JPH0963111A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and finely adjust a forward transmitting light power monitor of a semiconductor laser and positional relation between a package case and a hologram element by forming a reflection part for monitoring on the hologram element. SOLUTION: A grating lens pattern is formed in a monitoring reflection part 3 formed on the surface 2a on the side of a light source of a transmission hologram element 2, the reflection part 3 reflects a part of the transmitted light of a semiconductor laser 1 and the reflected diffraction light is converged on a monitoring light receiving part formed on a light receiving substrate 4. Thus, in the assembling process of an optical pickup device, at the time of fixing the element 2 to a package 7 on which the laser 1 and the element 4 are mounted, the transmitted light from the laser 1 is reflected with the reflection part 3, the reflected light is received by the monitoring light receiving part formed on the substrate 4 and the mounting position of the element 2 is finely adjusted while monitoring a photoelectric current. The photoelectric current is utilized as a power monitor of the transmitted light of the laser 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device for reading information from an optical disc such as a compact disc or a phase change rewritable disc.

[0002]

2. Description of the Related Art As an optical pickup device for reading information from an optical disc, an optical pickup device for reading information from a compact disc has been conventionally known. The record information of the compact disc is stored as a pit row arranged along the track provided on the disc surface. The light from the semiconductor laser light source is condensed by the objective lens, and when the coherent light condensed by this objective lens is applied to the pit row on the information track provided on the disk surface, the condensed coherent light If the spot of light hits the edge of the pit,
Due to the interference effect of the light reflected from the edge flat surface and the light irradiated from the concave portion, the amount of reflected light is reduced as compared with the case where the light is reflected at a flat place outside the pit. In the optical pickup device,
A decrease in the amount of reflected light corresponding to this pit row is detected by a light receiving element, and this detection signal is converted into an electric pulse signal and output to read the information.

By the way, in an actual optical disc,
Considering the warp and distortion on the disc surface, and the inclination of the rotation axis that supports and rotates the optical disc, the positional relationship between the objective lens of the optical pickup device and the disc surface must always be maintained for accurate information reading. You have to control to keep it right. That is, there are position control in the tracking direction so that the irradiation light does not deviate from the pit train on the track, and focusing control for always matching the focal position of the irradiation light with the information surface on which the pits of the disk are formed. Many efforts have been made to reduce the number of parts and downsize the device by integrating the optical system function for detecting the tracking shift signal and the focusing shift signal for performing such control in one hologram element. There is.

An example of such a conventional technique is shown in FIG.
In FIG. 4, the light flux emitted from the semiconductor laser 11 which is the light source is the light source side surface 12 a of the transmission hologram element 12.
The diffraction grating (not shown) formed on the
The primary light is split into three light beams, of which the zero-order light is used as a so-called main beam for reading recorded information, and the ± first-order light beams are tracking errors by the known so-called 3-beam method. Used as a side beam for detection.

The three light beams emitted from the objective lens 14 are focused on the optical disk 15, and the reflected light returns to the transmission hologram element 12 via the objective lens 14 again. Here, a hologram pattern (not shown) formed on the surface 12b on the objective lens side diffracts the three light beams of the reflected light, and the first-order diffracted light of each light beam is received by the light receiving element 13.
The light is deflected so that it is received by the corresponding light receiving region formed in the above. Among these, a known tracking error detection is performed by taking a difference between the signals corresponding to the reflected light of the two side beams, and the known Foucault method is performed by receiving the reflected light of the main beam using a multi-segment photodiode. Focusing error detection and RF information signal detection are performed by the spot size method or the like.

[0006]

As described above, the hologram pattern formed on the surface 12b on the objective lens side diffracts the three light beams reflected by the disk, and the diffracted light of each light beam is received in the light receiving element 13. In the optical pickup device which is deflected so as to be coupled to the corresponding light receiving area of
In order to accurately couple the reflected light to the corresponding light receiving region in the light receiving element 13, it is necessary to fix the hologram element 12 by finely adjusting the positional relationship with the package case 16 in the assembly process.

However, in order to carry out the fine adjustment as described above, the laser light passing through the hologram element 12 is condensed by the lens means and is reflected by the reflecting means such as a mirror installed at the focal position, and the reflected light is reflected. It is necessary to detect whether or not the hologram element 12 is coupled to a predetermined light receiving position by the hologram pattern formed on the hologram element 12, which makes the assembly and adjustment extremely complicated.

Further, in the optical pickup device shown in FIG. 4, the power of the laser light emitted from the semiconductor laser cannot be monitored and detected during the actual use operation for actually reading information from the disk. Also had the problem of requiring other optical systems.

In view of the above situation, the present invention provides a semiconductor laser of a semiconductor laser by forming a reflecting portion for monitoring on a hologram element without using a reflecting means such as a condensing lens means or a mirror which is conventionally required. It is an object of the present invention to provide a front emission light power monitor and an optical pickup device capable of easily and finely adjusting the positional relationship between a package case and a hologram element.

[0010]

In order to solve such a problem, in the optical pickup device according to claim 1, a reflective portion for monitoring is formed in a partial region of one surface of the transmissive hologram element, and a monitor light source is provided. A part of the emitted light that is emitted is reflected by the monitor reflection portion and is received by the monitor light receiving portion formed in the light receiving element. Further, in the invention of claim 2, the monitor reflection portion is formed on a surface of the transmission hologram element on the light source side, and in the invention of claim 3, the monitor reflection portion is a metal film. It is as a reflection type hologram pattern constituted by.

According to a fourth aspect of the invention, the light source and the light receiving element are housed in a package, and the transmissive hologram element is attached to the package in a positionally adjustable manner. Further, in the fifth aspect of the invention. A diffraction grating that splits a light beam emitted from the light source into three light beams is formed on a surface of the transmissive hologram element on the light source side, and a side opposite to the light source of the transmissive hologram element is formed. A hologram pattern is formed on the surface of (1) to allow the three light beams, which are the return light from the optical recording medium, to enter the corresponding light receiving surfaces of the light receiving element.

In the optical pickup device configured as described above, a monitor reflection portion is formed on one surface of the hologram element that transmits the light emitted from the light source, and a part of the laser light emitted from the light source is formed. Is configured to be reflected by the monitor reflection section and received by the monitor light receiving section formed on the light receiving element, and the output from the monitor light receiving section is used for position adjustment of the hologram element and semiconductor laser during actual operation. Used as a power monitor.

The monitor reflection portion can be formed on the surface of the transmission hologram element on the semiconductor laser light source side. In addition to the monitor reflection portion, a diffraction grating that splits the light beam emitted from the semiconductor laser light source into three light beams is formed on the surface of the transmission hologram element on the semiconductor laser light source side, and the transmission hologram is used. A hologram pattern may be formed on the surface of the element opposite to the semiconductor laser light source so that the three light beams reflected by the disk are incident on the corresponding light receiving surfaces.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of an optical pickup device of the present invention will be described with reference to FIGS.

[0015]

1 is a partial side sectional view showing the basic structure of an optical pickup device of the present invention. The optical pickup device described here is usually attached to a moving device that moves in the radial direction of the disc, and the objective lens facing the disc is held so that it can move in the focusing direction and the tracking direction. However, since these mechanisms are known techniques and are not the gist of the present invention, detailed description thereof will be omitted.

In FIG. 1, reference numeral 1 denotes a semiconductor laser light source, 2
Is a transmissive hologram element irradiated with laser light from the semiconductor laser light source 1, 3 is a monitor reflection portion formed by metal film vapor deposition in a central partial region of the light source side surface 2a of the transmissive hologram element 2, A reflective hologram pattern is formed. Reference numeral 4 denotes a light-receiving substrate made of a silicon substrate or the like on which the semiconductor laser light source 1 is attached and a light-receiving portion to be described later is formed. An objective lens provided, 6 is an optical disk on which the light from the objective lens 5 is condensed, and 7 is a package in which the semiconductor laser light source 1 and the light receiving substrate 4 are housed and the hologram element 2 is mounted on the upper part. This package 7 is fixed to the frame,
This frame is attached to the moving device that moves in the disk radial direction. A heat sink 8 is integrated with the semiconductor laser light source 1.

The light source side surface 2a of the transmissive hologram element 2
2A, a diffraction grating pattern 20 for detecting a tracking error signal by a known three-beam method is formed as shown in FIG. 2A. Laser light from the semiconductor laser light source 1 is formed by the diffraction grating pattern 20. It is demultiplexed into three light fluxes of 0th order light and ± 1st order light. Further, the hologram element 2
A reflective hologram pattern (diffraction grating pattern) formed by vapor deposition of a metal film is provided in a central partial area of the surface 2a on the light source side, and this reflective hologram pattern constitutes the monitor reflection portion 3.

On the surface 2b of the transmission hologram element 2 on the objective lens side, a diffraction grating pattern 21 having different pitches, as shown in FIG. 2B, for detecting a focusing error signal by the known Foucault method. , 22 is formed into a hologram pattern. The diffraction grating patterns 21 and 22 are for diffracting the three light beams reflected by the disk and deflecting the diffracted light of each light beam to be coupled to the corresponding light receiving region formed on the light receiving substrate 4.

As shown in FIG. 3A, the light receiving substrate 4 made of a silicon substrate or the like on which the semiconductor laser light source 1 is mounted has a monitor for receiving the reflected light from the monitor reflecting portion 3 formed on the hologram element 2. 3 is provided with a light receiving portion 4a for use and the detection is performed by the known Foucault method.
As shown in (b), two two-divided light receiving sections 4c and 4f are provided. These two light receiving portions 4c and 4f receive the reflected light in which the 0th order light which is the main beam is reflected by the optical disk 6, and are diffracted on the surface 2b of the transmission hologram element 2 on the objective lens side. The light demultiplexed and deflected by the grating patterns 21 and 22 is received, the detection result is output, and the error signal and the RF information signal are detected from this detection output by the known Foucault method detection method. Further, the light receiving portions 4b, 4d, 4e and 4g receive the reflected light from the optical disc 6 of the ± 1st order light which is a sub beam, and are formed on the surface 2b of the transmission hologram element 2 on the objective lens side. Diffraction grating patterns 21, 2
The light demultiplexed and deflected by 2 is received, the detection result is output, and a known 3-beam method tracking error signal is obtained from this detection result.

By the way, the monitor reflection portion 3 formed by the surface 2a on the light source side of the transmissive hologram element 2 has a structure shown in FIG.
As shown in FIG. 3A, a grating lens pattern is formed so as to have a condensing function. Therefore, the monitor reflection portion 3 is provided with the light emitted from the semiconductor laser 1 as shown in FIG. A part of the light is reflected and the reflected diffracted light is received by the light receiving substrate 4.
The light is focused on the monitor light receiving portion 4a formed in the above. Therefore, in the process of assembling the optical pickup device, when the hologram element 2 is fixed to the package 7 in which the semiconductor laser 1 and the light receiving element 4 are mounted, the emitted light from the semiconductor laser 1 is reflected by the monitor reflection portion 3 and The reflected light is received by the monitor light-receiving portion 4a formed on the light-receiving substrate 4, the photocurrent is monitored, and the mounting position of the hologram element 2 is finely adjusted. At the position where the photocurrent value is maximum, the package is formed by bonding or the like. The hologram element 2 is fixed to 7.

Next, in a normal operation state, the light beam emitted from the semiconductor laser 1 is converted into 0th order light and ± 1st order light by the diffraction grating 20 formed on the light source side surface 2a of the transmission hologram element 2. It is split into three light beams, of which the 0th order light beam is used for reading recorded information, and the 2nd light beams of ± 1st order light beams function as side beams for tracking error detection by the known so-called 3 beam method. However, in the present embodiment, since the monitor reflection portion 3 is formed on the light source side surface 2a of the transmissive hologram element 2, the reflected light from the monitor reflection portion 3 is formed on the light receiving substrate 4. The monitor light-receiving unit 4a receives the light, and the photocurrent generated as a result of the light-receiving can be used as a power monitor of the emitted light of the semiconductor laser 1.

The three outgoing luminous fluxes of the 0th order light and the ± 1st order light that have passed through the objective lens 5 are focused on the optical disk 6 as usual, and the reflected light passes through the objective lens 5 again. It returns to the transmission hologram element 2. Since the diffraction grating patterns 21 and 22 are formed on the surface 2b of the transmission hologram element 2 on the objective lens side, as described above, the diffraction lights of the above three light fluxes are reflected by the diffraction grating patterns 21 and 22, respectively. Six light receiving portions 4 formed on the light receiving substrate 4 by being diffracted and first-order diffracted light of each light beam.
Light is received by b, 4c, 4d, 4e, 4f and 4g.

The present invention is not limited to the hologram element for the three-beam method tracking error detection and the Foucault method focusing error detection described in the above-mentioned embodiments. For example, the known push-pull method tracking error detection, The hologram element for realizing focusing error detection such as the point aberration method or the spot size method can also be applied. In that case, the hologram pattern formed on the transmissive hologram element 2 and the pattern shape of the light receiving portion corresponding thereto may be changed according to each method.

By the way, when the push-pull method tracking error detection is adopted, the diffraction grating 2a for forming the three beams becomes unnecessary, so that the diffraction grating pattern provided in the transmission hologram element 2 has one surface of the hologram element 2. It is sufficient to form only on. In this case, the hologram pattern for focusing on the light receiving portion and the reflective hologram pattern for monitoring may be formed on the same surface on one side of the hologram element 2 or may be formed on opposite surfaces thereof.

In the above-described embodiment, the reflective hologram element part 3 for monitoring is formed on the light source side of the hologram element 2, but it may be formed on the surface 2b of the hologram element 2 on the objective lens side. Moreover, although the reflective hologram element unit 3 for monitoring is formed by vapor deposition of a metal film, it may be formed of a dielectric multilayer film or the like.

[0026]

As described above, according to the present invention,
A reflection part for monitoring is formed on one surface of the hologram element that transmits the light emitted from the light source, a part of the laser light emitted from the light source is reflected by the reflection part for monitoring, and the reflected light is received. Since the monitor light-receiving section formed on the element is configured to receive light, the output from this monitor light-receiving section can be used to fix the hologram element to the package case after adjusting its position. In addition, it can be used as a power monitor of a semiconductor laser during an actual use operation.

Further, since the monitoring reflection portion is formed on the semiconductor laser light source side surface of the transmissive hologram element, the light from the semiconductor laser light source can be directly monitored, and accurate monitoring is performed. be able to.

Further, since the semiconductor laser light source and the light receiving element are housed in a package, and the transmission type hologram element is attached to the package in a positionally adjustable manner, the reflected light from the monitor reflection portion is reflected. It is possible to monitor and monitor and adjust the transmissive hologram element to be mounted at an appropriate position with the laser light source, the light receiving element and the like housed in the package and only the transmissive hologram element.

Further, on the surface of the transmissive hologram element on the side of the semiconductor laser light source, a diffraction grating for demultiplexing the luminous flux emitted from the semiconductor laser light source into three luminous fluxes is formed, and the transmissive hologram element has the above-mentioned structure. The surface on the side opposite to the semiconductor laser light source has the above-mentioned 3
Since a hologram pattern is formed in which one light flux is incident on the corresponding light receiving surface of the light receiving element, the tracking shift signal and the focusing shift signal can also be detected by one hologram element.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical pickup device showing an embodiment of the present invention.

FIG. 2 is a diagram showing a hologram pattern of the hologram element of the present invention.

FIG. 3 is an explanatory diagram showing a light receiving state of the optical pickup device of the present invention.

FIG. 4 is a configuration diagram showing a conventional optical pickup device.

[Explanation of symbols]

First semiconductor laser light source 2 transmission type holographic optical element 3 for monitoring the reflected portion 4 receiving substrate 4a monitoring light-receiving section 4b, 4d, 4e, 4g receiving portion 4c, 4f 2 light receiving section 5 to objective lens 6 disc 7 package 20, 21, 22 Diffraction grating pattern

Claims (5)

[Claims] 1. A light emitted from a light source is condensed on an optical recording medium through a transmission hologram element and an objective lens, and return light from the optical recording medium is diffracted by the transmission hologram element, In an optical pickup device configured to detect diffracted return light by a light receiving element, a monitor reflection portion is formed in a partial area of one surface of the hologram element, and emitted from the light source. Part of the emitted light is reflected by the monitor reflection part,
An optical pickup device, characterized in that it is configured to receive light by a monitor light receiving portion formed on the light receiving element. 2. The optical pickup device according to claim 1, wherein the monitor reflection portion is formed on a surface of the transmission hologram element on the light source side. 3. The optical pickup device according to claim 2, wherein the monitor reflection portion is a reflection hologram pattern formed of a metal film. 4. The optical pickup device according to claim 2, wherein the light source and the light receiving element are housed in a package, and the transmissive hologram element is attached to the package in a positionally adjustable manner. 5. A diffraction grating that splits a light beam emitted from the light source into three light beams is formed on a surface of the transmissive hologram element on the light source side, and the light source of the transmissive hologram element is formed. 3. A hologram pattern is formed on the surface on the opposite side to, which makes the three light beams, which are the return light from the optical recording medium, incident on the corresponding light-receiving surfaces of the light-receiving element. Optical pickup device.