Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
2001-02-28
2003-07-08
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S248000
Reexamination Certificate
active
06590598
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus and an image forming method, and more particularly, to an image forming apparatus and a image forming method for effecting a so-called comb-teeth type printing.
2. Description of the Related Art
Among image forming apparatuses which form an image by scanning with an exposure head, it is disclosed an image forming apparatus which exposes an image on an exposure surface by carrying out a so-called “comb-teeth type exposure” (see Japanese Patent Application Publication (JP-B) No. 8-12335). Moreover, as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 64-075255, in ink jet recording, there has been known a method in which lines are formed in a backward path between lines recorded in a forward path.
In the image forming apparatus which carries out the comb-teeth type exposure, light emitting elements (not shown) are arranged in the subscanning direction with equal distances therebetween. The first main scanning is carried out such that main scanning lines are main-scanned with fixed distances therebetween. Next, subscanning is carried out at a predetermined feed amount. Further, subsequent main scannings are carried out. As a result, the second or subsequent main scanning lines are sequentially inserted between the first adjacent main scanning lines. The main scanning is repeated for plural times while subscanning at the predetermined feed amount, and a final image is formed.
Hereinafter, a specific explanation will be made with an example for forming an image by an image forming apparatus in which 31 LEDs serving as light emitting elements are arranged with equal distances therebetween.
To form an image by the image forming apparatus, as shown in
FIG. 13
, the first main scanning lines represented by ▴ are firstly formed on an exposed body such as a photosensitive material or the like. As a result, main scanning lines are formed with all intermittent relative feed direction (subscanning direction) distances between adjacent spot lights (LED lights) being 2×d.
Then, the exposed body is moved in the subscanning direction by a feed amount of 1=31×d and is stopped. At this time, second main scanning lines represented by &Dgr; are formed.
Further, the exposed body is moved in the subscanning direction by the feed amount 1. At this time, the third main scanning lines represented by &Circlesolid; are formed.
The fourth main scanning lines and subsequent lines are formed as described above.
In this way, an image with the distance between adjacent main scanning lines being d is formed.
In a case of carrying out such comb-teeth type exposure, if the subscanning direction feed amounts do not coincide correctly with each other for each subscanning, specific main scanning lines are close to each other such that a portion of the image corresponding to the lines is made dense. Alternatively, specific main scanning lines are apart such that a portion of the image corresponding to the lines are made fade. That is, irregularities in density is generated periodically on the image.
It is, however, difficult to coincide correctly subscanning direction feed amounts with each other. Accordingly, it is difficult to eliminate the irregularities in density of the image.
Such problems are not limited to a case in which the comb-teeth type exposure is carried out by an image forming apparatus which uses an exposure head. Such problems have also occurred in a case in which a so-called comb-teeth type printing (a method of printing with a recording head as the comb-teeth type exposure) is carried out by an apparatus having a general recording head such as an ink jet printer or the like.
SUMMARY OF THE INVENTION
In view of the aforementioned facts, an object of the present invention is to provide an image forming apparatus and an image forming method in which the visibility of irregularities in density is reduced even if there are intermittent relative direction feed amount errors and an image quality is improved.
In accordance with the first aspect of the present invention, an image forming apparatus, wherein each interval of plurality of recording elements provided at a recording head in an intermittent relative feed direction is set such that irregularities in density, generated in an image, due to a feed amount error between a recorded material and the recording head in the intermittent relative feed direction, is generated in an area with a spatial frequency of 1 lp/mm or more, is provided.
If the irregularities in density generated in the image is generated at an area with high spatial frequency, human eyes are difficult to view the irregularities in density. That is to say, in the area with high spatial frequency, even if there is relatively large irregularities in density, the irregularities in density is difficult to be viewed. Accordingly, in accordance with the first aspect of the present invention, the image quality can be improved.
In this specification, the irregularities in density means, for example, density distribution generated due to the difference between density distribution of an ideal image and density distribution of a actual image (between that of desired ideal image and that of actual printed image).
Representative examples of the recorded material and the recording head include an exposure head which exposes scanning light on a photosensitive paper, an ink jet head which ejects ink on an ink jet recording paper, and the like.
For example, in a case of an image forming apparatus having the exposure head which exposes scanning light on the photosensitive paper, recording elements are light emitting elements. The spatial frequency can be almost analyzed for each apparatus type by a subscanning direction feed amount of an exposed body and arrangement positions of the light emitting elements (or corresponding positions of spot lights from respective light emitting elements on the exposed body).
Here, the frequency analysis of the irregularities in density generated by an intermittent relative feed direction (subscanning direction) feed amount error of the exposed body is carried out with arrangement positions of light emitting elements (or the positions of the spot lights on the exposed body) being a parameter. On a basis of the analysis results, the subscanning direction distances between light emitting elements are set such that the irregularities in density is generated at high frequency area with the spatial frequency of at least 1 lp/mm, that is, the irregularities in density is sufficiently suppressed at low frequency area with the spatial frequency of less than 1 lp/mm.
As a result, the image quality of an image subjected to development and the like after exposure can be improved.
In accordance with a second aspect of the present invention, an image forming apparatus, wherein: each interval of plurality of pixels in an intermittent relative feed direction, recorded substantially simultaneously by a plurality of recording elements which are provided at a recording head, is a natural number multiplied by d, wherein a minimum interval of the pixel in the intermittent relative feed direction is d; a feed amount of the intermittent relative feed direction between a recorded material and the recording head is set to be (n×2×d/k), wherein a number of the recording elements is n, k is a natural number of 2 or more; and assuming that a pixel recorded by i th recording element is recorded on a position of the recorded material, which position is apart from a pixel recorded by a first recording element by a distance Li in the intermittent relative feed direction, each interval of plurality of the recording elements in the intermittent relative feed direction is set such that a pixel is not recorded on a position of the recorded material, which position is apart from the pixel recorded by the first recording element by a distance {Li+j×(n×2×d/k)} in the intermittent relative feed direction, wherein
Fuji Photo Film Co. , Ltd.
Pham Hai
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