JPH01182932A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To decrease the number of parts in a servo optical system and to attain a miniaturization and a weight-reducing by providing a lens array, whose converging element to have the different converging capacity of plural focal distances is arranged on the same flat, on the optical path of a light reflected by a polarization beam splitter. CONSTITUTION:A lens array 19 has a constitution in which plural converging elements 20-22 to have the different converging capacity of focal distances f1-f3 are arranged on the same flat 23. The lens array 19 is provided positioned on the optical path of a light which the reflecting light from an optical disk is reflected by a second polarization beam splitter. Besides, at a position to face to the lens array 19, a detector 24 is provided. The servo detection of a focus servo or a tracking servo can be executed with the lens array 19. Thus, the number of parts in a servo optical system can be decreased, and a miniaturization and a weight-reducing can be attained.

Description

TECHNICAL FIELD The present invention relates to an optical information recording and reproducing apparatus that records and reproduces information by irradiating an optical information recording medium with light from a semiconductor laser.

Prior Art A conventional optical information recording/reproducing device will be explained based on FIG. The light emitted from the semiconductor laser 1 is converted into parallel light by the coupling lens 2, and its polarization plane is transformed from an ellipse to a circle by the beam shaping splitter 3. The circularly deformed light passes through a first polarizing beam splitter 4 that transmits 100% of the P polarized light wave and reflects 66% of the S polarized light wave (this characteristic is the same for the second polarized beam splitter described later). Only the S-polarized light passes through the polarizing prism 5.
, is irradiated onto the optical disc 7 via the objective lens 6.

Thereafter, one reflected light beam is reflected as a P-polarized light wave according to the magnetic direction of the optical disk 7 as an optical information recording medium.

After the reflected light passes through the first polarizing beam splitter 4, it is further divided into two parts by the second polarizing beam splitter 8, one of which is transmitted and sent to the magneto-optical detection optical system 9, and the other is reflected and sent to the servo motor. It is guided to a detection system 10.

In the magneto-optical detection optical system 9, the reflected light having the P-polarized wave that has passed through the first polarizing beam splitter 4 is divided into 1/2
It is tilted at 45 degrees by the wave plate 11, separated into ordinary light and extraordinary light by the Wollaston prism 12, and the detection lens 1
3 to a light-receiving element 14 having a two-part light-receiving surface, the magneto-optical signal on the optical disk 7 is detected. As a result, the amounts of ordinary light and extraordinary light are determined, and it is detected whether the polarization direction has been changed.

Further, in the servo optical system 10, the S-polarized light reflected by the second polarizing beam splitter 8 is condensed by a condenser lens 15, and then split into two by a Knaifezi prism 16.

The light reflected by this Knifezi prism 16 is guided to the track light receiving element 17 and detected as a track error signal, thereby performing tracking servo, while the light that has been separated by one distance and traveling straight is guided to the focus light receiving element 18. Focus servo is performed by detecting this as a focus error signal.

In the case of the conventional device as described above, there are problems in that it takes time to assemble and adjust because it has a large number of parts, and the device itself becomes large-scale, resulting in high cost.

Purpose The present invention was made in view of these points, and by reducing the number of parts, it is inexpensive and compact.

The purpose is to obtain a lightweight optical information recording/reproducing device.

Structure The present invention provides a lens array in which a plurality of condensing elements having different focal lengths and having condensing abilities are arranged on the same plane on the optical path of the light reflected by the polarizing beam splitter. Since the array can be used to detect the focus servo and tracking servo, the number of parts in the servo optical system can be reduced.
This allows the device to be made inexpensive, small, and lightweight.

In addition, on the optical path of the light transmitted through the polarizing beam splitter,
We provided a lens array in which a plurality of condensing elements having different focal lengths and having the ability to condense light through a 1/2 wavelength plate and a polarization separation element were arranged on the same plane. In addition to servo detection, it is also possible to detect the magneto-optical signal of the optical disk, so the number of parts not only in the servo optical system but also in the magneto-optical detection optical system can be reduced, making it cheaper, smaller and lighter. be able to.

Furthermore, on the optical path of the reflected light reflected by the optical information recording medium, a 1/2 wavelength plate, a polarization separation element, and a plurality of condensing elements having different focal lengths and having condensing abilities are arranged on the same plane. Since the lens array is integrated with the lens array, the number of parts can be reduced and space can be significantly saved, thereby making it possible to reduce the cost, size, and weight.

A first embodiment of the present invention will be described based on FIGS. 1 and 2. The overall configuration of the optical information recording/reproducing apparatus in this embodiment has been explained in the prior art (see FIG. 5), so the explanation here will be omitted.

Note that the same reference numerals are used for the same parts.

The lens array 19 includes three condensing elements 20°21.2 having different focal lengths (f, f, , f3) and different condensing abilities.
2 are arranged on the same plane 23. This lens array 19 is located on the optical path of the light reflected from the optical disk 7 by the second polarizing beam splitter 8 (see FIG. 5).

Further, a detector 24 is provided at a position facing the lens array 19. This detector 24 has a light-receiving element A having a two-divided light-receiving surface a-all formed in its center, and a three-part light-receiving surface b1. b
2. Light-receiving elements B and C are formed, each having a light-receiving element b3 and cll Q21 c, respectively.

In such a configuration, a method of performing focus servo and tracking servo using the lens array 19 will be described. Three condensing elements 20, 21, and 22 are formed in the lens array 19.

Each focal length is different, and the distance is f, <
f, < f3. When the light reflected by the second polarizing beam splitter 8 is transmitted through such a lens array 19, the focal positions of the light beams condensed by the condensing lenses 20, 21, and 22 become P, Q, and R, respectively. .

Now, the optical disc 7 is in a focused state, and the light receiving elements B on both sides of the detector 24.

It is assumed that the spot diameters of the light beams irradiated onto C are the same. The amounts of light received at the light receiving surfaces B and C in such an initial state are as follows.

(bt+ba) -1), =Q... (1)
(81+ca) c*=o ++ (2) Similarly, the amount of light received on the light-receiving surface A is calculated as (a 1- a ,
)=O...(3).

A method for performing focus servo with such initial settings will be described. Now, if the position of the optical disc 7 shifts and the focal positions IMP, Q, and R move to the right in FIG. 1, the spot diameter on the light receiving surface B becomes smaller,
On the contrary, the spot diameter on the light-receiving surface C increases, and the amount of received light becomes as follows.

(b, +b,) -b,<O...(4)(c1+ 8
3) 82>'O・= (5) The focus error signal is detected by taking the difference between the values of equations (4) and (5) obtained in this way and outputting it through a circuit as shown in Figure 2. You can perform focus servo.

On the other hand, if the optical disc 7 is misaligned in the opposite direction to the above case and its focal positions P, Q, and R shift to the left in FIG. 1, the spot diameter on the light receiving surface B becomes larger,
On the contrary, the spot diameter on the light-receiving surface C becomes smaller, and the amounts of received light are as follows.

(b, +b,) bx>O...(6)(Q 1+
03) Oz < O... (7) In this case as well, the focus error signal is detected by taking the difference between the values of equations (6) and (7) and outputting it with a circuit as shown in Figure 2. You can perform focus servo.

Note that tracking servo can be performed by detecting a tracking error signal regardless of the spot diameter using the so-called bush-pull method using the condensing element 21 provided at the center of the lens array 19, but a description thereof will be omitted. do.

As mentioned above, by performing focus servo and tracking servo using the lens array 19, there is no need to use the Knifezi prism 16 in the prior art (see FIG. 5), which facilitates positioning during assembly. It can be made into an inexpensive and compact structure.

Next, a second embodiment of the present invention will be described based on FIGS. 3 and 4. Note that the same reference numerals are used for the same parts as in the first embodiment.

The lens array 19 is used here not only to perform servo detection of focus servo and tracking servo, but also to detect magneto-optical signals of the optical disk 7. Therefore, a description of the servo detection method will be omitted here.

The lens array 19 is provided on the optical path of the light that has passed through the 1/2 wavelength plate 11 and the polarization separation element 25. Note that, as shown in FIG. 3, these are usually used in an integrated structure.

In such a configuration, a method of detecting the magneto-optical signal of the optical disk 7 using the lens array 19 will be described. The reflected light reflected from the optical disk 7 passes through the first polarizing beam splitter 4 and then passes through the 172 wavelength plate 11.
The linearly polarized light 2 with different polarization directions is transmitted through the polarization separation element 25 having a polarization separation function as shown in FIG.
6°27 is formed, and unpolarized light 28 is formed at the center where these lights 26 and 27 intersect.

The thus formed lights 26 and 27 with polarization directions perpendicular to each other are focused on condensing elements 20 and 22 on both the left and right sides of the lens array 19, and the unpolarized light 28 is focused on the center of the lens array 19. The light is focused on the condensing element 21 in the section. Then, these lights 26, 27, and 28 are transmitted to the detector 24 (
(see Figure 2) and perform the following calculation based on the amount of received light.

(b, +b, +b,) - (c, +c, +c3) ・-(
s) The magneto-optical signal of the optical disk 7 can be detected by finding the positive and negative values using equation (8).

As mentioned above, by using the lens array 19, it is possible to detect the magneto-optical signal of the optical disk 7 in addition to servo detection, so it is possible to save a lot of space, and this allows the overall configuration of the device to be reduced. Even more compact,
It can be made lightweight.

Effect The present invention provides a lens array in which a plurality of condensing elements having different focal lengths and having condensing abilities are arranged on the same plane on the optical path of the light reflected by the polarizing beam splitter. Since the array can be used to detect the focus servo and tracking servo, the number of parts in the servo optical system can be reduced.
This allows the device to be made inexpensive, small, and lightweight.

In addition, on the optical path of the light transmitted through the polarizing beam splitter,
We provided a lens array in which a plurality of condensing elements having different focal lengths and having the ability to condense light through a 1/2 wavelength plate and a polarization separation element were arranged on the same plane. In addition to servo detection, it is also possible to detect the magneto-optical signal of the optical disk, so the number of parts not only in the servo optical system but also in the magneto-optical detection optical system can be reduced.

This allows the device to be made inexpensive, small, and lightweight.

Furthermore, a 1/2 wavelength plate and a polarization separation element are provided on the optical path of the reflected light reflected by the optical information recording medium.

Since multiple condensing elements with different focal lengths and lens arrays are arranged on the same plane, the number of parts can be reduced and space can be significantly saved. , This allows the device to be made inexpensive, compact, and lightweight.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a first embodiment of the present invention, FIG. 2 is an explanatory diagram of a detector including the circuit configuration, and FIG. 3 is a plan view showing a second embodiment of the present invention. FIG. 4 is an explanatory diagram of a polarization splitting element, and FIG. 5 is a perspective view showing a conventional example. 1... Semiconductor laser, 7... Optical information recording medium, 8.
...Polarizing beam splitter, 11...1/2 wavelength plate. 19... Lens array, 20, 21, 22... Condensing element, 23... Same plane, 25... Polarization separation element,
f. f,, f,... Focal length Applicant Ricoh Co., Ltd. -5.3 Figure J is [F] ■ ■

Claims (1)

[Claims] 1. Information is recorded by irradiating light from a semiconductor laser onto an optical information recording medium, the reflected light from the optical information recording medium is separated by a polarizing beam splitter, and the reflected light is used for tracking. In an optical information recording and reproducing apparatus that performs servo detection of a servo and a focus servo, and also detects a signal of the optical information recording medium using the transmitted light and reproduces information, the optical path of the light reflected by the polarizing beam splitter is An optical information recording/reproducing apparatus characterized in that a lens array is provided in which a plurality of condensing elements having different focal lengths and having condensing abilities are arranged on the same plane. 2. Light from a semiconductor laser is irradiated onto an optical information recording medium to record information, and the reflected light from the optical information recording medium is used to perform servo detection of tracking servo and focus servo, and the reflected light is used to detect the aforementioned light. In an optical information recording and reproducing device that detects a signal from an information recording medium and reproduces information, the optical path of the reflected light reflected by the optical information recording medium is sequentially transmitted through a 1/2 wavelength plate and a polarization splitting element. 1. An optical information recording/reproducing device comprising a lens array in which a plurality of condensing elements having different focal lengths and having condensing abilities are arranged on the same plane. 3. On the optical path of the reflected light reflected by the optical information recording medium, a 1/2 wavelength plate, a polarization separation element, and a plurality of condensing elements having different focal lengths and having condensing abilities are arranged on the same plane. 3. The optical information recording and reproducing apparatus according to claim 2, wherein the optical information recording and reproducing apparatus is provided integrally with a lens array.