JPH1052941A - Light-scanning apparatus and image-forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high-quality images by uniforming a resolution. SOLUTION: A plurality of light sources 12a of a light source array 12 are so constituted as to decrease a near field pattern diameter from the central light source 12a to the light sources 12a at both end parts in a main scanning direction. A photosensitive face 16a of a photosensitive drum 16 is arranged at a focal point 15a of the central light source 12a formed by lens systems 14, 15. When a plurality of light beams 13 modulated in accordance with an image signal are projected from the light source array 12, the light beam 13 projected from the central light source 12a forms an image at the focal point 15a on the photosensitive face 16a. The light beam 13 projected from the light source 12a at the end part forms an image on the focal point 15a in front of the photosensitive face 16a, then becomes thick gradually and forms on the photosensitive face 16a a spot diameter D equal to a central spot diameter D.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an LE in which LED light sources or laser light sources are arranged one-dimensionally or two-dimensionally.
The present invention relates to an optical scanning apparatus and an image forming apparatus using a light source array such as a D array and a laser array, and more particularly to an optical scanning apparatus and an image forming apparatus in which a spot diameter of a light beam applied to a scanning surface or an image forming surface is equal.

[0002]

2. Description of the Related Art FIG. 18 shows a conventional image forming apparatus, for example. The image forming apparatus 1 includes a semiconductor laser array 2 having a plurality of laser light sources 2a two-dimensionally arranged in a main scanning direction Y and a sub scanning direction Z.
A condenser lens system 4 for condensing a plurality of laser beams 3 emitted from each laser light source 2a in the optical axis direction X at a converging point 4a; and a plurality of laser beams 3 condensed at the converging point 4a.
Lens system 5 that forms an electrostatic latent image on a photoreceptor surface 6 a of a photoreceptor drum 6, and a rotatable support roller (not shown) that forms an electrostatic latent image by being exposed by a laser beam 3 And a drum 6. Reference numeral 7 denotes an image memory that stores image signals, 8 denotes a signal processing circuit that reads out the image signals from the image memory 7 and processes the image signals to output a recording signal according to a recording pattern, and 9 denotes a signal processing circuit 8 A laser drive circuit 10 for driving the laser array 2 by inputting a recording signal from the controller 10 outputs a control signal to the laser drive circuit 9 to drive the laser array 2.

In the image forming apparatus 1 configured as described above, when the signal processing circuit 8 reads an image signal from the image memory 7, processes the image signal and outputs a recording signal corresponding to a recording pattern, the laser driving The circuit 9 drives the laser array 2 by inputting a recording signal from the signal processing circuit 8 under the control of the control circuit 10. A laser beam 3 is emitted from each laser light source 2a of the laser array 2. The laser beam 3 emitted from each laser light source 2a is condensed on a condensing point 4a by a condensing lens system 4, and is imaged on a photoreceptor surface 6a by an imaging lens system 5. The photoreceptor drum 6 forms an electrostatic latent image by being exposed by the laser beam 3.

Another conventional image forming apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 7-314771. In order to enhance the positional accuracy of the light source, this image forming apparatus replaces an LED array, which has conventionally been manufactured by bonding a plurality of LED chips on which a plurality of LED light sources are formed, with a single unit having a width smaller than the width of the photoconductor. Multiple LEDs on one board
The light sources are arranged in a line, and an optical system having a convex lens that enlarges the width of light in the arrangement direction to the width of the photoconductor is provided in order to project a laser beam from each LED light source onto the photoconductor. . As a result, LEs arranged on a single substrate
The laser beam from the D light source can be enlarged and projected onto the surface of the photosensitive member up to the width of the photosensitive member to perform writing. Further, by forming the LED light sources on a single substrate, there is an advantage that errors in positional accuracy due to bonding are eliminated.

Another conventional image forming apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 8-62531. This image forming apparatus is provided with an optical system capable of correcting the laser array spot in a straight line on the photoreceptor surface even if the spot is not straight.

[0006]

However, according to the conventional image forming apparatus 1 shown in FIG. 18, since each light source 2a is similarly configured, the laser beam 3 from the light source 2a is condensed by a condenser lens system having a convex lens. When an image is formed on the photoreceptor surface 6a via the imaging lens system 4 and the imaging lens system 5, each light source 2
Even if the center position of a can be corrected by the manufacturing method of the array 2 or the optical system, it is affected by the spherical aberration and the like of the lens systems 4 and 5, and as shown in FIG.
There is a problem that the actual focal plane 5b connecting a is shifted from the surface of the photoreceptor 6a in the optical axis direction X, and the resolution is degraded on both sides. That is, as shown in FIG. 19, the laser beam 3 emitted from the light source 2 _{a0 at} the optical axis center 30 forms a focal point 5 a on the photoreceptor surface 6 a.
The laser beam 3 emitted from the light source 2 _ak located at a position away from the light source 2 _a0 along the main scanning direction Y has a focal point 5 a which is originally formed on the photoreceptor surface 6 a. As a result, a desired spot diameter D on the photosensitive member surface 6a is obtained.
A larger spot diameter (D + α) will be applied. This is the same when the light source 2a is an LED light source. The shift Δx (y) of the focal point 5a becomes larger as the light source 2a is located farther from the optical axis center 30. Therefore,
It is not possible to obtain an image with a uniform resolution simply by increasing the positional accuracy of the light source 2a.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an optical scanning device and an image forming apparatus capable of obtaining a high-quality image with uniform resolution.

[0008]

According to another aspect of the present invention, there is provided an optical scanning device for scanning a scanning surface with a plurality of light beams, wherein a plurality of light sources for emitting the plurality of light beams are provided. Comprises a light source array arranged one-dimensionally or two-dimensionally, and optical means for converging the plurality of light beams on the scanning surface, wherein the plurality of light sources of the light source array are focused by the optical means. It is characterized by having a near field pattern diameter corresponding to a degree of defocus of the plurality of light beams on the scanning surface with respect to a position.

According to another aspect of the present invention, there is provided an image forming apparatus for scanning an image forming surface with a plurality of light beams modulated according to an image signal to form an image on the image forming surface. A light source array in which a plurality of light sources for emitting the plurality of light beams are arranged one-dimensionally or two-dimensionally; an optical unit for condensing the plurality of light beams on the image forming surface; An image forming body that is arranged on an image forming surface and forms an electrostatic latent image according to the plurality of light beams, wherein the plurality of light sources of the light source array are arranged such that the plurality of light sources correspond to a focal position of the optical unit. It is characterized by having a near-field pattern diameter corresponding to the degree of out-of-focus of the beam on the image forming surface.

According to each of the above structures, the plurality of light sources have near-field pattern diameters corresponding to the degree of out-of-focus on the scanning surface or the image forming surface of the plurality of light beams with respect to the focal position of the optical means. It is possible to make the spot diameter of the light beam applied to the scanning surface or the image forming surface equal.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram for explaining the principle of the present invention. Image forming apparatus 11 according to the present invention
Includes a light source array 12 in which a plurality of light sources 12a for emitting a plurality of light beams are arranged one-dimensionally or two-dimensionally. The plurality of light sources 12a of the light source array 12
From the central light source 12a in the main scanning direction Y to the light sources 12 at both ends.
The configuration is such that the diameter of the near-field pattern becomes smaller toward a. The photoconductor surface 16a of the photoconductor drum 16 is
Central light source 12 formed by lens systems 14 and 15
a is located at the focal point 15a. With this configuration, when a plurality of light beams modulated in accordance with an image signal are emitted from the light source array 12, the light beam 13 emitted from the central light source 12a becomes a focal point 15a on the photosensitive member surface 16a.
Connect the image with. The light beam 13 emitted from the light source 12a at the end forms an image at the focal point 15a in front of the photoconductor surface 16a, and then gradually becomes thicker. On the photoconductor surface 16a, the light beam 13 has a spot diameter D equal to the central spot diameter D. Form.

FIG. 2 is a configuration diagram showing an image forming apparatus according to an embodiment of the present invention. This image forming apparatus 11 has n
× m (for example, thousands or more) laser light sources 12a are arranged in an array, and a semiconductor laser array 1 capable of simultaneously and independently emitting a laser beam 13 from each laser light source 12a.
2 (12A to 12F), a condensing lens system 14 for converging a plurality of laser beams 13 emitted from each laser light source 12a to a condensing point 14a, and a plurality of laser beams condensing at the condensing point 14a 13 as a scanning surface
a laser beam 13 supported rotatably by an imaging lens system 15 for forming an image on the
Drum 16 that forms an electrostatic latent image by being exposed by an image memory, and an image memory 17 that stores image signals
A signal processing circuit 18 for reading out an image signal from the image memory 17 and processing the image signal to output a recording signal according to a recording pattern; and driving the laser array 12 by inputting the recording signal from the signal processing circuit 18 A laser drive circuit 19 for outputting a drive signal to be driven, and a control circuit 20 for outputting a control signal to the laser drive circuit 19 to drive the laser array 12. In the figure, X indicates the optical axis direction, Y indicates the main scanning direction, and Z indicates the sub-scanning direction, and a indicates the surface of the laser array 12 and the condenser lens system 14.
And b indicates the distance between the condenser lens system 14 and the photoreceptor surface 16a. Further, one laser light source 12a of the laser array 12 corresponds to one pixel in the main scanning direction Y.

The photosensitive drum 16 is positioned so that an image forming point (focal point) 15a of the laser beam 13 emitted from the light source _{12a0 at} the optical axis center 130 coincides with the photosensitive member surface 16a. In the optical recording apparatus 11, a charging unit, a developing unit, a transfer unit, and the like are provided around the photosensitive drum 16, and a paper feed unit is provided before the transfer unit, and a fixing unit and a paper discharge unit are provided after the transfer unit. Parts etc. are provided. These units are not shown for the sake of explanation.

FIG. 3 illustrates the structure of the laser array 12.
FIG. 2A is a perspective view of the main part of FIG.
FIG. 2B is a detailed view of a portion A in FIG. Laser array
12 has a semiconductor substrate 120 of n-GaAs,
An n-type electrode 121 is formed on the back surface of the semiconductor substrate 1.
Al on the surface of 20_0.15Ga_0.85Alternating layers of As and AlAs
The n-type mirror layer 122 and the GaAs quantum well layer
Al _0.3Ga_0.7Activity including light emitting layer formed by sandwiching between As
Layer 123, Al_0.15Ga_0.85As and AlAs alternately stacked in multiple layers
Surface emission of the formed p-type mirror layer 124 and the laser beam 13
P-type electrode in which a plurality of light emitting holes 125 for emitting light in a state are formed.
The poles 126 are formed in this order, and the active layer 123 (or p
The high-resistance region 1 by injecting protons into the
27, the p-type electrode 126, the p-type mirror layer 124 and
And active layer 123 are separated by separation grooves 128 to form a plurality of
A light source 12a is formed. Separation of p-type mirror layer 124
An air post (see FIG. 5 described later) E is formed between the grooves 128.
And Ey is a half of the air post in the main scanning direction Y.
The diameter and Ez indicate the radius of the air post in the sub scanning direction Z. Ma
In addition, a current confinement portion exists between the high-resistance regions 127 of the active layer 123.
(See FIG. 5 described later.) S is formed, and Sy is the main running
The current constriction radius in the scanning direction Y, Sz is the current constriction radius in the sub-scanning direction Z.
The stenosis radius is shown.

FIG. 4 is a front view of a principal part of the laser array 12A according to the first embodiment, and FIG. 5 is a sectional view of a principal part in the main scanning direction Y of the laser array 12A. This laser array 12
A is n provided at predetermined intervals along the main scanning direction Y.
N × m light emitting holes 125 are provided at the intersections between the Y direction base lines N and the m θ direction base lines M provided at a predetermined interval at an angle θ with respect to the Y direction base lines N. I have. Each light emitting hole 1
Reference numeral 25 denotes a laser light source array on the θ-direction base line Mo passing through the center 130 of the optical axis as a starting point. In addition, the size of the light emitting holes 125 on the same θ direction base line M is made equal.

FIG. 6 is a diagram showing a near-field pattern of the light source 12a of the laser array 12A according to the first embodiment. In the drawing, r indicates the radius of the near field pattern of the light source 12a (the radius at 1 / e ² of the peak intensity). By forming the light emitting hole 125 so as to become smaller as it goes away along the main scanning direction Y, the radius r of the near field pattern of the light source 12a becomes smaller than the optical axis center 1
The further away from 30, the smaller. For example, the light source 12a
Is 2 μm, and the ratio (b / a) of the distance b to the distance a (b / a) is 6, the near-field pattern radius R on the photoconductor surface 16a is 12 μm.

FIG. 7 shows a laser array according to the first embodiment.
Rays emitted from light sources 12a at different positions
FIG. 4 is a diagram showing a comparison of the beam 13. On the optical axis center 130
Some light source 12_a0The near-field pattern radius of r₀,
Light source 12 located away from optical axis center 130_akNear
Field pattern radius to radius r₀Smaller r_kToss
You. Light source 12 at optical axis center 130_a0Is the focal plane 15b
Radius R on₀(= R₀× (b / a)).
On the other hand, the near field pattern radius r_kLight source 12
_akIs the radius R at the focal plane 15b._k(= R_k× (b / a)
After forming an image, it gradually becomes thicker, and at a position at a predetermined distance L
Is the radius R₀Spot radius W equal to_kTo form

Since there is a relationship between W _k and R _k as shown in the following equations (1) to (5), when this is solved, the deviation Δx (y) between the focal point 15a and the photoconductor surface 16a is obtained. near field pattern radius r _k of the corresponding light sources 12a to obtain. This is shown in the following equation (6). W _k ² = R _k ² (1+ (λL / πR _k ² ) ² ) (1)

(Equation 1) R _k = r _k × (b / a) (3) W _k = r ₀ × (b / a) (4) L = Δx (y) (5)

(Equation 2)

[0019] from the formula (6), a near field pattern radius r _k of the light source 12 _a0 than other light sources 12 _ak on the optical axis 130 of the focus 15a due to the spherical aberration light source 12
By setting the deviation Δx (y) to the a side to be equal to L, the photoconductor surface 16 is always maintained in all the light sources 12a.
The same spot diameter can be obtained on a.

Next, the operation of the apparatus 11 will be described. When the signal processing circuit 18 reads an image signal from the image memory 17 and processes the image signal to output a recording signal corresponding to a recording pattern, the laser driving circuit 19
Under the control of 0, the recording signal is input from the signal processing circuit 18 to drive the laser array 12. A laser beam 13 is emitted from each laser light source 12a of the laser array 12. Laser beam 1 emitted from each laser light source 12a
The light 3 is condensed on a condensing point 14a by a condensing lens system 14, and is imaged on a photoreceptor surface 16a by an imaging lens system 15. The photosensitive drum 16 forms an electrostatic latent image by being exposed by the laser beam 13. Thereafter, the electrostatic latent image is developed with toner by a developing device, the toner image is transferred by a transfer device to recording paper fed from a paper feeding unit, and after being fixed by a fixing device, the recording paper is discharged. It is sent to the paper department.

Next, the effect of the present apparatus 11 will be described with reference to FIG. FIG. 8 is a diagram showing a positional relationship between the photoconductor surface 16a and the focal plane 15b and a spot on the photoconductor surface 16a. According to the present apparatus 11, as shown in FIG. 8, the laser beam 13 from the light source 12 _a0 at the optical axis center 130 is focused on the focal point 15 a formed by the lens systems 14 and 15,
If is arranged 6a, focus first laser beam 13 from the light source 12 _ak away from the light source 12 _a0 center of the optical axis 130 in the main scanning direction Y by the spherical aberration or the like of the lens system 14 and 15
5a is formed before the photoconductor surface 16a, the light source 12
The near field pattern diameter r of a is set to the lens systems 14 and 15.
Is set so as to cancel the shift amount from the photoconductor surface 16a due to the spherical aberration of the photoconductor surface 16a.
Since the same spot diameter D can be obtained, an image having a uniform resolution can be obtained. Further, since the spherical aberration and the like of the lens systems 14 and 15 can be corrected on the light source 12a side, an inexpensive lens can be used, and the cost can be reduced.

FIG. 9 is a front view of a main part of a laser array 12B according to the second embodiment. In the laser array 12A according to the first embodiment, even when the lens systems 14 and 15 have spherical aberration, the plurality of light sources 12a
The spot diameter D formed above becomes equal, but when the radius r of the near-field pattern is changed, the laser beam 13
Is λ, the emission angle u of the light source 12a changes as in the following equation (7). tan (u) = (2λ) / (πr) (7) That is, when the frequency λ of the laser beam 13 is constant, the emission angle u increases as the radius r decreases. As in the first embodiment, when the radius r is reduced as the distance from the optical axis center 130 in the main scanning direction Y decreases,
Since the emission angle u of the endmost light source 12a is maximized, there is a possibility that the laser beam 13 from the endmost light source 12a is emitted by the imaging lens system 15. In the case of an optical system using a slit (pinhole) in the optical path, the larger the spread angle is, the larger the amount of light emitted by the slit (pinhole) becomes, so that the beam intensity obtained on the photoconductor surface 16a becomes uneven. Could be. In order to prevent these, in the second embodiment, even when the radius r changes, the emission angle u does not change.

As shown in FIG. 9, in the laser array 12B, as in the first embodiment, the light emitting holes 125 are formed so that the light source _12a0 at the optical axis center 130 is the starting point and the optical axis center 13
As the distance from 0 increases along the main scanning direction Y, the light source 1 is set to decrease gradually or stepwise.
Since the emission angle u of the laser beam 13 from the light source 2a is determined by λ / r, the wavelength λ from each light source 12a is also adjusted to the optical axis center 13 so that the emission angle u is the same for all the light sources 12a.
Starting from the light source 12 _a0 at 0, the distance from the optical axis center 130 along the main scanning direction Y is set to gradually or stepwise decrease.

The wavelength λ can be shortened by, for example, reducing the thickness of the mirror layers 121 and 123. When the light emitting hole 125 is gradually reduced,
This can be realized by forming the mirror layers 121 and 123 such that the film thickness distribution becomes maximum at the optical axis center 130 and becomes thinner toward the periphery. When the light emitting hole 125 is gradually reduced or when it is desired to increase the wavelength difference, the light emitting hole 125
A number of laser array chips having a wavelength λ corresponding to the size of the laser array 12B may be manufactured and bonded to form a laser array 12B. In the figure, the light source 1 on the θ direction base line M ₀
The wavelength of the laser beam 13 from 2 _a0 lambda _0, the wavelength of the laser beam 13 from the θ direction baseline M ₁ on the light source 12a lambda
_1, when the wavelength of the laser beam 13 from the θ direction baseline M ₂ on the light source 12a and lambda _2, in λ _0> λ _1> λ ₂ relationship. The emission angle u of the laser beam 13 of only the light source 12a near the end where the laser beam 13 may be blurred by the imaging lens system 15 may be reduced.

FIG. 10 shows laser beams 13 emitted from light sources 12a at different positions on a laser array 12B according to the second embodiment. In the case of the laser array 12B as well, the light source _12a0 located at the optical axis center 130 and the light source 12a having a smaller near-field pattern radius r have different beam diameters on the focal plane 15b, but the emission angle u is the same. It is. Laser beam 13 from the light source 12 _ak radius r _k, after a spot diameter r _k × focal plane 15b (b / a), gradually thickens in the light source 12 _a0 in the optical axis 130 at a certain position It becomes equal to the spot diameter to be formed. Assuming that this position is the position of the focal length + L, the focal point 15a from the light source 12a is closer to the light source 12a from the optical axis center 130 by the light source 1a by Δx (y) due to spherical aberration.
Since the shift is to the 2a side, the radius r of the light source 12a may be set so that L and the shift amount Δx (y) are equal.
The setting conditions are obtained by the mathematical expressions shown in the first embodiment.

According to the laser array 12B according to the second embodiment, the same spot diameter D can be obtained on the photoreceptor surface 16a even if there is a spherical aberration of the lens systems 14 and 15, and the laser beam 13 is not shaken by the imaging lens system 15. Also, in an optical system using a slit (pinhole) in the optical path, since the beam spread angle is constant, the amount of light emitted by the slit (pinhole) is almost the same, and the light intensity is stable.

FIG. 11 is a front view of a main part of a laser array 12C according to the third embodiment. This laser array 12
In C, the near-field pattern radius r is changed only in the main scanning direction Y, and the light emitting holes 125 of the plurality of light sources 12a are formed as ellipses whose major axis is in the sub scanning direction Z. in this case,
The spot formed on the photoconductor surface 16a has an elliptical shape. Although not shown, the radius r of the near-field pattern may be changed only in the sub-scanning direction Z. Further, the near field pattern radius r in the main scanning direction Y or the sub scanning direction Z may be changed at different ratios. This is effective when the magnification / reduction magnification of the imaging lens system 15 is different between the main scanning direction Y and the sub scanning direction Z.

FIG. 12 is a front view of a laser array 12D according to the fourth embodiment. This laser array 12D
Are formed so that the near-field pattern radius r of the light source 12a gradually or gradually decreases toward the optical axis center 130 from the light source 12a on the endmost θ-direction base line M as a starting point. In this case, photoconductor surface 1
As shown in FIG. 13, 6a is set so as to coincide with the focal point 15a of the laser beam 13 from the light source 12a on the extreme end θ direction base line M. According to the laser array 12D according to the fourth embodiment, the same effects as those of the laser array 12A according to the first embodiment can be obtained.

FIG. 14 is a front view of a main part of a laser array 12E according to a fifth embodiment. This laser array 12
E is formed such that the near-field pattern radius r of the light source 12a becomes smaller toward the optical axis center 130 and the end from the light source _12a2 at two predetermined positions between the optical axis center 130 and both ends. Things. In this case, the photoconductor surface 16a is set so as to coincide with the focal point 15a of the light source _12a2 at two predetermined positions as shown in FIG. Laser array 1 according to the fifth embodiment
According to 2E, the laser array 1 according to the first embodiment
It has the same effect as 2A.

FIG. 16 is a front view of a main part of a laser array 12F according to a sixth embodiment. The laser arrays 12A to 12E according to the first to fifth embodiments have the same θ.
Although the near field pattern radius r of the light source 12a on the direction base line M is made equal, even if the laser array 12F is the light source 12a on the same θ direction base line M, the optical axis center 1
The near-field pattern radius r is changed in accordance with the position in the main scanning direction Y starting from 30. Although FIG. 2 shows the case where the size is reduced, the case where the size is increased can be similarly applied. According to the laser array 12F according to the sixth embodiment, a more uniform resolution can be obtained as compared with the laser array 12A according to the first embodiment.

Next, another method of changing the radius r of the near field pattern of the light source 12a will be described. As a method of changing the radius r of the near-field pattern, the light emitting hole 12 is used.
Although the method of changing the diameter of 5 has been described, the current constriction S or the air post E may be changed. Current constriction S
Alternatively, the shape of the air post E is shown in FIG. 3 as being rectangular, but may be elliptical or circular. The mirror layers (air posts E) 122 and 124 may be formed by forming a current confined portion S by a method such as oxidation, proton injection, or diffusion, and this may be changed. The current confinement portion S of the active layer 123 is
Although it is formed by proton injection in FIG. 3, it may be formed by a method such as oxidation or diffusion. In the case of an edge-emitting laser, the thickness of the current constriction S and the thickness of the active layer 123 may be changed.

FIG. 17 is a diagram showing an example in which the radius r of the near field pattern of the light source 12a is changed by changing the air post E along the main scanning direction Y. In the figure, the air post E is different along the main scanning direction Y,
The diameters of the light emitting holes 125 are the same.

The present invention is not limited to the above embodiment, but various embodiments are possible. For example, in the above embodiment, a light source array in which a plurality of light sources are two-dimensionally arranged has been described.
The present invention can be similarly implemented for a light source array arranged in a dimension. In the above embodiment, the laser array is described as the light source array. However, the present invention is also applicable to an LED array in which LED light sources are arranged one-dimensionally in the main scanning direction or two-dimensionally in the main scanning direction and the sub-scanning direction. It can be implemented similarly. In this case, the area of the light emitting portion of the LED may be changed along the main scanning direction. In the above embodiment, the photosensitive drum is used as a recording medium, but another optical recording medium may be used. Further, in the above-described embodiment, the image forming apparatus has been described. However, the present invention can be similarly applied to an optical scanning apparatus that reads recorded information recorded on a recording medium and a shape of an object.

[0034]

As described above, according to the present invention, a plurality of light sources are arranged in a near-field pattern corresponding to a degree of out-of-focus on a scanning surface or an image forming surface of a plurality of light beams with respect to a focal position of an optical unit. By having a diameter, the spot diameter of the light beam applied to the scanning surface or the image forming surface can be made equal, so that the resolution can be made uniform and a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of the present invention.

FIG. 2 is a configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention.

3A and 3B are views showing the structure of a laser array, wherein FIG. 3A is a perspective view of a main part thereof, and FIG.
Part detail drawing

FIG. 4 is a front view of a main part of the laser array according to the first embodiment.

FIG. 5 is a cross-sectional view of a main part in the main scanning direction of the laser array according to the first embodiment.

FIG. 6 is a view showing a near-field pattern of the light source according to the first embodiment;

FIG. 7 is a diagram showing laser beams emitted from light sources at different positions in the laser array according to the first embodiment.

FIG. 8 is a diagram showing a positional relationship between a photoconductor surface and a focal plane according to the first embodiment.

FIG. 9 is a front view of a main part of a laser array according to a second embodiment.

FIG. 10 is a diagram showing laser beams emitted from light sources at different positions in the laser array according to the second embodiment.

FIG. 11 is a front view of a main part of a laser array according to a third embodiment;

FIG. 12 is a front view of a main part of a laser array according to a fourth embodiment;

FIG. 13 is a diagram illustrating a positional relationship between a photoconductor surface and a focal plane according to a fourth embodiment.

FIG. 14 is a front view of a main part of a laser array according to a fifth embodiment.

FIG. 15 is a diagram illustrating a positional relationship between a photoconductor surface and a focal plane according to a fifth embodiment.

FIG. 16 is a front view of a main part of a laser array according to a sixth embodiment.

FIG. 17 is a diagram showing an example in which a near-field pattern radius of a light source is changed by changing air posts along a main scanning direction.

FIG. 18 illustrates a conventional image forming apparatus.

FIG. 19 is a diagram illustrating a problem of a conventional image forming apparatus.

[Explanation of symbols]

Light source 13 a laser which is positioned between the light source 12 _a2 optical center and ends at the position away from the light source 12 _ak optical axis center in the 11 image forming apparatus 12,12A to 12F semiconductor laser array 12a the laser light source 12 _a0 optical axis Beam 14 Focusing lens system 14a Focusing point 15 Imaging lens system 15a Focus 16 Photoconductor drum 16a Photoconductor surface 17 Image memory 18 Signal processing circuit 19 Laser drive circuit 20 Control circuit 120 Semiconductor substrate 121 N-type electrode 122 N-type mirror layer 123 active layer 124 p-type mirror layer 125 light-emitting hole 126 p-type electrode 127 high-resistance region 128 separation groove 130 center of optical axis a distance between laser array surface and condensing lens system b distance between condensing lens system and photoconductor surface D Spot diameter E Air post Ey Air post radius in the main scanning direction Ez D in the sub scanning direction Distance M theta direction baseline M Mo theta direction baseline through the optical axis center N Y direction baseline r source near field pattern radius r _k of the light source in the near field pattern radius r ₀ the optical axis center of the post radius L focus and the photoreceptor surface a light source having a radius R _k radius r _k of the image light source of near field pattern radius R ₀ radius r ₀ on the near field pattern radius R photoreceptor surface of the light source is located away from the optical axis center is formed on the focal plane spot radius X of the light source of the emission angle W _k radius r _k of the current confinement radius u source of the current confinement radial Sz sub-scanning direction of a radius S current confinement portion Sy main scanning direction of the image formed on the focal plane is formed on the photoreceptor surface Optical axis direction Y Main scanning direction Z Sub scanning direction Δx (y) Defocus λ Laser beam frequency

Claims (22)

[Claims] An optical scanning device for scanning a scanning surface with a plurality of light beams, a light source array in which a plurality of light sources for emitting the plurality of light beams are arranged one-dimensionally or two-dimensionally; Optical means for condensing a light beam on the scanning surface, wherein the plurality of light sources of the light source array correspond to a degree of out-of-focus of the plurality of light beams on the scanning surface with respect to a focal position of the optical means. An optical scanning device characterized by having a near-field pattern diameter. 2. The light source according to claim 1, wherein the plurality of light sources have a structure in which the diameter of the near-field pattern is reduced from a central light source in the main scanning direction to light sources at both ends, and the scanning surface is formed by the optical means. 2. The optical scanning device according to claim 1, wherein the optical scanning device is arranged at a focal position of a central light source. 3. The plurality of light sources have a structure in which the diameter of the near-field pattern is reduced from the light sources at both ends in the main scanning direction to the central light source, and the scanning surface is formed by the optical means. The optical scanning device according to claim 1, wherein the optical scanning device is configured to be disposed at a focal position of a light source at both ends. 4. The first and second light sources arranged at a predetermined distance from the light sources at both ends in the main scanning direction.
Wherein the diameter of the near-field pattern is reduced from the light source to the central light source and the light sources at both ends, and the scanning surface is located at a focal position of the first and second light sources formed by the optical unit. 2. The optical scanning device according to claim 1, wherein the optical scanning device is arranged. 5. The optical scanning device according to claim 2, wherein the plurality of light sources have a configuration in which the diameter of the near-field pattern changes in two directions perpendicular to a cross section of the light beam. 6. The light according to claim 2, wherein said plurality of light sources have a configuration in which said near-field pattern diameter changes in a direction of one axis parallel to said main scanning direction of a cross section of said light beam. Scanning device. 7. The optical scanning device according to claim 2, wherein the plurality of light sources emit the plurality of light beams having wavelengths corresponding to the near-field pattern diameter. 8. The optical scanning device according to claim 7, wherein said plurality of light sources are constituted by a plurality of semiconductor lasers having a mirror layer having a thickness corresponding to said wavelength. 9. The light source array, wherein the plurality of light sources are arranged two-dimensionally, the plurality of light sources are provided in a plurality of main scanning direction base lines provided at predetermined intervals along the main scanning direction, It is provided at each intersection with a plurality of θ-direction baselines provided at a predetermined interval with an angle θ with respect to the main scanning direction baseline, and has a configuration in which the near-field pattern diameter changes for each θ-direction baseline. The optical scanning device according to claim 2, 3 or 4. 10. The light source array according to claim 1, wherein the plurality of light sources include two light sources.
The plurality of light sources are arranged in a dimension, and the plurality of light sources are provided at a plurality of main scanning direction base lines provided at a predetermined interval along the main scanning direction, and at a predetermined interval having an angle θ with respect to the main scanning direction base line. The near field pattern diameter is provided at each intersection with a plurality of θ direction base lines provided in the above, and the near field pattern diameter changes along the main scanning direction with reference to a predetermined base line along the sub scanning direction.
5. The optical scanning device according to 3 or 4. 11. A light source, comprising: an n-type electrode formed on a back surface of a semiconductor substrate; an n-type mirror layer; an active layer including a light-emitting layer; a p-type mirror layer; A p-type electrode having a light-emitting hole is formed in this order, protons are injected into the active layer or the p-type mirror layer to form a high-resistance region, and the p-type electrode, the p-type mirror layer, and the active layer are formed. Are formed into a plurality by separating grooves,
The near field is changed by changing one of a diameter of the light emitting hole, a diameter of an air post formed between the separation grooves of the p-type mirror layer, and a diameter of a current confinement formed between the high resistance regions of the active layer. 5. The optical scanning device according to claim 2, wherein the pattern diameter varies. 12. An image forming apparatus for scanning an image forming surface with a plurality of light beams modulated according to an image signal to form an image on the image forming surface, wherein a plurality of light sources for emitting the plurality of light beams A light source array arranged one-dimensionally or two-dimensionally; an optical unit for condensing the plurality of light beams on the image forming surface; and an optical unit arranged on the image forming surface and corresponding to the plurality of light beams. An image forming body that forms an electrostatic latent image, wherein the plurality of light sources of the light source array correspond to a degree of out-of-focus on the image forming surface of the plurality of light beams with respect to a focal position of the optical unit. An image forming apparatus having a near-field pattern diameter. 13. The light source according to claim 1, wherein the plurality of light sources have a structure in which the diameter of the near-field pattern is reduced from a central light source in the main scanning direction to light sources at both ends, and the image forming surface is formed by the optical means. 13. A configuration arranged at a focal position of the central light source.
The image forming apparatus as described in the above. 14. The plurality of light sources have a configuration in which the diameter of the near-field pattern decreases from the light sources at both ends in the main scanning direction to the central light source, and the image forming surface is formed by the optical means. 2. A structure according to claim 1, wherein said light sources are arranged at the focal positions of said light sources at both ends.
3. The image forming apparatus according to 2. 15. The near field light source extends from first and second light sources arranged at predetermined intervals to light sources at both ends in the main scanning direction to a central light source and light sources at both ends in the main scanning direction. 13. The image forming apparatus according to claim 12, wherein the pattern diameter is reduced, and the image forming surface is arranged at a focal position of the first and second light sources formed by the optical unit. 16. An image forming apparatus according to claim 13, wherein said plurality of light sources have a configuration in which said near-field pattern diameter changes in two directions orthogonal to a cross section of said light beam. 17. The light source according to claim 13, wherein the diameter of the near field pattern changes in a direction of one axis parallel to the main scanning direction of a cross section of the light beam.
16. The image forming apparatus according to 4 or 15. 18. The image forming apparatus according to claim 13, wherein the plurality of light sources emit the plurality of light beams having wavelengths corresponding to the diameter of the near-field pattern. 19. An image forming apparatus according to claim 18, wherein said plurality of light sources are constituted by a plurality of semiconductor lasers having a mirror layer having a thickness corresponding to said wavelength. 20. The light source array, wherein the plurality of light sources include two light sources.
The plurality of light sources are arranged in a dimension, and the plurality of light sources are provided at a plurality of main scanning direction base lines provided at a predetermined interval along the main scanning direction, and at a predetermined interval having an angle θ with respect to the main scanning direction base line. The image forming apparatus according to claim 13, wherein the near field pattern diameter is provided at each intersection with the plurality of θ-direction base lines provided in the above, and the near-field pattern diameter changes for each of the θ-direction base lines. 21. The light source array, wherein the plurality of light sources include two light sources.
The plurality of light sources are arranged in a dimension, and the plurality of light sources are provided at a plurality of main scanning direction base lines provided at a predetermined interval along the main scanning direction, and at a predetermined interval having an angle θ with respect to the main scanning direction base line. And wherein the near-field pattern diameter is changed along the main scanning direction with reference to a predetermined base line along the sub-scanning direction, provided at each intersection with the plurality of θ-direction base lines provided at (1).
16. The image forming apparatus according to 3, 14, or 15. 22. A light source, comprising: an n-type electrode formed on a back surface of a semiconductor substrate; an n-type mirror layer; an active layer including a light-emitting layer; a p-type mirror layer; A p-type electrode having a light-emitting hole is formed in this order, protons are injected into the active layer or the p-type mirror layer to form a high-resistance region, and the p-type electrode, the p-type mirror layer, and the active layer are formed. Are formed into a plurality by separating grooves,
The near field is changed by changing one of a diameter of the light emitting hole, a diameter of an air post formed between the separation grooves of the p-type mirror layer, and a diameter of a current confinement formed between the high resistance regions of the active layer. 16. The image forming apparatus according to claim 13, wherein the pattern diameter is changed.