JPH03224142A - Optical head and its control method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical head, and more particularly to an optical head that can write information on an information recording medium such as a portable thin optical disk and further read that information.

[Prior art] Various OA equipment including personal computers, H
The memories of devices A are becoming smaller and larger in capacity. Optical disks, which are large-capacity storage devices, are expected to see dramatic demand for laptop-type personal computers, word processors, and the like, as optical pickups can be made smaller and thinner. For this reason, efforts are being made in various fields to make optical heads smaller and thinner. One of these methods is to miniaturize the entire optical head by making it monolithic or hybrid.

This method performs focus control by floating a small and lightweight optical head above the disk, and is called a floating optical head.

Currently, it is considered difficult for floating optical heads to focus a diffraction-limited minute optical spot onto a disk. For this reason, attempts are being made to make the entire conventional bulk-type optical head as thin as possible by making the part that moves in the radial direction of the optical disk thinner, but this approach has reached its limits. has reached.

The data recording surface of an optical disc has a track width of 9, for example, 1.
A recording track with a fine structure of about μm and a track pitch of about 1.6 μm is formed, and this recording track is irradiated with a laser beam with a spot diameter of about 1 μm. Then, while rotating the optical disk,
Data is recorded by modulating the intensity of the laser beam in accordance with the data to be recorded, and the recorded data is reproduced by detecting changes in the level of the laser beam reflected from the data recording surface. .

In this way, the part that narrows the spot diameter of the laser beam to a predetermined size on the recording medium, makes the laser beam follow the high-density recording tracks as described above, and detects the reproduced signal from the recording tracks is the optical It is the head. An example of its schematic configuration is shown in FIG. In the figure, an optical head 200 uses a light beam 10 using the well-known Knifezi method.
0 focus detection is performed. The laser beam output from the light source 10 is converted into a parallel light beam 100 by the collimating lens 30. This light beam 100
is a polarizing beam splitter (hereinafter referred to as PBS) 120
PBS120
Transparent. Further, the optical path of the light beam 100 is bent at a right angle by a mirror 140, and then polarized by a quarter-wave plate 110 to become circularly polarized light. This circularly polarized light is condensed by a condensing lens 80 and focused on the film surface of the recording track of the optical disk 5o. The reflected light from the spot imaged on the optical disk 50 is converted into a parallel light beam by the condenser lens 80, and then further polarized by the quarter-wave plate 110 to change the plane of polarization to become S-polarized light. After the optical path of this S-polarized light is bent at right angles by the mirror 140, the PB812
0 and heads toward the Foucault prism 92 and the detection lens 90. Approximately half of this light flux is directed by a Foucault prism 92 forming a knife, and as shown in FIG. is imaged.

The remaining portion is imaged by the knife at the end of the prism 92 and the detection lens 90 on a focus servo photodetector 20F whose light receiving surface is divided into two in the vertical direction. Here, the condenser lens 80 is provided with a tracking actuator for positioning the condenser lens 80 in the radial direction of the optical disk 50 and a focusing actuator for focusing. (Hereinafter, the tracking actuator and focusing actuator are collectively referred to as the condenser lens actuator 81). To this condensing lens actuator 81, a focus error and a position error (tracking error) signal based on the output signal of the photodetector 20 is fed back to a servo control section (not shown). With this control, the optical disc 50 that is displaced by several tens of μm or more
On the other hand, as described above, a laser beam with a spot diameter narrowed to about 1 μm is irradiated onto tracks with a pitch of 1.6 μm. The reproduced signal is transmitted to the photodetector 20T described above.
, 20F signal addition circuit.

By the way, as shown in FIG. 13, the condenser lens 80 and the condenser lens actuator 81 are mounted on a linear actuator 150 that moves in the radial direction of the optical disk 50.
The other components of the optical head 200, namely the light source 10, collimating lens 30, PBS'120.1/4 wavelength plate 110, detection lens 90, prism 95, and photodetector 20 are housed in the housing. is common.

After the linear actuator 150 is moved to the vicinity of the target track, the condenser lens 80 is used to accurately position the linear actuator 150.

Further, it has been proposed in Japanese Patent Laid-Open No. 64-35734 to control the condenser lens and mirror integrally.

As shown in FIG. 14, this is a system in which only the condenser lens 8o and mirror 140 of the optical system of the optical head are moved, and is called a flying head. According to this, it is possible to reduce the weight of the moving unit and shorten the access time. However, in such a device, the relative distance between the fixed optical system 500 including the light source 10 and the moving optical system 540 including the condensing lens 8o changes, which deteriorates the linearity of focus and tracking errors. Therefore, as shown in the figure, a PB8120 is provided between the collimating lens 3o and the light source 10 to improve the linearity of the error signal due to changes in relative distance.

[Problem to be solved by the invention]

However, in the former of the above-mentioned conventional techniques (FIG. 13), it is necessary to provide the condenser lens actuator in a direction perpendicular to the disk, that is, in the thickness direction of the device. Also, to avoid contacting the disk within the working distance of the focusing lens, a certain amount of spacing must be provided between the focusing lens and the disk, increasing the overall thickness of the optical head. Therefore, such a condensing lens actuator system has the disadvantage that it hinders a thin design from the viewpoint of the device configuration.

Furthermore, in the latter case (FIG. 14), since the PBS is provided between the collimating lens and the light source, the focal length of the collimating lens becomes long. In order to ensure a certain degree of light utilization of the light source using a lens with a long focal length, a collimating lens with a large NA and a large lens diameter are required. If the lens diameter of the collimator lens is large, the mirror and condensing lens diameters will also become large, causing the problem that the entire optical system will become thicker.

An object of the present invention is to provide a thin optical head and a method for controlling the same.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a light source.

a collimating lens that converts the diverging light from the light source into substantially parallel light; a condensing lens that collects the parallel light and irradiates it onto an optical information recording medium; and detecting reflected light from the optical information recording medium. an optical head comprising a photodetector, a control means for relatively controlling the positions of the light source and the collimating lens in a direction to correct a positional deviation of a light spot formed on the optical information recording medium; It was established.

The present invention also provides a light source, a collimating lens that converts diverging light from the light source into substantially parallel light, a condensing lens that condenses the parallel light and irradiates it onto an optical information recording medium, and and a photodetector for detecting reflected light from a recording medium, the positions of the light source and the collimating lens are adjusted so that the position of the light spot formed on the optical recording medium is eliminated. A control means is provided for relatively controlling in the optical axis direction.

The present invention also provides a light source, a collimating lens that converts diverging light from the light source into substantially parallel light, a condensing lens that condenses the parallel light and irradiates it onto an optical information recording medium, and and a photodetector for detecting reflected light from a recording medium, the positions of the light source and the collimating lens are adjusted so that the position of the light spot formed on the optical recording medium is eliminated. A control means is provided to perform relative control in a direction perpendicular to the optical axis.

Further, the present invention is that any one of the above-mentioned optical heads is installed in an optical information recording/reproducing device.

Furthermore, the present invention makes the diverging light from the light source substantially parallel using a collimating lens, condenses the parallel light and irradiates it onto an optical information recording medium, and detects the reflected light from the optical information recording medium. The second method is to relatively control the positions of the light source and the collimating lens to correct a positional deviation of a light spot formed on the optical information recording medium.

[Effect]

According to the above configuration, an optical system is constructed in which the condensing lens is fixed and the light source and collimating lens are movable, so that the optical head main body can be made thin.

Further, since the optical beams having different wavelengths can be accurately tracked to a plurality of tracks, it is possible to access a plurality of tracks at the same time. As a result, data can be recorded and reproduced simultaneously on multiple tracks, improving transfer speed.

〔Example〕

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

(First Embodiment) FIG. 1 is a configuration diagram of an optical head according to a first embodiment of the present invention. Light emitted from a light source 10 made of a semiconductor laser is turned into a substantially parallel light beam 100 by a collimating lens 30, reflected by a PB 5120, passed through a 174-wave plate 110, and then reflected by a mirror 140 to change direction by 90 degrees. Further, the light beam 100 is focused onto a disk 50 as an optical information recording medium by a condensing lens 8o to form a light spot. The focused light beam 100 is directed to the disk 5
0 and further reflected by mirror 140, 1/4
The light passes through the wavelength plate 110 and changes into P-polarized light. P polarized light is PB
The light passes through S120 and is focused by the detection lens 90,
The photodetector 20 is reached.

This photodetector 20 detects reflected light from the disk 5o, and performs focus error detection using well-known astigmatism and tracking error detection using diffracted light. By feeding back this focus error signal to a servo circuit (not shown), the actuator 1 as a control means
Drive 30.

Since the light source 10 is mounted on the actuator 130, the light source 10 changes its position in the direction of the arrow or in the direction of the arrow B by feedback of the focus and tracking error signals. That is, the collimating lens 30 and the light source 10
The light beam 11 when the relative position in the traveling direction of the light beam 11 is changed.
0 becomes slightly diffused or convergent light and enters the condenser lens.

FIG. 2 shows only the lens system of the optical system of FIG. 1. As shown in the same figure (,), optical WX10
When the light beam 100 is at the focal length fc of the collimating lens 30, the light beam 100 becomes parallel light and enters the condensing lens 80, and is condensed at the focal length f0 of the condensing lens 80. Further, as shown in FIG. 2B, when the light source 10 is located at a distance of -Δfc from the focal length fc of the collimating lens 30, the light beam 100 becomes slightly diffused light and enters the condenser lens 80. +△f from the focal length f0 of the condenser lens 80. Focuses light on a shifted position. Furthermore, as shown in FIG. 2(c), when the light source 10 is located at +ΔfC from the focal length fc of the collimating lens 30, the light beam 1
00 becomes a slightly convergent light and enters the condensing lens 80,
The light is focused at a position shifted by −Δf0 from the focal length f0 of the focusing lens 80. In this way, when the light beam 100 is slightly diffused light, the light spot focused by the condenser lens 80 is far away from the lens, and when the light beam 100 is slightly convergent light, the light spot focused by the condenser lens 80 is focused. The illuminated light spot will be closer to the lens. Therefore, if the change in the relative distance between the condensing lens 80 and the surface of the disk 50 due to surface wobbling of the disk 50 is detected by the photodetector 20 as shown in FIG. 1, and the focus error signal at that time is fed back, the distance A light spot is formed according to the

Similarly, FIG. 3 shows only the lens system of the optical system shown in FIG. 1. As shown in Figure (a), the light source 1
When o is at the center of the optical axis of the collimator lens 30 and the condenser lens 80, the light beam 100 becomes parallel light, enters the center of the condenser lens 80, and is focused at the center of the optical axis of the condenser lens 80. Shine. In addition, as shown in FIG. 3B, when the light source 10 is at a position shifted by -ΔIC from the optical axis center of the collimating lens 30 and the condensing lens 80, the light beam 100
is incident on a position shifted from the center of the condenser lens 80, and is condensed at a position Δit from the center of the optical axis of the condenser lens 8o.

Further, as shown in FIG. 2(c), when the light source 10 is located at a position shifted by +ΔIC from the center of the optical axis of the collimating lens 30 and the condensing lens 80, the light beam 100 is
The light enters a position shifted from the center of the condenser lens 80 and is focused at a position -Δ1t from the center of the optical axis of the condenser lens 80. Changes in the relative position between the condenser lens 80 and the tracks provided on the disk 50 due to eccentricity of the disk 50 are detected using a photodetector 20 as shown in FIG. 1, and the tracking error signal at that time is detected. By feeding back, a light spot is formed according to the position. Therefore, by feeding back the tracking error signal to the radial actuator, tracking can be performed to control the light spot position in accordance with changes in the relative position between the track and the condensing lens 80.

(Second Embodiment) FIG. 4 is a configuration diagram showing an optical system according to a second embodiment of the present invention. A feature of this embodiment is that the position of the photodetector 20 is changed because the positional relationship between the light source 10 and the PBS 120 is different. The P-polarized light emitted from the light source 10 is turned into a substantially parallel light beam 100 by the collimating lens 30, and the PB
S120. The light passes through the 1/4 wavelength plate 110, becomes circularly polarized light, is reflected by the mirror 140, and is focused onto the disk 50 by the condenser lens 80 to form a light spot.

The focused light beam 100 is reflected from the disk 50, further reflected by the mirror 140, and transmitted through the 174-wave plate 110 again, thereby changing into S-polarized light. S polarized light is PB
The light is reflected from S120 and is focused by the detection lens 90 and reaches the photodetector 20. This photodetector 20 performs focus error detection and tracking error detection using diffracted light as in FIG. 1. This error detection amount is fed back to the light source 10 or the servo system actuator of the collimating lens 30, and focus and tracking control is performed.

(Third Embodiment) FIG. 5 is a configuration diagram showing an optical system according to a third embodiment of the present invention. The features of this embodiment include light sources 10 and 12 that emit light of different wavelengths, and wavelength separation filters 180 and 1.
81, 4-split photodetector 2 that detects reflected light with different wavelengths
0 and 22, and Foucault prisms 160 and 162 are provided, and the other configurations are the same as in FIG. The P-polarized light emitted from the light source 10 is made substantially parallel by the collimating lens 30, and is made into an almost perfect circle by the beam shaping prism 34 to have a wavelength of λ1.
becomes a light beam 100. This light beam 100 passes through a wavelength separation filter 181 and heads toward PBS 120 .

On the other hand, the P-polarized light emitted from the light source 12 is made substantially parallel by the collimating lens 32, and is made into a substantially perfect circle by the beam shaping prism 36 to become a light beam 102 with a wavelength λ2. This light beam 102 is reflected by the wavelength separation filter 181, and the PB
Head to S120. These light beams 100 and 102 are each independently reflected by a mirror 140 and passed through a quarter-wave plate 1.
10 to become circularly polarized light, which is focused onto the disk 50 by a condenser lens 80 to form a light spot. The focused light beams 100 and 102 are reflected from the disk 50 and are converted into S-polarized light by passing through the quarter-wave plate 100 again. Then, it is reflected by the mirror 140, and further PB8
120 and toward the wavelength separation filter 180. The wavelength separation filter 180 separates the light beam 100 with wavelength λ1.
is transmitted, and the light beam 102 with wavelength λ2 is reflected and transmitted through Foucault prisms 162 and 160, respectively, and then condensed by detection lens 92.90 to photodetector 22.2.
It reaches 0. In the photodetector 22.degree. 20, focus error detection and tracking error detection using diffracted light are performed in the same manner as in FIG. In this case, focus and tracking control can be performed independently by feeding back the focus error signal and the tracking error signal to the servo circuit of the actuator of each light source.

In the conventional focus and tracking control method that uses an actuator in the condenser lens, the light from two light sources is commonly controlled by the condenser lens, so one light source is subordinated to the other light source. Becomes control. In contrast, in this embodiment, the two light sources can accurately illuminate the target track. In this way, since a plurality of light sources can be accurately tracked, it becomes possible, for example, to simultaneously store and reproduce data in adjacent tracks, thereby increasing the data transfer rate.

(Fourth Embodiment) FIG. 6 is a configuration diagram showing an optical system according to a fourth embodiment of the present invention. A feature of this embodiment is that lenses 82.degree. 84 are provided. Linearly polarized light emitted from a light source 10 consisting of a semiconductor laser is converted into a substantially parallel light beam 1 by a collimating lens 30.
00, is reflected by the PBS 120, passes through the 1/4 wave long plate 110, changes to circularly polarized light, is reflected by the mirror 140, and changes direction by 90 degrees. The light beam 100 is then focused onto the disk 50 by lenses 82 and 84.

The lenses 82 and 84 are composed of so-called achromatic lenses whose focal lengths do not change even if a wavelength variation occurs when the light beam 100 is parallel and incident on the lens 82. This achromatic lens is necessary because the wavelength of a semiconductor laser changes depending on the temperature. With this configuration, the optical head can be made thinner than the conventional achromatic lens in which several lenses are combined in the optical axis direction. The focused light beam 100 reaches the photodetector 20 along a path similar to that shown in FIG. 1, with the amount of reflected light depending on the reflectance of the disk. This photodetector 20 detects reflected light from the disk 50, and focus error detection using a well-known knife is performed by a two-part detector at the center. Further, tracking error detection is performed by detecting diffracted light from the disk groove using a Foucault prism using a two-split detector. The actuator 130 is driven by feeding back this focus error signal to a servo circuit (not shown). Since the light source 10 is mounted on the actuator 130, the position of the light source 10 can be changed by feedback of focus and tracking error signals.

(Fifth Embodiment) FIG. 7 is a configuration diagram showing an optical system according to a fifth embodiment of the present invention. A feature of this embodiment is that a half mirror 70 is provided in front of the collimating lens 30. Half of the light emitted from the light source 10 is transmitted through the half mirror 70, and is turned into a substantially parallel light beam 100 by the collimating lens 30.
It is reflected by mirror 140 and changes direction by 90 degrees. Furthermore, the light beam 100 is focused onto the disk by a focusing lens 80. The focused light beam 100 is reflected from the disk 50, further reflected by the mirror 140, and reflected by the half mirror 70 while being focused by the collimating lens 30, and reaches the photodetector 20. This photodetector 20 performs focus error detection using well-known astigmatism and tracking error detection using diffracted light, and the error detection signal is fed back to a servo circuit (not shown) as described above.

Controls the actuator 130 of light@10.

In addition, in the first to fifth embodiments, the same effect can be obtained even if the light source 10 is fixed and the collimating lens 30 is moved.

Next, a recording medium suitable for realizing the present invention will be described. As the recording medium, read-only media such as compact discs, write-once optical recording media that utilize hexagonal or phase change, and reversible optical recording media that utilize magneto-optical effects or phase change can be used. can. That is, any medium that can be reproduced or recorded and erased by laser light can be used as the medium of the present invention. Here, an example of recording, erasing, and reproducing using a reversible phase change optical disk will be described.

FIG. 8 shows the principle of recording, erasing, and reproducing on a phase change optical disk. As shown in the figure, recording is achieved by irradiating the recording medium with pulsed light of relatively high power, melting the recording film 142, and then rapidly cooling it to make the recording film 142 into an amorphous state. On the other hand, erasing is achieved by irradiating the recording film 142 with continuous light of relatively low power to crystallize the amorphous recording film 142.

Furthermore, reproduction is achieved by irradiating the recording medium with continuous light of even lower power and reading the difference in reflectance between the amorphous and crystalline states as information.

As the recording film 142, Proc, Soc,
P photo -○pt, In5t, Eng, (SP
IE), Vol, 1078゜pp, 1l-p
p, 26. In-5 described in (1989)
b-Te based recording film or Proe.

S oc, P photo-〇pt, In5t, E
ng, (SPIE).

Vol, 1078. pp, 27-pp, 34.
(1989), any phase change medium can be used as long as it has an overridable recording film.

Moreover, FIG. 9 shows a film structure suitable for use as a medium for an optical disk. The optical disc 50 includes a light-transmitting substrate 52, a first optical interference film 53 having high refractive index characteristics, a recording film 54, a second optical interference film 55 having high refractive index characteristics, a reflective film 56, and a protective film 57. It is configured. In such an optical disc 50, the light beam is incident from the substrate 52 side. Here, the interference films 53 and 55 function as films that improve contrast by interference of light and control heat conduction characteristics.

FIG. 10 shows a method of modulating laser power during override. That is, during override, the laser power is modulated between the erasing power level and the recording power level. At this time, the eraser power for erasing is based on the power that can crystallize the recording film if this power is continued to be irradiated.
The recording power is selected from the powers that can make the recording film amorphous.

FIG. 11 provides a detailed explanation of the optical disk drive circuit system. The optical disk drive circuit system 260 is
data management section 261, track address control section 262,
Track control section 263, focus control section 264. Photodetector amplifier 265, data demodulator 266, data modulator 2
67, a laser drive 268, and a motor control section 269. With such a configuration, when overriding,
The track address controller 262 determines the track address to be recorded, and the data modulator 267 controls the processor 400.
The data given by the laser is converted into an "O", 11" pattern to be recorded on an optical disk using a modulation method. The modulation method includes 2-7 modulation and 4-15 modulation, which are used depending on the system. The drive 268 modulates the laser power between erasing power and recording power as shown in FIG. 10 according to the pattern of "0" and "1" determined by the data modulating section 267.
When reproducing data, the track address specified by the processor 400 is selected, and the laser power is approximately 1 to 2 mW.
is set to a constant value, the reflectance of the optical disk 50 is read out by the photodetection amplifier 265, and the data is demodulated by the data demodulation section 266. Further, the result from the photodetection amplifier 265 is also used as a signal for the track control section 263 and the focus control section 264, but the functions of this part can be realized by functions conventionally used in compact discs and optical disc devices. The motor control unit 269 also controls the optical disc 5o.
The rotation speed of the motor 240 for rotating the motor 240 is controlled.

For this rotation speed control, CA V (Con5tant
Angular Velocity) control type and CLV
(Constant Linear Velocity
) There is a control type.

〔Effect of the invention〕

As explained above, according to the present invention, focus tracking control can be performed with a configuration in which the condenser lens is fixed, so the work distance between the condenser lens actuator and the lens can be removed, and the optical head can be made thin. It becomes possible to

Furthermore, since the light from a plurality of light sources can be controlled and irradiated onto different tracks or the same track, simultaneous access and verification immediately after recording are possible, and high-speed data transfer can be realized.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an optical head according to a first embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams of the operation of the present invention, and FIGS. A schematic configuration diagram of an optical head according to the fifth embodiment, FIG. 8 is an explanatory diagram of recording, reproducing, and erasing of an optical disk, FIG. 9 is a cross-sectional view of the optical disk, and FIG.
The figure is an explanatory diagram of override power modulation, Figure 11 is a schematic block diagram of the optical disk drive circuit, and Figures 12 to 1.
FIG. 4 is a schematic diagram of a conventional optical head. 10.12... Light source, 20.22... Photodetector, 3
0.32...Collimating lens, 34.36...Beam shaping prism, 50...Optical disk, 70...
Half mirror 18o...condensing lens, 82.84...
・Lens, 90.92...Detection lens, 100,10
2... Light beam, 110... 174 Wave plate, 120
... PBS, 130 ... Actuator, 140,
142...Mirror, 160,162...Foucault prism, 180.181...Wavelength separation filter.

Claims (1)

[Claims] 1. A light source, a collimating lens that converts diverging light from the light source into substantially parallel light, a condensing lens that focuses the parallel light and irradiates it onto an optical information recording medium, and the optical a photodetector for detecting reflected light from an optical information recording medium, the light source and a collimating lens are arranged in a direction that corrects a positional deviation of a light spot formed on the optical information recording medium. An optical head characterized in that it is provided with a control means for relatively controlling the position of the optical head. 2. A light source, a collimating lens that converts the diverging light from the light source into substantially parallel light, a condensing lens that focuses the parallel light and irradiates it onto an optical information recording medium, and a collimating lens that converts the diverging light from the light source into substantially parallel light; and a photodetector for detecting reflected light, the light source and the collimating lens are moved in the direction of the optical axis of the collimating lens so as to eliminate positional deviation of the light spot formed on the optical recording medium. An optical head characterized in that it is provided with a control means for relative control. 3. A light source, a collimating lens that converts the diverging light from the light source into substantially parallel light, a condensing lens that focuses the parallel light and irradiates it onto an optical information recording medium, and a collimating lens that converts the diverging light from the light source into substantially parallel light; and a photodetector for detecting reflected light, the light source and the collimating lens are positioned at right angles to the optical axis of the collimating lens so as to eliminate positional deviation of the optical spot formed on the optical recording medium. An optical head characterized in that it is provided with a control means for relatively controlling the direction. 4. The optical head according to claim 1, 2 or 3, characterized in that a plurality of sets of the light source and collimating lens are provided. 5. The optical head according to claim 4, wherein each of the plurality of light sources emits light having a different wavelength. 6. The optical head according to claim 4 or 5, further comprising means for respectively irradiating different tracks with light from the plurality of light sources. 7. The optical head according to claim 6, further comprising means for independently controlling intensity modulation of the plurality of light sources. 8. The optical head according to claim 6, further comprising means for independently detecting the reflected light from the optical information recording medium by the plurality of light sources. 9. The optical head according to claim 4 or 5, further comprising means for irradiating the same track with light from the plurality of light sources. 10. The optical head according to claim 9, wherein one of the plurality of light sources is for recording/erasing, and the other one is for recording/erasing.
Another aspect of the present invention is an optical head characterized in that, when used for reproduction, means is provided for independently controlling intensity modulation of both the light sources. 11. The optical head according to claim 1, 2 or 3, characterized in that a half mirror is provided between the light source and the collimating lens. 12. The optical head according to claim 1, 2 or 3, wherein the condenser lens is an achromatic lens. 13. An optical information recording/reproducing device equipped with the optical head according to any one of claims 1 to 12. 14. When the diverging light from the light source is made substantially parallel by a collimating lens, the collimated light is focused and irradiated onto an optical information recording medium, and the reflected light from the optical information recording medium is detected,
A method for controlling an optical head, comprising controlling relative positions of the light source and a collimating lens to correct a positional deviation of a light spot formed on the optical information recording medium.