JPH0214437A - Optical information processor - Google Patents

Abstract

PURPOSE:To simplify a device constitution and to improve producibility by driving a converging lens in a surface perpendicular to an optical axis and correcting the deterioration of an image-forming performance due to the inclinations of the optical axis of the converging lens and the normal line of an optical disk. CONSTITUTION:A disk inclination detecting mechanism, for example, a detecting mechanism 25 to detect the inclination of an optical disk 24 by a reflected light from an optical disk 24 surface and a moving signal generating mechanism 26 to generate a signal to control a moving quantity in the disk radius direction of a converging lens 23 based on the inclined quantity are provided, and a converging lens moving mechanism 27 is moved in a prescribed quantity based on the control signal from the moving signal generating mechanism 26. Namely, based on a tracking error signal 28a of a pick-up head 28, a control signal 26a is generated by the moving signal generating mechanism 26, it is overlapped with an inclination signal 25a, and the converging lens 23 is shifted in the radius direction as a signal 27a to a forwarding mechanism 29. Thus, the producibility can be improved with a simple structure.

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) Conventionally, a pickup head mechanism used as an optical information processing device, particularly for recording and reproducing information on a disc such as a video disc or a digital audio disc, uses a semiconductor laser or the like, as shown in FIG. 3, for example. A laser beam 1a outputted from a light source 1 passes through a diffraction grating 2, passes through a beam splitter 3, enters a collimator lens 4, where it is made into parallel light, and is then sent to an optical disk 6 by a condenser lens 5. It is configured so that the light is focused on the top.

The laser beam reflected by the optical disk 6 passes through the condensing lens 5 and the collimating lens 4 again, and enters the beam splitter 3, where it is reflected, for example, in the right angle direction, and passes through the concave lens 7 and the cylindrical lens 8. The light is focused on a reading detector such as a photodiode 9.

Incidentally, with the recent spread of optical video discs, optical pickup heads are required to be convertible so that they can read not only digital sound reproduction signal information but also analog image signals at the same time.

However, when reading an analog signal, it is difficult to correct and correct the signal after reading like a digital signal, and aberrations occur due to the inclination of the optical axis of the condenser lens 5 and the normal line of the optical disc. In this case, the signal S
/N ratio deteriorates, and crosstalk etc. occur.

Furthermore, since video discs have a larger disc diameter than conventional compact discs, there is warpage and sagging especially in the radial direction of the disc, resulting in a difference in the slope of the normal line between the inner and outer peripheries of the disc.

FIG. 4(a) shows an example in which the outer periphery of such an optical disc 6 is drooped.

When the optical disc 6 is sagging in this way, as the pickup head 11 moves in the radial direction of the optical disc 6, the optical axis of the condenser lens and the tilt axis of the disc normal line are shifted, so it becomes necessary to correct it. .

As a means for correcting the inclination between the optical axis of the condensing lens and the normal line of the disk, conventionally, as shown in FIG. The optical disc was tilted at the appropriate time depending on who was using it.

(Problem to be Solved by the Invention) However, the conventional correction mechanism described above requires a mechanism to move the feed shaft at one end or both ends, which complicates the mechanism and becomes an obstacle to improving productivity and reducing costs. There was a problem.

The present invention was made to solve the above-mentioned problems, and the inclination of the optical axis of the condensing lens and the normal line of the disk is
It is an object of the present invention to provide an optical information processing device that can perform correction without using a complicated mechanism, improve productivity, and reduce costs.

[Structure of the Invention] (Means for Solving the Problems) The optical information processing device of the present invention includes a light source, a condensing optical system for condensing and irradiating a light beam from the light source onto an information recording medium. , a focusing optical system moving mechanism for moving the focusing optical system within the city perpendicular to the optical axis of the focusing optical system, and an inclination between the optical axis of the focusing optical system and the normal to the information recording medium. In an optical information processing device having a tilt detection mechanism that detects the tilt, the condensing optical system is moved in a city perpendicular to the optical axis based on the tilt information from the tilt detection mechanism, and the optical information generated by the tilt is moved. It is characterized by having an optical system correction mechanism that corrects system aberrations.

In addition, the light beam incident on a condensing optical system, for example, a condensing lens, has spherical aberration, and coma aberration occurs when the optical axis of the condensing lens is decentered from the optical axis of the incident beam. It is characterized by correcting the deterioration in imaging performance that occurs.

(Function) In a condensing optical system, for example, the deterioration in imaging performance due to the inclination between the optical axis of the condensing lens and the normal line of the optical disk can be corrected by driving the condensing lens within the city perpendicular to the optical axis. , the device configuration can be simplified, productivity can be improved, costs can be reduced, and reading accuracy can also be improved.

(Example) An embodiment of the present invention will be described below.

In general, third-order Seidel aberration EAb(x, y) is calculated as EAb(x, y) −b3 (x2+y” ) 2+b4 (x2+y
2) x+b5 x2...
...It can be expressed as (1).

However, (x, y) are orthogonal coordinates at the entrance pupil of the condenser lens, and b3, b4, and b5 are SA and CA, respectively.

It is the aberration coefficient of As, the first term is SA, the second term is CA,
The term m3 represents the aberration of As.

Now, consider the system shown in FIG.

That is, the system is such that a laser beam 21a from a semiconductor laser 21 as a light source, for example, is converted into a substantially parallel beam 21b by a collimating lens 22, and condensed onto the surface of an optical disk 24 by a condensing lens 23.

Here, the axis ze is the optical axis of the light incident on the condensing lens, that is, the optical axis of the collimating lens 22, and the axis Zol is the optical axis of the condensing lens 23.
輔Zd is the normal line of the optical disk 24, and x and y are each Zc
Assume that it is a Cartesian coordinate in a plane perpendicular to the axis.

Here, the incident light 21b to the condenser lens 23 is
) is assumed to have a spherical aberration E (x, y).

E(x,y)=bx-(x'+y2)
2...12) However, b3'' represents the spherical aberration coefficient of the incident light flux.

In this way, in order to impart spherical aberration to the incident light, for example, (1) a single spherical lens is used as a collimating lens.

■Insert a parallel plate into the light source collimating lens m1.

■Load on collimating lens (e.g. beam splitter,
(diffraction m7-, laser cover, etc.) is made thicker or thinner than the design value of the collimating lens.

It is possible to obtain it by simple means such as

Here, the optical axis Zol of the condenser lens is the collimating lens 2
If the optical axis Zc of 2 is shifted by xO in the X-axis direction, the aberration of the light beam 21b incident on the condenser lens 23 can be expressed by the following equation (3).

E (X-XO, y) = b3- f(x-XO) 2+721 2=b3-
(X2+y2) 2 4b3 - xo (x2+y2)+[2 of x, y
Next term co+[first-order term of X]... (3) Here, the meaning of each term in the above equation is: 1st term;
, second term of spherical aberration: 4b3−xo (x2+y2)
...Third term of coma aberration: [X% 2nd order term of y] ...4th term of defocus: [1st order term of x] ...Movement of the image point.

From this second term, it can be seen that when the condenser lens 23 is shifted from the incident optical axis, comatic aberration proportional to the shift amount xo occurs.

Further, the aberration Eθ when the normal line of the front disk 24 is tilted by θ with respect to the optical axis of the condenser lens 23 is expressed by the following equation (4), and can be approximated as shown in the equation (5).

The thickness of the optical disc is t1, the refractive index is 01, and the focal length of the condenser lens is foc. Further, the first term of equation (4) and equation (5) represent coma aberration, and the second term of equation (4) represents astigmatism, respectively.

From equations (3) and (5), the aberration when the optical disk 24 is tilted is dominated by coma aberration, and the condenser lens 23
It can be seen that it can be corrected by shifting in the direction of inclination according to the amount of inclination.

Generally, the tilt of an optical disc is due to warping or sagging, and occurs in the radial direction of the optical disc. Therefore, it is sufficient to shift the condenser lens in the radial direction of the optical disk.

Further, a general optical information processing device has a tracking servo loop for following an information signal string (bit string), and a mechanism for driving the condenser lens 23 in the disk radial direction.

Therefore, a disk tilt detection mechanism 25 for detecting the tilt of the optical disk 24 using reflected light from the surface of the optical disk 24, and a signal that controls the amount of movement of the condenser lens 23 in the disk radial direction based on this tilt. A movement signal generation mechanism 26 is provided to generate the movement signal generation mechanism 2.
The configuration may be such that the condenser lens moving mechanism 27 is moved by a predetermined amount based on a control signal from 6.

That is, as shown in FIG. 2, based on the tracking error signal 28a of the pickup head 28, the movement signal generation mechanism 26 generates a control signal 26a for driving and controlling the condensing lens movement mechanism 27, By superimposing the tilt signal 25a from the tilt detection device 25 and making it a signal 27a to the feed mechanism 29 that moves the entire pickup head along the feed axis, the pickup head feed mechanism 29 and the condenser lens can be connected. An offset occurs in between, allowing the container to shift the condenser lens 23 radially. In this case, the information is reproduced with the condensing lens 23 shifted. However, in a normal optical information processing device, the condensing lens 23 is shifted in order to cope with the eccentricity of the information bit string on the optical disk. It has been designed to be used in a shifted position, and there will be no problem.

Further, when performing a trick play such as a track jump, it is preferable to cut off the signal from the optical disk type detection device 25 and remove the offset.

[Effects of the Invention] As explained above, according to the optical information processing device of the present invention, it is possible to improve productivity and reduce costs due to the simple structure, and moreover, it is possible to realize a high-performance optical information processing device.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an optical information processing device according to one embodiment of the present invention, and FIG. 2 is a diagram showing the configuration of another embodiment according to the present invention.'! FIG. B3 is a diagram showing the configuration of an optical pickup head section which is a main component of a conventional optical information processing device, and FIG. 4 is a diagram showing a tilt correction mechanism of the conventional optical information processing device. 21...Traser light source 23...Condensing lens 24...Optical lens 25...Disk tilt detector 26 ...
...Movement signal creation mechanism 27...
Condensing lens moving mechanism 28...Pickup head 29...Feeding mechanism Applicant: Toshiba Corporation

Claims (1)

[Claims] A light source, a condensing optical system for condensing and irradiating a light beam from the light source onto an information recording medium, and a condensing optical system arranged perpendicular to the optical axis of the condensing optical system. An optical information processing device comprising: a condensing optical system movement mechanism that moves within a plane; and a tilt detection mechanism that detects an inclination between an optical axis of the condensing optical system and a normal line of the information recording medium; The present invention is characterized by comprising an optical system correction mechanism that moves the condensing optical system in a plane perpendicular to the optical axis based on tilt information from the detection mechanism and corrects aberrations of the optical system caused by the tilt. Optical information processing device.