JPS61269232A - Optical information processing device - Google Patents

Abstract

PURPOSE:To omit a conventional isolator optical system and to make an optical waveguide on a substrate unnecessary by emitting a laser beam in a diagonal upper direction from a substrate, also receiving a reflected light from the diagonal upper direction, projecting the rays of light from a light source to one face of the substrate, making it transmit through the substrate in a thickness direction and emitting it from the other face of the substrate. CONSTITUTION:A grating lens 13 emits the rays of light emitted from the semiconductor laser 12 of a lower part, also spread out and transmitted through a substrate 11 and reaches the lens 13, in the diagonal upper direction from the upper face of the substrate 11, and also condenses it two-dimensionally. A point where an emitted laser beam is condensed to form a spot (about 1mum diameter) is denoted by P. In case of reading the information recorded in an optical disk, this optical pickup head 9 is placed so that the laser spot P is positioned on the information recording surface of the optical disk.

Description

DETAILED DESCRIPTION OF THE INVENTION Summary of the Invention Off-axis lens means is formed on a transparent Φ substrate by projecting diffused light from a light source such as a semiconductor laser in a direction substantially perpendicular to one surface of the substrate. As a result, this projected light is emitted obliquely into the air from the other surface of the substrate and is condensed. Of the collected light, the light reflected by an optical disk or the like and returned is received by a light receiving means formed on the substrate.

Background of the Invention (1) Technical Field of the Invention The present invention relates to an optical pickup that focuses laser light from a semiconductor laser or the like, irradiates it onto the information recording section of an optical disk, and reads information on the optical disk based on changes in the intensity of the reflected light. The present invention relates to an optical information processing device typified by the device.

(2) Description of the Prior Art In recent years, as high-density optical discs and memories have been put into practical use, there are expectations for the development of high-performance, compact and lightweight optical pickup devices.

The main parts of a conventional optical pickup device consist of an optical system and a drive system.The optical system basically focuses a laser beam onto the information recording area of an optical disk using a focusing lens, and collects the reflected light from the optical disk. It has the function of converting light into an electrical signal using a photodiode, and changes in the amount of reflected light due to information recorded on the optical disk are extracted as electrical signals.

The optical system includes an isolator optical system that separates light irradiated onto the optical disc and light reflected from the optical disc, a beam focusing optical system that focuses the light irradiated onto the optical disc into a spot with a diameter of about 1 μm, and and an error detection optical system for detecting focusing errors and tracking errors. These optical systems are constructed by appropriately combining elements such as a semiconductor laser as a light source, various lenses, prisms, nine diffraction gratings, mirrors, 174-wave plates, and photodiodes.

The drive system includes a focusing drive system, a tracking drive system, and a radial feed drive system.

The focusing drive system is a mechanism for maintaining an appropriate distance between the focusing lens and the optical disk surface so that the light beam focused by the focusing lens forms a correct spot on the optical disk surface. The most common type is one in which the adjustment is made by moving the focusing lens in the direction of its tip axis.

The tracking drive system is a mechanism for tracking the laser spot so that it does not deviate from the track of the optical disk. This mechanism includes one that adjusts the focusing lens by moving it in a direction perpendicular to the optical axis, one that moves the entire optical pickup head in the radial direction of the optical disk, and one that adjusts the focusing lens by moving it in the radial direction of the optical disk. Those that adjust the angle of light are commonly used.

The radial feed drive system is a mechanism for feeding the optical pickup head in the radial direction of the optical disk, and generally uses a linear motor for this purpose.

Such conventional optical pickup devices have the following drawbacks.

The optical system is complicated and alignment of the optical axis is troublesome, and
The optical axis tends to shift due to vibration.

There are many parts, and it takes time to assemble two parts, which is bad for productivity.

Since the optical components are expensive, the overall cost is also high.

Since the optical components are large, the optical pickup device is also large, and a mechanism for holding the two optical components is also required, which increases the overall weight.

Summary of the Invention (1) Purpose of the Invention An object of the present invention is to provide an optical information processing device that is small, lightweight, and has a simple configuration.

(2) Structure and effect of the invention The optical information processing device according to the invention includes a substrate that is transparent to the light used, a light source that projects diffused light almost perpendicularly to one surface of the substrate, and a A lens means provided on the substrate for emitting light diagonally upward from the other surface of the substrate and condensing the light, a light receiving means provided on the substrate for receiving light reflected from diagonally above, and a position of the substrate. 1. It is characterized by comprising a focusing drive mechanism that adjusts the position of the substrate in the downward direction and a tracking drive mechanism that adjusts the position of the substrate in the lateral direction.

In this invention, since lenses, prisms, diffraction gratings, mirrors, quarter-wave plates, and the like are not used as optical components, the device can be made smaller and lighter.

In particular, since the laser beam is emitted diagonally upward from the substrate and the reflected light from diagonally upward is received, the isolator optical system required in the optical system of conventional optical pickup devices can be omitted. . Furthermore, in this invention, the light from the light source is projected onto one surface of the substrate, transmitted through the substrate in the thickness direction, and emitted from the other surface of the substrate, so there is no need to create an optical waveguide on the substrate. The structure is extremely simple and its manufacture is also easy.

DESCRIPTION OF THE EMBODIMENTS (1) Outline of structure of optical pickup head FIG. 1 shows the structure of an optical pickup head 9. As shown in FIG. Base 10
Second, the substrate 11 is provided and fixed via a suitable support member 19. The substrate 11 is made of a material, such as glass, that is transparent to the light used, that is, the output light of the semiconductor laser 12.

A part of the substrate 11 is off-axis (off'-ax).
is) a grating lens 13 is formed.

A semiconductor laser 12 as a light source is arranged below this grating lens 13, and a suitable means (as shown in the diagram)
It is fixed on the base 10 by. Grating・
The lens 13 allows the light that is emitted from the semiconductor laser I2 located below, spreads, passes through the substrate 11, and reaches the lens 13 to be emitted obliquely upward from the upper surface of the substrate 11, and
It focuses light dimensionally. P indicates a point where the emitted laser beam is condensed to form a spot (about 1 μm in diameter). When reading information recorded on an optical disc, the optical pickup head 9 is arranged so that the laser spot P is located on the information recording surface of the optical disc.

A light receiving section 20 is formed on the substrate 11 at a location separated from the grating lens 13 by an appropriate distance. The light receiving section 20 is for receiving reflected light from the information recording surface of the optical disc, and is arranged at a position where it can receive the light reflected diagonally downward from the position of the laser spot P described above.

The light receiving section 20 consists of four independent light receiving elements 21 to 24. The light receiving elements 21 and 22 are arranged adjacent to the center,
There are other light receiving elements 23 before and after these light receiving elements 21 and 22.
．． 24 are provided. These light receiving elements 21 to 24
is formed by depositing amorphous St on the substrate 11, for example. Output signals from the light receiving elements 21 to 24 are guided to electrodes 41 to 44, respectively, by a wiring pattern formed on the substrate 11, and further guided to electrodes (paths shown) on the base 10 by wire bonding. In FIG. 1, the a electrodes of the light receiving elements 21 to 24 are not shown.

Since the information recorded on the optical disc appears as a change in the intensity of two reflected lights, the sum signal of the output signals of all these light receiving elements 21 to 24 or the sum signal of the light receiving elements 21 and 22 becomes the read signal of the recorded information.

In addition to amorphous Si, CdTe can be used as a light receiving element.
or CdS can be used.

FIG. 2 shows another example of how to attach the semiconductor laser [2. A substrate 11 that is thicker than that shown in FIG. 1 is used. A concave portion 18 is formed on the lower surface of the substrate 11 at a position directly below the grating lens 13 formed on the surface of the substrate 11, and the semiconductor laser 2 is housed in the four portions 18 and fixed by being bonded to the substrate If. has been done. In this way, the semiconductor laser 1
By providing the optical pickup head 2 on the lower surface of the substrate 11, the structure of the optical pickup head 9 can be further simplified.

The positioning of the semiconductor laser 12 may be performed as follows. The semiconductor laser 12 is supported on a stage that can be finely adjusted in the x, y, z, and θ directions and is housed in the recess 18, so that the light emitted from the semiconductor laser 12 and collected by the grating lens 13 is reflected on the adjustment optical disk. This optical pickup head 9 is arranged with respect to the W optical disc so that the optical disc is reflected by the surface. The light receiving section 20 receives the reflected light from the adjustment optical disk. On the other hand, a circuit is provided that generates a reference voltage corresponding to the voltage that will be output from the light receiving section when the focusing and tracking of the optical spot on the adjustment optical disk become optimal. The output voltage of the light receiving section 20 and this reference voltage are compared, and the stage is moved to finely adjust the position of the semiconductor laser 12 so that the difference between them becomes minimum. When the position of the semiconductor laser 12 is optimized, the semiconductor laser 12 is fixed to the substrate using, for example, instant adhesive.

FIG. 3 shows the other side of the light receiving section 20. Light receiving section 20
The four light-receiving elements 21 to 24 constituting the structure are formed on a chip 25 that is separate from the substrate 11. These light receiving elements 21 to 24 are formed, for example, by creating four independent PN junctions (photodiodes) on the S1 chip 25. The light receiving chip 25 is bonded onto the substrate 11. This positioning of the chip 25 is also performed in the same manner as described above. The position of the semiconductor laser 12 is fixed, and the light receiving part 20 is adjusted while adjusting the position of the chip 25.
The chip 25 is fixed at the position where the output voltage is maximum.

(2) Off-axis condensing lens FIGS. 4 and 5 show the structure of the grating lens 13. This grating lens 13
can be fabricated by electron beam lithography. That is, a conductive film 1B is formed on a glass substrate 11, and an electron beam resist is uniformly applied thereon.

Then, a predetermined interference fringe pattern is drawn on the resist using an electron beam drawing device controlled by a computer. After this, when the resist is developed, a portion 17 of the resist remains.

1; A grating lens structure with corrugations in a grating pattern is created.

The interference fringe pattern shown in "-" is calculated by a computer as an interference fringe pattern of the diffused light emitted from the semiconductor laser 12 and the obliquely emitted and converged light from the lens 13.

Instead of the corrugations formed by the resist 17, corrugations made of 5n02 or I n O2 may be formed on the substrate 11, and this may be used as a grating lens.

In this case, the resist pattern described above may be formed as a mask on these materials, the unmasked portions of the material may be etched using dry etching techniques, and finally the resist pattern may be removed.

The off-axis condensing lens is not limited to the above-mentioned grating lens. For example, a hemispherical convex portion or concave portion may be formed on the substrate 11 as an optical lens. Since it is an off-axis optical lens that emits light obliquely upward, it is necessary to change the curvature of its convex or concave surface depending on the location.

Of course, such an off-axis condensing lens may be formed on the bottom surface of the substrate 11 instead of the top surface.

(3) Detection of focusing errors Bits (indentations) representing digital information by length and position are formed along the track on the information recording surface of an optical disk. Figure 6 is.

The positional relationship between the optical disk 81 and the optical pickup head 9 is shown by cutting the optical disk 81 along its circumferential direction. The laser beam emitted from the grating lens 13 is reflected by the information recording surface of the optical disk 81 (the portion including the bit 82 in FIG. 6) and is received by the light receiving section 20. FIG. 7 shows that the reflected light from the optical disc 81 is transmitted to the light receiving section 2.
The range of irradiation with 0 is shown.

In FIG. 6, the optical disk 81 and the bit 82 shown by solid lines have the optimum distance between the optical disk 81 and the first pickup head 9, and the optical disk 81 and the bit 82 of the output light are optimal.
This shows that focusing on 1 is performed correctly. The irradiation area of the reflected light on the light receiving section 20 at this time is indicated by Q. This irradiation area Q is located on the central light receiving element 21.22, and no reflected light is received by the other light receiving elements 23.24.

The position of the optical disc 81 when proper focusing cannot be performed because the distance between the optical disc 81 and the pickup head 9 becomes relatively large or small is the sixth position.
Indicated by dashed lines in the figure. When the distance between the optical disk 81 and the pickup head 9 becomes relatively small (a displacement of -Δd), the irradiation area of one reflected light (represented by Ql) shifts to the light receiving element 23 side. Stop by. Since the light receiving element 23 is connected to the negative side of the differential amplifier 7, and the light receiving element 24 is connected to the positive side, in this case, the output of the differential amplifier 71 shows a negative value, and this value is the displacement amount. - represents the magnitude of Δd.

When the distance between the optical disk 81 and the pickup head 9 becomes relatively large (displacement of +△d), the irradiation area (represented by Q2) of the 2-reflected light is
Move to the 4th side. The output of the differential amplifier 71 shows a positive value, and the value in parentheses represents the amount of displacement +Δd.

In this way, whether the focusing of the light beam emitted from the pickup head 9 is appropriate or not, and if a focusing error occurs, the direction and magnitude of the error are detected from the output of the differential amplifier 571. . If there is no focusing error, the output of the differential amplifier 71 is zero.

(4) Detection of tracking error FIG. 8 shows the bit 82 formed on the optical disc 81 and the light receiving elements 21 and 22 of the light receiving unit 20 arranged on the same plane. It is a diagram of the light receiving elements 21 and 22 seen through in the plane direction. The differential amplifier 72 is illustrated for the purpose of clarifying the electrical connection relationship with the light receiving elements 21 and 22.

FIG. 8(A) shows that the laser beam spot P is located exactly on the center of the track (bit 82) in the width direction. 8B and 8C show that the spot P is slightly shifted to the left and right of the track (bit 82), causing a tracking error. In either case, it is assumed that proper focusing is achieved.

The laser spot P hits the information recording surface of the optical disk 81, and the intensity of the reflected light is modulated by the presence of the bit 82. Since the spot size of bit 82 is slightly larger than that of bit 11, there is light reflected at the bottom of bit 82 and light reflected at parts other than bit 82, and the depth of bit 82 is λ/ 4 (λ is the wavelength of the laser beam), a phase difference of π occurs between the two types of reflected light, which cancel each other out and reduce the light intensity. There is an explanation that light scattering occurs at the edges of 82, which reduces the intensity of the reflected light received. In any case, the presence of the bit 82 reduces the intensity of light received by the light receiving section 30.

The light receiving elements 21 and 22 are divided into left and right parts with the optical axis as a boundary. When the center of the laser spot P and the center of the bit 82 in the middle direction match, the light receiving elements 21 and 22
The amount of light received by both is equal, and the output of the differential amplifier 72 is zero.

As shown in FIG. 8(B), when the laser spot P shifts to the left side of the bit 82, the amount of light received by the light receiving cable 21 increases, and the positive Output occurs. Conversely, as shown in FIG. 8(C), when the laser spot P shifts to the right side of the bit 82, a negative output is generated in the differential amplifier 72.

In this way, the output of the differential amplifier 72 allows the beam to be
It is detected whether the spot P is exactly along the track of the optical disc 81, whether a tracking error has occurred, and whether the error is shifted to the left or right.

(5) Focusing and tracking drive mechanism FIGS. 9 to 11 show a focusing drive mechanism and a tracking drive mechanism.

A support member 101 is erected at one end of the support plate ■00. Both lower end portions of this support member 101 are notched (numeral 102). A movable member 103 is located above the other end of the support plate 100 . "1 Four leaf springs that can be elastically bent downward 121. One end of 122 is a support member l
It is fixed to both sides of the upper end of the movable member 103 and to the lower notch 102, and the other end is fixed to both sides of the upper end and the lower end of the movable member 103, respectively. Therefore, movable member 103
is supported by the support member 101 via these leaf springs 121 and 122 so as to be able to move vertically.

The stage 110 on which the optical pickup head 9 is mounted is mounted on a rectangular frame 112 . It consists of both legs 114, 115 extending in the opposite direction from both ends of the square frame 112, and a central leg 113 extending downward from the center of the square frame 112. An optical pickup head 9 is mounted and fixed on a rectangular frame 112. Four leaf springs that can be elastically bent laterally
One end of the movable member 131 is fixed to the top and bottom of both sides of the movable member 103, and the other end is fixed to the bottom and top of both sides of the central leg +13 of the stage 110. The stage 110 is supported so as to be movable laterally (corresponding to the left-right direction in FIG. 8) via these leaf springs 131. Therefore, the stage 110 is movable in the vertical direction (focusing) and the horizontal direction (tracking).

Support plate 100. Support member 101. The movable member 103 and the stage 11G are made of non-magnetic material, such as plastic.

A yoke is provided on the inner surface of the support member 1 inch and the movable member 103.
104.105 are fixed. York 104 is.

A vertical part 104a fixed to the support part +4' 101 and another vertical part 10 located at a distance therefrom.
4b, and a horizontal portion joining these image portions 104a, 104b at their lower ends. The yoke 105 has exactly the same shape as the yoke 104, and has two vertical portions 105a and 105 spaced apart from each other by a certain distance.
5b.

The vertical part 104a of these yokes 104.105,
Permanent magnets 10B are fixed to the inner surfaces of the magnets 105a, respectively, with the inner surfaces serving as, for example, S poles. and.

the other vertical portion 104b of the yokes 104, 105;
Legs 114 and 115 of stage 110 are inserted between l05b and permanent magnet 106 without touching them.

A focusing drive coil 123 is wound horizontally around both legs 114 and 115 of the stage 110. Also on some of these legs 114.115.

A tracking drive coil 133 having a portion facing in the vertical direction is wound in a portion facing the permanent magnet IOB.

The focusing drive mechanism is best shown in FIG. The magnetic flux H generated from the permanent magnet 106 is directed to the vertical portion 10 of the yoke 104, 105 as shown by the chain line.
4b and 105b respectively. When a driving current is applied to the coil 123, which is disposed horizontally across this magnetic field, in a direction toward the plane of the paper in FIG. 1O, for example, an upward force F is generated. This force Ff causes the stage 110 to move upward. The amount of movement of the stage 110 can be adjusted by adjusting the magnitude of the current applied to the coil 123. Therefore, focusing control can be performed by switching the direction of this drive current according to the output signal of the differential amplifier 71 mentioned above, adjusting the magnitude of the current, or turning the current on and off.

The tracking drive mechanism is best illustrated in FIG. For example, in the direction toward the plane of the paper in FIG.
When a driving current is applied (downward in Figure 9), an upward force is applied in Figure 11 (lateral force in Figure 9).
Ft is generated and the stage 110 moves in the same direction.

Coil 13 according to the output signal of differential amplifier 72 described above.
Tracking control can be performed by turning on and off the current flowing through the sensor 3, and by adjusting the direction of the current and, if necessary, its magnitude.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an optical pickup head. FIG. 2 is a sectional view showing another example of the arrangement of semiconductor lasers. FIG. 3 is a perspective view showing another example of the light receiving section. 4 and 5 show the grating lens, with FIG. 4 being a plan view and FIG. 5 being a sectional view. FIG. 6 is a sectional view showing the positional relationship between the optical disk and the optical pickup head. FIG. 7 is a diagram showing the principle of detection of focusing errors on the light receiving section. FIG. 8 is a diagram showing the principle of detection of tracking◆error. 9 to 11 show the focusing and tracking drive mechanism. FIG. 9 is a perspective view, FIG. 1θ is a sectional view taken along line X-X in FIG. 9, and FIG. FIG. 3 is a plan view with the head removed. 9... Optical pickup head, 11... Board, 1
2... Semiconductor laser, 13... Grating
Lens, 20... Light receiving section, 21-24... Light receiving element, 1o4.105... Yoke, 106... Permanent magnet, 110... Stage, 121.122.131
... Leaf spring, 123... Focusing drive coil, 133... Tracking drive coil. Applicant for the above patents: Tateishi Electric Co., Ltd. Agent: Ken Tsukasa Ushiku and one other person Figure 4 Figure 5 Figure 7 Figure 8 Figure 10 Figure 11 Procedure amendment (film) May 1986 /2 days

Claims (1)

[Claims] A substrate that is transparent to the light used, a light source that projects diffused light substantially perpendicularly to one surface of the substrate, and a light source that projects the projected light diagonally upward from the other surface of the substrate. A lens means provided on the substrate for emitting and condensing light, a light receiving means provided on the substrate for receiving light reflected diagonally from above, a focusing drive mechanism for vertically adjusting the position of the substrate, and the substrate. An optical information processing device equipped with a tracking drive mechanism that horizontally adjusts the position of.