JP2012185876A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device with a temperature characteristic more excellent than a conventional optical pickup device.SOLUTION: An optical pickup device 1 includes: a light source 2 for emitting laser beams La; an objective lens 4 for collecting the laser beams La and making the laser beams La focused on an information record surface of an optical disk D; a hologram element 3 having a hologram region 11 for transmitting respectively the laser beams La emitted from the light source 2, diffracting respectively return light beams Lb reflected from the information record surface, and emitting a diffraction light beam Lc to which astigmatism is imparted, and a hologram region 12 for emitting a diffraction light beam Le to which astigmatism is not imparted; and a light receiving element 5 having a light receiving unit 20 for receiving the diffraction light beam Lc and a light receiving unit 30 for receiving the diffraction light beam Le. In the diffraction light beam Lc, a focal line L1 is positioned between the hologram element 3 and the light receiving element 5, and a focal line L2 is positioned at a position further than the light receiving element 5 with respect to the hologram element 3. In the diffraction light beam Le, both focal lines L3 and L4 are positioned close to each other between the hologram element 3 and the light receiving element 5.

Description

  The present invention relates to an optical pickup device for recording information on an optical disc such as a CD or a DVD or reproducing information recorded on an optical disc, and more particularly to an optical pickup device provided with a hologram element.

The optical pickup device is for recording information on an optical disc such as a CD or a DVD or reproducing information recorded on the optical disc.
In addition, as an optical pickup device, a device using a hologram element is adopted as a means for achieving both an astigmatism method, which is a standard focus error detection method, and miniaturization and high reliability.

  An optical pickup device using a hologram element generally has a laser light source that emits laser light toward an optical disk and a laser light emitted from the laser light source that is focused on a predetermined information recording surface of the optical disk. Objective lens, a hologram element having a hologram part that diffracts laser light (return light) reflected by the optical disk toward a light receiving part to be described later, and a light receiving element having a light receiving part that receives the return light diffracted by the hologram part And.

  The hologram element has one type of hologram coefficient and uses “+ 1st order diffracted light” and “−1st order diffracted light” generated by diffracting the return light from the optical disk (hereinafter referred to as a double-sided type). And two types of hologram coefficients, and diffracts the return light from the optical disk and uses only one of “+ 1st order diffracted light” and “−1st order diffracted light” (hereinafter, one side) And called the “take type”).

  In the double-sided type, a light receiving unit that receives “+ 1st order diffracted light” and a light receiving unit that receives “−1st order diffracted light” are arranged to face each other via a laser light source. For this reason, the double-sided type has a problem that the light receiving parts are spaced apart from each other via a laser light source, so that it is difficult to reduce the size of the light receiving element and the material cost increases.

On the other hand, in the single-sided type, a light receiving unit for receiving “+ 1st order diffracted light” (or “−1st order diffracted light”) diffracted in different directions according to two types of hologram coefficients is arranged on one side of the laser light source. Therefore, the light receiving element can be easily downsized as compared with the double-sided type, and the material cost can be reduced as compared with the double-sided type.
In the single-sided type, hologram coefficients are set so as to give astigmatism to each diffracted light.

  An example of a single-sided optical pickup device is disclosed in Patent Document 1, for example.

JP 2002-216368 A

  In general, an optical pickup device is affected by environmental temperature. Specifically, the laser light source in the optical pickup device is easily affected by the environmental temperature, and the center wavelength of the laser light emitted from the optical pickup device shifts to the longer wavelength side according to the degree of temperature rise of the laser light source itself. To do.

However, the conventional single-sided type optical pickup device disclosed in Patent Document 1, that is, a holographic area having two types of hologram coefficients, and diffracted light diffracted in each hologram area is astigmatism. In the optical pickup device that imparts aberration, the diffraction angle of the diffracted light changes according to the shift amount of the center wavelength of the laser light.
As a result, the irradiation position of the diffracted light applied to the light receiving portion of the light receiving element changes due to the change in the diffraction angle of the diffracted light, so that the light beam of the diffracted light deviates from the predetermined position of the light receiving portion or comes off the light receiving portion. To do. The positional deviation of the diffracted light beam causes, for example, a decrease in the S-shaped waveform level of FES (focus error signal) and a deviation in the S-shaped waveform balance. The decrease in the S-shaped waveform level may be erroneously determined when determining the type of the optical disk based on the size of the S-shaped waveform level, and the deviation in the S-shaped waveform balance may occur when a disk formed by a scratch described later is reproduced. In addition, there is a case where the focus servo is likely to come off, and improvement thereof is desired.

  Further, if the user repeatedly uses the optical disk, scratches may be formed on the surface of the optical disk due to a handling error or the like. Scratches cause a shift in the FES level, and when reproducing an optical disc, there are cases where problems such as skipping of sound and stop of reproduction may occur due to this scratch, and improvement thereof is desired.

Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide an optical pickup device that is more excellent in temperature characteristics than conventional ones.
It is another object of the present invention to provide an optical pickup device that is less susceptible to scratches on an optical disc than in the past.

In order to solve the above problems, the present invention provides the following optical pickup device.
1) a laser light source (2) that emits laser light (La), an objective lens (4) that focuses the laser light (La) and focuses on a predetermined information recording surface of the optical disc (D), and Astigmatism is given by diffracting the return light (Lb), which is the laser light transmitted through the laser light source (2) from the laser light source (2) and reflected by the predetermined information recording surface, respectively. The first hologram region (11, 13) that emits the first diffracted light (Lc, Ld) and the second hologram region that emits the second diffracted light (Le, Lf) not provided with astigmatism The hologram element (3) having (12, 14), the first light receiving part (20) for receiving the first diffracted light (Lc, Ld), and the second diffracted light (Le, Lf). A light receiving element (5) having a second light receiving part (30) for receiving light; The first diffracted light (Lc, Ld) has one focal line (L1) positioned between the hologram element (3) and the light receiving element (5), and the hologram element (3) The other focal line (L2) is located farther from the light receiving element (5) than the light receiving element (5), and the second diffracted light (Le, Lf) is transmitted from the hologram element (3) and the light receiving element ( 5), an optical pickup device (1), wherein one focal line (L3) and the other focal line (L4) are positioned close to each other.
2) The hologram part (10) is divided into four parts by a first dividing line (A10) parallel to the radial direction of the optical disk (D) and a second dividing line (B10) parallel to the tangential direction of the optical disk (D). The first to fourth divided areas (11 to 14) are divided, and the first divided area (11) and the third divided area (13) are in a diagonal position relative to each other, and It is a first hologram area, and the second divided area (12) and the fourth divided area (14) are in a diagonal relationship with each other, and are the second hologram area. 1) The optical pickup device (1) according to 1).
3) The first hologram region (42) and the second hologram region (42) each have a strip shape and are arranged alternately in the tangential direction of the optical disc (D). ) Optical pickup device (40).
4) The hologram section (51) includes a fifth divided area and a sixth divided area divided into two by a third dividing line (A51) parallel to the radial direction of the optical disc, and the fifth divided area In the sixth divided area, a plurality of first hologram areas (52, 54) and second hologram areas (53, 55) each having a strip shape are alternately arranged in the tangential direction of the optical disk (D). The optical pickup device (50) according to 1), wherein the optical pickup device (50) is arranged, and the fifth divided region and the sixth divided region are further alternately arranged.
5) The hologram section (61, 71) includes a seventh divided area and an eighth divided area divided into two by a fourth dividing line (B61, B71) parallel to the tangential direction of the optical disc (D), A ninth divided region disposed in the seventh divided region and not in contact with the fourth divided line; and a tenth divided region disposed in the eighth divided region and not in contact with the fourth divided line. And the seventh divided area and the tenth divided area are the first hologram areas, and the eighth divided area and the ninth divided area are the second hologram areas. The ninth divided area and the tenth divided area are arranged line-symmetrically with respect to the fourth dividing line, or arranged point-symmetrically with respect to the center position of the hologram part. 1) The optical pickup device according to 1) (60, 70).

According to the present invention, there is an effect that the temperature characteristics are superior to the conventional one.
In addition, according to the present invention, there is an effect that it is less susceptible to scratches on the optical disc than in the past.

It is typical sectional drawing for demonstrating Examples 1-5 of the optical pick-up apparatus of this invention. 1 is a schematic perspective view for explaining an optical pickup device of Example 1. FIG. FIG. 3 is a schematic plan view showing a light beam when diffracted light diffracted by a hologram part of Example 1 is irradiated to a light receiving part. It is a typical perspective view for demonstrating the optical pick-up apparatus of a comparative example. It is a typical top view which shows a light beam when the diffracted light diffracted by the hologram part of the comparative example is irradiated to the light-receiving part. FIG. 3 is a schematic plan view showing light beams for each defocus value when the diffracted light diffracted by the hologram unit is irradiated to the light receiving unit in a state where the temperature of the optical pickup device (laser light source) of Example 1 is raised. . FIG. 6 is a schematic plan view showing light beams for each defocus value when the diffracted light diffracted by the hologram unit is irradiated to the light receiving unit in a state where the temperature of the optical pickup device (laser light source) of the comparative example is increased. It is a figure which shows the temperature characteristic (center wavelength of a laser beam: 790 nm) of the optical pick-up apparatus of Example 1 and a comparative example. It is a figure which shows the temperature characteristic (center wavelength of a laser beam: 810 nm) of the optical pick-up apparatus of Example 1 and a comparative example. It is a figure which shows the temperature characteristic (center wavelength of a laser beam: 820 nm) of the optical pick-up apparatus of Example 1 and a comparative example. It is a figure which shows the temperature characteristic (center wavelength of a laser beam: 830 nm) of the optical pick-up apparatus of Example 1 and a comparative example. It is a figure which shows the temperature characteristic (center wavelength of a laser beam: 840 nm) of the optical pick-up apparatus of Example 1 and a comparative example. 6 is a schematic plan view for explaining a hologram part of the optical pickup device of Example 2. FIG. FIG. 3 is a schematic plan view showing a light beam when diffracted light diffracted by a hologram part of Example 1 is irradiated to a light receiving part. FIG. 6 is a schematic plan view showing a light beam when diffracted light diffracted by a hologram part of Example 2 is irradiated to a light receiving part. FIG. 10 is a schematic plan view showing light beams for each defocus value when the diffracted light diffracted by the hologram unit is irradiated to the light receiving unit in a state where the temperature of the optical pickup device (laser light source) of Example 2 is increased. . FIG. 6 is a schematic plan view showing light beams for each defocus value when the diffracted light diffracted by the hologram unit is irradiated to the light receiving unit in a state where the temperature of the optical pickup device (laser light source) of the comparative example is increased. FIG. 6 is a schematic plan view for explaining a hologram part of the optical pickup device of Example 3, and a schematic plan view showing a light beam when diffracted light diffracted by the hologram part of Example 3 is irradiated to the light receiving part. is there. FIG. 6 is a schematic plan view for explaining a hologram part of an optical pickup device of Example 4, and a schematic plan view showing a light beam when diffracted light diffracted by the hologram part of Example 4 is irradiated to a light receiving part. is there. FIG. 6 is a schematic plan view for explaining a hologram part of an optical pickup device of Example 5, and a schematic plan view showing a light beam when diffracted light diffracted by the hologram part of Example 5 is irradiated to a light receiving part. is there.

  The preferred embodiments of the present invention will be described with reference to FIGS.

<Example 1> [See FIGS. 1 to 12]
As shown in FIG. 1, the optical pickup apparatus 1 mainly transmits a laser light source 2 that emits laser light La toward the optical disc D, and transmits the laser light La emitted from the laser light source 2 and reflects it on the optical disc D. Hologram element 3 having hologram unit 10 that diffracts laser light (hereinafter referred to as return light) Lb and laser light La that has passed through hologram element 3 are condensed and focused on a predetermined information recording surface of optical disc D. The objective lens 4, the light receiving unit 20 that receives the diffracted lights Lc and Ld diffracted by the hologram unit 10 in accordance with the first hologram coefficient, and the hologram unit 10 returns the return light Lb to the first hologram coefficient. Includes a light receiving element 5 having a light receiving unit 30 that receives diffracted light beams Le and Lf diffracted according to different second hologram coefficients.

  Here, the relationship between the hologram unit 10 and the light receiving units 20 and 30 in the optical pickup device 1 of the first embodiment will be described with reference to FIG.

  As shown in FIG. 2, the hologram unit 10 has a substantially rectangular shape, and a center line A10 extending in the radial direction (radial direction) of the optical disc D (see FIG. 1) and the tangential direction (tangential direction) of the optical disc D. The hologram regions 11 to 14 are divided into four by a center line B10 extending in the horizontal direction. Note that the shape of the hologram portion 10 is not limited to a substantially rectangular shape.

The hologram region 11 and the hologram region 13 that are in a diagonal position relative to each other have a first hologram coefficient, and provide hologram regions that respectively give astigmatism to the diffracted lights Lc and Ld diffracted by the hologram regions 11 and 13. It is.
On the other hand, the hologram region 12 and the hologram region 14 that are in a diagonal positional relationship have a second hologram coefficient different from the first hologram coefficient, and the diffracted light Le, This is a hologram region where no astigmatism is given to Lf.

Similarly, as shown in FIG. 2, the light receiving unit 20 and the light receiving unit 30 are formed in the same plane in the light receiving element 5 (see FIG. 1).
The light receiving unit 20 is disposed so as to receive the diffracted lights Lc and Ld diffracted by the hologram regions 11 and 13, and two parallel dividing lines A20 and A2 extending in the radial direction (radial direction) of the optical disc D. Light receiving areas 21 to 23 divided into three by B20 are provided.
The light receiving unit 30 is disposed so as to receive the diffracted lights Le and Lf diffracted by the hologram regions 12 and 14, and two parallel dividing lines A30 and A2 extending in the radial direction (radial direction) of the optical disc D. Light receiving regions 31 to 33 divided into three by B30 are provided.

Then, the light beam Lcc of the diffracted light Lc diffracted by the hologram region 11 is irradiated over the light receiving region 21 and the light receiving region 22 of the light receiving unit 20.
Further, the light beam Ldd of the diffracted light Ld diffracted by the hologram region 13 is irradiated over the light receiving region 22 and the light receiving region 23 of the light receiving unit 20.

One focal line L1 formed by the hologram regions 11 and 13 having the first hologram coefficient is located between the hologram regions 11 and 13 (hologram element 3) and the light receiving unit 20 (light receiving element 5). The other focal line L2 is located farther from the light receiving unit 20 (light receiving element 5) than the hologram regions 11 and 13 (hologram element 3).
Here, what has the above relationship is defined as “astigmatism is given”.
Further, the distance between the light receiving unit 20 and one focal line L1 is H1, the distance between the light receiving unit 20 and the other focal line L2 is H2, and the distance between one focal line L1 and the other focal line L2 is H12. Then, it can be expressed as H12 = H1 + H2.

On the other hand, the light beam Lee of the diffracted light Le diffracted by the hologram region 12 is irradiated over the light receiving region 31 and the light receiving region 32 of the light receiving unit 30.
Further, the light beam Lff of the diffracted light Lf diffracted by the hologram region 14 is irradiated over the light receiving region 32 and the light receiving region 33 of the light receiving unit 30.

Further, one focal line L3 and the other focal line L4 formed by the hologram areas 12 and 14 having the second hologram coefficient are the hologram areas 12 and 14 (hologram element 3) and the light receiving unit 30 (light receiving element 5). It is located close to each other.
Here, what has the above relationship is defined as “no astigmatism is given”.
Further, the distance between the light receiving unit 30 and one focal line L3 is H3, the distance between the light receiving unit 30 and the other focal line L4 is H4, and the distance between one focal line L3 and the other focal line L4 is H34. Then, it can be expressed as H34 = | H3-H4 |. H12 and H34 have a relationship of H12> H34.

In general, the “no astigmatism” state is a state where H34 = 0, that is, the position of one focal line L3 and the other focal line L4 coincide.
Also in the present invention, H34 = 0 is most desirable, but even when H34 ≠ 0 due to variations in the manufacturing process or the like, if one focal line L3 and the other focal line L4 are close to each other, The effects of the present invention are exhibited.
Therefore, here, a state in which one focal line L3 and the other focal line L4 are close to each other is defined as a state in which "astigmatism is not given" in a broad sense.
Also, in Example 2 to Example 5 described later, a state where “astigmatism is not given” is broadly defined as in Example 1.

When the received light amounts when the diffracted lights Lc to Lf (light beams Lcc to Lff) are irradiated to the light receiving regions 21 to 23 and 31 to 33 are A1 to A3 and B1 to B3, respectively, the focus error signal FES is (1 ) Expression.
FES = | (B1 + A2 + B3) − (A1 + B2 + A3) | . . (1) Formula

Here, the relationship between the relative distance between the optical disc D (refer to FIG. 1 and FIG. 2 below) and the objective lens 4 and the shapes of the light beams Lcc to Lff of the diffracted beams Lc to Lf irradiated to the light receiving portions 20 and 30. Is shown in FIG.
FIG. 3B shows that the relative distance between the optical disk D and the objective lens 4 is such that the laser light La transmitted through the hologram element 3 is focused by the objective lens 4 and focused on a predetermined information recording surface of the optical disk D. The light beams Lcc to Lff of the diffracted lights Lc to Lf irradiated to the light receiving units 20 and 30 when the light is received are shown.
FIG. 3A shows a state in which the relative distance between the optical disc D and the objective lens 4 is shorter than the distance when the optical disc D is focused on a predetermined information recording surface, that is, the objective lens 4 is in the in-focus position. The light beams Lcc to Lff of the diffracted lights Lc to Lf irradiated to the light receiving portions 20 and 30 when the optical disk D is closer to the optical disk D are shown.
FIG. 3C shows a state in which the relative distance between the optical disc D and the objective lens 4 is longer than the distance when the optical disc D is focused on a predetermined information recording surface, that is, the objective lens 4 is located beyond the in-focus position. The light beams Lcc to Lff of the diffracted lights Lc to Lf irradiated to the light receiving portions 20 and 30 when being separated from the optical disk D are shown.

  Therefore, the light beams Lcc to Lff when the diffracted lights Lc to Lf diffracted by the hologram unit 10 are applied to the light receiving units 20 and 30 are shown in FIG. 3A according to the relative distance between the optical disc D and the objective lens 4. ), (B), and (c), the received light amounts A1 to A3 and B1 to B3 of the light receiving regions 21 to 23 and 31 to 33 change according to the relative distances.

Next, a conventional optical pickup apparatus 100 will be described with reference to FIGS. 4 and 5 as a comparative example for making the characteristics of the optical pickup apparatus 1 of the first embodiment easier to understand.
4 and 5 correspond to FIGS. 2 and 3, respectively.

  As shown in FIG. 4, the hologram portion 110 in the optical pickup device 100 of the comparative example has a substantially rectangular shape, and the center line A110 and the optical disc D extending in the radial direction (radial direction) of the optical disc D (see FIG. 1). Hologram regions 111 to 114 divided into four by a center line B110 extending in the tangential direction (tangential direction).

The hologram region 111 and the hologram region 113 that are in a diagonal position relative to each other have a third hologram coefficient, and are hologram regions that give astigmatism to the diffracted lights Lg and Lh diffracted by the hologram regions 111 and 113, respectively. is there.
In addition, the hologram region 112 and the hologram region 114 that are diagonally positioned to each other have a fourth hologram coefficient different from the third hologram coefficient, and the diffracted lights Li and Lj diffracted by the hologram regions 112 and 114 Each is a hologram region to which astigmatism is imparted.

  Since the light receiving units 20 and 30 of the conventional optical pickup device 100 have the same configuration as the light receiving units 20 and 30 of the optical pickup device 1 of the first embodiment, detailed description thereof is omitted.

The light beam Lgg of the diffracted light Lg diffracted by the hologram region 111 is irradiated over the light receiving region 21 and the light receiving region 22 of the light receiving unit 20.
The light beam Lhh of the diffracted light Lh diffracted by the hologram region 113 is irradiated over the light receiving region 22 and the light receiving region 23 of the light receiving unit 20.
In addition, one focal line L11 formed by the hologram areas 111 and 113 having the third hologram coefficient is located between the hologram areas 111 and 113 and the light receiving unit 20, and the other focal line L12 is the hologram area. 111 and 113 are located farther than the light receiving unit 20 (light receiving element 5).

On the other hand, the light beam Lii of the diffracted light Li diffracted by the hologram region 112 is irradiated over the light receiving region 31 and the light receiving region 32 of the light receiving unit 30.
The light beam Ljj of the diffracted light Lj diffracted by the hologram region 114 is irradiated over the light receiving region 32 and the light receiving region 33 of the light receiving unit 30.
In addition, one focal line L13 formed by the hologram areas 112 and 114 having the fourth hologram coefficient is located between the hologram areas 112 and 114 and the light receiving unit 30, and the other focal line L14 is the hologram area. 112 and 114 are located farther than the light receiving unit 30 (light receiving element 5).

The distance between the light receiving unit 20 and one focal line L11 is H11, the distance between the light receiving unit 20 and the other focal line L12 is H22, and the distance between one focal line L11 and the other focal line L12 is H112. , H112 = H11 + H12.
Further, the distance between the light receiving unit 30 and one focal line L13 is H13, the distance between the light receiving unit 30 and the other focal line L14 is H14, and the distance between one focal line L13 and the other focal line L14 is H134. Then, it can be expressed as H123 = H13 + H14.

  When the light receiving amounts when the diffracted lights Lg to Lj (light beams Lgg to Ljj) are irradiated to the light receiving regions 21 to 23 and 31 to 33 are A1 to A3 and B1 to B3, respectively, the focus error signal FES is It is represented by the formula (1).

Here, the relationship between the relative distance between the optical disc D (refer to FIGS. 1 and 4 below) and the objective lens 4 and the shapes of the light beams Lgg to Ljj of the diffracted beams Lg to Lj irradiated to the light receiving units 20 and 30. Is shown in FIG.
FIG. 5B shows that the relative distance between the optical disc D and the objective lens 4 is such that the laser light La transmitted through the hologram element 3 is focused by the objective lens 4 and focused on a predetermined information recording surface of the optical disc D. The light beams Lgg to Ljj of the diffracted lights Lg to Lj irradiated to the light receiving units 20 and 30 when the light is received are shown.
FIG. 5A shows a state in which the relative distance between the optical disc D and the objective lens 4 is shorter than the distance when the optical disc D is focused on a predetermined information recording surface, that is, the objective lens 4 is in the in-focus position. 2 shows the light beams Lgg to Ljj of the diffracted lights Lg to Lj irradiated to the light receiving units 20 and 30 when they are closer to the optical disc D.
FIG. 5C shows a state in which the relative distance between the optical disc D and the objective lens 4 is longer than the distance when the optical disc D is focused on a predetermined information recording surface, that is, the objective lens 4 is closer to the in-focus position. The light beams Lgg to Ljj of the diffracted lights Lg to Lj irradiated to the light receiving units 20 and 30 when they are separated from the optical disk D are shown.

  Therefore, the light beams Lgg to Ljj when the diffracted lights Lg to Lj diffracted by the hologram unit 110 are irradiated to the light receiving units 20 and 30 are shown in FIG. 5A according to the relative distance between the optical disc D and the objective lens 4. ), (B), and (c), the received light amounts A1 to A3 and B1 to B3 of the light receiving regions 21 to 23 and 31 to 33 change according to the relative distances.

  That is, in the optical pickup device 100 of the comparative example, astigmatism is imparted to both the one diffracted light Lg, Lh and the other diffracted light Li, Lj, whereas in the optical pickup device 1 of the first embodiment, one diffraction is performed. The difference is that astigmatism is given to the light La, lb, and no astigmatism is given to the other diffracted light Lc, ld.

  Next, temperature characteristics of the optical pickup device 1 of the first embodiment and the optical pickup device 100 of the comparative example will be described with reference to FIGS.

FIG. 6 shows the shape of the light beam (Lcc to Lff) irradiated with the diffracted light (Lc to Lf) diffracted by the hologram unit 10 on the light receiving units 20 and 30 in the optical pickup device 1 of the first embodiment shown in FIG. It is shown.
7 shows light beams (Lgg to Ljj) irradiated to the light receiving units 20 and 30 by the diffracted light (Lg to Lj) diffracted by the hologram unit 110 in the optical pickup device 100 of the comparative example shown in FIG.
6 and 7, (a), (b), (c), (d), (e), (f), (g), (h), (i), (j), (k) , (L), (m), (n), (o), (p), (q), (r), (s), (t), and (u) each have a defocus value of “−20 μm”. , “−18 μm”, “−16 μm”, “−14 μm”, “−12 μm”, “−10 μm”, “−8 μm”, “−6 μm”, “−4 μm”, “−2 μm”, “0 μm”, “+2 μm”, “+4 μm”, “+6 μm”, “+8 μm”, “+10 μm”, “+12 μm”, “+14 μm”, “+16 μm”, “+18 μm”, and “+20 μm” are shown.
In addition, in FIGS. 6 and 7, particularly, as shown in each (k) {defocus = 0 μm}, the light beams (Lcc to Lff) and (Lgg to Ljj) of diffracted light (Lc to Lf) and (Lg to Lj) are shown. It is shifted to the right side of the paper with respect to the light receiving units 20 and 30 (the same applies to (a) to (j) and (l) to (u)), which is the optical pickup device (laser light source) of Example 1 and the comparative example. It shows a state where the temperature of 1,100 has increased.

Comparing FIG. 6 and FIG. 7, particularly when comparing each of (f) {defocus = −10 μm} to (h) {defocus = −6 μm}, in FIG. In contrast to being located inside, in FIG. 7 (comparative example), a part of the light beam is located at a position away from the light receiving unit 30.
Therefore, in the comparative example, the amount of light received by the light receiving unit 30 is reduced, and the intensity of the focus error signal is reduced.

8 to 12 show the defocus value and the focus error signal (FES) when the center wavelength of the laser light emitted from the optical pickup devices 1 and 100 of the first embodiment and the comparative example is shifted due to the influence of the environmental temperature. It shows the relationship with relative signal strength.
8 to 12, the horizontal axis indicates the defocus value (unit: μm), and the vertical axis indicates the relative signal intensity of the focus error signal (FES).

As described above, since the optical pickup device and its laser light source are affected by the environmental temperature, the center wavelength of the laser light emitted from the optical pickup device is set to the longer wavelength side according to the degree of temperature rise of the laser light source itself. shift.
FIG. 8 shows characteristics when the wavelength of the laser light emitted from the laser light source of the optical pickup device (1, 100) is 790 nm. FIG. 9 shows characteristics when the center wavelength of the laser light emitted in accordance with the temperature rise of the optical pickup devices (laser light sources) 1 and 100 is shifted to 810 nm. FIG. 10 shows characteristics when the center wavelength of the laser light emitted in accordance with the temperature rise of the optical pickup devices (laser light sources) 1 and 100 is shifted to 820 nm. FIG. 11 shows characteristics when the center wavelength of the laser light emitted in accordance with the temperature rise of the optical pickup devices (laser light sources) 1 and 100 is shifted to 830 nm. FIG. 12 shows characteristics when the center wavelength of the laser light emitted in accordance with the temperature rise of the optical pickup devices (laser light sources) 1 and 100 is shifted to 840 nm.
That is, it shows a state in which the temperatures of the optical pickup devices (laser light sources) 1 and 100 of the first embodiment and the comparative example rise in the order of FIG. 8, FIG. 9, FIG. 10, FIG.

  When the characteristics of the optical pickup device 1 of the first embodiment and the characteristics of the optical pickup device 100 of the comparative example are compared in FIGS. 8 to 12, the defocus value particularly in FIGS. 10 to 12 is negative (−5 μm to −10 μm). ) FES peaks are different.

In the optical pickup device 100 of the comparative example, the peak of the FES having a negative defocus value hardly changes between FIGS. 8 and 9, but the peak height gradually increases in the order of FIG. 10 → FIG. 11 → FIG. It is low. This indicates that the deviation of the FES S-shaped waveform balance is large.
On the other hand, in the optical pickup device 1 of the first embodiment, the FES peak having a negative defocus value hardly changes in any of FIGS.
The comparison results between the optical pickup device 1 of Example 1 and the optical pickup device 100 of the comparative example in FIGS. 8 to 12 are in accordance with the comparison results of FIG. 6 (Example 1) and FIG. 7 (Comparative Example) described above. Is.
From the above results, it can be seen that the optical pickup device 1 of Example 1 can obtain better temperature characteristics than the optical pickup device 100 of the comparative example.

<Example 2> [Refer to Drawing 1 and Drawing 13-Drawing 17]
The optical pickup device 40 (see FIG. 1) of the second embodiment is different from the optical pickup device 1 of the first embodiment in the configuration of the hologram portion 41 of the hologram element 3, and the other configurations are the same as those in the first embodiment. This is the same as the pickup device 1.

Accordingly, the hologram portion 41 of the hologram element 3 in the optical pickup device 40 of the second embodiment will be described in detail below with reference to FIG.
FIG. 13A shows the hologram portion 10 of the optical pickup device 1 of the first embodiment, and FIG. 13B shows the hologram portion 41 of the optical pickup device 40 of the second embodiment.

  As shown in FIG. 13A, the hologram unit 10 of the optical pickup device 1 of the first embodiment described above includes the center line A10 extending in the radial direction (radial direction) of the optical disc D (see FIG. 1) and the optical disc D. The hologram regions 11 to 14 are divided into four by a center line B10 extending in the tangential direction (tangential direction). In addition, the hologram area 11 and the hologram area 13 that are in a diagonal positional relationship have a first hologram coefficient, and are hologram areas that respectively give astigmatism to the diffracted light diffracted by the hologram areas 11 and 13. . On the other hand, the hologram region 12 and the hologram region 14 that are in a diagonal position relative to each other have a second hologram coefficient that is different from the first hologram coefficient, and the diffracted light diffracted by the hologram regions 12 and 14 respectively. This is a hologram region that does not give astigmatism.

  On the other hand, as shown in FIG. 13B, the hologram section 41 of the optical pickup device 40 according to the second embodiment has a hologram area 42 and a hologram area 43 each having a strip shape in the radial direction (radial direction) of the optical disc D. It has the structure arranged alternately.

Each hologram area 42 has the above-described first hologram coefficient, and gives astigmatism to the diffracted light diffracted by each hologram area 42.
On the other hand, each hologram region 43 is a hologram region that has the above-described second hologram coefficient and does not give astigmatism to the diffracted light diffracted by each hologram region 43.
That is, the hologram area 42 of the second embodiment corresponds to the hologram areas 11 and 13 of the first embodiment, and the hologram area 43 of the second embodiment corresponds to the hologram areas 12 and 14 of the first embodiment.

  Here, a case where a scratch is formed on the optical disc D will be described with reference to FIGS.

First, a case where a scratch is formed on the optical disc D (see FIG. 1) with respect to the optical pickup device 1 of the first embodiment will be described with reference to FIG.
FIG. 14 shows each light beam when the light-receiving portions 20 and 30 are irradiated with the diffracted light diffracted by the hologram portion 10 of the first embodiment. FIG. 14A shows a case where no scratch is generated on the optical disc, and FIG. 14B shows a case where a scratch is formed on the optical disc. In FIGS. 14A and 14B, a black region is a region irradiated with diffracted light.

  When the optical disc D is formed with a scratch extending at an angle of about 45 ° with respect to the tangential direction, the light beam applied to the light receiving portions 20 and 30 is blocked by a light shielding region {FIG. In b), a white area diagonally appears}.

  The received light amounts A1, A2, A3, B1, B2, and B3 in the respective light receiving regions when the light receiving regions 21, 22, 23, 31, 32, and 33 are irradiated with the light beam are expressed by the above-described equation (1).

The light receiving area 21 is not affected by scratches.
The light receiving area 22 is affected by scratches to generate two light shielding areas.
The light receiving area 23 is not affected by scratches.
The light receiving area 31 is affected by scratches to generate one light shielding area.
The light receiving area 32 is affected by scratches to generate two light shielding areas.
The light receiving area 33 is affected by scratches to generate one light shielding area.
Here, when the amount of light reduction due to the light-shielding region per location is C and applied to the equation (1), the focus error signal FESa when the scratch is formed on the optical disk is expressed by the equation (2).
FESa = | {(B1-C) + (A2-2C) + (B3-C)}-{A1 + (B2-2C) + A3} | = | (B1 + A2 + B3)-(A1 + B2 + A3-2C) | . . Therefore, in the optical pickup device 1 according to the first embodiment, an error corresponding to 2C of light reduction due to the two light-shielding areas is generated in the focus error signal. Therefore, even if the laser beam is focused on the optical disc, it is recognized as a defocus state. As a result, it appears as noise in the control signal, which causes a problem such as skipping of sound or stop of reproduction when the optical disk is reproduced.

Next, a case where a scratch is formed on the optical disc D (see FIG. 1) with respect to the optical pickup device 40 of the second embodiment will be described with reference to FIG.
FIG. 15 is a schematic plan view showing each light beam when the light receiving portions 20 and 30 are irradiated with the diffracted light diffracted by the hologram portion 41 of the second embodiment. FIG. 15A shows a case where no scratch is generated on the optical disc, and FIG. 15B shows a case where a scratch is formed on the optical disc. In FIGS. 15A and 15B, a black area is an area (light beam) irradiated with diffracted light.

  When the optical disk D is formed with a scratch extending at an angle of about 45 ° with respect to the tangential direction, the light beam applied to the light receiving portions 20 and 30 is blocked by the scratch-shielding region {FIG. In b), a white area diagonally appears}.

All the light receiving regions 21 to 23 and 31 to 33 are affected by scratches.
Here, if the light reduction amount due to the light shielding regions of the light receiving regions 21, 23, 31 and 33 is D, the light reduction amount due to the light shielding regions of the light receiving regions 22 and 32 has two light shielding regions and the respective lengths are received. Since it is three times the light shielding area of the areas 21, 23, 31 and 33, it becomes 6D.
Therefore, when the light reduction amounts of the light receiving regions 21 to 23 and 31 to 33 are applied to the equation (1), the focus error signal FESb when the scratch is formed on the optical disk is represented by the equation (3).
FESb = | {(B1-D) + (A2-6D) + (B3-D)} − {(A1-D) + (B2-6D) + (A3-D)} | = | (B1 + A2 + B3) − ( A1 + B2 + A3) |. . . Therefore, in the optical pickup device 40 of the second embodiment, FESb = FES is obtained, and the influence of scratch can be offset.

  As described above, in the optical pickup device 40 of the second embodiment, the hologram region 42 that has the first hologram coefficient and imparts astigmatism to the diffracted light, and the second hologram coefficient, The hologram regions 43 to which astigmatism is not given have a configuration in which they are alternately arranged.

Therefore, the temperature characteristics of the optical pickup device 40 according to the second embodiment and the optical pickup device having a configuration in which the hologram regions 42 and 43 give astigmatism to the diffracted light as comparative examples will be described with reference to FIGS. 16 and 17. explain.
FIG. 16 shows a light beam irradiated to the light receiving portions 20 and 30 by the diffracted light diffracted by the hologram portion 41 shown in FIG. FIG. 17 shows the comparative example described above.
16 and 17, (a), (b), (c), (d), (e), (f), (g), (h), (i), (j), (k) , (L), (m), (n), (o), (p), (q), (r), (s), (t), and (u) each have a defocus value of “−20 μm”. , “−18 μm”, “−16 μm”, “−14 μm”, “−12 μm”, “−10 μm”, “−8 μm”, “−6 μm”, “−4 μm”, “−2 μm”, “0 μm”, “+2 μm”, “+4 μm”, “+6 μm”, “+8 μm”, “+10 μm”, “+12 μm”, “+14 μm”, “+16 μm”, “+18 μm”, and “+20 μm” are shown.
16 and 17, particularly, as shown in each (k) {defocus = 0 μm}, the light beam of the diffracted light is shifted to the right side of the paper with respect to the light receiving portions 20 and 30 {(a) to (j). The same applies to (l) to (u)}, which shows a state in which the temperatures of the optical pickup devices (laser light sources) of Example 2 and the comparative example have increased.

When comparing FIG. 16 with FIG. 17, particularly when comparing each of (f) {defocus = −10 μm} to (h) {defocus = −6 μm}, in FIG. In contrast to being located inside, in FIG. 17 (comparative example), a part of the light beam is located at a position away from the light receiving unit 30.
Therefore, in the comparative example, the amount of light received by the light receiving unit 30 is reduced, and the S-shaped waveform level of the focus error signal is lowered and the S-shaped waveform balance is shifted. This result is in line with the above-described result described in Embodiment 1 with reference to FIGS.

  Therefore, according to the optical pickup device 40 of the second embodiment, the temperature characteristics are improved as compared with the conventional optical pickup device, similarly to the optical pickup device 1 of the first embodiment, and moreover the optical disc than the optical pickup device 1 of the first embodiment. The effect of becoming less susceptible to the effects of scratches.

<Example 3> [See FIGS. 1 and 18]
The optical pickup device 50 according to the third embodiment (see FIG. 1) is different from the optical pickup device 1 according to the first embodiment and the optical pickup device 40 according to the second embodiment in the configuration of the hologram unit 51 of the hologram element 3. Other configurations are the same as those of the optical pickup device 1 of the first embodiment and the optical pickup device 40 of the second embodiment.

Accordingly, the hologram unit 51 of the hologram element 3 in the optical pickup device 50 of the third embodiment will be described in detail below with reference to FIG.
FIG. 18A is a schematic plan view for explaining the hologram unit 51 of the optical pickup device 50 according to the third embodiment. FIGS. 18B and 18C are schematic plan views showing the respective light beams when the light receiving portions 20 and 30 are irradiated with the diffracted light diffracted by the hologram portion 51. FIG. 18B shows a case where no scratch is generated on the optical disc, and FIG. 18C shows a case where a scratch is formed on the optical disc. In FIGS. 18B and 18C, black areas are areas (light beams) irradiated with diffracted light.

As shown in FIG. 18 (a), the hologram unit 51 of the optical pickup device 50 of the third embodiment has an up and down direction on the paper surface by a center line A51 extending in the radial direction (radial direction) of the optical disc D (see FIG. 1). The optical disk D is divided into two in the tangential direction (tangential direction)}.
One of the divided regions has a configuration in which the hologram regions 52 and the hologram regions 53 each having a strip shape are alternately arranged in the radial direction of the optical disc D.
Similarly, the other divided area has a configuration in which hologram areas 54 and hologram areas 55 each having a strip shape are alternately arranged in the radial direction of the optical disc D.

The hologram areas 52 and 54 have the first hologram coefficient, respectively, and give astigmatism to the diffracted light diffracted by the hologram areas 52 and 54, respectively.
On the other hand, the hologram regions 53 and 55 are hologram regions that have the second hologram coefficient, respectively, and do not give astigmatism to the diffracted light diffracted by the hologram regions 53 and 55, respectively.
Further, the hologram areas 52 and the hologram areas 54 are alternately arranged, and the hologram areas 53 and the hologram areas 55 are alternately arranged.
That is, the hologram regions 52 and 54 of the third embodiment correspond to the hologram regions 11 and 13 of the first embodiment and the hologram region 42 of the second embodiment, respectively. The hologram regions 53 and 55 of the third embodiment are the hologram regions of the first embodiment. 12, 14 and the hologram region 43 of the second embodiment.

  When the optical disk D (see FIG. 1) is formed with a scratch extending at an angle of about 45 ° with respect to the tangential direction, the light beam irradiated to the light receiving portions 20 and 30 is blocked by the scratch. A region {region shown in white diagonally in FIG. 18 (c)} is generated.

All the light receiving regions 21 to 23 and 31 to 33 are affected by scratches.
Here, assuming that the amount of light reduction due to the light-shielding areas of the light-receiving areas 21, 23, 31 and 33 is E, the amount of light reduction due to the light-shielding areas of the light-receiving areas 22 and 32 has two light-shielding areas and the respective lengths are Since it is three times the light shielding area of the areas 21, 23, 31 and 33, it becomes 6E.
Therefore, when the light reduction amount of each of the light receiving areas 21 to 23 and 31 to 33 is applied to the above-described equation (1), the focus error signal FESc when the scratch is formed on the optical disk is represented by the equation (4).
FESc = | {(B1−E) + (A2−6E) + (B3−E)} − {(A1−E) + (B2−6E) + (A3−E)} | = | (B1 + A2 + B3) − ( A1 + B2 + A3) |. . . Therefore, the optical pickup device 50 of the third embodiment also has the same FESc = FES as in the optical pickup device 40 of the second embodiment, so that the influence of scratches can be offset.

  In addition, according to the optical pickup device 50 of the third embodiment, the hologram regions 52 and 54 that have the first hologram coefficient and give astigmatism to the diffracted light, and the second hologram coefficient, and the diffracted light Are provided with hologram regions 53 and 55 that do not give astigmatism to the optical pickup device 1 of the first embodiment and the optical pickup device 40 of the second embodiment. Can be made.

<Example 4> [See FIGS. 1 and 19]
The optical pickup device 60 (see FIG. 1) according to the fourth embodiment is different from the optical pickup devices 1, 40, and 50 according to the first to third embodiments in the configuration of the hologram unit 61 of the hologram element 3. This configuration is the same as that of the optical pickup devices 1, 40, 50 of the first to third embodiments.

Accordingly, the hologram unit 61 of the hologram element 3 in the optical pickup device 60 of the fourth embodiment will be described in detail below with reference to FIG.
FIG. 19A is a schematic plan view for explaining the hologram unit 61 of the optical pickup device 60 of the fourth embodiment. FIGS. 19B and 19C are schematic plan views showing respective light beams when the light receiving portions 20 and 30 are irradiated with the diffracted light diffracted by the hologram portion 61. FIG. 19B shows a case where no scratch is generated on the optical disc, and FIG. 19C shows a case where a scratch is formed on the optical disc. In FIGS. 19B and 19C, the black area is an area (light beam) irradiated with diffracted light.

As shown in FIG. 19A, the hologram unit 61 of the optical pickup device 60 according to the fourth embodiment has a left-right direction on the paper surface by a center line B61 extending in the tangential direction (tangential direction) of the optical disc D (see FIG. 1). It is divided into two in {the radial direction (radial direction) of the optical disc D}.
A hologram area 62 and a hologram area 63 that does not contact the center line B61 are arranged in one divided area, and a hologram area 65 and a hologram area 64 that does not contact the center line B61 are arranged in the other divided area. Has been.
The hologram area 63 and the hologram area 64 are arranged point-symmetrically with respect to the center O61 of the hologram portion 61.
Assuming that the areas of the hologram regions 62, 63, 64, and 65 are S62, S63, S64, and S65, respectively, the relationship of S62 + S64 = S63 + S65 is satisfied.

  Further, as shown in FIG. 19A, a predetermined information recording surface of the optical disk D when the lens center of the objective lens 4 is at the center position of the hologram portion 61 during reproduction of the optical disk D (see FIG. 1). The return beam Lb, which is the laser beam reflected at, is represented by a circle A66 as a light beam incident on the hologram unit 61, and the hologram unit 61 when the objective lens 4 moves a maximum distance in one direction of the radial direction (radial direction). Is represented by a circle B66, and the light beam incident on the hologram unit 61 when the objective lens 4 is moved by the maximum distance in the other radial direction (radial direction) is represented by a circle C66. 63 and the hologram region 64 are designed so that at least a part thereof is included in the regions inside the three circles A66, B66, and C66, respectively.

The hologram regions 62 and 64 have the first hologram coefficient, respectively, and give astigmatism to the diffracted light diffracted by the hologram regions 62 and 64, respectively.
On the other hand, the hologram regions 63 and 65 are hologram regions that have the second hologram coefficient, respectively, and do not give astigmatism to the diffracted light diffracted by the hologram regions 63 and 65, respectively.
That is, the hologram regions 62 and 64 of Example 4 correspond to the hologram regions 11 and 13 of Example 1, the hologram region 42 of Example 2, and the hologram regions 52 and 54 of Example 3, respectively. The regions 63 and 65 correspond to the hologram regions 12 and 14 of the first embodiment, the hologram region 43 of the second embodiment, and the hologram regions 53 and 55 of the third embodiment, respectively.

  When the optical disk D (see FIG. 1) is formed with a scratch extending at an angle of about 45 ° with respect to the tangential direction, the light beam irradiated to the light receiving portions 20 and 30 is blocked by the scratch. A region {region shown in white diagonally in FIG. 19 (c)} is generated.

The light receiving areas 21 and 31 are not affected by scratches.
The other light receiving areas 22, 23, 32 and 33 are affected by scratches.
Here, if the light reduction amount due to the light shielding regions of the light receiving regions 23 and 33 is F, the light reduction amount due to the light shielding regions of the light receiving regions 22 and 32 is the length (area) of the light shielding region of the light shielding regions 23 and 33. Since it is 1.5 times, it becomes 1.5F.
Therefore, when the light reduction amounts of the light receiving regions 21 to 23 and 31 to 33 are applied to the above-described equation (1), the focus error signal FESd when the scratch is formed on the optical disk is represented by the equation (5).
FESd = | {B1 + (A2-1.5F) + (B3-F)}-{A1 + (B2-1.5F) + (A3-F)} | = | (B1 + A2 + B3)-(A1 + B2 + A3) | . . Accordingly, the optical pickup device 60 of the fourth embodiment also has the same FESd = FES as in the optical pickup device 40 of the second embodiment and the optical pickup device 50 of the third embodiment, and can cancel the influence of scratches.

  Further, according to the optical pickup device 60 of the fourth embodiment, the hologram regions 62 and 64 that have the first hologram coefficient and give astigmatism to the diffracted light, and the second hologram coefficient, and the diffracted light Are provided with hologram regions 63 and 65 to which no astigmatism is imparted, so that the temperature characteristics can be improved as compared with the conventional optical pickup devices as in the optical pickup devices 1, 40 and 50 of the first to third embodiments. it can.

<Example 5> [See FIGS. 1 and 20]
The optical pickup device 70 of Embodiment 5 (see FIG. 1) is different from the optical pickup devices 1, 40, 50, and 60 of Embodiments 1 to 4 in the configuration of the hologram unit 71 of the hologram element 3, Other configurations are the same as those of the optical pickup devices 1, 40, 50, 60 of the first to fourth embodiments.

Therefore, the hologram portion 71 of the hologram element 3 in the optical pickup device 70 of Embodiment 5 will be described in detail below with reference to FIG.
FIG. 20A is a schematic plan view for explaining the hologram portion 71 of the optical pickup device 70 of the fifth embodiment. FIGS. 20B and 20C are schematic plan views showing respective light beams when diffracted light diffracted by the hologram portion 71 is irradiated to the light receiving portions 20 and 30. FIG. FIG. 20B shows a case where no scratch is generated on the optical disc, and FIG. 20C shows a case where a scratch is formed on the optical disc. In FIGS. 20B and 20C, a black area is an area (light beam) irradiated with diffracted light.

As shown in FIG. 20 (a), the hologram portion 71 of the optical pickup device 70 of the fifth embodiment has a left-right direction on the paper surface by a center line B71 extending in the tangential direction (tangential direction) of the optical disc D (see FIG. 1). It is divided into two in {the radial direction (radial direction) of the optical disc D}.
A hologram area 73 and a hologram area 72 that does not contact the center line B71 are arranged in one divided area, and a hologram area 74 and a hologram area 75 that does not contact the center line B71 are arranged in the other divided area. Has been.
The hologram area 72 and the hologram area 75 are arranged symmetrically with respect to the center line B71 of the hologram portion 71.
If the areas of the hologram regions 72, 73, 74, and 75 are S72, S73, S74, and S75, respectively, the relationship of S72 + S74 = S73 + S75 is satisfied.

  Also, as shown in FIG. 20A, a predetermined information recording surface of the optical disc D when the lens center of the objective lens 4 is at the center position of the hologram portion 71 during reproduction of the optical disc D (see FIG. 1). The return beam Lb, which is the laser beam reflected at, is represented by a circle A76, and the hologram unit 61 when the objective lens 4 has moved a maximum distance in one of the radial directions (radial directions). Is represented by a circle B76, and the light beam incident on the hologram unit 61 when the objective lens 4 is moved by the maximum distance in the other radial direction (radial direction) is represented by a circle C76. 72 and the hologram region 75 are designed so that at least a part thereof is included in the regions inside the three circles A76, B76, and C76, respectively.

The hologram regions 72 and 74 have the first hologram coefficient, respectively, and give astigmatism to the diffracted light diffracted by the hologram regions 72 and 74, respectively.
On the other hand, the hologram regions 73 and 75 are hologram regions that have the second hologram coefficient, respectively, and do not give astigmatism to the diffracted light diffracted by the hologram regions 73 and 75, respectively.
That is, the hologram regions 72 and 74 of Example 5 are the hologram regions 11 and 13 of Example 1, the hologram region 42 of Example 2, the hologram regions 52 and 54 of Example 3, and the hologram regions 62 and 64 of Example 4. The hologram regions 73 and 75 of Example 5 correspond to the hologram regions 12 and 14 of Example 1, the hologram region 43 of Example 2, the hologram regions 53 and 55 of Example 3, and the hologram region of Example 4, respectively. 63 and 65, respectively.

  When a scratch extending on the optical disc D (see FIG. 1) at an angle of about 45 ° with respect to the tangential direction is formed, the light beam irradiated to the light receiving portions 20 and 30 is blocked by a scratch-shielding region { In FIG. 20 (c), a white region obliquely appears.

The light receiving area 23 is not affected by scratches.
The other light receiving regions 22, 23, 31, 32, and 33 are affected by scratches.
Here, assuming that the amount of light reduction due to the light shielding region of the light receiving region 21 is G, the amount of light reduction due to the light shielding region of the light receiving region 22 is determined from the ratio of the area (length) of the light shielding region to the light shielding region of the light receiving region 21. 2G, the amount of light reduction due to the light shielding region of the light receiving region 31 is G, the amount of light reduction due to the light shielding region of the light receiving region 32 is 3G, and the amount of light reduction due to the light shielding region of the light receiving region 33 is G.
Therefore, when the light reduction amounts of the light receiving areas 21 to 23 and 31 to 33 are applied to the above-described equation (1), the focus error signal FESe when the scratch is formed on the optical disk is represented by the equation (6).
FESe = | {(B1-G) + (A2-2G) + (B3-G)}-{(A1-G) + (B2-3G) + A3} | = | (B1 + A2 + B3)-(A1 + B2 + A3) | . . Accordingly, the optical pickup device 70 of the fifth embodiment also has the same FESe = FES as in the optical pickup devices 40, 50, and 60 of the second to fourth embodiments, and can cancel the influence of scratches.

  In addition, according to the optical pickup device 70 of the fifth embodiment, the hologram regions 72 and 74 that have the first hologram coefficient and give astigmatism to the diffracted light, and the second hologram coefficient have the diffracted light. Are provided with hologram regions 73 and 75 to which no astigmatism is imparted, so that the temperature characteristics are improved as compared with the conventional optical pickup devices as in the optical pickup devices 1, 40, 50 and 60 of the first to fourth embodiments. be able to.

  The embodiment of the present invention is not limited to the configuration and procedure described above, and it goes without saying that modifications may be made without departing from the scope of the present invention.

1, 40, 50, 60, 70_ Optical pickup device, 2_ Laser light source, 3_ Hologram element, 4_ Objective lens, 5_ Light receiving element, 10, 41, 51, 61, 71_ Hologram part, 11-14, 42, 43, 52 -55, 62-65, 72-75_hologram area, 20,30_light receiving part, 21-23, 31-33_light receiving area, La_laser light, D_optical disk, Lb_return light (laser light), Lc-Lf_diffracted light A10, B10, A51, B61_ center line, A20, B20, A30, B30_ dividing line, Lcc to Lff_ luminous flux, L1 to L4_ focal line, H1 to H4, H12, H34_ distance, O61_ center

Claims (5)

A laser light source for emitting laser light;
An objective lens that focuses the laser light and focuses it on a predetermined information recording surface of the optical disc;
Each of the laser light emitted from the laser light source is transmitted and diffracted by the return light that is the laser light reflected by the predetermined information recording surface, and the first diffracted light with astigmatism is emitted. A hologram element having a hologram portion including a first hologram region and a second hologram region that emits second diffracted light to which astigmatism is not applied;
A light-receiving element having a first light-receiving unit that receives the first diffracted light and a second light-receiving unit that receives the second diffracted light;
With
In the first diffracted light, one focal line is located between the hologram element and the light receiving element, and the other focal line is located farther from the light receiving element than the hologram element. ,
The optical pickup apparatus, wherein the second diffracted light has one focal line and the other focal line located close to each other between the hologram element and the light receiving element. The hologram portion includes first to fourth divided regions divided into four by a first dividing line parallel to the radial direction of the optical disc and a second dividing line parallel to the tangential direction of the optical disc,
The first divided region and the third divided region are diagonally positioned relative to each other, and are the first hologram region,
2. The optical pickup device according to claim 1, wherein the second divided region and the fourth divided region are in a diagonal positional relationship with each other and are the second hologram region.   2. The optical pickup device according to claim 1, wherein the first hologram area and the second hologram area each have a strip shape and are alternately arranged in a tangential direction of the optical disk. The hologram portion includes a fifth divided region and a sixth divided region which are divided into two by a third dividing line parallel to the radial direction of the optical disc,
In the fifth divided region and the sixth divided region, a plurality of the first hologram regions and the second hologram regions each having a strip shape are alternately arranged in the tangential direction of the optical disc, and 2. The optical pickup device according to claim 1, wherein the fifth divided area and the sixth divided area are further alternately arranged. The hologram portion is arranged in a seventh divided area and an eighth divided area divided into two by a fourth dividing line parallel to the tangential direction of the optical disc, and the fourth divided area is arranged in the seventh divided area. A ninth divided area that does not contact the dividing line; and a tenth divided area that is arranged in the eighth divided area and does not contact the fourth dividing line;
The seventh divided area and the tenth divided area are the first hologram areas,
The eighth divided area and the ninth divided area are the second hologram areas,
The ninth divided area and the tenth divided area are arranged symmetrically with respect to the fourth dividing line, or are arranged symmetrically with respect to the center position of the hologram part. The optical pickup device according to claim 1.