JPH0996768A - Light deflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light deflector which is of an extra-small size and has a large deflection angle. SOLUTION: Identical diffraction gratings 2a, 2b in which many slits 21(21a, 21b) having regular intervals and being of straight line shapes are cut are arranged so that slits 21 coincide in this device. A fixing diffraction grating 2a is fixed to a substrate 1. Supporting parts 3 having deformable thin wall parts 3a and support a movable diffraction grating 2b in a both-side holding state through spring parts 31. When the diffraction gratings 2a and 2b are made to be closely adhered by impressing voltages on piezoelectric elements 32 on the thin wall parts 3a, since they become equivalent to one diffraction grating, an incident light beam is emitted by receiving the diffraction effect of one time. In a state in which the diffraction grating 2b is separated from the diffraction grating 2a, the light beam receives diffraction effects of two times.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical deflector for changing the direction of a light beam.

[0002]

BACKGROUND ART Conventionally, as a device for deflecting or scanning a light beam, (1) a polygonal prism whose side surface is a mirror surface is rotated,
Polygon scanner that changes the direction of reflected light incident on the mirror surface, (2) Galvano scanner that rotates a plane mirror with an actuator, (3) Rotates a disk with multiple holographic lenses arranged in the circumferential direction Holographic scanners, (4) Those that change the refractive index of a transparent medium by an electric field are known.

However, in the polygon scanner, the galvano scanner, and the holographic scanner described above, the motor for rotating the mirror and the disk is miniaturized (in the order of millimeters) for reasons such as durability and output torque. Is difficult. Although the miniaturization of motors has been greatly advanced by micromachine technology in recent years, many problems (for example, abrasion in the motor bearing portion) remain for realizing a motor that can be used practically. Further, since the polygon scanner and the galvano scanner are configured to reflect light with a mirror, it is necessary to have an optical arrangement so that the light from the light source does not interfere with the scanning light (reflected light). As a result, a wasteful space is generated inside the device, which is a problem in reducing the size of the entire device.

Further, a device that changes the refractive index is suitable for miniaturization because there is no moving part such as a motor,
The deflection angle (scanning angle) that can be obtained is narrow, and there is a problem that the application is limited because it is limited to several degrees.

[0005]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a small-sized optical deflector having a large deflection angle.

In the transmission type light deflector according to the present invention, at least two diffraction gratings arranged in parallel and having an equal grating interval, and the above two diffraction gratings are relatively arranged in a direction perpendicular to their grating planes. A support member that supports the two diffraction gratings so that they can move closer to and away from each other, and a driving unit that moves at least one diffraction grating in a direction perpendicular to the grating surface so that the two diffraction gratings have at least two positions, a contact position and a separated position. Is equipped with.

When two diffraction gratings are in contact with or in close contact with each other, they are equivalent to one diffraction grating. When the two diffraction gratings are in contact, their slits or irregularities are preferably exactly aligned. The incident light is diffracted once by this one diffraction grating.

When the two diffraction gratings are separated, the incident light is diffracted twice by the two diffraction gratings.

Generally, the diffracted light that has been diffracted once and the diffracted light that has been diffracted twice have different diffraction angles, so that at least two different deflected light beams can be obtained.

The reflection type optical deflector according to the present invention is a support for supporting the diffraction grating and the mirror arranged in parallel, and the diffraction grating and the mirror so as to be relatively close to and away from each other in the direction perpendicular to their planes. A driving means for moving at least one of the diffraction grating and the mirror in a direction perpendicular to the member and the diffraction grating and the mirror is provided so as to take at least two positions of a contact position and a separated position.

Also in the reflection type optical deflector, since the reflection angle (diffraction angle) of the light reflected from the mirror differs depending on whether the diffraction grating is in close contact with the mirror or when the diffraction grating is separated from the mirror. At least two levels of light deflection are possible.

In a preferred embodiment of the above-mentioned transmission type light deflecting device, the supporting member includes a substrate having a hole and a supporting portion fixed on the substrate and having an elastically deformable portion. One of the two diffraction gratings is fixed to the substrate so as to close the hole, and the other diffraction grating is supported at both ends thereof by the elastically deformable portions of the support portion.

In a preferred embodiment of the reflection-type optical deflector, the supporting member includes a substrate and a supporting portion fixed on the substrate and having an elastically deformable portion, and one of the diffraction grating and the mirror. Is fixed to the substrate, and the other end is supported by the elastically deformable portions of the support portion at both ends thereof.

In both of these types of optical deflecting devices, in one embodiment, the driving means includes a piezoelectric element provided on the support portion, and the support portion is deformed by its inverse piezoelectric effect.

In another embodiment, the driving means includes a first electrode provided on the supporting portion and a second electrode arranged on the substrate at a position facing the first electrode. Including, the supporting portion is deformed by the electrostatic force generated between the first and second electrodes.

In still another embodiment, the driving means includes a member having a coefficient of thermal expansion different from that of the support portion provided on the support portion, and the support portion is heated by heating the member and the support portion. It transforms.

By supporting the diffraction grating or the mirror by the supporting portion including the elastically deformable portion, stable operation can be expected without causing wear.

According to the present invention, since the optical deflector can be constituted by the diffraction grating (and the mirror), the supporting member and the driving means, the miniaturization can be achieved. Further, it is possible to make a large change in the deflection angle. Since the driven diffraction grating is light, ultra high speed operation is possible.
With a transmissive optical deflector, adjustment of the optical axis is relatively easy.

In another transmission type optical deflector according to the present invention, at least two diffraction gratings arranged in contact with each other and having the same grating spacing, and at least one of the above two diffraction gratings are provided on a grating surface. A driving means for displacing in a parallel direction is provided.

Two diffraction gratings that are in contact with or in close contact with each other are equivalent to one diffraction grating. The grating constant of this diffraction grating is determined by the relative positional relationship between the two diffraction gratings.
For example, if the slits or concavities and convexities of the two diffraction gratings are exactly the same, the number of grating steps is equal to the grating constants of these diffraction gratings, and if they are exactly half the grating spacing apart, the grating constants are halved. In this way, the diffraction angle is determined according to the relative position of the two diffraction gratings, so that the light can be deflected by simply moving one diffraction grating in parallel.

This optical deflector also has the same effect as described above.

By arranging a plurality of such optical deflecting devices on the optical path of the light beam, an optical deflecting device capable of obtaining a larger deflection angle can be realized.

The optical deflector according to the present invention can be applied to an optical shutter device, an optical switch device and the like.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view showing the entire optical deflector, and FIG.
Is a sectional view taken along the line II-II of FIG. 1, and FIG. In these drawings, for convenience of drawing and for easy understanding, the wall thickness of the device and the spacing of the slits described below are drawn much more emphasized than they actually are. This also applies to the drawings showing other embodiments described below.

The optical deflector comprises a substrate 1, a fixed diffraction grating 2a fixed on the substrate 1, and a movable diffraction grating 2b arranged at a position facing the fixed diffraction grating 2a with a gap.
And elastically supporting the movable diffraction grating 2b at both ends thereof 2
Including one support part.

Fixed diffraction grating 2a and movable diffraction grating 2b
Is a number of linear slits with a lattice constant (lattice spacing) d
It is a transmission diffraction grating of the same shape with 21 engraved. These members are preferably formed from a single crystal silicon substrate and manufactured by microfabrication using silicon micromachine technology.

A hole 11 for passing an incident light beam is formed in the center of the fixed substrate 1. The fixed diffraction grating 2a is fixed on the fixed substrate 1 so as to close the hole 11.

Two supporting portions 3 are fixed on the fixed substrate 1 at positions outside the fixed diffraction grating 2a. The supporting portion 3 has a thin elastic portion 3a, and supports the movable diffraction grating 2b in a cantilevered manner via a spring portion 31. The supporting portion 3, the thin portion 3a, the spring portion 31 and the movable diffraction grating 2b are preferably integrally formed by a silicon substrate. The spring portion 31 is not limited to a double-supported shape, but has another shape, for example, one that supports the movable diffraction grating 2b from four sides, or a diaphragm (thin film) that continuously supports the ends of the movable diffraction grating 2b.
It may be a shape.

Fixed diffraction grating 2a and movable diffraction grating 2b
Is not limited to the one in which the linear slits 21 are formed on the silicon substrate, and one in which a large number of parallel straight lines made of a metal thin film such as aluminum is vapor-deposited at a minute interval on one surface of a transparent plate such as a glass substrate, or a lattice cross section. May be a sawtooth blazed diffraction grating. In the case of the blazed grating, only the diffracted light of a specific order, for example, the + 1st order light can be obtained, so that the diffraction effect of the light beam can be enhanced. In the case of a diffraction grating made of a metal thin film, fixed and movable diffraction gratings are arranged so that the metal thin films face each other.
In the case of the blazed diffraction grating, the fixed and movable diffraction gratings are arranged so that the surface on the opposite side to the surface with the serrated teeth faces.

A piezoelectric thin film actuator 32 is provided on the thin portion 3a of the support portion 3. Piezoelectric thin film actuator
The reference numeral 32 includes a piezoelectric layer 35 and two electrode layers 36 and 37 that sandwich the piezoelectric layer 35 from above and below. These electrode layers
External connection electrodes 36a and 37a extend from 36 and 37. When the thin portion 3a is made of silicon, the electrode layer 37 and the external connection electrodes 36a, 37a are provided via an insulator.

When a voltage is applied to the piezoelectric layer 35, stress is generated in the piezoelectric layer 35 due to the inverse piezoelectric effect. The thin portion 3a warps downward due to this stress. As a result, the movable diffraction grating 2b is displaced perpendicularly to the direction of the fixed diffraction grating 2a, the spring portion 31 extends, and the movable diffraction grating 2b contacts the fixed diffraction grating 2a (in FIG. 2, the movable diffraction grating 2a in contact with the fixed diffraction grating 2a is moved). Lattice 2b is shown in dashed lines). When the voltage application is stopped, the movable diffraction grating 2b returns to its original position due to the restoring force of the spring portion 31.

4A and 4B show the principle of deflection of the light beam. (A) shows a state where a voltage is applied to the piezoelectric thin film actuator 32 to bring the diffraction gratings 2a and 2b into contact with each other, and (B) shows a state where no voltage is applied, that is, the movable diffraction grating 2b is separated from the fixed diffraction grating 2a. The respective states are shown.

When the movable diffraction grating 2b is in contact with the fixed diffraction grating 2a, the slits 21a and 21b coincide with each other in the vertical direction. Therefore, in this state, the diffraction grating 2a
And 2b become one diffraction grating. The light beam incident on this diffraction grating is subjected to one diffraction effect. Movable diffraction grating 2
The light beam that is incident on the upper surface of b and is parallel to the normal P is emitted from the fixed diffraction grating 2a at an emission angle θ represented by the following equation.

Sin θ = mλ / d Equation 1

Where λ is the wavelength of the light beam, d is the grating constant (grating spacing) of the diffraction grating, and m is the diffraction order (m = 0, ±
1, ± 2, ...). For simplification, only the + 1st order diffracted light is shown in the drawings (the same applies to the following drawings).

When the fixed diffraction grating 2a and the movable diffraction grating 2b are separated without applying a voltage, the incident light beam undergoes the diffraction effect twice. Light beam is movable diffraction grating 2
When passing through b, it receives the diffraction effect shown in Expression 1 and exits at an angle θ. The light beam diffracted by the movable diffraction grating 2b is also diffracted by the fixed diffraction grating 2a.
The exit angle θ of the light beam incident on the diffraction grating at the incident angle θ
₁ is calculated from the following formula.

Sin θ ₁ −sin θ = mλ / d Equation 2

Substituting the equation 1 into the equation 2, the following equation is obtained. sin θ ₁ = 2 mλ / d Equation 3

Therefore, the light beam incident on the movable diffraction grating 2b is reflected by the fixed diffraction grating 2 at the angle θ ₁ expressed by the equation (3).
It will be emitted from a.

By thus adhering or separating the two diffraction gratings 2a and 2b, the deflection direction of the light beam can be changed. For example, the wavelength λ
Is 780 nm and the lattice constant d is 2 μm, the diffraction angle of the first-order diffracted light is about 23 degrees in the close contact state, and is about 30 degrees when they are separated.
It is 51 degrees and the difference is about 30 degrees.

Preferably, as shown in FIG. 5, an insulating film 53 is formed on the surface of either the fixed diffraction grating 2a or the movable diffraction grating 2b to prevent an electrical short circuit when they are in close contact with each other.

FIGS. 6A and 6B show an embodiment in which a mirror 4 is provided instead of the fixed diffraction grating 2a.

A mirror 4 is fixed on the substrate 1 instead of the fixed diffraction grating 2a. The direction of light deflection is changed by bringing the movable diffraction grating 2b into close contact with or separating it from the mirror 4. The diffracted light is reflected by the mirror 4 and emitted from the incident side. Therefore, it is not necessary to form the hole 11 in the substrate 1.

When the movable diffraction grating 2b is closely attached to the mirror 4 (FIG. 6 (A)), the light beam incident parallel to the normal P is diffracted by the movable diffraction grating 2b and reflected by the mirror 4. Then, the light is emitted from the movable diffraction grating 2b at the reflection angle θ expressed by the equation 1.

When the movable diffraction grating 2b is separated from the mirror 4 and a gap is provided between them (FIG. 6 (B)), the incident light beam is subjected to the diffraction effect by the movable diffraction grating 2b and is expressed by the equation (1). The light enters the mirror 4 at an angle θ. The light beam reflected by the mirror surface 4 is diffracted again by the movable diffraction grating 2b and is emitted from the movable diffraction grating 2b at the angle θ ₁ expressed by the equation 3. Conversely, the diffraction grating 2b may be fixed and the mirror 4 may be moved.

FIGS. 7A and 7B show an embodiment in which the movable diffraction grating 2b is displaced in its plane direction. The fixed diffraction grating 2a is fixed on the substrate, and the movable diffraction grating 2b is d / s on the fixed diffraction grating 2a by an actuator (not shown).
It is displaced a distance of two.

The slits 21 of these diffraction gratings 2a and 2b
Fixed diffraction grating 2 so that a and 21b are aligned vertically.
The movable diffraction grating 2b is arranged on a. The movable diffraction grating 2b is preferably a fixed diffraction grating 2a when displaced.
It is supported with a slight gap between it and that does not cause friction. The two diffraction gratings 2a and 2b are substantially 1
Since two diffraction gratings are formed, the diffraction angle of the light beam incident on this diffraction grating is the angle θ expressed by the equation 1.

When the movable diffraction grating 2b is moved in this state in the grating surface direction (horizontal direction) by half the slit spacing d, the two diffraction gratings 2a and 2b shift the grating spacing d.
A new diffraction grating of / 2 is formed. D in Expression 1 is d / 2
When it is replaced with, sin θ ₁ = 2mλ (d / 2) = 2mλ / d (4) This is the same formula as Formula 3. Movable diffraction grating 2
By shifting b in the horizontal direction by d / 2, it is possible to change the deflection angle of light from θ to θ ₁ by the two diffraction gratings 2a and 2b.

Two pairs of one pair of diffraction gratings consisting of the diffraction gratings 2a and 2b are provided.
It is also possible to arrange a pair of diffraction gratings in parallel at intervals. In this case, the light beam can be deflected in two orthogonal directions and the deflection angle can be changed.

FIG. 8 shows the movable diffraction grating 2b by electrostatic force.
FIG. 3 is a cross-sectional view corresponding to FIG.

The movable diffraction grating 2b is elastically supported by the support portion 3 via the spring portion 31. Recess on the fixed substrate 1
12 is formed, and the electrode 51 is embedded in the recess 12. An electrode 52 is provided on the surface of the thin portion 3a facing the electrode 51. An insulating film 53 is provided on the surfaces of the fixed diffraction grating 2a and the electrode 51 to prevent an electrical short circuit when the diffraction gratings 2a and 2b contact each other. Movable diffraction grating 2
An insulating film 53 may be formed on the surfaces of b and the electrode 52. The insulating film 53 can be formed of a nitride film or an oxide film. Needless to say, when the substrate 1 and the thin portion 3a are made of silicon, the electrodes 51 and 52 are provided via an insulator. These electrodes 51 and 52 are connected to a DC power source by a wiring pattern or wires.

When a voltage is applied between the electrodes 51 and 52, an electrostatic force is generated between them to attract each other. The thin portion 3a supporting the movable diffraction grating 2b by this electrostatic force
Elastically deforms, and the movable diffraction grating 2b contacts the fixed diffraction grating 2a. When the voltage application is stopped, the movable diffraction grating 2b returns to its original position due to the restoring force of the spring portion 31.

FIG. 9 shows an embodiment in which the movable diffraction grating 2b is moved by utilizing the difference in thermal expansion between two kinds of members having different thermal expansion coefficients, and is a sectional view corresponding to FIG.

The movable diffraction grating 2b is elastically supported by the support portion 3 via the spring portion 31. Thin portion 3 of support portion 3
On the a, a member 54 having a coefficient of thermal expansion different from that of the thin portion 3a
Is glued. The thin-walled portion 3a and the member 54 are heated by irradiating them with laser light, or forming the member 54 with a resistor and passing an electric current therethrough. Member 54 and thin portion 3a
The thin portion 3a is deformed due to the difference in thermal expansion between the movable diffraction grating 2b and the fixed diffraction grating 2a.

In the drive mechanism of the movable diffraction grating 2b described above, the displacement amount of the movable diffraction grating 2b can be known by monitoring the applied voltage and the like. This makes it possible to determine whether or not the movable diffraction grating 2b is in close contact with the fixed diffraction grating 2a. Both diffraction gratings 2a and 2b
It is also possible to detect the amount of displacement of the movable diffraction grating 2b based on the capacitance between them and the strain resistance of the thin portion 3a.

10 (A) and 10 (B) show an example in which the above-mentioned optical deflecting device is applied to an optical shutter device. FIG. 10 (A) shows a state in which the shutter is open, and FIG. 10 (B) shows the state in which the shutter is closed. The respective states are shown.

Two diffraction gratings 2a and 2a are used as an optical deflector.
Only b is shown. These diffraction gratings 2a and 2b
A laser light source 55 and a shutter plate 56 are arranged at positions separated from each other across the. The shutter plate 56 has a hole 57.

When the diffraction gratings 2a and 2b are in close contact with each other, the diffraction angle of the light beam emitted from the laser light source 55 is θ. When the fixed diffraction grating 2a and the movable diffraction grating 2b are separated, the light beam undergoes the diffraction effect twice and is deflected by the angle θ ₁ . Therefore, the passage of the light beam can be controlled by forming the hole 57 at a position through which only the first-order diffracted light having a deflection angle of θ passes. A small optical shutter device and optical filter device are realized.

FIGS. 11A and 11B are examples in which the optical deflecting device is applied to an optical switching device. The optical fiber 58a is arranged so that this light is incident on the optical path of the first-order diffracted light having the deflection angle θ from the end surface, and the optical fiber 58b is arranged so that this light is incident on the optical path of the first-order diffracted light of the deflection angle θ ₁ from the end surface. Are arranged respectively. The laser light from the laser light source 55 is switched to the optical fiber 58a or 58b according to the position of the movable diffraction grating 2a. A small optical switch device by light deflection is realized.

FIG. 12 shows an application example in which two optical deflecting devices are combined to form an optical scanning device. Two diffraction gratings 2a,
Two optical deflectors including 2b are arranged so that the directions in which the slits are formed are orthogonal to each other. Laser light source
The light beam emitted from 55 is deflected by these light deflecting devices in two orthogonal directions. As a result, the light emitted from the two light deflectors is two-dimensionally scanned.

[Brief description of drawings]

FIG. 1 is a perspective view showing an entire optical deflector.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is an enlarged view of the vicinity of a piezoelectric thin film actuator.

FIG. 4 is a cross-sectional view showing the deflection principle of a light beam, (A)
Shows the state where the two diffraction gratings are in contact, and (B) shows the state where the two diffraction gratings are separated.

FIG. 5 is an example in which an insulating film is formed on the surface of the diffraction grating.

FIG. 6 is a sectional view corresponding to FIGS. 4A and 4B, showing an embodiment in which a mirror is provided instead of the fixed diffraction grating.

FIG. 7 is a sectional view corresponding to FIGS. 4A and 4B, showing an embodiment in which the movable diffraction grating is moved in the plane direction thereof.

8 is a sectional view corresponding to FIG. 2, showing an embodiment in which a movable diffraction grating is moved by using electrostatic force.

FIG. 9 is a cross-sectional view corresponding to FIG. 2, showing an embodiment in which two members having different coefficients of thermal expansion are joined to move the movable diffraction grating.

10A and 10B show an example in which the optical deflecting device is applied to an optical shutter device.

11A and 11B show an example in which an optical deflecting device is applied to an optical switching device.

FIG. 12 shows an application example in which an optical scanning device is configured by combining a plurality of optical deflection devices.

[Explanation of symbols]

 1 Fixed Substrate 2a Fixed Diffraction Grating 2b Movable Diffraction Grating 3 Support Part 3a Thin Part 21a, 21b Slit 31 Spring Part 32 Piezoelectric Thin Film Actuator

Claims (11)

[Claims] 1. A parallel-arranged at least two diffraction gratings having an equal grating spacing, a support member for supporting the two diffraction gratings so that they can be moved toward and away from each other in a direction perpendicular to their grating planes. And a drive means for moving at least one diffraction grating in a direction perpendicular to the grating plane so that the two diffraction gratings take at least two positions, a contact position and a separated position. 2. A diffraction grating and a mirror that are arranged in parallel, a supporting member that supports the diffraction grating and the mirror so as to be relatively close to and away from each other in a direction perpendicular to their surfaces, and the diffraction grating and the mirror. An optical deflecting device comprising: a driving unit that moves at least one of a diffraction grating and a mirror in a direction perpendicular to a surface of the diffraction grating and a mirror so as to take at least two positions of a contact position and a separated position. 3. At least two diffraction gratings, which are arranged in contact with each other and have an equal grating interval, and said two diffraction gratings.
An optical deflecting device comprising a driving means for displacing at least one of the two diffraction gratings in a direction parallel to the grating surface. 4. An optical deflecting device in which a plurality of the optical deflecting devices according to claims 1 to 3 are arranged on an optical path of a light beam. 5. A substrate in which the supporting member is perforated,
A support portion fixed on the substrate and having an elastically deformable portion, one of the two diffraction gratings is fixed to the substrate so as to close the hole, and the other diffraction grating is The optical deflector according to claim 1, wherein both ends thereof are supported by elastically deformable portions of the support portion. 6. The supporting member includes a substrate and a supporting portion fixed on the substrate and having an elastically deformable portion, wherein one of the diffraction grating and the mirror is fixed to the substrate and the other is The optical deflector according to claim 1, wherein both ends are supported by elastically deformable portions of the support portion. 7. The optical deflector according to claim 5, wherein the driving means includes a piezoelectric element provided on the support portion, and the support portion is deformed by an inverse piezoelectric effect thereof. 8. The driving means includes a first electrode provided on the supporting portion and a second electrode arranged at a position facing the first electrode on the substrate. 7. The optical deflector according to claim 5, wherein the support is deformed by an electrostatic force generated between the first and second electrodes. 9. The drive means includes a member having a coefficient of thermal expansion different from that of the support portion provided on the support portion, and the support portion is deformed by heating the member and the support portion. The optical deflector according to claim 5. 10. The optical deflecting device according to claim 1, a light source for projecting a light beam toward the optical deflecting device, and a predetermined deflection angle emitted from the optical deflecting device. And a shutter plate having a hole on the optical path of the light beam. 11. The light deflecting device according to claim 1, a light source for projecting a light beam toward the light deflecting device, and a predetermined deflection angle emitted from the light deflecting device. An optical switch device having means for receiving a light beam.