JPS61237247A - Information reader - Google Patents

Abstract

PURPOSE:To allow one device to read information out of both a photomagnetic and an optical recording medium by deciding a recording medium being reproduced and controlling a selection part, and selecting a correct playback circuit output. CONSTITUTION:When the optical recording medium is reproduced, outputs of detection parts 8a and 8b vary with a recording information signal in the same way, the output of a differential amplifier 9 does not vary, and the output of an adder 10 varies, thereby obtaining an RF signal regarding the information signal. When the photomagnetic recording medium is reproduced, on the other hand, the RF signal regarding the information signal is obtained as the output of the amplifier 9 and output variations of the detection parts 8a and 8b are canceled by the adder 10. A decision part 11 decides which outputs the information signal on the basis of whether the level is high or low and sends a corresponding logical output to the selection part 12. The selection part 12 selects the output of the amplifier 9 or adder 10 according to the logical output and grounds the other. Consequently, one device reads recording information out of both the photomagnetic recording medium and optical recording medium.

Description

[Detailed Description of the Invention] 0) Industrial Field of Application This invention is applicable to information recorded on a recording medium. Related to a news bulletin reading device.

←) Conventional technology In general, when playing back information recorded on a recording medium such as an optical video disc, a laser beam is irradiated onto the recording medium, and the reflected or transmitted light is detected to record the information on the recording medium. The recorded text information is being read.

Recently, linearly polarized light is reflected by the surface of a magnetic material.
By applying the phenomenon in which the plane of polarization rotates due to the magnetic Kerr effect when passing through a magnetic material, attempts have been made to read textual information magnetically recorded on magneto-optical recording media. Is the magnetic Kerr effect a full-fledged effort to increase the density of information recording in magnetic recording media? To make it noticeable, perpendicular magnetic anisotropy, ie.

It is structured as a perpendicularly magnetized film having an axis of easy magnetization 7 in a direction perpendicular to the substrate surface.

By the way, the aforementioned magneto-optical recording medium vCtYIt
When recording information, is the entire recording area of the medium? After uniformly perpendicular magnetizing in the same direction in advance, a laser beam is irradiated to a specific region of the perpendicularly magnetized region to heat it to the Curie temperature or compensation temperature, and the direction of magnetization of the heated region is adjusted. All information is recorded by inverting it.

However, when reading the information recorded on a magneto-optical recording medium using the method described above, is there a principle in which the L plane of polarization rotates due to the magnetic Kerr effect? The information is read by irradiating the medium with a laser beam, receiving the reflection -yt from the medium, and completely detecting how much the plane of polarization of the reflected light has rotated. Conventionally, an information reading apparatus for reading information recorded on a magneto-optical recording medium in this manner has been constructed, for example, as shown in FIG. 2. Next, this information reading apparatus will be explained.

In FIG. 2, Il+ is a semiconductor t-hoop (laser light source), 12+ is a polarizer that converts the laser beam from the laser 111 into linearly polarized light, and +3+ is a first half mirror 1 that transmits the linearly polarized light from H polarizer (2). (41 is the first) -
- Humira - 131'ji Transmits nine linearly polarized light t - A convex lens that condenses light, (5) is a magneto-optical recording medium, which has high coercive force and perpendicular magnetic anisotropy, manganese-bismuth-6-gadolinium-iron, terbium- It is composed of a magnetic thin film made of an amorphous alloy of rare earths and transition metals such as iron and gadolinium-terbium-iron.

As indicated by the arrows in the figure, desired information is recorded in the form of the top and bottom of the magnetization of the magnetic thin model, and the linearly polarized light irradiated through the lens (4) is directed to the medium 151. The reflected light flux reaches @1 half mirror +31 via lens (4) and is reflected.

161 is the first half mirror +311cj? 7 Transmits and refracts the reflected light beam from the reflected medium (5) and branches it into two directions @ 2 Half mirrors 1 (7a) and (7b) are provided with polarizers 12 to polarize the linearly polarized light l7 to each other 7 is set at the same angle oppositely to the 1.1E2 analyzer,
(8a) and (8b) are bilateral photons (7a) and (7
b) A detection unit that detects light incident through w and outputs an electric signal @1. The second element detector is a differential amplifier which is a +91i differential regeneration circuit, and has both input terminals (-1,
(+) is connected to both party detectors (8a)% (8b) and differentially amplifies the signals from one and both party detectors (8a) and (8bJ).

When the medium (5) is irradiated with linearly polarized light having a plane of polarization in the direction of the solid arrow in FIG. Depending on the direction, the plane of polarization rotates with respect to the plane of polarization of the linearly polarized light, as shown by the dashed arrow and the dashed-dotted arrow in the figure, respectively, and the plane of polarization of a companion, for example, the first analyzer (7a), rotates in the same direction. Set it so that it is perpendicular to the dashed arrow as shown by the two-dot chain line in the figure.

The device is set so that when the plane of polarization rotates counterclockwise as shown by the dashed line in the same figure, the light passes through the first photon (7a), and in the same way, the second analyzer (7b) is set in the same way. The plane of polarization shown in the dashed line in the middle is set to transmit light whose plane of polarization rotates clockwise. When doing so, the reflected light beam does not pass through the second analyzer (7b)'@, but passes only through the first analyzer (7a) and is directed to the first photodetector (8).
a), and from the first and second party detectors (8a) and (8b), for example, a logic ``1'' signal of ``0'' is applied to both input terminals (-) and (-) of the differential amplifier (9; +) is input.

On the other hand, when the reflected light beam from the medium (51) has a polarization plane of violet as indicated by the broken line in the figure, the reflected light beam is
Photon (7a) passes through only the second analyzer (7b) without passing through t and enters @2 photodetector (8b) 11JJL,,l
From El, the second party detectors (8a) and (3b), logic "10" and "1" are obtained, contrary to the counterclockwise case.
The signals are both input terminals (-) of the differential amplifier 19+.

(+) is input.

Next, from the differential amplifier 191K, both party detectors (8&
).

The signals from (8b) are calculated, and the information recorded on the medium +51 in the form of upward and downward variations in magnetization is sent to the differential amplifier (9) as a digital signal of 9 logic 1'111.11011. The information is read out based on the reproduced digital signal.

By the way, the information reading device shown in FIG. 2 reads information recorded on a magneto-optical recording medium 151 which is reproduced by applying the magnetic Kerr effect, and the information is read using uneven P-J).
An optical recording medium recorded in the form of Detector (8a), ta
b) Since changes in the amount of reflected light from the h medium (5) and changes in the amount of returned light due to diffraction cannot be fully detected, no signal is output from the differential amplifier +91, and the recorded information 7
If it is impossible to reproduce, it is necessary to prepare the next information reading device 11't- according to the type of recording medium to be reproduced.69
Regarding distinguishing between discs, which have the drawbacks of being very inconvenient and expensive, Japanese Patent Publication No. 58-51351 describes how to distinguish between video discs, compact discs, and discs.
, a configuration is shown in which the determination is made based on nine recorded synchronization signals. However, the above method is not suitable for distinguishing between a magneto-optical recording medium that allows recording and reproduction and an optical recording medium that is only for reproduction, such as a compact disk.

(c) As stated above, in the prior art, information recorded on a magneto-optical recording medium and an optical recording medium cannot be read using a single information reading device. There wasn't.

Does the present invention have the above points? The present invention provides an improved and superior t-report reading device with one function.

B) Means for Solving the Problems The present invention provides a detection unit that temporarily detects reflected light from a recording medium;
A differential reproducing circuit for reproducing a magneto-optical recording medium that receives a detection signal from the detection section, a non-differential reproducing circuit for reproducing an optical recording medium that also receives a detection signal t from the detection section, and a differential reproducing circuit that receives a detection signal from the detection section. It consists of a determining section to which all the outputs of the circuit and the non-differential reproducing circuit are input, and a selecting section 19 for the output of the differential reproducing circuit and the output of the non-differential reproducing circuit, which is controlled by this determining section.

(E) Operation When reproducing sound from an optical recording medium, the VC can obtain information signals only from the non-differential type reproducing circuit. Conversely, when reproducing a magneto-optical recording medium, a refresh signal can be obtained only from the differential reproducing circuit. Therefore, the discrimination section 9 discriminates which recording medium is being reproduced and controls it with the selection section 1.

The correct regeneration circuit output can be selected.

(f) Example The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a circuit block diagram of an embodiment of the present invention.6 Components in common with FIG. 2 have the same symbols and tone materials. .

11tl adder, which is a non-differential regeneration circuit, 111r
x, the output of the differential amplifier (91) and the adder 1ll - a discriminating unit which inputs the output sound; f121 is controlled by the discriminating unit (111), This is a selection section that selects 10,000 of them and outputs them to the signal processing section (13).The output of the differential amplifier (91 and adder ++1j is connected to a DC coupler capacitor to remove the DC component. .

When reproducing an optical recording medium such as a compact disc, depending on the recorded information signal (uneven pits), the first.
Since the output signals of the second photodetector (13a), (8t), and (i') change in the same way, the output of the differential amplifier (9) does not change due to the information signal.

On the other hand, the output of the adder 11 (l) changes due to the uneven pits, and it is possible to obtain a 7j RF signal related to the information signal. Also, in this case, the output of the differential amplifier 191 is not completely zero. This is because even in compact discs, etc., the condition of the substrate, aluminum layer, and protective layer cannot be modified.
A change in the polarization component from the recording medium may occur, and this change appears as noise unrelated to the information signal at the output of the differential amplifier (9).

When reproducing the magneto-optical recording medium 2, as mentioned above, the f'IF signal related to the information signal is obtained as the output of the differential amplifier (91). zu (1@1, second photodetector (8a) (8
b) *The output changes are canceled by the adder circuit. However, the output of the adder +111 changes (noise component) in accordance with changes in the reflectance of the surface of the recording medium, regardless of the information signal.

Output to. For example, when the reproduced output appears in the differential amplifier (91), a logical output of H level is obtained, and when the reproduced output appears in the adder 1113, a logic output of iL level is obtained.

The selection section is a changeover switch that selects a differential amplifier (9) or an adder +1 (j
One of the outputs is selected and the other is all grounded. Since only one of the outputs of the differential amplifier (91 and adder 11) is selected, the influence of noise appearing in the other reproduction circuit as described above can be eliminated.

For example, the configuration of the discriminator is as follows: A differential amplifier (91) and two comparator outputs corresponding to the adder fl[l, which detect the respective outputs and compare them with a predetermined voltage. It is conceivable that the combination may include an output stage that generates the logic output as described above.

(G) Effects of the Invention As described above (5) If the present invention is implemented, it is effective because one information reading device can read all nine pieces of information recorded on the L9 magneto-optical recording medium and the optical recording medium.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 82 is a block diagram of a conventional information reading device, and Fig. 3 is an explanation of the reading operation.
FIG. (8a1(8bJ...photodetection section, (9t...differential amplifier, +1(1...adder, 1υ...discrimination section%(13
...Selection section. Figure 1 Figure 2

Claims (1)

[Claims] (1) A laser light source that irradiates a recording medium on which information is recorded with a laser beam, a photodetector that detects the reflected light flux from the recording medium and outputs a detection signal, and a magneto-optical recording that inputs the detection signal. A differential reproducing circuit for reproducing a medium, a non-differential reproducing circuit for reproducing an optical recording medium into which the detection signal is input, and an output of the differential reproducing circuit and an output of the non-differential reproducing circuit are input. An information reading device comprising a determining section and a selecting section that selects one of the differential reproducing circuit output and the non-differential reproducing circuit output according to the output of the determining section.