JPH04205726A - Offset eliminating device - Google Patents

Abstract

PURPOSE:To cancell a track offset with a simple constitution without being affected by the change of reflecting light quantity by comparing the light quantities of photodetector having plural groups of divided sensor parts which are arranged symmetrically to the direction of track. CONSTITUTION:The change of light quantities in the region where zero-th light T and 1st order light beams Ka, Kb among the lights reflected from an optical disk are superposed and interfered each other, is detected by 1st sensor parts (a),(b) of the photodetector 16. Besides, the change of light quantities in the region where zero-th light T and + or - 1st order light beams Ka, Kb are not superposed each other, is detected by 2nd sensor parts (c), (d). Then, the track error signal from a signal correcting means is corrected by using the signal of output difference obtained from the 1st sensor parts (a), (b) of photodetector 16 and the signal of output difference obtained from the 2nd sensor parts (c), (d). By this procedure, the amount of positional change of a light spot irradiating an optical information recording medium becomes possible to be detected, and the track offset can be cancelled with the simple constitution without being affected by the change of reflecting light quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an offset removal device equipped with an optical system for detecting a tracking error signal and a focus error signal.

2. Description of the Related Art An example of a conventional optical pickup device will be described with reference to FIG. After the light emitted from the semiconductor laser 1 as a light source is collimated by the collimating lens 2,
The light passes through the first beam splitter 3 (beam splitter) and is focused by the objective lens 4, thereby forming a light spot on the surface of the optical disc 5 as an optical information recording medium.

The reflected light from the optical disk 5 passes through the objective lens 4, is reflected by the first beam splitter 3, enters the second beam splitter 6 (beam splitter), and is transmitted or reflected thereby. Then, this second beam splitting element 6
The light that has passed through is detected by the two-split light receiving element 7, thereby detecting a tracking error signal. On the other hand, the light reflected by the second beam splitting element 6 is transmitted through two lenses 8
.

However, the semiconductor laser 1, the collimating lens 2, the first beam splitting element 3, and the objective lens 4 constitute an exposure optical system 11. Further, the second beam splitting element 6, the two-split light receiving element 7, the lenses 8 and 9, and the four-split light receiving element 10 constitute a signal detection optical system 12. Further, around the objective lens 4, there is a focus direction F and a tracking direction T.
An actuator section 13 is provided to control the movement.

"Problems to be Solved by the Invention" - In the conventional optical pickup device as described above,
When the objective lens 4 is moved horizontally (downward) by the actuator section 13 in accordance with the track error signal obtained by the two-split light receiving element 7, the returned light A shifts as shown in FIG.

As a result, the position of the light spot 14 irradiated onto the two-split light receiving element 7 is shifted downward from the position of the center dividing line in FIG. 7(a) as shown in FIG. 7(b). ,
A so-called "track offset" occurs. In this way, the shift to the returned light also occurs due to the inclination of the surface of the optical disk 5, so the position of the light spot 14 changes in all directions on the two-split light receiving element 7.

Furthermore, the light spot 1 is also
The position of 4 is from the center position of Fig. 7(c) to the position of Fig. 7(d).
), the light is irradiated at a position shifted to one side "obliquely", causing a so-called "focus offset".

As a track offset method as described above, there is a method in which the first beam splitting element 3 and the two-split light receiving element 7 are integrated with the objective lens 4 and driven within the housing 15, as shown in FIG. However, this method has the problem of being heavy and unsuitable for high-speed driving. Further, as other methods for removing the track offset, there are various methods as described below.

That is, the first method is disclosed in Japanese Patent Application Laid-open No. 64-4928.
As disclosed in the publication, the reflective spot is divided into two using a wedge prism, and the track offset is corrected by detecting the amount of light in the zero-order light region at the center.

As a second method, as disclosed in Japanese Unexamined Patent Publication No. 1-260637, the ±1st-order light region and the central region of the light spot are separately detected using a three-region diffraction grating, and the central region The track offset is corrected based on the amount of light in the area. Furthermore, as a third method, as disclosed in Japanese Patent Application Laid-Open No. 2-78029, a four-part light-receiving element having a light-receiving surface divided into four parts in a special shape is used. Near the center (
A track error signal is obtained by correcting the signal detected by the light-receiving surface formed in the inner region) by the signal detected by the light-receiving surface formed around it (outer region). This means canceling the .

However, in the first and second methods, there is a problem that the structure of the entire optical system becomes complicated, and changes in the amount of light from the semiconductor laser affect the corrected track error signal. In addition, in the third method, 4
Since the signal detected by the outer region of the divided light-receiving surface is affected by the tracking error, it does not become a perfect correction signal, and as a result, accurate tracking control cannot be performed.

Means for Solving the Problem Therefore, in order to solve such problems, claim 1
The invention described above includes a light source, an exposure optical system that focuses light from the light source on a track on an optical information recording medium, and a position where the light is focused and the track using reflected light from the optical information recording medium. An optical pickup device comprising: a signal detection optical system that detects a change in the position of the light; and an actuator section that changes the relative distance between the position of the light and the position of the track based on the output of the signal detection optical system. A first sensor section arranged symmetrically with respect to the direction of the track detects a change in the amount of light in a region where the 0th order light and the ±1st order light of the reflected light from the information recording medium overlap and interfere with each other; A light receiving element formed with a second sensor portion arranged symmetrically with respect to the direction of the track for detecting a change in light amount in an area where the light and the ±1st-order light do not overlap with each other is disposed within the signal detection optical system. and a signal correction means for correcting the output of the signal detection optical system using the output signal obtained from the first sensor section and the output signal obtained from the second sensor section.

In the invention according to claim 2, there is provided a light source, an exposure optical system that focuses light from the light source on a track on an optical information recording medium, and a position where the light is focused by reflected light from the optical information recording medium. An optical pickup device comprising: a signal detection optical system that detects a change in the position of the track; and an actuator section that changes the relative distance between the position of the light and the position of the track based on the output of the signal detection optical system, The light beam passes through the center of the light spot and a first sensor section arranged symmetrically with respect to the direction of the track, which detects a change in the amount of light in a region unaffected by the ±1st-order light among the reflected light from the optical information recording medium. A light receiving element formed with a second sensor section arranged symmetrically with respect to a straight line orthogonal to the track direction is provided in the signal detection optical system, and an output signal obtained from the first sensor section and a second sensor section are formed. A signal correction means is provided for correcting the output of the signal detection optical system using the output signal obtained from the sensor section.

In the invention according to claim 1, by comparing the amount of light of the light-receiving elements having at least two or more divided sensor sections arranged symmetrically with respect to the I/rack direction,
It becomes possible to detect the amount of change in the position of the light spot irradiated onto the optical information recording medium, and as a result, track offset can be canceled without being affected by changes in the amount of reflected light with a simple (1) η configuration. Therefore, a highly accurate track error signal can be obtained.

In the invention according to claim 2, at least three
By comparing the light intensity of the light-receiving element, which has a sensor section divided into two or more groups, it is possible to detect the amount of change in the position of the light spot irradiated onto the optical information recording medium, which makes focus offset easy. With this configuration, it is possible to cancel without being affected by changes in the amount of reflected light, so it is possible to obtain a highly accurate focus error signal.

Embodiment A first embodiment of the present invention will be explained based on FIGS. 1 and 3. The overall configuration of the optical pickup device has been described in the prior art (see FIG. 5), so a description of the same parts will be omitted and the same parts will be denoted by the same reference numerals.

First, before entering into the description of the present invention, the basic operating principle will be explained based on FIG. 3. When the light beam focused by the objective lens 4 is reflected on the surface of the optical disk 5 on which the track 5a is formed, O-order light T, +1st-order light Ka due to the groove, -
It is separated into primary light Kb. The track pattern is two areas P and Q (hatched areas) where the 0th-order light T and the ±1st-order lights Ka and Kb overlap, and their brightness changes due to track deviation.

The track error signal Tr has two areas P.

This can be obtained by comparing the change in light amount of Q, but the light amount of other areas of O-order light T does not change due to track deviation. Furthermore, since the light intensity distribution of the zero-order light "2" is a Gaussian distribution where the central part is brightest, the position of the light spot can be detected by detecting this distribution.

At this time, if one set of light-receiving elements is formed in the center as in the conventional example, an error will occur in the correction signal due to changes in laser light intensity, reflectance of the optical disk 5, etc., so at least two sets of light-receiving elements are used. It is necessary to detect the light amount distribution by comparison. Therefore, in this embodiment, such O-order light T1±1
Next light Ka.

The structure is as follows, taking advantage of the characteristics of Kb.

In the optical pickup device (see Fig. 5), Fig. 1 (
As shown in a) and (b), the light-receiving element 16 (this element is arranged at the position of the two-split light-receiving element 7) has a first light-receiving element 16 arranged symmetrically with respect to the track direction T. sensor parts a and b, and a second sensor part c arranged symmetrically with respect to the track direction T in the inner region of the first sensor parts a and b.
, d are formed. In this case, the first sensor part a,
b is the O-order light T and ± of the reflected light from the optical disc 5.
A change in light amount in a region where primary lights Ka and Kb overlap and interfere with each other is detected. Further, the second sensor section C9d detects a change in light amount in a region where the zero-order light T and the ±first-order lights Ka and Kb do not overlap with each other.

In addition, here, the first sensor portion a of the light receiving element 16,
The signal detection optical system 1 uses the output difference signal obtained from the sensor section b and the output difference signal obtained from the second sensor sections c and d.
A signal correction means is provided for correcting the second output signal, that is, the track error signal Tr.

In this case, a light receiving element 1 having a shape as shown in FIG.
The track error signal Tr in 6 can be determined by the following calculation formula using a signal correction means.

That is, the track error signal Tr is Tr-(a-b
)-k (c-d) -(1), it can be obtained by correcting the signal of (a-b) with the correction signal of k(c-d). In this case, the vertical direction of the light receiving element 16 (in the figure)
is not affected by the displacement of Note that k is a constant and is determined in advance experimentally or by calculation.

Further, the tracking error signal Tr in the light receiving element 16 having the shape as shown in FIG. 1(b) can be determined by the following calculation formula using a signal correction means.

Tr= (a-b)-k (c-d)-(2) first
In the case of figure (a), the change in (c-d) is caused by the light intensity distribution of the O-order light T, but in the case of figure 1 (b), it is caused by the difference in the total light intensity to each sensor part. Correction can be performed with higher sensitivity.

As described above, the sensor parts a, b, which are divided into at least two sets arranged symmetrically with respect to the track direction T,
By comparing the light amounts of the light receiving elements 16 having the light receiving elements c and d, it is possible to detect the amount of change in the position of the light spot irradiated onto the optical disc 5. This makes it possible to adjust the track offset by changing the amount of reflected light with a simple configuration. Since it is possible to cancel without being affected by the change, it is possible to obtain a track error signal Tr that is extremely accurate.

Next, a second embodiment of the present invention will be described based on FIGS. 2 and 4.

In the optical pickup device (see FIG. 5), the light-receiving element 17 includes first sensor parts a and b arranged symmetrically with respect to the track direction T, and a sensor part located inside the first sensor parts a and b. Second sensor portions c, d, e, and f are formed symmetrically with respect to a straight line perpendicular to the track direction T.

In this case, the first sensor parts a, b and the second sensor parts c, d
, e, and f detect changes in the light amount in areas that are not affected by the ±1st-order lights Ka and Kb among the reflected light from the optical disc 5.

Further, in the case of this embodiment, the output signals obtained from the first sensor sections a and b and the second sensor sections c, d, and e.

Using the output signal obtained from f, the signal detection optical system 1
A signal correction means is provided for correcting the two output signals, that is, the track error signal Tr and the focus error signal Fo.

In this case, a light receiving element 1 having a shape as shown in FIG.
The track error signal Tr in 7 can be determined by the following calculation formula using a signal correction means.

That is, the track error signal Tr is Tr=(a−
b) It can be determined by -k((c+e)-(d+f))-(3).

In addition, here, the optical spot position correction signal ΔFo to the focus error signal FO is expressed as ΔFO-k(c-d)(c-e)... (4)
Or ΔFo=k((c+e)-(d+f))・((c+d)
-(e+f)) ...(5), and the focus offset can also be canceled by this. Also, in the case of FIG. 2(b), it can be obtained in the same manner as in FIG. 2(a), so the explanation here will be omitted.

Note that the reason why the focus offset can also be canceled by the ΔFO will be described here. The focus offset in the astigmatism method in an optical pickup device as shown in FIG. 5 is as follows in FIG.
Lateral displacement amount ΔX and vertical displacement amount ΔY of the light spot 14
is proportional to the product of That is, if this is calculated, ΔFo= (A+C )-(B+D) = 4d = 4△X・ΔY. This is because the focus offset can be canceled by this ΔFo.

As described above, the sensor parts a, b, c, and d are divided into at least three sets arranged symmetrically with respect to the track direction T and a direction perpendicular thereto.

By comparing the light amounts of the light receiving elements 17 with e and f, it is possible to detect the amount of change in the position of the light spot irradiated onto the optical disc 5. This makes it possible to adjust the focus offset by changing the amount of reflected light with a simple configuration. Since it is possible to cancel without being affected by the change, a highly accurate focus error signal can be obtained.

Effects of the Invention The invention according to claim 1 includes: a light source; an exposure optical system that focuses light from the light source onto a track on an optical information recording medium;
a signal detection optical system that detects a change in the light convergence position and the track position by the reflected light from the optical information recording medium; In an optical pickup device equipped with an actuator unit that changes relative spacing, a change in light amount in a region where 0th-order light and ±1st-order light of the light reflected from the optical information recording medium overlap and interfere with each other is detected. A first sensor unit is arranged symmetrically with respect to the direction of the track, and a first sensor unit is arranged symmetrically with respect to the direction of the track, and a first sensor unit is arranged symmetrically with respect to the direction of the track. A light receiving element in which a second sensor section is formed is provided in the signal detection optical system, and the signal detection optical system uses an output signal obtained from the first sensor section and an output signal obtained from the second sensor section. Since a signal correction means for correcting the output of the system is provided, optical information can be obtained by comparing the light intensity of the light receiving element having at least two sets of sensor sections arranged symmetrically with respect to the track direction. It is now possible to detect the amount of change in the position of the light spot irradiated onto the recording medium, and as a result, track offset can be canceled with a simple configuration without being affected by changes in the amount of reflected light, resulting in high precision. track error signals can be obtained.

The invention according to claim 2 provides a light source; an exposure optical system that focuses light from the light source onto a track on an optical information recording medium;
a signal detection optical system that detects a change in the convergence position of the light and the position of the track by the reflected light from the optical information recording medium; In an optical pickup device comprising an actuator unit that changes a relative interval, a change in light amount in an area not affected by ±1st-order light of reflected light from the optical information recording medium is detected with respect to the direction of the track. A light receiving element having a first sensor section arranged symmetrically with respect to a line passing through the center of the light spot and a second sensor section arranged symmetrically with respect to a straight line passing through the center of the light spot and orthogonal to the direction of the track is placed in the signal detection optical system. Since the signal correction means for correcting the output of the signal detection optical system using the output signal obtained from the first sensor section and the output signal obtained from the second sensor section is provided, The amount of change in the position of the light spot irradiated onto the optical information recording medium can be determined by comparing the amount of light from a light receiving element that has sensor sections divided into at least three groups arranged symmetrically with respect to a direction perpendicular to the direction. This makes it possible to cancel focus offset with a simple configuration without being affected by changes in the amount of reflected light.
It is possible to obtain a highly accurate focus error signal.

[Brief explanation of the drawing]

Fig. 1 is a front view of a light receiving element showing a first embodiment of the present invention, Fig. 2 is a front view of a light receiving element showing a second embodiment of the invention, and Fig. 3 is a basic configuration of the present invention. Fig. 4 is a front view showing the situation when focus offset can be canceled, Fig. 5 is a configuration diagram showing a conventional example, and Fig. 6 is a diagram showing the case where the objective lens is moved. Operation explanatory diagram showing how return light is generated by
The figure is a front view of the light receiving element showing the occurrence of track offset and focus offset, and FIG. 8 is a side view showing the state when the light receiving element is integrated with the objective lens. ■ Light source, 5... Optical information recording medium, 11. Exposure optical system, 12... Signal detection optical system, 13... Actuator section, 16.17... Light receiving element, T... 0th order light, Ka
, Kb...±first-order light, a, b... first sensor, c,
c3. e, f...Second sensor applicant Rico Co., Ltd.: Figure f37

Claims (1)

[Scope of Claims] 1. A light source, an exposure optical system that focuses light from the light source on a track on an optical information recording medium, and a light converging position of the light by reflected light from the optical information recording medium. An optical pickup device comprising: a signal detection optical system that detects a change in the position of the track; and an actuator section that changes the relative distance between the position of the light and the position of the track based on the output of the signal detection optical system, a first sensor section arranged symmetrically with respect to the direction of the track, which detects a change in light amount in a region where 0th-order light and ±1st-order light of the reflected light from the optical information recording medium overlap and interfere with each other; The signal detection optical system includes a light receiving element formed with a second sensor section arranged symmetrically with respect to the direction of the track, which detects a change in light intensity in a region where the zero-order light and the ±1st-order light do not overlap with each other. A signal correction means is provided in the sensor and corrects the output of the signal detection optical system using the output signal obtained from the first sensor section and the output signal obtained from the second sensor section. Offset removal device. 2. A light source, an exposure optical system that focuses light from the light source onto a track on an optical information recording medium, and a change in the focusing position of the light and the position of the track due to reflected light from the optical information recording medium. An optical pickup device comprising a signal detection optical system for detecting a signal from the optical information recording medium, and an actuator section for changing the relative distance between the position of the light and the position of the track based on the output of the signal detection optical system. A first sensor unit arranged symmetrically with respect to the direction of the track and a light spot that passes through the center of the track and is orthogonal to the direction of the track, detecting a change in the amount of light in an area that is not affected by the ±1st-order light among the reflected light. A light receiving element formed with a second sensor section arranged symmetrically with respect to a straight line is provided in the signal detection optical system, and an output signal obtained from the first sensor section and an output obtained from the second sensor section are provided. 1. An offset removal device comprising: a signal correction means for correcting the output of the signal detection optical system using the signal.