JPH07169069A - Optical head device and optical information apparatus - Google Patents

Abstract

PURPOSE:To obtain a stable focus error signal by providing a photodetector for receiving diffracted light generated by directing a light beam to a hologram coupling lens by a photodetector. CONSTITUTION:A light beam reflected by an information recording/reproducing surface of an optical disk 4 is directed to an objective lens 1 coupled to a hologram. The + primary diffraction light 6 diffracted by the hologram falls on detector 7 disposed near a light source 2. Focus and tracking error signals are obtained from signal intensity of divided zones of the detector. Since the hologram is fixed by using coupling means to the lens, the diffracted light generated from the hologram is not moved on the detector 7 irrespective of the movement of the lens by tracking. Accordingly, a stable focus error signal can be obtained in parallel with the tracking follow-up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device used for irradiating a target object with a light beam and detecting the positional relationship between the focal position of the light beam and the target object. The optical information device is suitable for an optical head device that records or reproduces information on an information carrier such as an optical disc.

The present invention also relates to an optical information device for recording, erasing or reproducing information on an information carrier such as an optical disk using the optical head device.

[0003]

2. Description of the Related Art Recently, as a simplified optical system of an optical head using a hologram, for example, JP-A-62-1
There is one shown in FIG. 7 described in Japanese Patent No. 88032. This will be described below as a first conventional example.

In FIG. 7, 2 is a semiconductor laser light source,
The outward light beam 3 emitted from the light source 2 passes through the hologram 8 and enters the objective lens 110 and is converged on the optical disc 4. The returning light beam reflected by the optical disk traces the original optical path in reverse and enters the hologram 8. The diffracted light 6 generated from the hologram by the light beam on the return path is incident on the detector 7.

The diffracted light 6 is designed to have an astigmatic wavefront, and the objective lens 1 for the optical disk 4 is designed.
With 10 defocus or just focus,
The shape changes as shown in FIG. In FIG. 8, (b) shows the just focus state, and (a) and (c) show the defocus state. Reference numeral 9 is a diffracted light for detecting a focus error signal.

Therefore, the focus error signal FE is obtained by the calculation of FE = (S1 + S4)-(S2 + S3) ... (1).

Next, as another conventional example, there is a configuration as shown in FIG. 9 disclosed in, for example, Japanese Patent Application No. 60-72732 (Japanese Patent Laid-Open No. 61-233439). This will be described below as a second conventional example.

The object of this conventional example is to construct a small-sized, low-cost, differential-detection-type optical pickup for a magneto-optical disk signal by constructing two optical splitters having a diffractive structure in a stacked manner. To get the equipment.

In FIG. 1, after being emitted from the light source 2,
The light flux converged on the disc 4 by the objective lens 246 and reflected from the disc 4 is again reflected by the objective lens 246.
The first light splitter 243 splits the light into a diffracted light 247 and a transmitted light. The diffracted light 247 is transmitted to the first light splitter 24
The light reaches the optical sensor 250 through the polarizing plate 249 while being totally reflected by the upper and lower surfaces of No. 3. On the other hand, the transmitted light is incident on the second diffractive structure body 242 via the low refractive index layer 244, and the diffracted light 248 thereof similarly passes through the polarizing plate 249 to the optical sensor-2.
Reach 50.

The second light splitter 242 and the first light splitter 2
43, a low-refractive layer 244 having a lower refractive index than the base of the light splitter is provided, and either the second light splitter 242 or the first light splitter 243 has a diffracted light reflection surface. The phase adjustment film 251 is provided. By the phase adjusting film 251, the phase difference between the P-polarized component and the S-polarized component at the time of reflection can be set to 180 °, and the polarization plane of the diffracted light beam is rotated by 90 °. For this reason,
The polarization planes of the diffracted light beam 248 and the diffracted light beam 247 form 90 ° with each other.

These diffracted light beams 247 and 248 reach the optical sensor while being reflected in the light splitter in which the diffractive structure is formed. The diffractive portion of the diffractive structure is shown in FIG.
It has a configuration like. A focusing signal, a tracking signal, and a magneto-optical signal can be obtained by receiving the diffracted light beams 247 and 248 by the optical sensor 250 shown in FIG. 10B and calculating the output of the optical sensor 250.

[0012] Furthermore, as another conventional example, for example, actual opening
There is FIG. 11 disclosed in Japanese Patent Laid-Open No. 61-195534.
This will be described below as a third conventional example. This conventional example
The diffractive means are arranged in the optical paths of the incident light and the reflected light.
Formed integrally on one side of the optical means with lens action
Adjustment process is easy and can be installed
Space can be reduced, and weight and size can be reduced.
The diffractive means is arranged in the optical path of incident light and reflected light.
Integrated with one side of the optical means having a lens action
Form.

Since the diffracting means is a phase type diffractive plate and the depth of the groove is set to 1/2 of the wavelength λ of light, only the + 1st order diffracted light and the −1st order diffracted light are generated from the diffracting means. . For example, the + 1st-order diffracted light is converged on the disk without aberration by the objective lens, the -1st-order diffracted light has astigmatism, and the -1st-order diffracted light is received by the detector to obtain the focus error signal.

As another conventional example, there is FIG. 12 disclosed in, for example, Japanese Patent Laid-Open No. 61-112246. This will be described below as a fourth conventional example. The purpose of this conventional example is to arrange a diffraction grating between the light source and the converging lens, divide the return light from the record carrier by the diffraction grating, and guide it to the photodetector, so that it has symmetry and the number of parts is also large. It is small, small and lightweight, and it is possible to reduce the price as much as possible, and its configuration is as follows.

That is, the light emitted from the light source 2 is collimated by the collimating lens 224, and after passing through the diffraction grating 223, the zero-order light is the recording surface 22 of the disk 4.
The light travels in the direction orthogonal to 1 and is converged by the objective lens 222 to irradiate the recording surface 221.

The emitted light is modulated by the recorded information portion on the disk 4, condensed by the objective lens 222, and then diffracted by the diffraction grating 223. The light diffracted by the diffraction grating 223 is collimated by the collimating lens 22.
4, the information is converged on the detectors 226a and 226b, and the information on the disk 4 can be reproduced. As a result, the symmetry of the pickup is realized, and it is possible to reduce the size, weight and cost.

Further, in this field, for example, Japanese Patent Application No. Sho 6
2-219712 (Japanese Patent Laid-Open No. 64-62838)
13 is filed as This will be described below as a fifth conventional example. In addition, the same figure (a) is a front view,
(B) is a side view. An object of the present invention is to prevent the tracking deviation from occurring by providing the condensing means and the hologram element while maintaining a fixed relative position, and the configuration is as follows.

The condensing means 213 and the hologram element 212 are provided so as to maintain a fixed relative position. During the tracking operation, the condensing unit 213 and the hologram element 212 move at the same time. Therefore, the relative displacement between the reflected light beam incident via the condensing means and the hologram element hardly occurs. As a result, a good tracking servo signal can be obtained. For example, even when the focusing means is moved so that the focusing spot follows the deviation of the information recording area of the recording medium, the relative position of the focusing means and the hologram element does not shift.

[0019]

However, according to the optical system configurations of the first and second conventional examples, when the objective lens moves due to the function of the tracking servo mechanism (tracking tracking), the beam is incident on the hologram surface. The position moves as shown by the dotted line in FIG. 14 (however, the optical system from the light source to the optical disk and part of the light beam are omitted here).

Therefore, there is a problem that the diffracted light on the detector moves as shown by the dotted line in FIG. 15 and the characteristics of the focus error signal deteriorate. Then, such a problem also occurs in an optical system using a lens or a half mirror which is adopted in, for example, an optical head device which is currently commercialized.

Further, in the configuration of the second conventional example, FIG.
In the divided areas 243b and 24 of the first light splitter 243
The diffracted light diffracted from 3c is received by G and H of the optical sensor 250, and the divided area 242b of the second light splitter 242 is also received.
Or the diffracted light diffracted from 242c is detected by the C
The light is received at or D, and these outputs are calculated to obtain the tracking error signal.

However, in this configuration, when the objective lens moves by tracking following, the incident position of the beam on the surface of the light splitter moves, so that the amount of light incident on each of the divided regions (243b and 243c and 242b and 242c) changes. However, there is a problem that an offset occurs in the tracking error signal and accurate tracking cannot be performed.

Further, in the configuration of the second conventional example, as is apparent from FIG. 9, since the optical sensor 250 is attached to the end of the optical splitter, the light source 2 and the optical sensor 250 should be arranged close to each other. I can't. Therefore, there is a problem that the signal is likely to be deteriorated due to a temperature change or distortion with time. That is, when the light source 2 and the collimator lens 5 are displaced due to temperature change and distortion over time, the incident angle of light on the light splitter changes, and the diffracted light 247, 2 on the optical sensor 250 changes.
There is a problem that the position of 48 is displaced and the signal is easily deteriorated.

Further, in the structure of the second conventional example, since it is necessary to generate the diffracted light at a very large diffraction angle by the light splitting means, the diffraction grating pitch of the light splitting means becomes very small, which makes the fabrication difficult. Moreover, there is a problem that it becomes expensive.

In the third to fifth conventional examples, since the diffracting means and the objective lens are held in a fixed positional relationship, even if the objective lens moves due to tracking tracking, the incident position of the beam on the diffracting means remains unchanged. It doesn't move. However, it has the following problems.

First, in the third conventional example, only the + 1st-order diffracted light and the -1st-order diffracted light are generated from the diffracting means. For example +
The first-order diffracted light is converged onto the disk without aberration by the objective lens, and the -1st-order diffracted light has astigmatism.

However, the -1st-order diffracted light includes not only astigmatism but also unnecessary aberration such as spherical aberration.
It is not possible to obtain an ideal focal line as shown in (a) and (c). The reason for this is that the diffracting means cannot freely design the diffracted light in the return path with the main focus. Therefore, there are problems that the offset of the focus error signal is likely to occur, the differential sensitivity is low, and the offset due to the crosstalk to the focus error signal when crossing the groove occurs.

If the wavelength of the light source deviates from the design value or the relative position of the hologram and the lens deviates during the production, +1
There is also a problem in that aberration occurs in the second-order diffracted light and good convergence characteristics cannot be obtained on the information medium.

Further, since there is no degree of freedom to create a diffracting means region for generating diffracted light for detecting a tracking error signal, a method for obtaining a tracking error signal is not disclosed. Further, except for a concentric circle pattern having a common center with the center of the lens, it is technically difficult to directly form a lattice pattern of an arbitrary curve on the optical lens as shown in FIG. 11, which causes a cost increase. There is a problem of fear.

The fourth conventional example has the following problems. That is, the diffraction grating 223 is a so-called simple diffraction grating, which is a diffraction grating composed of straight lines and having an equal pitch. This is clear from the description in the specification of the fourth conventional example that "the astigmatism occurs in diffracted light only when a finite optical system in which the collimating lens 224 is omitted is used."

On the other hand, the diffracted light generated when the convergent light is obliquely incident on the simple diffraction grating includes not only astigmatism but also unnecessary aberrations such as spherical aberration.
It is not possible to obtain an ideal focal line as shown in (a) and (c). Therefore, there are problems that the offset of the focus error signal is likely to occur, the differential sensitivity is low, and the offset due to the crosstalk to the focus error signal when crossing the groove occurs.

Further, a method for obtaining the tracking error signal is not disclosed. In addition, the light source 2 and the photodetector 226
a and 226 b are fixed to the objective lens 222 by the housing 225. Here, the objective lens 222 needs to be moved at high speed by a mechanism of a focusing servo or a tracking servo, but the light source 2 and the photodetector 226.
Since a and 226b and the housing 225, which must be large to support them, are connected, there is a problem that it is difficult to move at high speed.

Further, the photodetectors 226a and 226b are arranged as separate components on the housing 225, and the number of components is large, which causes a problem of cost increase.

The fifth conventional example has the following problems. That is, the fifth conventional example is a tracking error signal detecting device, but the method for detecting a focus error signal is not described at all. Also, the photodetector 2
Since 17 and 218 are arranged as separate parts, there is a problem that the number of parts is large, which causes a cost increase.

[0035]

In the present invention, in order to solve the above-mentioned problems, by interlocking a hologram with the lens, all of the reflected light from the optical disk that has passed through the objective lens is a fixed part of the hologram. Incident on.

More specifically, a light source, a refraction-type objective lens that receives a light beam emitted from the light source and focuses it on a target object, and a first light beam reflected by the target object is transmitted through the objective lens. The hologram includes a hologram to be received and a detector to receive the diffracted light generated from the hologram and generate an output according to the amount of light. The hologram has a constant relative position with respect to the refraction-type objective lens by using a connecting means. A 0th-order diffracted light beam that is not connected to the hologram and is not diffracted by the hologram in the forward optical path until the light beam emitted from the light source is converged on the target object. Is converged to the target object by the refraction type lens, and the return light beam reflected from the target object by the first light beam is an objective lens. Diffracted light generated when passing through and entering a hologram has at least two different wavefronts connecting either focal points or focal lines extending in substantially the same direction at different convergence distances or a wavefront having only astigmatism. It is a configuration including.

Alternatively, the target object has a track structure,
The return light beam passes through the hologram to generate focus error signal detection diffracted light and tracking error signal detection diffracted light, and the focus error detection diffracted light and the tracking error detection diffracted light are received by the detector. The configuration is preferable in, for example, an information recording medium.

Further, it is preferable that the detector for receiving the focus error signal detecting diffracting element and the detector for receiving the tracking error signal detecting diffracting light are provided on the same substrate.

It is preferable that the objective lens having the hologram fixedly connected to the light source is relatively movable.

Further, the hologram is divided and used, and as the wavefront to be written therein, a spherical wave having a focus in front of or behind the astigmatic wavefront or the reference plane is used to obtain a focus error signal. It is also preferable to have a configuration.

When a hologram area for generating diffracted light for tracking error signal detection is also created, of the beams incident on the hologram, the light beam in the direction perpendicular to the tracking on the optical disk is detected. It is preferable to create it in a portion that changes most sensitively according to the movement.

[0042]

By using the objective lens of the present invention in which holograms are connected and fixed, the returning light beam is incident on a certain portion of the hologram regardless of the movement of the objective lens due to tracking follow-up. It does not move on the detector.

If multi-functionality is added by dividing the hologram, the number of parts can be reduced.
In particular, when a wavefront for obtaining a tracking error signal is created on the hologram, the distribution of the far field pattern incident on the hologram does not depend on the movement of the objective lens, so that very stable tracking servo can be realized.

As a method for obtaining the focus error signal, the focus servo can be performed with a simple optical system by using ideal astigmatism and one or more sets of spherical waves having a focus before and after the reference surface. realizable.

Further, by making all the detectors for detecting servo signals on one substrate, the number of parts can be reduced and the cost can be reduced.

Further, by making the objective lens movable relative to the light source, the objective lens can be made lightweight and can be driven at high speed.

Further, since the optical information device constructed by using this optical head device does not cause defocus due to tracking follow-up, it becomes a highly reliable and inexpensive optical information device.

[0048]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a lens in which holograms, which are essential to the present invention, are connected and fixed. In FIG. 1, the hologram 102 is interlocked with the refraction type optical lens 101 by using the connecting means 103.

That is, if the hologram 102 and the refraction type lens 101 are separately formed and connected by using the connecting means 103, a lens with a hologram can be realized more easily.

In particular, as will be described later, the hologram 10
In order to freely design the grating pattern of No. 2 and obtain a focus error signal and a tracking error signal with good characteristics, it is necessary to prepare an arbitrary curve as the grating pattern. Although it is technically difficult to directly manufacture it on the optical lens as in 11, there is a risk of cost increase, but as in the present invention, the hologram 102 and the refraction type lens 101 are
If they are made separately and connected using the connecting means 103, there is a practical effect that a lens with a hologram can be realized simply and at low cost.

FIG. 2 is a diagram for explaining in principle the configuration of an embodiment of the optical head of the present invention. The light source 2 may include an optical system for wavefront correction in some cases, but the description thereof is omitted because it is not directly related to the present invention.

The outward light beam 3 emitted from the light source 2 passes through the collimator lens 5 to become parallel light, and is converged on the optical disc 4 by the objective lens 1 in which holograms are connected and fixed. The returning optical beam reflected by the information recording / reproducing surface of the optical disc having the protective film 401 and the substrate 402 is incident on the objective lens 1 having holograms connected and fixed again. For example, as shown in FIG. 2, the + 1st-order diffracted light (or the −1st-order diffracted light) 6 diffracted by the hologram is condensed by the collimator lens 5 and enters the detectors 7 arranged near the light source 2.

Since the detector 7 is arranged close to the light source 2, the optical head optical system is arranged in the vicinity of almost one optical axis, so that the temperature change and the change with time. There is an effect that various signals can be stably detected with almost no influence from displacement of parts due to distortion.

Furthermore, by arranging the detector 7 close to the light source 2, the light source 2 and the detector 7 can be easily assembled with an accurate relative position.

Further, since the detector 7 is arranged close to the light source 2, the diffraction angle of the diffracted light in the hologram 102 becomes small, so that the pitch of the grating pattern of the hologram 102 becomes large (rough). Therefore, the hologram 102 can be easily manufactured, and the manufacturing cost can be reduced.

Since the signal intensity of each divided area of the detector obtained from the diffracted light incident on the detector 7 changes according to the focus state, a focus error signal is obtained from this signal. In particular, when astigmatism is used as a method for obtaining the focus error signal, the same hologram or four-division detector as in the conventional example such as the above-mentioned JP-A-62-188032 may be used.

In the embodiment of the present invention in which astigmatism is used as a method for obtaining a focus error signal, ideal astigmatism is used, and the shape change of diffracted light in two directions with respect to orthogonal dividing lines is used. Since the focus error signal is obtained by the above, it is possible to obtain the focus error signal with high differential sensitivity, and it is possible to further increase the (signal) / (noise) ratio of the focus error signal with respect to circuit noise and the like. . Moreover, since the diffracted light is not in a converged state and has a large spot, the position of the detector can be set with a margin when assembling the optical head device.

Therefore, the tolerance of the detector position shift,
That is, it is possible to reduce the assembly cost without requiring high accuracy in assembling the detector.

When diffracted light having a focus in front of or behind the reference surface is used as the diffracted light used to obtain the focus error signal, the hologram is a combination of off-axis Fresnel zone plates or Fresnel zone plates. become. In other words, the lattice pattern of the hologram is
It consists of curves with varying pitch.

In this case, the state of the diffracted light on the detector is as shown in FIG. 9A to 9C show changes in the shape of diffracted light on the detector surface due to changes in the positional relationship between the hologram coupling fixed lens 1 and the information carrier 4 in the optical axis direction. In this figure, (b) is just focus, and (a) and (c) are defocused states.

At this time, the focus error signal FE is FE = (S10 + S30-S20)-(S40 + S60
-S50) ... Can be obtained as (2).

As shown in FIGS. 2, 3 and 6, for example, the number of parts can be reduced by forming all the servo signal detectors on one substrate.
There is an effect that the price can be reduced.

According to the present invention, the focus error signal is detected from the hologram by using the light beams having the focal points on the rear side and the front side of the detector, respectively.
For example, as shown in FIG. 3B, when the size of the two diffracted lights 6 becomes the same size in the direction perpendicular to the dividing lines 601 to 604, the size of the detectors S20 and S5.
Can be designed to be wider than zero width. By designing the size of the diffracted light 6 to be large in this way, the position of the detector can be set with a margin when assembling the optical head device. In particular, the dividing lines 601 to 604 as shown in FIG.
, The detector shifts in the directions of the dividing lines 601 to 604 do not affect the focus error signal at all. Therefore, a particularly large detector displacement can be allowed. That is, it is possible to reduce the assembly cost without requiring high accuracy in assembling the detector.

Note that in FIG. 3, the two diffracted lights 6 are drawn as spherical waves that converge to one point for the sake of simplicity, and the subsequent description was also made according to this, but the FE signal using FIG. 3 and the equation (2) was used. As is clear from the detection method described above, according to the FE signal detection of the present invention, the magnitude of the diffracted light depends on the focus state of the light beam emitted from the lens 101 on the information carrier 4, and the division lines 601 to 604 of the detector. It uses the change in the vertical direction. Therefore, when the diffracted light 6 is viewed from the direction in which the dividing lines 601 to 604 of the detectors S10 to S60 extend (that is, from the surface of the detector),
It is a requirement that the light beam has a focal line (focus is a focal point in a spherical wave as a special example) on each of the back side and the front side of the detectors S10 to S60, and it is not necessarily a spherical wave that converges to one point. Absent.

As described above, the hologram is designed so as to generate two kinds of spherical waves having different curvatures or a wavefront having an ideal astigmatism as the first-order diffracted light, and the focus error signal can be detected. . Such a hologram can be easily realized by recording a light interference fringe or a method called a computer generated hologram (computer hologram) as is well known, but since it is not the essence of the present invention, its realization method is realized. The explanation is omitted.

As described above, in the present invention, by designing the size of the diffracted light for detecting the focus error signal to be large, the position of the detector can be set with a margin when assembling the optical head device. This has the effect of reducing the cost for assembly and providing an inexpensive optical head device. Further, by connecting and fixing the hologram to the objective lens by using the connecting means, the diffracted light having a large spread generated from the hologram does not move on the detector regardless of the movement of the objective lens due to tracking tracking. Therefore, a stable focus error signal can be obtained in parallel with the tracking following. Further, since the number of parts can be reduced, the optical head device can be downsized,
Cost reduction can be realized.

Further, in the present invention, as shown in FIG. 2 and FIG. 5, the outward light beam 3 emitted from the light source passes through the hologram 102 and enters the lens 101, and the information medium 4 is transmitted.
Converged on. The light reflected by the optical disk enters the hologram 102 as a return path that reverses the original optical path. At this time, the detector 7 receives the diffracted light generated from the hologram to obtain the focus error signal FE.

As described above, according to the present invention, the hologram 102 is used.
The light beam of the forward path transmitted through the
Since it converges upward, even if the light source wavelength deviates from the design value or the relative position of the hologram 102 and the lens 101 deviates at the time of manufacturing, it does not affect the optical characteristics of the optical head device at all, and on the information medium 4. There is an effect that good convergence characteristics can be obtained. In particular, since the lens 101 uses a refraction type lens, it is more effective than a hologram in that it is not affected by the deviation of the light source wavelength from the design value.

Furthermore, since the grating pattern of the hologram 102 does not affect the convergence characteristic on the information medium 4 at all, it can be designed in an optimum form for obtaining a servo signal such as a focus error signal. Therefore, for example, when the focus error signal is detected using astigmatism, the focus error signal is detected using a light beam that has only astigmatism and does not have unnecessary aberrations such as coma. be able to. For this reason, it is possible to obtain a very high quality focus error signal in which the offset of the focus error signal does not occur, the differential sensitivity is high, and the offset due to the crosstalk to the focus error signal when crossing the groove does not occur. There is.

The tracking error signal can also be obtained from the diffracted light for detecting the focus error signal,
For example, as shown in FIG. 4, the hologram 102 is divided and used,
It is also possible to obtain a tracking error signal by separating diffracted light different from the diffracted light for detecting the focus error signal from the holograms of the portions 1021 and 1022. In the case of the configuration shown in FIG. 4, the focus error signal is 10
It can be obtained from the hologram portions 23, 1024 and 1025.

For example, when a wavefront for obtaining a tracking error signal is created on a hologram as shown in FIG. 4, the return light beam incident on the hologram does not move depending on the movement of the objective lens. There is an effect that a very stable tracking servo can be realized without causing a tracking error signal offset due to the movement of the beam.

When the hologram area for generating the diffracted light for detecting the tracking error signal is also formed in the same hologram, among the beams incident on the hologram, the light beam in the direction perpendicular to the tracking on the optical disc. It is preferable to create it in a part that changes most sensitively according to the movement of. That is, as clearly shown in FIG. 4, the diffracted light generation region for tracking error signal detection is
If each area is less than half of the total area of the hologram, the ratio of the amplitude of the tracking error signal to the amount of light used for tracking error signal detection becomes large, and the ratio of (signal amplitude) / (noise) becomes large, There is an effect that a strong and stable tracking error signal can be obtained.

In particular, when the objective lens 1 in which holograms are connected and fixed moves with respect to the light source 2 due to tracking follow-up or the like, for example, when a semiconductor laser is used as the light source 2, the distribution of the light amount is not uniform. There is a possibility that a non-uniform amount of light occurs on the objective lens 1 in which is fixedly connected to cause a tracking error signal offset, but in this embodiment also (signal amplitude) /
Since the (noise) ratio becomes large, there is an effect that a stable tracking error signal can be obtained without causing the above-mentioned offset.

When it is necessary to make the optical head of the present invention smaller, the structure shown in FIG.
It is of course possible to omit the collimating lens 5 of FIG.

Further, for example, as shown in FIGS. 2 and 5, the hologram connection fixing lens is independently moved with respect to the light source 2 and the detector 7, so that focusing and tracking can be performed. The effect is that the movement can be made faster.

When the focus error signal detection and the tracking error detection are performed using the hologram shown in FIG. 4, for example, as shown in FIG. 16, the focus error signal detection detector area 71 and the tracking error signal detection 2 are used. Two detector areas 72 and 73
It is preferable that the and are separately provided on the same detector 7 because the number of parts is small, the cost required for the assembly process can be reduced, and the size can be reduced.

Finally, FIG. 6 shows an embodiment of an optical information device constructed using the optical head device described above. The optical disc 4 is rotated by the drive mechanism 14. The optical head device 10 is roughly moved to a desired track of the optical disk by an optical head device driving device 12. The optical head device 10 also sends a focus error signal and a tracking error signal to the electric circuit 11 in accordance with the positional relationship with the optical disc. In response to this signal, this electric circuit sends a signal for finely moving the objective lens to the optical head device. With this signal, the optical head performs focus servo and tracking servo for the optical disc,
Reading, writing, or erasing of information is performed on the optical disc 4.

[0078]

As described above, by using the objective lens in which holograms are connected and fixed according to the present invention, the diffracted light generated from the hologram does not move on the detector regardless of the movement of the objective lens due to tracking tracking. Therefore, a stable focus error signal can be obtained in parallel with the tracking following.

Since the number of parts can be reduced,
It is possible to reduce the size and cost of the optical head device. This effect becomes more remarkable when the hologram is divided and used.

Further, since the far field pattern of the beam incident on the hologram is stable, the tracking servo can be stabilized.

Further, the optical information device constructed by using the optical head device of the present invention is highly reliable because defocusing due to tracking follow-up does not occur, and the number of parts is small, so that it is an inexpensive and small-sized optical information device. Become.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a hologram connecting lens which is a requirement of the present invention.

FIG. 2 is a schematic sectional view of an optical head device according to an embodiment of the present invention.

FIG. 3A is a plan view showing a defocused state on a detector of diffracted light for detecting a focus error signal in another embodiment of the present invention, and FIG. 3B is a plan view of the same embodiment. The plan view showing the state of the just focus state on the detector of the diffracted light for detecting the error signal is a plane view showing the state of the defocus state on the detector of the diffracted light for detecting the focus error signal in the same embodiment. Figure

FIG. 4 is a plan view of a hologram used in another embodiment of the present invention.

FIG. 5 is a schematic sectional view of an optical head device according to another embodiment of the present invention.

FIG. 6 is a schematic sectional view of an optical information device according to an embodiment of the present invention.

FIG. 7 is a schematic sectional view of a conventional optical head device.

8A is a plan view showing a defocused state on a detector of diffracted light for detecting a focus error signal of an optical head device according to an embodiment of the present invention and FIG. 8B is a plan view of the present invention. The plan view (c) showing the state of the just focus state on the detector of the diffracted light for detecting the focus error signal of the example and the conventional optical head device is the focus error signal of the example and the conventional optical head device of the present invention. A plan view showing a state of a defocused state on the detector of the diffracted light for detection.

FIG. 9 is a schematic sectional view of a conventional optical head device.

FIG. 10A is a plan view showing a diffractive portion of a diffractive structure of an optical splitter of a conventional optical head device, and FIG. 10B is a plan view showing an optical sensor of the conventional optical head device.

FIG. 11 is a schematic sectional view of a conventional optical head device.

FIG. 12 is a schematic sectional view of a conventional optical head device.

13A is a schematic cross-sectional front view of a conventional optical head device, and FIG. 13B is a schematic facial side view of the device.

FIG. 14 is a cross-sectional view showing a state of a return path of a light beam in a conventional optical head device.

FIG. 15 is a plan view showing how diffracted light in a conventional optical head device moves on a detector.

FIG. 16 is a conceptual configuration diagram of an embodiment of an optical head device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 hologram connection lens 101 lens 102 hologram 103 connection means 2 light source 3 light beam 4 optical disk 5 collimating lens 7 detector 8 hologram 9 focus error signal detection diffracted light 10 optical head device 12 optical head device drive device 14 optical disk drive mechanism 601 to 604 Detector dividing line

Front page continued (72) Inventor Tetsuo Hosomi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. A light source, a refraction-type objective lens that receives a light beam emitted from the light source and converges the light beam on a target object, and receives a first light beam reflected by the target object through the objective lens. The hologram includes a hologram and a detector that receives the diffracted light generated from the hologram and generates an output according to the amount of light, and the hologram is located at a fixed relative position with respect to the refraction-type objective lens by using a connecting means. Among the light beams emitted from the light source, the 0th-order diffracted light beam that is not diffracted by the hologram is included in the forward optical path until the light beam emitted from the light source is fixedly connected and converges on the target object. , The refraction-type lens converges on the target object, and the return-direction light beam, which is the first light beam reflected by the target object, passes through the objective lens. Diffracted light generated when incident on the program is, the optical head device which comprises two wavefronts connecting one of at least different convergence distances to each focus or nearly the same direction to extend the focal line. 2. A light source, a refraction-type objective lens that receives a light beam emitted from the light source and focuses it on a target object, and receives a first light beam reflected by the target object through the objective lens. The hologram includes a hologram and a detector that receives the diffracted light generated from the hologram and generates an output according to the amount of light, and the hologram is located at a fixed relative position with respect to the refraction-type objective lens by using a connecting means. Among the light beams emitted from the light source, the 0th-order diffracted light beam that is not diffracted by the hologram is included in the forward optical path until the light beam emitted from the light source is fixedly connected and converges on the target object. , The refraction-type lens converges on the target object, and the return-direction light beam, which is the first light beam reflected by the target object, passes through the objective lens. Diffracted light generated when incident on the program is, the optical head device which comprises a wavefront having only least astigmatism. 3. A light source, a refraction-type objective lens for receiving a light beam emitted from the light source and converging the light beam to a target object having a track structure, and a first light beam reflected by the target object by the objective lens. The hologram is provided with a hologram that is transmitted and received, and a detector that receives the diffracted light generated from the hologram and generates an output according to the amount of light, and the hologram is fixed using a connecting means with respect to the refraction-type objective lens. Of the light beams emitted from the light source in the forward optical path until the light beam emitted from the light source is converged on the target object. A light beam of the second-order diffracted light is converged on the target object by the refraction type lens, and the first light beam is reflected by the target object to return to the optical path of the return path. The diffracted light generated when the beam passes through the objective lens and enters the hologram includes at least two diffracted lights for focus error signal detection and tracking error signal detection. Diffracted light for detection and the diffracted light for detecting the tracking error signal are received by the detector arranged in proximity to the light source, and a focus error signal and a tracking error signal are obtained by using an output obtained from the detector. Optical head device. 4. A detector for receiving the diffracted light for detecting a focus error signal and a detector for receiving the diffracted light for detecting a tracking error signal are provided on the same substrate. Optical head device. 5. A light source, a refraction-type objective lens that receives a light beam emitted from the light source and focuses it on a target object, and receives a first light beam reflected by the target object through the objective lens. The hologram includes a hologram and a detector that receives the diffracted light generated from the hologram and generates an output according to the amount of light, and the hologram is located at a fixed relative position with respect to the refraction-type objective lens by using a connecting means. The light beam emitted from the light source is connected and fixed, the objective lens is movable relative to the light source, and the light beam emitted from the light source is converged on a target object in an outward optical path. A light beam of 0th-order diffracted light that is not diffracted by the hologram is converged on the target object by the refraction type lens, and the first light beam is A characteristic is that a diffracted light generated when a return light beam reflected by an object passes through an objective lens and enters a hologram, is received by the detector, and a focus error signal is obtained using an output obtained from the detector. Optical head device. 6. A far-field diffraction pattern portion of the backward beam incident on the hologram, which is sensitively changed corresponding to the position of the convergent beam in the direction perpendicular to the track on the target object having the track structure. The optical head device according to any one of claims 1 to 4, wherein diffracted light for detecting a tracking error signal is generated from a hologram portion on which is incident. 7. A light source, a refraction-type objective lens for receiving a light beam emitted from the light source and converging the light beam to a target object having a track structure, and a first light beam reflected by the target object by the objective lens. The hologram is provided with a hologram that is transmitted and received, and a detector that receives the diffracted light generated from the hologram and generates an output according to the amount of light, and the hologram is fixed using a connecting means with respect to the refraction-type objective lens. Of the 0th-order diffracted light that is not fixed to the hologram among the light beams emitted from the light source in the forward optical path until the light beam emitted from the light source is converged on the target object. Is converged on the target object by the refracting lens, and the return light beam reflected by the first object is the first light beam. The diffracted light generated when the light passes through the object lens and enters the hologram has at least two focal points at different convergence distances, and two wavefronts connecting either a focal line extending in substantially the same direction or a wavefront having only astigmatism. Optical head mechanism including, a drive mechanism of the target object, a focus servo mechanism using a focus error signal obtained by the optical head mechanism, a tracking servo mechanism using a tracking error signal obtained by the optical head mechanism, the focus servo mechanism And an optical circuit for each of the tracking servo mechanisms, and a connecting portion between the electric circuit and a power source or an external power source.