JP2997277B2 - Measuring device for optical system for optical information recording / reproducing device and light beam measuring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to optical information for recording and reproducing information on and from a storage medium such as a magneto-optical disk using a laser beam emitted from a laser diode or the like. The present invention relates to a measuring device for an optical system for a recording / reproducing device.

2. Description of the Related Art In an optical system for an optical information recording / reproducing apparatus, writing and reading of information to and from a storage medium are performed by focusing a laser beam on a storage medium through an objective optical system. In order to write or read the information accurately, the laser beam must be focused on the storage medium to a minimum diameter.

However, if the laser beam incident on the objective optical system has astigmatism, the laser beam will not be focused at one point on the storage medium. Also, if the angle of incidence of the laser beam on the objective optical system is increased, coma aberration occurs, and the focal point of the laser beam greatly expands.

Further, if the intensity distribution of the laser beam at the entrance pupil of the objective optical system is abnormal, it adversely affects the servo signal detection system for detecting the signals of the focus servo and the tracking servo.

Therefore, in order to focus the laser beam on the storage medium to a minimum diameter, the astigmatism and incident angle of the laser beam must not be out of order, and the servo signal detection system will not be adversely affected. The intensity distribution in the entrance pupil of the objective optical system must not be out of order and must be measured to confirm it.

Therefore, in order to measure the astigmatism, incident angle, and intensity distribution of the laser beam, conventionally, dedicated devices have been used.

[Problems to be Solved by the Invention] Conventionally, dedicated devices have been used to measure astigmatism, incident angle and intensity distribution of a laser beam, respectively. Therefore, all measuring devices must be prepared. I had to. As a result, there is a drawback that the cost of the measuring equipment becomes very high.

SUMMARY OF THE INVENTION An object of the present invention is to provide a measuring apparatus for an optical system for an optical information recording / reproducing apparatus which can solve such a conventional drawback and can reduce the cost of a measuring apparatus.

[Means for Solving the Problems] In order to achieve the above object, a measuring device for an optical system for an optical information recording / reproducing apparatus of the present invention converts a light beam emitted from a laser diode into a parallel light beam by a collimator optical system. , Then after shaping with anamorphic optics,
A beam splitter for splitting the light beam into a plurality, at a position immediately before the objective optical system, of an optical information recording / reproducing device optical system for causing the light beam to enter an objective optical system for converging the light beam on a storage medium, In the measuring device of the optical system for an optical information recording / reproducing device, which has an interference unit that causes the light beams split by the beam splitter to interfere with each other to generate interference fringes, and an observation unit for observing the interference fringes, A shutter that can shield one of the plurality of divided light beams while leaving the other light beam provided so that the intensity distribution of the light beam not shielded by the shutter can be measured by the observation means; At least one polarizing filter rotatable about an axis may be disposed on an optical path between the interference unit and the observation unit.

Further, the measuring device of the optical system for an optical information recording / reproducing apparatus of the present invention converts a light beam emitted from a laser diode into a parallel light beam by a collimator optical system, then shapes the light beam by an anamorphic optical system, and then converts the light beam into a storage medium. In the optical information recording / reproducing apparatus optical system to be incident on the objective optical system for focusing on the beam splitter for splitting the light beam into a plurality of beams at the position immediately before the objective optical system, the beam splitter In the measuring device of the optical system for an optical information recording / reproducing device having interference means for causing interference of the light beams with each other to generate interference fringes,
A shutter capable of blocking one of the plurality of divided light beams while leaving the other light beam, and an incident angle of a light beam incident on the objective optical system from the focused position by converging a light beam not blocked by the shutter. And an at least one polarizing filter rotatable about an axis may be provided on the optical path of the light beam incident on the incident angle measuring means.

[Operation] The light beam immediately before entering the objective optical system is split into two by a beam splitter, and the split light beam is caused to interfere by interference means to generate an interference fringe. By observing the interference fringes by the observation means, the astigmatism of the light beam incident on the objective optical system can be measured.

Then, by leaving one of the light beams split by the beam splitter and blocking the other light with the shutter, the intensity distribution of the light beam not blocked by the shutter can be observed by the observation means.

Also, the incident angle of the light beam incident on the objective optical system can be measured by converging the light beam not blocked by the shutter by the incident angle measuring means and measuring the light condensing position.

The intensity of the laser beam incident on the observation unit can be adjusted by rotating the polarizing filter disposed on the optical path between the interference unit and the observation unit around the axis, and the incident light can be incident on the incident angle measurement unit. By rotating a polarizing filter provided on the optical path of the light beam to be rotated about the axis, the intensity of the laser light beam incident on the incident angle measuring means can also be adjusted.

Example An example will be described with reference to the drawings.

FIG. 1 shows an optical system for an optical information recording / reproducing apparatus. In the figure, reference numeral 1 denotes a magneto-optical disk serving as an information storage medium, which is provided so as to rotate about an axis 2. In FIG. 1, the magnetic thin film 1a formed on the upper surface of the magneto-optical disk 1 is irradiated with a laser beam, and the magnetic direction of the magnetic thin film 1a is changed only at the irradiated spot (pit), thereby obtaining digital information. Is stored.

This information can be easily written and read, but in order to perform it accurately, it is necessary to precisely focus the spot of the laser beam on the magnetic thin film 1a of the magneto-optical disk 1 with a diameter of about 1 μm. There is.

11 is a laser diode (LD) that generates a laser beam
And the laser beam emitted therefrom expands in an elliptical shape. That is, the spread of the laser beam in the direction horizontal to the bonding surface of the laser diode 11 is, for example, about one-third smaller than the spread in the direction perpendicular to that direction.

Reference numeral 12 denotes a collimator lens for converting a laser beam emitted from the laser diode 11 into a parallel beam, and a laser diode near the focal position of the collimator lens 12.
Eleven light emitting points are arranged. However, the distance between the laser diode 11 and the collimator lens 12 can be arbitrarily changed.

Reference numeral 13 denotes an anamorphic prism, which refracts and expands a laser beam incident on an elliptical cross section only in a direction (paper direction in FIG. 1) horizontal to the joint surface, and shapes the laser beam into a circular cross section for emission.

15 is a fixed mirror, 16 is a movable mirror, and both mirrors are arranged facing each other. Then, the laser beam that has passed through the anamorphic prism 13 is reflected at a right angle by the fixed mirror 15, and then reflected at a right angle by the movable mirror 16,
The light is focused on the magnetic thin film 1a of the magneto-optical disk 1 by passing through the objective lens 17.

In the present embodiment, the movable mirror 16 and the objective lens 17 are provided integrally, and are provided in the direction of arrow A, ie, both mirrors 1.
By moving in the direction of the optical axis between 5 and 16, the information stored in the magneto-optical disk 1 can be accessed.

Reference numeral 20 denotes a beam splitter fixed between the fixed mirror 15 and the movable mirror 16. Here, first, fixed mirror
The light beam incident from the 15th side is split and
Through the laser beam to the first photoelectric element 22 for monitoring the laser output.

The reflected light beam reflected from the magneto-optical disk 1 after passing through the beam splitter 20 returns to the beam splitter 20 again. The split light beam passes through the half-wave plate 25 and the direction of the polarization plane is rotated by 45 degrees. Then, the light is further divided by a sub-beam splitter 26 by a polarization reflection surface forming an angle of 45 degrees with respect to the polarization direction.
After passing through 7, 28, the light is focused on the second and third photoelectric elements 29, 30 for detecting the S-polarized light intensity and for detecting the P-polarized light intensity. Information is read by the output signals of the second and third photoelectric elements 29 and 30.

The reflected light flux from the magneto-optical disk 1 divided by another semi-transmissive surface in the beam splitter 20 passes through a fourth condenser lens 34 and a cylindrical lens 35 to perform servo control for focusing and tracking. It is focused on a fourth photoelectric element 36 for outputting a signal.

The focus servo finely moves the objective lens 17 in the direction B, that is, in the direction perpendicular to the surface of the magneto-optical disk 1, and focuses the minimum spot of the laser beam on the magnetic thin film 1a of the magneto-optical disk 1.
Focus on the surface. The tracking servo uses the objective lens 17
Is finely moved in the direction A, that is, in the direction perpendicular to the information recording track of the optical disk 1, and the laser beam is controlled so as not to protrude from the track. In the present embodiment, the light receiving surface of the fourth photoelectric element 36 is divided into, for example, four or more, and signals for focus servo and tracking servo can be obtained by combining output signals from the respective parts.

Next, the astigmatism correction method of the present invention will be described with reference to FIG. 1 and FIG.

H shown in FIG. 2 is a light emitting point in a direction horizontal to the bonding surface of the laser diode 11 (hereinafter, referred to as “horizontal light emitting point”).
And V is a light emitting point in a direction perpendicular to the bonding surface (hereinafter referred to as “vertical light emitting point”). The distance between the two light emitting points H and V, that is, the astigmatic difference of the laser diode 11 is ΔZ, the distance between the vertical light emitting point V and the focal position F of the collimator lens 12 is Z, and the collimator is perpendicular to the joint surface. Assuming that the numerical aperture of the laser beam incident on the lens 12 is NA (NA = sin θ _V ) and the anamorphic magnification is M (M = D2 / D1), the junction surface at the position where the laser beam having a circular cross section emerges from the anamorphic prism 13. Amount of defocus wavefront aberration (hereinafter referred to as defocus) Δ in a direction horizontal to the plane and in a direction perpendicular to the bonding surface.
Wh, DerutaWv respectively represented by ΔWh = (Z + ΔZ) ( NA) 2 / (2M 2) ΔWv = Z (NA) 2/2. Therefore, the amount of astigmatism wavefront aberration (hereinafter referred to as astigmatism) ΔWas generated at that position is as follows: ΔWas = ΔWh−ΔWv = {ΔZ + Z (1-M ² )} (NA) ² / (2M ² ) Z between the horizontal and vertical directions to the joint surface
The amount of astigmatism represented by the following function is generated.

Therefore, the laser diode 11 and the collimator lens
By changing the interval Z of 12, the astigmatism ΔWas at the position exiting the anamorphic prism 13 can be changed.

Therefore, in the present invention, by changing the distance Z between the laser diode 11 and the collimator lens 12, at the position exiting the anamorphic prism 13, an amount of astigmatism that offsets the astigmatism of the optical system downstream of the anamorphic prism 13 is provided. The aberration is positively generated.

In FIG. 1, the optical system downstream of the anamorphic prism 13 includes a fixed mirror 15, a beam splitter 20,
A movable mirror 16 and an objective lens 17 are arranged. If the astigmatism generated by the optical system at the subsequent stage is α, there is an interval Z between the laser diode 11 and the collimator lens 12 such that ΔWas = −α holds. Therefore, by adjusting the distance between the laser diode 11 and the collimator lens 12 to the distance Z, the astigmatism α generated by the subsequent optical system is canceled by the astigmatism ΔWas at the position where the anamorphic prism 13 exits. The astigmatism of the light beam focused on the magneto-optical disk 1 can be corrected to zero.

It is ideal that ΔWas is offset by astigmatism generated in all optical elements downstream of the anamorphic prism 13. However, since the astigmatism generated in the objective lens 17 is generally insignificant, ΔWas is
For example, the astigmatism generated in a part of the subsequent optical element may be canceled, such as canceling the astigmatism generated in the optical element up to the entrance 7.

In order to adjust the distance between the laser diode 11 and the collimator lens 12, for example, a mechanism shown in FIGS. 8 and 9 is used. That is, in the figure, reference numeral 190 denotes a laser pen body containing a laser diode 11 and a collimator lens 12, and the laser diode 11 is fixed to a base end of a hole 190a formed therein, and the collimator lens 12 is incorporated. A collimator lens frame 192 is fitted in the hole 190a so as to be movable in the optical axis direction. A groove 192a is formed on the outer periphery of the collimator lens frame 192 in a direction around the optical axis. 195
Is a pressing plate for fixing the collimator lens frame 192 to the laser pen main body 190, and is fixed to the laser pen main body 190 by fixing screws 196. The holding plate 195 is provided with an adjustment hole 195a for rotatably fitting the interval adjustment rod 194.

In such a mechanism, while the fixing screw 196 is slightly loosened, the protrusion of the spacing adjusting rod 194 is inserted into the groove 192a, and the spacing adjusting rod 194 is fitted into the adjusting hole 195a.
The collimator lens frame by rotating
192 moves in the optical axis direction, and the distance between the laser diode 11 and the collimator lens 12 can be adjusted. After adjustment, tighten the fixing screw 196 to set the collimator lens frame 1
Fix 92.

According to this wavefront aberration correction method, the objective lens
Defocus remains in the laser beam incident on the objective lens 17, but the amount of aberration such as spherical aberration of the objective lens 17 generated by the defocus of the incident beam is very small, and even if the defocus remains, there is almost no problem in practical use. . Also, the photoelectric element 36
, The focus servo operates, and the defocus at the position out of the objective lens 17 is automatically corrected, so that there is no practical problem with the defocus.

In this embodiment, the wavefront aberration correcting method is described using the laser diode 11 having the astigmatic difference ΔZ. However, according to the present invention, the focusing on the magneto-optical disk 1 is performed regardless of the presence or absence of the astigmatic difference. The astigmatism of the luminous flux can be corrected to zero. The anamorphic prism 13 is
Since the laser beam is refracted and expanded only in one direction, only the astigmatism generated in that direction and the direction perpendicular thereto is corrected. There is no problem in practical use.

FIG. 3 shows a measuring apparatus used for correcting astigmatism by the above-mentioned wavefront aberration correcting method. In the figure,
Reference numeral 3 denotes an optical system main unit, which is a unit in which the objective lens 17 is removed from the optical system for an optical information recording / reproducing apparatus shown in FIG.

Reference numeral 100 denotes an aperture for limiting the diameter of a laser beam incident on the objective lens 17. Reference numerals 102 and 103 denote a quarter-wave plate and a half-wave plate which are provided independently and rotatably about an axis in order to adjust the polarization state and the polarization plane of the laser beam to a predetermined state. is there.

Reference numeral 105 denotes a beam splitter, which has a semi-transparent surface having a direction perpendicular to the optical axis of the incident light beam and a direction at 45 degrees. The beam splitter 105 splits the laser beam incident from the optical system main unit 3 into two beams, a beam that passes straight and a beam that is reflected at right angles.

Reference numerals 106 and 107 denote image rotators for rotating the two light beams split by the beam splitter 105 about the optical axis. In this embodiment, two Dove prisms are used. Then, the two light beams are relatively rotated by approximately 90 degrees by the two image rotators 106 and 107. The two image rotators 106 and 107 have exactly the same shape and characteristics so as to improve the coherence by making the optical path lengths of the two light beams split by the beam splitter 105 the same. Note that if good coherence can be ensured, only one of the image rotators may be provided.

108 and 109 are right angle prisms for reflecting the light beams passing through the image rotators 106 and 107 in parallel in the direction inverted by 180 degrees, and have exactly the same shape and characteristics to improve the coherence by making the optical path length the same. And at least one of the right-angle prisms 108 and 109 is movable in the optical axis direction. The light beams reflected by the right-angle prisms 108 and 109 overlap and interfere with each other on the semi-transparent surface of the beam splitter 105, and after being emitted from the beam splitter 105, the direction is changed by the reflector 110.

Reference numeral 111 denotes an imaging lens, which is arranged, for example, to form an image of the diaphragm 100 on an imaging surface 112 of a solid-state imaging device. Then, the wavefront aberration immediately before the light enters the objective lens 17 can be observed as interference fringes using a CRT monitor (not shown) or the like. On the optical path between the imaging lens 111 and the imaging surface 112, two polarizing filters 113 that are rotatable about the axis independently of each other are arranged.
By rotating 13, the intensity of the laser beam incident on the imaging surface 112 can be adjusted. In addition, even if the number of polarizing filters is one, intensity adjustment can be performed to some extent. Further, an ND filter may be used.

Reference numeral 150 denotes a shutter for opening and closing the laser beam, which is reflected at right angles by the semi-transparent surface, out of the two laser beams split by the beam splitter 105.

Reference numeral 151 denotes a reference reflecting surface fixedly formed on the measuring device, and a measuring device for attaching an optical system for an optical information recording / reproducing device when measuring an incident angle of a laser beam incident on the objective lens 17. This is for adjusting the inclination of the mounting surface (not shown) provided on the base plate to the inclination serving as a measurement reference.

152 is a sub-rectangular prism provided in close contact with the side wall of the beam splitter 105, and reflects the laser light flux reflected by the right-angle prism 108 and transmitted through the semi-transparent surface of the beam splitter 105 to change its direction. belongs to.

FIG. 4 shows an optical system provided on an optical path reflected by the sub right-angle prism 152.

Reference numeral 155 denotes a collimator pen integrally formed by arranging a light emitting point of a laser diode at a focal position of a collimator lens, and a mounting surface for emitting a laser beam and mounting an optical system for an optical information recording / reproducing apparatus. (Not shown) is provided to adjust the inclination.

Reference numeral 156 denotes a beam splitter arranged between the sub right-angle prism 152 and the collimator pen 155. The beam splitter 156 reflects the laser beam from the right-angle prism 152 at right angles. Further, the laser beam from the collimator pen 155 passes straight through the beam splitter 156 and enters the sub right-angle prism 152.

157 is a collimator lens, and the beam splitter 1
The laser beam reflected by 56 is applied to the imaging surface 15 of the solid-state image sensor.
9 to be focused on.

On the optical path between the collimator lens 157 and the imaging surface 159, two polarizing filters 158 that are rotatable about the axis independently of each other are arranged, and by rotating the polarizing filters 158, the imaging surface is rotated. The intensity of the laser beam incident on 159 can be adjusted. The polarizing filter is 1
Even with a single sheet, the strength can be adjusted to some extent. Further, an ND filter may be used.

 Next, the measuring operation of the measuring device will be described.

First, when a laser beam is emitted from the collimator pen 155, the laser beam passes through the semi-transparent surface of the beam splitter 156, and the sub-right-angle prism 152, the beam splitter 105,
The light passes through the right-angle prism 108 and the image rotator 106 and is reflected by the reference reflecting surface 151. Thus the reference anti-slope 1
The laser beam reflected by 51 enters the measuring device again, is changed in direction by the beam splitter 156, and is focused on the imaging surface 159. The inclination of the mounting surface (not shown) of the optical system for an optical information recording / reproducing apparatus is adjusted so that the position of the convergence point coincides with a reference point of a scale attached to a CRT monitor (not shown). . Then, the optical system main unit 3
Is attached to a predetermined position of the measuring device.

Next, the shutter 150 is closed, and the emission of the laser beam from the collimator pen 155 is stopped. And
The laser beam is emitted from the laser diode 11, and the movable mirror 16 causes the laser beam to enter the measuring device.
Then, the laser beam not shielded by the shutter 150 passes through the beam splitter 105, the image rotator 106, the right-angle prism 108, and the sub-right-angle prism 152. And
The laser beam that has passed through the sub right-angle prism 152 is reflected by the semi-transparent surface of the beam splitter 156, and
Scaled CRT focused on imaging surface 159 by 57
The position of the focal point is observed by a monitor (not shown) or the like.

Then, the incident angle of the laser beam incident on the objective lens 17 can be measured by measuring the amount of deviation of the focal point position from the reference point on a scale. Assuming that the focal length of the collimator lens 157 is f and the position of the convergence point on the imaging surface 159 is R, the incident angle θ of the laser beam incident on the objective lens 17 is θ = R / f (rad).

On the other hand, the light flux that has passed through the right-angle prism 108 and has been reflected by the semi-transmissive surface of the beam splitter 105
The image is formed on the imaging surface 112 by the imaging lens 111, and the intensity distribution of the laser beam is observed by a CRT monitor (not shown) or the like. Note that, instead of the CRT monitor, the light intensity of the imaging surface 112 may be input to an image processing device or the like and calculated, and then the intensity distribution may be displayed.

Next, the shutter 150 is opened. Then, the laser beams split into two by the beam splitter 105 are relatively rotated about 90 degrees around the optical axis by the image rotators 106 and 107.
The beam is rotated by an angle and reflected by the right-angle prisms 108 and 109 in the direction of the semi-permeable surface of the beam splitter 105, and overlaps and interferes with the semi-permeable surface of the beam splitter 105. The direction of the overlapping and interfering laser beams is changed by the reflector 110, guided to the imaging surface 112 by the imaging lens 111, and interference fringes are observed by a CRT monitor (not shown) or the like.

At this time, tilting is performed by, for example, slightly tilting the optical system main unit 3 with respect to the measuring device, and for example, 2 to 4
About this number of interference fringes are observed.

In the interference fringes observed in this manner, the wavefronts of the two divided luminous fluxes are rotated by approximately 90 degrees about the optical axis center by the image rotators 106 and 107, and therefore, are asymmetric with respect to the optical axis. Components such as astigmatism and coma are detected, but components such as defocus which are symmetric with respect to the optical axis are not detected. Therefore, the collimator lens 12
Even if the distance between the laser diode 11 and the laser diode 11 is changed, no defocus is detected, and only astigmatism is detected, so that the wavefront aberration can be easily corrected. Since the two divided light beams are rotated by approximately 90 degrees to interfere with each other, as shown in FIG. 5, astigmatism components appear in the interference fringes with approximately twice the sensitivity.

This will be described with reference to the drawings. FIG. 6A shows 180a and FIG.
0b indicates the defocus component of the wavefront after passing through the image rotators 106 and 107, respectively, and the defocus components 180a and 180b that are relatively rotated by approximately 90 degrees are exactly the same, and 180c in FIG. As shown in (2), the component that is the difference between them becomes planar. Therefore, no defocus component is detected in the interference fringes.

7A and 181b in FIG. 7B show the astigmatism components of the wavefronts after passing through the image rotators 106 and 107, respectively, in the same manner as described above, and are in a relationship rotated by approximately 90 degrees. Taking the difference between certain astigmatism components 181a and 181b, as shown in 181c of FIG. 7C, components that are curved in opposite directions in two orthogonal directions are obtained. Therefore,
The astigmatism component is detected with twice the sensitivity in the interference fringes.

In this way, when the laser beam incident on the measuring device has no astigmatism, straight and parallel interference fringes are observed, and when there is astigmatism, curved interference fringes are observed.

When the interference fringes are observed to be bent, the distance between the laser diode 11 and the collimator lens 12 is adjusted by the wavefront aberration correction method of the present invention to straighten the interference fringes. When the interference fringes are straightened in this way, in the optical system for an optical information recording / reproducing apparatus, the amount of astigmatism that cancels out the astigmatism generated by the fixed mirror 15, the beam splitter 20, and the movable mirror 16 is anamorphic. Prism 13
This means that the astigmatism of the laser beam immediately before entering the objective lens 17 is corrected to zero.

When the present measurement apparatus is used, the objective lens 17 is excluded from the measurement target as described above. However, astigmatism generated by the majority of optical elements including the anamorphic prism 13 and the mirrors 15, 16 has been corrected,
Even if a small amount of astigmatism is generated by the objective lens 17, there is no practical problem at all.

When correcting astigmatism including the objective lens 17, the wavefront aberration measuring device may be provided with means for converting convergent light from the objective lens 17 into a parallel light beam.

[Effects of the Invention] According to the measuring device of the optical system for an optical information recording / reproducing device of the present invention, the astigmatism of the light beam incident on the objective optical system can be measured, and the light beam incident on the objective optical system can be measured. Can be measured, and the intensity distribution of the laser beam at the entrance pupil of the objective optical system can be measured. Therefore, when measuring the astigmatism and the incident angle or the intensity distribution, only one measuring device may be prepared, and there is an excellent effect that the measuring cost and the like can be significantly reduced.

Further, by providing the polarizing filter for adjusting the intensity of the observation light, accurate measurement can be performed even when, for example, a laser beam having extremely high intensity is measured.

[Brief description of the drawings]

1 is a schematic view of an optical system for an optical information recording / reproducing device, FIG. 2 is a partially enlarged view of FIG. 1, and FIGS. 3 and 4 are measuring devices of the optical system for an optical information recording / reproducing device. FIG. 5 is a characteristic diagram showing a relationship between a relative rotation angle of two light beams and measurement sensitivity, FIGS. 6A to 6C are schematic diagrams showing a wavefront defocus component, and FIG. 7A. 7A to 7C are schematic diagrams showing astigmatism components of the wavefront, FIG. 8 is a front view of the laser pen, and FIG. 9 is a sectional view taken along line IX-IX of FIG. 1 ... Magneto-optical disk, 11 ... Laser diode, 12 ...
… Collimator lens, 13 …… Anamorphic prism,
16 movable mirror, 17 objective lens, 105, 156 beam splitter, 106, 107 image rotator, 10
8,109 …… Right angle prism, 111 …… Imaging lens, 112,159
…… Imaging plane, 113,158… Polarizing filter, 155… Collimator pen, 157… Collimator lens.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuyoshi Hayashi 2-36-9 Maeno-cho, Itabashi-ku, Tokyo Asahi Optical Industry Co., Ltd. (72) Toshiyuki Kase 2-36-9 Maeno-cho, Itabashi-ku, Tokyo No. Asahi Optical Industry Co., Ltd. (56) References JP-A-60-149941 (JP, A) JP-A-63-182506 (JP, A) JP-A-64-53103 (JP, A)

Claims (5)

(57) [Claims] An optical system in which a light beam emitted from a laser diode is converted into a parallel light beam by a collimator optical system, then shaped by an anamorphic optical system, and then incident on an objective optical system for focusing the light beam on a storage medium. A beam splitter for splitting the light beam into first and second two light beams at a position immediately before the objective optical system of the information recording / reproducing device optical system, and the first and second light beams are separated by the beam. In the measuring device of the optical system for an optical information recording / reproducing apparatus, provided with an interference unit that generates interference fringes by overlapping and interfering with each other by a splitter and the observation unit for observing the interference fringes, A shutter capable of blocking a light beam is provided, and when the shutter blocks the second light beam, the beam splitter further splits the light beam into two light beams. The first light beam to be emitted is made incident on the objective optical system by allowing the observation means to observe the intensity distribution of one of the divided light beams of the first light beam, and converging the other divided light beam and measuring its converging position. An optical system measuring device for an optical information recording / reproducing device, comprising an incident angle measuring means for measuring an incident angle of a light beam. 2. The incident angle measuring means according to claim 1, wherein said incident angle measuring means compares said other divided light beam with a laser light beam emitted from a laser light source different from said laser diode and reflected by a reference reflecting surface. 2. The measuring apparatus for an optical system for an optical information recording / reproducing apparatus according to claim 1, wherein the measuring is performed. 3. An at least one polarizing filter rotatable about an axis is disposed on an optical path between the interference means and the observation means, and the other split light beam incident on the incident angle measuring means is provided. 3. The optical path according to claim 1, wherein at least one polarizing filter rotatable about an axis is provided on the optical path.
A measuring device for an optical system for an optical information recording / reproducing device according to the above. 4. An optical system in which a light beam emitted from a laser diode is converted into a parallel light beam by a collimator optical system, then shaped by an anamorphic optical system, and then incident on an objective optical system for focusing the light beam on a storage medium. In the optical system for the information recording / reproducing device, at a position immediately before the objective optical system, the light beam is divided into first and second two light beams by a beam splitter, and the first and second light beams are separated by the beam splitter. In a light beam measuring method for an optical system for an optical information recording / reproducing apparatus, wherein an interference fringe generated by superimposing and causing interference is observed by an observation unit, the second light beam is shielded and the first light beam is blocked. Is further divided into two light beams by the beam splitter, and the intensity distribution of one split light beam of the first light beam is observed by the observation means, A light beam measurement method for an optical system for an optical information recording / reproducing apparatus, wherein an incident angle of a light beam incident on the objective optical system is measured by converging the other divided light beam and measuring a converging position thereof. Method. 5. The incident angle measuring device according to claim 1, wherein the incident angle measuring means compares the other divided light beam with a laser light beam emitted from a laser light source different from the laser diode and reflected by a reference reflecting surface. 5. The method for measuring a light flux of an optical system for an optical information recording / reproducing apparatus according to claim 4, wherein