JP2579108B2 - Optical information recording / reproducing apparatus and adjustment method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus for recording and reproducing information by separately providing a recording light source and a reproducing light source and irradiating a light beam from the light sources onto a recording medium. Related to the device.

[0002]

2. Description of the Related Art Conventionally, various types of optical information media for recording and reproducing information by using light, such as a disk, a card, and a tape, are known. These optical information recording media include those capable of recording and reproduction and those capable of reproduction only. Information is recorded on a recordable medium by scanning the information track with a light beam modulated according to the recording information and narrowed down into a minute spot, and the information is recorded as an optically detectable information pit string. Is done.

In order to reproduce information from a recording medium, an information pit array on an information track is scanned with a light beam spot having a constant power so that recording is not performed on the medium. This is performed by detecting transmitted light.

[0004] The optical head used for recording and reproducing information on and from the recording medium described above is relatively movable with respect to the recording medium in the information track direction and in the direction crossing the direction. Information track scanning of the beam spot is performed. As a lens for narrowing a light beam spot in the optical head, for example, an objective lens is used. The objective lens moves independently of the optical head body in the optical axis direction (focusing direction) and the direction (tracking direction) orthogonal to both the optical axis direction and the information track direction of the recording medium. Is held so that you can. Such an objective lens is generally held via an elastic member, and the movement of the objective lens in the above two directions is generally driven by an actuator utilizing magnetic interaction.

[0005] Among the above-mentioned optical information recording media, a card-shaped optical information recording medium (hereinafter referred to as an optical card) will be a large and small-sized information recording medium that is convenient to carry in the future. Demand is expected.

FIG. 4 is a schematic plan view of a write-once optical card, and FIG. 5 is a partially enlarged view thereof.

In FIG. 4, on an information recording surface of an optical card 1, a large number of information tracks 2 are arranged in parallel to the LF direction. On the information recording surface of the optical card 1, a home position 3 serving as a reference position for accessing the information track 2 is provided. The information tracks 2 are arranged in the order of 2-1, 2-2, 2-3,... From the side closer to the home position 3, and as shown in FIG. -1,4-2,4
-3,... Are sequentially provided. These tracking tracks 4 are used as guides for auto tracking (hereinafter, referred to as AT) for controlling the beam spot so as not to deviate from a predetermined information track when scanning a light beam spot during information recording and reproduction. .

The AT servo detects a deviation (AT error) of the light beam spot from the information track in the optical head, gives a negative feedback to the detection signal to the tracking actuator, and connects the objective lens to the optical head body. This is performed by moving the light beam spot in a tracking direction (D direction) to follow a desired information track.

In information recording and reproduction, when an information track is scanned with a light beam spot, the light beam is formed into an appropriately sized spot on the optical card surface (focusing). Focusing (hereinafter, referred to as AF) servo is performed. The AF servo detects a deviation (AF error) of the light beam spot from the in-focus state in the optical head, feeds back the detection signal to the focusing actuator, and moves the objective lens to the optical head body in the focusing direction. To focus the light beam spot on the optical card surface.

In FIG. 5, S1, S2, and S3 denote light beam spots. Tracking is performed using the S1 and S3 light spots, and information pits during focusing and recording are performed using the S2 light spot. And read information pits during reproduction. In each information track, 6-1 and 6-2 and 7-1 and 7-2 indicate a preformatted left address portion and a right address portion, respectively. By reading these address portions, the track identification can be performed. Done. Numeral 5 (corresponding to 5-1 and 5-2 in the figure) is a data part, in which predetermined information is recorded.

Here, the method of optical information recording will be briefly described. Conventionally, there are roughly two types of optical information recording systems. One is a one light source system in which recording and reproduction are performed by the same light source, and the other is a two light source system in which recording and reproduction are performed by two different light sources. It is said that the two-light source method is advantageous over the one-light source method in terms of deterioration of reproduction light, speeding-up, and the like.

FIG. 6 is a schematic diagram of a conventional two-light source type optical head optical system. The two light source system uses different light sources for recording light and reproduction light, thereby preventing deterioration of reproduction light and enabling high-speed recording.

In FIG. 6, reference numerals 21 and 22 denote semiconductor lasers as light sources. The semiconductor laser 21 emits light having a wavelength of 780 nm, and the semiconductor laser 22 emits light having a wavelength of 830 nm. 23,
Reference numeral 24 denotes a collimator lens, 25 denotes a diffraction grating for splitting a light beam, 26 denotes a P-polarized component of 780 nm,
A dichroic prism designed to reflect light of 30 nm, 27 is a beam shaping prism, and 28 is a polarizing beam splitter. 29 is a quarter-wave plate, 3
Reference numeral 0 denotes an objective lens, 31 denotes a bandpass filter that transmits only light of 780 nm, 32 denotes a stopper, 33 denotes a toric lens, and 34 denotes a photodetector.

The light beams emitted from the semiconductor lasers 21 and 22 become divergent light beams and collimator lenses 23 and 2.
4 and is corrected by the lens into a parallel light beam. The light of 780 nm further enters the diffraction grating 25,
The diffraction grating divides the light into three effective light beams (0th-order diffracted light and ± 1st-order diffracted light). The 780 nm light beam and the 830 nm light beam enter the dielectric multilayer film laminated on the bonding surface of the dichroic prism 26 having the spectral characteristics as shown in FIG.

As is apparent from FIG. 7, the dichroic prism 26 transmits P-polarized light of 780 nm,
Since the light of 30 nm has a characteristic of being reflected, the light of 780 nm
Is transmitted, and the 830 nm light beam is reflected and emitted from the dichroic prism 26 in a state where both light beams are combined. The light beam having passed through the dichroic prism 26 is shaped into a predetermined light intensity distribution by a light beam shaping prism 27 and then enters a polarization beam splitter 28.

As shown in FIG. 8, the polarization beam splitter 28 has a spectral characteristic such that P-polarized light is transmitted and S-polarized light is reflected. Through.

Next, these two wavelength light beams are divided by 1 /
When transmitted through the four-wavelength plate 29, the light is converted into circularly polarized light, and is focused by the objective lens 30. Then, the 780 nm light beam forms three small beam spots S on the optical card 1.
1 (+ 1st order diffracted light), S2 (0th order diffracted light), S3 (-1
And is used as reproduction light and signal light for AT and AF control. The light beam of 830 nm is irradiated on the optical card 1 as a minute beam spot of S2 (zero-order diffracted light) and used as recording light.

The positions of the light beam spots on the optical card 1 are the same as those in FIG.
Is located on the adjacent tracking track 4, and the light beam spot S2 is located on the information track 2 between the tracking tracks. In addition, S2 of 780 nm and 830
The positional relationship of S2 in nm is 830n, which is the recording light.
It is better that the light beam spot S2 of m is located in the traveling direction, but is free in principle and coincides here. Thus, the reflected light from the light beam spot formed on the optical card 1 is made substantially parallel through the objective lens 30 and passes through the quarter-wave plate 29 again, so that the polarization direction is changed from that at the time of incidence. It becomes a light beam rotated by 90 °. Therefore, the beam enters the polarizing beam splitter 28 as an S-polarized beam, and the splitter 28
Since the polarized light is reflected, the light beam passes through the band-pass filter 3.
It is reflected to one side. Then, as shown in FIG.
The bandpass filter 31 having a spectral characteristic that transmits only light near m transmits only light near 780 nm, and reflects light of other wavelengths.
Only the light of 0 nm is guided to the detection optical system as a signal. The light transmitted through the bandpass filter 31 is focused by the toric lens 33 and enters the photodetector 34. The photodetector 34 has a configuration as shown in FIG. 10, and performs tracking control based on light receiving signals of the light receiving elements 11 and 13.
Focus control and reproduction signal detection are performed using the light receiving signal of the light receiving element 12 which is a four-divided element.

[0019]

However, in the above-described conventional example, since the reproducing light and the recording light are irradiated using different light sources, the positional deviation between the reproducing light spot and the recording light spot inevitably occurs. As a result, there is a disadvantage that the reproduced signal is deteriorated.

That is, the reproduction light beam and the recording light beam are applied to the optical card 1 through the same optical path after passing through the dichroic prism 26, but the focal length of the objective lens 30 is slightly different depending on the wavelength (780 nm, 830 nm). It is impossible to focus both light beams incident as parallel light beams on the optical card in a just-focused state.

Therefore, conventionally, the collimation adjustment of the recording light beam is completely performed, and the collimation adjustment of the reproduction light beam is
On the optical card, the recording light spot and the reproduction light spot are adjusted so as to be condensed in a just-focused state by making an adjustment so as to be in a slightly divergent state.

Conventionally, this adjustment has been performed by moving the light source. However, when trying to adjust the positional deviation by moving the light source, for example, when the focal lengths of the collimator lens and the objective lens are approximately the same (optical disk) In general, the light source must be moved by 0.1 μm in order to adjust the displacement amount by 0.1 μm.
When pursuing accuracy on the order of submicrons, there has been a problem that the time and cost for adjustment are increased.

(Object of the Invention) An object of the present invention is to realize a method and an apparatus for adjusting the positional deviation of a reproduction light spot and a recording light spot in a short time, simply and accurately without moving a light source. is there.

[0024]

According to the present invention, as a means for solving the above-mentioned problems, one of two light beams having different wavelengths is set as a divergent light beam, the other as a parallel light beam, and a light spot on a recording medium. An optical information recording / reproducing apparatus that performs recording and reproduction of information by irradiating, has a plane parallel glass plate inserted and arranged in the divergent light beam, and the plane parallel glass plate with respect to the optical axis of the light beam. Tilt and place,
In addition, the present invention provides an optical information recording / reproducing apparatus characterized in that the position of the light spot by the divergent light beam is adjusted by rotating the optical information recording / reproducing apparatus with respect to the optical axis. In the adjusting method of the optical information recording / reproducing apparatus for recording and reproducing information by irradiating one of the two luminous fluxes as a divergent luminous flux and the other as a parallel luminous flux as a light spot on a recording medium, the divergent luminous flux has a plane parallel By inserting a glass plate, tilting the plane parallel glass plate with respect to the optical axis of the light beam, and rotating the glass plate with respect to the optical axis, the position of the light spot by the divergent light beam is adjusted. The method for adjusting the optical information recording / reproducing apparatus described above is used as the means.

[0025]

According to the present invention, a plane-parallel glass plate inclined with respect to the optical axis is inserted into the optical path of reproduction light or recording light in a substantially parallel state (slight divergence state), and a parallel shift is performed. By doing so, a simulated object height can be given, and an image height associated with it can be obtained.

By utilizing this fact, the positional deviation of the recording light spot and the reproduction light spot in the tracking direction can be finely adjusted by rotating the plane parallel glass plate around the optical axis.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic structural view showing an embodiment of an optical head optical system in an information recording / reproducing apparatus according to the present invention. In FIG. 1, the same parts as those of the conventional device are denoted by the same reference numerals.

In FIG. 1, reference numeral 21 denotes a semiconductor laser as a light source for emitting a reproducing light beam, and reference numeral 22 denotes a semiconductor laser as a light source for emitting a recording light beam. Semiconductor laser 2
1 emits light having a wavelength of 780 nm as reproduction light, and the semiconductor laser 22 emits light having a wavelength of 830 nm as recording light. Reference numerals 23 and 24 denote collimator lenses, reference numeral 25 denotes a diffraction grating, and reference numeral 26 denotes a dichroic prism.
This is the same as the conventional one described above.

Numeral 41 denotes a plane parallel glass plate which is a feature of the present invention, and is arranged to be inclined with respect to the optical axis in order to shift the light beam in parallel.

Further, 27 is a beam shaping prism, 28 is a polarizing beam splitter, 29 is a quarter-wave plate, 30 is an objective lens, 31 is a bandpass filter that transmits only 780 nm light, 32 is a stopper, and 33 is a toric lens. , 34 are photodetectors and 1 is an optical card which is the same as the conventional one.

The present invention aims at aligning the positions of the reproduction light spot and the recording light spot in the tracking direction. Next, the characteristic features of the present invention will be described.

After passing through the dichroic prism 26, the reproduction light beam and the recording light beam are applied to the optical card 1 through the same optical path, but the focal length of the objective lens 30 is changed to the wavelength (780).
nm, 830 nm), it is impossible to focus both light beams incident as parallel light beams on the optical card in a just-focused state.

Therefore, conventionally, the collimation adjustment of the recording light beam is completely performed, and the collimation adjustment of the reproduction light beam is
On the optical card, the recording light spot and the reproduction light spot are adjusted so as to be condensed in a just-focused state by making an adjustment so as to be in a slightly divergent state.

In the present invention, the plane parallel glass plate 41 is used to adjust the positional deviation by positively utilizing the fact that the reproduction light beam is in a slightly divergent state.

Hereinafter, the principle of the present invention will be briefly described with reference to FIG.

As shown in FIG. 2A, when a parallel light beam is incident on a convex lens, a light beam passing through the center of the lens is always focused on a position F where the light reaches the image plane.

For example, even if the light beam A is shifted to the light beam B, the light beam is condensed at the position of the point F (the same applies even if the light beam is inclined with respect to the lens).

On the other hand, when a divergent light beam as shown in FIGS. 2B and 2C is incident, the story is different. For example, even if the same divergent light beam is incident, the image forming positions Fa ′ and F ′ on the image plane are different when the light beam is incident on the upper part of the convex lens (FIG. 2B) and when it is incident on the lower part (FIG. 2C).
b 'changes.

Therefore, in the present invention, by utilizing the above characteristics and inserting a plane-parallel glass plate at an angle to the optical axis into a reproducing light beam (divergent light beam), the light beam is intentionally transmitted to the objective lens. Shift, and furthermore, by rotating the plane-parallel glass plate with respect to the optical axis (about the optical axis) to move the light spot by the divergent light beam, and to adjust the position of the recording light spot and the reproduction light spot in the tracking direction with accuracy. It is something that can be done well.

The adjustment method of the present invention will be described below with reference to FIG.

FIG. 3 is a schematic diagram of the reproducing light optical system and the recording light optical system according to the present invention, and shows the position of each light spot.

First, a recording light beam as a reference for adjustment is adjusted.

As shown in FIG. 3A, the distance between the semiconductor laser 22 and the collimator lens 24 is adjusted by a jig (not shown), and the light is incident on the objective lens 30 as a parallel light beam. The distance between the objective lens 30 and the optical card 1 is adjusted so that a minimum spot forms an image on the optical card 1 and the spot is set at the center of the track.

Next, in this state, the reproduction light semiconductor laser 2
1 is emitted, and the distance between the semiconductor laser 21 and the collimator lens 23 is adjusted so that a minimum spot is formed on the optical card 1 as shown in FIG. At this time, the reproduction light beam is in a slightly divergent state due to the chromatic aberration relationship with the recording light beam in the objective lens 30.

Finally, the plane-parallel glass plate 41 is inserted into the light beam at an angle to the optical axis, and is inserted into the light beam (with the optical axis centered).
By adjusting the position of the recording light spot and the reproduction light spot in the track direction, the adjustment is completed.

FIG. 3C is a schematic plan view showing the positional relationship between spots on a track. Plane parallel glass plate 41
Are rotated, the reproduced light spots are R1-R in FIG.
4, and can be adjusted to the center of the track.

[Embodiment 2] In the above embodiment, the plane parallel glass plate is inserted only in the reproducing optical path, but the same effect can be obtained by inserting it in the reproducing and recording optical paths. . That is, the recording light is not affected because it is a parallel light beam, but the reproduction light beam is a divergent light beam, so that only this reproduction light beam can be moved and adjusted.

Although the case where the reproducing light beam is a divergent light beam has been described above, the present invention can also obtain the same effect when the recording light beam is a divergent light beam and the reproducing light beam is a parallel light beam.

In the above-described embodiment, a glass member is shown as a plane parallel glass plate. However, a plastic member or the like can be used as long as the optical characteristics are the same.

[0051]

As described above, according to the present invention, a plane-parallel glass plate is inserted into the optical path of recording light and / or reproduction light, which is made into a parallel light beam and a slightly divergent light beam, and is rotated. By moving a recording or reproduction spot on a recording medium such as an optical card, the positions of the recording light spot and the reproduction light spot can be finely adjusted. As a result, compared to the conventional adjustment by moving the light source, the adjustment can be performed easily and accurately in a short time. Therefore, an effect is obtained that the time and cost required for the adjustment are greatly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a two-light source optical head optical system embodying the present invention.

FIG. 2 is a schematic diagram for explaining a basic principle of the present invention.

FIG. 3 is a schematic diagram for explaining the movement of a light spot by the adjusting means of the present invention.

FIG. 4 is a schematic plan view of the optical card.

FIG. 5 is a partially enlarged view of an optical card.

FIG. 6 is a schematic configuration diagram of a conventional two-light-source optical head optical system.

FIG. 7 is a diagram showing spectral characteristics of a dichroic prism 26.

FIG. 8 is a diagram illustrating spectral characteristics of the a-plane of the polarizing beam splitter and the beam shaping prism 27.

FIG. 9 is a diagram illustrating spectral characteristics of a bandpass filter 31.

FIG. 10 is a schematic diagram showing a light receiving surface of a photodetector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical card 21, 22 Semiconductor laser 23, 24 Collimator lens 25 Diffraction grating 26 Dichroic prism 29 1/4 wavelength plate 34 Photodetector 41 Planar parallel glass plate

Claims (4)

(57) [Claims] 1. A light source for recording and a light source for reproduction are separately provided,
By irradiating the recording medium with light beams emitted from these light sources, an optical information recording / reproducing apparatus that records and reproduces information, wherein one of the light beams is a divergent light beam and the other is a parallel light beam, Means for connecting light spots, and a plane-parallel glass plate which is disposed in the divergent light beam and inclined with respect to the optical axis of the light beam, as means for adjusting the position of the light spot, An optical information recording / reproducing apparatus wherein the adjustment is performed by rotating the optical information recording / reproducing apparatus with respect to an optical axis. 2. The information recording / reproducing apparatus according to claim 1, wherein the position of the plane-parallel glass plate is in a light beam in which the reproducing or recording light beam, which is the divergent light beam, exists alone. . 3. The arrangement position of the plane-parallel glass plate is in an optical path where reproduction and recording light beams coexist, and one of the reproduction and recording light beams is a divergent light beam. 2. The information recording / reproducing apparatus according to 1. 4. A method for adjusting an optical information recording / reproducing apparatus which records and reproduces information by irradiating one of two light sources having different wavelengths as a divergent light beam and the other as a parallel light beam as a light spot on a recording medium. In the above, the light spot by the divergent light beam is inserted by inserting a plane parallel glass plate into the divergent light beam, tilting the plane parallel glass plate with respect to the optical axis of the light beam, and rotating the flat parallel glass plate with respect to the optical axis. Adjusting the position of the optical information recording / reproducing apparatus.