signal is obtained from [push-pull signal] = [16a-16b], and the movement amount of the light spots 18a and 18b in the X direction is [the movement amount in the X direction] = [ 16c + 16d + 16g + 16h] − [16e + 16f + 16i + 16j]. Therefore, the corrected push-pull signal in which the amount of movement of the objective lens 4 in the X direction is corrected can be obtained from the corrected push-pull signal = [push-pull signal] -k [movement amount in the X-direction].

In the present embodiment, the light spots 18a and 18b for detecting the position of the objective lens 4 are made of beams directly reflected by the optical disk 8 without being condensed by the objective lens 4. It is not diffracted by the optical disc 8 and therefore there is no error caused by the diffraction of light. Further, the entrance pupil 6 of the objective lens 4 has a conventional circular shape, and therefore the signal detection performance of the light spot 17 does not deteriorate.

When the critical angle detection method is used for focus error detection, it is also possible to detect the amount of movement of the light spots 18a, 18b in the Y direction and use this for offset correction of the focus error signal. Light spot 18
The amount of movement of a and 18b in the Y direction can be calculated by [the amount of movement in the Y direction] = [16c + 16e + 16g + 16i] − [16d + 16f + 16h + 16j]. Since the light spots 18a and 18b are not affected by the light diffraction by the optical disk 8 and are formed from the light beam that has not passed through the objective lens 4, the position of the objective lens 4 is deviated in the focusing direction or the tracking direction. Even if the light spot 1
The light amount of 8a and 18b does not change. Therefore, among the light receiving regions of the photodetector 16, 16c, 16d, 16e, 16
It is also possible to take the sum of f and use this for the measurement of the reflectance of the optical disk 8.

In this embodiment, the lens holder 5
Although the two openings 15a and 15b are provided in the above, the number of openings may be one. Further, although the openings 15a and 15b are provided on both sides of the entrance pupil 6 in the Y direction, they may be provided at any location such as on both sides of the entrance pupil 6 in the X direction. The shape of the entrance pupil is the first
Similar to the embodiment, an opening or a flat portion having a size that covers the notch is provided at the position of the objective lens 4 corresponding to the notch of the entrance pupil in the first embodiment, and the light is incident on the objective lens 4. Even if a part of the light is directly incident on the disk 8 without being condensed, the same effect as that of the present embodiment can be obtained.

FIG. 10 is a diagram showing a fifth embodiment of the present invention. In this embodiment, the shape of the objective lens 20 is modified so that a reflected beam that is not affected by diffraction on the optical disk 8 is taken out and the position of the objective lens 20 is detected. That is, a lens portion 20a for forming a signal reading spot and a lens portion 20b having a small NA for forming a position detecting spot of the objective lens 20 on the photodetector 9 are formed on the objective lens 20. After being formed, each reflected beam is received by a photodetector that is divided into two in the X direction, and by taking the respective differentials, the push-pull signal and the correction signal (the amount of movement of the objective lens) are obtained, and the objective A corrected push-pull signal in which the amount of lens movement is corrected is obtained.

FIG. 11 is a diagram showing a sixth embodiment of the present invention. In this example, instead of moving the objective lens 4 in the tracking direction, the galvano mirror 21 is used to adjust the tracking error. Even in this case, the photodetector 9 is changed according to the rotation angle of the galvanometer mirror 21.
Since the upper light spot 10 moves in the X direction, the rotation angle of the galvanometer mirror 21 can be detected by taking the differential output of [9c + 9e]-[9d + 9f] from the output of the light receiving area of the photodetector 9. It is possible to correct the push-pull signal using this signal.

In the above-described first to sixth embodiments, the amount of movement of the light spot on the photodetector 9 or 16 is detected, and this detection result is used to correct the tracking error signal. It is also possible to use the movement amount of the light spot on the photodetector detected by using the device of the invention for other purposes. For example, Japanese Patent Laid-Open No. 60-76037 discloses a means for measuring the amount of displacement of the objective lens from the reference position value and applying two-step tracking servo. Here, as a first tracking servo means for causing a light beam spot for information recording / reproducing to follow a track formed on an optical disk, a first position detecting means for detecting a relative positional deviation amount between the information track and the light beam spot. No. 1 detector and a first drive device for controlling the light beam spot so as to make this positional deviation amount zero, and the first drive device is movable by superposing on the first tracking servo system. A second detector for detecting the amount of displacement of the movable part of the first drive device from the reference position, as second tracking servo means for controlling the part so that it is always at its reference position;
By providing a second drive device for controlling the displacement amount to be zero, two-step tracking servo is realized. In the position detecting device for the objective lens of the present invention, the photodetector 6 or 1 is obtained by taking the differential of the predetermined light receiving region of the photodetector 9 or 16.
It is also possible to detect the amount of movement of the light spot formed on 6 in the X direction, and use the detection result for the two-stage servo means.

In this case, the position sensor provided around the objective lens for detecting the amount of displacement of the objective lens from the reference position as disclosed in Japanese Patent Laid-Open No. 60-76037 becomes unnecessary. The movable part including the objective lens and its surroundings can be made compact and lightweight. Also,
Since the push-pull signal can be corrected at the same time, only one optical detection means is required while realizing the two-step tracking servo.

[0040]

According to the apparatus of the present invention, the amount of movement of the objective lens can be detected and the push-pull signal can be corrected without separately providing a photodetector in the movable portion including the objective lens. It is possible to reduce the size and weight of the movable part including the objective lens and to improve the driving sensitivity of the movable part. Further, since the correction signal can be obtained by using the photodetector for detecting the information signal, the overall size and weight of the device can be reduced.

Further, by providing a cutout or the like in the entrance pupil of the objective lens, or by providing an opening in the entrance pupil, the output difference of the light receiving region corresponding to the cutout or the opening on the photodetector. Since the moving amount of the objective lens is obtained by moving, the moving amount of the objective lens can be obtained with high sensitivity.

Further, since the light beam reflected by the optical disk is used as the light beam for detecting the amount of movement of the objective lens, the light beam reflected by the optical disk is not affected by the inclination of the outgoing beam or the inclination of the objective lens. The amount of movement can be detected. In addition, since the photodetector and the reflection mirror are not attached to the objective lens, the size and weight of the movable part can be reduced.

Further, even when the optical disc surface and the light spot formed on the optical disc deviate in the focusing direction and the diameter of the light spot on the photodetector changes, the light spot on the photodetector changes. Since the differential output for measuring the movement amount also changes in the same manner, it is not affected by the deviation of the light spot in the focusing direction. Therefore, when the movement amount is used to correct the tracking error signal, The deviation of the correction value can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of an objective lens position detection device of the present invention.

FIG. 2 is a diagram showing the shape of an entrance pupil of the device shown in FIG.

FIG. 3 is a diagram showing the shape of an entrance pupil of a second embodiment of the position detecting device for an objective lens of the present invention.

FIG. 4 is a diagram showing the shape of a photodetector according to a second embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the amount of movement of the objective lens in the X direction and the amount of movement of the light spot in the X direction when simulating the second embodiment of the present invention.

FIG. 6 is a diagram showing a shape of an entrance pupil according to a third embodiment of the present invention.

FIG. 7 is a diagram showing the shape of a photodetector according to a third embodiment of the present invention.

FIG. 8 is a diagram showing the configuration of a fourth embodiment of the objective lens position detection device of the present invention.

FIG. 9 is a diagram showing the shape of an entrance pupil according to the fourth embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a fifth exemplary embodiment of the present invention.

FIG. 11 is a diagram showing a configuration of a sixth exemplary embodiment of the present invention.

FIG. 12 is a diagram showing a configuration of a conventional optical pickup device.

13 is a diagram showing a configuration of a photodetector of the optical pickup device shown in FIG.

FIG. 14 is a diagram showing a configuration of a conventional objective lens position detection device.

FIG. 15 is a diagram showing the configuration of another conventional position detecting device for an objective lens.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 semiconductor laser 2 collimator lens 3 half mirrors 4, 20 objective lens 5 lens holder 6 entrance pupils 7a, 7b notch 8 optical disks 9, 16, 31 photodetectors 10, 12, 17 light spots 11a, 11b, 30a, 30b, 30c, 30d Projection parts 15a, 15b Opening part 21 Galvano mirror

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[Procedure amendment]

[Submission date] January 27, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

As described above, in the position detecting device for the objective lens of the first invention of the present application, the central part of the reflected light beam reflected by the information recording medium and transmitted through the objective lens is not included, and the position of the information recording medium is reduced. A photodetector that receives a light beam that is not affected by diffraction is provided, and the position of the objective lens is detected based on the amount of movement of this light beam on the photodetector. In the objective lens position detecting device according to the second aspect of the present invention, the objective lens position detecting device detects the light beam that moves integrally with the objective lens and transmits the light beam that transmits the light beam onto the information recording medium. I am trying to detect the position. Therefore, the apparatus of the present invention can accurately detect the position of the objective lens, and
When the device of the present invention is applied to an optical pickup device or the like,
The offset value of the tracking error signal can be corrected with good sensitivity. Further, since the position of the objective lens is detected by using the reflected light from the information recording medium and the photodetector for detecting the signal, a photodetector dedicated to detecting the position of the objective lens is not required. The size and weight of can be reduced. Further, even if there is a tilt of the light emitted from the laser light source, a tilt of the objective lens itself, or the like, the position of the objective lens can be accurately detected, and the correction value does not shift due to these.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

The photodetector 9 is divided into two in the Y direction by a dividing line 9g. The dividing line 9g is divided into three parts so that the center is slightly shortened, and the photodetector 9 is directed toward this dividing point. Further dividing lines 9h, 9i, 9j, 9k from the respective corners of
Is provided, and is divided into 6 as a whole by these dividing lines 9g to 9k. The position of the light spot 10 on the disk 8 when the light spot is in the on-track state is shown by a solid line in FIG. The broken line shows the state in which the objective lens 4 moves in the X direction and the light spot 10 on the photodetector 9 moves in the X direction along with this movement.

[Procedure 3]

[Document name to be corrected] Drawing

[Correction target item name] Figure 8

[Correction method] Change

[Correction content]

[Figure 8]

Claims (2)

[Claims] 1. A light source, an objective lens for projecting a light beam emitted from the light source as a light spot on an information recording medium, and a reflected light beam reflected from the information recording medium and transmitted through the objective lens. A photodetector that receives a light beam that does not include a central portion and is not affected by diffraction in the information recording medium, and detects the position of the objective lens based on the output of the photodetector. Characteristic objective lens position detection device. 2. A light source, an objective lens for projecting a light beam emitted from the light source as a light spot on an information recording medium, and an objective lens that moves integrally with the objective lens to project the light beam onto the information recording medium. And a photodetector that receives a light beam that has passed through the light-transmitting part, and the position of the objective lens is detected based on the output of the photodetector.