JP2003099961A - Optical pickup device and hologram laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a miniaturized and low cost optical pickup device and a hologram laser device, in which the assemble and adjustment of optical components is facilitated. SOLUTION: When an objective lens 4 approaches the side of an information recording medium 5 than the focal position, light incident on hologram regions HA and HC of a hologram 7 is greatly defocused in photodetecting regions D1 and D3 of a photodetector 6 to form a 1/4 circular convergence spot 10, and light incident on hologram regions HB and HD is focused between photodetecting regions D1 and D2 and between photodetecting regions D3 and D4. A focus error signal (FES) can be detected on the basis of the difference between a signal in one of the photodetecting regions divided by a third division line L3 of the photodetector 6 an a signal in the other photodetecting region. According to the above method for detecting the FES, it can get off with a pair of photodetector, and a miniaturized and low cost optical pickup device and a hologram laser device can be provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a CD (Compact Di
sk) and MO (Magnet Optical Disk), and an optical pickup device and a hologram laser device for recording or reproducing information by light on an information recording medium.

[0002]

2. Description of the Related Art As a conventional optical pickup device, an "optical pickup device" described in JP-A-6-76340 is disclosed.
Is disclosed. This will be described as a first conventional example with reference to FIG. In the first conventional example, as a focus error signal (hereinafter referred to as FES) detection method,
The knife edge method is used. In the knife edge method, an optical system in which an element (knife edge) that divides the signal light into two is inserted in the optical path is used.

FIG. 8 is a block diagram of a conventional optical pickup device 51. As shown in FIG. 8, the optical pickup device 51 includes a semiconductor laser element 1, a hologram element 2, a collimator lens 3, an objective lens 4, and a photodetector 6. The semiconductor laser device 1 is used as a light source of the optical pickup device 51. The hologram element 2 includes a tracking beam generating diffraction grating 2a and an information recording medium 5 on the semiconductor laser element 1 side with respect to the optical axis direction.
An optical path refraction diffraction grating 2b is provided on the side.
The tracking beam generating diffraction grating 2a is used to divide incident light into three main beams and two sub beams, and to detect a tracking error signal (hereinafter referred to as TES) by a so-called three-beam method. It is a diffraction grating. The diffraction grating 2b for optical path refraction is a diffraction grating called a hologram, and in order to give appropriate wavefront conversion to the light reflected by the information recording medium 5 and returning, diffract it and guide it to the distant photodetector 6. Is used for. The collimating lens 3 is a lens that converts incident light into parallel light. The objective lens 4 is a lens for guiding the light emitted from the semiconductor laser element 1 to the information recording medium 5. The photodetector 6 is an optical element that converts the light diffracted by the diffraction grating 2b for refracting the optical path into a signal, and uses a photodiode. The photodiode is a light receiving element that reads the reflected light from the information recording medium 5, and is an element that converts a change in light amount into an electric signal.

In the optical pickup device 51, the light emitted from the semiconductor laser element 1 is split into one main beam and two sub beams by the tracking beam generating diffraction grating 2a provided in the hologram element 2. The light divided into three passes through the optical path refraction diffraction grating 2b provided in the hologram element 2, the collimator lens 3 and the objective lens 4, and is condensed on the information recording medium 5. The return light reflected by the information recording medium 5 follows a path opposite to the forward path, passes through the objective lens 4 and the collimator lens 3, enters the diffraction grating 2b for refracting the optical path, and is diffracted toward the photodetector 6. It The optical path refraction diffraction grating 2b is divided into two regions by a dividing line parallel to the radial direction of the information recording medium 5. In the optical pickup device 51, the reflected light from the information recording medium 5 is divided into two areas by the diffraction grating 2b for optical path refraction, and the diffracted light passing through one area is parallel to the radial direction of the information recording medium 5. The light enters the photodetector 6 having a light receiving region divided into five regions by the dividing line, and is used for FES detection. In this way, the diffraction grating for optical path refraction 2b serves as a knife edge.

Here, the distance between the objective lens 4 and the information recording medium 5 and the photodetector 6 when the knife edge method is used.
The relationship with the focused spot 10 will be described. When the objective lens 4 is at the in-focus position with respect to the information recording medium 5, a focused spot 10 is formed on each light receiving area of the photodetector 6 as a small round focused point. Further, when the objective lens 4 is closer to the information recording medium 5 side than the in-focus position, a semi-circularly spread focused spot 10 is formed on each light receiving area of the photodetector 6. Further, when the objective lens 4 is farther from the information recording medium 5 than the in-focus position, it spreads in a semicircular shape in the direction opposite to the condensing spot 10 when the distance between the objective lens 4 and the information recording medium 5 is short. A focused spot 10 is formed on each light receiving area of the photodetector 6.

From the above, when the objective lens 4 is at the in-focus position with respect to the information recording medium 5, the light incident on the photodetector 6 is focused on the dividing line of each light receiving region of the photodetector 6. If the connection is set, the ratio of the light incident on each light receiving area of the photodetector 6 changes according to the direction of defocus, and the FE is obtained by obtaining the difference between the signals output from each light receiving area.
S can be detected. That is, by controlling so that the difference between the signals output from the respective light receiving regions becomes 0, that is, the value of FES becomes 0, the information recording medium 5 and the objective lens 4 can be kept at a predetermined distance.

On the other hand, as an optical pickup device different from the first conventional example, an "optical pickup" described in Japanese Patent Laid-Open No. 5-307759 is disclosed. This will be described as a second conventional example with reference to FIG. In the second conventional example, the beam size method is used as the FES detection method.

FIG. 9 is a block diagram of a conventional optical pickup device 61. Second conventional optical pickup device 61
As shown in FIG. 9, the semiconductor laser element 1, the hologram element 2, the objective lens 4 and the two photodetectors 6a, 6 are
b. Since each optical element used in the second conventional example is the same as the optical element used in the first conventional example, description of each optical element is omitted.

The light emitted from the semiconductor laser device 1 is
After passing through the hologram element 2 and the collimator lens, it is focused on the information recording medium 5 by the objective lens 4. FIG. 9 shows an optical system called a finite system that guides the light from the semiconductor laser device 1 directly to the objective lens 4 without using a collimator lens. Since no collimating lens is used, the cost can be reduced, and the optical pickup device 61 can be downsized in the optical axis direction. The return light reflected by the information recording medium 5 follows a path opposite to the forward path and enters the hologram element 2 via the objective lens 4. The light incident on the hologram element 2 is diffracted by the diffraction grating 7 formed on the surface of the hologram element 2 on the information recording medium 5 side with respect to the optical axis direction, and the ± first-order diffracted light is detected by the photodetectors 6a and 6b. Incident on each. Since the diffraction grating 7 is configured to give powers in the opposite directions to the ± 1st order diffracted light, the −1st order diffracted light is generated between the hologram element 2 and the photodetector 6b as shown in FIG. 9, for example. The + 1st-order diffracted light is focused on the opposite side of the hologram element 2 with the other photodetector 6a in between in the optical axis direction.

When the objective lens 4 is at the in-focus position with respect to the information recording medium 5, the respective focused spots 10 incident on the two photodetectors 6a and 6b have the same size, and the focused spot 10 has the same size. If the centers are set so as to be located at the centers of the light receiving regions D2 and D5, respectively, the size of the focused spot 10 will be inverted depending on the direction of defocus. That is, when the objective lens 4 comes closer to the information recording medium 5 side than the in-focus position, for example, the light is incident on the other photodetector 6b rather than the diameter of the focused spot 10 incident on one photodetector 6a. The diameter of the focused spot 10 is larger. Further, when the objective lens 4 is farther from the information recording medium 5 than the in-focus position, the photodetectors 6a and 6a are compared to when the objective lens 4 is closer to the information recording medium 5 side.
The size is reversed from that of the focused spot 10 formed in b.
Therefore, the signals output from the light receiving regions D1, D2, and D3 of the photodetector 6a are S1, S2, and S, respectively.
3, and the light receiving regions D4, D5 and D6 of the photodetector 6b
If the signals output from S4, S5 and S6 are respectively, FES can be calculated by the following equation. FES = (S1 + S5 + S6)-(S2 + S3 + S4)

[0011]

In the first conventional example in which the knife edge method is used for detecting the FES, it is possible to minimize the total number of parts of the optical pickup device 51, but the hologram element 2 is used. Precision is required for adjustment of optical elements such as. Further, since only one of the ± 1st-order diffracted lights of the main beam diffracted by the optical path refraction diffraction grating 2b is used, there is a problem that the light utilization efficiency is low.

On the other hand, in the second conventional example in which the beam size method is used for detecting the FES, the adjustment of the optical element is easy, and both of the ± 1st order diffracted light diffracted by the hologram element 2 are diffracted light. Since light is used, the light is efficiently used. On the other hand, two sets of photodetectors are required, and there is a problem that an increase in the number of parts of the entire optical pickup device 61 causes an increase in cost and an adjustment process.

An object of the present invention is to provide an optical pickup device and a hologram laser device which are easy to assemble and adjust an optical element and which are small and inexpensive.

[0014]

The present invention provides a semiconductor laser element as a light source, a hologram for diffracting light emitted from the semiconductor laser element and reflected on a signal recording surface of an information recording medium, and the hologram. In the optical pickup device having a photodetector for detecting light diffracted by, the hologram is divided into four hologram areas by a first dividing line and a second dividing line orthogonal to the first dividing line. In the photodetector, the light-receiving regions arranged side by side in a direction substantially parallel to the first dividing line are divided by a third dividing line substantially parallel to the first dividing line, respectively. And a set of second light receiving regions, and the first set of light receiving regions diffracts light from two hologram regions on one side with respect to the first dividing line of the hologram. Incident, the second set of light receiving regions, with respect to said first division line diffracted light from the two hologram regions of the other side is an optical pickup apparatus which is characterized in that incident.

According to the present invention, the first diffracted light of the two diffracted lights incident on the set of the light receiving regions is focused between the hologram and the photodetector, and the second diffracted light is ,
It is characterized in that a focal point is formed on the opposite side of the hologram with the photodetector sandwiched in the optical axis direction.

According to the present invention, the two diffracted lights incident on the light receiving region are focused on between the hologram and the photodetector and on the opposite side of the hologram with the photodetector sandwiched in the optical axis direction. Since they are tied together, it is not necessary to focus light accurately on the third dividing line of the light receiving region, so that the assembly and adjustment of the optical element can be easily performed.

The present invention is also characterized in that the diffraction direction of the light diffracted by the hologram is a direction substantially parallel to the first dividing line.

According to the present invention, the diffraction direction of the light diffracted by the hologram is made to coincide with the direction substantially parallel to the first dividing line. Therefore, even if the temperature changes, the condensing position on the photodetector. The focus error signal can be detected accurately without being easily affected by the change of.

The present invention is also characterized in that the areas of the four divided hologram areas are substantially equal to each other.

According to the present invention, since the areas of the four divided hologram areas are substantially equal to each other, the focus error signal and the tracking error signal can be accurately detected.

The present invention also provides a signal in one of the light receiving regions divided by the third dividing line of the photodetector,
It is characterized in that the focus error signal is calculated based on the difference from the signal in the other light receiving region.

According to the present invention, the focus error signal is calculated based on the difference between the signal in one light receiving region and the signal in the other light receiving region divided by the third dividing line of the photodetector, The focus servo can be applied even when the diffracted light is not accurately focused on the third dividing line.

The present invention also provides a tracking error signal based on the difference between the phase of the signal in one light receiving area and the phase of the signal in the other light receiving area divided by the third dividing line of the photodetector. It is characterized by calculating.

According to the present invention, the tracking error signal is obtained based on the difference between the phase of the signal in one light receiving area and the phase of the signal in the other light receiving area divided by the third dividing line of the photodetector. It can be calculated and tracking servo can be applied.

Further, the present invention has a diffraction grating for splitting the light emitted from the semiconductor laser device into one main beam and two sub beams, and the photodetector has two sub beams diffracted by the hologram. Light receiving regions for the first and second sub-beams, the main beam is incident on the two sets of light-receiving regions, and signals of the signals output from the first and second light receiving regions for the sub-beams are received. The tracking error signal is detected by using the difference.

According to the invention, the two sub-beams formed by diffracting the light emitted from the semiconductor laser device are 2
The tracking error signal can be detected by using the difference between the signals that are incident on one of the sub-beam light-receiving regions and that are output therefrom.

The present invention is also a hologram laser device characterized in that the semiconductor laser element, the hologram and the photodetector are integrated into one package.

According to the present invention, the semiconductor laser element, the hologram element and the photodetector are integrated into one package to form a hologram laser device, and thus the actuator for driving the collimating lens and the objective lens is a hologram laser device. The optical pickup device can be easily assembled and adjusted.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical pickup device and a hologram laser device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a hologram laser device 11 according to the first embodiment of the present invention, in which light condensed by an objective lens 4 (see FIG. 2) is recorded on an information recording medium 5 (see FIG. 2). ) Shows a focused state (focused state) on the signal recording surface.

Hologram laser device 11 of this embodiment
Is a part of the optical pickup device 21 described later,
A semiconductor laser device 1, a photodetector 6, and a diffraction grating (hereinafter referred to as a hologram) 7 are provided. The semiconductor laser device 1 is used as a light source of the hologram laser device 11. The hologram 7 is a diffraction element called a hologram that diffracts the light emitted from the semiconductor laser element 1 and reflected on the signal recording surface of the information recording medium 5. As shown in FIG. 1, the hologram 7 is divided into four hologram areas HA, HB, HC and HD by a first dividing line L1 and a second dividing line L2 orthogonal to the first dividing line L1. When dividing, the areas of the four hologram areas HA, HB, HC and HD are made equal to each other. The photodetector 6 has the first
Light receiving areas arranged side by side in a direction substantially parallel to the dividing line L1 are divided by a third dividing line L3 that is substantially parallel to the first dividing line L1, respectively, and a set D1 of the first light receiving areas D1, D
2 and a second set of light receiving regions D3 and D4 are provided. An optical pickup device 21 including the hologram laser device 11 is configured to include a semiconductor laser element 1, a hologram element 2, a collimator lens 3, an objective lens 4, and a photodetector 6, as shown in FIG. The semiconductor laser device 1 is used as a light source of the optical pickup device 51. The hologram element 2 includes a hologram 7 on the information recording medium 5 side in the optical axis direction. The collimating lens 3 is a lens that converts incident light into parallel light. The objective lens 4 is a lens for guiding the light emitted from the semiconductor laser element 1 to the information recording medium 5. The photodetector 6 is an optical element that converts light diffracted by the diffraction grating 2b for refracting the optical path into a signal.

The light emitted from the semiconductor laser device 1 is
The return light, which is focused on the signal recording surface of the information recording medium 5 through the hologram element 2, the collimator lens 3, and the objective lens 4, and reflected on the signal recording surface, follows a path opposite to the forward path, and the objective lens It is diffracted by the hologram 7 formed on the surface of the hologram element 2 on the information recording medium 5 side with respect to the optical axis direction via the collimator lens 4 and the collimator lens 3. The light diffracted by the hologram 7 is detected by the photodetector 6
To the light receiving regions D1, D2, D3, and D4 of the respective. In the light receiving areas D1 and D2, two hologram areas H on one side of the first dividing line L1 of the hologram 7 are provided.
Diffracted light from A and HB is made incident, and light receiving regions D3 and D4 are received.
, The diffracted light from the two hologram areas HC and HD on the other side with respect to the first division line L1 is made incident. The two diffracted lights incident on the light receiving regions D1, D2, D3 and D4 of the photodetector 6 respectively pass through the two hologram regions. The first diffracted light passing through one of the hologram areas is focused between the hologram 7 and the photodetector 6, and the second diffracted light is directed toward the optical detector 6 in the optical axis direction.
It is adjusted so as to focus on the opposite side of the hologram 7 with the lens sandwiched therebetween.

In the present embodiment, the focal point HA 'of the light incident on the hologram area HA of the hologram 7 passes through the light receiving area D1 of the photodetector 6 and is detected in the optical axis direction.
It is on the opposite side of the hologram 7 across. Similarly, the focal point HC ′ of the light incident on the hologram area HC of the hologram 7
Passes through the light receiving region D3 of the photodetector 6 and is on the opposite side of the hologram 7 with the photodetector 6 in between in the optical axis direction. Further, the light incident on the hologram area HB of the hologram 7 is HB ′ between the hologram 7 and the photodetector 6.
The light is condensed at the position of and is incident on the light receiving region D2 of the photodetector 6. Similarly, the light incident on the hologram area HD of the hologram 7 is H between the hologram 7 and the photodetector 6.
The light is collected at the position D ′ and is incident on the light receiving region D4 of the photodetector 6.

Next, the objective lens 4 and the information recording medium 5
The relationship between the distance and the focused spot 10 of the photodetector 6 will be described.

FIG. 2 is a diagram showing the configuration of the photodetector 21 and the light-converging spot on the photodetector 6. Figure 2
FIGS. 2A and 2B show the case where the objective lens 4 is closer to the information recording medium 5 side than the focus position (Near state).
FIG. 3 is a diagram showing a configuration of the optical pickup device 21 in FIG. 4 and a diagram showing a relationship between the light receiving regions D1, D2, D3 and D4 of the photodetector 6 and the focused spot 10. The light incident on the hologram areas HA and HC of the hologram 7 is largely blurred at the light receiving areas D1 and D3 of the photodetector 6, and a ¼ circular focused spot 10 is formed. The light incident on the hologram areas HB and HD of the hologram 7 is received between the light receiving areas D1 and D2 of the photodetector 6 and the light receiving areas D3 and D, respectively.
The focus is between the four.

FIG. 3 is a diagram showing the configuration of the photodetector 21 and the light-converging spot on the photodetector 6. Figure 3
3A and FIG. 3B are configuration diagrams of the optical pickup device 21 and the photodetector 6 when the objective lens 4 is at the in-focus position with respect to the signal recording surface of the information recording medium 5 (in-focus state). 6 is a diagram showing the relationship between the light receiving areas D1, D2, D3 and D4 of FIG. Hologram 7
The light incident on the hologram areas HA, HB, HC, and HD is formed on the light receiving areas D1, D2, D3, and D4 of the photodetector 6 as semi-circular focused spots 10 of the same size.

FIG. 4 is a diagram showing the structure of the photodetector 21 and the light-converging spot in the photodetector 6. Figure 4
4A and 4B show the case where the objective lens 4 is farther from the information recording medium 5 than the in-focus position (Far state).
FIG. 3 is a diagram showing a configuration of the optical pickup device 21 in FIG. 4 and a diagram showing a relationship between the light receiving regions D1, D2, D3 and D4 of the photodetector 6 and the focused spot 10. The light incident on the hologram areas HA and HC of the hologram 7 is between the light receiving areas D1 and D2 of the photodetector 6 and the light receiving area D3, respectively.
Focusing on D4. Further, the light incident on the hologram areas HB and HD of the hologram 7 is largely blurred at the light receiving areas D2 and D4 of the photodetector 6, and a 1/4 circular focused spot 10 is formed. When the objective lens 4 is in the in-focus position with respect to the information recording medium 5, that is, in the so-called in-focus state, the four converging spots 10 incident on the four light receiving regions D1, D2, D3 and D4 of the photodetector 6 are detected. If the sizes are set to be equal and the centers of the focused spots 10 are respectively located at the centers of the third dividing lines L3 of the two sets of light receiving regions, the size of the focused spots 10 is changed according to the direction of defocus. Will be reversed. Therefore, regardless of the distance between the objective lens 4 and the information recording medium 5, it is not necessary to accurately focus the light diffracted by the hologram 7 on the third dividing line L3 of the photodetector 6, and thus the optical element Easy to assemble and adjust.

From the above, in the present embodiment, the FES is calculated based on the difference between the signal in one light receiving region divided by the third dividing line L3 of the photodetector 6 and the signal in the other light receiving region. Can be detected. That is,
If the difference between the signals output from the light receiving regions D1, D2, D3, and D4 of the photodetector 6 is controlled to 0, that is, the value of FES becomes 0, the information recording medium 5 and the objective lens 4 are controlled to a predetermined value. Can be kept at a distance. When the signals output from the light receiving areas D1, D2, D3 and D4 in the photodetector 6 are S1, S2, S3 and S4, respectively, FE
S can be calculated by the following equation. FES = (S1 + S3)-(S2 + S4)

In this embodiment, the DPD (Differential Phase Detection) method is adopted as the TES detection method. According to the DPD method, the photodetector 6 that receives the reflected light from the information recording medium 5 is divided into four in the shape of a square, and the minute focused spot 10 on the information recording medium 5 forms the information recording medium 5.
When scanning over the information pit row, the TES is calculated by a predetermined calculation process based on the phase difference of the light intensity modulation signals detected from the divided light receiving regions of the photodetector 6. In the present embodiment, the TES is calculated based on the difference between the phase of the signal in one light receiving region divided by the third dividing line L3 of the photodetector 6 and the phase of the signal in the other light receiving region. be able to. The reproduction signal (hereinafter, referred to as RF) is calculated as the sum of signals output from the light receiving area of the photodetector 6. Therefore, the light receiving regions D1, D2, D3 and D4 of the photodetector 6 are
If the signals output from S1, S2, S3, and S4 are respectively, TES (DPD) can be obtained by the phase difference between the waveform obtained by combining S1 and S3 and the waveform obtained by combining S2 and S3. RF can be calculated by the following equation. RF = S1 + S2 + S3 + S4

The focus servo and the tracking servo are applied by processing the signal detected by the above process as in the above equation. The focus servo is a control method in which the objective lens 4 is made to follow the surface wobbling of the information recording medium 5 and always kept in focus, and the tracking servo is made to make the objective lens 4 follow the eccentricity of the information recording medium 5. The control method is such that the beam spot always traces on the target track.

In the second conventional example using the beam size method, two sets of photodetectors were required, but if the FES, TES and RF detection methods of this embodiment are adopted,
Only one photodetector 6 is required, which can contribute to downsizing and cost reduction of the optical pickup device and the hologram laser device.

Further, since it is not necessary to accurately collect the diffracted light from the hologram 7 on the third dividing line L3 of the photodetector 6, it is easier to assemble and adjust the optical element as compared with the knife edge method. Even if the diffracted light from the hologram 7 is not accurately focused on the third division line L3 of the photodetector 6, the FES can be detected and the focus servo can be applied.

Further, in this embodiment, the diffraction direction of the light diffracted by the hologram 7 is set to a direction substantially parallel to the first dividing line L1. That is, the third of the photodetector 6
Since the direction along the parting line L3 of is matched with the fluctuation of the diffraction direction of the hologram 7 due to the temperature change, even if the temperature changes, it is less affected by the change of the focusing position in the photodetector 6, and the FES Can be accurately detected. From the above, in the present embodiment, it is possible to configure the optical pickup device and the hologram laser device, which are easy in optical adjustment, in a small size and at a low cost without increasing the number of parts.

FIG. 5 is a block diagram of a hologram laser device 31 according to the second embodiment of the present invention, in which the light condensed by the objective lens 4 is focused on the signal recording surface of the information recording medium 5. Is displayed (focused state).

Hologram laser device 31 of this embodiment
Is the hologram laser device 11 according to the first embodiment.
The configuration of each optical element, FES and RF
Are the same and the detection methods of the photodetector 6 and TES are different, so only the detection method of the photodetector 6 and TES will be described, and the other FES and RF detection methods will be omitted.

The photodetector 6 in the hologram laser device 31 of the present embodiment is located between the semiconductor laser element 1 and the hologram 7, and is usually the surface of the hologram element 2 on the semiconductor laser element 1 side with respect to the optical axis direction. It has first and second light receiving regions D5 and D6 for receiving the two sub beams diffracted by the tracking beam generating diffraction grating.

The TES detection method in this embodiment is as follows:
The 3-beam method is used. The three-beam method is a method of dividing the light emitted from the semiconductor laser device 1 into three main beams for signal reading and two sub-beams for TES detection. That is, the light emitted from the semiconductor laser element 1 which is the light source is divided into three beams, one main beam and two sub-beams, by passing through the tracking beam generating diffraction grating, and the light is divided in the optical axis direction. Then, the light is focused on the information recording medium 5 via the hologram 7, the collimator lens 3 and the objective lens 4 formed on the surface of the hologram element 2 on the information recording medium 5 side. The return light reflected by the information recording medium 5 follows the opposite path and is diffracted by the hologram 7 divided into four areas, and becomes 12 kinds of light, and the light receiving areas D1 to D1 of the photodetector 6 are obtained.
It is incident on D6. Of the 12 kinds of light, four lights by the + 1st order diffracted light of the main beam are incident on the light receiving regions D1, D2, D3 and D4 of the photodetector 6 and are detected by the FES as described in the first embodiment. Used for.

In addition, the sub-beam + 1st order diffracted light causes
Of the four lights, four lights enter the light receiving region D5 of the photodetector 6, and the remaining four lights enter the light receiving region D6 of the photodetector 6. When the signals output from the light receiving regions D5 and D6 are S5 and S6, respectively, TES can be calculated by the following equation. TES = S5-S6

FIG. 6 is a diagram showing the configuration of the optical pickup device 41 and the focused spot 10 on the photodetector 6. 6 (a) and 6 (b) are a configuration diagram and optical detection of the optical pickup device 41 when the objective lens 4 and the signal recording surface of the information recording medium 5 are at predetermined positions and the light source has a short wavelength. 6 is a diagram showing the relationship between the light receiving areas D1, D2, D3 and D4 of the container 6 and the focused spot 10. FIG.
FIG. 7 is a diagram showing the configuration of the optical pickup device 41 and the focused spot 10 on the photodetector 6. 7 (a) and 7 (b) are a configuration diagram and optical detection of the optical pickup device 41 when the objective lens 4 and the signal recording surface of the information recording medium 5 are at predetermined positions and the light source has a long wavelength. 6 is a diagram showing the relationship between the light receiving areas D1, D2, D3 and D4 of the container 6 and the focused spot 10. FIG. The configuration of the optical pickup device 41 and the optical elements used are
Since it is the same as the optical pickup device 21 in the first embodiment, the description of the configuration and the optical elements used is omitted.

When the light is diffracted by the hologram 7, the angle formed in the diffracting direction with respect to the optical axis, that is, the diffraction angle depends on the wavelength of the light incident on the hologram 7. The short-wavelength light source has a smaller diffraction angle than the long-wavelength light source. That is, as shown in FIG. 6, the light-collecting pattern positions on the light-receiving regions D1, D2, D3, and D4 of the photodetector 6 are shifted toward the semiconductor laser element 1 which is the light source. On the other hand, the long-wavelength light source has a larger diffraction angle than the short-wavelength light source. That is, as shown in FIG. 7, the position of the light collecting pattern on the light receiving regions D1, D2, D3 and D4 of the photodetector 6 shifts away from the semiconductor laser device 1 which is the light source. The spot position changes regardless of whether the light source has a short wavelength or a long wavelength, but the lengths of the first light receiving area set having D1 and D2 and the second light receiving area set having D3 and D4 are shifted. By making it longer than the amount, the focused spot 10 becomes the light receiving regions D1, D of the photodetector 6.
Since it can be prevented from protruding from 2, D3 and D4, it becomes possible to realize an optical pickup device with little wavelength dependence. Further, it is possible to cope with the multi-wavelength use by using light sources of a plurality of wavelengths in the same optical system.

Although the collimator lens is not shown in FIGS. 6 and 7, the first embodiment can also be configured with a finite optical system using only the objective lens 4 as in the present embodiment. is there.

Further, in this embodiment, it is desirable that the semiconductor laser device 1, the hologram device 2, and the photodetector 6 are integrated into one package as a hologram laser device. By integrating the three optical elements, the actuator for driving the collimating lens and the objective lens, which is the condenser lens, can be assembled with the hologram laser device as a reference, and the optical pickup device can be easily assembled. .

[0053]

As described above, according to the present invention, the assembly and adjustment of the optical element can be easily performed.

Further, according to the present invention, even if the temperature changes, the influence of the change of the focusing position in the photodetector is less likely to occur, and the focus error signal can be accurately detected.

Further, according to the present invention, the focus error signal and the tracking error signal can be accurately detected.

Further, according to the present invention, the focus servo can be applied even when the diffracted light is not accurately focused on the third dividing line.

Further, according to the present invention, the tracking servo can be performed by calculating the tracking error signal.

Further, according to the present invention, detection of a tracking error signal can be dealt with. Further, according to the present invention, the actuator that drives the collimator lens and the objective lens can be assembled with the hologram laser device as a reference, and the assembly and adjustment of the optical pickup device can be easily performed.

Further, according to the present invention, since the wavelength dependence of the signal light is weak, it is possible to handle lights of a plurality of wavelengths with the same optical pickup device and hologram laser device.
It is possible to support multiple wavelengths.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a hologram laser device 11 according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a photodetector 21 and a focused spot on the photodetector 6.

FIG. 3 is a diagram showing a configuration of a photodetector 21 and a focused spot on the photodetector 6.

FIG. 4 is a diagram showing a configuration of a photodetector 21 and a diagram showing a focused spot in the photodetector 6.

FIG. 5 is a configuration diagram of a hologram laser device 31 according to a second embodiment of the present invention.

6 is a diagram showing a configuration of an optical pickup device 41 and a diagram showing a focused spot 10 on a photodetector 6. FIG.

7 is a diagram showing a configuration of an optical pickup device 41 and a diagram showing a focused spot 10 on a photodetector 6. FIG.

FIG. 8 is a configuration diagram of a conventional optical pickup device 51.

FIG. 9 is a configuration diagram of a conventional optical pickup device 61.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 semiconductor laser element 2 hologram element 2a tracking beam generating diffraction grating 2b optical path refraction diffraction grating 3 collimating lens 4 objective lens 5 information recording medium 6, 6a, 6b photodetector 7 hologram 10 focused spot 11, 31 hologram laser device 21, 41, 51, 61 Optical pickup device D1, D2, D3, D4, D5, D6 Light receiving area HA, HB, HC, HD Hologram area HA ', HB', HC ', HD' Focus of light passing through hologram L1, L2, L3 dividing line

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5D118 AA01 AA06 BA01 BB01 BB06                       CC02 CC04 CC15 CD02 CD03                       CF05 DA20 DA21 DB27                 5D119 AA01 AA28 AA38 AA41 EA02                       EA03 EC41 EC47 FA30 JA15                       KA02 KA19 KA20                 5D789 AA01 AA28 AA38 AA41 EA02                       EA03 EC41 EC47 FA30 JA15                       KA02 KA19 KA20                 5F051 AA01 BA03 BA18 JA02 JA05

Claims (8)

[Claims] 1. A semiconductor laser element as a light source, a hologram for diffracting light emitted from the semiconductor laser element and reflected on a signal recording surface of an information recording medium, and light diffracted by the hologram are detected. In the optical pickup device having a photodetector, the hologram is divided into four hologram areas by a first dividing line and a second dividing line orthogonal to the first dividing line, and the photodetector has: The light receiving regions arranged side by side in the direction substantially parallel to the first dividing line are divided by the third dividing lines substantially parallel to the first dividing line, and the first set of light receiving regions and the second set. And a diffracted light beam from two hologram regions on one side with respect to the first dividing line of the hologram is incident on the first light receiving region set. region The first set of
The optical pickup device is characterized in that diffracted light from two hologram regions on the other side with respect to the dividing line is incident. 2. The first diffracted light of the two diffracted lights incident on the pair of light receiving regions is focused between the hologram and the photodetector, and the second diffracted light is the optical axis. The optical pickup device according to claim 1, wherein a focus is formed on the opposite side of the hologram with the photodetector interposed therebetween in the direction. 3. The optical pickup device according to claim 1, wherein a diffraction direction of light diffracted by the hologram is a direction substantially parallel to the first dividing line. 4. The optical pickup device according to claim 1, wherein the areas of the four divided hologram areas are substantially equal to each other. 5. A focus error signal is calculated based on a difference between a signal in one light receiving region and a signal in the other light receiving region divided by the third dividing line of the photodetector. Any one of claims 1 to 4.
The optical pickup device described in 1. 6. A tracking error signal is calculated based on the difference between the phase of the signal in one light receiving area and the phase of the signal in the other light receiving area divided by the third dividing line of the photodetector. Claim 1 characterized by
5. The optical pickup device according to any one of 5. 7. A diffraction grating that splits the light emitted from the semiconductor laser device into one main beam and two sub beams, and the photodetector receives the two sub beams diffracted by the hologram. A light receiving area for the first and second sub beams, the main beam is incident on the two light receiving areas of the two sets, and a difference between signals output from the light receiving areas for the first and second sub beams is used. The optical pickup device according to any one of claims 1 to 6, wherein the tracking error signal is detected. 8. A hologram laser device, wherein the semiconductor laser device according to any one of claims 1 to 7, the hologram, and the photodetector are integrated into one package.