JP3427564B2 - Optical scanning device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical scanning device.

[0002]

BACKGROUND ART An optical scanning device is used for scanning an optical beam in a bar code reader, a laser beam printer, an optical scanning type shape recognition sensor and the like.

An example of this type of optical scanning device is shown in FIG. This is disclosed in Japanese Patent Laid-Open No. 4-95917. This optical scanning device is composed of a plate 70 and a piezoelectric actuator 74. The plate 70 is composed of a mirror portion 71 for reflecting the light beam, a vibration input portion 72 for giving vibration from the outside, and an elongated elastic deformation portion 73 connecting these. The mirror portion 71 of the plate 70 is asymmetric with respect to the center line (Z axis) of the elastically deformable portion 73. That is, the center of gravity of the mirror portion 71 is located off the center line of the elastically deformable portion 73. The vibration input unit 72 is fixed to the piezoelectric actuator 74, and the minute vibration generated from the piezoelectric actuator 74 is applied.

The elastic deformation portion 73 has two resonance vibration modes, a twist deformation mode (θ _T direction) twisting around its center line and a bending deformation mode (θ _B direction) bending along the center line. There is. By causing the piezoelectric actuator 74 to generate vibration including the resonance frequencies of these two resonance vibration modes, the elastic deformation portion 73 resonates, and the mirror portion 71 becomes θ.
It vibrates by being amplified in the _T and θ _B directions. As a result, the reflected light of the light that has entered the mirror section 71 from the light source is two-dimensionally scanned. By including only one resonance frequency in the vibration generated by the piezoelectric actuator 74,
One-dimensional scanning of light is performed.

Such an optical scanning device is a laser beam for one-dimensional scanning of bar code reading light in a bar code reader and a laser beam for forming a latent image on the surface of a photosensitive drum in a light beam printer (laser printer). It is used for one-dimensional scanning, two-dimensional scanning when light is projected on an object in a shape recognition device, and the like.

This optical scanning device has a feature that it can be downsized as compared with a galvano scanner in which a plane mirror is rotated by a motor, a polygon scanner in which a polygon mirror is rotated, and the like.

Further, the optical scanning device having the structure shown in FIG. 18 is required to have improved performance such as increasing the scanning angle and reducing the driving voltage of the piezoelectric actuator.

The presence of air resistance is one of the causes of obstacles when trying to increase the scanning angle.
In order to overcome the air resistance and increase the scanning angle, it is necessary to increase the vibration amount of the piezoelectric actuator, and for that purpose, the voltage for driving the piezoelectric actuator must be increased. If a weight is added to the back surface of the mirror section to increase the moment of inertia and increase the scanning angle, the resonance frequency of the elastically deforming section is lowered and the scanning speed of light becomes slow. In the shape recognition device using such an optical scanning device, the amount of information obtained per unit time is reduced.

[0009]

DISCLOSURE OF THE INVENTION An object of the present invention is to increase the scanning angle without lowering the resonance frequency.

The optical scanning device according to the present invention comprises a box-shaped body having a sealed space therein, and at least a mirror portion for reflecting light is attached to the box-shaped body inside the box-shaped body. It is movably supported by an elastically deformable portion having one resonance vibration mode, and the inside of the box-shaped body is decompressed.

In one embodiment, the optical scanning device further includes a vibrating device that applies vibrations including the resonance frequency of the resonance vibration mode to the entire box-shaped body. In a preferred embodiment, the box-shaped body includes a scanner board formed with the mirror section, a rectangular frame section, and the elastically deformable section connecting the mirror section and the frame section, and the scanner board. It is composed of two protective substrates joined to the frame portion so as to be sandwiched therebetween.

According to the present invention, since the internal space of the box-shaped body provided with the mirror portion and the elastically deformable portion is sealed and decompressed, the air resistance received by these is reduced and the resonance frequency is not lowered. The scan angle can be increased. When the optical scanning device is applied to the shape recognition sensor, the amount of information obtained per unit time increases. Further, it becomes possible to reduce the driving voltage. Further, it is possible to prevent the mirror portion from being soiled, and since the corrosive substances and the like from the outside do not adhere to the elastically deformable portion, fatigue resistance is enhanced and reliability of the optical scanning device is improved. Since the inner layer of the box-shaped body functions as a stopper for the mirror portion, it is not necessary to provide a stopper, and it is possible to prevent the displacement of the mirror portion beyond the breaking strain of the elastically deformable portion.

In one embodiment, the scanner substrate and the protective substrate are made of the same material, and are formed in plane symmetry with respect to the center plane of the scanner substrate.

If the materials of the substrates are all the same, the coefficients of thermal expansion are also the same, warpage due to ambient temperature changes does not occur, and changes in the resonance frequency of the optical scanning device due to this are also prevented.

In another embodiment, the scanner substrate is made of silicon. The protective substrate is made of silicon or a material other than silicon.

Since silicon (especially (110) silicon substrate) can be vertically etched with an alkaline etching solution with high precision, it can be processed into a mirror portion and an elastically deformable portion having performance close to the designed value. In addition, since the silicon substrate can be batch processed, the cost in the shape processing process of the optical scanning device is reduced.

In yet another embodiment, a visible light transmitting portion is formed on the wall surface of the box-shaped body facing the mirror portion.

By providing a visible light transmitting portion on the wall surface of the box-shaped body, an inexpensive laser can be used as a light source, so that the cost of the entire optical sensing system including this optical scanning device can be reduced. Becomes Preferably, this visible light transmitting portion is formed of a SiN film. SiN
Since the film has a tensile stress and does not bend, high-precision optical scanning is possible without bending the optical path of the light incident on or reflected from the mirror surface.

In still another embodiment, a lens for collecting the light reflected by the mirror section is provided on the light transmitting section.

Since the light reflected by the mirror portion by the lens has a focal point, when the optical scanning device is applied to a shape recognition sensor, it is possible to selectively collect information about equidistant locations from the optical scanning device. . Preferably, this lens is composed of binary optics (a diffractive Fresnel zone plate). Since it is only necessary to form a pattern that blocks light on the light transmitting portion, the step of bonding the lenses is not necessary, and the lens itself can be manufactured by the semiconductor process, so that the cost can be reduced.

In yet another embodiment, a light receiving element is provided on the surface of the box-shaped body.

By integrating the light receiving element and the optical scanning device, the size of the optical sensing system can be reduced. Preferably, this light receiving element is formed by doping the protective substrate with n-type or p-type impurities. By making the light receiving element forming process common to the protective substrate forming process, the manufacturing process of the entire optical scanning device can be simplified.

In still another embodiment, a movable electrode is provided on at least one surface of the mirror portion, and a fixed electrode is provided on the inner surface of the box-shaped body facing the movable electrode.
The vibration frequency is detected based on the change in capacitance between the movable electrode and the fixed electrode.

This makes it possible to detect the change in the resonance frequency, and by feeding back the detection signal to the piezoelectric actuator (vibration device) that drives the optical scanning device, it is possible to scan the light in the resonance region set in advance. become.

In yet another embodiment, at least one strain detecting element is provided in the elastically deformable portion, and the vibration frequency is detected based on the change in the resistance value of the strain detecting element.

Similar to the embodiment in which the vibration frequency is detected based on the change in capacitance described above, the change in resonance frequency can be detected, and the detection signal is fed back to the piezoelectric actuator that drives the optical scanning device. It becomes possible to always scan the light in the set resonance region.
Preferably, this strain detecting element is a piezoresistive element formed by diffusing p-type or n-type impurities on a silicon substrate. More preferably, at least one piezoresistive element is formed with an inclination of 45 degrees with respect to the axial direction of the elastically deformable portion. When the piezoresistive element is arranged in a direction inclined by 45 degrees with respect to the axial direction of the elastically deformable portion, the sensitivity is highest for the torsional vibration of the elastically deformable portion, so that the optical scanning based on the torsional vibration can be controlled with high accuracy. .

In yet another embodiment, an inert gas is present in the inner space of the box-shaped body.

Strain detection elements such as a mirror section, an elastically deformable section, electrodes for detecting capacitance (movable electrodes and fixed electrodes), piezoresistive elements, etc., which are housed in the inner space of the box-shaped body, do not react with the inert gas. Therefore, there is no fear of deterioration due to chemical reaction, and the life of the optical scanning device is extended.

In still another embodiment, the distance between the mirror portion and the inner surface of the box-shaped body at rest is smaller than the maximum displacement amount of the mirror portion that causes breakage in the elastically deformable portion. It is manufactured so that.

Since the inner surface of the box-shaped body can prevent the displacement of the mirror portion exceeding the breaking strain of the elastically deformable portion, the reliability of the optical scanning device is improved.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view showing an optical scanning device, and FIG.
2 is a sectional view taken along line II-II, and FIG. 3 is a sectional view taken along line III-III in FIG. In FIGS. 2 and 3, the wall thickness is drawn thicker than the actual thickness for convenience of drawing and for easy understanding. This also applies to other drawings (cross-sectional views).

The optical scanning device 1 includes a scanner box-shaped body 2. The scanner box 2 is attached to a piezoelectric actuator 3 for applying high frequency vibration thereto.
The piezoelectric actuator 3 is fixed to a support plate 4 (for example, an electric circuit board).

The scanner box 2 is composed of two protective substrates 30 and 40, and a scanner substrate 20 which is partially sandwiched between and supported by these protective substrates 30 and 40.

Recesses 31 and 41 are formed on the inner surfaces of the two protective substrates 30 and 40, respectively. By this,
A projecting edge exists around the entire inner surfaces of the protective substrates 30 and 40.

On the other hand, the scanner board 20 has a rectangular frame portion 24, a mirror portion (vibrator) 25 formed inside the frame 24 and separated from the frame 24, and an elastic deformation portion (which integrally connects these portions). Beam part) 26.
The frame portion 24 is sandwiched and joined to the projecting edges of the protective substrates 30 and 40 on both sides thereof. One side of the frame portion 24 is slightly wide (this portion is indicated by reference numeral 24a), and the elastic deformation portion 26 integrally extends from the portion 24a. Frame part
The projecting edges of the protective substrates 30 and 40 corresponding to 24a are also formed to have a slightly wider width.

Due to the concave portions 31 and 41 of the protective substrates 30 and 40,
An internal space is formed in which the mirror portion 25 of the scanner board 20 vibrates. This internal space is sealed and decompressed (lower than atmospheric pressure). The internal space may be brought into a state close to a vacuum.

The elastically deforming portion 26 of the scanner substrate 20 is formed to be quite thin and has elasticity, and supports the mirror portion 25 in a cantilevered manner. At least one surface of the mirror section 25 is a mirror surface with respect to the light to be scanned. The mirror portion 25 is asymmetrical about the center line extending in the longitudinal direction of the elastically deformable portion 26. Therefore, the center of gravity of the mirror portion 25 is located off the center line of the elastically deforming portion 26. Therefore, JP-A-4-
Similar to the above-mentioned optical scanner described in Japanese Patent No. 95917, the elastically deformable portion 26 has two resonance vibration modes, that is, a torsional deformation mode and a bending deformation mode.

As will be described later, the scanner substrate 20 and the protective substrates 30 and 40 are made of silicon substrate.
The silicon substrate transmits infrared light. The optical scanning device of this embodiment scans infrared light, and the scanner box 2
Has no window for passing incident light and reflected light. In this case, the mirror surface of the mirror portion 25 of the scanner substrate 20 is formed by a metal having a high melting point (for example, a Pt / Ti layer formed by a vapor deposition process or a sputtering process).

When the piezoelectric actuator 3 is vibrated at a frequency in which the resonance frequency of the torsional deformation mode and the resonance frequency of the bending deformation mode are weighted, the vibration is transmitted from the protective substrate 40 to the frame portion 24a of the scanner substrate 20, and the elastically deformable portion. 26 resonates at these resonance frequencies and vibrates. The mirror section 25 vibrates around two axes orthogonal to each other.

Infrared light projected from the outside through the protective substrate 30 or 40 toward the mirror portion 25 is reflected by the mirror portion 25 and is emitted again through the protective substrate 30 or 40. Mirror section 25
Are oscillated in two directions orthogonal to each other, so that the reflected light from the mirror section 25 is two-dimensionally scanned.

If the vibration frequency of the piezoelectric actuator 3 is set to only one of the above two resonance frequencies, the mirror section 25 vibrates only in one direction (only around one axis). As a result, one-dimensional scanning of infrared light is achieved.

By adjusting the vibration intensity of the piezoelectric actuator 3 and changing the vibration amplitude of the mirror section 25,
It is also possible to adjust the scanning angle of the light beam.

Since the internal space of the scanner box 2 is decompressed, the resistance by the gas when the mirror portion 25 vibrates is small, and the vibration amplitude is large. This increases the light scanning angle. Since it is not necessary to attach a weight or the like to the mirror portion 25, it is possible to avoid the problem that the resonance frequency is lowered by attaching the weight.

When the scanner box-shaped body 2 is given an external shock, the mirror portion 25 may vibrate significantly. If the impact is too large, the elastically deformable portion 26 may be damaged. According to the above configuration, the protective substrate
Since 30 and 40 act as stoppers to prevent damage due to impact, it is not necessary to add new stoppers.

Preferably, the distance between the mirror portion (at a stationary position) and the inner surface of the protective substrate is smaller than the displacement amount of the mirror portion that exceeds the breaking strain of the elastically deformable portion.
As a result, it is possible to prevent the elastically deformable portion from being destroyed when excessive vibration of the mirror portion occurs.

Since the mirror part 25 is completely sealed in the scanner box-like body 2, the mirror part 25 can be prevented from being soiled and the reliability of the optical scanning device is improved. Since corrosive substances from the outside do not adhere to the elastically deformable portion 26, fatigue resistance is improved, and in this respect also, the reliability of the optical scanning device is improved.

It is possible to evenly scrape the surfaces of the mirror portion 25 and the elastically deformable portion 26 by dry etching or the like to provide a gap between the protective substrates 30 and 40 and the mirror portion 25.

The scanner board 20 and the protection boards 30 and 40 are
It is preferably formed by a silicon substrate. This is because silicon (particularly (001) silicon) can be subjected to highly accurate vertical etching with an alkaline etching solution, and by doing so, it can be processed into mirror parts and elastically deformed parts with performance close to the design value. In addition, since the silicon substrate can be batch processed, the cost of the shape processing process of the optical scanning device can be reduced.

The protective substrates 30 and 40 may be formed of a material such as a glass substrate. Preferably, the protective substrates 30 and 40 and the scanner substrate 20 are made of the same material.

More preferably, as shown in FIGS. 2 and 3, with respect to the center plane of the scanner substrate 20 (the plane passing through the center in the thickness direction as indicated by the symbol N), the protective substrates 30 and 40 are provided. And are formed in plane symmetry.

If the materials of the protective substrates 30 and 40 and the scanner substrate 20 are all the same, their thermal expansion coefficients are also the same, so that warpage due to ambient temperature change does not occur, and the optical scanning device is not affected by the warpage. This is because the resonance frequency change is also prevented. If the protective substrates 30 and 40 are plane-symmetric with respect to the center plane of the scanner substrate 20, this effect will be more remarkable. It is best that the scanner substrate 20 and the upper and lower protection substrates 30 and 40 are all formed of silicon substrates.

FIGS. 4 and 5 show the above-mentioned scanner board.
20 shows a manufacturing process of the protective substrate 20 and the protective substrates 30 and 40, respectively. These are sectional views corresponding to FIG.

Referring to FIG. 4, in the manufacturing process of the scanner substrate 20, first, the frame portion 2 on the (110) silicon substrate is formed.
4, a mask is formed on a portion corresponding to the mirror portion 25 and the elastically deforming portion 26 (a portion to be left) (FIG. 4 (A)). The portion of the silicon substrate where the mask is not formed is etched by the alkaline etching solution. By this etching, a wall perpendicular to the surface of the (110) silicon substrate is formed (FIG. 4 (B)). The scanner substrate 20 is completed by removing the mask (FIG. 4C). If necessary, in particular, as described above, when the infrared light is scanned without forming the window on the protective substrate, a reflective film (mirror surface) is formed on the surface of the mirror portion 25 of the scanner substrate 20. .

In the process of manufacturing the protective substrate, referring to FIG. 5, a mask is formed on the (100) silicon substrate or the (110) silicon substrate at a portion corresponding to the frame portion 24 of the scanner substrate 20 (see FIG. 5 (A)). The portion of the silicon substrate where the mask is not formed is evenly shaved to an appropriate depth by dry etching (FIG. 5 (B)).
Finally, the mask is removed (FIG. 5 (C)). With the protective substrate 20
30 is formed in exactly the same shape.

The scanner substrate 20 manufactured in this way
The protective substrates 30 and 40 are arranged on both sides of the scanner substrate 20 so as to sandwich them, and these silicon substrates are joined by fusion bonding in a high temperature atmosphere (FIG. 5 (D)).
). The frame part 24 of the scanner board 20 has both the protection boards 30 and 4
It will be joined to the corresponding part of 0. At this time,
Oxygen in the closed space formed in the scanner box 2 adheres to the inner wall to form an oxide film. Therefore, the closed space becomes a vacuum or a state close to it. As described above, since the air resistance during the vibration of the mirror portion 25 is reduced, the scanning angle is increased without lowering the resonance frequency.

The scanner substrate 20 and the protective substrates 30 and 40 may be joined by a fusion bonding method in a mixed gas atmosphere of oxygen and nitrogen. In this case, oxygen adheres to the inner wall of the closed space of the scanner box to form an oxide film, but nitrogen, which is an inert gas, remains in the closed space. Since nitrogen is an inert gas, the mirror section 25 contained in the closed space,
Since the elastic deformation portion 26, the electrostatic capacitance detection electrode and the strain detection element described later do not react with the surrounding gas, there is no risk of deterioration due to chemical reaction, and the life of the optical scanning device is extended.

FIG. 6 shows an example in which the visible light transmitting window 32 is formed on the protective substrate 30, and is a perspective view corresponding to FIG.
FIG. 7 is a sectional view taken along line VII-VII of FIG. The same components as those described above are designated by the same reference numerals to avoid redundant description.

By providing the visible light transmitting window 32 on the protective substrate 30, it becomes possible to use an inexpensive visible light laser as a light source, so that the cost of the device including this optical scanning device or the entire system can be reduced. Becomes As shown in FIG. 7, the light transmitting window 32 is formed by thinly dry-etching the portion of the protective substrate 30 where the visible light transmitting window 32 is to be formed (the portion corresponding to approximately the center of the mirror portion 25). During fusion bonding for bonding the substrates 20, 30, 40, oxygen in the closed space adheres to the inner wall, and the thin window 32 becomes an oxide film, so that visible light is transmitted. When the scanner substrate 20 is formed of a silicon substrate, the surface of the silicon substrate serves as a reflection surface, and therefore it is not always necessary to form a reflection film on the mirror portion 25.

FIG. 9 shows an example in which the SiN film 34 is formed on the protective substrate 30 as a visible light transmitting window.
It is a sectional view corresponding to.

A window 33 is opened in one protective substrate 30, and a SiN film 34 is provided from the inside so as to cover the window 33. Since the SiN film 34 transmits visible light, this SiN film
Visible light is made incident on the mirror section 25 through
The reflected light from can be taken outside. SiN film 34
Has a tensile stress and does not bend, so that high-precision optical scanning is possible without bending the optical path of the light incident on the surface of the mirror portion 25 or reflected from the surface of the mirror portion 25.

FIG. 10 shows the process of forming the SiN film on the protective substrate 30, and FIG. 11 shows the process of manufacturing the scanner cartridge.

A mask is formed in a portion corresponding to the frame portion 24 of the scanner substrate 20, and the unmasked portion of the silicon substrate to be the protective substrate 30 is evenly shaved by dry etching to remove the mask. 5 (A),
It is the same as that shown in (B), (C), (Fig. 10 (A),
(B), (C)). A place where a light transmitting portion should be formed on the inner surface of the protective substrate 30 (a portion corresponding to almost the center of the mirror portion 25)
Then, the SiN film 52 is formed by LPCVD (FIG. 10).
(D)). Further, a mask for alkali etching is formed on the outer surface of the protective substrate 30 except for the place where the window 33 is to be formed (the back side of the LPCVD-SiN film 34) (FIG. 10).
(E)).

The scanner substrate 20, the protective substrate 40, which is separately manufactured by the method shown in FIGS. 4 and 5, and the protective substrate 30, which is manufactured by the above method, are joined by fusion bonding in a high temperature atmosphere (FIG. 11 (F)). ).
A mask is previously formed on the entire outer surface of the protective substrate 40.

Thereafter, the window 33 is formed by performing anisotropic etching with an alkaline etching solution (FIG. 11 (G)). The etching cross section has an inverted mesa shape, and the etching stops at the SiN film 34 formed on the inner surface of the protective substrate 30. Finally, the external mask is removed (FIG. 11 (H)). In this manufacturing process, LPCVD (Low Pressure C
It is characterized in that the chemical vapor deposition-SiN film 34 is used as an etching stop layer.

FIG. 12 shows an example in which a condenser lens 53 is provided in the light transmitting window 32 of the scanner box-shaped body 2 shown in FIG. The scanner box 2 is emitted from the light source 54 and passes through the light transmitting window 32.
The light incident on the inside is reflected by the mirror unit 25. By vibrating the mirror unit 25, the reflected light is scanned one-dimensionally or two-dimensionally as described above. The light reflected from the mirror section 25 is condensed by the lens 53 when it is emitted to the outside through the light transmission window 32, and forms a spot on the surface of the object to be measured (when applied to a shape recognition sensor). As described above, since the light reflected by the mirror section 25 has a focus, it is possible to selectively collect information about the object to be measured at a position equidistant from the optical scanning device.

FIG. 13 shows S of the scanner box-like body shown in FIG.
FIG. 3 is an enlarged view of the SiN film 34 portion, showing an example in which a lens (diffractive Fresnel lens) 55 composed of binary optics is provided on the iN film 34. Since it is only necessary to form the pattern for blocking light on the SiN film 34 with a metal such as Al or Pt, the step of bonding the lens and the like is not necessary, and the lens itself can be manufactured by the semiconductor process, so that the cost can be reduced. Becomes Lens 55
Can also be formed by processing the surface of the SiN film 34 with an electron beam.

FIG. 14 shows an example in which one or a plurality of light receiving elements 56 for receiving the reflected light from the object to be measured are provided on the protective substrate 30 of the scanner box-like body shown in FIG. Light receiving element
By integrating 56 into the scanner box, the optical sensing system can be downsized.

In FIG. 15, the light receiving element 57 is connected to the protective substrate 30 by n.
An example formed by doping with a p-type or p-type impurity is shown. The protective substrate 30 is formed of a p-type or n-type silicon substrate. By implementing both the light receiving element forming process and the protective substrate manufacturing process by the semiconductor process, the manufacturing process of the entire optical scanning device can be simplified.

FIG. 16 shows an example in which an electrode for monitoring the angle (tilt) of the mirror portion 25 is provided on one surface of the mirror portion 25 and the inner surface of the protective substrate 40 facing the one surface.

A movable electrode 59 is provided on one surface of the mirror portion 25 of the scanner substrate 24. The fixed electrode 60 is provided on the surface of the protective substrate 40 facing the movable electrode 59. These electrodes 59 and 60 are formed by vapor-depositing a metal (for example, Pt) or by doping a silicon substrate with impurities. Electrode 59 is elastically deformable portion 26, frame portion
24 and the wiring pattern formed on the protective substrate 40,
The electrode 60 is connected to an external electrode 61 formed on the outer surface of the scanner box 2, and the electrode 60 is connected to an external electrode 62 via a wiring pattern formed on the protective substrate 40. A groove having a depth corresponding to the thickness of these wiring patterns is formed at the joint between the frame portion 24 of the scanner substrate 20 and the protective substrate 40, and the wiring pattern is formed in this groove.

The movable electrode 59 and the fixed electrode 60 may be provided on the other upper surface of the mirror portion 25 and the inner surface of the protective substrate 30, respectively. When the movable electrode acts as a mirror surface for the light used, the movable electrode may be provided on both surfaces of the mirror portion. In this case, fixed electrodes are formed on the inner surfaces of both protective substrates.

When high frequency vibration is applied to the scanner box-shaped body 2 by the piezoelectric actuator 3, the elastic deformation section 26 resonates and vibrates, and the mirror section 25 is displaced in the closed section of the scanner box-shaped body 2. A change in the gap between the movable electrode 59 and the fixed electrode 60 changes the electrostatic capacitance between the electrodes 59 and 60, and the vibration frequency is detected by setting the change in the electrostatic capacitance. This makes it possible to detect a change in the resonance frequency, and by feeding back a signal representing the resonance frequency to the piezoelectric actuator 3, it is possible to always scan the light in the preset resonance range.

FIG. 17 shows an example in which, instead of providing the movable electrode 59 and the fixed electrode 60, a strain detecting element (piezoresistive element) for monitoring the angle (tilt) of the mirror section 25 is provided in the elastically deforming section 26. Shows.

In FIG. 17A, the two strain detecting elements 63 are
The elastically deforming portions 26 are arranged in such a manner that they are inclined by 45 degrees in the axial direction. In FIG. 17B, one strain detecting element 63A is arranged at an angle of 45 degrees in the axial direction of the elastically deformable portion 26, and the other strain detecting elements 63B are respectively provided along the axial direction.

At least one strain detecting element (strain gauge) is provided in the elastic deformation portion 26, and is preferably a piezoresistive element formed by diffusion of p-type or n-type impurities. When the piezoresistive elements 63 and 63A are arranged in a direction inclined by 45 degrees with respect to the axial direction of the elastically deformable portion 26, the elastically deformable portion 26
The sensitivity is highest with respect to the torsional vibration of, and the scanning of light (resonance frequency) can be controlled with high accuracy. A piezoresistive element 63 arranged along the axial direction of the elastically deformable portion 26.
B is used to detect the frequency of bending vibration.

When high frequency vibration is applied to the scanner box-shaped body 2 by the piezoelectric actuator 3, the elastic deformation portion 26 resonates and vibrates, and the mirror portion 25 is displaced in the closed section. As the elastic deformation section 26 expands and contracts, the resistance value of the piezoresistive element changes, and the vibration frequency is detected based on the change in the resistance value. As a result, the resonance frequency change can be detected in the same manner as in the embodiment in which the vibration frequency is detected based on the electrostatic capacitance change described above, and the resonance frequency set in advance is fed back to the piezoelectric actuator 3 by feeding back a signal representing the detected frequency to the piezoelectric actuator 3. The area can always be scanned with light.

[Brief description of drawings]

FIG. 1 is a perspective view showing an optical scanning device.

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

FIG. 3 is a sectional view taken along line III-III in FIG.

4 (A), (B) and (C) show a manufacturing process of a scanner substrate.

5 (A), (B), (C) and (D) show a process for manufacturing a protective substrate.

FIG. 6 is a perspective view corresponding to FIG. 1, showing an embodiment in which a visible light transmitting window is formed on a protective substrate.

FIG. 7 is a sectional view taken along line VII-VII of FIG.

8A, 8B, and 8C show a manufacturing process of the protective substrate shown in FIG.

9 is a sectional view corresponding to FIG. 7, showing an embodiment in which a SiN film is formed on a protective substrate as a visible light transmitting window.

FIG. 10: (A), (B), (C), (D) and (E) are SiN
A manufacturing process for forming a film on a protective substrate is shown.

11 (F), (G) and (H) show a manufacturing process for forming a SiN film on a protective substrate.

12 is a cross-sectional view showing an embodiment in which a lens is provided on a light transmission window of the optical scanning device shown in FIG.

13 is an enlarged cross-sectional view of the SiN film portion, showing an embodiment in which a lens composed of binary optics is provided on the SiN film of the optical scanning device shown in FIG.

14 is a cross-sectional view showing an embodiment in which a light receiving element is provided on a protective substrate of the optical scanning device shown in FIG.

15 is a plan view showing an optical scanning device shown in FIG.
FIG. 7 is a cross-sectional view showing an example in which a light receiving element formed by p-type or p-type impurity doping is provided.

FIG. 16 is a cross-sectional view showing an embodiment in which electrodes for monitoring the angle of the mirror section are provided on the mirror section and the protective substrate.

17 (A) and 17 (B) respectively show embodiments in which the elastic deformation portion is provided with a strain detection element for monitoring the angle of the mirror portion.

FIG. 18 is a perspective view showing an example of a conventional optical scanning device.

[Explanation of symbols]

2 Scanner Box 3 Piezoelectric Actuator 4 Support Substrate 20 Scanner Substrate 24 Frame 25 Mirror 30, 40 Protective Substrate 31, 41 Recess 32, 33 Light Transmission Window 34 SiN Film 53 Lens 55 Binary Optics (Fresnel Zone Plate) ) 56 Light receiving element 59 Movable electrode 60 Fixed electrode 63, 63A, 63B Strain detection element (piezoresistive element)

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-7-92409 (JP, A) JP-A-4-211218 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 26/10

Claims (4)

(57) [Claims] 1. A box-shaped body having a sealed space inside, wherein a mirror part for reflecting light is provided inside the box-shaped body to provide at least one resonance vibration mode attached to the box-shaped body. It is movably supported by an elastically deformable portion, the inside of the box-shaped body is decompressed, and a light-transmitting section is formed at a portion of the box-shaped body facing the mirror section. The light-transmitting section is a SiN film. Optical scanning device formed by. 2. A box-shaped body having a sealed space inside, wherein a mirror part for reflecting light is provided inside the box-shaped body to provide at least one resonance vibration mode attached to the box-shaped body. It is movably supported by the elastically deformable part, the inside of the box-shaped body is decompressed, and a light-transmitting part is formed at a portion of the box-shaped body facing the mirror part, and a lens is provided on the light-transmitting part. An optical scanning device provided with. 3. A scanner substrate, wherein the box-shaped body is formed with the mirror portion, a rectangular frame portion, and the elastically deformable portion connecting the mirror portion and the frame portion, and the scanner substrate. The optical scanning device according to claim 1, wherein the optical scanning device is composed of two protective substrates that are bonded to the frame portion so as to be sandwiched therebetween. 4. The optical scanning device according to claim 3, wherein the scanner substrate and the protective substrate are made of the same material, and the scanner substrate and the protective substrate are plane-symmetric with respect to the center plane of the scanner substrate.