JP3736093B2 - Optical scanning device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning device, and more particularly, deflects light beams from a plurality of light sources along a predetermined direction, and irradiates the scanned surfaces with different incident angles at different incident angles. The present invention relates to an optical scanning device that scans a surface to be scanned with a plurality of light beams.
[0002]
[Prior art]
In recent years, with the spread of computers and higher performance, laser printers, which are output devices, require high-speed and high-resolution printing. In this laser printer, as one means for realizing high-speed printing and high resolution, a technique for increasing the scanning area per unit time by using a plurality of light sources and simultaneously scanning with a plurality of light beams. Is considered.
[0003]
As an optical scanning device provided with a plurality of light sources, Japanese Patent Application Laid-Open No. 63-266418 and Japanese Patent Application Laid-Open No. 5-183698 disclose an optical scanning device that simultaneously scans a surface to be scanned with light beams from a plurality of light sources. In Japanese Patent Laid-Open No. 5-264915, one scanning line is divided into a plurality of light sources, and a plurality of light sources assigned corresponding to the divided scanning line segments are used. An optical scanning device that simultaneously scans a surface to be scanned with a light beam of the above is disclosed.
[0004]
When exposure is performed by an optical scanning device using a plurality of scanning lines or divided scanning lines as described above, it is necessary to maintain the positional relationship between the scanned parts by the light beams from the respective light sources in a desired positional relationship.
[0005]
For this reason, Japanese Patent Application Laid-Open No. 1-183676 discloses a toner image formed by each of a plurality of scanning lines by a CCD, obtains a positional deviation amount of the toner image obtained by the readout, and obtains the obtained positional deviation amount. A technique for controlling the writing start time of each scanning line to correct the above is disclosed.
[0006]
By the way, since the position variation of the photoconductor cylindrical surface, which is the image plane of the scanning line, affects the quality of the printed image, high accuracy is required for mounting the photoconductor. On the other hand, since the photoconductor deteriorates with printing, it is desirable that the photoconductor needs to be easily replaced, and it is desirable that the photoconductor can be easily recovered from a failure such as a paper jam during printing. It is movably attached to the main body.
[0007]
[Problems to be solved by the invention]
However, in the case of an optical scanning device that uses a plurality of light sources and the scanning lines from the light sources are incident on the photosensitive member at different angles, it is possible to maintain a high-quality printed image by maintaining the relative positional relationship of the scanned portion on the photosensitive member. Although it is important to obtain the image quality, the slight change in the position of the photosensitive member described above shifts the scanning position of the scanning line on the photosensitive member, thereby deteriorating the quality of the printed image.
[0008]
Here, the positional deviation of the scanning line caused by the change in the position of the photosensitive member will be described with reference to FIGS. FIG. 2 and FIG. 3 are schematic diagrams of an overfilled split optical scanning device. This overfilled optical scanning device makes convergent light incident on a rotary polygon mirror used in a conventional optical scanning device. Unlike the method, a light beam wider than the split surface of the rotary polygon mirror is incident on the rotary polygon mirror. FIG. 4 shows how light from the light source enters the rotary polygon mirror of the overfilled optical scanning device. As apparent from FIG. 4, since the width R of the incident light beam 114 incident on the rotary polygon mirror 110 is wider than the width W of the split surface of the rotary polygon mirror 110, the light reflected by the rotary polygon mirror 110 is mainly reflected. The adjacent surface light 116 (that is, unnecessary light) reflected by the split surface adjacent to the split surface reflecting the light beam 115 and the principal light beam 115 is formed.
[0009]
Therefore, as shown in FIG. 3, the light deflected by the rotary polygonal mirror 110 is reflected by the folding mirrors 105 and 106 to the photoconductor 107, respectively. However, in order to prevent the adjacent surface light 116 from entering, the folding mirrors 105 and 106 are The folding mirrors 105 and 106 must be installed so that the scanning beams 112 and 113 are incident on the photosensitive member 107 at different angles.
[0010]
The positional deviation of the scanned portion due to the position variation of the photosensitive member on which the two scanning lines are incident at different angles will be described with reference to FIGS. 5C and 5D show the scanning beams 112 and 113 and the scanned portions 117 and 118 when the photosensitive member 107 is in an ideal position. The scanned portions 117 and 118 scanned by the scanning beam 112 and the scanning beam 113 are positioned in the sub-scanning direction so as to form an ideal scanning line 127 that can be regarded as one line segment on the photosensitive member 107. It has been adjusted.
[0011]
FIGS. 5A, 5B, 5E, and 5F show a state where the photoconductor 107 is displaced from this state due to the photoconductor replacement or the like. Among these, FIGS. 5A and 5B show a state in which the optical paths of the scanning scanning beams 112 and 113 become longer due to the position variation of the photoconductor 107. As the optical path becomes longer, the scanned parts 117 and 118 are displaced in the sub-scanning direction and extend in the main scanning direction. On the other hand, FIGS. 5E and 5F show a state in which the optical paths of the scanning scanning beams 112 and 113 are shortened due to the position variation of the photoconductor 107. As the optical path becomes shorter, the scanned parts 117 and 118 are displaced in the sub-scanning direction and contracted in the main scanning direction.
[0012]
The displacement amount Y in the sub-scanning direction of the scanned part will be described with reference to FIG. As shown in FIG. 6, the scanning beams 112 and 113 reflected by the folding mirrors 105 and 106 are adjusted so that the positions in the sub-scanning direction coincide with each other at the ideal photoconductor position 119.
[0013]
However, when the position of the photoconductor changes and the photoconductor 107 moves to the position of the photoconductor 107, the positions of the scanned portions 117 and 118 on the photoconductor 107 by the scanning beams 112 and 113 are shifted in the sub-scanning direction. The deviation Y in the sub-scanning direction of the scanned portion is expressed by the following equation (1) where L is the distance between the folding mirror and the photosensitive member, D is the distance between the folding mirrors, and X is the positional variation amount of the photosensitive member. ).
[0014]
Y = D × X / L (1)
Since only a small area on the surface of the photoconductor is considered, the influence of the curvature of the photoconductor can be ignored.
[0015]
The graph of FIG. 7 shows the characteristics of the positional deviation amount Y of the scanned portion when the photosensitive member position variation amount X is 1 mm (the actual machine tolerance range) according to the equation (1) (note that L = 120 mm, D = 5, 10, 15 mm). As is apparent from FIG. 7, the scanned portion positional deviation amount Y occurs about several dots even when the photosensitive member position variation value X is 1 mm (1 dot = 42 μm at 600 dpi). Then, the scanning line shift occurs due to the positional shift of the scanned portion, which causes a decrease in the print image quality.
[0016]
In the techniques disclosed in Japanese Patent Laid-Open Nos. 63-266418, 5-183698, and 5-264915, the scanning line shift due to the position change of the photosensitive member is not taken into consideration. In the technique disclosed in Japanese Patent Laid-Open No. 1-1836766, it is possible to correct the positional deviation of the scanned portion, but it is necessary to form a toner image for detecting the positional deviation amount before performing the correction. There is a problem that it takes time to start printing.
[0017]
The present invention has been made to solve the above-described problems, and provides an optical scanning apparatus capable of performing high-speed and high-precision optical scanning while shortening the position deviation correction time of the scanned portion. The purpose is to provide.
[0018]
[Means for Solving the Problems]
In order to achieve the above object, an optical scanning device according to claim 1, wherein a plurality of light sources for outputting a light beam, light beams from the plurality of light sources are deflected along a predetermined direction, and orthogonal to the predetermined direction. By irradiating the scanned surface that moves at a predetermined speed in the direction of rotation with the plurality of deflected light beams at different incident angles, the scanned surface is irradiated with the plurality of light beams. Split one main scan line above A scanning means for scanning and the surface to be scanned In the main scan line From the reference position along the normal direction Of the surface to be scanned Based on a detection unit that detects a positional deviation amount, a deviation amount of the scanning position of each light beam according to the positional deviation amount detected by the detection unit, and the predetermined speed, In a direction perpendicular to the predetermined direction. Control means for controlling the irradiation timing of the light beams from the plurality of light sources so as to eliminate the shift amount of the scanning position.
[0020]
In the optical scanning device according to claim 1, the scanning unit deflects the light beams from the plurality of light sources along a predetermined direction (main scanning direction) and has a predetermined speed in a direction orthogonal to the predetermined direction (sub-scanning direction). By irradiating a plurality of deflected light beams at different incident angles onto the surface to be scanned that moves at Split one main scan line above Scan.
[0021]
Here, as the scanning means, for example, a claim 1 As described in the above, it is possible to employ a scanning unit of a divided scanning method in which a single scanning line on a scanned surface is divided and scanned with a plurality of light beams, or a plurality of light beams on a scanned surface. An interlace scanning type scanning unit that simultaneously scans a plurality of scanning lines may be employed.
[0022]
As described above, when the surface to be scanned is scanned with the plurality of light beams by irradiating the moving surface to be scanned with different incident angles, the position of the surface to be scanned is as described above. Main scan line When shifted in the normal line direction, for example, as shown in FIGS. 5B and 5F in the divided scanning method, a shift occurs in one scanning line, and in the interlaced scanning method, the scanning line interval is uneven. End up. Therefore, the detection means is based on the reference position along the normal direction of the surface to be scanned. Of the scanned surface The amount of displacement is detected.
[0023]
As mentioned above, the surface to be scanned In the main scan line When the amount of positional deviation from the reference position along the normal direction is X, this positional deviation amount X has a predetermined relationship with the amount of deviation Y along the sub-scanning direction on the surface to be scanned. For example, in the configuration as shown in FIG. 6, when the distance between the reference position of the surface of the photoconductor 107 as the scanning surface and the folding mirrors 105 and 106 is L, and the distance between the folding mirrors is D, the sub-scanning direction The relationship between the amount of deviation Y and the amount of positional deviation X in the normal direction is expressed by the following equation (1).
[0024]
Y = D × X / L (1)
That is, the surface to be scanned In the main scan line From the amount of positional deviation in the normal direction, the amount of deviation in the sub-scanning direction of the scanning position can be obtained.
[0025]
Therefore, the control unit shifts the scanning position and the predetermined speed so as to eliminate the scanning position shift (shift amount Y in the sub-scanning direction) of each light beam according to the positional shift amount detected by the detection unit. Based on (= moving speed of the surface to be scanned), the irradiation timing of the light beams from the plurality of light sources is controlled.
[0026]
That is, when the position of the surface to be scanned is shifted to the side where the optical path length of the light beam becomes longer as shown in FIG. 5A, irradiation is performed on the downstream side in the moving direction (arrow direction) of the surface to be scanned in FIG. The irradiation timing of the light beam 112 is controlled to be delayed by (scan position deviation amount / predetermined speed).
[0027]
On the other hand, when the position of the surface to be scanned is shifted to the side where the optical path length of the light beam is shortened as shown in FIG. 5E, irradiation is performed downstream in the moving direction (arrow direction) of the surface to be scanned in FIG. The irradiation timing of the light beam 113 is controlled to be delayed by (scanning position shift amount / predetermined speed).
[0028]
As a result, the surface to be scanned In the main scan line It is possible to correct the deviation of the scanning position of each light beam due to the deviation in the normal direction. In addition, according to the first aspect of the present invention, it is not necessary to form a toner image for detecting the amount of misalignment prior to performing the correction, so that the displacement of the scanning position of each light beam can be corrected in a short time. That is, high-speed and high-precision optical scanning can be performed while shortening the correction time for the scanning position deviation.
[0029]
As is apparent from FIGS. 5B and 5F, when a division scanning type scanning unit is employed as the scanning unit, there is a break or a step in one scanning line due to a shift in the scanning position of each light beam. As a result, the scanning performance of the optical scanning device is significantly degraded. For example, when the optical scanning device according to the present invention is applied to the exposure of the image forming apparatus, the image quality of the formed image is significantly reduced.
[0030]
Therefore, the claim 1 As described above, the effect of correcting the shift of the scanning position of each light beam accompanying the positional shift in the normal direction of the surface to be scanned is great. When the optical scanning device is applied to the exposure of the image forming apparatus, the image quality of the formed image can be maintained satisfactorily.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an optical scanning device according to the present invention will be described with reference to the drawings. In the following, an example in which the present invention is applied to an optical scanning device built in an image forming apparatus will be described.
[0032]
[Configuration of Image Forming Apparatus with Built-in Optical Scanning Device]
First, the configuration of an image forming apparatus incorporating the optical scanning device according to the present invention will be described.
[0033]
As shown in FIG. 1, an image forming apparatus 100 incorporating an optical scanning device 150 is provided with two laser diodes (hereinafter referred to as LDs) 103A and 103B that output a light beam, from the LDs 103A and 103B. The surface of the photosensitive drum 107 that rotates at a constant speed in the direction of arrow J is divided and scanned with the light beam.
[0034]
The light beam from the LD 103A passes through a collimator lens and a cylinder lens (not shown), and then enters and deflects on the reflecting surface of the rotary polygon mirror 110. As shown in FIGS. 2 and 3, the deflected light beam 113 passes through the fθ lens 111, is reflected by the folding mirror 106, and is irradiated on the surface of the photosensitive drum 107. The light beam 113 scans the surface of the photosensitive drum 107 along the direction indicated by the arrow H in FIG. 2 by the rotation of the rotary polygonal mirror 110. Actually, the light beam 113 is scanned at the scanning center of one scanning line. It is set to scan the scanned portion R2 from C to the end of scanning.
[0035]
Similarly, the light beam from the LD 103B is transmitted through a collimator lens and a cylinder lens (not shown) and then incident on the reflecting surface of the rotary polygon mirror 110 and deflected. As shown in FIGS. 2 and 3, the deflected light beam 112 passes through the fθ lens 111, is reflected by the folding mirror 105, and is irradiated on the surface of the photosensitive drum 107. The light beam 112 scans the surface of the photosensitive drum 107 along the direction indicated by the arrow H in FIG. 2 by the rotation of the rotating polygonal mirror 110. Actually, the light beam 112 starts scanning one scanning line. It is set to scan the scanned portion R1 from the end to the scanning center C.
[0036]
The optical scanning device 150 has an overfilled configuration, and a light beam 114 having a width R wider than the surface width W of the rotating polygon mirror 110 is incident on the rotating polygon mirror 110 as shown in FIG. For this reason, the unnecessary reflected light 116 is reflected on the adjacent surface together with the regular reflected light 115 (corresponding to the light beams 112 and 113 in FIGS. 1 to 3).
[0037]
In the optical scanning device 150, the folding mirrors 105 and 106 are not arranged on the same straight line in order to avoid unnecessary light reflected by the rotary polygon mirror 110 from being reflected toward the photosensitive drum 107. For this reason, the light beams 112 and 113 are irradiated onto the surface of the photosensitive drum 107 at different incident angles.
[0038]
As shown in FIG. 2, the optical scanning device 150 is provided with a scanning start detection sensor (SOS sensor) 109 for detecting the scanning start timing by the light beam 112, and the light beam 112S at the scanning start position is mirrored. The light is reflected by 130 and enters the SOS sensor 109. When detecting the light beam 112S, the SOS sensor 109 outputs an SOS detection signal to the control unit 102 described later.
[0039]
As shown in FIG. 1, the image forming apparatus 100 is provided with a control unit 102 that is configured by a microcomputer and monitors and controls operations of various components of the image forming apparatus 100. The control unit 102 includes an LD 103A. The LD driver 104A that drives the LD driver 104B and the LD driver 104B that drives the LD 103B are controlled.
[0040]
Further, the control unit 102 includes a display 132 for displaying a processing status and a message to the operator, an operation unit 134 for the operator to input various operation instructions and setting information, digital image data, and a photosensitive drum described later. A misalignment amount detection table 107 and a storage unit 136 storing various control information are connected.
[0041]
Note that the image forming apparatus 100 is provided with devices necessary for the electrophotographic process, such as charging, developing, transferring, fixing, cleaning, and static eliminating devices, not shown.
[0042]
By the way, the optical scanning device 150 is provided with a position detection device 108 for detecting the position of the photosensitive drum 107 along the direction of the arrow P. As an example, as shown in FIG. 11, the position detection device 108 detects a voltage corresponding to the position along the arrow P direction of the photosensitive drum 107 with a voltmeter 108A, and outputs a signal corresponding to the detected voltage value. The potentiometer is configured to output to the control unit 102. In this potentiometer, resistance R, applied voltage V ₀ Is constant, and the voltmeter 108A detects a potential difference between the fixed contact S1 and the moving contact S2 that varies according to the position of the photosensitive drum 107 along the arrow P direction. FIG. 11 is a diagram in which the photosensitive drum 107 and the position detection device 108 are projected in the direction opposite to the arrow Q in FIG.
[0043]
When a signal corresponding to the voltage value detected by the voltmeter 108 </ b> A is input to the control unit 102, the control unit 102 is based on a table for detecting the positional deviation amount of the photosensitive drum 107 stored in the storage unit 136. Then, a positional deviation amount X of the photosensitive drum 107 corresponding to the detected voltage value is detected. The positional deviation amount detection table shows the correspondence between the detected voltage value and the positional deviation amount X from the original position with respect to the position of the photosensitive drum 107 corresponding to the voltage value. Contains information.
[0044]
As described above with reference to FIG. 6, when the normal distance between the surface of the photosensitive drum 107 and the folding mirrors 105 and 106 is L and the distance between the folding mirrors 105 and 106 is D, the surface of the photosensitive drum 107. The displacement amount Y in the sub-scanning direction of the scanned parts 117 and 118 and the positional displacement amount X can be obtained by the following equation (1).
[0045]
Y = D × X / L (1)
Therefore, the control unit 102 (deviation amount Y / line on the surface of the photosensitive drum 107 so as to eliminate the deviation amount Y of the scanned portions 117 and 118 by each light beam according to the detected positional deviation amount X. The image data input start time input to the LD drivers 104A and 104B is controlled so as to delay the light beam irradiation timing from the LDs 103A and 103B by the speed V).
[0046]
In the present embodiment, as shown in FIG. 10, six boundary values L1 to L6 (L6 <L5 <L4 <0 <L3 <L2 <L1) relating to the positional deviation amount X are determined in advance, and the positional deviation amount X Depending on which range between the six boundary values L1 to L6, adjustment processing of light beam irradiation timing set in advance for each range is performed (details will be described later).
[0047]
In addition, let the shift | offset | difference to the arrow P direction of FIG. 1, FIG. 11 be a positive direction. That is, when the position of the photosensitive drum 107 is shifted in the direction of the arrow P (in the case of FIG. 5E), the positional shift amount X is expressed as a positive value, and is shifted in the direction opposite to the arrow P (FIG. 5). In the case of (A), the positional deviation amount X is represented by a negative value.
[0048]
By the way, the positional fluctuation of the photosensitive drum 107 along the arrow Q direction in FIG. 1 hardly causes the scanning line shift due to the positional shift of the scanned portion. For example, FIG. 8 shows the displacement of the distance L between the folding mirror and the photosensitive drum 107 with respect to the diameter of the photosensitive drum 107 when the position variation in the arrow Q direction occurs (however, the distance between the folding mirrors). D is 10 mm, the distance L between the folding mirror and the photosensitive drum 107 at the reference position is 120 mm, and the positional variation X of the photosensitive drum 107 in the direction of arrow Q is 1 mm). As can be seen from FIG. 8, even when the average diameter of the photosensitive drum 107 is 120 mm, the displacement of the distance L is about 10 μm, and the displacement of the scanned portion caused by the displacement of the distance L can be ignored. Amount.
[0049]
Further, the positional fluctuation of the photosensitive drum 107 along the direction perpendicular to the paper surface of FIG. 1 hardly causes the scanning line shift due to the positional shift of the scanned portion.
[0050]
Therefore, a large number of detection means for detecting the position of the photosensitive drum 107 may be arranged so that the three-dimensional position of the photosensitive drum 107 can be accurately detected. It is sufficient to install a position detection device 108 for detecting the position along the line.
[0051]
[Operation of this embodiment]
Next, as an operation of the present embodiment, a control routine related to elimination of the shift amount Y of the scanned parts 117 and 118 executed by the control unit 102 will be described.
[0052]
In step 202 of FIG. 9, as an initialization process, the delay amount of the LD 103A and the delay amount of the LD 103B are each initialized to “0”. In the next step 204, the voltage value detected by the voltmeter 108A of the position detecting device 108 is taken in as a physical quantity corresponding to the surface position of the photosensitive drum 107, and in the next step 206, the photosensitive drum stored in the storage unit 136 is acquired. Based on the position deviation amount detection table 107, a position deviation amount X of the photosensitive drum 107 corresponding to the detected voltage value is detected.
[0053]
In the next steps 208, 210, 212, 214, 216, and 218, it is determined which range (see FIG. 10) the positional deviation amount X is between the six boundary values L1 to L6.
[0054]
When the positional deviation amount X is greater than or equal to the boundary value L1 (when an affirmative determination is made at step 208) and when the positional deviation amount X is less than or equal to the boundary value L6 (when an affirmative determination is made at step 214), it is difficult to adjust the positional deviation. Therefore, the process proceeds to step 230, where a warning message indicating that an error that makes it difficult to adjust the positional deviation has occurred is displayed on the display 132 to warn the operator. Then, the process ends without performing exposure.
[0055]
If the positional deviation amount X is less than the boundary value L1 and greater than or equal to the boundary value L2 (when affirmative determination is made in step 210), the process proceeds to step 220, and the delay amount of the LD 103A is set to 2K.
[0056]
Note that K means a predetermined adjustment unit amount for adjusting the light beam irradiation timing. That is, the delay amount 2K described above is used to eliminate the shift amount Y of the scanned portions 117 and 118 corresponding to the positional shift amount X when the positional shift amount X is less than the boundary value L1 and equal to or larger than the boundary value L2. This corresponds to the delay amount of the LD 103A (= shift amount Y / linear velocity V of the surface of the photosensitive drum 107).
[0057]
If the positional deviation amount X is less than the boundary value L2 and greater than or equal to the boundary value L3 (when an affirmative determination is made in step 212), the process proceeds to step 222, and the delay amount of the LD 103A is set to K. This delay amount K is the delay of the LD 103A for eliminating the displacement amount Y of the scanned parts 117 and 118 according to the positional displacement amount X when the positional displacement amount X is less than the boundary value L2 and greater than or equal to the boundary value L3. This corresponds to the amount (= shift amount Y / linear velocity V of the surface of the photosensitive drum 107).
[0058]
If the positional deviation amount X is greater than the boundary value L6 and less than or equal to the boundary value L5 (if affirmative determination is made in step 216), the process proceeds to step 224, and the delay amount of the LD 103B is set to 2K. This delay amount 2K is the delay amount of the LD 103B for eliminating the shift amount Y of the scanned parts 117 and 118 according to the positional shift amount X when the positional shift amount X is larger than the boundary value and not more than the boundary value L5. (= Shift amount Y / linear velocity V of the surface of the photosensitive drum 107).
[0059]
If the positional deviation amount X is greater than the boundary value L5 and equal to or less than the boundary value L4 (if affirmative determination is made in step 218), the process proceeds to step 226, and the delay amount of the LD 103B is set to K. This delay amount K is the delay of the LD 103B for eliminating the displacement amount Y of the scanned parts 117 and 118 according to the positional deviation amount X when the positional deviation amount X is larger than the boundary value L5 and smaller than or equal to the boundary value L4. This corresponds to the amount (= shift amount Y / linear velocity V of the surface of the photosensitive drum 107).
[0060]
Further, when the positional deviation amount X is larger than the boundary value L4 and smaller than or equal to the boundary value L3 (when a negative determination is made in step 218), the positional deviation can be ignored and the irradiation of the light beam from the LDs 103A and 103B is delayed. The delay amounts of the LDs 103A and 103B are left at the initial set value “0”.
[0061]
In the next step 228, the drive timing of each LD by the LD drivers 104A and 104B is adjusted based on the set delay amount, and modulated based on the digital image data from each LD at the adjusted drive timing. The light beam is output. Here, the delay amount is counted, for example, by counting signals based on the SOS signal from the SOS sensor 109. Thus, exposure based on digital image data is performed.
[0062]
According to the embodiment described above, the irradiation of the light beams from the two LDs is performed so that the positional deviation amount of the surface of the photosensitive drum is detected and the deviation of the scanning position of each light beam corresponding to the positional deviation amount is eliminated. Since the timing is adjusted by (scanning position shift amount L / photosensitive drum 107 surface linear velocity V), the scanning position shift of each light beam can be accurately corrected. Further, since the shift of the scanning position of each light beam can be corrected in a short time without performing the operation of forming a toner image for detecting the shift amount as in the prior art, the time required for the correction operation is shortened. be able to.
[0063]
In addition, since the shift of the scanning position of each light beam can be corrected with high accuracy, the image quality of the image formed by the image forming apparatus 100 can be maintained well.
[0064]
In the above-described embodiment, an example in which the present invention is applied to the division scanning optical scanning device has been described. However, an interlace scanning optical scanning that simultaneously scans a plurality of scanning lines on a surface to be scanned with a plurality of light beams. The present invention can also be applied to an apparatus, and the same effect can be obtained.
[0065]
Further, by applying the optical scanning device according to the present invention to a scanning device that scans a document surface with an optical scanning device and reads the document based on reflected light or transmitted light from the document surface, scanning of the light beam can be performed. The performance can be stabilized, and the reading performance of the reading apparatus can be maintained well.
[0066]
Further, the position detection device 108 of the photosensitive drum 107 is not limited to the potentiometer as described above. For example, the position detection device 108 is in accordance with the distance to the surface of the photosensitive drum 107 or another material surface fixed to the surface of the photosensitive drum 107. A device that outputs a signal may be used. For example, an eddy current displacement meter in which information about distance is output as voltage may be used.
[0067]
【The invention's effect】
As described above, according to the present invention, the positional deviation amount in the normal direction of the surface to be scanned is detected, and the deviation of the scanning position in the sub-scanning direction of each light beam according to the positional deviation amount is eliminated. Since the irradiation timings of the light beams from the plurality of light sources are controlled, the operation of forming a toner image for detecting the displacement amount can be omitted, and the displacement of the scanning position of each light beam can be corrected in a short time.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the invention.
FIG. 2 is a diagram in which an optical scanning device is projected along a sub-scanning direction.
FIG. 3 is a diagram in which an optical scanning device is projected along a main scanning direction.
FIG. 4 is a diagram showing light incident on a rotating polygon mirror and light emitted from the rotating polygon mirror.
5A is a diagram showing a case where the position of the photosensitive drum is shifted in the direction in which the optical path length becomes longer, and FIG. 5B is a diagram showing scanning lines by each light beam in the case of FIG. 5A. (C) is a diagram showing a case where the position of the photosensitive drum is not displaced, (D) is a diagram showing scanning lines by each light beam in the case of (C), and (E) is a diagram. It is a figure which shows the case where the position of the photoconductive drum shifted | deviated to the direction in which an optical path length becomes short, (F) is a figure which shows the scanning line by each light beam in the case of (E).
FIG. 6 is a diagram for explaining a scanning line shift.
FIG. 7 is a graph showing a change in a scanning line shift amount Y with respect to a distance L between a folding mirror and a photosensitive drum.
FIG. 8 is a graph showing a change in a distance L between the folding mirror and the photosensitive drum with respect to the diameter of the photosensitive drum.
FIG. 9 is a flowchart showing a control routine executed by the control unit.
FIG. 10 is a diagram illustrating an LD delay amount set in accordance with a photosensitive drum shift amount X;
FIG. 11 is a diagram illustrating a configuration example of a position detection device.
[Explanation of symbols]
100 Image forming apparatus
102 Control unit
103A, 103B LD
104A, 104B LD driver
107 Photosensitive drum
108 Position detection device
110 Rotating polygon mirror
150 Optical scanning device

Claims (1)

A plurality of light sources for outputting light beams;
Deflecting light beams from the plurality of light sources along a predetermined direction and irradiating the scanned surface moving at a predetermined speed in a direction perpendicular to the predetermined direction with the plurality of deflected light beams at different incident angles; Scanning means for dividing and scanning one main scanning line on the scanned surface with the plurality of light beams,
Detecting means for detecting a positional deviation amount of the scanned surface from a reference position along a normal direction in the main scanning line of the scanned surface ;
Based on the amount of displacement of the scanning position of each light beam according to the amount of displacement detected by the detection means and the predetermined speed, the amount of displacement of the scanning position in the direction orthogonal to the predetermined direction is eliminated. Control means for controlling the irradiation timing of the light beams from the plurality of light sources;
An optical scanning device.

Images