JP2005266762A - Long length optical element holding mechanism, optical scanning device, image forming device, shape adjusting method and device for long length optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long length optical element holding mechanism which corrects the curb and the tilt of the scanning line of a long length optical element and restrains color shift of a color image forming device effectively, and also to provide an optical scanning device, an image forming device, and a deflection deformation adjusting method for a long length optical element. <P>SOLUTION: There are provided: an elastic member 61 which presses a long length optical element 15-2 by elasticity into the direction that crosses at right angles with an optical axis direction, and also crosses at right angles with a longitudinal direction; and a supporting member 63 which forms a pair with the elastic member and which supports the long length optical element facing the pressing power from the elastic member. Three or more pairs of the elastic members and the supporting members are provided. It is desirable that two of these pairs of the elastic members and the supporting members are disposed at both the end parts in the longitudinal direction of the long length optical element. At least one of the supporting members 63 holds another holder member 66, and it is movable in the pressure power direction. An adjusting mechanism which adjusts the amount of traveling of the supporting member is provided, and the adjusting mechanism at least consists of screw elements. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a holding mechanism for a long optical element applicable to an optical writing unit of a laser writing optical system such as a laser printer, a digital copying machine, and a laser facsimile, an optical scanning device and an image forming apparatus using the holding mechanism Furthermore, the present invention relates to a shape adjusting method for a long optical element and a shape adjusting apparatus for a long optical element.

  In recent years, in an image forming apparatus such as a laser printer, a digital copying machine, and a laser facsimile, a plastic material is often used as a material of an optical element constituting a scanning optical system. While plastic is excellent in mass productivity, its shape deviates from its ideal shape due to factors such as the temperature distribution in the mold during molding and cooling after removal from the mold. There are many things.

  In a scanning optical system, there are many optical elements having a long shape in the main scanning direction, and the optical element may be bent in the sub-scanning direction. Depending on the method for holding the long optical element as described above, The bending causes a scanning position shift in the sub-scanning corresponding direction such as scanning line inclination and scanning line bending. In addition, an error in attaching the optical element to the housing also causes a scanning position shift in the sub-scanning corresponding direction on the surface to be scanned, and this scanning position shift often becomes a size that cannot be ignored.

  Further, in an image forming apparatus having a plurality of scanning means for speeding up image formation or color image formation (hereinafter referred to as “tandem type”), temperature deviation between housings holding and fixing the scanning means. Therefore, the amount of scanning position deviation in the sub-scanning corresponding direction, such as scanning line bending, differs for each scanning unit, which causes deterioration in the quality of the formed image, color deviation, and the like. Also, in a system in which a plurality of light beams are incident on a single deflector for scanning and optical elements are superposed in the sub-scanning direction, that is, a system in which all scanning means are held in the same optical housing. In addition, due to the influence of the shape error and mounting error of the optical elements constituting each scanning optical system, and the temperature distribution in the same housing, for example, the scanning line tilt on the surface of the photoconductor, the scanning line bending, etc. Therefore, the amount of scanning position shift in the sub-scanning corresponding direction is different, and the formed image quality is deteriorated.

  One type of full-color image forming apparatus is a tandem type. For example, four photosensitive drums are arranged along the transfer surface of the transfer belt corresponding to each color of cyan (C), magenta (M), yellow (Y), and black (K). A light beam is scanned by an optical scanning device provided corresponding to the body drum to form an electrostatic latent image on the peripheral surface of each photosensitive drum, and the electrostatic latent image is visualized with toner of a corresponding color. An image is formed, and this is sequentially transferred onto a sheet conveyed by a transfer belt to form a multicolor image. Therefore, if a scanning position shift in the sub-scanning corresponding direction occurs for each color, it may cause a decrease in quality of the formed image or a color shift.

Many proposals have been made as means for solving the problems described above. Among these proposals, some related to the present invention are listed below.
As one example, there has been proposed an optical scanning device provided with an adjustment mechanism for forcibly deforming an optical member in a scanning optical system such as a mirror with an adjustment screw, etc., and correcting the bending of the scanning line (for example, Patent Document 1). However, in this method, there is a difficulty in that the magnification in the main scanning direction changes due to correction of scanning line bending. For this reason, particularly in a tandem writing optical system, a dot position shift in the main scanning direction occurs between the stations including the optical scanning device and the corresponding photosensitive member, and a color shift due to the dot position shift occurs. In addition, since the scan line tilt cannot be adjusted, even if the scan line bending amount at each station is reduced to a predetermined range, if the scan line tilt varies from station to station, color unevenness or color misregistration may occur, resulting in image quality being formed. Deterioration.

  As another example, a plurality of adjustment screws screwed into the housing and a spring means disposed at a position opposed to each adjustment screw are configured to press and support a plastic lens disposed in the housing, and each adjustment screw. There has been proposed a scanning optical device that corrects the deflection deformation of the plastic lens by adjusting the pressing force of the lens and corrects the scanning line bending and / or inclination on the surface to be scanned (for example, Patent Documents). 2). In the adjustment method according to the present invention, since the plastic lens is arranged in the housing, there is a problem that the optical scanning device is enlarged, and since the housing is fixed to the optical housing, the inclination of the scanning line is reduced. It cannot be corrected.

  As yet another example, in a tandem type image forming apparatus using a plurality of scanning means, the entire scanning means, in other words, the individual scanning means are assembled in individual housings, and the entire individual housings are assembled into corresponding photoreceptors. A scanning optical device and a color image forming apparatus using the same have been proposed (for example, see Patent Document 3). However, according to the present invention, the mechanism for adjustment becomes complicated and it takes time for adjustment. In addition, the scanning line bending cannot be adjusted when the temperature varies from the normal temperature state to have a temperature distribution between the scanning units, and there is a possibility of color misregistration. Further, it cannot cope with a change over time due to a temperature change or the like, and color misregistration during printing or in a use environment cannot be corrected with high accuracy.

  As yet another example, an adjustment screw is abutted near the center of the toroidal lens made of a plastic lens constituting the scanning optical system to deflect the toroidal lens in the sub-scanning direction. There has been proposed an optical scanning device of a multicolor image forming apparatus of a type in which the curvature of the scanning line is corrected by correcting the degree of curvature (see, for example, Patent Document 4). According to the present invention, it is possible to correct the scanning line bending between the photoconductors in the initial state, but it cannot cope with a change over time due to a temperature change or the like, and a color shift based on a change in environmental conditions during printing. Or, color misregistration based on the use environment cannot be corrected with high accuracy.

JP-A-11-231240 JP 2001-166235 A JP 2001-133718 A Japanese Patent Laid-Open No. 10-268217

  As described above, in any of the conventional techniques, the position of the dot in the main scanning direction on the surface to be scanned is shifted, the scanning line inclination cannot be corrected, or the scanning line is associated with a change with time and / or a temperature change. There remains a technical problem that the curve cannot be corrected.

  An object of the present invention is to correct bending or inclination of a scanning line caused by a shape error or assembly error of a long optical element having a shape deviated from an ideal state and / or an optical component other than the long optical element. The present invention provides a long optical element holding mechanism, an optical scanning device, an image forming apparatus, and a deflection deformation adjusting method for a long optical element that can effectively suppress the occurrence of color misregistration in a color image forming apparatus. is there.

  The present invention relates to an elastic member that presses a long optical element with an elastic force in a direction orthogonal to the optical axis direction and orthogonal to the longitudinal direction, and a pressing force from the elastic member that forms a pair with the elastic member. And a support member for supporting the long optical element opposite to the long optical element, wherein three or more sets of the elastic member and the support member are provided. The most important feature. Two pairs of the elastic member and the support member may be arranged at both ends in the longitudinal direction of the long optical element. At least one of the support members may be held by another holder member and movable in the direction of the pressing force. Furthermore, an adjustment mechanism capable of adjusting the amount of movement of the support member is provided, and the adjustment mechanism is preferably constituted by at least a screw element.

The present invention also includes a long optical element, and a holding member that is disposed on at least one of the upper side and the lower side of the long optical element and has two support portions that support the long optical element at a distance L apart from each other. An adjustment member that is provided in the holding member and that presses and deforms the long optical element; and an elastic member that is disposed to face the adjustment member in order to press and fix the long optical element to the holding member. In the holding mechanism for the long optical element, the two ends of the long optical element (subscript i = 1) and the holding member (subscript i = 2) are separated by a distance L. The deflection when the load Wi is applied to the central portion is δi, and the elastic modulus Ki is
Ki = (Wi × L ³ ) / (48 × δi)
When the elastic coefficients of the long optical element and the holding member are K1 and K2, respectively,
K2 / K1 ≧ 0.5
It is characterized by being.

  The present invention also provides an optical scanning device provided with a holding mechanism for a long optical element having the above-described configuration, an image forming apparatus provided with this optical scanning device as an exposure device, and a method for adjusting deflection deformation of the long optical element. To do.

According to the long optical element holding mechanism of the present invention, the following effects can be obtained.
-The “degree of deflection” of the long optical element can be kept good.
By adjusting the amount of deflection deformation of the long optical element, the shape of the scanning line, that is, the scanning line bending and / or the scanning line inclination can be corrected.
-The flexure deformation can be adjusted easily and with high accuracy in a short time by using a component structure that can reduce costs.
-Scan line bending and scan line inclination can be corrected independently.
It is possible to reduce the adjustable portions without reducing the adjustment accuracy and without increasing the adjustment time and / or complicating the adjustment procedure.
-Two independent scanning line bending correction mechanisms can be provided.
-As the number of parts is reduced, the cost of the device can be reduced, and the size and weight can be reduced.

According to the holding mechanism for another long optical element according to the present invention, the following effects can be obtained.
Deflection deformation of the holder member that holds the long optical element can be suppressed, and deterioration of the mounting accuracy of the long optical element holding mechanism can be avoided.
It is not necessary to increase the pressing force of the elastic member that presses and fixes the long optical element, and the bending correction of the long optical element can be performed with high accuracy.
-The number of parts can be reduced and the size can be reduced.
-In addition to correcting the bending of long optical elements, tilt correction can also be performed.

  According to the optical scanning device of the present invention, it is possible to draw a scanning line having a good shape as intended on the surface to be scanned. Further, it is possible to correct the deformation of the scanning line shape due to the influence of vibration, change with time, change in temperature, and the like. Furthermore, the scanning line shape can be detected easily and with high accuracy, and the scanning line shape can be corrected easily and with high accuracy based on the detection result.

  The image forming apparatus according to the present invention can output a high-quality image. Further, by detecting the deflection amount of the long optical element, it is possible to perform simple and highly accurate feedback correction of the deflection amount of the long optical element, and it is possible to form a higher quality image.

  According to the shape adjusting method or the shape adjusting apparatus for the long optical element according to the present invention, the holding mechanism for the long optical element capable of obtaining the above-described effect is used, and the deflection of the long optical element is performed by the adjusting member. By adjusting the deformation, the long optical element can be flexed and deformed into an intended shape, and the shape can be adjusted.

  First, an outline of the optical scanning device will be described, and the cause of occurrence of scanning line bending and scanning line inclination on the surface to be scanned of the optical scanning device will be described. FIG. 1 shows an example of an “optical scanning device” used in an image forming apparatus. This optical scanning device is an example of an optical scanning device that scans a surface to be scanned with a single laser beam emitted from one light source, but a plurality of light beams emitted from a plurality of light sources (for example, semiconductor laser arrays). The present invention can also be applied to a “multi-beam optical scanning device” that simultaneously scans a laser beam. In FIG. 1, a laser beam 21 emitted from a semiconductor laser 11 as a light source is converted into a substantially parallel laser beam by a coupling lens 12 and coupled to a subsequent optical system. This laser beam is converged only in the sub-scanning direction by the action of the cylindrical lens 13 and is formed as a long line image in the main scanning direction on the deflection reflection surface of the polygon mirror 14 which is an optical deflector. Yes. The polygon mirror 14 is driven to rotate at a constant speed by a polygon motor, and the laser beam is deflected at a constant angular speed. The deflected laser beam is imaged as a beam spot on the surface of the photosensitive drum 16 which is a surface to be scanned by the scanning optical system 15 including the first scanning lens 15-1 and the second scanning lens 15-2. The scanning optical system 15 has the fθ function to scan the scanned surface at a constant speed. Reference numeral 18 indicates a scanning line by a laser beam on the surface of the photosensitive drum as the scanned surface 16. Such an apparatus that images and scans the light beam emitted from the light source unit as a beam spot on the scanned surface 16 is referred to as an “optical scanning apparatus”. I will attach it.

  FIG. 2 is a diagram for explaining in detail the configuration of the second scanning lens 15-2 in the optical scanning device, using a set coordinate system (direction). The second scanning lens 15-2 is a long lens that is long in the main scanning direction. In FIG. 2, the longitudinal direction of the second scanning lens 15-2 is the scanning direction of the laser beam deflected by the polygon mirror 14 which is an optical deflector, and this direction is the “main scanning direction”; the Y-axis direction. To do. The short direction of the second scanning lens 15-2, which is the direction corresponding to the moving direction of the photosensitive drum surface serving as the scanned surface 16, is the "sub-scanning direction"; the Z-axis direction, and the Y-axis direction and the Z-axis direction. A direction (X-axis direction) orthogonal to is referred to as an “optical axis direction”. The “optical axis direction” usually coincides with the central axis of the lens. In addition, a curve that envelops the vertex of each sub-scan section in the main scanning direction of the second scanning lens 15-2, which is a long lens, is called a “bus” of the long lens. It is considered as a parameter representative of “degree of deflection”. In other words, “bending of the long lens” refers to “bending of the bus of the long lens”.

  In recent years, plastic materials are often used for optical elements constituting the scanning optical system 15. Optical elements made of plastic materials are excellent in mass productivity, but their shape after processing due to reasons such as temperature distribution in the mold during molding and cooling after removal from the mold is not uniform. Often deviate from the ideal shape. In particular, since the second scanning lens 15-2 is arranged on the surface to be scanned 16 side, it tends to have a relatively long shape (long shape) in the main scanning direction. The amount tends to increase. Furthermore, it has an imaging performance in the sub-scanning direction and a surface tilt correction function for the polygon mirror, and the power in the sub-scanning direction is often large. The influence on the shape, so-called “scan line bending” and “scan line tilt” is also significant.

Scan line bending and scan line tilt are causes other than deformation of the bus line of the second scan lens 15-2, for example,
-Deformation and mounting errors of the folding mirror, the first scanning lens, dustproof glass, etc. provided in the optical scanning device (particularly the scanning optical system),
-The rotation axis of the polygon mirror (rotating polygonal mirror) as an optical deflector collapses,
It is known that the error occurs due to an error in the emission direction of the outgoing beam from the light source device. The “scanning line curve” caused by the shape error and assembly error of components other than the long lens may reach several hundreds of μm, but this correction is performed by adjusting the curve of the long lens. Is also possible.

  The “long optical element” described in the claims is not limited to a “plastic long lens”. For example, the “long optical element” is provided between a polygon mirror as an optical deflector and a surface to be scanned. A relatively elongated optical component such as a folding mirror provided to bend the optical path or a long mirror having an imaging function is also an object.

  Next, examples of the image forming apparatus according to the present invention will be described. FIG. 4 is a central sectional view showing an embodiment of the image forming apparatus according to the present invention. In FIG. 4, the image forming apparatus includes a photosensitive member 16 and an optical scanning device 20, and includes a charger 51, a developing device 52, a transfer device 53, a fixing device 54, and a cleaning unit 55 arranged around the photosensitive member 16. Have. The optical scanning device 20 performs optical writing by optically scanning the surface of the photoconductor 16 as an image carrier. An electrostatic latent image is formed on the photoreceptor 16 by performing an electrophotographic process. The optical scanning device 20 is responsible for an exposure process in the electrophotographic process. The principle of image formation by this image forming apparatus is well known and will be described below. The surface of the photoconductor 16 is uniformly charged by the charger 51, and the optical scanning device 20 optically scans the uniformly charged surface of the photoconductor 16 to form an image. The potential of the surface of the photoconductor 16 decreases according to the exposure distribution by optical scanning, and an electrostatic latent image is formed on the photoconductor 16. The electrostatic latent image is visualized by attaching toner supplied by the developing device 52. The toner adhering to the photoconductor 16 is transferred onto the paper by the transfer device 53 and then fused and fixed to the paper by the fixing device 54. The cleaning unit 55 removes residual toner on the photoconductor 16.

  As described above, the tandem method is often adopted in the color image forming apparatus. The 4-drum tandem system is usually used as the tandem system. Prior to the description of the 4-drum tandem system image forming apparatus, a simpler optical scanning apparatus for the 2-drum tandem system image forming apparatus will be described with reference to FIG. To do. In FIG. 3, two laser beams emitted from a light source (not shown) are deflected and reflected by a polygon mirror 14 that is an optical deflector, and pass through a common first scanning lens 15-1. Yes. The two laser beams that have passed through the first scanning lens 15-1 have their optical paths bent by different mirrors, passed through different second scanning lenses 15-2M and 15-2Y, and then photosensitive drums 16M and 16Y, respectively. To reach. In general, the first scanning lens 15-1 has a large power in the main scanning direction in order to ensure the imaging performance in the main scanning direction and the constant speed scanning performance on the surfaces of the photosensitive drums 16M and 16Y which are the scanned surfaces. There are many. In the case where the first scanning lens 15-1 is made of plastic, if a temperature distribution in the main scanning direction is generated in this lens, the constant speed scanning property on the surface to be scanned is deteriorated, and a dot position shift in the main scanning direction occurs. .

  Unlike the configuration of the embodiment shown in FIG. 3, in the configuration in which two laser beams pass through different first scanning lenses and different temperature distributions occur, the dots in the main scanning direction on each photosensitive drum Since a deviation occurs in the amount of positional deviation, when the toner on each photosensitive drum is transferred in a superimposed manner, it results in a color deviation of the output image. However, when the two laser beams pass through the common first scanning lens 15-1 as in the embodiment shown in FIG. 3, even if the temperature distribution occurs, the deviation in constant speed scanning is suppressed. Therefore, there is an advantage that it is possible to suppress the occurrence of positional deviation in the main scanning direction between the photosensitive members.

  Next, a 4-drum tandem type image forming apparatus will be described. FIG. 5 shows an example of a 4-drum tandem type image forming apparatus. The basic configuration of the optical scanning device is the same as that of the optical scanning device for the two-drum tandem image forming apparatus described above. Reference numerals 22a, 22b, 22c, and 22d denote light source units. Each light source unit includes a semiconductor laser 11 as a light source, and a coupling lens 12 that converts a laser beam emitted from the semiconductor laser into a substantially parallel light beam and couples it to a subsequent optical system. The laser beam having the substantially parallel luminous flux passes through the cylindrical lens 13 and is converged only in the sub-scanning direction, and a long line image is formed in the main scanning direction in the vicinity of the deflection reflection surface of the polygon mirror 14 as an optical deflector. It is supposed to be. Each light source unit, coupling lens, and cylindrical lens constitute four different sets of optical scanning devices, and four laser beams that are deflected and scanned are emitted.

  In the embodiment shown in FIG. 5, the four laser beams deflected and reflected by the polygon mirror 14 pass through the common first scanning lens 15-1. The four laser beams are beams emitted from different optical scanning devices. The optical scanning device having the same configuration as the optical scanning device shown in FIGS. 1 and 2 can be used. The four laser beams emitted from the first scanning lens 15-1 are reflected by mirrors through different optical paths, pass through the second scanning lens, and then reach the photosensitive drums 16K, 16C, 16M, and 16Y. The surface of each photosensitive drum is exposed by optical scanning to form an electrostatic ray image. The synchronization detection sensor 19 shown in FIG. 5 is provided in order to obtain a signal for timing to start writing to each photosensitive drum by each laser beam.

  The toner images formed on the respective photosensitive drums are transferred onto the transfer belt 31 and overlapped to form a color image. The color image on the transfer belt 31 is transferred to transfer paper and fixed on the transfer paper by a fixing device. When the toner images on the respective photosensitive drums are superimposed on the transfer belt 31, if there is a deviation in the shape of the scanning line on each photosensitive drum, the color superimposition state in the sub-scanning direction deteriorates and color misregistration occurs. As a result, the output image quality deteriorates. The present invention mainly aims to reduce such scanning line shape errors. In the example of the 4-drum tandem image forming apparatus shown in FIG. 5, “color misregistration detection toner images” 55 for detecting the color misregistration amount are formed at three locations on the transfer belt 31. The color misregistration detection toner image 55 can be detected by each “color misregistration detection sensor” 56.

  Next, an outline of a long lens made of plastic and a shape error of the long lens will be described. As described above, among the optical components constituting the scanning optical system, the “long lens” that is arranged on the scanning surface side and has a large power in the sub-scanning direction has its deflection deformation, that is, the bending of the bus line, The scanning line shape on the surface is greatly affected. FIG. 17 shows various examples of the shape of the long lens after molding, that is, various examples of deflection deformation. The upper surface of both ends in the longitudinal direction of the long lens is fixed, and is elastically held by being pressed from the lower surface side of the long lens toward the fixed portion by a spring. FIG. 17A shows the design median value, that is, the ideal shape. However, usually, the shape has one extreme value, for example, as shown in FIGS. 17B and 17C, it often has a protruding shape toward the upper side or a protruding shape toward the lower side. Although it varies depending on the conditions depending on the plastic material, the cooling conditions after taking out from the mold, the magnification of the optical system, etc., in the case of a long lens having a total length of about 200 [mm], it is empirically about several tens [μm] to A bus line bending of about several hundreds [μm] occurs. Further, an N shape having two extreme values (see FIG. 17D), a shape having three extreme values, for example, an M shape shown in FIG. 17C, and a W shape shown in FIG. It may become.

  The correction of the shape error due to the bending of the bus of the long lens will be described. As shown in FIG. 18 (a), a configuration is considered in which the upper ends of both ends of the long lens are fixed and elastically held from below by a spring or the like so as to oppose them. When the long lens bus has a shape having one extreme value (the shape shown in FIG. 18B or FIG. 18C), one or a plurality of adjustment screws, for example, near the center of the long lens. By pressing with the movable holding portion, it is possible to correct the long lens bus so as to approach a straight ideal shape. A pressing means such as a spring is also provided from below at a position facing the movable holding portion.

When the “flexural rigidity: EI” (product of Young's modulus E and cross-sectional secondary moment I) of the long lens is constant in the longitudinal direction of the long lens, a load W is applied to the center portion of the both ends supporting beam of length L. Deflection v when added is
v = (WL ³ / 48EI) {(3x / L) − (4x ³ / L ³ )}; 0 ≦ x ≦ L / 2,
x is represented by a distance from one end. That is, when an adjustment screw is provided only in the central portion in the longitudinal direction of the long lens, correction according to the above equation is possible. However, for example, more complicated shape errors as shown in FIGS. 18C to 18F cannot be removed. Therefore, it is necessary to increase the number of adjustment screws as the number of extremums of the bending of the bus line of the long lens shape increases. Generally, if the same number of adjustment screws as the expected number of extremums are provided, Good.

In addition, as described above, scanning line bending and / or scanning line inclination may occur due to the influence of not only the shape of the long lens but also the shape error and / or assembly error of other components. is there. The scanning line bending and / or inclination generated in this way can also be corrected by adjusting the deformation of the long lens. Therefore, it is desirable to provide a plurality of adjustment screws even when a long lens having a single extremum bus line is used. However, as the number of adjustment screws increases,
・ The adjustment process may become complicated and the adjustment time may increase.
In the case of a normal optical system, the number of extreme values of scanning lines on the surface to be scanned is about 3 at the maximum,
In consideration of the above, it is usually sufficient to set the adjustment screw at 3 to 4 positions.

Next, various embodiments of the holding mechanism for the long optical element will be described.
Example 1
In FIG. 6, the long lens 15-2, which is the above-described second scanning lens, is paired with three compression springs (elastic members) 61 installed on the housing bottom surface 68 serving as a reference surface, Opposed to the pressing force from the compression spring 61, the long lens 15-2 is held by three support members 63 that support it from below. There are three sets of compression springs 61 and support members 63, which are elastic members, two of which are arranged at both ends in the longitudinal direction of the long lens 15-2, and one set is arranged at the center in the longitudinal direction. Yes. In this embodiment, the support member 63 is formed by bending or cutting and raising a part of the holder member 66 processed by pressing such as a steel plate, but other materials include aluminum. A metal cut product or sintered product such as a resin mold product or the like may be employed.

  Further, as an elastic member for applying a pressing force to the long lens 15-2, a leaf spring 65 as shown in FIGS. 15A to 15D may be employed in addition to the compression spring 61 described above. Absent. In FIG. 15, the long lens 15-2 has projecting edges 15-21 and 15-22 in the vertical width direction along the longitudinal direction, and the “H” shape in which the cross-sectional shape parallel to the optical axis direction is horizontal. It has become. The leaf spring 65 shown in FIG. 15 (c) is hooked between the edge of the holder member 66 and the protruding edge 15-21 on the upper side of the long lens 15-2. It is biased in a direction to draw 15-2 toward the holder member 66 side. An adjustment screw 62 in place of the support member 63 is screwed into the holder member 66, and the tip of the adjustment screw 62 comes into contact with the upper surface of the long lens 15-2. -2 movement is restricted. The leaf spring 65 shown in FIG. 15 (d) has its bent edge at both ends hooked over the edge of the holder member 66 and the protruding edge 15-21 below the long lens 15-2. However, this is only different from the example shown in FIG. 15 (c), and it does not change that a pressing force is applied to the long lens 15-2. Thus, by adopting the leaf spring 65, compared to a configuration using the compression spring 61 as shown in FIG. 6, no wasteful space is generated, and the apparatus can be downsized.

Example 2
FIG. 7 shows a second embodiment of the holding mechanism for the long optical element. In FIG. 7, the holder member 66 is fixed on two spacing members 53 whose longitudinal ends are disposed on the housing bottom surface 68, and a plurality of adjusting screws 62 (three in this figure) are attached to the holder member 66. Are screwed together. A compression spring 61 as an elastic member is disposed on the housing bottom surface 68 so as to face each adjustment screw 62. A long lens 15-2 is disposed between each adjustment screw 62 and each compression spring 61, and the long lens 15-2 is pressed against the lower end of the adjustment screw 62 by the pressing force of the compression spring 61. The adjustment screw 62 has a function of a support member that supports the long lens 15-2. By adjusting the protruding amount of each adjustment screw 62, the "flexion degree" of the bus bar shape of the long lens 15-2 can be adjusted. It can be corrected. A total of three sets of the adjusting screw 62 and the compression spring 61 are arranged at both ends and the center in the longitudinal direction of the long lens 15-2.

  As another configuration of the adjusting screw constituting the support member, the configuration shown in FIG. 20 may be adopted. In FIG. 20, the adjusting screw 62 includes a roller 70 and a tapered adjusting screw 71. The roller 70 has a cylindrical shape, is inserted into a window hole formed in the holder member 66, and is placed on the upper surface of the long lens 15-2. The taper adjusting screw 71 is disposed so that the central axis thereof faces the longitudinal direction of the long lens 15-2 and intersects the axis of the roller 70, and the screw portion rises from the holder member 66. Screwed into the piece 73. The taper adjusting screw 71 has a taper portion 72, and a tip portion is held by a bearing piece rising from the holder member 66. The tapered portion 72 abuts on the roller 70 and restricts the upward movement of the long lens 15-2 by the urging force of the compression spring 61 so as to function as a support member for the long lens 15-2. It is configured. A total of three sets of the adjusting screw 62 and the compression spring 61 as an elastic member, which are configured as described above, are arranged at both ends and the center of the long lens 15-2 in the longitudinal direction.

  The configuration of the adjusting screw 62 shown in FIG. 20 also corresponds to “consisting at least of screw elements” recited in the claims. The long lens 15-2 can be pressed with the roller 70 by pressing the roller 70 with the tapered adjusting screw 71 in contact with the columnar or cylindrical roller 70. According to the angle of the taper provided on the tapered adjustment screw 71, it is possible to appropriately set the “adjustment sensitivity”, that is, the pressing amount of the long lens 15-2 by the roller 70 with respect to the rotation angle of the adjustment screw.

  In the case of Example 1 shown in FIG. 6, since the support member 63 cut and raised from the holder member 66 is in a state of being fixed to the holder member 66, the correction of the “degree of deflection” of the bus bar shape of the long lens 15-2 is corrected. Can't do it. Further, even when it is desired to make the long lens 15-2 straight, since the long lens 15-2 is in contact with and supported by the support member 63, the height of the three support members 63 is maintained with high accuracy. However, it is generally difficult to ensure the accuracy required for press working. Therefore, it is more desirable that at least one of the support members be movable as in the second embodiment shown in FIG.

  8 to 12 show Embodiments 3 to 7 of the holding mechanism for the long optical element. Each of Embodiments 3 to 7 shown in FIGS. 8 to 12 includes a support member 64 as an attachment portion formed to protrude upward on the housing bottom surface 68. Further, the fourth, fifth, and sixth embodiments shown in FIGS. 9, 10, and 11 are each provided with a pair of compression springs 61 as elastic members that are assembled to the holder portion 51 so as to face the support member 64. Yes. Further, in the case of the embodiment shown in FIGS. 9 and 11, a set of a compression spring 61 as an elastic member attached to the bottom surface 68 of the housing and an adjustment screw 62 as a support member screwed to the holder member 66 is provided. Two sets are added, and in the case of the fifth embodiment shown in FIG. 10, four sets of the compression spring 61 and the adjusting screw 62 are additionally provided. 8 to 10 and FIG. 12, the support member 64 is provided at the center in the longitudinal direction of the long lens 15-2. In the embodiment shown in FIG. 11, the support member 64 is the long lens 15-. 2 at one end in the longitudinal direction.

  In the case of the configuration shown in FIGS. 8 to 12, the long lens 15-2 has a contact point with the support member 64 as an attachment member as a rotation axis, as shown by an arrow 69 in the figure. The rotation can be adjusted in a rotation direction (referred to as “γ direction”) centered on a line substantially parallel to the optical axis 15-2. The “scanning line inclination” on the surface to be scanned can be corrected by the γ rotation component of the long lens 15-2.

  In the case of the embodiment shown in FIGS. 9 and 11 with two adjustment screws 62, correction of a long lens having a relatively simple shape as shown in FIGS. 17B and 17C is made close to straight. In order to correct a more complicatedly distorted shape as shown in FIGS. 17D to 17F, four (as shown in FIG. 10) ( It is necessary to add an adjustment screw 62 (or more).

  In the first and second embodiments, the fourth to sixth embodiments, and the seventh embodiment described above (see FIGS. 6, 7 and 9 to 11), the holder member 66 is located above the long lens 15-2 (sub-scanning). (The direction is the vertical direction). In the case of such a configuration, as compared with a configuration in which holder members 66 and 67 are provided on the upper side and the lower side as shown in FIG. It is possible to reduce the weight. These examples will be further described.

Example 3
FIG. 8 shows a third embodiment of the holding mechanism for the long optical element. In FIG. 8, two holder members 66 and 67 are integrally formed with the spacing member 53 at two intervals members 53 provided on both ends in the longitudinal direction of the long lens 15-2. . Three compression springs (elastic members) 61 are attached to the upper surface of the lower holder member 67, and three adjustment screws (support members) 62 are screwed into the upper holder member 66 so as to face the compression spring 61. The holding mechanism is configured. More specifically, the long lens 15-2 is held by the holding mechanism so as to be sandwiched between the three sets of the adjusting screw 62 and the compression spring 61. This holding mechanism is rotatably held on a mounting portion 64 provided on the housing bottom surface 68 (in the γ direction of the arrow in the figure). By adjusting the γ rotation of the long lens 15-2 accompanying the γ rotation of the holding mechanism, it is possible to correct the “scanning line inclination” on the surface to be scanned.

  As described above, even with the configuration shown in FIG. 8 and FIGS. 9 to 11, the scanning line inclination can be adjusted by the substantial γ rotation adjustment of the long lens 15-2. However, when the scanning line inclination is adjusted, bending of the long lens 15-2 bus line (scanning line bending) is likely to occur, and it is generally difficult to independently correct the scanning line bending and the scanning line inclination. . In that respect, according to the third embodiment shown in FIG. 8, the bending of the bus of the long lens 15-2 can be corrected in the holding mechanism, and the holding mechanism of the long lens 15-2 is adjusted by γ rotation. The scanning line inclination can be adjusted independently of the correction of the above-mentioned bend of the bus, and the adjustment process can be facilitated and the adjustment time can be shortened.

Examples 4-6
9 to 11 show Examples 4 to 6 of the holding mechanism for the long optical element, respectively. Since these embodiments have already been described, description thereof is omitted here.

Example 7
FIG. 12 shows Embodiment 7 of the long optical element holding mechanism according to the present invention. The embodiment shown in FIG. 12 is similar to the configuration of the third embodiment shown in FIG. 8, but, unlike the configuration of the third embodiment shown in FIG. 8, of the support members provided on the holder member 66, The two support members 63 are formed integrally with the holder member 66. The support member 63 can be formed, for example, by bending or cutting and raising a part of the holder member 66 made of a sheet metal part. The holding mechanism for the long lens 15-2 in this embodiment is capable of γ rotation around the mounting portion 63 provided on the bottom surface 68 of the housing while holding the long lens 15-2, thereby correcting the scanning line inclination. It can be performed. Therefore, the γ rotation adjustment (scan line inclination correction) by the adjustment screw 62 is unnecessary, and the adjustment screw 62 can provide only the function of adjusting the bus shape of the long lens 15-2 (scan line bending correction). . That is, even in the configuration of the seventh embodiment shown in FIG. 12, the scanning line bending correction and the scanning line inclination correction can be performed independently. Therefore, although the degree of freedom of adjustment is lower than that of the third embodiment shown in FIG. 8, it is possible to complete the correction of the scanning line shape with substantially the same adjustment time and adjustment accuracy.

Example 8
FIG. 13 shows an embodiment 8 of a holding mechanism for a long optical element capable of reducing the number of components for reducing the cost and reducing the size and / or weight of the apparatus. In FIG. 13, a holder member 66 is held by an appropriate rotation mechanism so as to be rotatable about an axis parallel to the optical axis of the long optical element 15-2. The long optical element 15-2 is configured such that the upper surfaces of both end portions in the longitudinal direction are attached to the holder member 66 via attachment members 63 formed integrally with the holder member 66. Between the lower surface of the long optical element 15-2 and the housing bottom surface 68, compression springs 61 as elastic members are interposed at both ends and the center in the longitudinal direction of the long optical element 15-2. An adjustment screw 62 is screwed into the holder member 66 at a position facing the compression spring 61 in the center, and the tip of the adjustment screw 62 is in contact with the upper surface of the long optical element 15-2. The long optical element 15-2 is pressed against the mounting member 63 and the adjusting screw 62 by the pressing force of each compression spring 61, so that the long optical element 15-2 is substantially attached to the holder member 66. . The tilt adjustment can be performed by rotating the holder member 66 together with the long optical element 15-2, and the bending adjustment can be performed by the adjustment screw 62 independently of this.

Example 9
FIG. 14 shows an embodiment in which the number of adjusting screws 62 is three in order to correct the scanning line shape with higher accuracy. In the example of FIG. 14A, the bent portion 63 serving as a support member is positioned on the outermost side in the longitudinal direction of the long optical element 15-2, and the three adjustment screws 62 are arranged at predetermined intervals on the inner side. However, as in the example of FIG. 14B, the bent portion 63 serving as a support member is arranged on the inner side, and the three adjusting screws 62 are arranged on the outermost sides of the long optical element 15-2 in the longitudinal direction. You may arrange | position in an outer side and a center part.

  Second Embodiment of Holding Mechanism for Long Optical Element Also in each of the following embodiments, the leaf spring 65 described with reference to FIG. 15 may be used as the elastic member in place of the compression spring 61. Such effects can be obtained.

  As shown in FIG. 16A, when the right and / or left support members 63 are processed by bending a sheet metal, the bending height of the left and right support members 63 is several hundred [μm due to processing errors. ] May occur and the long lens 15-2 may be assembled in a tilted state. Even when a machining error of this level occurs, as shown in FIG. 16B, the holding mechanism having the holder members 66 and 67 that are paired up and down is rotated by γ to cause the machining error. It is possible to eliminate the influence of a long lens mounting error.

  When the shape in the main scanning section (YZ plane) of the long lens has a relatively large curvature, it is preferable that the rotation adjustment in the sub-scanning section (XZ plane) of this lens is possible. By doing so, it is possible to correct the scanning line bending.

  Another embodiment of the long optical element holding mechanism according to the present invention will be described.

Example 10
In FIG. 19, a housing bottom surface 68 serving as a reference surface is provided with a support member 64 as an attachment portion formed so as to protrude upward. The support member 64 has a triangular shape, and the center in the longitudinal direction of the bottom surface of the long lens 15-2 serving as the second scanning lens is placed on the apex of the support member 64 corresponding to the apex of the triangle. As shown in FIG. 19 (c), the long lens 15-2 has an "H" shape in which the side cross-sectional shape is lateral, and has protruding edges at the top and bottom with a portion having a lens action interposed therebetween. . The long lens 15-2 is formed by cutting and raising or the like at both ends in the longitudinal direction of the upper metal plate 66 as a holder member by two leaf springs 65 which are elastic members provided at both ends in the longitudinal direction. The portion (support portion) 63 is pressed and fixed by the elasticity of a leaf spring 65 which will be described in detail later.

  An adjustment screw 62 that is an adjustment member is screwed into the center portion of the upper metal plate 66, and the tip of the adjustment screw 62 abuts on the upper surface of the long lens 15-2 to press the long lens 15-2. ing. Opposing to the pressing force of the adjusting screw 62, a third leaf spring 65 as an elastic member is disposed. As shown in FIG. 19 (c), the plate spring 65 is formed by being bent in a substantially “M” shape, and both ends thereof protrude from the upper surface of the upper sheet metal 66 and the upper side of the long lens 15-2. The upper sheet metal 66 and the long lens 15-2 are urged to be attracted to each other by the elasticity of the leaf spring 65. Due to this urging force, the bent portion 63 comes into contact with the upper surface of the long lens 15-2, and the upper metal plate 66 and the long lens 15-2 are substantially integrated. The long lens 15-2 can be pressed and deformed by rotating and adjusting the adjusting screw 62 and pushing or pulling it out of the upper metal plate 66, thereby removing the shape error of the long lens 15-2. be able to.

  In the leaf spring 65 shown in FIG. 19D, the bent edges of the leaf spring 65 are hooked across the edge of the upper metal plate 66 as the holder member and the lower protruding edge 15-21 of the long lens 15-2. The only difference is that it is different from the example shown in FIG. 19C, and the long lens 15-2 is applied with a pressing force against the upper metal plate 66. In the modification shown in FIG. 19 (e), two leaf springs 65 in the example shown in FIG. 19 (c) are used as a pair, and the long lenses 15-2 are arranged symmetrically when viewed from the side. . Similarly, two leaf springs 65 shown in FIG. 19D may be used as a pair and arranged symmetrically with respect to the long lens 15-2. In this way, by adopting the leaf spring 65, it is possible to reduce the size of the apparatus without generating a useless space as compared with a configuration using the compression spring 61 as in an example described later. Become.

Example 11
In order to improve the adjustment resolution when removing the shape error of the long lens 15-2, as an alternative to the adjustment screw 62 used in the above embodiment, a taper is used as in the embodiment shown in FIGS. An adjustment screw 71 having a portion 72 and an adjustment member 67 having a roller 70 can be employed. Since the embodiment shown in FIG. 20 has already been described, a detailed description thereof will be omitted.

  In the embodiment shown in FIG. 20, the adjustment sensitivity, that is, the moving distance of the roller with respect to the rotation angle of the adjusting screw 71 can be varied according to the taper angle of the tapered portion 72 of the tapered adjusting screw 71. In the illustrated embodiment, the shape of the roller 70 is a cylindrical shape, but other shapes such as a spherical shape may be used. As in the embodiment shown in FIG. 19, the long lens 15-2 is arranged on the attachment portion 64 provided on the optical housing bottom surface 68, and the apex of the attachment portion 64 is used as a rotation shaft 76, not shown. You may comprise so that rotation or inclination may be adjusted in the direction of the arrow 69 (gamma rotation direction) in FIG. 19 using an actuator means, for example, a stepping motor. By configuring the taper adjusting screw 71 in the embodiment shown in FIG. 20 to be rotationally driven by the actuator means, mechanical automatic adjustment becomes possible. The rotation axis in the γ rotation direction may be set on the bottom surface of the long lens 15-2 as in the embodiment of FIG. 19, or an attachment reference is provided on the bottom surface of the long lens 15-2. If not, the upper sheet metal 66 may be provided. However, in order to suppress the movement of the position of the optical axis 75 of the long lens 15-2, ideally, it is desirable to provide a rotation axis in the vicinity of the optical axis of the long lens 15-2.

As described in the outline of the optical scanning device, the shape error adjustment and the inclination adjustment of the long lens 15-2, in other words, the error adjustment and the inclination adjustment of the “bus” of the long lens 15-2 are performed. The scanning line shape on the surface to be scanned such as the photosensitive drum surface can be corrected.
Next, in the case where the initial shape (the shape after molding) of the long lens 15-2 is a curve having one extreme value, “curvature” due to the pressing of the adjusting screw 62 in the embodiment shown in FIG. Consider “adjustment”. Hereinafter, correcting the shape of the long lens (that is, the shape of the generatrix) by pressing the adjustment screw 62 is simply referred to as “bend adjustment”.

As shown in FIG. 23A, when the initial shape of the long lens 15-2 is “convex upward”, after the bending adjustment is completed, the long lens 15-2 is in a straight state. As shown in FIG. 12 (b), the upper sheet metal 66 becomes “convex upward” by the pressing force of the adjusting screw 62. In contrast, when the initial shape of the long lens 15-2 is “convex downward” as shown in FIG. 24 (a), the bending is adjusted as shown in FIG. 24 (b). Due to the elastic force of 65, the upper sheet metal becomes “convex downward”. Now, as shown in FIG. 21, the long lens 15-2 and the upper metal plate 66 are rotatably supported by two support portions separated by a length Li, and a load Wi is applied to the center portion. When the deflection amount is δi, the elastic coefficients Ki of the lower long lens 15-2 and the upper metal plate 66 are defined by the following equation.
Ki = (Wi × L ³ ) / (48 × δi) (Formula 1)
[However, the suffix i = 1 represents the long lens 15-2, and i = 2 represents the upper sheet metal 66]

In the case of the present embodiment, since the load W1 = W2, it can be seen from Equation 1 that the deflection amount δi is inversely proportional to the “elastic coefficient” Ki. That is, the ratio of the deflection amounts is a ratio of the reciprocal of the elastic modulus.
δ1 / δ2 = K2 / K1 (Formula 2)
In (Equation 2), δ1 corresponds to the amount of deflection of the long lens 15-2 before bending adjustment, and δ2 corresponds to the amount of deflection of the upper metal plate 66 after bending adjustment. That is, when δ2 increases, it means that the amount of deflection of the adjusted upper metal plate 66 increases. As the deflection of the adjusted upper metal plate 66 increases,
When the rotation axis for γ rotation adjustment is arranged on the upper metal plate 66, the influence of displacement of the rotation axis in the vertical direction (sub-scanning direction) cannot be ignored, and the beam spot diameter on the surface to be scanned, etc. Other optical performance may be adversely affected.
If the adjustment member 67 shown in FIG. 12 is applied to improve the adjustment resolution, the adjustment stroke may be insufficient.
There is a concern that problems such as these may occur. Therefore, it is desirable to set δ1 / δ2 to be at least 0.5 or more, and it is further desirable to set δ1 / δ2 to be 1.0 or more in order to avoid the above problem more effectively.
That is, the following expression can be derived from (Expression 2).
K2 / K1 ≧ 0.5 (Formula 3)

  As described above, the range of the elastic modulus ratio K2 / K1 is derived using the adjustment of the bending of the long lens by one adjusting screw. However, when the number of adjusting screws is plural as in the embodiment shown in FIG. The same relationship holds true for.

Example 12
FIG. 25 shows an embodiment in which three adjustment screws are provided. In the embodiment shown in FIGS. 19 and 20, the adjusting screw 62 or the adjusting member 62 as the adjusting member has one set, whereas the embodiment shown in FIG. 25 has the adjusting screw as the adjusting member. 62 and two leaf springs 65 as elastic members are added. More specifically, a set of an adjusting screw 62 (c) and a leaf spring 65 (c) is arranged at the longitudinal center of the long lens 15-2, and the adjusting screw 62 (c) at the center is arranged. Between the pair of leaf springs 65 (c) and both ends in the longitudinal direction of the long lens 15-2, the pair of adjustment screws 62 (b) and leaf springs 65 (b) and the adjustment screws 62 (d) A set of leaf springs 65 (d) is arranged. Further, leaf springs 65 (a) and 65 (e) are disposed at both ends in the longitudinal direction of the long lens 15-2. The configuration of each adjusting screw and leaf spring is the same as the configuration shown in FIG. In addition, you may arrange | position three sets or more of adjustment members 67 as shown in FIG.

  By adopting such a configuration, it is possible to adjust when the initial shape of the long lens is more complex than the configuration of the embodiment shown in FIG. In the case of Example 9 with one adjustment member, only the adjustment of the long lens with the initial shape of “one extreme value” is possible, but on the other hand, Example 12 with three adjustment members. In this case, it is possible to support a long lens having “three extreme values”.

  As in the embodiment shown in FIG. 25, the length of the long lens 15-2 (and the upper metal plate 66) is L (± L / 2), its central portion (Y = 0), and its central and peripheral portions. The adjusting screws 62 (c), (b), and (d) are respectively provided in the intermediate portion (Y = ± A). A cross-sectional shape near the center of the long lens 15-2 is shown in FIG. Now, as the initial shape of the long lens 15-2, the three shapes shown in FIGS. 26A to 26C, that is, the virtual shape when the number of extreme values is 1 to 3, respectively. To do. FIG. 31 collectively shows a graph in which the adjustment residual of the bending adjustment by the positions (± A) of the adjustment screws 62 (b) and 62 (d) is derived with respect to the initial shapes of these long lenses. Considering the change in the bent shape at the time of temperature change and the alignment accuracy between the photosensitive drums, if the allowable value of the adjustment residual is 10 [μm] or less, the positions of the adjustment screws 62 (b) and 62 (d) are Y = ± 40 to ± 90 [mm]. Assuming that the length of the long lens 15-2 of the third embodiment is L1, L1 = 220 [mm]. Therefore, when normalized by this numerical value, Y = ± 0.18L1 to ± 0.41L1. In FIG. 31, when the arrangement position of the adjusting screws 62 (b) and 62 (d) is Y = ± 30 [mm] or less, or Y = ± 100 [mm] or more, the adjustment residual is 10 [μm] or more. Since it is out of the allowable value, the corresponding items are hatched.

  The numerical range (± 0.2L1 to ± 0.4L1) was derived by modeling the long lens as a “beam” having a constant cross section shown in FIG. In the present study, the long lens shown in FIG. 28 was assumed. However, the “thickness deviation” of the long lens, that is, “thickness (optical axis direction) d0 of the central portion of the long lens” is a reference (1.0). , The rate of change of the thickness d in the longitudinal direction = d / d0 is about 0.4 to 1.2 (see FIG. 29). Even in the case of a long lens having such a degree of deviation, as shown in FIGS. 30 (a) and 30 (b), the calculation result is considered as a “beam” having a constant cross section, that is, a constant second moment, The measurement results for the long lens samples are relatively consistent, and it is clear that the above numerical range has generality for the resin-made long optical elements currently installed in the products of each manufacturer. is there.

  In general, in the case of a so-called “long optical element” made of a resin mold, ribs 15-21 and 15-22 are provided above and below the optical surface to maintain the optical surface shape created by molding. (See FIG. 22). The height of the rib in the sub-scanning direction is sufficiently smaller than the height of the optical surface 15-20 in the sub-scanning direction, and the second-order moment of the section between the optical surface 15-20 on the entrance surface side and the exit surface side. Therefore, it is sufficient to consider only the thickness deviation between the optical surfaces.

Next, the pressing force of the leaf spring will be examined. As explained in the outline of the long lens shape made of plastic lenses, as the number of adjusting screws increases,
・ The adjustment process may become complicated and the adjustment time may increase.
In the case of a normal optical system, the number of extreme values of scanning lines on the surface to be scanned should be about 3 at the maximum,
And considering the fact that the amount of bending becomes smaller as the number of extreme values of the long lens shape increases, the adjusting screw is located at one place in the center and in the middle between the center and the periphery. It is sufficient to set two places, a total of three places.

  In the adjustment residual list in the case where the adjustment screws 62 are arranged at three locations shown in FIG. 31, the adjustment screws 62 (c) and 62 (d) are arranged at Y = ± 40 [mm]. The pressing force of the adjusting screw (or leaf spring) against the long lens is the largest, and a pressing force of about 30 [N] is required. Accordingly, in order to correct the bending of the long lens of any initial shape, it is estimated that a safety factor (= 1.33) is expected and a pressing force F0 = 40 [N] of the adjusting screw is necessary.

On the other hand, as is well known from the calculation of material dynamics, when the cross-sectional secondary moment I and the Young's modulus of the material are constant, assuming that the length L and the pressing force F to the central portion, the deflection δ at the central portion is
δ = (F × L ³ ) / (48 × EI) (Formula 4)
It is represented by That is, in order to correct the initial bending that causes the same deflection δ, when the cross-sectional secondary moment I of the long lens is M times, the pressing force F is also required M times. When the length becomes N times, the pressing force F needs to be 1 / N ³ times. However, when the length becomes N times, the initial bending of the long lens 15-2 also becomes N times (because it is roughly proportional to the length). To correct this N times bending, the pressing force is N times are required. When the effects of the above three items are multiplied, the pressing force obtained by the following equation 5 is required.
M × (1 / N ³ ) × N = M × (1 / N ² ) times (Formula 5)

In the examination of FIG. 31, the length L = 220 [mm], the Young's modulus E = 2500 [MPa], and the cross-sectional secondary moment I = 2100 [mm ⁴ ] near the center portion, When the cross-sectional secondary moment is I1 [mm ⁴ ] and the length is L1 [mm], when M = I1 / 2100 and N = L1 / 220, where (Equation 5) is a coefficient, the pressing force F1 is Max,
F1, max = F0 × M × (1 / N ² )
= 40 × (I1 / 2100) × (220 / L1) ²
= 920 × (I1 / L1 ² )
If there is enough. That is, when the cross-sectional secondary moment near the center of the long lens 15-2 is I1 and the length is L1, the pressing force F1 of the elastic member (leaf spring) 65 against the long lens 15-2 is:
F1 ≦ 920 × (I1 / L1 ² ) (Formula 8)
Range.

  In the case of a plastic material generally used as a long optical element (scanning lens) for an optical scanning device, the Young's modulus E is about E = 1500 to 2500 [MPa]. This is generally true for industrially produced plastic lenses.

  Next, the arrangement of the elastic member will be examined. In the above-mentioned Example 10 and Example 11, the structure which press-fixes a long lens with the elastic member (plate spring) with which the upper sheet metal as a holder member was equipped was employ | adopted. As another configuration (comparative example), it is possible to employ a configuration in which a coil spring 65 as an elastic member is provided between the long lens 15-2 and the optical housing bottom surface 68 as shown in FIG. . In this embodiment, three coil springs 65 are used. However, in such a configuration, it is necessary to set a downward pressing force from the outside against the pressing force (upward) of the coil spring 65, which complicates the device, increases the number of parts, There is a risk of increasing the size. Therefore, it can be said that the structure shown in Example 10 and Example 11 is a more desirable structure.

  Further, as shown in FIG. 19 (d), the leaf springs 65 (a) and 65 (e) corresponding to the support portions 63 provided at both ends of the holder member 66 are provided at both ends of the long lens 15-2. Is pressed and does not interfere with the optical path of the laser beam. Therefore, the bottom of the long lens may be pressed as shown in FIG. Further, as shown in FIG. 19 (e), by providing leaf springs 65 on the entrance surface side and the exit surface side of the long lens, the in-plane view shown in FIG. It is possible to suppress the generation of the rotational moment of the long lens, and it is possible to hold it stably.

Next, the conditions of the cross-sectional secondary moment I and the length L of the long lens will be examined. As described for the pressing force of the leaf spring, the pressing force required for adjusting the bending of the long lens is proportional to the cross-sectional secondary moment I of the long lens and inversely proportional to the square of the length L. Therefore, when a coefficient: P = I / L ² is defined, and L = 220 [mm] and a sectional secondary moment I = 2100 [mm ⁴ ] is substituted, P = 2100/220 ² = 0.0434 [mm ² ]. It becomes. In addition, when the adjustment screws are provided at three locations (the number of extreme values of the initial bending of the long lens can be three), it is sufficient that the pressing force of the adjustment screw is about F0 = 40 [N] at the maximum. However, as a more general expression,
P = I / L ² ≦ 0.0434 [mm ² ] (Formula 6)
In this range, it is possible to adjust with a pressing force of 40 [N] or less.

Next, a configuration that can handle the case where the number of extreme values of the initial bending of the long lens is one, that is, a configuration that has one adjustment screw is considered. For long lenses mounted on products by manufacturers, when the number of extreme values is 3, the bending width (PV) is about 40 [μm] at maximum, whereas extreme values When the number is one, the width of the bend is often about 100 [μm] at the maximum (that is, 100/40 = 2.5 times). Further, when the number of extreme values is one, the substantial length of the portion to be bent is tripled compared to the case of three extreme values. The following equation is obtained by multiplying the right side of (Equation 6) by a coefficient [2.5 × (1/3 ² ) = 0.277] obtained by multiplying these effects.
P = I / L ² ≦ 0.012 [mm ² ] (Formula 7)
This equation shows the condition of the secondary moment of inertia and the length of the long lens that can be adjusted with a pressing force of 40 [N] or less in a configuration with one adjusting screw.

  Next, an example of an optical scanning device provided with the long optical element holding mechanism described above will be described. In the optical scanning device equipped with the long optical element holding mechanism described above, the shape of the scanning line on the surface to be scanned can be made highly accurate. There is a possibility that the shape of the long optical element by the holding mechanism may change due to the influence of the passage of time or the change in environmental temperature and humidity. In such a case, a separate detection means for detecting the change in the shape is provided, and the protrusion amount of the support member made of, for example, an adjusting screw and the γ rotation angle of the holding mechanism are variable based on the detection result by the detection means. do it. For adjusting the γ rotation angle of the adjusting screw and holding mechanism, for example, an actuator such as a stepping motor that can be driven by a pulse signal is used to downsize the holding mechanism for the long optical element and the optical scanning device using the same. In addition, the cost can be reduced.

  Further, by detecting the shape of the scanning line, it is possible to predict the shape change of the long optical element. Therefore, instead of the shape of the long optical element, the scanning line shape on the surface to be scanned or a surface optically equivalent thereto may be detected. As this means, for example, a color misregistration detection toner image 55 shown in FIG. 5 may be formed, and a detection sensor 56 for detecting this toner image may be used.

Reconsidering the correction of the long lens bending due to the load. Now, as shown in FIG. 35A, consider a configuration in which both ends of a straight long lens 15-2 are simply supported (rotated). FIG. 35B shows the shape of the long lens when a load W is applied to the position L1 (y = L1) from the left end of the long lens 15-2. In the region from the left end of the long lens to the load position (0 ≦ y ≦ L1), the shape of the long lens (deflection curve: Vz) is expressed by the following equation.
Where I: sectional moment of inertia
E: Young's modulus
L: Length of the long lens 15-2 Vz = (WL1 ³ L2 ³ / 6EIL)
X {2 (L-y) / L2 + (L-y) / L1- (L-y) ³ / L1L2 ² }
... (Formula 11)
When a load W is applied to the central portion (y = L1 = L / 2) of the long lens 15-2, the region from the left end to the central portion of the long lens 15-2 (0 ≦ y ≦ In (L / 2), the long lens shape (deflection curve: Vz) is expressed by the following equation.
Vz = (WL ³ / 48EI) × {(3y / L) − (4y ³ / L ³ )} (Expression 12)
In the region from the center of the long lens to the right end (L / 2 ≦ y ≦ L), the above formula is symmetrical to the above equation with respect to y = L / 2.

Next, the bending correction of the long lens 15-2 when a bending moment is applied from the outside will be examined. FIG. 35 (c) shows the shape of the long lens when bending moments M1 and M2 are applied to the left and right ends of the long lens 15-2, respectively. In the region from the left end to the right end portion of the long lens 15-2 (0 ≦ y ≦ L), the long lens shape (deflection curve: Vz) is expressed by the following equation.
Vz = (y / 6EIL) ×
{(M1-M2) y ² −3M1 · L · y + (2M1 + M2) L ² } (Formula 21)
In the case of M1 = M2 = M, it can be transformed as the following equation.
Vz = (M / 2EI) × y (L−y) (Equation 22)

  The result of the bending correction of the long lens 15-2 by the action of the external force is as follows. The shape when the load W is applied to the central portion of the long lens (long lens having an initial curve) 15-2 before the curve shape adjustment is “initial shape of the long lens” and “(formula 11 ) Or (Formula 12) (Cubic polynomial) ”. Similarly, when the bending moments M1 and M2 are applied to the left and right ends of the long lens 15-2 before the bent shape adjustment, “the initial shape of the long lens” and “(Formula 21) or (Formula 22)”. The shape (second-order polynomial) ”is superimposed.

An example is shown in FIG. As shown in FIGS. 34 (a) and 34 (b), a resin long lens model (Young's modulus E) having a cross-sectional secondary moment I = 2123 [mm ⁴ ] and a total length L = 220 [mm] in a cross section orthogonal to the longitudinal direction. = 2500 [MPa]) both ends are supported by rotation, and a case where a load W = 5.0 [N] is applied to the central portion is examined. The initial shape (the shape before correction) of the long lens represented by a thin solid line in FIG. 34 (c) has a shape of “convex upward” (number of extreme values: 1) having a width (PV) of 190 μm. Yes. When a load (external force) W is applied to the center of the long lens, an M-shaped curve (PV 40 μm, number of extreme values 3) represented by a thick solid line in FIG. 34C is obtained. The broken line in FIG. 34 (c) is a deflection curve when the load W is applied to the central portion of the virtual straight long lens, and is corrected when the load is applied to the arbitrarily shaped long lens. Curve, in other words, the amount of correction due to the action of external force. That is, the above-mentioned M-shaped curve can be derived by superimposing the initial shape of the long lens and the correction curve. This correction curve is a cubic curve as is clear from (Equation 12).

  In the process of adjusting the shape of the long lens, it may be divided into coarse adjustment and fine adjustment. As described above, by applying one external force (load, bending moment, etc.) to the long lens 15-2, as a “rough adjustment”, a “large bending component” is obtained from the long lens before shape adjustment. Can be removed. In the subsequent adjustment step, as the “fine adjustment”, the above-described “shape of the long lens after removing a large bending component” may be corrected. When performing this fine adjustment, in addition to the external force used for the coarse adjustment, another external force can be used. Therefore, in general, the adjustment accuracy (adjustment residual amount) after the end of the shape adjustment (at the end of the fine adjustment) is not the width (PV) in the initial shape (the shape before the coarse adjustment), but the shape at the end of the coarse adjustment ( In particular, it depends on the number of extreme values. If the shape has an extreme value of 3 or less, as will be described later, it is possible to make an adjustment that does not complicate the adjustment work and can achieve high-precision adjustment accuracy.

  As described above, by applying an external force in the temporary assembly stage (stage before starting the adjustment operation) of the “bending adjustment process of the long lens 15-2”, the long lens 15-2 before adjustment is applied. It is possible to remove the “large bent shape” component of the. By removing a large bending component in the initial stage of bending adjustment, the bending state (trend) of the long lens 15-2 can be grasped, and the adjustment work after the next process can be efficiently performed. It becomes possible. After the molding conditions are stable and the individual differences in the initial shape have become small, or after the initial shape can be predicted with high accuracy, it is possible to set the initial shape, that is, the number of extreme values and the external force suitable for the position. Is possible. The external force adapted to the initial shape means the number of adjustment points by the external force and the position where the external force is applied.

  In the process from trial production to mass production of long lenses, the long lens molding conditions (eg, molding temperature, molding pressure, cooling time, etc.) are optimized. In many cases, priority is given to reducing the variation (individual difference) between samples rather than reducing the size of the bend (PV). Therefore, as described above, it is often possible to remove a large bending component of the long lens at the set value in the temporary assembly stage.

  On the other hand, if the molding conditions such as immediately after changing the molding conditions by changing the molding material or correcting the mold are not sufficiently stable, it is not the set value in the temporary assembly stage, but the first stage of the adjustment process, In the first adjustment work after the start of the adjustment work, it is only necessary to remove a large bending component by applying an external force and grasp the bending state (trend). Further, when the initial bending of the long lens occurs, it often occurs symmetrically with respect to the central portion of the long lens. Therefore, it is desirable to apply the external force to the long lens symmetrically.

  Next, the long lens shape and fine adjustment after removing a large bending component (that is, a second-order polynomial or a third-order polynomial) by the above-described external force (load or bending moment) will be examined. Naturally, it is desirable to have a large number of adjustment points (the number of external forces acting on the long lens) in order to realize a highly accurate adjustment of the long lens, but the adjustment process increases as the number of adjustment points increases. Complicated / lengthened, resulting in increased adjustment costs. If the number of adjustment points is 3 (or less), even if each adjustment point does not operate independently (if one external force is applied, it affects other adjustment points) It is possible to complete the adjustment work relatively easily. If the number of adjustment points is 3, it is possible to relatively easily adjust the shape of the curved long lens having three extreme values with high accuracy, as will be described later. If there are four or more adjustment points and each adjustment point does not operate independently, the adjustment work becomes complicated, and it is difficult to complete high-precision adjustment in a short time.

Next, another embodiment of the long lens shape adjusting mechanism incorporating the above-described concept will be described.
Example 13
In FIG. 37, the long lens 15-2 is formed by bending portions (supporting portions) formed on both end sides of the upper metal plate 66 by two elastic members (compression springs) 61a and 61e provided below both end portions. It is fixed to 63 by pressing. Three adjustment members (adjustment screws) 62b, 62c, and 62d are screwed into the center portion and the middle portion of the upper metal plate 66, and three adjustment members 62b to 62d can be opposed to the pressing force. Compression springs 61b, 61c, 61d are arranged. By pushing or pulling out these adjusting screws 62, the long lens 15-2 can be pressed and deformed. The above-described shape adjusting mechanism is provided on the attachment portion 64 provided on the bottom surface of the optical housing, and the actuator means (for example, a stepping motor) (not shown) is used with the apex of the attachment portion 64 as the rotation axis. It is possible to adjust the rotation (tilt) in the direction of the arrow in the middle (γ rotation direction).

More specifically, in the optical scanning device having the long lens 15-2, the surface to be scanned ( For example, it is possible to correct the scanning line shape (“scanning line bending” and “scanning line inclination”) on the photosensitive drum surface.
In order to improve the adjustment resolution, as an alternative to the adjustment screw 62, an adjustment member composed of an “adjustment screw having a tapered portion” 71 and a “roller (cylindrical shape)” 70 as described with reference to FIGS. 71 can be employed.

Next, an adjustment error when the shape adjustment mechanism shown in FIG. 37 is applied to the long lens model schematically shown in FIG. Both ends of the long lens 15-2 having a length L = ± 110 [mm] from the lengthwise ends to the center and a total length of 220 [mm] are simply supported (rotated), and the three loads W1 to W3 are
W1 → Y = −75 [mm] (Adjustment screw 62b)
W2 → Y = 0 [mm] (Adjustment screw 62c)
W3 → Y = + 75 [mm] (Adjustment screw 62d)
To act as. The cross-sectional secondary moment I and the Young's modulus E of the material are I = 2123 [mm ⁴ ] and E = 2500 [MPa].

  Now, as the initial shape of the long lens 15-2, there are three virtual shapes (the number of extreme values is 1 to 3 and PV is 100 μm, respectively) shown by broken lines in FIGS. 36 (a) to 36 (c). Assume. The results of deriving the adjustment residual when these long lenses having the initial shape are bent and adjusted by the above W1 to W3 are shown by solid lines in FIGS. The adjustment residual is preferably about 10 [μm] or less in consideration of the change in the bent shape at the time of temperature change and the alignment accuracy between the photosensitive drums, but within the scope of this study, it is 7 [μm] or less. Was achievable. Table 2 shows the results.

Table 2

  In Table 2, “before adjustment” indicated by (* 1) means that a large bending (second order polynomial or third order polynomial) component is caused by applying an external force to the long lens in the temporary assembly stage or the first stage of the adjustment process. It means a long lens shape in a removed state (after coarse adjustment), that is, “before fine adjustment”. Moreover, the positive sign of the part shown by (* 2) has shown that it is a downward pressing force, and the negative sign has shown that it is an upward pressing force.

  In this example, at the first stage of the adjustment process (the first adjustment work after the start of the adjustment work), a large bending component (third-order polynomial) is caused by the pressing (load W2) of the adjustment screw 62c at the center of the long lens. It is assumed that a virtual shape indicated by a broken line in FIGS. 36A to 36C is obtained by removing.

As shown in Table 2, when the number of extreme values is 3 or less, each pressing force is 40 [N] or less (more precisely, 33.2 [N] or less), and high-precision adjustment can be realized. it can. When the pressing force exceeds 40 [N], an elastic member (coil spring, leaf spring, etc.) that generates the pressing force is increased in size, and each component constituting the adjusting mechanism needs to be highly rigid. In many cases, restrictions on the layout of the mechanism (which makes it difficult to reduce the size and weight) occur, and the cost of the parts increases.
On the other hand, if a long lens having a shape error (bending shape width: PV) of a long lens shape before fine adjustment is 100 [μm] or less, an external force (pressing force) required for adjustment is 40 [N The adjustment mechanism can be made smaller / lighter and the cost can be reduced.

Example 14
FIG. 39 shows Embodiment 14 of the long lens shape adjusting mechanism. FIG. 39A shows an outline of the components of the fourteenth embodiment. “Upper sheet metal 66” and “lower sheet metal 67”, which are longer than the long lens 15-2, are disposed on the upper and lower sides of the long lens 15-2. On both the left and right sides of the long lens 15-2, a spacing member 68 made up of a block for holding the spacing between the upper sheet metal 66 and the lower sheet metal 67 is disposed. The height of the spacing member 68 in the vertical direction is set slightly lower than the height of the long lens 15-2 (for example, about several tens μm to several hundreds μm). Three adjustment members (adjustment screws) 62b, 62c, and 62d are screwed into the upper metal plate 66. In the gap between the lower metal plate 67 and the long lens 15-2, two spacer members 69b and 69d are provided immediately below the two adjustment screws 62b and 62d, respectively. The height of the spacer members 69b and 69d is about several tens of μm to several hundreds of μm depending on the specifications of other components, for example, the thickness and width of the upper and lower sheet metals 66 and 67, the height of the spacing member 68, and the like. Should be set.

  The upper metal plate 66 is provided with a plate spring 65 as an elastic member. The pressing force (elastic force) acting on the long lens 15-2 of the leaf spring 65 is opposed to the pressing force by the remaining one of the adjusting screws (62c), and regardless of the amount of pressing of the adjusting screw 62c. A pressing force that is always upward (toward the upper metal plate 66) is applied to the long lens 15-2.

  After arranging the respective components in this manner, the upper sheet metal 66 and the lower sheet metal 67 are fastened to the two spacing members 68 by the four fastening screws 70 a to 70 d. The state at this time is shown in FIG. As shown in FIG. 39B, the long lens 15-2 is sandwiched between upper and lower ends (indicated by symbols D, E, F, and G) by an upper sheet metal 66 and a lower sheet metal 67, and this embodiment is applied. It is held (fixed) inside the long lens shape adjusting mechanism. Since the height of the spacing member 68 is set to be lower than that of the long lens 15-2, and the spacer member 69 is inserted between the long lens 15-2 and the lower metal plate 67, this state. Then, the long lens 15-2 and the upper metal plate 66 have a “convex upward” shape, and the lower metal plate 67 has a “convex downward” shape. At this time, the upper sheet metal 66 and the lower sheet metal 67 function as elastic bodies. In particular, the lower sheet metal 67 has a function of elastically pressing the lower surface of the long lens 15-2 via the two spacer members 69. Plays. This stage of shape adjustment is called a “temporary assembly stage”.

  As the next step of the temporary assembly stage shown in FIG. 39 (b), the shape of the long lens 15-2 may be corrected while appropriately adjusting the pushing amount or the drawing amount of the adjusting screws 62b, 62c, 62d. At this time, the shape of the long lens 15-2 may be directly monitored, or may be corrected by using a result of monitoring “bending of scanning line” on the surface to be scanned according to the purpose. As described above, since the leaf spring 65 is disposed opposite to the adjustment screw 62c provided in the center portion, the adjustment screw 62c is always in a state of pressing the long lens 15-2. Can do. On the other hand, with respect to the adjusting screws 62b and 62d provided in the intermediate portion, the long lens 15-2 is always pressed by the action of the pressing force of the spacer member 69 by the elastic force of the lower metal plate 67 which is an elastic body. It can be.

  As described above, the long lens 15-2 is elastically pressed and fixed at five locations (AJ, BH, CI, DF, and EG) from the vertical direction. Even if a change with time or a change in environmental temperature occurs, it is possible to suppress fluctuations in the adjustment value of the shape. FIG. 39 (c) shows a state in which the bending adjustment is completed. In this figure, the long lens 15-2 has a straight shape. By pushing the three adjusting screws 62b, 62c, 62d to the vicinity of the straight line connecting the symbols D and E at both ends in the length direction of the long lens 15-2 (that is, arranging the symbols A to E on a straight line) The long lens 15-2 having a “convex upward” shape can be adjusted to a substantially straight state at the assembly stage. Of course, in order to create a desired (arbitrary) long lens shape (resulting in a scanning line shape), the push-in amounts of the three adjusting screws may be appropriately adjusted.

By adopting the configuration of the fourteenth embodiment, compared to the adjustment mechanism according to the thirteenth embodiment, it is not necessary to provide an elastic member (such as a compression spring) on the lower side of the long lens. And cost reduction can be realized.
On the other hand, as an alternative to the leaf spring 65 corresponding to the adjustment screw 62c at the center, a third spacer member 69c is inserted between the long lens 15-2 and the lower metal plate 67 as shown in FIG. Configuration is also conceivable. However, in such a configuration, the lower sheet metal 67 has a downwardly convex shape, and therefore, as shown in FIG. 40B, the spacer member 69c corresponding to the adjustment screw 62c in the center is connected to the long lens 15-2. There is a possibility that it does not contact and may not function as a pressing means, which is not a desirable configuration.

  As an alternative to the spacer member 69c in the example shown in FIG. 40, as shown in FIG. 41 (a), an elasticity that generates an elastic force opposing the adjustment screw 62c between the long lens 15-2 and the lower sheet metal 67 is provided. If the member 61c (plate spring, coil spring, etc.) is arranged, as shown in FIG. 41 (b), it is possible to always apply a pressing force to the long lens 15-2, which is a desirable configuration.

  The long optical element holding mechanism and the long optical element shape adjusting method according to each of the embodiments described above can be mounted on, for example, the optical scanning apparatus as shown in FIG. In this optical scanning device, it is possible to increase the accuracy of the shape of the scanning line on the surface to be scanned.

  The shape of the long optical element by the holding mechanism may change due to the influence of the passage of time and / or environmental temperature and humidity. In such a case, a detection means for detecting the change in the shape is separately provided, and the amount of protrusion of the support member (adjustment screw) and the γ rotation angle of the holding mechanism are determined based on the detection result by the detection means. It may be variable. For adjustment using the adjustment screw and adjustment of the γ rotation angle of the holding mechanism, an actuator such as a stepping motor that can be driven by a pulse signal, for example, can be used as the drive source, thereby reducing the size and cost. Become.

  Further, by detecting the shape of the scanning line, it is possible to predict the shape change of the long optical element. Therefore, instead of the shape of the long optical element, the scanning line shape on the surface to be scanned or a surface optically equivalent thereto may be detected. The scanning line shape detection means may be selected and used as an arbitrary detection sensor, and thus detailed description thereof is omitted.

  The optical scanning device may be applied to an image forming apparatus to which an electrophotographic process is applied and a 4-drum tandem image forming apparatus. These image forming apparatuses are as described above. In the case of an image forming apparatus such as a four-drum tandem type image forming apparatus that obtains a color image by superimposing images formed by different photosensitive drums, If there is a deviation in the scanning line shape, a sub-scanning dot position shift occurs, resulting in deterioration of the quality of the output image such as a color shift of the output image. Assembling and adjusting in the factory, the image forming apparatus after shipment from the factory or when installed at the user's site, vibrations and fluctuations over time, or temperature rise due to continuous print output during use at the user's site, etc. Often causes.

  When the optical scanning apparatus according to the present invention is used as an apparatus for executing an exposure process of an image forming apparatus that outputs an image by executing an electrophotographic process, the deviation of the scanning line shape between the photosensitive drums is suppressed. Therefore, it is possible to obtain a high-quality output image (with little color misregistration).

  Further, as in the four-drum tandem type image forming apparatus shown in FIG. 6, a color misregistration detection toner image 55 for detecting color misregistration between the photosensitive drums is formed on the transfer belt 31, and this color misregistration detection is performed. The sensor 56 may be configured to detect. By setting it as such a structure, it is possible to derive | lead-out the shape of a long lens (for example, 2nd scanning lens), and it can adjust based on this. Since the detection means is provided on the transfer belt 31 that is closer to the output image that is the final output, rather than bending or tilting of the long lens itself or scanning line bending, it becomes possible to perform feedback adjustment with higher accuracy, A higher quality image can be formed.

It is a perspective view which shows the Example of the optical scanning device concerning this invention. It is a perspective view which shows the elongate optical element in an optical scanning device same as the above. It is a front view which shows another Example of the optical scanning device concerning this invention. 1 is a front view showing an embodiment of an image forming apparatus according to the present invention. It is a perspective view which shows another Example of the image forming apparatus concerning this invention. It is a front view which shows Example 1 of the holding mechanism of the elongate optical element concerning this invention. It is a front view which shows Example 2 of the holding mechanism of the long optical element concerning this invention. It is a front view which shows Example 3 of the holding mechanism of the long optical element concerning this invention. It is a front view which shows Example 4 of the holding mechanism of the elongate optical element concerning this invention. It is a front view which shows Example 5 of the holding mechanism of the elongate optical element concerning this invention. It is a front view which shows Example 6 of the holding mechanism of the elongate optical element concerning this invention. It is a front view which shows Example 7 of the holding mechanism of the long optical element concerning this invention. It is a front view which shows Example 8 of the holding mechanism of the long optical element concerning this invention. 9 shows an embodiment 9 of a holding mechanism for a long optical element according to the present invention, and (a) and (b) are front views of parts different from each other in configuration. FIG. 6 shows still another embodiment of the holding mechanism for the long optical element according to the present invention, in which (a) is a plan view, (b) is a front view, (c) is a side view, and (d) is a modified example. It is a side view. (A) in the holding mechanism of the long optical element concerning Example 9 is a front view which shows the mode of inclination of a long optical element, (b) is a mode which adjusts the inclination of a long optical element. It is a front view which shows the various modifications of a long optical element. It is a front view which shows the various modifications of a long optical element, and the various shape correction example with respect to it. (A) which shows Example 10 of the holding mechanism of the long optical element concerning this invention is a top view, (b) is a front view, (c) is a side view, (d) is an example of the said holding mechanism as a leaf | plate spring. The side view shown with (e) The side view which shows the said holding mechanism with another example of a leaf | plate spring. It is a front view which shows Example 11 of the holding mechanism of the long optical element concerning this invention. It is a front view for demonstrating the definition of the elastic coefficient of a long optical element. (A) which shows the example of the external appearance of the elongate optical element used for this invention is a front view, (b) is a side view. It is a front view which shows the example before the shape adjustment of a long optical element, and after an adjustment. It is a front view which shows another example before and after the shape adjustment of a long optical element. (A) which shows Example 12 of the holding mechanism of the elongate optical element concerning this invention is a top view, (b) is a front view, (c) is a side view. It is a graph which shows the various modifications of a long optical element with a virtual shape. It is side surface sectional drawing which shows the example of the cross-sectional shape of a long optical element. It is a graph which shows the example of the surface shape of a long optical element. It is a graph which shows the example of the thickness of a long optical element. (A) is a model figure and (b) is a graph which shows a displacement at the time of applying a load by supporting both ends of a long optical element rotatably. It is a graph which shows the measurement result of the amount of adjustment residuals with respect to various examples of arrangement of an adjustment screw. It is a front view which shows the comparative example with respect to the holding mechanism of the elongate optical element concerning this invention. It is a front view which shows Example 13 of the holding mechanism of the long optical element concerning this invention. It shows a state of bending correction of a long optical element by the action of an external force, (a) is a side view showing a cross-sectional secondary moment, (b) is a front view showing a state of applying a weight, and (c) is an external force. It is a graph which shows the elongate optical element shape when there is no effect | action, the correction amount by the effect | action of an external force, and the elongate optical element shape when an effect | action of an external force exists. This figure shows the deformation of a long optical element due to the action of external force. (A) Before applying external force, (b) When applying external force, (c) Applying bending moment to both ends FIG. It is a graph which shows virtually the example of various modifications of a long optical element, and the example of adjustment residual. It is a front view which shows Example 14 of the holding mechanism of the long optical element concerning this invention. It is a front view which shows the numerical example of the shape adjustment mechanism of the elongate optical element concerning this invention. It is a front view which shows another example before the shape adjustment of a long optical element, and after an adjustment. It is a front view which shows another example before the shape adjustment of a long optical element, and after an adjustment. It is a front view which shows another example before the shape adjustment of a long optical element, and after an adjustment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Light source 12 Coupling lens 13 Cylindrical lens 14 Polygon mirror as an optical deflector 15 Scanning optical system 15-2 Long optical element 16 Photoconductor 20 Optical scanning device 61 Elastic member 62 Adjustment screw 63 Support member 65 Plate as elastic member Spring 66 Holder member 67 Holder member

Claims (32)

An elastic member that presses the long optical element with an elastic force in a direction orthogonal to the optical axis direction and orthogonal to the longitudinal direction, and is paired with the elastic member to face the pressing force from the elastic member. A long optical element holding mechanism comprising a support member for supporting the long optical element,
A holding mechanism for a long optical element, wherein three or more sets of the elastic member and the support member are provided. The long optical element holding mechanism according to claim 1, wherein two sets of the elastic member and the support member are arranged at both ends in the longitudinal direction of the long optical element. 2. The long optical element holding mechanism according to claim 1, wherein at least one of the support members is held by another holder member and is movable in the direction of the pressing force. The holding mechanism for a long optical element according to claim 3, further comprising an adjusting mechanism capable of adjusting an amount of movement of the support member, wherein the adjusting mechanism includes at least a screw element. The long optical element holding mechanism according to claim 1, wherein the long optical element is held so as to be rotatable about a rotation axis substantially parallel to the optical axis. 6. The long optical element holding mechanism according to claim 5, wherein two of the support members are fixed to the holder member or formed integrally with the holder member. The long optical element holding mechanism according to claim 1, wherein the long optical element is held so as to be rotatable about a rotation axis substantially parallel to the longitudinal direction thereof. 2. The length according to claim 1, wherein all of the supporting members are held by another holder member, and the holder member is provided only on one of the upper side and the lower side with respect to the long optical element. A holding mechanism for the optical element. A long optical element;
A holding member that is disposed on at least one of the upper side or the lower side of the long optical element and has two support portions that support the long optical element by a distance L;
An adjusting member provided in the holding member, for pressing and deforming the long optical element;
In order to press and fix the long optical element to the holding member, an elastic member disposed to face the adjusting member, and a holding mechanism for the long optical element,
When both ends of the long optical element (subscript i = 1) and the holding member (subscript i = 2) are rotatably supported by two support portions separated by a distance L, and a load Wi is applied to the center portion And the elastic modulus Ki is
Ki = (Wi × L ³ ) / (48 × δi)
Stipulated in
When the elastic coefficients of the long optical element and the holding member are K1 and K2, respectively.
K2 / K1 ≧ 0.5
A holding mechanism for a long optical element. 10. The long optical element holding mechanism according to claim 9, wherein the two support portions arranged on the holding member support both end portions of the long optical element, and the adjusting member is 3 in the longitudinal direction. And a pair of adjustment members that press at least the central portion of the long optical element and a pair that presses the positions of ± 0.2L1 to ± 0.4L1 in the left-right direction from the central portion of the long optical element. A holding mechanism for a long optical element, comprising an adjustment member. When the cross-sectional secondary moment of the cross section orthogonal to the longitudinal direction at the center of the long optical element is I1, and the length is L1, the pressing force F1 of the long optical element by the elastic member is:
F1 ≦ 920 × (I1 / L1 ² ) [N]
The holding mechanism for a long optical element according to claim 9. The long optical element holding mechanism according to claim 9, wherein the elastic member is disposed on the holding member. The long optical element holding mechanism according to claim 9, wherein the holding mechanism is rotatably held around a rotation axis substantially parallel to the optical axis of the long optical element. Both end portions of the long optical element are supported by two support portions arranged on the holding member, and an adjustment portion that presses the long optical element is provided at least in the central portion. The long optical element is made of resin. Yes, when the sectional moment at the center is I1 [mm ⁴ ] and the length is L1 [mm]
I1 / L1 ² ≦ 0.0434 [mm ² ]
The long optical element holding mechanism according to claim 9, wherein: 11. The holding mechanism for a long optical element according to claim 10, wherein the long optical element is made of resin, the cross-sectional secondary moment of the cross section perpendicular to the longitudinal direction at the center is I1 [mm ⁴ ], and the length is When L1 [mm]
I1 / L1 ² ≦ 0.012 [mm ² ]
A holding mechanism for a long optical element. An optical scanning device having an optical deflector for deflecting and reflecting a light beam emitted from a light source and an imaging optical system comprising at least one optical element for converging the deflected and reflected light beam as a beam spot on a surface to be scanned Because
The at least one optical element is a long optical element, and the long optical element is held by the long optical element holding mechanism according to claim 1. Scanning device. It has a detecting means for detecting the deflection amount of the long optical element, and based on the detection result by the detecting means, the moving amount of the support member that supports the long optical element can be adjusted. The optical scanning device according to claim 16. 18. The optical scanning device according to claim 17, wherein the detecting means is a detecting means for detecting a scan line bending of the surface to be scanned. An image forming apparatus for forming an image by executing an electrophotographic process, wherein the optical scanning device according to any one of claims 16 to 18 is mounted as an apparatus for performing an exposure process of an electrophotographic process. An image forming apparatus. An image forming apparatus for forming an image by executing an electrophotographic process, wherein the optical scanning apparatus according to any one of claims 16 to 18 is mounted as an apparatus for performing an exposure process of an electrophotographic process, and is long. An image forming apparatus, characterized in that the means for detecting the amount of deformation of the optical element detects from the toner image formed on the transfer belt. Using the holding mechanism for a long optical element according to any one of claims 1 to 14, the deflection deformation of the long optical element is adjusted by adjusting the position of the support member that forms a pair with the elastic member. A method for adjusting the shape of a long optical element. A long optical element holding mechanism according to any one of claims 9 to 15, wherein the bending deformation of the long optical element is adjusted by adjusting with the adjusting member. Shape adjustment method. In the method of adjusting the shape of the long optical element by applying an external force to the long optical element, the shape of the long optical element after deformation by applying the external force to one place is the number of extreme values. A shape adjusting method for a long optical element, wherein the shape is 3 or less. 24. The shape adjusting method for a long optical element according to claim 23, wherein the external force acts so as to be symmetric in the longitudinal direction of the long optical element. 24. The shape adjusting method for a long optical element according to claim 23, wherein the external force is applied at a temporary assembly stage in the adjusting step. 24. The shape adjusting method for a long optical element according to claim 23, wherein, among the external forces acting on the long optical element, the number of adjustment points where an adjustable external force is applied is 3 or less. A method for adjusting the shape of the optical element. 26. The shape adjusting method for a long optical element according to claim 25, wherein an opposing elastic force is applied to each of the adjustable external forces applied to the long optical element. Shape adjustment method. 24. The shape adjusting method for a long optical element according to claim 23, wherein the long optical element has a shape error of 0.1 [mm] or less when the number of extreme values is 3 or less due to an external force. A method for adjusting the shape of a long optical element, characterized in that it is used. A shape adjusting mechanism for a long optical element, wherein the shape adjusting method for a long optical element according to any one of claims 23 to 28 is applied. A shape adjusting mechanism for a long optical element to which the shape adjusting method for a long optical element according to claim 27 can be applied,
A plate-like first elastic member and a second elastic member which are longer than the long optical element and are disposed on both sides in the short direction of the long optical element, and sandwich the long optical element;
In order to press-deform the long optical element, one of the first and second elastic members, three press adjusting members arranged in the longitudinal direction;
Two supporting members arranged between the other of the first and second elastic members and the long optical element, facing two of the three pressing adjustment members,
A third elastic member that is disposed on the first and second elastic members and applies an elastic force that opposes the pressing force by the remaining one of the pressing adjusting members to the long optical element. A shape adjusting mechanism for a long optical element. 31. An optical scanning device comprising the long optical element shape adjusting mechanism according to claim 29, wherein the shape of the long optical element can be adjusted in a state where the long optical element is mounted on the optical scanning device. An optical scanning device characterized by that. An image forming apparatus for forming an image by executing an electrophotographic process, wherein the optical scanning apparatus according to claim 31 is used as an apparatus for performing an exposure process of an electrophotographic process. .

Images