JP2010054651A - Optical scanner - Google Patents

Abstract

To provide an inexpensive apparatus that does not deteriorate in performance even when the environmental temperature changes in an optical scanning apparatus using a vibrating mirror formed by bonding different materials.
An optical scanning device using a vibrating mirror 10 formed by joining a mirror 5 and a vibrator 1 made of materials having different linear expansion coefficients. A reflection mirror 57 that reflects light from the light source 52 to the vibration mirror 10 is configured by laminating a mirror 58 and a holding plate 59 made of materials having different linear expansion coefficients. The beam imaging position can be maintained at a constant position by configuring the vibration mirror 10 and the reflection mirror 57 to have the same curvature in the opposite direction to the light traveling direction when the environmental temperature changes. It is possible to provide an apparatus that does not cause performance degradation.
[Selection] Figure 2

Description

  The present invention relates to an optical scanning device that scans light from a light source with a vibrating mirror and forms an image on a predetermined image plane.

  An image forming apparatus such as a laser printer forms a latent image on a photosensitive member (photosensitive drum) by scanning with laser light. Such laser beam scanning is realized by an optical scanning device called a laser scanning unit. The laser scanning unit deflects the laser beam modulated according to the formed image and emitted from the light source by a mirror, and forms the deflected laser beam in a spot shape on the photosensitive member. A polygon mirror having a plurality of reflecting surfaces is widely known as a deflection mirror used in this type of laser scanning unit. A laser scanning unit including a polygon mirror deflects laser light by rotating the polygon mirror in one direction by driving means such as a motor.

  The rotation speed of polygon mirrors has increased in response to the recent demand for higher writing speeds. However, when the number of rotations of the polygon mirror is increased, the noise generated due to wind noise, motor vibration, etc. increases. It becomes difficult to ensure quietness. In addition, since the laser scanning unit including a polygon mirror needs to include a driving unit such as a motor, there is a problem that it is difficult to reduce the size and weight. For this reason, a reciprocating deflection mirror may be used for the laser scanning unit.

  A vibrating mirror is known as such a reciprocating deflection mirror. This oscillating mirror is constituted by a mechanical vibrator having a torsional rotation axis arranged in a direction perpendicular to the scanning direction of the laser beam. Then, the laser beam is scanned by reciprocally vibrating the mirror supported by the vibrator.

In recent years, semiconductor manufacturing techniques have been applied to the manufacture of such oscillating mirrors. Such a vibrating mirror is formed by processing a semiconductor substrate such as a single crystal silicon substrate, and has attracted attention as a MEMS (Micro Electro Mechanical Systems) vibrating mirror (see, for example, Patent Documents 1 and 2).
JP 2003-84226 A JP 2001-305472 A

  However, in order to manufacture the MEMS oscillating mirror to which the semiconductor manufacturing technique as described above is applied, very expensive manufacturing equipment such as a lithography apparatus is necessary, and it is difficult to manufacture at low cost. In addition, a MEMS vibrating mirror formed using a semiconductor substrate such as a silicon single crystal substrate as a base material has a problem that it is easily broken because it is cleaved relatively easily.

  On the other hand, it is also possible to form a vibration plate by processing a metal material, and to attach a mirror for reflecting laser light to the vibration plate to form a vibration mirror. At this time, it is preferable to use a relatively inexpensive material that easily forms a mirror surface, such as glass or silicon, for the mirror substrate. Furthermore, it is preferable to reduce the moment of inertia of the diaphragm and the mirror from the viewpoint of speeding up, and therefore this configuration cannot increase the thickness.

  Here, in the configuration in which the diaphragm and the mirror are bonded with another material having different linear expansion coefficients, warpage deformation occurs due to the bimetallic effect when the environmental temperature changes. Further, when the mirror is warped, the imaging position in the optical axis direction of the beam changes, and there is a problem that the beam is not narrowed on a predetermined image plane and the resolution is lowered. In this configuration, as described above, since the thickness cannot be increased so much, there is a problem that such a problem cannot be avoided.

  SUMMARY OF THE INVENTION The present invention solves the conventional problems in view of such a situation, and an object of the present invention is to provide an optical scanning device that does not deteriorate in quality even in a vibrating mirror formed by bonding different types of materials. .

  In order to achieve the above object, the present invention employs the following technical means.

  The optical scanning device of the present invention includes a light source that emits light and a reflection mirror that is formed by laminating materials having different linear expansion coefficients and reflects light from the light source on the layer surface. Further, it is configured by laminating materials having different linear expansion coefficients, and the reflection mirror reciprocally vibrates around one line along the layer surface, so that the light received from the reflection mirror is reflected by the layer surface and scanned. A vibrating mirror is provided. Furthermore, an optical system for forming an image of light emitted from the light source on an image plane is provided, and the reflection mirror and the vibration mirror are opposite to each other on the side that reflects the light when the environmental temperature changes. It is configured to warp and deform in the direction.

  The optical scanning device of the present invention includes a light source that emits light, a reflection mirror that reflects light from the light source, and a warp amount adjusting unit that variably warps and deforms the reflection mirror. Further, the vibrating mirror is configured by laminating materials having different linear expansion coefficients, and reciprocally vibrates around one line along the layer surface to reflect and scan the light received from the reflecting mirror on the layer surface. It has. And an optical system for forming an image of light emitted from the light source on an image plane, and changing the amount of warping of the reflecting mirror by the amount of warpage adjusting means, thereby changing the imaging position of the light from the light source. You may comprise so that it may change.

  The optical scanning device of the present invention includes a light source that emits light, a reflection mirror that reflects light from the light source, and a warp amount adjusting unit that warps and deforms the reflection mirror in a variable amount. Further, the vibrating mirror is configured by laminating materials having different linear expansion coefficients, and reciprocally vibrates around one line along the layer surface to reflect and scan the light received from the reflecting mirror on the layer surface. Is provided. Furthermore, an optical system for forming an image of light emitted from the light source on an image plane, and detection means for detecting an imaging position of the light emitted from the light source are provided. Further, the image forming position of the light from the light source may be changed by changing the amount of warping of the reflecting mirror by the amount of warpage adjusting means according to the detection result of the detecting means.

  The present invention provides an optical scanning device in which a vibrating mirror is formed by bonding a vibrating plate made of different materials having different linear expansion coefficients and a mirror. In such an optical scanning device, the beam imaging position can be corrected by the reflection mirror warpage with respect to the change in the beam imaging position caused by the warpage of the vibrating mirror when the environmental temperature changes. In addition, it is possible to provide an inexpensive optical scanner with good quality.

  That is, according to the configuration of the present invention, even if the environmental temperature changes and the oscillating mirror is warped and deformed, the reflecting mirror is warped and deformed in the opposite direction, so that the beam imaging position is corrected and the quality can be maintained.

  Further, the warp amount adjusting means is provided, and the warp amount adjusting means changes the warp amount of the reflecting mirror to change the image forming position of the light from the light source. As a result, the amount of warping of the reflecting mirror can be adjusted even when the light imaging position is not at the desired position due to the warping of the oscillating mirror, so that the light imaging position can be moved onto the image plane, resulting in a reduction in quality. Can be prevented.

  In addition, if the detection means for detecting the imaging position of the light emitted from the light source is provided, the detection means can detect whether the imaging position of the light is at a desired position. Thereby, the image formation position of the light from the light source can be accurately moved on the image plane by adjusting the amount of warping of the reflection mirror.

  The first embodiment of the present invention is an optical scanning device including a light source that emits light and a reflection mirror that is laminated with materials having different linear expansion coefficients and reflects light from the light source on the layer surface. . Then, by reciprocatingly oscillating about one line along the layer surface as an axis, the vibration mirror that reflects and scans the light received from the reflection mirror on the surface of the layer, and the light emitted from the light source on the image surface And an optical system for forming an image. Further, the reflection mirror and the vibration mirror are configured to warp and deform in opposite directions with respect to the light reflecting side when the environmental temperature changes.

  With such a configuration, even if the environmental temperature changes and the oscillating mirror is warped and deformed, the reflecting mirror is warped and deformed in the opposite direction, so that the beam imaging position is corrected and the quality can be maintained.

  Further, according to the second embodiment of the present invention, in the optical scanning device according to the first embodiment, the reflecting mirror and the vibrating mirror are both a mirror that reflects light and a holding plate that holds the mirror. Has been configured. The mirror of the reflection mirror and the mirror of the vibration mirror are the same material with the same thickness, and the holding plate of the reflection mirror and the holding plate of the vibration mirror are the same material with the same thickness. Further, the stacking order of the mirror and the holding plate is opposite to each other on the reflecting mirror and the vibrating mirror.

  With such a configuration, by reversing only the stacking order of the same material with the same thickness, the same amount of warpage can be generated in the reverse direction, and correction can be made with a simple configuration.

  According to the third embodiment of the present invention, in the optical scanning device according to the second embodiment, the holding plate is made of an opaque material. Then, when the holding plate is located on the light reflecting side of the reflecting mirror or the mirror in the oscillating mirror, the holding plate has a shape having a transmission window that is a region through which the light beam can pass. It is a scanning device.

  With such a configuration, even when the holding plate material is an opaque material, the stacking order can be reversed.

  According to a fourth embodiment of the present invention, there is provided a light source that emits light, a reflection mirror that reflects light from the light source, a warp amount adjustment that deforms the reflection mirror and has a variable warp amount. And an optical scanning device. This optical scanning device is configured by laminating materials having different linear expansion coefficients, and reciprocally vibrates around one line along the layer surface to reflect light received from the reflection mirror on the layer surface, A vibrating mirror for scanning is provided. And an optical system for forming an image of light emitted from the light source on an image plane, and changing the amount of warping of the reflecting mirror by the amount of warpage adjusting means to change the imaging position of the light from the light source. It is configured to change.

  Such a warp amount adjusting means is provided, and the warp amount adjusting means changes the warp amount of the reflecting mirror to change the image formation position of light from the light source. As a result, the amount of warping of the reflecting mirror can be adjusted even when the light imaging position is not at the desired position due to the warping of the oscillating mirror, so that the light imaging position can be moved onto the image plane, resulting in a reduction in quality. Can be prevented.

  According to a fifth embodiment of the present invention, a light source that emits light, a reflection mirror that reflects light from the light source, a warp amount adjustment that causes the warp deformation of the reflection mirror and the amount of warpage is variable. And an optical scanning device. Further, the vibrating mirror is configured by laminating materials having different linear expansion coefficients, and reciprocally vibrates around one line along the layer surface to reflect and scan the light received from the reflecting mirror on the layer surface. It has. Furthermore, an optical system for forming an image of light emitted from the light source on an image plane and a detecting unit for detecting an imaging position of the light emitted from the light source are provided. Then, according to the detection result of the detecting means, the amount of warping of the reflecting mirror is changed by the amount of warping adjusting means to change the imaging position of the light from the light source.

  With such a configuration, if the detection unit that detects the imaging position of the light emitted from the light source is provided, the detection unit can detect whether the imaging position of the light is at a desired position. it can. Therefore, the image formation position of the light from the light source can be accurately moved on the image plane by adjusting the amount of warping of the reflection mirror.

  Further, according to a sixth embodiment of the present invention, in the optical scanning device according to the fourth or fifth embodiment, the warp amount adjusting means is laminated and joined with a reflection mirror, and the piezoelectric material is bonded to the piezoelectric material. Drive means for applying a voltage. With such a configuration, it is possible to freely adjust the amount of warping of the reflecting mirror.

  Further, according to the seventh embodiment of the present invention, in the optical scanning device according to the fourth or fifth embodiment, the first-time warpage amount adjusting means is laminated and joined to the reflection mirror, and the reflection mirror is linearly expanded. Holding members made of different materials and temperature adjusting means for changing the temperature of the reflecting mirror. With such a configuration, it is possible to adjust the amount of warping of the reflecting mirror with a simple configuration.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

Example 1
(Configuration of vibrating mirror)
First, the structure of the oscillating mirror 10 mounted on a laser scanning unit which is an example of an optical scanning device according to the present invention will be described in detail.

  FIG. 1 is a schematic perspective view showing the structure of the vibrating mirror 10 of the present embodiment. As shown in FIG. 1, the vibrating mirror 10 includes a vibrator 1, a mirror 5, and a permanent magnet 6 that are formed by press processing, which will be described later. Here, the vibrator 1 is made of a metal material such as a titanium alloy, and the mirror 5 is made of a material such as silicon or glass, but silicon is used in this embodiment. The vibrator 1 has a structure in which a support portion 4 to which a mirror 5 and a permanent magnet 6 are fixed is supported by two beams 3 arranged on the same straight line. The other end of the beam 3 is supported by a rectangular frame 2 integrally formed as the vibrator 1, and the vibrator 1 reciprocally vibrates using the beam 3 as a torsional rotation shaft. This reciprocating vibration is sustained by applying an alternating magnetic field to the permanent magnet 6.

  The alternating magnetic field to be applied to the permanent magnet 6 can be generated by, for example, driving means 11 (see FIG. 2) that applies AC power to the electromagnet. In this case, if the frequency of reciprocating vibration, that is, the frequency of AC power applied to the electromagnet (hereinafter referred to as drive frequency) and the resonance frequency of the oscillating mirror 10 coincide with each other, consumption for driving the oscillating mirror 10 is achieved. Electric power can be reduced. This is because when the oscillating mirror 10 reciprocates at the resonance frequency, the magnitude of the external force required to maintain the vibration is minimized.

  In the laser scanning unit that scans the photosensitive member with laser light via the vibrating mirror 10, the driving frequency is closely related to the recording density on the photosensitive member and the printing speed (feeding speed of the photosensitive member). That is, the drive frequency f is expressed by the following formula 1 by the recording density D (dpi) and the printing speed V (mm / sec).

  Formula 1 is premised on reciprocating printing in which printing is performed when the vibrating mirror 10 rotates in any direction with respect to the torsional rotation axis. In the case of unidirectional printing in which printing is performed only when the oscillating mirror 10 rotates in one direction with respect to the torsional rotation axis, the drive frequency f is doubled. For example, when the recording density D is 600 dpi and the printing speed V is 180 mm / sec, the drive frequency f is about 2126 Hz (reciprocal printing).

The resonance frequency f ₀ of the vibrating mirror 10 having the above structure is determined by the spring constant K of the beam 3 (the sum of both beams 3) and the moment of inertia J of the support portion 4 including the mirror 5 and the permanent magnet 6. Is expressed by the following formula 2.

On the other hand, in this embodiment, since the vibrator 1 is made of a metal material, the vibrator 1 is damaged when the shear stress applied to the beam 3 during the reciprocating vibration exceeds the allowable stress of the beam 3. . For this reason, structurally, the vibrator 1 is required to have a shear stress applied to the beam 3 equal to or less than an allowable stress of the beam 3. Assuming that the length of each beam 3 in the torsional rotation axis direction is L, the width of the beam 3 is b, the thickness of the beam 3 is t (here, t ≦ b), and the torque applied to the beam 3 is T. The shear stress τ _A at the midpoint in the width direction on the surface of 3 is expressed by the following Equation 3.

Further, the shear stress τ _B at the middle point in the thickness direction on the surface of the beam 3 is expressed by the following expression 4.

  Further, the twist angle ω per unit length of the beam 3 (maximum swing angle θ when reciprocally oscillating at the resonance frequency / beam length L) is expressed by the following equation using the lateral elastic modulus G of the beam 3. It is expressed by 5.

  In this case, the spring constant K satisfies the following Expression 6.

Therefore, the beam 3 needs to have the shear stress τ _A and τ _B shown in Equations 3 and 4 below the allowable stress of the beam 3 and satisfy Equations 2, 5, and 6.

  Hereinafter, a specific structure of the vibrating mirror 10 will be described together with a design procedure thereof.

When designing the oscillating mirror 10, first, a metal material constituting the vibrator 1 is selected. As described above, the vibrator 1 is formed by press working. In order to enable such molding, the metal material is desirably a hoop material. Further, from the viewpoint of preventing metal fatigue due to reciprocating vibration and increasing the allowable stress of the beam 3, the metal material constituting the vibrator 1 desirably has a large fatigue limit. Further, from the viewpoint of reducing the moment of inertia J (increasing the resonance frequency f ₀ ), the density is preferably small, and from the viewpoint of increasing the swing angle θ of the reciprocating vibration, the transverse elastic modulus G is preferably small (above (See Equation 5). In addition, from the viewpoint of environmental resistance, it is preferable that the material is stable and the price is low. Therefore, in this embodiment, a titanium alloy (Ti-15V-3Cr-3Sn-3Al, AMS4914) is adopted as a metal material that satisfies all the above conditions. The fatigue strength of the titanium alloy is 350 MPa, and the density is 4.7 g / cm ³ . It should be noted that other metals can be employed as the metal material constituting the vibrator 1.

  After selecting the metal material constituting the vibrator 1, the swing angle of the vibrating mirror 10, the material and size of the mirror 5, and the material and size of the permanent magnet 6 are determined. The swing angle of the oscillating mirror 10 and the size of the mirror 5 are determined to be a swing angle and a size necessary for obtaining a desired beam characteristic as a laser scanning unit. The beam characteristics are determined depending on the structure of the laser scanning unit such as the distance between the oscillating mirror 10 and a lens that forms an image of the beam reflected by the oscillating mirror 10 on the photosensitive member. For example, when the recording density D is 600 dpi and the printing speed V is 180 mm / sec, the swing angle is ± 23 degrees and the size of the mirror 5 is 4.7 mm width × length (twist rotation axis direction) 0.8 mm × The thickness can be 0.15 mm. Here, the planar shape of the mirror 5 is rectangular, but other planar shapes such as an elliptical shape may be used as long as the laser beam having a desired beam shape can be reflected. The mirror 5 may be made of any material that can reflect laser light. Here, a reflective film made of a material such as aluminum is provided on a base material made of silicon, and a protective film is further provided thereon. Yes.

  Next, the allowable stress is determined based on the fatigue strength of the titanium alloy. The allowable stress can be determined based on the fatigue strength curve (SN curve) of the titanium alloy. FIG. 3 is a diagram showing an SN curve of the titanium alloy. As described above, the fatigue limit of the titanium alloy is 350 MPa, and if the maximum stress applied to the beam 3 at the maximum swing angle is less than or equal to the fatigue limit, a semi-permanent life can be realized. Here, the allowable stress is 250 Mpa with a margin of 100 MPa for the fatigue limit of 350 MPa.

The mirror 5 is bonded to the support portion 4 of the vibrator 1 with an adhesive. As described above, the vibrator 1 and the mirror 5 are made of different materials and have different linear expansion coefficients. The linear expansion coefficient of the titanium alloy constituting the vibrator 1 is 8.5 × 10 ⁻⁶ / ° C., and the linear expansion coefficient of silicon constituting the mirror 5 is 3 × 10 ⁻⁶ / ° C. Since materials having different linear expansion coefficients are joined to each other, the amount of expansion / contraction of each material differs when the environmental temperature changes, and thus warp deformation occurs at a constant curvature due to the bimetallic effect at the joint portion. The curvature ρ of the warp at this time is the longitudinal elastic modulus, thickness, and linear expansion coefficient of the vibrator material as E ₁ , t ₁ , α ₁ , respectively, and the longitudinal elastic coefficient, thickness, and linear expansion coefficient of the mirror material are each, E _2, t _2, and alpha _2, when the environmental temperature changes and [Delta] t, the formula 7.

  FIG. 4 shows an example of a deformed state of the mirror 5 and the vibrator 1 when viewed from the torsional axis direction (direction in which the beam 3 is twisted) when the environmental temperature is changed to a higher temperature than that during bonding. Since the extension of the vibrator 1 is larger than that of the mirror 5, it is deformed into a concave shape on the mirror surface side. When the mirror 5 is warped with a certain curvature, although the imaging position in the optical axis direction changes, the reflected light from the mirror can be condensed at one point by means such as an imaging lens. On the other hand, when there are portions with different curvatures in the mirror, the image forming position is different for each portion, so that the light cannot be condensed at one point, and the beam cannot be sufficiently focused. For this reason, in this invention, it is comprised so that the junction length in the mirror scanning direction of the mirror 5 and the vibrator | oscillator support part 4 may become 70% or more of a mirror effective area | region. By providing a region with a constant curvature at the center of the mirror of 70% or more, it is possible to narrow the beam to a level where there is no practical problem.

  The permanent magnet 6 may be any size that can be fixed to the vibrator support portion 4 and can generate an external force that reciprocally vibrates the vibrating mirror 10. Here, a rare earth magnet having a diameter of 0.8 mm and a thickness of 0.4 mm is used as the permanent magnet 6.

Subsequently, the thickness of the vibrator 1 is temporarily set, and the mirror 5 and the permanent magnet 6 are fixed, that is, the mirror 5, the permanent magnet 6, and the adhesive member and the permanent magnet 6 for fixing the mirror 5 to the support portion 4. The moment of inertia J of the support portion 4 is calculated in a state including the adhesive member for fixing to the support portion 4. Then, a spring constant K at which a desired resonance frequency f ₀ is obtained is calculated from the moment of inertia J and Equation 2. Then, using the calculated spring constant K and Equations 3 to 6, the beam width b and the beam length L are determined under the condition that the shear stresses τ _A and τ _B in Equations 3 and 4 become an allowable stress of 250 MPa or less. To do. The beam thickness t is the same as the temporarily set thickness of the support portion 4.

(Configuration of laser scanning unit)
Next, the configuration of a laser scanning unit that is an example of the optical scanning device of the present invention including the vibrating mirror configured as described above will be described.

  FIG. 2 is a schematic configuration diagram showing the laser scanning unit. The laser scanning unit 50 includes a light source 52, a reflection mirror 57, a deflector 53, an imaging lens system 54 as a secondary optical system, an amplitude detection mirror 64, and an amplitude detection sensor 65 in a housing 51.

  The light source 52 is configured as an integrated unit including a laser diode 61 mounted on a circuit board 63 and a collimator lens 62. The circuit board 63 modulates the intensity of the laser beam emitted from the laser diode 61 in accordance with an image signal input from the outside. The modulated laser light is incident on the collimator lens 62. The collimator lens 62 is formed of a cylindrical glass or plastic lens, and converts the laser light output from the laser diode 61 into substantially parallel light that matches the optical axis of the collimator lens 62 and outputs the parallel light. The light emitting point of the laser diode 61 is disposed at the focal point of the collimator lens 62.

  The laser beam output from the light source 52 is incident on the reflection surface of the reflection mirror 57 through the aperture 55 and the cylindrical lens 56. The reflection mirror 57 is configured by laminating a mirror material 58 having a reflective film on the surface and a holding material 59, and the mirror material 58 and the holding material 59 are made of materials having different linear expansion coefficients. For example, a glass material can be used as the mirror material 58, and a titanium-based material can be used as the holding material 59. At this time, the linear expansion coefficient, the longitudinal elastic modulus, and the thickness of the material of the mirror material 58 and the holding material 59 are the same so that the curvature ρ at the time of temperature change represented by Equation 7 is the same as the curvature of the vibrating mirror 10 and in the opposite direction. Selected. The laser beam reflected by the reflecting mirror 57 is then incident on the reflecting surface of the deflector 53. The deflector 53 includes an oscillating mirror 10 having a torsional rotation axis arranged in a direction perpendicular to the scanning direction of the laser beam on the photosensitive member, and a driving unit 11 that oscillates the oscillating mirror 10 in a sine manner. It is configured. The cylindrical lens 56 projects the laser light on the reflecting surface of the vibrating mirror 10 in a state where only the direction of the torsional rotation axis of the laser light is converged.

  The laser beam deflected by the deflector 53 is incident on the imaging lens system 54. Here, the imaging lens system 54 is composed of two acrylic lenses, and the laser beam deflected by the deflector 53 is spotted on the photoconductor in a state where the scanning speed on the photoconductor is substantially the same. Form an image. That is, the imaging lens system 54 is an arc that forms an image of a laser beam reflected by the oscillating mirror 10 that oscillates sinusoidally and whose incident angle changes trigonometrically with time as an evenly spaced spot array on the photosensitive member. It is a sine θ lens.

  One set of the amplitude detection mirror 64 and the amplitude detection sensor 65 are provided outside both areas scanned by the vibrating mirror 10 and recorded on the photosensitive member, and the scanned laser light is the amplitude detection mirror 64. And is incident on the amplitude detection sensor 65. The oscillating mirror 10 is driven to vibrate with a large amplitude so as to be scanned to the outside beyond the amplitude detecting mirrors 64, and thereby, from each amplitude detecting sensor 65 twice during one reciprocal vibration. Detection signals are output one by one. Here, if the time between the signals from the two amplitude detection sensors 65 is controlled to be constant, the amplitude of the vibrating mirror 10 is kept constant, whereby an image is also recorded at a predetermined position.

  In the apparatus configured as described above, when the environmental temperature changes, the reflection mirror 57 and the vibration mirror 10 are warped in the same direction in the opposite direction to the light traveling direction as described above. For example, when the environmental temperature rises, the reflecting mirror 57 is warped with the mirror surface convex, and the oscillating mirror 10 is warped with the mirror surface concave. At this time, when these curvatures are the same amount and in the opposite direction, the parallel light beam that has entered the reflection mirror 57 is reflected and spread by the reflection mirror 57, but when this light beam is reflected by the vibration mirror 10, it is narrowed down again. It returns to parallel rays. Therefore, the imaging position can be kept constant even when the environmental temperature changes. This is shown schematically in FIG. When the environmental temperature is lowered, the direction of warping of each mirror is reversed, but the correction action works in the same way.

(Example 2)
Next, a second embodiment of the present invention will be described.

  As shown in FIG. 6, in this embodiment, the reflection mirror 57 is configured by joining a mirror 58 and a holding material 59. The mirror 58 is made of the same material with the same thickness as the mirror 5 of the vibration mirror 10, and the holding plate 59 is made of the same material with the same thickness as the vibrator support portion 4 of the vibration mirror 10, and becomes an opaque material. Yes. Further, the holding plate 59 is arranged in front of the light traveling direction, and the transmission window 59 (a) is opened in the region where the beam of the holding plate 59 hits. The opening size of the transmission window 59a is about 10% of the area of the holding plate 59. Thus, the light that has passed through the transmission window 59 (a) is reflected by the mirror 58. Other configurations are the same as those in the first embodiment.

  In the configuration as described above, in the reflecting mirror 57 and the vibrating mirror 10, the mirror and the support material are made of the same material with the same thickness and the stacking order is reversed with respect to the traveling direction of the light beam. When there is a temperature change, the same amount of warpage in the opposite direction is shown. For this reason, the imaging position can be kept constant as in the first embodiment.

(Example 3)
Next, a third embodiment of the present invention will be described.

  In the present embodiment, the reflecting mirror 57 is configured by joining a mirror 58 and a piezoelectric member 71 as shown in FIG. 7, and electrodes are provided on the front and back of the piezoelectric member 71. When a voltage is applied to the piezoelectric member 71 by a driving means (not shown), the reflecting mirror 57 is warped due to expansion and contraction due to the piezoelectric effect. The amount of warping can be controlled by the applied voltage, and the beam imaging position can be changed by the warping of the reflecting mirror 57. That is, the piezoelectric member 71 acts as a warp amount adjusting means for variably adjusting the warp amount of the reflection mirror 57. Other configurations are the same as those in the first embodiment.

  In the configuration as described above, when the environmental temperature changes, the mirror 5 in the oscillating mirror 10 is warped due to a difference in linear expansion coefficient from the vibrator support portion 4. When the mirror 5 is warped, the imaging position in the optical axis direction is changed, and the beam cannot be focused on the photosensitive member. The amplitude detection sensor 65 is installed at a distance corresponding to the position where the photoconductor is extended via the amplitude detection mirror 64. Therefore, if the beam is narrowed at the position of the amplitude detection sensor 65, the beam can be narrowed even on the photosensitive member. Whether or not the beam is narrowed in the amplitude detection sensor 65 can be determined by the time that the beam passes through each amplitude detection sensor 65. That is, since the beam width is small when the beam is narrowed, the time required for the beam to pass is small, and the pulse width output from the amplitude detection sensor 65 is narrow. On the other hand, if the beam is not narrowed, the beam width is large, so that the time required for the beam to pass is large, and the pulse width output from the amplitude detection sensor 65 is wide.

  In accordance with the detection result, a voltage is applied to the piezoelectric member 71 to cause the reflection mirror 57 to warp and change the imaging position of the beam. Here, if the pulse width in the amplitude detection sensor 65 is controlled to be a predetermined value, the beam can be controlled to be imaged on the photosensitive member. According to this configuration, the imaging position of the beam can be freely changed by the voltage applied to the piezoelectric material 71, and the controllability is good. Further, the amplitude detection sensor 65 for making the amplitude of the oscillating mirror 10 constant can be used for examining the imaging state of the beam, and an inexpensive configuration can be realized.

Example 4
Next, a fourth embodiment of the present invention will be described.

  In this embodiment, as shown in FIG. 8, the reflection mirror 57 is formed by laminating a mirror 58 and a holding material 59, and the reflection mirror 57 is provided with a heater 72 as temperature adjusting means. The mirror 58 and the holding member 59 are made of materials having different linear expansion coefficients, and when the reflection mirror 57 is heated by the heater 72, warpage occurs due to the bimetal effect. The amount of warpage varies depending on the temperature of the reflection mirror 57 and can be controlled by the amount of heating by the heater 72. The image formation position of the beam can be changed by the warpage of the reflection mirror 57. That is, in this embodiment, the heater 72 acts as a warp amount adjusting means for variably adjusting the warp amount of the reflection mirror 57. Other configurations are the same as those in the first embodiment.

  In the configuration as described above, when the environmental temperature changes, the mirror 5 in the oscillating mirror 10 is warped due to a difference in linear expansion coefficient from the vibrator support portion 4. Similarly, the reflection mirror 57 is warped. When these mirrors are warped, the imaging position in the optical axis direction changes, and the beam cannot be focused on the photosensitive member. The imaging state in the optical axis direction can be detected by the amplitude detection sensor 65 in the same manner as in the third embodiment. In accordance with the detection result of the amplitude detection sensor 65, the heater 72 is energized to cause the reflection mirror 57 to warp and change the imaging position of the beam. If the pulse width in the amplitude detection sensor 65 is controlled to be a predetermined value, the beam can be controlled to be imaged on the photosensitive member.

  According to this configuration, the beam imaging position can be freely changed by energizing the heater 72, and the controllability is good. Further, the amplitude detection sensor 65 for making the amplitude of the oscillating mirror 10 constant can be used for examining the imaging state of the beam, and an inexpensive configuration can be realized.

  Here, if the temperature control means is only the heater 72, it can be controlled only on the temperature raising side. For this reason, an image forming position is offset and adjusted in advance according to the warpage of each mirror at the time of temperature change so that the beam can be imaged on the photosensitive member when the temperature is raised. Is also possible.

  Further, a Peltier element or the like can be used as the temperature control means, and the temperature of the reflection mirror 57 can be controlled to be lowered by the Peltier element. In this case, conversely to the above example, the imaging position can be offset and adjusted in advance so that the beam can be imaged on the photosensitive member when the temperature is lowered. It is also possible to install both a heater and a Peltier element as temperature control means.

  The present invention is not limited to the above-described embodiments, and various modifications and applications can be made without departing from the technical idea of the present invention. For example, in the above-described embodiment, a configuration has been described in which a permanent magnet is mounted on a vibrating mirror, and a driving unit applies an alternating magnetic field to the permanent magnet. However, the driving method of the vibrating mirror is arbitrary as long as the effect of the present invention is achieved. Can be changed.

  As described above, according to the present invention, in the optical scanning device using the vibration mirror in which the vibration plate and the mirror are made of materials having different linear expansion coefficients, the vibration mirror is warped when the environmental temperature changes. By canceling the change of the beam imaging position by the warping of the reflecting mirror, the beam imaging position can be kept constant, and it is possible to provide a device of good quality regardless of the environmental temperature.

  The optical scanning device of the present invention can be used for an image forming apparatus, a laser printer, a digital copying machine, and the like.

The schematic perspective view which shows the structure of the vibration mirror in this invention. 1 is a schematic configuration diagram showing a structure of an optical scanning device according to the present invention. The figure which shows the SN curve of a titanium alloy. The figure which shows an example of the curvature state of a mirror and a vibrator | oscillator when environmental temperature changes. The schematic diagram which shows the correction | amendment state of the light ray by a mirror. The figure which shows the reflective mirror in the 2nd Example of this invention. The figure which shows the reflective mirror in the 3rd Example of this invention. The figure which shows the reflective mirror in the 4th Example of this invention.

Explanation of symbols

1 vibrator 2 frame 3 beam (torsional rotation axis)
4 Supporting Section 5 Mirror 6 Permanent Magnet 10 Vibrating Mirror 50 Laser Scanning Unit 52 Light Source 53 Deflector 54 Imaging Lens System (Arc Sine θ Lens)
56 Cylindrical Lens 57 Reflection Mirror 58 Mirror 59 Holding Member 64 Amplitude Detection Mirror 65 Amplitude Detection Sensor 71 Piezoelectric Member 72 Heater

Claims (7)

A light source that emits light;
It is configured by laminating materials having different linear expansion coefficients, and a reflection mirror that reflects light from the light source;
A material is formed by laminating materials having different linear expansion coefficients, and by reciprocatingly oscillating around one line along the laminated surface, a vibrating mirror that reflects and scans light received from the reflecting mirror;
An optical system for imaging light emitted from the light source on an image plane;
With
The optical scanning device, wherein the reflecting mirror and the vibrating mirror are configured to warp and deform in opposite directions with respect to the light reflecting side when the environmental temperature changes. The reflecting mirror and the vibrating mirror are both configured by laminating a mirror that reflects light and a holding plate that holds the mirror,
The mirror of the reflection mirror and the mirror of the vibration mirror are the same material with the same thickness, and the holding plate of the reflection mirror and the holding plate of the vibration mirror are the same material with the same thickness,
The optical scanning device according to claim 1, wherein the reflecting mirror and the vibrating mirror are configured such that the order of stacking the mirror and the holding plate is opposite to each other on the side that reflects each light. The holding plate is
Composed of opaque material,
In the reflecting mirror or the vibrating mirror, when the holding plate is located on the side that reflects the light with respect to the mirror, the reflecting mirror or the oscillating mirror has a shape having a transmission window that is a region through which light can pass. The optical scanning device according to claim 2. A light source that emits light;
A reflection mirror that reflects light from the light source;
A warp amount adjusting means for warping and deforming the reflecting mirror and having a variable amount of warpage;
A vibration mirror that is configured by laminating materials having different linear expansion coefficients and reciprocatingly vibrates around one line along the layer surface to reflect and scan light received from the reflection mirror on the layer surface;
An optical system for imaging light emitted from the light source on an image plane;
With
An optical scanning device, wherein the amount of warp of the reflecting mirror is changed by the amount of warp adjusting means to change the imaging position of light from the light source. Detecting means for detecting an imaging position of light emitted from the light source;
The optical scanning device according to claim 4, wherein an image formation position of light from the light source is changed by changing a warpage amount of the reflection mirror by the warpage amount adjusting means according to a detection result of the detection means. 6. The optical scanning according to claim 4, wherein the warp amount adjusting means includes a piezoelectric material laminated and bonded to the reflecting mirror, and a driving means for applying a voltage to the piezoelectric material. apparatus. The warpage amount adjusting means includes a holding member made of a material laminated and bonded to the reflecting mirror and having a coefficient of linear expansion different from that of the reflecting mirror, and a temperature adjusting means for changing the temperature of the reflecting mirror. The optical scanning device according to claim 4 or 5, wherein

Images