Deflection angle detecting device Number:7,151,596 from the United States Patent and Trademark Office (PTO) owispatent A deflection angle detecting device includes a light source, a path switching plane switching the optical path of part of light radiated from the light source, a detecting reflection surface placed on the optical path switched by the path switching plane and provided to the light-deflecting element, and a photodetector receiving light reflected by the detecting reflection surface to detect the deflection angle of the light-deflecting element in accordance with the position where the light is received. In this case, a transmission surface with positive power is interposed between the detecting reflection surface and the photodetector.<H Deflection, detecting, Deflection, angl, 7151596.html, Patent, pto, 7151596

Title: Deflection angle detecting device

Abstract: A deflection angle detecting device includes a light source, a path switching plane switching the optical path of part of light radiated from the light source, a detecting reflection surface placed on the optical path switched by the path switching plane and provided to the light-deflecting element, and a photodetector receiving light reflected by the detecting reflection surface to detect the deflection angle of the light-deflecting element in accordance with the position where the light is received. In this case, a transmission surface with positive power is interposed between the detecting reflection surface and the photodetector.

Patent Number: 7,151,596 Issued on 12/19/2006 to Takahashi, et al.

Inventors: Takahashi; Koichi (Hachioji, JP), Takahashi; Junko (Atsugi, JP)
Assignee: Olympus Optical Co., Ltd. (Tokyo, JP)

Appl. No.: 10/609,635

Filed: July 1, 2003

Foreign Application Priority Data


Jul 05, 2002 [JP]			2002-197602
Jul 23, 2002 [JP]			2002-213551
Jul 24, 2002 [JP]			2002-215598

Current U.S. Class: 356/138 ; 385/18

Current International Class: G01B 11/26 (20060101)

References Cited [Referenced By]

U.S. Patent Documents


4984892	January 1991	Hofmann
5185676	February 1993	Nishiberi
5705810	January 1998	Wang et al.
5784168	July 1998	Ophey et al.
5815255	September 1998	Van Ochten et al.
6333910	December 2001	Nishikawa et al.
6404485	June 2002	Kubo et al.
6480289	November 2002	Shimomura et al.
6975389	December 2005	Takahashi
2003/0053742	March 2003	Maruyama

Foreign Patent Documents


07-066554	Jul., 1995	JP
08-227552	Sep., 1996	JP
11-144273	May., 1999	JP
11-144274	May., 1999	JP

Primary Examiner: Lauchman; Layla G.
Assistant Examiner: Valentin, II; Juan D.
Attorney, Agent or Firm: Kenyon & Kenyon LLP

Claims

What is claimed is:

1. A deflection angle detecting device for detecting a deflection angle of a reflection surface for detection disposed in a path of rays, the deflection angle detecting device comprising: a light source for irradiating the reflection surface for detection with a beam of rays; an optical element comprising a curved reflection surface with positive power arranged to be decentered from a center axis of the beam of rays as reflected from the reflection surface for detection; and a photodetector having a light-receiving surface, for detecting the deflection angle of the reflection surface for detection in accordance with a position where the beam of rays reflected from the optical element is received on the light-receiving surface.

2. A deflection angle detecting device according to claim 1, wherein the detecting reflection surface is decentered with respect to the optical axis of the light radiated form the light source.

3. A deflection angle detecting device according to claim 1, wherein a path switching element switching at least one part of the light radiated from the light source is placed on the optical axis.

4. A deflection angle detecting device according to claim 1, wherein an optical element with positive power is interposed between the light source and the detecting reflection surface.

5. A deflection angle detecting device according to claim 1, wherein an optical element with positive power is interposed between the detecting reflection surface and the photodetector.

6. A deflection angle detecting device according to claim 4 or 5, wherein the optical element with positive power is provided with a rotational symmetrical surface.

7. A deflection angle detecting device according to claim 4 or 5, wherein the optical element with positive power includes a Fresnel lens surface.

8. A deflection angle detecting device according to claim 1, wherein the detecting reflection surface is a front surface mirror reflection surface.

9. A deflection angle detecting device according to claim 1, wherein the detecting reflection surface is a back surface mirror reflection surface configured of a medium with a refractive index of 1 or more.

10. A deflection angle detecting device according to claim 1, wherein the detecting reflection surface has rotational symmetrical optical power.

11. A deflection angle detecting device according to claim 1, wherein the detecting reflection surface has irrotational symmetrical optical power.

12. A deflection angle detecting device according to claim 1, wherein optical elements with positive powers are interposed in optical paths between the light source and the detecting reflection surface and between the detecting reflection surface and the photodetector, at least one for each optical path.

13. A deflection angle detecting device according to claim 1, wherein an optical element with positive power including a common member is interposed between the light source and the detecting reflection surface and between the detecting reflection surface and the photodetector.

14. A deflection angle detecting device according to claim 13, wherein the detecting reflection surface is provided on a back surface of the optical element with positive power including the common member.

15. A deflection angle detecting device according to claim 12, wherein at least one optical surface of one of the optical elements is configured into an irrotational symmetrical profile.

16. A deflection angle detecting device according to claim 12, wherein at least one optical surface of one of the optical elements has a function of reflecting light.

17. A deflection angle detecting device according to claim 16, wherein the optical surface having the function of reflecting light of one of the optical elements combines a function of reflecting light with a function transmitting light.

18. A deflection angle detecting device according to claim 1, wherein two sets of light-deflecting elements and detecting reflection surfaces are provided and a light beam radiated from the light source is split so that reflection angles of a plurality of light-deflecting elements provided with the detecting reflection surfaces are detected.

19. A deflection angle detecting device according to claim 1, wherein the detecting reflection surface has a reflection surface position detecting means outside an effective diameter.

20. A deflection angle detecting device for detecting a deflection angle of a reflection surface for detection, the deflection angle detecting device comprising: a light source for radiating a beam of rays; a light-deflecting element having the reflection surface for detection, inclined by a preset angle with respect to a center axis of the beam of rays radiated from the light source; an optical element comprising a curved reflection surface with positive power arranged to be decentered from a center axis of the beam of rays as reflected from the reflection surface for detection; and a photodetector having a light-receiving surface, for detecting the deflection angle of the reflection surface for detection in accordance with a position where the beam of rays reflected from the optical element is received on the light-receiving surface.

21. A deflection angle detecting device according to claim 20, satisfying the following condition: 100.degree.<.theta.<70.degree. where .theta. is an angle of incidence of a ray traveling along the center axis of the beam of rays radiated from the light source on the reflection surface for detection.

22. A deflection angle detecting device according to claim 21, wherein at least one of optical working surfaces of the optical element has a rotationally asymmetric surface.

23. A deflection angle detecting device according to claim 20, wherein when a ray passing through a center of a position of the photodetector where the light is received, from a center of the light source, is called an axial chief ray, the reflection surface with positive power of the reflected-light condensing optical element is inclined and placed so that the axial chief ray reflected by the detecting reflection surface is reflected back toward the light source.

24. A deflection angle detecting device according to claim 22, wherein the curved reflection surface with positive power of the optical element is configured as a rotationally asymmetric surface.

25. A deflection angle detecting device according to claim 22, satisfying the following condition: 20.degree.<.alpha.<110.degree. where .alpha. is an angle made by an axial chief ray incident on the curved reflection surface with positive power of the optical element with an axial chief ray reflected by the curved reflection surface with positive power.

26. A deflection angle detecting device according to claim 20, wherein the photodetector is placed close to the light source, with a light-receiving surface directed toward an exit side of the light source.

27. A deflection angle detecting device according to claim 20, wherein each of two of optical working surfaces of the reflected-light condensing optical element is configured as a reflection surface.

28. A deflection angle detecting device according to claim 20, wherein each of at least three of optical working surfaces of the reflected-light condensing optical element is configured as a reflection surface.

29. A deflection angle detecting device according to claim 20, wherein an entrance surface and a reflection surface of the reflected-light condensing optical element are configured as a common surface.

30. A deflection angle detecting device according to claim 1 or 20, wherein an incident-light condensing optical element with positive power is interposed between the light source and the reflection surface for detection.

31. A deflection angle detecting device according to claim 30, wherein each of optical working surfaces of the incident-light condensing optical element is configured as a rotational symmetrical surface.

32. A deflection angle detecting device according to claim 30, wherein the incident-light condensing optical element is constructed integrally with the reflected-light condensing optical element.

33. A deflection angle detecting device according to claim 1 or 20, wherein the photodetector comprises a one-dimensional position sensor detector.

34. A deflection angle detecting device according to claim 1 or 20, wherein the photodetector comprises a two-dimensional position sensor detector.

35. A deflection angle detecting device according to claim 1 or 20, wherein the photodetector has a four-segmented light-receiving surface.

36. An optical signal switching system for performing switching among a plurality of light-transmitting paths so that a path of an optical signal, which is conveyed through one of the light-transmitting paths, is switched to another path, the optical signal switching system comprising: at least one light-deflecting element for switching the path of the optical signal; a reflection surface for detection provided integrally with the light-deflecting element for detecting a deflection angle of the light-deflecting element; a deflection angle detecting device comprising: a light source for irradiating the reflection surface for detection with a beam of rays; an optical element comprising a curved reflection surface with positive power arranged to be decentered from a center axis of the beam of rays as reflected from the reflection surface for detection; and a photodetector having a light-receiving surface, for detecting a deflection angle of the reflection surface for detection in accordance with a position where the beam of rays reflected from the optical element is received on the light-receiving surface; and a deflection angle control unit for controlling the deflection angle of the light-deflecting element through the deflection angle of the reflection surface for detection detected by the deflection angle detecting device.

37. An information recording and presenting system for recording, presenting or both recording and presenting information signals by irradiating a recording surface of a recording medium with light, the information recording and presenting system comprising: a light source for radiating a beam of rays; an optical system that images the beam of rays on the recording medium; a light-deflecting element arranged in the optical system and having a reflection surface for detection constructed and arranged to change an inclination angle thereof in accordance with a deflection angle where the beam of rays is deflected in a plane parallel with the recording surface; and a deflection angle detecting device comprising: another light source for irradiating the reflection surface for detection with a beam of rays; an optical element comprising a curved reflection surface with positive power arranged to be decentered from a center axis of the beam of rays radiated from the another light source as reflected from the reflection surface for detection; and a photodetector having a light-receiving surface, for detecting a deflection angle of the reflection surface for detection in accordance with a position where the beam of rays reflected from the optical element is received on the light-receiving surface.

38. A light-deflecting system using light an angle of which is detected, the light-deflecting system comprising: a light-deflecting element having a reflection surface for detection; and a deflection angle detecting device comprising: a light source for irradiating the reflection surface for detection with a beam of rays; an optical element comprising a curved reflection surface with positive power arranged to be decentered from a center axis of the beam of rays radiated from the light source as reflected from the reflection surface for detection; and a photodetector having a light-receiving surface, for detecting a deflection angle of the reflection surface for detection in accordance with a position where the beam of rays reflected from the optical element is received on the light-receiving surface.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a deflection angle detecting device and a system provided with the deflection angle detecting device, and in particular, to a deflection angle detecting device constructed as a tracking detecting means used for light pickup or a light-switching means of an optical fiber used for optical communication and a system provided with this deflection angle detecting device.

2. Description of Related Art

Recently, the techniques of optical information communication and record have been conspicuously developed and the densities of information transfer and record have been significantly improved. In these fields, it is essential to improve the technique that a deflection state of a light-deflecting mirror element, such as an optical signal switch optically switching an optical fiber circuit at a relay station or the tracking control of light pickup of an optical information record reproducing system, is detected with a high degree of accuracy to control its behavior. As such, various deflection angle detecting devices have been proposed.

Deflection angle detecting devices of this type are disclosed, for example, in Japanese Patent Publication No. Hei 7-66554 and Japanese Patent Kokai Nos. Hei 8-227552, Hei 11-144273, Hei 11-144274, and Hei 11-195236.

A deflection angle detecting device set forth in Hei 7-66554 is designed to detect a relative angle made by the optical axis of a light beam emerging toward the recording medium of light pickup with the recording surface of the recording medium. This device includes a light-emitting element for irradiating the recording surface with diffused light and two light-receiving elements arranged on both sides of the light-emitting element to detect reflected light from the recording surface. The device uses a difference between the amounts of reflected light detected by the two light-receiving elements to thereby detect the amount of deflection where deflection is caused to the recording medium.

A deflection angle detecting device disclosed in Hei 8-227552 is similarly designed to detect a relative angle made by the optical axis of a light beam emerging toward the recording medium of light pickup with the recording surface of the recording medium. This device receives reflected light from the recording medium on the light-receiving surface which is divided into four, and uses a difference between the amounts of received light to thereby detect the amounts of defection in two directions.

A deflection angle detecting device set forth in each of Hei 11-144273 and Hei 11-144274 is such that reflected light from a deflecting mirror is passed through a beam splitter in which the reflectance is changed in accordance with an angle of incidence and the amount of light is detected by a photodetector to thereby detect the amount of deflection.

A deflection angle detecting device described in Hei 11-195236 is designed to detect the position of rotation of a deflecting mirror in an optical information reproducing apparatus. A light beam from a laser source is condensed into a linear beam on the deflecting mirror, and thereby measurement accuracy in one direction is improved to detect the deflection angle.

SUMMARY OF THE INVENTION

The deflection angle detecting device according to the present invention is designed to detect the deflection angle of a light-deflecting element, and comprises a light source for radiating light to the light-deflecting element; a detecting reflection surface with positive power provided to the light-deflecting element, placed on the optical axis of light radiated form the light source; and a photodetector receiving light reflected by the detecting reflection surface to detect the deflection angle of the light-deflecting element in accordance with the position where the light is received.

Also, in this specification, the deflection angle of the light-deflecting element refers to the inclination angle of the reflection surface of the light-deflecting element.

In the deflection angle detecting device of the present invention, it is desirable that the detecting reflection surface is decentered with respect to the optical axis of light radiated from the light source.

In the deflection angle detecting device of the present invention, it is desirable that a path switching element switching the optical path of part of the light radiated from the light source is placed on the optical axis.

When optical power is imparted to the detecting reflection surface provided to the light-deflecting element as in the present invention, the deflection angle detecting device which shows a wide detection range, allows one- or two-dimensional detection, and has a high degree of accuracy and a compact design, can be realized.

The deflection angle detecting device according to the present invention is designed to detect the deflection angle of a light-deflecting element, and comprises a light source for radiating light to the light-deflecting element; a detecting reflection surface inclined by a preset angle with respect to the optical axis of light radiated form the light source and provided to the light-deflecting element; a reflected-light condensing optical element with positive power for condensing light reflected by the detecting reflection surface; and a photodetector receiving light from the reflected-light condensing optical element to detect the deflection angle of the light-deflecting element in accordance with the position where the light is received.

In the deflection angle detecting device according to the present invention, when an angle of incidence of a ray traveling along the optical axis of light radiated from the light source on the detecting reflection surface is represented by .theta., it is desirable to satisfy the following condition: 10.degree.<.theta.<70.degree.

In the deflection angle detecting device according to the present invention, it is desirable that, of optical working surfaces of the reflected-light condensing optical element, at least one surface is configured as a rotationally symmetrical surface.

When the detecting reflection surface is inclined by a preset angle with respect to the optical axis of light radiated from the light source, there is no need to provide a path switching means such as a half mirror, a beam splitter, or a polarization beam splitter. Consequently, the number of parts is lessened, and cost and assembly man-hour can be reduced. Furthermore, the number of degrees of freedom of mechanical layout is increased. Since the path switching means is not required, there is no loss of the amount of light received by the photodetector, and thus detection accuracy is higher than in the case where the half mirror, the beam splitter, or the polarization beam splitter is provided.

The deflection angle detecting device according to the present invention is designed to detect the deflection angle of the light-deflecting element, and comprises a light source for radiating light; a path switching plane switching the optical path of part of light radiated from the light source; a detecting reflection surface placed on an optical path switched by the path switching plane and provided to the light-deflecting element; and a photodetector receiving light reflected by the detecting reflection surface to detect the deflection angle of the light-deflecting element in accordance with the position where the light is received. In this case, a transmission surface with positive power is interposed between the detecting reflection surface and the photodetector.

The deflection angle detecting device according to the present invention is designed to detect the deflection angle of the light-deflecting element, and comprises a light source for radiating light; a prism constructed with at least three surfaces; a decentered lens constructed with two surfaces; a detecting reflection surface placed on the optical path of light from the light source, switched through the prism, and provided to the light-deflecting element; and a photodetector receiving light reflected by the detecting reflection surface to detect the deflection angle of the light-deflecting element in accordance with the position where the light is received. The prism includes a first surface having a function of transmitting incident light from the light source through the prism; a second surface having a function of reflecting light transmitted through the first surface, a function of transmitting light reflected by another optical working surface of the prism so that the light leaves the prism toward the detecting reflection surface, and a function of transmitting incident light from the detecting reflection surface through the prism; and a third surface having a function of reflecting light reflected by the second surface toward the detecting reflection surface and a function of transmitting light transmitted through the second surface toward the photodetector. The decentered lens includes a fourth surface provided opposite to the third surface and a fifth surface which is a transmission surface situated between the fourth surface and the photodetector, having positive power.

The deflection angle detecting device according to the present invention is designed to detect the deflection angle of the light-deflecting element, and comprises a light source radiating light; a prism constructed with at least four surfaces; a detecting reflection surface placed on the optical path of light from the light source, switched through the prism, and provided to the light-deflecting element; and a photodetector receiving light reflected by the detecting reflection surface to detect the deflection angle of the light-deflecting element in accordance with the position where the light is received. The prism includes a first surface having a function of transmitting incident light from the light source through the prism; a second surface having a function of reflecting light transmitted through the first surface toward the detecting reflection surface and a function of transmitting light transmitted through another optical working surface of the prism so that the light leaves the prism toward the photodetector; a third surface having a function of transmitting light reflected by the second surface so that the light leaves the prism toward the detecting reflection surface; and a fourth surface having a function of transmitting incident light from the detecting reflection surface through the prism. At least one of the first surface and the second surface has positive power.

When the present invention is constructed as mentioned above, the deflection angle detecting device which shows a wide detection range, allows one- or two-dimensional detection, and has a high degree of accuracy and a compact design, can be realized.

These and other features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing schematically the construction of a deflection angle detecting device in which a beam splitter is used as prior art which affords the basis of the present invention and a position detector is used a photodetector;

FIGS. 2A and 2B are views showing schematically an example of the deflection angle detecting device and a modified example, respectively, in a first embodiment of the present invention;

FIG. 3 is a conceptual view showing a position sensitive detector which is applicable to the photodetector in the deflection angle detecting device of the present invention;

FIG. 4 is an explanatory view showing a state where a detecting reflection surface is inclined in a one-dimensional direction (the X direction or the Y direction) and a spot is formed on a sensor light-receiving surface of the photodetector;

FIG. 5 is a graph showing the relation between the amount of inclination of the detecting reflection surface and the output of the photodetector;

FIG. 6 is an explanatory view showing a state where the detecting reflection surface is inclined in a two-dimensional direction and a spot is formed on the sensor light-receiving surface of the photodetector;

FIG. 7 is an explanatory view showing a state where a spot s formed on the sensor light-receiving surface of the photodetector using a divided light-receiver (a four-divided position detector);

FIG. 8 is a view showing schematically the deflection angle detecting device in a second embodiment of the present invention;

FIG. 9 is a view showing schematically the deflection angle detecting device in a modified example of the second embodiment;

FIG. 10 is a view showing schematically the deflection angle detecting device in a third embodiment of the present invention;

FIG. 11 is a view showing schematically the deflection angle detecting device in a fourth embodiment of the present invention;

FIGS. 12A, 12B, and 12C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in a fifth embodiment of the present invention;

FIGS. 13A, 13B, and 13C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in a sixth embodiment of the present invention;

FIGS. 14A, 14B, and 14C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in a seventh embodiment of the present invention;

FIGS. 15A, 15B, and 15C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in an eighth embodiment of the present invention;

FIGS. 16A, 16B, and 16C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in a ninth embodiment of the present invention;

FIGS. 17A, 17B, and 17C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in a tenth embodiment of the present invention;

FIGS. 18A, 18B, and 18C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in an eleventh embodiment of the present invention;

FIGS. 19A, 19B, and 19C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in a twelfth embodiment of the present invention;

FIGS. 20A, 20B, and 20C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in a thirteenth embodiment of the present invention;

FIGS. 21A, 21B, and 21C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in a fourteenth embodiment of the present invention;

FIGS. 22A, 22B, and 22C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in a fifteenth embodiment of the present invention;

FIGS. 23A, 23B, and 23C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in a sixteenth embodiment of the present invention;

FIGS. 24A, 24B, and 24C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in a seventeenth embodiment of the present invention;

FIGS. 25A, 25B, and 25C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in an eighteenth embodiment of the present invention;

FIGS. 26A, 26B, and 26C are views showing schematically constructions where the mirror of the deflection angle detecting device is variously rotated in a nineteenth embodiment of the present invention;

FIG. 27 is a view showing schematically the deflection angle detecting device in a state where the rotation angle of the mirror is 0.degree. in a twentieth embodiment of the present invention;

FIG. 28 is a view showing schematically the deflection angle detecting device in a state where the mirror is rotated by -10.degree. around the X axis in a Y-Z plane in the twentieth embodiment;

FIG. 29 is a view showing schematically the deflection angle detecting device in a state where the mirror is rotated by 10.degree. around the X axis in a Y-Z plane in the twentieth embodiment;

FIG. 30 is a view showing schematically the deflection angle detecting device in a twenty-first embodiment of the present invention;

FIG. 31 is a view showing schematically the deflection angle detecting device in a twenty-second embodiment of the present invention;

FIG. 32 is a view showing schematically the deflection angle detecting device in a twenty-third embodiment of the present invention;

FIG. 33 is a view showing schematically the deflection angle detecting device in a twenty-fourth embodiment of the present invention;

FIGS. 34A and 34B are diagrams showing transverse aberrations in the optical path of FIG. 27 where the rotation angle of the mirror is 0.degree.;

FIGS. 35A and 35B are diagrams showing transverse aberrations in a state of the optical path of FIG. 28 (where the rotation angle of the mirror around the X axis is -10.degree.);

FIGS. 36A and 36B are diagrams showing transverse aberrations in a state of the optical path of FIG. 29 (where the rotation angle of the mirror around the X axis is 10.degree.);

FIG. 37 is an explanatory view showing schematically an example of an optical signal switch system using the deflection angle detecting device of the present invention;

FIG. 38 is an explanatory view showing a cross section perpendicular to the reflection surface of a rotating mirror and its surrounding construction;

FIG. 39 is a control block diagram showing another example of an apparatus using the deflection angle detecting device according to the present invention; and

FIG. 40 is a plan view showing schematically an information record reproducing system using the deflection angle detecting device according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present invention will be explained below with reference to the drawings.

The deflection angle detecting device according to the present invention is designed to detect the deflection angle by radiating the light-deflecting element deflecting light with different light. The present invention, therefore, can be applied to various systems provided with such light-deflecting elements.

In distinction from light deflected by the light-deflecting element, light radiated to detect the deflection angle is hereinafter referred to as detection light.

As examples of such light-deflecting elements, there are galvanomirrors in which a mirror for deflecting light is retained to be rotatable by a rotating means such as an electromagnetic coil, rotating polyhedral mirrors in which a plurality of mirror surfaces for deflecting light are mounted to a motor shaft, movable mirrors in which a mirror for deflecting light is retained by an actuator to change a setting angle, and elements in which a prism or hologram is provided to be rotatable in order to deflect light.

As systems provided with such light-deflecting elements, for example, there are an optical signal switch system and an information record reproducing system (an optical information record reproducing system).

The deflection angle detecting device of prior art is first explained as a typical example. After that, a description will be given of the embodiments of the deflection angle detecting device of the present invention and the construction examples of the optical signal switch system and the information record reproducing system, each using the deflection angle detecting device of the present invention.

First, reference is made to the deflection angle detecting device, as a typical example of prior art which affords the basis of the present invention, in which a beam splitter is used and a position detector is used as a photodetector.

FIG. 1 shows its schematic construction. An XYZ coordinate system shown in the figure is a rectangular coordinate system in which X refers to a direction perpendicular to the plane of the paper, and Y and Z refer to directions parallel to the plane of the paper is and take positive directions with respect to the upper side and the right side, respectively, of the figure.

The deflection angle detecting device of this typical example is provided with a semiconductor laser 77 as a light source for radiating light, on the optical axis of which are arranged a stop 76, a polarization beam splitter 73, a quarter-wave plate 72, and a condenser lens 71 in this order along the direction in which light travels. The condenser lens 71 is placed opposite to a detecting reflection surface 70c provided to a part of a rotating mirror 70. A position sensitive detector 74 is placed in the direction in which light is split by the polarization beam splitter 73.

The rotating mirror 70 is the light-deflecting element, such as the galvanomirror, for example, used in an optical signal switch or an optical information record reproducing apparatus. The rotating mirror 70 is provided with the detecting reflection surface 70c on the back side of a deflection mirror surface 70a used for light deflection through a fixed member 70b so that an angle of inclination is changed in cooperation with variation of the deflection angle of the deflection mirror surface 70a.

The stop 76 has a circular aperture which reforms the shape of a laser beam radiated from the semiconductor laser 77.

The polarization beam splitter 73 has a polarization beam splitter plane 73a through which a p-polarized component of the laser beam is transmitted about 100% along an optical axis 78 and an S polarizes component is reflected about 100% in the Y direction perpendicular to the optical axis 78.

The condenser lens 71 is constructed with a lens having positive power.

The position sensitive detector 74 is provided with a light-receiving surface 75 including a photoelectric element, which is directed toward the polarization beam splitter 73. The light-receiving surface 75 is a one-dimensional position sensitive detector (the position sensitive detector is commonly abbreviated to PSD) that when a light spot is radiated, a voltage corresponding to the position of the center of the light intensity of the spot is produced to detect the position of the spot.

In the deflection angle detecting device of the typical example constructed as mentioned above, when the detection light for detecting the deflection angle is radiated as the laser beam from the semiconductor laser 77, the shape of the beam is first reformed through the stop 76. The laser beam is incident on the polarization beam splitter 73, and the p-polarized component of the laser beam is transmitted through the polarized beam splitter plane, travels in straight lines, and is converted into circularly polarized light by the quarter-wave plate 72. The laser beam is condensed by the condenser lens 71 to radiate the detecting reflection surface. The laser beam, after being reflected back by the detecting reflection surface 70c, is transmitted through the condenser lens 71 and is further condensed. The laser beam is transmitted through the quarter-wave plate 72 and thereby is converted into linearly polarized light of only the s-polarized component from the circularly polarized light. The laser beam is further reflected in a positive Y direction by the polarization beam splitter plane to form a spot of preset size on the position sensitive detector 74.

In this way, the position of the spot is sensed from the output of the position sensitive detector 74. The position of the spot and the deflection angle of the detecting reflection surface 70c have a relationship corresponding to optical layout so that the deflection angle can be detected.

Subsequently, the embodiments of the deflection angle detecting device in the present invention are described.

First Embodiment

FIGS. 2A and 2B show an example of the deflection angle detecting device and a modified example, respectively, in the first embodiment of the present invention. The XYZ coordinate system shown in each of the figures is a rectangular coordinate system in which X refers to a direction perpendicular to the plane of the paper, and Y and Z refer to directions parallel to the plane of the paper and take positive directions with respect to the upper side and the right side, respectively, of each figure. Arrows in the figure indicate the directions of inclination of the detecting reflection surface. Also, this coordinate system is also used for embodiments to be described later.

The deflection angle detecting device of this embodiment has a light source, a detecting reflection surface 4, a beam splitter 3, and photodetector 5.

The light source is a semiconductor laser 1 (a semiconductor laser element) emitting a laser beam (detection light) toward the detecting reflection surface 4 provided to a light-deflecting element. Reference symbol A denotes an optical axis which coincides with the optical axis of the semiconductor laser 1. The semiconductor laser 1 is placed opposite to the detecting reflection surface 4 so that the optical axis A is nearly perpendicular to the detecting reflection surface 4.

On the optical axis A is placed the stop 2 which restricts the transmission range of the laser beam to reform the laser beam into a preset shape such as a circle. Optically, the same state that a stop is provided, depending on the size of the laser beam, is brought about, and thus the stop 2 need not necessarily be used.

The beam splitter 3 which reflects part of the laser beam to switch the optical path to the direction of an optical axis B is placed on the optical axis A between the stop 2 and the detecting reflection surface 4. The beam splitter 3 is constructed of a coating with a transmittance of about 50% and a reflectance of about 50%, deposited on a surface 3a of a flat plate, with OHARA S-BSL7, glass such as a white plate, or plastic such as ZEONEX as a material. There is no limit to the angle of the beam splitter surface 3a, but in each figure, the surface 3a is inclined by 45.degree. with respect to the optical axis A. The beam splitter surface 3a is placed parallel with the X axis over the entire length of the flat plate extending in the X direction.

The photodetector 5 is placed on the optical axis B split by the beam splitter 3. Reference numeral 6 represents a sensor light-receiving surface of the photodetector 5.

The detecting reflection surface 4 has positive power. The detecting reflection surface 4 may be constructed with a back-surface mirror configured into a concave shape, having a medium with a refractive index of 1 or more, or a front surface mirror.

Also, although any semiconductor laser may be used as the semiconductor laser 1, it is natural to select a laser provided with a proper wavelength in the relationship with the detection sensitivity of the photodetector 5. Since any well-known means may be used, it is needless to say that the semiconductor laser 1 is connected to a driving means including a power supply and a modulation driving circuit, not shown, for properly emitting light.

As the photodetector 5, the position sensitive detector (the so-called PSD) can be adopted in which when the sensor light-receiving surface 6 is radiated with the spot of the laser beam, a voltage corresponding to the center position of the light intensity of the spot is output to sense the position of the spot. The PSD is constructed with an array of many photodiodes, for example, as shown in FIG. 3, so that when a preset part is radiated with the light beam, voltages corresponding to distances D1, D2, D3, and D4 from the corners of the PSD to the center of the light beam are output from four terminals T1, T2, T3, and T4, and the position (the inclination in X and Y directions) can be detected by calculating these output values.

As the photodetector 5, a detector is adopted in which a one- or two-dimensional position is detected in accordance with whether the inclination of the detecting reflection surface 4 is one-dimensional (in the X or Y direction) or two-dimensional (in the X and Y directions). Also, it is needless to say that the photodetector 5, because of its operation, is provided with a proper driving means, not to speak of the power supply, but this is well known and thus its explanation is omitted.

In the deflection angle detecting device of the first embodiment constructed as mentioned above, laser light emitted from the semiconductor laser 1 which is the light source, as shown in FIG. 2A, is restricted in its beam size by the stop 2 and is incident on the flat-plate-shaped beam splitter 3. About 50% of the laser light is transmitted through the beam splitter surface 3a and is reflected by the detecting reflection surface 4. In this case, reflected laser light is condensed by receiving optical positive power by the detecting reflection surface. The laser light is incident again on the beam splitter 3 and is split into transmitted light and reflected light by the beam splitter surface 3a. The reflected light is switched to an optical path bent nearly perpendicular to the optical path of incidence and enters the photodetector 5 to form a light spot.

When the detecting reflection surface 4 is inclined in the X and Y directions, the photodetector 5 detects the amount of inclination by detecting the position of the spot on the sensor light-receiving surface 6.

FIG. 4 shows a state where the detecting reflection surface 4 is inclined in the one-dimensional direction (the X or Y direction) and a spot 7a is formed on the sensor light-receiving surface 6 of the photodetector 5. FIG. 5 shows the relationship between the amount of inclination of the detecting reflection surface 4 and the output of the photodetector 5.

When the detecting reflection surface 4 is inclined one-dimensionally, the position of the spot 7a on the light-receiving surface 6 of the photodetector 5 is shifted. In this case, the output of the photodetector 5, as shown in the graph of FIG. 5, is almost linearly changed. FIG. 6 shows a state where the detecting reflection surface 4 is inclined in the two-dimensional direction and a spot 7b is formed on the sensor light-receiving surface 6 of the photodetector 5. When the detecting reflection surface 4 is inclined in the X and Y directions, the spot 7b on the light-receiving surface 6 is moved in the two-dimensional direction. In this case, an output in each direction likewise is as shown in 15 the graph of FIG. 5, and the relationship between the amount of inclination (angle) of the detecting reflection surface and the output becomes favorable in linearity. In the first embodiment, the inclination of the detecting reflection surface 4 can be detected within around .+-.10.degree..

In the construction of the first embodiment, therefore, it becomes possible to use path switching of light pickup, the tracking means, and a light switching means of optical communication which require detection in a wide range of the inclination of the detecting reflection surface.

Also, in the embodiment of the present invention, a four-divided light-receiver (a four-divided position detector) is used as the photodetector, instead of the position sensitive detector (PSD), and thereby the deflection angle can also be detected.

FIG. 7 shows a state where a spot 7 is formed on the sensor light-receiving surface 6 of the photodetector 5 using the divided light-receiver (the four-divided position detector).

The spot diameter of the laser light A condensed on the photodetector 5 using the four-divided light-receiver (the four-divided position detector) is such as to be larger than that of the laser light condensed on the photodetector using the PSD. A light-receiving surface 8 of the photodetector 5 is divided into four light-receiving subsurfaces (represented by 8a, 8b, 8c, and 8d). When the detecting reflection surface 4 is two-dimensionally inclined in the X and Y directions, the spot 7 on the light-receiving surface 8 is moved in a two-dimensional direction. In this case, when outputs corresponding to the areas of the light-receiving subsurfaces 8a, 8b, 8c, and 8d, radiated with the laser light are represented by A, B, C, and D, the output corresponding to the position in the X direction is obtained by calculating (A+D-B-C)/(A+B+C+D) and the output corresponding to the position in the Y direction by calculating (A+B-C-D)/(A+B+C+D). The calculated output in each direction is almost linearly changed as far as the spot is uniform in shape.

According to the deflection angle detecting device of the first embodiment constructed as mentioned above, the following advantages are obtained.

Where the laser light from the light source is condensed by a positive lens alone, considerable curvature of field is produced in order to form the spot, and the spot changes markedly in size at the center and the end of the photodetector 5. According to the deflection angle detecting device of the first embodiment, however, major power for condensing light is imparted to the concave mirror which is the detecting reflection surface, so that the surface of the mirror can be made smaller in curvature than that of a convex lens, such as the condenser lens 71 of the conventional deflection angle detecting device shown in FIG. 1, and the production of curvature of field can be lessened. Hence, the spot is formed with little change in size at the center and the end of the photodetector 5, and read accuracy at the photodetector 5 can be improved.

In the deflection angle detecting device of the first embodiment, the detecting reflection surface 4 is configured as a curved surface (the concave mirror) having a function of condensing light. Consequently, the spot can be formed on the photodetector, the condenser lens is not required, the number of parts is reduced, cost and fabrication are advantageous, and lightweight and compact design can be achieved.

According to the deflection angle detecting device of the first embodiment, a major condensing function is performed by the concave mirror of the detecting reflection surface, and thus a loss in the amount of laser light is reduced so that the laser light can be effectively used. Even when the layout is mechanically limited, the diameter of the spot formed on the photodetector 5 and the amount of movement of the spot can be optimized by changing the focal length of the concave mirror, and a wide range of detection becomes possible with respect to the inclination of the detecting reflection surface 4.

The present applicant has considered the construction that a concave mirror is used as the condenser lens and a beam splitter is used for the path switching element, as a deflection angle detecting device. Specifically, the light source and the detecting reflection surface are arranged opposite to each other, with the beam splitter between them, and the concave mirror and the photodetector are arranged opposite to each other, with the beam splitter between them, so as to intersect with the optical path connecting the light source and the detecting reflection surface.

In this construction, however, the light beam from the light source is transmitted through the beam splitter with a transmittance of about 50%, and after being reflected by the detecting reflection surface, is reflected by the beam splitter with a reflectance of about 50% to switch the optical path and by the concave mirror which is the condenser lens, and is again transmitted through the beam splitter with a transmittance of about 50% to reach the photodetector. That is, the light beam from the light source passes three times through the beam splitter, and thus the amount of laser light is reduced to 1/8 when the laser light reaches the photodetector.

According to the deflection angle detecting device of the first embodiment, by contrast, the detecting reflection surface 4 is constructed with the concave mirror whose back side has a function of condensing light. The light beam from the light source is transmitted through the beam splitter, and after being reflected by the detecting reflection surface 4 having the function of condensing light, is reflected by the beam splitter to switch the optical path and reach the photodetector 5. Consequently, the laser beam passes only twice through the beam splitter, and 1/4 of the amount of laser light can be used in the photodetector so that read accuracy can be improved.

The present applicant has considered the construction that a concave mirror is used as the condenser lens and a polarization beam splitter is used for the path switching element, as another deflection angle detecting device. Specifically, the light source and the detecting reflection surface are arranged opposite to each other, with the polarization beam splitter between them, and the concave mirror and the photodetector are arranged opposite to each other, with the polarization beam splitter between them, so as to intersect with the optical path connecting the light source and the detecting reflection surface. In this construction, the use of the concave mirror as the condenser lens and the polarization beam splitter as the path switching element allows a loss in the amount of light to be lessened.

In the case of the above construction, however, quarter-wave plates must be placed, for example, between the polarization beam splitter and the detecting reflection surface and between the concave mirror and the polarization beam splitter, and a plurality of quarter-wave plates are required, with a resulting increase in cost.

According to the deflection angle detecting device of the first embodiment, by contrast, neither the polarization beam splitter nor the quarter-wave plate is required, and a large amount of light can be introduced into the photodetector.

Also, in the deflection angle detecting device of the first embodiment, the path switching element or the path switching plane may be constructed with a half mirror, a holographic surface, or a total reflection surface. When the light source and the detecting reflection surface provided with the concave side are arranged opposite to each other as the deflection angle detecting device of the first embodiment, the number of quarter-wave plates can be reduced by one, compared with the example before the above description, even though the path switching element or the path switching plane is constructed with the polarization beam splitter. When the polarization beam splitter is used, a loss in the amount of light is halved even though a source beam is very faint, and hence it becomes possible to make measurement with a high degree of accuracy through the photodetector.

According to the deflection angle detecting device of the first embodiment, reflected light from the detecting reflection surface 4 is bent through the beam splitter 3 and is introduced into the photodetector 5. Since the optical path is bent in this way, compact mechanical layout can be achieved.

The beam splitter which is the path switching element in the deflection angle detecting device of the first embodiment, as shown in FIG. 2A, may be constructed so that the beam splitter surface 3a is configured on one surface of a triangular prism and is sandwiched between two triangular prisms. In this case, the beam splitter can be assembled on the basis of a flat surface 3b which is not the optical working surface, and thus the efficiency and accuracy of assembly are improved. Even in each of remaining three surfaces, a positioning means can be set outside an effective area which has no optical work.

Second Embodiment

FIG. 8 shows the deflection angle detecting device of the second embodiment in the present invention. The deflection angle detecting device of this embodiment is the same as that of the first embodiment with the exception that the photodetector and the detecting reflection surface are arranged opposite to each other through the beam splitter. Reference is made to only a construction different from the first embodiment.

In the deflection angle detecting device of the second embodiment, as shown in FIG. 8, laser light emitted from the semiconductor laser 1 which is the light source and after its beam diameter is stopped down by the stop 2, is incident on the flat-plate-shaped beam splitter 3. The laser light is reflected by the beam splitter surface 3a with a reflectance of about 50% and is incident on the detecting reflection surface 4 after the optical path is bent at nearly right angles. The detecting reflection surface 4 has optical power, and the laser light reflected thereby is split again into transmitted light and reflected light by the beam splitter surface 3a, and after passing through the beam splitter 3 as 50% transmitted light to enter the photodetector 5, forms a light spot on the light-receiving surface 6. The photodetector 5, like the first embodiment, is the PSD.

In FIG. 8, since the concave mirror of the detecting reflection surface 4 is inclined, with the X and Z axes as centers, and thus when the mirror has a rotationally symmetrical surface profile, a load due to the rotation angle is the same, it becomes easy to control the mirror mechanically and electrically. In the second embodiment, the concave mirror is configured into a spherical shape. Moreover, when the surface of the concave mirror is configured as a rotationally symmetrical aspherical surface, aberration can be further suppressed. Where much account of aberration is made, it is also possible to configure the detecting reflection surface 4 as a free-formed surface which has a rotationally asymmetric surface profile. In this case, it is desirable that the difference of the amounts of SAG (the amounts of change at the Z axis) of the mirror at four corners of the effective diameter is small.

As a modified example of the deflection angle detecting device of a type such as that of the second embodiment, as shown in FIG. 9, it is also possible to arrange, in parallel, first and second flat-plate-shaped beam splitters 31 and 32 having beam splitter surfaces 31a and 32a, respectively, as well as first and second detecting reflection surfaces 41 and 42. In this case, laser light emitted from the single light source 1 is incident on the first beam splitter 31 and is split into 50% reflected light 71 and 50% transmitted light 72. The reflected light 71 follows the same optical path as in the description of FIG. 8, and after being reflected by the detecting reflection surface 41 to enter the first beam splitter 31, is split into transmitted light and reflected light. The light transmitted through the first beam splitter 31 reaches a first photodetector 51. The 50% transmitted light 72 transmitted through the first beam splitter 31 is incident on the second beam splitter 32 having the beam splitter surface 32a, placed adjacent thereto. The light reflected by the detecting reflection surface 42 is incident on the second beam splitter 32 and is split into transmitted light and reflected light, and the light transmitted through the second beam splitter 32 is incident on a second photodetector 52 to form a light spot. Whereby, the angles of the two detecting reflection surfaces can be measured simultaneously by providing only a single light source which is the semiconductor laser, and a sensor which is low in cost and small in size can be obtained. Also, by changing the curvatures of the detecting reflection surfaces 41 and 42, identically constructed PSDs may be used instead of the PSDs 51 and 52. Alternatively, different PSDs may be used without changing the curvatures of the detecting reflection surfaces 41 and 42. It is only necessary that such matter is properly selected in view of the mechanical factor and the factor of cost of the device.

Third Embodiment

FIG. 10 shows the deflection angle detecting device of the third embodiment in the present invention. In this embodiment, instead of the beam splitter in the deflection angle detecting device of the second embodiment, a polarization beam s