JP2002127493A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus which can prevent a positional deviation of dots for forming images in both a horizontal scanning direction and a vertical scanning direction and can obtain high-quality images. SOLUTION: A laser array 12A has a plurality of semiconductor lasers 26 arranged in arrays in two dimensions. In this case, an element interval Lm(1)- Lm(n) in the horizontal scanning direction is changed so as to suppress positional defects of images on the basis of vertical scanning direction positions. Therefore, a distortion of images by a curvature of an outer circumferential face of a photoreceptor drum can be suppressed when images are formed on the outer circumferential face. Accurate images can be formed accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image on a photosensitive drum by using light beams emitted from a plurality of light emitting elements arranged two-dimensionally via an optical system.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Patent Application Laid-Open No. 9-200431, a light beam emitted from a plurality of two-dimensionally arranged light emitting elements via an optical system is applied onto a photosensitive drum. 2. Related Art An image forming apparatus using a scanning optical system for forming an image is known.

FIGS. 12 to 1 show the above-described image forming apparatus.
This will be specifically described with reference to FIG. FIG. 12A is a plan view of the image forming apparatus, and FIG. 12B is a side view thereof.

The image forming apparatus 100 shown in FIG.
As shown in FIG. 2B, a laser array package 102 including a semiconductor laser array 102A for emitting a plurality of laser beams, and a photosensitive member rotatably supported by enlarging the plurality of laser beams emitted from the semiconductor laser array 102A. An imaging lens system 106 for forming an image on the outer peripheral surface (scanning surface) 104A of the body drum 104; and an outer peripheral surface (scanning surface) 10 of the photosensitive drum 104 that transmits a plurality of laser beams.
4A, a beam splitter 108 that guides the laser beam onto the 4A, a cylindrical mirror 110 that collects a plurality of laser beams reflected by the beam splitter 108, and a light amount sensor 112 that measures the light amount of the laser beam collected by the cylindrical mirror 110. I have. FIG.
2, reference numeral 114 denotes an optical axis center connecting the center of the semiconductor laser array 102A and the center of the photosensitive drum 104.

FIG. 13A shows a laser array package 1.
FIG. 2B shows the laser array package 10.
FIG. 2 is an enlarged view of a second semiconductor laser array 102A.
In the semiconductor laser array 102A shown in FIG. 13B, the semiconductor laser 116 has n in the sub-scanning direction (Z direction).
And m in the main scanning direction (X direction), that is, a total of n × m arrays are arranged. In order to form one line of dots on the outer peripheral surface (scanning surface) 104A of the photosensitive drum 104 with the nxm semiconductor laser arrays 102A, each laser beam emission point of the semiconductor laser array 102A is Are arranged so that the projected images on the outer peripheral surface (scanning surface) 104A of the camera do not overlap. That is, as shown in FIG. 13B, the semiconductor lasers 116 are arranged at element intervals L in the main scanning direction and the sub-scanning direction, and the center line 118 of the lasers arranged in the sub-scanning direction of the semiconductor laser array 102A is aligned. Line perpendicular to the main scanning direction (Z
Direction) to form an angle φ. The angle φ is an angle at which the projected images (dots) of the laser beam do not overlap on the imaging plane.

The laser array 1 thus formed
The laser beam emitted from the semiconductor laser 02A (semiconductor laser 116) enlarges the space between adjacent dots by the optical magnification and forms a spot image on the outer peripheral surface 104A of the photosensitive drum 104.

That is, as shown in FIG. 14, when the element spacing of the semiconductor laser 116 in the main scanning direction and the sub-scanning direction is L and the optical magnification is B times, the semiconductor laser 116 emits light sequentially and the outer peripheral surface of the drum 104. When 104A moves L × B, dots by the adjacent semiconductor laser 116 are arranged. This is repeated (n-1) times, and when the outer peripheral surface 104A of the drum 104 moves by L × B × (n-1),
Dots 12 formed by all semiconductor lasers 116
2 draws straight lines in the main scanning direction without interruption.

Further, since the imaging lens system 106 used in the image forming apparatus 100 is required to have a wide angle and a high resolution, for example, a retrofocus as disclosed in Japanese Patent Laid-Open No. 9-43511 is disclosed. Type lens,
A telecentric type lens as shown in JP-A-16297 is used.

The image forming apparatus 100 thus configured
The semiconductor laser array 102 according to the image signal.
When A is driven by a drive circuit (not shown), the laser beam emitted from the semiconductor laser array 102A becomes
An image is formed two-dimensionally by being formed on the scanning surface 104A of the rotating photosensitive drum 104 by being enlarged by the imaging lens system 106. At this time, the light amount of each laser beam is measured by the light amount sensor 112, and the driving condition of each laser beam is set by a driving circuit (not shown) so that the light amount of each laser beam becomes a predetermined value. Accordingly, a desired image can be formed on the photosensitive drum 104 (scanning surface 104A) with high accuracy.

[0010]

The above-described image forming apparatus 1
In FIG. 00, since the outer peripheral surface 104A of the photosensitive drum 104 is a cylindrical side surface, the semiconductor laser array 102A
Is formed on a curved surface. However, in an optical system as disclosed in JP-A-9-43511 and JP-A-10-16297, when applied to the image forming apparatus 100 in order to form an image of an input laser beam on a plane, There is a problem that an image formed on a curved surface (outer peripheral surface 104A) is distorted in both the main scanning direction and the sub-scanning direction depending on the dimensions and the like of the semiconductor laser array 102A and the photosensitive drum 104. In particular, in recent years, the size of the printer has been reduced, and the photoconductor drum has a tendency to become thinner.

That is, in FIG. 12, the position of the outer peripheral surface 104A of the drum for actually forming an image is separated from the optical axis center 114 in the sub-scanning direction with respect to the image plane 120 of the laser beam by the image forming lens system 106. The more the position is, the more the semiconductor laser array 102A and the imaging surface 120
Are longer, and the laser located farther from the optical axis center 114 in the sub-scanning direction than the width L × B × m of the image by the laser array located at the optical axis center 114 in the sub-scanning direction. The width of the image by the array is increased. Further, compared to the distance L × B in the sub-scanning direction between the laser arrays located near the optical axis center 114 in the sub-scanning direction, the distance between the laser arrays located far from the optical axis center 114 in the sub-scanning direction is reduced. The distance in the scanning direction increases.

Further, as shown in FIG. 15, a semiconductor laser array 10 in which n × m semiconductor lasers 116 are arranged.
The image width nxB in the sub-scanning direction in which 2A is enlarged and projected by the imaging lens system 106 having an optical magnification of B times the photosensitive drum 104
If the curvature is not sufficiently small, the dots 122 (solid circles) constituting an image obtained by developing the image formed on the outer peripheral surface 104A of the drum on a plane as shown in FIG.
Is a dot 122A forming an image formed on the image plane 120.
(Dotted circle) is greatly distorted. As a result, when trying to draw a straight line on the outer peripheral surface 104A of the photosensitive drum 104 by one row in the sub-scanning direction in the procedure shown in FIG. 14, the dots 12 forming the image as shown in FIG.
In addition to the position shift in the sub-scanning direction, there is a problem in that the dots 122 overlap or move apart in the main scanning direction, thereby deteriorating the quality of the formed image.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of preventing displacement of dots forming an image in both main scanning and sub-scanning directions and obtaining a high quality image.

[0014]

According to the present invention, in order to achieve the above object, according to the first aspect of the present invention, a plurality of light emitting elements are emitted from a light source arranged two-dimensionally via an optical system. In an image forming apparatus for forming an image on an outer peripheral surface of a photosensitive drum by a light beam, an optical path length from the light emitting element to an image forming surface of a light beam emitted from the light emitting element via the optical system; A defect that cancels a position defect occurring in an image formed on the outer peripheral surface of the photosensitive drum due to a difference in an optical path length to an outer peripheral surface of the photosensitive drum on which a light beam emitted through the system forms an image. It is characterized by having a removing means.

The operation of the first aspect of the present invention will be described.

Since the outer peripheral surface of the photosensitive drum is a curved surface,
The difference between the optical path length of the light beams emitted from the plurality of light emitting elements to the image plane and the optical path length up to the outer peripheral surface of the photosensitive drum increases as the distance from the optical axis on the outer peripheral surface increases. Therefore, due to the difference in the optical path length, the dots forming the image formed on the outer peripheral surface of the photosensitive drum may be shifted from the positions where they should be formed. Thus, a highly accurate image can be formed.

According to a second aspect of the present invention, in the first aspect of the present invention, the defect removing means includes a light source for an adjacent light emitting element in the light source according to a distance from the light emitting element to an outer peripheral surface of the photosensitive drum. The arrangement is such that the intervals are changed in the main scanning direction, and the emission timing of the laser beam emitted from the light emitting element at a different position in the sub scanning direction is changed.

The operation of the second aspect of the invention will be described.

According to the above arrangement, the plurality of light emitting elements are adjacent to each other according to the difference in the optical path length from the light emitting element to the image forming surface of the optical system and to the outer peripheral surface of the photosensitive drum for forming an image. Because they are arranged with the interval in the main scanning direction changed,
Image displacement in the main scanning direction based on the difference in optical path length between the image forming surface and the outer peripheral surface is suppressed. The light is emitted from the light emitting element at a different position in the sub-scanning direction based on a difference in an optical path length from the light emitting element to the image forming surface of the optical system and to the outer peripheral surface of the photosensitive drum for forming an image. In order to change the emission timing of the laser beam,
Image displacement in the sub-scanning direction based on the difference in optical path length between the image forming surface and the outer peripheral surface is suppressed.

That is, it is possible to form an image having no position defect on the outer peripheral surface.

According to a third aspect of the present invention, in the first aspect of the present invention, the defect removing means includes a light source for an adjacent light emitting element in the light source according to a distance from the light emitting element to an outer peripheral surface of the photosensitive drum. The arrangement is such that the intervals in the main scanning direction and the sub-scanning direction are changed.

The operation of the third aspect of the present invention will be described.

According to the above arrangement, the plurality of light emitting elements are adjacent to each other according to the difference in the optical path length from the light emitting element to the image forming surface of the optical system and to the outer peripheral surface of the photosensitive drum for forming an image. Are arranged with the intervals in the main scanning direction and the sub-scanning direction changed, so that the image shift in the main scanning direction and the sub-scanning direction based on the difference in the optical path length from the imaging surface to the outer peripheral surface is suppressed. . That is, it is possible to form an image having no position defect on the outer peripheral surface.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An image forming apparatus according to a first embodiment of the present invention will be described in detail with reference to FIGS.

FIG. 1 shows an image forming apparatus according to an embodiment of the present invention. FIG. 1A is a plan view thereof, and FIG. 1B is a side view thereof.

The image forming apparatus 10 includes a laser array package 12 having a semiconductor laser array 12A for emitting a plurality of laser beams, and a semiconductor laser array 12A.
Outer peripheral surface 14 by a plurality of laser beams emitted from
A photoconductor drum 14 on which an image is formed on A and an outer peripheral surface (scanning surface) 14A of the photoconductor drum 14 rotatably supported by expanding a plurality of laser beams emitted from the semiconductor laser array 12A. An image forming lens system 18 for forming an image on the image forming surface 16 of a laser beam; and an outer peripheral surface (scanning surface) 14A of the photosensitive drum 14 through a plurality of laser beams.
The apparatus includes a beam splitter 20 that guides upward, a cylindrical mirror 22 that collects a plurality of laser beams reflected by the beam splitter 20, and a light amount sensor 24 that measures the light amount of the laser beam collected by the cylindrical mirror 22. .

FIG. 2A shows the laser array package 12.
FIG. 2B is a diagram illustrating a semiconductor laser array 12A of the laser array package 12. FIG.
As shown in (B), the semiconductor laser array 12A of the laser array package 12 has n semiconductor lasers 26 in the sub-scanning direction (Z direction) and m semiconductor lasers in the main scanning direction (X direction).
And a total of n × m arrays. In addition,
The laser array 12A of the present embodiment includes a semiconductor laser 26.
In this case, the number n of arrays in the sub-scanning direction and the number m of arrays in the main scanning direction are both even numbers. In addition, the semiconductor laser array 1
2A, dots of one line in the main scanning direction are transferred to the photosensitive drum 1
4 is formed on the outer peripheral surface (scanning surface) 14A of the photosensitive drum 14 because the laser beam emission point (semiconductor laser 26) of the semiconductor laser array 12A is formed on the outer peripheral surface (scanning surface) 14A
They are arranged so that the projected images on A do not overlap.

The center line 28 of the semiconductor laser array 12A in the main scanning direction is inclined by an angle φ with respect to a line 30 perpendicular to the main scanning direction. This angle φ is an angle at which the projection images of the conventional laser beam do not overlap on the imaging plane (the angle at which the projection images do not overlap on the imaging plane 16). The center line 32 in the sub-scanning direction of the semiconductor laser array 12A is a line perpendicular to the sub-scanning direction.

The element spacing L in the sub-scanning direction of the semiconductor lasers 26 arranged in the semiconductor laser array 12A is the same as that of the conventional example, and the element spacing Lm (l) of the first to n-th rows in the main scanning direction. Lm (n) is changed according to the sub-scanning position. Accordingly, the total length of the semiconductor laser arrays in the first to nth rows in the main scanning direction is Lm.
(L) × (ml) to Lm (n) × (ml).

That is, by changing the element intervals Lm (l) to Lm (n) in accordance with the position of the laser 26 in the sub-scanning direction, displacement of the image in the main scanning direction is prevented. In addition, the displacement of the image in the sub-scanning direction is dealt with by changing the emission timing of the semiconductor laser 26 of the laser array 12A by the control unit 34.

First, the element interval Lm in the main scanning direction
A method for obtaining (l) to Lm (n) will be described. FIG. 3 is a diagram schematically showing the image forming apparatus 10 according to the first embodiment for obtaining Lm (l) to Lm (n) in FIG. 2, and FIG. 3A is a plan view thereof. FIG. (B) is a side view thereof.

As shown in FIG. 3, the semiconductor laser array 1
The plurality of laser beams emitted from 2A are formed by an imaging lens system 18 on the outer peripheral surface (scanning surface) 14A of the photosensitive drum 14.
Is formed on the image plane 16 of the laser beam in contact with.

In FIG. 3, P is a semiconductor laser array 1
The center of the stop of the plurality of laser beams emitted from 2A in the imaging lens system 18, A is a tangent between the outer peripheral surface (scanning surface) 14A of the photosensitive drum 14 and the imaging surface 16 of the laser beam, and C is a semiconductor laser array. An image point (line) of the n-th row of laser beams emitted from 12A onto the outer peripheral surface (scanning surface) 14A of the photosensitive drum 14; Hc is a point (line) at which the straight line PC intersects the imaging surface 16; O is the rotation axis of the photosensitive drum 14, r is the radius of the bottom surface of the photosensitive drum 14, θ is the angle between the straight line OC and the straight line OA (OP), and f is the angle of view of the imaging lens system 18.

In FIG. 3, when the projection image width Wc on the projection image line C is the element interval L of the semiconductor laser in the conventional image forming apparatus shown in FIG. 13, the projection formed on the image plane 16 of the laser beam. The element interval Lm (n) of the semiconductor laser array 12A is determined so as to be the same as the image W.

First, the element interval Lm in the n-th row main scanning direction
(N) is determined according to the following equation (1). Equation (1)
L is the element spacing of the semiconductor laser in the image forming apparatus according to the conventional example shown in FIG.
And AHc in equation (2) is calculated by equation (3). Also, PC in equation (1) is calculated by equation (4), and PA in equation (4) is calculated by equation (5).

[0036]

(Equation 1)

[0037]

(Equation 2)

[0038]

(Equation 3)

[0039]

(Equation 4)

[0040]

(Equation 5)

When the element spacing Lm (n) of the semiconductor laser array 12A in the main scanning direction of the nth row is determined according to the equation (1), the projected image width Wc on C is given by the following equation (6).

[0042]

(Equation 6)

Next, the n-th semiconductor laser array 12A
The element spacing Lm (n-1) in the main scanning direction of the first row is set to a value similarly calculated by replacing (n-1) in equation (3) with [(n-1) -1]. Similarly, the semiconductor laser array 12
Element spacing Lm (n−2) in the main scanning direction of the (n−2) th row of A
To the (n / 2 + 1) th row element spacing Lm (n / 2
+1). Further, the element interval Lm (n / 2) to 1 in the main scanning direction of the n / 2-th row of the semiconductor laser array 12A
The element interval Lm (1) in the main scanning direction of the row is set to Lm (n / 2 +
1) to Lm (n).

When laser beams are simultaneously emitted from all the semiconductor lasers 26 constituting the laser array 12A, an image formed on the outer peripheral surface (scanning surface) 14A of the photosensitive drum 14 is developed into a flat image (dots). 36) is shown in FIG. FIG. 24 in the conventional image forming apparatus 100
Compared with (A), it can be seen that the image width in the main scanning direction is constant irrespective of the position in the sub-scanning direction, and is improved.

In order to improve the image in the sub-scanning direction, J (1) to J (1) to J (1) to J (1) which are the distances from the center line 40 in the sub-scanning direction to the image (dots 36) formed by the laser in each row in FIG. Calculate (n). First, J (n)
Is the arc AC in FIG. 3 and is calculated by equation (7).
Θ in Expression (7) is calculated by Expression (8), and A in Expression (8)
Hc, PHc, and PC are calculated by the above equations (3), (2), and (4), respectively.

[0046]

(Equation 7)

[0047]

(Equation 8)

Next, J (n-1) is obtained by calculating (n) in equation (3).
-1) is similarly calculated as {(n-1) -1}. Similarly, J (n−2) to J (n / 2 + 1) are calculated. J
(N / 2) to J (1) have the same values as J (n / 2 + 1) to J (n), respectively.

From these calculation results, the image forming apparatus 10
, The semiconductor laser array 12A according to the image signal
Is driven by the drive circuit (control section 34), the outer peripheral surface 14A of the photosensitive drum 14 is J (n) -J (n-1).
When moved, the dots 36 by the semiconductor laser 26 in the (n-1) th row adjacent to the semiconductor laser 26 in the nth row are arranged,
Similarly, the outer peripheral surface 14A of the photosensitive drum 14
The semiconductor laser array 12 </ b> A is arranged such that the dots 36 formed by the semiconductor lasers 26 in adjacent rows are lined up when moved by (n−1) −J (n−2) to J (2) −J (1).
Is controlled.

As a result, as shown in FIG. 5, the emission timing of each semiconductor laser 26 is controlled by the control unit 34 on the outer peripheral surface 14A of the photosensitive drum 14.
When a straight line is drawn, there is no displacement in the sub-scanning direction of the dots 36 forming the image, and no displacement in the main scanning direction where the dots overlap or move apart.
A desired image can be formed with high accuracy. (Second Embodiment) Next, an image forming apparatus according to a second embodiment of the present invention will be described. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. The difference between the present embodiment and the first embodiment is only the arrangement of the semiconductor lasers 26 of the laser array 12, and therefore only the relevant portions will be described.

FIG. 6 is a view for explaining a semiconductor laser array 12A of a laser array package 12 according to a second embodiment of the present invention.

As shown in FIG. 6, the semiconductor laser array 12A of the laser array package 12 has n semiconductor lasers 26 in the sub-scanning direction (Z direction) and m semiconductor lasers in the main scanning direction (X direction). In this case, the number n of the semiconductor lasers 22 in the sub-scanning direction and the number m of the semiconductor lasers 22 in the main scanning direction are both odd numbers.

Accordingly, the center line 28 in the main scanning direction of the semiconductor laser array 12A is on the (m + 1) / 2-th column of semiconductor lasers, and the center line 32 in the sub-scanning direction is the (n + 1) th line.
/ 2 on the laser in the second row.

In the image forming apparatus according to the second embodiment, similarly to the first embodiment, the semiconductor laser array 1
Element intervals Lm (1) to L in the main scanning direction of the 1st to nth rows of 2A
m (n) is determined according to equation (1). The only difference from the image forming apparatus according to the first embodiment is that Lm [(n11) / 2] is used as the element interval L of the semiconductor laser in the image forming apparatus according to the conventional example. Lm (n) to Lm [(n +
3) / 2], and Lm [(n-1) / 2] to Lm (1)
Are the same as Lm [(n + 3) / 2] to Lm (n), respectively, as in the first embodiment.

When laser beams are simultaneously emitted from all the semiconductor lasers 26 constituting the laser array 12A, an image formed on the outer peripheral surface (scanning surface) 14A of the photosensitive drum 14 is developed into a flat image (dots). 36) is shown in FIG. Compared to FIG. 16 in the image forming apparatus 100 according to the conventional example, it can be seen that the image width in the main scanning direction is constant regardless of the position in the sub-scanning direction, and is improved.

Further, in the image forming apparatus according to the second embodiment, similarly to the first embodiment, in order to improve the image in the sub-scanning direction, the center line 4 in the sub-scanning direction in FIG.
J (1) to J (n), which are distances from 0 to an image (dot 36) formed by the semiconductor laser 26 in each row, are calculated. The difference from the first embodiment is that J [(n + 1) /
2] is zero. J (n)-J [(n +
3) / 2] and J [(n-1) / 2] to J (1)
Is the same as J [(n + 3) / 2] to J (n), as in the first embodiment.

Based on these calculation results, the image forming apparatus 10 controls the light emission timing when the drive circuit (control section 34) drives the semiconductor laser array 12A in the same manner as in the first embodiment.

As a result, as in the image forming apparatus according to the first embodiment, there is no positional deviation in the sub-scanning direction of dots forming an image, and no positional deviation in which dots overlap or separate in the main scanning direction. A desired image can be formed on the body drum 14 with high accuracy (see FIG. 5).

In the first and second embodiments, the case where the arrangement of the semiconductor lasers 26 of the laser array 12A in the sub-scanning direction and the main scanning direction is both an even number or both odd numbers has been described. Is an even number and one of them is an odd number, it is only necessary to carry out a combination of modes from the case of both even numbers and the case of both odd numbers. Third Embodiment Next, an image forming apparatus according to a third embodiment of the present invention will be described with reference to FIGS. Note that the same components as those in the first and second embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted. In the present embodiment, unlike the first and second embodiments, the element spacing in the sub-scanning direction of the semiconductor laser in the laser array is also changed.

FIG. 8 is an explanatory view of a semiconductor laser array 12A of a laser array package 12 according to a third embodiment of the present invention.

As shown in FIG. 8, the semiconductor laser array 12A of the laser array package 12 includes n semiconductor lasers 26 in the sub-scanning direction (Z direction) and the semiconductor laser 26 in the main scanning direction (X
M) in a total n × m array, and the number n of the semiconductor lasers 22 in the sub-scanning direction is an even number, and the number m in the main scanning direction is an even number and an odd number. It doesn't matter.

In the laser array 12A, Ln, which is the distance from the center line 32 in the sub-scanning direction to the laser in each row,
(1) to Ln (n) are determined.

FIG. 9 is a diagram schematically showing an image forming apparatus according to the third embodiment for determining Ln (1) to Ln (n) in FIG. In FIG. 9, the same reference numerals as those in FIG. 3B are assigned, and the signs whose values change are marked with “′”.

Incidentally, Ha is the semiconductor laser array 102.
In the image forming apparatus 100 according to the related art in which the element spacing in the sub-scanning direction of A is L, the laser beam in the nth row emitted from the semiconductor laser array 12A is a point (line) at which the laser beam intersects the imaging plane 120. (See FIG. 15).

Ln (1) to Ln (n) are obtained as follows.

First, in FIG. 9, Ln (n) is determined so that the length of the arc AC 'is equal to the straight line AHa. AHa
Is calculated by Expression (9), and the arc AC ′ is calculated by Expression (10). Θ ′ in Expression (10) is calculated by Expression (11), and PC ′, PHc ′, and AHc ′ in Expression (11) are
PA calculated in equations (12) to (14) and in equation (12)
Is calculated by equation (5). Ln (n) in Expression (14) is determined so that Expression (9) = Expression (10).

[0067]

(Equation 9)

[0068]

(Equation 10)

[0069]

[Equation 11]

[0070]

(Equation 12)

[0071]

(Equation 13)

[0072]

[Equation 14]

Next, Ln (n-1) is similarly determined by replacing (n-1) in equation (9) with [(n-1) -1].
Similarly, Ln (n-2) to Ln (n / 2 + 1) are determined. Ln (n / 2) to Ln (1) are Ln (n / 2 + 1)
To Ln (n).

When laser beams are simultaneously emitted from all the semiconductor lasers 26 constituting the laser array 12A, an image formed on the outer peripheral surface (scanning surface) 14A of the photosensitive drum 14 is developed into a flat image (dots). 36) is shown in FIG. Compared to FIG. 16 in the image forming apparatus 100 according to the conventional example, it can be seen that the image width in the sub-scanning direction and the main scanning direction is constant and is improved. As a result, as shown in FIG. 14 of the related art, the light emitting control of the photosensitive drum 14 is performed so as to control the light emission of the conventional laser array in which the element spacing of the semiconductor laser 26 is L in both the main running left direction and the sub-scanning direction. The drive circuit (control unit 34) may be controlled such that dots formed by the semiconductor lasers 26 in adjacent rows are arranged when the outer peripheral surface 14A moves L × B. This is repeated (n-1) times, and the outer peripheral surface 14A of the drum is L × B
By moving by (n-1), a straight line can be drawn by dots formed by n semiconductor lasers 26 in the sub-scanning direction.

Therefore, the displacement of the dots forming the image in the sub-scanning direction and the displacement of the dots overlapping or separating in the main scanning direction, which are problems in the prior art, are eliminated, and the desired image on the photosensitive drum 14 can be heightened. It can be formed with high precision. Further, there is an advantage that the emission control of the laser array 12A does not need to be changed from the conventional example in which the element intervals are equal. (Fourth Embodiment) An image forming apparatus according to a fourth embodiment of the present invention will be described with reference to FIG. The same components as those in the first to third embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG. 11 is a diagram illustrating a semiconductor laser array 12A of a laser array package 12 according to a fourth embodiment of the present invention.

This embodiment differs from the third embodiment in that the number n of semiconductor lasers 26 arranged in the sub-scanning direction is an odd number, as shown in FIG. Therefore, the center line 32 in the sub-scanning direction has the (n + 1) / 2-row semiconductor laser 26
Over the center of the Ln (1) to Ln (n), which are intervals from the center line 32 to the lasers in each row, are determined.

The difference from the image forming apparatus according to the third embodiment is only that Ln [(n + 1) / 2] is set to zero. Ln (n) to Ln [(n + 3) / 2] are determined, and Ln
[(N-1) / 2] to Ln (1) are Ln [(n + 3) / 2]
The same value as in the third embodiment is set to the same value as Ln (n).

According to the image forming apparatus according to the fourth embodiment, similarly to the image forming apparatus according to the third embodiment, a dot for forming an image, which has been a conventional problem, is obtained only by employing the conventional driving method. This eliminates positional deviation in the vertical scanning direction and positional deviation in which dots overlap or separate in the main running left direction, and a desired image can be formed on the photosensitive drum 14 with high accuracy.

[0079]

As described above, according to the image forming apparatus of the present invention, a light beam emitted from a light source, in which a plurality of light emitting elements are arranged two-dimensionally, is emitted through an optical system through an optical system. In an image forming apparatus for forming an image on a surface, an image forming plane of a light beam emitted from the plurality of light emitting elements arranged in a two-dimensional manner through the optical system and the plurality of light emitting elements arranged in a two-dimensional manner. The plurality of light sources are two-dimensionally arranged so that a light beam emitted from the light emitting element via the optical system forms an image, and a position defect in the main scanning direction of the image due to an optical path difference on the surface of the photosensitive drum is canceled. By arranging and determining the timing of driving the plurality of light sources in accordance with the calculated value of the position defect in the sub-scanning direction, the displacement of the dots forming an image in the sub-scanning direction and the overlapping or separating of the dots in the main scanning direction. Eliminating the positional deviation or can form a desired image on the photosensitive drum with high accuracy.

In addition to the main scanning direction, the plurality of light emitting elements are arranged two-dimensionally in the sub-scanning direction so as to cancel image position defects due to the optical path difference between the image plane of the light beam and the surface of the photosensitive drum. This arrangement eliminates misalignment of dots forming an image in the sub-scanning direction and misalignment of dots overlapping or separating in the main scanning direction by the conventional drive timing method. Since it can be formed with high precision, it is possible to suppress an increase in cost of the drive circuit.

[Brief description of the drawings]

1A and 1B show an image forming apparatus according to an embodiment of the present invention, FIG. 1A is a plan view thereof, and FIG. 1B is a side view thereof.

FIGS. 2A and 2B show a laser array package used in the apparatus of the present invention. FIG. 2A is a front view thereof, and FIG. 2B is a diagram showing a semiconductor laser array of the laser array package according to the first embodiment of the present invention. FIG.

FIG. 3 is a diagram schematically illustrating an image forming apparatus according to a first embodiment of the present invention for determining an element interval in a main scanning direction of a semiconductor laser array.

FIG. 4 is a diagram in which an image formed on the outer peripheral surface of the photosensitive drum is developed in a plane by the image forming apparatus according to the first embodiment of the present invention.

FIG. 5 shows a result of a straight line drawn by the image forming apparatus according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a semiconductor laser array of a laser array package according to a second embodiment of the present invention.

FIG. 7 is a diagram in which an image formed on an outer peripheral surface of a photosensitive drum is developed in a plane by an image forming apparatus according to a second embodiment of the present invention.

FIG. 8 is a diagram illustrating a semiconductor laser array of a laser array package according to a third embodiment of the present invention.

FIG. 9 is a diagram schematically illustrating an image forming apparatus according to a third embodiment of the present invention for determining an element interval in a main scanning direction of a semiconductor laser array.

FIG. 10 is a diagram in which an image formed on an outer peripheral surface of a photosensitive drum is developed in a plane by an image forming apparatus according to a third embodiment of the present invention.

FIG. 11 is a diagram illustrating a semiconductor laser array of a laser array package according to a fourth embodiment of the present invention.

FIG. 12 shows an example of a conventional image forming apparatus, wherein FIG. 12 (A) is a plan view thereof, and FIG. 12 (M) is a side view thereof.

13A and 13B show a laser array package used in the apparatus shown in FIG. 12, wherein FIG. 13A is a front view and FIG.
FIG. 13 is a diagram illustrating a semiconductor laser array of a laser array package used in the apparatus of FIG.

FIG. 14 is a view for explaining the principle of image drawing by the apparatus of FIG.

FIG. 15 is a diagram illustrating a case where the image width in the sub-constant omnidirectional direction obtained by enlarging and projecting the semiconductor laser array in the apparatus of FIG. 12 is not sufficiently small with respect to the curvature of the photosensitive drum.

16 is a diagram in which an image formed on the outer peripheral surface of the photosensitive drum in the case of FIG. 15 is developed on a plane.

17 shows a straight line drawing result in the case of FIG.

[Explanation of symbols]

 Reference Signs List 10 image forming apparatus 12A semiconductor laser array (light source) 14 photosensitive drum 14A outer peripheral surface (scanning surface) of photosensitive drum 16 imaging surface of laser beam 18 imaging lens system

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04N 1/036 F term (reference) 2C162 AE28 AF01 AF13 AF53 AF73 FA04 FA18 FA23 2C362 AA13 AA14 AA16 AA42 AA47 AA48 BA28 BA60 BA61 BA68 BA70 BA71 BA90 BB28 BB37 BB46 DA04 2H045 BA22 BA23 CA98 2H076 AB42 AB53 AB66 5C051 AA02 CA07 DA06 DA09 DB02 DB07 DC02 DC04 DE02 DE07

Claims (3)

[Claims] 1. An image forming apparatus for forming an image on an outer peripheral surface of a photosensitive drum by a light beam emitted from a light source in which a plurality of light emitting elements are arranged two-dimensionally through an optical system, wherein: The optical path length of the light beam emitted through the optical system to the image forming surface and the light beam emitted from the light emitting element through the optical system to the outer peripheral surface of the photosensitive drum on which an image is formed. An image forming apparatus comprising: a defect removing unit that cancels a position defect generated in an image formed on an outer peripheral surface of the photosensitive drum due to a difference in an optical path length. 2. The light source device according to claim 1, wherein the defect removing unit changes an interval between adjacent light emitting elements in the main scanning direction in the light source according to a distance from the light emitting elements to an outer peripheral surface of the photosensitive drum, and performs sub scanning. The image forming apparatus according to claim 1, wherein timing of emitting a laser beam emitted from the light emitting element at a different position in a direction is changed. 3. The light emitting device according to claim 2, wherein the defect removing unit changes an interval between adjacent light emitting elements in the main scanning direction and the sub scanning direction in the light source according to a distance from the light emitting elements to an outer peripheral surface of the photosensitive drum. The image forming apparatus according to claim 1, wherein: