JPH02308438A - Detecting structure for light intensity of emitted light - Google Patents

Abstract

PURPOSE:To prevent an undesirable influence exerted on other optical element caused by a reflected light from the photodetecting surface of a photodetector by using the photodetector having the photodetecting surface inclined from the surface vertical to an optical axis of a reflected emitted light. CONSTITUTION:An emitted light from a semiconductor laser 1 is reflected and deflected by a polarization beam splitter 4, becomes light for measuring the intensity of the emitted light, passes through a glass cover 16 of the photodetecting surface of a light intensity detector inclined agains the surface vertical to an optical axis of this light, made incident on a photodiode 17 of the same inclination, and a light intensity of the emitted light is measured. By this inclined photodetecting surface, a reflected light from the photodetecting surface is not made incident on a photometric sensor 9, etc., of an optical element for controlling an optical head of other optical element, and it is prevented that such an undesirable influence as a noise is generated, etc., is exerted.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention relates to a method for detecting the light intensity of emitted light for detecting the light intensity of emitted light emitted from a light source toward an irradiated object. Regarding structure.

<Prior Art> Conventionally, there has been an optical information recording and reproducing device that performs recording and reproducing by irradiating convergent light onto the recording surface of an optical disk as an optical recording medium and detecting the reflected light. be. This device detects each error in focusing and tracking of an optical head with respect to a recording track of an optical disk, controls the position of the optical head, and reproduces information using the detected light.

As shown in FIG. 6, the above device has a polarizing beam splitter 33 disposed in the optical path of the emitted light 32 emitted from a semiconductor laser 31 as a light source, and in the case of a magneto-optical recording/reproducing device, In order to reproduce data based on the effect, the polarizing beam splitter 33 has a transmittance of approximately 60 to 80% for the P-polarized light component and a reflectance of 100% for the S-polarized light component. Reflected light 34 from a magneto-optical disk (not shown) enters the polarizing beam splitter 33 from the left side as shown by the broken line in the figure, but a part of the reflected light 34 enters the polarizing beam splitter 33 as an output light. The light is deflected in a direction different from the optical path of the polarizing beam splitter 33, and is emitted downward from the bottom surface of the polarizing beam splitter 33 as a data detection light 35. A photometric sensor 36 for detecting the above-mentioned focusing and tracking errors and for data reproduction is arranged on the optical path of the data detection light 35.

By the way, when recording or reproducing data, it is necessary to detect the light intensity of the emitted light 32 in order to irradiate the magneto-optical disk with an appropriate light intensity.
The light intensity of the emitted light 32 can be detected by a monitor photodiode of a known type (not shown) provided in the light emitting device 1 . However, since the optical paths of the reflected light 34 and the emitted light 32 coincide with each other, the remainder of the reflected light 34 passing through the polarizing beam splitter 33 enters the semiconductor laser 31, so that the remaining reflected light 34 also dissipates the incident light. Since it is detected by the monitor photodiode, the emitted light 32
It is not possible to detect only the light intensity of .

In addition, by detecting a part of the emitted light 32 that has been deflected upward in the figure by the polarizing beam splitter 33, the light intensity of the emitted light 32 can be detected, and the light intensity of the emitted light 32 can be detected. Optical path of detection light 37 consisting of a part of emitted light 32
A light intensity detector 38 may be placed second. However, the detected light 3 is detected on the surface of the glass cover 39 provided on the casing as the light receiving surface of the light intensity detector 38 and on the light receiving surface of the photodiode 41 provided inside the casing.
7 is reflected. These reflected lights 40 enter the photometric sensor 36 arranged on the optical path of the data detection light 35 that coincides with the optical path of the detection light 37, as shown by the imaginary lines in the figure. Therefore, since there is a risk that the noise may become noise in each error detection signal and reproduction signal detected by the photometric sensor 36 and cause deterioration of each signal, it is desirable to remove the noise described in 2.

<Problems to be Solved by the Invention> In view of the problems of the prior art, the main object of the present invention is to provide an output capable of preventing the adverse effects of light reflected from the light-receiving surface of a photodetector on other optical elements. An object of the present invention is to provide a light intensity detection structure for emitted light.

[Structure of the Invention] <Means for Solving the Problems> According to the present invention, such an object is to deflect a part of the emitted light emitted from the light source toward the irradiated object in a different direction. and a photodetector disposed in the optical path of the deflected emitted light to detect the light intensity of the emitted light. This is achieved by providing a light intensity detection structure for emitted light, characterized in that the light receiving surface of the device is inclined with respect to a plane perpendicular to the optical axis of the deflected emitted light.

Further, the support supporting the photodetector has a through hole for passing the deflected emitted light and prevents reflected light from the light receiving surface from traveling in the opposite direction within the through hole. It is preferable to include reflection prevention means provided on the inner wall surface of the through hole.

<Operation> By doing this, the reflected light from the light-receiving surface of the photodetector is
Since the light is directed in a direction different from the optical path of the detection light, it is possible to prevent adverse effects on other optical elements on the optical path of the detection light.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing the main parts of a magneto-optical recording and reproducing apparatus to which the present invention is applied. As shown in FIG. 1, a collimator lens 3 and a polarizing beam splitter 4 are arranged on the optical path of the emitted light 2 emitted from a semiconductor laser 1 as a light source toward a magneto-optical disk (not shown). There is.

The emitted light 2 that has passed through the polarizing beam splitter 4 is reflected by the magneto-optical disk to become reflected light 5, which enters the polarizing beam splitter 4 as shown by the broken line in the figure. In the case of magneto-optical recording, since signals are read by the Kerr effect, the polarizing film 6 generally has a transmittance of 60 to 80% for the P-polarized light component and a reflectance of 100% for the S-polarized light component.
A part of the P-polarized light component and the S-polarized light component are reflected by the polarizing film 6 disposed diagonally within the polarizing beam splitter 4. Therefore, a part of the reflected light 5 is transmitted to the polarizing film 6 in the polarizing beam splitter 4.
The direction of the polarizing beam splitter 4 is changed, and the data signal detection light 7 is emitted downward from the bottom surface of the polarizing beam splitter 4 in the figure.

A condenser lens 8 and a photometric sensor 9 are coaxially disposed on the optical path of this data signal detection light 7, and the data signal detection light 7 is converged onto the photometric sensor 9 by the condenser lens 8 for focusing. and tracking errors and data detection.

By the way, a part of the emitted light 2 has its optical path changed by the polarizing film 6 in the same way as described above, and is emitted upward from the top surface of the polarizing beam splitter 4 as the detection light 11. A condensing lens 12 and a light intensity detector 13 as a light receiving element are arranged on the optical path of this detection light 11, and the detection light 11 is converged on the light intensity detector 13, and the output light 2 is Detect intensity. By outputting the detection value of the light intensity detector 13 to a control circuit (not shown) through the lead wire 14, the output of the semiconductor laser 1 can be monitored and the light intensity of the emitted light 2 can be appropriately controlled.

The light intensity detector 13 described above is of a can package type as clearly shown in the figure, and its casing 15
A photodiode 17 is fixed to a base (not shown) inside, and a detection light 11 is directed toward the photodiode 17.
It has a glass cover 16 for passing through. The incident surface of the glass cover 16 as a light receiving surface of the light intensity detector 13 and the light receiving surface of the photodiode 17 are connected to the detection light 1.
The light intensity detector 13 is attached to the support member 18 so as to be inclined with respect to a plane perpendicular to the optical axis of the light intensity detector 13 . Therefore, the reflected light 19 from the incident surface of the glass cover 16,
Since the reflected light 20 of the detected light 11 from the light receiving surface of the photodiode 17 is reflected in a direction different from the optical axis of the detected light 11 as shown by the imaginary lines in the figure, each of the reflected light 19 and 20 However, it is possible to easily prevent the data signal detection light 7 from entering the photometric sensor 9 as noise through the optical path of the data signal detection light 7 that coincides with the optical path of the detection light 11.

As the light intensity detector 13, not only the can package type described above but also a plastic mold type light intensity detector 21 as shown in FIG. 2, for example, can be used. In this second embodiment, the same parts as those in the previous embodiment are given the same reference numerals and their explanations are omitted. The entrance surface 22 of the light intensity detector 21 is formed to be inclined, and the photodiode 17 is also molded to be inclined. Therefore, similarly to the above, it is possible to prevent each of the reflected lights 19 and 20 from entering the photometric sensor 9 through the optical path -1- of the detection light 11.

In addition, a plastic mold type light intensity detector 21
Since the shape of the casing can be formed freely, the entrance surface 22 may be formed to be inclined in the opposite direction to the photodiode 17, as shown in FIG. In this case as well, each of the reflected lights 19 and 20 can be prevented from being reflected in different directions as shown in the figure and entering the photometric sensor 9 in the same manner as described above.

FIG. 4 shows the main body 23 of the optical head of the magneto-optical recording/reproducing device.
A plastic mold type detector 21 is shown fixed to the support member 18 through the support member 18 . In this embodiment, the detector 21 is installed at an angle as in the first embodiment, but the main body 23 is provided with a through hole 24 through which the detection light 11 passes. An inward protrusion 25 is provided in the opening on the light intensity detector 21 side, which is formed so as to leave an opening area large enough to allow the light beam of the detection light 11 to pass through. By doing this, each reflected light 19.20 from the light intensity detector 21 is blocked by the inward protrusion 25, so that the reflected light 19.20 is prevented from reflecting off the inner wall surface of the through hole 24. It is possible to suitably prevent the photometric sensor 9 from traveling in the opposite direction and reaching the photometric sensor 9. Further, as shown in FIG. 5, a plurality of thread-shaped protrusions 26 may be formed on the inner wall surface of the through hole 24, and in this case as well, similar to the embodiment shown in FIG. effective. Furthermore, it is not limited to providing some kind of convex portion on the inner wall surface of the through hole 24 as shown in the above embodiment, but for example, coating the inner wall surface of the through hole 24 with a paint having extremely low reflectance, etc. You may do so.

In this way, for example, in a magneto-optical recording and reproducing device, the photometric sensor 9 for detecting tracking and focusing errors and data, and the light intensity detector 21 for detecting the light intensity of the emitted light 2, are configured to detect polarized light. When placed at opposite positions via the beam splitter 4, the reflected light from the light receiving surface of the light intensity detector 21 can be prevented from being mixed into each detection signal as noise, allowing stable position control. In addition, the noise-to-noise ratio of the data signal can be improved.

[Effects of the Invention] As described above, according to the present invention, the reflected light from the light intensity detector is prevented from reaching other optical elements through the optical path toward the light intensity detector, and the reflected light is prevented from reaching other optical elements. The light intensity detection structure that can prevent adverse effects on the light intensity can be formed with a simple structure and at low cost, so the effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a main part of a light intensity detection structure for emitted light based on the present invention applied to a magneto-optical recording/reproducing device. FIG. 2 is a diagram showing a second embodiment. FIG. 3 is a diagram similar to FIG. 2 showing a third embodiment. FIG. 4 is a diagram showing a fourth embodiment. FIG. 5 is a diagram similar to FIG. 4 showing the fifth embodiment. FIG. 6 is a schematic diagram showing a conventional embodiment.

Claims (2)

[Claims] (1) Direction changing means for redirecting a part of the emitted light emitted from the light source toward the irradiated object in a different direction, and the redirected emitted light for detecting the light intensity of the emitted light. and a photodetector disposed in the optical path of the emitted light, wherein the light receiving surface of the photodetector is perpendicular to the optical axis of the deflected emitted light. A light intensity detection structure for emitted light, characterized by being tilted. (2) A support supporting the photodetector has a through hole for passing the deflected output light and prevents reflected light from the light receiving surface from traveling in the reverse direction within the through hole. 2. The light intensity detection structure for emitted light according to claim 1, further comprising reflection preventing means provided on an inner wall surface of said through hole.