JPH05257072A - Two-dimensional optical scanning device - Google Patents

Abstract

PURPOSE:To speed up the operation of the two-dimensional optical scanning device and reduce its size. CONSTITUTION:A plane mirror 12 exclusively for scanning rotates and vibrates around a 1st axis 4 in two directions to make an angular scan with scanning light 14 along a Y-Z plane. The plane mirror 12 is displaced slantingly to the 1st axis 4 at the same time to make an angular scan with the scanning light 14 along an X-Z plane. Return light 15 parallel to the scanning light 14 is reflected and converged by a concave mirror 1 which is fixedly arranged and photodetected by a photodetecting element 9. A 3rd axis 10 connecting a sphere center point 5 and the photodetecting element 9 is set invariably parallel to the scanning light 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-dimensional optical scanning device which two-dimensionally scans a laser beam and receives and detects scattered light or return light reflected from a target. Such a device is incorporated in a bar code reader for reading a bar code attached to an article, a laser radar for identifying a remote object, or the like.

[0002]

2. Description of the Related Art As a conventional two-dimensional optical scanning device, a pair of galvanometers having plane mirrors are arranged in a laser optical path, and one of them is oscillated in a horizontal direction and the other is oscillated in a vertical direction. There is a method of two-dimensional scanning.

As another conventional method, there is known a structure in which one plane mirror is rotated horizontally and vertically by two galvanometers to perform two-dimensional scanning. In order to clarify the background of the present invention, the latter conventional structure will be briefly described with reference to FIG. A substantially U-shaped vibrating member 10
1 is rotationally oscillated about a horizontal axis 102 by a galvanometer (not shown). A galvanometer 103 is attached to the vibrating member 101. Galvanometer 10
A plane mirror 104 is fixed to the shaft of No. 3, and rotationally vibrates about a vertical axis 105. Laser light source 10
The laser light 107 emitted from the laser beam 6 is incident on the plane mirror 104 that is rotationally oscillated in the horizontal direction and the vertical direction through the opening 109 provided in the central portion of the condenser mirror 108, is reflected, and is two-dimensionally scanned. The projected light 110 is obtained. The return light 111 from the target travels backward through the plane mirror 104 to the condenser mirror 108, is condensed by the lens 112, and is received and detected by the light receiving element 113. The latter conventional method requires only one plane mirror and the structure is simplified as compared with the former conventional method.

[0004]

In any of the conventional examples, the plane mirror serves both for emission and reception. The larger the area size of the plane mirror, the larger the amount of light received and the higher the detection sensitivity. Although a large area is not required for emission, the area size of the plane mirror must be increased in order to secure a predetermined amount of received light. On the other hand, high-speed driving of the plane mirror is required to achieve high performance. In order to suppress the mechanical distortion of the plane mirror caused by the high-speed rotation vibration, the thickness dimension must be increased to provide rigidity. If the predetermined area size and thickness are secured, the mass of the plane mirror inevitably increases, and a high-output galvanometer is required, which limits the miniaturization.

As described above, in the conventional two-dimensional optical scanning device comprising a combination of a galvanometer and a plane mirror for both emission and reception, the area size cannot be reduced in order to secure the amount of received light, and the speed and size are reduced. There is a problem that it is difficult to achieve both of these at the same time. In order to increase the speed, it is necessary to increase the thickness of the plane mirror and use a high output galvanometer, which conflicts with miniaturization.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, an object of the present invention is to provide a structure capable of simultaneously achieving high speed and miniaturization of a two-dimensional optical scanning device. In order to achieve such an object, the mirror is divided into a structure using a plane mirror dedicated to scanning and a spherical concave mirror dedicated to light reception. As a result, the plane mirror dedicated to scanning was made as small as possible, and a concave mirror dedicated to receiving light was used to collect the return light and secure a sufficient amount of received light. Further, the light receiving element is made to interlock with a plane mirror dedicated to scanning so that the light is always focused on the light receiving surface.

Alternatively, as a modification of the above-described structure, the laser light source itself may be rotationally vibrated instead of rotationally vibrating the plane mirror.

The basic configuration of the two-dimensional optical scanning device according to the present invention will be described with reference to FIG. The concave mirror 1 fixedly arranged has a reflecting surface 2 in which a part of the spherical surface is cut off.
Have. A first vibrating member 3 is arranged above the concave mirror 1. The vibrating member 3 rotationally vibrates bidirectionally around the first shaft 4 (X axis). The first axis 4 coincides with the sphere diameter lying on the plane facing the concave mirror 1 including the sphere center point 5.

A second vibrating member 6 is attached to the first vibrating member 3. This vibrating member 6 has a second shaft 7 (Y
It is possible to rotate and oscillate in both directions around the axis. The second axis 7 is orthogonal to the first axis 4 (X axis) at the sphere center point 5 described above, and is perpendicular to the paper surface. A light receiving element 9 is attached to the second vibrating member 6 via an arm portion 8, and its light receiving surface faces the reflecting surface 2 of the concave mirror. The light receiving element 9 is arranged on the third axis 10 at a substantially center point of the spherical radius. The third shaft 10 is fixed to the second vibrating member 6 and coincides with the sphere radius orthogonal to the second shaft 7 at the sphere center point 5. Therefore, the third shaft 10 moves along with the rotational vibration of the second vibrating member 6.

A conversion mechanism 11 is interposed between the first vibrating member 3 and the second vibrating member 6. This conversion mechanism 11 is for producing an angular displacement corresponding to 1/2 of the angular displacement of the second vibrating member 6. A plane mirror 12 is mounted on the conversion mechanism 11. The plane mirror 12 transmits the laser beam 13 incident along the first axis 4 to the third axis 10 described above.
It is installed so that it reflects in parallel with. The reflected light is projected as scanning light 14 toward the target. The angle φ formed by the scanning light 14 and the Z axis changes depending on the decelerated angular displacement of the conversion mechanism 11. Although not shown, a first drive unit for rotationally driving the first vibrating member 3 about the first shaft 4 and the second vibrating member 6 about the second shaft 7 are provided. And a second drive unit that rotationally vibrates. The second drive unit is mounted on the first vibrating member. The return light 15 parallel to the third axis 10 is reflected by the concave mirror 1 and then collected and detected by the light receiving element 9.

[0011]

The operation of the present invention will be described in detail with reference to FIG. The plane mirror 12 mounted on the conversion mechanism 11 is arranged so as to be inclined with respect to the first axis 4, and its inclination angle changes. Therefore, the scanning light 14 is angularly scanned along the XZ plane. On the other hand, of the light reflected from the target, the return light 15 parallel to the third axis 10 is reflected and condensed by the concave mirror 1. The geometrical condition for the light to be received by the light receiving element 9 is that the third axis 10 and the scanning light 14 always remain parallel. By the way, incident light, that is, laser beam 1
When the normal line is angularly displaced in a plane including 3 and the normal line of the plane mirror 12, that is, the XZ plane, the angular displacement of the emitted light, that is, the scan light 14 is doubled. Therefore, a mechanism for multiplying the mechanical angular displacement, that is, a conversion mechanism 11 is used to set the angular displacement of the light receiving element 9 and the angular displacement of the scanning light 14 to be the same. In this way, the parallelism between the scanning light 14 and the third axis 10 is always maintained.

In the illustrated example, the second vibrating member 6 is composed of a fan gear, and its rotation shaft is fixed to the first vibrating member 3 and coincides with the second shaft 7. The light receiving element 9 is attached to the fan gear via the arm 8. On the other hand, the conversion mechanism 11 is also composed of a fan gear, and its rotating shaft 16 is fixed to the first vibrating member 3. The teeth formed on the inner circumference of the outer fan gear (11) mesh with the teeth formed on the outer circumference of the inner fan gear (6) described above. The outer gear has twice the number of teeth as the inner gear. It should be noted that the outer gear has a relief groove 1
7 are formed. The plane mirror 12 is attached to the outer gear, that is, the conversion mechanism 11, reflects the laser beam 13 parallel to the first axis 4 (X axis), and the scanning light 14 passes through the spherical center point 5 and the light receiving element 9. It is installed so as to be parallel to the third axis 10. When the second vibrating member 6, that is, the inner fan gear is rotationally vibrated about the second shaft 7, the angular displacement of the plane mirror 12 is always 1/2 of the angular displacement of the light receiving element 9, so that the scanning light 14 and the third The axes 10 of are always parallel.
Therefore, the return light 15 is always focused on the light receiving surface of the light receiving element 9.

The above is the optical scanning along the XZ plane. Next, the optical scanning along the YZ plane orthogonal to this will be described. FIG. 2 is a perspective view of the two-dimensional optical scanning device shown in FIG. However, the second vibrating member and the conversion mechanism are not shown in order to make the drawings easy to see.
The above-mentioned plane mirror 12 is arranged on the end face portion of the first vibrating member 3 in an inclined posture of, for example, 45 ° with respect to the first axis 4, that is, the X axis. The first vibrating member 3 is rotationally vibrated bidirectionally about the X axis by the first driving means, that is, the galvanometer 19. The laser beam 13 emitted from the laser light source 18 along the X axis is reflected by the plane mirror 12 that is rotationally oscillated, and is angularly scanned in the YZ plane. Scanning light 14
The scanning angle θ is equal to the rotation angle of the galvanometer 19. At this time, the light receiving element 9 located on the third axis 10 is also displaced at the same rotation angle. Therefore, the parallelism between the scan light 14 and the arm portion 8 is always maintained, and the return light 15 is reflected and condensed by the concave mirror 1 and then received by the light receiving element 9. Like this
Since the scanning light 14 is simultaneously scanned along the YZ plane and the XZ plane, two-dimensional scanning is possible.
In addition, when scanning along the YZ plane,
Since the normal line of the plane mirror 12 is kept constant with respect to the first axis 4, that is, the X axis, no angular displacement conversion mechanism is required unlike the scanning in the XZ plane.

FIG. 3 is a geometrical optical view on an arbitrary plane including the Z axis. In the figure, the outer circle 20 is drawn along the spherical reflecting surface of the concave mirror. Also, the inner circle 21
Is drawn along the movement trajectory of the light receiving element 9.
The return light 15 that passes through the sphere center point 5 and is parallel to the third axis 10 is reflected by the concave mirror and is condensed on the light receiving element 9 located at the midpoint of the sphere radius on the third axis 10. This geometrical optical relationship holds when the return light 15 is near the third axis 10. As the return light 15 moves away from the third axis 10, the condensing point shifts from the light receiving element 9 toward the reflection surface of the concave mirror. However, this error does not pose a problem in practice, and can be solved by providing a margin in the light receiving area size of the light receiving element 9.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 4 is a schematic diagram showing a first embodiment of a two-dimensional optical scanning device according to the present invention. A concave mirror 32 having a spherical reflecting surface 31 is fixedly installed. A plate-shaped vibrating member 34, which rotatively vibrates about a spherical diameter axis, that is, a first axis 33, which is opposed to the concave mirror 32, is provided. The first vibrating member 34 is connected via a shaft 35 to a first drive unit (not shown) such as a galvanometer. The second vibrating member 3 is provided on the surface of the plate-shaped vibrating member 34.
6 is mounted. The second vibrating member 36 is fixed to the first vibrating member 34 and is located at the center point of the sphere.
Rotationally oscillates about a second axis 37 (perpendicular to the paper surface) orthogonal to The vibrating member 36 has fan-shaped outer teeth.
Further, an angular displacement conversion member 38 is mounted. The conversion member 38 is a rotary shaft 3 fixed to the first vibrating member 34.
It is rotatable about 9. The conversion member 38 has fan-shaped inner teeth and meshes with the outer teeth of the second vibrating member 36 described above. The internal teeth have twice as many teeth as the external teeth. The light receiving element 40 is connected to the second vibrating member 3 via the arm portion 41.
It is attached to 6. The light receiving element 40 is arranged at the center point of the radius of the sphere on the third axis 42 orthogonal to the second axis 37 at the center of the sphere. The light receiving surface is a concave mirror 3
Face to face 2. A plane mirror 43 is attached to the conversion member 38 so that the laser light 45 emitted from the light emitting source 44 in parallel with the first axis 33 can be reflected to generate the scan light 46 parallel to the third axis 42. It is arranged to adjust. Since the return light 47 from the target is substantially parallel to the third axis 42, it is always focused on the light receiving surface of the light receiving element 40. The electric output from the light receiving element 40 is guided to an electronic circuit (not shown) via a flexible lead wire.

A hollow coil 48 is fixed to the angular displacement converting member 38, and a fork magnet 49 is fixed to the first vibrating member 34. One pole of the magnet 49 is inserted inside the hollow coil 48 and constitutes a second drive unit. The end of the coil 48 is connected to an electronic circuit via a flexible lead wire.

When an alternating current is passed through the hollow coil 48, the coil 48 receives a vertical driving force by the action of the magnetic flux generated between the pole gaps of the fork-shaped magnet 49 and the current of the coil 48. Therefore, the angular displacement converting member 38 rotationally vibrates in the vertical direction and transmits the torque to the second vibrating member 36. The angular displacement of the second vibrating member 36 is set to twice the angular displacement of the converting member 38, and the scanning light 46 and the third axis 42 are always kept parallel. At the same time, the first vibrating member 34 is rotationally vibrated bidirectionally about the first shaft 33. In this way, the scanning light 46 is two-dimensionally scanned. Note that, in FIG. 4, the respective constituent elements mounted on the first vibrating member 34 are illustrated as partially blocking the return light 47, but in reality, they are made small and thin, and the respective constituent elements are formed. The light-shielding area can be made sufficiently small by devising the arrangement of the elements.

In addition to the above-mentioned embodiments, there are various types of angular displacement conversion mechanisms, which will be exemplified below. FIG. 5 shows a configuration in which the principle of leverage is applied. A plate-shaped first vibrating member 52 is attached to the shaft 51 of the galvanometer. An L-shaped second vibrating member 53 is mounted on the first vibrating member 52. The L-shaped vibrating member 53 is rotatable bidirectionally about a second shaft 54 fixed to the plate-shaped vibrating member 52. L-shaped vibrating member 53
An operating pin 55 is planted at the tip of the. A fulcrum pin 56 is planted at the tip of the plate-like vibrating member 52. The operation pin 55 and the fulcrum pin 56 are implanted in parallel with the second shaft 54 and are arranged on the same circumference centered on the second shaft 54. A lever member 57 is incorporated, and the fulcrum pin 56 is the center of rotation. A sliding slit 58 is provided at the tip of the lever member 57 and engages with the operating pin 55 to follow this movement. The angular displacement of the lever member 57 is half the angular displacement of the L-shaped vibrating member 53 according to the principle of leverage. A plane mirror 59 is mounted on the top of the lever member 57.

FIG. 6 shows an angular displacement conversion mechanism using a pulley. A plate-shaped first vibrating member 62 is attached to the shaft 61 of the galvanometer. The vibrating member 62 rotationally vibrates bidirectionally about the first shaft 63. A small diameter pulley 65 is fixed to a second shaft 64 fixed to the vibrating member 62. A large-diameter pulley 66 is also mounted adjacent to this. The radius of the large-diameter pulley 66 is twice that of the small-diameter pulley 65. The pair of pulleys are connected via a belt 67. A light receiving element 69 is attached to the small diameter pulley 65 along the third shaft 68. On the other hand, a plane mirror 70 is attached to the large-diameter pulley 66. The scan light 71 and the third axis 68 are parallel to each other, and the angular displacement amounts are also equal.

FIG. 7 is a schematic diagram showing a second embodiment of a two-dimensional optical scanning device according to the present invention, in which two-dimensional scanning is performed by directly rotating and oscillating a light emitting source such as a laser diode without using a plane mirror for scanning. It is structured to do. A plate-shaped first vibrating member 74 is attached to the tip of the galvanometer shaft 73. The vibrating member 74 rotationally vibrates bidirectionally around the first shaft 75. The second shaft 76 fixed to the first vibrating member 74
A second vibrating member 77 is rotatably attached to. A light emitting source 78 is directly mounted on the top of the second vibrating member 77. This light emitting source 78 is a laser diode 79.
It is composed of a collimator lens 80 and a lens barrel 81 that houses them, and is connected to an external drive circuit via a flexible lead wire 82. Second vibrating member 77
A hollow coil 83 is fixed to the side portion of the. Further, a U-shaped magnet 84 is fixed on the first vibrating member 74. The second vibrating member 77 rotationally vibrates about the second shaft 76 by the interaction between the coil 83 and the magnet 84. When the output light 85 from the light emitting source 78 is adjusted so as to be parallel to the third axis 86, the return light 87 is reflected and condensed by the reflecting surface 89 of the concave mirror 88 and is constantly detected by the light receiving element 90.

[0021]

As described above, according to the present invention, the two-dimensional optical scanning can be speeded up by providing the scanning plane mirror and the light receiving concave mirror separately, and downsizing the scanning plane mirror. There is an effect.
Further, since the concave mirror having excellent light collecting efficiency is used for receiving light, there is an effect that it is not necessary to use a collecting lens as in the conventional case. Furthermore, by rotating and oscillating the light emitting source itself including the laser diode and the collimator lens, the plane mirror for scanning can be eliminated, and the structure can be simplified.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic structure of a two-dimensional optical scanning device according to the present invention.

FIG. 2 is a perspective view for explaining the operation of the two-dimensional optical scanning device shown in FIG.

FIG. 3 is a geometrical optical diagram for explaining the same operation.

FIG. 4 is a schematic view showing an embodiment of a two-dimensional optical scanning device according to the present invention.

5 is a schematic view showing a modification of the angular displacement conversion mechanism used in the embodiment shown in FIG.

FIG. 6 is a schematic view showing another modification of the same.

FIG. 7 is a schematic view showing a second embodiment of the two-dimensional optical scanning device according to the present invention.

FIG. 8 is a schematic perspective view showing an example of a conventional two-dimensional optical scanning device.

[Explanation of symbols]

 1 concave mirror 2 spherical reflecting surface 3 first vibrating member 4 first axis 5 sphere center point 6 second vibrating member 7 second axis 9 light receiving element 10 third axis 11 conversion mechanism 12 plane mirror 13 laser beam 14 scan Light 15 Return light 18 Laser light source 19 Galvanometer 48 Hollow coil 49 Fork type magnet 78 Light emitting source

Claims (2)

[Claims] 1. A two-dimensional optical scanning device that two-dimensionally rotationally oscillates one plane mirror to project a light beam to detect scattered light reflected from a target and detect the scattered light. A concave mirror having a reflection surface of, a first vibrating member having a sphere diameter on a plane including the sphere center point and facing the concave mirror as a first axis, and rotating and vibrating about the first axis, A second vibrating member fixed to the first vibrating member, having a second axis orthogonal to the first axis at the sphere center point, and vibrating rotationally around the second axis; The second vibration is fixed to the second vibrating member, and the sphere radius perpendicular to the second axis at the sphere center point is the third axis, and the second vibration is on the third axis at a substantially midpoint of the sphere radius. A light-receiving element attached to a member, the light-receiving surface of which is oriented toward the concave mirror; A conversion mechanism provided between the one vibration member and the second vibration member so as to obtain an angular displacement of 1/2 of the angular displacement of the second vibration member, and a conversion mechanism provided on the conversion mechanism. A plane mirror installed so as to reflect a light beam incident along the first axis parallel to the third axis, and the first vibrating member rotationally vibrating about the first axis. A two-dimensional optical scanning device comprising: a first driving unit that drives and a second driving unit that rotationally vibrates the second vibrating member about the second axis. 2. A two-dimensional optical scanning device for two-dimensionally scanning a light beam and receiving and detecting scattered light reflected from a target, comprising: a concave mirror having a reflective surface in which a part of a spherical surface is cut off. A first oscillating member that rotationally oscillates around the first axis, with a sphere diameter lying on a plane including the sphere center point and facing the concave mirror as a first axis, and fixed to the first oscillating member. A second vibrating member having a second axis orthogonal to the first axis at the sphere center point and rotationally vibrating around the second axis; and fixed to the second vibrating member, A sphere radius orthogonal to the second axis at the sphere center point is defined as a third axis, and the light receiving surface is attached to the second vibrating member at a substantially midpoint of the sphere radius on the third axis. A light-receiving element installed in the direction of the concave mirror, and attached to the second vibrating member. A light emitting portion whose output optical axis is set parallel to the third axis and which is installed so as to emit scanning light in a direction opposite to the light receiving element; A two-dimensional optical scanning device comprising: a first drive unit that is rotationally driven around the center of the second drive unit; and a second drive unit that is rotationally driven about the second axis of the second vibrating member. ..