JP2002273930A - Light emitting device array, printer head, method for assembling printer head, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an image forming apparatus by which periodical fluctuation of optical performances of a lens element array is reduced and a latent image with a high quality of an image with no fluctuation can be formed on a photo- sensitive body. SOLUTION: A light emitting device in which a plurality of light emitting parts A, B and C are arranged in a line is characterized by placing the light emitting parts A with a wide area, the light emitting parts B with an intermediate area and the light emitting parts C with a narrow area in order and increasing and decreasing thereby the light emitting area by a definite period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light emitting element array,
The present invention relates to a printer head, a method of assembling a printer head, and an image forming apparatus, and more particularly, to an image forming apparatus used in a recording apparatus such as an electrophotographic printer, a light emitting element array as a component thereof, a printer head, and a method of assembling the printer head.

[0002]

2. Description of the Related Art In recent years, with the development of information processing technology and communication technology, a small and inexpensive electrophotographic printer capable of outputting a large amount of arbitrary characters and graphics on plain paper at high speed and with high quality has been developed. Has been requested. In order to meet such demands, a plurality of light emitting diode elements (LEs) are provided on one main surface of an electrically insulating substrate as a light source of such a printer.
An electrophotographic printer using an optical printer head having D) mounted linearly has been proposed as a small-sized, high-resolution one.

[0003] An optical printer head as an image forming apparatus used in this conventional electrophotographic printer includes:
Normally, as shown in FIG. 6, a base plate 1 in which a light emitting diode element array 13 composed of a plurality of light emitting diode elements 13a is linearly arranged on an electrically insulating substrate 12 is mounted.
1 and a rod-shaped self-focusing lens 1
Lens element array 1 in which a large number of lens elements 6 are linearly arranged in two rows
4 and housing 17 made of polycarbonate resin or the like
The base plate 11 and the lens element array 14 are mounted on a housing 17, and each of the light emitting diode elements 13 a is a rod-shaped self-focusing lens 16.
Are fixed via an adhesive so as to be located on the optical axis of the optical disk.

In the optical printer head as the image forming apparatus, each light emitting diode element 13a of the light emitting diode element array 13 selectively emits light individually according to an external electric signal.
The light emitted by 3a is imaged on the surface of an external photoconductor 18 via the lens element array 14, and a latent image is formed on the photoconductor 18, thereby functioning as an image forming apparatus. However, in this conventional image forming apparatus, the light emitting portion of the LED is located at any position of the lens forming the lens element array due to the aberration of the rod lens (rod-shaped lens) forming the lens element array. There is a problem that the diameter of the beam formed on the photoreceptor differs depending on the situation.

[0005] This phenomenon will be described with reference to FIG. This means that a bar-shaped self-focusing lens 16 is
It is an example of a lens element array in which a large number of lens elements are linearly arranged in a row. Generally, two rows of lens element arrays that are commercially available are stacked such that the upper row and the lower row are shifted by the lens radius as shown in FIG. Therefore, when this is mounted on the LED head, the LED array is arranged so that the LEDs are located on the line 19 passing through the center of the upper stage and the lower stage. The diameter of a rod lens constituting a commercially available lens element array is generally about 0.5 to 1.0 mm. On the other hand, the LE of the LED array constituting the LED head
The arrangement of D light emitting units is 0.0 for 600 DPI printer.
42 mm pitch, 0.0 for 1200 DPI printer
21 mm, which is smaller than the arrangement pitch of the rod lenses. Therefore, the light emitting portion of the LED takes various positions with respect to the rod lenses constituting the lens element array.

In FIG. 7, an arbitrary rod lens 16a of the rod lenses constituting the lens element array and the rod lens 1 closest to the rod lens 16a are shown.
Consider the positional relationship between 6b and the LED. A line passing through the center of the rod lens 16a and orthogonal to a line 19 passing through the center of the lens element array is defined as 20a. Similarly, a line passing through the center of the rod lens 16b and orthogonal to the line 19 passing through the center of the lens element array is defined as 20b. Also the line 20a
A line passing through the middle between the line 20b and the line 20b is referred to as a line 21. Looking at the arrangement of the rod lenses, the rod lenses 16a and 16b
It can be seen that it is rotationally symmetric about the intersection of 1 and the line 19. That is, the lens element array stacked in two rows has a repetitive structure in which the radius of the constituent rod lenses is the pitch.

Further, it is known that the imaging performance of the lens changes depending on where the light emitting portion of the LED is located on the rod lens. That is, when the object is located on the line 20a, the light exiting the object is distributed almost evenly to the rod lens 16a and the rod lens adjacent to the lower right and the lower left thereof, and is combined again after passing through the rod lens. To form a light image. On the other hand, if the object is located on the line 21, the light leaving the object passes mainly through the rod lenses 16 a and 16 b and the right lens of the rod lens 16 a and the left lens of the rod lens 16 b, and is then synthesized again. An optical image is formed. As described above, since the arrangement of the passing rod lenses is different, a phenomenon occurs in which the imaging states of the objects at the corresponding positions are also different.

As an example, a two-row lens element array composed of rod lenses having a diameter of 0.9 mm is used, and the light emitting portion is made up of eight rows.
When the image of the μm LED was formed, the LED
Alternatively, when it is located at a position corresponding to the position on 10b, its beam diameter is 42 μm, and when it is located at a position corresponding to the position on line 11, its beam diameter is 45 μm. Since this phenomenon is caused by the periodicity of the lens element array, the beam diameter formed in the direction in which the lens element arrays are arranged also has a periodicity as shown in FIG.

FIG. 9 shows the measurement results of the beam diameter. It can be seen that the beam diameter distribution shows a periodic distribution in both the main scanning direction and the sub-scanning direction. As a result of the analysis, it has been clarified that this period is caused by uneven performance of the lens period of the lens element array. Further, when the printing result of the LED printer using this printer head is measured, this effect is noticeable.

FIG. 10 shows the result of Fourier analysis in the LED arrangement direction of an image output by a printer using an LED head using a lens element array in which two rod lenses each having a lens diameter of 0.9 mm are stacked in two rows. The image is 600 DPI
LED is turned on for each dot of the head. Looking at the results of the measurement, it can be seen that lines at intervals of about 2.2 lines / mm appear remarkably. This corresponds to a repetition cycle of the arrangement of the rod lenses of 0.9 mm of 0.45 mm. As described above, L using the conventional lens integrated type lens element array is
In the ED printer, unevenness corresponding to the lens integration cycle occurs. Due to this unevenness, a streak-like unevenness, that is, a vertical streak occurs in the direction perpendicular to the arrangement direction of the LED array in the LED printer. Therefore, particularly when printing a pattern that fills a uniform surface or the like, there is a problem that roughness due to streak-like unevenness appears and the quality of an image is reduced.

To solve this problem, conventionally, in order to make the beam diameter after passing through the lens element array uniform,
By adjusting the current injected to each LED, increasing the current injected to the LED with a smaller beam diameter compared to the others, and decreasing the current injected to the LED with a larger beam diameter compared to the others, it is possible to connect to the photoconductor surface. There are attempts to make the size of the image beam uniform. However, in this method, if the injection current to the LED is increased in order to increase the beam diameter, the beam diameter to be imaged becomes large, and in addition, the amount of light from the LED increases, so that it is injected into the beam to be imaged on the photoconductor. Energy is increased, and when an image is formed by electrophotography, unevenness in the density of the image occurs, thereby deteriorating the quality of the image.

[0012]

As described above, the beam diameter formed on the photoreceptor varies depending on the positional relationship between the rod lens forming the lens element array and the light emitting portion of the LED. There is a problem that streak-like unevenness occurs. SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of forming a high-quality latent image without unevenness on a photoreceptor by reducing the periodic fluctuation of the optical performance of a lens element array.

[0013]

According to a first aspect of the present invention, there is provided a light-emitting element array having a plurality of light-emitting portions, the light-emitting portions being arranged in a line. , Wherein the area of the light emitting portion increases and decreases at a certain period.

According to a second aspect of the present invention, there is provided a light emitting element used in a printer head having a lens element array composed of a unit-magnification image forming optical system, a light emitting element array, and a housing for housing these elements. In the element array, the period of the periodic distribution of the imaging performance of the lens element array and the period of the increase and decrease of the area of the light emitting unit are approximately matched.

Further, in the invention of claim 3 of the present invention, the cycle of increasing or decreasing the area of the light emitting portion of the light emitting element array is two or more.

Further, in the invention according to claim 4 of the present invention, the length of the light emitting element array in the longitudinal direction is approximately an integral multiple of the period of the periodic distribution of the imaging performance of the lens element array. It is characterized by.

According to a fifth aspect of the present invention, there is provided a lens element array comprising an equal-magnification image forming optical system, the light-emitting element array according to the first aspect, and a housing for incorporating and storing these. In the printer head, the lens element array is arranged such that the lens element array and the light emitting element array are arranged in the longitudinal direction at least for one cycle of a periodic distribution of imaging performance of the lens element array. The relative position can be changed.

According to a sixth aspect of the present invention, in a method for assembling a printer head in which a lens element array including a unit-magnification imaging optical system and a light-emitting element array are incorporated in a housing, While the lens element array is moved in the longitudinal direction in the lit state, a beam shape formed by the light emitting element array after passing through the lens is measured, and the lens element is positioned at a position where a deviation of a plurality of beam shapes is minimized. The method is characterized in that the array is fixed.

Further, according to the invention of claim 7 of the present invention, an electrostatic latent image is formed on a surface located on a surface to be irradiated by the printer head according to claim 5 and light condensed and irradiated by the printer head. A photoreceptor to be formed, a developing device for developing an electrostatic latent image formed on the photoreceptor into a visible image, and a transfer for transferring the visible image developed by the developing device onto a recording medium And an apparatus.

Thus, the area of the light emitting portion of the light emitting element corresponding to the portion where the beam diameter becomes large due to the structural period unevenness of the lens element array is reduced, and the beam diameter becomes small due to the structural period unevenness of the lens element array. To provide a printer head capable of increasing the area of the light-emitting portion of the light-emitting element corresponding to the above, thereby suppressing the variation of the beam diameter on the image forming surface on the photosensitive member after passing through the lens element array. Can be. Further, by using this printer head, it is possible to provide an electrophotographic image forming apparatus capable of forming a high quality image with less unevenness.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a light emitting element array, a printer head, a method of assembling a printer head, and an image forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a part of a light emitting portion of an LED light emitting element array according to an embodiment of the present invention. This embodiment corresponds to claims 1 and 2 of the present invention. This embodiment is a 600 dpi LED element array,
The pitch of the light emitting units is 42 μm. Each light emitting portion of this LED element array is composed of three types of shapes. In the figure, the three types of light emitting units are shown as A, B, and C, respectively. In the present embodiment, the dimensions in the sub-scanning direction are all 25 μm for each light emitting unit. On the other hand, the dimensions in the main scanning direction are 25 μm for A, 24 μm for B, and
Is changed to 23 μm.

As shown in FIG.
The arrangement is such that B, B, B, C, C, C, B, B, B, A form one cycle in the order. By repeating the above pattern on the LED element array as shown in FIG.
One dot forms a repetitive pattern having a cycle of 0.46 mm. By using the method of adjusting the size of the light emitting portion with the size in the main scanning direction as in the present embodiment, the spread of the toner image of the formed image in the main scanning direction can be easily controlled, and the toner with small variation can be controlled. An image can be formed.

FIG. 2 shows a measurement result of a beam diameter of an LED printer using an LED printer head using the LED element array of the present embodiment. In the conventional LED element array in the graph, the size of the light-emitting portion is a square of 25 μm square. In the conventional type, the variation in the beam diameter is large.
When the element array is used, the variation in the beam diameter is smaller.

FIG. 3 shows a part of a light emitting section of an LED element array according to another embodiment. This embodiment is 600d
pi LED element array, and the pitch of the light emitting units is 42
μm. In the present embodiment, each light emitting unit is constituted by four types of shapes. The four types of light emitting parts are A, B,
C and D are shown. In the present embodiment, the dimension in the main scanning direction is set to 25 μm for each light emitting unit. On the other hand, the dimension A in the main scanning direction is 28 μm,
B is 27 μm, C is 26 μm, and D is 25 μm. These light emitting portions are denoted by A, B, B, and B as shown in FIG.
One cycle is arranged in the order of C, C, D, C, C, B, B, and A. Figure 3 on the LED element array
As shown in (B), the above pattern is repeated to form a repeated pattern having a period of 0.46 mm with 11 dots.

When the method of adjusting the size of the light emitting portion in the sub-scanning direction as in the above embodiment is used, the size of the light emitting portion in the main scanning direction can be kept constant. Even when the distance between the light emitting units is small, the area of the light emitting unit can be easily controlled. Therefore, such a method is suitable for a high-density light-emitting element array in which the dot pitch of the light-emitting portion is narrow, particularly a light-emitting element array having a density of 1200 dpi or more.

FIG. 4 is an explanatory diagram of an example of the fourth embodiment. FIG. 4A is an explanatory diagram illustrating both end portions of the light emitting element array. This light emitting element array is a 600 dpi light emitting element array for a lens element array having a repetition period of 0.45 mm (specifically, a SELFOC lens array: SLA). In this embodiment, a light emitting portion pattern of 11 dots is repeated 22 times, and a light emitting portion of 242 dots is formed per one element array. Accordingly, when a plurality of these light emitting element arrays are arranged side by side as shown in FIG. 4B, the light emitting elements of the same pattern adjacent to each other at both ends of the element can emit light without repetition period being out of order. A repetitive pattern of the area of the part can be formed. As described above, in the light emitting element array according to the fourth aspect, since the head according to the present invention can be constituted only by the element array of one kind of repetitive pattern, there is an advantage that the manufacturing process of the light emitting element array is simplified. .

FIG. 5 shows claims 5 and 6 of the present invention.
It is an explanatory view of an embodiment concerning. This embodiment is a printer head in which a lens element array 1 and a light emitting element array 2 each composed of an equal-magnification image forming optical system are incorporated in a housing 4. A wedge-shaped position adjustment mechanism 5 is provided between the housing 4 and the lens element array 1. By moving the position adjusting mechanism 5 up and down, the relative position between the lens element array 1 and the housing 4 can be adjusted. Since the light emitting element array 2 is fixed to the housing 4 via the substrate 3, the position adjusting mechanism 5 controls the lens element array 1 and the light emitting element array 2.
Can be variably adjusted.

At the time of adjusting the LED head, a plurality of light emitting portions of the light emitting element array 2 are turned on, an image forming point of light in the light emitting portion after passing through the lens element array 1 is measured, and a beam diameter of each light emitting portion is measured. I do. Then, in this state, the position adjusting mechanism 5
Is used to variably adjust the relative position between the lens element array 1 and the light emitting element array 2 to obtain a position at which the variation of each beam diameter becomes smaller. By fixing the position adjusting mechanism 5 in a state where the position where the variation is reduced is obtained, the variation in the beam diameter of each light emitting unit of the printer head can be reduced. In the printer using the printer head adjusted so that the variation of the beam diameter of each light emitting unit is reduced in this way, the output image does not have a periodic image unevenness unlike a conventional printer, and is excellent. An image is obtained.

[0030]

As described above, according to the first and second aspects of the present invention, in the printer head using the lens element array having the periodic distribution of the imaging performance, the beam area on the imaging plane is reduced. It is possible to suppress the variation and to obtain an imaging point with a small variation on the imaging surface of the photoconductor.

Further, according to the third aspect of the present invention, it is possible to reduce the number of times of alignment processing between the lens element array and the light emitting element array, and to increase the work efficiency. According to the fourth aspect of the present invention, the lens element arrays of the first and second aspects can be realized with one kind of light emitting element array, so that the process can be simplified.

According to claim 5 of the present invention, claim 1
Thus, it is possible to realize a printer head in which the lens element array can be installed at a position where the size of the light emitting portion area of the light emitting element array and the periodic distribution of the imaging performance of the lens element array overlap.

According to the printer head assembling method of the sixth aspect of the present invention, the periodicity of the size of the light emitting area of the light emitting element array and the periodic distribution of the imaging performance of the lens element array can be easily determined. Superposition can be performed.

According to the seventh aspect of the present invention, it is possible to realize an electrophotographic image forming apparatus capable of forming a high quality image with less unevenness.

[Brief description of the drawings]

FIG. 1 is a diagram showing a part of a light emitting unit of an embodiment of an LED light emitting element array of the present invention.

FIG. 2 is a diagram showing a measurement result of a beam diameter of an LED printer by an LED printer head using the LED light emitting element array of the embodiment of FIG. 1;

FIG. 3 is a diagram showing a part of a light emitting unit according to another embodiment of the LED light emitting element array of the present invention.

FIG. 4 is a diagram showing a part of a light emitting unit according to another embodiment of the LED light emitting element array of the present invention.

FIG. 5 is a configuration diagram of an embodiment of a printer head according to the present invention.

FIG. 6 is a configuration diagram of a conventional printer head.

FIG. 7 is an explanatory diagram of a problem of a conventional printer head.

FIG. 8 is an explanatory diagram showing the relationship between the position of a lens element array and the diameter of an imaged beam in a conventional printer head.

FIG. 9 is a diagram showing a measurement result of a beam diameter with a conventional printer head.

FIG. 10 is a diagram illustrating a result of Fourier analysis of an image with a conventional printer head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lens element array 2 Light emitting element array 3 Substrate 4 Case 5 Position adjustment mechanism 11 Base plate 12 Electrically insulating substrate 13 Light emitting diode element array 13a Light emitting diode element 14 Lens element array 15 Frame body 16, 16a, 16b Self-focusing lens 17 Housing 18 Photoconductors 19, 20, 21 Auxiliary lines A-C issuing unit

Claims (7)

[Claims] 1. A light-emitting element array having a plurality of light-emitting portions and the light-emitting portions arranged in a line, wherein the area of the light-emitting portions increases and decreases at a certain period. Light emitting element array. 2. A light-emitting element array used for a printer head having a lens element array including a unit-magnification imaging optical system, a light-emitting element array, and a housing for housing the lens element array. 2. The light emitting element array according to claim 1, wherein the period of the periodic distribution of the imaging performance and the period of increase / decrease of the area of the light emitting unit are substantially matched. 3. The light emitting element array according to claim 2, wherein a cycle of increasing or decreasing the area of the light emitting unit is two cycles or more. 4. The light emitting device according to claim 2, wherein the length in the longitudinal direction is approximately an integral multiple of the period of the periodic distribution of the imaging performance of the lens element array. array. 5. A printer head comprising: a lens element array comprising an equal-magnification image forming optical system; the light-emitting element array according to claim 1; The relative position of the lens element array and the light emitting element array can be changed in at least one period of the periodic distribution of the imaging performance of the lens element array in the longitudinal direction of the lens element array. A printer head. 6. A method for assembling a printer head in which a lens element array including a unit-magnification imaging optical system and a light emitting element array are incorporated in a housing, wherein the lens element array is turned on with the light emitting element array turned on. A printer that measures a beam shape formed by the light emitting element array after passing through the lens while moving in the longitudinal direction, and fixes the lens element array at a position where a deviation of a plurality of beam shapes is minimized. How to assemble the head. 7. A printer head according to claim 5,
A photoconductor in which an electrostatic latent image is formed on the surface located on the irradiated surface by light condensed and irradiated by the printer head, and a visible image formed by developing the electrostatic latent image formed on the photoconductor. An image forming apparatus, comprising: a developing device for developing a toner image; and a transfer device for transferring a visible image developed by the developing device onto a recording medium.