JP2924738B2 - Optical deflection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light deflecting device for changing the direction of a light beam.

[0002]

2. Description of the Related 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,
A polygon scanner that changes the direction of reflected light incident on the mirror surface, (2) a galvano scanner that rotates a plane mirror by an actuator, and (3) a disk that has 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 or the like are known.

However, in the above-described polygon scanner, galvano scanner, and holographic scanner, a motor for rotating a mirror or a disk is miniaturized (on the order of millimeters) for reasons such as durability and output torque. It is difficult. Although the miniaturization of motors has been greatly advanced by micromachine technology in recent years, there are still many problems (for example, abrasion in motor bearings) 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 make an optical arrangement such that light from a light source does not interfere with scanning light (reflected light). For this reason, useless space is generated inside the device, and there is a problem in reducing the size of the entire device.

A device that changes the refractive index is suitable for miniaturization without a movable portion such as a motor.
There is a problem that the obtained deflection angle (scanning angle) is narrow, several degrees is the limit, and the application is limited.

[0005]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a light deflecting device which is small and has a large deflection angle.

The transmission type light deflecting device according to the present invention is characterized in that at least two diffraction gratings arranged in parallel and having the same grating interval, the two diffraction gratings described above are relatively moved in a direction perpendicular to their grating surfaces. A support member that supports the two diffraction gratings so that the two diffraction gratings take at least two positions, i.e., a contact position and a position separated from the contact position, and a driving unit that moves at least one of the diffraction gratings in a direction perpendicular to the grating surface It has.

When two diffraction gratings are in contact or in close contact with each other, they are equivalent to one diffraction grating. In a state where the two diffraction gratings are in contact with each other, their slits or irregularities preferably coincide exactly. 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 having undergone one diffraction and the diffracted light having undergone two diffractions have different diffraction angles, so that polarized light having at least two different angles can be obtained.

The reflection type light deflecting device 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 separated from each other in a direction perpendicular to their surfaces. And a driving means for moving at least one of the diffraction grating and the mirror in a direction perpendicular to their surfaces such that the member takes at least two positions, i.e., positions where the diffraction grating and the mirror are separated from the contact position.

Also in the reflection type light deflector, the reflection angle (diffraction angle) of the light reflected from the mirror differs between the case where the diffraction grating is in close contact with the mirror and the case where the diffraction grating is away from the mirror. At least two stages 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 a portion which is elastically deformed. One of the diffraction gratings is fixed to the substrate so as to cover the hole, and the other diffraction grating is supported at both ends by elastically deforming portions of the support.

In a preferred embodiment of the reflection type light deflecting device, the support member includes a substrate and a support portion fixed on the substrate and having a portion that is elastically deformed, and one of the diffraction grating and the mirror is provided. Is fixed to the substrate, and the other end is supported by the elastically deformable portion of the support portion at both ends.

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

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

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

By supporting the diffraction grating or the mirror with a supporting portion including a portion that is elastically deformed, stable operation can be expected without wear.

According to the present invention, since the light deflecting device can be constituted by the diffraction grating (and the mirror), the supporting member and the driving means, it is possible to reduce the size of the device. Further, the change in the deflection angle can be made large. Since the driven diffraction grating is light, ultrahigh-speed operation is possible.
In the transmission type light deflecting device, optical axis adjustment and the like are relatively easy.

According to another aspect of the present invention, there is provided a transmission type light deflecting device comprising: at least two diffraction gratings arranged in contact with each other and having the same grating interval; and at least one of the two diffraction gratings, on a grating surface. A driving means for displacing in a parallel direction is provided.

Two diffraction gratings that are in contact or close contact 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 two diffraction gratings are exactly the same, the number of gratings is equal to the lattice constant of these diffraction gratings. In this manner, since the diffraction angle is determined according to the relative position of the two diffraction gratings, light can be deflected only by moving one of the diffraction gratings in parallel.

This light deflecting device also has the same effects as those described above.

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

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

[0024]

FIG. 1 is a perspective view showing the entire light deflecting device, and FIG.
1 is a sectional view taken along the line II-II in FIG. 1, and FIG. In these figures, the thickness of the apparatus and the distance between slits described later are emphasized considerably more than actual in order to facilitate drawing and facilitate understanding. This is the same in the drawings showing other embodiments described below.

The light deflecting device 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.
And two supports.

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

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

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

Fixed diffraction grating 2a and movable diffraction grating 2b
Is not limited to a silicon substrate with a straight slit 21 cut, for example, a glass plate or other transparent plate on which a number of parallel straight lines made of a thin metal film such as aluminum are deposited at minute intervals, May be a sawtooth-shaped blazed diffraction grating. In the case of a blazed grating, it is possible to obtain only a specific order of diffracted light, for example, + 1st order light, so that the diffraction effect of the light beam can be enhanced. In the case of a diffraction grating using a metal thin film, fixed and movable diffraction gratings are arranged so that the metal thin films face each other.
In the case of a blazed diffraction grating, a fixed and movable diffraction grating is arranged such that the surface on the side opposite to the surface with the sawtooth-shaped teeth faces the other.

The piezoelectric thin film actuator 32 is provided on the thin portion 3a of the support portion 3. Piezoelectric thin film actuator
Reference numeral 32 denotes a piezoelectric layer 35 and two electrode layers 36 and 37 sandwiching the piezoelectric layer 35 from above and below. These electrode layers
External connection electrodes 36a and 37a extend from 36 and 37, respectively. 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, a stress is generated in the piezoelectric layer 35 due to the inverse piezoelectric effect. This stress causes the thin portion 3a to warp downward. As a result, the movable diffraction grating 2b is displaced perpendicularly to the direction of the fixed diffraction grating 2a, the spring portion 31 is extended, and the movable diffraction grating 2b is in contact with the fixed diffraction grating 2a (in FIG. 2, the movable diffraction grating in contact with the fixed diffraction grating 2a). Lattice 2b is shown by dashed lines). When the application of the voltage is stopped, the movable diffraction grating 2b returns to the original position by the restoring force of the spring portion 31.

FIGS. 4A and 4B show the principle of light beam deflection. (A) shows a state in which a voltage is applied to the piezoelectric thin film actuator 32 to bring the diffraction gratings 2a and 2b into contact, and (B) shows a state in which no voltage is applied, that is, the movable diffraction grating 2b is separated from the fixed diffraction grating 2a. Each state is shown.

When the movable diffraction grating 2b is in contact with the fixed diffraction grating 2a, the slits 21a and 21b are vertically aligned. Therefore, in this state, the diffraction grating 2a
And 2b become one diffraction grating. The light beam incident on the diffraction grating receives one diffraction effect. Movable diffraction grating 2
The light beam incident on the upper surface of b and parallel to the normal line 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

Here, λ is the wavelength of the light beam, d is the lattice constant (grating interval) of the diffraction grating, and m is the diffraction order (m = 0, ±
1, ± 2, ...). Only + 1st-order diffracted light is shown in the drawings for simplification (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 is subjected to two diffraction effects. The light beam is a movable diffraction grating 2
When passing through b, it undergoes the diffraction effect shown in Equation 1 and exits at an angle θ. The light beam diffracted by the movable diffraction grating 2b is also subjected to the diffraction effect by the fixed diffraction grating 2a.
Emission angle θ of light beam incident on diffraction grating at incident angle θ
₁ is calculated from the following equation.

Sin θ ₁ −sin θ = mλ / d Equation 2

By substituting Equation 1 into Equation 2, the following equation is obtained. sinθ ₁ = 2mλ / d Equation 3

Therefore, the light beam incident on the movable diffraction grating 2b is converted into the fixed diffraction grating 2 at the angle θ ₁ represented by the equation (3).
a.

By thus bringing the two diffraction gratings 2a and 2b into close contact with each other or separating them, the deflection direction of the light beam can be changed. For example, 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 contact state, and about 23 degrees when separated.
51 degrees, the difference is about 30 degrees.

Preferably, as shown in FIG. 5, an insulating film 53 is formed on one of the surfaces of the fixed diffraction grating 2a and the movable diffraction grating 2b to prevent an electric short circuit when the surfaces 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 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 holes 11 in the substrate 1.

When the movable diffraction grating 2b is brought into close contact with the mirror 4 (FIG. 6A), 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 represented by the equation (1).

When the movable diffraction grating 2b is separated from the mirror 4 and a gap is provided between them (FIG. 6B), the incident light beam is subjected to the diffraction effect by the movable diffraction grating 2b, and is expressed by the following equation (1). Incident on the mirror 4 at the given angle θ. The light beam reflected by the mirror surface 4 is diffracted again by the movable diffraction grating 2b, it will be emitted from the movable diffraction grating 2b at an angle theta ₁ of the formula 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 the plane direction. The fixed diffraction grating 2a is fixed on the substrate, and the movable diffraction grating 2b is moved d / d above the fixed diffraction grating 2a by an actuator (not shown).
2 distances.

The slits 21 of these diffraction gratings 2a, 2b
a, 21b so that the fixed diffraction grating 2
The movable diffraction grating 2b is arranged on the line a. The movable diffraction grating 2b is preferably a fixed diffraction grating 2a when displaced.
Are supported with a slight gap that does not cause friction between them. The two diffraction gratings 2a and 2b are substantially 1
Since one diffraction grating is formed, the diffraction angle of the light beam incident on the diffraction grating is the angle θ represented by the equation (1).

In this state, when the movable diffraction grating 2b is moved in the direction of the grating plane (horizontal direction) by half the slit interval d, the two gratings 2a and 2b reduce the grating interval to d.
/ 2 new diffraction gratings are formed. D in Equation 1 is d / 2
Is replaced by sin θ ₁ = 2mλ (d / 2) = 2mλ / d Equation 4 This is the same expression as Expression 3. Movable diffraction grating 2
By shifting b by d / 2 in the horizontal direction, the light deflection angle can be changed from θ to θ ₁ by the two diffraction gratings 2a and 2b.

Two pairs of diffraction gratings consisting of diffraction gratings 2a and 2b are provided, and the two
A pair of diffraction gratings can be arranged in parallel at an interval. In this case, the light beam can be deflected in two orthogonal directions, and the deflection angle can be changed.

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

The movable diffraction grating 2b is elastically supported by the support 3 via the spring 31. Recess on fixed substrate 1
12 are formed, and the electrode 51 is embedded in the concave portion 12. An electrode 52 is provided on a 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 come into contact with each other. Movable diffraction grating 2
An insulating film 53 may be formed on the surface of the electrode 52 and the electrode b. This insulating film 53 can be formed of a nitride film or an oxide film. When the substrate 1 and the thin portion 3a are formed of silicon, it goes without saying that the electrodes 51 and 52 are provided via an insulator. These electrodes 51 and 52 are connected to a DC power supply by a wiring pattern or a wire.

When a voltage is applied between the electrodes 51 and 52, an electrostatic force is generated and attracted between them. The thin portion 3a supporting the movable diffraction grating 2b by this electrostatic force
Are elastically deformed, and the movable diffraction grating 2b comes into contact with the fixed diffraction grating 2a. When the application of the voltage is stopped, the movable diffraction grating 2b returns to the original position by the restoring force of the spring portion 31.

FIG. 9 is a cross-sectional view corresponding to FIG. 2, showing an embodiment in which the movable diffraction grating 2b is moved by utilizing the difference in thermal expansion between two types of members having different thermal expansion rates.

The movable diffraction grating 2b is elastically supported by the support 3 via the spring 31. Thin part 3 of support part 3
a member 54 having a different coefficient of thermal expansion from the thin portion 3a.
Is glued. The thin portion 3a and the member 54 are heated by irradiating the member 54 with a laser beam or by forming the member 54 with a resistor and passing an electric current. 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 driving mechanism of the movable diffraction grating 2b, the displacement of the movable diffraction grating 2b can be known by monitoring the applied voltage and the like. This makes it possible to determine whether the movable diffraction grating 2b is in close contact with the fixed diffraction grating 2a. Both diffraction gratings 2a, 2b
The displacement of the movable diffraction grating 2b can also be detected based on the capacitance between the movable diffraction grating 2b and the strain resistance of the thin portion 3a.

FIGS. 10A and 10B show an example in which the above-described optical deflecting device is applied to an optical shutter device. FIG. 10A shows a state in which the shutter is opened, and FIG. Each state is shown.

Two diffraction gratings 2a and 2
Only b is shown. These diffraction gratings 2a, 2b
A laser light source 55 and a shutter plate 56 are arranged at positions distant from these with the. A hole 57 is formed in the shutter plate 56.

When the diffraction gratings 2a and 2b are in close contact, 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 is deflected by an angle θ ₁ under the effect of two diffractions. Therefore, the passage of the light beam can be controlled by forming the hole 57 at a position where only the first-order diffracted light having a deflection angle θ passes. A compact optical shutter device and optical filter device are realized.

FIGS. 11A and 11B show an example in which the optical deflection device is applied to an optical switch device. Optical fiber 58a to the light to the light path of the first-order diffracted light having a deflection angle theta is incident from the end surface, the optical fiber 58b as the light is incident from the end face on the optical path of the first-order diffracted light of the deflection angle theta ₁ 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 an optical scanning device is constructed by combining two optical deflection devices. Two diffraction gratings 2a,
Two light deflectors including 2b are arranged so that the directions in which the slits are formed are orthogonal. Laser light source
The light beam emitted from 55 is deflected in two orthogonal directions by these light deflectors. Thus, the light emitted from the two light deflection devices is scanned two-dimensionally.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the entire light deflecting device.

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

FIG. 3 is an enlarged view near a piezoelectric thin film actuator.

FIG. 4 is a sectional view showing the principle of light beam deflection, and FIG.
(B) shows a state where two diffraction gratings are in contact with each other, and (B) shows a state where the two diffraction gratings are separated from each other.

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

FIG. 6 is a cross-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.

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

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

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

FIGS. 11A and 11B show examples in which an optical deflection device is applied to an optical switch 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]

 DESCRIPTION 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 (8)

(57) [Claims] At least two diffraction gratings arranged in parallel and having the same grating interval, a support member for supporting the two diffraction gratings relatively close to and away from each other in a direction perpendicular to their grating surfaces, And a driving means for moving at least one of the diffraction gratings in a direction perpendicular to the grating surface such that the two diffraction gratings take at least two positions apart from the contact position. 2. A diffraction grating and a mirror arranged in parallel, a support member for supporting the diffraction grating and the mirror relatively close to and away from each other in a direction perpendicular to their surfaces, and the diffraction grating and the mirror. A driving means for moving at least one of the diffraction grating and the mirror in a direction perpendicular to their surfaces so as to take at least two positions, ie, positions separated from the contact position. 3. At least two diffraction gratings, which are arranged in contact with each other and have the same grating interval,
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 according to claim 1, wherein a plurality of optical deflecting devices are arranged on an optical path of a light beam. 5. The substrate according to claim 5, wherein said support member has a hole.
A supporting portion fixed on the substrate and having a portion that is elastically deformed, wherein one of the two diffraction gratings is fixed to the substrate so as to cover the hole, and the other diffraction grating is 2. The light deflecting device according to claim 1, wherein both ends thereof are supported by elastically deformable portions of said 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 a mirror. 2. The light deflecting device according to claim 1, wherein both ends are supported by elastically deformable portions of the support portion. 7. A 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. And a shutter plate having a hole on the optical path of the light beam. 8. A 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. Means for receiving a light beam from the optical switch.