JP2007028509A - Scan line pitch interval adjusting method and multi-beam scanning optical device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scan line pitch interval adjusting method and multi-beam scanning optical device using the same, wherein a scan line pitch interval is unified to a predetermined value, the occurrence of pitch non-uniformity or color slippage is suppressed and a high-quality image can be formed. <P>SOLUTION: A deflection means 5 deflects a plurality of light flux emitted from light emitting points of a light source means 1 including three or more light emitting points disposed linearly separately at predetermined intervals, an optical image forming system 6 guides the plurality of light flux deflected by the deflection means onto a plane 8 to be scanned and when scanning the plane to be scanned in a main scan direction using the plurality of light flux through the deflecting operation of the deflection means, a measuring means 9 measures an interval of two scan lines which are separated most in a sub scan direction, among a plurality of scan lines scanning the plane to be scanned. Based on a result of the measurement, scan line pitch intervals in the sub scan direction are adjusted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a scanning line pitch interval adjusting method and a multi-beam scanning optical apparatus using the same, and is suitable for an electrophotographic apparatus such as a laser beam printer, a digital copying machine, and a digital FAX.

  In recent years, in an electrophotographic apparatus such as a laser beam printer, a multi-beam scanning optical apparatus for simultaneously writing a plurality of lines using a plurality of laser beams (light beams) has been developed in order to cope with high speed and high definition.

  A scanning optical device used in such a laser beam printer is required to be capable of high-speed scanning by increasing the speed and definition of the laser beam printer. In particular, there is a growing demand for a multi-beam scanning optical apparatus capable of simultaneously scanning a plurality of light beams due to limitations on the number and size of polygon mirrors.

  Also, due to the demand for higher speed and higher definition of laser beam printers, the scanning line pitch interval in the sub-scanning direction, which was about 42 μm at 600 DPI resolution, is narrowed to about 21 μm at 1200 DPI and about 10.5 μm at 2400 DPI. The accuracy required by the is becoming stricter.

  FIG. 9 is a schematic view of a main part of a conventional multi-beam scanning optical apparatus.

  In the figure, a plurality (two) of divergent light beams emitted independently modulated from a multi-beam semiconductor laser 91 as a light source means are converted into parallel light beams by a collimator lens 92, and the light beam (light quantity) is limited by a diaphragm 93. The light enters the cylindrical lens 94. Of the parallel light beams incident on the cylindrical lens 94, the light beams are emitted as they are in the main scanning plane. In the sub-scanning plane, the light beam is focused and formed as a substantially linear image on a deflection surface (reflection surface) 95a of an optical deflector 95 composed of a rotating polygon mirror (polygon mirror). A plurality of light beams deflected and reflected by the deflecting surface 95a of the optical deflector 95 are passed through imaging optical systems (fθ lens systems) 96 having fθ characteristics to different regions on the photosensitive drum surface 98 as a scanning surface. By guiding the light and rotating the optical deflector 95 in the direction of arrow A, the photosensitive drum surface 98 is simultaneously scanned with a plurality of light beams in the direction of arrow B (main scanning direction) to record image information. ing.

  FIG. 10 is a schematic diagram of a main part of a conventional multi-beam semiconductor laser unit 900.

  In the figure, a multi-beam semiconductor laser unit 900 includes a semiconductor laser light source 902, a holder 903, and a lens barrel 905 in which a collimator lens 904 is built. The semiconductor laser light source 902 is fixed to a holder 903 by press-fitting or bonding, and the holder 903 is bonded and fixed to a lens barrel 905 in which a collimator lens 904 is built. The multi-beam semiconductor laser unit 900 is temporarily fixed to the press-fitting hole 907 of the optical box 906 by press-fitting. Thereafter, adjustment of the scanning line pitch interval in the sub-scanning direction is performed by rotating the multi-beam semiconductor laser unit 900 in the BB ′ direction. The rotation adjustment in the BB ′ direction is performed by fitting the rotation adjustment pin 911 provided in the rotation adjustment jig 910 into the rotation adjustment hole 909 provided in the holder 903, so that the rotation adjustment jig is used. The rotation adjustment is completed, and the rotation adjustment is completed when a pitch interval corresponding to a predetermined resolution is reached.

  FIG. 11 is a layout diagram of light emitting points of the conventional multi-beam semiconductor laser unit 900 shown in FIG. In the figure, the same elements as those shown in FIG. In the figure, 801 and 802 are light emission points.

  FIG. 12 is an enlarged view of the photosensitive drum surface 98 as the surface to be scanned in FIG. 9, and illustrates a conventional measurement position of the scanning line pitch interval in the sub-scanning direction. In the figure, the same elements as those shown in FIG.

  In the same figure, reference numerals 811 and 812 denote scanning lines when the surface to be scanned 98 is scanned (formed) by light beams emitted from the light emitting points 801 and 802 in FIG.

  Various multi-beam scanning optical devices for adjusting the scanning line pitch interval in the sub-scanning direction have been proposed (see Patent Document 1).

  In detecting the pitch interval in the scanning line pitch interval measurement, as shown in FIG. 13, the output is continuous and wide in range with respect to the passing position change in the direction orthogonal to the scanning direction of the laser beam (light beam). When the changing sensor pattern S1 is used, the output value of the first beam passing through the sensor pattern S1 is first stored in the memory, and when the second beam passes through the sensor pattern S1 and the output is output. A method of detecting the relative distance of the scanning interval by taking a difference from the output value of the first beam stored in the memory and comparing it with a predetermined value is used. In the figure, reference numerals 811, 812, and 813 denote scanning lines when the surface to be scanned is scanned with light beams emitted from the corresponding light emitting points.

Conventionally, when a resolution of 600 dpi is desired, the interval L between a pair of adjacent scanning lines indicated by the black arrows in FIG. 12 is detected and measured as described above so that the scanning line pitch interval is about 42 μm. The multi-beam semiconductor laser unit 900 is rotated and adjusted in the BB ′ direction of FIG. When the scanning line pitch interval is larger than 42 μm, the multi-beam semiconductor laser unit 900 is rotated in the direction B in FIG. 11, and when the scanning line pitch interval is smaller than 42 μm, the multi-beam semiconductor laser unit 900 is moved to B ′ of FIG. By rotating in the direction, a desired scanning line pitch interval can be obtained.
JP 2000-180745 A

  However, when the pitch interval adjustment is performed by rotating the multi-beam semiconductor laser unit 900 as in the above-described conventional example, there is a limit to the measurement accuracy of the scanning line pitch interval measurement. There is a problem that it becomes impossible to meet the demand for refinement.

  The present invention unifies scanning line pitch intervals to a predetermined value, and suppresses the occurrence of pitch unevenness and color misregistration and can form a high-quality image, and a multi-beam scanning optical apparatus using the same The purpose is to provide.

The scanning line pitch interval adjusting method according to the invention of claim 1 comprises:
A plurality of light beams emitted from each light emitting point of a light source unit having three or more light emitting points arranged linearly at a predetermined interval are deflected by the deflecting unit, and the plurality of light beams deflected by the deflecting unit Is guided onto the surface to be scanned by the imaging optical system, and the surface to be scanned is scanned in the main scanning direction with a plurality of light beams by the deflection operation of the deflecting means.
Among the plurality of scanning lines that scan the surface to be scanned, the distance between two scanning lines that are the farthest in the sub-scanning direction is measured by the measuring means, and the scanning line pitch interval in the sub-scanning direction is adjusted based on the result. It is characterized by doing.

The scanning line pitch interval adjusting method of the invention of claim 2
A sequence of light emitting points in which n (n is an integer of 3 or more) light emitting points are linearly arranged at a predetermined interval, and m (m is an integer of 2 or more) is arranged in a direction orthogonal to the straight line. The plurality of light beams emitted from the light source means are deflected by the deflecting means, the plurality of light beams deflected by the deflecting means are guided onto the surface to be scanned by the imaging optical system, and the deflecting operation of the deflecting means When scanning the surface to be scanned in the main scanning direction with a plurality of light beams,
Among the plurality of scanning lines that scan the surface to be scanned, the distance between two scanning lines that are the farthest in the sub-scanning direction is measured by the measuring means, and the scanning line pitch interval in the sub-scanning direction is adjusted based on the result. It is characterized by doing.

The scanning line pitch interval adjusting method according to the invention of claim 3 comprises:
A sequence of light emitting points in which n (n is an integer of 3 or more) light emitting points are linearly arranged at a predetermined interval, and m (m is an integer of 2 or more) is arranged in a direction orthogonal to the straight line. The plurality of light beams emitted from the light source means are deflected by the deflecting means, the plurality of light beams deflected by the deflecting means are guided onto the surface to be scanned by the imaging optical system, and the deflecting operation of the deflecting means When scanning the surface to be scanned in the main scanning direction with a plurality of light beams,
A first step of measuring a distance between two scanning lines farthest in the sub-scanning direction among a plurality of scanning lines scanning the surface to be scanned by a measuring unit;
Among the n scanning lines when the surface to be scanned is scanned with n light beams emitted from n light emitting points in the i-th column (i = 1, 2,..., m−1). Thus, the scanning line closest to the n scanning lines when the surface to be scanned is scanned with the n light beams emitted from the n light emitting points in the i + 1 column and the n light emission in the i + 1 column. Of the n scanning lines when scanning the surface to be scanned with n light beams emitted from a point, the n light beams emitted from n light emitting points in the i-th column are scanned with the light beam. A second step of measuring the distance from the scanning line closest to the n scanning lines when scanning on the surface with the measuring means,
The scanning line pitch interval in the sub-scanning direction is adjusted based on the measurement results in the first and second steps.

The invention of claim 4 is the invention of claim 1, 2 or 3,
The interval between the two most distant scanning lines is measured at at least two points within the effective scanning width, and the scanning line pitch interval is adjusted based on the result.

The invention of claim 5 is the invention of any one of claims 1 to 4,
On the surface to be scanned, the distance between two scanning lines that are most separated in the sub-scanning direction is L (mm), the number of scanning lines is Pn, and the pixel density in the sub-scanning direction on the surface to be scanned is A (dot / inch) over the entire scanning effective width,
2/3 × (Pn−1) × 25.4 / A <L <4/3 × (Pn−1) × 25.4 / A
However, Pn = n × m
The scanning line pitch interval is adjusted so as to satisfy the above.

The invention of claim 6 is the invention of claim 5,
The pixel density A is 1200 dpi or more.

The invention of claim 7 is the invention of claim 2 or 3,
On the surface to be scanned, an interval between two scanning lines that are most separated in the sub-scanning direction is L (mm), and an imaging point that draws the first scanning line at the same time is adjacent to the first scanning line. The angle formed between the second scanning line and the straight line connecting the two scanning lines and the imaging point is θ, and the imaging point drawing the first scanning line at the same time is adjacent to the first scanning line. When the length of the straight line connecting the image forming point that draws the scanning line is a,
0.9L / (mn-1) <(L-am (n-1) sin θ) / (m-1) <1.1L / (mn-1)
The scanning line pitch interval is adjusted to satisfy the above.

The invention of claim 8 is the invention of any one of claims 1 to 7,
A scanning line pitch interval adjustment is performed by rotating the light source means around the optical axis with the center of a line segment connecting two light emitting points farthest apart as a rotation center.

The multi-beam scanning optical device according to claim 9 is provided.
A sequence of light emitting points in which n (n is an integer of 3 or more) light emitting points are linearly arranged at a predetermined interval, and m (m is an integer of 2 or more) is arranged in a direction orthogonal to the straight line. A surface-emitting light source means, a deflecting means for deflecting a plurality of light beams emitted from the light source means, and an imaging optical system for imaging the plurality of light beams deflected by the deflecting means on the surface to be scanned; A multi-beam scanning optical apparatus that scans the scanned surface with a plurality of light beams in the main scanning direction by a deflection operation of the deflecting unit.
Among the plurality of scanning lines that scan on the surface to be scanned, an interval between two scanning lines that are most separated in the sub-scanning direction;
Among the n scanning lines when the surface to be scanned is scanned with n light beams emitted from n light emitting points in the i-th column (i = 1, 2,..., m−1). Thus, the scanning line closest to the n scanning lines when the surface to be scanned is scanned with the n light beams emitted from the n light emitting points in the i + 1 column and the n light emission in the i + 1 column. Of the n scanning lines when scanning the surface to be scanned with n light beams emitted from a point, the n light beams emitted from n light emitting points in the i-th column are scanned with the light beam. Measuring means for measuring the distance from the scanning line closest to the n scanning lines when scanning on the surface;
It has an adjusting means for adjusting the scanning line pitch interval in the sub-scanning direction based on the measurement result of the measuring means.

The invention of claim 10 is the invention of claim 9,
The adjustment means sets the interval between the two scanning lines that are most separated in the sub-scanning direction to L (mm) on the surface to be scanned, the imaging point that draws the first scanning line at the same time, and the first scanning The angle formed by the second scanning line and the straight line connecting the second scanning line adjacent to the line and the second scanning line is θ, and the imaging point and the first scanning line depicting the first scanning line at the same time And the length of the straight line connecting the image forming point that draws the second scanning line adjacent to the second scanning line,
0.9L / (mn-1) <(L-am (n-1) sin θ) / (m-1) <1.1L / (mn-1)
The scanning line pitch interval is adjusted so as to satisfy the above.

An image forming apparatus according to an eleventh aspect of the present invention comprises:
11. The multi-beam scanning optical device according to claim 9 or 10, a photoconductor disposed on the surface to be scanned, and electrostatic formed on the photoconductor by a light beam scanned by the multi-beam scanning optical device. The image forming apparatus includes a developing device that develops a latent image as a toner image, a transfer device that transfers the developed toner image onto a transfer material, and a fixing device that fixes the transferred toner image onto the transfer material. .

An image forming apparatus according to the invention of claim 12
A multi-beam scanning optical apparatus according to claim 9 or 10, and a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the multi-beam scanning optical apparatus. Yes.

The color image forming apparatus of the invention of claim 13
Each of the plurality of image carriers is arranged on a surface to be scanned of the multi-beam scanning optical apparatus according to claim 9 or 10 and forms a plurality of different color images.

The invention of claim 14 is the invention of claim 13,
It has a printer controller that converts color signals input from an external device into image data of different colors and inputs them to each multi-beam scanning optical device.

  According to the present invention, the distance between two scanning lines that are the farthest apart among a plurality of scanning lines when scanning the surface to be scanned with a plurality of light beams emitted from a plurality of light emitting points of the light source means is measured. By adjusting the scanning line pitch interval in the sub-scanning direction based on the result, the scanning line pitch interval can be unified to a predetermined value, and the occurrence of pitch unevenness and color misregistration can be suppressed to form a high quality image. A scanning line pitch interval adjusting method and a multi-beam scanning optical apparatus using the same can be achieved.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic diagram of a main part of a multi-beam scanning optical apparatus according to Embodiment 1 of the present invention.

  In the following description, the main scanning direction is a direction perpendicular to the rotation axis of the rotating polygon mirror and the optical axis of the imaging optical system (the direction in which the light beam is reflected and deflected (deflected and scanned) by the rotating polygon mirror). The sub-scanning direction is a direction parallel to the rotation axis of the rotary polygon mirror. The main scanning section is a plane including the main scanning direction and the optical axis of the imaging optical system. The sub-scanning section is a section perpendicular to the main scanning section.

  In the figure, reference numeral 1 denotes a light source means having three light emitting points (light emitting portions) that can be independently modulated and arranged linearly at predetermined intervals (for example, equal intervals). It consists of a beam semiconductor laser. Note that the number of light emitting points may be three or more.

  A light beam conversion element (collimator lens) 2 converts a light beam emitted from the light source means 1 into a parallel light beam (or a divergent light beam or a convergent light beam). Reference numeral 3 denotes an aperture stop which shapes the beam shape by limiting the passing light flux. An optical system (cylindrical lens) 4 has a predetermined power (refractive power) only in the sub-scanning direction, and deflects a light beam that has passed through the aperture stop 3 by an optical deflector 5 to be described later in the sub-scan section. A substantially linear image is formed on the surface (reflection surface) 5a.

  Each element such as the collimator lens 2, the aperture stop 3, and the cylindrical lens 4 constitutes one element of the incident optical means LA. Further, the cylindrical lens 4 and the collimator lens 2 may be constituted by one optical element (anamorphic lens).

  An optical deflector 5 as a deflecting means is composed of, for example, a six-sided polygon mirror (rotating polygon mirror), and is rotated at a constant speed in the direction of arrow A in the figure by a driving means (not shown) such as a motor. ing.

  Reference numeral 6 denotes an imaging optical system (fθ lens system) having a condensing function and an fθ characteristic. The imaging optical system 6 includes an aspheric toric lens (imaging lens) formed of a single plastic material, and is reflected by the optical deflector 5. A light beam based on the deflected image information is imaged on the photosensitive drum surface 8 as a surface to be scanned, and the deflection surface 5a of the optical deflector 5 and the photosensitive drum surface 7 are in a conjugate relationship in the sub-scan section. By doing so, compensation for falling down is performed.

  Reference numeral 8 denotes a photosensitive drum surface as a surface to be scanned.

  Reference numeral 9 denotes a measuring device (sensor) as a measuring means. When the surface to be scanned 8 is scanned in the main scanning direction with a plurality of light beams by the deflection operation of the optical deflector 5, a plurality of scans for scanning the surface to be scanned 8 are performed. Among the lines, the distance between two scanning lines that are the most spaced apart in the sub-scanning direction is measured. Reference numeral 10 denotes an adjusting unit which adjusts the scanning line pitch interval in the sub-scanning direction based on the result measured by the measuring unit 9.

  The surface shape of the refractive surface of the imaging lens 6 in the present embodiment is expressed by the following shape expression. The intersection of the optical surface and the optical axis is the origin, the optical axis direction is the X axis, the axis orthogonal to the optical axis in the main scanning section is the Y axis, and the axis orthogonal to the optical axis in the sub-scanning section is the Z axis. When the bus direction corresponding to the main scanning direction is

(Where R is the radius of curvature, and K, B ₄ , B ₆ , B ₈ , and B ₁₀ are aspheric coefficients) and corresponds to the sub-scanning direction (including the optical axis and perpendicular to the main scanning direction). Child line direction is

It can be expressed. Where r ′ = r0 (1 + D ₂ Y ² + D ₄ Y ⁴ + D ₆ Y ⁶ + D ₈ Y ⁸ + D ₁₀ Y ¹⁰ )
(However, r0 is the sagittal curvature radius on the optical _{axis, D 2, D 4, D} 6, D 8, D 10 are coefficients)
S is a child line shape defined in a plane perpendicular to the main scanning section including the normal line of the bus bar at each position in the bus bar direction.

  In this expression, the order in the surface shape expression is limited. However, the scope of the present embodiment does not limit this, and the higher the order, the greater the degree of design freedom and the smaller the aberration. Needless to say. If the surface shape expression itself is an expression having the same degree of freedom of surface expression, the effect of this embodiment can be obtained without any problem.

  The imaging lens 6 in this embodiment is composed of a single lens having anamorphic surfaces on both sides, and the first surface (incident surface) is an aspherical surface and a second surface (with the convex surface facing the deflector side) in the main scanning surface ( The exit surface is a circular arc with a convex surface facing the surface to be scanned. Within the sub-scanning surface, the first surface is a flat surface, the second surface is a circular arc with the convex surface facing the surface to be scanned, and its curvature is a lens. In the effective part of the head, it is continuously changed from on-axis to off-axis.

  In this embodiment, the three light beams emitted from the light source means 1 are converted into parallel light beams by the collimator lens 2, and the light beam (light amount) is limited by the diaphragm 3 and is incident on the cylindrical lens 4. Of the two parallel light beams incident on the cylindrical lens 4, the parallel light beams are emitted as they are in the main scanning section. In the sub-scan section, the light beam is converged and formed on the deflection surface 5a of the optical deflector 5 as a substantially line image (a line image that is long in the main scanning direction). The three light beams deflected and reflected by the deflecting surface of the optical deflector 5 are guided to different regions on the photosensitive drum surface 8 via the imaging lens 6 having different refractive powers in the main scanning direction and the sub-scanning direction. By rotating the light deflector 5 in the direction of arrow A, the photosensitive drum surface 8 is simultaneously scanned in the direction of arrow B (main scanning direction) with three light beams. As a result, an image is recorded on the photosensitive drum surface 18 as a recording medium.

  FIG. 2 is a schematic view of the main part of a multi-beam semiconductor laser unit 200 as light source means in the present embodiment.

  A multi-beam semiconductor laser unit 200 shown in FIG. 1 includes a semiconductor laser light source 202, a holder 203, and a lens barrel 205 in which a collimator lens 204 is built. The semiconductor laser light source 202 is fixed to a holder 203 by press-fitting or bonding, and the holder 203 is bonded and fixed to a lens barrel 205 in which a collimator lens 204 is built. The multi-beam semiconductor laser unit 200 is temporarily fixed to the press-fitting hole 207 of the optical box 206 by press-fitting. Thereafter, the scanning line pitch interval in the sub-scanning direction is adjusted by rotating the multi-beam semiconductor laser unit 200 in the B-B ′ direction. The rotation adjustment in the BB ′ direction is performed by fitting the rotation adjustment pin 211 provided in the rotation adjustment jig 210 into the rotation adjustment hole 209 provided in the holder 203, and The rotation adjustment is completed, and the rotation adjustment is completed when a pitch interval corresponding to a predetermined resolution is reached.

  Next, a method of adjusting the scanning line pitch interval scanned by three light beams emitted from the multi-beam semiconductor laser unit 200 having three light emitting points, which is a feature of the present embodiment, to suppress the adjustment error to be small will be described. To do.

  FIG. 3 is a diagram showing the arrangement of the three light emitting points 301, 302, and 303 included in the multi-beam semiconductor laser unit 200 in this embodiment. In the figure, the same elements as those shown in FIG.

  As shown in the figure, the multi-beam semiconductor laser unit 200 in this embodiment has three light emitting points 301, 302, and 303, and the three light emitting points 301, 302, and 303 are respectively set at predetermined intervals in the main scanning direction and the sub-scanning direction. For example, they are arranged at regular intervals.

  In the detection of the pitch interval in the scanning line pitch interval measurement, the output changes continuously and over a wide range with respect to the passing position change in the direction orthogonal to the scanning direction of the laser beam, which is the known method shown in FIG. When the sensor pattern S1 is used, the output value of the first beam passing through the sensor pattern S1 is first stored in the memory, and when the second beam passes through the sensor pattern S1 and the output is output, A method of detecting the relative distance of the scanning interval by taking a difference from the output value of the first beam stored in the memory and comparing it with a predetermined value is used. The scanning line pitch interval detection method is not limited to the above method, and other methods may be used within the scope of the gist.

  FIG. 4 is an explanatory diagram of the scanning line pitch interval measurement location in this embodiment.

  In the figure, reference numerals 311, 312, and 313 denote scanning lines when the surface to be scanned 8 is scanned (formed) by light beams emitted from the light emitting points 301, 302, and 303, respectively.

  For example, the scanning line pitch interval of the three scanning lines when the scanning surface 8 is scanned with the three light beams emitted from the three light emitting points 301, 302, and 303 included in the multi-beam semiconductor laser unit 200 used as the light source means is, for example, In order to adjust to 21 μm corresponding to a pixel density (resolution) of 1200 dpi, the interval between the three scanning lines is measured with a measuring instrument.

  The measurement method is performed near the center and both ends of the effective scanning area, and the scanning line pitch interval is adjusted based on the result.

  Conventionally, when adjusting the pitch interval by rotating the multi-beam semiconductor laser unit, the interval between adjacent scanning lines among the scanning lines scanned by a plurality of light beams emitted from a plurality of light emitting points is measured. Adjustments were made based on

  However, since there is a limit to the measurement accuracy of the scanning line pitch interval measuring device, even if the adjustment as described above is performed, it becomes impossible to meet the demand for higher speed and higher definition of the laser beam printer.

  Therefore, in this embodiment, as shown by the black arrows in FIG. 4, the three scanning lines 311, 312 and 313 are the most separated when the scanning surface 8 is scanned with the three light beams emitted from the three light emitting points 301, 302 and 303. The distance L between the two scanning lines 311 and 313 is measured by the measuring means 9 at at least two places within the effective scanning width, and the scanning line pitch interval in the sub-scanning direction is adjusted by the adjusting means 10 based on the result. .

  Here, if the measurement accuracy of the scanning line pitch interval measuring device is ± 2 μm, the adjustment error of the most separated scanning line pitch interval is ± 2 μm. If the number of scanning lines is Pn, the pitch interval adjustment of each adjacent scanning line is adjusted. The error is ± 2 μm / (Pn−1), and the error can be reduced as compared with the conventional case. In this embodiment, since the number of scanning lines is three, the scanning line pitch interval adjustment error is conventionally about ± 4 μm, whereas in this embodiment, it can be suppressed to about ± 1 μm. From this, it can be seen that the present embodiment is more effective as the number of scanning lines increases.

In this embodiment, on the surface to be scanned, the distance between the two scanning lines that are most separated in the sub-scanning direction is L (mm), the number of scanning lines is Pn, and the pixel density in the sub-scanning direction on the surface to be scanned is When A (dot / inch) is assumed,
2/3 × (Pn−1) × 25.4 / A <L <4/3 × (Pn−1) × 25.4 / A
... (3)
The scanning line pitch interval is adjusted to satisfy the above. However, Pn = n × m
In this embodiment, the pixel density (resolution) A in the sub-scanning direction on the surface to be scanned is 1200 dpi or more.

  More preferably, the conditional expression (3) should be set as follows.

5/6 × (Pn−1) × 25.4 / A <L <7/6 × (Pn−1) × 25.4 / A
... (3a)
In this embodiment, in order to obtain a pixel density of 1200 dpi in the sub-scanning direction, the desired scanning line pitch interval is about 21 μm, and the interval between the two most separated scanning lines is within 42 ± 14 μm, that is, the scanning line pitch interval is If it is 21 ± 7 μm, the scanning line spacing is practically acceptable.

  When the interval between the three scanning lines 311, 312 and 313 when the surface 8 is scanned with the three light beams emitted from the respective light emitting points 301, 302 and 303 is larger than 21 μm, multiple lines are formed in the direction indicated by the arrow B in FIG. When the distance between the three scanning lines 311, 312 and 313 when the beam semiconductor laser unit 200 is rotated and the surface 8 to be scanned is scanned with three light beams emitted from the light emitting points 301, 302 and 303 is smaller than 21 μm, The multi-beam semiconductor laser unit 200 is rotated in the B ′ direction to adjust the interval.

  Note that the rotation center of the multi-beam semiconductor laser unit 200 is the center of a line segment that connects two light emitting points 301 and 303 that are the farthest apart. The scanning line pitch interval in the sub-scanning direction is adjusted by rotating around the optical axis with the center of this line segment as the rotation center.

  In this embodiment, the distance between two scanning lines that are the farthest among the scanning lines scanned by the three light beams emitted from the multi-beam semiconductor laser unit 200 is measured near the center of the effective scanning area and at both ends. The scanning line pitch interval is adjusted based on the result. However, the present invention is not limited to this. For example, the scanning line pitch interval may be measured at at least two points within the effective scanning width, and the measurement values may be averaged. As a result, the measurement accuracy is further improved, so that the scanning line pitch interval within the effective scanning width can be kept more uniform.

  In this embodiment, as described above, when the pitch interval of the three scanning lines is adjusted to a desired value, as shown in FIG. 4, the two light beams emitted from the two light emitting points 301 and 303 farthest away from each other are used. The pitch interval L between the two scanning lines 311 and 313 when the scanning surface 8 is scanned is measured, and the adjustment by the rotation of the multi-beam semiconductor laser unit 200 is performed based on the result. With this method of measuring the pitch interval of the scanning lines, in this embodiment, it is possible to reduce the adjustment error when adjusting the pitch interval. As a result, it is possible to unify the scanning line interval to a predetermined value and suppress the occurrence of pitch unevenness and color misregistration to form a high-quality image.

  In this embodiment, the edge-emitting multi-beam semiconductor laser is used as the light source means. However, the present invention is not limited to this. For example, a surface-emitting multi-beam semiconductor laser may be used. When a surface-emitting type multi-beam semiconductor laser is used, all light emitting points can be brought close to the optical axis, so that optical aberration can be reduced.

  In this embodiment, the imaging optical system is composed of an aspheric toric lens formed of a single plastic material. However, the number of lenses is not limited to the number of materials, and the number of lenses may be two or more. A molded glass lens may be used. In this embodiment, in particular, a plastic lens may be formed by providing a diffraction grating surface on at least one surface of the imaging optical system in order to compensate for the focus movement at the time of remarkable environmental fluctuation. It goes without saying that the adjustment error of the pitch interval can be similarly reduced according to the adjustment method of this embodiment.

  As described above, in this embodiment, when the multi-beam semiconductor laser unit 200 is used as the light source means as described above, and the surface to be scanned 8 is scanned with a plurality of light beams emitted from the light emitting points of the multi-beam semiconductor laser unit 200. By measuring the distance between the two scanning lines that are the farthest among the plurality of scanning lines, and adjusting the scanning line pitch interval in the sub-scanning direction based on the result, the pitch interval adjustment error can be reduced more than in the conventional case. It is possible to reduce. Thus, in this embodiment, it is possible to suppress the occurrence of pitch unevenness and color misregistration and form a high quality image.

  FIG. 5 is an arrangement diagram of the light emitting points of the light source means having a plurality of light emitting points according to the second embodiment of the present invention, and FIG. 6 is an explanatory diagram of the scanning line pitch interval measurement points in the second embodiment of the present invention.

  The present embodiment is different from the above-described first embodiment in that the light source means 11 is composed of a surface-emitting type multi-beam semiconductor laser unit having m × n light emitting points constituted by an m × n matrix. Other configurations and optical actions are substantially the same as those in the first embodiment, and the same effects are obtained.

  That is, in FIG. 5, 11 is a light source means, and a light emitting point sequence in which n (n is an integer of 3 or more and n = 3 in this embodiment) light emitting points are linearly arranged at predetermined intervals. It consists of a surface emitting type multi-beam semiconductor laser unit arranged in m (m is an integer of 2 or more and m = 2 in this embodiment) rows at a predetermined interval in a direction orthogonal to the straight line.

  This multi-beam semiconductor laser unit 11 has two light emitting point rows in which three light emitting points are arranged in a straight line at equal intervals, and has six light emitting points 401 and 402 configured in a 3 × 2 matrix. , 403, 404, 405, and 406. In FIG. 6, reference numerals 411, 412, 413, 414, 415, and 416 denote scanning lines when the surface to be scanned 8 is scanned (formed) by light beams emitted from the light emitting points 401, 402, 403, 404, 405, and 406, respectively. It is.

  In the present embodiment, when the surface to be scanned 8 is scanned with six light beams emitted from the six light emitting points 401, 402, 403, 404, 405, and 406 included in the light source means 11 as in the first embodiment. Among the six scanning lines 411, 412, 413, 414, 415, and 416, the distance L between the two scanning lines 411 and 416 that are the farthest apart as shown by the black arrows in FIG. Based on the result, the scanning line pitch interval in the sub-scanning direction is adjusted by the adjusting means (first step).

  Further, in this embodiment, not only the distance between the two most separated scanning lines 411 and 416 is measured, but three light beams emitted from the first light emitting point row as shown by the white arrows in FIG. Of the three scanning lines 411, 412, and 413 when the scanning surface 8 is scanned by the three scanning lines when the scanning surface 8 is scanned by the three light beams emitted from the second light emitting point sequence. The scanning line 413 close to the lines 414, 415, and 416 and the light emitting point in the first row among the three scanning lines 414, 415, and 416 when the surface to be scanned 8 is scanned by three light beams emitted from the second light emitting point row The distance H between the scanning lines 414 close to the three scanning lines 411, 412, and 413 when the surface 8 is scanned with the three light beams emitted from the columns is measured by the measuring means, and is adjusted based on the result ( Second step). As a result, all pitch intervals can be adjusted with low error and evenness.

  Here, θ is defined in the adjacent scanning line 411 and the scanning line 412 existing in the effective scanning area. The angle formed by the scanning line 412 and the straight line connecting the imaging point 401 that draws the scanning line 411 and the imaging point 402 that draws the scanning line 412 at the same time is defined as θ.

  In FIG. 6, the imaging point 402 that draws the scanning line 412 runs ahead of the imaging point 401 that draws the scanning line 411 (in FIG. 6, the scanning line is drawn from left to right. To go). The reason is that in the light source means 11, as shown in FIG. 5, the light emitting point 401 and the light emitting point 402 are separated in the main scanning direction.

  As the polygon mirror (rotating polygonal mirror) rotates with time, the imaging point 401 is scanned from the left side to the right side as shown in FIG. 6, and the scanning line 411 is drawn.

  An imaging point 401 for drawing the scanning line 411 at the same time and an imaging point 402 for drawing the scanning line 412 are the imaging points for drawing the scanning line 411 at an arbitrary rotation angle of the polygon mirror (rotating polygonal mirror) at an arbitrary time. This means an imaging point 402 where 401 and a scanning line 412 are drawn. That is, the image formation point 401 and the image formation point 402 are defined at the same rotation angle.

  a is defined as the length of a straight line connecting the imaging point 401 for drawing the scanning line 411 and the imaging point 402 for drawing the scanning line 412 at the same time.

  Similarly, θ is defined in the adjacent scanning line 412 and scanning line 413 existing in the effective scanning area. The angle formed by the straight line connecting the imaging point 402 that draws the scanning line 412 and the imaging point 403 that draws the scanning line 413 and the scanning line 413 at the same time is defined as θ.

  Similarly, it is defined as the length of a straight line connecting the imaging point 402 that draws the scanning line 412 and the imaging point 403 that draws the scanning line 413 at the same time.

  The measurement method of this embodiment is performed near the center and both ends of the effective scanning area in the same manner as in the first embodiment, and the scanning line pitch interval is adjusted based on the result.

  In this embodiment, the pitch interval adjustment in the sub-scanning direction is performed by rotating the multi-beam semiconductor laser unit 200 having a plurality of light emitting points around the optical axis, and the rotation center of the multi-beam semiconductor laser unit 200 is adjusted. Is the center of the line segment connecting the two most spaced light emitting points. The scanning line pitch interval in the sub-scanning direction is adjusted by rotating around the optical axis with the center of this line segment as the rotation center.

  The first scanning at the same time within the effective scanning area in the light source means comprising an m × n matrix in which there are m light emitting point arrays in which n light emitting points are arranged in a straight line at equal intervals. The angle formed by the second scanning line and the straight line connecting the imaging point that draws the line and the imaging point that draws the second scanning line adjacent to the first scanning line is θ, and the first scanning line at the same time The length of the straight line connecting the image forming point for drawing the image forming point for drawing the second scanning line adjacent to the first scanning line is a on the surface to be scanned by a plurality of light beams emitted from the light emitting point. Of the plurality of scanning lines when scanning, if the pitch interval between the two most distant scanning lines is L, the number of pitch intervals per column is n−1, and there are m columns. Since the number of intervals is m−1, the ideal value of the pitch interval is

It becomes. Further, since the distance a (n−1) sin θ in the sub-scanning direction per column and the number of intervals between the columns are m−1, the pitch interval before adjustment is

It becomes. Therefore, 0.9 L / (mn−1) <(L−am (n−1) sin θ) / (m−1) <1.1 L / (mn−1) in order to set the pitch interval to a desired value. (6)
Need to be satisfied.

  In conditional expression (6), if the pitch interval P (L-am (n−1) sin θ) / (m−1) before adjustment is an ideal value L / (mn−1) of the pitch interval, the scanning line is completely obtained. The interval can be set to a value similar to the ideal value. If the pitch interval P (L-am (n-1) sin θ) / (m-1) before adjustment is larger than L / (mn-1), the scanning line interval is wider than the ideal value, and if it is smaller, it is larger than the ideal value. Although narrow, within the range of conditional expression (6), the scanning line spacing is practically acceptable.

  More preferably, the conditional expression (6) should be set as follows.

5/6 · L / (mn−1) <(L-am (n−1) sin θ) / (m−1) <7/6 · L / (mn−1) (6a)
In this embodiment, the two scanning lines that are the farthest apart among the scanning lines scanned by the six light beams emitted from the multi-beam semiconductor laser unit having six light emitting points as the light source means of the multi-beam optical scanning device. The interval was measured near the center and both ends of the effective scanning area, and the scanning line pitch interval was adjusted based on the results. However, the measurement is not limited to this. You may make it perform. As a result, the measurement accuracy is improved, so that the scanning line pitch interval within the scanning effective width can be kept more uniform.

  In this embodiment, a surface-emitting multi-beam semiconductor laser is used as the light source means. However, the present invention is not limited to this, and an edge-emitting multi-beam semiconductor laser may be used.

As described above, in this embodiment, the surface-emitting multi-beam semiconductor laser is used as the light source means as described above, and the scanning line interval in the sub-scanning direction scanned by the two light beams emitted from the two most spaced light emitting points is used. And adjusting the scanning line pitch interval, it is possible to reduce the adjustment error at the time of adjusting the pitch interval. Also, m _i-th column (i = 1,2, ···, m -1) n of scanning lines when scanning a surface to be scanned by the n n optical flux emitted from the light emitting point of when, among the n scan lines when scanning a surface to be scanned by the n optical beam emitted from the n light emitting points m i ₊₁ row, two scan that is closest to each other The distance between the lines is measured, and the pitch interval of the scanning lines is also adjusted based on the measurement result, so that there are m light emitting point arrays in which n light emitting points are arranged in a straight line at equal intervals. Even in an optical scanning apparatus having a multi-beam semiconductor laser unit having a light emitting point composed of a matrix of the above, all pitch intervals can be adjusted with low error and evenly. Accordingly, in the present embodiment, the scanning line interval in the sub-scanning direction is unified to a predetermined interval, and the occurrence of pitch unevenness and color misregistration is suppressed and a high quality image is formed.

[Image forming apparatus]
FIG. 7 is a cross-sectional view of the main part in the sub-scanning direction showing an embodiment of the image forming apparatus of the present invention. In the figure, reference numeral 104 denotes an image forming apparatus. Code data Dc is input to the image forming apparatus 104 from an external device 117 such as a personal computer. The code data Dc is converted into image data (dot data) Di by a printer controller 111 in the apparatus. This image data Di is input to an optical scanning unit (multi-beam scanning optical apparatus) 100 having the configuration shown in either the first or second embodiment. The light scanning unit 100 emits a light beam 103 modulated in accordance with the image data Di, and the light beam 103 scans the photosensitive surface of the photosensitive drum 101 in the main scanning direction.

  The photosensitive drum 101 serving as an electrostatic latent image carrier (photoconductor) is rotated clockwise by a motor 115. With this rotation, the photosensitive surface of the photosensitive drum 101 moves in the sub-scanning direction perpendicular to the main scanning direction with respect to the light beam 103. Above the photosensitive drum 101, a charging roller 102 for uniformly charging the surface of the photosensitive drum 101 is provided so as to contact the surface. The surface of the photosensitive drum 101 charged by the charging roller 102 is irradiated with the light beam 103 scanned by the optical scanning unit 100.

  As described above, the light beam 103 is modulated based on the image data Di, and by irradiating the light beam 103, an electrostatic latent image is formed on the surface of the photosensitive drum 101. The electrostatic latent image is developed as a toner image by a developing unit 107 disposed so as to contact the photosensitive drum 101 further downstream in the rotation direction of the photosensitive drum 101 than the irradiation position of the light beam 103.

  The toner image developed by the developing unit 107 is transferred onto a sheet 112 as a transfer material by a transfer roller 108 disposed below the photosensitive drum 101 so as to face the photosensitive drum 101. The paper 112 is stored in a paper cassette 109 in front of the photosensitive drum 101 (on the right side in FIG. 7), but can be fed manually. A paper feed roller 110 is provided at the end of the paper cassette 109, and feeds the paper 112 in the paper cassette 109 into the transport path.

  As described above, the sheet 112 on which the unfixed toner image has been transferred is further conveyed to a fixing device behind the photosensitive drum 101 (left side in FIG. 7). The fixing device includes a fixing roller 113 having a fixing heater (not shown) therein, and a pressure roller 114 disposed so as to be in pressure contact with the fixing roller 113, and the sheet conveyed from the transfer unit. The unfixed toner image on the paper 112 is fixed by heating 112 while applying pressure at the pressure contact portion between the fixing roller 113 and the pressure roller 114. Further, a paper discharge roller 116 is disposed behind the fixing roller 113, and the fixed paper 112 is discharged out of the image forming apparatus.

  Although not shown in FIG. 7, the print controller 111 controls not only the data conversion described above, but also controls each part in the image forming apparatus including the motor 115 and a polygon motor in the optical scanning unit described later. I do.

  The recording density of the image forming apparatus used in the present invention is 1200 dpi or more, and the configuration of Example 1 or 2 of the present invention is more effective.

[Color image forming apparatus]
FIG. 8 is a schematic view of a main part of a color image forming apparatus according to an embodiment of the present invention. This embodiment is a tandem type color image forming apparatus in which four optical scanning devices are arranged in parallel and image information is recorded on a photosensitive drum surface as an image carrier. In FIG. 8, 60 is a color image forming apparatus, 61, 62, 63, and 64 are optical scanning devices (multi-beam scanning optical devices), 21, 22, and 23 each having one of the configurations shown in the first or second embodiment. , 24 are photosensitive drums as image carriers, 31, 32, 33, and 34 are developing units, and 51 is a conveyor belt.

  In FIG. 8, the color image forming apparatus 60 receives R (red), G (green), and B (blue) color signals from an external device 52 such as a personal computer. These color signals are converted into C (cyan), M (magenta), Y (yellow), and B (black) image data (dot data) by a printer controller 53 in the apparatus. These image data are input to the optical scanning devices 61, 62, 63 and 64, respectively. From these optical scanning devices, light beams 41, 42, 43, and 44 modulated according to each image data are emitted, and the photosensitive surfaces of the photosensitive drums 21, 22, 23, and 24 are caused by these light beams. Scanned in the main scanning direction.

  The color image forming apparatus in this embodiment has four optical scanning devices (61, 62, 63, 64) arranged in each color of C (cyan), M (magenta), Y (yellow), and B (black). Correspondingly, image signals (image information) are recorded on the photosensitive drums 21, 22, 23, and 24 in parallel, and a color image is printed at high speed.

  As described above, the color image forming apparatus in this embodiment uses the light beams based on the respective image data by the four optical scanning devices 61, 62, 63 and 64, and the photosensitive drums 21 and 22 respectively corresponding the latent images of the respective colors. , 23, 24 on the surface. Thereafter, a single full color image is formed by multiple transfer onto a recording material.

  As the external device 52, for example, a color image reading device including a CCD sensor may be used. In this case, the color image reading apparatus and the color image forming apparatus 60 constitute a color digital copying machine.

  As described above, in this embodiment, the imaging optical system is constituted by a single lens having a toric surface as described above, and the scanning line interval in the sub-scanning direction is set by two light beams emitted from the two most spaced light emitting points. By measuring and adjusting the scanning line spacing in the sub-scanning direction, it is possible to realize a multi-beam scanning optical apparatus with little scanning line spacing adjustment error. Further, by mounting this apparatus on an image forming apparatus or a color image forming apparatus, it is possible to realize a high-quality apparatus with little scanning line unevenness.

  As mentioned above, although the preferable Example of this invention was described, it cannot be overemphasized that this invention is not limited to these Examples, A various deformation | transformation and change are possible within the range of the summary.

1 is a schematic view of the main part of a multi-beam scanning optical apparatus according to a first embodiment of the present invention. 1 is a schematic view of the main part of a multi-beam semiconductor laser unit according to Embodiment 1 of the present invention. Arrangement of light emitting points of the multi-beam semiconductor laser unit of Example 1 of the present invention Explanatory drawing of the scanning line pitch space | interval measurement location of Example 1 of this invention. Arrangement of light emitting points of the multi-beam semiconductor laser unit of Example 2 of the present invention Explanatory drawing of the scanning line pitch space | interval measurement location of Example 2 of this invention. FIG. 3 is a sub-scan sectional view showing an embodiment of the image forming apparatus of the present invention. FIG. 3 is a sub-scan sectional view showing an embodiment of a color image forming apparatus according to the present invention. Schematic diagram of main parts of a conventional multi-beam scanning optical device Schematic diagram of the main parts of a conventional multi-beam semiconductor laser unit Arrangement of emission points of conventional multi-beam semiconductor laser unit Explanatory drawing of conventional scanning line pitch interval measurement points The figure which showed the measuring method of the scanning line pitch space | interval of a subscanning direction

Explanation of symbols

1 Light source means (surface emitting semiconductor laser)
2 Light flux conversion element (collimator lens)
3 Aperture stop 4 Optical system (cylindrical lens)
5 Deflection means (optical deflector)
LA Incident optical system 6 Imaging optical system (imaging lens)
8 Scanned surface (photosensitive drum surface)
61, 62, 63, 64 Multi-beam scanning optical device 21, 22, 23, 24 Image carrier (photosensitive drum)
31, 32, 33, 34 Developer 41, 42, 43, 44 Light beam 51 Conveying belt 52 External device 53 Printer controller 60 Color image forming device 100 Scanning optical device 101 Photosensitive drum 102 Charging roller 103 Light beam 104 Image forming device 107 Development Device 108 Transfer roller 109 Paper cassette 110 Paper feed roller 111 Printer controller 112 Transfer material (paper)
113 Fixing Roller 114 Pressure Roller 115 Motor 116 Paper Discharge Roller 117 External Equipment

Claims (14)

A plurality of light beams emitted from each light emitting point of a light source unit having three or more light emitting points arranged linearly at a predetermined interval are deflected by the deflecting unit, and the plurality of light beams deflected by the deflecting unit Is guided onto the surface to be scanned by the imaging optical system, and the surface to be scanned is scanned in the main scanning direction with a plurality of light beams by the deflection operation of the deflecting means.
Among the plurality of scanning lines that scan the surface to be scanned, the distance between two scanning lines that are the farthest in the sub-scanning direction is measured by the measuring means, and the scanning line pitch interval in the sub-scanning direction is adjusted based on the result. A method for adjusting a scanning line pitch interval. A sequence of light emitting points in which n (n is an integer of 3 or more) light emitting points are linearly arranged at a predetermined interval, and m (m is an integer of 2 or more) is arranged in a direction orthogonal to the straight line. The plurality of light beams emitted from the light source means are deflected by the deflecting means, the plurality of light beams deflected by the deflecting means are guided onto the surface to be scanned by the imaging optical system, and the deflecting operation of the deflecting means When scanning the surface to be scanned in the main scanning direction with a plurality of light beams,
Among the plurality of scanning lines that scan the surface to be scanned, the distance between two scanning lines that are the farthest in the sub-scanning direction is measured by the measuring means, and the scanning line pitch interval in the sub-scanning direction is adjusted based on the result. A method for adjusting a scanning line pitch interval. A sequence of light emitting points in which n (n is an integer of 3 or more) light emitting points are linearly arranged at a predetermined interval, and m (m is an integer of 2 or more) is arranged in a direction orthogonal to the straight line. The plurality of light beams emitted from the light source means are deflected by the deflecting means, the plurality of light beams deflected by the deflecting means are guided onto the surface to be scanned by the imaging optical system, and the deflecting operation of the deflecting means When scanning the surface to be scanned in the main scanning direction with a plurality of light beams,
A first step of measuring a distance between two scanning lines farthest in the sub-scanning direction among a plurality of scanning lines scanning the surface to be scanned by a measuring unit;
Among the n scanning lines when the surface to be scanned is scanned with n light beams emitted from n light emitting points in the i-th column (i = 1, 2,..., m−1). Thus, the scanning line closest to the n scanning lines when the surface to be scanned is scanned with the n light beams emitted from the n light emitting points in the i + 1 column and the n light emission in the i + 1 column. Of the n scanning lines when scanning the surface to be scanned with n light beams emitted from a point, the n light beams emitted from n light emitting points in the i-th column are scanned with the light beam. A second step of measuring the distance from the scanning line closest to the n scanning lines when scanning on the surface with the measuring means,
A scanning line pitch interval adjusting method, wherein the scanning line pitch interval in the sub-scanning direction is adjusted based on the measurement results in the first and second steps.   4. The distance between the two most distant scanning lines is measured at at least two points within a scanning effective width, and the scanning line pitch interval is adjusted based on the result. 2. A method for adjusting a scanning line pitch interval according to 1. On the surface to be scanned, the distance between two scanning lines that are most separated in the sub-scanning direction is L (mm), the number of scanning lines is Pn, and the pixel density in the sub-scanning direction on the surface to be scanned is A (dot / inch) over the entire scanning effective width,
2/3 × (Pn−1) × 25.4 / A <L <4/3 × (Pn−1) × 25.4 / A
However, Pn = n × m
5. The scanning line pitch interval adjusting method according to claim 1, wherein the scanning line pitch interval is adjusted so as to satisfy the above.   6. The scanning line pitch interval adjusting method according to claim 5, wherein the pixel density A is 1200 dpi or more. On the surface to be scanned, an interval between two scanning lines that are most separated in the sub-scanning direction is L (mm), and an imaging point that draws the first scanning line at the same time is adjacent to the first scanning line. The angle formed between the second scanning line and the straight line connecting the two scanning lines and the imaging point is θ, and the imaging point drawing the first scanning line at the same time is adjacent to the first scanning line. When the length of the straight line connecting the image forming point that draws the scanning line is a,
0.9L / (mn-1) <(L-am (n-1) sin θ) / (m-1) <1.1L / (mn-1)
4. The scanning line pitch interval adjusting method according to claim 2, wherein the scanning line pitch interval is adjusted so as to satisfy the above.   8. The scanning line pitch interval adjustment is performed by rotating the light source means around the optical axis with the center of a line segment connecting two light emitting points farthest apart as a rotation center. The scanning line pitch interval adjusting method according to Item. A sequence of light emitting points in which n (n is an integer of 3 or more) light emitting points are linearly arranged at a predetermined interval, and m (m is an integer of 2 or more) is arranged in a direction orthogonal to the straight line. A surface-emitting light source means, a deflecting means for deflecting a plurality of light beams emitted from the light source means, and an imaging optical system for imaging the plurality of light beams deflected by the deflecting means on the surface to be scanned; A multi-beam scanning optical apparatus that scans the scanned surface with a plurality of light beams in the main scanning direction by a deflection operation of the deflecting unit.
Among the plurality of scanning lines that scan on the surface to be scanned, an interval between two scanning lines that are most separated in the sub-scanning direction;
Among the n scanning lines when the surface to be scanned is scanned with n light beams emitted from n light emitting points in the i-th column (i = 1, 2,..., m−1). Thus, the scanning line closest to the n scanning lines when the surface to be scanned is scanned with the n light beams emitted from the n light emitting points in the i + 1 column and the n light emission in the i + 1 column. Of the n scanning lines when scanning the surface to be scanned with n light beams emitted from a point, the n light beams emitted from n light emitting points in the i-th column are scanned with the light beam. Measuring means for measuring the distance from the scanning line closest to the n scanning lines when scanning on the surface;
A multi-beam scanning optical apparatus comprising adjusting means for adjusting a scanning line pitch interval in the sub-scanning direction based on a measurement result of the measuring means. The adjustment means sets the interval between the two scanning lines that are most separated in the sub-scanning direction to L (mm) on the surface to be scanned, the imaging point that draws the first scanning line at the same time, and the first scanning The angle formed by the second scanning line and the straight line connecting the second scanning line adjacent to the line and the second scanning line is θ, and the imaging point and the first scanning line depicting the first scanning line at the same time And the length of the straight line connecting the image forming point that draws the second scanning line adjacent to the second scanning line,
0.9L / (mn-1) <(L-am (n-1) sin θ) / (m-1) <1.1L / (mn-1)
The multi-beam scanning optical apparatus according to claim 9, wherein the scanning line pitch interval is adjusted so as to satisfy the above.   11. The multi-beam scanning optical device according to claim 9 or 10, a photoconductor disposed on the surface to be scanned, and electrostatic formed on the photoconductor by a light beam scanned by the multi-beam scanning optical device. A developing device that develops a latent image as a toner image, a transfer device that transfers the developed toner image onto a transfer material, and a fixing device that fixes the transferred toner image onto the transfer material. Image forming apparatus.   11. A multi-beam scanning optical apparatus according to claim 9 or 10, and a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the multi-beam scanning optical apparatus. Image forming apparatus.   A color image forming apparatus, comprising: a plurality of image carriers, each of which is disposed on a surface to be scanned of the multi-beam scanning optical apparatus according to claim 9 or 10 and forms images of different colors.   14. The color image forming apparatus according to claim 13, further comprising a printer controller that converts color signals input from an external device into image data of different colors and inputs the converted image data to each multi-beam scanning optical apparatus.