JP2003317294A - Optical head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a light quantity collected onto an optical disk is varied due to the variation of the light quantity transmitted through an objective lens when an actuator is driven accompanying servo operation and the objective lens is moved. <P>SOLUTION: The optical head is provided with: a light source; a first light receiving means for detecting a part of light beams from the light source; a light collecting means which is constituted to collect the light beams from the light source on an information track on an information recording medium and which has a light transmission effective diameter smaller than the optical flux diameter of the light beams from the light source; a moving means for moving the light collecting means in a direction orthogonal to a light axis; and a second light receiving means which is constituted so as to move according to moving of the light collecting means and which detects the light beams of a part which is not incident on the light collecting means in the light beams emitted from the light source toward the light collecting means. The light emitting quantity of the light source is controlled by a signal obtained by calculating signals detected by the first light receiving means and the second light receiving means. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head for an optical disk device for recording and reproducing information, which can be controlled so that a predetermined amount of light is irradiated onto a focused spot on the optical disk.

[0002]

2. Description of the Related Art As a recordable optical disk, a phase change optical disk, a magneto-optical disk, a dye-based optical disk capable of recording only once, and the like have been conventionally known. These optical disks focus laser light on the recording surface of the optical disk,
Information is recorded by irradiating and raising the temperature locally to cause phase change and decomposition of the dye, or the temperature of the recording surface is raised by laser light and an external magnetic field is applied to control the magnetization direction. By doing so, information is recorded, and the recording surface is irradiated with a laser light amount weaker than that at the time of recording, and the light amount of the reflected light or polarization is detected to reproduce the information.

In the optical disc device for recording and reproducing information as described above, if the laser light amount at the time of recording is too small, the information cannot be surely recorded, and if the laser light amount at the time of reproducing is too large, the information is recorded. Since there is a risk of serious damage such as destruction of the existing information, it is necessary to sufficiently control the laser light amount in the recording / reproducing operation. Especially in the case of a phase change optical disk, there are two levels of laser light at the time of recording (amorphization power,
In addition, it is necessary to control the laser light amount in three steps, including the crystallization power) and the reproduction.

However, a semiconductor laser used as a light source of an optical disk device generally has a temperature characteristic, and its threshold current fluctuates depending on the ambient temperature. Therefore, the drive current during recording and reproduction is controlled to a predetermined value. However, the amount of light emission varies depending on the temperature. Therefore, conventionally, in an optical disk device for recording / reproducing information, in order to suppress the fluctuation of the emission amount of the semiconductor laser, the emission amount is monitored and the feedback control of the laser drive circuit is performed. Automatic light output control for obtaining such a constant intensity of output light is performed by an APC (Automati).
c Power Control).

FIG. 8 is a block diagram of a conventional optical head used in such an optical disk device. Reference numeral 61 is a semiconductor laser, 62 is a beam splitter that splits light by transmission and reflection, 63 is an objective lens, 64 is an optical disk having an information track on the recording surface, 65 is a light receiving element, 66 is a detection lens, prism, diffractive element, or the like. Although not shown in detail, the signal detecting means 67 for receiving the return light from the optical disc 64, which has an optical element and a light receiving element and is reflected by the beam splitter 62, converts it into a signal according to the received light amount, and detects it. , An actuator that drives the objective lens 63 in a horizontal direction and a vertical direction with respect to the optical disc 64.

In the optical head having such a structure, the light emitted from the semiconductor laser 61 is partially transmitted and partially reflected by the beam splitter 62. The light reflected by the beam splitter 62 is received by the light receiving element 65, and the light emission amount of the semiconductor laser 61 is controlled by the APC circuit so that the detected light amount becomes a predetermined value.

The light transmitted through the beam splitter 62 is condensed on the optical disc 64 by the objective lens 63, and the light reflected by the optical disc 64 passes through the objective lens 63 again and is reflected by the beam splitter 62, and the signal detecting means 6
6, the servo signal and the information recording signal are detected.

The servo signal detected by the signal detecting means 66 is an error signal between the information track and the focused spot on the optical disc 64 which fluctuates due to surface wobbling and eccentricity, and the actuator 67 is driven according to this signal. By controlling the position of the objective lens 63, recording and reproduction are performed by causing the focused spot to follow the information track.

In the above optical head, the amount of light detected by the light receiving element 65 is substantially proportional to the amount of light transmitted through the beam splitter 62, and the amount of light condensed on the optical disc 64 is the amount of light transmitted through the beam splitter 62. Since they are substantially proportional, the amount of laser light focused on the optical disc 64 is substantially proportional to the amount of light detected by the light receiving element 65. Therefore, if the signal received by the light receiving element 65 is controlled so as to have a predetermined value, the optical disk 6 is controlled even when the ambient temperature changes.
It is possible to control the amount of laser light focused on the laser beam 4 on a predetermined value.

[0010]

However, in such an optical disk device, the light emission amount of the semiconductor laser is only controlled to be constant, and when the objective lens is moved by driving the actuator in accordance with the servo operation, the objective lens is moved. There is a problem that the amount of light that passes through the lens changes, and the amount of light that is condensed on the optical disk also changes. Such fluctuations in the amount of light cause variations in the formation of recording marks during recording, causing incomplete recording marks or destruction of recording marks in the vicinity of recording to cause a recording error, or S of a reproduction signal during reproduction. Since the / N ratio is deteriorated to cause a reproduction error, the performance is deteriorated.

[0011]

The optical head of the present invention comprises:
A light source, a first light receiving means for detecting a part of the light from the light source, and a light from the light source, which is configured to focus the light from the light source on an information track on an information recording medium. A light collecting means having a light transmission effective diameter smaller than the light flux diameter, a moving means for moving the light collecting means in a direction orthogonal to the optical axis, and a moving means for moving the light collecting means. And, of the light traveling from the light source to the condensing means,
The light source is provided with a second light receiving unit that detects light in a portion that does not enter the light collecting unit, and the signal obtained by calculating the signals detected by the first light receiving unit and the second light receiving unit. It is characterized in that it is configured to control the amount of light.

Further, a third light receiving element for receiving reflected light from the information recording medium may be provided, and the light source and the third light receiving element may be arranged in the same housing.

The first light receiving means may include a light branching element provided between the light source and the light collecting means and a light receiving element for receiving the light branched by the light branching element.

The light source comprises a semiconductor laser,
The first light receiving means may be a light receiving element that receives light emitted from a back surface of a surface of the semiconductor laser from which light directed to the light focusing means is emitted.

Further, the second light receiving means may be a light receiving element arranged on the moving means.

The second light receiving means may have a reflecting means arranged on the moving means and a light receiving element for receiving the light reflected by the reflecting means.

Further, the light receiving element has a plurality of light receiving regions symmetrically arranged with respect to a straight line parallel to the information track, and by calculating signals detected in the plurality of light receiving regions. It may be configured to detect the amount of movement of the condensing unit.

Further, the reflection means has a plurality of reflection areas symmetrically arranged with respect to a straight line parallel to the information track, and calculates the signals detected by the plurality of light receiving elements. It may be configured to detect the amount of movement of the condensing unit.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a configuration diagram of an optical head according to Embodiment 1 of the present invention. Reference numeral 1 is a semiconductor laser corresponding to a light source, 2 is an opening for blocking unnecessary light emitted from the semiconductor laser, 3 is a beam splitter for splitting light by transmission and reflection, 4 is a light receiving element corresponding to a first light receiving means, 5 Is an objective lens corresponding to the condensing means, 6 is an objective lens holder, 7 is a light receiving element corresponding to the second light receiving means provided integrally with the objective lens holder 6, 8 is an optical disk corresponding to an information recording medium, 9 Is a detection lens, prism,
Alternatively, the signal detecting means 10 which has an optical element such as a diffraction element and a light receiving element, receives the return light from the optical disc 64 reflected by the beam splitter 62, converts it into a signal according to the received light amount, and detects the signal. Beam splitter 3
, 11 is a light beam reflected by the beam splitter 3, and 12 is an actuator corresponding to a moving means for driving the objective lens 5 in a horizontal direction and a vertical direction with respect to the optical disk 8, although not shown in detail.

FIG. 2 shows the objective lens 5 in the first embodiment.
FIG. 2 is a view of the arrangement of the light receiving element 7 and the light receiving element 7 as seen from the light source side.
Reference numeral 5 denotes an area through which the light from the light source passes through the objective lens, 17 denotes a light receiving area of the light receiving element 7, and the light receiving area 17 has, for example, a donut shape, and receives light around the light flux passing through the objective lens 5. To be configured.

In the optical head having such a structure, the light emitted from the semiconductor laser 1 passes through the opening 2 and
The light enters the beam splitter 3 and is partially transmitted and partially reflected. The light beam 11 reflected by the beam splitter 3 is received by the light receiving element 4, and a part of the light beam 10 that has passed through the beam splitter 3 (a light beam near the center) is condensed on the optical disk 8 by the objective lens 5 and The rest (light flux near the periphery) is received by the light receiving element 7.

Here, the semiconductor laser 1 is controlled by the APC circuit so that the signal obtained by calculating the light amount detected by the light receiving element 4 and the light amount detected by the light receiving element 7 becomes a predetermined value.
Is controlled.

The light reflected by the optical disk 8 again passes through the objective lens 5, is reflected by the beam splitter 3, and the signal detecting means 9 detects the servo signal and the information recording signal. The servo signal detected by the signal detecting means 9 is an error signal between the information track and the focused spot on the optical disc 8 which varies due to surface wobbling and eccentricity, and the actuator 12 is driven according to this signal to drive the objective lens. 5
By controlling the position of, the focused spot is made to follow the information track for recording and reproduction.

In the above optical head, the aperture 2
The amount of light passing through P0, the amount of light received by the light receiving element 4 is P1,
The amount of light received by the light receiving element 7 is P2, the amount of light condensed on the optical disk 8 is P3, the transmittance of the beam splitter 3 is Kt,
When the reflectance is Kr, Kt × P0 = P2 + P3 in the amount of light transmitted through the beam splitter 3 and Kr × P0 = P1 in the amount of reflected light, so that the following equation holds.

P3 = (Kt / Kr) × P1-P2 (Equation 1) The amount of light P3 condensed on the optical disk 8 by (Equation 1) is the amount of light received by the light receiving elements 4 and 7, and the existing value. Can be obtained from

In the example of FIG. 1, P obtained from the light receiving element 4 is used.
The difference between the output signal corresponding to 1 and the output signal corresponding to P2 obtained from the light receiving element 12 is different from the one obtained by amplifying the output signal corresponding to the amplification factor G of P1 by the amplifier corresponding to Kt / Kr times. By outputting by the dynamic amplifier, the light amount P3 condensed on the optical disk 8 can be indirectly obtained. The obtained signal is sent to the APC circuit, and the APC circuit controls the light emission amount of the semiconductor laser so that the obtained signal becomes constant.

Therefore, in the optical head of the present invention, the amount of light that actually passes through the objective lens 5 and is condensed on the optical disk 8 can be indirectly monitored by the calculation of (Equation 1). By controlling the light emission amount of the semiconductor laser 1 so that the signal obtained by the calculation becomes constant, the light amount condensed on the optical disk 8 can be controlled to a predetermined value.

As described above, in the optical head of the present invention,
Conventionally, the amount of light emitted from a semiconductor laser, which is a light source, is monitored
In contrast to PC, the amount of light actually condensed on the optical disk is indirectly monitored to perform APC. Therefore, even when the objective lens moves due to servo drive, the amount of light on the optical disk is set to a predetermined value. Can be controlled.

The arithmetic expression of (Equation 1) is based on the assumption that the light receiving element 4 receives all the light fluxes of the light flux 11, and the light receiving element 7 receives all the light fluxes of the light fluxes 10 which do not pass through the objective lens 5. However, these received light amounts P1 and P2 are substantially
The light flux to be received may be a part of the region as long as the light amount substantially proportional to can be detected. However, in that case, the received signal is calculated by applying a gain that is a proportional coefficient multiple.

(Second Embodiment) FIG. 3 is a block diagram of an optical head according to a second embodiment of the present invention. Reference numeral 21 is a semiconductor laser corresponding to a light source, 22 is an opening for blocking unnecessary light emitted from the semiconductor laser, 23 is a beam splitter, and 24 is a beam splitter.
Is a light receiving element corresponding to the first light receiving means, 25 is an objective lens corresponding to the light collecting means, 26 is an objective lens holder, and 27
Is a mirror corresponding to the reflecting means provided integrally with the objective lens holder 26, 28 is an optical disk corresponding to the information recording medium, 29 is a light receiving element having a plurality of light receiving regions and corresponding to the second light receiving means, and 30 is Signal detecting means including an optical element such as a detection lens, a prism, or a diffraction element and a light receiving element 29, 31 is a light beam transmitted by the beam splitter 23, 32 is a light beam reflected by the beam splitter 23, 33
The broken line indicates a light beam reflected by the mirror 27, and 34, which is not shown in detail, is an actuator that is a moving unit that drives the objective lens 25 in the horizontal and vertical directions with respect to the optical disc 28.

The mirror 27 in this embodiment is shown in FIG.
Of the light receiving element 7 in the first embodiment shown in FIG.
It is arranged at the same position as 7, and is configured to reflect the light around the light flux passing through the objective lens 25 and guide it to the light receiving element 29.

In the optical head constructed as described above, the light emitted from the semiconductor laser 21 passes through the opening 22, enters the beam splitter 23, and is partially transmitted and partially reflected. The light beam 31 reflected by the beam splitter 23 is received by the light receiving element 24, and the beam splitter 23
A part of the light beam 30 that has passed through is condensed on the optical disk 28 by the objective lens 25, and the rest of the light beam 30 is reflected by the mirror 27.
After being reflected by the beam splitter 23, the beam is reflected by the beam splitter 23 as a light flux 33 shown by a broken line and is received by the light receiving element 29.

Here, the light emission amount of the semiconductor laser 1 is controlled by the APC circuit so that the signal obtained by calculating the light amount detected by the light receiving element 24 and the light amount detected by the light receiving element 29 becomes a predetermined value. To be done.

The light reflected by the optical disk 28 again passes through the objective lens 25 and is reflected by the beam splitter 23.
The signal detecting means 30 detects the servo signal and the information recording signal. For the detection of the servo signal and the information recording signal, another light receiving area provided on the substrate of the light receiving element 29 that receives the reflected light of the mirror 27 is used.

In the above optical head, the opening 2
2 is P0, the amount of light received by the light receiving element 24 is P
1, the amount of light received by the light receiving element 29 is P4, the amount of light condensed on the optical disk 28 is P3, the transmittance of the beam splitter 23 is Kt, and the reflectance is Kr.
Since Kt × P0 = P3 + P4 in the amount of light transmitted through 3 and Kr × P0 = P1 in the amount of reflected light, the following equation holds.

P3 = (Kt / Kr) × P1-P4 (Equation 2) (Equation 2) Amount of light P3 condensed on the optical disc 28
Can be obtained from the amount of light received by the light receiving element 24 and the light receiving element 29 and the existing value.

In the example of FIG. 3, the output signal corresponding to P1 obtained from the light receiving element 24 is amplified by an amplifier corresponding to multiplying the output signal corresponding to the amplification factor G of P1 by Kt / Kr, and the light receiving element. By outputting the difference from the output signal corresponding to P2 obtained from 29 with the differential amplifier, the light amount P4 condensed on the optical disk 28 can be indirectly obtained. The obtained signal is sent to the APC circuit, and the APC circuit
The emission amount of the semiconductor laser is controlled so that the obtained signal becomes constant.

Therefore, also in this embodiment, it is possible to indirectly monitor the amount of light that actually passes through the objective lens 25 and is condensed on the optical disc 28 by the calculation of (Equation 2). By controlling the light emission amount of the semiconductor laser 21 so that the signal obtained by the calculation becomes constant, the light amount condensed on the optical disk 28 can be controlled to a predetermined value.

Furthermore, in the present embodiment, the first embodiment is used.
In addition to the above effect, by integrating the light receiving element for detecting the servo signal and the information recording signal and the light receiving element for detecting the light around the objective lens 25, the number of light receiving elements can be reduced, so that the cost can be reduced. Can be achieved. Further, since it is not necessary to provide the light receiving element in the actuator, the structure of the wiring and the like becomes simple.

In this embodiment, the mirror 27 is provided integrally with the objective lens holder 26, but it may be provided at the edge of the objective lens 25 by means of vapor deposition or the like.

(Third Embodiment) FIG. 4 is a configuration diagram of an optical head according to a third embodiment of the present invention. 41 is a semiconductor laser corresponding to the light source, 42 is a light receiving element corresponding to the first light receiving means for receiving the light emitted from the back surface of the semiconductor laser 41, 43 is a beam splitter, 44 is an objective lens corresponding to the light converging means, Reference numeral 45 is an objective lens holder, 46 is a light receiving element corresponding to the second light receiving means provided integrally with the objective lens holder 45, 47 is an optical disk corresponding to an information recording medium, 48 is a detection lens, a prism, a diffraction element, or the like. Signal detecting means comprising an optical element and a light receiving element of
Is a light beam emitted from the semiconductor laser 41 toward the objective lens 44, 50 is a light beam emitted from the rear surface of the surface of the semiconductor laser 41 from which the light beam 47 is emitted, 51 is a housing having the semiconductor laser 41 and the light receiving element 42 therein, Although not shown in detail, 54 is an actuator corresponding to a moving unit that drives the objective lens 44 in the horizontal and vertical directions with respect to the optical disk 47.

Light receiving element 46 in the present embodiment has the same structure as light receiving element 7 in the first embodiment, and has the same light receiving area as light receiving area 17 shown in FIG. In the optical head configured as described above, the semiconductor laser 41
The light flux 49 emitted from the
Part of the light is focused on the optical disk 47 by the objective lens 44, and the rest of the light flux 49 is received by the light receiving element 46. The light reflected by the optical disk 47 passes through the objective lens 44 again, is reflected by the beam splitter 43, and is detected by the signal detecting means 4.
8, the servo signal and the information recording signal are detected.

On the other hand, the light flux 50 emitted from the back surface of the semiconductor laser 41 is received by the light receiving element 42, and a signal obtained by calculating the amount of light detected by the light receiving element 42 and the amount of light detected by the light receiving element 46 is predetermined. The emission amount of the semiconductor laser 41 is controlled by the APC circuit so that the value becomes a value.

Also in the present embodiment configured as described above, the luminous flux 50 emitted from the back surface of the semiconductor laser 41 is also included.
After the amount of light is detected by the light receiving element 42, an appropriate gain is applied using an amplifier to estimate the amount of light of the light flux 49, and a differential calculation with the amount of light received by the light receiving element 46 is performed,
The amount of light collected on the optical disc 47 can be indirectly monitored, and the amount of light emitted from the semiconductor laser 41 is controlled by the APC circuit so that the signal obtained by this calculation becomes constant. It is possible to control the amount of light condensed above to a predetermined value.

Further, in the present embodiment, the first embodiment will be described.
In addition to the above effect, by using a so-called back monitor that receives light emitted from the back surface of the semiconductor laser, the semiconductor laser 41 and the light receiving element 42 can be housed in one housing 51, so that the configuration is simplified. it can.

(Fourth Embodiment) FIG. 5 is a block diagram of an optical head according to a fourth embodiment of the present invention. Reference numeral 71 is a semiconductor laser corresponding to a light source, 72 is a light receiving element corresponding to a first light receiving means for receiving light emitted from the back surface of the semiconductor laser 71, 73 is a trapezoidal prism having a reflecting surface 73a and a beam splitter surface 73b, 74 Is an objective lens corresponding to the condensing means, 75 is an objective lens holder, 76 is a light receiving element corresponding to the second light receiving means provided integrally with the objective lens holder 75, 77 is an optical disk corresponding to an information recording carrier, 78 Is a signal branching means composed of a detection lens, a prism, or an optical element such as a diffractive element, 79 is a light receiving element for receiving the light beam branched by the signal branching means, and 80 is a semiconductor laser 71, a light receiving element 72 and a light receiving element 79. The housing has, 81 is a light beam emitted from the trapezoidal prism 73 toward the objective lens 74, and 82 is light in the semiconductor laser 71. Light beam 81 is emitted from the back surface to be emitted, 83
Although not shown in detail, is an actuator corresponding to a moving unit that drives the objective lens 74 in a horizontal direction and a vertical direction with respect to the optical disc 77.

In the optical head having such a structure, the light beam 81 emitted from the semiconductor laser 71 is incident on the trapezoidal prism 73, is reflected by the reflecting surface 73a and the beam splitter surface 73b, and is partially reflected by the objective lens 74 on the optical disk. The light beam 81 is condensed on the light beam 77 and the rest of the light beam 81 is received by the light receiving element 76. The light reflected by the optical disk 77 again passes through the objective lens 74, the beam splitter surface 73b of the trapezoidal prism 73, and the signal branching unit 78
The servo signal and the information recording signal are guided to the light receiving element 79 and detected.

On the other hand, the light beam 82 emitted from the back surface of the semiconductor laser 71 is received by the light receiving element 72, detected by the light receiving element 72, and then the gain of the light beam 81 is estimated by applying an appropriate gain using an amplifier. Then, the light emission amount of the semiconductor laser 71 is controlled by controlling the signal obtained by differentially calculating the light amount detected by the light receiving element 76 using the APC circuit so that the signal has a predetermined value.

Also in the above-described structure, as in the third embodiment shown in FIG. 4, the light amount of the light beam 82 emitted from the back surface of the semiconductor laser 71 is multiplied by an appropriate gain to obtain the light beam 81.
It is possible to indirectly monitor the amount of light condensed on the optical disk 77 by estimating the amount of light of the light and performing a differential calculation with the amount of light received by the light receiving element 76, which is obtained by this calculation. The optical disc 77 is controlled by controlling the light emission amount of the semiconductor laser 71 so that the signal becomes constant.
It is possible to control the amount of light condensed above to a predetermined value.

Further, in this embodiment, the semiconductor laser 71, the light receiving element 72 and the light receiving element 79 can be housed in the same housing 80, so that the structure can be further simplified.

In this embodiment shown in FIG. 5, the light receiving element 76 is integrally provided on the objective lens holder 75, but as in the second embodiment, the objective lens holder 75 is provided with a mirror. Alternatively, the reflected light may be received by a light receiving element inside the housing 80.

If a diffractive element 84 such as a hologram is used as the signal branching means 78, the trapezoidal prism 73 can be omitted as shown in FIG. In FIG. 8, reference numeral 84 is a diffractive element, and the other constituent elements are denoted by the same reference numerals as those in FIG. 5, and description thereof is omitted.

(Fifth Embodiment) In the fifth embodiment,
Only the light receiving element 7 is different from the first embodiment shown in FIG. 1, and the other components are the same as those in FIG.

FIG. 7 shows the objective lens 5 according to the fourth embodiment.
FIG. 2 is a view of the arrangement of the light receiving element 7 and the light receiving element 7 as seen from the light source side.
Reference numeral 5 denotes a region where the light from the light source passes through the objective lens, and 17
Reference numerals a and 17b are light receiving regions of the light receiving element 7, and the light receiving region 1
7a and 17b are arranged symmetrically with respect to a straight line parallel to the information track, and are configured to receive light around the light flux passing through the objective lens 5. The operation of the optical head thus configured will be described with reference to FIG.

The light emitted from the semiconductor laser 1 passes through the opening 2, enters the beam splitter 3, and is partially transmitted and partially reflected. The light beam 11 reflected by the beam splitter 3 is received by the light receiving element 4, a part of the light beam 10 transmitted through the beam splitter 3 is condensed on the optical disk 8 by the objective lens 5, and the rest of the light beam 10 is received by the light receiving element 7. The light is received by the light receiving regions 17a and 17b.

Here, the amount of light detected by the light receiving element 4,
The light emission amount of the semiconductor laser 1 is controlled by the APC circuit so that the signal obtained by calculating the sum signal of the light amounts detected by the light receiving regions 17a and 17b of the light receiving element 7 has a predetermined value. In addition, the light receiving regions 17a and 17a of the light receiving element 7
The position of the objective lens 6 is detected by the difference signal of the signals detected by 7b, and the tracking signal is corrected. The light reflected by the optical disk 8 again passes through the objective lens 5, is reflected by the beam splitter 3, and the signal detecting means 9 detects the servo signal and the information recording signal.

Also in the present embodiment configured as described above, the calculation of (Equation 1) is performed using the sum signal of the light receiving amounts in the light receiving regions 17a and 17b, and the same as in the first embodiment. The effect is obtained.

Further, in the present embodiment, the light receiving area 17
By calculating the difference in the amount of light received at a and 17b,
It is possible to detect the moving distance of the objective lens in the radial direction of the optical disc. This is because the light intensity distribution of the light flux emitted from the semiconductor laser 1 has a high light intensity at the center of the light flux and a lower light intensity as it moves away from the center. This is because there is a difference in the amount of light detected in the light receiving regions 17a and 17b due to the deviation from the center of the lens, and this difference in light amount obviously changes according to the amount of movement of the objective lens.

The push-pull method known as the one-beam tracking method has a simple optical head configuration,
Although this method is suitable for downsizing and cost reduction, there is a problem that the tracking error signal is offset by the movement of the objective lens in the radial direction of the optical disc. In this embodiment,
Since the position of the objective lens can be detected as described above, it is also possible to correct the offset of the push-pull method.

Therefore, in the present embodiment, the first embodiment
In addition to the effect of 1., the push-pull method or the one-beam tracking method to which the push-pull method is applied can be used to correct the offset, which is the problem, and obtain good servo characteristics.

In the present embodiment, the objective lens holder is integrally provided with the two-divided light receiving element. However, as in the second embodiment, a mirror is provided in the objective lens holder instead of the light receiving element. Similar effects can be obtained even if a plurality of light receiving elements that receive the reflected light are provided.

The method for detecting the light emission amount of the semiconductor laser 1 may be a back monitor as in the third embodiment.

[0064]

According to the optical head of the present invention, the light source, the first light receiving means for detecting a part of the light from the light source, and the light from the light source are focused on the information track on the information recording medium. And a moving means for moving the light collecting means in a direction orthogonal to the optical axis, the light collecting means having a smaller effective light transmission diameter than the light beam diameter of the light from the light source, and the light collecting means. A second light receiving unit configured to move in accordance with the movement, and detecting a portion of the light traveling from the light source to the light collecting unit that does not enter the light collecting unit, The light emission amount of the light source is controlled by the signal obtained by calculating the signals detected by the second light receiving unit and the second light receiving unit, so that the fluctuation of the light amount on the optical disk due to the movement of the objective lens during the servo operation is controlled. Can be suppressed. As a result, it is possible to provide an optical head having good recording and reproducing characteristics by suppressing uneven writing of information during recording and deterioration of the S / N ratio during reproduction.

Further, if the third light receiving element for receiving the reflected light from the information recording medium is provided, and the light source and the third light receiving element are arranged in the same housing, the structure is simplified. Therefore, the size can be reduced.

Further, if the first light receiving means has a light branching element provided between the light source and the light collecting means and a light receiving element for receiving the light branched by the light branching element, It is possible to detect the light emitted from the light source with high precision, and it is possible to further suppress the fluctuation of the light amount on the optical disc.

The light source comprises a semiconductor laser,
Assuming that the first light receiving means is a light receiving element that receives light emitted from the back surface of the surface of the semiconductor laser that emits light toward the light converging means, the semiconductor laser and the light receiving element are provided in one housing. Therefore, the structure can be simplified and the size can be reduced.

Further, if the second light receiving means is a light receiving element arranged on the moving means, the second light receiving means moves in accordance with the movement of the light collecting means and does not enter the light collecting means. The light receiving means for detecting light can be realized without increasing the number of parts.

Further, if the second light receiving means is a reflecting means arranged on the moving means and a light receiving element for receiving the light reflected by the reflecting means, the second light receiving means detects a servo signal and an information recording signal. Since the light receiving element and the light receiving element that detects the light around the objective lens can be integrated, and the number of light receiving elements can be reduced, the cost can be reduced. Further, since it is not necessary to provide a light receiving element on the moving means, the configuration of wiring and the like becomes simple.

Further, the light receiving element has a plurality of light receiving regions symmetrically arranged with respect to a straight line parallel to the information track, and the signals detected by the plurality of light receiving regions are calculated. By detecting the amount of movement of the light condensing means, it is possible to correct the offset due to the movement of the objective lens, which is a problem of the push-pull method of the one-beam tracking method having a simple structure, and obtain good servo characteristics.

Further, the reflecting means has a plurality of reflecting areas symmetrically arranged with respect to a straight line parallel to the information track, and calculates signals detected by the plurality of light receiving elements. If the amount of movement of the condensing means is detected, the light receiving element for detecting the servo signal and the information recording signal and the light receiving element for detecting the light around the objective lens can be integrated, and the number of light receiving elements can be reduced. Therefore, the cost can be reduced, and the offset due to the movement of the objective lens, which is a problem of the push-pull method of the one-beam tracking system having a simple structure, can be corrected and good servo characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical head according to a first embodiment of the present invention.

FIG. 2 is a diagram of an arrangement of an objective lens and a light receiving element viewed from the light source side in the optical head according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram of an optical head according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of an optical head according to a third embodiment of the present invention.

FIG. 5 is a configuration diagram of an optical head according to a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram when a diffraction element is used as a signal branching unit in the optical head according to the fourth embodiment of the present invention.

FIG. 7 is a diagram of an arrangement of an objective lens and a light receiving element viewed from a light source side in an optical head according to a fifth embodiment of the present invention.

FIG. 8 is a configuration diagram of a conventional embodiment.

[Explanation of symbols] 1 Semiconductor laser 2 openings 3 beam splitter 4 Light receiving element 5 Objective lens 6 Objective lens holder 7 Light receiving element 8 optical disks 9 Signal detection means 10,11 luminous flux 12 actuators 15 Area where light passes through the objective lens 17 Light receiving area 17a, 17b Light receiving area 21 Semiconductor laser 22 opening 23 Beam splitter 24 Light receiving element 25 Objective lens 26 Objective Lens Holder 27 mirror 28 optical disks 29 Light receiving element 30 signal detection means 31, 32, 33 luminous flux 34 Actuator 41 Semiconductor laser 42 Light receiving element 43 beam splitter 44 Objective lens 45 Objective lens holder 46 Light receiving element 47 optical disk 48 signal detection means 49,50 luminous flux 51 housing 54 Actuator 61 Semiconductor laser 62 beam splitter 63 Objective lens 64 optical disks 65 Light receiving element 66 signal detection means 67 Actuator 71 Semiconductor laser 72 Light receiving element 73 Trapezoidal prism 73a reflective surface 73b Beam splitter surface 74 Objective lens 75 Objective lens holder 76 Light receiving element 77 optical disc 78 signal branching means 79 Light receiving element 80 housing 81,82 luminous flux 83 Actuator 84 diffractive element

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hirotoshi Tomita             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Takao Hayashi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 5D118 AA01 AA04 AA21 BA01 BB03                       BB06 BB07 BF02 BF03 CA13                       CA22 CD03 CD11 CF03 CG02                       DB05 DC03                 5D119 AA01 AA05 AA23 AA26 AA29                       AA31 BA01 BB02 BB04 BB05                       DA01 DA05 EA02 EC16 FA05                       HA13 HA14 HA46 HA53 HA55                       JA57 KA17 KA22 LB08                 5D789 AA01 AA05 AA23 AA26 AA29                       AA31 BA01 BB02 BB04 BB05                       DA01 DA05 EA02 EC16 FA05                       HA13 HA14 HA46 HA53 HA55                       JA57 KA17 KA22 LB08

Claims (8)

[Claims] 1. A light source, a first light receiving means for detecting a part of the light from the light source, a light source configured to focus the light from the light source on an information track on an information recording medium, and Condensing means having an effective light transmission diameter smaller than the luminous flux diameter of the light from the light source, moving means for moving the condensing means in a direction orthogonal to the optical axis, and moving according to the movement of the condensing means. Is configured as
Further, a second light receiving unit that detects a portion of the light that goes from the light source to the light collecting unit and does not enter the light collecting unit is provided, and the first light receiving unit and the second light receiving unit are provided. An optical head characterized in that the light emission amount of the light source is controlled by a signal obtained by calculating a detected signal. 2. A third light receiving element for receiving the reflected light from the information recording medium, wherein the light source and the third light receiving element are arranged in the same housing. Optical head. 3. The first light receiving means includes a light branching element provided between the light source and the light collecting means, and a light receiving element for receiving light branched by the light branching element. The optical head according to claim 1 or 2. 4. The light source comprises a semiconductor laser, and the first light receiving means is a light receiving element for receiving light emitted from a back surface of a surface of the semiconductor laser from which light directed to the light converging means is emitted. The optical head according to claim 1 or 2, characterized in that. 5. The second light receiving means is a light receiving element arranged on the moving means.
5. The optical head according to claim 4. 6. The second light receiving means comprises a reflecting means arranged on the moving means and a light receiving element for receiving the light reflected by the reflecting means. 4. The optical head according to any one of 4 above. 7. The light receiving element has a plurality of light receiving regions symmetrically arranged with respect to a straight line parallel to the information track, and calculates signals detected in the plurality of light receiving regions. The optical head according to claim 5, wherein the movement amount of the light converging unit is detected. 8. The reflection means has a plurality of reflection areas symmetrically arranged with respect to a straight line parallel to the information track, and calculates the signals detected by the plurality of light receiving elements. 7. The optical head according to claim 6, wherein the amount of movement of the condensing unit is detected.