JP7328005B2 - Optical scanning device and image forming device - Google Patents

Description

The present invention relates to an optical scanning device and an image forming apparatus, and more particularly to an image forming apparatus such as a copier, printer, facsimile machine and the like.

2. Description of the Related Art Conventionally, optical scanners have been used in laser beam printers (hereinafter referred to as printers), digital copiers, and the like. In an optical scanning device, a light beam emitted from a light source after being light-modulated according to an image signal is deflected by a rotating polygonal mirror or the like. The deflected light flux is converged into a spot on the surface of the photoreceptor (surface to be scanned) by an imaging optical system (scanning optical system) having an fθ characteristic, and the surface of the photoreceptor is scanned to record an image. 2. Description of the Related Art In recent years, along with the miniaturization of printers, there is a demand for miniaturization of optical scanning devices used in printers. In particular, since the height direction of the optical scanning device is directly related to the height of the printer, there is a high demand for thinning the optical scanning device.

Further, in color printers, an optical scanning device in which a plurality of scanning optical systems are arranged facing each other with one optical deflector interposed therebetween is widely used. When optical scanning of multiple colors is performed by a single optical deflector, for example, in Patent Document 1, in order to reduce the thickness of a rotating polygon mirror, a light beam is incident obliquely on one deflecting surface within the sub-scanning cross section. (hereinafter referred to as oblique incidence). Making the light beam obliquely incident on the deflecting surface facilitates separation of the light beam after deflection. In addition, the optical path length of the scanning optical system that scans the surface to be scanned that is farthest from the optical deflector and the optical path length of the scanning optical system that scans the surface to be scanned that is closest to the optical deflector is basically the same. generally the same length. Therefore, in a scanning optical system that scans a surface to be scanned near an optical deflector, a plurality of folding mirrors are used to route the optical path. Arranging the optical path complicates the entire optical scanning device, making it difficult to satisfy the demand for thinning the optical scanning device. As a solution to this problem, for example, as shown in FIG. 7 of Patent Document 2, two optical deflectors are mounted in an optical scanning device to form a path from the optical deflector to the photoreceptor in one turn without oblique incidence. configuration is conceivable. However, by installing two optical deflectors, the vibration energy due to rotation is doubled, and the positional deviation of the light beam in the sub-scanning direction (perpendicular to the scanning direction) due to the vibration of the housing that houses the optical components is an issue. can be. Patent Documents 2 and 3 propose measures to prevent vibration in an optical scanning device equipped with two optical deflectors. For example, in Patent Document 2, in order to specify the weight imbalance direction of the deflection scanning means, the weight imbalance direction of the deflection scanning means is marked in advance, and furthermore, in order to optimize the combination, a detection means such as a rotary encoder is provided. are provided. Further, for example, in Japanese Patent Laid-Open No. 2002-100002, a detecting means for detecting a positional deviation of a light beam in the sub-scanning direction by using a BD or the like, which is a positional deviation detecting means, is provided in an optical scanning device.

JP 2009-092915 A JP-A-2005-156919 Japanese Patent Application Laid-Open No. 2007-232770

However, in the conventional example, a detection means such as a rotary encoder is separately required, the manufacturing process is complicated, and the configuration of the optical scanning device is also complicated, large, and costly. Further, in the conventional example, since the detection means is provided in the optical scanning device, it is impossible to detect the displacement of the irradiation position on the photosensitive member (hereinafter referred to as "irradiation position displacement"). In particular, since the luminous flux after passing through all the optical components is not detected, it does not include irradiation position shifts in the case of large vibrations such as folding mirrors. There is a difference. For this reason, banding (uneven density in the sub-scanning direction), moiré, and operation noise may occur due to the optical scanning device.

The present invention has been devised under such circumstances, and aims to precisely reduce banding, moire, and operating noise caused by an optical scanning device, and achieve high image quality, miniaturization, and low cost. for the purpose.

In order to solve the above problems, the present invention has the following configurations.

(1) A first light source, a second light source, and a plurality of surfaces for reflecting a light beam emitted from the first light source, and the light beam is deflected by the surfaces by rotating . a rotating polygonal mirror, a second rotating polygonal mirror having a plurality of surfaces that reflect the light beam emitted from the second light source, and deflecting the light beam by the surfaces by rotating the rotating polygonal mirror; first driving means and second driving means for respectively rotating the polygon mirror and the second rotating polygon mirror ; a plurality of first optical members guided to the first rotating polygon mirror and the second rotating polygon mirror; and light beams deflected by the first rotating polygon mirror and the second rotating polygon mirror; a plurality of second optical members leading to respective corresponding objects to be scanned, the first light source, the second light source, the first rotating polygon mirror, the second rotating polygon mirror, the first light deflected by driving means, said second driving means, said plurality of first optical members, said housing housing said plurality of second optical members, and said first rotary polygon mirror ; first output means for outputting a first signal in response to receiving the beam; and second output means for outputting a second signal in response to receiving the light beam deflected by the second rotating polygon mirror. 2 output means; and control means for controlling the first driving means based on the first signal and controlling the second driving means based on the second signal. an apparatus for synchronizing information on the reference reflecting surface of the first rotating polygon mirror, the reference reflecting surface of the first rotating polygon mirror, and the plurality of surfaces of the second rotating polygon mirror; measuring a deviation amount in a direction perpendicular to the scanning direction of the light beam irradiated onto the object to be scanned, and measuring the reference reflecting surface of the first rotating polygon mirror having the smallest deviation amount among the measured deviation amounts; and information on the combination of the surfaces of the second rotating polygon mirror. An optical scanning device, wherein the first driving means and the second driving means are controlled so that the surfaces of the rotating polygon mirror are in the combination stored in the storage section.
(2) the optical scanning device of (1) above, the photoreceptor as the object to be scanned, and developing means for developing the latent image formed on the photoreceptor by the optical scanning device to form a toner image; and a transfer means for transferring the toner image onto a transfer material.

According to the present invention, it is possible to accurately reduce banding, moire, and operation noise caused by an optical scanning device, and achieve high image quality, miniaturization, and low cost.

Schematic cross-sectional view showing the image forming apparatus of Example 1 Schematic diagram showing the optical scanning device of Embodiment 1, schematic perspective view of a scanner motor Schematic diagram showing a vibration state of the optical scanning device of the first embodiment. Schematic diagram showing a difference in perpendicularity between reflecting surfaces of the rotating polygon mirror of Example 1. FIG. 2 is a block diagram regarding drive control of the optical scanning device according to the first embodiment; FIG. 10 is a diagram showing a rotating polygon mirror having interior angles with angular differences in Example 1, and a BD signal period; 7 is a graph showing the relationship between the combination of reflecting surfaces of the rotating polygon mirror of Example 1 and the irradiation position deviation amount in the sub-scanning direction; FIG. 10 is a block diagram regarding drive control of the optical scanning device according to the second embodiment;

An embodiment of an image forming apparatus having an optical scanning device according to the present invention will be described with reference to the drawings. Unless otherwise specified, the dimensions, materials, shapes, and relative positions of components described in the following examples are not intended to limit the scope of the present invention.

In the following description, the direction in which a light beam deflected by a rotating polygon mirror having a plurality of reflecting surfaces scans the photosensitive member is called the main scanning direction, and the direction perpendicular to the main scanning direction is called the sub-scanning direction. A plane defined by the scanning light beam is called a main scanning plane, and a cross section by the main scanning plane is called a main scanning cross section. A plane perpendicular to the main scanning plane is called a sub-scanning plane, and a cross section along the sub-scanning plane is called a sub-scanning plane.

<Image forming apparatus>
FIG. 1 is a schematic cross-sectional view of an image forming apparatus D1 of Example 1. FIG. The image forming apparatus D1 includes an optical scanning device S1, from which light beams Lk, Lc, Lm, and Ly optically modulated based on image information are emitted. Here, the suffixes k, c, m, and y of the reference numerals represent black, cyan, magenta, and yellow, and the suffixes are omitted except for the case of describing members related to specific colors. The light beam L irradiates the surface of a photosensitive drum 90, which is a photosensitive member (to be scanned) uniformly charged by a primary charger 91, and remains statically on the photosensitive drum 90 (to be scanned, on the photosensitive member). Forms an electrostatic latent image. The electrostatic latent image formed on the surface of the photosensitive drum 90 is visualized into black, cyan, magenta, and yellow toner images by a developing device 92, which is developing means. The visualized toner image is sequentially transferred to the transfer belt 94 at the nip portion between the transfer belt 94 and each photosensitive drum 90 so that the toner images of black, cyan, magenta, and yellow are superimposed (hereinafter referred to as primary toner images). called transcription).

On the other hand, the transfer material P placed on the feeding tray is fed by the feeding roller 93 and conveyed to the nip portion between the transfer belt 94 and the transfer roller 95 . The toner image transferred onto the transfer belt 94 is transferred onto the transfer material P by a transfer roller 95, which is transfer means, to form a color image (hereinafter referred to as secondary transfer). The unfixed color image formed on the transfer material P is heated and fixed by a fixing device 96 having an internal heater, and then discharged outside the apparatus by a discharge roller 97 or the like. The image forming apparatus D1 forms an image at an image forming speed corresponding to the paper type of the transfer material P, for example.

The image forming apparatus D1 has an engine controller 100 for controlling various operations of the image forming apparatus D1. The engine controller 100 has, for example, a CPU, a ROM that stores various programs and data necessary for executing the programs, and a RAM that serves as a working memory. In the first embodiment, the image forming apparatus D1 including the transfer belt 94 has been described. good too.

<Optical scanning device>
Next, the configuration of the optical scanning device S1 will be described with reference to FIG. FIG. 2(a) is a schematic top view showing the configuration of the optical scanning device S1. FIG. 2B is a schematic cross-sectional view showing the configuration of the optical scanning device S1. The optical scanning device S1 of the first embodiment is a unit mounted in a tandem-type color image forming apparatus, and is fixed to the frame of the image forming apparatus D1 by fixing members such as springs and screws (not shown). In the following description, for convenience, the scanning optical systems corresponding to each color are referred to as Y station, M station, C station, and K station.

The optical scanning device S1 includes two scanner motors 103a and 103b, which are a plurality of driving means having a plurality of rotating polygonal mirrors 102a and 102b, housed in an optical box 101, which is a housing made of resin or the like. . The rotating polygon mirror 102a, which is the first rotating polygon mirror, and the rotating polygon mirror 102b, which is the second rotating polygon mirror, each have, for example, four reflecting surfaces. The scanner motor 103a corresponds to the Y station and M station, and the scanner motor 103b corresponds to the C station and K station. Since the construction and optical action of the Y station and M station are the same as those of the C station and K station, the following description will focus on the Y station and M station.

A light beam Ly emitted from a semiconductor laser 111y, which is a light source mounted on a control board 115y, is collimated by a collimator lens 112y and enters a cylindrical lens 113y. The substantially collimated luminous flux Ly is referred to as substantially parallel luminous flux. The substantially parallel light flux incident on the cylindrical lens 113y is emitted in the state of parallel light flux as it is in the main scanning cross section, the light amount is limited by the aperture diaphragm 114y, and the light amount is deflected by the scanner motor 103a equipped with the rotary polygon mirror 102a. The collimator lens 112y and the cylindrical lens 113y function as a first optical member. The deflected light flux Ly is incident on the light receiving surface of a beam detector (hereinafter referred to as BD) 116 y which is output means mounted on the control board 115 . At this time, the BD 116y detects the writing position of the light flux Ly in the main scanning direction, which is the direction in which the surface to be scanned is scanned, and outputs a BD signal corresponding to the detected timing. The BD signal is output from the BD 116y for each reflecting surface of the rotating polygon mirror 102a, and serves as a trigger signal for control to align writing positions in the main scanning direction. After the deflected light beam Ly passes through the first scanning lens 105y, the optical path is deflected by the folding mirror 107y and passes through the second scanning lens 106y to form a spot image on the photosensitive drum 90y and scan at a constant speed. be done. The first scanning lens 105y, the folding mirror 107y, and the second scanning lens 106y function as a second optical member.

A light beam Lm emitted from a semiconductor laser 111m mounted on a control board 115m arranged in parallel with the semiconductor laser 111y similarly passes through a collimator lens 112m, a cylindrical lens 113m, and an aperture stop 114m. After that, the light flux Lm is deflected by a surface of the rotating polygon mirror 102a that is different from the surface that deflects the light flux Ly. At the M station, the light flux Lm does not enter the BD 116y, and the writing position of the light flux Lm in the main scanning direction is controlled based on the BD signal from the Y station. The deflected light beam Lm is guided to the photosensitive drum 90m by the first scanning lens 105m, the folding mirror 107m, and the second scanning lens 106m.

The same applies to the light beams Lc and Lk emitted from the semiconductor lasers 111c and 111k mounted on the control boards 115c and 115k in the C station and K station. The BD 116c, which is output means, is mounted on the control board 115c. Collimator lenses 112c and 112k, cylindrical lenses 113c and 113k, and aperture stops 114c and 114k are the same as those of the Y station and the like. The first scanning lenses 105c and 105k, the folding mirrors 107c and 107k, and the second scanning lenses 106c and 106k are the same as those of the Y station and the like. For example, the scanner motor 103b corresponding to the C station and K station and the scanner motor 103a corresponding to the Y station and M station are controlled as follows. As shown in FIG. 2A, the scanner motor 103b and the scanner motor 103a are controlled, for example, by PLL control (Phase Locked Loop) so that the reflecting surfaces of the respective rotating polygon mirrors 102a and 102b are aligned in substantially the same direction, that is, in phase. be done. By synchronizing the phases of the rotating polygon mirrors 102a and 102b by PLL control, the accuracy of color superimposition of the toner images of the respective colors on the transfer belt 94 is improved.

<Scanner motor>
Next, the scanner motors 103a and 103b will be described in detail. FIG. 2C is a schematic perspective view showing scanner motors 103a and 103b in the first embodiment. Since the scanner motors 103a and 103b have the same configuration, they are collectively referred to as the scanner motor 103, and the suffixes a and b may be omitted. The scanner motor 103 is composed of a rotating polygon mirror 102 , a rotor 201 , a rotating shaft 202 , a plate spring 203 and a circuit board 204 . The rotating polygon mirror 102 reflects the light flux L and guides it to the first scanning lens 105 . The rotor 201 mounts the rotating polygon mirror 102 and rotates together with the rotating polygon mirror 102 . A leaf spring 203 presses and fixes the rotating polygon mirror 102 to the rotor 201 . The rotor 201, rotating polygon mirror 102, leaf spring 203, and rotating shaft 202 are included in the rotating portion. However, considering the assembly of the rotating polygon mirror 102 to the rotor 201 , a certain amount of clearance is required in the radial direction between the outer diameter of the rotating shaft 202 and the inner diameter of the rotating polygon mirror 102 . Further, the leaf spring 203 also needs to have a certain amount of clearance from the rotating shaft 202 in the radial direction. In addition to this gap, the weight imbalance of the rotating portion occurs due to the coaxiality of the rotating shaft 202, the eccentricity of the reflecting surface of the rotating polygon mirror 102 itself, uneven weight distribution, and the like.

Therefore, in order to improve the weight imbalance of the rotating portion of the scanner motor 103, the balance is conventionally corrected. Balance correction is performed by applying a balance correction putty (for example, an ultraviolet curable resin) to the rotor 201 . There are two application surfaces of the rotor 201 on which the balance correction putty is applied, for example, a rotor upper portion 201A (Upper) and a rotor lower portion 201B (Lower). By applying the balance correction putty to two points in the thrust direction (the direction of the rotating shaft 202), the Lissajous motion of the rotating shaft 202 whirling when the rotor 201 rotates can be reduced as much as possible. The balance correction performed by applying the balance correction putty to two locations in the thrust direction of the rotor 201 is hereinafter referred to as two-surface balance correction.

The amount and direction of the weight imbalance after performing the two-plane balance correction can be expressed as follows. That is, when the scanner motor 103 is viewed from above, the weight unbalance amount (vector) on the upper side and the weight unbalance amount (vector) on the lower side can be represented by a combined vector (static). In general, in an optical scanning device provided with a plurality of such deflection means and a color image forming apparatus provided with a plurality of optical scanning devices, the balance (dynamic imbalance) of the deflection means is corrected to be as small as possible. There is a need to. The same applies to an optical scanning device in which the deflection means rotates at a high speed. However, even with the two-side balance correction, considering the weight of the balance correction putty, the application accuracy, the balance correction radius, etc., it is difficult to make the static balance completely 0 from the viewpoint of securing the yield. . Therefore, the higher the rotational speed of the rotating polygon mirror 102, the greater the amount of vibration caused by the scanner motor 103, causing vibrations in the optical box 101 and optical components, resulting in deterioration of image quality and operation noise. cause.

<Vibration of housing and displacement of irradiation position>
Next, vibration of the optical box 101 having a plurality of scanner motors 103a and 103b will be described. FIG. 3 is a schematic diagram showing how vibrations generated by the scanner motors 103a and 103b are propagated through the optical box 101 and the like. The horizontal axis of FIG. 3 represents the transition of time, and the vertical axis represents the amount of displacement due to vibration (hereinafter referred to as the amount of vibrational displacement). 3A and 3B, (a) shows the amount of vibration displacement generated by the scanner motor 103a, (b) shows the amount of vibration displacement generated by the scanner motor 103b, and (c) shows (a). (b) is synthesized to show the amount of vibration displacement.

When the phases of the vibration displacement amounts are synchronized as shown in (a) and (b) of FIG. become that way. That is, in the case of FIG. 3A, the amount of vibrational displacement of the optical box 101 and the like is greater than the amount of vibrational displacement caused by one scanner motor. Therefore, in order to reduce the synthesized vibration displacement amount as shown in FIGS. 3A and 3C, the phase of the vibration shown in FIGS. It is better to shift the phase of

FIG. 3B is a schematic diagram of a state in which the phases of vibrations generated from the scanner motors 103a and 103b are shifted. Since the phase of the vibration of (b) is out of phase with respect to the vibration of (a) in FIG. 3B, the vibration state obtained by synthesizing the vibrations of (a) and (b) is as shown in (c). By shifting the phase of the vibration of the scanner motor 103a and the phase of the vibration of the scanner motor 103b, an effect of canceling out the amount of vibration occurs, and the vibration displacement caused by two scanner motors is greater than the amount of vibration displacement caused by one scanner motor. can be reduced in quantity.

In addition, the vibration of the scanner motors 103a and 103b is not only transmitted to the optical box 101, but also affects the amount of vibration of the optical box 101. In some cases, the vibration of 107 becomes large. The vibration of the scanner motors 103a and 103b vibrates the optical box 101 and various optical members housed in the optical box 101, and the irradiation position of the light flux L on the photosensitive drum 90 in the sub-scanning direction (rotational direction of the photosensitive drum 90) is changed. cause deviation.

Further, in addition to the above-described vibration, the cause of the deviation of the irradiation position of the light flux L on the photosensitive drum 90 in the sub-scanning direction includes optical deviation of the irradiation position. FIG. 4 is a schematic diagram showing the displacement of the irradiation position of the light flux L on the photosensitive drum 90 in the sub-scanning direction. Specifically, as shown in FIG. 4, the perpendicularity of each reflecting surface 119A (solid line) and 119B (broken line) of the rotating polygon mirror 102 has a slight difference between the reflecting surfaces. A luminous flux La indicated by a solid line indicates a luminous flux reflected by the reflecting surface 119A of the rotary polygon mirror 102, and a luminous flux Lb indicated by a broken line indicates a luminous flux reflected by the reflecting surface 119B also indicated by a broken line. The reflective surface 119B and the reflective surface 119A have a relatively small angle α difference. This slight difference in angle α results in an irradiation position shift of distance d in the sub-scanning direction on the photosensitive drum 90 via an optical element (not shown) and a folding mirror (not shown). Hereinafter, the distance d in the sub-scanning direction is referred to as irradiation position shift d. In addition, the shape accuracy, position accuracy, etc. of a single lens also cause the irradiation position deviation d on the photosensitive drum 90 .

<Method of controlling phase of vibration>
Next, a method for correcting the phase of vibration caused by the scanner motor 103 will be specifically described. FIG. 5 is a block diagram relating to drive control of the optical scanning device S1 of the first embodiment. 5, the internal configuration of the optical scanning device S1 is simplified. A control unit 118 controls the optical scanning device S1. The memory 117, which is a storage unit, stores information and the like required when the control unit 118 controls the optical scanning device S1. The control unit 118 reads information stored in the memory 117 and controls the scanner motors 103a and 103b (rotating polygon mirrors 102a and 102b) based on the BD signals input from the BDs 116y and 116c. A control unit 118 controls the rotational speed of the scanner motors 103a and 103b and the rotational phases of the rotary polygon mirrors 102a and 102b. Based on the BD signals input from the BDs 116y and 116c, the controller 118 adjusts the rotation speeds (or rotation speed). Accordingly, the control unit 118 controls the rotation speeds (or rotation speeds) of the scanner motors 103a and 103b so as to reach the target rotation speeds (or target rotation speeds).

When the engine controller 100 receives the print signal in the image forming apparatus D1, the engine controller 100 causes the controller 118 to start controlling the optical scanning device S1. Specifically, the scanner motors 103a and 103b start rotating substantially simultaneously, phase control is performed by the controller 118, and the rotating polygon mirrors 102a and 102b rotate substantially in the same phase. Normally, the phases of the rotary polygon mirrors 102a and 102b of the stopped scanner motors 103a and 103b are random. Since the phases of the rotating polygon mirrors 102a and 102b are controlled to match at the shortest time during driving, conventionally, the surfaces of the rotating polygon mirror 102a and the rotating polygon mirror 102b that are synchronized each time printing are also random. . Since the rotating polygon mirrors 102a and 102b in the first embodiment have, for example, four surfaces, there are four combinations of one surface (predetermined surface) of one rotating polygon mirror and the surface of the other rotating polygon mirror. That is, there are four types of phase relationships for two rotating polygon mirrors each having four reflecting surfaces, and the amount of vibrational displacement of the optical box 101 and the optical components also varies randomly.

Here, a means for determining a combination having the smallest amount of vibration displacement among the four combinations (phase relationships) will be described. In the manufacturing process of the optical scanning device S1, at the time of the final inspection before shipment, the reflective surfaces (hereinafter referred to as reference reflective surfaces) that serve as a reference for control are specified in each of the rotary polygon mirrors 102a and 102b. A known method is used to identify the reflecting surfaces of the rotary polygon mirrors 102a and 102b. For example, there is a method of specifying the reference reflecting surface from the characteristics of the period of the BD signal, which is the period of light flux L received by the BD 116, by giving an angular difference to the internal angles of the rotating polygon mirror 102. FIG. Hereinafter, the suffixes a and b of the symbols may be omitted.

(Method for Identifying Reflecting Surface of Rotating Polygonal Mirror)
A specific method for identifying the reflecting surfaces of the rotating polygon mirror 102 will be described. FIG. 6A shows the shape of the rotary polygon mirror 102. As shown in FIG. The rotating polygon mirror 102 has four reflective surfaces: reflective surface 1 , reflective surface 2 , reflective surface 3 , and reflective surface 4 . The angle formed by the reflecting surface 1 and the reflecting surface 2 is defined as a fourth interior angle θ12. The angle formed by the reflecting surface 2 and the reflecting surface 3 is defined as a first internal angle θ23. The angle formed by the reflecting surface 3 and the reflecting surface 4 is defined as a second interior angle θ34. The angle formed by the reflecting surface 4 and the reflecting surface 1 is defined as a third interior angle θ41. In FIG. 6(a), the design value of the first internal angle θ23 is 90-2a°. The design value of the third interior angle θ41 diagonal to the first interior angle θ23 is 90+2a°. The design value of the second interior angle θ34 and the fourth interior angle θ12 diagonal to the second interior angle θ34 is 90°.

FIG. 6B shows the relationship between the periods of the BD signal in the case of such a shape of the rotating polygon mirror 102 . The graph in FIG. 6B shows the time (BD signal cycle) required for switching of the reflecting surface 1, reflecting surface 2, reflecting surface 3, and reflecting surface 4 of the rotating polygon mirror 102 while the rotating polygon mirror 102 is rotating. represents. T12 represents the time required from the output of the BD signal by the reflecting surface 1 to the output of the BD signal by the reflecting surface 2; T23 represents the time required from the output of the BD signal by the reflecting surface 2 to the output of the BD signal by the reflecting surface 3; T34 represents the time required from the output of the BD signal by the reflecting surface 3 to the output of the BD signal by the reflecting surface 4; T41 represents the time required from the output of the BD signal by the reflecting surface 4 to the output of the BD signal by the reflecting surface 1; The BD signal period on each reflecting surface has a time width corresponding to the angle ±2a. Note that the average value of the BD signal period corresponds to 90°. Thus, by providing a difference in the internal angle θ between the reflecting surfaces of the rotating polygon mirror 102, it is possible to intentionally create a characteristic BD signal period, making it easier to identify the reference reflecting surface of the rotating polygon mirror 102. . Information about the reference reflecting surfaces of the rotating polygon mirrors 102 a and 102 b specified by this method is stored in the memory 117 .

(combination of phases)
Next, determination of the combination of the phase of the rotating polygon mirror 102a and the phase of the rotating polygon mirror 102b will be described. The irradiation position deviation d in the sub-scanning direction is measured by a sensor arranged at a position corresponding to the photosensitive drum 90 by shifting the phase of the rotating polygon mirror 102b by one surface with respect to one reflecting surface of the rotating polygon mirror 102a. . Since the rotary polygon mirror 102b has four reflecting surfaces, a total of four measurements are performed, and four irradiation position deviations d for four combinations are measured. Then, a combination of reflecting surfaces that minimizes the irradiation position shift d of the light flux L in the sub-scanning direction is selected from among the four combinations.

FIG. 7 is a graph in which the horizontal axis indicates the combination of the reflecting surfaces of the rotating polygon mirror 102a and the rotating polygon mirror 102b at a specific station, and the vertical axis indicates the irradiation position deviation amount [μm] in the sub-scanning direction. The surface specified as the reference reflecting surface by the above-described known method is defined as the first surface, and the surfaces facing the light source when the rotary polygon mirror 102 is rotated clockwise from the first surface are the second surface, the third surface, and the second surface. Define 4 sides. At this time, the horizontal axis of the graph in FIG. 7 indicates a combination of surfaces with which the rotating polygon mirror 102b is synchronized with the first surface of the rotating polygon mirror 102a. For example, the state in which the first surface of the rotating polygon mirror 102a and the second surface of the rotating polygon mirror 102b are controlled in the same phase is indicated by "1-2" in the graph of FIG. The vertical axis indicates the amount of irradiation position deviation d in the sub-scanning direction on the sensor arranged at the position corresponding to the photosensitive drum 90 . In the example shown in FIG. 7, the combination in which the first surface of the rotating polygon mirror 102a and the fourth surface of the rotating polygon mirror 102b are controlled in the same phase is the irradiation position closest to the sub-scanning direction among the four combinations. The deviation d can be reduced. It should be noted that the irradiation position deviation d includes the difference in perpendicularity between the reflecting surfaces described with reference to FIG. Information on the combination of the reflecting surfaces of the rotating polygon mirrors 102a and 102b is stored in the memory 117 or the like together with information on the reference reflecting surface. The storage unit is not limited to the memory 117, and other means such as writing information in a bar code or the like and attaching it to the optical box 101 may be used.

When the optical scanning device S1 is installed in the image forming apparatus D1, the control unit 118 reads information on the reference reflecting surface and combination information on the reflecting surfaces of the rotary polygon mirrors 102a and 102b from the memory 117. FIG. The control unit 118 performs phase control of the rotating polygon mirrors 102a and 102b based on the read information and the timing of receiving the BD signals from the BDs 116y and 116c. As a result, when the rotating polygon mirrors 102a and 102b reach the target number of rotations according to the image forming speed, the phases of the reflecting surfaces are also controlled so that the irradiation position deviation d is minimized. The control unit 118 uses a reference signal generated by a reference signal generation unit (not shown) to perform phase control (for example, known phase control) for controlling acceleration or deceleration of the scanner motor 103 . The control unit 118 performs phase control so that the combination of the reflecting surfaces of the rotating polygon mirror 102a and the reflecting surface of the rotating polygon mirror 102b is the combination read out from the memory 117 (for example, the combination of "1-4" in FIG. 7). do. Normally, as described above, the phase of rotating polygon mirror 102a and the phase of rotating polygon mirror 102b are randomly combined. However, when the configuration of the first embodiment is used, the rotating polygon mirrors 102a and 102b are always controlled to have a predetermined phase and the irradiation position deviation d to be the smallest among the four combinations when printing is driven.

In this way, vibrations of the housing and optical parts of the optical scanning device caused by the weight imbalance of the scanner motor are reduced, and a stable image can be obtained by suppressing the periodic displacement of the laser beam in the sub-scanning direction. can be formed. Also, it is possible to reduce the vibration noise caused by the weight imbalance of the scanner motor, and to provide a high-quality image forming apparatus.

As described above, according to the first embodiment, it is possible to accurately reduce banding, moire, and operation noise caused by the optical scanning device, and realize high image quality, miniaturization, and low cost.

Next, the image forming apparatus D1 of Example 2 will be described. It should be noted that components configured in the same manner as in Embodiment 1 are denoted by the same reference numerals or the same member names even if the reference numerals are different, and the description thereof is omitted. FIG. 8 is a block diagram relating to drive control of the optical scanning device S1. A characteristic configuration in the second embodiment will be described. In the second embodiment, a microphone 301, which is measuring means for measuring sound, is provided in the image forming apparatus D1. The microphone 301 may be a small one such as a MEMS microphone, and may be installed at any location within the housing of the image forming apparatus D1, as long as it responds to the vibration sound of the optical scanning device S1. Sound information measured by the microphone 301 is output to the control unit 118 .

Next, the control of Example 2 is demonstrated. When the engine controller 100 receives the print signal, the controller 118 starts controlling the scanner motors 103a and 103b. The scanner motors 103a and 103b start rotating substantially at the same time, and are phase-synchronized with random predetermined reflecting surfaces of the rotary polygon mirror 102 by PLL control, for example. The controller 118 measures the operation sound with the microphone 301 at the timing when the predetermined reflecting surface of the rotating polygon mirror 102a and the predetermined reflecting surface of the rotating polygon mirror 102b are synchronized, and records it in the memory 117, for example. When the recording is completed, the control unit 118 performs phase control to shift the phase of the rotating polygon mirror 102b by 90° while maintaining the predetermined reflecting surface of the rotating polygon mirror 102a. change the combination. At the timing when the predetermined reflecting surface of the rotating polygon mirror 102a and the next reflecting surface adjacent to the predetermined reflecting surface of the rotating polygon mirror 102b are synchronized, the control unit 118 measures the operation sound again with the microphone 301 and stores the operation sound in the memory 117. to record.

The control unit 118 performs this operation (hereinafter referred to as learning operation) for all the reflecting surfaces of the rotating polygon mirror 102b, in other words, for all combinations (four ways) of operation sound measurement and recording by the microphone 301 is completed. Repeat until The control unit 118 acquires the measurement results of the four operating sounds for the four combinations recorded in the memory 117 . The control unit 118 selects a combination that minimizes the operation noise among the obtained four measurement results. The control unit 118 controls the phases of the rotating polygon mirrors 102a and 102b so as to obtain the selected combination that minimizes the operation noise, and executes the printing operation.

Here, the operation sound is generated by the vibration of the optical scanning device S1, and the combination that minimizes the operation sound means that the amount of vibration displacement is the smallest, and at the same time, the irradiation position deviation d in the sub-scanning direction is also the smallest. combination. As a result, the image forming apparatus D1 can always operate with the lowest operating noise and the smallest irradiation position deviation d in the sub-scanning direction.

Also, the learning operation may be performed at the time of each print signal, but is not limited to this. For example, the control unit 118 performs a learning operation once when the power of the image forming apparatus D1 is turned on (when it is turned on), and associates it with the reference reflecting surface of the rotary polygon mirror 102 specified by the above-described known method. This information is stored in the memory 117 by pressing. Then, the control unit 118 may perform control so that the two rotating polygon mirrors 102a and 102b are always driven in phase synchronization with the combination stored in the memory 117 until the power of the image forming apparatus D1 is turned off next time. . Further, the information of the optimum combination may be stored in the memory 117 by a learning operation at the time of inspection before shipment of the image forming apparatus D1. The optimum combination is once stored in the memory 117, and the control unit 118 periodically performs a learning operation, so that it is possible to cope with changes in the weight imbalance over time.

Further, in the measurement of the operating sound, by providing a band-pass filter or the like for filtering information measured by the microphone 301, the operating sound of the optical scanning device S1 can be specified without being confused with the operating sound of other driving units. Further, in order to further improve accuracy, it is possible to more reliably detect the operation sound of the scanner motor 103 by performing frequency analysis of the operation sound measured by the microphone 301 using a CPU (not shown). Furthermore, when the learning operation is performed periodically, the measurement may be performed by driving only the scanner motor 103 while the other driving units are stopped.

With such a configuration, it is possible to reduce the vibration of the housing and optical parts of the optical scanning device caused by the weight imbalance of the scanner motor, and to suppress the periodic displacement of the laser beam in the sub-scanning direction. A stable image can be formed. Also, it is possible to reduce the vibration noise caused by the weight imbalance of the scanner motor, and to provide a high-quality image forming apparatus. Although the rotating polygon mirror 102 of Examples 1 and 2 has four reflecting surfaces, the present invention is not limited to this. For example, if the rotating polygon mirror has another number of reflecting surfaces, such as five, the number of combinations increases and the angle of rotation to the next reflecting surface differs. is selected (or the operation noise is reduced).

As described above, according to the second embodiment, it is possible to accurately reduce banding, moire, and operation noise caused by the optical scanning device, and to realize high image quality, miniaturization, and low cost.

101 optical box 102 rotary polygon mirror 103 scanner motor 105 first scanning lens 106 second scanning lens 107 folding mirror 111 semiconductor laser 116 BD
117 memory 118 control unit

Claims (4)

a first light source;
a second light source;
a first rotating polygon mirror having a plurality of surfaces for reflecting the light beam emitted from the first light source and deflecting the light beam by the surfaces by rotating;
a second rotating polygon mirror having a plurality of surfaces that reflect the light beam emitted from the second light source, and that rotates to deflect the light beam by the surfaces;
first driving means and second driving means for respectively rotating the first rotating polygon mirror and the second rotating polygon mirror;
a plurality of first optical members that guide the light beams emitted from the first light source and the second light source to the corresponding first rotating polygon mirror and the second rotating polygon mirror ;
a plurality of second optical members that guide the light beams deflected by the first rotating polygon mirror and the second rotating polygon mirror to the corresponding objects to be scanned;
said first light source, said second light source, said first rotating polygon mirror, said second rotating polygon mirror, said first driving means, said second driving means, and said plurality of first optical members a housing in which the plurality of second optical members are housed;
first output means for outputting a first signal in response to receiving the light beam deflected by the first rotating polygon mirror;
a second output means for outputting a second signal in response to receiving the light beam deflected by the second rotating polygon mirror;
a control means for controlling the first driving means based on the first signal and controlling the second driving means based on the second signal ;
An optical scanning device comprising:
Synchronizing the information on the reference reflecting surface of the first rotating polygon mirror, the reference reflecting surface of the first rotating polygon mirror, and the plurality of surfaces of the second rotating polygon mirror, measuring the amount of deviation in the direction orthogonal to the scanning direction of the light beam irradiated to the optical beam, and comparing the reference reflecting surface of the first rotary polygon mirror and the second reflecting surface with the smallest deviation amount among the measured deviation amounts a storage unit that stores information on the combination of faces of the rotating polygon mirror;
When forming an image, the control means performs the first driving so that the surfaces of the first rotating polygon mirror and the surfaces of the second rotating polygon mirror are in the combination stored in the storage unit. and said second driving means . The first rotating polygon mirror and the second rotating polygon mirror have four faces,
The control means rotates the second rotating polygon mirror with respect to the reference reflecting surface of the first rotating polygon mirror while shifting one surface at a time, measures the amount of deviation, and measures the amount of deviation for each of the four combinations. 2. The optical scanning device according to claim 1, wherein four measurement results are obtained by means of said scanning device. 3. The first rotating polygon mirror and the second rotating polygon mirror are formed such that two adjacent surfaces of the four surfaces have different interior angles. 3. The optical scanning device according to claim 2. an optical scanning device according to any one of claims 1 to 3 ;
a photoreceptor, which is the object to be scanned;
a developing means for developing a latent image formed on the photoreceptor by the optical scanning device to form a toner image;
a transfer means for transferring the toner image onto a transfer material;
An image forming apparatus comprising: