JP2983088B2 - Optical deflector array - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small mechanical optical deflector array.

[0002]

2. Description of the Related Art Conventionally, optical deflectors that are mainly used include an acousto-optic type optical deflector utilizing distortion of a crystal due to ultrasonic waves and an electro-optical type optical deflector utilizing a change in refractive index of a crystal due to an electric field. Or a mechanical optical deflector using a galvanometer, a rotating mirror, or the like.

[0003] Above all, a mechanical optical deflector can perform equiangular deflection irrespective of the wavelength of light, and is therefore very useful when a multi-wavelength light source is used or when the light source has wavelength fluctuations. Further, in order to obtain a stable rotation speed and a highly accurate deflection angle, a rotating shaft is made heavy and a large electromagnet is used for a rotor.

On the other hand, various studies have been made for the purpose of weight reduction and miniaturization. In recent years, very small optical deflectors based on micromechanics technology using a silicon process have been proposed. There are two forms of this proposal, one is a cantilever type (KEPetersen, Applied Physics Letters,
Vol. 31, P521, 1977), and the other one is a double-supported beam type (K.
E. Petersen, IBM J. Res. Devove., Vol. 24, P631, 1980). Of these, a spatial light deflector (Larry Jay Hornbeck, Japanese Patent Application Laid-Open No. 2-8812) is known as the double-supported beam type in consideration of improvement of optical efficiency and bending stability.

FIG. 14 is a perspective view showing a partial cross section of one pixel of the spatial light deflector. In FIG. 14, a pixel 1 has a configuration in which a reflective surface is formed by two bendable beams based on monolithic silicon. That is, the insulating spacer 4, the metal hinge layer 5, and the metal beam layer 6 are stacked on the silicon substrate 2 via the insulating layer 3. That is,
To change the angle of the flexible beam 7 and the flexible beam 8 in the same layer as the metal hinge layer 5, the reflecting surface 9 in the same layer as the metal beam layer 6, and the reflecting surface 9 through a gap below the reflecting surface 9. , A fixed electrode for driving 10, a fixed electrode 11, and a fixed electrode 12.

For example, when a voltage is applied to the fixed electrode 11, an electrostatic force is generated between the reflecting surface 9 and the fixed electrode 11, and the flexible beams 7 and 8 are twisted, and a bending angle is generated on the reflecting surface 9. Light incident on the surface 9 is deflected by obtaining a reflection angle corresponding to the amount of deflection angle. Such an optical deflector is configured to deflect light only in one axis, and can be manufactured by a silicon process based on the silicon substrate 2. Therefore, it can be manufactured at a relatively low cost, and it is considered to be applied to a printer such as electrostatic printing or a projection type display by two-dimensionally arranging and arraying them on the silicon substrate 2. .

[0007]

However, the above-described optical deflector can form a line or two-dimensional image only by forming an array, but its application as a single pixel is limited. . In addition, since light is not reflected in the gap 13 between pixels required to form the flexible beams 7 and 8, there is a very large problem that the image becomes a dark portion on an image.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide an optical deflector array that enables light reflection in two axial directions independently by individual light deflectors and eliminates dark areas on an image by arranging a plurality of light deflectors two-dimensionally. is there.

[0009]

According to a first aspect of the present invention, there is provided an optical deflector array comprising a plurality of optical deflectors arranged two-dimensionally on the same substrate. , A first movable portion supported by a first rotating shaft,
A second movable part supported by a second rotational axis in a direction orthogonal to the rotational axis of the second movable part, and a reflection surface is provided on the second movable part;
A plurality of fixed electrodes opposed to each other via a gap are provided on the lower surface of the two movable parts, and a voltage is applied to these fixed electrodes to separate the first and second movable parts independently by the two rotation axes. Rotatable, and the reflecting surfaces of all of the optical deflectors are rotated in the scanning direction by the first or second rotation axis, and all of the optical deflectors are rotated by the second or first rotation axis. The reflecting surface is swung in a direction orthogonal to the scanning direction.

[0010]

The optical deflector array having the above-described configuration deflects the reflecting surfaces of the plurality of optical deflectors in the scanning direction and eliminates dark portions on the image by deflecting the light in the direction perpendicular to the scanning direction.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a perspective view of an optical deflector 21 composed of one pixel. The light deflector 21 is made of a substrate having electrical conductivity, and a flexible beam 23 is provided inside the outer frame 21.
An inner frame 25 supported by 24 is provided, and a reflection plate 28 is supported inside the inner frame 25 by flexible beams 26 and 27 in a direction orthogonal to the flexible beams 23 and 24. Here, the positions of the centers of gravity of the rotation axes of the reflection plate 28 and the inner frame 25 are set to be the same, and the flexible beams 26 and 27 are provided on the AA axis shown in the figure and can rotate around the y axis. The flexible beams 23 and 24 are provided on the BB axis and are rotatable around the x axis.

FIG. 2A is a sectional view taken along the line AA in FIG.
(b) is a BB cross-sectional view, in which an insulating spacer 30 corresponding to the thickness of the gap below the reflection plate 28 and the inner frame 25 is provided,
Below the fixed electrodes 31, 32, 33, and 34, and a support 35 that supports these fixed electrodes 31 to 34 are provided.

FIG. 3 is a plan view of the optical deflector 21. The patterns of the fixed electrodes 31 to 34 are arranged so as to face the reflection plate 28 and the inner frame 25, respectively, as shown by dotted lines.

In such a configuration, as shown in FIG. 2A, the inner frame 25 has fixed electrodes 31, 32 provided on the lower surface.
When a voltage is applied to one of the fixed electrodes 33 and, the reflective plate is bent by the flexible beams 23 and 24 as a rotation axis due to an electrostatic force. In FIG. When a voltage is applied, the flexible beams 26 and 27 receive electrostatic force.
Is used as a rotation axis.

FIGS. 4 and 5 are explanatory diagrams of the operation of the optical deflector 21 when a voltage is applied to the fixed electrodes 31 to 34. FIG. When a positive voltage is applied to the fixed electrode 31 shown in FIG. 3, the reflector 28 rotates around the flexible beams 23 and 24 by .theta.1 in the y direction as shown in FIG. , The light beam is deflected by 2.times..theta.1 in the y direction. Similarly, when a positive voltage is applied to the fixed electrode 33 shown in FIG. 3, as shown in FIG.
8 and the inner frame 25 rotate in the x-axis direction,
× θ2.

The angle at which the reflection plate 28 bends depends on the angle of the flexible beam 2.
Reflector 28, inner frame 2 when 3, 24, 26, 27 are twisted
It is determined by the balance between the restoring force due to the spring constant of 5 and the rotational moment due to the electrostatic force generated by applying a voltage to the fixed electrodes 31 to 34.

As is clear from the above description, in the optical deflector 21 according to the present embodiment, the reflection plate 2 in the -y or -x direction is used.
The deflection angle of 8 can be obtained by applying a voltage to the fixed electrode 32 or the fixed electrode 33. Therefore, it is possible to bend the reflecting plate 28 in a free direction on the xy plane. For example, when it is desired to bend in the first quadrant direction on the xy plane, the reflection electrodes 28 An appropriate voltage may be applied to both at the same time.

Next, the manufacturing process of the optical deflector 21 will be specifically described. FIG. 6 is a schematic view showing a manufacturing process of the outer frame 22, the inner frame 25, the reflection plate 28, and the flexible beam. As shown in FIG. Si ₃ N ₄ films 4 on both surfaces of substrate 40 by CVD) method
1 and 42 are formed. As the Si substrate 40, a substrate having a small resistance that generates an electrostatic force when a voltage is applied to the fixed electrode is used. Next, an opening is patterned on the Si ₃ N ₄ film 42 on one side by photolithography. Next, as shown in FIG. 6B, a Si membrane 43 is manufactured by anisotropic etching utilizing an etching rate difference between Si crystal orientation planes. The anisotropic etching at this time is performed by heating a KOH aqueous solution. Thereafter, as shown in FIG. 6C, when the membrane 43 is removed from the other surface of the Si substrate 40 by reactive ion etching (RIE) using a reactive gas such as SF ₆ , CF _4, etc. The beams 26 and 27, the reflection plate 28, and the inner frame 25 are formed. Finally, when the Si ₃ N ₄ films 41 and 42 are removed by RIE, a reflector 28 and flexible beams 26 and 27 as shown in FIG. 6D are obtained.

FIG. 7 is a schematic view showing the steps of manufacturing the insulating spacer and the fixed electrode. As shown in FIG.
For 5, an Si substrate having an insulating layer such as a Si ₃ N ₄ film 44 formed on the surface is used, and a metal thin film 45 having electrical conductivity such as Al is deposited on one surface thereof by a vacuum evaporation method.
Next, the metal thin film 45 is patterned by photolithography as shown in FIG.
1 and 32 are formed. Further, as shown in FIG. 7 (c), an insulating material 46 such as glass is formed on the fixed electrodes 31 and 32 by a vacuum evaporation method, and is patterned to form a film shown in FIG.
An insulating spacer 30 as shown in FIG. 1D is manufactured, and the distance between the reflector 28 and the fixed electrodes 31 and 32 is determined by the thickness of the insulating spacer 30.

The outer frame 22, the inner frame 25, the reflecting plate 28 and the flexible beams 23, 2 manufactured by the processes shown in FIGS.
Substrate 40 having 4, 26, 27 and fixed electrodes 31 to 3
By joining the support 35 on which the 4 is formed, the optical deflector 21 as shown in FIG. 8 can be completed. At this time, the bonding method includes anodic bonding (Esashi, Sensors and Actuat
or, A21-A23, P931, 1990), and using a glass material (Corning's # 7740) that can be bonded at a low temperature as the insulating material so that the fixed electrode is not thermally damaged. Spacer 30 that can be anodically bonded by
Is formed.

FIGS. 9 to 11 are schematic views showing another manufacturing process of the optical deflector. These steps further facilitate the fabrication of an array of optical deflectors as compared to the steps described above.

FIG. 9 shows a process of manufacturing layers used for insulating spacers, fixed electrodes, and flexible beams. As shown in FIG. 9A, a high resistance or P-type Si substrate is used as a support 35, and ion implantation is performed. Thereby, n ⁺ -type fixed electrodes 31 and 32 having low resistance are formed on the Si substrate. Next, FIG.
As shown in FIG. 3, an insulating thin film such as SiO _{2 is applied} by high frequency sputtering or CVD to form an insulating spacer 3.
0 is formed. On this insulating spacer 30, FIG.
The sacrificial layer 4 to be removed in the final step as shown in FIG.
6 and a metal thin film 4 serving as a flexible beam as shown in FIG.
7 is formed.

FIG. 10 shows a manufacturing process of the flexible beam and the reflection plate 28. As shown in FIG. 10A, a metal thin film 48 is further formed on a metal thin film 47 and patterned. In the patterning, the metal thin film 47 is formed using the resist 49 as a mask.
Then, the metal thin film 48 is removed by masking the resist 49 while leaving the reflection plate 28 as shown in FIG. 10B. Finally, as shown in FIG.
9 'is removed to form flexible beams 26 and 27.

FIG. 11 is a schematic view showing a manufacturing process of the gap. As shown in FIG. 11A, the sacrificial layer 46 on the lower surface of the reflector 28 and the flexible beam manufactured in the previous step is removed by etching,
After forming a gap corresponding to the thickness of the sacrificial layer 46, FIG.
As shown in FIG. 7, the insulating spacer 30 on the lower surface of the sacrificial layer 46 is removed by etching.

In the above-described manufacturing process, the fixed electrode 3
It is necessary to consider the etching selectivity of the insulating spacers 30, the sacrificial layer 46, and the metal thin films 47 and 48. As an example, the insulating spacer 30 is made of SiO ₂ ,
The sacrificial layer 46 can be manufactured using ZnO, and the metal thin films 47 and 48 can be manufactured using a two-layer thin film in which Au is provided on a Cr layer having a thickness of several tens angstroms. In removing the metal thin films 47 and 48 in the process of FIG.
The etching may be performed by RIE using a KI aqueous solution and using CCl ₄ gas for Cr. That is, this etching may be performed once for forming the flexible beams 26 and 27, and may be repeated twice for forming the reflector 28 and the like. Acetic acid is used to remove ZnO, and the sacrificial layer 46 of ZnO is etched. The insulating spacer 30 may be removed by using buffered hydrofluoric acid, and no etching damage occurs in other layers.

In FIG. 12, a plurality of light deflectors 21 are arrayed on one substrate to form a light deflection array 53. FIG. 13 shows the application of the light deflection array 53 to electrostatic printing. FIG.

In FIG. 13, a beam L 1 from a laser light source 54 is converted into a sheet light L 2 by a first lens system 55 and applied to a light deflection array 53. The reflected light from the reflection plate of the light polarization array 53 passes through the slit 56 and the second lens system 57, and forms a line L on the photosensitive drum 58. Here, since the light deflection array 53 deflects the light around the x-axis as shown in FIG. 5, the sheet light L2 is subjected to the rotation rotated from the sheet light L3 to the sheet light L4.

Since the conventional optical deflector has a flexible beam portion that does not reflect light and a wiring portion between the optical deflectors, it is inevitable that the line L will be shaded by the amount of light. The gap and the flexible beam portion become dark portions on the line L. In order to correct the dark portion, it is necessary to take an undesired means on the image, such as shifting the focus of the imaged light to increase the spot diameter of the light.

However, the optical deflector 21 of this embodiment is
Since the light can be deflected around the y-axis as shown in FIG. 4, the light beam is applied to the photosensitive drum 58 in FIG.
A scanning path L ′ is formed above, and it is possible to eliminate a dark part while maintaining a focus position.

In order to perform the above-mentioned operation by the optical deflector 21, the deflection speed around the y-axis should be made larger than the deflection speed around the x-axis. As a method thereof, vibration may be performed at a resonance frequency determined by the dimensions of the reflection plate 28 and the flexible beams 26 and 27. In addition, since the light can be deflected around two axes, the resolution of an image to be formed can be increased. In other words, when scanning around the y-axis by reversing the deflection speed difference for each axis, by deflecting around the x-axis faster than the scanning speed around the y-axis, a plurality of scans are newly added in the scanning path L ′. And the resolution of the line L can be improved.

[0031]

As described above, in the optical deflector array according to the present invention, the light deflecting units are two-dimensionally arranged, the reflecting surfaces of the respective light deflecting units are deflected in the scanning direction, and are orthogonal to the scanning direction. By shaking in the direction, dark portions on the image are eliminated, and a high-resolution image can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment.

FIG. 2 is a sectional view.

FIG. 3 is a plan view.

FIG. 4 is an explanatory diagram of an operation in a y direction.

FIG. 5 is an explanatory diagram of an operation in an x direction.

FIG. 6 is an explanatory diagram of a manufacturing process.

FIG. 7 is an explanatory diagram of a manufacturing process.

FIG. 8 is a sectional view of an optical deflector.

FIG. 9 is an explanatory diagram of another manufacturing process.

FIG. 10 is an explanatory diagram of a manufacturing process.

FIG. 11 is an explanatory diagram of a manufacturing process.

FIG. 12 is a perspective view of a light deflection array.

FIG. 13 is a configuration diagram of an electrostatic printing apparatus using a light deflection array.

FIG. 14 is a perspective view of a conventional example.

[Explanation of symbols]

 Reference Signs List 21 light deflector 22 outer frame 23, 24, 26, 27 flexible beam 25 inner frame 28 reflector 30 insulating spacer 31, 32, 33, 34 fixed electrode 35 support base 45 light deflection array 50 photosensitive drum

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Osamu Takamatsu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Hirai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Hiroyasu Nose 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Katsuhiko Shinjo 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc. ( 56) References JP-A-56-140316 (JP, A) JP-A-60-107017 (JP, A) JP-A-4-211217 (JP, A) JP-A-3-174112 (JP, A) (58) ) Surveyed field (Int.Cl. ⁶ , DB name) G02B 26/10 101 G02B 26/08

Claims (2)

(57) [Claims] A plurality of optical deflectors are two-dimensionally arranged on the same substrate.
And each optical deflector is supported by a first rotation axis.
In the first movable part, the one orthogonal to the first rotation axis.
A second movable part supported by a second rotating shaft of
A reflection surface is provided on the second movable portion, and a plurality of fixed electrodes facing each other via a gap are provided on the lower surface of the two movable portions, and a voltage is applied to these fixed electrodes to be moved forward by the two rotation axes.
The first and second movable parts can be independently rotated.
And all the light deflections by the first or second rotation axis.
Rotating the reflection surface of the container in the scanning direction,
2 or the first rotation axis allows the counter of all the optical deflectors
An optical deflector array , wherein the projection surface is swung in a direction orthogonal to the scanning direction . Wherein irradiating the light on the reflecting surface, the reflecting surface
Scans the light beam in a direction orthogonal to the scanning direction.
2. The optical deflector array according to claim 1, wherein said optical deflector vibrates at a resonance frequency .