JPH0240141A - Optical information processor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to an optical information processing device used for optical discs such as video discs and digital audio discs.

(Prior Art) In recent years, optical information processing devices that use optical disks as information recording media have been put into practical use as high-density, large-capacity information recording and reproducing devices.

In the pickup head mechanism of such an optical information processing device, for example, as shown in FIG. The light then enters a collimator lens 5, where it is made into parallel light, and then condensed onto an optical disk 7 by a condenser lens 6.

The laser beam 2 reflected by the information recording surface of the optical disk 7 passes through the condensing lens 6 and the collimator lens 5 again and enters the beam splitter 4. Here, the light is reflected, for example, in the right angle direction, passes through a concave lens 8 and a cylindrical lens 9 in order, and is focused on a reading detector, for example, a photodiode 10.

The photodiode 10 is configured to read an increase or decrease in the amount of reflected light on the information recording surface of the optical disk 7 as an electrical signal.

In the optical information processing device configured as described above, the width and spacing of the pits recorded on the information recording surface of the optical disk 7 are set to values close to the diffraction limit in order to record information at high density. . In order to reduce the width of the pit, etc., it is necessary to reduce the spot focused by the condenser lens 6, and the NA (aperture ratio of the lens) of the condenser lens 6 must be reduced.
becomes very large.

Therefore, the inclination of the optical disc 7 with respect to the optical axis of the condensing lens 6, that is, the inclination between the normal direction of the optical disc 7 and the optical axis of the condensing lens 6, produces comatic aberration in the spot formed by the condensing lens 6, and this comatic aberration This makes it impossible to read the signal correctly.

In addition, with the spread of optical video discs in recent years, optical pickup heads are required to read not only digital audio signal information but also analog image signals. Since it is difficult to correct or correct the signal after reading, if coma aberration occurs due to the tilt of the optical disc 7, the signal-to-noise ratio of the signal deteriorates and crosstalk etc. occur.

Furthermore, since video discs have a larger disc diameter than conventional compact discs, when the center of the optical disc 7 is supported, the outer periphery of the disc may warp or sag. The inclination of the normal line with respect to the optical axis will be different.

Therefore, as the pickup head moves in the radial direction of the optical disc 7, it is necessary to detect and correct the inclination of the normal axis of the optical disc 7 with respect to the optical axis of the condenser lens 6.

(Problem to be Solved by the Invention) In order to detect the inclination of the optical disc 7 in this way, as shown in FIG. 11, conventionally, as shown in FIG. A tilt sensor consisting of two photodetectors 12 that detect reflected light from the pickup head is attached to the pickup head body, and the tilt of the optical disk 7 is detected by detecting changes in the amount of light received by the two photodetectors 12. things were being done.

However, in such a tilt detection mechanism, a separate light source 11 is required in addition to the light source 1 necessary for information recording and reproduction, so the entire optical information processing device has a complicated configuration. It was a cause of whelk.

Furthermore, in order to accurately detect the inclination, a special adjustment is required, which requires the operator to be skilled, which poses a problem from the viewpoint of work efficiency.

The present invention has been made to solve the above-mentioned problems, and it uses a special light source in addition to the light source for reading information to simplify the device and detect the tilt of an optical disc with high precision. An object of the present invention is to provide an optical information processing device that can perform the following steps.

[Structure of the Invention] (Means for Solving the Problems) The optical information processing device of the present invention includes a light emitting source and a condensing optical system that condenses a luminous flux from the light emitting source onto an information recording surface of an information recording medium. and a light beam separation mechanism interposed in the optical path between the light emitting source and the condensing optical system, and a detection mechanism for reading information based on the reflected light reflected by the information recording surface of the information recording medium. In the optical information processing device, an irradiation optical system that irradiates the information recording medium almost perpendicularly with a ray that does not enter the condensing optical system out of the rays separated by the ray beam separation mechanism; a photodetector divided into at least two parts for detecting the intensity of the reflected light from the information recording medium of the irradiated light; The present invention is characterized in that it is configured to detect the inclination of the light optical system with respect to the optical axis.

Furthermore, the present invention is based on a light emitting source, a condensing optical system that focuses a light beam from the light emitting source onto an information recording surface of an information recording medium, and a light reflected from the information recording surface of the information recording medium. an irradiation optical system that irradiates a part of the light from the light source almost perpendicularly onto the information recording medium without making it enter the condensing optical system; a photodetector divided into at least two parts for detecting the intensity of the reflected light from the information recording medium of the irradiation light irradiated from the irradiation optical system; The present invention is characterized in that it is configured to detect the inclination of the information recording medium with respect to the optical axis of the condensing optical system.

(Function) In the first aspect of the present invention, among the light beams emitted from the light emitting source and separated into at least two directions by the light beam separation means, a part of the light beams that do not enter the condenser lens and do not contribute to reading. ', the information recording medium is irradiated almost perpendicularly by optical means.

Then, the reflected light of this light beam is received by each light receiving element of the photodetector which is divided into two parts, and the tilt of the information recording medium with respect to the optical axis of the condensing lens is detected from the difference in the amount of light received by these two parts. be done.

Further, in the second invention, a part of the luminous flux from the light source is
The light does not enter the condenser lens, but is directly irradiated onto the information recording medium by optical means. Then, as in the first invention, the reflected light from the information recording medium is received by each light receiving element of the photodetector divided into two parts, and the tilt of the information recording medium is detected based on the difference in the amount of received light. .

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. Incidentally, the same parts as in FIG. 8 are given the same reference numerals, and the explanation of the overlapping parts is omitted.

FIG. 1 is an explanatory diagram showing the configuration of an embodiment according to the first aspect of the present invention.

As shown in the figure, a light emitting source 1 such as a semiconductor laser, a diffraction grating 3, a prism type beam splitter 4, a collimator lens 5, and a condensing lens 6 are placed in order on the optical path of the laser beam 2 at predetermined intervals. It is arranged. In addition, in a direction perpendicular to the optical path of the laser beam 2 of the beam splitter 4,
A concave lens 8, a cylindrical lens 9, and a photodiode 10 are arranged in this order, and the photodiode 10 is configured to capture the reflected light of the laser beam 2 and convert the intensity of the pits of the optical disk 7 into an electrical signal. .

Further, near the beam splitter 4 on the opposite side from the concave lens 8, a reflecting mirror 13 is arranged to bend the light beam separated by the beam splitter 4 in the right angle direction, and both sides of the optical path between the reflecting mirror 13 and the optical disk 7 are arranged. , there are two light receiving elements 14a and 1 that constitute the two-segment photodetector 14.
4b are arranged respectively.

In the optical information processing device having such a structure, the laser beam 2 output from the light emitting source 1 and transmitted through the diffraction grating 3 is
The transmitted light 2a passes through the beam splitter 4 and enters the collimator lens 5, and the reflected light 2b travels in a direction perpendicular to the transmitted light 2a.

This reflected light 2b is bent by the reflecting mirror 13 in a right angle direction so that its optical axis is substantially perpendicular to the optical disc 7, and is irradiated onto the optical disc 7.

The reflected light from the optical disk 7 of this irradiation light is 2
The light is received by each of the light receiving elements 14a14b of the split type photodetector]4, and electrical signals corresponding to the amount of light received are output from these light receiving elements 14a114b, respectively.

Here, if the optical disc 7 and the optical axis of the irradiated light are perpendicular,
The outputs from the two light receiving elements 14a and 14b are equal, and the difference between them is zero.

However, as shown in FIG. 2, when the optical disk 7 is tilted to one side and is not perpendicular to the optical axis of the irradiated light, each light receiving element 14
A difference occurs in the amount of light received by the light receiving elements 14a and 14b, and the difference in output va1vb from each light receiving element 14a and 14b (Va-V
b) It negative (Fig. 2(a)) or positive (Fig. 2(b))
The value is .

The difference in the amount of light received by each of the light receiving elements 14a and 14b may be measured using a detector such as the differential amplifier 15, for example.

In this way, the tilt of the optical disc 7 can be detected by measuring the difference in output from the two light receiving elements 14a, 14b.

FIG. 3 is a diagram showing the configuration of another embodiment of the first invention.

In this embodiment, an electrically driven galvano mirror 16 is used in place of the reflecting mirror 13 as an optical means for irradiating the optical disk 7 with the laser beam 2b separated by the beam splitter 4 almost perpendicularly. , so that the inclination of the reflecting surface can be electrically changed. Therefore, in this embodiment, the inclination of the galvanometer mirror 16 can be adjusted in advance using an optical disk as a reference, and the zero point can be corrected, so that even higher precision inclination detection is possible.

In the above-described embodiment of the first invention, the prism-type beam splitter 4 is used as the beam separation means, but the same effect can also be achieved by using a flat-plate beam splitter, grating, etc. instead. can.

Next, an embodiment of the second aspect of the present invention will be described below. Note that the same parts as in FIG. 1 are given the same reference numerals, and the explanation of the overlapping parts will be omitted.

FIG. 4 is a diagram showing the configuration of an embodiment of the second invention, FIG. 5 is a diagram explaining its operation, and FIG. 6 is a plan view of the condenser lens section of the embodiment.

In this embodiment, the effective diameter of the collimator lens 5 is ensured to be larger than the entrance pupil of the condenser lens 6, and the light beam that passes through the collimator lens 5 and spreads outward from the outer periphery of the condenser lens 6 is transmitted through the condenser lens. The light beam is configured to transmit through flat transparent plates 17a and 17b arranged near the outer periphery of the frame 6 and on both sides thereof. On the outside of the transmission plates 17a and 17b, there are two light receiving elements 14a of the split type photodetector 14.
114b are arranged respectively.

In the embodiment configured in this manner, as shown in FIG. 5, when the optical disk 7 is perpendicular to the optical axis of the condenser lens 6 and the inclination angle of the normal line is 0°, the transmitting plate 17a, 17
The light transmitted through the light receiving element 14a, 1.4b is reflected by the optical disk 7 and returns along the optical path, so the output Va of each light receiving element 14a, 1.4b is
, Vb are equal, so the output from the differential amplifier 15 is 0
(Figure 5(b)).

However, if the optical disc 7 is tilted to one side, for example, if the light receiving element 14b side is tilted lower, the amount of light received by the light receiving element 14b located in the tilted direction decreases, so that the light receiving element 14b The output vb of the light receiving element 14a is smaller than the output Va of the differential amplifier 15.
The output from is negative (FIG. 5(a)).

Also, if the optical disc 7 is tilted in the opposite direction to the above example, Vb
>Va, and the output from the differential amplifier 15 becomes positive (
Figure 5(C)).

Since such a deviation in the amount of received light increases or decreases linearly depending on the magnitude of the tilt, the direction and angle of the tilt of the optical disk 7 can be detected by taking the difference between the outputs from the two light receiving probes 14a114b. .

Furthermore, if all the optical means arranged on the main optical path, such as the light emitting source 1, beam splitter 4, collimator lens 5, and condensing lens 6, are held by a holding member equipped with a tilt adjustment mechanism, two By inputting the difference signal between the outputs of the two light receiving elements 14a and 14b to the tilt adjustment mechanism,
The inclinations of the collimator lens 5 and the condensing lens 6 can also be adjusted according to the inclination of the optical disc 7.

Furthermore, the transmission plates 17a and 17b can be formed integrally with the condensing lens 6, and the photodetector 14 can also be formed integrally with them.

Next, another embodiment of the second invention is shown in FIG.

In this embodiment, the condensing lens 6 is placed on a movable plate 18, and is configured to be able to move in the horizontal direction according to the surface wobbling and eccentricity of the optical disk 7.

Transmission holes 19a and 19b are provided on both sides of the condenser lens 6 mounting position of the movable plate 18, and a portion of the light beam that has passed through the collimator lens 5 is transmitted through these transmission holes 18a and 18b. It is configured so that the light is irradiated onto the optical disc 7.

The light reflected by the optical disk 7 is received by two light receiving elements 14a and 14b arranged outside of the transmission holes 19a and 19b, respectively, as in the previous embodiment. The tilt of the optical disc is detected based on the difference in output.

Furthermore, another embodiment of the present invention is shown in FIG.

In this embodiment, two sets of flat transmitting plates 17a, 17b and light receiving elements 14a, 14b shown in FIG. They are provided along two directions. In the optical information processing device of this embodiment, the inclination of the optical disc 7 in the radial direction and in the direction perpendicular thereto can be detected by light receiving elements along the respective directions.

FIG. 9 is a diagram showing still another embodiment. In this embodiment, flat transparent plates 17a and 17b are integrated with the housing 20 of the condensing lens 6. FIG.

It can be molded from plastic or the like, and has a structure that makes it easy to manufacture the device.

[Effects of the Invention] As explained above, according to the optical information processing device of the present invention, the tilt of the information recording medium can be detected with high sensitivity, and the spot of the condenser lens caused by the tilt of the information recording medium can be detected with high sensitivity. comatic aberration can be prevented.

Furthermore, no special light source is required to detect the tilt, and product costs can be kept low.

[Brief explanation of the drawing]

1 is an explanatory diagram showing the configuration of an optical system in an embodiment of the first aspect of the present invention; FIG. 2 is a diagram illustrating the principle of tilt detection in the embodiment of FIG. 1; Figure 3 is the first
FIG. 4 is a diagram showing the configuration of an optical system in an embodiment of the second invention of the present invention, and FIG. 5 is a diagram showing the configuration of another embodiment of the second invention of the present invention. 6 is a plan view of the condensing lens section of FIG. 4, and FIGS. 7 to 9 are diagrams showing other embodiments of the second invention, respectively. FIG. 10 is a diagram showing the configuration of an optical system of a conventional optical pickup head, and FIG. 11 is a diagram showing the configuration of a conventional tilt detection mechanism. 1...... Light source 4... Beam splitter 5...
... Collimator lens 6 ... Condenser lens 7 ... Optical disk 10 ... Photodiode 13 ... Reflection mirror 14 ... ... Two-segment photodetector 16 ... Galvano mirror 17a, 17b - Transmission plate 18 ... Movable plate 19a, 19b - Transmission hole Applicant: Toshiba Corporation

Claims (2)

[Claims] (1) A light emitting source, a condensing optical system that condenses the luminous flux from the light emitting source onto the information recording surface of the information recording medium, and a luminous flux separation interposed in the optical path between the light emitting source and the condensing optical system. and a detection mechanism that reads information based on the reflected light reflected by the information recording surface of the information recording medium, in which the condensed light beam is separated by the light beam separation mechanism. an irradiation optical system that irradiates the information recording medium almost perpendicularly with a light beam that does not enter the optical system; and an irradiation optical system that is divided into at least two parts that detects the intensity of the reflected light from the information recording medium of the irradiation light irradiated from the irradiation optical system. and a photodetector, the optical system being configured to detect an inclination of the information recording medium with respect to the optical axis of the condensing optical system based on a difference in intensity of reflected light from each of the photodetectors. Expression information processing device. (2) A light emitting source, a condensing optical system that focuses the light flux from the light emitting source onto the information recording surface of the information recording medium, and information based on the reflected light reflected from the information recording surface of the information recording medium. an irradiation optical system that irradiates a part of the light from the light source almost perpendicularly onto the information recording medium without making it incident on the condensing optical system; and a photodetector divided into at least two parts for detecting the intensity of reflected light from the information recording medium of the irradiation light irradiated from the optical system, and detects the information based on the difference in the intensity of the reflected light from each of the photodetectors. An optical information processing apparatus characterized in that the apparatus is configured to detect an inclination of a recording medium with respect to an optical axis of the condensing optical system.