JPH08338904A - Optical element and optical information recording and reproducing device - Google Patents

Abstract

PURPOSE: To suppress the change in the light quantity of a light spot by the optical axis misalignment of a region where a diffraction phenomenon with an incident luminous flux is induced. CONSTITUTION: This optical element splits the luminous flux to a plurality by utilizing the diffraction phenomenon. The region where the diffraction phenomenon is induced is divided to a plurality (AT, D, V, RF regions). The exit direction of the diffracted light from the respective divided regions vary respectively and the region where the diffraction phenomenon is induced is larger than the region (broken line region) to be irradiated with the luminous flux from the light source. Such optical element is irradiated with the luminous flux from an optical system for irradiation and the luminous flux emitted from the respective divided regions is cast to an optical information recording medium, by which the information recording to the optical information recording medium and/or the reproducing of the recorded information by detecting the luminous flux from the optical information recording medium is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical information for recording information on an optical information recording medium, reproducing the information recorded on the recording medium and / or erasing the information recorded on the recording medium. The present invention relates to a recording / reproducing apparatus and an optical element preferably used in the optical information recording / reproducing apparatus.

[0002]

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

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

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

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

FIG. 6 shows a schematic plan view of a write-once type optical card, and FIG. 7 shows a partially enlarged view thereof.

In FIG. 6, a large number of information tracks 2 are arranged in parallel on the information recording surface of the optical card 1 in the LF direction. The information recording surface of the optical card 1 is provided with a home position 3 which serves as a reference position for accessing the information track 2. The information track 2 is in the order of 2-1, 2-2, 2-3, ...
As shown in FIG. 7, tracking tracks 4 are provided adjacent to these information tracks 4-1 and 4-.
2, 4, 3, ... are sequentially provided. These tracking tracks 4 are used as guides for auto-tracking (hereinafter, referred to as AT) that controls the beam spot so that the beam spot does not deviate from a predetermined information track at the time of scanning the light beam spot during information recording / reproduction. .

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

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

In FIG. 7, S₁, S₂, S₃Is
Shows the light beam spot, S₁And S ₃Use the light spot of
And use AT to do S₂AF using the light spot of
And the creation of information bits during recording and
Read out. In each information track, 6-
1, 6-2 and 7-1, 7-2 are preformatted respectively
The left side address part and the right side address part are shown.
The information track can be identified by reading the address section.
Be played. 5 (corresponding to 5-1 and 5-2 in the figure) is the data
This is a data section in which predetermined information is recorded.

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

In FIG. 8, reference numeral 21 denotes a semiconductor laser which is a light source, and in this example, it emits light having a wavelength of 830 nm (having an electric field oscillation plane) which is polarized in a direction perpendicular to the track. Further, 22 is a collimator lens, 23 is a beam shaping prism, 24 is a diffraction grating for splitting a light beam, and 25 is a polarization beam splitter. Further, 26 is a quarter wavelength plate, 20 is a total reflection mirror (total reflection prism), 27 is an objective lens, 28 is a spherical lens, 29 is a cylindrical lens, and 30 is a photodetector. The photodetector 30 is composed of two light receiving elements 30a and 30c and a four-divided light receiving element 30b.

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

Next, the three light beams are converted into a quarter wave plate 2
It is converted into circularly polarized light when passing through 6, and is focused on the optical card 1 by the objective lens 27. As shown in FIG. 7, the focused light has three small beam spots S.
₁ (+ _1st-order diffracted light), S ₂ (0th-order diffracted light), S ₃ (-1
The next diffracted light). S ₂ is used for recording, reproduction and AF control, and S ₁ and S ₃ are used for AT control. Optical card 1
As shown in FIG. 7, the upper spot positions are such that the light beam spots S ₁ and S ₃ are located on the adjacent tracking tracks 4 and the light beam spot S ₂ is located on the information track 2 between the tracking tracks. are doing. Thus, the reflected light from the light beam spot formed on the optical card 1 passes through the objective lens 27 again to be a parallel light beam, and passes through the quarter-wave plate 26 so that the polarization direction is 90 degrees from that at the time of incidence. ° Converted to a rotated light beam. Then, it enters the polarization beam splitter 25 as an S-polarized beam, is reflected by nearly 100% due to the spectral characteristics shown in FIG. 9, and is guided to the detection optical system.

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

The optical head optical system as described above is divided into a fixed portion and a movable portion as shown in FIG. 8, and only the movable portion is moved as shown by an arrow to obtain a light beam spot. It is also possible to scan the information track in S ₂ . In such a separation type optical head, the moving amount of the movable portion needs to be about the length of the optical card 1 in the vertical direction, and is usually 100 m.
m.

[0017]

In the above-mentioned conventional example, the verification at the time of recording can be performed only from one direction.
Each time a track is recorded, the optical head and the optical card have to be reciprocated relative to each other. Also, since each track must be read during reproduction, a great deal of time must be spent.

It is an object of the present invention to provide an optical information recording / reproducing apparatus capable of dividing light from one light source into a plurality of portions and performing reciprocal recording and reproducing a plurality of tracks simultaneously.

[0019]

The optical element of the present invention is an optical element which divides a light beam from a light source into a plurality of light beams by utilizing a diffraction phenomenon, and a region in which the diffraction phenomenon is generated is divided into a plurality of areas. The emission directions of the diffracted light from the respective regions are different from each other, and the region in which the diffraction phenomenon occurs is larger than the region irradiated with the light flux from the light source.

Further, in the optical information recording / reproducing apparatus of the present invention, the optical element is irradiated with the light flux from the irradiation optical system,
By irradiating the optical information recording medium with a light beam emitted from each of the divided areas, information is recorded on the optical information recording medium and / or a light beam from the optical information recording medium is detected to reproduce recorded information. It is characterized by performing.

[0021]

According to the present invention, by dividing the region of the optical element which causes the diffraction phenomenon into a plurality of areas, reciprocal recording and / or reproduction of a plurality of tracks are simultaneously performed, and further, the area where the diffraction phenomenon occurs is larger than the incident light beam diameter. Thus, the amount of light emitted from each of the divided regions does not change with respect to some deviation of the optical axis of the incident light beam.

For example, in the optical element shown in FIG. 1, the areas in which the diffraction phenomenon occurs are for the direct verification area (D.V area), the auto-tracking area (AT area), and the reproduction area (RF area). Is divided into three, and seven light beam spots as shown in FIG. 4 are formed so that reciprocal recording and plural tracks can be simultaneously reproduced. Further, the area (three areas) in which the diffraction phenomenon is generated is made larger than the incident light beam diameter (the broken line portion in the figure), and each divided area is provided even if the optical axis of the incident light beam is slightly displaced. The amount of light emitted from each of the light sources does not change, and in particular, when the incident light flux moves in the vertical direction of FIG. 1 (the direction of the arrow in the figure), the amount of each light does not change at all.

Further, also in the optical element of FIG. 2, if the diffraction efficiency of the entire region is the same, at least the amount of W light (0th order light) does not change at all.

[0024]

Embodiments of the present invention will now be described in detail with reference to the drawings. The optical element of the present invention is not particularly limited to the optical information recording / reproducing device.

First, prior to the description of the embodiments of the present invention,
The structure of the diffraction grating as an optical element used in the present invention will be described. The diffraction grating 24 'shown in FIG. 3 divides an incident light beam by using a direct verification area (D.V area), an auto-tracking area (AT area), and a reproduction area (RF area). You can Then, the divided luminous flux is arranged as seven beam spots on the optical card as shown in FIG. 4, and the optical system in which light is received by the sensor as shown in FIG. 5 is used for reciprocal recording and simultaneous recording of a plurality of tracks (3 tracks). Playback is possible.

That is, as shown in FIG. Since there is a V light spot, it is possible to perform reciprocal recording because verification can be performed immediately regardless of which way the optical card (track) is heading.
Two RF light spots and D.I. Light spot for V or 0
It is possible to simultaneously reproduce three tracks with three light spots of the next spot (W light spot).

When the diffraction grating for reciprocal recording and simultaneous reproduction of a plurality of tracks is used, since the size of the incident light beam and the size of the area of the diffraction grating are the same, if the positions of the incident light beam and the diffraction grating deviate, the AT , DV, RF and W light (0th order light) are changed. In particular, when the optical head optical system is of a system in which a fixed part and a movable part are separated and the diffraction grating is arranged in the movable optical system, the light quantity of each light spot fluctuates as the movable part moves. ,
Each detected signal may fluctuate, and light and shade may occur in the recording pit.

Therefore, in the present invention, the region where the diffraction grating exists is made larger than the incident light beam diameter. FIG. 1 is a schematic diagram showing an example of a diffraction grating used in an optical head of an optical information recording / reproducing apparatus according to the present invention.

The optical information recording / reproducing apparatus of this embodiment uses the diffraction grating 50 shown in FIG. 1 instead of the diffraction grating 24 in the conventional apparatus shown in FIG. Only the shape of the light receiving element shown in FIG. 5 that receives the light beam divided by the diffraction grating is different from that of the device shown in FIG. 8 above, and the detailed description of the same components will be omitted here.

In this embodiment, as shown in FIG. 1, a diffraction grating having three diffraction regions (D.V region, AT region, RF region) as in the diffraction grating shown in FIG. By arranging 50 in the irradiation optical system, seven spots can be imaged on the optical card as shown in FIG. 7
One spot is composed of six spots of ± 1st-order light spots of the diffraction grating of each region shown in FIG. 1 and one spot of a 0th-order light beam that has passed through the diffraction grating 50 without being diffracted. ing. Needless to say, each spot on the optical card shown in FIG. 4 corresponds to the spot on the light receiving element shown in FIG. 5 and is detected. Such a diffraction grating can be formed by a method of mechanically cutting, a method of dissolving with a chemical, a method of vapor deposition, or the like.

In the present invention, as can be seen by comparing the diffraction grating shown in FIG. 3 with the diffraction grating shown in FIG. 1, the area where the diffraction grating exists is larger than the diameter of the incident light beam. Even if the optical axis shift of the diffraction grating occurs, it is possible to suppress the light amount fluctuations of the light spots of AT, DV, RF and W light (0th order). Especially for the diffraction grating of the shape shown in FIG. 1, the vertical direction of the drawing (the direction of the arrow in the drawing)
This is effective because the light amount of each light spot does not fluctuate at all with respect to the optical axis shift of.

Further, when the diffraction efficiency in the entire region is the same, even in the diffraction grating 51 having a shape as shown in FIG. The amount of light) is constantly constant. Assuming that the incident light flux has a Gaussian distribution, in the case of a diffraction grating divided as shown in FIG. 2, when the center of the incident light flux comes to any area of the diffraction grating, the light quantity of the light flux by that area increases. (For example, when the center of the D.V region and the center of the incident light beam are coincident with each other, the light amount of the light beam for the D.V becomes largest). On the other hand, W light is the light that has passed through without being diffracted, so
If the diffraction efficiency of each area of the diffraction grating is different, the light quantity of the transmitted light flux will change each time the position of the incident light beam and the diffraction grating changes, but if the diffraction efficiency of each area of the diffraction grating is the same Even if the positions of the light flux and the diffraction grating change, the amount of transmitted light remains the same. Therefore, the amount of W light (0th order light) is constantly constant.

As a result, the density of recording pits caused by the optical axis shift can be eliminated, and a stable reproduction signal can be obtained.

As a result, it is possible to eliminate an error and a signal instability factor associated with the operation of the movable optical system.

The conditions such as the grating interval and the tilt angle of the diffraction grating pattern in each of the divided regions shown in FIGS. 1 and 2 are determined by the required light beam spot pattern. Although the optical information recording / reproducing apparatus relating to the optical card has been described in the present embodiment, it is needless to say that the present invention can be applied to other recording media such as a magneto-optical disk and a card.

[0036]

As described above, according to the present invention,
By making the area of the optical element that causes the diffraction phenomenon larger than the diameter of the incident light flux, a change in the amount of light due to the optical axis shift of the area where the incident light flux and the diffraction phenomenon occur, for example, AT, D
It is possible to suppress a change in the light amount of each of the V, RF, and W (0th order) light spots.

Further, when the diffraction efficiency is made constant in the entire region where the diffraction phenomenon is caused, the light amount of the W light is invariable with respect to the incident light beam and the optical axis shift of the region where the diffraction phenomenon is caused.

[Brief description of drawings]

FIG. 1 is a schematic view of a first embodiment of a diffraction grating used in the present invention.

FIG. 2 is a schematic view of a diffraction grating according to a second embodiment of the present invention.

FIG. 3 is a schematic view of a diffraction grating for reciprocal recording and simultaneous reproduction of a plurality of tracks.

FIG. 4 is a layout diagram of light spots for performing reciprocal recording and simultaneous reproduction of a plurality of tracks.

FIG. 5 is an arrangement diagram of sensor elements when performing reciprocal recording and simultaneous reproduction of a plurality of tracks.

FIG. 6 is a schematic plan view of an optical card.

FIG. 7 is a partially enlarged view of the optical card.

FIG. 8 is a configuration diagram of a separation type optical head optical system.

FIG. 9 is a spectral characteristic diagram of a polarization beam splitter.

FIG. 10 is a diagram showing the relationship between the shape and arrangement of photodetectors and the light spot in the optical head of the conventional optical information recording / reproducing apparatus.

[Explanation of symbols]

1 Optical Card 20 Total Reflection Prism 21 Semiconductor Laser 22 Collimator Lens 23 Beam Shaping Prism 24, 24 'Diffraction Grating 25 Polarizing Beam Splitter 26 1/4 Wave Plate 27 Objective Lens 28 Spherical Lens 29 Cylindrical Lens 30 Photodetectors 30a, 30b, 30c light receiving element S ₁ , S ₂ , S ₃ light spot S _a , S _b , S _c light spot 50 diffraction grating 51 diffraction grating

Claims (4)

[Claims] 1. In an optical element for splitting a light flux from a light source into a plurality of light fluxes by utilizing a diffraction phenomenon, a region in which the diffraction phenomenon is generated is divided into a plurality of regions, and the diffracted light is emitted from each of the divided regions. Are different from each other, and the region in which the diffraction phenomenon is generated is a region larger than the region irradiated with the light beam from the light source. 2. The optical element according to claim 1 is irradiated with a light beam from an irradiation optical system, and a light beam emitted from each of the divided areas is irradiated onto an optical information recording medium, whereby optical information is recorded. An optical information recording / reproducing apparatus for recording information on a recording medium and / or reproducing a recorded information by detecting a light flux from the optical information recording medium. 3. The optical information recording / reproducing apparatus according to claim 2, wherein the area where the diffraction phenomenon of the optical element occurs is 3
Of the light beams divided by the optical element, the light that has not been affected by the diffraction phenomenon is used as the recording light flux, and the light that has undergone the other diffraction phenomenon is used for direct verification light and auto-tracking. Optical information recording / reproducing device used as light and reproducing light. 4. The optical information recording / reproducing apparatus according to claim 2 or 3, wherein the plurality of divided regions that generate a diffraction phenomenon have the same diffraction efficiency over the entire region. Information recording / reproducing apparatus.