JP2000231732A - Method for adjustment of position of light spot and optical information recording reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high accuracy alignment by adjusting the position of a light spot from an incident side light source on a recording medium based on changes in the power of the other side light source. SOLUTION: The emitting point of a semiconductor laser 201 for reproducing and the position of a light spot on an optical card 1 are in the conjugate relation. When a light spot of a semiconductor laser 202 for recording is to be adjusted in the three dimensions of x, y and z, the emitting point of the recording laser 202 is regarded as conjugate with the emitting point of the reproducing laser 201 by controlling the recording light spot on the optical card 1 to be three-dimensionally consistent with the reproducing light spot. When the position of the light spot of the recording laser 202 is to be adjusted, the recording light beam can be introduced into the emitting point of the reproducing laser 201 by a dichroic mirror 204. Therefore, the position in x, y, z directions of the light spot of the recording laser 202 is adjusted based on the oscillation state of the reproducing laser 201 and the recording laser 202 is fixed at the position where the variance in the oscillation state of the reproducing laser 201 is the max.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting the position of a light spot in an optical information recording / reproducing apparatus of a two-light source type.
The present invention relates to an optical information recording / reproducing apparatus that records or reproduces information on a recording medium using two light sources.

[0002]

2. Description of the Related Art Various types of recording media for recording or reproducing information optically, such as a disk, a card, and a tape, are conventionally known. When information is recorded on these information recording media, recording is performed by irradiating a light spot having a power sufficient to cause a shape change, a reflectance change, or a structural change in accordance with the characteristics of the recording medium. When reproducing information, the information pit array is scanned with a light spot having a constant power enough to prevent recording on the recording medium, and reflected light or transmitted light from the recording medium is detected. The recorded information is reproduced based on the information. An optical head used for recording / reproducing information on such a recording medium is configured to be relatively movable with respect to the recording medium in an information track direction including information pits in the information area and in a direction crossing the information track. The relative movement in both directions allows the light spot to access a desired information track and scan the information track.

The optical head is provided with a focusing lens for focusing the light beam, and an objective lens is used as the lens. The objective lens is held by the optical head so that it can move independently in the optical axis direction (focus direction) and in the direction perpendicular to the optical axis, that is, in the direction perpendicular to the information tracks of the recording medium (tracking direction). Such an objective lens is generally held via an elastic member, and the movement of the objective lens in the focusing and tracking directions is generally driven by an actuator utilizing magnetic interaction.

FIG. 8 is a schematic plan view of a write-once optical card. In FIG. 8, a large number of information tracks 2 and tracking tracks 4 are alternately arranged on the information recording surface of the optical card 1. The optical card 1 has an information track 2
There is provided a home position 3 serving as a reference position for access to. The home position 3 is set as a start position of the information recording and reproducing operation of the optical card inserted into the optical information recording / reproducing apparatus or as a standby position of the light spot. Therefore, the home position 3 is formed of the same recording layer as the information track in order to obtain the same light reflectance as the information track. However, the tracking track is not provided because it is not necessary for the function, and is a flat surface. The information tracks 2 are arranged in the order from 2-1 to 2-2, 2-3,.

[0005] As shown in FIG. 8, tracking tracks 4-1 and 4 are located adjacent to each information track 2.
−2, 4-3,... These tracking tracks are used as a guide for auto tracking (hereinafter abbreviated as AT) for controlling the light spot so as not to deviate from the target information track during light spot scanning during information recording and reproduction. Such an AT
The control is performed by a servo control circuit that detects a deviation (AT error) of the light spot from the information track in the optical head and feeds back the detected information to a tracking actuator that drives the objective lens in the tracking direction. That is, the tracking control is performed by moving the objective lens in the tracking direction (D direction) with respect to the optical head body so that the light spot does not deviate from the target information track.

In recording / reproducing information, when a light spot is scanned on an information track, a light beam is formed on the recording surface of the optical card into a spot of an appropriate size (focusing). Autofocus (hereinafter abbreviated as AF) control is performed on the objective lens. Such AF control is based on the deviation (AF) of the light spot from the focused state in the optical head.
Error), the detection signal is fed back to a focus actuator that moves the objective lens along the optical axis direction, and the objective spot is moved in the focus direction with respect to the optical head main body, so that the light spot is formed on the optical card. Focus control is performed so as to focus on the recording layer.

Here, in FIG. 9, S1, S2, S3,
S4 indicates a light spot irradiated on the optical card 1. AT control is performed by using the light spots of S2 and S3 partially applied to the tracking tracks 4-2 and 4-3, AF control and information pit reproduction are performed by using the light spot of S1. Record information pits. In the figure, 5-1 to 3 represent information pit strings, and 6-1 to 3 represent track numbers (addresses) arranged on both sides of the information pit strings 5-1 to 5-1. Each information track is provided with a track number indicating which track the position is. As shown in FIG. 9, the width of the information track 2, which is an information area, is wider than the width of the tracking track 4. According to the standard, the width of the tracking track 2 is about 3 μm, the width of the information track 4 is 9 μm, and the width of the information pit is about 3 μm.

FIG. 10 is a block diagram showing an example of an optical system (optical head) of an optical information recording / reproducing apparatus using an optical card as an information recording medium. In FIG. 10, reference numeral 10 denotes a reproducing semiconductor laser serving as a reproducing light source, and reference numeral 11 denotes a recording semiconductor laser serving as a recording light source. Also,
12 and 13 are collimator lenses, 14 is a wedge plate, 15
Is a diffraction grating, 16 is a dichroic prism as an optical multiplexer, 17 is a dichroic prism as an optical splitter,
18 is a quarter wavelength plate, 19 is an objective lens, 20 is a spherical lens, 21 is a cylindrical lens, and 22 is a photodetector. As shown in FIG. 13, the photodetector 22 is divided into six light receiving elements 22-1, 22-2, 22-3, and 22-.
4, 22-5 and 22-6.

The luminous flux emitted from the semiconductor laser 10 is shown in FIG.
0, which is a linearly polarized light beam parallel to the paper surface, becomes a parallel light beam by the collimator lens 12, enters the diffraction grating 15, and is split by the diffraction grating 15 into a plurality of diffracted light beams. The 0th-order diffracted light of the split light flux is used for information reproduction and AF control, and the two ± 1st-order diffracted lights are used for AT control. The three diffracted light beams are reflected by the dichroic prism 16, transmitted through the dichroic prism 17, converted into circularly polarized light by the 波長 wavelength plate 18, and incident on the objective lens 19.

The light beam incident on the objective lens 19 is narrowed down to a minute light spot and focused on the optical card 1. The focused light is the minute light spots S2 (+ 1st-order diffracted light), S1 (0th-order diffracted light), and S3 (-1st-order diffracted light) shown in FIG. The light spot S1 is used for reproduction and AF control as described above.
S2 and S3 are used for AT control. The position of the spot on the optical card 1 is the light spot S as shown in FIG.
The spots 2 and S3 are located on two adjacent tracking tracks, and the spot S1 is located on an information track 2 which is an information area between the tracking tracks. The degree of tracking of the light spots S2 and S3 is determined by rotating the diffraction grating 12 about the optical axis.
Fine rotation adjustment is performed so that desired AT control can be performed.

In this manner, a light spot is irradiated on the optical card 1, and a part of the light spot is reflected on the optical card surface and is reflected by the objective lens 19.
Incident on. This reflected light is converted into a linearly polarized light flux in a direction perpendicular to the paper surface of FIG. 10 by a quarter wavelength plate 18, reflected by a dichroic prism 17, and transmitted through a sensor lens system including a spherical lens 20 and a cylindrical lens 21. The light enters the detector 22.

On the other hand, the light beam emitted from the recording semiconductor laser 11 is a linearly polarized light beam parallel to the plane of FIG. 10 and becomes a parallel light beam by the collimator lens 13 and passes through the wedge plate 14, the dichroic prism 16, and the dichroic prism 17. Then, the light is converted into circularly polarized light by the 波長 wavelength plate 18,
The light is irradiated as a light spot on the optical card 1 by the objective lens 19. Information recording is performed by the irradiated light spot. A part of the recording light is reflected by the optical card 1, passes through the objective lens 19, is converted by the quarter-wave plate 18 into a linearly polarized light flux in the direction perpendicular to the plane of FIG. 10, and the dichroic prism 17 and the dichroic prism 16 Through.

Here, the wavelength characteristics of the semiconductor lasers 10 and 11 and the wavelength characteristics of the dichroic prisms 16 and 17 will be described. The wavelength of the semiconductor laser 10 for reproduction is 790
nm, and the wavelength of the recording semiconductor laser 11 is 830 nm. FIG. 11 shows the wavelength characteristics of the dichroic prism 16. The dichroic prism 16 transmits the 830 nm P-polarized component and the S-polarized component as shown in FIG.
The 90-nm P-polarized light component is reflected and the S-polarized light component is transmitted. FIG. 12 shows a dichroic prism 1
7 shows the wavelength characteristic. Dichroic prism 17 is 8
A 30 nm P-polarized component and an S-polarized component are transmitted, and 790
The P-polarized light component having a wavelength of nm is transmitted, and the S-polarized light component is reflected. Therefore, the light emitted from the recording semiconductor laser 11 having a wavelength of 830 nm is reflected by the optical card 1 and returns to the semiconductor laser 11 again. The light emitted from the 790 nm reproducing semiconductor laser 10 is reflected by the optical card 1 and travels to the photodetector 22.

FIG. 13 shows a signal processing circuit for generating an AT, an AF error signal and an information reproduction signal. In FIG. 13, reference numeral 22 denotes the photodetector of FIG.
5, 22-6, and 4 divided light receiving elements 22-1 to 22-4. Light spots S1, S on the light receiving surface of each light receiving element
Reference numerals 2 and S3 denote reflected light from the optical card 1. ± 1
The AT control light spots S2 and S3 of the order diffracted light are received by the light receiving elements 22-5 and 22-6, respectively, and the light spot for AF control and reproduction of the 0 order diffracted light is divided into four divided light receiving elements 22-1.
-4. The output signals of the light receiving elements 22-5 and 22-6 are output to a subtraction circuit 122, and the subtraction circuit 122 detects the difference to generate an AT control signal.

Also, the four-divided light receiving elements 22-2 and 22-4
Are output by an adder circuit 111, and the output signals of 22-1 and 22-3 are added by an adder circuit 112, respectively. The difference between the output signals of the adding circuits 111 and 112 is detected by a subtracting circuit 121 and output as an AF control signal. The outputs of the adders 111 and 112 are added by the adder 113 to generate a sum signal of the four-divided light receiving elements, which is output as the information reproduction signal RF. An AT servo circuit (not shown) performs AT control based on an AT control signal, and an AF servo circuit performs AF control based on an AF control signal. Further, information is reproduced by performing predetermined signal processing using the information reproduction signal RF. Recording of information on the optical card 1 is performed by performing AT and AF control with a reproducing semiconductor laser, and modulating and driving the recording semiconductor laser with a modulation signal based on information in accordance with a recording command from a CPU (not shown). Do.

[0016]

What is important for an optical head composed of two light sources as described above is as follows.
It is an object of the present invention to connect a reproducing spot, an AT spot, an AF spot, and a recording spot to the medium surface of an optical card, and to position the reproducing spot and the recording spot substantially at the center of the information track. If the focus position of the reproduction spot is different from the focus position of the recording spot, the reproduction spot is A
This is because the recording spot is in a defocused state even when the medium surface is in focus by the F control. When the recording spot is in a defocused state, the recording spot becomes large and the energy density in the spot is reduced, so that a stable information pit cannot be recorded. Can not be.

Although the reproduction spot is in focus on the medium surface by the AT and AF control and can be positioned substantially at the center of the information track, even when the recording spot is in focus on the medium. On the other hand, if the information pit is shifted from the center of the information track, the information pit is generated at a position shifted from the center of the information track, so that the amplitude of the information reproduction signal is reduced.

In order to solve such a problem, FIG.
In the optical head, a wedge plate 14 is disposed between the collimator lens 13 and the dichroic prism 16. By rotating the wedge plate 14 about the optical axis, the position of the recording spot on the medium surface is changed, and the wedge plate is fixed when the reproduction spot and the recording spot are located on a straight line in the track direction. I have. The positional relationship between the reproduction spot and the recording spot will be described with reference to FIG. S1 is a reproduction spot, S4 is a recording spot,
The dotted circle indicates the locus of the recording spot when the wedge plate 14 is rotated about the optical axis, and Q indicates the information track direction.

FIG. 14A shows a state before adjustment, and the light spots S1 and S4 do not coincide with the Q direction. FIG. 14 (b)
In the state after the adjustment, the light spots S1 and S4 coincide with the Q direction. FIG. 15A shows the intensity distribution of each light spot when viewed from the Q direction. On the other hand, FIG. 15B shows the intensity distribution of the light spot when the wedge plate is rotated about the optical axis to make the two spots coincide with each other in the Q direction as shown in FIG. 14B. . It can be seen that in the state after the adjustment, the intensity distributions of the light spots S1 and S4 match.

In reproducing / recording information on an optical card, the light spot must be moved relative to the optical card two-dimensionally. In the prior art, the optical card is moved in the direction D in FIG. 8 and the optical head is reciprocated in the LF direction, or the optical card is reciprocated in the LF direction and the optical head is moved in the D direction. One of the methods is adopted. In any case, in order to realize high-speed access, it is necessary to reduce the weight of the optical head. However, the conventional optical head has an increased number of components, such as a wedge plate, which is a mechanism for aligning a recording spot and a reproducing spot, and is not suitable for weight reduction.

Further, as an assembling adjustment method for aligning the recording spot and the reproducing spot with the center of the information track, for example, a jig chart is irradiated with a light spot, and the jig chart, the light spot and the position of the TV camera are adjusted. The two spots on the jig chart surface can be matched on TV
An adjustment method is adopted in which a wedge plate is turned around the optical axis while monitoring the intensity center deviation of the two spots with a waveform monitor or the like while monitoring with a camera or the like. Considering the reliability of the device or compatibility between devices, internal / external vibration, temperature change, various assembly tolerances, etc., the allowable displacement of the recording spot with respect to the reproduction spot must be within 0.2-0.3 microns. Therefore, the adjustment is very accurate.

However, in the conventional adjusting method, the resolution of the waveform monitor for measuring the displacement is about 0.1 μm. It had to rely on the adjustment experience, and it was very time-consuming because it was not an adjustment that anyone could do. Also, position adjustment requires high-performance jigs and tools and many expensive facilities such as TV cameras and waveform monitors.
The equipment cost is reflected in the product cost, which has been an obstacle to reducing the price of the product.

The present invention has been made in view of the above-mentioned conventional problems, and has been made in consideration of the above-described problems. Accordingly, the present invention provides a light spot position adjusting method and optical information capable of performing high-accuracy position adjustment without requiring expensive equipment or personal experience. An object of the present invention is to provide a recording and reproducing device.

[0024]

SUMMARY OF THE INVENTION It is an object of the present invention to use a first light source and a second light source having wavelengths different from each other, and to apply a light beam emitted from each of the first and second light sources to a minute light spot on a recording medium. Of a light spot of an information recording / reproducing apparatus for recording information on a recording medium by a light spot of one of the first and second light sources and reproducing the recorded information by a light spot of the other light source. In the position adjusting method, the first
And causing the reflected light of one of the light sources of the reflected light from the recording medium of the second light source to be incident on the other light source, and on the recording medium of the light spot of the incident light source based on the power change of the other light source. The position is adjusted by adjusting the position of the light spot.

Another object of the present invention is to provide first and second light sources having different wavelengths from each other, means for synthesizing the light beams emitted from the first and second light sources, An objective lens for focusing light onto a minute spot, and a unit for guiding one of the light beams of the first and second light sources reflected from the recording medium to a photodetector, wherein the light beam is detected by the photodetector. An optical information recording / reproducing apparatus which records information on a recording medium while performing focus servo and tracking servo on the basis of the obtained signal, or reproduces the recording, the reflection of the first and second light sources from the recording medium. The reflected light of one of the light sources is incident on the other light source, and the position of the light spot of the incident light source on the recording medium is adjusted based on the power change of the other light source. It is achieved by histological information recording and reproducing apparatus.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows the first embodiment of the present invention.
It is a figure showing composition of an embodiment. In FIG.
1 is a semiconductor laser for reproduction, 202 is a semiconductor laser for recording, 203 is a diffraction grating, and 204 is a semiconductor laser for reproduction.
A dichroic mirror having a film functioning as a half mirror for the wavelength of 01 and a reflecting mirror for the wavelength of the recording semiconductor laser 202, a beam splitter 205 having the characteristics of a half mirror, 206
Is a collimator lens, 207 is an objective lens, and 208 is a photodetector. Further, reference numeral 1 denotes an optical card which is shown in FIG.

FIG. 2 is a diagram showing the wavelength characteristics of the dichroic mirror 204. In the present embodiment, for example, the wavelength of the reproducing semiconductor laser 201 is 790 nm, and the wavelength of the recording semiconductor laser 202 is 830 nm. As shown in FIG. 2, a film that transmits about half of the light at 790 nm regardless of the polarization direction, reflects the remaining light, and reflects at 830 nm regardless of the polarization component is deposited on the dichroic mirror 204 as shown in FIG. .

Next, the optical path of each light beam will be described. The reproducing semiconductor laser 201 is disposed so as to be linearly polarized in a direction parallel to the plane of FIG. Reproduction semiconductor laser 2
The divergent light emitted from 01 is split into three light beams by the diffraction grating 203, partly reflected by the dichroic mirror 204, partially transmitted by the beam splitter 205, and incident on the collimator lens 206. This incident light is collimated by the collimator lens 206 and illuminated as three light spots on the optical card 1 by the objective lens 207. The arrangement and functions of the three light spots are the same as those shown in FIG. The light beam reflected by the optical card 1 is applied to the objective lens 207 and the collimator lens 20.
6 to form a convergent light beam,
, A part of the light passes through the dichroic mirror 204, and enters the photodetector 208. Photodetector 208
The configuration and the signal processing circuit are the same as those shown in FIG.

On the other hand, the recording semiconductor laser 202 arranged substantially conjugate with the reproducing semiconductor laser 201 is arranged so as to be linearly polarized in a direction perpendicular to the plane of FIG. Part of the divergent light beam emitted from the recording semiconductor laser 202 is reflected by the beam splitter 205 and the collimator lens 206
, And is illuminated as a light spot on the optical card 1 by the objective lens 207. The light flux reflected from the optical card 1 is applied to the objective lens 207 and the collimator lens 206.
, And partly reflected by the beam splitter 205,
Some are transparent. The transmitted light flux is totally reflected by the dichroic mirror 204 and enters the reproducing semiconductor laser 201.

Incidentally, the light emitting point of the reproducing semiconductor laser 201 and the light spot position on the optical card 1 have a conjugate relationship. On the other hand, as shown in FIG. 3, when the light spot of the recording semiconductor laser 202 is adjusted in three dimensions of x, y, and z, the recording light spot on the optical card 1 is three-dimensionally different from the reproduction light spot. If they match, the light emitting point of the recording semiconductor laser 202 has a conjugate relationship with the light emitting point of the reproducing semiconductor laser 201. Here, the recording semiconductor laser 2
When the position of the light spot 02 is adjusted, the recording light beam can be made incident on the light emitting point of the reproducing semiconductor laser 201 by the dichroic mirror 204 as described above.

As a characteristic of a semiconductor laser, a gain width enabling laser oscillation is about ± 40 nm. When light having a wavelength within the gain width is incident on the light emitting point of the semiconductor laser, the distribution of carriers is disturbed, that is, a change occurs in the internal refractive index distribution. As a result, the laser oscillation state is disturbed, and fluctuations in the emission power are observed. Can be FIG. 4 shows the oscillation state of the semiconductor laser 201 for reproduction. In FIG. 4, the level of n1 indicates a case where the recording light beam is not incident on the light emitting point of the reproducing semiconductor laser 201, and when light is incident on the light emitting point, the light beam oscillates like n2 or n3 in the incident state. The level changes while disturbing the state. FIG. 4 shows an example in which the light emission level is increased by the incidence of light. However, the level may decrease due to the difference in the amount of incident light or the structure of the semiconductor laser.

In the present embodiment, utilizing the characteristic that the level of the optical output changes, the semiconductor laser 20 for reproduction is used.
3, the position of the light spot of the recording semiconductor laser 202 is adjusted in the x, y, and z directions in FIG. The laser 202 is fixed. The sensor for monitoring the oscillation state of the reproducing semiconductor laser 201 is a sensor (A) disposed inside the semiconductor laser.
PC control sensor) or the photodetector 208 of FIG. 1 can be used. When the photodetector 208 is used, the signal processing circuit in FIG. 13 can be used as it is, which is the most efficient. In addition, the luminous flux of the recording semiconductor laser always enters the reproducing semiconductor laser.
Since the amount of change in the oscillation state of the semiconductor laser for reproduction is several percent, there is substantially no problem. However, if the light emission amount of the semiconductor laser for reproduction is controlled by a sensor for auto power control (not shown), there is no problem at all.

FIG. 5 is a diagram showing the configuration of the second embodiment of the present invention. 5, the same parts as those in FIG. 1 are denoted by the same reference numerals. In FIG. 5, reference numeral 201 denotes a semiconductor laser for reproduction;
202 is a recording semiconductor laser, and 203 is a diffraction grating. Reference numeral 204 denotes a dichroic mirror having characteristics as a half mirror with respect to the wavelength of the reproducing semiconductor laser 201 and reflecting characteristics with respect to the wavelength of the recording semiconductor laser 202; 210, a dichroic prism; A collimator lens, 207 is an objective lens,
Reference numeral 208 denotes a photodetector, and reference numeral 300 denotes a polarization conversion jig for adjustment.

The adjusting polarization conversion jig 300 has a structure in which a reflective film 302 is deposited on the back surface of a quarter-wave plate 301 as a phase difference generating element. Adjustment polarization conversion jig 3
00 indicates that light enters the quarter-wave plate 301 and the reflecting surface 3
02 so that the optical path length until the light is reflected from the quarter wave plate 301 and exits from the quarter-wave plate 301 coincides with the optical path length from the time when the light enters the optical card 1 and is reflected on the medium surface and exits from the optical card 1.
The thickness of the quarter-wave plate 301 is set in consideration of the refractive index of the quarter-wave plate 301 and the refractive index of the light transmitting member of the optical card 1.

Next, the wavelength characteristics of the dichroic prism 210 will be described. In the present embodiment, for example, the wavelength of the reproducing semiconductor laser 201 is 790 nm, and the wavelength of the recording semiconductor laser 202 is 830 nm. The dichroic prism 210 has a wavelength of 790 nm as shown in FIG.
Has a property of transmitting both the P-polarized component and the S-polarized component regardless of the polarization direction, and has a characteristic of reflecting the S-polarized component and transmitting the P-polarized component at a wavelength of 830 nm. The wavelength characteristics of the dichroic mirror 204 include:
For example, as shown in FIG. 2, with respect to 790 nm, it functions as a half mirror, a part is transmitted, and the rest is reflected.
With respect to 0 nm, it has the property of reflecting all light regardless of the polarization state.

Next, the optical path of each light beam will be described. It is assumed that the optical card 1 is arranged at the position of the adjustment polarization conversion jig 300. The reproducing semiconductor laser 201 is disposed so as to be linearly polarized in a direction parallel to the plane of FIG. The divergent light emitted from the reproducing semiconductor laser 201 is split into three light beams by the diffraction grating 203, partially reflected by the dichroic mirror 204, transmitted through the dichroic prism 210 as P-polarized light, and enters the collimator lens 206. The collimator lens 206 forms a parallel light beam, and the object lens 207 irradiates the optical card 1 with three light spots. The arrangement and functions of the three light spots are the same as in FIG. The light beam reflected by the optical card 1 passes through the objective lens 207 and the collimator lens 206 to become a convergent light beam, passes through the dichroic prism 210 as P-polarized light, partially passes through the dichroic mirror 204, and is detected by the photodetector 208. Is done. Photodetector 20
8 and the signal processing circuit are the same as those in FIG.

On the other hand, the recording semiconductor laser 202 arranged substantially conjugate with the reproducing semiconductor laser 201 is arranged so as to be linearly polarized in the direction perpendicular to the plane of FIG. The divergent light beam emitted from the recording semiconductor laser 202 is reflected by the dichroic prism 210 as S-polarized light, becomes a parallel light beam by the collimator lens 206, and is irradiated as a light spot on the optical card 1 by the objective lens 207. The light reflected from the optical card 1 passes through the objective lens 207 and the collimator lens 206, and is reflected by the dichroic prism 210 as S-polarized light.

Next, a method of adjusting the position of the recording semiconductor laser 202 will be described. First, the objective lens 20 shown in FIG.
7 adjusts the polarization conversion jig 30 to the light spot irradiation position.
A quarter-wave plate 301 having a reflecting surface 302 of 0 is arranged. At this time, the optical axis of the quarter-wave plate 301 is arranged at an angle of 45 degrees with respect to the linear polarization direction of the recording semiconductor laser 202. A linearly polarized light beam emitted from the recording semiconductor laser 202 is converted into a circularly polarized light beam by a quarter-wave plate 301, reflected on a reflection surface 302, and again returned to a quarter-wave plate 302.
, And becomes a linearly polarized light beam rotated by 90 degrees, and enters the dichroic prism 210 as P-polarized light. Due to the wavelength characteristic of the dichroic prism 210, P
The polarized light component is transmitted, is totally reflected by the dichroic mirror 204, and is incident on the semiconductor laser 201 for reproduction. By using the adjustment polarization conversion jig 300 in this manner,
As in the first embodiment, the reflected light of the recording semiconductor laser 202 can be made incident on the reproduction semiconductor laser 201.

Here, similarly to the first embodiment, the light emitting point of the reproducing semiconductor laser 201 and the light spot position on the optical card have a conjugate relationship. On the other hand, when the recording semiconductor laser 202 is adjusted in three dimensions of x, y, and z as shown in FIG. 3, if the recording light spot on the optical card coincides with the reproduction light spot in three dimensions, Recording semiconductor laser 202
Are conjugate with the light emitting point of the semiconductor laser 201 for reproduction. Also in the present embodiment, when the position of the recording semiconductor laser 202 is adjusted, the recording light beam is made incident on the emission point of the reproduction semiconductor laser 201 by the adjustment polarization conversion jig 300 as described above. As a characteristic of a semiconductor laser, a gain width enabling laser oscillation is approximately ± 40 nm.
is there. When light having a wavelength within the gain width is incident on the light emitting point of the semiconductor laser, the carrier distribution is disturbed, that is, the internal refractive index distribution is changed. As a result, the laser oscillation state is disturbed, and the emission power fluctuates.

In this case, as shown in FIG. 4, the level of n1 is when the recording light beam is not incident on the light emitting point of the reproducing semiconductor laser 201. When light is incident on the light emitting point, the level changes while the oscillation state is disturbed like n2 or n3 in the incident state. In FIG. 4, the light emission level is increased by the incidence of light, but the level may decrease due to the difference in the amount of incident light and the structure of the semiconductor laser. In the present embodiment, the position of the recording semiconductor laser 202 is adjusted based on the oscillation state of the reproducing semiconductor laser 201 by utilizing the characteristic that the level of the optical output changes as in the first embodiment, and Semiconductor laser 20
The recording semiconductor laser 202 is fixed at a position where the fluctuation of the oscillation state of 1 becomes maximum. As a sensor for monitoring the oscillation state of the semiconductor laser 201 for reproduction, a sensor or a photodetector 208 disposed inside the semiconductor laser can be used.

When using a recording medium having birefringence,
Part of the recording light beam passes through the dichroic prism 210, is reflected by the dichroic mirror 204, and enters the reproducing semiconductor laser 201. When the recording light beam enters the reproducing semiconductor laser 201, the oscillation state of the reproducing semiconductor laser 201 changes. However, the change amount is several percent, so that there is no substantial problem, but the reproduction is performed by an auto power control sensor (not shown). There is no problem if the light emission amount of the semiconductor laser is controlled. Further, instead of the dichroic mirror 204, one that functions as a half mirror for the recording light beam and the reproducing light beam may be used.
Incident on the half mirror may adversely affect the reproduction signal and the AT / AF control signal. Therefore, a film for reflecting the recording light beam may be formed on the back surface of the half mirror, or the film between the half mirror and the photodetector 208 may be formed. It is necessary to arrange an element which does not transmit the recording light beam in the optical path.

FIG. 7 is a diagram showing the configuration of the third embodiment of the present invention. In this embodiment, in addition to the configuration of the second embodiment shown in FIG.
A quarter-wave plate 211 for generating a phase difference between the two is disposed. The configuration other than the quarter wavelength plate 211 is the same as that of FIG. The quarter-wave plate 211
Is used only when the position adjustment of the light spot of the recording semiconductor laser 202 is performed, and is removed when the position adjustment is completed.

Next, a method for adjusting the position of the light spot of the recording semiconductor laser 202 will be described. When performing the position adjustment, the quarter-wave plate 211 is inserted into the optical path between the collimator lens 206 and the objective lens 207, and at this time, the optical axis of the quarter-wave plate 211 is They are arranged at an angle of 45 degrees with respect to the direction of linear polarization.
The linearly polarized light beam emitted from the recording semiconductor laser 202 is
The light is converted into a circularly-polarized light beam by the quarter-wave plate 211, reflected by the optical card 1, and incident on the quarter-wave plate 211 again.
Then, the light becomes a linearly polarized light beam rotated by 90 degrees by the 波長 wavelength plate 211, and enters the dichroic prism 210 as P-polarized light. The P-polarized light component is transmitted due to the wavelength characteristics of the dichroic prism 210, and all of the light is reflected by the dichroic mirror 204 and enters the reproducing semiconductor laser 201. By using the quarter-wave plate 211 in this way, the reflected light of the recording semiconductor laser 202 from the optical card 1 enters the reproduction semiconductor laser 201.

The method of adjusting the light spot later is based on the first and second light spots.
This is exactly the same as the embodiment. When the recording light beam enters the light emitting point of the reproducing semiconductor laser 201, the laser oscillation is disturbed as described above, and the light emitting power fluctuates as shown in FIG. Also in the present embodiment, the semiconductor laser 201 for reproduction
The oscillation state of the semiconductor laser 201 is observed by the output of the photodetector 208 and the like, and the position of the light spot of the recording semiconductor laser 202 is adjusted based on the output. The semiconductor laser 202 is fixed.

Although it is possible to form a part of the optical system without removing the quarter-wave plate 211, if the recording medium has no birefringence, the quarter-wave plate 211 is removed and the recording is performed. The recording luminous flux is reflected by the recording semiconductor laser 202 entirely, so that the recording luminous flux is reflected by the reproduction semiconductor laser 20.
Since the laser beam does not enter the laser diode 1, the power of the reproducing semiconductor laser does not fluctuate at all, and more stable recording and reproducing can be performed.

When a recording medium having birefringence is used, when the quarter-wave plate 211 is removed, a part of the recording light beam passes through the dichroic prism 210, is reflected by the dichroic mirror 204, and is reproduced. Laser 20
Incident on 1. When the recording light beam enters the semiconductor laser 201 for reproduction, the oscillation state of the semiconductor laser 201 for reproduction changes. However, since the change amount is several%, there is substantially no problem. If the light emission amount of the semiconductor laser for reproduction is controlled by the sensor, there is no problem at all.

Further, instead of the dichroic mirror 204, a mirror functioning as a half mirror for the recording light beam and the reproducing light beam may be used.
8 may adversely affect the reproduction signal and the AT / AF control signal. Therefore, a film for reflecting the recording light beam may be formed on the back surface of the half mirror, or between the half mirror and the photodetector 208. It is necessary to arrange an element which does not transmit the recording light beam in the optical path of the recording medium.

In each of the first to third embodiments, in each case, the light beam of the recording semiconductor laser is made to enter the reproducing semiconductor laser, and the light of the recording semiconductor laser is output based on the optical output of the reproducing semiconductor laser. Although it has been described that the position of the spot is adjusted, the present invention, on the contrary, impinges the light beam of the reproducing semiconductor laser on the recording semiconductor laser and adjusts the reproducing semiconductor laser based on the optical output of the recording semiconductor laser. The position adjustment of the light spot may be performed.

[0049]

As described above, according to the present invention, a light beam emitted from one light source is made incident on the other light source.
By adjusting the position of the light spot of the incident side light source based on the power change of the other side light source, the position adjustment of the light spot can be easily performed without requiring expensive equipment and relying on personal experience. It can be performed with high precision. Further, since no position adjusting component such as a wedge plate is required in the optical head, the weight of the optical head can be reduced, and the access speed can be increased. Further, since the position adjustment of the light spot can be simplified, the cost of the apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a dichroic mirror 204 of the embodiment of FIG.
FIG. 4 is a diagram showing the wavelength characteristics of FIG.

FIG. 3 is a diagram for explaining a position adjustment method of a light spot according to the embodiment of FIG. 1;

FIG. 4 is a diagram showing an oscillation state of a reproducing semiconductor laser due to incidence of a light beam of a recording semiconductor laser.

FIG. 5 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 6 shows a dichroic prism 21 of the embodiment of FIG.
FIG. 4 is a diagram illustrating a wavelength characteristic of 0.

FIG. 7 is a diagram illustrating a configuration of a third exemplary embodiment of the present invention.

FIG. 8 is a plan view showing an optical card.

FIG. 9 is a diagram showing a light spot on an optical card.

FIG. 10 is a diagram showing an optical system of a conventional optical information recording / reproducing apparatus.

FIG. 11 shows a dichroic prism 1 of the optical system shown in FIG.
6 is a diagram illustrating a wavelength characteristic of No. 6. FIG.

FIG. 12 shows a dichroic prism 1 of the optical system shown in FIG.
7 is a diagram illustrating a wavelength characteristic of FIG.

FIG. 13 is a diagram showing a signal processing circuit of a conventional optical information recording / reproducing device.

FIG. 14 is a diagram showing the positions of a reproducing light spot and a recording light spot of a conventional optical information recording / reproducing apparatus before and after adjustment.

FIG. 15 is a diagram showing a comparison between the intensity distributions of a reproduction light spot and a recording light spot before and after adjustment in FIG. 14;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical card 201 Reproduction semiconductor laser 202 Recording semiconductor laser 203 Diffraction grating 204 Dichroic mirror 205 Beam splitter 206 Collimator lens 207 Objective lens 208 Photodetector 210 Dichroic prism 211 Quarter-wave plate 300 Adjustment polarization conversion jig 301 1 / 4 wavelength plate 302 reflective film

Claims (9)

[Claims] 1. A first light source and a second light source having wavelengths different from each other, and light beams emitted from the first and second light sources are condensed into minute light spots on a recording medium, respectively. In the method of adjusting the position of a light spot of an information recording / reproducing apparatus for recording information on a recording medium by a light spot of one of the light sources and reproducing the recorded information by a light spot of the other light source, The reflected light of one light source among the reflected light from the recording medium of the second light source is made incident on the other light source, and the position of the light spot of the incident light source on the recording medium based on the power change of the other light source. Adjusting the position of the light spot. 2. An adjusting polarization conversion jig comprising a phase difference generating member and a reflection film formed on the back surface thereof is disposed at a position of a recording medium, and the conversion jig causes a light flux of one light source to be emitted from a light source on the other side. 2. The method for adjusting the position of a light spot according to claim 1, wherein the light spot is incident on the light spot. 3. The apparatus according to claim 1, wherein a polarization conversion unit is arranged in an optical path of the reflected light from the recording medium, and the light flux of one light source is made incident on the other light source by the polarization conversion element. Adjustment method of light spot position. 4. The apparatus according to claim 1, wherein the position adjustment of the light spot is performed in an optical axis direction and a direction orthogonal to the optical axis.
3. The method for adjusting the position of a light spot according to item 1. 5. The method according to claim 1, wherein the position of the light spot is adjusted so that the power change becomes maximum. 6. The method according to claim 1, wherein the power change is detected by an information reproducing photodetector. 7. The apparatus according to claim 2, wherein an optical path length of the adjustment polarization conversion jig passing through the phase difference generating member is set to be equal to an optical path length of transmitting the recording medium. Adjustment method of light spot position. 8. The light spot position adjusting method according to claim 3, wherein said polarization conversion means is a phase difference generating element. 9. A first light source and a second light source having different wavelengths from each other, means for synthesizing light beams emitted from the first and second light sources, and each of the synthesized light beams is collected in a minute spot on a recording medium. An objective lens that emits light, and a unit that guides one of the light beams of the first and second light sources reflected from the recording medium to a photodetector, based on a signal detected by the photodetector. An optical information recording / reproducing apparatus for recording information on a recording medium while reproducing focus information and recording information while performing focus servo and tracking servo.
And causing the reflected light of one of the light sources of the reflected light from the recording medium of the second light source to be incident on the other light source, and on the recording medium of the light spot of the incident light source based on the power change of the other light source. An optical information recording / reproducing apparatus, wherein the position of the optical information recording / reproducing apparatus is adjusted.