JP3759482B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning device and an image forming apparatus using the same.
[0002]
[Prior art]
The light beam from the light source side is deflected by light deflecting means such as a rotating polygon mirror, and the deflected light beam is condensed toward the scanned surface by using a scanning imaging optical system such as an fθ lens. 2. Description of the Related Art An optical scanning apparatus that forms a light spot on a surface and scans a surface to be scanned with the light spot is widely known in connection with image forming apparatuses such as an optical printer, an optical plotter, and a digital copying machine.
[0003]
In an image forming apparatus using an optical scanning device, an image writing process for writing an image by optical scanning is adopted as one step in the image forming process. It is affected by the quality of optical scanning. The quality of optical scanning depends on the scanning characteristics of the optical scanning device in the main scanning direction and the sub-scanning direction.
[0004]
One of the scanning characteristics in the main scanning direction is the constant speed of optical scanning.
For example, when a rotating polygon mirror is used as the light deflecting means, the light beam is deflected at a constant angular velocity, so that a scanning imaging optical system having an fθ characteristic is used in order to realize a constant speed of optical scanning. ing.
[0005]
However, it is not easy to realize perfect fθ characteristics due to the relationship with other performance required for the scanning imaging optical system. For this reason, in the actual optical scanning, the optical scanning is not performed at a completely constant speed, and the constant speed as the scanning characteristic is accompanied by a deviation from the ideal constant speed scanning.
[0006]
The scanning characteristics in the sub-scanning direction include scanning line bending and scanning line inclination.
The scanning line is the trajectory of the light spot on the surface to be scanned and is ideally a straight line, and the optical scanning device is designed so that the scanning line is a straight line. In general, the scanning line is bent due to the assembly error or the like.
[0007]
In addition, if an imaging mirror is used as the scanning imaging optical system and an angle is set in the sub-scanning direction of the deflected beam between the direction of incidence of the deflected beam and the direction of reflection on the imaging mirror, the principle Therefore, even when the scanning line is bent and the scanning imaging optical system is configured as a lens system, the scanning line is scanned in the multi-beam scanning method in which the scanning surface is optically scanned with a plurality of light spots separated in the sub-scanning direction. Bending is inevitable.
[0008]
The inclination of the scanning line is a phenomenon in which the scanning line is not correctly orthogonal to the sub-scanning direction, and is a kind of bending of the scanning line. Therefore, in the following description, unless otherwise specified, the inclination of the scanning line is included in the expression of scanning line bending.
[0009]
If the constant speed of optical scanning is not perfect, distortion in the main scanning direction occurs in the formed image, and scanning line bending causes distortion in the sub-scanning direction in the formed image.
If the image is so-called monochrome and is formed by writing with a single optical scanning device, scanning line bending and constant velocity imperfections (deviation from ideal constant velocity scanning) can be suppressed to some extent. Although the “formed distortion” is not generated in the formed image, the distortion of such an image is never small.
[0010]
Separately from a monochrome image, three colors of magenta, cyan, and yellow, or four colors with black added thereto, are formed as color component images, and these color component images are superimposed to form a color image synthetically. Forming is conventionally performed by a color copying machine or the like.
As one method for forming such a color image, an image for each color component is formed on a photoconductor that can form an image for each color component by using an optical scanning device provided for each color component image. There is a so-called tandem type image forming method. In the case of such an image forming method, if the scanning line bending degree or inclination differs between the optical scanning devices, even if the scanning line bending for each optical scanning device is corrected, An abnormal image called “deviation” appears, degrading the image quality of the color image.
[0011]
Further, as a way of causing the color misregistration phenomenon, there is a phenomenon that the color tone in the color image does not become a desired one.
[0012]
Conventionally, in order to prevent the occurrence of the above-mentioned problems such as color misregistration, the support portion on one side that sandwiches the optical axis of the long lens in the sub-scanning direction is provided with an adjustment screw that can move the long lens in the optical axis direction. There has been proposed a configuration in which the adjustment of the scanning line is corrected by rotating and adjusting the long lens within a cross section orthogonal to the deflection scanning direction by adjusting the adjustment distance (for example, Patent Document 1). .
[0013]
[Patent Document 1]
JP 2002-131684 A (Claim 1, FIG. 3)
[0014]
[Problems to be solved by the invention]
However, the configuration disclosed in Patent Document 1 has the following problems.
In some cases, it is still impossible to correct scanning line bending with respect to environmental fluctuations that affect the lens material used in the imaging optical system. The reason is as follows.
[0015]
In recent years, in order to improve scanning characteristics, it has become common to adopt special surfaces typified by aspherical surfaces in the imaging optical system of optical scanning devices, and such special surfaces can be easily formed. An imaging optical system made of a resin material that can be manufactured at a low cost is often used.
[0016]
An imaging optical system made of a resin material is susceptible to changes in optical characteristics under the influence of changes in temperature and humidity, and such changes in optical characteristics also change the degree of scanning line bending and the constant velocity. For this reason, for example, when several tens of color images are continuously formed, the internal temperature rises due to the continuous operation of the image forming apparatus, and the optical characteristics of the imaging optical system change. The curve and constant velocity of the scanning lines written by the device gradually change, and due to the phenomenon of color misregistration, the color image obtained in the initial stage may be completely different from the color image obtained in the final stage. is there.
[0017]
A scanning imaging lens such as an fθ lens, which is a typical scanning optical system, is generally formed as a strip-shaped lens that is long in the main scanning direction by cutting a lens unnecessary portion (portion where no deflected light beam is incident) in the sub-scanning direction. When the scanning imaging lens is composed of a plurality of lenses, the lens length in the main scanning direction increases as the disposition position is farther from the light deflecting means, and the length has a length of 10 centimeters to 20 centimeters or more. A scale lens is required. Such a long lens is generally formed by resin molding using a resin material. However, if the temperature distribution in the lens becomes non-uniform due to a change in the external temperature, the lens is warped and the lens becomes a bow shape in the sub-scanning direction. become. Such warpage of the long lens causes the scanning line bending described above, but when the warping is significant, the scanning line bending occurs extremely. Such a phenomenon occurs even when the initial adjustment is performed using the configuration shown in Patent Document 1. In addition, in the configuration of Patent Document 1, no countermeasure is taken against the inclination of the scanning line that causes problems such as color misregistration other than the scanning line bending. Furthermore, the configuration disclosed in Patent Document 1 has a problem that it is difficult to ensure positioning accuracy because the positioning of the lens in the optical axis direction changes depending on the fastening condition of the screw.
[0018]
An object of the present invention is to effectively suppress deformation caused by a temperature change of a resin imaging element included in a scanning imaging optical system in view of the problems in the above-described conventional optical scanning device, and also to scan line bending and / or Another object of the present invention is to provide an optical scanning apparatus and an image forming apparatus having a configuration capable of accurately correcting isokineticity.
[0019]
[Means for Solving the Problems]
According to the first aspect of the present invention, the light beam from one or more light sources is deflected by the light deflecting means, and the deflected light beam is formed on the surface to be scanned in accordance with the light source by one or more scanning imaging optical systems. In the optical scanning device that is formed and performs optical scanning, the interval holding means is set to be equal to or thinner than the height in the sub-scanning direction of the scanning imaging optical system, and is made of resin resin used in the scanning imaging optical system. A flat plate that sandwiches both sides in the height direction of the image element in the sub-scanning direction over the entire surface in the main scanning direction, and these flat plates are fastened at both ends in the main scanning direction to maintain a distance therebetween, and is generated in the resin imaging element An interval holding means for maintaining the warpage in a prevented state; By rotating the resin imaging element about the optical axis direction or the main scanning direction as a rotation axis, with the reference pin contacting the flat plate as a fulcrum, which is substantially the center of the resin imaging element in the main scanning direction. , Sandwiched using the flat plate and spacing means The Bending of a scanning line caused by displacement of a member other than the resinous imaging element due to fluctuation over time, targeting the resinous imaging element that maintains a state in which warpage is prevented Or And a means for correcting the inclination.
[0020]
According to a second aspect of the present invention, there is provided the optical scanning device according to the first aspect, wherein the scanning line is bent. Or As a means to correct the tilt, On a surface to be scanned which is arranged between the light deflection means and the scanning imaging optical system. Adjustable light spot position liquid crystal Deflection hand Further provided with a stage It is characterized by that.
[0021]
A third aspect of the invention is characterized in that the optical scanning device according to the first or second aspect is used in an image forming apparatus.
[0022]
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, a plurality of photoconductors are provided as surfaces to be scanned.
[0033]
According to a fifteenth aspect of the present invention, in the image forming apparatus according to the fourteenth aspect, a plurality of photoconductors are provided as scanning surfaces.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to examples shown in the drawings.
Before describing the configuration of an optical scanning device according to an embodiment of the present invention, an image forming apparatus to which the optical scanning device is applied will be described.
FIG. 17 shows an image forming apparatus to which the optical scanning device according to the embodiment of the present invention is applied. The image forming apparatus shown in FIG. 17 uses a copier or a printer capable of forming a full-color image. In addition to this, there is a facsimile apparatus capable of performing the same image forming process as the above-described copying machine and printer based on a received image signal. Note that the image forming apparatus includes not only the above-described color image but also an apparatus that targets a single color image.
[0035]
The image forming apparatus 1 shown in FIG. 17 has a tandem structure in which a plurality of photosensitive drums 1A, 2A, 3A, and 4A that can form an image corresponding to a color-separated color (yellow, cyan, magenta, and black) are juxtaposed. The visible image formed on each photoconductive drum is used so as to be superimposed and transferred onto a transfer sheet S that is a recording medium conveyed by a transfer belt 5 that is movable while facing the photoconductive drum. It has become.
[0036]
Now, the configuration relating to the image forming process will be described on behalf of one photosensitive drum 1A as follows. Since the other photosensitive drums 2A to 4A have the same configuration, for convenience, reference numerals assigned to the photosensitive drum 1A are attached to the part numbers of the photosensitive drums.
Around the photosensitive drum 1A, a charging device 1B using a configuration such as a corotron or a scoroton for executing an image forming process along the rotation direction indicated by an arrow (in FIG. 17, a configuration using a roller is shown). 1) and the subsequent drawings, the optical scanning device 20, the developing device 1D, and the cleaning device 1E using the laser light from the laser light source are respectively arranged.
[0037]
In the image forming apparatus 1 shown in FIG. 1, a document reading unit 6 is disposed above an image forming unit in which these devices for performing image forming processing are disposed, and a document placed on a document placing table 6A. The image information read by the reading device 7 is output to an image processing control unit (not shown), and writing information for the optical scanning device 20 described above can be obtained. The charging device 1B is not limited to a contact type using a roller, but can also use a corona discharge type using a discharge wire.
In this embodiment, the developing devices are arranged in the order in which yellow, cyan, magenta and black toners can be supplied from the right side of the extended portion of the transfer belt 5 in FIG.
[0038]
The reading device 7 forms an image on a light source 7A for scanning a document placed on the document placing table 6A and a reflected light from the document on a CCD 7B provided for each color separation. A plurality of reflecting mirrors 7C and an imaging lens 7D are provided, and image information corresponding to the light intensity for each color separation is output from each CCD 7B to the image processing control unit.
[0039]
The transfer belt 5 is a member made of a dielectric material such as a polyester film wound around a plurality of rollers, and one of the extended portions faces each of the photosensitive drums 1A to 4A, and faces the respective photosensitive drums. Inside the position, transfer devices 8A, 8B, 8C and 8D are arranged. To the transfer belt 5, the recording medium S fed from the inside of the paper feeding cassette 9 </ b> A of the paper feeding device 10 is fed via the registration rollers 9, and the recording medium S is transferred from the transfer device 8 </ b> A to the transfer belt 5. Is electrostatically adsorbed by the corona discharge and conveyed.
[0040]
The separation device 11 of the recording medium S is located at the position where the recording medium S after the image transfer from each of the photosensitive drums 1A to 4A has moved, and the neutralizing device facing the other portion of the stretched portion with a belt interposed therebetween. 12 is arranged. In FIG. 1, reference numeral 13 denotes a cleaning device that removes the toner remaining on the transfer belt 5. The transfer devices 8 </ b> A to 8 </ b> D have a characteristic of electrostatically attracting the images carried on the photosensitive drums 1 </ b> A to 4 </ b> A toward the recording medium S using positive corona discharge.
[0041]
The separation device 11 performs negative AC corona discharge from the upper surface of the recording medium S to neutralize the electric charge accumulated in the recording medium S and release the electrostatic adsorption state. Separation using curvature is made possible and toner dust is prevented from being generated due to peeling discharge during separation. Further, the static eliminator 12 neutralizes the accumulated charge of the transfer belt 5 by performing negative AC corona discharge having a polarity opposite to the charging characteristics of the transfer devices 8A to 8D from both the front and back surfaces of the transfer belt 5. Initialization is to be performed.
[0042]
In each of the photosensitive drums 1A to 4A, the surfaces of the photosensitive drums 1A to 4A are uniformly charged by the charging devices 1B to 4B, and based on image information for each color separation color read by the reading device 7 in the document reading unit 6. An electrostatic latent image is formed on the photosensitive drum using the writing devices 1C to 4C, and the electrostatic latent image can be formed by toner of a color having a complementary color relationship corresponding to the color separation color supplied from the developing devices 1D to 4D. After the visual image processing, the image is electrostatically transferred to the recording medium S carried by the transfer belt 5 via the transfer devices 8A to 8D.
[0043]
The recording medium S to which the image for each color separation carried on each of the photosensitive drums 1A to 4A is transferred is discharged by the charge removing device 11 and then is separated by using the curvature of the transfer belt 5, and then the fixing device. 14, the toner in the unfixed image is fixed and discharged.
[0044]
FIG. 1 is a diagram showing a basic configuration of an optical scanning device 20 for a plurality of the above-described photosensitive members.
In FIG. 1, two light beams 21A ′ and 21B ′ emitted from a light source device 21 using two semiconductor lasers 21A and 21B are applied to a deflecting reflection surface of a polygon mirror 23 as a deflector by the action of a cylindrical lens 22. After being imaged as a line image (imaged in the sub-scanning direction and long in the main-scanning direction), the surface to be scanned (photosensitive drum: denoted by reference numeral 1A for convenience) by the second imaging system 24 using the fθ lens. ) The top is scanned as a light spot. In FIG. 1, the light source device 21 is composed of a semiconductor laser and a coupling lens, but is not limited to such a configuration.
[0045]
When the optical scanning device 20 is used as an optical writing device of an image output device, the light beam is modulated corresponding to the output image data, but the electrical signal (synchronization signal) for the modulation start timing is synchronized detection. It is obtained when a light beam is incident on the plate 25.
[0046]
As shown in FIG. 2, the two light beams 21A ′ and 21B ′ have a configuration (main scanning section) that intersects at an angle θ in the vicinity of the deflecting reflection surface of the polygon mirror 23. As a result, it is possible to suppress the occurrence of deviation in optical characteristics (field curvature, magnification error, etc.) between the two beams.
[0047]
As shown in FIG. 3, the two spot lights BS1 and BS2 on the surface to be scanned corresponding to the photosensitive drum (for convenience, reference numeral 1A) are predetermined in the sub-scanning direction according to the scanning density. It is required to maintain the interval (beam pitch: PZ). In order to make this beam pitch predetermined, as shown in FIG. 4, an angle φ formed by the two light beams 21A ′ and 21B ′ may be set.
[0048]
The scanning device shown in FIG. For A liquid crystal deflection element 26 is disposed between the polygon mirror 23 and the second imaging system 24. The liquid crystal deflecting element 26 has an effective area corresponding to the main scanning region, and is divided and arranged in the main scanning direction or the sub-scanning direction, or is arranged so as to overlap the main scanning and sub-scanning in the optical axis direction. The position of the light spot on the surface to be scanned can be adjusted by deflecting the beam. The light beam is deflected by driving / controlling (modulating) the liquid crystal deflecting element 26 with an electric signal from a control means (not shown). In this case, the control method can be either feedback or open loop.
[0049]
The scanning line is bent and tilted due to the accuracy of the optical element alone, mainly due to the bending of the bus line and the accumulation of arrangement errors attached to the optical housing. For this reason, in the present embodiment, means (not shown) for detecting the bend and inclination of the scanning line on the surface to be scanned 1A is provided in the optical scanning device, or the color shift of the color patch formed on the transfer belt is detected. Then, the liquid crystal deflecting element 26 is driven / controlled (modulated) by an electric signal based on the detection result, thereby correcting the bending inclination of the scanning line.
[0050]
Here, a description will be given of the amount (size) of the bending inclination of the scanning line. The amount of inclination generated by the optical scanning apparatus itself and the bending inclination generated due to factors other than the optical scanning apparatus such as the inclination caused by the inclination of the photosensitive drum shaft. Is caused by the bending inclination of the image, and an inclination of up to several hundred microns may occur. In the present embodiment, the optical scanning device 20 aims to correct factors other than those occurring in the optical scanning device 20.
The correction / correction means described later corrects the bending inclination of several hundreds of microns to several tens of microns or less, and the liquid crystal deflecting element 26 enables correction of several tens of microns or less. It is intended to improve accuracy. In order to correct several hundred microns by the liquid crystal deflecting element 26, the deflection angle must be increased. If the deflection angle is increased, there is a side effect that the response speed of the liquid crystal deflecting element is lowered. Become.
[0051]
The scanning position detection means has the configuration shown in FIG.
5A and 5B show the case where the scanning line detecting means is arranged in or near the optical scanning device. In FIG. 5A, the liquid crystal deflecting element 26 is tilted to reflect the reflected light of the light beam into the area. A scanning position shift is detected by a sensor (indicated by the symbol AS for convenience), and a half mirror (indicated by the symbol HM for convenience) is separately provided and detected in (B).
[0052]
5C and 5D uses a color shift (transfer position shift between color images) of the toner image T on the photoreceptor 1A and the toner image T on the transfer belt 5 (see FIG. 17) as a light source. This is a method of detecting the reflection state of the irradiation light from P by the area sensor AS, and may be highly accurate because it is detected in a process close to the final image.
[0053]
The optical scanning device 20 having the above-described configuration is provided with means for correcting / correcting the bending and / or inclination of the scanning line. Hereinafter, this configuration will be described. FIG. 6 is a diagram showing a scanning line bending inclination correcting / correcting means 100 integrated with a long resin lens used in the second imaging system 24.
The bending of the scanning line in this embodiment is eliminated by correcting and correcting the inclination (indicated by the symbol β in FIG. 6) in the direction orthogonal to the optical axis of the long lens 101, and the inclination of the scanning line. Is corrected by correcting the inclination (indicated by reference numeral γ in FIG. 6) around the optical axis of the long lens 101. The configuration for this will be described below.
[0054]
In FIG. 6, the scanning line curve inclination correction / correction unit 100 includes a shape holding unit 102 and an attitude control unit 103 of the long lens 101.
The shape holding means 102 functions as a means for correcting the shape of the long lens 101 when the long lens 101 undergoes deformation such as warping due to a temperature change. For this reason, the long lens 101 is mounted as a configuration. The lower sheet metal member 102A that can be positioned and positioned, the upper sheet metal member 102B that can press the upper surface of the long lens 101, and the sheet metal members 102A and 102B on the upper and lower sides are arranged at both longitudinal ends of the long lens 101. And an interval holding member 102C to be attached.
[0055]
The lower sheet metal member 102 </ b> A and the upper sheet metal member 102 </ b> B are opposed to each other by fastening both ends in the longitudinal direction to the interval holding member 102 </ b> C, and this interval is defined in the sub-scanning direction of the long lens 101. The height (thickness) is equal to or somewhat lower (thin). As a result, the long lens 101 is sandwiched at both ends in the sub-scanning direction by the lower and upper sheet metal members 102A and 102B, and is prevented from being deformed when warping occurs, and the bending of the busbar is corrected and held. It is like that.
[0056]
On the lower sheet metal member 102A, a positioning projection 102A1 of the long lens 101 is formed on the surface of the central portion in the longitudinal direction, and the engaging portion 101A formed on the mounted long lens 101 side is provided. The long lens 101 is positioned in the longitudinal direction (main scanning direction) by being sandwiched.
[0057]
A protruding piece 102A2 is formed at the front end edge of the central portion in the longitudinal direction of the lower sheet metal member 102A, that is, at the edge of the scanning light emission side on one side in the optical axis direction, and the protruding piece 102A2 has the β direction described above. An adjustment screw 104 for adjusting the tilt at is fastened to a non-illustrated non-illustrated portion of the optical housing.
A compression spring 105 inserted into the adjustment screw 104 is arranged between the lower surface of the protruding piece 102A2 and the stationary part of the optical housing, and pushes up the protruding piece 102A1 in the lower sheet metal member 102A from below.
[0058]
The lower sheet metal member 102A can tilt the front end edge in the direction indicated by the symbol β by adjusting the fastening state of the adjustment screw 104, and thereby the inclination in the direction perpendicular to the optical axis of the long lens 101 can be increased. Adjustment is made to correct the bending of the scanning line. For this reason, the protruding piece 102A2 functions as a scanning line bending correction unit.
[0059]
As shown in FIG. 8, one end of a U-shaped plate spring 107 spanned between the upper base metal member 102B and the support base 106 provided in a part of the optical housing is fastened and attached. It has been.
The plate spring 107 supports the upper sheet metal member 102B, and the shape holding means 102 including the lower sheet metal member 102A, the upper sheet metal member 102B, and the interval holding member 102C is swung with the R sphere tip of the reference pin 108 as a fulcrum. It is supported by pressing in the sub-scanning direction. That is, the two plate springs 107 have a stronger elastic force than the compression spring 105 of the projecting piece 102A2 included in the lower sheet metal member 102A. Β tilt can be performed in contact with the.
[0060]
As shown in FIGS. 7 and 8, the shape holding means 102 has a longitudinal central portion placed on a reference pin 108 provided on the support base portion 106 side of the optical housing, in other words, in the longitudinal direction. The lens 101 can be tilted in the γ direction in addition to the β direction around the optical axis of the lens 101, and the γ direction, that is, the tilt around the optical axis in the tilt direction is adjusted by the attitude control means 103. As a result, the curve and / or inclination of the scanning line can be corrected and corrected.
[0061]
The attitude control means 103 includes a drive source 109 using a stepping motor disposed on one side in the longitudinal direction of the shape holding means 102 around the reference pin 108 provided on the support base portion 106 of the optical housing. Yes.
[0062]
In the present embodiment, the position of the reference pin 108 is positioned substantially coaxially with the center position of the long lens 101 in the main scanning direction and the sub-scanning direction, and the protruding piece 102A2 in the shape holding means 102 described above, that is, scanning. The position of the member that adjusts the line bending is on the extension line of the optical axis, and the position of the driving source 109 in the posture control means 103, that is, the member that adjusts the inclination of the scanning line is perpendicular to the optical axis. Located on the centerline extension.
[0063]
As shown in FIG. 9, a lead screw 109A is formed on the output shaft of the drive source 109, and a nut 110 is attached to the lead screw 109A.
The nut 110 is provided with an adjustment lever 112 that supports a swing fulcrum shaft on a drive source support bracket 111 installed on the support base 106. As a result, as indicated by an arrow in FIG. 9, the adjustment lever 112 swings according to the direction in which the nut 110 moves in the axial direction of the lead screw 109A according to the rotation direction of the lead screw 109A.
[0064]
The oscillating end of the adjustment lever 112 can be interlocked with the support pin 102C1 provided on the interval holding member 102C on the shape holding means 102 side by pressing from above. As a result, the shape holding means 102 can be tilted about the optical axis in accordance with the swinging state of the adjusting lever 112 (inclination in the direction indicated by symbol γ in FIG. 6), and correction is performed by correcting the inclination of the scanning line. can do.
[0065]
FIGS. 10 to 13 are views showing the installation structure of the long lens 101 with respect to the shape holding means 102. The long lens 101 is formed at both ends in the longitudinal direction on the interval holding member 102C as shown in FIG. The stepped portion 102C2 serving as the optical axis direction abutting portion is mounted, and is in close contact with the stepped portion 102C2 by the pressing spring 113 and is placed in the optical axis direction.
[0066]
The lower sheet metal member 102A and the upper sheet metal member 102B sandwiching the long lens 101 are integrated with each other by being fastened to the spacing member 102C, and one of the support pins 102C1 fitted to the spacing member 102C is inserted. The adjustment lever 112 of the posture control means 103 that can be pressed is integrated because of the interlocking relationship, and the drive source 109 that constitutes the posture control means 103 causes the long lens 101 to tilt (γ direction) in the optical axis direction. By adjusting, the curve of the scanning line is corrected and corrected.
[0067]
The lower sheet metal member 102A and the upper sheet metal member 102B configured to sandwich the long lens 101 on both sides in the sub-scanning direction are attached to the spacing member 102C with the configuration illustrated in FIG. That is, the lower sheet metal member 102A and the upper sheet metal member 102B are fixed to the spacing member 102C using separate screws 114 and 114 ′. In addition, the spacing member 102C is set to have substantially the same relationship as the linear expansion coefficient of the long lens 101, and the influence of the difference in linear expansion coefficient between the screws 114 and 114 ′ is eliminated. . As a result, even when the environmental temperature changes, a constant compressive stress is maintained to minimize the influence of the optical characteristic change in the long lens 101. That is, when the lower and upper sheet metal members 102A and 102B are tightened together by passing a metal screw through the gap adjusting member 102C, the linear expansion coefficient of the screw becomes dominant, and the screw changes when the environmental temperature changes. The expansion effect directly affects the pinching force between the sheet metal members 102A and 102B and the long lens 101, and it becomes impossible to maintain a constant compressive stress between the long metal sheet 101 and the long sheet 101. It can suppress that the optical characteristic in the lens 101 will change.
[0068]
In the present embodiment, as a result of an experiment conducted by the inventor in the case of using the above-described configuration, in particular, a scanning line bending and / or inclination correction / correction unit corresponding to a shape change of the long lens 101 with respect to a temperature change, FIG. And the result shown in FIG. 15 was obtained. FIG. 14 shows a time series of changes in shape when a single resin long lens (a member denoted by reference numeral 101 in FIG. 11) is placed on a reference plate in a thermostat and the temperature is changed from 25 ° C. to 45 ° C. As a result of the three-point measurement, a temperature difference occurs between the bottom surface and the top surface that are in contact with the reference plate due to the hot air hitting the surface of the long plastic lens. To do. It shows that the temperature inside the lens becomes uniform and the shape returns to its original state after a certain period of time. If a temperature difference occurs due to the heat generated by the polygon scanner and the heat of fixing during the mounting of the main body, a bending inclination occurs, and this causes color misregistration in the tandem system. FIG. 15 shows the result when the above-described scanning line bending and / or inclination correction / correction means is provided, and is the result of measuring the shape change of the resin long lens provided with the correction / correction means. It can be seen that there is a sufficient change suppressing effect.
[0069]
The scanning line bending and / or inclination correcting / correcting means having the above-described configuration is applied to the optical scanning device 20 including the tandem optical system shown in FIG. Figure 16.
In FIG. 16, the optical scanning device 20 comprising a tandem optical system is different from that shown in FIG. 1 for a plurality of photosensitive drums (for convenience, using the symbols 1A and 1B shown in FIG. 1). The basic configuration shown is applied, and in the configuration, the integral bending and / or inclination correcting / correcting means 100 is applied to a long lens (indicated by reference numerals 101 and 101 ′ for convenience), For Polygon mirrors (denoted by symbols PM and PM ′ for convenience) and a first fθ lens L2. Liquid crystal deflecting elements 26 and 26 'are respectively arranged between L3 and L3. In FIG. 16, reference numerals 27 and 27 ′ denote first and second scanning semiconductor lasers forming a light source, reference numerals 28 and 28 ′ denote first scanning folding mirrors, and reference numerals 29 and 29 ′ denote reference numerals. The second scanning folding mirror is shown, and the optical member disposed in the optical path after the liquid crystal deflecting elements 26, 26 'with respect to the photosensitive drums 1A, 2A is shown in the second connection shown by reference numeral 24 in FIG. Each photosensitive drum is configured as an object as an image system.
[0070]
By using the optical scanning device including the tandem optical system having such a configuration, it is possible to suppress the shape change due to the change in the environmental temperature in the long lenses 101 and 101 ′, and to suppress the bending and / or the inclination of the scanning line due to the shape change. Further, by using the liquid crystal deflecting elements 26 and 26 ', light in a state in which the amount of inclination and bending is reduced by the scanning line bending and / or inclination correcting / correcting means 100 and 100' and is easily changed. The spot position can be optimized.
[0071]
【The invention's effect】
According to invention of Claim 1, It is in a state where there is no shape change such as warpage generated in the resin imaging element. In other words, the resin imaging element is sandwiched on both sides of the height in the sub-scanning direction over the entire surface in the sub-scanning direction by a flat plate whose facing interval is set by a height holding means in the sub-scanning direction or the like, or a thin interval holding means. Therefore, even when warping occurs, the warping itself is prevented by the flat plate. This It is possible to prevent the occurrence of color misregistration caused by the shape change such as warping of the resin imaging element.
[0072]
According to the second aspect of the present invention, the means for correcting the bending and inclination of the scanning line includes the means for correcting the attitude of the resin imaging element and the deflecting means for adjusting the light spot position. It is possible to correct the posture on the premise that there is no warp in the imaging element itself, in other words, the same state as there is no shape change, and it is possible to improve the accuracy of curve correction and tilt correction of the scanning line, Since the scanning line bending and tilt correction can be performed, the burden of adjusting the light spot position can be reduced, and the scanning line bending and tilt correction accuracy due to environmental fluctuations can be further improved. It becomes possible.
[0073]
According to the third and fourth aspects of the invention, when used as an optical scanning device of a tandem multicolor image forming apparatus using an electrophotographic process, the scanning line bending and / or inclination of each photoconductor is corrected and corrected. Therefore, it is possible to increase the density of monochromatic and multicolor output images, increase the speed by multibeam, and improve the image quality with little color shift. Furthermore, it leads to reduction of power consumption, vibration noise reduction, and heat generation, and environmental load can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram for explaining a basic configuration of an optical scanning device according to an embodiment of the present invention.
FIG. 2 is a schematic diagram for explaining one of the operations of the optical scanning device shown in FIG. 1;
FIG. 3 is a schematic diagram for explaining another function of the optical scanning device shown in FIG. 1;
4 is a schematic diagram for explaining another operation of the optical scanning device shown in FIG. 1. FIG.
FIG. 5 is a diagram for explaining an example of a configuration for detecting misregistration and color misregistration used in the optical scanning device shown in FIG. 1;
6 is a perspective view showing a configuration of scanning line bending and / or inclination correction / correction means used in the optical scanning device shown in FIG. 1; FIG.
7 is a plan view of scanning line bending and / or inclination correcting / correcting means shown in FIG. 7. FIG.
8 is a cross-sectional view partially in the direction indicated by reference numeral (8) in FIG.
FIG. 9 is a cross-sectional view taken partially in the direction indicated by reference numeral (9) in FIG.
FIG. 10 is a perspective view showing an installation structure of a long lens.
11 is a plan view of the installation structure shown in FIG.
FIG. 12 is an arrow view in the direction indicated by reference numeral (12) in FIG. 11, (A) is a front view, and (B) is an arrow view in the direction indicated by reference numeral (B) in (A). is there.
FIG. 13 is a view taken in the direction indicated by the reference numeral (13) in FIG.
FIG. 14 is a diagram showing a positional deviation state of a light spot due to a temperature change of a long lens.
15 is a diagram showing a result when the positional deviation shown in FIG. 14 is corrected and corrected. FIG.
FIG. 16 is a perspective view for explaining the configuration of an optical system that provides scanning line bending and / or tilt correction / correction means in the optical scanning apparatus of the present embodiment for a plurality of scanned surfaces.
FIG. 17 is a schematic diagram for explaining a configuration of an image forming apparatus to which the optical scanning device described in the embodiment of the present invention is applied.
[Explanation of symbols]
1 Image forming device
1A-4A Photosensitive drum
20 Optical scanning device
21 Light source device
24 Second imaging system
26 Liquid crystal deflection elements
100 Scan line bending and / or tilt correction / correction means
101 Long lens
102 Shape holding means
102A Lower sheet metal member
102A2 Protruding piece as a scanning line bending correction unit
102B Upper sheet metal member
102C spacing member
102C1 Support pin
102C2 Step
103 Attitude control means
107 leaf spring
108 Reference pin
109 Drive source
109A Lead screw
110 nuts
112 Adjustment lever

Claims (4)

Light that performs light scanning by deflecting light beams from one or more light sources by a light deflecting means and forming a light spot on the surface to be scanned according to the light sources by one or more scanning imaging optical systems. In the scanning device,
An interval holding means set to be equal to or thinner than the height in the sub-scanning direction of the scanning imaging optical system, the both sides of the resin imaging element used in the scanning imaging optical system in the height direction in the sub-scanning direction. A flat plate sandwiched over the entire surface in the main scanning direction, and interval holding means for maintaining the state in which the flat plates are fastened at both ends in the main scanning direction and the interval is maintained to prevent warping occurring in the resin imaging element. ,
By rotating the resin imaging element about the optical axis direction or the main scanning direction as a rotation axis, with the reference pin contacting the flat plate being a substantial center in the main scanning direction of the resin imaging element , and subject the resin imaging element to maintain the state of being prevented from occurrence of warpage is sandwiched with the flat plate and the spacing holding means, temporal fluctuations due to members other than the resinous imaging element An optical scanning device comprising: means for correcting bending or inclination of a scanning line caused by displacement. The optical scanning device according to claim 1,
As a means for correcting the bending or inclination of the scanning lines, further comprising the light deflecting means and adjustable liquid crystal deflecting hand stage light spot position on the scanned surface which is disposed between the scanning and imaging optical system An optical scanning device characterized by the above.   An image forming apparatus using the optical scanning device according to claim 1. The image forming apparatus according to claim 3.
An image forming apparatus comprising a plurality of photoconductors as a surface to be scanned.

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