JPH02260142A - Optical device - Google Patents

Abstract

PURPOSE:To independently adjust the light emission quantities of plural laser light sources, and to prevent the influence of the reflected light, etc., on the optical system by separating plural lights emitted toward on object into two directions respectively, and further, converging them. CONSTITUTION:Laser lights 34, 36 advancing from the laser light sources 12, 14 toward on optical disk 30 are separated into two directions respectively, and the laser lights 38, 40 in one direction are converged by a lens 24, and beam waits are converged respectively. Then, photo-detecting cells 26a, 26b are arranged at the positions of the light converging points of the lens 24, and the lights from the light sources 12, 14 are detected separately, and the respective light emission quantities are controlled independently. As the result, the influence of a laser noise or drift at the light sources 12, 14 can be reduced, and an information signal can be recorded by high density.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to an optical device that can be applied to a multi-beam optical system of an optical head used in an optical disk device, for example.

(Prior Art) Recently, information has been recorded. Optical discs are attracting attention as a type of large-capacity recording medium. When recording, erasing, or reproducing information signals at high recording density on this optical disk, it is necessary to use a minute spot of laser light modulated by the information signal or a minute spot of electron beam modulated by the information signal. Place the spot on the recording film of the optical disc (
For example, there is a method of irradiating light onto a metal film). Among the above-mentioned methods, since the method using an electron beam requires the use of expensive equipment, an inexpensive optical recording method using a laser beam is used, except when the rotational speed of the optical disk is set low. is often adopted.

In addition, if an optical disk device uses a single laser light source, after recording or erasing information, it is necessary to check whether the information was recorded or erased accurately. This requires irradiation with laser light, which requires a lot of time to operate.

Therefore, a method has been introduced in which a second laser is used to record or erase information and at the same time check whether the information is recorded or erased to shorten the operating time.

By the way, as is well known, the laser light emitted from the laser light source is affected by light intensity drift (fluctuations and fluctuations in light intensity) due to laser noise accompanying laser oscillation, power source fluctuations of the light source, and other factors. included. In an optical recording device using laser light, the presence of laser noise and drift prevents accurate recording, erasing, or reproduction of information on an optical disk. In particular, this becomes a problem when trying to optically record or erase information signals on an optical disk at a high recording density. Therefore, in order to reduce the effects of laser noise and drift on this laser light, various methods have been tried to adjust the amount of light emitted from a plurality of laser light sources.

For example, as disclosed in Japanese Patent Application Laid-Open No. 62-200541, in a plurality of laser light sources that emit light,
The light emitted in the opposite direction to the direction of the light toward the optical disk is formed into images, and a magnifying lens is arranged to make the distance between the images wider than the distance between the laser light sources, and each light is detected. Some devices adjust the amount of light emitted from a plurality of laser light sources based on the detection results.

(Problem to be Solved by the Invention) However, in this detection method, each light can be detected independently, but the light emitted in the opposite direction to the direction of the light toward the optical disk is detected. However, in addition to this light, the optical disk had a structural defect in that light directed toward the optical disk was reflected and detected at the same time.

Therefore, the present invention makes it possible to independently adjust the amount of light emitted from a plurality of laser light sources, and to adjust the amount of light emitted without being affected by reflected light from the optical system. An object of the present invention is to provide an optical device.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides a first method that emits light.
and a second light emitting means, an irradiation means for irradiating the object with light from the first and second light emitting means, and a first and second light emitting means.
an optical means disposed between the light emitting means and the object and separating the respective lights from the first and second light emitting means into two directions; a light condensing means that separates and condenses the light from the first light emitting means and the light from the second light emitting means;
first and second detection means for independently detecting light separated into light from the light emitting means and light from the second light emitting means, and detection by the first and second detection means; According to the results, there is provided an optical device characterized by comprising an adjusting means for independently adjusting the amount of light emitted from the first and second light emitting means.

(Function) In the optical device of the present invention, the first and second light emitting means separate the light emitted from the first and second light emitting means toward the object into two directions, and separate the light from the first and second light emitting means. The light from the first light emitting means and the light from the second light emitting means are respectively
The light from the light emitting means is separated and focused. and,
By independently detecting each light at the position where these lights are separated and condensed, and independently adjusting the amount of light emitted from each of the first and second light emitting means, the light is directed toward the target. By detecting a plurality of emitted lights and adjusting the amount of light emitted, it is possible to adjust the amount of light emitted without being affected by reflected light from the optical system.

(Example) An example of the present invention will be described below with reference to the drawings.

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

In this device, a laser light source array 10 consisting of a first and a second laser light source 12, 14 is arranged. A collimating lens 16 that converts the light from the laser light source array 10 into parallel light. A prism 20 having a refractive surface 18 that corrects the light transmitted through the collimating lens 16 into a substantially circular shape, and a half prism 22 that transmits and reflects the light from the prism 20 are provided. In addition, in this device, a condenser lens 24 for detecting and controlling the output of the laser light source 10 condenses the light reflected by the half prism 22. A photodetector 26 separately detects the condensed light from the first and second laser light sources 12.14 using the condensing lens 24, and a signal detected separately by the photodetector 26. A signal conversion system 27 is provided for converting into a feedback signal to the first and second laser light sources 12.14. Furthermore, this device includes an information recording medium 30.
As an optical system for irradiating light onto the information recording medium 30, an objective lens 28. A condensing lens 31a that condenses each light reflected by the information recording medium 30, passed through the objective lens 28, and reflected by the half prism 22; and one of the lights condensed by the condensing lens 31a. A light shielding member 31b that shields the light and a photodetector 32 that detects the other light.
is provided. Further, a signal processing system 33a for processing the signal detected by the photodetector 32 is provided, and the adjustment system 33a adjusts the position of the objective lens 28 with respect to the information recording medium 30.
It is configured to be adjusted by b.

In this optical device, a first laser light source 12 generates a laser beam 34 for reproducing information recorded on an optical disk serving as an information recording medium 30. Further, the second laser light source 14 generates a laser light 36 for recording or erasing information on the optical disc 30.

The first laser light source 12 and the second laser light? The laser beams 34 and 36 emitted from the Wj 14 pass through the collimating lens 16 and are converted into parallel beams.

The laser beams 34 and 36 converted into parallel beams by the collimating lens 16 are
6 (laser beam 36 and laser beam 7) travel in slightly different directions. These laser beams 34.36 traveling in slightly different directions are directed to the refractive surface 1 of the prism 20, which is arranged at an angle with respect to the optical axis of the laser beam 34.36.
8, each half prism 2 is converted into a substantially circular shape.
2, it is separated into reflected light 38.40 and transmitted light 42.44.

The transmitted light 42° 44 that has passed through the half prism 22 is focused onto the optical disk 30 by the objective lens 28. Also, transmitted light 42. Since the transmitted light 44 also travels in slightly different directions, the irradiation positions 50 and 52 irradiated onto the optical disk 30 are different. Here the irradiation position is 50.5
2 means the position on the optical disc 30 where the optical disc 30 is irradiated with the transmitted light 42.44. This optical disc 30 is provided with concentric or spiral grooves (not shown). This optical disc 30
As the transmitted light 44 rotates, the transmitted light 42
The irradiation can be traced. At this time, the transmitted light 44 irradiated from the second laser light source 14 is used to record or erase information on the optical disc 30.

Also, transmitted light 42 irradiated from the first laser light source 12
This is to check whether the information recorded on the optical disk 30 is reproduced or whether the transmitted light 44 irradiated from the second laser light source 14 accurately records or erases information on the optical disk 30. used for. The transmitted light 42.44 irradiated onto the optical disc 30 is reflected by the optical disc 30, passes through the objective lens 28 again, and /
The light is reflected by the 1-f prism 22 and guided to the condenser lens 31a. Transmitted light 42 guided to this condensing lens 31a
．． 44 is an angle at which the incident angle of the transmitted light 42 and 44 to the half prism 22 (the incident angle of the transmitted light 44 with respect to the transmitted light 42 or the incident angle of the transmitted light 42 with respect to the transmitted light 44) is slightly different. Since these are the reflected lights, they each travel in slightly different directions. Therefore, the condensing points of the transmitted light 42 and 44 by the condenser lens 31a are different. Therefore, the transmitted light 44 is blocked by a light shielding member 31b (for example, a knife wedge, etc.) that is placed at the focal point position of the transmitted light 44 and whose tip is in contact with the focal point of the transmitted light 42. The light 42 is the photodetector 32
It is something that is irradiated onto the top.

As shown in the signal processing circuit diagram shown in FIG. 2, this photodetector 32 includes photodetection cells 32a, 32b, and 32c arranged on the left and right sides of the groove provided in the optical disk 30.
and 32d. This photodetection cell 32
a, 32b, :32 ke.

The 32 pots are assembled with no gaps between them, and are used for detecting track deviation errors, defocus errors, and reproducing information signals. First, regarding track deviation error detection, when the center of the light flux of the light irradiated onto the optical disc 30 by the objective lens 28 is on the center line of the groove formed on the optical disc 30 on this photodetector 32, the photodetector 32 The light is symmetrically directed to the photodetector 3 with respect to the direction along the groove provided in the optical disc 30.
2. In other words, the photodetection cells 32a32b and 32
The same amount of light is irradiated on each of c and 32d. On the other hand, when the center of the luminous flux of the light irradiated onto the optical disc 30 deviates from the center line of the groove formed in the optical disc 30, the photodetector 32 is irradiated with light that is asymmetrical with respect to the direction along the groove of the optical disc 30. Ru. This photodetection cell 32a, 3
The light irradiated onto 2b, 32c, and 32d is converted into a signal corresponding to the amount of light, and the signals are added by arithmetic units 100 and 102, respectively. The addition results in the calculation units 100 and 102 are input to the calculation unit 104, and the tracking error is detected by checking the difference between the signals detected from the photodetection cells 32a, 32b and 32c, 32d. be done.

The signal calculated by this calculator 104 is transmitted to the drive circuit 1
06, and by this drive circuit 106, the drive section 1
08, the objective lens 28 is moved in the direction of the arrow, the positional relationship between the objective lens 28 and the optical disc 30 is adjusted, and compensation is made to eliminate track deviation errors. When performing defocus error detection, the photodetection cells 32a, 32
d, 32b, and 32c, are converted into signals according to the amount of light, and are added by arithmetic units 110 and 112, respectively. The addition results from the arithmetic units 110 and 112 are input to the arithmetic unit 114.
A defocus error is detected by detecting the difference between the signals detected from a32d, 32b, and 32c. The signal calculated by this calculator 114 is sent to the drive circuit 116.
is input to the drive unit 118 by this drive circuit 116.
to move the objective lens 28 in the direction of arrow B,
The positional relationship between the objective lens 28 and the optical disk 30 is adjusted to compensate for defocus errors.

Further, when reproducing information recorded on the optical disc 30, the arithmetic units 100 and 102 use the photodetection cell 32a.
Information is reproduced by detecting the sum of signals converted according to the amount of light irradiated to %B 2b, 32c, and 32d.

Next, adjustment of the amount of light emitted from the first and second laser light sources 12, 14 will be explained based on FIGS. 1, 3, and 4. As shown in FIG. 1, the reflected light 38.40 reflected by the half prism 22 is a parallel light whose incident angle to the half prism 22 is slightly different. When the light is condensed by the optical lens 24, the spatially shared portion of the light is reduced, and the light is spatially separated in the vicinity. Among the separated lights, a converging point 46 of the reflected light 38 condensed by the condensing lens 24 and a condensing point 4 of the reflected light 40 condensed by the condensing lens 24
8 exists on the condensing point plane, but since the incident angles of the reflected lights 38.40 to the condensing lens 24 are different, the condensing points 46.48 on this condensing point plane are slightly separated. ing. This photodetector 26 includes a photodetection cell 26 as shown in FIG.
a and 26b, and is arranged at a focal point 46.48 on the focal plane of the reflected light 38.40 by the condenser lens 24, and has a relatively small spot size 5.
4.56 is irradiated. The light 34 from the first laser light source 12 is irradiated only to the photodetection cell 26a, and the light 36 from the second laser light source 14 is irradiated only to the photodetection cell 26b.

By arranging the photodetection cells 26a and 26b in this manner, the amount of these lights can be processed using a signal processing circuit as shown in FIG. 4.

That is, the amount of light irradiated onto the photodetection cell 26a is converted into voltage by the amplifier 60. Here, the reference voltage generator 62
In this case, the light intensity of the first laser light source 12 is set to emit approximately 4 mW. The voltage detected by the photodetection cell 26a and converted by the amplifier 60 and the reference voltage generated by the reference voltage generator 62 are compared by the comparator 64, and a current corresponding to the comparison amount is sent to the current driver. 66
The amount of light emitted by the first laser light source 12 is adjusted by generating the light. Further, the amount of light irradiated onto the photodetection cell 26b is converted into a voltage by an amplifier 68. Here, in the reference voltage generator 62, the second laser light source 1
The light intensity at the peak time of 4 is set to emit approximately 10 mW. The voltage detected by the photodetection cell 26b and converted by the amplifier 68 and this reference voltage generator 70
The amount of light emitted from the second laser light source 14 is adjusted by comparing the reference voltage generated by the second laser light source 14 with the reference voltage generated by the comparator 72 and generating a current in the current driver 74 according to the comparison amount. This second
The laser light source 14 is a light source that generates light for recording or erasing information. Therefore, when information is being recorded, when information is being erased, or when information is not being recorded and erased, it is necessary to emit light of different amounts of light.

Therefore, when the second laser light source 14 records or erases information, a switching circuit 76 is provided to adjust the amount of light. The switching circuit 76 is configured to adjust the amount of light of the second laser light source 14 when recording or erasing information. Further, the driving voltage generated by the reference voltage generator 70 described above is generated in synchronization with the operation of the switching circuit 76.

As explained above, in the optical device according to the present invention, the laser beams 34,36 directed toward the optical disk 30 from the first and second laser light sources 12,14 are separated into two directions, and the laser beams 38, 38 in one direction are separated into two directions. The laser beams 38 and 40 are condensed by the condenser lens 24, and in the vicinity of the condensing point position where each beam waist is narrowest, the laser beams 38 and 40 have no shared space and are separated. Therefore, this condensing lens 24
By arranging the photodetection cells 26a and 26b at the focal point positions of and separately detecting the light from the first and second laser light sources 12.14, the first and second laser light sources 12.
．． The amount of light emitted from 14 can be adjusted independently. Therefore, since the effects of laser noise and drift in the first and second laser light sources 12 and 14 can be reduced, information can be recorded or erased on the optical disk at high speed, and information signals can be recorded at high recording density. It becomes possible to do so.

In addition, in this embodiment, the half prism 22 shown in FIG.
, the laser beams 34.36 were separated, and the separated reflected beams 38.40 were used to adjust the amount of light emitted by the first and second laser light sources 12.14. However, at this time, the laser light sources 34 and 36 entering the prism 20
is divided into refracted light and reflected light at the refracting surface 18 of the prism 20. Therefore, by detecting this reflected light with a configuration similar to the condenser lens 24 and photodetector 26 shown in FIG. 1, and feeding it back to the first and second laser light sources 1214, it is possible to 2
The amount of light emitted by the laser light sources 12 and 14 can be adjusted.

Furthermore, the condenser lens 24 in FIG. Since the light from the two laser light sources 12 and 14 can be divided and focused at two positions, the same effect can be obtained. Further, the photodetector 26 only needs to be placed at a position where the light transmitted through the condenser lens 24 is separated, and may be placed before or after the condensing point of the condenser lens 24 .

[Effects of the Invention] As explained above, according to the light emitting device of the present invention, it is possible to independently adjust the amount of light emitted from a plurality of laser light sources, and the amount of light emitted when performing the adjustment is Quantity detection can be performed without being affected by reflected light from the optical system.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a light emitting device showing an embodiment of the present invention, FIGS. 2 and 4 are diagrams showing a signal processing circuit used in this embodiment, and FIG. 3 is a diagram showing a signal processing circuit used in this embodiment. FIG. DESCRIPTION OF SYMBOLS 10... Laser light source array, 16... Collimating lens, 22... Half prism, 24... Condensing lens, 26... Photodetector, 28... Objective lens, 30
...information recording medium

Claims (1)

[Scope of Claims] First and second light emitting means that emit light; irradiation means that irradiates an object with light from the first and second light emitting means; and the first and second light emitting means. an optical means disposed between the means and the object and separating the respective lights from the first and second light emitting means into two directions; a light condensing means for separating and condensing the light from the first light emitting means and the light from the second light emitting means, and the light condensing means separating the light from the first light emitting means and the light from the second light emitting means. first and second detection means each independently detecting the light separated into the light from the first and second detection means; An optical device comprising: adjusting means for independently adjusting the amount of light emitted by each of the light emitting means.