JPH09106555A - Optical information recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the deviation in the optical axis of luminous flux made incident on a diffraction grating by adjusting diffracted light spots at respective positions, obtained from a DV (direct verify) diffraction part and an RF (reproductory) diffraction part, so that the sectional intensity distribution curve peaks of the diffracted light spots meet each other by using a luminous flux axis adjusting mechanism. SOLUTION: A diffraction grating 50 is provided and a luminous flux axis adjusting mechanism 60 for adjusting the luminous flux emitted by a semiconductor laser 2 so that it is made incident on a proper position on the diffraction grating 50 is provided in the form of a parallel flat plate so as to correct an X-directional parallel shift. The luminous flux emitted by the semiconductor laser 22 is made into parallel luminous flux by a collimator lens 23 and the luminous flux is made incident on a shaping prism 24. The light reflected by the surface of this prism 24 is projected on a photodetector 33 and its transmitted light is passed through the luminous flux axis adjusting mechanism 60 and made incident on the diffraction grating 50, which splits it into luminous flux of 0th order and diffracted luminous flux; and the luminous flux of 0th order and the diffracted luminous flux are further passed through a polarization beam splitter 26, a bending prism 27, a 1/4-wavelength plate 28, and an objective 29 to form a light spot.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus provided with a diffraction grating element having a plurality of diffraction grating forming portions in an optical path from a light source. The present invention is particularly effective when applied to an optical information recording / reproducing apparatus having a separation optical system in which a constituent element of an optical head is divided into a fixed portion and a movable portion.

[0002]

2. Description of the Related Art Conventionally, various types of information recording media such as discs, cards and tapes have been known as information recording media for recording and reproducing information using light. Among these, for example, a card-shaped optical information recording medium (hereinafter referred to as an optical card) is convenient for carrying, has a relatively large capacity, and is an information recording that cannot be erased or rewritten at present. As a medium, it is expected to be applied in a field where this characteristic is an advantage.

FIG. 3 is a schematic plan view of a general optical card. Here, in the optical recording area C1, as shown in a partially enlarged view, an information track T for recording information is formed.
a and a large number of tracking tracks Tb which are guides for automatic tracking (AT) for controlling the light spot so as not to deviate from a predetermined information track when recording / reproducing information are arranged in parallel.

Further, there is provided a home position HP which serves as a reference position for access to the information track, and the information track Ta is assigned track numbers in order from the one closer to the home position. Then, the target information track is accessed by a seek operation of moving the light spot in a direction perpendicular to the information tracks arranged in parallel and an operation of following and scanning the light spot on the information track. .

Further, when actually recording / reproducing information, the light spot is focused on the surface of the recording medium.
Autofocusing (AF) control is being performed. These AT and AF controls are general techniques that have been often used in the optical information recording / reproducing apparatus.

FIG. 7 is a block diagram showing a conventional optical card information recording / reproducing apparatus. In the figure, reference numeral 1 is an optical card information recording / reproducing apparatus (hereinafter referred to as a drive), and 2 is a host controller. However, it is a CPU. Drive 1 is CP
Recording and reproduction for the optical card are executed based on the command issued from U2.

In the structure of this drive 1, the optical card C is introduced into the drive 1 by the motor 8 through an appropriate transport mechanism, and the optical card C is reciprocated in the X direction at a predetermined position. , The optical card C can be ejected to the outside of the drive 1. A sensor 7 is provided near the card insertion slot 6.
Is provided, and when the sensor 7 detects that the optical card C is inserted into the drive 1, the optical card C is transported to a predetermined position as described above.

Further, reference numeral 21 is an irradiation optical system including a light source, and at the time of recording / reproducing, the light flux from the irradiation optical system is focused and irradiated on the optical card C as a light spot. Then, the light spot and the optical card C relatively move back and forth to scan the information track with the light spot. Also,
Reference numeral 34 is a photodetector for receiving the reflected light of the light spot on the optical card C, and the recorded information is reproduced based on this detection signal.

Reference numeral 13 denotes an AF actuator for driving a part of the irradiation optical system 21 to move the light spot in the Z direction, that is, in a direction perpendicular to the card surface, to perform AF control. , By driving a part of the irradiation optical system 21,
AT for performing AT control by moving the light spot in the Y direction, that is, in the direction orthogonal to both the R direction and the Z direction.
Actuator.

The optical head 20 includes the irradiation optical system 21,
The photodetector 34, the AF actuator 13, and the AT actuator 14 are incorporated as its constituent elements.
Reference numeral 3 is an MPU having a built-in ROM and RAM, which controls each unit such as the card feed motor 8 and C
By controlling the PU2, data communication with the CPU2 and control are performed. Further, reference numeral 10 is an A for driving the above-mentioned AF actuator 13 and AT actuator 14 based on the detection signal of the photodetector to perform AF control and AT control.
It is a T / AF control circuit.

Further, reference numeral 4 is a modulation / demodulation circuit for reproducing the detection signal of the photodetector, demodulating the reproduction signal to reproduce the original recorded data, and 5 is an output of the modulation / demodulation circuit 4. This is a light source drive circuit that modulates and controls the intensity of the light source, and by this, information by optical modulation is recorded on the information track.

FIG. 8 is a perspective view showing the internal structure of the optical head in detail. In the figure, 22 is a semiconductor laser, and the light flux emitted from this is a collimator lens 23.
Then, it becomes a parallel light flux and enters the shaping prism 24. The light reflected by the surface of the shaping prism 24 is projected on the photodetector 33, and the transmitted light is the diffraction grating 25.
And is split into a 0th-order light beam and a diffracted light beam.

The 0th-order light beam and the diffracted light beam generated by the diffraction grating 25 are further polarized by a polarization beam splitter 26, a bending prism 27, a quarter-wave plate 28, and an objective lens 2.
Via the tracking track Ta on the optical card C.
Also, an image is formed as a light spot on the information track Tb.

The light irradiated on the optical card C is reflected here, and again passes through the objective lens 29, the quarter-wave plate 28, and the bending prism 27, and the polarization beam splitter 2
Reach 6. The light beam reflected by the card surface is reflected by the polarization beam splitter 26 and projected onto the photodetector 34 via the detection optical system 30. The detection optical system 30 is an astigmatism system composed of a spherical lens 31 and a cylindrical lens 32 which is arranged at an angle of 45 ° with respect to the track. Therefore, based on the output of the photodetector, The apparatus performs AF control by the astigmatism method and AT control by the three-beam method. Information is recorded / reproduced by scanning the light spot in the X and Y directions of the arrow.

FIG. 9 is a schematic view of a diffraction grating in a conventional example, in which reference numeral 25a is an AT diffraction grating forming portion (AT diffraction portion) for generating an AT control light beam, and 25b.
Is a DV diffraction grating forming unit (DV) that generates a direct verification (DV) light flux that can reproduce information immediately after recording.
Information reproducing (R) for reproducing information of an information track adjacent to the information track irradiated with the recording light
Reference numeral 45 denotes an RF diffraction grating forming portion (RF diffracting portion) for generating a light flux for F), and 45 is an incident light flux.

In the figure, the X'axis and the Y'axis are orthogonal to each other, and the intersection point is the center of the light beam considered in design, that is, the ideal optical axis point. The X'axis and the Y'axis correspond to the X axis and the Y axis in FIG.

The diffracted light beam and the 0th-order light beam diffracted by the diffraction grating 25 are, as shown in FIG. 10, passed through an objective lens to appropriate spots on the optical card, such as optical spots SO, SAT, SDV,
Irradiated as SRF, reciprocal recording and simultaneous reproduction of 3Tr are performed.

[0018]

However, if there is a deviation of the optical axis due to factors such as mechanical tolerances and assembly errors, for example, a parallel shift of the optical axis occurs in the X'axis direction in FIG. , DV or RF decreases its light amount, and the other increases, resulting in an incorrect light amount. Further, since the shape of the light beam irradiated on each diffraction grating forming portion changes, the spot shape of the diffracted light on the medium surface also changes.

When these things occur, it becomes impossible to carry out stable recording and reproduction due to a decrease in contrast and the like. Further, in the separation type optical head in which the optical head is divided into a movable part including a diffraction grating and a fixed part, when the light flux emitted from the fixed part is tilted with respect to the ideal optical axis, the position of the movable part is changed. Due to this, the position of the light beam incident on the diffraction grating changes, and the same problem occurs as when parallel shift occurs.

Further, when the center of the incident light beam passes through the ideal optical axis point of the diffraction grating, the sectional intensity distribution curve of the AT light spot diffracted by the AT diffraction grating forming portion is as shown in FIG. , But it becomes symmetrical about the intensity peak, but if there is an optical axis shift caused by factors such as mechanical tolerances and assembly errors, the cross-sectional intensity distribution curve becomes asymmetrical, as shown in FIG. 11 (b). The AT control such as the one-beam push-pull method and the three-beam method cannot be normally performed.

In order to eliminate such an optical axis shift, it is sufficient to make the processing accuracy and the assembly accuracy of each component strict, but the manufacturing cost increases. In particular, in the case of the separate type optical head as described above, the movable part becomes large in order to obtain accuracy, and the drive system for driving this also becomes large, which is a significant disadvantage in reducing the size and weight.

An object of the present invention is to provide an optical information recording / reproducing apparatus equipped with a diffraction grating element having a plurality of diffraction grating forming portions having different diffraction angles, at a relatively low cost, while avoiding an increase in the size of an optical head. An object of the present invention is to provide an optical information recording / reproducing device with little optical axis deviation.

[0023]

In order to achieve the above object, according to the present invention, a diffraction grating element having a plurality of diffraction grating forming portions is arranged so as to be positioned in an optical path from a light source and separated. An optical information recording / reproducing apparatus for recording and / or reproducing information by converging a plurality of light fluxes by an objective lens and irradiating the information tracks and tracking tracks on a surface of an optical information recording medium as a plurality of light spots. Wherein a light beam axis adjusting mechanism is provided in the optical path from the light source to the diffraction grating element, and each diffraction grating forming portion of the diffraction grating optical element is irradiated with a part of the incident light beam, Among the diffraction grating forming portions, at least two diffracted light spots obtained from the diffraction grating forming portions are adjusted by using the luminous flux axis adjusting mechanism so as to have a fixed relationship.

In the present invention, the above-mentioned fixed relationship means that at least the ratio of the peaks of the cross-sectional intensity distribution curve of the diffracted light spots obtained from two or more diffraction grating forming portions is equal to a predetermined peak ratio. Relationship. In addition, this relationship may be that at least the peaks of the sectional intensity distribution curve of the diffracted light spots obtained from two or more diffraction grating formation portions match. Furthermore, this relationship is
It may be that the light quantity ratio of the diffracted light spots obtained from at least two or more diffraction grating formation portions matches a predetermined light quantity ratio, and the diffraction obtained from at least two or more diffraction grating formation portions The light amounts of the light spots may be the same. Further, if necessary, this relationship may be that at least the shapes of the diffracted light spots obtained from the two or more diffraction grating formation portions match.

Further, in order to achieve the above-mentioned object,
In the present invention, a diffraction grating element having a plurality of diffraction grating forming portions is arranged so as to be positioned in an optical path from a light source, and a plurality of separated light beams are focused by an objective lens to form a plurality of light spots. An optical information recording / reproducing apparatus for irradiating an information track and a tracking track on a surface of an optical information recording medium to record or / and reproduce information, in an optical path from the light source to the diffraction grating element. A light beam axis adjusting mechanism is provided, and each diffraction grating forming portion of the diffraction grating element is irradiated with a part of the incident light beam, and an X axis or ( And) a cross-sectional intensity distribution curve of the diffracted light spot obtained from the diffraction grating forming portion having an axially symmetric shape with respect to the Y-axis, the cross-sectional intensity distribution curve of the Y-axis or (and) the X-axis,
Using the luminous flux axis adjustment mechanism so as to be symmetrical,
It is configured to adjust.

In this case, the diffracted light beam diffracted by the axially symmetric diffraction grating forming portion is preferably an auto-tracking light beam.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) Hereinafter, one of the embodiments of the present invention will be described in detail with reference to the drawings. FIG.
FIG. 3 is a perspective view showing an internal configuration of an optical head in the optical information recording / reproducing apparatus according to the present invention. The same parts as those in FIG. 8 are designated by the same reference numerals, and the description thereof will be omitted. Here, in particular, reference numeral 50 is a diffraction grating, and 60 is a light beam axis adjusting mechanism for adjusting the light beam emitted from the semiconductor laser 22 so as to enter an appropriate position of the diffraction grating 50. It is a parallel plate that corrects the parallel shift.

FIG. 2 shows the positional relationship between the incident light beam and the diffraction grating 50, and the diffracted light spot (hereinafter referred to as "SDV") obtained by the DV diffracting portion and the diffracted light spot (hereinafter referred to as "SRF" by the RF diffracting portion). It is a figure which shows the X-axis cross-section intensity distribution curve. The X ′ and Y ′ directions in the figure correspond to the X and Y directions shown in FIG. 1, respectively, and will be simply referred to as “X” and “Y” in the following description.

Further, in FIG. 2, reference numeral 50a is an AT diffracting portion, 50b is a DV diffracting portion, 50c is an RF diffracting portion, and 45.
Is an incident light beam, the diffraction efficiencies of the DV diffracting portion 50b and the RF diffracting portion 50c are equal, and when the incident light optical axis passes through the ideal optical axis point on the diffraction grating surface, that is, in FIG. 2B,
The light beams incident on the respective portions of the DV and RF diffractive portions have the same shape and the same light amount. Therefore, at this time, the peak of the sectional intensity distribution curve, the light amount, and the light spot shape are equal.

The operation will be described below with reference to FIGS. 1 and 2. The light flux emitted from the semiconductor laser 22 is made into a parallel light flux by the collimator lens 23 and is incident on the shaping prism 24. The light reflected by the surface of the shaping prism 24 is projected on the photodetector 33, and the transmitted light is incident on the diffraction grating 50 via the light flux axis adjusting mechanism 60 and is split into a 0th-order light flux and a diffracted light flux. Diffraction grating 50
The 0th-order light flux and the diffracted light flux generated by are further polarized beam splitter 26, bending prism 27, 1 /
It becomes a light spot via the four-wave plate 28 and the objective lens 29.

Here, when the optical axis of the light beam incident on the diffraction grating 50 is parallel-shifted from the ideal optical axis point in the (+) direction of the X axis, that is, the positional relationship between the incident light beam and the diffraction grating is. In the case of FIG. 2A, the amount of light incident on the RF diffractive part 50c is larger than the amount of light incident on the DV diffractive part 50b, so that the sectional intensity distribution curve peak PRF of the SRF is as shown in the figure.
It becomes larger than PDV of SDV (PRF> PDV). Therefore, the parallel plate 60 that corrects the parallel shift in the X direction, which is the light beam axis adjusting mechanism, is tilted by an appropriate amount in the direction in which it is corrected, and as shown in FIG. 2B, the cross-sectional intensity distribution of SRF and SDV. Adjust so that the peaks of the curves are equal (PRF = PDV).

As a result, the incident light optical axis passes through the ideal optical axis point on the diffraction grating surface. In this embodiment,
When the peaks of the cross-sectional strength distribution curves are the same, the cross-sectional strength distribution curves of SDV and SRF have the same relationship when one of the cross-sectional strength distribution curves is flipped to the left and right. can do.

On the other hand, when the light beam is parallel-shifted in the (-) direction, the positional relationship between the incident light beam and the diffraction grating is as shown in FIG. 2C, and the peak PRF of the cross-sectional intensity distribution curve of SRF is
It becomes smaller than PDV of SDV (PRF <PDV). Therefore, adjustment is performed by inclining the parallel flat plate 60 by an appropriate amount in the opposite direction to the parallel shift in the (+) direction described above.

In this embodiment, DV and RF are used.
The diffraction efficiency of the diffractive portion is equal, and the light beams incident on the respective portions of the DV and RF diffractive portions have the same shape and the same light amount. Therefore, the peak ratio and light amount ratio of the cross-sectional intensity distribution curve are 1:
Since it is 1, it is possible to adjust with such a ratio, but by adjusting by matching the peaks of the cross-sectional strength distribution curve, which is an absolute amount, it is possible to determine whether the peak of the proper cross-sectional strength distribution curve is correct or not. You can know at the same time.

Although the adjustment is made at the peak of the cross-sectional intensity distribution curve here, the adjustment may be made by the spot shape such as the light amount and the spot diameter. Considering this, an appropriate selection can be made if necessary. (Embodiment 2) Hereinafter, another embodiment of the present invention will be described in detail with reference to the drawings. FIG. 4 is a perspective view showing the internal structure of the separation type optical head in the optical information recording / reproducing apparatus according to the present invention. Here, FIG.
The same parts as those in FIG. Reference numeral 40 is a diffraction grating 25 and a polarization beam splitter 2
6, a bending prism 27, a quarter-wave plate 28, and an objective lens 29, which is an optical head movable part, and 60 is
Reference numeral 61 is a light beam axis adjusting mechanism for adjusting the light beam emitted from the semiconductor laser 22 so as to be incident on an appropriate position of the diffraction grating 50. Reference numeral 61 is a parallel plate for correcting a parallel shift in the X direction in the figure, and 62. Is a parallel plate that corrects the parallel shift in the Y direction in the figure, 63 is a wedge prism that corrects the tilt in the X direction in the figure, and 64 is a wedge prism that corrects the tilt in the Y direction in the figure. is there.

FIG. 5 shows the positional relationship between the incident light beam and the diffraction grating,
And, the AT diffraction grating forming portion having an axially symmetric shape with respect to the X ′ axis and the Y ′ axis orthogonal to the ideal optical axis point on the diffraction grating element surface at that time diffracts, and through the objective lens. FIG. 10 is a diagram showing an X′-axis cross-sectional intensity distribution curve of the obtained diffracted light spot SAT, the same parts as those in FIG. 9 are denoted by the same reference numerals, and description thereof is omitted here. The X'and Y'directions in the figure correspond to the X and Y directions shown in FIG. 4, respectively, as in the above-described embodiment, and will be simply referred to as "X" and "Y" hereinafter.

The operation will be described below with reference to FIGS. 4 and 5. The light flux emitted from the semiconductor laser 22 is made into a parallel light flux by the collimator lens 23 and is incident on the shaping prism 24. The light reflected by the surface of the shaping prism 24 is projected on the photodetector 33, and the transmitted light is incident on the diffraction grating 50 via the light flux axis adjusting mechanism 60 and is split into a 0th-order light flux and a diffracted light flux. Diffraction grating 5
The 0th-order light flux and the diffracted light flux generated by 0 are further reflected by the polarization beam splitter 26, the bending prism 27, 1 /
It becomes a light spot via the four-wave plate 28 and the objective lens 29.

Here, when the optical axis of the light beam incident on the diffraction grating 50 is parallel-shifted from the ideal optical axis point in the (+) direction of the X axis, that is, the positional relationship between the incident light beam and the diffraction grating is illustrated. 5
In the case of (a), the X-axis cross-sectional intensity distribution curve of the AT light spot SAT is gentler on the left side curve than on the right side of the peak position and is asymmetrical about the peak position, as shown in the figure. . Therefore, the parallel plate 61 that corrects the parallel shift in the X direction is tilted with respect to the X axis by an appropriate amount, and the SAT X
As shown in FIG. 5B, adjustment is performed so that the axial cross-section strength distribution curve is symmetrical about the peak position. As a result, the incident light optical axis passes through the ideal optical axis point on the diffraction grating surface.

When the SAT is parallel-shifted, the SAT cross-sectional intensity distribution curve on the right side becomes gentler than that on the left side of the peak position as shown in FIG. 5 (c). Therefore, the adjustment is performed in the same operation as the parallel shift in the (+) direction so that the peak position is bilaterally symmetric. Further, when the parallel shift is made in the (±) direction of the Y-axis, the SAT Y-axis cross-sectional strength distribution curve is shown in FIG.
And (c), the parallel plate 62 for correcting the parallel shift in the Y direction is tilted by an appropriate amount with respect to the Y axis for adjustment.

Further, when the optical axis is inclined, when the movable part 40 is moved in the direction of the arrow Z in the figure, the peak position of the cross-sectional intensity distribution curve of the SAT is caused by the optical axis shift or the light beam vignetting. Since the left-right symmetry with respect to the center is broken, the wedge prisms 63 and 64 are tilted with respect to the X-axis and the Y-axis, respectively, to correct this. Note that the wedge-shaped prisms 63 and 64 are similar to those shown in FIG.
It can be placed in the opposite direction.

[0041]

As described above, in the present invention, the luminous flux axis adjusting mechanism is used so that the peaks of the sectional intensity distribution curves of the diffracted light spots of the respective portions obtained from the DV diffracting section and the RF diffracting section coincide with each other. Since the adjustment is performed, the optical axis shift of the light beam incident on the diffraction grating is eliminated. As a result, there is an effect that the optical axis shift is eliminated and stable recording / reproducing can be performed while avoiding an increase in the size of the movable portion of the optical head at a relatively low cost.

Further, in the present invention, by using the luminous flux axis adjusting mechanism, X which is orthogonal to the ideal optical axis point on the surface of the diffraction grating element as a center.
Of the diffracted light spot diffracted by the AT diffraction grating forming portion having an axially symmetric shape with respect to the axis and / or the Y axis,
Since the axial or (and) X-axis cross-sectional intensity distribution curve is adjusted so as to be bilaterally symmetric with respect to the peak position, the optical axis deviation of the light beam incident on the diffraction grating is eliminated. As a result, there is an effect that the optical axis shift is eliminated and stable recording / reproducing can be performed while avoiding an increase in the size of the movable portion of the optical head at a relatively low cost.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an internal configuration of an optical head in an optical information recording / reproducing apparatus according to the present invention.

FIG. 2 is a diagram showing a positional relationship between an incident light beam and a diffraction grating, and an X-axis cross-sectional intensity distribution curve of a diffracted light spot diffracted by a DV and RF diffraction grating forming portion at that time.

FIG. 3 is a schematic plan view of an optical card.

FIG. 4 is a schematic diagram showing an internal configuration of a separation type optical head in an optical information recording / reproducing apparatus according to the present invention.

FIG. 5 is a positional relationship between an incident light beam and a diffraction grating, and an AT.
It is a figure which shows the X-axis cross-section intensity distribution curve of the diffracted light spot diffracted in the diffraction grating formation part.

FIG. 6 is a layout view of a wedge prism.

FIG. 7 is a block diagram showing a conventional optical card recording / reproducing apparatus.

FIG. 8 is a perspective view of a conventional optical head.

FIG. 9 is a schematic view of a diffraction grating used in a conventional optical information recording / reproducing apparatus.

FIG. 10 is a diagram showing a light spot arrangement on the medium surface.

FIG. 11: X of a diffracted light spot obtained from the AT diffraction section
It is a figure which shows an axial cross-section strength distribution curve.

[Explanation of symbols]

 C Optical card 22 Semiconductor laser 25,50 Diffraction grating 25a, 50a AT diffraction grating forming part 25b, 50b DV diffraction grating forming part 25c, 50c RF diffraction grating forming part 40 Optical head movable part 45 Incident light beam 60 Light beam axis adjustment mechanism

Claims (8)

[Claims] 1. A diffraction grating element having a plurality of diffraction grating forming portions is arranged so as to be positioned in an optical path from a light source, and a plurality of separated light beams are focused by an objective lens to form a plurality of light spots. An optical information recording / reproducing apparatus for irradiating an information track and a tracking track on an optical information recording medium surface to record and / or reproduce information, wherein an optical path from the light source to the diffraction grating element is provided. A light beam axis adjusting mechanism is provided, and each diffraction grating forming portion of the diffraction grating optical element is irradiated with a part of the incident light beam, and at least two or more diffraction gratings among the plurality of diffraction grating forming portions are provided. An optical information recording / reproducing apparatus, characterized in that the light beam axis adjusting mechanism is used to adjust so that the diffracted light spots obtained from the forming section have a fixed relationship. 2. The constant relationship is at least a relationship in which a ratio of peaks of a cross-sectional intensity distribution curve of the diffracted light spots obtained from two or more diffraction grating forming portions matches a predetermined peak ratio. The optical information recording / reproducing apparatus according to claim 1, wherein: 3. The constant relationship is a relationship in which at least peaks of a cross-sectional intensity distribution curve of the diffracted light spots obtained from two or more diffraction grating formation portions match each other. Item 2. The optical information recording / reproducing apparatus according to item 2. 4. The fixed relationship is a relationship in which a light quantity ratio of the diffracted light spots obtained from at least two or more diffraction grating formation portions matches a predetermined light quantity ratio. The optical information recording / reproducing apparatus according to claim 1. 5. The fixed relationship is a relationship in which at least light amounts of the diffracted light spots obtained from two or more diffraction grating formation portions are in agreement with each other. Optical information recording / reproducing device. 6. The optical system according to claim 1, wherein the fixed relationship is a relationship in which the shapes of the diffracted light spots obtained from at least two or more diffraction grating formation portions match each other. Information recording / reproducing apparatus. 7. A diffraction grating element having a plurality of diffraction grating forming portions is arranged so as to be positioned in an optical path from a light source, and a plurality of separated light beams are focused by an objective lens to obtain a plurality of light spots. Is an optical information recording / reproducing apparatus for irradiating an information track and a tracking track on the surface of an optical information recording medium to record and / or reproduce information in the optical path from the light source to the diffraction grating element. Is provided with a luminous flux axis adjusting mechanism, each diffraction grating forming portion of the diffraction grating element is irradiated with a part of the incident luminous flux, and an X axis orthogonal to an ideal optical axis point on the diffraction grating element surface or (as well as)
The cross-sectional intensity distribution curve of the Y-axis or (and) X-axis of the diffracted light spot obtained from the diffraction grating forming portion having an axially symmetric shape with respect to the Y-axis should be symmetrical about the peak position. An optical information recording / reproducing apparatus, characterized in that the light beam axis adjusting mechanism is used for adjustment. 8. The optical information recording / reproducing apparatus according to claim 7, wherein the diffracted light flux diffracted by the diffraction grating formation portion having an axially symmetrical shape is a light flux for auto-tracking.