JPH115328A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out the accurate tone representation and form the intermediate tone printing well-balanced as a whole by a comparatively simple constitution. SOLUTION: Light, which is emitted from light emitting devices 2a and 3a of respective light emitting device arrays of a first light emitting device array formed of a number of light emitting devices 2a disposed in the linear shape and a second light emitting device array formed of a number of light emitting device groups composed of a plurality of light emitting devices 3a gathered together in compliance with one unit of light emitting devices 2a constituting the first light emitting device array and disposed almost in parallel with the first light emitting device array, is emitted to one photosensitive body P through arrays 4 and 5 to form an image.

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 which realizes halftone printing using a plurality of light emitting elements.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, a light emitting element array composed of an LED array (light emitting diode array) or the like is linearly arranged and mounted on a predetermined circuit board, and a plurality of lenses are arranged above the light emitting element array. In addition, it has a structure in which this is arranged to face the photoreceptor.

In such an image forming apparatus, a light emitting element in a light emitting element array is selectively and individually illuminated based on print data, and the emitted light is irradiated on a photosensitive member through the lens, so that a predetermined amount of light is applied to the photosensitive member. An image is formed by forming a latent image.

When halftone printing is performed using such an image forming apparatus, an area gradation method and an energy gradation method are known as gradation expression methods. In the area gray scale method, one print pixel is constituted by a matrix of a plurality of print dots, for example, 4 × 4, a total of 16 print dots, and the number of print dots in the print pixels is increased / decreased in proportion to the gray level. To express the gradation. In the energy gray scale method, gray scale is expressed by increasing or decreasing the amount of power applied to the light emitting element in proportion to the gray level.

[0005]

However, in this conventional image forming apparatus, the density is insufficient in a low density area even when halftone printing is performed by any of the area gradation method and the energy gradation method. There was a tendency. This is because the number of printing dots in the printing pixels and the power applied to the light-emitting element are not actually proportional to the gradation level. In the case of the method, for example, the size of the matrix constituting the printing pixels is further reduced, and these are finely allocated according to the area corresponding to each gradation level. It is necessary to adjust the shape of the light-emitting element and the electrode shape so that the light-emitting intensity distribution of the light-emitting element changes uniformly, and to control the applied power with high accuracy, and in any case, the image forming apparatus becomes complicated. ,
There is a disadvantage that the image forming apparatus as a product is expensive.

[0006]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks. An image forming apparatus according to the present invention comprises a first light-emitting element row in which a large number of light-emitting elements are linearly arranged; Each of the second light-emitting element rows in which a light-emitting element group in which a plurality of light-emitting elements are arranged corresponding to one light-emitting element constituting the first light-emitting element row is arranged substantially in parallel with the first light-emitting element row. The light from the light emitting elements of the light emitting element row is irradiated and imaged on the same photoreceptor through a lens.

Further, in the image forming apparatus of the present invention, each light emitting element of the first light emitting element row is driven to emit light based on print data for energy gradation, and the light emitting element of the light emitting element group of the second light emitting element row is driven. By driving the light emission based on the correction data, the density of print pixels formed by the first light emitting element row is adjusted by the second light emitting element row.

Further, in the image forming apparatus of the present invention, the light emitting elements of the light emitting element group of the second light emitting element row are driven to emit light based on the print data for area gradation, and the light emitting elements of the first light emitting element row are corrected. The light emitting drive based on the data adjusts the density of the printing pixels formed by the second light emitting element row by the first light emitting element row.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a plan view showing an embodiment of the image forming apparatus of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, and FIG.
FIG. 2 is a side view of the first light-emitting element row,
Reference numeral 3 denotes a second light emitting element array, reference numerals 4 and 5 denote lenses, and reference numeral P denotes a photoconductor.

The image forming apparatus shown in FIG. 1 receives light from the light emitting elements 2a of the first light emitting element array 2 on a circuit board 1 on which the first light emitting element array 2 and the second light emitting element array 3 are mounted. A plurality of lenses 4 for forming an image on a body P;
And a plurality of lenses 5 for imaging the light of the light emitting element 3a on the photoconductor P.

The circuit board 1 is formed by applying a predetermined circuit pattern on the surface of an insulating substrate made of glass, alumina, or the like, and supports the first light emitting element row 2 and the second light emitting element row 3 on the upper surface. An external power supply is supplied to the light emitting element arrays 2 and 3 via the circuit pattern.

The first and second light emitting element arrays on the circuit board 1 irradiate the photosensitive member P with light via lenses 4 and 5, which will be described later, to form a predetermined latent image on the surface of the photosensitive member P. The first light-emitting element row 2 is composed of a large number of light-emitting elements 2a arranged in a straight line, and the second light-emitting element row 3 has M for each light-emitting element 2a of the first light-emitting element row 2. A large number of light emitting element groups 3A, each of which includes one light emitting element 3a (M is a natural number of 2 or more), are arranged substantially in parallel with the first light emitting element row 2. When forming an image forming apparatus of A4 size and 300 dpi, the first light emitting element row 2 is composed of 2560 light emitting elements 2a, and the second light emitting element row 3
Is constituted by 10240 light emitting elements 3a when M is 4.

The first and second light emitting element arrays are composed of, for example, a plurality of light emitting diode array chips (hereinafter referred to as LED chips). For example, the first light emitting element array 2 includes a 300 dpi LED chip L2. The second light emitting element row 3 is configured by arranging 40 1200 dpi LED chips L3. These LED chips L2 and L3 are arranged and mounted at predetermined positions on the upper surface of the circuit board by a conventionally known face-down bonding method or the like.

Further, on the circuit board 1 on which the first and second light emitting element arrays are mounted, the light of each light emitting element of the first and second light emitting element arrays is formed on the photosensitive member P. A plurality of lenses 4 and 5 are provided.

Each of the plurality of lenses 4 and 5 is formed of an aspherical lens. The lens 4 emits light of each light emitting element 2 a of the first light emitting element array 2, and the lens 5 emits second light. The light from the light emitting elements 3a of each light emitting element group 3A in the element row 3 is formed on the photoconductor P. Each lens 4 is provided in one-to-one correspondence with the LED chip L2, and each lens 5 is provided in one-to-one correspondence with the LED chip L3.

Here, the lenses 4 and 5 are arranged so that the light of the light emitting element 2a of the first light emitting element row 2 and the corresponding light of the light emitting element 3a of the light emitting element group 3A of the second light emitting element row 3 correspond to the photosensitive member surface. The first and second P and P are illuminated and imaged on the same area of P.
It is arranged between the surface of the light emitting element rows 2 and 3 and the photoconductor P, and its optical axis is located between the first light emitting element row 2 and the second light emitting element row 3 so that the first and second light emitting element rows are arranged. Light from the light emitting elements 2a and 3a of the light emitting element rows 2 and 3 is superimposed on the photoconductor P.

The lenses 4 and 5 are manufactured by, for example, injection molding using a transparent resin such as an acrylic resin or a polycarbonate resin, or by hot press molding a transparent inorganic material such as glass. The optical axes of the lenses 4 and 5 are supported and fixed at predetermined positions on the circuit board 1 such that the optical axes of the lenses 4 and 5 are orthogonal to the upper surface of the circuit board 1 by a lens plate or the like. For example, 508dp
When it is desired to obtain an image of 300 dpi using the LED chip of i, an aspherical lens with a magnification of 1.692 times is used, and the focal length is set to 23.28 mm.

Next, two types of image forming methods for performing halftone printing using the above-described image forming apparatus will be sequentially described.

(First Image Forming Method) The first image forming method is a method in which the area gradation printing using the second light emitting element array 3 is corrected in density by the first light emitting element array 2. Here, the light emitting elements 3a of each light emitting element group 3A constituting the second light emitting element row 3
Is provided with print data for area gradation. Based on the print data for area gradation, each light emitting element 3a is turned N times (N is 2
By moving the photoconductor surface relatively N rows (N is a natural number of 2 or more) in a direction orthogonal to the second light emitting element column 3 while driving light emission (the above natural number), M × corresponding to the light emitting element group 3A is obtained. A plurality of printing pixels composed of N matrix printing dots are formed in a row. For example, when gradation expression is performed at 16 gradations, 16-bit area gradation print data is given in 4 times, each of 4 bits, and each time, the light emitting element 3a is selectively provided based on the area gradation print data. Emit light. During this time, the photoreceptor surface moves relatively four rows in a direction orthogonal to the second light emitting element column 3, so that a plurality of printing pixels composed of 4 × 4 matrix printing dots are arranged in a row on the photoreceptor surface. It is formed. At this time, the magnitude of the applied power applied to each light emitting element 3a is all constant, for example, 4
大 き 6 mA.

On the other hand, the light emitting elements 2 of the first light emitting element row 2
To a, predetermined correction data set in accordance with the gradation level of the print data for area gradation given to the corresponding light emitting element group 3A is given. Light emitting element 2 of first light emitting element row 2
“a” emits light at a lower intensity than the light emitting elements 3 a of the second light emitting element row 3, and forms printing dots having a lower density than the printing dots in the printing pixels by the second light emitting element row 3. The correction data is created with, for example, 4 bits, and the current value given to the light emitting element 2a is set, for example, as shown in Table 1.

[0021]

[Table 1]

FIG. 4 shows an example of a print pattern using the above-described correction data. The first light emission is performed only in the case of level 1 to level 12 gradation printing, which tends to be insufficient in density when performing area gradation printing. The light emitting elements 2a in the element row 2 emit light to perform density correction.

In this case, the light emitting elements 2 in the first light emitting element row 2
The current value supplied to a is set to six levels, and by selecting the current value according to the gradation level of the printing pixel by the light emitting element group 3A, it is possible to form a printing dot of an appropriate density. Therefore, more accurate gradation expression corresponding to the number of gradations of the print data for area gradation can be performed, and a good halftone print with a good balance can be obtained as a whole.

(Second Image Forming Method) Next, a second image forming method will be described. The second image forming method includes the first image forming method.
This is a method in which the energy gradation printing using the light emitting element array 2 is density-corrected by the second light emitting element array 3.

Here, the light emitting elements 2a constituting the first light emitting element array 2 are provided with print data for energy gradation, and the light emitting elements 2a are driven to emit light based on the print data for energy gradation to expose the light. A plurality of printing pixels are formed on the body surface.

On the other hand, each light emitting element 3a constituting the light emitting element group 3A of the second light emitting element row 3 is set according to the gradation level of the energy gradation print data given to the corresponding light emitting element 2a. Given correction data is given,
The light emitting element 3a is driven to emit light by the correction data. The second light emitting element row 3 is driven to emit light N times (N is a natural number of 2 or more) while the light emitting element 2a of the first light emitting element row 2 is driven to emit light once. A plurality of M × N correction print dots corresponding to the light emitting element group 3A are formed in rows on the body surface. For example, 16
In the case of performing density correction in stages, 16-bit correction data is provided in four times, each of 4 bits, and each time, the light emitting element 3a emits light based on the correction data. At this time, the magnitude of the power applied to each light emitting element 3a is all constant, and is set to, for example, 0.1 to 2 mA.

FIG. 5 shows an example of a printing pattern according to the second image forming method. In this case, since the density correction level by the light emitting element group 3A of the second light emitting element row 3 is set to 16 levels, the light emitting element By selecting the correction level according to the gradation level of the printing pixel in 2a, it is possible to form a printing dot having an appropriate density. Therefore, a more accurate gradation expression corresponding to the number of gradations of the print data for the energy gradation can be achieved, and as a result, a good halftone printing with a good balance can be obtained.

The present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention. For example, a plurality of image forming apparatuses can be used. It goes without saying that a tandem type color image forming apparatus may be formed, or an image forming apparatus having a linear density different from that of the above-described embodiment may be formed.

In the above embodiment, the optical axes of the lenses 4 and 5 are located between the first light emitting element array 2 and the second light emitting element array 3, but instead of this, as shown in FIG. Lens 5
Is positioned just above the second light emitting element row 3 and the lens 4
May be shifted from directly above the first light emitting element array to the second light emitting element array 3 side. In this case, the light of the light emitting elements 3a of the second light emitting element array 3 illuminated on the photoconductor surface P via the lens 4 causes a beam blur, and the light spreads around, so that the connection between the adjacent printing pixels is natural. And higher quality halftone printing can be realized.

Further, in the above embodiment, one of the two light emitting element rows is driven to emit light based on the gradation print data. For example, when printing a character or the like, a thick line portion and a thin line portion are added to each light emitting element row. It may be used for sorting and printing.

[0031]

According to the image forming apparatus of the present invention, accurate gradation expression can be achieved with a relatively simple configuration, and a good balanced halftone print can be obtained as a whole.

[Brief description of the drawings]

FIG. 1 is a plan view illustrating one embodiment of an image forming apparatus of the present invention.

FIG. 2 is a partially enlarged view of the image forming apparatus of FIG.

FIG. 3 is a side view of the image forming apparatus of FIG. 1 as viewed from an X direction.

FIG. 4 is a diagram illustrating an example of a print pattern by the image forming apparatus of the present invention.

FIG. 5 is a diagram illustrating an example of a print pattern by the image forming apparatus of the present invention.

FIG. 6 is a side view showing another embodiment of the image forming apparatus of the present invention.

[Description of Signs] 2... First light emitting element row 2a... Light emitting element 3... Second light emitting element row 3A... Light emitting element group 3a. , 5 ... Lens P ... Photoconductor

Claims (3)

[Claims] 1. A first light emitting element array in which a large number of light emitting elements are linearly arranged, and a plurality of light emitting elements corresponding to one light emitting element constituting the first light emitting element array. An image forming apparatus that irradiates light from the light emitting elements of each light emitting element row of the second light emitting element row, in which the element group is arranged substantially in parallel with the first light emitting element row, onto the same photosensitive body through a lens and forms an image. . 2. The light-emitting elements of the first light-emitting element row are driven to emit light based on printing data for energy gradation, and the light-emitting elements of the light-emitting element group of the second light-emitting element row are driven to emit light based on correction data. 2. The image forming apparatus according to claim 1, wherein the density of the printing pixels formed by the first light emitting element row is adjusted by the second light emitting element row. 3. A light emitting element of the light emitting element group of the second light emitting element row is driven to emit light based on print data for area gradation, and a light emitting element of the first light emitting element row is driven to emit light based on correction data. 2. The image forming apparatus according to claim 1, wherein the density of the printing pixels formed by the second light emitting element row is adjusted by the first light emitting element row.