JP2003302513A - Optical element equipped with binary blaze grating, metal mold for molding, and optical pickup unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose an optical axis adjusting element equipped with a binary blaze grating for adjusting the optical axis of light of each wavelength of a two-wavelength light source type optical pickup unit. <P>SOLUTION: The optical axis adjusting element 10 is equipped with the binary blaze grating 11, its step height (h) is 650/(n-1) (≥1 μm) and its blaze height H is 5×780/(n-1). For DVD laser light L1 of 650 nm in wavelength, diffracted light L1(0) of (0)th order is generated with maximum efficiency and for CD laser light L2 of 780 nm in wavelength, 1st-order diffracted light L2(1) is generated with maximum efficiency. The binary blaze grating is formed by cutting, so the binary blaze grading is precisely formed in a short processing time differently from etching. The optical axis adjusting element can be manufactured at low cost and optical axis adjustments can securely be made. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as an optical axis adjusting element for adjusting the optical axes of a two-wavelength light source type optical pickup device so that light of each wavelength can be received by a common photodetector. The present invention relates to an optical element having a binary blazed grating suitable for. The present invention also relates to a molding die for molding such an optical element and an optical element formed by the molding die. Furthermore, the present invention relates to an optical pickup device in which such an optical element is incorporated as an optical axis adjusting element.

[0002]

2. Description of the Related Art As an optical pickup device, a DVD laser light source having a wavelength of 650 nm and a wavelength of 780 nm are used for recording and / or reproducing a DVD and a CD.
There is known a two-wavelength type optical pickup device equipped with a laser light source for CD. In recent years, in order to miniaturize and downsize a two-wavelength light source, a monolithic twin laser light source in which two laser diodes are formed on a semiconductor substrate housed in a single package is used. ing.

In the case of such a twin laser light source, since the distances between the light emitting points of the two laser diodes arranged in parallel are apart from each other by about 100 μm, the optical axis of one laser diode coincides with the system optical axis. And let
The optical axis of the laser light from the other laser diode deviates from the system optical axis. In this state, the return light emitted from both laser diodes and reflected by the optical recording medium cannot be received by the common photodetector. Therefore, by diffracting one of the return lights by using an optical axis adjusting element such as a diffraction grating or a diffraction grating called an optical path combining element,
Both return lights can be received by a common photodetector.

A two-source type optical pickup device provided with such an optical axis adjusting element or an optical path synthesizing element is disclosed in Japanese Patent Application Laid-Open No.
001-143312 gazette, Unexamined-Japanese-Patent No. 2001-25667.
No. 0 publication and the like.

[0005]

It is considered that a binary blazed diffraction grating is used as the optical axis adjusting element of the optical pickup device. This diffraction grating has a structure in which a blazed grating surface formed on the light incident surface or the light emitting surface is stepped.

An optical element provided with a binary blazed grating is generally made of an inorganic material such as glass, and the number of levels is 2 ^a (a) such as 2 levels, 4 levels and 8 levels.
Is usually a positive integer). Here, the x level (x is a positive integer) means a binary blazed structure having a step number (x-1), and is also used in this meaning in this specification. The number of levels is an even number,
This is because the work efficiency in manufacturing the binary blazed grating surface in the optical element is taken into consideration.

That is, the step shape of the lattice molding surface is generally formed by etching, and as shown in the table below, the number of etchings required for the number of levels is
In the cases other than the ^2a level, such as 3, 5, 6, 7, 9, 10, etc., such as 3 times for the 3rd and 4th levels, 3 times for the 5, 6, 7, 8 level, This is because the number of etchings tends to increase as compared with the ^2a level, and it is necessary to form a resist film having a complicated shape, resulting in poor work efficiency. Number of levels Number of etchings 2 1 time 3 2 times 4 2 times 5 3 times 6 3 times 7 3 times 8 3 times For example, when a 5-level binary blazed lattice plane shown in FIG. In the process, it is necessary to form the resist film so as to entirely cover the step surfaces already formed. For example, in the final etching step, as shown in FIG. 3A, the resist film 105 is formed so as to cover the already formed step surfaces 101, 102, 103 and a half of the lowest step surface 104. It is necessary to form the mask pattern 106 on which the glass is formed on the surface of the glass substrate 100, and perform dry etching such as ion milling on the mask pattern 106 to etch the exposed portion on the surface of the glass substrate to the depth shown by the dotted line.

In addition to this, when a step is formed by etching, if one step has a size of 1 μm or more, it takes a long processing time, the processing accuracy is lowered, and the stability of optical characteristics is deteriorated. For this reason, the step height of the conventional binary blazed grating is generally less than 1 μm.

Here, the wavelength of the DVD laser light source in the two-wavelength type optical pickup device is 650 nm,
Since the wavelength of the laser light source for CD is 780 nm, if one attempts to manufacture a binary blazed grating so that one of these can be transmitted without being diffracted and only the other can be diffracted, the level of the step can be changed to ^a level other than 2 ^a level. You may want to set it. Further, the step difference of the lattice is 1 μm or more.

However, as described above, when a binary blazed grating having a step height of 1 μm or more is manufactured by etching at ^a level other than the ^2a level, it takes a long processing time, resulting in high cost and high processing accuracy. And the performance stability is also reduced. For this reason, there is a problem in that an inexpensive optical element equipped with a binary blazed grating with stable optical characteristics, which is suitable for use as an optical axis adjusting element for an optical pickup device, cannot be manufactured with high accuracy, simplicity, and cost. is there.

In addition to this, 2^aFor levels other than levels
Fabricate binary blazed grating by etching the surface
In that case, the number of etchings tends to increase as described above.
Moreover, since the resist film forming process becomes complicated, the number of steps is reduced.
However, the accuracy and quality stability are reduced.
Therefore, the conventional binary blazed lattice is effectively 2 ^a
Limited to level and step height less than 1 μm
There is a constraint that^aBinary blur other than level
That it is not possible to manufacture an optical element with a laser grid at a low cost
There is a problem.

Further, such a problem also occurs when the binary blazed grating is manufactured by subjecting the surface of a molding die for molding the binary blazed grating to a process such as dry etching.

The object of the present invention is to solve the above problems.
Another object is to make it possible to manufacture an inexpensive optical element having a binary blazed grating having ^a level number other than the ^2a level accurately in a short time.

That is, an object of the present invention is to propose an inexpensive optical element in which a binary blazed grating having ^a level other than the ^2a level is formed accurately in a short time.

Another object of the present invention is to accurately form a binary blazed grating of ^a level other than the ^2a level.
It is to propose a molding die that is accurately manufactured in a short time.

Further, the object of the present invention is that the number of levels is 2 ^a.
An object of the present invention is to propose an optical pickup device using an inexpensive optical element in which a binary blazed grating of a level other than the level is accurately formed.

[0017]

In order to solve the above-mentioned problems, the present invention provides an optical element having a binary blazed grating formed on the surface thereof, wherein the binary blazed grating is formed by machining such as cutting. The number of levels is 5 or more levels other than 2 ^a , and the step height is 1 μm or more.

The optical element of the present invention is machined to 2 ^a
Binary blazed lattices with other levels have been produced. Therefore, as compared with the case of etching, the processing time is shorter, the processing accuracy is not reduced, and the repeated processing accuracy is high, so that the optical characteristics of the binary blazed grating are stable. Furthermore, in the case of machining, the machining time does not increase significantly regardless of the number of stages, and the machining accuracy is stable, so the binary blazed grating with high yield and high quality stability can be manufactured at low cost. Can be manufactured.

Here, the machining accuracy of machining is several tens nm even with the most accurate machine, and this does not depend on the height of the step. Therefore, in the case of a step height of 1 μm or less, the rate of variation due to this accuracy is large, and the lower the step height, the more advantageous etching is than machining. However, when the step height is 1 μm or more, the rate of variation due to machining becomes small, which makes machining extremely advantageous. Therefore, according to the present invention, a binary blazed grating with stable processing accuracy can be manufactured.

Further, in the present invention, since the number of levels of the binary blazed grating is 5 or more other than ^2a , compared with the conventional binary blazed grating manufactured through a large number of etching steps, it is machined. Great advantage.

Further, the step level of the binary blazed grating can be 5x level or 6x level, where x is a positive integer. For example, there can be 5 and 6 levels (x = 1) or 10 and 12 levels (x = 2). Even in the case of such a multi-stage, there is an advantage that the machining time is shorter and the machining accuracy is higher in the case of machining than in the case of etching.

Next, the optical element according to the present invention has a wavelength λ1.
Also, it can be used as a diffraction grating having a binary blazed grating used for diffracting only one of the light of wavelength λ1 and the light of wavelength λ2 of the light of wavelength λ2. This optical element has the binary blazed grating formed by machining. Further, the height of the step is 1 μm or more. Further, when diffracting light of wavelength λ1, assuming that the refractive index of the diffraction grating is n, the height of the step is λ2 / (n-1), and the number of levels is x
Is 5x, where is a positive integer. When diffracting light of wavelength λ2, the step height is λ1 / (n-1) and the number of levels is 6x.

In particular, a DVD light source that emits light of wavelength λ1, a CD light source that emits light of wavelength λ2, and a photodetector that receives return light emitted from these light sources and reflected by an optical recording medium. An optical axis adjusting element used to adjust an optical axis of one return light so that both return lights are received by a photodetector, wherein a diffraction grating having the above configuration is provided in the optical axis adjusting element. Can be used as

In this case, the wavelength λ of the DVD light source is generally used.
1 is 650 nm, and the wavelength λ2 of the light source for CD is 780
Since the wavelength is nm, the wavelength of the light for CD is 1.2 times the wavelength of the light for DVD. Therefore, the step height of the binary blazed grating corresponding to 5 wavelengths of light for CD corresponds to 6 wavelengths of light for DVD. Therefore, when the blazed height of the binary blazed grating for the light for CD is set to a dimension corresponding to 5 wavelengths or an integral multiple thereof, it is possible to form a binary blazed grating of 6 levels (the number of steps is 5 steps) or an integral multiple thereof. For example, the height dimension of one stage of the binary blazed grating corresponds to the dimension of one wavelength of DVD light.

As a result, when the DVD light is incident on the optical axis adjusting element on which the binary blazed grating is formed, the DVD light does not undergo a phase difference due to the step, so that the DVD light is not substantially diffracted. To Penetrate. In other words, the 0th order diffracted light is generated with maximum efficiency. On the other hand, when the CD light is incident, the first-order diffracted light is generated with the maximum efficiency.

650 generally used as a light source for DVD
Since the laser diode having the wavelength of nm has a lower durability than the laser diode having the wavelength of 780 nm, the driving power is suppressed to be low, and the light quantity of the output laser tends to be insufficient.

However, the optical axis of the DVD light source is made to coincide with the system optical axis of the optical pickup device, and
The DV light source by passing it through the optical axis adjustment element.
It is possible to minimize the loss of light emitted from the D light source. Further, the light for CD can also be diffracted and guided to the photodetector in a state where the light utilization efficiency is high.

When the blaze height of the binary blazed grating for DVD light is set to a size corresponding to 6 wavelengths or an integral multiple thereof, if a binary blazed grating of 5 levels or an integral multiple thereof is formed, the binary The height of one stage of the blazed grating corresponds to the size of one wavelength of the light for CD. In this case, when the CD light is incident on the optical axis adjusting element in which the binary blazed grating is formed, the CD light does not cause a phase difference due to the step, so that the CD light is substantially transmitted without being diffracted. To do. In other words, 0
Second-order diffracted light is generated with maximum efficiency. On the other hand, DV
When the D light is incident, the first-order diffracted light is generated with the maximum efficiency.

Next, the present invention relates to a molding die used for molding an optical element having a binary blazed grating on its surface, and the molding die according to the present invention comprises:
There is a grid forming surface for forming the binary blazed grid, and this grid forming surface is formed by machining, and the number of levels is 5 or more levels other than ^2a , and the step height is higher. Is 1 μm or more.

Here, the number of levels of the lattice forming surface is x
Can be 5x and 6x levels. For example, there may be 5, 6 levels or 10, 12 levels.

Further, the lattice molding surface may be formed by cutting.

On the other hand, according to the present invention, the wavelength λ1 and the wavelength λ2 are
Of the light of wavelengths λ1 and λ2 among the above lights, the binary blaze grating is molded in a molding die for molding a diffraction grating having a binary blaze grating used for diffracting the light. Has a grid forming surface for forming the grid forming surface by machining, and the height of the step is 1 μm or more.
When diffracting light of wavelength λ1, the step height is λ2 / (n−1), where n is the refractive index of the diffraction grating, and the number of levels is x is a positive integer, 5x level. When diffracting light of wavelength λ2, the step height is λ1 / (n-1), and the number of levels is 6x levels.

Here, the number of steps on the lattice molding surface is 5, 6
It can be level or 10, 12 levels. Further, the lattice molding surface may be formed by cutting.

Next, the present invention relates to an optical element that can be used as an optical axis adjusting element or the like in an optical pickup device, and the optical element is formed by using the molding die having the above construction. I am trying. The optical element as a molded product formed by using the molding die according to the present invention has the binary blazed grating with the number of levels other than the 2 ^a level with the step height of 1 μm or more being accurately formed. The performance is stable with no variation in dynamic characteristics.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION An example of a two-wavelength light source type optical pickup device including an optical element to which the present invention is applied will be described below with reference to the drawings.

(Optical System of Optical Pickup Device) FIG.
It is a schematic block diagram which shows the optical system of the optical pickup apparatus of this example. The optical system of the optical pickup device 1 of the present example is made into a parallel light through the two-wavelength light source 2, the half mirror 4 that reflects the laser light emitted from the light source 2 and guides it to the collimator lens 3, and the collimator lens 3. A laser beam is used as the optical recording medium 5
And a bifocal objective lens 6 for converging the light. Further, it has a photodetector 7 which receives the return light of the laser light reflected by the optical recording medium 5 via the objective lens 6, the collimator lens 3 and the half mirror 4. A diffraction grating 8 is arranged between the two-wavelength light source 2 and the half mirror 4, and the laser light from the two-wavelength light source 2 is diffracted into three beams toward the optical recording medium 5, and the photodetector 7 is An error signal is detected based on the amount of the returned light of each beam reflected by the recording medium 5.

The optical pickup device 1 of this embodiment is for recording and / or reproducing DVD and CD as the optical recording medium 5, and the two-wavelength light source 2 is, for example, D.
A laser diode that emits a laser beam with a wavelength of 650 nm for VD and a laser diode that emits a laser beam with a wavelength of 780 nm for CD are built on a common semiconductor substrate in the package. There is. Also,
The optical axis of the DVD laser light emitted from the DVD laser diode matches the system optical axis (objective lens optical axis), and the optical axis of the CD laser light is slightly displaced from the system optical axis. There is.

A binary blazed grating is provided between the half mirror 4 and the photodetector 7 so that the return light of each laser beam can be received by the common photodetector 7 by adjusting the deviation of the optical axis. The optical axis adjusting element 10 is arranged. The optical axis adjusting element 10 of the present example generates 0th-order diffracted light with maximum efficiency for laser light of 650 nm wavelength (that is, maximizes the light component that goes straight without diffracting) and converts it into laser light of 780 nm wavelength. On the other hand, the binary blazed grating is formed so as to generate the first-order diffracted light with maximum efficiency. By appropriately setting the diffraction direction of the first-order diffracted light, the optical axis shift of the CD laser light can be adjusted and the return light of the laser light can be guided to the light receiving surface of the photodetector 7.

(Optical Axis Adjustment Element) FIG. 2A shows a sectional shape of the optical axis adjustment element 10 of this example. Explaining with reference to this figure, a binary blazed grating 11 is formed on the light incident surface of the optical axis adjusting element 10 of this example, and the light emitting surface is a flat surface orthogonal to the optical axis. The binary blazed grating 11 has a structure in which stepwise gratings of the same number of steps inclined in the same direction are periodically arranged on the light incident surface, and in this example, 6-level (5 steps) stepwise gratings for multiple cycles. Are formed (only three cycles are shown in the figure for easy understanding). Further, the step height h is 650 / (n-1) (n when the refractive index of the element is n.
m), which is 1 μm or more.

The diffractive action of the optical axis adjusting element 10 of this example will be described. Since the wavelength λ1 of the laser light for DVD is 650 nm and the wavelength λ2 of the laser light for CD is 780 nm, the wavelength of the laser light for CD is 1.2 times the wavelength of the laser light for DVD. Therefore, as shown in FIG. 2B, the blazed height H (= 5λ2 / (n−1)) of the binary blazed grating 11 corresponding to five wavelengths of the CD laser light.
= 5 * 780 / (n-1) corresponds to 6 wavelengths of the laser light for DVD.

Therefore, when the step height (blaze height) H for one cycle of the binary blazed grating 11 with respect to the laser light for CD is set to a dimension corresponding to 5 wavelengths or an integral multiple thereof, 6 levels (the number of steps is (5 steps) or a binary blazed grating having an integral multiple thereof, the step height h of one step of the binary blazed grating 11 corresponds to the size of one wavelength of the laser light for DVD.

In this example, as described above, the step height h for one step is 650 / (n-1), and the step height H for one cycle.
Is 5 × 780 / (n−1). Therefore, FIG.
As shown in (a), when the return light of the DVD laser light L1 is incident on the optical axis adjusting element 10 in which the binary blazed grating 11 is formed, the DVD laser light L1 does not cause a phase difference due to a step, and therefore, is substantially The light directly passes through without being diffracted. In other words, the 0th-order diffracted light L1 (0) is generated with maximum efficiency. On the other hand, when the CD laser light L2 is incident, the first-order diffracted light L2 (1) is generated with maximum efficiency.

In this example, since the diffraction direction of the first-order diffracted light L2 (1) is properly set, the optical axis of the CD laser light emitted from the two-wavelength laser light source 2 should be aligned with the system optical axis. Can be adjusted. Further, in the optical axis adjusting element 10, since the 0th-order diffracted light L1 (0) and the 1st-order diffracted light L2 (1) are set to be generated with the maximum efficiency, the utilization efficiency of the laser light of each wavelength is improved. You can

Here, the optical axis adjusting element 10 of this example can be a molded product made of plastic or the like molded by using a molding die. It can also be formed by directly machining the surface of an optical material such as glass or plastic.

In the case of a molded product, machining of the lattice molding surface for binary blazed lattice molding in the molding die is performed. It is preferable to employ cutting as the machining because the surface roughness is small. The grating forming surface is the binary blazed grating 1 of the optical axis adjusting element 10 described above.
The stepped surface may have the number of levels corresponding to 1.

Similarly, when a binary blazed grating is formed by machining the surface of an optical material,
It is preferable to use cutting because the surface roughness can be reduced.

In the optical axis adjusting element 10 of this example, the step height h of one step is larger than 1 μm, but a step is formed on the lattice molding surface of the molding die by machining such as cutting. Or a step is formed on the surface of the optical material by machining such as cutting. Therefore, unlike the conventional case where a step is formed by etching, it is possible to form a grating formation surface for binary blazed grating formation or a binary blazed grating with a short processing time and with high accuracy. Therefore, the optical axis adjusting element 10 including the binary blazed grating 11 can be manufactured at low cost. Further, it is possible to obtain the optical axis adjusting element 10 having stable performance with little variation in optical characteristics.

Although the binary blazed grating of this example has 6 levels, the same effect can be obtained when a binary blazed grating having an integral multiple level is manufactured.
It is practical to make a 6-level or 12-level binary blazed grating.

(Other Embodiments) In the above example, the binary blazed grating has 6 levels, but the number of levels is 5 or 10 and the step height is 78.
It can also be 0 / (n-1). In this case, D
It is possible to manufacture an optical axis adjusting element in which the 1st-order diffraction efficiency of the VD light is the maximum and the 0th-order diffraction efficiency of the CD light is the maximum.

Further, the present invention is different from the above embodiment 2
^It can also be applied to an optical element provided with a binary blazed grating having a number of levels other than the ^a level. In particular, when the configuration of the present invention is applied to a binary blazed grating having a large number of steps (high number of levels), the effect of the present invention that the binary blazed grating can be manufactured with a short processing time and high processing accuracy is remarkable. Become.

[0051]

As described above, in the present invention, the step height is 1 μm or more and the number of levels is 5 other than 2 ^a.
The above binary blazed grating is manufactured by machining such as cutting. Therefore, unlike the case where the binary blazed grating is formed by the conventional etching, the binary blazed grating can be formed without increasing the processing time and lowering the processing accuracy. Similarly, the lattice forming surface for forming the binary blazed lattice in the forming die can be formed accurately in a short time. Furthermore, the processing time and processing accuracy can be kept the same regardless of the number of steps.
Since the repeated machining accuracy is high, it is possible to manufacture the binary blazed grating and the molding die thereof at low cost with high quality stability and high yield.

In particular, even when the number of stages is large such as 5, 6, 10, 12, etc., the binary blazed grating and its molding die can be manufactured at a low cost with a short processing time and high processing accuracy. .

Next, when the optical element according to the present invention is used as an optical axis adjusting element in a two-wavelength light source type optical pickup device, a maximum of 0 for one of the DVD light and the CD light is obtained. It is possible to obtain an element that can obtain the first-order diffraction efficiency and obtain the maximum first-order diffraction efficiency with respect to the other of the DVD light and the CD light with high accuracy and at low cost.

Further, in the optical pickup device using such an optical axis adjusting element, the utilization efficiency of the light of each wavelength is high and the performance of the optical axis adjusting element is stable, so that the optical axis adjustment can be performed accurately and easily. This is advantageous for stabilizing the performance of the optical pickup device and reducing its cost.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an optical system of a dual wavelength light source type optical pickup device to which the present invention is applied.

2A is a sectional view showing the optical axis adjusting element of FIG. 1, and FIG. 2B is an explanatory view showing a step height and a blaze height of the binary blazed grating.

FIG. 3 is an explanatory diagram showing a masking pattern when a 5-level binary blazed grating is manufactured by etching.

[Explanation of symbols]

1 Optical pickup device 2 2 wavelength light source 3 Collimating lens 4 half mirror 5 Optical recording media 6 Objective lens 7 Photodetector 8 diffraction grating 10 Optical axis adjustment element 11 Binary Blazed Lattice

Continued front page    F term (reference) 2H049 AA03 AA32 AA57 AA63 AA64                 5D119 AA05 AA38 AA41 BA01 BB01                       BB02 BB03 DA01 DA05 EC45                       EC47 FA05 FA08 FA28 JA27                       NA05                 5D789 AA05 AA38 AA41 BA01 BB01                       BB02 BB03 DA01 DA05 EC45                       EC47 FA05 FA08 FA28 JA27                       NA05

Claims (25)

[Claims] 1. An optical element having a binary blazed grating formed on a surface thereof, wherein the binary blazed grating is formed by machining, the number of levels is 5 levels or more, and the step height is 1 μm or more. Is an optical element. 2. The optical element according to claim 1, wherein the number of levels of the binary blazed grating is 5x or more, where x is a positive integer. 3. The number of levels of the binary blazed grating according to claim 2,
Is an optical element. 4. The optical element according to claim 1, wherein the number of levels of the binary blazed grating is 6x or more, where x is a positive integer. 5. The number of levels of the binary blazed grating according to claim 4,
Is an optical element. 6. The optical element according to any one of claims 1 to 5, wherein the binary blazed element is formed by cutting. 7. A diffraction grating having a binary blazed grating used for diffracting only the light of the wavelength λ1 among the lights of the wavelength λ1 and the wavelength λ2, wherein the binary blazed grating is formed by machining. , The step height of the binary blazed grating is 1 μm or more, and when the refractive index of the diffraction grating is n, then λ2 /
(N-1), and the number of levels of the binary blazed grating is 5x, where x is a positive integer. 8. The number of levels of the binary blazed lattice according to claim 7,
A diffraction grating characterized in that. 9. A diffraction grating having a binary blazed grating used for diffracting only the light of wavelength λ2 among the lights of wavelength λ1 and wavelength λ2, wherein the binary blazed grating is formed by machining. , The height of the step of the binary blazed grating is 1 μm or more, and when the refractive index of the diffraction grating is n, λ1 /
(N-1), and the number of levels of the binary blazed grating is 6x, where x is a positive integer. 10. The number of levels of the binary blazed grating according to claim 9,
A diffraction grating characterized in that. 11. The diffraction grating according to claim 7, 8, 9 or 10, wherein the binary blazed grating is formed by cutting. 12. A light source for DVD which emits light of wavelength λ1, a light source for CD which emits light of wavelength λ2, and light for receiving each return light emitted from these light sources and reflected by an optical recording medium. An optical pickup device comprising a detector and an optical axis adjusting element for adjusting an optical axis of one returning light so that each returning light is received by the photodetector, wherein the optical axis adjusting element is: An optical pickup device, which is the diffraction grating according to any one of items 7 to 11. 13. A molding die used for molding an optical element having a binary blazed grating on a surface thereof, which has a grating molding surface for molding the binary blazed grating, the grating molding surface being machined. The molding die is characterized in that the number of steps is a number corresponding to a binary blazed grating of 5 levels or more, and the step height is 1 μm or more. 14. The number of steps of the lattice molding surface according to claim 13, wherein x is a positive integer.
A molding die having a number corresponding to an x-level binary blaze lattice. 15. The molding die according to claim 14, wherein the number of steps on the lattice molding surface corresponds to a 5-level or 10-level binary blazed lattice. 16. The number of steps of the lattice molding surface according to claim 13, wherein x is a positive integer.
A molding die having a number corresponding to an x-level binary blaze lattice. 17. The molding die according to claim 16, wherein the number of steps on the lattice molding surface corresponds to a 6-level or 12-level binary blazed lattice. 18. The molding die according to any one of claims 13 to 17, wherein the lattice molding surface is formed by cutting. 19. Of the lights of wavelength λ1 and wavelength λ2,
A molding die for molding a diffraction grating having a binary blazed grating used to diffract only light of wavelength λ1, having a grating molding surface for molding the binary blazed grating, Is formed by machining, the step height of the grating molding surface is 1 μm or more, and when the refractive index of the diffraction grating is n, λ2 / (n−
1), and the number of steps on the lattice molding surface is 5 when x is a positive integer.
A molding die having a number corresponding to an x-level binary blaze lattice. 20. The molding die according to claim 19, wherein the number of steps on the lattice molding surface corresponds to a 5-level or 10-level binary blazed lattice. 21. Among the lights of wavelength λ1 and wavelength λ2,
A molding die for molding a diffraction grating having a binary blazed grating used to diffract only light of wavelength λ2, having a grating molding surface for molding the binary blazed grating. Is formed by machining, and the step height of the grating molding surface is 1 μm or more, and when the refractive index of the diffraction grating is n, λ1 / (n−
1), and the number of steps on the lattice molding surface is 6 when x is a positive integer.
A molding die having a number corresponding to an x-level binary blaze lattice. 22. The molding die according to claim 21, wherein the number of steps on the lattice molding surface corresponds to a 6-level or 12-level binary blazed lattice. 23. The molding die according to any one of claims 19 to 22, wherein the lattice molding surface is formed by cutting. 24. An optical element formed using the molding die according to any one of claims 13 to 23. 25. A light source for DVD which emits light of wavelength λ1, a light source for CD which emits light of wavelength λ2, and light for receiving each return light emitted from these light sources and reflected by an optical recording medium. An optical pickup device comprising a detector and an optical axis adjusting element for adjusting an optical axis of one returning light so that each returning light is received by the photodetector, wherein the optical axis adjusting element is: An optical pickup device, which is a molded product formed by using the molding die according to any one of items 19 to 23.