JPH0933720A - Multi-image prism and optical pickup device utilizing same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-image prism which splits an incident light beam into three light beams and is inexpensive and easily manufactured and to provide an optical pickup device utilizing it. SOLUTION: Of the multi-image prism constituted by joining three crystal bodies 11-13 together, two joint surfaces S2 and S3 are parallel and the directional vectors of optical axes 11a and 13a of the 1st crystal body 11 and 3rd crystal body 13 are almost parallel; and the two direction vectors are almost perpendicular to the normal vector 14 of a multi-image prism incidence surface S1, the 2nd crystal body 12 is a crystal body in which light traveling along the optical axis had a circular polarization characteristic, and the directional vector of the optical axis 12a is almost parallel to the normal vector of the multi-image prism incidence surface S1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device for reproducing a signal recorded on a magneto-optical recording medium, and more particularly to detecting rotation of a plane of polarization of reflected light from the magneto-optical recording medium. The present invention relates to a suitable double image prism and an optical pickup device using the same.

[0002]

2. Description of the Related Art Conventionally, FIG.
Known are the (a) Rochon prism, the (b) Senarmont prism, the (c) Wollaston prism, the (d) double Wollaston prism, and the like as shown in FIG. These double image prisms are prisms composed of a plurality of crystal bodies, and the directions of the optical axes of the crystal bodies are set as shown in FIGS. 8A to 8D (31 to 32 in FIG. 8). Indicates a crystal body, and 31a to 33a indicate its optical axis). And
The light beam incident on these compound image prisms is
Separate the light beam into a book.

On the other hand, the three-beam Wollaston prism shown in FIG. 7 is designed to separate an incident light beam into three light beams on the exit side, and downsize the optical pickup device and reduce the number of parts. It is a prism suitable for reduction of (Japanese Patent Publication No. 19522/1992 and Japanese Patent Publication No. 19522/1992).
Reference).

The Wollaston prism has an optical axis 31a of the first crystal body 31 and an optical axis 32 of the second crystal body 32.
Two crystal bodies are joined so as to be non-perpendicular to a, and the separation ratio at the time of separation into three light beams changes depending on the angle formed by the two optical axes. Of the light beam 33 that has entered the Wollaston prism, the light that has passed through the first crystal body 31 and the second crystal body 32 as ordinary rays, and the first crystal body 31 and the second crystal body 32. The light that has passed through as an extraordinary ray becomes a single light beam 35,
Light that has passed through the first crystal body 31 as an ordinary ray and light that has passed through the second crystal body 32 as an extraordinary ray, and light that has passed through the first crystal body 31 as an extraordinary ray and that through the second crystal body 32 as an ordinary ray. One of the reflected lights becomes a light beam 34 and the other becomes a light beam 36.

FIG. 8 shows an example of an optical pickup device using the Wollaston prism. In the figure, the light source 4
The light beam emitted from the beam No. 1 is collimated by the collimator lens 42, reflected by the beam splitter 43, and converged by the objective lens 44 to form a spot on the surface of the magneto-optical recording medium 45. The light beam focused on the surface of the magneto-optical recording medium 45, modulated here according to the recording signal, and reflected is collimated by the objective lens 44, passes through the beam splitter 43, and passes through the three-beam Wollaston prism. 3 light beams. These three light beams are collected by the condenser lens 4
The light becomes convergent light at 7, and after being given astigmatism for focusing by the cylindrical lens 48, it is condensed at the light receiving portion of the light receiving element 49. Here, the three light beams received by the light receiving element 49 are converted into voltage signals, of which the central light beam is used for focusing error signal detection and the light beams on both sides thereof are used for information signal detection. It

In the above optical pickup device, each of the beam splitter and the condenser lens is composed of one, but when a conventional double image prism (a prism which splits into two beams on the emission side) is used, it is further , A beam splitter and a condenser lens are required, and the light receiving element also needs to be separately arranged in two places (for focusing error signal detection and information signal detection). That is, by using the 3-beam Wollaston prism, the structure of the optical pickup device can be simplified, and the device can be downsized and the number of parts can be reduced.

[0007]

However, the optical pickup device using the three-beam Wollaston prism can be downsized and the number of parts can be reduced, but the three-beam Wollaston prism itself is manufactured. In that case, a complicated manufacturing process was required, and it was not possible to manufacture at low cost. In other words, in the three-beam Wollaston prism, two crystal bodies are joined so that the optical axis of the first crystal body and the optical axis of the second crystal body are non-perpendicular, so that the crystal body is It was necessary to cut out along a complicated crystal orientation.

Further, when changing the polarization separation ratio, it is necessary to change the direction in which the crystal is cut out. Therefore, when manufacturing a three-beam Wollaston prism of various specifications, its manufacturing control and different crystals are used. It was not easy to manage the inventory of crystals cut out in the azimuth direction.

Therefore, according to the present invention, the incident light beam is converted into three beams.
It is an object of the present invention to provide an inexpensive and easy-to-manufacture double-image prism for separating a light beam of a book and an optical pickup device using the same.

[0010]

A double-image prism according to claim 1 is a double-image prism in which three crystal bodies are joined, and the first crystal body and the second crystal body are joined together. Face and
The joint surface between the second crystal body and the third crystal body is parallel, the direction vector of the optical axis of the first crystal body and the direction vector of the optical axis of the third crystal body are substantially parallel, and Both of the two direction vectors are substantially perpendicular to the normal vector of the entrance surface of the double image prism, and the second crystal body is a crystal body in which the light traveling along the optical axis direction exhibits optical rotatory power. It is characterized in that the direction vector of the optical axis is substantially parallel to the normal vector of the entrance surface of the double image prism.

According to a second aspect of the present invention, there is provided a double image prism in which three crystal bodies are cemented together, wherein a cemented surface between the first crystal body and the second crystal body, and a second crystal body. And the joint surface of the third crystal body are parallel to each other, the direction vector of the optical axis of the first crystal body and the direction vector of the optical axis of the third crystal body are substantially perpendicular, and the two direction vectors are Both are almost perpendicular to the normal vector of the entrance surface of the compound image prism, and the second crystal body is a crystal body in which the light traveling along the optical axis direction exhibits optical rotatory power. It is characterized in that it is substantially parallel to the normal vector of the image prism entrance surface.

According to a third aspect of the present invention, there is provided a double-image prism in which three crystal bodies are joined together, and a joint surface between the first crystal body and the second crystal body and a second crystal body are provided. And the third crystal body are parallel to each other, the direction vector of the optical axis of the first crystal body and the direction vector of the optical axis of the third crystal body are substantially parallel, and the two direction vectors are Both are substantially perpendicular to the normal vector of the entrance surface of the double image prism, and the second crystal is a crystal exhibiting optical rotatory power of light traveling along the optical axis direction, and the direction vector of the optical axis is the first vector. Crystal of 1 and 2
It is characterized in that it is substantially parallel to the normal vector of the joint surface with the crystal body.

According to a fourth aspect of the present invention, there is provided a double image prism in which three crystal bodies are cemented together, wherein a cemented surface between the first crystal body and the second crystal body and a second crystal body. And the joint surface of the third crystal body are parallel to each other, the direction vector of the optical axis of the first crystal body and the direction vector of the optical axis of the third crystal body are substantially perpendicular, and the two direction vectors are Both are substantially perpendicular to the normal vector of the entrance surface of the double image prism, and the second crystal is a crystal exhibiting optical rotatory power of light traveling along the optical axis direction, and the direction vector of the optical axis is the first vector. Crystal of 1 and 2
It is characterized in that it is substantially parallel to the normal vector of the joint surface with the crystal body.

According to a fifth aspect of the present invention, there is provided the double image prism of the first aspect.
In the compound image prism according to claim 4, the angle (smaller angle) between the direction vector of the optical axis of the second crystal and the normal vector of the incident surface of the compound image prism is 30 ° or less. It is characterized by.

According to a sixth aspect of the present invention, there is provided a double image prism according to the first aspect.
According to the fifth aspect of the present invention, in the double image prism, the second crystal body is quartz.

An optical pickup device according to a seventh aspect is
It utilizes the double image prism according to any one of claims 1 to 6.

According to the double image prism of the first to sixth aspects, with the above configuration, the incident light beam can be separated into three light beams on the emission side.

According to the optical pickup device of the seventh aspect, by using the double image prism of the first to sixth aspects, it is possible to provide an inexpensive and compact optical pickup device.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1A is a perspective view of a compound image prism of Embodiment 1, and FIG. 1B is a plan view thereof (a view seen from the direction B of FIG. 1A). In this double image prism, lithium niobate is added to the first crystal body 11 and the third crystal body,
Quartz is used for the second crystal body 12.

In the figure, the optical axis 11a of the first crystal body 11 and the optical axis 13a of the third crystal body 13 are the incident plane S.
The optical axis 12 a of the second crystal body 12 is parallel to the normal direction 14 and is perpendicular to the normal direction 14. The optical axis 13a of the third crystal body 13 is joined in a state where the optical axis 11a of the first crystal body 11 is rotated by 90 ° in a plane parallel to the incident surface S1.

Further, the entrance surface S1, the exit surface S4, and the joint surface S2
(Joint surface between first crystal body and second crystal body) and joint surface S
3 (bonding surface between the second crystal body and the third crystal body) are parallel to each other.

The double-image prism of this embodiment has a light beam 15
When used in an optical pickup device using a red semiconductor laser light having a wavelength of 780 nm as
The prism apex angle α of the first crystal body 11 and the third crystal body 13 is 9 ° so that the separation ratio of 6, 17, and 18 is 2: 1: 2 and the separation angle β is about 25 mrad.
In addition, the thickness d (thickness along the light transmission path) of the second crystal body was set to 2.2 mm.

The thickness d of the second crystal must be changed according to the wavelength of the light (it must be made thinner as the wavelength of the light used becomes shorter), and the prism apex angle It is necessary to set α appropriately according to the desired separation angle β (the separation angle β becomes larger as the prism apex angle α becomes larger).

Next, the operation of the compound image prism according to the present invention will be described with reference to FIGS. These figures show the optical axis of each crystal and the linearly polarized light component in each crystal when the double-image prism is viewed from the incident side (direction A in FIG. 1A).

As shown in FIG. 2 (a), the light beam of the linearly polarized light 15a incident on the incident surface S1 is an extraordinary ray parallel to the ordinary ray 21b perpendicular to the optical axis 11a of the first crystal body. 21a is separated. Here, when the angle formed by the optical axis 11a of the first crystal body and the polarization direction of the linearly polarized light 15a incident on the incident surface S1 is θ1, the amplitude W _o of the ordinary ray 21b in the first crystal body and amplitude _{W e} of the extraordinary ray 21a is given by the following equation.

W _o = sin θ1 (1) W _e = cos θ1 (2) The light separated into the ordinary ray 21b and the extraordinary ray 21a and transmitted through the first crystal is the first ray. Reaching the bonding surface S2 between the crystal body and the second crystal body (shown in (b)), the polarization direction rotates in the second crystal body, and the second crystal body and the third crystal body The rotation amount in the polarization direction (shown in (c)) becomes θ2 when it reaches the junction surface S3 of. Here, the direction in which the polarization direction rotates in the second crystal body depends on whether the material crystal is right-handed or left-handed.

FIG. 3 shows that the ordinary ray and the extraordinary ray which are separated into the ordinary ray and the extraordinary ray in the first crystal body, and the ordinary ray and the extraordinary ray whose polarization directions are rotated in the second crystal body are It shows how the ordinary ray and the extraordinary ray are separated again. As shown in (a), the extraordinary ray 21a separated in the first crystal is the third ray
Ordinary ray 22b perpendicular to the optical axis 13a in the crystal of
And the extraordinary ray 22a parallel to On the other hand, the first
The ordinary ray 21a separated in the crystal body is separated into an ordinary ray 23b perpendicular to the optical axis 13a and an extraordinary ray 23a parallel to the optical axis 13a in the third crystal body as shown in (b).

Therefore, the light beam transmitted through the third crystal is (m1) the light transmitted through the first crystal and the third crystal as ordinary rays (23b in FIG. 3) (m2) Light transmitted through the first crystal as an ordinary ray and through the third crystal as an extraordinary ray (23a in FIG. 3) (m3) The first crystal as an extraordinary ray and the ordinary ray in the third crystal (22b in FIG. 3) (m4) Light transmitted as extraordinary rays through the first crystal body and the third crystal body (22a in FIG. 3) is divided into four types. Further, the amplitude _W m1 _{to W-m4} of light (m1) ~ (m4) is given by the following equation.

[0030] _{W m1 = W o sinθ2 = sinθ1} · sinθ2 ··· (3) W m2 = W o cosθ2 = sinθ1 · cosθ2 ··· (4) W m3 = W e cosθ2 = cosθ1 · cosθ2 ··· (5 ) W _m4 = W _e sin θ2 = cos θ1 · sin θ2 (6) Here, the light corresponding to the above (m1) and (m4) travels the same path and becomes a central light beam on the exit side, (M
2) and (m3) become light beams on both sides of the light beam. Therefore, the separation ratio of the three light beams a: b: c (a is m2
, B corresponds to m1 and m4, and c corresponds to m3) are given by the following equations.

A: b: c = sin ² θ1 · cos ² θ2: (sin ² θ1 · sin ² θ2 + cos ² θ1 · sin ² θ2): cos ² θ1 · cos ² θ2 (7) Usually, θ1 is set to 45 °, and the separation ratio at that time is given by the following equation.

A: b: c = cos ² θ2: 2sin ² θ2: cos ² θ2 (8) Therefore, if the rotation amount θ2 in the polarization direction of the second crystal is set to 26.6 °. , The separation ratio a: b: c is 2:
It will be 1: 2.

In the crystal (second crystal), a wavelength of 78
When 0 nm light is transmitted (travels in the optical axis direction), the polarization direction of light rotates by about 12 ° per 1 mm. Further, in this embodiment, the thickness d of the second crystal body is set to 2.2.
mm, the rotation amount θ2 in the polarization direction in the second crystal is set to 26.6 °, and the separation ratio a: b: c
Is set to 2: 1: 2, but the thickness d of the second crystal is d
Is another value (other than 2.2 mm), the light beam incident on this double image prism is split into three light beams.
Then, the separation ratio a: b: c at this time is given by Expression 8 (here, θ2≈12 × d).

Further, as is apparent from the above description, the second
The rotation amount θ2 in the polarization direction in the second crystal body changes according to the thickness d of the crystal body, and the separation ratio also changes accordingly. Therefore, it is necessary to set the thickness d of the second crystal body according to the desired separation ratio. Further, the rotation amount θ2 in the polarization direction per unit length changes depending on the wavelength of light (the rotation amount θ2 in the polarization direction per unit length increases as the wavelength of light becomes shorter), but the wavelength 780 nm 1 to 4 when
mm, 0.6 to 2.5 mm when the wavelength is 630 nm
If the wavelength is 500 nm and the wavelength is 500 to 0.4 mm, the separation ratio that can be used in an ordinary optical pickup device can be obtained.

Further, in the above embodiment, quartz is used as the second crystal body, but other material exhibiting optical activity may be used.

(Embodiment 2) FIG. 4A is a perspective view of a compound image prism of Embodiment 2, and FIG. 4B is a plan view thereof (a view seen from the B direction in FIG. 4A). As shown in the figure, the double image prism of the present embodiment is the third crystal body 1 of the first embodiment.
The optical axis 13a of the first crystal body 11
It is in the same direction as 1a. Therefore, since the first crystal body 11 and the third crystal body 13 in the present example are the same prism, manufacturing is easier and part management is further simplified.

In the double image prism of this embodiment, the entrance surface S1
The light beam incident on the optical axis reaches the junction surface S3 between the second crystal body and the third crystal body and operates in the same manner as the double-image prism of the first embodiment.

However, in the double-image prism of Example 1, the optical axis 13a of the third crystal body 13 is rotated by 90 ° in the plane parallel to the incident surface S1 with respect to the optical axis 11a of the first crystal body 11. Since they are cemented in the state, the light that was an ordinary ray in the third crystal body of the double-image prism of Example 1 becomes an extraordinary ray in the third crystal body of the double-image prism of this embodiment. The light which is an extraordinary ray in the third crystal body of the double image prism of the first embodiment becomes an ordinary ray in the third crystal body of the double image prism of the present embodiment.

As described above, in this embodiment, the ordinary ray and the extraordinary ray in the third crystal body are opposite to those in the first embodiment. However, also in the case of this embodiment, the third crystal body The light beam passing through is (m1) light that has passed through the first and third crystal bodies as an ordinary ray. (M2) an ordinary light ray that passes through the first crystal body and an inside ray of the third crystal body. Light transmitted as extraordinary ray (m3) Light transmitted through the first crystal body as extraordinary ray and transmitted through the third crystal body as ordinary ray (m4) Extraordinary ray through the first crystal body and the third crystal body There are four types of light that are transmitted as. Further, the amplitudes W _{m1 to} W _m4 of the light of (m1) to (m4) were changed as in the following formula because the ordinary ray and the extraordinary ray in the third crystal body were opposite to those in the case of Example 1. It

W _m1 = W _o cos θ 2 = sin θ 1 · cos θ 2 (9) W _{m 2} = W _o sin θ 2 = sin θ 1 · sin θ 2 (10) W _{m 3} = W _e sin θ 2 = cos θ 1 · sin θ 2 (11) ) W _m4 = W _e cos θ2 = cos θ1 · cos θ2 (12) Here, the light corresponding to the above (m1) and (m4) travels the same path and becomes a central light beam on the exit side, (M
2) and (m3) become light beams on both sides of the light beam. Therefore, the separation ratio of the three light beams a: b: c (a is m2
, B corresponds to m1 and m4, and c corresponds to m3) are given by the following equations.

A: b: c = sin ² θ1 · sin ² θ2: (sin ² θ1 · cos ² θ2 + cos ² θ1 · cos ² θ2): cos ² θ1 · sin ² θ2 (13) The separation ratio when set to 45 ° is given by the following equation.

A: b: c = sin ² θ2: 2cos ² θ2: sin ² θ2 (14) As is clear from the above equation 14, in this embodiment, the same separation as in the first embodiment is performed. To obtain the ratio a: b: c,
If the value of θ2 in the first embodiment is θ2 _k , the value of θ2 must be 90 ° −θ2 _k in the present embodiment. Further, as is clear from the equations 8 and 14, when it is desired to increase the separation ratio of the central light beam (when it is desired to increase a: b: c to more than 1: 2: 1), the duplication of the present embodiment is performed. When the image prism configuration can reduce the thickness d of the second crystal body and want to reduce the separation ratio of the central light beam (when a: b: c is desired to be less than 1: 2: 1). In particular, the thickness d of the second crystal body can be made smaller in the double-image prism configuration of the first embodiment.

(Example 3) FIG. 5A is a perspective view of a compound image prism of Example 3, and FIG. 5B is a plan view of the same (viewed from the direction B of FIG. 5A). As shown in the figure, the double image prism of the present embodiment is the second crystal body 1 of the second embodiment.
The direction of the second optical axis 12a is set to be the direction perpendicular to the joint surfaces S2 and S3. In this case, the second crystal body 12 is a parallel plate whose optical axis is perpendicular to the joint surface, and therefore the manufacturing is easier.

In the case of the present embodiment, the rotation amount θ2 in the polarization direction of the second crystal body is the value of d'cosα, where d'is the thickness d'in the direction perpendicular to the joint surface of the second crystal body 12. Change according to.

The angle formed by the optical axis of the light transmitted through the second crystal body 12 and the optical axis 12a of the second crystal body 12 is defined by the normal direction 14 of the incident surface S1 and the second crystal body 12. Optical axis 1
It substantially coincides with the angle δ formed by 2a. Since δ coincides with the prism apex angle α, if α is about 30 ° or less, then δ becomes 30 ° or less. In this case, the second crystal 1
2 and the optical axis 12 of the second crystal 12
The same effect as when a is parallel is obtained.

In the above-described double image prism of the present invention (for example, Examples 1 to 3), the angle formed by the optical axis 11a of the first crystal body 11 and the normal direction 14 of the incident surface S1 and The angle formed by the optical axis 13a of the crystal body 13 of No. 3 and the normal direction 14 of the incident surface S1 is preferably 90 °, but the same effect can be obtained if it is about 90 ± 5 °.
Further, the angle formed by the optical axis 12a of the second crystal body 12 and the normal direction 14 of the incident surface S1 is preferably 0 °, but if it is about 0 ± 30 °, the same effect can be obtained. To be

Further, the angle formed by the optical axis 11a of the first crystal body 11 and the optical axis 13a of the third crystal body 13 is preferably 0 ° or 90 °, but the variation of the separation ratio is allowed. There is no hindrance to the operation if it is within the range.

(Embodiment 4) As shown in FIG. 6, in a conventional optical pickup device using a 3-beam Wollaston prism, the 3-beam Wollaston prism is used as a compound image prism as shown in the above embodiment. Even if it is replaced by 50, the same optical pickup device can be configured. Here, the light beam incident on the compound image prism 50 is separated into three light beams on the exit side as in the case of using the three-beam Wollaston prism, and the central light beam is used for focusing error signal detection. , The light beams on both sides are used for information signal detection.

Since the polarization direction of the light beam reflected by the optical disk rotates according to the magnetization direction of the recording section, the polarization direction of the light beam incident on the compound image prism 50 changes according to the recording signal. . When the polarization direction of the incident light beam changes, the ratio of the separation ratio a: b: c of a: c corresponding to the light beam for detecting the information signal changes, so that the recording signal can be detected. .

[0050]

As described above, the double-image prism according to the present invention is made by joining the crystal bodies cut out in the simple crystal orientation, so that the manufacturing becomes easy and the parts management can be simplified. Furthermore, since the setting of the separation ratio of the three beams can be changed simply by changing the thickness of the second crystal, it is possible to flexibly deal with the production of compound image prisms of different specifications with different separation ratios. can do.

By using this double-image prism, it is possible to provide an inexpensive and compact optical pickup device.

[Brief description of drawings]

1A and 1B are a perspective view and a plan view showing a double image prism of Example 1. FIG.

FIG. 2 is a diagram for explaining the operation of the double image prism of the first embodiment.

FIG. 3 is a diagram for explaining the operation of the double image prism of the first embodiment.

4A and 4B are a perspective view and a plan view showing a double image prism of Example 2. FIG.

5A and 5B are a perspective view and a plan view showing a double image prism of Example 3. FIG.

FIG. 6 is a diagram showing an optical pickup device using a double image prism according to the present invention.

FIG. 7 is a perspective view showing a three-beam Wollaston prism.

FIG. 8 is a diagram showing an optical pickup device using a 3-beam Wollaston prism.

FIG. 9 is a plan view showing a conventional double image prism.

[Explanation of symbols]

Claims (7)

[Claims] 1. A double-image prism in which three crystal bodies are joined, wherein a joining surface between the first crystal body and the second crystal body and a second crystal body and the third crystal body are joined together. First, parallel to the joint surface
The optic axis direction vector of the crystal body and the optic axis direction vector of the third crystal body are substantially parallel to each other, and the two direction vectors are both substantially perpendicular to the normal vector of the entrance plane of the double image prism, The second crystal body is a crystal body in which light traveling along the optical axis direction exhibits optical rotatory power, and the direction vector of the optical axis is substantially parallel to the normal vector of the entrance plane of the double image prism. Characteristic compound image prism. 2. A double-image prism in which three crystal bodies are joined, wherein a joint surface between the first crystal body and the second crystal body, and a second crystal body and a third crystal body are joined. First, parallel to the joint surface
The optical axis direction vector of the crystal body of and the optical axis direction vector of the third crystal body are substantially perpendicular to each other, and the two direction vectors are both substantially perpendicular to the normal vector of the entrance plane of the double image prism, The second crystal body is a crystal body in which light traveling along the optical axis direction exhibits optical rotatory power, and the directional vector of the optical axis is substantially parallel to the normal vector of the entrance plane of the double image prism. A compound image prism. 3. A compound image prism in which three crystal bodies are cemented, wherein a cemented surface between the first crystal body and the second crystal body and a second crystal body and the third crystal body are joined. First, parallel to the joint surface
The optic axis direction vector of the crystal body and the optic axis direction vector of the third crystal body are substantially parallel to each other, and the two direction vectors are both substantially perpendicular to the normal vector of the entrance plane of the double image prism, The second crystal body is a crystal body in which light traveling along the optical axis direction exhibits optical rotatory power, and a direction vector of the optical axis is a normal line of a bonding surface between the first crystal body and the second crystal body. A compound image prism characterized by being almost parallel to the vector. 4. A compound image prism in which three crystal bodies are joined, wherein a joint surface between the first crystal body and the second crystal body and a second crystal body and the third crystal body are joined together. First, parallel to the joint surface
The optical axis direction vector of the crystal body of and the optical axis direction vector of the third crystal body are substantially perpendicular to each other, and the two direction vectors are both substantially perpendicular to the normal vector of the entrance plane of the double image prism, The second crystal body is a crystal body in which light traveling along the optical axis direction exhibits optical rotatory power, and a direction vector of the optical axis is a normal line of a bonding surface between the first crystal body and the second crystal body. A compound image prism characterized by being almost parallel to the vector. 5. The angle (smaller angle) formed by the direction vector of the optical axis of the second crystal and the normal vector of the entrance plane of the double image prism is 30 ° or less. The compound image prism according to claim 4. 6. The double image prism according to claim 1, wherein the second crystal is quartz. 7. An optical pickup device using the double image prism according to claim 1. Description: