JP2003107387A - Optical scanner and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner capable of correcting deflection of scanning lines attended with multiple reflection so as to attain image recording with high quality and downsizing. SOLUTION: This invention relates to the optical scanner comprising; a movable mirror 3 for deflecting a light beam from an LD chip; a Si substrate 3b for pivotally supporting the movable mirror 3; and opposed mirrors 1, 2 facing the movable mirror 3 and reciprocally reflecting the light beam with the movable mirror 3. The opposed mirrors 1, 2 having a reflection face with a tilt in the subscanning direction from the Si substrate are placed opposite to each other with a light beam passing part 23a inbetween, the opposed mirrors 1, 2 are placed overlappingly on the Si substrate 3b, and the reflection faces of the opposed mirrors 1, 2 have reflection areas overlapped on a movable mirror face in a vertical direction and facing with each other in parallel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an optical scanning device for optical equipment, an optical scanning device used in an image forming apparatus such as a digital copying machine and a laser printer, and an image forming apparatus equipped with this optical scanning device. To be done.

[0002]

2. Description of the Related Art Conventionally, a writing optical system of a laser printer obtains an angle of view (hereinafter referred to as a scanning angle) by scanning a light beam in a main scanning direction using a polygon mirror and forms an image on a photoconductor. is doing.

In order to improve the image quality of the printer, it is necessary to reduce the beam spot size of the beam, but since the beam spot size is proportional to the product of the laser wavelength and the focal length, (1) How to shorten the wavelength of the laser,
(2) A method of shortening the focal length can be considered. (1) When shortening the wavelength of the laser, it is necessary to use a blue laser diode and design an optical system such as a lens corresponding to the blue laser diode. Further, (2) in the case of shortening the focal length, it is necessary to bring the optical system after the deflecting unit for deflecting the light beam closer to the photoconductor. In that case, in order to make the pixels uniform in the main scanning direction, it is difficult to realize with one deflection unit, and it is necessary to arrange and use a plurality of modularized deflection units in the main scanning direction. The use of one deflection unit is called the batch scanning method, while it is called the division scanning method.

In a conventional optical scanning device, a polygon mirror or a galvano mirror is used as a deflector for scanning a light beam, but in order to achieve a higher resolution image and high speed printing, this rotation must be made faster. No
Bearing durability, heat generation due to windage, and noise pose problems, limiting high-speed scanning.

On the other hand, in recent years, research on an optical deflector using silicon micromachining has been promoted, and as disclosed in Japanese Patent Nos. 2722314 and 3011144, a movable mirror and its axis are supported by a Si substrate. A method of integrally forming a torsion bar has been proposed. According to this method, resonance is used to reciprocally oscillate, so high speed operation is possible, but there is an advantage that noise is low. Furthermore, since the driving force for rotating the movable mirror can be small, the power consumption can be kept low.

Further, among the micromirrors, there are three types, that is, an electromagnetic force type, a piezoelectric type, and an electrostatic force type, depending on the driving method. While the electromagnetic force method and the piezoelectric method can easily obtain a large scanning angle, the permanent magnet and the piezoelectric element are used, so that the number of parts is large and the miniaturization is difficult. On the other hand, although the electrostatic force method is easily miniaturized, it has a trade-off relationship between the scanning angle and the driving voltage, and it is difficult to obtain a large scanning angle. Therefore, in the electrostatic force method, there is an attempt to obtain a large scanning angle by providing a reflection mirror (hereinafter referred to as a facing mirror) at a position facing the micro mirror and causing multiple reflection between the micro mirror and the reflection mirror. .

The above-mentioned Japanese Patent Nos. 2722314 and 301
As disclosed in Japanese Patent No. 1144, there has been proposed a system in which a movable mirror and a torsion bar that axially supports the movable mirror are integrally formed on a Si substrate. According to this method, resonance is used to reciprocally oscillate, so high speed operation is possible, but there is an advantage that noise is low. Furthermore, since the driving force for rotating the movable mirror can be small, the power consumption can be kept low.
On the other hand, when the light beam is scanned by the resonance oscillating mirror, the amplitude is very small. Therefore, in order to obtain a recording width similar to that of a conventional deflector, for example, a polygon mirror, a means for enlarging the scanning angle is required. Japanese Patent Laid-Open No. 4-080709 discloses an example in which a fixed mirror is provided so as to face a rotating mirror and multiple reflection is performed. According to this method, the scanning angle can be easily expanded.

[0008]

However, as shown in FIG.
When the light beam B is incident at an angle α in the sub-scanning direction with respect to the mirror surface normal 3c as shown in FIG. 3, the locus L of the deflected scanning line is curved, which causes deterioration of image quality. Similarly, when incident at an angle of -α from the opposite direction, the locus L of the scanning line which is the reverse of the above is drawn.

Accordingly, the scanning line is made straight by canceling the bending caused by the reflection having the positive incident angle with respect to the mirror surface normal 3c and the bending caused by the reflection having the negative incident angle to be substantially equal to each other. Can be corrected. In order to realize this, it is necessary to provide a reflecting surface facing the mirror surface and inclined by a predetermined angle in the sub-scanning direction, reverse the positive / negative of the incident angle, and make the incident again on the mirror surface.

Therefore, it is an object of the present invention to provide an optical scanning device and an image forming apparatus capable of correcting the curve of the scanning line due to multiple reflection and performing high-quality image recording and capable of downsizing. is there.

[0011]

In order to achieve the above object, the invention of claim 1 is directed to a movable mirror for deflecting a light beam from a light emitting source, a first substrate for axially supporting the movable mirror, and a movable mirror. In the optical scanning device having an opposed mirror that faces the movable mirror and reciprocally reflects a light beam between the movable mirror and the movable mirror, an opposed mirror having a reflective surface formed to be inclined from the first substrate surface in the sub-scanning direction is provided. The opposing mirror is provided in a direction opposite to each other with a light beam passing portion interposed therebetween, and the opposing mirror is disposed so as to be superposed on the first substrate. The reflecting surface of the opposing mirror is parallel to a direction perpendicular to the movable mirror surface. The optical scanning device is characterized in that it has a reflective region facing to.

The invention according to claim 2 is the optical scanning device according to claim 1, characterized in that the opposed mirror is formed on a support substrate having a light beam passage portion.

Further, the invention of claim 3 is characterized in that a frame substrate forming a movable space of the movable mirror is provided on the first substrate, and the opposed mirror is superposed on and supported by the frame substrate. The optical scanning device according to claim 1 or 2.

According to a fourth aspect of the present invention, there is provided positioning means for aligning the counter mirror and the first substrate between the movable mirror side substrate and the counter mirror side substrate. The optical scanning device according to claim 1 or 2.

Further, the invention of claim 5 is characterized in that the opposed mirrors are arranged so that respective reflecting surface ends of the opposed mirrors are aligned in a plane parallel to the movable mirror. 2 is an optical scanning device.

According to a sixth aspect of the present invention, the facing mirror is made of a Si substrate, and its inclination angle is defined by a plane orientation [111] plane and a slice plane of the Si substrate, and The optical scanning device according to claim 1, further comprising a contact surface parallel to the substrate, wherein one of the surfaces is in contact with the contact surface and the other surface is a reflection surface.

According to a seventh aspect of the invention, the contact surface is
7. The optical scanning device according to claim 6, wherein movable mirrors are provided at both ends that bridge in the main scanning direction.

The invention of claim 8 is the optical scanning device according to claim 6, wherein the width of the reflecting surface of the opposed mirror in the sub-scanning direction is defined by the plane orientation [111] plane. is there.

According to a ninth aspect of the present invention, the facing mirror is made of a Si substrate, and an inclination angle thereof is defined by a plane orientation [111] plane and a slice plane of the Si substrate, and the supporting substrate is provided with: The contact surface parallel to the movable mirror is provided, and the contact surface is joined to the slice surface in the same surface.
The optical scanning device described in 1.

According to a tenth aspect of the present invention, the facing mirror is made of a Si substrate, and the tilt angle is [111].
Surface and the sliced surface of the Si substrate,
3. The supporting substrate includes an abutting surface parallel to the movable mirror and a joint surface arranged parallel to the movable mirror, and one of the surfaces is aligned with the joint surface. The optical scanning device described in 1.

Further, the invention of claim 11 is characterized in that it has a portion aligned with the plane orientation [111] also on the surface opposite to the contact surface parallel to the movable mirror. It is an optical scanning device.

The twelfth aspect of the present invention includes the first to first aspects.
The optical scanning device according to any one of 1, the photoconductor on which an electrostatic image is formed by the optical scanning device, a developing unit that visualizes the electrostatic image with toner, and the visualized toner image. The image forming apparatus includes a transfer unit that transfers a recording sheet.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. One embodiment of the facing mirror substrate of the present invention is shown in FIG. In FIG. 1A, as a reference example, a facing mirror 1 having an inclination angle of 9.5 ° with respect to the substrate surface.
And a counter mirror substrate in which two substrates of a counter mirror 2 having an inclination angle of 26.3 ° are bonded together (a joint portion and a reflective metal film are not shown). Movable mirror 3 at the opposite position
The movable mirror 3 which is a micromirror having a frame substrate 4 for securing the swinging space is also shown. The movable mirror 3 is manufactured using an SOI (silicon on insulator) substrate, and the thick Si substrate of the SOI substrate also serves as the frame substrate 4. The substrate material of the facing mirrors 1 and 2 is not particularly limited, but a Si substrate or a glass substrate, which has good bonding reliability with Si that is the material of the frame substrate 4, is preferable. Also,
The method of forming the inclination angle may be etching or cutting. The advantage of this opposed mirror substrate is that since two substrates can be bonded at the wafer level, a large number of opposed mirror chips can be manufactured at once.

However, although the opposed mirrors 1 and 2 are provided so as to face each other with the passage portion 23a of the light beam B interposed therebetween, there is no area where they face each other. That is, the opposed mirrors 1 and 2 are displaced in the normal direction of the micromirror.

In this case, the light beam enters and exits (light beam separation)
Is difficult in terms of shape, in order to enable separation of the light flux, the distance between the opposing mirrors 1 and 2 is lengthened, the optical path length is lengthened, and layout restrictions are large when optimizing optical characteristics. There is a problem in optical characteristics such as points. When the optical path length becomes longer, the effective mirror diameter in the main scanning direction becomes longer,
The required areas of the facing mirrors 1 and 2 and the micro mirror 3 are increased. When the area of the micromirror 3 becomes large, surface accuracy is required in a large area, and the micromirror in a large area needs to be driven. Therefore, it is difficult to achieve the specifications of the micromirror.

Therefore, as one embodiment, the facing mirror 1,
FIG. 1B shows a case in which the light beams 2 are facing each other with the passing portion 23a of the light beam B sandwiched therebetween, and both are facing each other. The facing mirrors 1 and 2 are made of the same material as that shown in FIG. 1A, and the tilt angle is made by the same processing method. The point different from FIG. 1 (A) is that when the micro mirror 3 is bonded, the chips are bonded by different chips. If you make in this way,
The above-mentioned problems in optical characteristics can be avoided.

As a modified example, FIG. 1C shows another case in which the opposed mirrors 1 and 2 face each other with the passage portion 23a for the light beam B in between, and both face each other. This is one in which the light-transmissive material 16 is integrally processed such as a cutting process of a glass substrate or a plastic mold.

FIG. 2 shows another embodiment of the present invention including the manufacturing method. First, as shown in FIG. 2 (A), a plane direction in which SiO ₂ 5 serving as a supporting substrate is formed with a thickness of 0.5 μm
45.2 ° from [100] Si substrate 6 and plane orientation [100]
A Si substrate 7 having a tilted slice angle is prepared.

Next, as shown in FIG. 2B, both substrates are bonded by direct bonding, for example, and then SiO ₂ is removed. Next, as shown in FIG. 2C, the LPCVD method is used.
After forming the SiN film 8 on both sides, a desired pattern is formed by photolithography and dry etching of the SiN film 8.

After that, as shown in FIG. 2D, crystal anisotropic etching is performed using a KOH aqueous solution having a concentration of 25 wt% and a temperature of 80 °, for example. Normally, when a crystal plane orientation [100] Si substrate with a slice angle of 0 ° is subjected to crystal anisotropic etching, Si
A tapered surface forming 54.7 ° with respect to the substrate surface appears. This is because the crystal plane orientation [11] whose etching rate is extremely slow in the direction forming 54.7 ° with respect to the Si substrate surface.
1] surface appears. Therefore, the crystal plane orientation [10
[0], the taper surface of 9.5 ° appears on the Si substrate 7 inclined by the slice angle of 45.2 °. Here 9.5 °
, And the Si substrate 7 remains in an island shape.

Next, as shown in FIG. 2E, the surface of the substrate is subjected to photolithography and Si dry etching techniques.
A slit 12, which is a light beam passage portion, which is aligned with a 9.5 ° taper edge, is opened.

[0032] Next, as shown in FIG. 2 (F), a photoresist 9, SiN film, after removing the SiO _2, to reform the SiO ₂ 5 example 0.5μm of by thermal oxidation method. On the other hand, a Si substrate 10 tilted by a slice angle of 28.4 ° from the plane orientation [100] is prepared, and the SiN film 8 is used as a mask to perform crystal anisotropic etching with a KOH aqueous solution having a concentration of 25 wt% and a temperature of 80 °, for example. To penetrate the substrate. At this time, a tapered surface of 26.3 ° is formed by the same theory as described above.

After that, a 9.5 ° taper surface and 26.3
The taper of 2 ° faces each other, and the taper edge of 26.3 ° is aligned with the slit opening and bonded by, for example, direct bonding. At this time, the Si substrate having the taper surface of 26.3 ° has the taper surface of 9.5.
It must be thicker than the Si substrate. In addition, in the substrate bonding by this series of alignment, 9.5 ° taper surface, slit opening, regardless of the thickness variation of the Si substrate,
The 26.3 ° tapered surface can be aligned with high accuracy.

Next, as shown in FIG. 2G, LPCV
S by D (low presure chemical vapor deposition) method
After forming the iN film 8 on both sides, a desired pattern is formed by photolithography and dry etching of the SiN film.
The desired pattern is a pattern in which the slit opening remains tapered on the upper surface side of the substrate and the tapered surface of 26.3 ° remains on the lower surface side of the substrate in an island shape by the subsequent crystal anisotropic etching.

Subsequently, as shown in FIG. 2H, crystal anisotropic etching is performed to obtain the above-described shape. Finally, as shown in Fig. 2 (I), SiN
After removing the film and SiO ₂ , a mirror metal 11 is formed,
The desired facing mirror is obtained.

The opposing mirror thus prepared is
FIG. 2 (J) shows what is superposed with the micromirror 3 manufactured using the I substrate. In this figure, the alignment marks a, which are the positioning means used to align the opposing mirrors 1 and 2 and the supporting substrate of the micromirror 3 with each other, are shown. Each alignment mark a
Although not shown in the middle of the process, it can be manufactured at the same time when the respective mirrors are manufactured without increasing the number of processes. Therefore, the structure has an accurate positioning means without increasing the number of steps. Further, since the supporting substrates of the facing mirror substrate and the micromirror substrate are bonded to each other, the accuracy of the gap is high. Furthermore, even if the shapes of the plurality of opposed mirrors are changed, there are few changes in the process and design. Further, the facing mirror substrate can be manufactured by batch processing of the wafer, and the bonding with the micromirror substrate can be processed at the wafer level, and the mounting cost can be reduced.

In this case, a Si substrate having a slice angle of 45.2 ° and a slice angle of 28.4 ° tilted from the crystal plane orientation [100] was used, but 9.5 ° and 26 respectively from the crystal plane orientation [111]. You may use the Si substrate which inclined the slice angle of 0.3 degree. Thus, the crystal plane orientation [1
The slice angle and the crystal plane orientation serving as a reference thereof are not limited as long as the taper surface of the [11] plane can be exposed. It is also found that an arbitrary taper angle can be obtained by adjusting the slice angle.

Crystal plane orientation that is the above-mentioned tapered surface [11]
Since the 1] plane has a significantly slower etching rate than the [110] and [100] planes, it has an advantage that the etching plane is smooth and the taper angle is high in accuracy and can be applied as a suitable reflecting surface.

Further, as the supporting substrate, another material such as a glass substrate may be used. Here, the plane orientation [100] Si
Although the substrate is used, the Si process can be used, and the slit opening is formed by crystal anisotropic etching.
It is preferably used because it can be processed into a 7 ° taper shape and can be used as a measure to prevent light beam eclipse.

Another embodiment of the present invention is shown in FIG. Figure 3
The Si substrate 7 tilted at a slice angle of 45.2 ° from the plane orientation [100] shown in (A) and the plane orientation [1 shown in FIG.
00] to the Si substrate 10 with a slice angle of 28.4 ° tilted
Using, and using the SiN film as a mask pattern, crystal anisotropic etching is performed with a KOH aqueous solution having a concentration of 25 wt% and a temperature of 80 °, for example. The desired tilt angle from each substrate is 9.5.
The [111] taper surface of 2 ° and 26.3 ° is obtained. Opposing mirror chips are formed by dicing the respective substrates at the positions indicated by the broken lines.

As shown in FIG. 3C, in each of the facing mirror chips, an opening to be the light beam passage portion 23a and an opening for the alignment mark a were formed in a tapered shape by crystal anisotropic etching. , The plane direction of the supporting substrate
It is fixed to the [100] Si substrate 6 by joining using an adhesive, for example. Here, although the mounting cost by chip-bonding the facing mirror chips respectively,
The part forming process is simple and the cost is low. Also, [11
1] Since the anisotropic etching surface is used as the bonding surface to the supporting substrate, the polishing surface can be used as the reflecting surface, which is suitable as a mirror. Further, as the supporting substrate, the above-mentioned Si
Needless to say, it is not limited to the substrate. FIG. 3 is a plan view of the opposing mirror thus produced and the micromirror 3 produced in the same manner as in FIG.
It shows in (D).

Another embodiment of the present invention is shown in FIGS.
It shows in (D). Figure 3 shows the Si substrate used and the basic process.
However, the difference is that when the taper of the opposed mirrors 1 and 2 is formed by anisotropic etching, patterning is formed on both surfaces and etching is performed from both surfaces. By properly patterning the surface orientation of the Si substrate, it becomes a joint surface (specifically, the same pattern is etched even if the front and back of the Si substrate are swapped). [11
[1] An anisotropic etching surface is also formed at a position parallel to the anisotropic etching surface. Therefore, when bonding the facing mirror chip to the supporting substrate, chip handling
(Adsorption) and the uniformity of pressurization at the time of joining are improved.

Another embodiment of the present invention is shown in FIGS.
It shows in (C). 28. The Si substrate 7 tilted at a slice angle of 45.2 ° from the plane orientation [100] and the plane orientation [100] to 28.
Using the Si substrate 10 with a tilt angle of 4 °, the SiN film is used as a mask pattern, for example, the concentration is 25 wt% and the temperature is 80%.
Crystal anisotropic etching is performed with a KOH aqueous solution of ° C. The desired tilt angles of 9.5 ° and 26.3 ° from the respective substrates
A [111] tapered surface is obtained. Opposing mirror chips are formed by dicing the respective substrates at the positions indicated by the broken lines. Each facing mirror chip,
It is fixed directly to the frame substrate 4 provided on the micromirror substrate side, for example, by joining using an adhesive (joining in the main scanning direction (not shown)). Here, although the mounting cost is required by chip-bonding the facing mirror chips, the component forming process is simple and the cost is low. Further, since the [111] anisotropically etched surface is used as the bonding surface to the supporting substrate, the polishing surface can be used as the reflecting surface, which is suitable as a mirror. The mirror end that defines the light beam passage portion 23a is defined by dicing here, and the mirror has high rigidity and high accuracy. However, in the case of machining by dicing, chips such as chipping may occur on the mirror surface.

The countermeasure plan is shown in FIGS. 6 (A) to 6 (C). Here, when the tapered surfaces of the facing mirrors 1 and 2 are formed by anisotropic etching, a pattern capable of defining the mirror width in the sub-scanning direction is also formed at the same time. Also, during dicing, the mechanical damage to the mirror surface is suppressed by cutting with a half cut as indicated by the broken line in the middle of the substrate in the figure.

Further, FIGS. 7A to 7C are shown in FIG.
In an embodiment in which the embodiment shown in FIG. 4 is combined with the embodiment shown in FIGS. 6A to 6C, chip handling (adsorption) at the time of joining a facing mirror chip to a supporting substrate and uniform pressing at the time of joining. The property is improved.

A top view and a sectional view of the embodiment shown in FIG. 5 are shown in FIG. 8 together with a micromirror substrate. The opposing mirror chip is bonded to the frame substrate 4 provided on the micromirror substrate at both ends that bridge only in the main scanning direction. Therefore, even if the [111] bonding surface has unevenness due to etching, It has little effect and improves the flatness of the joint. Therefore, the facing mirror chip is processed so as not to be bonded to the frame substrate 4 in the sub-scanning direction.

Finally, the structure and operation of a color laser printer incorporating the opposed mirror substrate formed by such a method will be described with reference to FIGS. FIG. 9 shows an exploded perspective view of an optical scanning module provided in the optical scanning device. As the movable mirror substrate, a SOI substrate in which two Si substrates are bonded, that is, a frame substrate 4 that is a Si substrate that secures a swinging space of the movable mirror 3 and a Si substrate 3b that forms the movable mirror 3 is used. After the frame substrate 4 is etched into a square to form a swing space, Si is
By etching the substrate 3b, the movable mirror 3 and the torsion bar 32 that pivotally supports the movable mirror 3 are formed so as to penetrate the periphery thereof. A mirror surface is formed by vapor-depositing a metal coating on the center of the movable mirror 3, and both ends of the mirror with the torsion bar 32 sandwiched are formed into a comb-shaped uneven surface. The fixed electrode 31 and the movable electrode 24 are provided. To form. The comb-like shape can increase the area of the electrodes facing each other and can reduce the driving voltage.

A metal coating is formed on the upper surface of the frame substrate 4 in which the swinging space of the movable mirror 3 is formed, and the opposing mirror 2 having a reflecting surface 2a having an inclination angle of 26.3 ° and the metal coating are formed. , The opposing mirror 1 having the reflecting surface 1a having an inclination angle of 9.5 ° is joined. The light beam passage portion 23a is defined by the distance between the reflecting surfaces of the opposing mirrors.

The prism 26 has a light beam incident surface 26.
b, an exit surface 26d, and a reflecting surface 26a for reflecting the light beam to the movable mirror 3 are formed, and are arranged above the facing mirrors 1 and 2.

As shown in FIG. 14, the light beam incident on the movable mirror 3 from the passage portion 23a, which is an opening, at a predetermined angle is reflected by the reflecting surface 2a, reflected again by the movable mirror 3, and then reflected by the reflecting surface 1a. While repeating reflection a plurality of times (three times in the embodiment) between the and, while moving back and forth between the reflection points in the sub-scanning direction, the light passes through the passing portion 23a and again enters the prism 26, and exits from the exit surface 26d. .

In the embodiment, by repeating the reflection a plurality of times as described above, a large scanning angle can be obtained with a small deflection angle of the movable mirror 3. For example, if the total number of reflections at the movable mirror 3 is N and the shake angle is α, the scanning angle θ is 2Nα, and in the embodiment, N = 5.

When a voltage is applied to one of the fixed electrodes 31 of the movable mirror 3, an electrostatic attractive force is generated between the movable mirror 24 and the movable electrode 24 facing the fixed electrode 31, and the torsion bar 32 is twisted to generate an electrostatic attractive force and a twisting force from a horizontal state. When the voltage is released, the torsion bar 32 is restored to return to a horizontal state, and when the voltage is applied to the other fixed electrode, the movable mirror 3 tilts in the reverse direction. Movable mirror 3 by switching periodically
Can be reciprocally vibrated.

When the frequency to which this voltage is applied is brought close to the natural frequency of the movable mirror 3, a resonance state occurs, which is amplified more than the displacement due to the electrostatic attractive force and the swing angle remarkably expands.
In the embodiment, the natural frequency of the movable mirror 3 is set to match the recording speed, that is, the thickness of the movable mirror 3, the thickness of the torsion bar 32, and the length are determined.

In general, the maximum deflection angle θ ₀ is the elastic constant G of the torsion bar 32 supporting the movable mirror 3, the second moment of area I, the spring constant K determined by the length L, and the torque T given by the electrostatic attraction. Is expressed by the following equation, θ ₀ = T / K. Here, K = G · I / L.

The resonance frequency fd of the movable mirror is given by the following equation, fd = √ (K / J), where J is the moment of inertia.

By utilizing the resonance, the applied voltage is minute and the heat generation is small, but as the recording speed increases, the rigidity of the torsion bar increases and the deflection angle cannot be obtained. Therefore, as described above, the counter mirror is provided to expand the scanning angle so that the necessary and sufficient scanning angle can be obtained regardless of the recording speed. The support frame 27 is formed of a sintered metal or the like, and the lead terminals 25 are inserted through an insulating material.

On the support frame 27, the bonding surface 27a for mounting the above-mentioned mirror substrate, the V groove 27b for positioning and bonding the coupling lens 20, and the mounting surface 27c of the LD chip 28 which is a light emitting source formed perpendicular to the bonding surface 27a. , The mounting surface 27d of the monitor PD chip 29 that receives the back light of the LD is formed.

In the coupling lens 20 in which the upper and lower sides of the cylinder are cut, the first surface is an axisymmetric aspherical surface, and the second surface is a cylinder surface having a curvature in the sub-scanning direction. The width and angle of the V groove 27b are set so that the optical axis matches the light emitting point of the LD chip 28 when the cylindrical outer peripheral surface of the coupling lens 20 is in contact, and the divergent light flux is adjusted in the main scanning direction by adjusting the optical axis direction. In the sub-scanning direction, a substantially parallel light beam is not focused on the movable mirror surface in the sub-scanning direction, and is bonded and fixed. The cut surface is formed parallel to the generatrix of the cylinder surface, and is positioned around the optical axis so that the generatrix is horizontal.

An aperture mask for shaping the light beam from the coupling lens 20 into a predetermined diameter is formed on the incident surface 26b of the prism 26, and the light beam passing through the prism 26 and scanned by the movable mirror 3 is formed. It is emitted above the emission surface 26d.

The cover 21 is formed of a sheet metal into a cap shape, a glass plate 22 is joined to the light beam emission opening from the inside, and the cover 21 is fitted into a step portion 27f provided on the outer periphery of the support frame 27. Protects LD chips, mirror substrates, etc. in an airtight state. LD chip 28, monitor PD chip 2
9. The fixed electrodes are connected to the tips of the lead terminals 25 protruding above by wire bonding.

FIG. 10 shows a sectional view of the optical scanning device in the embodiment, and FIG. 11 and FIG. 12 show its external view and perspective view. A plurality (three in the embodiment) of the optical scanning modules 40 having the above-described configuration are arranged in the main scanning direction on the printed circuit board 41 on which the electronic components forming the LD drive circuit and the movable mirror drive circuit are mounted. To be done. At the time of mounting, the bottom surface of the support frame 27 is inserted into the through hole through the lead terminal 25 projecting downward, and is brought into contact with the printed circuit board so that the optical scanning modules are aligned on the board within the clearance of the through hole. After that, they are temporarily fixed and soldered together like other electronic components and fixed together.

The printed board 41 supporting a plurality of optical scanning modules is abutted so as to close the lower opening of the housing 42, and is held by being held between a pair of snap claws 42a provided integrally with the housing.

This snap claw 42 is provided on the printed circuit board 41.
A notch that engages with the width of a is provided for positioning in the main scanning direction, and at the same time, the locking portion is engaged with the substrate edge to fix the sub scanning direction. Further, by bending the locking portion in the direction of the arrow, the projection pushes down the upper end of the substrate, and it can be easily removed.

Inside the housing, a positioning surface for arranging and joining the first scanning lenses 43 constituting the image forming means in the main scanning direction, a positioning portion for holding the second scanning lens 44 and a holding portion for the synchronous mirror 48. Is formed. In the embodiment, the second scanning lens of each optical scanning module is integrally formed of resin, and the synchronous mirror 48 is also formed by being connected by a high-brightness aluminum plate, and is formed in the opening for emitting the light beam from the outside. It is fitted and attached by abutting on the back side. The projection 52c is formed in the center of the opening, and the second scanning lens 4
The concave portion 44a provided in the central portion of 4 and the concave portion 48a provided in the central portion of the synchronous mirror are engaged and positioned in the main scanning direction by being pressed against one end of the opening in the sub scanning direction. In addition, the first scanning lens 43 has positioning projections 43a formed on the bottom surface of the central portion of the main scanning, and the positioning projections 43a are mounted in the engaging holes 42b arranged at equal intervals in the housing.
The relative position in the main scanning direction is maintained, and at the same time, the bottom surface in the sub-scanning direction is abutted against the adhesive surface that is abutted against one end in the optical axis direction and has the same height in the same central portion. Positioned in contact.

Synchronous detection sensor (PIN photodiode) 4
9 are arranged at the intermediate position and both end positions shared by the adjacent optical scanning modules, and are mounted on the printed board 41 so that the beam can be detected on the scanning start side and the scanning end side of each optical scanning module. The synchronous mirror 48 is formed in a V shape so that the reflection surfaces of the scanning start side and the scanning end side of the adjacent optical scanning modules face each other, and reflects the respective light beams so that they can be guided to a common synchronization detection sensor 49. ing. In the figure, reference numeral 50 is a connector for collectively supplying power to all the optical scanning modules and exchanging data signals.

Positioning members 51 having abutting surfaces are attached to both side surfaces of the housing 42 so as to match a cylindrical surface provided concentrically with a drum for holding a photosensitive drum, which will be described later. After the positioning member 51 is screwed to the protrusion 52, the L-shaped seating surface is mounted on the pin 53 provided on the frame of the apparatus body via the spring 54, so that the positioning member is always pressed against the cartridge. In this state, the plurality of optical scanning modules can be collectively and reliably positioned with respect to the photoconductor drum.

FIG. 13 shows an example in which the optical scanning device is applied to a color laser printer. The optical scanning device housed in the housing 42 and the process cartridge 70 are individually positioned for each color (yellow, magenta, cyan, black), and are arranged in series along the paper transport direction. A sheet is supplied from a sheet feed tray 76 by a sheet feed roller 77, sent out by a pair of registration rollers 78 at a printing timing, and placed on a conveyor belt 81 and conveyed. Toners of the respective color images are transferred by electrostatic attraction when the sheets pass through the respective photoconductor drums, so that the colors are sequentially overlapped, fixed by the fixing roller 79, and ejected to the sheet ejection tray 80 by the sheet ejection roller 82.

The process cartridges of the respective colors have the same structure except that the toner colors are different. Around the photoconductor drum 60, a charging roller 72 that charges the photoconductor to a high voltage, a developing roller 73 that is a developing unit that attaches the charged toner to the electrostatic latent image recorded by the optical scanning device to visualize it. A toner hopper 74 for storing toner and a cleaning case 75 for scraping and storing the residual toner after being transferred to a sheet are provided.

As described above, the optical scanning device is configured by connecting the scanning lines of a plurality of optical scanning modules into one line, and the total number of dots L is divided into 1 to L1, L from the image start end, respectively.
1 + 1 to L2 and L2 + 1 to L dots are allotted and printed. However, in the embodiment, the number of dots to be allotted is made different for each color so that the seams of the scanning lines of the respective colors that scan the same line do not overlap. I am trying.

In the embodiment, the method of generating the electrostatic attraction to drive the movable mirror is shown. However, a coil is formed on the movable mirror so that the magnetic field lines pass in the direction intersecting with the torsion bar. Even with the method of applying a voltage to generate and drive an electromagnetic force, there is a method of connecting a piezoelectric element to a torsion bar and applying a voltage to the piezoelectric element to directly generate a displacement on a movable mirror for driving. Can be implemented with a similar configuration.

Further, although the optical scanning device is composed of three optical scanning modules, the number may be any number, and the number can be increased or decreased according to the recording width of the image forming apparatus. The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the gist of the present invention.

[0072]

As described above, according to the first aspect of the invention, when the scanning angle in the main scanning direction is enlarged by the multiple reflection between the movable mirror and the counter mirror, the counter mirror is tilted in the sub scanning direction. Since they are formed, the bending in the sub-scanning direction can be suppressed, the image quality can be improved, the optical path length of the beam for obtaining the same scanning angle can be shortened, and the facing mirror and the movable mirror can be downsized. In addition, the margin in optical path design (light beam separation) also increases.

According to the invention of claim 2, further,
When a plurality of opposed mirrors are formed, the positional relationship among the opposed mirrors, the movable mirror, and the light beam passage portion can be unified, so that the reflection point position of the light beam and the optical path length can be easily designed. Further, by setting the gap position between the movable mirror and the supporting substrate, it is possible to secure high gap accuracy. Further, even when the shapes of the plurality of opposed mirrors are changed, there is little change in the process.

According to the invention of claim 3, further,
Since the positional relationship between the facing mirror and the movable mirror can be freely defined by the frame substrate, when a plurality of facing mirrors are formed, it becomes easy to design the reflection point position of the light beam and the optical path length. The gap accuracy is also high.

According to the invention of claim 4, further,
By providing the abutting surface with the positioning means, the counter mirror and the first substrate can be aligned with high accuracy. Further, when the swing space of the movable mirror is formed on the frame substrate, a groove or the like that can be used for alignment is simultaneously formed, so that the alignment with the facing mirror can be performed with high accuracy without increasing the number of steps. .

According to the invention of claim 5, further,
Since the light beam enters and exits with an inclination in the sub-scanning direction, the configuration according to claim 5 can prevent beam eclipse and widen the design margin of the entrance and exit angles.

According to the invention of claim 6, further,
By arbitrarily setting the slice angle, it is possible to obtain an arbitrary tilt angle. In addition, by exposing the [111] plane, which is a stable surface having etching resistance, by crystal anisotropic etching, a suitable etched surface having a smooth and accurate angle can be obtained. The Si wafer process makes it possible to manufacture a large number of opposed mirrors with highly accurate inclined surfaces. When the [111] surface is used as the contact surface, a polishing surface that is a slice surface can be used as the reflecting surface, and thus it is more suitable as a mirror. When the slice surface is used as the contact surface, processing at the wafer level becomes possible.

According to the invention of claim 7, further,
Even if the [111] bonding surface has irregularities due to etching,
Since the joining is performed only at both ends in the main scanning direction, the unevenness is small and the joining flatness is good.

According to the invention of claim 8, further,
High dimensional accuracy due to Si process (photolithography, anisotropic etching). If it is specified by dicing, chipping (surface chipping) occurs, but it also prevents it.

According to the invention of claim 9, further,
By arbitrarily setting the slice angle, it is possible to obtain an arbitrary tilt angle. For crystal anisotropic etching,
By using the [111] plane, which is a stable surface having etching resistance, as a reflecting surface, a suitable reflecting surface having a smooth and accurate angle can be obtained. Also, because Si wafer processing is possible,
Mounting cost can be reduced.

Further, according to the invention of claim 10, an arbitrary inclination angle can be obtained by setting the slice angle arbitrarily. By exposing the [111] plane, which is stable and resistant to crystal anisotropic etching, it is possible to obtain a smooth and angle-etched surface. The Si wafer process makes it possible to manufacture a large number of opposed mirrors with highly accurate inclined surfaces. Since a polished surface, which is a sliced surface, can be used as the reflecting surface, it is suitable as a mirror.

Further, according to the invention of claim 11, the opposite surface of the abutting surface is also aligned with the [111] surface, so that the opposing mirror is formed with parallel surfaces in the vertical direction in the direction parallel to the movable mirror. Therefore, when the contact surfaces are joined, the parallel opposite surfaces can be pressed, and chip handling and pressurization uniformity at the time of joining are improved.

Further, according to the invention of claim 12, the power consumption is smaller than that of the conventional polygon mirror.
An image forming apparatus with low noise can be obtained.

[Brief description of drawings]

1A and 1B are diagrams showing an embodiment of a facing mirror substrate of the present invention, in which FIG. 1A is a reference example, FIG. 1B is an embodiment of the facing mirror substrate of the present invention, and FIG. is there.

FIG. 2 is a diagram showing a method of manufacturing a facing mirror according to another embodiment of the present invention.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing another embodiment of the present invention.

FIG. 5 is a diagram showing another embodiment of the present invention.

FIG. 6 is a diagram showing another embodiment of the present invention.

FIG. 7 is a diagram showing another embodiment of the present invention.

FIG. 8A is a plan view of a facing mirror substrate in which the facing mirror of the embodiment of the present invention is incorporated in a micromirror substrate;
FIG. 8B is a sectional view taken along line XX in FIG.

FIG. 9 is an exploded perspective view of the optical scanning device.

FIG. 10 is a cross-sectional view of an optical scanning device.

FIG. 11 is a perspective view of an optical scanning module.

FIG. 12 is an exploded perspective view of the optical scanning module.

FIG. 13 is an explanatory diagram of an image forming apparatus using an optical scanning device.

FIG. 14 is a sectional view of an optical scanning module.

15A and 15B are explanatory diagrams of an image writing line by the optical scanning device.

[Explanation of symbols]

1 facing mirror 2 facing mirrors 3 movable mirrors 3b Si substrate (first substrate) 4 frame board 6 plane orientation [100] Si substrate (support substrate) 23a Passing part 28 LD chips (light source) 60 photoconductor drum 73 developing roller (developing means) a Alignment mark (positioning means) B light beam

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C362 AA43 AA45 BA17 BA83 BA87                       BA90 DA03                 2H042 DA01 DA12 DB14 DC01 DC08                       DE07                 2H045 AB02 AB62 AB73 BA22 BA34                       BA36

Claims (12)

[Claims] 1. A movable mirror that deflects a light beam from a light emitting source, a first substrate that axially supports the movable mirror, and a facing mirror that faces the movable mirror and that reciprocally reflects the light beam between the movable mirror and the movable mirror. In the optical scanning device having, a facing mirror having a reflecting surface formed to be inclined in the sub-scanning direction from the first substrate surface is provided in a direction facing each other with a light beam passing portion interposed therebetween, and the facing mirror is The reflective surface of the facing mirror is arranged so as to be superposed on the first substrate.
An optical scanning device comprising: a reflection region overlapping in a direction perpendicular to the movable mirror surface and facing in a parallel direction. 2. The optical scanning device according to claim 1, wherein the opposed mirror is formed on a support substrate having a light beam passage portion. 3. A frame substrate that forms a movable space of the movable mirror is provided on the first substrate, and the opposed mirror is superposed on and supported by the frame substrate. The optical scanning device according to. 4. The positioning means for aligning the counter mirror and the first substrate is provided between the substrate on the movable mirror side and the substrate on the counter mirror side. 2. The optical scanning device according to item 2. 5. The optical scanning device according to claim 1, wherein the opposed mirror is arranged so that each reflection surface end of the opposed mirror coincides with a plane parallel to the movable mirror. . 6. The facing mirror is made of a Si substrate, and its inclination angle is defined by a plane orientation [111] plane and a slice plane of the Si substrate, and a contact surface parallel to the substrate on the movable mirror side. 2. The optical scanning device according to claim 1, further comprising: one of the surfaces that is in contact with the contact surface, and the other surface that is a reflection surface. 7. The optical scanning device according to claim 6, wherein the contact surfaces are provided at both ends that bridge the movable mirror in the main scanning direction. 8. The optical scanning device according to claim 6, wherein the reflection surface width of the opposed mirror in the sub-scanning direction is defined by a plane orientation [111] plane. 9. The facing mirror is made of a Si substrate, and its inclination angle is defined by a plane orientation [111] plane and a sliced surface of the Si substrate, and the supporting substrate is in contact with the movable mirror in parallel. The optical scanning device according to claim 2, further comprising a surface, and the surface is joined to the slice surface. 10. The opposing mirror is made of a Si substrate, and its inclination angle is defined by a plane orientation [111] plane and a slice plane of the Si substrate, and the supporting substrate is in contact with the movable mirror in parallel. 3. The optical scanning device according to claim 2, further comprising a surface and a joint surface arranged in parallel with the same surface, and one of the surfaces is aligned with the joint surface. 11. The optical scanning device according to claim 6, further comprising a portion aligned with the plane orientation [111] on the surface opposite to the contact surface parallel to the movable mirror. 12. An optical scanning device according to claim 1, a photoconductor on which an electrostatic image is formed by the optical scanning device, and a developing unit which visualizes the electrostatic image with toner. An image forming apparatus having: a transfer unit configured to transfer the visualized toner image onto a recording sheet.