JPH07128608A - Luminous flux scanner - Google Patents

Abstract

PURPOSE:To provide the luminous flux scanner which has a high resolving power and responsiveness and consumes less electric power. CONSTITUTION:A reflection surface is formed on a plane part 13 of a rare earth bonded magnet 10 magnetized toward an arrow 11 and righting couple to reset this magnet 10 to a neutral position is applied to the magnet by righting leaf springs 25, 25a. If the coils in coil grooves 23, 23a are energized by a driving current source 30, the magnet 10 is rotated at the angle meeting this current and the direction of the luminous flux reflecting on the plane part 13 is scanned. The magnetic force is powerful and the reflection surface is integrally formed on the magnet 10 and, therefore, the resolving power and responsiveness are high and the electric power consumption is low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam scanning device (scanner) for controlling the direction of reflection or refraction (diffraction) of a light beam in accordance with an input signal, and more particularly to the direction of a reflecting mirror using an electromagnetic force. The present invention relates to an electromagnetic light beam scanning device that controls according to the above.

[0002]

2. Description of the Related Art Conventionally, as an electromagnetic beam scanning device,
Like a moving coil type ammeter, a moving coil supported rotatably around an axis perpendicular to the magnetic flux is arranged in the magnetic path formed between the magnetic pole gaps of the fixed permanent magnet. There is a device in which a restoring couple is applied by a spring or the like, the reflecting mirror is fixed, and the angle is changed by driving the moving coil to drive the reflecting mirror. Alternatively,
Like a movable magnet type ammeter, a rotatable movable permanent magnet is arranged instead of the movable coil, and a fixed current path parallel to the rotation axis is provided in the magnetic path that sandwiches the movable permanent magnet. There is one that drives a reflecting mirror fixed to a movable permanent magnet by energizing.

On the other hand, in order to control the rotation angle of the reflecting mirror to a target angle, the difference signal between the value detected by the rotation angle sensor and the angle command value is fed back to the drive current of the current path, which is a precise control. Beam scanning is performed. Here, as the rotation angle sensor, an electric capacitance type sensor having a relatively light weight is used.

[0004]

The capabilities required for such a light beam scanning device are high resolution and high responsiveness, and it is necessary that the shake of the reflecting mirror with respect to the target angle be as small as possible. However, in order to improve these capabilities, it is necessary to form a strong magnetic circuit and to increase the current value in order to generate an electromagnetic force corresponding thereto. However, in order to increase the current of the coil arranged in the magnetic path, it is necessary to increase the coil cross-sectional area and reduce the resistance. Increasing the area leads to an increase in the mass of the coil, which increases the inertial performance rate of the moving coil. As a result, under the limited power consumption, the reduction of the inertial performance rate of the coil and the reduction of the ohmic loss are in conflict with each other, and it is impossible to achieve high resolution and high responsiveness.

On the other hand, in the one in which the rotation angle of the reflecting mirror is controlled by the rotation angle sensor, the electric capacity type rotation angle sensor cannot obtain sufficient accuracy with a light weight one having a small inertial performance ratio.
In order to obtain a certain degree of accuracy, it is necessary to use a material having a large inertial performance rate, which is a conflict with the above-mentioned high resolution and high responsiveness.

A first object of the present invention is to provide a light beam scanning device which can obtain a high resolution and a high responsivity without causing a large increase in power consumption, and a second object thereof is a light beam scanning device. It is an object of the present invention to provide a rotation angle sensor capable of accurately detecting a rotation angle without increasing the inertial performance rate.

[0007]

According to a first aspect of the present invention, the magnetic path forming member is supported so as to rotate about a first axis and is attached in a second axial direction orthogonal to the first axis. A magnetized permanent magnet is provided, and a parallel surface parallel to a plane including the first axis and the second axis is provided on a surface of the permanent magnet to form a reflection surface of a light flux on the parallel surface, and Restoration couple means for giving a restoration couple for returning the permanent magnet in one direction around the first axis, and current passing means for generating an electromagnetic force against the restoration couple with respect to the permanent magnet. The technical means to have. In claim 2,
A second parallel surface parallel to the parallel surface is provided on the surface of the permanent magnet, a second reflecting surface is formed on the second parallel surface, and the reflected light of the second reflecting surface causes the permanent magnet to move. It is a technical means to have a rotation angle detecting means for detecting the rotation angle. Each reflecting surface of the light flux in claims 1 and 2 is formed by applying a precision mold or a resin coating on the entire surface of the permanent magnet including parallel surfaces and then mirror-finishing the thin film, and further applying an aluminum coating. be able to.

According to a third aspect of the present invention, the rotation angle detecting means reflects the image of the light receiving diffraction grating dispersed in the second axis direction and the image of the original diffraction grating on the second reflecting surface to form the image on the light receiving diffraction grating. The technical means is provided with an optical system for forming an image to generate moire fringes and a photodetector for detecting the moire fringes. The original diffraction grating includes a first original diffraction grating and a second original diffraction grating whose phase is shifted by 90 degrees at the same pitch as the first original diffraction grating.
The original diffraction gratings of 1 are arranged side by side in the direction perpendicular to the rotation direction, two photodetectors are provided at the imaging positions of the respective original diffraction gratings, and the number of moire fringes of each photodetector is calculated and used as the rotation angle. In a fourth aspect, the technical means is that the permanent magnet is, for example, a rare earth bond magnet such as an NdFeB bond magnet.

[0009]

According to the present invention, in claim 1, the light flux reflecting surface is formed on the surface of the permanent magnet itself, and when the current is not supplied by the current supplying means, the permanent magnet is the restoring couple means. Thus, when it is in a position where it returns to one direction around the first axis and a current is applied, it rotates by an angle deviated from the one direction by a rotation angle corresponding to the current. In the second aspect, since the reflecting surface and the second reflecting surface are parallel to each other, the rotation angle when the permanent magnet rotates is detected by the rotation angle detecting means from the reflection direction of the light reflected on the second reflecting surface. Can do

In the third aspect, when the permanent magnet rotates, the reflected light on the second reflecting surface is displaced in the second axis direction, and the diffraction grating is dispersed in the direction of the displacement. The rotation angle of the permanent magnet can be detected by detecting the moire fringes generated when the light reflected on the surface is imaged on the diffraction grating by the photodetector. According to the fourth aspect, by using the NdFeB bond magnet which is a rare earth bond magnet, the gap magnetic flux density can be increased and the precision molding becomes easy.

[0011]

According to the present invention, in claim 1, since the permanent magnet is magnetized in the direction of the second axis orthogonal to the first axis,
The magnetic flux passes through the magnetic path of the magnetic path forming member and is confined in the magnetic path forming member. The permanent couple is given a restoring couple by the restoring couple means. Therefore, when energized, the permanent magnet rotates at a rotation angle corresponding to the current value, is stable, and does not vibrate. Therefore, high resolution and high responsiveness can be obtained without causing a large increase in power consumption. In the second aspect, since the rotation angle of the permanent magnet is detected by the light reflected by the second reflection surface formed on the surface of the permanent magnet itself, the inertia ratio does not increase due to the member for detecting the rotation angle. .

In the third aspect, since the rotation angle can be detected by detecting the moire fringes due to the diffraction grating with the photodetector, the rotation angle can be detected with high accuracy. According to the fourth aspect, since the gap magnetic flux density can be increased without increasing the inertia factor, a strong magnetic circuit can be formed. Therefore, it is easy to increase the resolution and responsiveness.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on the embodiments shown in the drawings. In the light beam scanning device 1 shown in FIG. 1, 10 is a rare earth bonded magnet as an inertial ellipsoid having a shape cut by two planes parallel to the axis of the cylinder, and on the axis of the cylinder which is the first axis. Rotating shafts 20 are provided above and below.
The rare earth bonded magnet 10 includes a second axis orthogonal to the first axis so that its magnetization direction goes from the side surface 12 that is one outer circumference of the cylinder to the side surface 12a that is the opposite outer circumference, as indicated by an arrow 11. Plane portions 13 and 13a that are magnetized in the direction and are formed on the front and back of the rare earth bonded magnet 10.
Is formed as a plane parallel to the plane including the first axis and the second axis.

The surface of the rare earth bonded magnet 10 is covered with a thin resin coating that also functions as a moisture barrier. This resin coating is for making the flat surface portions 13 and 13a of the rare earth bonded magnet 10 into an optical mirror surface, for example, using a precision mold, or after the resin coating, the flat surface portions 13 and 13a.
An optical mirror surface is obtained by mirror-polishing only 3a. An aluminum coating and a protective coating are further provided on the flat surface portions 13 and 13a provided with the optical mirror surface to integrally form a reflection surface for reflecting the light flux with the rare earth bonded magnet 10. In this embodiment, the flat surface portion 13a does not necessarily have to be finished as a reflecting surface.

A frame body 21 is provided outside the rare earth bonded magnet 10 to form a magnetic path for the magnetic flux generated by the rare earth bonded magnet 10. Side 1 of rare earth bonded magnet 10
The adjacent portions 22, 2 of the frame body 21 are provided on the outer sides of 2, 2a.
2a is provided, and the side surfaces 12, 12a and the proximity portions 22, 22 are provided.
Magnetic gaps 14 and 14a are formed between a and a. In addition, at the center of each of the adjacent portions 22 and 22a, a coil groove 23, which divides each of the adjacent portions 22 and 22a into two, is formed.
23a is formed, and a coil 31 for generating an electromagnetic force acting on the rare earth bonded magnet 10 is arranged in each coil groove 23, 23a (see FIG. 2). The frame body 21 includes an upper frame body 21a and a lower frame body 21b.

The upper and lower ends of the rotary shaft 20 provided in the rare earth bonded magnet 10 are polished to have a conical surface, and the upper frame 21a and the lower frame 21b are provided at the portions corresponding to the respective ends of the rotary shaft 20. The upper pivot receiver 24 and the lower pivot receiver 24a are fixed, respectively, and the rotary shaft 20 is stably supported by the small friction between the respective pivot receivers 24, 24a. Restoration leaf springs 25, 25a for stabilizing the rare earth bonded magnet 10 in a neutral position are provided between the upper frame 21a and the rotary shaft 20. By the above support mechanism, the rare earth bonded magnet 10 is
It will be rotatably supported around a neutral position.

Reference numeral 30 is a drive current source for supplying currents in mutually opposite directions to the coils 31 arranged in the coil grooves 23, 23a. These coil grooves 23, 2
When the coil 31 in the coil 3a is energized, a torque is applied to the rare earth bonded magnet 10 by its electromagnetic force, and this torque is balanced with the restoring force given by the restoring leaf springs 25 and 25a. To rotate.

In the above structure, when the direction orthogonal to the first axis and the second axis is the third axis, the first axis and the third axis
Assuming that the plane including the axis is the incident plane in which the incident light path 90 is provided on the plane portion 13 of the rare earth bonded magnet 10, the plane portion 1
When the rare earth bonded magnet 10 is in the neutral position, the luminous flux irradiating the laser beam 3 becomes reflected light 91 which is reflected in the same plane as the incident plane.
, The rare-earth bonded magnet 10 rotates in accordance with the current value, so that the polarized reflected light 92 forms an angle θ corresponding to the rotation angle with respect to the incident plane, and the current of each coil 31. When the direction is reversed, the deflected reflected light 93 has the reversed deflection direction. As described above, since the reflected light corresponding to the driving current source 30 is obtained, the driving current source 30
By changing the current value of, the reflection direction of the luminous flux can be arbitrarily scanned.

FIG. 2 shows the essential parts of the second embodiment of the present invention. In FIG. 2, the light beam scanning device 1 reflects a light beam incident on the incident light path 90 at the neutral position to the neutral reflection light path 91,
In addition, the rare earth bonded magnet 10 is provided with the rotation angle detection unit 50.
The flat surface portion 13a is formed as a reflecting surface and is used for sensing the rotation angle of the rare earth bonded magnet 10.
Reference numeral 51 denotes a lens which is placed close to the rare earth bonded magnet 10 and parallel to the third axis direction. On the focal plane of the lens 51 in the third axis direction, the cos component original diffraction grating 61 and sin
An original component diffraction grating 62 is placed, and a light source 52 is placed behind it. Further, a light receiving diffraction grating 60 is provided on the focal plane of the lens 51 in the third axis direction,
Behind it, a cos component photodetector 71 and a sin component photodetector 72 are provided in two stages in order to detect the light passing through the light receiving diffraction grating 60. As shown in FIG. 3, the cosine component original diffraction grating 61 and the sin component original diffraction grating 62 are gratings whose phases are mutually shifted by 90 degrees, and the light receiving diffraction grating 60 is a grating whose pitch is equal to these. The cosine component original diffraction grating 61 and the sine component original diffraction grating 62 have a height of two steps, and the width thereof largely spreads in the direction of the rotation angle of the rare earth bonded magnet 10. Reference numeral 80 denotes a rotation angle control device, which issues a rotation angle error signal to the drive current source 30 from the light receiving signals of the respective component light detectors 71 and 72 and the rotation angle command signal.

The original diffraction grating 6 for each component emitted from the light source 52
The light rays that have passed through 1 and 62 pass through the lens 51, are reflected by the flat surface portion 13a as the second reflecting surface formed in parallel with the rear surface of the flat earth portion 13 on the rare earth bonded magnet 10, and again pass through the lens 51. Then, an image is formed on the light receiving diffraction grating 60 placed on the focal plane of the lens 51. That is, at the neutral position of the rare earth bonded magnet, the light beam emitted from the image point O indicated by the tip of the arrow in each of the component original diffraction gratings 61 and 62 is reflected by the plane portion 13a via the outgoing optical path 94, and An image is formed on the neutral image point I on the light receiving diffraction grating 60 via the sex return optical path 95. When the rare earth bonded magnet 10 has a rotation angle θ,
The light ray exiting from the image point O passes through the outgoing optical path 94, and the plane portion 13a.
It is reflected by and is imaged on the deflected image point J on the light receiving diffraction grating 60 through the deflection return optical path.

Therefore, while the rare earth bonded magnet 10 is driven according to the driving current source 30 and the light beam is reflected by the flat surface portion 13 and scanned, the image of the cos component original diffraction grating 61 is received by the light reception diffraction grating 60. The lower half is scanned, and the image of the sin component original diffraction grating 62 is scanned in the upper half of the light receiving diffraction grating 60. In FIG. 3, the portion surrounded by the alternate long and short dash line of the light receiving diffraction grating 60 is the original cos component diffraction grating 6 for a specific rotation angle.
1 is an image of the sin component original diffraction grating 62. In FIG. 3, a boundary part between the cos component original diffraction grating 61 and the sin component original diffraction grating 62 surrounded by a dotted line, and a part surrounded by a dotted line of the light receiving diffraction grating 60 on which the part is projected are enlarged and shown. .

In the above structure, each diffraction grating 60, 6
The diffraction grating pitches of 1 and 62 are the same, and
And the focal length of the lens 51 is f, the change in the total amount of light passing through the lower half of the light receiving diffraction grating 60 is p / 2f.
Is a function of the rotation angle θ, and is approximately cos (4πθf
/ P). This change in the amount of light is detected by the cos component photodetector 71 and added to the cos input terminal of the rotation angle control device 80. The amount of change in the total amount of light that passes through the upper half of the light receiving diffraction grating 60 is a function of the rotation angle θ having a period of p / 2f and is approximately proportional to sin (4πθp / f). This change in the amount of light is detected by the sin component photodetector 72 and added to the sin input terminal of the rotation angle control device 80. The rotation angle control device 80 calculates the rotation angle of the rare earth bonded magnet 10 from these inputs, compares it with a rotation angle command input given by a separate device, and obtains a rotation angle error signal,
It is given to the driving current source 30 as a command input. Thus, when the feedback control loop is closed, the rotation angle is accurately controlled according to the rotation angle command input.

[Brief description of drawings]

FIG. 1 is a perspective view showing an outline of an embodiment of the present invention.

FIG. 2 is a configuration diagram showing an outline of another embodiment of the present invention.

FIG. 3 is a partially enlarged view showing the diffraction grating of the embodiment shown in FIG.

[Explanation of symbols]

 1 Luminous Flux Scanner 10 Rare Earth Bonded Magnet (Permanent Magnet) 11 Magnetization Direction (Second Axis) 13 Flat Surface (Parallel Surface) 13a Flat Surface (Second Parallel Surface) 20 Rotation Axis (First Axis) 21 Frame ( Magnetic path forming member) 25 Restoring leaf spring (restoring couple means) 30 Driving current source (current energizing means) 50 Rotation angle detection unit (rotation angle detection means) 52 Lens (optical system) 60 Light receiving diffraction grating 61 Cos component original diffraction Grating (original diffraction grating) 62 sin component Original diffraction grating (original diffraction grating)

Claims (4)

[Claims] 1. A permanent magnet that is supported inside a magnetic path forming member so as to rotate about a first axis and is magnetized in a second axial direction that is orthogonal to the first axis. And a parallel surface parallel to a plane including the second axis is provided on the surface of the permanent magnet to form a reflection surface of a light flux on the parallel surface, and the permanent magnet is arranged in one direction around the first axis. A light flux scanning device comprising: a restoring couple means for giving a restoring couple for returning; and a current conducting means for generating an electromagnetic force against the restoring couple with respect to the permanent magnet. 2. A second parallel surface parallel to the parallel surface is provided on the surface of the permanent magnet, and a second reflecting surface is formed on the second parallel surface. Reflected light from the second reflecting surface. 2. The light beam scanning device according to claim 1, further comprising a rotation angle detecting means for detecting a rotation angle of the permanent magnet. 3. The rotation angle detecting means forms an image of the light receiving diffraction grating dispersed in the second axis direction and an image of the original diffraction grating into the second diffraction grating.
3. A light beam scanning apparatus according to claim 2, further comprising: an optical system that produces a moire fringe by forming an image on the light-receiving diffraction grating by reflecting the light from the reflection surface of the optical system, and a photodetector that detects the moire fringe. apparatus. 4. The light beam scanning device according to claim 1, wherein the permanent magnet is a rare earth bonded magnet.