JP2009069272A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably and precisely detect misalignment of a luminous flux condensed on a face to be scanned in a subscanning direction. <P>SOLUTION: A portion of the luminous flux which is deflected with a polygon mirror 13, passing through a scanning optical system and not used for image formation is made incident to a synchronization detection sensor 18 via two synchronization detection mirrors (19a and 19b) as a luminous flux for synchronization detection. Thus, the difference in the number of the mirror faces through which the luminous flux directed from the polygon mirror 13 to a photoreceptor drum 1030 passes and the number of the mirror faces through which the luminous flux directed from the polygon mirror 13 to the synchronization detection sensor 18 passes is two. Thus, when the housing 21 is deformed due to the heat generation at the polygon mirror 13 or the like, even when the tilt angle and the position of the respective synchronization detection mirrors are changed, the subscanning misalignment is precisely detected. Accordingly, the misalignment in the subscanning direction of the luminous flux condensed on the surface of the photoreceptor drum 1030 is stably and precisely detected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical scanning apparatus and an image forming apparatus, and more particularly to an optical scanning apparatus that scans a surface to be scanned with a light beam and an image forming apparatus including the optical scanning apparatus.

  In electrophotographic image recording, an image forming apparatus using a laser beam is widely used. In this case, the image forming apparatus includes an optical scanning device, and scans the laser beam using a deflector (for example, a polygon mirror) in the axial direction of the photosensitive drum, and rotates the photosensitive drum to form a latent image. Is common.

  The laser beam that scans the photosensitive drum may be displaced in the sub-scanning direction due to a temperature change or the like. Therefore, a feedback correction method has been proposed in which a positional deviation is detected using a beam detection element or the like, and the positional deviation is reduced based on the detection result.

  For example, Patent Document 1 discloses an optical scanning including a light source that generates a light beam, a light deflecting unit that deflects and scans the light beam from the light source, and a scanning optical system that scans the light beam at a substantially constant speed. In the apparatus, a plurality of sensors are arranged side by side, at least two opposite edges are parallel and form a straight line, and at least one of the opposite edges of each sensor has an angle that is not parallel to the main scanning direction. A light beam position detecting means for detecting the positions of the plurality of light beams arranged, a sub scanning position detecting means for detecting a scanning position in the sub scanning direction based on a beam position detection signal from the light beam position detecting means, A scanning position control means for controlling the scanning position in the sub-scanning direction and returning the scanning position to the prescribed scanning position when the scanning position of the sub-scan detected by the scanning position detection means deviates from the prescribed position. Apparatus is disclosed.

JP 2005-62597 A

  Incidentally, a deflector, a scanning optical system, a beam detection element, a detection mirror for guiding laser light to the beam detection element, and the like are accommodated in predetermined positions in the housing. The housing may be deformed by heat generated from the deflector during operation. At this time, if the attitude of the detection mirror disposed in the housing also changes, an error occurs in the detection result of the beam detection element, and as a result, accurate feedback correction may not be possible.

  The present invention has been made under such circumstances, and a first object thereof is light that can stably and accurately detect a positional deviation of a light beam condensed on a surface to be scanned in the sub-scanning direction. It is to provide a scanning device.

  A second object of the present invention is to provide an image forming apparatus capable of stably forming a high quality image.

  According to a first aspect of the present invention, there is provided an optical scanning device that scans a surface to be scanned in a main scanning direction with a light beam, a light source; a deflector that deflects the light beam from the light source; and at least one mirror surface A scanning optical system for condensing the light beam deflected by the deflector on the surface to be scanned; and for detecting a positional deviation of the light beam condensed on the surface to be scanned in the sub-scanning direction. A beam detection sensor; and a housing in which each of the light source, the deflector, the scanning optical system, and the beam detection sensor is arranged in a predetermined positional relationship, and a light beam traveling from the deflector toward the scanned surface. The first optical scanning device is characterized in that the difference between the number of mirror surfaces interposed and the number of mirror surfaces through which the light beam traveling from the deflector toward the beam detection sensor passes is zero or an even number.

  According to a second aspect of the present invention, there is provided an optical scanning device that scans a surface to be scanned in a main scanning direction with a light beam, a light source; a deflector that deflects the light beam from the light source; and a plurality of mirror surfaces. A scanning optical system for condensing the light beam deflected by the deflector on the surface to be scanned; and a beam for detecting a positional deviation of the light beam collected on the surface to be scanned in the sub-scanning direction. A detection sensor; and a beam detection optical system that guides, to the beam detection sensor, a light beam reflected by a mirror surface that is optically closest to the scanned surface among a plurality of mirror surfaces of the scanning optical system. A housing in which each of the light source, the deflector, the scanning optical system, and the beam detection sensor is arranged in a predetermined positional relationship, and the beam detection optical system has an even number of mirror surfaces. Characteristic second A scanning device.

  According to the first or second optical scanning device, since the number of mirror surfaces is regulated, the tilt angle and position of the mirror surface change when the housing is deformed by heat generated from the deflector during operation. Even in this case, it is possible to accurately detect the positional deviation in the sub-scanning direction of the light beam condensed on the surface to be scanned. Accordingly, it is possible to stably detect the positional deviation in the sub-scanning direction of the light beam condensed on the surface to be scanned.

  According to a third aspect of the present invention, there is provided at least one image carrier; and at least one optical scanning device according to the invention that scans a light beam including image information on the at least one image carrier. An image forming apparatus provided.

  According to this, since at least one optical scanning device of the present invention is provided, as a result, a high-quality image can be stably formed.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a laser printer 1000 as an image forming apparatus according to an embodiment of the present invention.

  The laser printer 1000 includes an optical scanning device 1010, a photosensitive drum 1030, a charging charger 1031, a developing roller 1032, a transfer charger 1033, a static elimination unit 1034, a cleaning blade 1035, a toner cartridge 1036, a paper supply roller 1037, a paper supply tray 1038, A registration roller pair 1039, a fixing roller 1041, a paper discharge roller 1042, a paper discharge tray 1043, a communication control device 1050, a printer control device 1060 that comprehensively controls the above-described units, and the like are provided. These are housed in predetermined positions in the printer housing 1044.

  The communication control device 1050 controls bidirectional communication with an external device via a network or the like.

  The photosensitive drum 1030 is a cylindrical member, and a photosensitive layer is formed on the surface thereof. That is, the surface of the photoconductor drum 1030 is a scanned surface. The photosensitive drum 1030 rotates in the direction of the arrow in FIG.

  The charging charger 1031, the developing roller 1032, the transfer charger 1033, the charge removal unit 1034, and the cleaning blade 1035 are each arranged in the vicinity of the surface of the photosensitive drum 1030. Then, along the rotation direction of the photosensitive drum 1030, the charging charger 1031 → the developing roller 1032 → the transfer charger 1033 → the discharging unit 1034 → the cleaning blade 1035 are arranged in this order.

  The charging charger 1031 uniformly charges the surface of the photosensitive drum 1030.

  The optical scanning device 1010 irradiates the surface of the photosensitive drum 1030 charged by the charging charger 1031 with a light beam modulated based on image information from a host device (for example, a personal computer). As a result, a latent image corresponding to the image information is formed on the surface of the photosensitive drum 1030 on the surface of the photosensitive drum 1030. The latent image formed here moves in the direction of the developing roller 1032 as the photosensitive drum 1030 rotates. The configuration of the optical scanning device 1010 will be described later.

  The toner cartridge 1036 stores toner, and the toner is supplied to the developing roller 1032.

  The developing roller 1032 causes the toner supplied from the toner cartridge 1036 to adhere to the latent image formed on the surface of the photosensitive drum 1030 to visualize the image information. Here, the latent image to which the toner is attached (hereinafter also referred to as “toner image” for the sake of convenience) moves in the direction of the transfer charger 1033 as the photosensitive drum 1030 rotates.

  Recording paper 1040 is stored in the paper feed tray 1038. A paper feed roller 1037 is disposed in the vicinity of the paper feed tray 1038, and the paper feed roller 1037 takes out the recording paper 1040 one by one from the paper feed tray 1038 and conveys it to the registration roller pair 1039. The registration roller pair 1039 temporarily holds the recording paper 1040 taken out by the paper supply roller 1037, and in the gap between the photosensitive drum 1030 and the transfer charger 1033 according to the rotation of the photosensitive drum 1030. Send it out.

  A voltage having a polarity opposite to that of the toner is applied to the transfer charger 1033 in order to electrically attract the toner on the surface of the photosensitive drum 1030 to the recording paper 1040. With this voltage, the toner image on the surface of the photosensitive drum 1030 is transferred to the recording paper 1040. The recording sheet 1040 transferred here is sent to the fixing roller 1041.

  In the fixing roller 1041, heat and pressure are applied to the recording paper 1040, whereby the toner is fixed on the recording paper 1040. The recording paper 1040 fixed here is sent to the paper discharge tray 1043 via the paper discharge roller 1042 and is sequentially stacked on the paper discharge tray 1043.

  The neutralization unit 1034 neutralizes the surface of the photosensitive drum 1030.

  The cleaning blade 1035 removes toner (residual toner) remaining on the surface of the photosensitive drum 1030. The removed residual toner is used again. The surface of the photosensitive drum 1030 from which the residual toner has been removed returns to the position of the charging charger 1031 again.

  Next, the configuration of the optical scanning device 1010 will be described.

  2 and 3, the optical scanning device 1010 includes a light source 14, a coupling lens 15, an aperture plate 16, a cylindrical lens 17, a polygon mirror 13, a deflector side scanning lens 11a, and an image plane side scanning lens. 11b, three scanning mirrors (12a, 12b, 12c), synchronization detection sensor 18, two synchronization detection mirrors (19a, 19b), liquid crystal deflecting element 20, and scanning control device 22 (in FIGS. 2 and 3) (Not shown, see FIG. 13). These are assembled at predetermined positions in the housing 21. In this specification, in the XYZ three-dimensional orthogonal coordinate system, the direction along the longitudinal direction of the photosensitive drum 1030 is defined as the Y-axis direction, and the direction along the optical axis of each scanning lens (11a, 11b) is defined as the X-axis direction. explain.

  As shown in FIG. 4 as an example, the light source 14 includes a two-dimensional array 100 in which 40 light emitting units are formed on one substrate. The M direction in FIG. 4 is a direction corresponding to the main scanning direction, and the S direction is a direction corresponding to the sub scanning direction (here, the same as the Z-axis direction). The T direction is a direction that forms an inclination angle α (0 ° <α <90 °) from the M direction toward the S direction.

  This two-dimensional array 100 has four light emitting part rows in which ten light emitting parts are arranged at equal intervals along the T direction. These four light emitting unit rows are arranged at equal intervals in the S direction. That is, the 40 light emitting units are two-dimensionally arranged along the T direction and the S direction, respectively. Here, for the sake of convenience, each light emitting unit row is referred to as a first light emitting unit row, a second light emitting unit row, a third light emitting unit row, and a fourth light emitting unit row from top to bottom in FIG. In this specification, the “light emitting portion interval” refers to the distance between the centers of two light emitting portions.

  Further, in order to specify each light emitting unit, for convenience, the ten light emitting units constituting the first light emitting unit row are configured as v1 to v10 and the second light emitting unit row are configured from the lower left to the upper right in FIG. The ten light emitting units are designated as v11 to v20, the ten light emitting units constituting the third light emitting unit row are designated as v21 to v30, and the ten light emitting units constituting the fourth light emitting unit row are designated as v31 to v40.

  Each light emitting unit is a vertical cavity surface emitting semiconductor (VCSEL) having a design oscillation wavelength of 655 nm. That is, the two-dimensional array 100 is a so-called surface emitting laser array.

  Returning to FIG. 2, the coupling lens 15 converts the light beam emitted from the light source 14 into substantially parallel light.

  The aperture plate 16 has an aperture and defines the beam diameter of the light beam through the coupling lens 15.

  The liquid crystal deflecting element 20 is disposed on the optical path of the light beam that has passed through the opening of the aperture plate 16, and deflects incident light in the direction corresponding to the sub-scanning direction (here, the Z-axis direction) according to the applied voltage. be able to. The liquid crystal deflecting element 20 has a configuration in which liquid crystal is sealed between two transparent glass plates. As an example, as shown in FIG. 5A, electrodes are formed above and below the surface of one glass plate. ing. When a potential difference is applied between the electrodes, as shown in FIG. 5B as an example, a potential gradient occurs in the direction corresponding to the sub-scanning direction, and the alignment of the liquid crystal changes accordingly. In addition, a refractive index gradient occurs in a direction corresponding to the sub-scanning direction. As a result, like the prism, the light emission axis can be slightly tilted with respect to the direction corresponding to the sub-scanning direction. As the liquid crystal, nematic liquid crystal having dielectric anisotropy is used.

  The cylindrical lens 17 forms an image of the light beam that has passed through the liquid crystal deflecting element 20 in the vicinity of the deflection reflection surface of the polygon mirror 13 in the direction corresponding to the sub-scanning direction (here, the Z-axis direction).

  The optical system arranged on the optical path between the light source 14 and the polygon mirror 13 is also called a pre-deflector optical system. In the present embodiment, the pre-deflector optical system includes a coupling lens 15, an aperture plate 16, a liquid crystal deflecting element 20, and a cylindrical lens 17.

  The polygon mirror 13 has a four-sided mirror, and each mirror serves as a deflection reflection surface. The polygon mirror 13 rotates at a constant speed around an axis parallel to a direction corresponding to the sub-scanning direction (here, the Z-axis direction), and deflects the light beam from the cylindrical lens 17.

  The deflector-side scanning lens 11 a is disposed on the optical path of the light beam deflected by the polygon mirror 13.

  The image plane side scanning lens 11b is disposed on the optical path of the light beam via the deflector side scanning lens 11a.

  The scanning mirror 12a reflects the light beam that has passed through the image plane side scanning lens 11b and bends its optical path.

  The scanning mirror 12b reflects the light beam that has passed through the scanning mirror 12a and bends its optical path.

  The scanning mirror 12c reflects the light beam that has passed through the scanning mirror 12b and bends its optical path. The light beam reflected by the scanning mirror 12c is irradiated onto the surface of the photosensitive drum 1030, and a light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 1030 as the polygon mirror 13 rotates. That is, the photoconductor drum 1030 is scanned. The moving direction of the light spot at this time is the “main scanning direction”.

Each surface (incident surface, exit surface) of the deflector side scanning lens 11a and the image surface side scanning lens 11b is an aspherical surface expressed by the following equations (1) and (2). Here, X represents the coordinate in the X-axis direction, and Y represents the coordinate in the Y-axis direction. The center of the incident surface is Y = 0. C _m0 indicates the curvature in the direction corresponding to the main scanning direction when Y = 0, and is the reciprocal of the curvature radius R _m . a ₀₀ , a ₀₁ , a ₀₂ ,... are main scanning aspherical coefficients. Cs (Y) is the curvature of Y in the direction corresponding to the sub-scanning direction, R _s0 is the radius of curvature on the optical axis in the direction corresponding to the sub-scanning direction, b ₀₀ , b ₀₁ , b ₀₂ ,. It is an aspheric coefficient in a direction corresponding to the sub-scanning direction. The optical axis is an axis passing through a central point in a direction corresponding to the sub-scanning direction with Y = 0.

FIG. 6 shows an example of values of R _m , R _s0, and each aspheric coefficient on each surface (incident surface (first surface), exit surface (second surface)) of the deflector-side scanning lens 11a.

FIG. 7 shows an example of values of R _m , R _s0, and each aspheric coefficient on each surface (incident surface (third surface), exit surface (fourth surface)) of the image surface side scanning lens 11b.

  The optical system arranged on the optical path between the polygon mirror 13 and the photosensitive drum 1030 is also called a scanning optical system. In the present embodiment, the scanning optical system includes a deflector side scanning lens 11a, an image plane side scanning lens 11b, and three scanning mirrors (12a, 12b, 12c).

  Incidentally, FIG. 8 shows the positional relationship between main optical elements of the pre-deflector optical system and the scanning optical system. FIG. 9 shows an example of specific values (unit: mm) of the symbols d1 to d11 in FIG.

  In addition, the direction of emission of the light beam from the cylindrical lens 17 and the light beam reflected toward the position of the image height 0 on the surface of the photosensitive drum 1030 (position p0 in FIG. 8) by the deflection reflection surface of the polygon mirror 13. The angle formed with the traveling direction (θr in FIG. 8) is 60 degrees.

  2 and 3, a part of the light beam that is deflected by the polygon mirror 13 and does not participate in image formation out of the light beam that passes through the scanning optical system is used as the synchronization detection light beam. 19a, 19b) and enters the synchronous detection sensor 18. The incident position of the synchronization detection light beam in the synchronization detection sensor 18 moves in the direction corresponding to the main scanning direction (for convenience, the m direction) as the polygon mirror 13 rotates.

  That is, the difference between the number of mirror surfaces through which the light beam traveling from the polygon mirror 13 toward the photosensitive drum 1030 passes and the number of mirror surfaces through which the light beam traveling from the polygon mirror 13 toward the synchronization detection sensor 18 is two.

  Of the three scanning mirrors, the mirror surface through which the light beam reflected by the scanning mirror 12c optically disposed at the position closest to the photosensitive drum 1030 is received by the synchronization detection sensor 18 is also shown. The number is two.

《Synchronous detection sensor》
As shown in FIG. 10 as an example, the synchronization detection sensor 18 is disposed so that its light receiving surface is optically substantially parallel to the image plane (designed image plane). In addition, the code | symbol 18 'in FIG. 10 has shown the position of the synchronous detection sensor 18 when it assumes that there are no two synchronous detection mirrors (19a, 19b). In addition, the normal direction of the light receiving surface of the synchronization detection sensor 18 is inclined with respect to the incident direction of the synchronization detection light beam (see FIG. 10).

As shown in FIG. 11 as an example, the synchronization detection sensor 18 includes a light receiving element having two light receiving parts (first light receiving part 18 ₁ , second light receiving part 18 ₂ ), and the amount of light received from the light receiving element. An amplifier (AMP) 18 ₃ that amplifies a signal (photoelectric conversion signal), a comparator (CMP) 18 that compares the output signal level of the amplifier 18 ₃ with a preset reference level Vs and outputs the comparison result. ₄ . The output signal of the comparator 18 ₄ is supplied to the scanning control device 22.

  The respective light receiving portions of the light receiving elements have different intervals in the m direction depending on positions in a direction corresponding to the sub-scanning direction (for convenience, the s direction).

The first light receiving portion 18 ₁ is a rectangular light-receiving section as an example, are arranged so that the longitudinal direction coincides with the direction s. That is, the two sides through which the synchronization detection light beam passes are parallel to the s direction.

Second light receiving section 18 ₂ is a parallelogram-shaped light-receiving section as an example, it is arranged in the 1 + m side of the light receiving portion 18 _1. The second longitudinal direction of the light receiving portion 18 ₂ is inclined by an angle theta with respect to the first longitudinal direction of the light receiving portion 18 ₁ in the light-receiving surface (0 <θ <90 °) . That is, the two sides through which the synchronization detection light beam passes are inclined with respect to the m direction.

In amplifier 18 _3, the inverted input signals. Therefore, as the amount of light received by the light receiving element is large, the output signal level of the amplifier 18 ₃ becomes low.

The reference level Vs is set slightly higher level than the amplifier 18 _third output signal level (minimum value) when the synchronization detection light beam is received by the light receiving element. Therefore, when any of the light receiving portion has received the synchronization detection light beam, the judgment result of the comparator 18 ₄ is changed, the output signal of the comparator 18 ₄ changes accordingly.

The synchronization detection sensor 18 is adjusted so that the synchronization detection light beam passes through almost the center of each light receiving portion when the incident position of the light beam on the surface of the photosensitive drum 1030 is a designed position (FIG. 12 (A)). Then, in this case, the time until the synchronization detection light beam is detected after it is detected by the first light receiving portion 18 ₁ in the second light receiving portion 18 _2, obtained in advance as the reference time Ts (Fig. 12 ( B)). For convenience, the movement path of the incident position of the synchronization detection light beam in the synchronization detection sensor 18 at this time, that is, the design movement path is referred to as “path A”.

  By the way, the optical path of the light beam directed to the photosensitive drum 1030 corresponds to the designed optical path in the sub-scanning direction due to an error in the mounting position when mounting each optical element in the housing 21 or deformation of the housing 21. May be displaced in the direction (here, the Z-axis direction). In this case, the synchronization detection light beam is also shifted in the direction corresponding to the sub-scanning direction (here, the s direction) with respect to the designed optical path, similarly to the light beam traveling toward the photosensitive drum 1030. As an example, as shown in FIG. 12C, the movement path of the incident position of the synchronization detection light beam in the synchronization detection sensor 18 is also shifted in the direction corresponding to the sub-scanning direction with respect to the path A. For convenience, the movement route at this time is referred to as a route B.

Then, the shift amount Δh (see FIG. 12C) of the movement path at this time can be obtained from the following equation (3). Here, [Delta] T is from the falling of the output signal of the comparator 18 ₄ is the difference between the time T and the reference time Ts until the next falling (see FIG. 12 (D)), V is for detecting synchronization This is the moving speed (scanning speed) of the light beam. This deviation amount Δh has a correlation with the deviation amount in the direction corresponding to the sub-scanning direction with respect to the designed optical path of the optical path of the light beam toward the photosensitive drum 1030 (here, the Z-axis direction).

  Δh = (V / tan θ) × ΔT (3)

Further, when the first light receiving portion 18 ₁ has received the synchronization detection light beam, falling in the output signal of the comparator 18 ₄ is not affected by the incident position of the synchronization detection light beam in the s direction (FIG. 12 ( B) and FIG. 12 (D)). Therefore, when the first light receiving portion 18 ₁ has received the synchronization detection light beam, it is possible to determine the timing of the start scanning from the falling of the output signal of the comparator 18 _4.

<Scanning control device>
As shown in FIG. 13 as an example, the scanning control device 22 includes a CPU 210, a flash memory 211, a RAM 212, a liquid crystal element driving circuit 213, an IF (interface) 214, a pixel clock generation circuit 215, an image processing circuit 216, and a frame memory 217. , Line buffers 218 _{1 to} 218 ₄₀ , a writing control circuit 219, a light source driving circuit 221, and the like. Note that the arrows in FIG. 13 indicate the flow of typical signals and information, and do not represent the entire connection relationship of each block.

  The pixel clock generation circuit 215 generates a pixel clock signal. The pixel clock signal can be phase-modulated with a resolution of 1/8 clock.

  The frame memory 217 temporarily stores image data rasterized by the CPU 210 (hereinafter abbreviated as “raster data” for convenience).

The image processing circuit 216 reads raster data stored in the frame memory 217, performs predetermined halftone processing, etc., and then creates dot data for each light emitting unit, and a line buffer 218 ₁ corresponding to each light emitting unit. To 218 ₄₀ .

Write control circuit 219, based on the output signal of the synchronous detection sensor 18, when the first light receiving portion 18 ₁ has received the light beam for detecting synchronization, monitoring the fall in the output signal of the comparator 18 _4. When the fall is detected, the scanning start timing is obtained. Then, in accordance with the scanning start timing, the dot data of each light emitting unit is read from the line buffers 218 _{1 to} 218 ₄₀ and superimposed on the pixel clock signal from the pixel clock generation circuit 215, and independent modulation is performed for each light emitting unit. Generate data.

  The light source driving circuit 221 drives each light emitting unit of the two-dimensional array 100 according to the modulation data from the writing control circuit 219.

  The flash memory 211 stores various programs described by codes that can be decoded by the CPU 210.

  The RAM 212 is a working memory.

  The CPU 210 operates according to a program stored in the flash memory 211 and controls the entire optical scanning device 1010.

  For example, the CPU 210 obtains the deviation amount Δh based on the output signal of the synchronization detection sensor 18 at every predetermined timing, and the positional deviation amount in the sub-scanning direction of the light beam on the surface of the photosensitive drum 1030 (hereinafter referred to as convenience). The voltage applied to the liquid crystal deflecting element 20 is determined so that the “sub-scanning deviation amount”) is substantially zero. Note that the shift amount Δh and the sub-scanning shift amount have a linear relationship as shown in FIG. 14 as an example, and the relationship between the sub-scanning shift amount and the applied voltage is obtained in advance and stored in the flash memory 211. Yes.

  Note that when the sub-scanning deviation amount is ½ or more of the scanning line interval on the photosensitive drum 1030, the CPU 210 shifts the image data so that the sub-scanning deviation amount is reduced.

  The liquid crystal element driving circuit 215 applies the applied voltage determined by the CPU 210 to the liquid crystal deflecting element 20.

  An IF (interface) 214 is a communication interface that controls bidirectional communication with the printer control apparatus 1060. Image data from the host device is supplied via an IF (interface) 214.

  By the way, the optical scanning device 1010 is fixed to the structural member 1044a of the printer casing 1044 through the fastening portion 21a at the lower part of the housing 21, as shown in FIG. And the synchronous detection sensor 18 is arrange | positioned in the vicinity of the fastening part 21a.

  When the optical scanning device 1010 is driven, the housing 21 is deformed by heat generated by the polygon mirror 13 or the like as shown in FIG. 15B as an example.

  Here, the housing 21 is deformed so that the central portion is lifted because the peripheral portion thereof is fastened. Therefore, as shown in FIG. 16 as an example, the two synchronization detection mirrors (19a, 19b) change in inclination angle or position.

As an example, FIG. 17 shows a change in the optical path of a light beam for synchronization detection due to a change in tilt angle (tilt) of two synchronization detection mirrors (19a, 19b). At this time, the reflection direction of the synchronization detection light beam at each synchronization detection mirror changes. However, since the synchronization detection mirror 19a and the synchronization detection mirror 19b are arranged at positions close to each other, the amount of change in the tilt angle is substantially equal. That is, θ ₁ ≈θ ₂ and the synchronization detection light beam received by the synchronization detection sensor 18 is shifted substantially in parallel.

As an example, FIG. 18 shows a change in the optical path of the light beam for synchronization detection due to a position change (shift) in the Z-axis direction of the two synchronization detection mirrors (19a, 19b). Since the synchronization detection mirror 19a and the synchronization detection mirror 19b are arranged at positions close to each other, their positional change amounts (shift amounts) are substantially equal. That is, ΔZ ₁ = ΔZ ₂ , and there is no change in the synchronization detection light beam received by the synchronization detection sensor 18. The same applies to the X-axis direction.

  Therefore, when the housing 21 is deformed and the inclination angle change and the position change occur in the two synchronization detection mirrors (19a, 19b), the synchronization detection light beam received by the synchronization detection sensor 18 is synchronized with two synchronization detection beams. A substantially parallel shift occurs due to a change in the tilt angle of the detection mirror (19a, 19b).

  As an example, in FIG. 19, as a comparative example, one synchronization detection mirror 19 is used instead of the two synchronization detection mirrors (19 a, 19 b), and the synchronization detection mirror 19 is deformed by deformation of the housing 21. The optical path change of the synchronous detection light beam is shown when the tilt angle changes. At this time, the tilt angle of the sync detection sensor 18 also changes so that the change in the reflection direction of the sync detection beam caused by the tilt angle change of the sync detection mirror 19 is canceled out. In this case, since the amount of change in the light receiving position of the synchronization detection light beam in the synchronization detection sensor 18 becomes small, the dynamic range becomes small, and the detection accuracy of the sub-scanning deviation amount decreases.

  However, in the present embodiment, since two synchronization detection mirrors are provided, the light receiving position of the synchronization detection light beam by the synchronization detection sensor 18 changes corresponding to the deformation of the housing 21. That is, the sub-scanning deviation amount can be detected with high accuracy.

  Moreover, in this embodiment, since the synchronous detection sensor 18 is arrange | positioned in the vicinity of the fastening part 21a, the attitude | position change of the synchronous detection sensor 18 by the deformation | transformation of the housing 21 can be suppressed.

  As is clear from the above description, in the optical scanning device 1010 according to the present embodiment, a beam detection sensor is configured by the synchronization detection sensor 18, and a beam detection optical system is configured by the synchronization detection mirror 19a and the synchronization detection mirror 19b. It is configured.

  The scanning control device 22 constitutes a control device.

  Further, at least a part of the processing according to the program by the CPU 210 may be configured by hardware, or all may be configured by hardware.

  As described above, according to the optical scanning device 1010 according to the present embodiment, a part of the light beam that is deflected by the polygon mirror 13 and does not participate in image formation out of the light beam that passes through the scanning optical system is a synchronization detection light beam. Then, the light enters the synchronization detection sensor 18 through the two synchronization detection mirrors (19a, 19b). Therefore, the difference between the number of mirror surfaces through which the light beam traveling from the polygon mirror 13 toward the photosensitive drum 1030 passes and the number of mirror surfaces through which the light beam traveling from the polygon mirror 13 toward the synchronization detection sensor 18 is two is two. Thereby, when the housing 21 is deformed by heat generated from the polygon mirror 13 during operation, the amount of sub-scanning deviation can be accurately detected even if the tilt angle and position of each synchronization detection mirror change. It becomes. That is, the sub-scanning deviation amount can be detected stably and accurately.

  Then, the CPU 210 determines the applied voltage of the liquid crystal deflecting element 20 so that the obtained sub-scanning deviation amount becomes substantially zero, and applies it to the liquid crystal deflecting element 20 via the liquid crystal element driving circuit 215. Therefore, the sub-scanning deviation amount can be stably reduced.

The synchronous detection sensor 18, due to the provision of a light receiving element having a first light receiving portion 18 ₁ mutual spacing m direction by the position of the s-direction is different from the second light receiving portion 18 _2, facilitate the shift amount Δh Can be detected with high accuracy.

  Further, since the light source 14 has the two-dimensional array 100, a plurality of scans can be performed simultaneously.

  In addition, since the light receiving surface of the synchronization detection sensor 18 is optically substantially parallel to the image surface, the scanning speed on the image surface can be equivalent to the scanning speed on the light receiving surface of the synchronization detection sensor 18. It becomes. Moreover, it can suppress that the reflected light in the light-receiving surface of the synchronous detection sensor 18 arrives at the light source 14 as return light.

  In addition, according to the laser printer 1000 according to the present embodiment, since the optical scanning device 1010 having a small and small amount of sub-scanning deviation is provided, as a result, a high-quality image can be stably formed. .

  Furthermore, since the optical scanning device 1010 includes the light source 14 having the two-dimensional array 100, an image can be formed at high speed. In addition, the density of the formed image can be increased.

  In addition, by connecting the laser printer 1000 to an electronic arithmetic device (computer or the like), an image information communication system (facsimile or the like), etc. via a network, a single image forming apparatus can output from a plurality of devices. An information processing system that can be processed can be formed. In addition, if multiple image forming devices are connected to the network, the status of each image forming device (the degree of job congestion, whether the power is on, whether it is broken, etc.) can be known from each output request. The image forming apparatus having the best state (most suitable for the user's request) can be selected and image formation can be performed.

  In the above-described embodiment, the case where the synchronization detection sensor outputs a signal including main scanning start information and information regarding the shift amount Δh has been described. However, the present invention is not limited to this. For example, when a sensor for detecting the end of main scanning is provided, the sensor may be provided with a function of outputting information related to the shift amount Δh. Further, both the sensor for detecting the start of the main scan and the sensor for detecting the end of the main scan may have a function of outputting information regarding the shift amount Δh. In this case, it is possible to obtain the curve information of the scanning line.

In the above embodiment, the first is the light receiving portion 18 ₁ has been described for the case of rectangular shape, not limited thereto, two sides synchronization detection light beam to pass through in parallel shape s direction I need it.

In the above embodiment, the second light receiving unit 18 _2, the description has been given of the parallelogram, is not limited to this, with respect to two sides m direction in which the light flux for synchronization detection passes And any shape that is inclined.

  Moreover, although the said embodiment demonstrated the case where the light source 14 had 40 light emission parts, it is not limited to this.

  Further, in the above embodiment, instead of the liquid crystal deflecting element 20, a non-parallel plate or a galvano mirror that can be rotated around an axis parallel to a direction corresponding to the sub-scanning direction (here, the Z-axis direction) is used. Also good.

  In the above embodiment, the difference between the number of mirror surfaces through which the light flux from the polygon mirror 13 toward the photosensitive drum 1030 passes and the number of mirror surfaces through which the light flux from the polygon mirror 13 toward the synchronization detection sensor 18 passes is two. However, the present invention is not limited to this. In short, the difference between the number of mirror surfaces through which the light beam from the polygon mirror 13 toward the photosensitive drum 1030 passes and the number of mirror surfaces through which the light beam from the polygon mirror 13 toward the synchronization detection sensor 18 passes is zero or even. It ’s fine.

  In the above-described embodiment, the light beam reflected by the scanning mirror 12c optically disposed closest to the photosensitive drum 1030 among the three scanning mirrors is received by the synchronization detection sensor 18. Although the case where the number of mirror surfaces interposed between the two is two has been described, the present invention is not limited to this. In short, among the plurality of scanning mirrors, the number of mirror surfaces through which the light beam reflected by the scanning mirror optically disposed at the position closest to the photosensitive drum 1030 is received by the synchronization detection sensor 18 is determined. Even number is sufficient.

  In the above embodiment, the case of the laser printer 1000 as the image forming apparatus has been described. However, the present invention is not limited to this. In short, if the image forming apparatus includes the optical scanning device 1010, a high-quality image can be stably formed as a result.

  For example, an image forming apparatus that directly irradiates laser light onto a medium (for example, paper) that develops color with laser light may be used.

  Further, an image forming apparatus using a silver salt film as the image carrier may be used. In this case, a latent image is formed on the silver salt film by optical scanning, and this latent image can be visualized by a process equivalent to a developing process in a normal silver salt photographic process. Then, it can be transferred to photographic paper by a process equivalent to a printing process in a normal silver salt photographic process. Such an image forming apparatus can be implemented as an optical plate making apparatus or an optical drawing apparatus that draws a CT scan image or the like.

  In addition, even an image forming apparatus that forms a multi-color image can stably form a high-quality color image by using an optical scanning device corresponding to the color image.

  For example, as shown in FIG. 20, a printer 2000 corresponding to a color image and including a plurality of photosensitive drums may be used.

  The printer 2000 is a tandem multicolor printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow), and includes an optical scanning device 2010, four photosensitive drums (2030a, 2030b, 2030c, 2030d), 4 charging chargers (2032a, 2032b, 2032c, 2032d), 4 developing rollers (2033a, 2033b, 2033c, 2033d), 4 toner cartridges (2034a, 2034b, 2034c, 2034d) ) Four cleaning cases (2031a, 2031b, 2031c, 2031d), transfer belt 2040, paper feed tray 2060, paper feed roller 2054, registration roller pair 2056, fixing roller 2050, paper discharge tray 2070, paper discharge roller 2 58, the communication control unit 2050, and a printer control unit 2060 for centrally controlling the above units.

  As shown in FIG. 21 and FIG. 22 as an example, the optical scanning device 2010 includes two light source units (2200a, 2200b), two aperture plates (2201a, 2201b), two light beam splitting prisms (2202a, 2202b), polygon mirror 2104, four liquid crystal deflecting elements (2203a, 2203b, 2203c, 2203d), four cylinder lenses (2204a, 2204b, 2204c, 2204d), four fθ lenses (2105a, 2105b, 2105c, 2105d), 8 scanning mirrors (2106a, 2106b, 2106c, 2106d, 2108a, 2108b, 2108c, 2108d), 4 toroidal lenses (2107a, 2107b, 2107c, 2107d), 4 synchronization detection sensors (2205a) , 22 5b, 2205c, 2205d), and a like scan control device (not shown).

  Photosensitive drum 2030a, charging charger 2032a, developing roller 2033a, toner cartridge 2034a, cleaning case 2031a, liquid crystal deflection element 2203a, cylinder lens 2204a, fθ lens 2105a, scanning mirror 2106a, toroidal lens 2107a, scanning mirror 2108a, synchronization detection The sensor 2205a is used as a set and forms an image forming station (hereinafter also referred to as “K station” for convenience) that forms a black image.

  Photosensitive drum 2030b, charging charger 2032b, developing roller 2033b, toner cartridge 2034b, cleaning case 2031b, liquid crystal deflection element 2203b, cylinder lens 2204b, fθ lens 2105b, scanning mirror 2106b, toroidal lens 2107b, scanning mirror 2108b, synchronization detection The sensor 2205b is used as a set and forms an image forming station (hereinafter, also referred to as “C station” for convenience) that forms a cyan image.

  Photosensitive drum 2030c, charging charger 2032c, developing roller 2033c, toner cartridge 2034c, cleaning case 2031c, liquid crystal deflection element 2203c, cylinder lens 2204c, fθ lens 2105c, scanning mirror 2106c, toroidal lens 2107c, scanning mirror 2108c, synchronization detection The sensor 2205c is used as a set and constitutes an image forming station (hereinafter also referred to as “M station” for convenience) that forms a magenta image.

  Photosensitive drum 2030d, charging charger 2032d, developing roller 2033d, toner cartridge 2034d, cleaning case 2031d, liquid crystal deflection element 2203d, cylinder lens 2204d, fθ lens 2105d, scanning mirror 2106d, toroidal lens 2107d, scanning mirror 2108d, synchronization detection The sensor 2205d is used as a set and forms an image forming station (hereinafter, also referred to as “Y station” for convenience) that forms a yellow image.

  Each light source unit has the two-dimensional array 100.

  The light beam emitted from the light source unit 2200a and passing through the opening of the aperture plate 2201a is split into a light beam for the K station and a light beam for the C station by the light beam splitting prism 2202a. The light beam emitted from the light source unit 2200b and having passed through the opening of the aperture plate 2201b is split into a light beam for the M station and a light beam for the Y station by the light beam splitting prism 2202b.

  Each of the synchronization detection sensors is the same sensor as the synchronization detection sensor 18 and is disposed at the same position as the synchronization detection sensor 18 with respect to a surface equivalent to the corresponding image plane, and corresponds to the shift amount Δh. It is used to detect the start of main scanning on the photosensitive drum.

  Similarly to the scanning control device 22, the scanning control device acquires the sub-scanning deviation amount in each photosensitive drum based on the output signal of each synchronization detection sensor. Then, the scanning control device applies a voltage to each liquid crystal deflecting element so that the sub-scanning deviation is substantially zero.

  The scanning control device detects the start of scanning on each photosensitive drum in the same manner as the scanning control device 22.

  Similarly to the scanning control device 22, the scanning control apparatus responds so that the sub-scanning deviation is canceled when the sub-scanning deviation amount is ½ or more of the scanning line interval on the photosensitive drum. Shift image data.

  In this printer 2000, the difference between the number of mirror surfaces through which the light flux from the polygon mirror 2104 goes to each photosensitive drum and the number of mirror surfaces through which the light beam goes from the polygon mirror 2104 to each synchronization detection sensor is zero. . Therefore, the same effect as the above embodiment can be obtained.

  In this printer 2000, an image is formed at a speed four times that of an image forming apparatus having only one photosensitive drum, that is, an image forming apparatus that requires four writing operations corresponding to four colors. It becomes possible.

  In this printer 2000, an optical scanning device may be provided for each color, or may be provided for every two colors.

  As described above, according to the optical scanning device of the present invention, it is suitable for stably detecting the positional deviation in the sub-scanning direction of the light beam condensed on the surface to be scanned. The image forming apparatus of the present invention is suitable for stably forming a high quality image.

It is a figure for demonstrating schematic structure of the laser printer which concerns on one Embodiment of this invention. It is a perspective view which shows schematic structure of the optical scanning device in FIG. It is a top view which shows schematic structure of the optical scanning device in FIG. It is a figure for demonstrating the two-dimensional array of VCSEL contained in the light source in FIG. 5A and 5B are diagrams for explaining the liquid crystal deflecting element in FIG. It is a figure for demonstrating the optical surface shape of the deflector side scanning lens in FIG. It is a figure for demonstrating the optical surface shape of the image surface side scanning lens in FIG. It is a figure for demonstrating the positional relationship of the main optical elements in the optical scanning device of FIG. It is a figure for demonstrating the specific example in FIG. It is a figure for demonstrating the surface substantially parallel to an image surface optically. It is a figure for demonstrating schematic structure of the synchronous detection sensor in FIG. FIGS. 12A to 12D are diagrams for explaining the operation of the synchronization detection sensor of FIG. 11. It is a block diagram for demonstrating the structure of a scanning control apparatus. It is a figure for demonstrating the relationship between subscanning deviation | shift amount and (DELTA) h. FIGS. 15A and 15B are diagrams for explaining the deformation of the housing of the optical scanning device. It is a figure for demonstrating the displacement of the mirror for a synchronous detection by deformation | transformation of a housing. It is a figure for demonstrating the optical path change of the light beam for synchronous detection by the inclination-angle change of the mirror for synchronous detection. It is a figure for demonstrating the optical path change of the light beam for synchronous detection by the position change regarding the Z-axis direction of the mirror for synchronous detection. It is a figure for demonstrating the optical path change of the light beam for synchronous detection by the inclination-angle change when the mirror for synchronous detection is one sheet. It is a figure which shows schematic structure of a tandem color machine. It is a perspective view which shows schematic structure of the optical scanning device in FIG. It is a side view which shows schematic structure of the optical scanning device in FIG.

Explanation of symbols

11a: deflector side scanning lens (part of scanning optical system), 11b: image plane side scanning lens (part of scanning optical system), 12a-12c: scanning mirror (part of scanning optical system), 13 ... Polygon mirror (deflector), 14 ... light source, 18 ... synchronization detection sensor (beam detection sensor), 18 ₁ ... first light receiving part, 18 ₂ ... second light receiving part, 19a ... synchronization detection mirror (of the beam detection optical system) Part), 19b ... synchronization detection mirror (part of beam detection optical system), 20 ... liquid crystal deflection element, 21 ... housing, 22 ... scanning control device (control device), 1000 ... laser printer (image forming device), DESCRIPTION OF SYMBOLS 1010 ... Optical scanning apparatus, 1030 ... Photosensitive drum (image carrier), 1050 ... Communication control apparatus (communication apparatus), 2000 ... Printer (image forming apparatus), 2010 ... Optical scanning apparatus, 2030a, 2030b, 2 030c, 2030d ... photosensitive drum (image carrier), 2050 ... communication control device (communication device), 2104 ... polygon mirror (deflector), 2105a-2105d ... fθ lens (part of scanning optical system), 2106a-2106d ... Scanning mirror (part of scanning optical system), 2107a to 2107d ... Toroidal lens (part of scanning optical system), 2108a to 2108d ... Scanning mirror (part of scanning optical system), 2205a to 2205d ... Synchronization detection Sensor (beam detection sensor).

Claims (13)

An optical scanning device that scans a surface to be scanned in a main scanning direction with a light beam,
With a light source;
A deflector for deflecting a light beam from the light source;
A scanning optical system having at least one mirror surface and condensing the light beam deflected by the deflector onto the surface to be scanned;
A beam detection sensor for detecting a positional shift of a light beam condensed on the surface to be scanned in a sub-scanning direction;
A housing in which each of the light source, the deflector, the scanning optical system, and the beam detection sensor is disposed in a predetermined positional relationship;
The difference between the number of mirror surfaces through which the light beam traveling from the deflector toward the scanned surface passes and the number of mirror surfaces through which the light beam traveling from the deflector toward the beam detection sensor passes is zero or an even number. An optical scanning device. An optical scanning device that scans a surface to be scanned in a main scanning direction with a light beam,
With a light source;
A deflector for deflecting a light beam from the light source;
A scanning optical system having a plurality of mirror surfaces and condensing the light beam deflected by the deflector onto the surface to be scanned;
A beam detection sensor for detecting a positional shift of a light beam condensed on the surface to be scanned in a sub-scanning direction;
A beam detection optical system for guiding a light beam reflected by a mirror surface optically disposed at a position closest to the surface to be scanned among the plurality of mirror surfaces of the scanning optical system to the beam detection sensor;
A housing in which each of the light source, the deflector, the scanning optical system, and the beam detection sensor is disposed in a predetermined positional relationship;
The beam scanning optical system has an even number of mirror surfaces.   The beam detection sensor has a light receiving element having a first light receiving portion and a second light receiving portion in the light receiving surface, in which the distance in the direction corresponding to the main scanning direction differs depending on the position in the direction corresponding to the sub scanning direction. The optical scanning device according to claim 1, comprising:   The optical scanning device according to claim 1, wherein a light receiving surface of the beam detection sensor is optically substantially parallel to an image surface.   5. The optical scanning device according to claim 1, wherein the output signal of the beam detection sensor further includes information on a main scanning start timing. 6.   The apparatus further comprises a correction device that obtains correction information for correcting a positional shift in a sub-scanning direction of a light beam condensed on the surface to be scanned based on an output signal of the beam detection sensor. The optical scanning device according to any one of 1 to 5. A liquid crystal deflecting element that is disposed on an optical path of a light beam from the light source toward the scanned surface and deflects the traveling direction of the incident light beam according to an applied voltage in a plane orthogonal to a direction corresponding to the main scanning direction; ;
The optical scanning device according to claim 6, wherein the correction information is a voltage applied to the liquid crystal deflecting element.   The optical scanning device according to claim 1, wherein the light source includes a plurality of light emitting units arranged two-dimensionally. An image is formed by the scanning on the surface to be scanned,
A control device for controlling each drive signal of the plurality of light emitting units according to image data;
The control device may reduce the misalignment when the misalignment in the sub-scanning direction of the light beam condensed on the scanned surface is 1/2 or more of the scanning line interval on the scanned surface. 9. The optical scanning device according to claim 8, wherein the image data is shifted by one line. The housing has a fastening portion for fastening the housing to another structure,
The optical scanning device according to claim 1, wherein the beam detection sensor is disposed in the vicinity of the fastening portion. At least one image carrier;
An image forming apparatus comprising: at least one optical scanning device according to any one of claims 1 to 10 that scans a light beam including image information with respect to the at least one image carrier.   The image forming apparatus according to claim 11, wherein the image information is multicolor image information.   The image forming apparatus according to claim 11, further comprising a communication device that communicates various information including the image information with an external device via a network.

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