JPS6370930A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To erase the offset of a positional shift information such as a focus error signal, etc., with a light quantity distribution signal detected (mentioned in the following) by providing a light quantity distribution detecting means that detects the light quantity distribution in the tangential direction of a recording medium of a reflected light from a far field position of the recording medium. CONSTITUTION:For instance, on focus error signals SFE from the light receiving elements 9A, 9B of a light detector 9, the offset due to the irregularity in the light quantity distribution in the tangential direction of a reflected light from the recording medium is superposed. The light quantity distribution detecting means 31 consists of a light detector 33 in which light receiving elements 33C, 33D are disposed neighboring in the tangential direction at a far field position and an arithmetic circuit 34 to operates a differential signal C-D from an output CD, and outputs the differential signal C-D as a light quantity distribution signal Sd. An offset erasing means 32, for instance, comprises of an arithmetic circuit 35 to operate a differential signal SFE-Sd=(A-B)-(C-D), and outputs the differential signal SFE-Sd as a focus error signal S'FE from which the offset has already been erased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording and reproducing apparatus that can erase offsets of positional deviation information signals such as focus error signals and tracking error signals during recording.

[Problems to be solved by conventional techniques and inventions] In recent years,
By condensing a light beam and irradiating it onto an optical recording medium, information can be recorded with high density on this recording medium, and by receiving the return light from this recording medium with a photodetector, recording can be performed. 2. Description of the Related Art Optical information recording and reproducing devices that can read (reproduce) recorded information stored in a medium at high speed have been attracting attention.

In the above-mentioned apparatus, in order to perform high-density recording or reproduction, it is necessary to maintain the light beam focused and irradiated onto the recording medium in a focused state and an on-track state. Therefore, the device usually includes a focus control means and a
- racking (radial) control means are provided;

These control means detect focus and radial positional deviation information contained in the return light from the recording medium as a focus error signal and a tracking error signal, and adjust the focus state and the light beam of the light beam based on these error signals. It is designed to stay on track.

Various detection methods for the focus error signal and tracking error signal have been proposed. FIG. 6 shows a conventional example of an optical information recording/reproducing apparatus using the critical angle method as a focus error signal detection method.

As shown in this figure, the optical information recording/reproducing apparatus (optical information recording/reproducing apparatus) is equipped with an optical pickup 20 which is arranged in Ra so as to face the surface of a disk-shaped recording medium (hereinafter referred to as a disk) 60.

This optical pickup 20 can be moved by a moving means (not shown) in a direction across the recording track J3 on the disk 6, which is rotationally driven in the direction indicated by an arrow T, for example.

A laser diode 1 as a light source is housed in the housing of the optical pickup 20, and diffused light, e.g., P-polarized light, emitted from the laser diode 1 is converted into a parallel beam by a coupling lens 2. This collimated light beam is incident on the polarizing beam splitter 3, where almost 100% of the beam is transmitted, and after being converted into circularly polarized light by the λ/4 plate 4, it is condensed and irradiated onto the disk 6 by the objective lens 5.

The light beam condensed and irradiated onto the disc 6 is irradiated onto the recording layer of the disc 6 in the form of a spot in a nearly focused state. The reflected light from the recording layer of the disk 6 is condensed by the objective lens 5 into a nearly parallel beam, and is converted into S-polarized light whose polarization direction is 90 degrees different from the outgoing path by the λ/4 plate 4. The beam is incident on the beam splitter 3. Almost 100% of the reflected light from the disk 6 is reflected by the polarizing beam splitter 3, further reflected by the reflecting prism 7, and then incident on the critical angle prism 8. The light beam reflected by the slope of the critical angle prism 8 is received by a photodetector disposed at a position to receive the diffracted light in the far field. This photodetector 9 is formed of a light receiving element such as a photodiode divided into four parts, for example. Therefore, the light receiving elements 9 adjacent to each other in the left and right direction in FIG.
A difference signal 88-B is generated from the outputs A and B of the signals A and 9B by an output circuit 10 such as a differential amplifier, and a focus error signal @srE is generated by this difference signal A-8. On the other hand, a tracking error signal is generated by the difference signals of the light receiving elements adjacent in the direction perpendicular to the plane of the paper in FIG.

The focus error signal SFE is sent to the phase compensation circuit 11.
, is applied to the focus coil 13a of the lens actuator 13 via the objective lens drive circuit 12. The objective lens 5 is moved to the disk 6 by the lens actuator 13 based on the focus error signal 3FE.
It is moved in a direction perpendicular to the surface, and focus control is performed.

Moreover, the tracking error signal also has a phase (not shown)? The spot light is applied to a tracking coil (not shown) of the lens actuator 13 through the i++ compensation circuit and the objective lens drive circuit, and is focused and irradiated by the objective lens 5 so that the spot light can be made to follow a predetermined track. .

Further, data (No. 4 is 15I) is obtained from the sum signal of all the light receiving elements of the photodetector 9.

By the way, in an apparatus that records or reproduces information by a structural change or a beep that causes a change in the recording medium at a rate of 1%, an offset may occur in the focus error signal S. Possible causes of this include a positional shift of the components of the optical pickup 21 such as the photodetector 9, and an offset generated in the signal processing circuit J3 of the focus error signal SrE.This offset occurs during playback. Offsets during recording can also be eliminated by making adjustments to eliminate positional deviations and offsets in the signal processing 11!! circuit.

Unlike this offset, there is an offset that does not occur during playback but occurs during recording.

That is, during recording, the light beam is set to a light emitting power with a high energy density in a pulsed manner according to the recorded data, and the light beam is focused on this line 1 with the emitted light power to record. As shown in FIG. 7, pits 21 and the like are formed in the land portion of the medium. These pits 21 do not occur uniformly over the entire beam spots 1 to 22 that are scanned at a high speed on the recording medium, and the pits 21 do not occur uniformly over the entire beam spots 1 to 22, which are scanned at a high speed, but at an irradiation energy of -1! The part with the largest − is generated first. Therefore, as shown in FIG. 7, the unrecorded portion 23 and the recorded green portion 24 exist simultaneously in the rotational direction (tangential direction) shown by the arrow T within the beam spots 1 to 22 on the recording medium. Therefore, the hall record red record section 23 and the existing record green section 24
As a result of the diffraction effect due to the reflectance difference between the recording medium and the phase difference, the light m distribution in the tangential direction T of the far field pattern 25 of the reflected light from the recording medium becomes non-uniform. As a result, an offset occurs in the focus error signal SFE between the reproduction section and the recording section. FIG. 8 shows how the focus error signal Q3FE changes.

The optical adjustment is performed so that the offset becomes O during reproduction, and the reproduction state R and the recording medium W are switched in accordance with a recording command pulse as shown in (a). Immediately after switching from the reproduction state R to the recording state W, as shown in FIG. The offset O8 occurs because the light m distribution becomes non-uniform. The focus error signal S[E gradually converges toward the ground level GND even while being photographed due to the transient response of the servo system. In the figure, TR indicates a transient response section of the servo system. above) A-cass error signal S
The reason why the FE swings greatly immediately after switching from the reproduction state R to the recording state HW and hardly swings immediately after switching from the recording state iw to the reproduction state iR is because of the far field pattern 25 of the reflected light. This is because the non-uniformity of the distribution of light m in the tangential direction T and the degree of the non-uniformity change depending on the defocus m, or it only occurs during recording.

In this way, in the conventional optical information recording and reproducing apparatus, the focus error signal SI'E is generated in the reproduction state R and the recording state W.
Since an offset occurs in both states, it is difficult to perform optimal focus control in both states.

If an offset occurs in the focus error signal SFE, the light spot 22 will expand, especially during recording, and the irradiation power will be insufficient, making it impossible to write data in a normal state. Therefore, a problem arises in that the reliability of the optical information recording/reproducing device is reduced.

Note that the offset occurs not only in the focus error signal obtained by the critical angle method but also in the focus error signal obtained by other methods, or the tracking error signal depending on the method.

[Object of the Invention] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical information recording/reproducing device capable of erasing the offset of a positional deviation information signal during recording. .

Means for Solving Problems] As shown in the conceptual diagram of FIG. A light amount distribution detection means 31 for detecting the light amount distribution in the direction is provided,
The optical distribution signal S detected by the a-distribution detection means 31 in the future
Offset erasing means 3 for erasing the offset of the positional deviation information signal such as the focus error signal SFE by d.
2.

[Function] For example, the arithmetic circuit 10 calculates 11? from the outputs A and B of the light receiving elements 9A and 9B of the photodetector 9, respectively. The difference signal A-8, that is, the focus error signal SFE, is as follows:
An offset due to non-uniformity of the light m distribution in the tangential direction of the return light from the recording medium is superimposed.

The light amount distribution detecting means 31 is, for example, a light detecting device in which light receiving elements 33C and 33D are arranged adjacent to each other in the tangential direction at a far field position. S33 and a difference signal (,
−D, and a calculation circuit 34 for calculating the difference signal C.
-D is output as an optical h1/15 signal Sd. This light amount distribution signal Sd corresponds to the offset.

The off-resolution 1 to erasing means 32 each include, for example, an arithmetic circuit 35 that calculates a difference signal 5FE-8d - (A-8) - (C-D) between the focus error signal SFE and the light m distribution signal Sd, The difference signal 5FE-8d is output as a focus error signal S'FE with the offset removed.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

2 and 3 relate to a first embodiment of the present invention, FIG. 2 is a configuration diagram of an optical information recording/reproducing apparatus, and FIG. 3 is a waveform diagram illustrating the operation of this embodiment.

As shown in FIG. 2, the optical information recording/reproducing apparatus of this embodiment includes an optical pickup 20 disposed facing the surface of a disk 60. As shown in FIG. This optical pickup 20 can be moved by a moving means (not shown), for example, in a direction across recording tracks on the disk 6 which is rotationally driven in the direction of arrow T.

A laser diode 1 as a light source is housed in the housing of the optical pickup 20, and the diffused light of, for example, P-polarized light emitted from the laser diode 7 is converted into a parallel beam by a coupling lens 2. It looks like this. This parallel light beam is incident on the polarizing beam splitter 3, transmits almost 100% of the beam, is made into circularly polarized light by the λ/4 plate 4, and is condensed and irradiated onto the disk 6 by the objective lens 5. It has become. The light beam condensed onto the disk 6 is irradiated onto the recording layer of the disk 6 in the form of a spot in a nearly focused state. The light beam condensed and irradiated onto this recording layer forms a recess or hole called a bit because the emission intensity of the laser diode 1 is set to be large during light emission in the recording state.

The reflected light from the recording layer of the disk 6 is condensed by the objective lens 5 and turned into an almost parallel beam, and the λ/4
The plate 4 converts the light into S-polarized light whose polarization direction is 90 degrees different from the outgoing light.
The light is incident on the polarizing beam splitter 3. Almost 100% of the reflected light from the disk 6 is reflected by the polarizing beam splitter 3.

In this embodiment, the light beam reflected by the polarizing beam splitter 3 is split into two by a half prism 36. One of the light beams reflected by the half prism 36 is incident on the critical angle prism 8, and the light beam reflected by the slope of the critical angle prism 8 is a light beam arranged at a position to receive the far field diffracted light. The light is received by a detector 9. This photodetector 9 is formed of a light receiving element such as a photodiode divided into four parts, for example. Then, the light receiving element 9A adjacent in the left and right direction in FIG.
, 9B, a differential signal @A-B is obtained by an arithmetic circuit 10 such as a differential amplifier, and a focus error signal SFE is generated from this differential signal A-8. .

Note that the tracking error signal is generated by the difference signals of the light receiving elements adjacent in the direction perpendicular to the plane of the paper in FIG.

The critical angle prism 8 is arranged so that the photon distribution in the tangential direction of the light reflected from the disk 6 changes depending on the shift in the focal position of the light beam with respect to the disk 6. Therefore, the photodetector 9 detects the light amount distribution in the tangential direction of the light reflected by the critical angle prism 8 using the two light receiving elements 9A and 9B. Therefore, the focus error signal SFE is superimposed with an offset due to the non-uniformity of the photon distribution in the full tangential direction of the reflected light from the disk 6.

On the other hand, the other beam transmitted through the half prism 36 is received by a photodetector 33 disposed at a position to receive far-field diffracted light. The photodetector 33 is formed of a light-receiving element such as a photodiode divided into two or four parts, for example. The light receiving element 33C is arranged adjacent to the tangential direction.
, 33D, the light amount distribution in the tangential direction of the light reflected from the disk 6 is detected. Each output C of the light receiving elements 33C and 33D
, D are input to an arithmetic circuit 34 serving as a light amount distribution detecting means. This calculation circuit 34 calculates a difference signal CD between the outputs C and D of the light receiving elements 33C and 33D, and outputs this as a light amount distribution signal Sd.

Further, in this embodiment, an arithmetic circuit 35 is provided as offset erasing means. This calculation circuit 35 calculates a difference signal 5FE-8d = (A-B)-(C-D) between the focus error signal SFE and the light m distribution signal Sd,
This is the focus error signal S' with the offset removed.
It is designed to be output as F[.

The focus error signal S'FE is sent to the phase compensation circuit 1.
1. The signal is applied to the focus coil 13a of the lens actuator 13 via the objective lens drive circuit 12. The objective lens 5 is moved in a direction perpendicular to the surface of the disk 6 by the lens actuator 13 based on the focus error signal S'FE to perform focus control.

The tracking error signal is applied to a tracking coil (not shown) of the lens actuator 13 via a phase compensation circuit (not shown) and an objective lens drive circuit (not shown), and causes the spot light focused and irradiated by the objective lens 5 to follow a predetermined track. It is now possible to do so.

Further, a data signal can be obtained from the sum signal of all the light receiving elements of the photodetector 9.

Next, the operation of this embodiment will be explained with reference to FIG.

The optical adjustment is performed so that the offset becomes 0 during reproduction, and the reproduction state FJR and the recording state W are switched in accordance with a recording command pulse as shown in (a). Immediately after switching from the reproduction state R to the recording state W, as shown in FIG. Offset occurs because the directional light amount distribution becomes non-uniform.

On the other hand, the light m distribution signal 3d obtained by the photodetector 33 and the arithmetic circuit 1o is as shown in FIG.
The signal corresponds to the light amount distribution in the tangential direction of the reflected light from.

Therefore, the arithmetic circuit 35 generates a difference signal SFE- between the focus error signal SFE and the light m distribution signal Sd.
Focus error signal 3'F obtained by calculating S d
As shown in (d), E is obtained by eliminating the offset caused by the non-uniformity of the light amount distribution in the tangential direction of the light reflected from the disk 6.

As described above, according to this embodiment, this is caused by non-uniformity in the light amount direction in the tangential direction of the reflected light from the disk 6 that occurs during recording. Since the offset of the focus error signal can be eliminated, the optimal<h focus lens points of the reproduction state R and the recording state W are matched, and optimal focus control can be performed in both states.

Further, according to the present embodiment, even if the diffraction pattern of the reflected light from the disk 6 at the far field position varies from disk to disk, the diffraction patterns on the photodetector 9 and the photodetector 33 are the same. The focus changes to always be optimal! I11 control can be performed.

Furthermore, between the preformat section and the data section of the disk 6, the servo gain is switched because the amount of incident light is switched, but if this servo gain switching is incomplete, the offset of the focus error signal will change, causing the focus error signal to change. may be shaken. According to this embodiment,
Since the offset is erased, it is possible to eliminate fluctuations in the focus error signal between the preformat section and the data section.

FIG. 4 is a block diagram of an optical information recording/reproducing apparatus according to a second example of the present invention.

This embodiment is an example in which the present invention is applied to a focus error signal detection method using the Knifezi method.

In this embodiment, one of the light beams reflected by the half prism 36 is condensed by a condensing lens 37. A wedge-shaped light shielding plate (knife) 38 is arranged near the focal point of the condensing lens 37, and is positioned at a position to receive the far-field diffracted light that is added to the light beam partially blocked by the knife 38. , a photodetector 9 are arranged. Then, the arithmetic circuit 10 generates a difference signal A between the outputs A and B of the light receiving elements 9A and 9B of the photodetector 9.
-8 is calculated and used as the focus error signal SFE.

Further, the other light beam transmitted through the half prism 36 is received by a photodetector 33 as a light 1 distribution detecting means, as in the first embodiment.

Note that the light receiving elements 9A, 913 of the photodetector 9 and the light receiving elements 33A, 33B of the photodetector 33 have the following characteristics with respect to the light amount distribution in the tangential direction of the reflected light from the disk 6:
The focus error signal SFE and the light amount distribution signal Sd are arranged so that their polarities match.

Other configurations, operations, and effects are the same as those in the first embodiment.

FIG. 5 is a block diagram of a third actual IM PA optical information recording/reproducing apparatus of the present invention.

This embodiment is an example in which the present invention is applied to a focus error signal detection method using an astigmatism method.

In this embodiment, the cylindrical lens 14 is arranged in the optical path of one of the light beams reflected by the half prism 36. And this cylindrical lens 41
A four-divided photodetector 42 is arranged at a position where the light beam converged to an astigmatic point becomes a perfect circle in the focused state. The focus error signal SFE is transmitted to the photodetector 4.
After calculating the sum (A+C) and (B+D) of the outputs of the two diagonal elements, the arithmetic circuit 10 calculates the difference signal (A10) - (B+
D).

On the other hand, a cylindrical lens 43 is disposed in the optical path of the other beam that has passed through the half prism 36. The light beam converged to an astigmatic point by this cylindrical lens 43 is placed in a position where it becomes a perfect circle in the focused state.
A photodetector 44 divided into four parts is arranged. Then, the sum of the outputs of the diagonal elements of this photodetector 44 (A' + C')
, (8' + D'), and then the arithmetic circuit 34 calculates the difference signal (Δ' + C') - (B' + D'), so that the light amount distribution signal Sd is multiplied by 1q.

Note that in each of the light receiving elements of the photodetector 42 and the photodetector 44, the polarity of the focus error signal SFE and the light amount distribution signal Sd match with respect to the light amount distribution in the tangential direction of the reflected light from the disk 6. It is arranged like this.

Other configurations, actions, and effects are the same as in the first example (it is a drug).

J3, the present invention is not limited to the above embodiments, for example, the first embodiment
and in a second embodiment, a difference signal A-C.

After calculating B-D, these difference signals (A-C
)-(B-D>, and offset/removes this to create a focus error @S' ``[You may also do this.

Further, in order to reliably eliminate the offset, a means for adjusting the gains of the focus error signal SFE and the light quantity distribution signal Sd may be provided.

It should be noted that the present invention can also be applied to the case of erasing the focus error signal by a method other than the above-mentioned embodiments, or the offset of the tracking error signal depending on the method.

Furthermore, the present invention is not limited to recording formats in which bits are formed, but can also be applied to recording formats in which reflectance or transmittance is changed by phase transition or the like.

In general, the present invention is applicable not only to discs that are rotated, but also to writing on card-shaped recording media.

[Effects of the Invention] As described above, according to the present invention, a light amount distribution detecting means is provided for detecting the light amount distribution of the return light from the recording medium at the far field position in the tangential direction of the recording medium, and this light 1. Since the offset erasing means is provided for erasing the offset of the positional deviation information signal using the light amount distribution signal detected by the distribution detecting means, there is an effect that the offset of the positional deviation information signal at the time of recording can be erased. .

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of the present invention, FIGS. 2 and 3 are related to the first embodiment of the present invention, FIG. 2 is a configuration diagram of an optical information recording/reproducing device, and FIG. 3 is a diagram of the present embodiment. A waveform diagram explaining the operation, FIG. 4 is a configuration diagram of an optical information recording/reproducing apparatus according to a second embodiment of the present invention, and FIG. 5 is a configuration diagram of an optical information recording/reproducing apparatus according to a third embodiment of the present invention. , FIGS. 6 to 8 relate to conventional examples, FIG. 6 is a configuration diagram of an optical information recording and reproducing apparatus, FIG. FIG. 8 is a waveform diagram for explaining the offset of the focus error signal. 5...Disk (recording medium) 9.33...Photodetector 10.34.35...Arithmetic circuit 20...Optical pickup 31...Light amount distribution detection means 32...Offset erasing means 36... Half prism Figure 1 Figure 2 Figure 3 S'FE 'SFE-3d

Claims (1)

[Claims] An optical system that causes a change in the light intensity distribution of return light from the recording medium at a far field position in accordance with a positional deviation of a light beam with respect to a recording medium, and generates a positional deviation information signal from the changed light intensity distribution. In the type information recording and reproducing device, a light amount distribution detecting means is provided for detecting a light amount distribution of return light from the recording medium in a tangential direction of the recording medium at a far field position,
An optical information recording/reproducing apparatus characterized in that an offset erasing means is provided for erasing the offset of the positional deviation information signal using the light quantity distribution signal detected by the light quantity distribution detecting means.