JP3755269B2 - Optical scanning device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning used in an image recording apparatus such as a laser printer or a digital copying machine for recording an image by modulating a laser beam in accordance with image information and performing scanning exposure on a surface to be scanned such as a photosensitive member. More particularly, the present invention relates to an optical scanning apparatus that divides one scanning line on a photosensitive member into two by two light beams and scans simultaneously.
[0002]
[Prior art]
In the conventional general optical scanning device, the surface width of each deflection surface of the rotary polygon mirror is larger than the width of the light beam incident on the rotary polygon mirror as the deflector in the main scanning direction. The surface width of each deflection surface of the mirror is set to a size that can cover the light beam of the incident light beam regardless of the scanning angle. This is called an underfilled type optical scanning device.
[0003]
Incidentally, image recording apparatuses such as laser printers and digital copying machines using such an optical scanning apparatus have recently been required to increase the speed and resolution of image recording. In order to respond to the demand for higher recording speed and higher resolution, it is necessary to increase the number of scanning lines scanned per unit time. In an optical scanning apparatus using a rotating polygon mirror, a scanner motor that drives the rotating polygon mirror The number of revolutions must be increased.
[0004]
However, the rotational speed of the scanner motor for driving the rotary polygon mirror is currently limited to about 15,000 rpm when a ball bearing is used, and is limited to about 40,000 rpm even if an air bearing is used. Therefore, there is a limit to increasing the speed and resolution of image recording by increasing the rotational speed of the rotary polygon mirror.
[0005]
In addition, in order to perform high-definition image writing, it is necessary to reduce the beam diameter of the light beam that scans on the photosensitive member. However, when a laser is used as the light source, the image is formed due to the focusing characteristics of the laser beam. In order to reduce the beam diameter at the position, the beam diameter incident on the imaging optical system must be increased. Therefore, in order to perform high-definition image writing with an optical scanning device using a rotating polygon mirror, the optical beam is rotated so that a large-diameter light beam does not protrude from the mirror surface of the rotating polygon mirror for all scanning angles. The polygon mirror had to be enlarged. In other words, when trying to realize high-speed and high-quality image writing with a conventional underfilled optical scanning device, it is necessary to rotate a large-diameter rotary polygon mirror at high speed, increasing power consumption and increasing the load on the scanner motor. This causes a problem of deterioration in reliability.
[0006]
Here, to suppress the number of rotations of the scanner motor, it is conceivable to increase the number of mirror surfaces of the rotary polygon mirror. However, as the number of mirror surfaces increases, the deflection angle decreases, which is necessary for writing images of the same size. Since the optical path length becomes long, another problem that the apparatus becomes large arises.
[0007]
As an apparatus for solving these problems, an optical apparatus described in Japanese Patent Application No. 08-338636 is known. In this patent application specification, an overfilled beam in which light beams respectively emitted from two light sources are simultaneously deflected by the same plane of a deflector, and the scanned surface is divided and scanned by the two deflected beams. A type optical scanning device is disclosed.
[0008]
Here, the divided scanning means that light beams respectively emitted from two light sources are simultaneously deflected by the same plane of the deflector, and the scanning lines on the photosensitive member are divided and scanned by the two deflected beams. That is. According to this divided scanning, the scanning angle for each scanning line can be divided into small portions, so that the image recording can be performed at a high speed, and the optical path length from the light source to the photoconductor as the scanned surface is one light source. Since it becomes 1/2 of the optical path length in the case of scanning, it has the feature which suppresses the enlargement of an apparatus.
[0009]
An overfilled optical scanning device is a laser beam that is wider than the surface width of the mirror surface (deflection surface) of the rotating polygon mirror. It is characterized in that one mirror surface is used to cut off the incident beam.
[0010]
That is, by making the optical scanning device an overfilled type optical scanning device, it becomes possible to reduce the diameter of the rotary polygon mirror.
[0011]
[Problems to be solved by the invention]
However, in the scanning optical device disclosed in Japanese Patent Application No. 08-338636, the light beams emitted from the two light sources are simultaneously deflected by the same plane of the deflector, and the two light beams deflected on the surface to be scanned. In the overfilled type optical scanning apparatus that scans by dividing the first light beam, only the writing position of the first light beam is detected, and after a predetermined time has elapsed, the scanning of the two light beams is started. When the angle incident on the polygon mirror is deviated, or when it is adjusted to be deviated, the images at the joints overlap, or the image at the joints is separated, resulting in a blank part at the joints. appear.
[0012]
Here, the image shift at the joint portion of the surface to be scanned that occurs in the overfilled type optical scanning device that performs the division scanning with the two light beams described above will be described with reference to FIGS. 9 to 11. In these figures, an SOS (SOS) that detects the first light beam outside the image area on the path of the first light beam deflected outside the image area on the scanning line by the rotary polygon mirror 110 and passed through the fθ lens 112. A Start of scan) sensor 114 is arranged. After a predetermined time has elapsed from the time when the output signal of the SOS sensor 114 is detected, scanning of the first and second light beams emitted from the two light sources based on the image information is started. Here, the scanning angles of the first and second light beams are ± 2α with respect to the center line CL indicating the center of the scanning range, respectively, and in FIGS. The incident direction of the light beam is the brass direction. When the scanning angle is ± 2α, the incident angle of the first light beam with respect to the center line CL of the incident optical axis is −α, and the incident angle of the second light beam with respect to the center line CL of the incident optical axis is + α. . While the rotary polygonal mirror 110 is rotated by an angle α in the direction of the arrow, the first light beam is deflected from the scanning start end (SOS) to the center line CL by the one deflecting surface, and at the same time, the second light beam. Is deflected from the center line CL to the end of scanning (EOS). As a result, one scanning line on the photosensitive member 118 is simultaneously scanned in two.
[0013]
Reference numeral 116 denotes a cylinder mirror, 118 denotes a photosensitive member serving as a scanning surface, and 120a, 120b, and 122 denote plane mirrors.
[0014]
FIG. 9 shows a state in which the angles at which the first light beam and the second light beam are incident on the rotating polygon mirror 110 are as designed. In this case, when the scanning of the first and second light beams emitted from the two light sources based on the image information is started after a predetermined time has elapsed from the time when the output signal of the SOS sensor 114 is detected, the photosensitive member 118 is used. There is no shift in the image at the joint on the scanned surface.
[0015]
FIG. 10 shows a case where the angle at which the second light beam enters the rotary polygon mirror 110 is smaller than the state shown in FIG. 9 by a minute angle s °, and the time point when the output signal of the SOS sensor 114 is detected. When the first and second light beams emitted from the two light sources are started based on the image information after a lapse of a predetermined time, the joints on the surface to be scanned of the photosensitive member 118 as shown in FIG. The problem of overlapping images occurs.
[0016]
FIG. 11 shows a case where the angle at which the second light beam is incident on the rotary polygon mirror 110 is larger than the state shown in FIG. 9 by a minute angle s °, and the time point when the output signal of the SOS sensor ll4 is detected. When the first and second light beams emitted from the two light sources are started based on the image information after a predetermined time has elapsed, the joint portion on the surface to be scanned of the photosensitive member 118 is illustrated as shown in the figure. The problem arises that the image is separated and a blank portion occurs.
[0017]
That is, in the case of a divided optical scanning device in which two light beams emitted from two light sources are incident on the same deflection surface of the rotary polygon mirror and simultaneously scan, the scanning range of one scanning line is divided into two and the scanning is performed. Since it is shared by the two light beams, it is important to synchronize and align the scanning at the joint.
1 In order to solve the above problem, as shown in FIG. 12, a method of detecting a light beam immediately before each scanning line image area shared by the first light beam and the second light beam is generally considered. .
[0018]
However, if an optical path for detecting the writing position of the second light beam that opens the scanning from the middle of one scanning line is ensured and separated, the folding mirror 126 for detecting the writing position of the second light beam is provided. There is a problem that it is difficult to synchronize / align the scanning at the joint portion because it is necessary to provide it within the image area of the first light beam and the folding mirror 126 interferes with the first beam.
[0019]
In particular, when the overfilled optical system technique is used, it is more difficult to secure and separate the optical path because of the high duty.
[0020]
Here, the duty is the length from the maximum scanning length, that is, the SOS sensor 11 arranged at an equivalent position on the photosensitive member to the SOS sensor 11 arranged at the equivalent position on the photosensitive member by the next scanning. The ratio of the image area to the height.
[0021]
In the conventional underfilled type optical scanning device, the light beam incident on the SOS sensor is separated from the image area, so that the duty must be suppressed to about 80% or less. However, in the overfilled type optical scanning device, the duty can be set to 90% or more.
[0022]
A method of detecting a light beam immediately after an image area (scanning range) on the EOS (End of Scan) (scanning end) side is also known. In this method, separation from the scanning line image area is easy, but the purpose is to detect image magnification and registration. To use it for detecting the writing position of the beam, it is just after the image area. If the main scanning plane (deflection plane) of the mirror is the N plane, it is necessary to store video data up to the amount scanned by the (N-1) plane of the rotary polygon mirror that will be the main scanning plane next. There is.
[0023]
The present invention has been made in view of such circumstances. When two light beams are incident on the same deflection surface of a rotary polygon mirror and one scanning line is divided and simultaneously scanned, the joint of the scanning lines is formed. It is an object of the present invention to provide an optical scanning device capable of forming a portion well.
[0024]
[Means for Solving the Problems]
In order to achieve the above object, the first aspect of the present invention provides a first light beam and a second light beam having a plurality of deflection surfaces, respectively incident from two light sources and converged over the plurality of deflection surfaces. In the optical scanning apparatus, the scanning surface is divided and scanned so that one scanning line is recorded by the two deflected beams simultaneously with the same deflection surface serving as the main scanning surface. The writing position on the scanned surface of the image data by the second light beam that starts scanning in the middle of the full width of the main scanning line on the scanning surface is reflected from the deflection surface adjacent to the main scanning surface of the rotary polygon mirror. And a writing position detecting means for detecting the reflected light of the second light beam, and a writing operation on the surface to be scanned of the image data by the second light beam is controlled based on a detection output of the writing position detecting means. System And having a means.
[0025]
In the optical scanning device having the above-described configuration, the first and second light beams respectively incident from the two light sources and converged over the plurality of deflection surfaces of the rotary polygon mirror are simultaneously deflected by the same deflection surface of the rotary polygon mirror. Then, the scanning surface is divided and scanned so that one scanning line is recorded by the two deflected beams.
[0026]
The writing position detection means sets the writing position on the scanned surface of the image data by the second light beam that starts scanning from the middle of the full width of the main scanning line on the scanned surface on the main scanning surface of the rotary polygon mirror. Detection is performed by detecting reflected light of the second light beam reflected from the adjacent deflecting surface.
[0027]
The control means controls the writing operation on the surface to be scanned of the image data by the second light beam based on the detection output of the writing position detecting means.
[0028]
Therefore, according to the first aspect of the present invention, it is easy to secure and separate an optical path for detecting the writing position of the image data by the second light beam on the surface to be scanned. The synchronization and alignment of scanning at the joint portion can be performed with high accuracy.
[0029]
According to the second aspect of the present invention, the first and second light beams that have a plurality of deflection surfaces and are respectively incident from two light sources and converged over the plurality of deflection surfaces are the same as the main scanning surface. In an optical scanning apparatus that divides and scans a surface to be scanned so that one scanning line is recorded by the two beams deflected simultaneously by the deflection surface, the full width of the main scanning line on the surface to be scanned The writing position on the surface to be scanned of the image data by the second light beam that starts scanning in the middle of the rotation becomes the main scanning surface next to the current main scanning surface of the rotating polygon mirror as the rotating polygon mirror rotates. A writing position detecting means for detecting the reflected light of the second light beam reflected from the deflection surface adjacent to the current main scanning surface, and the second light beam based on the detection output of the writing position detecting means. Of image data Serial and having a control means for controlling the write operation on the scanned surface.
[0030]
In the optical scanning device having the above configuration, the first and second light beams incident from the two light sources and converged over the plurality of deflection surfaces of the rotary polygon mirror are simultaneously deflected by the same deflection surface as the main scanning surface. Then, the scanning lines on the scanning surface are divided and scanned so that one scanning line is recorded by the two deflected beams.
[0031]
The writing position detecting means detects the writing position on the scanned surface of the image data by the second light beam that starts scanning from the middle of the full width of the main scanning line on the scanned surface as the rotating polygon mirror rotates. This is detected by detecting the reflected light of the second light beam reflected from the deflection surface adjacent to the current main scanning surface which becomes the main scanning surface next to the current main scanning surface.
[0032]
The control means controls the writing operation on the scanned surface of the image data by the second light beam based on the detection output of the writing position detecting means.
[0033]
Therefore, according to the second aspect of the present invention, it is easy to secure and separate an optical path for detecting the writing position of the image data by the second light beam on the surface to be scanned. The synchronization and alignment of scanning at the joint portion can be performed with high accuracy.
[0034]
In addition, since the waiting time from the synchronous detection of the image data writing position to the start of the image data writing operation is only the time required for the deflection surface of the rotary polygon mirror to rotate by one surface, an expensive memory having a large storage capacity can be used. There is no need to accumulate data.
[0040]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0041]
FIG. 1 shows the configuration of an optical scanning device according to the first embodiment of the present invention. In the figure, two light source units for emitting a scanning light beam are respectively arranged at positions that are symmetrical with respect to a center line CL indicating the center of the scanning range. Each of the two light source units includes semiconductor lasers 10a and 10b that emit light beams having a substantially Gaussian distribution. In the present embodiment, the light beam emitted from the semiconductor laser 10a is a first light beam, and the light beam emitted from the semiconductor laser 10b is a second light beam. A collimator lens 12a having an action of making light beams having substantially different divergence angles in the vertical and horizontal directions from the focal position of the semiconductor lasers 10a and 10b in the light source unit to make the light beams substantially parallel light; 12b, beam shaping slits 14a and 14b that allow only the central light beam to pass therethrough, and cylinder lenses 16a and 16b for converging the incident light beam in the sub-scanning direction in the vicinity of the deflection surface of the rotary polygon mirror described later are disposed. ing.
[0042]
The semiconductor lasers 10a and 10b are connected to a control unit (not shown), and the control unit controls the light beam outputs of the semiconductor lasers 10a and 10b to be modulated based on image information.
[0043]
Further, the collimator lenses 12a and 12b are disposed at positions where the distance between the semiconductor lasers 10a and 10b is approximately 1 mm shorter than the focal length of the collimator lenses 12a and 12b, and this arrangement allows the collimator lenses 12a and 12b to pass through. The light beam thus obtained is not divergent light but becomes loose divergent light.
[0044]
Further, planar mirrors 18a and 18b for reflecting the emitted light beam are respectively disposed at positions symmetrical with respect to the center line CL at the extension of the cylinder lenses 16a and 16b on the light beam emission side. Then, on the reflection side of the plane mirrors 18a and 18b, a regular polygonal column having a plurality of deflecting surfaces (mirror surfaces) with the same surface width is formed on the side surface, and in the direction of the arrow by a driving means (not shown) around the central axis. A rotating polygon mirror 20 that rotates at an equiangular speed is provided. The rotary polygon mirror 20 is disposed at a position where the center line CL passes through the central axis.
[0045]
Further, between the plane mirrors 18a and 18b and the rotary polygon mirror 20, an fθ lens 22 composed of a double lens having a lens power only in the main scanning direction is arranged so that its optical axis coincides with the center line CL. ing. In the case of an overfilled type optical system, the fθ lens 22 is a long and narrow elongated first light beam and second light beam reflected by the plane mirrors 18 a and 18 b wider than the surface width of the rotary polygon mirror 20. It converges in the sub-scanning direction as a line image. At this time, the first light beam and the second light beam are incident so that their centers reach the same deflection surface of the rotary polygon mirror 6. Thus, the first and second light beams converge so as to cross a plurality of deflection surfaces.
[0046]
Further, the fθ lens 22 is arranged so that the light beam deflected by the rotary polygon mirror 20 passes through the fθ lens 22 again, and converges the light beam that has passed again as a light spot on the photoreceptor 34 described later. The light spot has a function of moving the light spot on the photosensitive member 34 at a substantially constant speed in the main scanning direction.
[0047]
Further, on the opposite side of the rotary polygon mirror 20 from the side where the fθ lens 22 is disposed, in order to correct a positional deviation in the sub-scanning direction caused by variations in the inclination of the deflection surface of the rotary polygon mirror 20 in the sub-scanning direction. Cylinder mirrors 32a and 32b are arranged. The first and second light beams for image recording deflected by the rotary polygon mirror 20 are reflected by the cylinder mirrors 32a and 32b, and then light is incident on the photosensitive member 34 disposed below the cylinder mirrors 32a and 32b. It converges as a spot. .
[0048]
The photosensitive member 34 has an elongated cylindrical shape in which a photosensitive material sensitive to a light beam is applied on the surface thereof, and is arranged so that the main scanning direction coincides with the longitudinal direction of the photosensitive member 34. Yes. That is, the light spot converged on the photosensitive member 34 along with the rotation direction of the rotary polygon mirror 20 moves along the main scanning direction, and image recording on the scanning line becomes possible.
[0049]
The photosensitive member 34 is rotated at a constant rotational speed by a driving unit (not shown) around the rotation axis, and the scanning lines on the photosensitive member 34 are sequentially moved in the sub-scanning direction. The deflection corresponding to the image recording of one scanning line by the rotary polygon mirror 20 is performed by one deflection surface.
[0050]
Further, on the l-th light beam path deflected by the main scanning surface before starting image recording on one scanning line and re-passing through the fθ lens 22, the flat mirror 26a that turns back the l-th light beam before starting image recording. A cylinder lens 28 for forming a beam in the sub-scanning direction and an SOS sensor 30 for detecting the l-th light beam before the start of image recording are arranged.
[0051]
Further, the second light that has been deflected by the next adjacent surface (the deflection surface that becomes the main scanning surface) of the rotary polygon mirror 20 and re-passed through the fθ lens 22 before the start of image recording on one scanning line. On the beam path, a flat mirror 26b that turns back the second light beam before the start of image recording, a cylinder lens 28 that focuses the beam in the sub-scanning direction, and an SOS sensor that detects the second light beam before the start of image recording. 30 is arranged.
[0052]
In this case, the SOS sensor 30 and the cylinder lens 28 for detecting the writing position of the image data of the first light beam and the second light beam before the start of image recording are the same, but for each beam separately. May be provided.
[0053]
The detection output of the SOS sensor 30 is input to the writing position detection circuit 50. The writing position detection circuit 50 determines the writing position on the photosensitive member 34 by the first light beam and the second light beam from the detection output of the SOS sensor 30. A reference synchronization signal is output to the control circuit 60.
[0054]
With the above configuration, the first light beam and the second light beam before the start of image recording can be detected without blocking the light beam in the image area.
[0055]
FIG. 2 shows specific parameters and behavior of each light beam when the first light beam and the second light beam enter the SOS sensor 30.
[0056]
As for the set value of the optical system, the number of surfaces of the rotary polygon mirror 20 is 24, the angle between the center line CL and the first light beam incident on the rotary polygon mirror 20 and the second light beam is 12.8 °, The angle formed by the main scanning plane and the center line CL when the first light beam is incident on the SOS sensor 30 (FIG. 1) is 27.2 °. At this time, it can be seen that the reflected light on the next adjacent surface of the second light beam forms 31.6 ° with the center line and goes toward the outside of the image area. These light beams pass through an fθ lens 22 (FIG. 1) (not shown), and then are reflected by plane mirrors 26a and 26b (FIG. 1) to form a beam lens in the sub-scanning direction (FIG. 1). ) Is incident on the SOS sensor 30.
[0057]
Next, FIG. 3 shows the configuration of a writing position detection circuit for detecting the writing position of image data on the photosensitive member 34 by the first and second light beams emitted by the semiconductor lasers 10a and 10b in FIG. In the figure, the writing position detection circuit 50 separates the detection output S1 of the SOS sensor 30 by the first light beam and the detection output S2 of the SOS sensor 30 by the second light beam from the detection output of the SOS sensor 30. Flip-flop (F / F) 52, an OR gate 54 that takes the logical sum of the Q output of the flip-flop (F / F) 52 and the detection output of the SOS sensor 30, and an inverter 56 that inverts the output of the OR gate 54 And an OR gate 58 that takes the logical sum of the output of the inverter 56 and the detection output of the SOS sensor 30. The SOS sensor 30 and the writing position detection circuit 50 correspond to writing position detection means of the present invention.
[0058]
Reference numeral 60 denotes a control circuit which takes in the detection outputs S1 and S2 of the writing position detection circuit 50, and controls the image data writing operation on the photoconductor 34 which is the surface to be scanned based on these detection outputs S1 and S2. The control circuit 60 corresponds to the control means of the present invention.
[0059]
In the optical scanning apparatus shown in FIG. 1, since there is one SOS sensor 30, the first light beam SOS detection signal S1 and the second light beam SOS detection signal S1 for detecting the writing position of the image data by the first light beam are used. It is necessary to separate the SOS detection signal S2 of the second light beam for detecting the writing position of the image data by the light beam in order to distinguish. In the present embodiment, the first light beam and the second light beam are changed in advance by changing the DUTY of the first light beam and the second light beam, or by adjusting the angle of the mirror that turns the light toward the SOS sensor 30. The time difference in which the light beam enters the SOS sensor 30 is provided.
[0060]
Next, the operation of the writing position detection circuit 50 will be described with reference to the timing chart of FIG. The detection output (FIG. 4C) of the SOS sensor 30 by the first and second light beams emitted by the semiconductor lasers 10a and 10b is input to one input terminal of the flip-flop 52 and the OR gates 54 and 58. .
[0061]
The Q output of the flip-flop 52 (FIG. 4D) and the detection output of the SOS sensor 30 are ORed by the OR gate 54, and the OR output (FIG. 4E) is the SOS of the second light beam. The detection signal S2 is output to the control circuit 60. Here, the logical sum of the Q output of the flip-flop 52 and the detection output of the SOS sensor 30 is determined by the light beam with the earlier incident timing of the first and second light beams input to the SOS sensor 30. This is because the detection output of the SOS sensor 30 is taken out. In the present embodiment, the detection output of the SOS sensor 30 by the second light beam can be taken out.
[0062]
The output of the OR gate 54 is inverted by the inverter 56. The output of the inverter 56 (FIG. 4F) is logically ORed with the detection output of the SOS sensor 30 by the OR gate 58, and the detection output S1 of the SOS sensor 30 by the first light beam is detected (FIG. 4 (FIG. 4 (F)). G)), and is output to the control circuit 60. Here, the logical sum of the output of the inverter 56 and the detection output of the SOS sensor 30 is obtained by a signal obtained by inverting the detection output of the SOS sensor 30 by the light beam with the earlier timing incident on the SOS sensor 30 by the inverter 56. This is because the detection output of the SOS sensor 30 by the light beam with the later timing incident on the SOS sensor 30 is taken out by taking the logical sum of the detection outputs of the SOS sensor 30. In the present embodiment, the detection output of the SOS sensor 30 by the lth light beam can be taken out.
[0063]
If the writing position detection circuit 50 shown in FIG. 3 is used, even if the first light beam and the second light beam are incident on one SOS sensor 30, the detection output of the SOS sensor 30 for each light beam is output. It is possible to separate.
[0064]
In addition, in order to accurately connect the scanning lines by the first and second light beams, it is necessary to detect and scan the writing position of the image data by the reflected light on the same deflection surface of the rotary polygon mirror. This is because if the division accuracy according to the number of deflection surfaces of the rotary polygon mirror 20 is not obtained, the error will appear in the reflected light on the adjacent surface of the main scanning surface. The time chart of FIG. 4 is premised on scanning on the same deflection surface as described above.
[0065]
Image data writing timing is shown in FIGS. As for the image data VDATA A written by the first light beam, the image data 1A, 2A, 3A,... Are sequentially written on the photosensitive member 34 after a predetermined time has elapsed since the detection output S1 of the SOS sensor 30 was detected (FIG. 5). 4 (A)).
[0066]
On the other hand, the image data VDATA B written by the second light beam is output at the next timing from when the detection output S2 of the SOS sensor 30 is detected until the image data is output. S2 is required (FIG. 4B). That is, the image data 1B, 2B,... Are written on the photosensitive member 34 sequentially each time the detection output S2 of the two SOS sensors 30 is detected. In order to write the image data VDATA B every time the detection output S2 of one 6OS sensor 30 is detected, separate SOS sensors are provided for the first and second light beams, and the second light This can be realized by separating the detection output of the beam SOS sensor into two systems.
[0067]
Next, another configuration example of the writing position detection circuit is shown in FIG. In the figure, a writing position detection circuit 50 ′ takes in the detection output of the SOS sensor B74 that detects the writing position of the image data by the second light beam, and outputs a counter 76 delayed for a fixed time, A flip-flop 78 and OR gates 80 and 82 are provided. Note that the writing position detection circuit 50 ′ outputs the detection output of the SOS sensor A 72 for detecting the writing position by the first light beam as it is to the control circuit 60 described later. The SOS sensor A72, the SOS sensor B74, and the writing position detection circuit 50 'correspond to writing position detection means of the present invention.
[0068]
Reference numeral 60 denotes a control circuit which takes in the detection outputs SA, SB1 and SB2 of the writing position detection circuit 50 ', and based on these detection outputs SA, SB1 and SB2, the first and the first on the photosensitive member 34 which is the surface to be scanned. The writing operation of the light beam image data 2 is controlled. The control circuit 60 corresponds to the control means of the present invention as in the case of FIG.
[0069]
Next, the operation of the write position detection circuit 50 ′ will be described with reference to FIG. The detection output of the SOS sensor B 74 (FIG. 6C) is input to one input terminal of the counter 76 and the OR gates 80 and 82. In the counter 76, an inverted signal (FIG. 6D) obtained by delaying the detection output of the SOS sensor B 74 by a fixed time shorter than the output timing interval is output to the flip-flop 78. Then, the OR gates 80 and 82 logically OR the Q output (FIG. 6E) and Q ′ output (FIG. 6F) of the flip-flop 78 with the detection output of the SOS sensor B74, respectively. 80, the detection output SB1 of the odd order of the SOS sensor B74 (FIG. 6G) and the detection output SB2 of the even order of the SOS sensor B74 from the OR gate 82 (FIG. 6H) are the control circuit. 60.
[0070]
The control circuit 60 sequentially writes the odd-order image data 1B, 3B,... Based on the detection output SB1, and the odd-order image data 2B, 4B,.
[0071]
As described above, according to the writing position detection circuit 50 ′ shown in FIG. 5, the detection output of the SOS sensor B74 for the second light beam is separated into two systems, as shown in FIGS. 6 (A) and 6 (B). Unlike the writing position detection circuit 50 shown in FIG. 3, the image data is output without receiving the next SOS sensor detection signal, unlike the writing position detection circuit 50 shown in FIG. 3, after receiving the detection signal of the SOS sensor. Can be written.
[0072]
As described above, according to the first embodiment of the present invention, it is easy to secure and separate the optical path for detecting the writing position on the scanned surface of the image data by the second light beam, Scanning synchronization and alignment at the joints of the scanning lines can be performed with high accuracy.
[0073]
Next, FIG. 7 shows a configuration of an optical scanning device according to the second embodiment of the present invention. The optical scanning device according to the present embodiment differs from the optical scanning device according to the first embodiment in configuration in that the light beam reflected by the next adjacent surface of the rotary polygon mirror 20 in FIG. 22 is configured such that an image is formed on the light receiving surface of the SOS sensor 30 by the imaging optical system 90 disposed outside the left of the fθ lens 22, that is, outside the image area, without passing through the lens 22 again.
[0074]
The imaging optical system 90 has lens power in both the main and sub scanning directions, and is constituted by a lens or a mirror, and the number of components is not limited. However, since it has lens power in the main scanning direction, it is desirable to block light beams that deviate from the incident angle on the light receiving surface of the SOS sensor 30 by the light blocking member.
[0075]
Next, the configuration of an optical scanning device according to the third embodiment of the present invention is shown in FIG. The optical scanning apparatus according to the present embodiment differs from the optical scanning apparatus according to the first embodiment in configuration in that the beam reflected by the front adjacent surface of the rotary polygon mirror 22 in FIG. The image is formed on the light receiving surface of the SOS sensor 30 by the imaging optical system 90 disposed outside the right side of the fθ lens 22, that is, outside the image area. The imaging optical system 90 has lens power in both the main and sub scanning directions, and is constituted by a lens or a mirror, and the number of components is not limited. However, since it has lens power in the main scanning direction, it is desirable to block light beams that deviate from the incident angle on the light receiving surface of the SOS sensor 30 by the light blocking member.
[0076]
Also, the output time point of the detection output of the SOS sensor, which is a writing position detection signal of image data on the scanned surface by the first light beam, and the SOS, which is a writing position detection signal of image data on the scanned surface by the second light beam. An average value is obtained from time difference data corresponding to the number of surfaces of the rotary polygon mirror 20 with respect to the output point of the detection output of the sensor, and an image writing position by the second light beam is calculated from the average value. One SOS sensor may be used for the first and second light beams, or may be provided separately for the first and second light beams.
[0077]
According to the second and third embodiments, as in the first embodiment, the image quality at the joint portion of the scanning line can be improved, and the joint portion can be formed satisfactorily.
[0078]
【The invention's effect】
According to the present invention, in an overfilled type optical system that performs division scanning, a light beam having a width of at least three faces is incident on the deflector, so that the reflected light from the deflecting surface adjacent to the main scanning surface of the rotary polygon mirror is used. Since synchronization can be established, it is easy to secure and separate an optical path for detecting the writing position of image data on the surface to be scanned, and it is possible to improve the synchronization and alignment accuracy of the joint portion.
[0079]
Further, the reflected light from the deflection surface adjacent to the main scanning surface of the rotary polygon mirror, which has conventionally been unnecessary, can be effectively used for synchronization detection.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a configuration of an optical scanning device according to a first embodiment of the invention.
FIG. 2 is an explanatory diagram showing a state when a first light beam and a second light beam are incident on an SOS sensor in the optical scanning device shown in FIG. 1;
3 is a block diagram showing a configuration example of a writing position detection circuit in the optical scanning device shown in FIG. 1. FIG.
4 is a timing chart showing an operation state of the writing position detection circuit shown in FIG. 3;
5 is a block diagram showing another configuration example of a writing position detection circuit in the optical scanning device shown in FIG.
6 is a timing chart showing an operation state of the writing position detection circuit shown in FIG. 5;
7A and 7B are a plan view and a side view showing a configuration of an optical scanning device according to a second embodiment of the invention.
FIGS. 8A and 8B are a plan view and a side view showing a configuration of an optical scanning device according to a third embodiment of the invention. FIGS.
FIG. 9 is an explanatory diagram illustrating an example of a state of divided scanning by two light beams on a surface to be scanned of a conventional optical scanning device.
FIG. 10 is an explanatory diagram showing another example of a state of divided scanning by two light beams on a surface to be scanned of a conventional optical scanning device.
FIG. 11 is an explanatory diagram showing still another example of a state of divided scanning by two light beams on a surface to be scanned of a conventional optical scanning device.
FIG. 12 is an explanatory diagram showing a state of divided scanning by two light beams when the writing position is detected by the SOS sensor for each of the two light beams in the conventional optical scanning device.
[Explanation of symbols]
10a, 10b Semiconductor laser
12a, 12b Collimator lens
14a, 14b Slit
16a, 16b cylinder lens
18a, 18b Flat mirror
20 rotating polygon mirror
22 fθ lens
24 Flat mirror
26a, 26b Flat mirror
28 Cylinder lens
30 SOS sensor (writing position detection means)
32a, 32b Cylinder mirror
34 Photoconductor (scanned surface)
50, 50 'writing position detection circuit (writing position detection means)
60 Control circuit (control means)

Claims (2)

The first and second light beams that have a plurality of deflection surfaces and are respectively incident from two light sources and converged over the plurality of deflection surfaces are simultaneously deflected and deflected by the same deflection surface as the main scanning surface. In the optical scanning device that divides and scans the surface to be scanned so that one scanning line is recorded by the two beams,
The writing position on the scanned surface of the image data by the second light beam that starts scanning in the middle of the full width of the main scanning line on the scanned surface is reflected from the deflection surface adjacent to the main scanning surface of the rotary polygon mirror. Writing position detecting means for detecting by detecting the reflected light of the second light beam,
Control means for controlling the writing operation on the scanned surface of the image data by the second light beam based on the detection output of the writing position detecting means;
An optical scanning device comprising: The first and second light beams that have a plurality of deflection surfaces and are respectively incident from two light sources and converged over the plurality of deflection surfaces are simultaneously deflected and deflected by the same deflection surface as the main scanning surface. In the optical scanning device that divides and scans the surface to be scanned so that one scanning line is recorded by the two beams,
The writing position on the scanned surface of the image data by the second light beam that starts scanning in the middle of the full width of the main scanning line on the scanned surface is the current main position of the rotating polygon mirror as the rotating polygon mirror is rotated. A writing position detecting means for detecting by detecting the reflected light of the second light beam reflected from the deflection surface adjacent to the current main scanning surface which becomes the main scanning surface next to the scanning surface;
Control means for controlling the writing operation on the scanned surface of the image data by the second light beam based on the detection output of the writing position detecting means;
An optical scanning device comprising:

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