JPH10294878A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain development with prescribed density to image signals having uniform density by providing an image correcting means for detecting an image signal at a part, where the prescribed density can not be provided, in the image signals having the uniform density among image signals stored in an image storage means, and for correcting the detected image signal. SOLUTION: An image input part 1 converts an analog signal read by a scanner or the like to a digital signal and a Log converting part 2 converts this signal from a reflection factor linear K signal to a density linear K' signal and outputs it. An image memory part/rear end blur correcting part 3 stores (m) pixels in main scanning direction and (n+1) pixels in subscanning direction. Next, the blur correcting part 3 outputs a K" signal for which a halftone rear end blur is corrected from the K' signal preceding for (n) pixels in the subscanning direction. While using the signal executing the gradation processing of K" signal through an intermediate processing part 4, an image output part 5 forms an image and outputs it. Thus, exact correction can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus such as a copying machine or a laser printer.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic image processing apparatus such as a copying machine or a laser printer includes, for example, an image input section 91, a Log conversion section 92, a halftone processing section 93, as shown in FIG. In an image processing apparatus such as a color copying machine or the like, for example, as shown in FIG. 10, an image input unit 101, a Log converter 102 for each of R, G, and B, a color correction / black Generation unit 103,
It comprises a UCR unit 104, a halftone processing unit 105, and an image output unit 106.

However, in the conventional image processing apparatus, there has been a problem that a portion where a predetermined density cannot be obtained by a developing process occurs for an image signal having a uniform density. One of the problems is a halftone trailing edge blur phenomenon.

Here, the halftone trailing edge blur phenomenon will be briefly described. As an example, consider a case where image processing is performed on a batch of L × L halftones. In FIG. 11A,
A potential pattern of a halftone portion exposed by an exposure device on a photosensitive member charged to a uniform potential VD is shown. When this latent image is developed, toner adheres to the photoreceptor as shown in FIG.

In the area B in the figure, the target toner adhesion amount is developed, but in the area C, the toner is scraped off by the magnetic brush during the development, and the toner adhesion amount decreases with a certain inclination. The desired toner adhesion has not been obtained. This phenomenon is called a halftone trailing edge blur phenomenon. Note that regions A and B in the figure are background portions.

Heretofore, as a means for preventing the halftone trailing edge blurring phenomenon, there has been a method of enhancing the edge portion of the halftone trailing edge. FIG. 12A shows a potential pattern diagram of a latent image in which the edge portion at the rear end of the halftone is emphasized, and FIG. 12B shows an example of the amount of adhered toner when the latent image is developed. ing. However, according to this method, although the image density at the rear end edge is high, the blur is not necessarily reduced, so that a portion with a low image density occurs slightly inside the edge portion, which causes a sense of incongruity as seen. Was.

Further, as other means for preventing the halftone trailing edge blur phenomenon, a method of setting a main pole angle of a mag roller of a developing machine on a downstream side, a method of setting a magnetic force distribution of a main pole portion to two peaks, There is a method of reducing the half width of the magnetic force distribution of the portion, a method of reducing the photosensitive member charging potential VD-the developing bias VB, or a method of reducing the linear velocity Vs of the developing device sleeve / the linear velocity Vp of the photosensitive member. However, as shown in FIGS. 13 and 14, VD-VB or Vs
When the value of / Vp is reduced, the degree of trailing edge blur is improved,
On the other hand, there has been a problem that background contamination is caused by an increase in the density of the background portion.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image processing apparatus which can solve the conventional drawbacks and can develop an image signal having a uniform density at a predetermined density. .

[0009]

According to the present invention, there is provided an image forming apparatus, comprising: an image storage means for storing image signals; and a predetermined density image signal among image signals stored in the storage means. Detects the image signal of the part where the density cannot be obtained,
It is characterized by having an image correcting means for correcting the detected image signal.

The image forming apparatus according to the present invention further comprises a color correcting means for converting the image signal of the original into an image signal for each toner color to be developed, and an image output for outputting the image signal color-corrected by the color correcting means. In the image processing apparatus having the means, the storage means and the image correction means may be arranged between the correction means and the image output means.

[0011] In the image forming system of the present invention, the storage means and the image correction means are preferably provided immediately before the image output means.

[0012]

FIG. 1 shows an embodiment of an image forming apparatus equipped with an image processing apparatus of the present invention.
The image forming apparatus 100 according to the present embodiment mainly includes an image input unit 1, a Log conversion unit 2, an image memory / rear-end blur correction unit 3 as a storage unit and an image correction unit, a halftone processing unit 4, and an image output unit. And an image output unit 5.

The image input unit 1 includes an image reading unit (not shown) such as a scanner, and converts an analog signal read by the image reading unit into a digital signal.
Output to

A Log conversion unit 2 converts the digital signal K input from the image input unit 1 from a K signal that is linear with respect to reflectance to a K ′ signal that is linear in density. Output to

The image memory / rear-end blur correction section 3 accumulates signals for m pixels in the main scanning direction and n + 1 pixels in the sub-scanning direction. From the output signal K ′ from the Log converter 2, a signal K ″ in which the trailing edge of the halftone is corrected is output to the intermediate processor 4.

The intermediate processing unit 4 performs a gradation process on the signal K ″ corrected for the halftone rear end blurring inputted from the image memory / rear end blurring correction unit 3, and outputs the signal after the gradation processing to the image output unit. 5, the image processing unit forms an image using the signal subjected to the above processing, and outputs the image.

FIG. 2 shows an operation flow of the image memory / rear-end blur correction section 3. First, when the image signal K'x of the x-th pixel in the sub-scanning direction is input, n in the sub-scanning direction is stored in the image memory as shown in FIG.
+1 pixels and m pixels which are the maximum number of pixels in the main scanning direction are accumulated (step 201).

From the image signal stored in the image memory in step 201, it is determined whether or not there is a trailing edge of the halftone portion currently stored in the image memory (step 20).
2). More specifically, it is determined whether “the signal K ′ from the (xn) th to the xyth is the halftone part and the signal K ′ from the (xy + 1) th to the xth is the background part (1 <y <n). It is determined whether or not the signal K ′ is a background portion (step 202). If the signal K ′ is determined to be a background portion, the image signal stored in the image memory is determined to be a rear end of a halftone, and the The length of the blurred area is determined using the previously prepared relationship between the halftone density and the length of the blurred area (area C) shown in FIG. 4 (step 203).

Next, it is determined whether or not the (xn) th pixel is in the area C (step 204). If it is determined that the pixel is in the area C, the image signal K'x-n The end blur correction ΔK'x-n is added (step 205),
If it is determined in step 202 that the signal K ′ is not a background portion, or if it is determined in step 204 that the xn-th pixel is not in the area C, the image signal K′x−n is output. n is directly output as K ″ x−n (step 206).

As shown in FIG. 5A, the correction amount .DELTA.K'x-n corrects the blur correction in the area C in a continuous function. The correction curve at this time is a continuous function that monotonically increases as shown in FIG. As a result, the correction of the potential pattern of the latent image formed on the photoreceptor is added as shown in FIG. When this latent image pattern is developed, an image equivalent to an image in which the trailing edge blurring phenomenon does not occur as shown in FIG. 5C is formed even when the toner for the correction in the area C is scraped off. Is done.

In the present embodiment, an example of preventing the trailing edge fogging phenomenon is shown. However, not only the trailing edge fogging phenomenon but also the leading edge fogging phenomenon can be corrected by the above method. is there.

FIG. 6 shows an embodiment in which the image processing apparatus of the present invention is applied to an image forming apparatus equipped with a plurality of developing devices such as a color copying machine. The image forming apparatus 200 according to the present embodiment mainly includes the image input unit 11 and the L
og conversion section 12, color correction section / black generation section 13 as color correction means, UCR section (background removal processing section) 14, image memory / back end blur correction section 15, halftone processing section 16, and image output section 17. It is composed of The image input unit 11
Including an image reading unit not shown such as a color scanner,
The analog signal read by the image reading unit is converted into R, G, and B signals, which are digital color signals, and output to the Log conversion unit 12.

The Log conversion unit 12 converts the R, G, and B signals, which are digital color signals input from the image input unit 11, from a K signal that is linear in reflectance to a R, G signal that is linear in density.
The signals are converted into G and B signals and output to the color correction / black generation unit 13.

The color correction / black generation unit 13 includes an image input unit 11
In consideration of the characteristics of the image output unit 17 and the
R, G, and B signals input from 2 are complemented by Y, M, C,
Convert to black plate K signal.

The UCR section (background removal processing section) 14 performs background removal on the output signals Y, M, C, and K from the color correction / black generation section 13, and outputs Y ', M', C ', and K' signals. Output as

The image memory / rear end blur correction unit 15 accumulates signals for m pixels in the main scanning direction and n pixels in the sub-scanning direction. U
From the output signals Y ', M', C ', K' from the CR unit 14, signals Y ", M",
C ″, K ″ are output to the intermediate processing unit 16.

The intermediate processing unit 16 performs gradation processing of the signals Y ″, M ″, C ″, and K ″ corrected for the halftone trailing edge blur input from the image memory / back edge blur correcting unit 15, The signal after the tone processing is sent to the image output unit 17. The image output unit 17 forms and outputs an image using the signal subjected to the above processing.

Note that the image memory / rear end blur correction unit 15
This operation is similar to the operation of the image memory / rear end blurring correction unit 3 in the above embodiment, and will not be described in detail here. Further, the correction amounts ΔY′x−n, ΔM′x−n,
The same applies to ΔC′x−n and ΔK′x−n.

In the image processing apparatus of this embodiment, Y, Y,
Since the trailing edge blur correction processing is performed after the signals are converted into the M, C, and K signals, the processing is easier than performing the same processing at the stage of the R, G, and B signals, and the processing to the image processing apparatus is performed. The burden can be reduced.

FIGS. 7 and 8 show another embodiment of the image forming apparatus equipped with the image processing apparatus of the present invention. In the embodiment shown in FIGS. 1 and 6, the signals processed by the image memory / tail blur correction units 3 and 15 are further subjected to gradation processing by the halftone processing units 4 and 16.
In the embodiment of FIG. 8, the tone processing is performed by the halftone processing units 73 and 85, and then the signal processing is performed by the image memory / back end blur correction units 74 and 86.

In the image forming apparatus having the configuration shown in FIGS. 7 and 8, in the configuration shown in FIGS. 1 and 6, the halftone processing sections 4 and 16 perform processing on the image signal corrected according to the halftone density. Since the gradation processing is performed, the correction amount may not be appropriate. Therefore, more accurate correction according to the actual density of the halftone part output from the image output units 5 and 17 can be performed.

[0032]

As apparent from the above description, according to the image processing apparatus of the present invention, since the image processing apparatus is provided with the image memory and the trailing edge blur correcting section, the image processing apparatus has a uniform uniformity in the developing process. Since an image signal of a portion where a predetermined density cannot be obtained with respect to the image signal of the density can be corrected, development can be performed at a predetermined density.

Further, since the image memory / rear end blur correction section is provided between the color correction section and the image output section of an image forming apparatus having a plurality of developing devices such as a color copying machine,
The image processing can be facilitated and the load on the image processing apparatus can be reduced.

Further, since the signal processing is performed in the image memory / rear-end blur correction section after the gradation processing is performed in the halftone processing section, the actual image output from the image output section is performed. More accurate correction according to the density of the halftone portion can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of an image forming apparatus according to the present invention.

FIG. 2 is a flowchart illustrating an operation example of the image forming apparatus of FIG. 1;

FIG. 3 is a diagram illustrating an image signal stored in an image memory.

FIG. 4 is a diagram illustrating a relationship between a halftone density and a blurring length.

5A is a diagram illustrating an example of an image signal after trailing edge blur correction, FIG. 5B is a diagram illustrating a latent image potential pattern at the time of trailing edge blurring correction, and FIG. It is a figure which shows an adhesion amount.

FIG. 6 is a diagram illustrating another configuration example of the image forming apparatus of the present invention.

FIG. 7 is a diagram illustrating another configuration example of the image forming apparatus of the present invention.

FIG. 8 is a diagram illustrating another configuration example of the image forming apparatus of the present invention.

FIG. 9 is a diagram illustrating a configuration example of a conventional image forming apparatus.

FIG. 10 is a diagram illustrating another configuration example of a conventional image forming apparatus.

11A is a diagram illustrating a latent image potential pattern of a halftone trailing edge blur, and FIG. 11B is a diagram illustrating a density pattern of a halftone trailing edge blur.

FIG. 12A is a diagram illustrating a latent image potential pattern of a halftone trailing edge blur with edge emphasis, and FIG. 12B is a diagram illustrating a density pattern of the halftone trailing edge blur with edge emphasis.

FIG. 13 is a diagram showing the relationship between VD-VB and background contamination.

FIG. 14 is a diagram showing a relationship between Vs / Vp and background contamination.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image input part 2 Log conversion part 3 Image memory / trailing edge blur correction part 4 Halftone processing part 5 Image output part 11 Image input part 12 Log conversion part 13 Color correction part / black generation part 14 UCR part 15 Image memory / Back Edge blur correction unit 16 Halftone processing unit 17 Image output unit 71 Image input unit 72 Log conversion unit 73 Halftone processing unit 74 Image memory / rear edge blur correction unit 75 Image output unit 81 Image input unit 82 Log conversion unit 83 Color correction Section / black generation section 84 UCR section 85 halftone processing section 86 image memory / back end blur correction section 87 image output section

Claims (3)

[Claims] An image storage means for storing an image signal, and, among the image signals stored in the storage means, an image signal of a portion where a predetermined density cannot be obtained with respect to an image signal having a uniform density. An image processing apparatus comprising: image correction means for detecting and correcting the detected image signal. 2. An image processing apparatus comprising: a color correction means for converting an image signal of a document into an image signal for each toner color to be developed; and an image output means for outputting an image signal color-corrected by the color correction means. In the apparatus, the storage unit and the image correction unit are provided between the correction unit and the image output unit. 3. The image processing apparatus according to claim 1, wherein the storage unit and the image correction unit are disposed immediately before the image output unit.