JP2801746B2 - Optical information recording / reproducing device and double diffraction grating - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus and a double diffraction grating which perform information recording and the like using an optical information recording medium and perform tracking servo and focus servo. .

2. Description of the Related Art Conventionally, in an optical information recording / reproducing device, as a device using a diffraction grating as a light beam separating means, a device disclosed in JP-A-61-230634 as a first conventional example is first disclosed. is there. That is, as shown in FIG. 36, the laser light emitted from the semiconductor laser 1 is collimated by the collimator lens 2 and enters the polarization beam splitter 3. In this case, since the polarization direction of the incident light is set to be parallel to the groove of the polarization beam splitter 3, it is diffracted and enters the quarter-wave plate 4 to become a circularly polarized wave, and the objective lens 5
And irradiates the optical disk 6 as an optical information recording medium, thereby recording information and the like. Also,
The reflected light from the optical disk 6 is converted into a linearly polarized wave by the quarter-wave plate 4, thereby passing through the polarization beam splitter 3, being guided to the signal detection optical system 7, and entering the critical angle diffraction grating 8. In this case, the incident light undergoes two critical angle diffractions and total reflection, becomes a diffracted light, enters the four-divided light-receiving element 9, and is detected by the divided light-receiving elements 9 to obtain information. And a focus error signal and a track error signal are detected.

Next, as a second conventional example, as shown in FIG. 37, there is one using a dual type diffraction grating 10. That is, the emitted light from the semiconductor laser 11 is collimated by the collimating lens 12, and then condensed by the objective lens 15 reflected by the beam splitter 14 through two shaping prisms 13 and irradiated on the magneto-optical disk 16. By doing so, information recording and the like are performed. The reflected light from the magneto-optical disk 16 passes through the beam splitter 14 and is guided to the signal detection optical system 17, where it is focused by the condenser lens 18 and formed on both surfaces of the dual-type diffraction grating 10. The light is transmitted or diffracted through the grating 10a. Of these, 0 passed straight through
The next light T is guided to the four-divided light receiving element 19a, while the diffracted primary light K is guided to the two-divided light receiving element 19b. As a result, a magneto-optical signal serving as a reproduction signal is detected based on a light amount difference between the zero-order light T and the primary light K, and a focus error signal is detected using the zero-order light T by an astigmatism method. The error signal is detected using the primary light K by a push-pull method or the like.

Next, a third conventional example will be described. Light emitted from a semiconductor laser as a laser light source is collimated by a collimating lens, and the parallel light is reflected by an optical path separating means and condensed by an objective lens to form a magneto-optical disk as an optical information recording medium. The surface is illuminated, thereby recording information. The reflected light from the magneto-optical disk passes through the optical path separating means, is guided into the signal detection optical system, and is detected by the light receiving element, thereby reproducing information and detecting a focus error signal and a track error signal. Is going.

A fourth conventional example will be described with reference to FIG. Light emitted from the semiconductor laser 20 is reflected by a diffraction grating 22 formed on one surface of a light beam splitting element 21 and a collimator lens 23
After being collimated, the light is condensed by the objective lens 24 and irradiated onto the surface of the magneto-optical disk 25, thereby recording information. The reflected light from the magneto-optical disk 25 is transmitted through the objective lens 24 and the collimating lens 23 sequentially, and then transmitted through the diffraction grating 22 of the light beam separating element 21 to be separated into the 0th order light T and the 1st order light K. After being reflected by the total reflection surface 26 formed on the back surface, the light is again transmitted through the diffraction grating 22 and emitted to the outside. As a result, the 0th-order light T and the 1st-order light K have different optical path lengths from each other, and are guided to the two light receiving elements 27 disposed in the same plane as the semiconductor laser 20, thereby detecting various signals. It can be performed.

Problems to be Solved by the Invention First, the first problem will be described. In the case of the first conventional example as shown in FIG. 36, a write-once optical disc or CD can be applied to the optical information recording medium, but since there is no magneto-optical signal detection function, a rewritable optical disc is not available. It cannot be used as a head.

Next, the second problem will be described. In the case of the second conventional example as shown in FIG. 37, a dual-type diffraction grating is used, and the emission directions of the 0th-order light T and the 1st-order light K formed therethrough are directed substantially in the same direction. Therefore, it is possible to save a certain amount of space in the signal detection optical system 17, however, when viewed as a whole, the optical components such as the beam splitter 14 and the condenser lens 18 remain and are sufficiently small. There is a problem that weight reduction and weight reduction cannot be achieved.

Next, the third problem will be described. In the case of the third conventional example, an optical path separating means is used to separate the light flux of the emitted light emitted from the laser light source and the reflected light from the magneto-optical disk. In general, many light beam separating means use a prism such as a beam splitter. However, in recent years, in order to shorten the access time, it has become important to reduce the size and weight of the optical pickup optical system. As one means for solving such a problem, there is an apparatus using a dual diffraction grating having diffraction gratings formed on both front and back surfaces as the light beam separating means as described above. By using this dual diffraction grating, the number of components in the entire optical pickup optical system is reduced, the space is omitted, and seek movement is speeded up.

However, the diffraction grating formed in such a dual type diffraction grating is susceptible to wavelength fluctuations due to its properties, and the surface on which the diffraction grating is formed is brittle, and the grating shape is likely to be lost. Therefore, the use of such a diffraction grating degrades the accuracy of the reflected, transmitted, and diffracted wavefronts and increases the size of the condensed light spot. As a result, it is not possible to perform accurate information recording and reproduction. Occurs.

Next, the fourth problem will be described. In the case of the second conventional example as shown in FIG. 37, the layout of the entire optical system is
Since it is divided into the emission optical system A and the signal detection optical system B, there is a problem that the number of parts is increased as a whole, and as a result, the cost is increased.

Next, the fifth problem will be described. In the case of the fourth conventional example as shown in FIG. 38, the semiconductor laser 20 and the light receiving element 27
And a single diffraction grating 22
As in the case of a single diffraction grating, the variation in the diffraction angle with respect to the variation in the wavelength is reduced. However, since the separation between the irradiation light to the magneto-optical disk 25 and the reflected light from the magneto-optical disk 25 is determined by the thickness of the substrate 28 of the optical path separating element 21, the distance between the light-emitting point and the light-receiving point and the focus sensitivity Therefore, there is a problem that the degree of freedom of design is narrowed, and adjustment, assembling, and manufacturing are severe. Further, in this case, there is a problem that light utilization efficiency is reduced due to reflection on the surface of the diffraction grating 22.

Next, the sixth problem will be described. In the case of the fourth conventional example as shown in FIG. 38, by disposing the light beam separating element 21 having the diffraction grating 22 and the total reflection surface 26, the number of components of the optical system is reduced, and the space is reduced. Can be achieved. However, in this case, the two light receiving elements 27 for detecting the transmitted light T and the diffracted light K are mounted on one substrate in such a manner that they are arranged at positions on both sides of the semiconductor laser 20. Therefore, when mounting the two light receiving elements 27
Positioning of the semiconductor laser 20 with the semiconductor laser 20, that is, fine adjustment is extremely difficult. In this case, the semiconductor laser
Since the distance between the light receiving element 27 and the light receiving element 27 differs from each other, a separate height adjusting device is required. As described above, since the light receiving elements 27 are arranged on both sides of the semiconductor laser 20, there is a problem that the assembling adjustment is troublesome and troublesome.

Means for Solving the Problems According to the invention described in claim 1, light emitted from a laser light source is condensed by an objective lens and irradiated on an optical information recording medium to record information. In an optical information recording / reproducing apparatus that detects a reproduction signal for information, a track error signal, and a focus error signal by detecting reflected light of the laser beam, the light emitted from the laser light source is directed toward the objective lens. Providing a first diffractive member having a semi-reflective film on the path, disposing a second diffractive member on the optical path where the reflected light from the optical information recording medium has passed through the first diffractive member, the first diffractive member and A light receiving element for detecting the transmitted light and the diffracted light obtained by being separated by passing through the second diffraction member was provided.

According to the second aspect of the present invention, the light emitted from the laser light source is collimated by a collimator lens, and the collimated light is condensed by an objective lens and irradiated on an optical information recording medium to record information. In an optical information recording / reproducing apparatus for reproducing information, detecting a track error signal, and detecting a focus error signal by guiding the reflected light from the optical information recording medium to a light receiving element, the optical information recording / reproducing apparatus has a light path side of light emitted from the laser light source. A surface diffraction grating having a semi-reflective film for reflecting a part of the light incident on the surface to be located, and a light beam separating means having a back surface diffraction grating formed on a surface opposite to this surface; The light-receiving element was disposed on the optical path on the side where is formed.

According to the third aspect of the present invention, the light emitted from the laser light source is collimated by a collimating lens, and the collimated light is condensed by an objective lens and irradiated on an optical information recording medium to record information. In an optical information recording / reproducing apparatus for reproducing information, detecting a track error signal, and detecting a focus error signal by guiding reflected light from the optical information recording medium to a light receiving element, an optical path side of light emitted from the laser light source A diffraction grating having a semi-reflective film that reflects a part of the light incident on the surface located on the surface is formed, and a light beam separating unit having a total reflection surface formed on a surface on the side opposite to this surface is provided, and the laser light source of the laser light source is provided. The light receiving element was arranged on the optical path on the side provided.

According to the fourth aspect of the present invention, the light emitted from the laser light source is collimated by a collimating lens, and the parallel light is condensed by an objective lens and irradiated on an optical information recording medium to record information. In an optical information recording / reproducing apparatus that reproduces information by guiding reflected light from an optical information recording medium to a light receiving element in a signal detection optical system and detects a focus error signal and a track error signal, the laser light emitted from the laser light source is used. On the optical path of the light, a semi-reflective first substrate having a first diffractive member formed on one surface and a surface of the first substrate on which the first diffractive member is formed are opposed to each other via a spacer. A double diffraction grating element comprising a transparent second substrate on which a second diffraction member was formed was disposed on the surface on the other side.

According to the fifth aspect of the present invention, the light emitted from the laser light source is collimated by a collimator lens, and then condensed by an objective lens to irradiate an optical information recording medium to record information. In an optical information recording / reproducing apparatus which detects reflected light from a medium to reproduce information, and detects a track error signal and a focus error signal, a wedge is formed on an optical path between the collimating lens and the objective lens. A diffraction grating having a semi-reflection film is formed on one surface of the non-parallel substrate, and a light beam separation means having a total reflection surface formed on the other surface is provided, and light reflected by this light beam separation means passes through the collimating lens. Two light receiving elements for detecting reflected light from the optical information recording medium were provided on the optical path on the side of the laser light source.

According to the sixth aspect of the present invention, the light emitted from the laser light source is collimated by a collimating lens, and then condensed by an objective lens to irradiate an optical information recording medium to record information. In an optical information recording / reproducing apparatus that detects reflected light from a medium and reproduces information or detects a track error signal and a focus error signal, a non-parallel substrate is provided on an optical path between the collimator lens and the objective lens. A light beam separating means having a diffraction grating having a semi-reflective film on one surface and a total reflection surface in the form of a wedge prism formed on the other surface is provided, and the light reflected by the light beam separating means passes through the collimating lens. Two sets of two light receiving elements for detecting the reflected light from the optical information recording medium were provided on the optical path on the side of the laser light source.

In the invention according to claim 7, information is recorded by condensing light emitted from a laser light source by an objective lens and irradiating the optical information recording medium, and detecting reflected light from the optical information recording medium. In the optical information recording / reproducing apparatus for reproducing information and detecting a track error signal and a focus error signal, a diffraction grating is provided on one surface of a substrate on an optical path while light emitted from the laser light source is directed to the objective lens. And a light beam separating means having a semi-reflective film on one surface and a total reflection surface formed on the other surface, and a first light beam on the optical path of the primary light diffracted by the light beam separating device and traveling. A light receiving element is provided, and a second light receiving element is provided on the optical path of the zero-order light which is refracted by the light beam separating means and travels.

According to an eighth aspect of the present invention, in the configuration of the seventh aspect of the present invention, a collimating lens is disposed on an optical path while the light emitted from the laser light source travels toward the light beam separating means.

According to the ninth aspect of the present invention, information is recorded by emitting light emitted from a laser light source through a collimator lens by an objective lens and irradiating the optical information recording medium with the light. In the optical information recording / reproducing device which detects reflected light from the optical disc to reproduce information, and detects a track error signal and a focus error signal, the light emitted from the output light passes through the collimating lens and travels toward the objective lens. A diffraction grating is formed on one surface of the substrate on the road, and a wedge-shaped light beam separating means having a semi-reflective film on the surface and a total reflection surface formed on the other surface is provided, and the emitted light is reflected by the semi-reflective film. The wedge-shaped light beam separating means has a wedge shape so that one main beam obtained by reflection and two sub-beams obtained by transmitting through the semi-reflective film are guided to the optical information recording medium. Set the corner.

According to a tenth aspect of the present invention, in the configuration of the ninth aspect of the present invention, of the main beam and the sub-beam reflected by the optical information recording medium, the main beam and the sub-beam are received.
Two three-divided light receiving elements for receiving the sub-beam
Two non-divided light receiving elements were provided.

In the invention according to claim 11, after the light emitted from the laser light source is collimated by the collimating lens, the light is condensed by the objective lens and irradiated on the surface of the optical information recording medium to record information, and the optical information is recorded. In an optical information recording / reproducing apparatus which detects a reflected light from a recording medium by a light receiving element and detects a focus error signal and a track error signal,
On the optical path while the light emitted from the laser light source is directed to the collimating lens, a light beam separating means having a transmission type diffraction grating and a high reflection surface disposed at an angle to the transmission type diffraction grating. Provided.

In the invention according to claim 12, a semi-reflective first substrate having a first diffractive member formed on one surface thereof is opposed to a surface of the first substrate on which the first diffractive member is formed via a spacer. A double diffraction grating consisting of a transparent second substrate on which the first diffraction member was formed was provided on the surface on the side where it was arranged.

According to the first aspect of the present invention, the light emitted from the laser light source is reflected by the semi-reflective film formed on the first diffraction member, then reflected by the optical information recording medium, and guided again to the first diffraction member. By passing through the first diffractive member and the second diffractive member, is separated into transmitted light and diffracted light, and these two separated lights are detected by the light receiving element,
It is possible to reproduce information and detect a track error signal and a focus error signal.

According to the second aspect of the present invention, the light emitted from the laser light source is reflected by the semi-reflective film formed on the surface diffraction grating of the light beam separating means, reflected by the optical information recording medium, and guided again to the surface diffraction grating. Then, by passing through the back-side diffraction grating, the light is separated into the 0th-order light and the 1st-order light having the emission directions in almost the same direction, and emitted in almost the same direction. These two separated lights are detected by the light receiving element. As a result, it is possible to reproduce information and detect a track error signal and a focus error signal.

According to the third aspect of the present invention, the light emitted from the laser light source is reflected by the semi-reflective film formed on the surface diffraction grating of the light beam separating means, then reflected by the optical information recording medium, and guided again to the surface diffraction grating. It is further reflected by the total reflection surface, passes through the surface diffraction grating again, and is detected by the light receiving element arranged in the same plane as the laser light source,
It is possible to reproduce information and detect a track error signal and a focus error signal.

According to the fourth aspect of the present invention, the light emitted from the laser light source is reflected by the semi-reflective first substrate of the double diffraction grating element, collimated by the collimating lens, and reflected by the optical information recording medium. Again, guided to the double diffraction grating element, separated by the first diffractive member of the first substrate into two lights of transmitted light and diffracted light, and after passing through both spacers, the transmitted light is The transmitted light passes through the second diffraction grating as it is, and the diffracted light is further diffracted by the second diffraction grating, passes through the double diffraction grating in a separated state, and is guided into the signal detection optical system, so that information can be reproduced or reproduced. , A focus error signal and a track error signal can be detected.

According to the fifth aspect of the present invention, the 0th-order light and the 1st-order light are spot-separated using the light beam separation means formed on both surfaces of the substrate in which the diffraction grating and the total reflection surface are not parallel. The layout design is easy, and since the light beam separating means is disposed between the collimator lens and the objective lens, the collimated light is incident on the diffraction grating, thereby providing a high-performance Since the polarization separation can be performed, the light use efficiency can be improved.

According to the invention of claim 6, it is possible to detect a focus error signal by using the double knife edge method by making the total reflection surface into a wedge prism shape and arranging two sets of two light receiving elements. As a result, the assembling accuracy can be further reduced than before, and a stable signal can always be detected.

According to the seventh aspect of the present invention, the light emitted from the laser light source is reflected by the semi-reflective film of the light beam separating means, guided to the optical information recording medium, thereby recording information, and from the optical information recording medium. The reflected light passes through the semi-reflective film of the light beam separating means and is separated into 0th-order light and 1st-order light. These 0th-order light and 1st-order light pass through the diffraction grating other than the semi-reflective film and pass through the outside. And the light is guided to the first and second light receiving elements, respectively, to reproduce information and detect signals, whereby the 0th-order light and the 1st-order light separated by the diffraction grating of the light beam separating means can be obtained. When light is reflected by the total reflection surface and emitted to the outside, the light passes through a transmission region other than the semi-reflective film in the diffraction grating, so that the light use efficiency can be further improved as compared with the related art.

According to the eighth aspect of the present invention, since the light emitted from the laser light source is guided to the light beam separating means after passing through the collimator lens, only parallel light out of the emitted light is incident on the diffraction grating, so that high performance is achieved. Polarization separation can be performed, thereby further increasing the light use efficiency.

According to the ninth aspect of the present invention, out of the light whose outgoing light is incident on the semi-reflective film formed on the surface of the diffraction grating of the light beam separating means, the reflected light by the semi-reflective film is used as a main beam and the transmitted light is used as a sub beam. Therefore, it is possible to perform three-beam tracking, and this allows the apparatus to be compatible with various apparatuses using a magneto-optical disk, CD, or the like as an optical information recording medium. Can be spread.

According to the tenth aspect of the present invention, the main beam and the sub beam reflected by the optical information recording medium are all received by the respective light receiving elements without waste, so that the light use efficiency can be further improved as compared with the related art.

According to the invention of claim 11, by providing a light beam separating means having a transmission type diffraction grating and a high reflection surface disposed at a constant angle to the transmission type diffraction grating, the transmitted light separated by the light beam separating means and Since the optical path to the reflected light can be changed, there is no need to provide light receiving elements on both sides of the laser light source as in the past, thereby separately creating a substrate for the laser light source and a substrate for the light receiving element. The mounting and adjustment can be simplified and the work efficiency can be increased as compared with the related art.

According to the invention of claim 12, since the first diffraction member and the second diffraction grating are configured to face each other, the surface of the diffraction grating is sealed inside, whereby the grating shape is stabilized and two diffraction gratings are formed. Because the grids are so close,
It is possible to make it difficult to receive the shift fluctuation of the primary light due to the wavelength fluctuation.

Embodiment One embodiment of the invention described in claims 1 and 2 is shown in FIGS.
Description will be made based on the drawings. This embodiment addresses the first problem and the second problem.

On an optical path of light emitted from a semiconductor laser 30 as a laser light source, a dual type diffraction grating 31 as a light beam separating means is provided. In this dual type diffraction grating 31, a surface diffraction grating 33 as a first diffraction member having a semi-reflective film 32 in a surface layer portion for reflecting a part of light incident on a surface located on the semiconductor laser 30 side is formed. On the surface facing the front diffraction grating 33, a back diffraction grating 34 as a second diffraction member is formed. The diffraction efficiencies of the diffraction gratings 33 and 34 formed on both the front and back surfaces change according to the polarization direction. A collimating lens 3 is provided on the optical path on the side where the surface diffraction grating 33 is formed.
5. An objective lens 36 and a magneto-optical disk 37 as an optical information recording medium are sequentially arranged. Further, a light receiving element 38 for detecting a focus error signal, a track error signal and the like is provided on the optical path on the side where the back diffraction grating 34 is formed. In such a configuration, the semiconductor laser 30
Is reflected by the semi-reflective film 32 on the surface diffraction grating 33. The semi-reflective film 32 is
Is irradiated with a desired optical power. The reflected light becomes parallel light by the collimator lens 35. This parallel light is simply reflected light, and the surface diffraction grating 33
Therefore, no aberration occurs, and thus the shape of the surface diffraction grating 33 does not need to be particularly curved or modulated. The parallel light is condensed by the objective lens 36 and is irradiated on the surface of the magneto-optical disk 37 in a spot state. The irradiated light is reflected by the Kerr effect in a state where the polarization direction is inclined according to the information signal on the magneto-optical disk 37, returns to the collimating lens 35 again, and converges from the collimating lens 35. It becomes light and the surface diffraction grating 33
Is incident on. In this case, the dual-type diffraction grating 31 is arranged such that the diffraction gratings 33 and 34 formed on the front and back surfaces thereof have a black angle with respect to the reflected light from the magneto-optical disk 37. That is, as shown in FIG. 5, the diffraction gratings 33 and 34 formed on the front and back surfaces are formed so as to form an angle of 45 ° with respect to the polarization direction of the light from the semiconductor laser 30. Then, the light incident on the front diffraction grating 33 is separated into transmitted light T and diffracted light K, and then is incident on the back diffraction grating 34. This back surface diffraction grating 34 is a transmission type diffraction grating,
The grating direction is the same as that of the surface diffraction grating 33. That is, the transmitted light (zero-order light) of the front diffraction grating 33 is transmitted to the back diffraction grating.
Even at 34, the light passes through as it is to become the zero-order light, and the surface diffraction grating 33
(First-order light) is also diffracted by the back-side diffraction grating 34 to become the first-order light K. In this way, the second order of the zero-order light T and the first-order light K
The light separated into two lights is received by the light receiving element 38, so that an optical information signal, a focus error signal, and a track error signal are detected from the light intensity difference between the 0th order light T and the 1st order light K. be able to.

In this case, as a method of detecting the focus error signal, first, as shown in FIG. 4 (a), astigmatism method using a parallel plate using the zero-order light T, and second, 4
As shown in FIG. 4B, the front diffraction grating 33 and the back diffraction grating 34 are modulated with a modulation pitch and the astigmatism method using the primary light K. Third, as shown in FIG. Next order light T and first order light K
And a beam size method utilizing an optical path difference existing between the two. As a method of detecting a track error signal,
In the case of the push-pull method, the light receiving element 38 is divided into two.
When the detection is performed by the sample servo method, the reflected light intensity can be detected by receiving the reflected light intensity by the light receiving element 38.

As described above, the dual diffraction grating 31 is provided to
By allowing the light to pass through multiple times, it is possible to reduce the displacement of the spot due to the wavelength variation, and to provide a semi-reflective semi-reflective film on one surface of one surface diffraction grating 33.
By forming the 32, the luminous flux separation between the emission optical system and the signal detection optical system can be performed by merely providing the dual type diffraction grating 31, thereby greatly reducing the number of optical components. Therefore, the configuration of the entire device can be reduced in size and weight, and the cost can be reduced.

Next, an embodiment of the present invention will be described with reference to FIG. This embodiment addresses the first problem and the second problem. Further, the same reference numerals are used for the same portions as those of the second aspect of the present invention.

The single-sided diffraction grating 39 as a light beam separating means has a diffraction grating 40 as a first diffraction member whose diffraction efficiency changes depending on the polarization direction on a surface located on the semiconductor laser 30 side,
On the surface opposite to the diffraction grating 40, a total reflection surface 41 as a second diffraction member is formed. The diffraction grating 40 is formed with a semi-reflective film 42 having a constant reflectance so that the magneto-optical disk 37 is irradiated with a desired optical power.
The light receiving element 38 is formed integrally with the semiconductor laser 30 on the side where the diffraction grating 40 is formed. The single-sided diffraction grating 39 is disposed so as to have a black angle with respect to the light reflected from the magneto-optical disk 37.

In such a configuration, light emitted from the semiconductor laser 30 is reflected by the semi-reflective film 42 on the diffraction grating 40, becomes parallel light by the collimator lens 35, is collected by the objective lens 36, and is converged on the surface of the magneto-optical disk 37. And an information signal is read. And this magneto-optical disk 37
Reflected light returns to the diffraction grating 40 again, and the incident light is separated into the 0th-order light T and the 1st-order light K, and is reflected by the total reflection surface 41 formed on the back surface. Diffraction grating 40
And is detected by the light receiving element 38 integrally formed with the semiconductor laser 30, thereby reproducing an information signal,
A focus error signal and a track error signal are detected. The method of detecting these signals has been described in the second aspect of the present invention, and a description thereof will be omitted.

Therefore, by forming the diffraction grating 40 on only one side as in this embodiment, the fabrication and handling of the diffraction grating 40 are further facilitated, and light is emitted by the total reflection surface 41 formed on the back surface. Since the optical system is returned to the optical system, the semiconductor laser 30 and the light receiving element 38 can be integrally formed, whereby the number of parts can be reduced and a more compact device can be obtained.

Next, the first embodiment of the invention described in claims 1, 4 and 12 will be described in the seventh embodiment.
Explanation will be made based on FIG. 8 and FIG. In this embodiment,
It addresses the third problem.

On an optical path of light emitted from a semiconductor laser 43 as a laser light source, a dual diffraction grating 44 as a double diffraction grating element is formed. This dual type diffraction grating 44
As shown in FIG. 8, a semi-reflective first substrate 45 having a first diffraction grating 45a as a first diffraction member formed on one surface.
A second diffraction grating 47a as a second diffraction member was formed on the surface of the first substrate 45 on the side on which the first diffraction grating 45a was formed and on the surface on the side oppositely disposed via the spacer 46. It is composed of a transparent second substrate 47. Further, a collimating lens 48 and an objective lens 49 are sequentially arranged on the first substrate 45 side of the dual-type diffraction grating 44, and a position facing the objective lens 49 is used as an optical information recording medium. A magneto-optical disk 50 is provided. Further, in the signal detection optical system 51 located on the second substrate 47 side of the dual diffraction grating 44, a four-divided light receiving element 52a as a light receiving element and a two-divided light receiving element 52b are arranged.

In the dual diffraction grating 44, the surface 45b of the first substrate 45 located on the side of the incident light where the first diffraction grating 45a is not formed is finished to a highly accurate semi-reflective polished surface. The reflected wavefront is not disturbed, and the surface 47b of the second substrate 47 on the outgoing light side where the second diffraction grating 47a is not formed is configured to prevent irregular reflection by a non-reflective coating or the like. I have.

In such a configuration, the divergent light A emitted from the semiconductor laser 43 is reflected by the surface of the semi-reflective first substrate 45 of the dual-type diffraction grating 44 and collimated by the collimating lens 48, and further, The parallel light is an objective lens
The light is condensed by 49 and is irradiated on the surface of the magneto-optical disk 50, thereby recording information. The reflected light from the magneto-optical disk 50 is guided again to the dual diffraction grating 44 via the objective lens 49 and the collimating lens 48 in order. The reflected light incident on the dual type diffraction grating 44 is, as shown in FIG.
The light is separated into transmitted light (zero-order light) T and diffracted light (first-order light) K by a (point P). The 0-order light T is a spacer
The second diffraction grating 47a formed on the second substrate 47 passing through 46
Is transmitted as it is (point Q), while the primary light K passes through the spacer 46 and is further diffracted by the second diffraction grating 47a formed on the second substrate 47 (point R).

Thereafter, of the zero-order light T and the first-order light K guided into the signal detection optical system 51 in this way, the zero-order light T is astigmatic because the thickness of the substrate of the dual diffraction grating 44 is relatively large. A state in which an aberration has occurred is established, whereby a focus error signal can be detected by the astigmatism method using the four-divided light receiving element 52a. Similarly, the primary light T is also in a state in which astigmatism is generated. In this case, the astigmatism is canceled by the action of the diffraction grating, and the track error is generated by the push-pull method using the two-divided light receiving element 52b. The signal can be detected. Further, by comparing the intensities of both light beams detected by the four-divided light receiving element 52a and the two-divided light receiving element 52b based on the polarization separation characteristics of the first diffraction grating 45a and the second diffraction grating 47a having a minute pitch, the magneto-optical is obtained. The signal can be detected.

As described above, by using the dual-type diffraction grating 44 having the semi-reflective surface 45b and the two diffraction gratings 45a and 47a inside, only one of the zero-order light T and the first-order light K is used. Since the astigmatism is generated, the diffraction grating is sealed inside and the shape of the grating is stabilized, and since the two diffraction gratings are arranged close to each other, the primary light due to wavelength fluctuation is generated. , Which is less susceptible to shift fluctuations, whereby stable and reliable signal detection can always be performed. In addition, since one surface of the dual-type diffraction grating 44 is a semi-reflective surface 45b, a high-precision beam splitter function can be provided, thereby reducing the number of parts of the optical system and reducing the size and weight. As a result, high-speed seek movement can be performed, and the access time can be further reduced.

Next, a second embodiment of the invention described in claims 1, 4 and 12 will be described in ninth embodiment.
Description will be made based on the drawings. This embodiment also addresses the third problem.

Here, a collimator lens 48 is provided on the optical path between the semiconductor laser 43 and the dual type diffraction grating 44, and
The condenser lens 53 is disposed on the side of the second substrate 47 of the dual type diffraction grating 44. As a result, the light emitted from the semiconductor laser 43 enters the dual diffraction grating 44 in a state where the light is collimated by the collimating lens 48, and the reflected light from the magneto-optical disk 50 is also in the state of a parallel light beam. With this, the light enters the dual diffraction grating 44.
Therefore, of the light that has passed through the dual type diffraction grating 44,
Since the next light T does not generate astigmatism, it is divided into two light receiving elements 52b.
Can be used to detect a track error signal, while the primary light K can be given astigmatism by a diffraction grating, so that a focus error signal can be detected using the four-divided light receiving element 52a. . The magneto-optical signal can be detected in the same manner as described above.

Next, a third embodiment of the invention described in claims 1, 4 and 12 will be described as a tenth embodiment.
Description will be made based on the drawings. This embodiment also addresses the third problem.

Here, a cylindrical lens 54 is disposed between the dual diffraction grating 44 and the condenser lens 53 in the second embodiment (see FIG. 9). As a result, as shown in FIG. 11 (a) viewed from a direction parallel to the plane of the paper, the dual type diffraction grating 44 condenses the primary light K in the plane of the paper, and the condensing point B and the concave cylindrical lens When the focus of 54 coincides, the 1 that passed through the cylindrical lens 54
The next light K has no astigmatism. FIG. 11 (b) shows a state when the signal detection optical system 51 is viewed from a direction perpendicular to the paper surface. Therefore, 1 which does not have the astigmatism
A track error signal can be detected by detecting the secondary light K by the two-division light receiving element 52b. Further, since the zero-order light T has astigmatism by the cylindrical lens 54, the four-division light receiving element 52a is used. A focus error signal can be detected.

Next, the first embodiment of the invention described in claims 1, 5, and 6 will be described in the twelfth embodiment.
This will be described with reference to FIGS. This embodiment addresses the fourth problem and the fifth problem.

First, the overall configuration of the present apparatus will be described with reference to FIG.
On the optical path of the light emitted from the semiconductor laser 55 as the laser light source and transmitted through the collimator lens 56, a prism 58 as a light beam separating means including a wedge-shaped non-parallel substrate 57 is provided. On one surface of the non-parallel substrate 57, a diffraction grating 59 as a first diffraction member having a modulated pitch as shown in FIG. 13 is formed, and on the other surface, a total reflection surface 60 as a second diffraction member. Are formed. A coating layer as a semi-reflective film is formed on the surface of the diffraction grating 59.
59a is formed. Note that the diffraction grating 5
9. If the angles formed by the total reflection surface 60 are α and β, respectively, β
−α can be expressed as a wedge angle.

Further, an objective lens 61 is provided on the side of the prism 58 on which the diffraction grating 59 is formed. At a position close to the objective lens 61, a magneto-optical disk 62 is provided as an optical information recording medium. On the other hand, on the optical path on the side of the optical system 63 provided with the semiconductor laser 55, two light receiving elements 64 and 65 for detecting the reflected light from the magneto-optical disk 62 are arranged in the same plane.

In such a configuration, the light emitted from the semiconductor laser 55 becomes parallel light by the collimator lens 56, and is guided to the diffraction grating 59 whose diffraction efficiency changes depending on the polarization direction of the prism 58. A coating layer 59a is formed on the diffraction grating 59 so as to have a polarization dependency as shown in FIG. 14 and a desired reflectance for irradiating the magneto-optical disk 62 with an appropriate optical power. However, a part of the parallel light from the collimator lens 56 is reflected by the coating layer 59a and proceeds toward the objective lens 61. On the other hand, the parallel light transmitted as it is without being reflected is
As a result, the light is separated into the zero-order light T and the first-order light K, and travels toward the total reflection surface 60. Since the total reflection surface 60 is not parallel to the diffraction grating 59 but is wedge-shaped, the light reflected here is not parallel to the light reflected by the coating layer 59a but travels in a different direction and is separated. It does not adversely affect the light. Then the objective lens
The reflected light from the coating layer 59a that has proceeded to 61 is irradiated onto the surface of the magneto-optical disk 62, whereby information can be recorded.

The reflected light from the magneto-optical disk 62 reads the signal of the recorded information, is in a state where the polarization direction is rotated by the Kerr effect, and is guided to the diffraction grating 59 again. The reflected light is separated into the zero-order light T and the first-order light K by the diffraction grating 59, reflected by the total reflection surface 60 on the back surface, and passed through the diffraction grating 59 again to be emitted outside.
At this time, the zero-order light T and the first-order light K are emitted from the diffraction grating 59 at an angle different from that of the parallel light emitted from the semiconductor laser 55.

Then, the zero-order light T and the first-order light K pass through the collimating lens 56 and are detected by the light receiving elements 64 and 65. In this case, since the primary light K passes through the diffraction grating 59 twice, the diffraction angle shift due to the wavelength fluctuation can be almost canceled. Also, since the diffraction grating 59 has a modulation pitch, it is possible to generate astigmatism in the primary light K, thereby guiding the primary light K to one light receiving element 65 to detect a focus error signal. can do. On the other hand, 0
Since astigmatism does not occur in the next light T, by guiding this light to one of the light receiving elements 64, a stable tracking error signal can be detected using the push-pull method. Further, a magneto-optical signal is detected by obtaining a difference in intensity between the signals detected by the two light receiving elements 64 and 65, thereby reproducing information.

As described above, by shifting the polarization direction of the light emitted from the semiconductor laser 55 by 45 degrees from the grating direction of the diffraction grating 59, the conventionally required λ / 2 plate can be omitted. Thereby, the number of parts can be reduced. The 0th order light T and the 1st order light K depend on the wedge angle of the prism 58.
The focus sensitivity is determined by the degree of the modulation pitch, so that the degree of freedom in design is increased and the optimal design of each part becomes possible. A magneto-optical head can be realized.

Next, a second embodiment of the invention described in claims 1, 5, and 6 will be described as a fifteenth embodiment.
This will be described with reference to FIGS. The present embodiment addresses the fourth problem and the fifth problem. This is the same as the light receiving element in the first embodiment described above.
The arrangement positions of 64 and 65 are changed, and the other configurations are not changed at all.

FIG. 16 shows the light receiving elements 64 and 65 as viewed from the collimating lens 56 side, and each has a shape divided into three. Further, in this case, the light receiving elements 64 and 65 are disposed so as to be shifted back and forth in the optical axis direction. For this reason, the focus error signal here is detected not by the astigmatism method but by the beam size method.

By detecting a signal in such a manner, it is possible to increase the tolerance of assembly and position adjustment, thereby facilitating assembly adjustment and achieving further mass production. In addition, in the case of the present embodiment, since the astigmatism is not required, the pitch of the gratings 59 can be formed at the same pitch, so that the fabrication of the grating 59 can be facilitated accordingly.

Next, a third embodiment of the invention described in claims 1, 5, and 6 will be described as an eighteenth embodiment.
Explanation will be made based on FIG. 19 and FIG. In this embodiment,
It addresses the fourth and fifth problems.

This is a modification of the first embodiment (see FIG. 12) in which the shape of the light beam separating means is changed. That is, the prism 58 as the light beam separating means has a grating 59 for polarization separation formed on one surface of the non-parallel substrate 57 and a total reflection surface 60 formed on the other surface. The shape of the total reflection surface 60 is not a plane but a wedge prism shape as shown in FIG.

For this reason, if the layout of the entire optical system is the same as that in FIG. 12, the light receiving optical system viewed from the collimator lens 56 side is:
As shown in FIG. 19, it is constituted by using a total of four two-divided light receiving elements 66, 67, 68 and 69. That is, in this case, the focus error signal Fo is detected by the double knife edge method using two spots formed by the zero-order light T or the primary light K, and the other two spots (1
The tracking error signal Tr is detected by the push-pull method using the following method. In addition, magneto-optical signals
Mo can be detected by the light intensity difference between the 0th order light T and the 1st order light K. Therefore, by performing signal detection by such a method, the two-divided light receiving elements 66, 67, 68, and 69 are all disposed in the same plane, so that they can be integrally formed. By detecting the focus error signal using the method, there is an advantage that the influence of wavelength fluctuation can be reduced as compared with the astigmatism method.

Next, an embodiment of the invention described in claims 1, 7, and 8 will be described with reference to FIGS. 20 to 22. This embodiment addresses the fourth problem and the fifth problem.

On the optical path of light emitted from the semiconductor laser 70 as a laser light source, a transmission type diffraction grating 72 as a diffraction grating (first diffraction grating) is formed on one surface of a parallel substrate 71 as a substrate, and a transmission type diffraction grating 72 is formed on the other surface. A light beam separating element 74 as a light beam separating means provided with a total reflection surface 73 as a two diffraction grating is provided. At a part of the center of the transmission type diffraction grating 72, a semi-transmission type diffraction grating 75 as a semi-reflection film is formed. Also,
On the optical path of the light reflected by the transflective grating 75, a magneto-optical disk 77 as an optical information recording medium is provided via an objective lens. Further, the light reflected by the magneto-optical disk 77 is diffracted by the light beam splitting element 74 and the first light receiving element is provided on the optical path of the primary light K.
A second light receiving element 79 is provided on the optical path of the zero-order light T which is refracted by the light beam separating element 74 and travels.

In such a configuration, light emitted from the semiconductor laser 70 travels in the direction of the light beam separating element 74 as diffused light. A part of the light incident on the light beam separating element 74 is reflected by the semi-transmissive diffraction grating 75 having a high reflectance, condensed by the objective lens 76, and irradiated on the surface of the magneto-optical disk 77. Information recording and the like are performed.

The reflected light from the magneto-optical disk 77 is rotated by the Kerr effect to rotate the polarized light according to the signal by reading the signal of the recorded information, and is again transmitted through the light separating element 74. Guided to the diffraction grating 75.
Then, the light is separated into the 0th-order light T and the 1st-order light K by passing through this semi-transmission type diffraction grating 75, and is separately reflected by the total reflection surface 73 on the back surface. Thereafter, the primary light K is transmitted through the transmission type diffraction grating 72 and emitted to the outside to
The zero-order light T is guided to the light receiving element 78, while the zero-order light T passes through the transmission type diffraction grating 72 located at another place and is emitted to the outside to be guided to the second light receiving element 79.

In this case, the first light receiving element 78 and the second light receiving element 79 are
As shown in FIGS. 22A and 22B, the focus error signal can be detected by using the beam size method and the track error signal can be detected by using the push-pull method. Further, the detection of the magneto-optical signal can be detected by calculating the difference between the signal outputs detected by the first light receiving element 78 and the signal output detected by the second light receiving element 79, respectively. However, when a magneto-optical signal is detected by such a method, as shown in FIG. 21 (a), the polarization direction and the lattice direction of the light emitted from the semiconductor laser 70 should be 45 °. It needs to be adjusted.

Accordingly, as described above, by forming the transflective grating 75 and the transmissive grating 72 in the light beam separating element 74,
When the 0th-order light T and the 1st-order light K obtained by the reflected light from the magneto-optical disk 77 being incident on the semi-transmission type diffraction grating 75 of the light beam separating element 74 are reflected by the total reflection surface 73 and emitted to the outside. Since the diffraction grating is a transmission type diffraction grating 72, the light use efficiency can be further increased as compared with the conventional one, and
An optical head that is small, lightweight, and low in cost can be obtained.

Further, in the configuration as described above, the semiconductor laser 70
By arranging a collimating lens (not shown) on the optical path between the light emitted from the semiconductor device and the light separating element 74, the light emitted from the semiconductor laser 70 passes through the collimating lens and is guided to the light separating element 74. As a result, only parallel light out of the outgoing light is incident on the transflective grating 75, so that high-performance polarization separation can be performed, and the light use efficiency can be further increased.

Next, a modification in which signal detection is performed using the first light receiving element 78 and the second light receiving element 79 will be described. First, as a first modified example, a case where an astigmatism method is used to detect a focus error signal will be described. FIGS. 23 (a) and 23 (b) show the configuration. In this case, FIG. 23 (a)
The second light-receiving element 79 for detecting the zero-order light T is divided into four parts, and astigmatism is generated in the zero-order light T by appropriately changing the thickness, inclination, and refractive index of the light beam separating element 74. By arranging the four divided second light receiving elements 79 at the optimum positions, it is possible to detect a focus error signal using the astigmatism method. On the other hand, by forming the first light receiving element 78 for detecting the primary light K into a two-divided shape, it is possible to detect the track error signal using the push-pull method.

As a second modification, a method of detecting a focus error signal using another astigmatism method will be described. Transflective grating 75 or transmissive grating 72
This is a method in which astigmatism is generated on the primary light K side by converting at least one of them into a modulation pitch. In this case, since the focus sensitivity is optimized by the degree of modulation of the grating pitch, the degree of freedom in design can be further increased as compared with the astigmatism method of the first modification.

The focus error signal can be detected by either the beam size method or the astigmatism method. The track error signal can be detected by the sample servo method in addition to the continuous method described above. But it can be detected. In addition, since the transmission type diffraction grating 72 provided in one region through which only the zero-order light T passes simply transmits the zero-order light T, there is no problem in performance even if it is not separately provided if there is no problem in fabrication. Does not happen. Further, the substrate of the light beam splitting element 74 here is a parallel plate, but the first light receiving element
A similar effect can be obtained even if the space between the second light receiving element 79 and the second light receiving element 79 is made to have a shape such as a wedge prism (not shown) in order to optimize the distance.

Next, an embodiment of the invention described in claims 1, 9 and 10 will be described with reference to FIGS. 25 to 29. This embodiment addresses the fourth problem and the fifth problem.

On the optical path while the emitted light a emitted from the semiconductor laser 80 as the laser light source passes through the collimator lens 81 and travels toward the objective lens 82, the polarization as a diffraction grating (first diffraction member) is formed on one surface of the substrate 83. A wedge-shaped light beam separating element 86 as a wedge-shaped light beam separating means having a separation diffraction grating 84 formed on the other surface and a total reflection surface 85 as a second diffraction member is provided. The surface of the polarization separation diffraction grating 84 has a semi-reflective film.
87 are formed. On the optical path of the light reflected by the semi-reflective film 87, an optical disk 88 as an optical information recording medium is provided via a condenser lens.

In this case, one reflected light 89 obtained by being reflected by the semi-reflective film 87 and two reflected lights 89 obtained by transmitting through the semi-reflective film 87.
The transmitted light 90, 91a, b (see FIG. 26) of the book
The light beam separating element 86 having a wedge shape to be led to 88
The wedge angle θ was set. Here, assuming that the angle between the horizontal surface of the surface on which the polarization splitting diffraction grating 84 is formed and the horizontal surface of the surface on which the total reflection surface 85 is formed is β, the wedge angle θ is θ = It can be represented as α-β.

Also, as shown in FIGS. 27 to 29, the optical disk
Among the reflected light (main beam) 89 and transmitted light (sub-beam) 91a, 91b reflected by 88, two three-divided light receiving elements 92, 93 for receiving the reflected light 89 and the transmitted light 91a, 91b are received. The two non-divided light receiving elements 94 and 95 are disposed on the optical path of the collimator lens 81 on the semiconductor laser 80 side.

In such a configuration, the outgoing light a emitted from the semiconductor laser 80 becomes parallel light by the collimator lens 81, and the polarization separation diffraction grating of the wedge-shaped light beam separation means 86
The light enters the surface on the side where 84 is formed. At this time, the outgoing light a
Is the grating direction of the polarization separation diffraction grating 84 (perpendicular to the paper) and
Assuming a linear polarization of 45 °, first, as shown in FIG. 26, the emitted light a is partially reflected by the semi-reflective film 87,
Optical disk as reflected light 89 (hereinafter referred to as main beam 89)
The transmitted light 90 (hereinafter, referred to as a sub-beam 90) that has been irradiated on the surface of the mirror 88 and transmitted through the semi-reflective film 87 is converted into a polarization separation diffraction grating.
The light is split into two at 84, and the 0th order light 91a (transmitted light) and the 1st order light 91b
(Diffraction light).

Then, the zero-order light 91a is reflected by the total reflection surface 85 and transmits through the polarization splitting diffraction grating 84 again. At this time, since the total reflection surface 85 is shifted from the surface on which the polarization splitting diffraction grating 84 is formed by the wedge angle θ, the zero-order light 91a is not parallel to the main beam 89 and has a desired value. Objective lens with an angle of 82
Head in the direction of. On the other hand, the primary light 91b is diffracted by the polarization splitting diffraction grating 84, is reflected by the total reflection surface 85, and is diffracted again by the polarization splitting diffraction grating 84. Also in this case, since the total reflection surface 85 has the wedge angle θ, the incident angle when passing through the polarization splitting diffraction grating 84 for the second time increases, and the diffraction angle also increases accordingly. The beam 91b is not parallel to the main beam 89, but goes to the objective lens 82 at a certain desired angle. Accordingly, one main beam 29 (reflected light) and two sub-beams 90 (0-order light 91a and primary light 91b) obtained in this way are condensed by the objective lens 82 to form three beams. A spot is formed to irradiate the surface of the optical disk 88, whereby information can be recorded and a three-beam tracking method can be performed.

The three beams (one main beam 89 and two sub-beams 91a and 91b) reflected by the optical disk 88 pass through the objective lens 82 and again enter the semi-reflective film 87 of the light beam separating element 86. . Of these, the two sub-beams 91a and 91b are reflected by the semi-reflective film 87 and condensed by the collimating lens 81, and the two non-divided light receiving elements 94 and 9 as shown in FIG.
The track error signal Tr can be detected from the difference in light intensity.

On the other hand, one main beam reflected by the optical disk 88
As shown in FIG. 27, the light 89 is transmitted through the semi-reflective film 87 (partially reflected), and is transmitted by the polarization separation diffraction grating 84 so that the transmitted light 89a
And the diffracted light 89b according to the polarization direction. The transmitted light 89a is totally reflected by the total reflection surface 85, and then passes through the polarization splitting diffraction grating 84 again to travel toward the three-divided light receiving elements 92 and 93. In this case, the transmitted light 89a does not become parallel to the optical axis a ₀ of the emitted light a by reflection by the plane in which the wedge-shaped, one 3 is thereby condensed enters the collimator lens 81 at a predetermined angle The light is detected by the divided light receiving element 92. Also, after the diffracted light 89b is reflected by the total reflection surface 85,
The light again goes to the polarization splitting diffraction grating 84. At this time, the angle of incidence on the polarization splitting diffraction grating 84 becomes smaller than that of the first time due to the reflection by the wedge-shaped surface. Is done. Also in this case, the diffracted light 89
b is not parallel to the optical axis of the emitted light a, enters the collimator lens 81 at a predetermined angle, is condensed by this, and is detected by the other three-division light receiving element 93. Accordingly, since the main beam 89 is separated into the transmitted light 89a and the diffracted light 89b in this manner, the magneto-optical signal Mo can be detected from the difference in the light intensity, and thereby the information recorded on the optical disk 88 can be detected. Playback can be performed.

FIG. 29 shows the non-segmented light receiving element described so far.
9 shows a positional relationship between 94, 95 and two three-division light receiving elements 92, 93. In this case, the main beam 89, from being detected by the two 3-division light receiving elements 92 and 93 having different shifting are arranged focal length from each other back and forth relative to the direction of the optical axis a _0, a focus error signal Fo beam It can be detected using the size method.

As described above, the main beam 89 is divided into three light receiving elements 92 and 93.
In this case, the sub-beam 90 is detected by the non-divided light receiving elements 94 and 95, so that the magneto-optical signal Mo, the focus error signal Fo, and the track error signal Tr can be detected. As a method of detecting the signal Tr, a three-beam method, a push-pull method, and a sample servo method can be adopted, and thereby, it is possible to correspond to various types of optical disks 88.

Further, since the light beam separating element 86 is formed in a wedge shape, three beams can be formed, thereby enabling a three-beam tracking method. Therefore, a CD, a write-once optical disk, and a magneto-optical disk can be used. It is possible to obtain an optical pickup that is compatible and that is reduced in size and weight.

Next, an embodiment of the invention described in claims 1 and 11 will be described with reference to FIGS. 30 to 34. The present embodiment addresses the sixth problem. In addition, the conventional technology (No. 38
The description of the same parts as those in FIG.

As shown in FIG. 31, a light beam separating element 96 serving as a light beam separating means is provided with a transmission type diffraction grating 97 serving as a first diffraction member and a fixed angle (wedge angle) Δθ formed on the transmission type diffraction grating 97. And a high reflection surface 98 as a second diffraction member. The light beam separating element 96 is provided with a light emitted from a semiconductor laser 99 as a laser light source.
Is provided on the optical path between the two.

In such a configuration, the reflected light from the magneto-optical disk 101 passes through the objective lens 102 and the collimating lens 100 sequentially, then enters the transmission type diffraction grating 97 of the light beam separating means 96, where the transmitted light T and the diffracted light K And separated. The transmitted light T
Is reflected by the high-reflection surface 98 and transmitted again through the transmission type diffraction grating 97, thereby becoming light that has been transmitted twice. On the other hand, the diffracted light K is reflected by the high reflection surface 98 and is diffracted again by the transmission type diffraction grating 97, thereby becoming light diffracted twice.

In this case, the diffraction condition equation of the diffracted light K is as follows (see FIG. 32).

sin θi + sin θ ₀ = λ / Λ (1) sin (θ ₀ -2Δθ) + sin θ ₁ (2) θi: incident angle, θ ₀ : one-time diffraction angle Δθ: wedge angle, θ ₁ : two-time diffraction angle λ: wavelength , Λ: pitch of diffraction grating Here, when θ ₁ is obtained, Becomes

Here, the diffraction axis shift angle Δd and the transmission axis shift angle Δt are defined as follows, respectively.

ψd = incident angle−diffraction angle = θi−θ ₁ (4) ψt = 2Δθ (5) Then, using these equations (4) and (5), the diffracted light K and 2 diffracted twice. When the angle difference (separation angle) ψs from the transmitted light T that has been transmitted each time is obtained, the following is obtained: 差 s = ψd-ψt = θi-θ ₁ -2Δθ (6)

Therefore, from this, as shown in FIG. 30,
Since the two light receiving elements 103 and 104 can be arranged close to and adjacent to the semiconductor laser 99, a semiconductor laser substrate and a light receiving element substrate can be separately formed. Therefore, by this, the semiconductor laser 99 and the light receiving element
Since it can be mounted separately from 103 and 104, assembly adjustment becomes easy.

In this case, as shown in FIG. 33, one of the light receiving elements 103 and 104 may be a four-divided light receiving surface 105 and the other may be a two-divided light receiving surface 106, as shown in FIG. In this case, a track error signal can be detected by the two-part light receiving surface 106 using the push-pull method, and a focus error signal can be detected from the four-part light receiving surface 105 by the astigmatism method. In the case of sample servo tracking, the two-divided light receiving surface may be undivided. The light receiving surface in FIG. 34 (a) is for detecting a focus error signal by the beam size method. When a track error signal is detected by the push-pull method, as shown in FIG. 34 (b), by adding a dividing line 107 on the left and right at a broken line portion, it is possible to detect the difference on the left and right light amounts. In the case of sample servo tracking, the dividing line
107 is unnecessary.

Next, a modification of the present embodiment is shown in FIG. In the above-described embodiment, as shown in FIG. 31, the transmission type diffraction grating 97 and the high reflection surface 98 constituting the light beam separation means 96 are separated, but here, the wedge 108 having a constant angle Δθ is used. The transmission type diffraction grating 97 is formed on one side of the substrate, and the high reflection surface 98 is formed on the other side. A similar effect can be obtained by forming the substrate in this manner.

According to the first aspect of the present invention, light emitted from a laser light source is condensed by an objective lens and irradiated on an optical information recording medium to record information, and reflected light from the optical information recording medium is reflected. In an optical information recording / reproducing apparatus for detecting a reproduction signal for information, a track error signal, and a focus error signal by detecting, a semi-reflective film is formed on an optical path while light emitted from a laser light source is directed to an objective lens. Providing a first diffractive member having a second diffractive member disposed on the optical path where the reflected light from the optical information recording medium has passed through the first diffractive member, passing the first diffractive member and the second diffractive member As a result, the light receiving elements that respectively detect the transmitted light and the diffracted light obtained by the separation are provided, so that it is possible to reduce the space and integrate the emission optical system and the signal detection optical system. , As a result, the number of components of the entire apparatus can be reduced, and a compact, lightweight, and inexpensive apparatus can be obtained.

According to a second aspect of the present invention, the light emitted from the laser light source is collimated by a collimating lens, and the collimated light is condensed by an objective lens and irradiated on an optical information recording medium to record information. In an optical information recording / reproducing apparatus that reproduces information and detects a track error signal and a focus error signal by guiding the reflected light from the optical information recording medium to a light receiving element, a half of the light emitted from the laser light source is placed on the optical path. Since the light beam separating means provided with the front surface diffraction grating and the back surface diffraction grating having the reflection film is provided, the space can be reduced, and the emission optical system and the signal detection optical system can be integrated and configured. Thus, the number of components of the entire apparatus can be reduced, and a compact, lightweight, and inexpensive apparatus can be obtained.

According to a third aspect of the present invention, light emitted from a laser light source is collimated by a collimator lens, and the collimated light is condensed by an objective lens and irradiated on an optical information recording medium to record information. In an optical information recording / reproducing apparatus for reproducing information, detecting a track error signal, and detecting a focus error signal by guiding the reflected light from the optical information recording medium to a light receiving element, the optical information recording / reproducing apparatus may be arranged on an optical path of light emitted from a laser light source. Since a diffraction grating having a semi-reflective film and a light beam separating means having a total reflection surface are provided, it is only necessary to manufacture a diffraction grating having only one surface. And the light receiving element can be integrated, so that the number of parts can be greatly reduced, thereby simplifying the assembling work and making the device even more compact and lightweight. Those that can be obtained.

The invention according to claim 4 records information by collimating light emitted from a laser light source by a collimating lens, condensing the parallel light by an objective lens, and irradiating the collimated light on an optical information recording medium. In an optical information recording / reproducing apparatus that reproduces information by guiding reflected light from an optical information recording medium to a light receiving element in a signal detection optical system and detects a focus error signal and a track error signal, the light emitted from a laser light source is used. On the optical path of light, a semi-reflective first substrate having a first diffraction grating formed on one surface and a surface of the first substrate on which the first diffraction grating was formed were arranged to face each other via a spacer. A double diffraction grating element comprising a transparent second substrate on which a second diffraction grating is formed is disposed on the side surface, so that transmitted light and diffracted light can be generated using this double diffraction grating element. Astigmatism on one side By generating a difference and detecting a focus error signal, stable signal detection can be performed without being affected by wavelength fluctuation.In addition, a double diffraction grating element is arranged with diffraction grating surfaces close to each other. Since it is hardly affected by the primary light shift fluctuation due to the wavelength fluctuation, the signal detection can be performed with higher reliability than before.

According to a fifth aspect of the present invention, information emitted from a laser light source is collimated by a collimating lens, and then condensed by an objective lens to irradiate an optical information recording medium to record information. In an optical information recording / reproducing apparatus which detects reflected light from a medium to reproduce information, and detects a track error signal and a focus error signal, a wedge is formed on an optical path between the collimating lens and the objective lens. A diffraction grating having a semi-reflection film is formed on one surface of the non-parallel substrate, and a light beam separation means having a total reflection surface formed on the other surface is provided, and light reflected by this light beam separation means passes through the collimating lens. Since two light receiving elements for detecting the reflected light from the optical information recording medium are provided on the optical path on the side of the laser light source, such a diffraction grating and the total reflection surface are not in contact with each other. Design layout of the entire optical system is facilitated because it spot separating the 0-order light and first order light by using a light flux separating means formed on both sides of the row substrate,
In addition, since the light beam separating means is disposed between the collimator lens and the objective lens, the collimated light is incident on the diffraction grating, whereby high-performance polarization separation can be performed. Therefore, the light use efficiency can be further improved.

The invention according to claim 6 records information by collimating light emitted from a laser light source by a collimating lens, and thereafter condensing the light by an objective lens and irradiating the collimated lens with an optical information recording medium. In an optical information recording / reproducing apparatus that detects reflected light from a medium and reproduces information or detects a track error signal and a focus error signal, a non-parallel substrate is provided on an optical path between the collimator lens and the objective lens. A light beam separating means having a diffraction grating having a semi-reflective film on one surface and a total reflection surface in the form of a wedge prism formed on the other surface is provided, and the light reflected by the light beam separating means passes through the collimating lens. Since two sets of two light receiving elements for detecting the reflected light from the optical information recording medium are arranged on the optical path on the side of the semiconductor laser, the total reflection is performed as described above. It was a wedge prism shape 2
By arranging two sets of light receiving elements, it is possible to detect a focus error signal by using the double knife edge method, whereby the mounting accuracy can be further reduced than before, and the A stable signal can be detected.

According to a seventh aspect of the present invention, information emitted from a laser light source is condensed by an objective lens and irradiated onto an optical information recording medium to record information, and reflected light from the optical information recording medium is detected. In the optical information recording / reproducing apparatus for reproducing information and detecting a track error signal and a focus error signal, a diffraction grating is provided on one surface of a substrate on an optical path while light emitted from the laser light source is directed to the objective lens. Is formed, a light beam separating means having a semi-transmissive layer on one surface and a total reflection surface formed on the other surface is disposed, and a first light beam is diffracted by the light beam separating device on the optical path of the primary light. Since the light receiving element is provided, and the second light receiving element is provided on the optical path of the zero order light which is refracted by the light beam separating means and travels, the zero order light and the primary light separated by the diffraction grating of the light beam separating means are provided. And are reflected by the total reflection surface Re when emitted to the outside, because that will pass through the transparent area other than the semi-transparent layer of the diffraction grating, in which it makes it possible to increase the more light use efficiency than conventional.

According to an eighth aspect of the present invention, in the configuration of the seventh aspect of the present invention, a collimating lens is further provided on an optical path while light emitted from the laser light source is directed to the light beam separating means. Since only the parallel light out of the outgoing light is incident on the diffraction grating, it is possible to perform high-performance polarization separation, thereby further improving the light use efficiency.

According to a ninth aspect of the present invention, information is recorded by irradiating an optical information recording medium by condensing an emitted light emitted from a laser light source through an objective lens via a collimating lens, and recording the information on the optical information recording medium. In the optical information recording / reproducing device which detects reflected light from the optical disc to reproduce information, and detects a track error signal and a focus error signal, the light emitted from the output light passes through the collimating lens and travels toward the objective lens. A diffraction grating is formed on one surface of the substrate on the road, and a wedge-shaped light beam separating means having a semi-reflective film on the surface and a total reflection surface formed on the other surface is provided, and the emitted light is reflected by the semi-reflective film. A wedge of the light beam separating means having a wedge shape such that one main beam obtained by reflection and two sub beams obtained by transmitting through the semi-reflective film are guided to the optical information recording medium. Since the outgoing light is incident on the semi-reflective film formed on the surface of the diffraction grating of the light beam separating means, the light reflected by the semi-reflective film is used as the main beam and the transmitted light is used as the sub beam. This makes it possible to perform three-beam tracking, which makes this device compatible with various devices that use magneto-optical disks, CDs, etc. as optical information recording media, and further expands the range of applications compared to conventional devices. Can be done.

According to a tenth aspect of the present invention, in the configuration of the ninth aspect described above, two three-divided light receiving portions for receiving the main beam out of the main beam and the sub beam reflected by the optical information recording medium are further provided. An element and two non-divided light receiving elements for receiving the sub beam are provided, so that the main beam and the sub beam reflected by the optical information recording medium are all received by the respective light receiving elements without waste. The light use efficiency can be further improved.

In the invention according to claim 11, after the light emitted from the laser light source is collimated by a collimating lens, the light is condensed by an objective lens and irradiated on the surface of an optical information recording medium to record information, and the optical information is recorded. In an optical information recording / reproducing apparatus for detecting a focus error signal and a track error signal by detecting reflected light from a recording medium by a light receiving element, a transmission type diffraction grating and a transmission type diffraction grating are arranged at a fixed angle. By providing the light beam separating means having a highly reflective surface, the optical path between the transmitted light and the reflected light separated by the light beam separating means can be changed. There is no need to provide a light receiving element, which allows a laser light source substrate and a light receiving element substrate to be separately prepared and mounted.
As a result, the assembly adjustment can be simplified and the work efficiency can be increased.

According to a twelfth aspect of the present invention, there is provided a semi-reflective first substrate having a first diffraction grating formed on one side, and a surface of the first substrate on which the first diffraction grating is formed, which is opposed to the first substrate via a spacer. A double diffraction grating element comprising a transparent second substrate on which a second diffraction grating is formed is provided on the surface on the side where the first diffraction grating and the second diffraction grating face each other and are sealed. And the lattice shape is stable.
Since the two diffraction gratings are close to each other, it is possible to make the shift of primary light less susceptible to wavelength fluctuation, and the outer surface on which the diffraction grating is formed is made to be a semi-transmissive surface. It has an accurate beam splitter function and can be applied to optical information recording / reproducing devices.
The number of parts can be further reduced to obtain a compact and lightweight device.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the invention according to claims 1 and 2, FIG. 2 is a block diagram showing a state of a dual type diffraction grating,
FIG. 3 is an explanatory view showing the direction of a dual type diffraction grating from behind a laser light source, FIG. 4 is an explanatory view showing a principle of detecting a focus error signal by a light receiving element, and FIG. 5 is a diffraction efficiency of a high-density diffraction grating. FIG. 6 is a configuration diagram showing one embodiment of the invention according to claims 1 and 3, and FIG.
FIG. 8 is a block diagram showing a first embodiment of the invention according to claims 1, 4 and 12, FIG. 8 is a side view showing an optical path state of light incident on and split by the dual type diffraction grating, and FIG. The figure shows claims 1, 4, 12
FIG. 10 is a block diagram showing a second embodiment of the invention described, FIG. 10 is a block diagram showing a third embodiment of the invention described in claims 1, 4, and 12, and FIG.
FIG. 12 is an explanatory diagram showing the arrangement of cylindrical lenses in the signal detection optical system, FIG. 12 is a configuration diagram showing a first embodiment of the invention according to claims 1, 5, and 6, and FIG. FIG. 14 is a front view showing the state of the modulated diffraction grating, FIG. 14 is a characteristic diagram showing the polarization dependence of the diffraction grating, and FIG. 15 is a second embodiment of the invention according to claims 1, 5, and 6. FIG. 16 is a front view showing the state of the arrangement of the light receiving element, FIG. 17 is a front view showing the state of a diffraction grating of equal pitch, and FIG. 18 is the claim 1, 5 or 6. FIG. 19 is a perspective view showing a state of a light beam separating means according to a third embodiment of the invention, FIG. 19 is a front view showing an arrangement state of the light receiving element, and FIG. 20 is claims 1, 7, and 8. FIG. 21 is a configuration diagram showing one embodiment of the present invention, FIG.
FIG. 22 is an explanatory view showing the appearance of the surface shape of the light receiving element, FIGS. 23 and 24 are front views showing modified examples of the light receiving element, and FIGS.
The figure is a configuration diagram showing one embodiment of the invention according to claims 1, 9, and 10,
FIG. 26 is an optical path diagram showing a traveling path in the emitted light beam separating means, FIG. 27 is an optical path diagram showing a traveling path in the light beam separating means of return light from the optical information recording medium, and FIG. FIG. 29 is a circuit diagram showing a state of a wiring circuit connected to the three-divided light receiving element, FIG. 29 is an optical path diagram showing a relationship between arrangement positions of the non-divided and three-divided light receiving elements on an optical path, and FIG.
FIG. 31 is a side view showing a light beam separating means of the invention, FIG. 32 is an explanatory view showing various diffraction angles, and FIG. 33 is a front view of a light receiving element. FIG. 34 is a side view showing a modified example of the light receiving element, FIG. 35 is a front view showing a modified example of the light beam separating means, FIG. 36 is a configuration diagram showing a first conventional example, and FIG. FIG. 38 is a configuration diagram showing a second conventional example, and FIG. 38 is a configuration diagram showing a fourth conventional example. 30: High laser source, 32: Semi-reflective film, 33: Front diffraction grating, 34: Back diffraction grating, 35: Collimating lens, 36
... objective lens, 37 ... optical information recording medium, 38 ... light receiving element, 40 ... diffraction grating, 41 ... total reflection surface, 42 ... semi-reflection film, 43 ... laser light source, 45 ... first Substrate, 45a ... First diffraction grating, 47 ... Second substrate, 47a ... Second diffraction grating, 48
…… Collimator lens, 49 …… Objective lens, 50 …… Optical information recording medium, 51 …… Signal detection optical system, 52a, 52b …… Light receiving element, 55 …… Laser light source, 56 …… Collimate lens, 57
... non-parallel substrate, 58 ... light beam separating means, 59 ... diffraction grating, 59a ... semi-reflective film, 60 ... total reflection surface, 61 ... objective lens, 62 ... optical information recording medium, 64, 65 ...... Light-receiving element, 70
…… Laser light source, 71 …… Substrate, 72 …… Diffraction grating, 73 ……
Total reflection surface, 74: Light beam separating means, 75: Translucent layer, 76 ...
... objective lens, 77 ... optical information recording medium, 78 ... first light receiving element, 79 ... second light receiving element, 80 ... laser light source, 81 ...
Collimating lens, 82 Objective lens, 83 Substrate, 84
…… Diffraction grating, 85 …… Total reflection surface, 86 …… Light beam separation means,
87 ... Semi-reflective film, 92,93 ... Three-segment light receiving element, 94,95 ...
Non-divided light receiving element, 96: light beam separating means, 97: transmissive diffraction grating, 98: high reflection surface, 99: laser light source, 100 ...
Collimating lens, 101: Optical information recording medium, 102: Objective lens, 103, 104: Light receiving element

──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. 1-304414 (32) Priority date Hei 1 (1989) November 22, (33) Priority claim country Japan (JP) (31) Priority Claim number Japanese Patent Application No. 1-337773 (32) Priority Date Hei 1 (1989) December 26 (33) Priority claiming country Japan (JP) (31) Priority claim number Japanese Patent Application No. 2-18623 (32) Priority (2) Japan (JP) (56) References JP-A-63-228431 (JP, A) JP-A-63-167431 (JP, A) JP JP-A-62-103857 (JP, A) JP-A-64-4926 (JP, A) JP-A-64-86337 (JP, A) JP-A-1-2533843 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) G11B 7/135

Claims (12)

(57) [Claims] 1. An information recording device comprising: an optical information recording medium that records light by condensing light emitted from a laser light source by an objective lens and irradiating the optical information recording medium; and detects reflected light from the optical information recording medium. An optical information recording / reproducing apparatus for detecting a reproduced signal, a track error signal, and a focus error signal, wherein a first diffraction pattern having a semi-reflective film on an optical path while light emitted from the laser light source is directed to the objective lens is provided. Providing a member, arranging a second diffraction member on the optical path where the reflected light from the optical information recording medium has passed through the first diffraction member, and passing the first diffraction member and the second diffraction member An optical information recording / reproducing apparatus, comprising: a light receiving element for detecting a transmitted light and a diffracted light obtained by being separated by the method. 2. The light emitted from a laser light source is collimated by a collimating lens, and the collimated light is condensed by an objective lens and irradiated on an optical information recording medium to record information. By guiding the reflected light from the recording medium to the light receiving element, information reproduction and track error signals,
In an optical information recording / reproducing apparatus for detecting a focus error signal, a surface diffraction grating having a semi-reflective film that reflects a part of light incident on a surface located on an optical path side of light emitted from the laser light source is formed. An optical information recording device comprising: a light beam separating means provided with a back surface diffraction grating on a surface opposite to the surface; and the light receiving element provided on an optical path on the side provided with the back surface diffraction grating. Playback device. 3. The light emitted from a laser light source is collimated by a collimating lens, and the collimated light is condensed by an objective lens and irradiated on an optical information recording medium to record information. In an optical information recording / reproducing apparatus for reproducing information, detecting a track error signal, and detecting a focus error signal by guiding reflected light from an information recording medium to a light receiving element, the optical information recording / reproducing apparatus is located on the optical path side of light emitted from the laser light source. A diffraction grating having a semi-reflective film for reflecting a part of the light incident on the surface is formed, and a light beam separating means having a total reflection surface formed on a surface opposite to this surface is provided, and the laser light source is provided. An optical information recording / reproducing apparatus, wherein the light receiving element is disposed on an optical path on a side of the optical information recording and reproducing apparatus. 4. A method of recording information by collimating light emitted from a laser light source by a collimating lens, condensing the parallel light by an objective lens, and irradiating the collimated light on an optical information recording medium. In an optical information recording / reproducing apparatus that reproduces information by guiding reflected light from a medium to a light receiving element in a signal detection optical system and detects a focus error signal and a track error signal, the light emitted from the laser light source is On the optical path, the semi-reflective first substrate on which the first diffractive member is formed on one side, and the surface of the first substrate on which the first diffractive member is formed and the side on which the first diffractive member is formed are opposed to each other via a spacer. An optical information recording / reproducing apparatus, comprising: a double diffraction grating element comprising a transparent second substrate having a second diffraction member formed on a surface thereof. 5. A method of recording information by collimating light emitted from a laser light source by a collimating lens, irradiating the collimated light with an objective lens, and irradiating the collimated lens with an optical information recording medium. In an optical information recording / reproducing apparatus that detects reflected light to reproduce information, and detects a track error signal and a focus error signal, a non-parallel substrate that forms a wedge on an optical path between the collimator lens and the objective lens A light beam separating means in which a diffraction grating having a semi-reflective film is formed on one surface and a total reflection surface is formed on the other surface, and the light reflected by the light beam separating means is transmitted through the collimating lens. An optical information recording / reproducing apparatus, wherein two light receiving elements for detecting reflected light from the optical information recording medium are arranged on the optical path on the side. 6. A method of recording information by collimating light emitted from a laser light source by a collimating lens, and then condensing the light by an objective lens and irradiating the light on an optical information recording medium. In an optical information recording / reproducing apparatus that detects reflected light to reproduce information, and detects a track error signal and a focus error signal, a half of a non-parallel substrate is provided on an optical path between the collimating lens and the objective lens. A light beam separating means provided with a diffraction grating having a reflection film and a total reflection surface in the form of a wedge prism formed on the other surface, wherein the light reflected by the light beam separating means passes through the collimating lens. An optical information recording / reproducing apparatus, comprising two sets of two light receiving elements for detecting reflected light from the optical information recording medium on an optical path on a light source side. 7. Recording of information by condensing light emitted from a laser light source by an objective lens and irradiating the light on an optical information recording medium, and detecting reflected light from the optical information recording medium to obtain information. In the optical information recording / reproducing apparatus which performs reproduction of a track error signal and a focus error signal, a diffraction grating is formed on one surface of a substrate on an optical path while light emitted from the laser light source goes to the objective lens. A light beam separating means having a semi-reflective film on a part of the surface and a total reflection surface formed on the other surface is provided, and a first light receiving element is provided on an optical path of primary light diffracted by the light beam separating means and traveling. An optical information recording / reproducing apparatus, wherein a second light receiving element is disposed on an optical path of 0-order light which is refracted by the light beam separating means and travels. 8. The optical information recording / reproducing apparatus according to claim 7, wherein a collimating lens is provided on an optical path while the light emitted from the laser light source travels toward the light beam separating means. 9. Recording information by converging an emitted light emitted from a laser light source through an objective lens via a collimator lens and irradiating the collected light with an optical information recording medium;
In an optical information recording / reproducing apparatus that detects reflected light from the optical information recording medium to reproduce information or detect a track error signal and a focus error signal, the emitted light passes through the collimating lens and the objective lens A wedge-shaped light beam separating means in which a diffraction grating is formed on one surface of the substrate on the optical path and has a semi-reflective film on the surface and a total reflection surface is formed on the other surface is provided, and the emitted light is The wedge-shaped one main beam obtained by being reflected by the semi-reflective film and the two sub-beams obtained by passing through the semi-reflective film are guided to the optical information recording medium. An optical information recording / reproducing apparatus, wherein a wedge angle of a light beam separating means is set. 10. A three-divided light receiving element for receiving the main beam of the main beam and the sub beam reflected by the optical information recording medium, and two non-divided light receiving elements for receiving the sub beam are provided. 10. The optical information recording / reproducing apparatus according to claim 9, wherein: 11. A light emitted from a laser light source is collimated by a collimating lens, and then condensed by an objective lens to irradiate the surface of an optical information recording medium to record information. In the optical information recording / reproducing apparatus for detecting the focus error signal and the track error signal by detecting the reflected light of the laser light by the light receiving element, the transmission type light is transmitted on the optical path while the light emitted from the laser light source goes to the collimating lens. An optical information recording / reproducing apparatus, comprising: a light beam separating means having a diffraction grating and a high reflection surface disposed at an angle to the transmission type diffraction grating. 12. A semi-transmissive first substrate having a first diffractive member formed on one surface thereof, and a first substrate opposed to a surface of the first substrate on which the first diffractive member is formed is disposed via a spacer. A double diffraction grating element comprising: a transparent second substrate having a second diffraction member formed on a side surface.