JPH07272309A - Optical information recording/reproducing device - Google Patents

Abstract

PURPOSE:To provide a small-sized optical information recording/reproducing device capable of preventing a light spot from deviation from a sensor without increasing a cost. CONSTITUTION:A distance between a center of a quadripartite sensor 30b constituting a detection optical system and the center of AT sensors 30a, 30c is defined D. The quadripartite sensor 30b and the AT sensors 30a, 30c are arranged so that the distance D becomes D=fS/fTd (where, an fT is a focal distance of an objective lens for irradiating a luminous flux on a recording medium, and an fS is the focal distance of a sensor lens of the detection optical system, and a (d) is the distance between a zero-order light spot and (+ or -) 1st order light spots in the track traverse direction on the recording medium).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus for recording and / or reproducing information on an optical information recording medium.

Further, the present invention particularly relates to an optical information recording / reproducing apparatus in which the constituent elements of the optical head are divided into a movable portion and a fixed portion.

[0003]

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 a light 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 optical head used for recording / reproducing information on / from the recording medium is relatively movable with respect to the recording medium in the information track direction and in a direction transverse to the direction. 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 mediums, a card-shaped optical information recording medium (hereinafter referred to as an optical card) is a small-sized and light-weight portable information recording medium having a relatively large capacity, which will be large in the future. Demand is expected.

FIG. 3 is a schematic plan view of the write-once type optical card, and FIG. 4 is a partially enlarged view thereof.

In FIG. 3, 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. 4, 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. .

The AT servo detects a 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 an objective lens is provided 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, at the time of recording / reproducing information, when scanning an information track with a light beam spot, in order to make the light beam into a spot shape of an appropriate size (focus) on the surface of an optical card, Focusing (hereinafter referred to as AF) servo is performed. The 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. 4, S₁ , S₂ , S₃ Is
Shows the light beam spot, S₁ And S ₃ Use the light spot of
And use AT to do S₂ AF using the light spot of
And the creation of information bits during recording and
Read out. In each information track, 6-
1, 6-2 and 7-1, 7-2 are preformatted respectively
The left side address part and the right side address part are shown.
The information track can be identified by reading the address section.
Be played. 5 (corresponding to 5-1 and 5-2 in the figure) is the data
This is a data section in which predetermined information is recorded.

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

In FIG. 5, reference numeral 21 denotes a semiconductor laser which is a light source, and in this example, emits light having a wavelength of 830 nm which is polarized in the direction perpendicular to the track. Further, 22 is a collimator lens, 23 is a beam shaping prism, 24 is a diffraction grating for splitting a light beam, and 25 is a polarization beam splitter. Further, 26 is a quarter wave plate, 20 is a mirror, 27
Is an objective lens, 28 is a spherical lens (sensor lens of the detection optical system), 29 is a cylindrical lens, and 30 is a photodetector. The photodetector 30 includes two light receiving elements 30a, 3
0c and the light receiving element 30b divided into four.

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. 5, the focused light is converted into three small beam spots S ₁
(+ 1st-order diffracted light), S ₂ (0th-order diffracted light), and S ₃ (−1st-order diffracted light). S ₂ is used for recording, reproduction and AF control, and S ₁ and S ₃ are used for AT control. As shown in FIG. 4, the spot positions on the optical card 1 are such that the light beam spots S ₁ and S ₃ are located on the adjacent tracking tracks 4 and the light beam spot S ₂ is the information track 2 between the tracking tracks. Located on top. Thus, the reflected light from the light beam spot formed on the optical card 1 passes through the objective lens 27 again to be a parallel light beam, and passes through the quarter-wave plate 26 so that the polarization direction is 90 degrees from that at the time of incidence. ° Converted to a rotated light beam. Then, it enters the polarization beam splitter 25 as an S-polarized beam, is reflected by nearly 100% due to the spectral characteristics shown in FIG. 6, 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 by this combination, AF control by the astigmatism method is performed. 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, fourth light receiving 30b of split light spot S ₂
The reflected light is received and the output is used for AF control and the recorded information is reproduced. Light receiving elements 30a, 30
FIG. 7 shows how the light spots are formed at points b and 30c. The formed light spots S _a , S _b , and S _c are included in the light receiving elements 30a, 30b, and 30c.

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

By the way, the optical head optical system as described above is
As shown in FIG. 5, the information track can be scanned with the light beam spot S _b by dividing it into a fixed part and a movable part, and moving only the movable part as shown by the arrow in FIG. . In such a separation type optical head, the amount of movement of the movable portion needs to be about the length of the optical card 1 in the vertical direction, and is usually about 100 mm. When the AT control of the three-beam method is performed in the separation type optical head, its optical length is long, and it is necessary to reduce the diffraction angle in order to prevent vignetting of ± first-order light. Therefore, the distance of the three beams on the optical card becomes small, and in order to expand the small distance on the sensor and separate the three beams, a lens having a long focal length must be used for the detection optical system.

[0019]

[Problems to be Solved by the Invention]

(Problems A and B) However, conventionally, the diffraction angle fluctuates due to a manufacturing error of the diffraction grating, and accordingly, the groove of the optical card and the positions of the ± first-order light fluxes must be matched by rotating the diffraction grating. Since the light spot has to be moved, the light spot may move on the sensor and may be displaced from the sensor, which causes a problem that the AT control signal is deteriorated.

FIG. 2 is a diagram for explaining such a problem. FIG. 2 (a) shows the light spots S ₁ and S on the recording medium.
_As examples of the positions of ₂ and S ₃ , examples of A, B and C are shown. Further, (b) is a diagram showing a positional relationship between the light spot position on the conventional photodetector, the AT sensors 30a and 30c, and the four-division sensor 30b.

As shown in FIG. 2B, at the positions of the conventional AT sensors 30a and 30c, when the light spot shifts to the positions A and C, the light spots also shift from the position of the sensor, and good tracking is difficult. The problem arises that

The above problem can be dealt with by selecting the diffraction grating, but there is a problem that the cost is increased.

(Problem C) Further, when the AT control of the three-beam method is performed in the separation type optical head, its optical length is long, and it is necessary to reduce the diffraction angle in order to prevent vignetting of ± first-order light. there were. Therefore, the distance of the three beams on the optical card becomes small, and in order to expand the small distance on the sensor and separate the three beams, a lens having a long focal length must be used for the detection optical system. There is also a problem that the entire optical head becomes large.

[Object of the Invention] An object of the present invention is to provide an optical information recording / reproducing apparatus capable of preventing the sensor displacement of the light spot without increasing the cost.

Another object of the present invention is to realize an optical information recording / reproducing apparatus with a miniaturized optical head.

[0026]

[Means and Actions for Solving the Problems]

(Means and Action A) According to the present invention, the AT on the photodetector
The distance D between the center of the sensor and the center of the four-division sensor is D = f _S · d / f _T (where f _T is the focal length of the objective lens, f _S is the focal length of the sensor lens (convex lens), and d is the recording distance). The distance between the 0th-order light spot and the ± 1st-order light spots on the medium in the track crossing direction) and the rectangular sensor shape that is long in the track advancing direction are used to shift the light spots on the photodetector. Can also be kept on the sensor.

(Means and Action B) According to the present invention, the optical inspection
Set the output device at θ = 90 ° + cos relative to the direction of travel of the truck.
^-1(L / L) -cos^-1Rotate only (D / L)
Causes the light spot due to the ± 1st-order light flux to stick out from the sensor.
You can prevent it.

Further, since the four-division sensor also rotates at the same time, by rotating the cylindrical lens accordingly, a good AF control signal can be obtained as in the conventional case.

(Means and Action C) According to the present invention, the angle between the rotation angle β of the diffraction grating (the inclination angle of the ± first-order light flux with respect to the track traveling direction) and the line connecting the two AT sensors and the track traveling direction. By making α almost equal, ± 1
Since the focal length of the lens of the detection optical system can be minimized within the range where the next light flux does not protrude from the sensor, the optical head can be downsized.

At the same time, by rotating the cylindrical lens in the detection optical system in accordance with the rotation of the 4-division sensor, the AF control signal can be as good as the conventional one.

[0031]

【Example】

(Embodiment A1) Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. The components of the optical system are the same as those of the conventional device shown in FIG. 5 except for the photodetector, and the description thereof will be omitted.

FIG. 1 is a diagram showing the positions of light spots and sensors on a photodetector embodying the present invention.

As shown in FIG. 1, the four-division sensor 30
The distance D in the track crossing direction on the sensor surface between the center of b and the centers of the AT sensors 30a and 30c is defined by D = f _S / f _T · d, which is a feature of the present invention. f _S is the focal length of the sensor lens, which is a convex lens shown in 28 of FIG. 5, f _T is the focal length of the objective lens, d is the 0th-order light spot and ± 1st-order light spot on the optical recording medium such as an optical card. Represents the distance in the cross-track direction from and.

Each of the AT sensors 30a and 30c has a rectangular shape that is long in the track traveling direction on the sensor surface, and its length is set to a length that can cover variations due to manufacturing errors of the diffraction grating and variations due to other factors. Further, it is preferable that the length in the cross-track direction is such that one light spot can be suppressed without vignetting.

The reason why such a shape is adopted will be described below.

It is known that the smaller the AT sensor, the more sensitive the AT control is. Therefore, it is nonsense to make the sensor large so as to absorb the manufacturing error of the diffraction grating, and the size should be set to the minimum necessary. Also, ±
Even if the distance between the 1st-order light spot and the 0th-order light spot varies due to the manufacturing error of the diffraction grating, by rotating the diffraction grating, the degree of the ± 1st-order light spot applied to the groove is always adjusted to be equal. Since it is possible, the distance D is constantly constant.

In other words, even if the distance between the 0th-order light and the ± 1st-order light changes due to the manufacturing error of the diffraction grating, the ± 1st-order light spot is 4
It can be seen that it only moves on a straight line separated from the center of the divided sensor by D in the track crossing direction. Therefore, it is understood that such a sensor arrangement is most preferable.

FIG. 2 is a diagram for explaining such a problem. FIG. 2 (a) shows the light spots S ₁ and S on the recording medium.
_As examples of the positions of ₂ and S ₃ , examples of A, B and C are shown. Further, (b) is a diagram showing a positional relationship between the light spot position on the conventional photodetector, the AT sensors 30a and 30c, and the four-division sensor 30b.

As shown in FIG. 2B, at the positions of the conventional AT sensors 30a and 30c, when the light spots are displaced to the positions A and C, they are also displaced from above the sensor.
In the present embodiment shown in (2), even if the light spot is deviated to the positions of A and C, it stays on the AT sensors 30a and 30c, and good tracking becomes possible.

(Embodiment B1) An embodiment of the present invention will be described in detail below with reference to FIGS. 8 and 5.
The components of the optical system are the same as those of the conventional example, and the description thereof is omitted.

FIG. 8 shows the light on the photodetector embodying the present invention.
It is a figure showing the position of a spot and a sensor. Angle θ
Is two in the direction of track travel on the photodetector.
The angle formed by the line connecting the AT sensors 30a, 30c of
And θ = 90 ° + cos ^-1(L / L) -cos^-1
(D / L). In addition, the AT sensors 30a, 30
The shape of b is a quadrangle.

With such a sensor shape and arrangement, even if a manufacturing error of the diffraction grating occurs, it is possible to prevent the sensor from being separated from the AT sensor.

Needless to say, if the direction of the generatrix or the sagittal line of the cylindrical lens in the detection optical system is rotated accordingly, the AF signal by the astigmatism method can obtain the same good signal as the conventional one. Yes.

That is, conventionally, the generatrix or the sagittal line of the cylindrical lens is arranged inclined by 45 ° with respect to the track traveling direction, but in the present embodiment, it is 45-θ or 45.
It means to arrange as + θ.

By arranging the ± 1st-order light spots and the sensor as described above, the ± 1st-order light spots can be detected by the AT sensor 3 even though the same photodetector as the conventional one is used.
It can be arranged so as not to overflow from 0a and 30c.

As a result, the present invention can contribute to miniaturization of the optical head and the entire device.

(Embodiment C1) An embodiment of the present invention will be described in detail below with reference to FIGS. 9 and 5.
The components of the optical system are the same as those of the conventional example shown in FIG.

FIG. 9 is a diagram showing the positions of light spots and sensors on the photodetector embodying the present invention.

The angle α is the track advance on the photodetector.
Connects two AT sensors 30a and 30c in the row direction
It defines the angle formed by the line and
Line that connects the three beams with the direction of travel (the 0th-order light spot S₂ 
And ± primary light spot S₁ , S ₃ Angle β formed by the line
They are arranged almost equally.

FIG. 10 is a diagram for explaining the effect of this embodiment, (a) shows the positions of the light spots S ₁ , S ₂ , S ₃ on the recording medium such as an optical card, and (b). ) Shows the positions of the respective sensors 30a, 30b, 30c and the light spots S _a , S _b , S _c on the conventional photodetector.

As is clear with reference to FIG. 10, taking the state of the light spot B as an example, the conventional AT sensors 30a and 30c of FIG. It can be seen that if the sensor is tilted and arranged as α = β as in the present embodiment, the sensor stays on the sensor and the vignetting of the light spot becomes significantly stronger.

Needless to say, if the direction of the generatrix or the sagittal line of the cylindrical lens in the detection optical system is rotated accordingly, the AF signal by the astigmatism method can obtain the same good signal as the conventional one. Yes.

That is, conventionally, the generatrix or the sagittal line of the cylindrical lens is arranged at an angle of 45 ° with respect to the track traveling direction, but in the present embodiment, it is 45-α or 4.
It means to arrange as 5 + α.

By arranging the ± first-order light spots and the sensor in this way, the ± first-order light flux is transmitted to the AT sensor 30.
Since the focal length of the lens of the detection optical system can be minimized within a range that does not protrude from a and 30c, the optical head and the entire apparatus can be downsized.

[0055]

As described above, according to the present invention,
By making the shape of the AT sensor a rectangle long in the track traveling direction, or by arranging the AT sensor while rotating it by a predetermined angle with respect to the track traveling direction, the light spot position is displaced on the photodetector. However, since it is possible to prevent the sensor from being displaced from the sensor, it is possible to obtain a good AT signal.

Further, since no new parts or processes are used, there is an effect that there is no cost increase.

Further, even if the focal length of the lens of the detection optical system is minimized, the light spot can be prevented from protruding from the sensor, so that the effect of miniaturizing the optical head portion can be obtained.

Further, even if the diffraction angle fluctuates due to a manufacturing error of the diffraction grating and the position of the light spot on the photodetector shifts, it can be prevented from shifting from the sensor, which facilitates the adjustment. At the same time, the manufacturing of the diffraction grating becomes easy.

[Brief description of drawings]

FIG. 1 is a diagram showing a position of a light spot and a sensor according to an embodiment A1 of the present invention.

FIG. 2 is a diagram showing the positions of a conventional light spot and a sensor.

FIG. 3 is a schematic plan view of an optical card.

FIG. 4 is a partially enlarged view of an optical card.

FIG. 5 is a schematic diagram of an optical head optical system.

FIG. 6 is a spectral characteristic diagram of a polarization beam splitter.

FIG. 7 is a diagram showing a relationship between a shape and an arrangement of a photodetector and an optical spot in an optical head of an optical information recording / reproducing apparatus.

FIG. 8 is a diagram showing the positions of a light spot and a sensor in Example B1 of the present invention.

FIG. 9 is a diagram showing the positions of a light spot and a sensor in Example C1 of the present invention.

FIG. 10 is a diagram showing the positions of a conventional light spot and a sensor.

[Explanation of symbols]

1 Optical Card 2 Mirror 21 Semiconductor Laser 22 Collimator Lens 23 Beam Shaping Prism 24 Diffraction Grating 25 Polarizing Beam Splitter 26 1/4 Wave Plate 27 Objective Lens 28 Spherical Lens (Sensor Lens of Detection Optical System) 29 Cylindrical Lens 30 Photodetector 30a , 30c light receiving element (AT sensor) 30b light receiving element (four-division sensor) S ₁ , S ₂ , S ₃ light spots _Sa , S _b , S _c light spots

Claims (7)

[Claims] 1. An optical head, which focuses a light beam from an irradiation optical system to irradiate the optical information recording medium as a light spot and projects the light beam from the light spot on the recording medium onto a detection optical system, In an optical information recording / reproducing apparatus for recording information on the recording medium and / or reproducing recorded information by irradiation of a light beam from the irradiation optical system, a center of a four-division sensor and an AT sensor constituting the detection optical system. Assuming that the distance corresponding to the central track crossing direction is D, D = f _S / f _T d (where f _T is the focal length of the objective lens for irradiating the recording medium with a light beam, and f _S is The focal length of the sensor lens of the detection optical system, d is the distance between the 0th-order light spot and the ± 1st-order light spots in the track crossing direction on the recording medium). And the AT An optical information recording / reproducing apparatus having a sensor. 2. The AT sensor is a rectangle that is long in the track traveling direction on the sensor surface, and at least the AT sensor
2. The optical information recording / reproducing apparatus according to claim 1, wherein one AT sensor is vertically and horizontally symmetrically arranged about the four-division sensor. 3. An optical head is provided which focuses a light beam from an irradiation optical system and irradiates the optical information recording medium as a light spot, and projects a light beam from the light spot on the recording medium onto a detection optical system. In an optical information recording / reproducing apparatus for recording information on the recording medium and / or reproducing the recorded information by irradiation of a light beam from the irradiation optical system, a rectangular AT sensor and a four-division sensor constituting the detection optical system. An optical information recording / reproducing apparatus, wherein the photodetector consisting of is arranged so as to be rotated and inclined with respect to the track traveling direction on the photodetector. 4. The optical information recording / reproducing apparatus according to claim 3, wherein the inclination of the photodetector is arranged so as to rotate by an angle θ shown below with respect to the track traveling direction. θ = 90 ° + cos ^-1 (l / L) -cos ^-1 (D / L) (where l is the side of the AT sensor divided by a straight line drawn from the center of the 4-division sensor to the center of the AT sensor) 1/2 length L is the length from the center of the 4-division sensor to the corner farther from the 4-division sensor of the AT sensor D is the ± 1st order light spot of the groove on the optical recording medium Is a line projected on the container, and is an amount defined by D = f _S / f _T d, f _S is the focal length of the sensor lens of the detection optical system, f _T is the focal length of the objective lens, and d is (It is the distance between the 0th order light and ± 1st order light spots in the track crossing direction.) 5. An angle formed by a generatrix or a sagittal line of a cylindrical lens forming the detection optical system of the optical information recording / reproducing apparatus and a line projecting the track traveling direction is 45 ° −θ or 45 ° + θ (θ is The optical information recording / reproducing apparatus according to claim 3 or 4, wherein a rotation angle θ) of the photodetector according to claim 4 with respect to the track traveling direction. 6. An optical head is provided which narrows a light beam from an irradiation optical system and irradiates the optical information recording medium as a light spot, and projects the light beam from the light spot on the recording medium onto a detection optical system. A fixed part including the irradiation optical system and the detection optical system for recording information on the recording medium and / or reproducing the recorded information by irradiation of a light beam from the irradiation optical system, and an objective movable relative to the fixed part. In an optical information recording / reproducing apparatus including a movable portion including a lens, an angle formed by a line connecting two AT sensors of the detection optical system with respect to a track traveling direction on the sensor surface is α, When the angle connecting the 0th-order light spot and the ± 1st-order light spots on the recording medium to the track traveling direction on the recording medium is β, the α and β are substantially equal to each other. The optical information recording and reproducing apparatus, characterized in that the. 7. An angle formed by a generatrix or a sagittal line of a cylindrical lens forming the detection optical system and a line projecting the track traveling direction is 45-α or 45 + α (α is the angle α according to claim 6). 7. The optical information recording / reproducing apparatus according to claim 6, wherein