JP2003022562A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify constitution and to lower costs by reducing the time and operation procedure for adjusting positions where an optical detector detects two kinds of light beams differing in wavelength. SOLUTION: The photodetector 22 comprises 16 photodetecting elements arranged in a matrix of four rows by four columns and the photodetection position of light reflected by an optical recording medium can be obtained according to an arithmetic result obtained by combining AND and NOT of detection signals that the respective photodetecting elements generate. The photodetecting element group is sectioned into four areas corresponding to the obtained photodetection positions of the reflected light and a focus error signal(FES) can be obtained from detection signals of the reflected light detected in the four sectioned areas. Consequently, focusing can be completed by finding the FES without making correction by moving the photodetection positions of the reflected light to the center of the optical detector 22, so the time and operation procedure for adjusting the photodetection positions can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device for recording / reproducing information on / from an optical recording medium using two kinds of light having different wavelengths.

[0002]

2. Description of the Related Art In recent years, as the recording capacity of an optical recording medium has been increased, the wavelength of light used for an optical pickup has been shortened. The size of the light spot focused on the optical recording medium is proportional to the wavelength of light, and the recording capacity of the optical recording medium is inversely proportional to the square of the wavelength. Therefore, the shorter the wavelength of the light used, the larger the amount of information that can be recorded on or reproduced from the optical recording medium. Since the optical recording medium has a strong wavelength dependency on the light reflectance and the recording capacity of information, a light having a wavelength different from the wavelength of the light used for recording or reproducing information on one optical recording medium is used. In that case, there is a problem that information cannot be reproduced or recorded on the one optical recording medium. Therefore, in order to use an optical recording medium having a small recording capacity and an optical recording medium having a large recording capacity together by using one optical pickup device, light having a long wavelength and light having a short wavelength are used. An optical pickup device having a configuration capable of reproducing or recording information on two types of optical recording media is required.

FIG. 15 is a system diagram showing a simplified configuration of a conventional optical pickup device 1 provided with two light sources for respectively emitting lights of different wavelengths. In the conventional optical pickup device 1, two laser chips 2 and 3 which are light sources are used.
Are provided on individual bases 4 and 5, respectively. The first laser chip 2 emits light 6 having a wavelength λ1 (for example, 645 nm).
And the second laser chip 3 emits light 7 having a wavelength λ2 (for example, 780 nm). The light 6 emitted from the first laser chip 2 is made into substantially parallel light by the collimator lens 8 and bent by 90 degrees by the half mirror 9.
The bent light is further bent 90 degrees by the rising mirror 10 and guided toward the optical recording medium 11, and is condensed on the optical recording medium 11 by the objective lens 12. The light 7 having the wavelength λ2 emitted from the second laser chip 3 is also condensed on the optical recording medium 11 in the same manner as the light 6 having the wavelength λ1 emitted from the first laser chip 2. Information is reproduced or recorded on the optical recording medium 11 by the condensed light spot. The wavelength of light used for reproducing or recording information is selected according to the type of optical recording medium used.

The light reflected by the optical recording medium 11 is
The light is made into substantially parallel light again by the objective lens 12, bent 90 degrees by the rising mirror 10, and then transmitted through the half mirror 9 to be converged light by the condenser lens 13. The reflected light that has passed through the condenser lens 13 is astigmatized by the cylindrical lens 14 and then received by the photodetector 15. Information on the light receiving position on the light receiving element and a focus error signal are obtained based on the amount of light received by the photodetector 15.

In the conventional optical pickup device 1, the optical axes of the reflected lights of the lights 6 and 7 having the two wavelengths coincide with each other. However, the first and second laser chips 2 and 3 for emitting lights of different wavelengths are provided as light sources, and the collimator lens 8 and the half mirror 9 are provided for each light source, that is, for the light of each wavelength. In the configuration including two sets of the same means, the storage space for the members increases, so that the size of the device increases and the cost of the device increases due to the increase in the number of members.

FIG. 16 is a system diagram showing a simplified structure of another conventional optical pickup device 16 having two light sources. Another conventional optical pickup device 1
Reference numeral 6 is provided with laser chips 2 and 3 which are two light sources which respectively emit light of two kinds of wavelengths suitable for the optical storage medium so that it can be applied to any of two kinds of optical recording media having different recording capacities. .

Another conventional optical pickup device 16
Then, the two laser chips 2 and 3 are provided in parallel on the integrated base 17. Since the optical axis of the light 18 of the wavelength λ1 emitted from the first laser chip 2 and the optical axis of the light 19 of the wavelength λ2 emitted from the second laser chip 3 are deviated, the light of the wavelength λ1 and the light of the wavelength λ2 are shifted. And the positions where they are focused on the optical recording medium 15 are different.

Therefore, the reflected lights from the optical recording medium 11 due to the lights of two different wavelengths are received by the photodetector 15 at different positions. That is, as the type of the optical recording medium is changed, the light used for recording or reproducing is changed with respect to the optical recording medium 11, so that the position of the light spot received by the photodetector 15 is changed. .
If the position of the light spot received by the photodetector 15 changes, the detection signal of the reflected light used for focusing, for example, by the photodetector 15 changes greatly, so that accurate focusing cannot be performed.

In order to solve this problem, in another conventional optical pickup device 16, a correction prism 20 for correcting the optical axis of the reflected light is provided between the optical recording medium 11 and the photodetector 15. The correction prism 20 corrects the optical axis of the reflected light for each light having a different wavelength, and the photodetector 1
It is possible to receive reflected light at almost the same position of 5.

[0010]

In the other conventional optical pickup device 16, although the problem that the size of the device is increased due to the increase of the storage space and the cost is increased due to the increase of the number of members, the light 18 of two different wavelengths is provided. , 19, the optical axes are deviated, so the angle of the correction prism 20 is set to 0.05.
By adjusting with a high degree of accuracy, the photodetector 1
There is a problem in that the light receiving positions of the light spots on 5 must be matched. Further, since a device for controlling the inclination of the correction prism 20 with high accuracy is required, there is a problem that the cost becomes high. Further, when adjusting the light receiving position of the light spot on the photodetector 15, it is necessary to replace the optical recording medium with an optical recording medium suitable for the wavelength of the light emitted from the laser chip. It is not possible to adjust the correction prism 20 and other optical members so that the light receiving position of the light spot received by the photodetector 15 and the light receiving position of the photodetector 15 are substantially the same for the light 18 of wavelength λ1 and the light 19 of wavelength λ2. It is impossible. Therefore,
For example, if the light receiving position on the photodetector 15 is adjusted by the light 18 having the wavelength λ1, the light receiving position on the photodetector 15 is shifted by the light 19 having the wavelength λ2, and an accurate detection signal cannot be obtained. There is a problem that a large amount of operation procedure and time are required to readjust the light receiving element on the photodetector 15 to the proper position with the light 19 having the wavelength λ2.

An object of the present invention is to reduce the time and operation procedure for adjusting the light receiving positions of two types of light having different wavelengths and adapted to optical recording media having different recording capacities by a photodetector. An object of the present invention is to provide an optical pickup device having a simple structure and capable of reducing cost.

[0012]

The present invention provides an optical recording medium for recording or reproducing information, a light source for emitting two kinds of light having different wavelengths toward the optical recording medium, a light source and an optical recording medium. A first condensing unit arranged between the optical recording medium and condensing the light emitted from the light source onto the optical recording medium, and a light detecting unit detecting the reflected light from the optical recording medium. Photodetection means in which light receiving elements are arranged in a matrix, and second condensing means arranged between the photodetection means and the optical recording medium and condensing reflected light reflected by the optical recording medium on the photodetection means. The optical pickup device is characterized by including and.

Further, the present invention is characterized in that the light detecting means comprises 16 light receiving elements arranged in a matrix of 4 rows and 4 columns.

According to the present invention, the light emitted from the light source is condensed on the optical recording medium by the first condensing means.
The light reflected by the optical recording medium is condensed by the second condensing means and given astigmatism, and then a plurality of, for example, 16 light receiving elements are arranged in a matrix of 4 rows and 4 columns. After being focused on the detection means, a detection signal of the reflected light is obtained. When the light receiving position of the reflected light from the optical recording medium by the light detecting means is deviated from the center of the light detecting means, the matrix is set at or near the center of the light spot of the reflected light to detect the signal of the reflected light. It is possible to shift the centers of the four light-receiving elements arranged in a line, which are formed by the corners that are in contact with each other, in the row direction and the column direction of the light-receiving elements arranged in a matrix in accordance with the light receiving position of the reflected light. Therefore, even when the light receiving position of the reflected light is deviated from the center of the light detecting means, the signal of the reflected light can be accurately detected,
It is not necessary to control the inclination of the correction prism in order to match the center with the optical axis of the reflected light. As a result, the operating procedure and time can be reduced, and since the control member for the correction prism can be omitted, the structure of the device can be simplified and the cost can be reduced.

According to the present invention, the light source includes two laser chips which respectively emit two kinds of light having different wavelengths,
It is characterized by including two casings that individually accommodate two laser chips.

According to the present invention, the light source includes two laser chips which respectively emit two types of light having different wavelengths,
It is characterized by including one casing for accommodating two laser chips in parallel.

According to the invention, two casings for individually accommodating two laser chips are arranged side by side, or two laser chips are accommodated side by side in one casing. As a result, the distance between the optical axes of the light emitted from the two laser chips is reduced, and the deviation of the optical axes of the two types of light having different wavelengths can be reduced.

Further, the invention is characterized in that the first condensing means includes an objective lens coated with an antireflection film.

According to the present invention, since the antireflection film is coated on the objective lens, the reflection loss of light by the objective lens can be reduced. As a result, the same objective lens can be used even when the light intensity of at least one of the two types of light having different wavelengths is weak.

Further, the present invention is characterized in that the second condensing means includes parallel plate glass.

According to the present invention, astigmatism can be generated by the parallel plate glass. Since the parallel plate glass has a simple structure and is easy to manufacture, the cost of the device can be reduced.

According to the present invention, the second condensing means includes a spot lens for condensing the reflected light, and a moving means for moving the spot lens close to and away from the light detecting means in parallel to the optical axis of the reflected light. And an angular displacement means for angularly displacing the spot lens around an axis line that passes through the center of gravity of the spot lens and is orthogonal to the optical axis of the reflected light.

According to the present invention, since the spot lens can move in parallel with the optical axis of the light reflected by the optical recording medium, it is possible to adjust the condensing position of the reflected light. Further, since the spot lens can be angularly displaced, it is possible to correct the coma aberration generated in the reflected light due to the undesired inclination of the optical member in the first condensing unit. As a result, the light detecting means can obtain an accurate detection signal of the reflected light.

According to the present invention, in the light detecting means, a plurality of light receiving elements are divided into four regions, the four regions are arranged in a matrix of 2 rows and 2 columns, and the 2 regions of the first row are arranged. The difference between the detection signal of the reflected light detected by the light receiving element group constituting the light receiving element and the detection signal of the reflected light detected by the light receiving element group forming the two areas of the second row, and the two regions of the first column are Due to the difference between the detection signal of the reflected light detected by the light receiving element group constituting the light and the detection signal of the reflected light detected by the light receiving element group constituting the two regions of the second row,
It is characterized in that the light receiving position of the reflected light is detected.

According to the present invention, the plurality of light receiving elements constituting the light detecting means are divided into four regions and arranged in a matrix of 2 rows and 2 columns, and the reflected light is condensed on the light detecting means. Then, the detection signal of the reflected light detected by the light receiving element group forming the two regions of the first row and the detection signal of the reflected light detected by the light receiving element group forming the two regions of the second row The light receiving position in the row direction of the reflected light is detected by the difference between the two, and the detection signal of the reflected light detected by the light receiving element group forming the two regions in the first column and the light receiving element forming the two regions in the second column Since the light receiving position of the reflected light in the column direction is detected by the difference between the detection signal of the reflected light detected by the group, the light receiving position of the reflected light in the photodetector can be accurately detected. Thus, the detection signal of the reflected light obtained from the four regions at the position where the light detecting means receives the reflected light without correcting the optical axis of the reflected light is used for controlling focusing, for example. You can

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a light detecting means 22 provided in an optical pickup device 21 according to a first embodiment of the present invention.
2 is a plan view showing a simplified configuration of FIG. 2, and FIG. 2 is a system diagram showing a simplified configuration of an optical pickup device 21 including the photodetecting means 22 shown in FIG.

The optical pickup device 21 includes a light source 23 for emitting two kinds of light having different wavelengths, an optical recording medium 24 for recording or reproducing information, a light source 23 and an optical recording medium 24.
A first condensing unit 25 arranged between the optical recording medium 24 and the first condensing unit 25 for condensing light emitted from the light source 23 onto the optical recording medium 24;
Light detection means 22 in which 16 light receiving elements are arranged in a matrix, and reflected light which is arranged between the light detection means 22 and the optical recording medium 24 and reflected by the optical recording medium 24 are transmitted to the light detection means 22. The 2nd condensing means 26 for condensing is included.

FIG. 3 shows the optical pickup device 21 shown in FIG.
It is a top view which simplifies and shows the structure of the light source 23 with which it is equipped. The light source 23 includes two first and second laser chips 2
7, 28 are provided. The first laser chip 27 emits the first light 29 having a wavelength of 780 nm, for example, and the second laser chip 28 emits the second light 30 having a wavelength of 645 nm, for example. The first laser chip 27 is provided in the first casing 31,
The second laser chips 28 are housed in the second casing 32, respectively. First and second casings 31, 3
2 is mounted close to the base 33. The base 33 has
A cover member 34 is provided to cover the first and second casings 31 and 32 so that the scattered light from the first and second laser chips 27 and 28 does not affect the surroundings. The first and second casings 31, 32 are close to each other and the base 33
Two laser chips 2 can be mounted on top
Since the distance between the optical axes of the lights emitted from 7, 28 is small, it is possible to reduce the deviation of the optical axes of the two types of light having different wavelengths.

The optical recording medium 24 has a diameter of 8 cm or 1
It has a thin disk-like shape of 2 cm, and is formed, for example, by vapor-depositing aluminum on one surface of a polycarbonate substrate and covering the vapor-deposited aluminum layer with a resin protective film. The optical recording medium 24 includes optical discs such as compact discs and digital versatile discs, and is widely used as a recording medium that can be randomly accessed, is easy to handle, and can record a large amount of information.

The first condenser means 25 is a collimator lens 3
5, a half mirror 36, a rising mirror 37, and an objective lens 38. The collimator lens 35 has a first
The first or second light 29, 30 emitted from the laser chip 27 or the second laser chip 28 is collimated. The half mirror 36 receives the first or second light 2 from the light source 23.
The emitted light of 9 and 30 is reflected, and the reflected light from the optical recording medium 24 is transmitted. The rising mirror 37 reflects the light reflected and incident on the half mirror 36 toward the optical recording medium 24, and reflects the light reflected and incident on the optical recording medium 24 toward the half mirror 36. The objective lens 38 focuses the incident light on the information recording surface of the optical recording medium 24 and forms a light spot on the information recording surface. The objective lens 38 is coated with an antireflection film made of MgF ₂ , for example. This makes it possible to reduce the reflection loss of light by the objective lens 38, so that the same objective lens 38 is used even when the light intensity of at least one of the two types of light having different wavelengths is weak. be able to.

The second light collecting means 26 includes a correction prism 39.
, Spot lens 40, and cylindrical lens 41
Including and The correction prism 39 refracts the reflected light reflected by the optical recording medium 24 and changes the direction of the optical axis.
The spot lens 40 focuses the reflected light. The cylindrical lens 41 has a refracting power only in the cross section in one direction, and has no refracting power in the cross section in the other direction orthogonal to the one direction, and produces astigmatism in the transmitted reflected light.

The photo-detecting means 22 is a photo-detector 22 composed of light-receiving elements consisting of 16 photodiodes arranged in a matrix of 4 rows and 4 columns. The 16 light receiving elements include four light receiving elements A1, A2, A in the first row.
3 and A4 are arranged, and four light receiving elements B1 and B are provided in the second row.
2, B3, B4 are arranged, and four light receiving elements C are provided in the third row.
1, C2, C3, C4 are arranged, and four light receiving elements D1, D2, D3, D4 are arranged in the fourth row. In other words, this is arranged in rows, that is, four light-receiving elements A1, B are arranged in the first row.
1, C1 and D1 are arranged, and four light receiving elements A are arranged in the second row.
2, B2, C2, D2 are arranged, four light receiving elements A3, B3, C3, D3 are arranged in the third row, and four light receiving elements A4, B4, C4, D4 are arranged in the fourth row. Each light receiving element converts the received reflected light into a current corresponding to the light intensity, and uses it as a detection signal of the reflected light. Also photo detector 2
2 includes a signal amplification circuit that amplifies the detection signal of the reflected light and a calculation circuit that calculates the detection signal.

The first light 29 emitted from the first laser chip 27 of the light source 23 is collimated by the collimator lens 35 and then reflected by the half mirror 36. The reflected light enters the rising mirror 37, is reflected toward the optical recording medium 24, and then is focused on the optical recording medium 24 by the objective lens 38 to form a light spot to record or reproduce information. Is done. The reflected light reflected by the optical recording medium 24 is the objective lens 38.
Through the half mirror 36.

The reflected light transmitted through the half mirror 36 is refracted by the correction prism 39, and the spot lens 40
The light is collected by the photodetector 22 after the astigmatism is given by passing through the cylindrical lens 41.
Is received by.

Second laser beam emitted from the second laser chip 28
The light 30 emits the first light emitted from the first laser chip 27.
The photodetector 2 passes through an optical path slightly deviated from the optical path of the light 29.
2 is received.

FIG. 4 shows a photodetector 4 including four light receiving elements.
2 is a plan view showing a simplified configuration of FIG. 2, and FIGS. 5 to 7 show an arithmetic circuit 4 for arithmetically processing a detection signal from the photodetector 42.
It is a block diagram which simplifies and shows the structure of FIG.

The photodetector 42 comprises four light receiving elements 44, 4
It consists of 5,46,47. Here, for the sake of convenience, the light receiving element 4
The detection signal of the reflected light received by 4 is called a, the detection signal of the light receiving element 45 is called b, the detection signal of the light receiving element 46 is called c, and the detection signal of the light receiving element 47 is called d. Photo detector 4
The arithmetic circuit 43 provided in No. 2 includes first and second OR circuits 48 and 49 and a logical difference circuit 50. The respective detection signals a, b, c, d obtained from the four light receiving elements 44, 45, 46, 47 are converted into first and second OR circuits 48, 4
9 and the logical difference circuit 50 are combined to perform a calculation process, whereby a focus error signal used for focus control of reflected light (hereinafter, abbreviated as FES) and an arrow 51 of a light spot on the photodetector 42 of reflected light. It is possible to obtain the first error signal indicating the deviation in the direction parallel to the track direction of the optical recording medium and the second error signal indicating the deviation in the direction orthogonal to the track direction of the optical recording medium.

FES is given by equation (1), and the first and second error signals are given by equations (2) and (3), respectively. FES = (a + c) − (b + d) (1) First error signal = (a + d) − (b + c) (2) Second error signal = (a + b) − (c + d) (3)

In FIG. 8, the photodetector 42 converts the reflected light into the photodetector 4
2 is a plan view showing a state of receiving light at the center 52 of 2.
FIG. 9 is a diagram showing the waveforms of the detection signals from the light receiving elements 44, 45, 46, 47 and the signals arithmetically processed by the arithmetic circuit 43.

In the photodetector 42 shown in FIG. 8, the center of the light spot 53 of the reflected light is the four light receiving elements 44, 45, 4
The light is received so as to be substantially coincident with the center 52 of the photodetector 42 which is formed by contacting with each other. The light spot 53 received by the photodetector 42 has a substantially circular cross-sectional shape orthogonal to the optical axis of the reflected light. FIG. 9 (a)
The waveforms a, b, c, and d shown in FIG. 9D are signal waveforms detected by the four light receiving elements 44, 45, 46, and 47, respectively. Each light receiving element 44, 45, 46, 47
, Respectively, receive one-fourth of the light spot 53 evenly, so that the signal waveforms a, b, c, d have the same line-symmetrical shape.

The waveform e shown in FIG. 8 (e) is the FES signal waveform given by the equation (1). When the cross-sectional shape of the light spot 53 is circular, the signal waveform e has a point-symmetrical shape and the absolute values of the positive component and the negative component are equal to each other, and the calculation result by the equation (1) becomes zero. Therefore, conversely, by controlling so that the calculation result obtained by the equation (1) becomes zero, it is possible to focus the light spot of the reflected light.

That is, with reference to the state of the in-focus point where the FES calculation result becomes zero and the circular light spot 53 is presented,
When the objective lens moves away from the optical recording medium, the reflected light becomes a substantially elliptical light spot 54 in which the light receiving elements 44 and 46 occupy a large light receiving area. At this time, the calculation result of the FES based on the equation (1) is positive, and it is detected that the reflected light is out of focus. On the contrary, when the objective lens moves in the direction of approaching the optical recording medium, the reflected light becomes a substantially elliptical light spot 55 in which the light receiving elements 45 and 47 occupy a large light receiving area. At this time (1)
Since the result of FES calculation based on the equation is negative, it is detected that the reflected light is out of focus.

Further, when the light spot 53 of the reflected light is received so that the center thereof coincides with the center 52 of the photodetector, the signal waveform f representing the first error signal has a large positive component and a negative component. There is no bias. Further, in the signal waveform g representing the second error signal, the absolute values of the positive component and the negative component are equal, and the calculation result by the equation (3) becomes zero.

FIG. 10 is a plan view showing a state in which the photodetector 42 receives the reflected light at a position deviated from the center 52 of the photodetector 42, and FIG. 11 is a light receiving element 44, 45, 4
FIG. 6 is a diagram showing waveforms of detection signals of 6, 47 and signals processed by a calculation circuit 43.

In the photodetector 42 shown in FIG. 10, the center 90 of the light spot 53 of the reflected light is shifted and received from the center 52 of the photodetector. The light spot 53 received by the photodetector 42 has a substantially circular cross-sectional shape orthogonal to the optical axis of the reflected light. 11 (a) to 11 (d),
The signal waveforms are respectively detected by the light receiving elements 44, 45, 46, 47. Since the light spot 53 of the reflected light is deviated from the center 52 of the photodetector 42, each light receiving element 4
Reference numerals 4, 45, 46 and 47 respectively receive lights having different intensities, and signal waveforms a, b, c and d show different waveforms.

The waveform e shown in FIG. 11E is (1)
It is a signal waveform of FES given by a formula. The center 90 of the light spot 53 of the reflected light is the center 5 of the photodetector 42.
Since it is deviated from 2, the signal waveform is biased to the positive component, and the calculation result obtained by the equation (1) is positive. Further, the light receiving positions of the light spot 54 of the reflected light when the objective lens moves away from the optical recording medium and the light spot 55 of the reflected light when the objective lens moves toward the optical recording medium. , FE obtained by the equation (1) by shifting from the center 52 of the photodetector 42
The positive / negative of the calculation result of S and the distance of the objective lens from the optical recording medium do not correspond. Therefore, when the light spot 53 of the reflected light is deviated from the center 52 of the photodetector 42,
Focusing of the light spot of reflected light cannot be performed.

When the center 90 of the light spot 53 of the reflected light is deviated from the center 52 of the photodetector 42, the signal waveforms f and g representing the first and second error signals are biased to the negative component,
The calculation result by the expressions (2) and (3) becomes negative. The bias of the signal waveforms f and g representing the first and second error signals is
Since it corresponds to the deviation of the light spot 53 from the center 52 of the photodetector 42, the first and second error signals
The light receiving position of the reflected light can be detected.

As described above, when the center 90 of the light spot 53 of the reflected light is deviated from the center 52 of the photodetector 42, accurate FES cannot be obtained, so that the focusing of the light spot of the reflected light is performed. Can't do. In order to obtain a highly accurate signal that can be focused, it is necessary to correct the optical axis by the correction prism so that the center 90 of the light spot 53 of the reflected light can be received by the center 52 of the photodetector 42. is there. Light receiving element 4
Signal waveforms obtained from 4, 45, 46, 47 and F
The angle of the correction prism must be adjusted with high accuracy of about 0.05 degrees so that the ES signal waveform becomes the signal waveforms shown in FIGS. 9A to 9E. That is, a device for controlling the inclination of the correction prism with high accuracy is required, which increases the manufacturing cost of the device. Also, when the optical recording medium to be recorded or reproduced changes, the laser chip used must be changed accordingly, so that the optical axis shifts each time the optical recording medium is changed. Therefore, it is necessary to adjust the angle of the correction prism each time the optical recording medium changes, which causes a problem that a large operation procedure and adjustment time are required.

Returning to FIG. 1, the photodetector 22 included in the optical pickup device 21 of the present embodiment is composed of 16 light receiving elements. Here, for convenience, the light receiving element A1,
The detection signals of the reflected light received by A2, A3 and A4 are a
1, a2, a3, a4, and so on.
1, B2, B3, B4 detected signals are b1, b2, b
3, b4, the detection signals of the light receiving elements C1, C2, C3, C4, c1, c2, c3, c4, the light receiving elements D1, D2, D
The detection signals of 3 and D4 are called d1, d2, d3 and d4. Further, the corner portion formed by the light receiving elements B2, B3, C2, C3 contacting each other is the center 56 of the photodetector 22.
By dividing the 16 light-receiving elements into four areas that are in contact with each other at the center 56, the detection signals obtained from the respective areas formed by the four light-receiving elements are converted into the four light-receiving elements 4 shown in FIG.
It can be considered in correspondence with the respective detection signals a, b, c and d obtained from 4, 45, 46 and 47 respectively. a = a1 + a2 + b1 + b2 b = c1 + c2 + d1 + d2 c = c3 + c4 + d3 + d4 d = a3 + a4 + b3 + b4

Thus, FES is given by equation (4), and the first and second error signals are given by equations (5) and (6), respectively. FES = [(a1 + a2 + b1 + b2) + (c3 + c4 + d3 + d4)]-[(c1 + c2 + d1 + d2) + (a3 + a4 + b3 + b4)] (4) 1st error signal = [(a1 + a2 + c4 + c4 + c4 + c4 + c4 + c4 + c4 + d4) + (a3 + a2 + c4 + d4 + c4 + d4) (5) Second error signal = [(a1 + a2 + b1 + b2) + (c1 + c2 + d1 + d2)]-[(c3 + c4 + d3 + d4) + (a3 + a4 + b3 + b4)] (6)

When the reflected light is received by the photodetector 22, the first calculation result based on the equations (5) and (6) is obtained.
And the light receiving position of the reflected light is detected by the second error signal. Light spot 57 received by the photodetector 22
Has a substantially circular cross section orthogonal to the optical axis of the reflected light. When the calculation results of the expressions (5) and (6) are zero, the center of the light spot 57 of the reflected light is the center 56 of the photodetector 22.
FES can be obtained by the equation (4) when the values almost match. However, when the calculation results by the equations (5) and (6) are not zero and the center of the light spot 57 of the reflected light is deviated from the center 56 of the photodetector 22, FES is obtained by the equation (4). I can't.

Here, the light spot 57 is arranged so that the light receiving element A1 of the photodetector 22 shown in FIG. 1 occupies the widest light receiving area.
In the case I, the light receiving element D1 occupies the widest light receiving area, and the light receiving point of the light spot 57 shifts in the case II, and the light receiving element D4 occupies the widest light receiving area. Case III is a case where the light receiving position of is shifted, and Case IV is a case where the light receiving position of the light spot 57 is shifted so that the light receiving element A4 occupies the largest light receiving area. In each of the above cases
Table 1 shows the results of calculating the first and second error signals based on the equations (5) and (6). In case I,
The calculation result of the first error signal is positive, the calculation result of the second error signal is positive, in Case II, the calculation result of the first error signal is negative, and the calculation result of the second error signal equation is positive, in Case III. , The calculation result of the first error signal is negative, the calculation result of the second error signal expression is negative, and in case IV, the calculation result of the first error signal is positive and the calculation result of the second error signal expression is a negative combination. Therefore, cases I to IV, that is, the deviation direction of the light receiving position of the light spot 57 can be identified by the positive and negative combinations of the first and second error signals.

[0053]

[Table 1]

Corresponding to cases I to IV of the calculation results shown in Table 1, four combinations of light receiving element groups are used to calculate FES.
By predetermining the center of division into regions (hereinafter referred to as the detection center), the detection center can be determined at a position that substantially coincides with the center of the light spot 57 according to the shift of the light receiving position of the light spot 57. .

For example, a case III in which the light receiving position of the light spot 57 is displaced so that the light receiving element D4 occupies the widest light receiving element will be described as an example. When the light spot 57 is received by the photodetector 22, the first and second error signals are calculated. The output of the calculation result is input to a CPU (Central Processing Unit) equipped with a microchip. The CPU selects the predetermined detection center 58 corresponding to the case III according to the logic of selecting the predetermined detection center corresponding to each of the cases I to IV shown in Table 1. The detection center 58 is the light receiving element C3.
C4, D3 and D4 are set at the corners where they touch each other. In the CPU, in response to the selective output of the detection center 58,
The 16 light-receiving elements are newly divided into light-receiving element groups A, B, C and D in four areas which are in contact with each other at the detection center 58. The newly divided light receiving element groups A, B, C and D are shown in the following equations (7) to (10). A = A1 + A2 + A3 + B1 + B2 + B3 + C1 + C2 + C3 (7) B = D1 + D2 + D3 (8) C = D4 (9) D = A4 + B4 + C4 (10)

Detection center 58 which is the center of the light spot 57
By newly dividing into the light receiving element groups A, B, C, and D in, the state becomes almost the same as the case where the center 56 of the photodetector 22 and the center of the light spot 57 coincide with each other and are received. The newly divided light receiving element groups A, B, C, and D are given to the arithmetic circuit as outputs from the CPU, and FES is (11).
It is calculated by an expression. FES = [(a1 + a2 + a3 + b1 + b2 + b3 + c1 + c2 + c3) + d4]-[(d1 + d2 + d3) + (a4 + b4 + c4)] (11)

Further, when the objective lens 38 moves in the direction away from the optical recording medium 24 or the objective lens 38 moves with the objective lens 38 as a reference, the state of the in-focus point presenting the circular light spot 57 where the FES calculation result becomes zero. Elliptical light spot 5 when moved in a direction approaching the optical recording medium 24
Also for 9 and 60, since it is detected that the reflected light is out of focus depending on whether the calculation result of the equation (11) is positive or negative, the reflected light can be focused. Therefore, in the photodetector 22 included in the optical pickup device 21 according to the first embodiment of the present invention, the center of the light spot 57 of the reflected light does not coincide with the center 56 of the photodetector 22. Also, the detection center 58 is set by regarding it as the center of the light spot 57 of the reflected light, and the light detection element group is newly divided into four regions of the detection center 58 which are in contact with each other. The FES can be calculated based on the detection signals by the light receiving element groups of the four newly divided regions without performing the correction for shifting the position, and the accurate signal can be detected. Further, even when the optical axis is deviated by changing the laser chip used, it is not necessary to correct the optical axis.

As described above, even when the receiving position of the reflected light is deviated from the center 56 of the light detecting means 22, the signal of the reflected light can be accurately detected, so that the center 56 and the optical axis of the reflected light are detected. It is not necessary to control the inclination of the correction prism 39 in order to match Therefore, the operation procedure and time can be reduced, and the control member of the correction prism 39 can be omitted, so that the structure of the device can be simplified and the cost can be reduced.

FIG. 12 is a system diagram showing a simplified configuration of the second condensing means 61 included in the optical pickup device according to the second embodiment of the present invention. The second condensing means 61 of the present embodiment is similar to the second condensing means 26 provided in the optical pickup device 21 of the first embodiment, and corresponding parts are designated by the same reference numerals and described. Is omitted. It should be noted that the second condensing means 61 is the cylindrical lens 41.
Instead of the parallel flat glass 62.

The parallel plate glass 62 is arranged so as to be tilted with respect to the optical axis 63 of the reflected light from the optical recording medium 24, thereby causing astigmatism in the reflected light. Further, since the coma aberration is generated at the same time by inclining the parallel plate glass 62, in order to correct the coma aberration, the same optical element 64 as the parallel plate glass 62 is inclined with respect to the optical axis 63 of the parallel plate glass 62. It is tilted in the opposite direction and placed on the optical axis 63.

According to the present embodiment, the second condensing means 61
Can generate astigmatism by the parallel plate glass 62. Since the parallel plate glass 62 has a simpler structure and is easier to manufacture than the cylindrical lens 41, the cost can be reduced.

FIG. 13 is a system diagram showing a simplified configuration of the second condensing means 65 provided in the optical pickup device according to the third embodiment of the present invention. The second condensing means 65 of the present embodiment is similar to the second condensing means 26 provided in the optical pickup device 21 of the first embodiment, and corresponding parts are designated by the same reference numerals and described. Is omitted. It should be noted that the second condenser means 65 includes a spot lens 68 including an angular displacement means 66 and a movement means 67.

When the optical member of the first condenser means 25 has an undesired inclination, coma aberration occurs in the reflected light transmitted through the correction prism 39. The spot lens 68 is provided with an angular displacement means 66, passes through the center of gravity 69 of the spot lens 68 located on the optical axis 63 of the reflected light, and rotates in the direction shown by the arrow 70 around the axis perpendicular to the paper surface of FIG. It can be displaced. Further, the spot lens 68 is a means for moving 6
It is possible to move in the direction indicated by arrow 71 by 7.

As described above, since the spot lens 68 can move in parallel with the optical axis 63 of the light reflected by the optical recording medium 24, it is possible to adjust the condensing position of the reflected light, and Since it can be angularly displaced about the axis passing through the center of gravity 69, it is possible to correct the coma aberration generated in the reflected light due to the undesired inclination of the optical member in the first focusing means 25.

FIG. 14 is a plan view showing a simplified structure of a light source 72 included in an optical pickup device according to a fourth embodiment of the present invention. The light source 72 of the present embodiment is the first
Light source 2 provided in the optical pickup device 21 of the embodiment
3 is similar, and corresponding parts are designated by the same reference numerals, and description thereof will be omitted. It should be noted that the light source 72 includes two laser chips 27 and 28 arranged side by side in one casing 73.
Is to be housed in.

In the light source 72, the two first and second laser chips 27 and 28 are housed in one third casing 73, and the base 33 is mounted with the third casing 73 and the cover member 34.

As described above, the light source 72 accommodates the two first and second laser chips 27 and 28 in one third casing 73, and the first and second laser chips 27 and 28 are included.
Since the distance between the optical axes of the light emitted from the optical system is small, the deviation of the optical axes of the two types of the first and second lights 29 and 30 having different wavelengths can be reduced.

As described above, the first to fourth aspects of the present invention
In the embodiment, the photodetector 22 is composed of 16 light receiving elements, but the present invention is not limited to this, and the photodetector 22 may be composed of more than 4 light receiving elements.

[0069]

According to the present invention, the light emitted from the light source is focused on the optical recording medium by the first focusing means.
The light reflected by the optical recording medium is condensed by the second condensing means and given astigmatism, and then a plurality of, for example, 16 light receiving elements are arranged in a matrix of 4 rows and 4 columns. After being focused on the detection means, a detection signal of the reflected light is obtained. When the light receiving position of the reflected light from the optical recording medium by the light detecting means is deviated from the center of the light detecting means, the matrix is set at or near the center of the light spot of the reflected light to detect the signal of the reflected light. It is possible to shift the centers of the four light-receiving elements arranged in a line, which are formed by the corners that are in contact with each other, in the row direction and the column direction of the light-receiving elements arranged in a matrix in accordance with the light receiving position of the reflected light. Therefore, even when the light receiving position of the reflected light is deviated from the center of the light detecting means, the signal of the reflected light can be accurately detected,
It is not necessary to control the inclination of the correction prism in order to match the center with the optical axis of the reflected light. As a result, the operating procedure and time can be reduced, and since the control member for the correction prism can be omitted, the structure of the device can be simplified and the cost can be reduced.

Further, according to the present invention, two casings for individually accommodating two laser chips are arranged in parallel, or two laser chips are accommodated in parallel in one casing. As a result, the distance between the optical axes of the light emitted from the two laser chips becomes smaller,
It is possible to reduce the deviation of the optical axes of two types of light having different wavelengths.

Further, according to the present invention, since the antireflection film is coated on the objective lens, the reflection loss of light by the objective lens can be reduced. As a result, the same objective lens can be used even when the light intensity of at least one of the two types of light having different wavelengths is weak.

Further, according to the present invention, astigmatism can be generated by the parallel plate glass. Since the parallel plate glass has a simple structure and is easy to manufacture, the cost of the device can be reduced.

According to the invention, the spot lens is
Since it is possible to move the light reflected by the optical recording medium in parallel with the optical axis, it is possible to adjust the condensing position of the reflected light. Further, since the spot lens can be angularly displaced, it is possible to correct the coma aberration generated in the reflected light due to the undesired inclination of the optical member in the first condensing unit. As a result, the light detecting means can obtain an accurate detection signal of the reflected light.

Further, according to the present invention, the plurality of light receiving elements forming the light detecting means are divided into four regions and arranged in a matrix of 2 rows and 2 columns, and the reflected light is collected on the light detecting means. When illuminated, a detection signal of reflected light detected by the light receiving element group forming the two regions of the first row and a detection signal of reflected light detected by the light receiving element group forming the two regions of the second row The light receiving position in the row direction of the reflected light is detected by the difference between the received light and the detection signal of the reflected light detected by the light receiving element group forming the two regions of the first column and the light receiving forming the two regions of the second column. Since the light receiving position in the column direction of the reflected light is detected by the difference between the detection signal of the reflected light detected by the element group, the light receiving position of the reflected light in the light detecting means can be accurately detected. Thus, the detection signal of the reflected light obtained from the four regions at the position where the light detecting means receives the reflected light without correcting the optical axis of the reflected light is used for controlling focusing, for example. You can

[Brief description of drawings]

FIG. 1 is a plan view showing a simplified configuration of a photodetector means 22 included in an optical pickup device 21 according to a first embodiment of the present invention.

FIG. 2 is a photodetector means 2 according to the first embodiment of the present invention.
2 is a system diagram showing a simplified configuration of the optical pickup device 21 including the optical pickup device 21. FIG.

FIG. 3 is a plan view showing a simplified configuration of a light source 23 included in the optical pickup device 21 according to the first embodiment of the present invention.

FIG. 4 is a plan view showing a simplified configuration of a photodetector 42 including four light receiving elements.

5 is a block diagram showing a simplified configuration of an arithmetic circuit 43 that arithmetically processes a detection signal from the photodetector 42. FIG.

FIG. 6 is a block diagram showing a simplified configuration of an arithmetic circuit 43 that arithmetically processes a detection signal from the photodetector 42.

FIG. 7 is a block diagram showing a simplified configuration of an arithmetic circuit 43 that arithmetically processes a detection signal from the photodetector.

FIG. 8: The photodetector 42 transmits the reflected light to the center 5 of the photodetector 42.
It is a top view which shows the state which is receiving light by 2.

FIG. 9 is a diagram showing waveforms of detection signals by the light receiving elements 44, 45, 46, 47 and signals which are arithmetically processed by the arithmetic circuit 43.

10 is a plan view showing a state where the photodetector 42 receives reflected light at a position deviated from the center 52 of the photodetector 42. FIG.

11 is a diagram showing waveforms of detection signals from the light receiving elements 44, 45, 46, and 47 and signals processed by the arithmetic circuit 43. FIG.

FIG. 12 is a system diagram showing a simplified configuration of a second condensing means 61 included in the optical pickup device according to the second embodiment of the present invention.

FIG. 13 is a system diagram showing a simplified configuration of a second condensing unit 65 included in the optical pickup device according to the third embodiment of the present invention.

FIG. 14 is a plan view showing a simplified configuration of a light source 72 included in an optical pickup device according to a fourth embodiment of the present invention.

FIG. 15 is a system diagram showing a simplified configuration of a conventional optical pickup device 1 including two light sources that respectively emit lights of different wavelengths.

FIG. 16 is a system diagram showing a simplified configuration of another conventional optical pickup device 16 including two light sources.

[Explanation of symbols]

21 Optical pickup device 22 Light detection means 23 Light source 24 Optical recording medium 25 First Condensing Means 26 Second Condensing Means

Claims (8)

[Claims] 1. An optical recording medium for recording or reproducing information, a light source for emitting two types of light having different wavelengths toward the optical recording medium, and an optical source arranged between the light source and the optical recording medium for emitting light. First light collecting means for collecting the reflected light on the optical recording medium, and light detecting means for detecting the reflected light from the optical recording medium. More than four light receiving elements are arranged in a matrix. A second photodetector, which is arranged between the photodetector and the optical recording medium, and collects reflected light reflected by the optical recording medium on the photodetector.
An optical pickup device comprising: a light collecting unit. 2. The optical pickup device according to claim 1, wherein the light detecting means comprises 16 light receiving elements arranged in a matrix of 4 rows and 4 columns. 3. The light source includes two laser chips that respectively emit two types of light having different wavelengths, and two casings that individually house the two laser chips. 2. The optical pickup device described in 2. 4. The light source includes two laser chips that respectively emit two types of light having different wavelengths, and one casing that houses the two laser chips in parallel. Or the optical pickup device described in 2. 5. The optical pickup device according to claim 1, wherein the first condensing unit includes an objective lens coated with an antireflection film. 6. The optical pickup device according to claim 1, wherein the second condensing unit includes a parallel flat plate glass. 7. The second condensing means includes: a spot lens that condenses the reflected light; a moving means that moves the spot lens closer to and away from the light detecting means in parallel with the optical axis of the reflected light; 7. The pickup device according to claim 1, further comprising an angular displacement means for angularly displacing the spot lens about an axis passing through the center of gravity and orthogonal to the optical axis of the reflected light. 8. The light detecting means is configured such that a plurality of light receiving elements are divided into four regions, the four regions are arranged in a matrix of two rows and two columns, and the two light receiving regions constituting the first row are formed. The difference between the detection signal of the reflected light detected by the element group and the detection signal of the reflected light detected by the light receiving element group forming the two regions of the second row, and the light reception forming the two regions of the first column The light receiving position of the reflected light is detected by the difference between the detection signal of the reflected light detected by the element group and the detection signal of the reflected light detected by the light receiving element group forming the two regions of the second row. The optical pickup device according to any one of claims 1 to 7.