JPH07169085A - Optical information recorder/reproducer - Google Patents

Abstract

PURPOSE:To reduce generation of luminous flux eclips and automatic tracking (AT) offset with gentle accuracy to be required for prevention of a deviation of an optical axis of an optical system and large.allowance required for processing and assembling of components by disposing a diffraction grating for dividing a luminous flux in a route of an incident optical path not superposed with a reflecting optical path in a movable unit. CONSTITUTION:A movable unit of an optical system has two polarization beam splitters 35, 35', a l/4-wavelength plate 36, an objective lens 37, two 1/2-wavelength plates 40, 40', total reflection prisms 41, 41' and further a diffraction grating 34. An incident optical path and a reflecting optical path are formed at partly different routes and the grating 34 is disposed only on the incident path. Thus, a distance between a (+) primary luminous flux center returned to a stationary unit and a (-) primary luminous flux center becomes about a half of a conventional unit, a deviation of an optical axis is reduced. Luminous flux eclips can be prevented without considerably increasing sizes of the components, and generation of light quantity loss and disused light can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical information for recording information on an optical information recording medium, reproducing the information recorded on the recording medium and / or erasing the information recorded on the recording medium. The present invention relates to a recording / reproducing device. The present invention particularly relates to an optical information recording / reproducing apparatus in which an optical head optical system is divided into a fixed portion and a movable portion.

[0002]

2. Description of the Related Art Heretofore, various types of information recording media such as discs, cards, tapes, etc. have been known as information recording media for recording and reproducing information using light. Some of these optical information recording media are recordable and reproducible, and only reproducible. Recording of information on a recordable medium is performed by scanning an information track with a light beam that is modulated according to the record information and focused into a minute spot, and the information is recorded as an optically detectable information bit string. .

Information is reproduced from a recording medium by scanning an information bit string of an information track with an optical beam spot having a constant power such that recording is not performed on the medium and reflecting or transmitting light from the medium. Is detected.

The above-mentioned optical head used for recording and reproducing information on the recording medium is movable relative to the recording medium in the information track direction and in the direction transverse to the direction, and by this movement, the optical head is moved. Information track scanning of the beam spot is performed. An objective lens, for example, is used as a lens for narrowing the light beam spot in the optical head. The objective lens can be independently moved in its optical axis direction (focusing direction) and in a direction (tracking direction) orthogonal to both the optical axis direction and the information track direction of the recording medium. Held in. Such holding of the objective lens is generally performed through an elastic member, and the movement of the objective lens in the above two directions is generally driven by an actuator utilizing magnetic interaction.

Among the above-mentioned optical information recording media, a card-shaped optical information recording medium (hereinafter referred to as an optical card) is a small-sized, light-weight, convenient-to-carry, relatively large-capacity information recording medium, which will be large in the future. Demand is expected.

FIG. 5 shows a schematic plan view of a write-once optical card, and FIG. 6 shows a partially enlarged view thereof.

In FIG. 5, a large number of information tracks 2 are arranged in parallel on the information recording surface of the optical card 1 in the LF direction. The information recording surface of the optical card 1 is provided with a home position 3 which serves as a reference position for accessing the information track 2. The information track 2 is in the order of 2-1, 2-2, 2-3, ...
As shown in FIG. 6, tracking tracks 4 are provided adjacent to these information tracks 4-1 and 4-.
2, 4, 3, ... are sequentially provided. These tracking tracks 4 are used as guides for auto-tracking (hereinafter, referred to as AT) that controls the beam spot so that the beam spot does not deviate from a predetermined information track at the time of scanning the light beam spot during information recording / reproduction. .

This AT servo detects the deviation (AT error) of the light beam spot from the information track in the optical head, negatively feeds back the detection signal to the tracking actuator, and the objective lens is attached to the optical head main body. This is performed by moving in the tracking direction (D direction) and causing the light beam spot to follow a desired information track.

Further, during information recording / reproduction, when scanning an information track with a light beam spot, in order to make the light beam into a spot shape (focus) of an appropriate size on the optical card surface, Focusing (hereinafter referred to as AF) servo is performed. This AF servo detects a deviation (AF error) from the focused state of the light beam spot in the optical head, negatively feeds back the detection signal to the focusing actuator, and moves the objective lens to the optical head main body in the focusing direction. By moving the light beam spot to the optical card surface to focus the light beam spot on the optical card surface.

In FIG. 6, S₁ , S₂ , S₃ Is
Shows the light beam spot, S₁ And S ₃ Use the light spot of
And use AT to do S₂ AF using the light spot of
And the creation of information bits during recording and
Read out. In each information track, 6-
1, 6-2 and 7-1, 7-2 are preformatted respectively
The left side address part and the right side address part are shown.
The information track can be identified by reading the address section.
Be played. 5 (corresponding to 5-1 and 5-2 in the figure) is the data
This is a data section in which predetermined information is recorded.

Here, the optical information recording method will be described with reference to the schematic view of the optical head optical system shown in FIG.

In FIG. 7, reference numeral 21 denotes a semiconductor laser which is a light source, and in this example, emits light having a wavelength of 830 nm which is polarized in the direction perpendicular to the track. Further, 22 is a collimator lens, 23 is a beam shaping prism, 24 is a diffraction grating for splitting a light beam, and 25 is a polarization beam splitter. Further, 26 is a quarter wave plate, 20 is a mirror, 27
Is an objective lens, 28 is a spherical lens, 29 is a cylindrical lens, and 30 is a photodetector. The photodetector 30 is 2
It is composed of one light receiving element 30a, 30c and four light receiving elements 30b.

The light beam emitted from the semiconductor laser 21 enters the collimator lens 22 as a divergent light beam. Then, it is made into a parallel light beam by the lens, and is further shaped by the beam shaping prism 23 into a beam having a predetermined light intensity distribution, that is, a circular intensity distribution. After that, the light enters the diffraction grating 24 and is split into three effective light beams (0th-order diffracted light and ± 1st-order diffracted light) by the diffraction grating 24. These three light fluxes are transmitted by the polarization beam splitter 2
It is incident on P5 as P-polarized light flux. The polarization beam splitter 25 has a spectral characteristic as shown in FIG.
Nearly 100% of polarized light is transmitted.

Next, the three light beams are converted into a quarter wave plate 2
It is converted into circularly polarized light when passing through 6, and is focused on the optical card 1 by the objective lens 27. This focused light is converted into three small beam spots S ₁ as shown in FIG.
(+ 1st-order diffracted light), S ₂ (0th-order diffracted light), and S ₃ (−1st-order diffracted light). S ₂ is used for recording, reproduction and AF control, and S ₁ and S ₃ are used for AT control. As shown in FIG. 6, the spot positions on the optical card 1 are such that the light beam spots S ₁ and S ₃ are located on the adjacent tracking tracks 4 and the light beam spot S ₂ is the information track 2 between the tracking tracks. Located on top. Thus, the reflected light from the light beam spot formed on the optical card 1 passes through the objective lens 27 again to be a parallel light beam, and passes through the quarter-wave plate 26 so that the polarization direction is 90 degrees from that at the time of incidence. ° Converted to a rotated light beam. Then, it enters the polarization beam splitter 25 as an S-polarized beam, is reflected by nearly 100% due to the spectral characteristics shown in FIG. 8, and is guided to the detection optical system.

In the detection optical system, a spherical lens 28 and a cylindrical lens 29 are combined, and this combination performs AF control by the astigmatism method. The three light beams reflected from the optical card 1 are respectively collected by the detection optical system and enter the photodetector 30,
Form three light spots. Light receiving elements 30a, 30c
Receives the reflected light from the light spots S ₁ and S ₃ described above, and AT control is performed using the difference between the outputs of these two light receiving elements. Further, the four-divided light receiving element 30b is used for the light spot S ₂
The reflected light is received and the output is used for AF control and the recorded information is reproduced. Light receiving elements 30a, 30
FIG. 9 shows how the light spots are formed at points b and 30c. The formed light spots S _a , S _b and S _c are completely included in the light receiving elements 30a, 30b and 30c.

By moving the entire optical system of the optical head as shown by the arrow, the information track can be scanned with the light beam spot S _b .

By the way, the optical head optical system as described above is
As shown in FIG. 7, the information track can be scanned with the light beam spot S _b by dividing the fixed part and the movable part and moving only the movable part as shown by the arrow. In such a separation type optical head, the amount of movement of the movable portion needs to be about the length of the optical card 1 in the vertical direction, and is usually about 100 mm.

[0018]

In the case of the above-mentioned separated type optical head, the optical path length, especially the diffraction grating 2 depends on the position of the movable portion.
The optical path length from 4 to the movable portion, the optical card 1, and the movable portion again to the photodetector 30 changes. This change in the optical path length is approximately twice the amount of movement of the movable part, and therefore the precision required to prevent the optical axis shift of the optical system becomes strict, and the precision of each component and the assembling precision thereof become strict. Also, the time and labor required for assembly are large, and it is difficult to reduce costs.

Further, when the optical axis shift becomes large, only one of the two AT control light beams will be subject to the objective lens 27.
Vignetting occurs due to the effective diameter of optical components such as AT, and AT offset occurs.

For example, if the diffraction angle of the diffraction grating 24 is 30 ',
The distance between the diffraction grating 24 and the objective lens 27 is 100 mm,
The effective diameter of the objective lens 27 is φ5 mm, and the diameter of each light beam is φ3 m.
When m, the positional relationship of the three beams on the objective lens is as shown in FIG. 3, and the two AT control light beams (± first-order light beams) are close to the effective diameter of the objective lens by 0.2 mm. If there is an inclination or parallel shift of the optical axis, only one light beam is vignetted on the effective diameter of the objective lens, which causes AT offset. That is, in this case, if the optical axis parallel shift is 0.2 mm or the optical axis tilt 8'is exceeded, an AT offset will occur. FIG. 4 shows a light spot formation state when light beam vignetting occurs. 4A shows a case where only the power of the spherical lens 28 is affected, and FIG. 4B shows a case where the power of the spherical lens 28 and the power of the cylindrical lens 29 have the maximum effect. Actually, the above-mentioned (a) and (b) or various states in between are realized, and the light spot S _a or the light spot S formed on the light receiving element of the photodetector placed at the position of the circle of least confusion. Vignetting occurs in _c and AT offset occurs.

In the case of the above-mentioned conventional separation type head, the optical path length changes depending on the position of the movable part, and the AT offset amount changes accordingly, and the change amount is large, so that it is difficult to cope with it. .

In order to make such AT offset less likely to occur, it is necessary to increase the effective diameter of each optical component of the optical system, but this is disadvantageous in downsizing and weight reduction, and the optical head moving speed is increased. That is, it is difficult to improve the recording / reproducing speed. Further, in order to make the AT offset less likely to occur, the processing accuracy and the assembly accuracy of each component may be made strict, but this significantly increases the manufacturing cost.

In view of the problems of the prior art as described above, the present invention has a low accuracy required for preventing the optical axis deviation of the optical system, and has a high tolerance required for processing and assembling each component. It is an object of the present invention to provide an optical information recording / reproducing device that can be easily reduced in cost.

Further, in view of the problems of the prior art as described above, the present invention is less likely to cause AT offset,
It is an object of the present invention to provide an optical information recording / reproducing apparatus whose size is small even if it occurs and which can be easily dealt with.

[0025]

According to the present invention, in order to achieve the above-mentioned object, a light beam from an irradiation optical system is focused to irradiate an optical information recording medium as a light spot and the light on the recording medium is irradiated. An optical information recording / reproducing apparatus having an optical head for projecting a light beam from a spot onto a detection optical system, and recording and / or reproducing information on the recording medium by irradiation of the light beam from the irradiation optical system. At
The optical system of the optical head is composed of a fixed portion including the irradiation optical system and the detection optical system, and a movable portion that is movable with respect to the fixed portion and includes an objective lens, and the movable portion is the irradiation optical system. An incident light path for spot-irradiating the light flux from the optical disc on the recording medium and a reflected optical path for guiding the light flux from the light spot on the recording medium to the detection optical system. An optical information recording / reproducing apparatus is provided, in which the light path splitting means is arranged only in the path of the incident light path.

In one aspect of the present invention, the light beam splitting means is a diffraction grating.

In one aspect of the present invention, the member of the movable part on which the light beam from the irradiation optical system is incident is the same as the member of the movable part on which the light beam is emitted to the detection optical system.

In one aspect of the present invention, a polarizing beam splitter for branching an incident light path and a reflected light path is arranged in the movable portion.

In one aspect of the present invention, half-wave plates are arranged in the path of only the incident light path of the movable section and in the path of only the reflected light path of the movable section.

In one aspect of the present invention, two sets of a polarization beam splitter, a quarter-wave plate and a reflecting means are arranged in the movable part, and the sets are accompanied by rotation of the polarization direction by 90 °. The polarized beam splitter that constitutes one of the two sets is a polarized beam splitter for splitting the incident light path and the reflected light path, and The other of the set constitutes a path only for the incident light path or a path only for the reflected light path.

In one aspect of the present invention, the polarization beam splitter, the quarter-wave plate and the reflecting means which constitute the above-mentioned set are integrated.

[0032]

Embodiments of the present invention will now be described in detail with reference to the drawings.

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

In FIG. 1, reference numeral 1 is an optical card. The fixed part of the optical system of the optical head has a configuration similar to that described with reference to FIG. That is, although not shown in FIG.
The optical system fixing portion of this embodiment has the semiconductor laser 21, the collimator lens 22, the beam shaping prism 23, the polarization beam splitter 25, the spherical lens 28, the cylindrical lens 29, and the photodetector 30 as described with reference to FIG. . This photodetector 30 includes two light receiving elements 30a,
30c and a light receiving element 30b divided into four parts. However, the optical system fixing portion of the present embodiment is the same as that shown in FIG.
Diffraction grating 24 and quarter wave plate 26 as described above
Does not include.

On the other hand, the movable part of the optical system of this embodiment includes two polarization beam splitters 35 and 35 'and a quarter wavelength plate 3.
6, objective lens 37, two half-wave plates 40, 40 '
And two total reflection prisms 41, 41 ',
You can move in the direction of the arrow.

The parallel light flux emitted from the fixed portion travels straight in parallel with the surface of the optical card 1 and enters the polarization beam splitter 35 of the movable portion. The parallel light flux emitted from the fixed portion is polarized in the in-plane direction of the paper, and is incident on the polarization beam splitter 35 as P-polarized light and transmitted. This transmitted light flux is rotated by 90 ° in the direction perpendicular to the plane of the drawing by the half-wave plate 40, and is converted into 3 by the diffraction grating 34.
The light beam is divided into two light beams (0th-order diffracted light beam, + 1st-order diffracted light beam and -1st-order diffracted light beam), and S
It enters as polarized light, is reflected here, and is transmitted by the quarter-wave plate 36.
After passing through, the light is collected by the objective lens 37, and the optical card 1
Form a light spot on top. The light beam from the light spot passes through the objective lens 37 and the quarter-wave plate 36, and then enters the polarization beam splitter 35 'again. Since the light has been transmitted through the quarter-wave plate 36 twice before this incidence, the light flux enters the polarization beam splitter 35 'as P-polarized light and is transmitted. After that, it is reflected by the total reflection prism 41,
The polarization direction is rotated by 90 ° by the two-wavelength plate 40 ′, further reflected by the total reflection prism 41 ′, made incident on the polarization beam splitter 35 as S-polarized light, reflected here, and advances to the fixed portion. The traveling direction of the light beam from the polarization beam splitter 35 to the fixed portion is the same as (but opposite to) the traveling direction of the light beam incident on the polarizing beam splitter 35 of the movable portion from the fixed portion. The luminous flux that has reached the fixed portion from the movable portion is detected in the same manner as in the above conventional device.

In the movable part, the optical path from the polarization beam splitter 35 to the optical card 1 through the half wave plate 40, the diffraction grating 34, the polarization beam splitter 35 ', the quarter wave plate 36 and the objective lens 37. Is an incident optical path, and from the optical card 1, the objective lens 37, the quarter-wave plate 3
6, polarization beam splitter 35 ', total reflection prism 4
The optical path leading to the polarization beam splitter 35 via the 1, 1/2 wavelength plate 40 'and the total reflection prism 41' is a reflected optical path, and the incident optical path and the reflected optical path are partially different paths. The diffraction grating 34 is arranged in the path of the chisel.

According to this embodiment as described above, the following effects can be obtained. That is, as described with reference to FIGS. 3 and 4, in the conventional device, +1 on the optical card 1 is used.
The distance between the center of the next luminous flux spot and the center of the −1st-order luminous flux spot is 1.6 mm, and when these luminous fluxes return to the fixed portion, the distance between the luminous flux centers is about twice that. Two
In order to prevent the light beam vignetting, the dimensions of each optical component had to be increased. On the other hand, in the embodiment of the present invention described above, since the diffraction grating for splitting the light beam is arranged in the movable portion, it returns to the fixed portion +1.
The distance between the center of the secondary luminous flux and the center of the −1st-order luminous flux is about half that of the above-mentioned conventional device, the deviation of the optical axis is small, and the vignetting can be prevented without increasing the size (aperture, etc.) of each optical component. be able to. In the movable part,
Since the diffraction grating is arranged in the path in the incident light path that does not overlap the reflected light path, it is possible to cause a light amount loss or unnecessary light as in the case where the light flux passes through the diffraction grating in a reciprocating manner. There is nothing.

In the above embodiment, a reflecting member such as a mirror may be used instead of the total reflection prism in the movable part.

FIG. 2 is a schematic diagram showing another example of the optical head of the optical information recording / reproducing apparatus according to the present invention. In this figure, the same members as those in FIG. 1 are designated by the same reference numerals.

In this embodiment, a set of a polarization beam splitter 35 ', a quarter wave plate 42 and a reflecting member 43 is used, and a polarization beam splitter 35 "and a quarter wave plate having the same structure are used. A set of 42 'and a reflecting member 43' is used.

The parallel light flux emitted from the fixed portion travels straight in parallel to the surface of the optical card 1 and enters the polarization beam splitter 35 of the movable portion. The parallel light flux emitted from the fixed portion is polarized in the in-plane direction of the paper, and is incident on the polarization beam splitter 35 as P-polarized light and transmitted. This transmitted light flux is converted into three light fluxes (zero-order diffracted light flux, +
1st-order diffracted light flux and -1st-order diffracted light flux), and is incident on the polarization beam splitter 35 'as P-polarized light and transmitted,
The quarter-wave plate 42 and the reflection member 43 allow the polarization plane to be 90 degrees.
It is reflected with rotation, and this time it is incident on the polarization beam splitter 35 'as S-polarized light and reflected there,
After passing through the quarter-wave plate 36, it is condensed by the objective lens 37 to form a light spot on the optical card 1. The light flux from the light spot is generated by the objective lens 37 and the quarter-wave plate 3
After passing through 6, the light beam enters the polarization beam splitter 35 ′ again. Since the light has been transmitted through the quarter-wave plate 36 twice before this incidence, the light flux enters the polarization beam splitter 35 'as P-polarized light and is transmitted. After that, the polarization beam splitter 3
It is incident on the 5 "as P-polarized light and transmitted therethrough, and the quarter-wave plate 4
2'and the reflection member 43 'cause the plane of polarization to be reflected by 90 °, and this time the polarization beam splitter 3
5 "is incident as S-polarized light, is reflected here, is further reflected by the total reflection prism 41 ', is incident on the polarization beam splitter 35 as S-polarized light, is reflected here, and advances to the fixed portion. The traveling direction of the light beam from the splitter 35 to the fixed portion is the same as (but opposite to) the traveling direction of the light beam incident on the polarization beam splitter 35 of the movable portion from the fixed portion.

In the movable part, from the polarization beam splitter 35 to the diffraction grating 34 and the polarization beam splitter 3
An optical path from the optical card 1 to the objective lens 37, 5 ′, the quarter-wave plate 42, the reflecting member 43, the quarter-wave plate 36, and the objective lens 37 is an optical path to the optical card 1.
The optical path from the quarter-wave plate 36, the polarization beam splitter 35 ′, the polarization beam splitter 35 ″, the quarter-wave plate 42 ′, the reflection member 43 ′, and the total reflection prism 41 ′ to the polarization beam splitter 35 is a reflection optical path. The incident light path and the reflected light path are partially different paths, and the diffraction grating 34 is arranged in the path of only the reflected light path.

Also in this embodiment, the same operational effect as that of the embodiment of FIG. 1 can be obtained.

In the above embodiment, each member in the set of the polarization beam splitter, the quarter wavelength plate and the reflecting member may be arranged separately.

[0046]

As described above, according to the present invention,
Provided is an optical information recording / reproducing apparatus which has a low degree of accuracy required for preventing the optical axis shift of an optical system, has a high degree of tolerance required for processing and assembling each component, and can be easily reduced in cost.

Further, according to the present invention, the optical information recording / reproducing apparatus is less likely to cause the light beam vignetting and the AT offset due to the light beam vignetting, is small in size even if it is generated, and is easy to deal with. Will be provided.

Further, according to the present invention, since the light beam splitting means is arranged on the path in the incident light path which does not overlap with the reflected light path,
There is no occurrence of loss of light amount or generation of useless light as in the case where the light beam is passed back and forth through the light beam splitting means.

[Brief description of drawings]

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

FIG. 2 is a schematic configuration diagram showing another example of the optical head of the optical information recording / reproducing apparatus according to the present invention.

FIG. 3 is a diagram showing a positional relationship of three beams on an objective lens in an optical head of an optical information recording / reproducing apparatus.

FIG. 4 is a diagram showing a light spot formation state when light beam vignetting occurs.

FIG. 5 is a schematic plan view of an optical card.

FIG. 6 is a partially enlarged view of the optical card.

FIG. 7 is a diagram of a separated optical head optical system.

FIG. 8 is a spectral characteristic diagram of a polarization beam splitter.

FIG. 9 is a diagram showing a relationship between the shape and arrangement of a photodetector and an optical spot in an optical head of an optical information recording / reproducing apparatus.

[Explanation of symbols]

1 Optical Card 20 Mirror 21 Semiconductor Laser 22 Collimator Lens 23 Beam Shaping Prism 24 Diffraction Grating 25 Polarizing Beam Splitter 26 1/4 Wave Plate 27 Objective Lens 28 Spherical Lens 29 Cylindrical Lens 30 Photodetector 30a, 30b, 30c Photoreceptor 34 Diffraction Grating 35, 35 ', 35 "Polarizing beam splitter 36 1/4 wave plate 37 Objective lens 40, 40' 1/2 wave plate 41, 41 'Total reflection prism 42, 42' 1/4 wave plate 43, 43 'Reflection Material S ₁ , S ₂ , S ₃ light spots _Sa , S _b , S _c light spots

Claims (7)

[Claims] 1. An optical head is provided which narrows a light beam from an irradiation optical system and irradiates the optical information recording medium as a light spot, and projects the light beam from the light spot on the recording medium onto a detection optical system. In an optical information recording / reproducing apparatus for recording information on the recording medium and / or reproducing recorded information by irradiation of a light beam from an irradiation optical system, an optical system of the optical head comprises the irradiation optical system and the detection optical system. And a movable portion that is movable with respect to the fixed portion and that includes an objective lens, the movable portion being an incident optical path for spot-irradiating the light flux from the irradiation optical system onto the recording medium. And a reflected light path for guiding a light beam from a light spot on the recording medium to the detection optical system, and the incident light path and the reflected light path are partially different paths, Fill in The optical information recording and reproducing apparatus characterized by the light beam splitting means in the path of the optical path only are arranged. 2. The optical information recording / reproducing apparatus according to claim 1, wherein the light beam splitting means is a diffraction grating. 3. The member of the movable part on which the light beam from the irradiation optical system is incident and the member of the movable part on which the light beam is emitted to the detection optical system are the same. The optical information recording / reproducing apparatus according to claim 2. 4. The optical device according to claim 1, wherein a polarizing beam splitter for branching an incident light path and a reflected light path is arranged in the movable portion. Information recording / reproducing apparatus. 5. The half-wave plate is arranged in each of the path of only the incident light path of the movable section and in the path of only the reflected light path of the movable section. 4. The optical information recording / reproducing device according to any one of 4 above. 6. Two sets of a polarization beam splitter, a quarter-wave plate, and a reflecting means are arranged in the movable part,
The set produces a polarized light flux of 90 ° with a 90 ° rotation of the polarization direction.
The polarization beam splitter which is capable of deflecting and constitutes one of the two sets is a polarization beam splitter for branching the incident light path and the reflection light path, and the other of the two sets is Characterized in that it constitutes a path only for the incident light path or a path only for the reflected light path,
The optical information recording / reproducing apparatus according to claim 4. 7. The optical information recording / reproducing apparatus according to claim 6, wherein the polarization beam splitter, the quarter-wave plate and the reflecting means which constitute the set are integrated.