JP5273559B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably form a high quality image by performing a stable and accurate optical scanning, thereby attaining reduction in color misregistration, high precision in scanning line pitch of multiple beams and switching of writing density, and making the improvements realized with compatibility with the attainment of optical characteristics, such as, superior wavefront aberrations. <P>SOLUTION: A divergent luminous flux emitted from a semiconductor laser 1 is transformed into a predetermined luminous flux with a coupling lens 2 held as a unit. The luminous flux emitted from the coupling lens 2 is condensed in sub scanning direction with a cylindrical lens 5 successively via a liquid deflecting element 3 and an aperture 4, reflected on a deflective reflecting face of a polygon mirror 6, condensed by an imaging optical system 7, focused on a face to be scanned on the outer periphery of a photoreceptor drum 9 via a folding mirror 8 to form a light spot, and scans the face to be scanned. The long-side direction and the short-side direction of a liquid-sealed part of the liquid crystal deflecting element 3 are made to correspond to the long-side direction and the short-side direction of the cross section of the luminous flux, respectively. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a so-called electrophotographic image forming apparatus such as a digital copying machine, a laser printer, and a laser facsimile, and more particularly, an optical scanning apparatus suitable for image formation, and an image forming apparatus using such an optical scanning apparatus. It is about.

An optical image forming apparatus is widely used for electrophotographic image recording, and this type of image forming apparatus is usually provided with an optical scanning device using a laser. The optical scanning device causes a light beam (light beam) from a laser light source to enter a photosensitive drum on an outer peripheral surface through, for example, an optical deflector using a polygon mirror, and in a direction parallel to the drum axis (main scanning). In general, a method of forming a latent image on the outer peripheral surface of the drum by rotating the drum in the sub-scanning direction about the axis while scanning using an optical deflector in the direction). On the outer peripheral surface of the drum, a light beam is condensed by an imaging optical system such as an fθ lens to form a light spot. In this case, if the position of the light spot formed on the outer peripheral surface of the drum in the sub-scanning direction is deviated from the required position, the quality of the image (output image) formed and output by the image forming apparatus may be deteriorated. .
As an example of a full-color image forming apparatus, a so-called tandem image forming apparatus will be described. In this type of image forming apparatus, four photosensitive drums are sequentially arranged in the conveyance direction of the recording paper, and light beams emitted from a plurality of light source devices respectively corresponding to the respective photosensitive members are deflected by deflection means. A developer that uses a developer of different colors such as yellow, magenta, cyan, and black to scan and expose each photoconductor almost simultaneously by a plurality of imaging optical systems corresponding to each photoconductor to form a latent image Thus, after the latent image is made visible, these visible images are sequentially superimposed and transferred and fixed on the same recording paper to obtain a color image. In such a full-color image forming apparatus, if the position in the sub-scanning direction of the light spot formed on the outer peripheral surface of the drum corresponding to each color is deviated from a required proper position, the color misregistration is performed when the respective colors are superimposed. As a result, the image quality is significantly reduced.

The configuration of this type of conventional image forming apparatus includes, for example, Japanese Patent Application Laid-Open No. 11-133326, Japanese Patent Application Laid-Open No. 9-131920, Japanese Patent Application Laid-Open No. 2005-292349, and Japanese Patent Application Laid-Open No. 2005-292349. Patent Document 4 (Japanese Patent Application Laid-Open No. 2005-166084) and the like.
In recent years, in an image forming apparatus, in order to improve the image quality, it is required to increase the image density and to increase the image output speed in order to improve operability. As one method for achieving both high density and high speed, so-called multi-beam scanning, in which scanning is performed simultaneously using a plurality of light beams, is considered. In order to realize multi-beam using a multi-beam light source having a plurality of light emitting units, a pitch (scan line interval) in the sub-scanning direction of a plurality of light beams (light beams) emitted from the multi-beam light source is used. Proper adjustment is required.
As a method for adjusting the pitch in the sub-scanning direction, for example, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 11-133326), a light source unit including a multi-beam light source is rotated around the optical axis. For example, as disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 9-131920), a method using a pitch adjusting optical element has been proposed.

Further, by switching the writing density by the pitch adjustment as described above, for example, 600 dpi, 1200 dpi, etc. according to the output image, the sub-scanning direction of the plurality of light beams emitted from the multi-beam light source is changed. It has also been proposed that the user can switch the pitch (scan line interval).
Further, as disclosed in, for example, Patent Document 3 (Japanese Patent Application Laid-Open No. 2005-292349), as a pitch adjusting means as described above, a liquid crystal element is used to deflect an optical path and a deflection angle can be variably controlled. Proposed. Such a liquid crystal element has excellent characteristics such as low voltage driving, no heat generation, no noise, no vibration, and small / light weight, and therefore, the sub-scanning direction of the light spot formed on the outer peripheral surface of the drum This is considered to be suitable for the correction of the positional deviation related to or the adjustment of the pitch in the sub-scanning direction of a plurality of light beams.
For example, Patent Document 4 (Japanese Patent Application Laid-Open No. 2005-166084) discloses an example of a method for fixing a liquid crystal element to an apparatus.

As described above, the deflection of the light beam by the liquid crystal element has many effects, but on the other hand, the liquid crystal element such as deterioration of wavefront aberration due to shape error of the liquid crystal element, change of wavefront aberration due to driving / non-driving of the liquid crystal element, etc. There is a concern about the influence on the optical characteristics when mounting the device on the optical scanning device, and it is a problem to deal with the influence on the optical characteristics.
That is, in the optical scanning device, stable and highly accurate optical scanning is performed to reduce color misregistration, increase the accuracy of the multi-beam scanning line interval, and change the writing density. It is desired to achieve both achievement of optical characteristics such as good wavefront aberration. In addition, in an image forming apparatus, it is desired to stably form a high-quality image using the optical scanning device as described above.
The present invention has been made in view of the above-described circumstances, and realizes stable and highly accurate optical scanning, reduction of color misregistration, high precision of multi-beam scanning line intervals, and switching of writing density. In addition, it is possible to achieve both of these realizations and achievement of good optical characteristics such as wavefront aberration, and stable formation of high-quality images by such an optical scanning device. An object of the present invention is to provide an image forming apparatus.

The object of the first aspect of the present invention is to perform stable and high-precision optical scanning more effectively , in particular, to reduce color misregistration, to increase the accuracy of multi-beam scanning line intervals, and to switch writing density. It is an object of the present invention to provide an optical scanning device that realizes optical characteristics such as wavefront aberration and the like.
The object of claim 2 of the present invention is to effectively perform stable and highly accurate optical scanning, reduce color misregistration, increase the accuracy of multi-beam scanning line spacing, and switch writing density. The present invention also provides an optical scanning device that can achieve good optical characteristics such as wavefront aberration.
The object of the third aspect of the present invention is to perform stable and high-precision optical scanning more effectively, reduce color misregistration, increase the accuracy of multi-beam scanning line intervals, and switch writing density. It is an object of the present invention to provide an optical scanning device which can be realized and can achieve good optical characteristics such as wavefront aberration.
The object of claim 4 of the present invention is to perform stable and high-precision optical scanning more effectively, reduce color misregistration, increase the accuracy of multi-beam scanning line intervals, and switch writing density. It is an object of the present invention to provide an optical scanning device which can be realized and can achieve good optical characteristics such as wavefront aberration.

The object of claim 5 of the present invention is to perform stable and highly accurate optical scanning, particularly more effectively, to reduce color misregistration, to increase the accuracy of scanning line intervals of multi-beams, and to switch writing density. It is an object of the present invention to provide an optical scanning device that realizes optical characteristics such as wavefront aberration and the like.
The object of claim 6 of the present invention is to perform stable and highly accurate optical scanning, particularly with an optical scanning device, to reduce color misregistration, to increase the accuracy of scanning line intervals of multi-beams, and to switch writing density. It is an object of the present invention to provide an image forming apparatus that achieves optical characteristics such as wavefront aberration that is realized and enables stable formation of a high-quality image.

In order to achieve the above-described object, an optical scanning device according to the present invention described in claim 1 is provided.
The light beam emitted from the light source is converted into a required light beam state by a coupling lens held integrally with the light source, and the light beam is deflected by an optical deflector and then condensed on the surface to be scanned by the imaging optical system. In the optical scanning device to be
In the optical path between the light source and the optical deflector, a liquid crystal deflecting element that changes the traveling direction of the light beam is provided.
The longitudinal and lateral direction of the liquid crystal filling portion in which the liquid crystal in the liquid crystal deflection element is sealed, Ri Na in correspondence with the longitudinal direction and the transverse direction of the cross-section of the light beam,
A plurality of effective areas in which the liquid crystal is driven are juxtaposed in the longitudinal direction of the liquid crystal sealing part in the liquid crystal sealing part,
With respect to the longitudinal direction of the liquid crystal sealing portion, the interval between the effective regions for driving the liquid crystal is shorter than the distance from the end of the liquid crystal sealing portion to the effective region .
An optical scanning device according to the present invention described in claim 2 is the optical scanning device according to claim 1,
The direction deflected by the liquid crystal deflecting element corresponds to the short direction of the liquid crystal sealing portion in the liquid crystal deflecting element.
An optical scanning device according to a third aspect of the present invention is the optical scanning device according to the first or second aspect,
The imaging position deviation in the optical axis direction generated in the imaging optical system and the imaging position deviation in the optical axis direction generated in the liquid crystal deflecting element when the temperature rises are directions that cancel each other. Yes.

An optical scanning device according to a fourth aspect of the present invention is the optical scanning device according to any one of the first to third aspects,
The light source and the coupling lens are integrally held by a common holding member, and the linear expansion coefficient of the holding member is caused by an imaging position shift in the optical axis direction generated in the imaging optical system when the temperature rises. It corrected so as to lack for
It is characterized a call.

An optical scanning device according to the present invention described in claim 5 is the optical scanning device according to claim 4 ,
An input terminal for applying a voltage to each effective area of liquid crystal driving is arranged on the end side of the liquid crystal deflecting element.
According to a sixth aspect of the present invention, there is provided an image forming apparatus according to the present invention.
In an image forming apparatus that forms an image using an electrophotographic process,
As an exposure processing means for performing an exposure process in the electrophotographic process,
The optical scanning device according to any one of claims 1 to 5 is provided.

According to the present invention, stable and highly accurate optical scanning is performed, color misregistration is reduced, multi-beam scanning line spacing is highly accurate, and writing density is switched. It is possible to provide an optical scanning device capable of achieving both achievement of optical characteristics such as wavefront aberration and an image forming device capable of stably forming a high-quality image by using such an optical scanning device. .
That is, according to the optical scanning device of claim 1 of the present invention,
The light beam emitted from the light source is converted into a required light beam state by a coupling lens held integrally with the light source, and the light beam is deflected by an optical deflector and then condensed on the surface to be scanned by the imaging optical system. In the optical scanning device to be
In the optical path between the light source and the optical deflector, a liquid crystal deflecting element that changes the traveling direction of the light beam is provided.
The longitudinal and lateral direction of the liquid crystal filling portion in which the liquid crystal in the liquid crystal deflection element is sealed, Ri Na in correspondence with the longitudinal direction and the transverse direction of the cross-section of the light beam,
A plurality of effective areas in which the liquid crystal is driven are juxtaposed in the longitudinal direction of the liquid crystal sealing part in the liquid crystal sealing part,
With respect to the longitudinal direction of the liquid crystal encapsulated part, the interval between the effective areas of the liquid crystal drive is shorter than the distance from the end of the liquid crystal encapsulated part to the effective area ,
In particular, more effective, stable and highly accurate optical scanning is achieved, color shift reduction, multi-beam scanning line interval accuracy, writing density switching, and good wavefront aberration, etc. It is possible to achieve the optical characteristics of

According to the optical scanning device of claim 2 of the present invention, in the optical scanning device of claim 1,
The direction deflected by the liquid crystal deflecting element corresponds to the short direction of the liquid crystal encapsulating part in the liquid crystal deflecting element,
In particular, it effectively performs stable and high-precision optical scanning, reduces color misregistration, increases the accuracy of multi-beam scanning line spacing, switches the writing density, and provides excellent optical properties such as wavefront aberration. It is possible to achieve the characteristics.
According to the optical scanning device of claim 3 of the present invention, in the optical scanning device of claim 1 or 2,
When the temperature rises , the imaging position deviation in the optical axis direction that occurs in the imaging optical system and the imaging position deviation in the optical axis direction that occurs in the liquid crystal deflection element are directions that cancel each other,
In particular, more effective and stable optical scanning is performed, color misregistration is reduced, multi-beam scanning line spacing is highly accurate, and writing density is switched. Optical characteristics can be achieved.

According to an optical scanning device of a fourth aspect of the present invention, in the optical scanning device of any one of the first to third aspects,
The light source and the coupling lens are integrally held by a common holding member, and the linear expansion coefficient of the holding member is caused by an imaging position shift in the optical axis direction generated in the imaging optical system when the temperature rises. It corrected so as to lack for
By and this,
In particular, more effective and stable optical scanning is performed, color shift reduction, multi-beam scanning line spacing accuracy, writing density switching, and excellent wavefront aberration are achieved. Optical characteristics can be achieved .

According to the optical scanning device of claim 5 of the present invention, in the optical scanning device of claim 4 ,
By arranging an input terminal for applying a voltage to each effective area of the liquid crystal drive on the end side of the liquid crystal deflection element,
In particular, even more effective, stable and highly accurate optical scanning is achieved, color shift reduction, multi-beam scanning line spacing accuracy, writing density switching, and good wavefront aberration, etc. It is possible to achieve the optical characteristics of
According to the image forming apparatus of claim 6 of the present invention,
In an image forming apparatus that forms an image using an electrophotographic process,
As an exposure processing means for performing an exposure process in the electrophotographic process,
By comprising the optical scanning device according to any one of claims 1 to 5 ,
In particular, the optical scanning device performs stable and high-precision optical scanning, achieves color shift reduction, multi-beam scanning line interval high accuracy, and writing density switching, and good wavefront aberration, etc. By achieving the optical characteristics, it is possible to stably form a high-quality image.

1 is a perspective view schematically showing a configuration of a main part of an optical scanning device according to a first embodiment of the present invention. It is sectional drawing seen from the side which shows typically the structure of an example of the liquid-crystal deflection | deviation element used for the optical scanning device of FIG. It is a front view which shows typically the structure of the 1st transparent electrode in an example of the liquid crystal deflection | deviation element used for the optical scanning device of FIG. It is a front view which shows typically the concept of the effective area | region of the liquid-crystal layer in an example of the liquid-crystal deflection | deviation element used for the optical scanning device of FIG. FIG. 2 is a voltage-phase modulation characteristic diagram showing an example of a relationship between an effective voltage applied to a liquid crystal deflecting element at 20 ° C. and retardation in an example of the liquid crystal deflecting element used in the optical scanning device of FIG. 1. In order to explain the principle of the deflection operation in one example of the liquid crystal deflection element used in the optical scanning device of FIG. 1, the alignment state of the liquid crystal molecules when the same potential voltage is applied to the input terminals T1 and T2 is schematically shown. It is side surface sectional drawing. In order to explain the principle of the deflection operation in one example of the liquid crystal deflection element used in the optical scanning device of FIG. 1, the alignment state of the liquid crystal molecules when voltages having different potentials are applied to the input terminals T1 and T2 is schematically shown. It is side surface sectional drawing. FIG. 2 is a displacement-voltage characteristic diagram showing a potential gradient in which the potential changes linearly with displacement in the Z direction of an effective region of a liquid crystal layer in an example of a liquid crystal deflecting element used in the optical scanning device of FIG. FIG. 3 is a displacement-refractive index characteristic diagram showing a refractive index distribution gradient in which the refractive index changes linearly with displacement in the Z direction of an effective region of a liquid crystal layer in an example of a liquid crystal deflection element used in the optical scanning device of FIG. 1. FIG. 2 is a schematic cross-sectional view for explaining the principle of generation of wavefront aberration in a liquid crystal layer as an example of a liquid crystal deflection element used in the optical scanning device of FIG. 1. FIG. 2 is a front view schematically showing a conceptual arrangement relationship of a liquid crystal sealing portion, an effective region, and a light beam cross section of an optical beam in an example of a liquid crystal deflection element used in the optical scanning device of FIG. 1. FIG. 10 is a front view schematically showing a conceptual arrangement relationship between two effective areas and a light beam transverse section in an example of a liquid crystal deflection element of an optical scanning device according to a fourth embodiment of the present invention. It is sectional drawing which shows typically the structure of the image forming apparatus which concerns on the 5th Embodiment of this invention.

  Hereinafter, based on an embodiment of the present invention, an optical scanning device according to the present invention and an image forming apparatus of the present invention using the same will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a perspective view showing a configuration of an optical scanning device according to a first embodiment (corresponding to claim 1) of the present invention, and schematically shows a configuration of a main part of the optical scanning device. .
1 includes a semiconductor laser 1, a coupling lens 2, a liquid crystal deflecting element 3, an aperture 4, a cylindrical lens 5, a polygon mirror 6, an imaging optical system 7, a folding mirror 8, a photosensitive drum 9, and a synchronization. A detection sensor 10 is provided.
In FIG. 1, a divergent light beam emitted from a semiconductor laser 1 serving as a light source is a light beam suitable for a subsequent optical system by a coupling lens 2 held integrally with the semiconductor laser 1 by a common holding member, for example. Is converted into a luminous flux form. The form of the light beam converted by the coupling lens 2 may be a parallel light beam, or may be a weak divergent or weakly convergent light beam. The light beam emitted from the coupling lens 2 enters the cylindrical lens 5 sequentially through the liquid crystal deflecting element 3 and the aperture 4, and is condensed in the direction corresponding to the sub-scanning direction by the cylindrical lens 5, and serves as an optical deflector. The light enters the deflecting / reflecting surface of the polygon mirror 6.

The light beam reflected by the deflecting and reflecting surface of the polygon mirror 6 is deflected at an equal angular speed along with the constant speed rotation of the polygon mirror 6, condensed by the imaging optical system 7 including an fθ lens (scanning lens), and the folding mirror. 8 is reflected and deflected to form an image on the scanning surface on the outer periphery of the photosensitive drum 9. Thus, the light beam deflected by the polygon mirror 6 forms a light spot on the surface to be scanned of the photosensitive drum 9 and optically scans the surface to be scanned.
The synchronization detection sensor 10 detects the light beam deflected and scanned by the rotating polygon mirror 6 at the edge of the deflection scanning range (slightly deviated from the effective scanning range), and performs main scanning by the polygon mirror 6. Get synchronization information. In FIG. 1, the synchronization detection sensor 10 directly enters the light beam emitted from the imaging optical system 7, but may detect the light beam folded by a mirror.
Next, the structure and operation of the liquid crystal deflection element 3 described above will be described. In FIG. 1, the liquid crystal deflecting element 3 is provided between the coupling lens 2 and the aperture 4 in the vicinity of the aperture 4, but in the vicinity of the aperture 4 between the aperture 4 and the polygon mirror 6. For example, it can be appropriately disposed between a light source such as the semiconductor laser 1 and an optical deflector such as the polygon mirror 6 and at a convenient location near the aperture 4.

FIG. 2 is a schematic cross-sectional view showing a cross-sectional structure of the liquid crystal deflecting element 3 in order to explain an example of a detailed configuration of the liquid crystal deflecting element 3. The coordinates in FIG. 2 are (+) X direction in the right direction in the figure, (+) Y direction in the forward direction (perpendicular to the paper surface) approaching from the back side to the front side in the figure, and (+) Z direction in the up direction in the figure. It is said. 2 includes a liquid crystal layer 31, a first alignment film 32, a second alignment film 33, a first transparent electrode 34, a second transparent electrode 35, a first glass substrate 36, and a first glass substrate 36. Two glass substrates 37 are provided.
In the liquid crystal deflection element 3 shown in FIG. 2, the liquid crystal layer 31 is sandwiched between the first alignment film 32 and the second alignment film 33, and these are sandwiched between the first transparent electrode 34 and the second transparent electrode 35. These are further sandwiched between the first glass substrate 36 and the second glass substrate 37. The first and second glass substrates 36 and 37 and the peripheral portion of the laminated structure between them are sealed with a sealing material (not clearly shown) to form a so-called cell structure.
The thickness of the liquid crystal layer 31, that is, the length in the X-axis direction in the drawing, is about several [μm] to several tens [μm]. Here, a liquid crystal layer in which nematic liquid crystal molecules are homogeneously arranged is used as the liquid crystal layer 31. The second transparent electrode 35 on the + X side of the liquid crystal layer 31 is connected to a ground (GND) that is a common potential. For example, the first transparent electrode 34 on the −X side of the liquid crystal layer 31 is configured as shown in FIG. 3.

The coordinates in FIG. 3 are defined as the (+) X direction in the back direction (perpendicular to the paper surface) moving away from the front side to the back side in the drawing, the (+) Y direction in the right direction in the drawing, and the (+) Z direction in the upper direction in the drawing Yes. That is, each of the first transparent electrodes 34 has a stripe shape with the Y-axis direction as the longitudinal direction, and a plurality of stripe electrodes 34A arranged in the Z-axis direction, and −Y side end portions of these stripe electrodes 34A, A thin wire electrode 34B having a predetermined resistance value is connected across all the stripe electrodes 34A.
An input terminal T1 is provided at the −Z side end of the thin wire electrode 34B, and an input terminal T2 is provided at the + Z side end. An example of an effective area in which the liquid crystal is driven in this case is shown in FIG. In this case, a region where the liquid crystal is driven by an external electric signal and the phase of incident light can be modulated is referred to as an effective region. In addition, the coordinates in FIG. 4 are the same as in FIG. 3, the back direction (perpendicular to the paper surface) moving away from the front side to the back side in the drawing is the (+) X direction, the right direction in the figure is the (+) Y direction, The direction is the (+) Z direction.

  The voltage applied to each of the input terminals T1 and T2 is an AC voltage having a frequency of about several hundred Hz to several kHz and having no DC component. In the following, the effective value of the alternating voltage applied to the input terminal T1 is referred to as an applied voltage V1, and the effective value of the alternating voltage applied to the input terminal T2 is referred to as an applied voltage V2.

An example of the relationship between the effective voltage applied to the liquid crystal deflecting element at 20 ° C. and the retardation (voltage-phase modulation characteristics) is shown in FIG.
[1] When no voltage is applied to the input terminals T1 and T2, that is, when the applied voltage V1 = 0 [V] and the applied voltage V2 = 0 [V], the liquid crystal molecules of the liquid crystal layer 31 are as shown in FIG. As shown, the alignment state is substantially parallel to the Z-axis. Usually, in order to improve the responsiveness, the alignment films 32 and 33 are set so that the liquid crystal molecules are slightly tilted in the X direction with respect to the Z axis. That is, the liquid crystal molecules are not completely parallel to the Z axis. The tilt angle of the liquid crystal molecules in the X direction with respect to the Z axis is referred to as an orientation angle. When a voltage is applied to each input terminal T1 and T2, the liquid crystal molecules of the liquid crystal layer 31 exhibit an alignment state having an alignment angle corresponding to the applied voltage.
[2] When the same potential voltage is applied to each of the input terminals T1 and T2, that is, the alignment state of the liquid crystal molecules when the applied voltage V1 = 1.5 [V] and the applied voltage V2 = 1.5 [V] Is shown in FIG. As in FIG. 2, the coordinates in FIG. 6 are also the (+) X direction in the right direction in the figure, the forward direction (perpendicular to the page) approaching from the back side to the front side in the figure (+) Y direction, and the upward direction in the figure. Is the (+) Z direction. In FIG. 6, the liquid crystal molecules have the same orientation angle with respect to the thickness direction of the liquid crystal layer 31 (here, the X direction) for easy understanding. In this case, in the liquid crystal layer, since the potential is uniform in the Z direction, the light beam incident on the liquid crystal deflecting element 3 is transmitted without bending its optical path.

[3] When voltages having different potentials are applied to the input terminals T1 and T2, that is, the alignment state of liquid crystal molecules when the applied voltage V1 = 1.7 [V] and the applied voltage V2 = 1.3 [V]. Is shown in FIG. As in FIG. 2, the coordinates in FIG. 7 are also the (+) X direction in the right direction in the figure, the forward direction (perpendicular to the page) approaching from the back side to the front side in the figure (+) Y direction, and the upward direction in the figure. Is the (+) Z direction.
In this case, in the liquid crystal layer 31, as shown in FIG. 8, a potential gradient in which the potential changes linearly due to the displacement in the Z direction is generated between the + Z side end and the −Z side end of the effective region. The alignment state of the liquid crystal molecules gradually changes according to this potential gradient. In accordance with this potential gradient, as shown in FIG. 9, the refractive index linearly changes depending on the position corresponding to the phase difference Δφ between the + Z side end and the −Z side end of the effective region. A distribution, i.e. a refractive index gradient, occurs. Therefore, the optical path of the light beam incident on the liquid crystal deflecting element 3 is bent in the Z direction by an angle corresponding to the potential gradient, that is, the deflection angle, θ. When the width of the effective region in the Z-axis direction is H and the phase difference between both ends in the Z-axis direction in the effective region is Δφ, the deflection angle θ is
tan θ = Δφ / H
It is expressed.

In the above, the principle of light beam deflection by the liquid crystal deflection element 3 has been described. By using such a liquid crystal deflecting element 3, when the position of the light spot formed on the outer peripheral surface of the photosensitive drum 9 in the sub-scanning direction is deviated from a required position, the position deviation is corrected. It becomes possible.
The amount of movement of the light spot in the sub-scanning direction on the outer peripheral surface of the photosensitive drum 9 is Δz, the width of the effective area in the Z-axis direction is H, and the image is on the optical path between the polygon mirror 6 and the photosensitive drum 9. When the magnification in the direction corresponding to the sub-scanning direction of the optical system 7 is m, the focal length of the cylindrical lens 5 is Fcyl, and the phase difference between both ends in the Z-axis direction in the effective region is Δφ, the following (1) The relationship of the formula holds.
Δφ = (Δz × H) / (m × Fcyl) (1)
For example, when H = 2.0 [mm], m = 1.5 times, and Fcyl = 100 [mm], in order to move the light spot in the sub-scanning direction by +10.6 [μm], the wavelength of the incident light beam It is necessary to generate a phase distribution (gradient) that satisfies Δφ = 0.22 [λ] in units of λ (in this case, for example, 655 nm).

That is, when the liquid crystal deflecting element 3 has a characteristic of Δφ = 0.55 [λ] when (V1−V2) = 1.0 [V], Δφ = 0.22 [λ. ] To obtain the phase difference of (V1−V2) = 0.4 [V]. By optimally setting the amount of movement in the sub-scanning direction on the outer peripheral surface of the photosensitive drum 9, it is possible to correct the position variation in the sub-scanning direction caused by variations in the shape of the optical element, assembly variations, and the like.
While the effects described above are obtained, the liquid crystal deflecting element 3 has a refractive power, which causes a problem of generating curvature of field when mounted on the optical scanning device. The liquid crystal deflection element 3 is an element having a light beam deflection function, and preferably has no refractive power.

  In an optical scanning apparatus applied to an image forming apparatus such as a laser printer or a digital copying machine that is currently industrially produced by each manufacturer, a surface to be scanned (photosensitive member) in order to ensure image quality at the output. It is necessary to maintain a good beam spot shape in the vicinity of the outer peripheral surface of the drum 9. For this purpose, it is desirable to suppress the wavefront aberration generated in the optical system in the optical scanning device as much as possible. However, even when the liquid crystal deflecting element 3 is not driven due to the surface accuracy of the glass substrates 36 and 37, the influence of variations in pressure management when the liquid crystal layer 31 is sealed, the influence of the liquid crystal structure, etc., for example, λ / There is a possibility that 10 or more transmitted wavefront aberrations may occur. This transmitted wavefront aberration is particularly likely to generate a power component having a light beam converging / diverging action. By generating curvature of field on the surface to be scanned (the outer peripheral surface of the photosensitive drum 9), the beam spot diameter is increased. As a result, the image quality is degraded.

  The generation of the wavefront aberration is largely caused by the structure of the liquid crystal deflection element 3 as schematically shown in FIG. As already described, the glass substrates 36 and 37 made of two flat glass plates of the liquid crystal deflecting element 3 have a cell structure in which the periphery is sealed with a sealing material 38. A liquid crystal layer 31 is formed by encapsulating liquid crystal therein, and a spacer for keeping the distance between the two glass substrates, that is, the distance between the glass substrate 36 and the glass substrate 37 inside the liquid crystal layer 31. A substance functioning as 39 is mixed.

As shown in FIG. 10, the glass substrate 36 and the glass substrate 37 are disposed so as to be spaced apart by a spacer 39, but the glass substrate 36 and the glass substrate 37 are bonded together by a sealing material 38 at the periphery. In doing so, the glass substrate 36 and the glass substrate 37 are deformed and have refractive power in the vicinity of the sealing material 38, that is, in the vicinity of the peripheral edge (in the example of FIG. 10, it has convex refractive power). As a result, the light beam transmitted through the liquid crystal deflecting element 3 is affected by the convex refractive power component even when the liquid crystal is not driven, thereby causing curvature of field. That is, the beam spot diameter deteriorates on the outer peripheral surface of the photosensitive drum 9 as the surface to be scanned, and the image quality is lowered.
Therefore, in the optical scanning device according to the first embodiment of the present invention, the longitudinal direction and the short direction of the liquid crystal deflecting element 3 where the liquid crystal is sealed are further defined as the longitudinal direction in the cross section of the light beam and It corresponds to each short direction.
As already described, the liquid crystal deflecting element 3 is provided in the vicinity of the aperture 4 between the coupling lens 2 and the cylindrical lens 5, in this case, for example, between the coupling lens 2 and the aperture 4 as shown in FIG. In the vicinity of the aperture 4. The light flux after the coupling lens 2 is almost a parallel light flux. The shape of the aperture 4 is generally different in dimensions in the main scanning direction and the sub-scanning direction due to differences in magnification of the optical system, and the cross section of the light beam transmitted through the liquid crystal deflecting element 3 is also short and long. It has a shape such as a rectangle having a direction (in some cases, it may be an ellipse instead of a rectangle, but in this case, it is a shape having a longitudinal direction and a short direction).

In the optical scanning device according to the first embodiment, as shown in FIG. 11, the portion of the liquid crystal deflecting element 3 in which the liquid crystal is sealed, that is, the long and short sides (longitudinal and short sides) of the liquid crystal filling portion CA. ) And the long and short side directions (longitudinal direction and short side direction) of the light beam LB. As described above, the wavefront aberration is deteriorated around the liquid crystal deflecting element 3 and has a refractive power. However, the vicinity of the center is also helped by the effect of the spacer 39, and the deterioration of the wavefront aberration is small. Therefore, in this embodiment, the size of the liquid crystal deflecting element 3 is determined so as to allow the light beam LB to pass in the vicinity of the center, that is, the liquid crystal deflecting element 3 with respect to the light beam that is long in the main scanning direction and short in the sub scanning direction. Since the liquid crystal sealing portion CA is also formed in a shape that is long in the main scanning direction and short in the sub-scanning direction, it is possible to reduce deterioration of wavefront aberration at the light beam passage position.
If the short direction of the cross section of the light beam LB is made to coincide with the longitudinal direction of the liquid crystal sealing portion CA of the liquid crystal deflecting element 3, the liquid crystal deflecting element 3 becomes unnecessarily large, and the optical scanning device is small in terms of cost. There is almost no merit in terms of conversion.

[Second Embodiment]
Next, an optical scanning device according to a second embodiment (corresponding to claim 2) of the present invention will be described. The basic configuration of the optical scanning device according to the second embodiment of the present invention is substantially the same as that of the optical scanning device according to the first embodiment of the present invention described above.
In the configuration of the optical scanning device according to the second embodiment of the present invention, the direction deflected by the liquid crystal deflecting element 3 is made to coincide with the short direction of the liquid crystal sealing portion CA of the liquid crystal deflecting element 3.
In many cases, such as for the purpose of correcting misregistration in the sub-scanning direction for reducing color misregistration as mentioned above, the deflection direction by the liquid crystal deflecting element 3 is the sub-scanning direction. At this time, the short direction of the liquid crystal sealing portion CA of the liquid crystal deflecting element 3 is set as the sub-scanning direction, and the short direction of the light flux is also set to the sub-scanning direction as already described in the first embodiment. It is desirable to set the magnification of the optical system.
If the dimension of the liquid crystal deflection element 3 in the sub-scanning direction is short, it contributes to miniaturization of the optical scanning device in the sub-scanning direction. In recent years, there is a tendency that there is a large demand for downsizing of the apparatus, and the optical scanning apparatus is required to be thin, and the sub-scanning direction of the liquid crystal deflecting element 3 often corresponds to the height direction of the optical scanning apparatus. Therefore, when the dimension in this direction is shortened, the height of the optical scanning device is reduced, and the effect of thinning the optical scanning device can be obtained.

Also, when driving the liquid crystal for deflecting the light beam, it is desirable that the direction deflected by the liquid crystal deflecting element 3 is the short direction of the liquid crystal sealing portion CA of the liquid crystal deflecting element 3. This point will be described in more detail below.
The present invention described above that the wavefront aberration caused by the structure of the liquid crystal element itself can be reduced by optimally setting the longitudinal direction and the transverse direction of the cross section of the liquid crystal sealing portion and the light beam. The first embodiment has been described. That is, if the liquid crystal is in a non-driven state, it is possible to reduce optical characteristic deterioration due to wavefront aberration generated in the liquid crystal element. However, when a constant potential gradient is applied in the effective region of the liquid crystal element when the liquid crystal element is driven, the refractive index distribution does not have a constant gradient but is substantially curved. Due to such a refractive index distribution, a wavefront aberration occurs in the light beam emitted from the liquid crystal element.
In order to obtain a desired deflection angle by the liquid crystal element, it is necessary to give an appropriate potential difference. With respect to the deflection direction, this potential difference can be set large if the size of the effective region is large, and the potential difference can be set small if the size of the effective region is small. As shown in FIG. 5, if the potential difference is small, it is easy to select a portion where the slope of the graph is linear. This means that if the phase changes linearly depending on the position, the refractive index has a linear distribution gradient, so that the occurrence of wavefront aberration due to the power component is small.

That is, by making the direction deflected by the liquid crystal deflecting element the short direction of the liquid crystal encapsulating portion of the liquid crystal deflecting element, it becomes possible to greatly reduce the influence of wavefront aberration when driving the liquid crystal. The liquid crystal is driven to deflect the light beam within the effective region, but it goes without saying that the effective region is also shortened in the short direction of the liquid crystal sealing portion of the liquid crystal deflecting element.
Further, in this case, the transverse direction of the cross section of the light beam corresponds to the sub-scanning direction, and the magnification of the scanning optical system is reduced with respect to the longitudinal direction, so that the influence can be reduced. That is, as in the optical scanning device of this embodiment, the direction in which the light beam is deflected by the liquid crystal deflecting element 3 is made to correspond to the short direction of the liquid crystal sealing portion of the liquid crystal deflecting element 3, and the light beam transmitted through the liquid crystal deflecting element. Scanning is performed so that the deflection direction of the liquid crystal deflecting element substantially coincides with the sub-scanning direction, and the transverse direction of the light beam cross-section corresponds to the sub-scanning direction. By setting the magnification of the optical system, the influence of wavefront aberration caused by driving the liquid crystal can be made to correspond to the sub-scanning direction where the magnification of the scanning optical system is low, and the deterioration of the optical characteristics can be reduced. .
On the other hand, when the magnification of the scanning optical system is high and the cross section of the light beam when transmitted through the liquid crystal is large in the sub-scanning direction (long in the sub-scanning direction), the wavefront aberration generated when the liquid crystal element is driven The effect is magnified and the optical properties are greatly degraded. In addition, the size of the liquid crystal element itself increases, which causes many problems such as an increase in the size and cost of the optical scanning device.

[Third Embodiment]
Next, an optical scanning device according to a third embodiment of the present invention (corresponding to claims 3 and 4) will be described. The basic configuration of the optical scanning device according to the third embodiment of the present invention is also substantially the same as that of the optical scanning device according to the first embodiment of the present invention described above.
It is desirable that the imaging position deviation in the optical axis direction generated by the imaging optical system 7 and the imaging position deviation in the optical axis direction generated by the liquid crystal deflecting element 3 cancel each other at a high temperature.
That is, when the temperature is high, a normal optical element such as a resin scanning lens expands, the focus position shifts, and the image formation position moves in the direction of indenting from the outer peripheral surface of the photosensitive drum 9 to the inside. To do. For this reason, the beam spot diameter on the outer peripheral surface of the photosensitive drum 9 is increased, and the image quality is deteriorated.
On the other hand, the liquid crystal deflecting element 3 has a liquid crystal layer 31 of about several [μm] to several tens [μm] sandwiched between two glass substrates 36 and 37, and a portion sandwiched between these glass substrates 36 and 37 is sealed. The cell structure is sealed with a material 38. Therefore, when the ambient temperature changes, the liquid crystal layer 31 having a relatively high expansion coefficient thermally expands as the ambient temperature rises, and the central portion of the liquid crystal deflecting element 3 expands, resulting in a positive power lens effect. Is generated.

By increasing the thickness of the two glass substrates 36 and 37 or by releasing the liquid crystal, it is possible to reduce the liquid crystal deflecting element from having a positive power. By having it, the image forming position shift in the optical axis direction generated by the liquid crystal deflecting element can be moved from the outer peripheral surface of the photosensitive drum 9 to the polygon mirror (optical deflector) side. The imaging position shift in the system 7 can be reduced.
Further, the linear expansion coefficient of the holding member between the light source such as the semiconductor laser 1 and the coupling lens 2 is insufficiently corrected with respect to the imaging position shift generated in the imaging optical system 7 at a high temperature. It is desirable to set.
That is, in this embodiment, the semiconductor laser 1 as the light source and the coupling lens 2 are not clearly illustrated, but are integrally held by, for example, a common holding member. The linear expansion coefficient of the holding member between the coupling lens 2 and the coupling lens 2 is set so as to be insufficiently corrected with respect to the imaging position shift generated in the imaging optical system 7 at a high temperature.
As described above, at a high temperature, a normal optical element such as a resin-made fθ lens included in the imaging optical system 7 expands so that the imaging position of the outer periphery of the photosensitive drum 9 is increased. Move in the direction of sinking from the surface.

On the other hand, a holding member (not shown) that integrally holds the semiconductor laser 1 and the coupling lens 2 as a light source also expands and expands due to a high temperature, and the distance between the semiconductor laser 1 and the coupling lens 2 is increased. The image forming position moves away from the surface of the photosensitive drum 9 and moves toward the polygon mirror 6 as an optical deflector. As described above, the liquid crystal deflecting element 3 has a convex power, that is, a positive refractive power at a high temperature, unlike a normal optical element, due to its configuration. For this reason, the movement of the imaging position in the imaging optical system 7 such as the fθ lens is not completely corrected by the light source unit such as the semiconductor laser 1, but is insufficiently corrected. It is desirable to be in the direction of sinking from the surface.
By doing so, as a result, even when the liquid crystal deflecting element 3 exhibits a positive refractive power (convex power) at a high temperature, the imaging position can be returned to the outer peripheral surface of the photosensitive drum 9. It becomes. By appropriately selecting the linear expansion coefficients of the holding members of the semiconductor laser 1 and the coupling lens 2 serving as the light source, it is possible to maintain stable optical characteristics against environmental changes.
On the other hand, when the change of the imaging position due to the optical elements included in the imaging optical system is corrected by the light source unit as in the conventional optical scanning device, the correction becomes overcorrected by using the liquid crystal deflecting element. The position is moved from the surface of the photosensitive drum to the side of the optical deflector such as the polygon mirror 6 and the optical characteristics are deteriorated. Therefore, in order to cancel out the imaging position shift generated in the imaging optical system 7 between the liquid crystal deflecting element 3 and the light source unit, the imaging position generated in the imaging optical system 7 at a high temperature is used as the material of the light source unit. It is desirable to set the linear expansion coefficient so that the correction is insufficient for the deviation.

At low temperatures, even when the liquid crystal layer 31 contracts, the spacer 39 for maintaining the distance between the glass substrates 36 and 37 is mixed therein, so that the generation of negative refractive power (concave power) is extremely small. That is, the liquid crystal deflecting element 3 has a positive refractive power at a high temperature, but a change at a low temperature is small. At a low temperature, the image forming position is hardly changed by the liquid crystal deflecting element 3, but the image forming position is changed by other optical elements. In general, since elements serving as heat sources such as an optical deflector and a light source are disposed inside the optical scanning device, the temperature of the optical scanning device often increases. Further, as described above, the temperature variation of the liquid crystal deflecting element 3 is large on the high temperature side, and the variation of the image forming position is also large on the high temperature side, so that it is possible to reduce the deterioration of the optical characteristics at a high temperature, which is a substantial problem. The effect is greater.
The expansion of the liquid crystal layer 31 generates a larger wavefront aberration in the portion where the liquid crystal is sealed, that is, in the short direction of the liquid crystal sealing portion CA. As described above, the lateral direction of the liquid crystal sealing portion CA corresponds to the lateral direction of the light beam LB, and the magnification of the scanning optical system is low. For this reason, the influence of this wavefront aberration can be reduced. In the main scanning direction, the magnification is high, but the occurrence of wavefront aberration is also small, so the configuration of this embodiment is suitable for environmental fluctuations.
Of course, since the occurrence of wavefront aberration is not zero, in order to obtain more stable optical characteristics, the linear expansion coefficient of the holding member between the semiconductor laser 1 of the light source and the coupling lens 2 is an imaging optical system at high temperatures. It is desirable to set so that the correction of the image formation position deviation occurring at 7 is insufficiently corrected to reduce the environmental fluctuation.

[Fourth Embodiment]
Next, an optical scanning device according to a fourth embodiment (corresponding to claims 1 and 5 ) of the present invention will be described. The basic configuration of the optical scanning device according to the fourth embodiment of the present invention is also substantially the same as that of the optical scanning device according to the first embodiment of the present invention described above.
In the optical scanning device of this embodiment, as one form of the liquid crystal deflecting element 3, as shown in FIG. 12, a liquid crystal deflecting element 3A having two effective areas VA1 and VA2 is used.
FIG. 12 is a schematic front view showing the structure of the liquid crystal sealing portion of the liquid crystal deflection element 3A in order to explain an example of the detailed configuration of the liquid crystal deflection element 3A. The coordinates in FIG. 12 are the (+) X direction in the back direction (perpendicular to the paper surface) moving away from the front side to the back side in the drawing, the (+) Y direction in the right direction in the figure, and the (+) Z direction in the up direction in the figure. Yes.
In FIG. 12, the liquid crystal deflecting element 3A uses a liquid crystal element having two effective areas VA1 and VA2. The effective areas VA1 and VA2 have the same structure. Here, the effective area VA2 is the same as the state in which the effective area VA1 is rotated 180 degrees around an axis parallel to the X axis. ) It is arranged on the Y side.

The effective areas VA1 and VA2 deflect the light beams LB1 and LB2 that pass through the effective areas VA1 and VA2, respectively, but their deflection directions are shifted by 180 degrees. These light beams LB1 and LB2 scan the surface to be scanned of the photosensitive drum 9 side by side in the sub-scanning direction. For example, when the liquid crystal deflection element 3A is not driven, the light beams LB1 and LB2 scan the surface to be scanned at a distance of about 42 μm in the sub-scanning direction to form a 600 dpi image. Further, when the liquid crystal deflecting element 3A is driven, the light beams LB1 and LB2 are deflected in directions in which the light beams LB1 and LB2 approach each other by about 10.5 μm on the surface to be scanned of the photosensitive drum 9, and the sub-scanning direction interval of about 21 μm is provided. By having it, it becomes possible to form a high-quality image of 1200 dpi. At this time, since the light beams LB1 and LB2 move in the direction of narrowing the interval in the sub-scanning direction, in the liquid crystal deflection element 3A, the deflection directions in the effective areas VA1 and VA2 are opposite (the deflection amount and the effective area VA1). And VA2 are the same size, the potential difference in each is the same).
As described above, in the liquid crystal deflecting element 3A in which a plurality of effective areas in which the liquid crystal is driven are arranged in the longitudinal direction in the liquid crystal encapsulating part CA, the interval between the effective areas in the longitudinal direction of the liquid crystal enclosing part CA is It is desirable that the distance is shorter than the distance from the end portion of the liquid crystal sealing portion CA to the effective area closest to the end portion.

As already described in relation to the first embodiment of the present invention described above, the liquid crystal deflecting element has a structure in the vicinity of the sealing material 38, that is, in the vicinity of the liquid crystal sealing portion where the liquid crystal is sealed ( A large wavefront aberration is generated). For this reason, it is desirable that the effective area is close to the center in the liquid crystal sealing portion where the liquid crystal is sealed. The configuration of this embodiment described above, that is, the interval between the effective regions arranged in parallel with the liquid crystal sealing portion in the longitudinal direction of the liquid crystal sealing portion is the liquid crystal sealing portion in the longitudinal direction of the liquid crystal sealing portion. By adopting a configuration that is shorter than the distance from the end portion of the liquid crystal to the nearest effective region, even in a liquid crystal deflecting element having a plurality of effective regions, it is possible to reduce the influence of wavefront aberration deterioration and obtain good optical characteristics. It becomes possible.
Further, when two effective areas VA1 and VA2 are juxtaposed as in the example shown in FIG. 12, an input terminal T1a for applying a voltage for driving the liquid crystal layer 31 to deflect the light beam, By providing T2a, T1b, and T2b on the end side of the liquid crystal deflecting element 3A, it is possible to set a narrow interval between the two effective areas VA1 and VA2. 3 and 4, the input terminals T1a and T2a are provided at both ends of the thin wire electrode RLa which is a transparent electrode, and the input terminals T1b and T2b are provided at both ends of the thin wire electrode RLb which is a transparent electrode. It has been.
In many cases, ITO (Indium Tin Oxide) is used as the transparent electrode, but the ITO pattern of the transparent electrode for voltage input is irrelevant to the occurrence of wavefront aberration, and as an effective region By passing the end portion which is difficult to use, the interval between the effective areas VA1 and VA2 can be narrowed and the vicinity of the sealing material can be used effectively, so that the liquid crystal deflecting element 3A itself is effective without increasing wastefully. It can be set as a simple structure.

[Fifth Embodiment]
Next, an image forming apparatus according to a fifth embodiment (corresponding to claim 6 ) of the present invention using the optical scanning device according to the present invention will be described.
FIG. 13 schematically shows a schematic configuration of an image forming apparatus according to the fifth embodiment of the present invention. This image forming apparatus is a so-called tandem type full-color optical scanning apparatus according to the present invention. This is applied to a laser printer.
An image forming apparatus which is a tandem type full color laser printer shown in FIG. 13 includes a light source unit (not shown in the figure), an optical scanning optical system 106 (106Y, 106M, 106C, 106K), and a photosensitive drum 107 (107Y, 107M, 107C, 107K), charger 108 (108Y, 108M, 108C, 108K), developing device 110 (110Y, 110M, 110C, 110K), transfer charger 111 (111Y, 111M, 111C, 111K), cleaning device 112 ( 112Y, 112M, 112C, 112K), paper feed cassette 113, paper feed roller 114, feed roller 115, registration roller 116, transport belt 117, first belt pulley 118, second belt pulley 119, belt charging charger 120. The belt separation cha Ja 121, belt discharger 122, and a belt cleaning device 123, a fixing device 124, paper discharging roller 125 and the discharge tray 126.

  In FIG. 13, on the lower side in the image forming apparatus, sheets are taken out one by one by a sheet feeding roller 114 from a sheet feeding cassette 113 arranged almost horizontally, and fed through a feeding roller 115 and a registration roller 116. A conveying belt 117 that conveys the transfer sheet S to be transferred is stretched between a first belt pulley 118 and a second belt pulley 119. On the conveyor belt 117, a yellow (Y) photosensitive drum 107Y, a magenta (M) photosensitive drum 107M, a cyan (C) photosensitive drum 107C, and a black (K) photosensitive drum. 107K are sequentially arranged at equal intervals from the upstream side to the downstream side in the conveyance direction of the transfer paper S. Here, the configuration provided for each color as in the photosensitive drum is appropriately distinguished by adding subscripts Y, M, C, and K to the end of the reference numerals. These photosensitive drums 107Y, 107M, 107C, and 107K are all formed to have the same diameter, and processing means for executing each process according to the electrophotographic process is sequentially arranged around each photosensitive drum. ing. Taking a yellow (Y) photosensitive drum 107Y as an example, a yellow (Y) charging charger 108Y, an optical scanning optical system 106Y, a developing device 110Y, and a transfer charger 111Y are disposed around the photosensitive drum 107Y, respectively. The cleaning device 112Y and the like are sequentially arranged in the clockwise direction in the drawing. Such a configuration is the same for the photosensitive drums 107M, 107C, and 107K of other colors.

That is, around the photosensitive drum 107M for magenta (M), there are a charging charger 108M, an optical scanning optical system 106M, a developing device 110M, a transfer charger 111M, a cleaning device 112M, etc. for magenta (M), respectively. They are sequentially arranged in the clockwise direction in the figure. Around the photosensitive drum 107C for cyan (C), a charging charger 108C, an optical scanning optical system 106C, a developing device 110C, a transfer charger 111C, a cleaning device 112C and the like for cyan (C) are shown in the figure. It is sequentially arranged in the direction. Around the black (K) photosensitive drum 107K, there are a black (K) charging charger 108K, an optical scanning optical system 106K, a developing device 110K, a transfer charger 111K, a cleaning device 112K, and the like. They are sequentially arranged in the clockwise direction in the figure.
Therefore, in this embodiment, the outer peripheral surface of each of the photosensitive drums 107Y, 107M, 107C, and 107K is an irradiated surface that is set for each color, that is, a scanned surface, and each of the photosensitive drums 107Y, 107M. , 107C and 107K are optically scanned by the optical scanning device.

In this case, the optical scanning device is disposed almost directly below the paper discharge tray 126 at the top of the image forming apparatus, and the light source unit for each color, that is, the light source unit for yellow (Y) and the light source unit for magenta (M). , Cyan (C) light source section, black (K) light source section and optical scanning optical system 106 for each color, that is, yellow (Y) optical scanning optical system 106Y, magenta (M) optical scanning. The optical system 106M, the cyan (C) optical scanning optical system 106C, the black (K) optical scanning optical system 106K, and the like. The optical scanning device in this case is configured as the optical scanning device according to each of the above-described embodiments, and the light source unit 101 includes the semiconductor laser 1, the coupling lens 2, the liquid crystal deflecting element 3, the aperture 4, and the cylindrical. The liquid crystal deflecting element 3 includes a liquid crystal layer 31, alignment films 32 and 33, transparent electrodes 34 and 35, glass substrates 36 and 37, and the like. The optical scanning optical system 106 includes a configuration such as a polygon mirror 6 and an imaging optical system 7, and a necessary number of folding mirrors 8 are appropriately arranged as necessary. The light source unit 101 for each color may include the liquid crystal deflecting element 3 configured for each color, but a plurality of the light source units 101 are configured using the configuration of the liquid crystal deflecting element 3A as described in the fourth embodiment. The configuration for color may be integrated.
In addition, a registration roller 116 and a belt charging charger 120 are provided around the conveyance belt 117 so as to be positioned upstream of the photosensitive drum 107Y. The rotation direction of the conveyance belt 17 is greater than that of the photosensitive drum 107K. In addition, a belt separation charger 121, a belt neutralization charger 122, a cleaning device 123, and the like are sequentially provided. Further, a fixing device 124 is provided downstream of the belt separation charger 121 in the transfer paper conveyance direction, and is discharged toward the paper discharge tray 126 by the paper discharge roller 125.

  In the image forming apparatus configured as described above, in the multi-color mode, for example, the full-color mode, the photosensitive drum 107Y for each color of yellow (Y), magenta (M), cyan (C), and black (K). , 107M, 107C and 107K, based on the image signals of the respective colors for yellow (Y), magenta (M), cyan (C) and black (K), the optical scanning optical systems 106Y, 106M, 106C for the respective colors And 106K scan the light beam to form electrostatic latent images corresponding to the respective color signals on the outer peripheral surfaces of the photosensitive drums 107Y, 107M, 107C and 107K for the respective colors. These electrostatic latent images for each color are developed with the respective color toners in the corresponding developing devices 110Y, 110M, 110C, and 110K to form visible toner images, and are electrostatically attracted onto the conveyance belt 17. The images are sequentially transferred and superimposed on the common transfer paper S to be conveyed, and a full color image is formed on the transfer paper S. This full-color image is fixed by the fixing device 124 and then discharged to the discharge tray 126 by the discharge roller 125.

As described above, in the optical scanning device according to the present invention, by using a liquid crystal element, optical scanning is stably performed with high accuracy, color misregistration is reduced, multi-beam scanning line spacing is improved, and writing is performed. It is possible to switch the density of the recording medium and the like, and to achieve both good optical characteristics, that is, good wavefront aberration. Further, an image forming apparatus configured using such an optical scanning device can stably form a high-quality image.
Further, in the optical scanning device and the image forming apparatus according to the present invention, the configuration of the liquid crystal deflecting element according to the purpose is used to suppress the increase in size and cost of the liquid crystal element, and in recent years, high image quality and high functionality are achieved. In addition to the increase in size, the optical scanning device and the image forming apparatus, which are highly demanded, can be reduced in size, and the optical scanning device and the image forming apparatus can be prevented from being enlarged, and high image quality and high functionality can be obtained.

DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Coupling lens 3, 3A Liquid crystal deflecting element 4 Aperture 5 Cylindrical lens 6 Polygon mirror 7 Imaging optical system 8 Folding mirror 9 Photosensitive drum 10 Synchronous detection sensor 31 Liquid crystal layer 32 1st alignment film 33 2nd alignment film 33 Alignment film 34 First transparent electrode 35 Second transparent electrode 36 First glass substrate 37 Second glass substrate 106 (106Y, 106M, 106C, 106K) Optical scanning optical system 107 (107Y, 107M, 107C, 107K) Photoconductor drum 108 (108Y, 108M, 108C, 108K) Charging charger 110 (110Y, 110M, 110C, 110K) Developing device 111 (111Y, 111M, 111C, 111K) Transfer charger 112 (112Y, 112M, 112C, 112K) CREE 113 Feeding device 115 Feeding roller 115 Feeding roller 116 Registration roller 117 Conveying belt 118 First belt pulley 119 Second belt pulley 120 Belt charging charger 121 Belt separation charger 122 Belt neutralization charger 123 Belt cleaning device 124 Fixing Device 125 Paper discharge roller 126 Paper output tray

JP-A-11-133326 JP-A-9-131920 JP 2005-292349 A Japanese Patent Laying-Open No. 2005-166084

Claims (6)

The light beam emitted from the light source is converted into a required light beam state by a coupling lens held integrally with the light source, and the light beam is deflected by an optical deflector and then condensed on the surface to be scanned by the imaging optical system. In the optical scanning device to be
In the optical path between the light source and the optical deflector, a liquid crystal deflecting element that changes the traveling direction of the light beam is provided.
The longitudinal and lateral direction of the liquid crystal filling portion in which the liquid crystal in the liquid crystal deflection element is sealed, Ri Na in correspondence with the longitudinal direction and the transverse direction of the cross-section of the light beam,
A plurality of effective areas in which the liquid crystal is driven are juxtaposed in the longitudinal direction of the liquid crystal sealing part in the liquid crystal sealing part,
The optical scanning device characterized in that, in the longitudinal direction of the liquid crystal encapsulated part, the interval between the liquid crystal driving effective areas is shorter than the distance from the end of the liquid crystal encapsulated part to the effective area .   2. The optical scanning device according to claim 1, wherein a direction in which the liquid crystal deflecting element deflects corresponds to a short direction of the liquid crystal sealing portion in the liquid crystal deflecting element. The imaging position deviation in the optical axis direction that occurs in the imaging optical system and the imaging position deviation in the optical axis direction that occurs in the liquid crystal deflecting element when the temperature rises are directions that cancel each other. The optical scanning device according to claim 1 or 2. The light source and the coupling lens are integrally held by a common holding member, and the linear expansion coefficient of the holding member is caused by an imaging position shift in the optical axis direction generated in the imaging optical system when the temperature rises. the optical scanning device according to any one of claims 1 to 3, wherein the benzalkonium be corrected to insufficient against. 5. The optical scanning device according to claim 4 , wherein an input terminal for applying a voltage to each effective region of liquid crystal driving is disposed on an end portion side of the liquid crystal deflecting element. In an image forming apparatus that forms an image using an electrophotographic process,
As an exposure processing means for performing an exposure process in the electrophotographic process,
An image forming apparatus characterized by including the optical scanning device of any one of claims 1 to 5.

Images