JP3250960B2 - Optical head device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical head device in an optical recording apparatus.

[0002]

2. Description of the Related Art An optical head device for optically writing and reading data on and from a storage medium is a compact disk device or a CD-ROM which is a peripheral device of a personal computer.
It is known that it is used for ROM, MO and the like.
The above-mentioned optical head device is a device for writing data by using a semiconductor laser and focusing this oscillation light on an optical recording medium using an imaging lens, or for reading data by picking up reflected light. is there.

One of the conventional examples for reading data stored on the surface of an optical recording medium is disclosed in Japanese Patent Publication No. 7-118087. Briefly explaining what is disclosed in this publication, light emitted from a semiconductor laser passes through a hologram lens. The light that has passed through the hologram lens further passes through the imaging lens and is focused on the optical recording medium surface. The signal light reflected from the optical recording surface passes through the imaging lens in the opposite direction along the same path as the irradiation light, returns to the hologram lens, is refracted by the hologram lens, reaches the signal receiver, and is converted into an electric signal.

In the above conventional example, the hologram lens has two passes of light back and forth. Since the light transmission efficiency of the hologram lens itself is about 40.5%, the passage of light through the hologram lens itself leads to a reduction in the light transmission efficiency of the optical pickup. Furthermore, when data is read from the optical medium, the light is transmitted twice roundtrip. For this reason, only 16% of the light reaches the light receiver at the maximum because of two passes. Therefore, when storing data on an optical storage medium or reading data, the output of a semiconductor laser must be increased in order to increase the amount of light received by a signal light receiver. Attempting to increase this would result in a problem of very short life.

The present invention has been made in view of such circumstances, and in an optical head device of an optical recording apparatus, a distance between a light source that emits light and an optical storage medium or from a light source that emits light via an optical storage medium. It is an object of the present invention to provide an optical head device in an optical recording device capable of minimizing the loss of light before reaching a signal light receiver.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an optical recording apparatus which forms an image of a light beam emitted from a light source on an optical storage medium using an imaging lens. In the optical head device according to the above, there are two surfaces parallel to each other, the two surfaces being at least partially overlapping in the vertical direction, and the two surfaces parallel to each other are each a surface of the parallel transmission surface. Intersects with
These two surfaces are provided with a parallel refracting surface that at least partially overlaps in the vertical direction, and a shield that covers a part of one parallel transmitting surface on which the light beam is incident. A polyhedral optical element is provided between the light source and the imaging lens. And the polyhedron is arranged such that the optical axis passing through the center of the light source passes through the edge of the shield and another parallel transmission surface, and passes through the optical axis of the imaging lens. An optical head device in an optical recording device that provides an optical head device and forms an optical beam emitted from a light source on an optical storage medium using an imaging lens,
It has two planes parallel to each other, these two planes at least partially overlap in the vertical direction, and the two planes parallel to each other intersect with the respective planes of the parallel transmission planes. A polyhedral optical element provided with a parallel refraction surface that partially overlaps at least in the vertical direction and a shield that partially covers one of the parallel transmission surfaces on which the light beam is incident is positioned between the light source and the imaging lens. The polyhedron is arranged such that the optical axis passing through the center of the light source passes through the edge of the shield and another parallel transmission surface, and passes through the optical axis of the imaging lens, and is reflected by the optical storage medium. The present invention also provides an optical head device characterized in that light condensed by an imaging lens passes through two parallel refraction surfaces of a polyhedral optical element and is received by a light receiving unit. In these devices, the shielding body is a metal vapor-deposited film that reflects light, and the optical axis passes along the radiation direction of the light beam from the center of the light beam emitted from the light source, and is emitted from the light source. The light beam is cut in half at the edge of the shield. A second light receiving unit that receives an optical image generated by astigmatism adjacent to the light receiving unit;
And controlling the position of the position adjusting unit by a negative feedback circuit using a light receiving signal obtained from the second light receiving unit to control the formation of a light image on the optical disk. Things.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing a basic structure of the present invention. The optical head device 1 of the present invention is provided so as to face an optical disc 2 that rotates and moves in the direction of the arrow. The optical head device 1 is provided with an outer casing 3 and, as will be described later, accommodates various components of the optical head device. A position adjuster 4 for moving the optical head device closer to or away from the optical disk 2 is attached to the outer casing 3. A circuit board 5 is fixed to the bottom of the outer casing 3, and a semiconductor laser 6 serving as a light emitting source and a light receiving unit 7 are provided on the circuit board 5. A polyhedral optical element 8 is fixed to the outer casing 3 on the circuit board 5 at a predetermined interval. The polyhedral optical element 8 is formed of transparent glass, is formed in an octahedron as shown in FIGS. 2 and 3, and has parallel side walls 9 and 10 on both sides, and has front and rear sides. A wall 11 and a rear wall 12 are formed. In addition, parallel refraction surfaces 13 and 14 are formed in the upper and lower portions, and parallel transmission surfaces 15 and 16 are formed adjacent thereto. The parallel refraction surface 13 and the parallel transmission surface 15 are in contact at an upper ridge line, and the parallel refraction surface 14 and the parallel transmission surface 16 are in contact at a lower ridge line. 1 to 3, reference numeral 17 denotes an optical axis. As can be seen from FIGS. 1 to 3, the optical axis 17 extends from the tangent portion between the parallel refraction surface 13 and the parallel transmission surface 15 to the parallel transmission surface 16. Therefore, the point where the optical axis 17 is missing is that the parallel refraction surface 14 and the parallel transmission surface 1
6 is a position that enters the inside of the parallel transmission surface 16 from the tangent to 6. In the parallel transmission surface 16, the optical axis 17 is parallel to the tangent between the parallel refraction surface 14 and the parallel transmission surface 16.
In a region extending from the straight line 18 passing through the point where the light exits to the tangent to the front wall 11, a reflecting portion 19 on which a metal having a high reflectance such as gold or aluminum is deposited is formed.

An imaging lens 20 composed of a convex lens is fixed to the outer casing 3 above the polyhedral optical element 8. As can be seen from FIG. 1, the optical axis 17 passes through the light emitting portion of the semiconductor laser, the polyhedral optical element 8, and the optical axis of the imaging lens 20. Then, when the optical head device 1 is at the normal position,
The focal point of the imaging lens 20 is focused on the optical disk 2.

Next, the operation of the present invention will be described. FIG.
As can be seen from the overall basic configuration diagram shown in FIG. 1, the polyhedral optical element 8 and the imaging lens 20 are placed on the optical axis 17 of the semiconductor laser 6, and the laser light is focused on the optical disk 2 as the optical recording surface. As shown in FIGS. 2 and 4, a light transmitting surface 21 satisfying the spread angle of the light beam 22 emitted from the semiconductor laser 6 is provided at an end of the parallel transmitting surface 16 of the polyhedral optical element 8, and the light is provided at the center thereof. Although there is an axis 17 and it is not an essential configuration, it is set so that the optical axis 17 is located at the boundary between the parallel refraction surface 13 and the parallel transmission surface 15.

As shown in FIG. 5, when data is written on the optical disk 2 by the optical head device 1 as in an MO device, half of the light beam 17 emitted from the semiconductor laser 6 is reflected by the reflecting portion 19 on the lower surface. Then, only the other half enters the polyhedral optical element 10 from the parallel transmission surface 16, and the light beam 17 emitted from the parallel transmission surface 15 reaches the optical recording surface of the optical disk 2 through the imaging lens 20 and the data signal Light beam 1 emitted from semiconductor laser 6 modulated by
7 writes data on the optical disk surface. As described above, since the light beam 17 emitted from the semiconductor laser 6 does not pass through the hologram lens as in the conventional case, it reaches the optical disk 2 efficiently with approximately 50% efficiency. At this time, when the light beam 17 emitted from the semiconductor laser 6 passes through the polyhedral optical element 8 and the imaging lens 20, the light beam 17 is slightly absorbed by the glass forming them. Is very small as compared with the loss when passing through.

As shown in FIG. 6, when reading data written on the optical disk 2 by the optical head device 1 as in a CD-ROM device, half of the light beam 17 emitted from the semiconductor laser 6 has a lower surface. Only the other half reflected by the reflection unit 19 enters the polyhedral optical element 8, passes through the imaging lens 20, reaches the optical recording surface of the optical disk 2, and is reflected. The reflected light beam 17 is deflected and reflected according to the data written on the optical disc 2. The reflected light beam 17 passes through the imaging lens 20 and is incident on the parallel refraction surface 1.
3, the light enters the polygonal optical element 12, exits from the parallel refraction surface 14, forms an image on the light receiving unit 7, and the data stored on the optical disk is read by the light receiving unit 7. As described above, since the light beam 17 emitted from the semiconductor laser 6 does not pass through the hologram lens unlike the conventional one, it reaches the light receiving section 7 efficiently. At this time, the light beam 17 emitted from the semiconductor laser 6 is applied to the polyhedral optical element 1.
When the light passes through the lens 0 and the imaging lens 20 twice, it is slightly absorbed by the glass forming them. However, the amount of absorption is extremely small as compared with the loss when passing through the hologram lens. Therefore, the laser beam emitted from the semiconductor laser passes through the polyhedral optical element 8 and has a utilization efficiency of 50%.

In the present invention, as shown in FIG. 1, the polyhedron optical element 8
The parallel refraction surfaces 13 and 14 and the parallel passage surfaces 15 and 21 respectively
Therefore, coma due to refraction can be eliminated. Therefore, a signal read from the optical disc 2 can be obtained from the light receiving unit 7. On the other hand, as can be seen from FIG. 7, the light beam 22 causes astigmatism due to the refraction phenomenon on the return path. Therefore, light images 24 and 25 as shown in FIG. 8 are generated on the light receiving surface of the light receiving unit 7. The light image 23 is of a light beam shown on the left side of FIG. Therefore, an image is formed on the light receiving surface, and the light image is read by the light receiving unit 7 arranged in this portion. The light images 24 and 25 are light images generated by astigmatism, and are generated adjacent to the light image 23 and symmetrically with respect to the light image 23. These light images 24 and 25 are received by other light receiving elements 7 'and 7 ", and using these signals,
For example, if the position adjusting device 4 shown in FIG. 1 is operated using a well-known negative feedback circuit so that the intensity of the light receiving signals obtained from the left and right light receiving elements is the same, the light emitted from the semiconductor laser 6 can be obtained. The obtained light beam 22 can be imaged on the light receiving section 7.

[0013]

As described in detail above, according to the present invention,
Unlike the conventional device, a light beam emitted from the light source is not used in the optical path of the light beam emitted from the light source, such as a hologram lens. In an optical head device in an optical recording device that forms an image on an optical storage medium, the efficiency of light can be greatly improved, and the sensitivity of reading an optical recording signal can be improved. Since the light efficiency is greatly improved, the light emission amount of the semiconductor laser can be reduced as compared with the conventional optical head device, and the life of the semiconductor laser can be extended. In addition, since the amount of light emitted by the semiconductor laser is small and the current consumption is small, heat generation can be suppressed and the heat sink can be made small. In addition, the light beam can be received almost perpendicularly to the light receiving part, and coma aberration does not occur and light receiving sensitivity is improved. I do. In addition, since astigmatism can be obtained in the vicinity of the light receiving portion, there is no need to separately provide a focus error detecting lens, and the polyhedral optical element has many advantages such as easy processing, and an inexpensive optical head device can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a side view of a polyhedral optical element.

FIG. 3 is a perspective view of a polyhedral optical element.

FIG. 4 is a perspective view showing a light beam passage path;

FIG. 5 is an explanatory diagram of a forward path of a light beam.

FIG. 6 is an explanatory diagram of a reciprocating path of a light beam.

FIG. 7 is an explanatory diagram for explaining an outline of occurrence of astigmatism.

FIG. 8 is an explanatory diagram of a light image generated by astigmatism.

[Explanation of symbols]

 1 optical head device 2 optical disk 3 outer casing 4 position adjustment unit 5 circuit board 6 semiconductor laser 7 ········ Light receiving section 8 ····· Polyhedral optical element 9 ····· Side wall 10 ····· Side wall 11 ····· Front wall 12 ····· Rear wall 13 ··· ..Parallel refraction surface 14 Parallel refraction surface 15 Parallel transmission surface 16 Parallel transmission surface 17 Optical axis 18 Straight line 19 ... Reflector 20 ... Imaging lens 21 ... Light transmitting surface 22 ... Light beam 23 ... Light image 24 ... Light image 25 ... .... Light image

────────────────────────────────────────────────── (5) References JP-A-58-224442 (JP, A) JP-A-53-47804 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/12-7/22

Claims (6)

(57) [Claims] An optical head device in an optical recording apparatus for imaging a light beam emitted from a light source on an optical storage medium using an imaging lens has two surfaces parallel to each other, and the two surfaces are perpendicular to each other. A parallel transmissive surface that at least partially overlaps in a direction, and two surfaces that are parallel to each other intersect with the respective surfaces of the parallel transmissive surfaces, and these two surfaces at least partially overlap in a vertical direction; A shield covering a part of the one parallel transmission surface on which the beam is incident, and a polyhedral optical element provided with the shield positioned between the light source and the imaging lens, and an optical axis passing through the center of the light source is positioned at an edge of the shield. An optical head device, wherein a polyhedron is arranged so as to pass through a portion and another parallel transmission surface and pass through the optical axis of the imaging lens. 2. An optical head device in an optical recording apparatus for imaging a light beam emitted from a light source onto an optical storage medium by using an imaging lens, the optical head device having two surfaces parallel to each other, and these two surfaces being at least two. A parallel transmission surface partially overlapping in the vertical direction, and two surfaces parallel to each other intersect with the respective surfaces of the parallel transmission surface, and these two surfaces are parallel refraction surfaces partially overlapping at least in the vertical direction. A shield covering a part of the one parallel transmission surface on which the beam is incident, and a polyhedral optical element provided with the shield positioned between the light source and the imaging lens, and an optical axis passing through the center of the light source is positioned at an edge of the shield. A polyhedron is arranged so as to pass through the portion and another parallel transmission surface and pass through the optical axis of the imaging lens, and to reflect light reflected by the optical storage medium and condensed by the imaging lens into a polyhedral optical element 2. Through two parallel refracting surfaces An optical head device, characterized in that the light is received by a light receiving unit. 3. The optical head device according to claim 1, wherein the shield is a metal vapor-deposited film that reflects light. 4. The optical head device according to claim 1, wherein an optical axis passes from a center of the light beam emitted from the light source along a radiation direction of the light beam. 5. The optical head device according to claim 1, wherein the light beam emitted from the light source is cut in half at the edge of the shield. 6. A second light receiving section for receiving a light image generated by astigmatism is provided adjacent to the light receiving section, and a negative feedback circuit is provided by using a light receiving signal obtained from the second light receiving section. 3. The optical head device according to claim 2, wherein the position of the position adjusting unit is adjusted to control the formation of the optical image on the optical disk.