JP2594957B2 - Optical recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus, and more specifically, has means for detecting a defect at the time of information recording, and is provided along a guide groove of an information recording medium. The present invention relates to optical recording / reproduction in which recording is performed with a first beam modulated with a recording signal, and information immediately after recording is reproduced with a second beam behind the first beam with respect to an information recording direction on an information recording medium. It is.

[Conventional technology]

2. Description of the Related Art Hitherto, an optical recording / reproducing apparatus for recording / reproducing information concentrically or spirally on a rotating disk-shaped information recording medium using an optical means, for example, a laser beam, is well known. This type of device has the advantages of being able to perform high-density recording and having a large recording capacity as compared with a magnetic disk device. However, on the other hand, since the information recording medium has more defects than the magnetic disk, a function for securing the reliability of the recorded information is particularly required.

For this reason, a method of determining the presence or absence of an information recording defect by detecting the reproduction signal by rotating the information recording medium on which the information is recorded by one rotation is conceivable. However, there is a disadvantage that it takes time for one rotation to detect the defect. is there. In order to prevent this, in recent years, optical recording / reproducing apparatuses capable of detecting a reproduced signal in real time have been considered.

FIG. 4 shows a conventional optical recording / reproducing apparatus described in, for example, pages 107 to 112 of the paper collection of "Optical Memory Symposium 85". In the figure, a two-beam semiconductor laser (1) having two light emitting sources is used. As shown in FIG. 5, the recording beam (2) and the reproducing beam (3) are emitted in parallel to each other. Although an array type two-beam semiconductor laser (1) having two active regions in one element is shown here, any two-beam semiconductor laser (2) and (3) can be driven independently of each other. A device in which two ordinary elements each having one active region are arranged in parallel may be used.

A collimator lens (4) is arranged on the beam emission side of the two-beam semiconductor laser (1), and a polarizing beam splitter (5) is arranged to receive the beam that has passed through the collimator lens (4). The reflecting mirror (6) directs the beam transmitted through the polarizing beam splitter (5) upward, and a quarter-wave plate (7) and an objective lens (8) are arranged in the optical path. The information recording medium (9) is arranged close to the objective lens (8). Information recording medium (9)
A guide groove (10) is formed along the information recording direction, and the recording spot (11) and the reproducing spot are formed by the beams (2) and (3) irradiated along the guide groove (10). A service spot (12) is formed.

A half prism (13) for splitting the beam reflected by the polarizing beam splitter (5) into reflected light and transmitted light is disposed on the side of the polarizing beam splitter (5). A two-divided photodetector (14) having (14a) and (14b) and receiving a beam transmitted through the half prism (13) is arranged.

The convex lens (15) converges the beam reflected by the half prism (13). The pinhole mirror (16) has a pinhole (17) for passing only the reproducing beam (3) out of the beams from the convex lens (15). The reproducing beam (3) passing through the pinhole (17) is split by the half prism (18). Knife edge (19) on the optical path of the reproducing beam (3) transmitted through the half prism (18)
Are arranged, and the two-segment photodetector (20) having two light receiving surfaces (20a) and (20b) receives the reproducing beam (3) via the knife edge (19).

The photodetector (21) receives the recording beam (2) reflected by the pinhole mirror (16) and generates a recording beam monitor signal E. The light detector (22) receives the reproduction beam (3) reflected by the half prism (18) and generates a reproduction output C. The circuit (23) is a reproduction signal detection circuit for obtaining a reproduction signal D from a reproduction output C from the photodetector (22).

The recording signal generation circuit (24) outputs the recording signal A as a pulse train, and the driver circuit (25) drives the two-beam semiconductor laser (1) based on the recording signal A.

Output signals from the respective light receiving surfaces (14a) and (14b) are input to a differential amplifier (26) that detects an output signal TS of the two-segment photodetector (14). Output signals from the respective light receiving surfaces (20a) and (20b) are input to a differential amplifier (27) that detects an output signal FS of the two-segment photodetector (20).

The split photodetector (14) and differential amplifier (26)
Constitutes a well-known tracking error detecting optical system called a push-pull method, and a knife edge (19), a two-divided photodetector (20) and a differential amplifier (27) include a well-known focusing error called a knife edge method. It constitutes a detection optical system.

FIG. 6 shows a recording spot (1) on the information recording medium (9).
FIG. 2 is a perspective view showing in detail 1) and a reproduction spot (12). Here, the case where each spot (11), (12) is irradiated between the guide grooves (10) to perform recording and reproduction is shown, but recording and reproduction may be performed on the guide grooves (10). In the figure, 1 is the distance between the recording spot (11) and the reproducing spot (12) following it, and the arrow is the direction of rotation of the information recording medium (9). The pit (28) is written on the information recording medium (9) by the recording spot (11).

Next, the operation of the conventional optical recording / reproducing apparatus shown in FIGS. 4 to 6 will be described.

First, when a recording signal A as shown in FIG. 4 is generated,
A two-beam semiconductor laser (1) based on the recording signal A
Is driven. The recording beam (2) and the reproducing beam (3) emitted from the two-beam semiconductor laser (1) are converted into parallel beams by a collimator lens (4), and are split into a polarizing beam splitter (5), reflecting mirrors (6), and 1. The information recording medium (9) is irradiated through the quarter-wave plate (7) and the objective lens (8) to form a recording spot (11) and a reproduction spot (12) as shown in FIG.

The recording spot (11) includes recording information (for example, a pulse width) of the recording signal A, and a spot (28) having a shape B corresponding to the information is sequentially formed on the information recording medium (9). On the other hand, the reproducing spot (12) which moves by a distance 1 from the recording spot (11) is driven at a constant light intensity.
The written pit (28) is converted to the time tl corresponding to the distance l.
(Several microseconds) later playback.

That is, the recording spot (11) is formed and reflected at the same time as the spot (28), and the reproducing spot (12) is reflected at the post-written spot (28). As described above, the recording beam (2) and the reproducing beam (3) reflected by the information recording medium (9) are again transmitted to the objective lens (8) and 1 /
The light passes through the four-wavelength plate (7), but is reflected by the polarization beam splitter (5) because the polarization direction is rotated by 90 ° by going back and forth through the quarter-wavelength plate (7).

Subsequently, each of the beams (2) and (3) is reflected by the half prism (13), and a part of the beams is transmitted through the half prism (13) and input to a tracking error detecting optical system to be described later. It is used for correcting a tracking error of a beam irradiated on the recording medium (9).

Each beam (2) reflected by the half prism (13),
In (3), after being converged by the convex lens (15), the recording beam (2) is reflected by the pinhole mirror (16), and the reproduction beam (3) passes through the pinhole (17) and becomes a half prism. Reflected at (18). At this time, a part of the reproduction beam (3) is transmitted through the half prism (18), is input to a focusing error detection optical system described later, and is focused on the beam for irradiation on the information recording medium (9). Used for correcting the caching error.

The recording beam (2) reflected by the pinhole mirror (16) is received by the photodetector (21) and detected as a pulse waveform E corresponding to the recording signal A, and is used as an information recording medium (9) and an optical path. Is used to determine the presence or absence of a fault.

On the other hand, the reproduction beam (3) reflected by the half prism (18) is received by the photodetector (22) and detected as a reproduction output C corresponding to a pit shape B as shown in FIG. The reproduced signal is subjected to waveform processing by a reproduced signal detection circuit (23) and detected as a reproduced signal D in a pulse train. The reproduction signal D thus obtained is compared with the recording signal A, and is used for determining the presence or absence of a defect in information recording.

Here, the case where the reflectance of the information recording medium (9) is reduced by the formation of the bit (28) is shown, but the information recording medium (9) whose reflectance is increased by the pit (28) is shown.
Also, the information recording state can be determined in the same manner.

The reproduction signal D is delayed from the recording signal A by the time tl, but since the time tl is on the order of several μsec, it is considered that the presence / absence of a recording defect can be determined almost in real time.

When reproducing information recorded on the information recording medium (9), only the reproducing beam (3) should be emitted from the two-beam semiconductor laser (1) and detected by the reproduction signal detection circuit (23).

Next, the operation of the conventional focusing error detecting optical system based on the knife edge method composed of the knife edge (19), the split optical detector (20) and the differential amplifier (27) will be described with reference to FIG. I do. FIG. 8 shows only those parts necessary for explaining the principle of focusing error detection. FIG. 3A shows a case where the information recording medium (9) is in focus with respect to the objective lens (8), and the reproducing beam (3) having a semicircular cross-sectional shape by the knife edge (19) is 2. The two light receiving surfaces (20
Focus on the center of a) and (20b).

In this case, the output signal FS of the differential amplifier (27) becomes zero. FIG. 9B shows a case where the information recording medium 9 is farther than the focal point of the objective lens 8, and the reproduction beam 3 partially shielded by the knife edge 19 is used as the light receiving surface 20 a. ), The output signal SF obtained from the differential amplifier (27) is positive. Conversely, FIG. 3C shows the case where the information recording medium (9) is closer than the focal point of the objective lens (8), and the reproducing beam (3) is incident on the light receiving surface (20b). The output signal FS obtained from 27) is negative. Therefore, the direction and magnitude of the defocus are determined by the differential amplifier (2
7) It is obtained from the output signal FS.

Next, the operation of the conventional tracking error detecting optical system based on the push-pull method composed of the two-part photodetector (14) and the differential amplifier (26) will be described with reference to FIG. FIG. 9 shows only those parts necessary for explaining the principle of tracking error detection. 2A shows a case where there is no tracking deviation, FIG. 2B shows a case where the guide groove (10) is shifted in the + X direction, and FIG. 2C shows a case where it is shifted in the −X direction. In the figures (a) to (c), the distributions of the first-order diffracted light diffracted by both edges of the guide groove (10) are shown by curves (29) and (30). FIGS. 4D, 4E, and 4F are shown in FIGS.
The shape of the incident light on two light receiving surfaces (14a) and (14b) of the two-segment photodetector (14) in (c) is shown. The outer shape of the incident light is such that the center of each of the circular shape of the reproducing beam (3) and the recording beam (2) is two light receiving surfaces (14).
a) and (14b) are located on the dividing line and are shifted from each other in the direction along the dividing line. Distribution of first-order diffracted light (2
9) and (30) are indicated by hatching in the figure.

When there is no tracking deviation as shown in FIGS. 9 (a) and 9 (b), the first-order diffracted light distributions (29) and (30) by both edges of the guide groove (10) provided in the information recording medium (9). ) Are equal to each other, so that the outputs from the two light receiving surfaces (14a) and (14b) of the two-segment photodetector (14) shown in FIG. The output signal TS becomes zero. Further, as shown in FIGS. 9 (b) and 9 (e), when the guide groove (10) is shifted in the + X direction, the first-order diffracted light distributions (29) and (30) by both edges of the guide groove (10) are changed. Since they are not equal to each other and the intensity distribution is biased on the light receiving surface (14a) as shown in FIG. 11E, the output signal TS of the differential amplifier (26) becomes positive. On the other hand, as shown in FIGS. 7C and 7F, when the guide groove (10) is shifted in the −X direction, the first-order diffracted light distribution (2
9) and (30) are in opposite directions, and the differential amplifier (2
6) The output signal TS becomes negative. Accordingly, the direction and magnitude of the displacement of the guide groove can be obtained from the output signal TS of the differential amplifier (26).

[Problems to be solved by the invention]

As described above, the conventional optical recording / reproducing apparatus separates, from the reflected beam from the information recording medium (9), a beam for detecting a reproduction signal and a beam for recording monitoring by using a pinhole mirror (16), Since each signal is detected by an individual photodetector, strict arrangement accuracy is required for the pinhole mirror, and the optical system is complicated and the number of optical components is increased.

The present invention has been made to solve the above problems, and has as its object to obtain an optical recording / reproducing apparatus which is economical and has excellent assemblability with a simple optical system.

[Means for solving the problem]

An optical recording / reproducing apparatus according to the present invention uses a wedge prism having two refracting surfaces for detecting a tracking error and a reproduction signal with respect to a recording beam and a reproduction beam reflected by an information recording medium. The ridge line is arranged in parallel with the guide groove of the information recording medium, and is arranged so as to divide the reproducing beam into two equal parts. In this figure, a detector and a photodetector for receiving a recording beam are arranged.

(Operation)

According to the present invention, the separation of the recording beam and the reproduction beam reflected by the information recording medium can be performed without requiring a complicated optical system, and the tracking error can be detected using only the reproduction beam. Can be.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an optical path diagram showing an embodiment of the present invention, wherein reference numerals (1) to (5), (7) to (12), (19),
(20) and (23) to (27) are the same parts as those of the above-mentioned conventional reference numerals.

The convex lens (31) is for converting the reflected beam from the information recording medium (9) reflected by the polarizing beam splitter (5) into a convergent beam. The half prism (32) divides the convergent beam into transmitted light and reflected light. The optical path of the transmitted light of the half prism (32) includes a knife edge (19), a two-divided photodetector (20), Differential amplifier (2
The focusing error detecting optical system according to the knife edge method described in 7) is configured.

The roof-shaped wedge prism (33) is arranged in the optical path of the reflected light of the half prism (32), has two refraction surfaces (33a) and (33b) and a ridge line (33c), and has a ridge line (33c). 33c) is arranged optically parallel to the guide groove (10) of the information recording medium (9). Although the wedge prism (33) is bonded to the half prism (32) in this embodiment, the wedge prism (33) may be disposed separately.

The beams (34a) and (34b) are recording beams (2) emitted from the wedge prism (33), the beam (34a) is a beam refracted by the refraction surface (33a), and the beam (34b) is refraction. The beam is refracted by the surface (33b). Similarly, beams (35a) and (35b) are the reproducing beam (3) emitted from the wedge prism (33), and the beam (35a) is a beam refracted by the refracting surface (33a), a beam (35b). Is a beam refracted by the refraction surface (33b).

Four beams (34) emitted from the wedge prism (33)
a), (34b), (35a), (35b)
A three-divided photodetector (36) having three light receiving surfaces (36a), (36b) and (36c) is arranged, and a beam (35a) is received by the light receiving surface (36a), and a beam (35) is received by the light receiving surface (36b). 35b) is configured to receive the beams (34a) and (34b) on the light receiving surface (36c), respectively, and is disposed at the condensing position of each beam. The differential amplifier (26) has two light receiving surfaces (36
Calculate the difference between each output from a) and (36b). Adder (3
7) generates a reproduction output C by adding the respective outputs from the two light receiving surfaces (36a) and (36b). Reproduction signal detection circuit (23)
Obtains a reproduction signal D from a reproduction output C from the adder (37).

Next, the operation of the above configuration will be described. The operation of recording and reproducing information on and from the information recording medium (9) with the recording beam (2) and the reproducing beam (3) from the two-beam semiconductor laser (1) is the same as in the prior art. Here, the principle of the separation of the recording beam (2) and the reproducing beam (3), the principle of operation of the tracking error detecting optical system and the focusing error detecting optical system, which are main parts of the present invention, will be described in detail.

In FIG. 1, the three-division photodetector (36) includes recording beams (34a) and (34b) and reproducing beams (35a) and (35).
Since they are arranged at the focal point b), the focal points of the four beams are four points spatially separated, so that the recording beams (34a) and (34b) are reflected by the light receiving surface (36c). By receiving the light, a monitor signal E of the recording beam is obtained.

Next, regarding the tracking error detection, the ridge (33c) sandwiched between the two refracting surfaces (33a) and (33b) of the wedge prism (33) is optically viewed from the guide groove of the information recording medium (9). Since it is arranged so as to be parallel to (10), one of the first-order diffracted light components diffracted at both edges of the guide groove (10) is included in the reproduction beam (35a), and the other first-order diffracted light is included. The component is contained in the reproducing beam (35b). Therefore, these beams (35a) and (35b) are received by the light receiving surfaces (36a) and (36b), respectively, and each output is operated by the differential amplifier (26) to obtain a signal according to the prior art. An output signal TS for tracking error detection based on the detection principle of the push-pull method described above can be obtained. In addition, the light receiving surface (36
By adding each output of (a) and (36b) by an adder (37), it is detected as a reproduction output C corresponding to the pit shape B as shown in FIG.
The signal is subjected to waveform processing in 3) and detected as a reproduced signal D in a pulse train. Therefore, as described in the prior art, the reproduction signal D thus obtained is compared with the recording signal A generated by the recording signal generating circuit (24) and used for determining whether or not there is a defect in information recording.

The principle of focusing error detection will be described with reference to FIG. FIG. 2 shows only those parts necessary for explanation of the principle. FIG. 3A shows the case where the information recording medium 9 is at the focal point of the objective lens 8, FIG. 3B shows the case where the information recording medium 9 is farther from the focal point of the objective lens 9, and FIG. Is also close. In FIG. 3A, a knife edge (19) is arranged so as to completely block the recording beam (2) and to block just half of the cross section of the reproducing beam (3). Therefore, if attention is paid to the reproducing beam (3), the knife edge (19), the split photodetector (20) and the differential amplifier (27), the same as the knife edge method shown in FIG. It is clear that the focusing error can be detected using only the reproducing beam (3) without being affected by the recording beam (2).

As described above, if the knife edge (19) is arranged so as to completely block the recording beam (3), and the reproducing beam (3) is divided into two by using the wedge prism (33),
Focusing error detection, tracking error detection and reproduction signal detection by the reproduction beam (3), and separation of the recording beam (2) and the reproduction beam (3) do not require a complicated optical system, and Many optical components are not required.

In the above embodiment, a wedge prism (33) is used as an optical component for splitting the reproduction beam (3) into two parts for detecting a tracking error, but as shown in FIG. Two symmetrical lens pieces may be used.

FIG. 3 (a) is a cross-sectional view of the convex lens (38), in which the central part (38c) of the lens is cut out, and two lens pieces (38a)
And (38b). FIG. 3 (b) is a perspective view showing a configuration using two lens pieces (38a) and (38b), and the cut portions (38d) and (38e) of the two lens pieces (38a) and (38b), respectively. ) Are bonded, and the bonding surface is disposed in a direction (shown by an arrow) that is optically parallel to a guide groove (not shown) of the information recording medium. Has the effect of

In the above modification, two lens pieces (38a)
And (38b) are used, but an integrally molded product such as plastic or glass material may be used.

Further, in the above-described embodiment and modified examples, the half prism (32) and the wedge prism (33) or the lens pieces (38a) and (38b) are configured by individual optical components, and are further bonded. However, it may be an integral product.

〔The invention's effect〕

As described above, according to the present invention, with respect to the recording beam and the reproduction beam reflected by the information recording medium, the reproduction beam is guided to the information recording medium to detect the tracking error and the reproduction signal. A means for splitting the beam into two in the direction parallel to the groove, a split photodetector for receiving each beam at the focal point of the split beam, and a photodetector for receiving the recording beam are arranged. With such a configuration, there is an effect that an optical recording / reproducing apparatus which is economical and has excellent assembling properties can be obtained with a simple optical system without requiring a complicated optical system.

[Brief description of the drawings]

FIG. 1 is an optical path diagram of one embodiment of the present invention, FIG. 2 is an optical path diagram for explaining the operation of the focus error detecting optical system of FIG. 1, and FIG. 3 is another embodiment. (A) is a partial cross-sectional view, (b) is a partial optical path diagram, FIG. 4 is an optical path diagram of a conventional optical recording / reproducing apparatus, FIG. 5 is a perspective view of the two-beam semiconductor laser in FIG. FIG. 6 is a perspective view for explaining the irradiation position of each spot in FIG. 4, FIG. 7 is a timing chart for explaining the operation of FIG. 4, and FIG. 8 is a timing chart for FIG. FIG. 9 is an optical path diagram for explaining the operation of the focus error detecting optical system, and FIG. 9 is an optical path diagram for explaining the operation of the tracking error detecting optical system of FIG. (1) ... two-beam semiconductor laser, (2) ... recording beam (first beam), (3) ... reproduction beam (second beam)
(5) polarization beam splitter, (9) ...
Information recording medium, (10) Guide groove, (19) Knife edge, (20) Two-split photodetector, (20a), (20b)
... Light receiving surface, (23) ... Reproduction signal detection circuit, (24) ... Recording signal generation circuit, (25) ... Driver circuit, (26),
(27) ... differential amplifier, (31) ... convex lens, (32) ...
… Half prism, (33) …… wet prism, (33)
a), (33b) ... refractive surface, (33c) ... ridgeline, (34a),
(34b): Recording beam, (35a), (35b): Reproduction beam, (36): 3-split photodetector, (36a), (36)
b), (36c): Light receiving surface, (37): Adder, (38)
a), (38b) ... Lens pieces. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] A first beam modulated by a recording signal along a guide groove provided in an information recording medium and a second beam having a constant light intensity are irradiated behind the first beam. An optical recording / reproducing apparatus that performs recording and reproduction of information with a second beam, respectively; a unit that divides a reflected light beam of each of the first and second beams from the information recording medium into reflected light and transmitted light; Means for splitting one of the reflected light and the transmitted light along the guide groove of the information recording medium into two halves, and the push-pull method using the bisected second beam. A tracking error detecting means for detecting a tracking error of the information recording medium; and a detecting means for detecting a reproduction signal of the second beam from a reflected light flux of the bisected second beam from the information recording medium. Raw signal detection means, and monitor signal detection means for detecting a monitor signal of the first beam from a reflected light flux of the first beam, which has been reflected from the information recording medium, and further comprising: A tracking error detection unit and the reproduction signal detection unit, each of which receives a reflected light beam of the second beam, which is divided into two, from the information recording medium at a focal point position; Wherein the monitor signal detecting means comprises:
A light detector comprising at least one or more light receiving surfaces provided so as to receive the reflected light flux of the beam at the focal point position, comprising the two-divided light detector and the at least one light receiving surface An optical recording / reproducing apparatus, wherein a photodetector is integrated.