JPH07131651A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent malfunction by finding any abnormal part in the read density value of a gradation test pattern and informing a user of device abnor mality. CONSTITUTION:The specified gradation pattern outputted from a pattern generator built in a printer is converted into a laser beam by starting a semiconductor laser 107 and passes through a polygon mirror 1 and a reflection mirror 2, and the surface of a photoreceptor drum 4 is irradiated with that laser beam. The photoreceptor drum 4 for which a latent image is formed by scanning the laser beam is developed for each color by a rotary developer 3, and transfer is completed by rotating transfer paper once a color on a transfer drum 5 and totally rotating it four times. Then, the transfer paper is separated from the transfer drum 5, fixed by a fixing roller pair 7 and outputted. This output is read, mounted on a platen 102 as an original 101, irradiated with a light source 103, passes through a color separating optical system 104, is converted into a reflected light quantity signal by a CCD 105, read and defined as density data and when there is any abnormality in these density data, it is informed.

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.

[0002]

2. Description of the Related Art Conventionally, the following method has been known as a method for adjusting the image processing characteristics of an image forming apparatus such as a copying machine or a printer. That is, the image forming apparatus is activated to form one specific gradation test pattern on the recording material, and then the density of the gradation test pattern formed on the recording material is read by the image reading means, A method has been known in which, on the basis of image information, feedback is made to a means for determining an image forming condition such as a γ correction means. By this method, it was possible to stabilize the image quality according to the characteristic variation due to durability and the environmental condition variation.

[0003]

However, in the above-mentioned conventional example, although the image forming apparatus outputs a uniform density over the entire surface of the recording material, an abnormal density jump occurs due to an abnormality in the image forming apparatus. There are cases. If this data is used to feed back the image forming conditions, there is a drawback that an optimum image cannot be obtained.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and as one means for solving the above-mentioned problems, the following structure is provided. That is, an image forming means for forming an image, a pattern forming means for forming a specific gradation test pattern, a reading means for reading the gradation test pattern formed by the pattern forming means, and a reading means for reading by the reading means. Storage means for storing the density data of the gradation test pattern; gradation correction means for correcting the gradation of the image formed by the image forming means based on the density data stored by the storage means;
Abnormality determining means for determining whether or not the concentration data stored by the storage means is abnormal, and first notifying means for notifying that there is an abnormality in the data when the abnormality determining means determines that the concentration data is abnormal. And the gradation correction by the gradation correction means sets a look-up table for performing γ correction.

Furthermore, when the abnormality determining means determines that the density data is abnormal, a detecting means for detecting at least one image forming parameter, and the abnormal portion is estimated based on the data detected by the detecting means. It is characterized by having an abnormal point estimating means and a second notifying means for notifying an abnormal point estimated by the abnormal point estimating means.

[0006]

With the above configuration, when an abnormal portion is found in the density value when the gradation test pattern is read, the gradation correction is not performed by notifying that an abnormality has occurred. It is possible to prevent malfunctions. Further, by estimating the location where the abnormality has occurred, there is a unique effect that maintenance can be facilitated.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described in detail below with reference to the drawings. <First Embodiment> A schematic configuration of an embodiment according to the present invention is shown in FIG.
Shown in. In FIG. 1, an image signal is a laser driver 10
By driving the semiconductor laser 103 at 2, it is converted into laser light. Laser light from the semiconductor laser 103 is scanned by the polygon mirror 1 and reflected by the reflection mirror 2, so that the photosensitive drum 4 is irradiated with the laser light and scanned. The photosensitive drum 4 on which a latent image has been formed by scanning with laser light rotates in the direction of the arrow shown in the figure. Then, development is performed for each color by the rotary developing device 3 (in FIG. 1, a development state with yellow toner is shown).

On the other hand, the transfer paper is wound around the transfer drum 5 to be Y (yellow), M (magenta), C (cyan),
It is rotated once in the order of Bk (black), and the transfer is completed after a total of four rotations. When the transfer is completed, the transfer paper leaves the transfer drum 5 and is fixed by the fixing roller pair 7,
The color image print is completed.

Further, 301 is a read original, 302 is an original platen glass, 303 is a light source, 304 is a color separation optical system, 2
1 is a CCD. The toner used in this example is
Yellow, magenta, and cyan toners are used, and a styrene copolymer resin is used as a binder, and a color image print is formed by dispersing color materials of respective colors.

Next, the image signal processing section of this embodiment will be described with reference to FIG. In FIG. 2, the luminance signal of the original image read by the CCD 21 is input to the A / D converter 22 and converted into a digital luminance signal. This digital luminance signal is sent to the shading unit 23, and C
The shading correction is performed for the light amount unevenness due to the sensitivity variations of the individual elements of the CD 21. By performing the shading correction, the measurement reproducibility of the CCD 21 is improved. The luminance signal corrected by the shading unit 23 is further LOG
The conversion unit 24 performs LOG conversion. Then, the LOG-converted signal is converted into a gamma lookup table (γ-LU
T) 25, and the γ-LUT 25 is used to convert the image signal so that the original image density at the time of initial setting of the printer 100 and the output image density processed according to the γ characteristic match.

The image signal thus converted becomes a signal which is pulse width modulated by the pulse width modulation circuit 26 and is input to the laser driver 102, and the semiconductor laser 10 shown in FIG.
3 is driving. Further, 28 is a CPU and 29 is a pattern generator, which generates various gradation test patterns described later. An operation panel 30 is used in the procedure described below.

In this embodiment, the gradation reproduction means is used for all colors in which the pixels are arranged in the sub-scanning direction by pulse width conversion processing, and the photosensitive drum 4 has gradation characteristics due to the dot area change by scanning the laser light. An electrostatic latent image is formed, and a gradation image is obtained through processes such as development, transfer and fixing. Next, FIG. 3 shows a four-limit chart showing characteristics for reproducing the density of the original image.

In FIG. 3, the quadrant I shows the reading characteristic for converting the document density into the density signal, and the quadrant II shows the characteristic of the γ-LUT 25 for converting the density signal into the laser output signal. The third quadrant shows the characteristics of the printer that converts the laser output signal to the printer output density, and the fourth quadrant shows the relationship between the document density and the printer output density, that is, the characteristics shown in the fourth quadrant are 3 shows the overall gradation characteristics of the copying machine of the embodiment.

In this embodiment, in order to make the gradation characteristics linear as shown in the fourth quadrant of FIG. 3, the distortion of the recording characteristics of the printer section shown in the third quadrant is shown in the second quadrant. It is corrected by the γ-LUT 25. Since the image signal is processed as an 8-bit digital signal in this embodiment, the number of gradations is 256.

Hereinafter, referring to FIG. 4, C in this embodiment will be described.
The process of setting the γ-LUT 25 by the PU 28 will be described. FIG. 4 shows the γ-L by the CPU 28 in this embodiment.
It is a flowchart which shows the process of UT25 setting. First, in step S21, a color for which the gradation characteristic is determined to be corrected is designated from the operation panel 30 of FIG. 2, and the gradation correction start switch is turned on.
In step 22, the pattern generator 29 shown in FIG. 2 forms and outputs a gradation test pattern of 256 gradations of the designated color.

FIG. 5 shows an example in which the gradation test pattern is output on the recording material. In FIG. 5, the density of the gradation test pattern is the lowest at the upper left corner and the darkest at the lower right corner, and during that time, the density gradually increases from the upper left corner to the lower right corner. In addition, in FIG. 5, the display of the intermediate portion is partially omitted.
Next, in step S23, the gradation test pattern (FIG. 5) output in step S22 is read as an original document 30.
The image is placed on the platen glass 302 as No. 1, illuminated by the light source 303, and then converted into a reflected light amount signal by the CCD 21 through the color separation optical system 304. Then, the reflected light amount signal is LOG-converted by the LOG converter 24 shown in FIG. 2, and is read by the CPU 28 as read density data.

Next, in step S24, the relationship between the laser output level at the time of reading the gradation test pattern and the density value of the read gradation test pattern is determined in correspondence with the coordinates of each gradation test pattern, and FIG. Memory 32
To store. Then, in step S25, step S24
It is determined whether or not there is any abnormality in the relationship between the laser output level and the read density obtained in step.

In step S25, the gradation test pattern is sequentially compared with the pattern with the lowest density, and the pattern with the next lowest density is compared, and the difference in the density is within a predetermined range (0
~ X: When X exceeds a value set in advance in the apparatus), it is determined that the relationship between the laser output level and the read density is abnormal. If it is determined in step S25 that the relationship between the laser output level and the read density is normal,
Next, in step S26, the relationship between the laser output level and the read density obtained in step S24 is determined as shown in FIG.
The printer characteristics shown in the third quadrant of are obtained. By exchanging the input / output relationships of the printer characteristics with each other, the characteristics of the γ-LUT 25 of the printer shown in the second quadrant are determined, and all γ-LUT 25 for 256 gradations are set.

On the other hand, if it is determined in step S25 that the relationship between the laser output level and the read density is abnormal,
In step S27, a message such as "Call a service person" is displayed on the display 31 of FIG. 2 to prompt the user to call the service person, and the γ-LUT 25 is displayed.
The process ends without performing the setting. This completes the setting process of the γ-LUT 25 in the present embodiment.

When the message of the serviceman call is displayed in step S27 of FIG. 4 described above, there is a high possibility that a device abnormality has occurred. Therefore, after eliminating the cause of the device abnormality, gradation correction is performed again, that is, Step S2
The process starts from 1. As described above, according to this embodiment, it is possible to detect malfunctions such as device malfunctions during gradation correction and prevent malfunctions.

<Second Embodiment> In the above-described first embodiment, when some kind of apparatus abnormality occurs, the user is only prompted to call a service person. However, in the second embodiment, the location of the abnormality occurs. Is also intended to be notified at the same time. The setting of the γ-LUT 25 of the second embodiment is shown in FIG. 4 as in the first embodiment, and therefore the description of the same processing as that of the first embodiment will be omitted.

In the second embodiment, step S in FIG.
When determining whether there is an abnormality in the relationship between the laser output level and the read density at 25, data such as the T / C ratio (ratio between toner and carrier) is also referred to. The method of obtaining the T / C ratio will be described below with reference to FIG. 6 is shown in FIG.
3 is a diagram showing a detailed configuration of a developing device 3 in FIG. In FIG. 6, the developing device 3 develops the toner so that the image latent image formed on the photosensitive drum 4 can be visually observed. In the present embodiment, a developer composed of two components, a carrier and a toner, is used.

The image density is the toner density (T / T) in the developer.
C / C ratio) and therefore the T / C ratio must be kept constant. The developing device 3 includes screws 91a and 91b for uniformly agitating the developer, the screw 91a conveys the developer by rotating toward the other side in the drawing, and the screw 91b rotates toward the front side in the drawing. The developer is circulated in the developing device 3 by being conveyed by the developer.

Since the carrier in the developer has magnetism, the magnet contained in the developing sleeve 90 scoops up the carrier and the toner in a mixed state, and the blade 94 uniformly applies the toner onto the photosensitive drum 4. To be done. Next, the amount of toner corresponding to the difference between the voltage applied to the developing sleeve 90 and the potential of the latent image on the photosensitive drum 4 adheres to the photosensitive drum 4, so that development is performed.

Further, the developing device 3 incorporates an optical sensor composed of an LED 92 and a photodiode 93 toward the developer drawn up by the developing sleeve 90. LED9
2 and the photodiode 93 both have a peak at a wavelength of 950 nm, the toner used is one that reflects in this wavelength range, and the carrier that absorbs in this wavelength range is used. If output is high, T
The / C ratio is high, and conversely, if the output of the photodiode 93 is low, the T / C ratio is low.

The output of the photodiode 93 in the state of the set T / C ratio is stored in advance and compared with the current output of the photodiode 93 to detect the current T / C ratio from the difference. it can. When it is detected that the current T / C ratio is low, the toner is replenished into the developing device 3 from a toner replenishing unit (not shown) in order to return the T / C ratio to the set value.

The T / C ratio obtained as described above is referred to when determining whether or not there is an abnormality in the relationship between the laser output level and the read density in step S25 of FIG. If it is determined in step S25 of FIG. 4 that the relationship between the laser output level and the read density is abnormal, the process proceeds to step S27 and a message is displayed on the display 31 of FIG. At this time, a message for estimating the location of the abnormality is displayed based on the T / C ratio and the like obtained by the optical sensor in the developing device 3 described above.

A specific example of the message for estimating the above-mentioned abnormal place will be described below. For example, if the reading density is set to three levels of "dark", "general", and "thin", and the T / C ratio is similarly set to three levels of "dark", "general", and "thin", There are nine possible states as shown.

[0029]

[Table 1]

The message for each state shown in Table 1 can be set as shown in Table 2 below.

[0031]

[Table 2]

As described above, according to the second embodiment,
When any abnormality such as an apparatus abnormality is detected during gradation correction, this is detected and the location of the abnormality is estimated to prevent malfunction and facilitate maintenance. <Third Embodiment> In the above-described first embodiment, the detection of a device abnormality at the time of gradation correction for a designated single color has been described. However, gradation correction is also performed for all color toner types used.
Will be needed. Therefore, in the third embodiment, detection of a device abnormality when gradation correction is simultaneously performed for all colors of yellow, magenta, cyan, and black will be described.

The configuration of the third embodiment is the same as the first embodiment described above.
It is common to FIGS. 1 and 2 shown in the embodiment. Hereinafter, with reference to FIG. 7, the γ-LUT 25 in the third embodiment.
The setting process of will be described. FIG. 7 is a flow chart showing the process of setting the γ-LUT 25 in the third embodiment. First, in step S31, the tone correction start switch is turned on from the operation panel, and then the process proceeds to step S32, in which the pattern generator 2 shown in FIG.
9, a gradation test pattern of 16 gradations for all colors is formed on the recording material and output.

FIG. 8 shows an example in which gradation test patterns of all colors are output on the recording material. In FIG. 8, the density of the gradation test pattern is the lowest at the upper left corner and the darkest at the lower right corner, and during that time, the density gradually increases from the upper left corner to the lower right corner. In FIG. 8, the display of the intermediate portion is partially omitted. Next, in step S33, the gradation test patterns (FIG. 8) for all the colors output in step S32 are placed on the platen glass 302 as the read document 301, illuminated by the light source 303, and then C through the color separation optical system 304.
The reflected light amount signal is converted by the CD 21. Then, the reflected light amount signal is LOG-converted by the LOG converter 24 shown in FIG. 2, and is read by the CPU 28 as read density data.

Next, in step S34, the relationship between the laser output level at the time of reading the gradation test pattern and the density value of the read gradation test pattern is obtained in correspondence with the coordinates of each gradation test pattern, Memory 32
To store. Then, in step S35, step S34
It is determined whether or not there is any abnormality in the relationship between the laser output level and the read density obtained in step.

In step S35, the gradation test pattern is sequentially compared with the pattern having the lowest density, and the pattern having the next lowest density is compared, and the difference in the density is within a predetermined range (0
~ X: When X exceeds a value set in advance in the apparatus), it is determined that the relationship between the laser output level and the read density is abnormal. If it is determined in step S35 that the relationship between the laser output level and the read density is normal,
Next, in step S36, the relationship between the laser output level and the read density obtained in step S34
The printer characteristics shown in the third quadrant of are obtained. By exchanging the input / output relationships of the printer characteristics with each other, the characteristics of the γ-LUT 25 of the printer shown in the second quadrant are determined, and all γ-LUT 25 for 256 gradations are set.

When the data of the γ-LUT 25 is created in step S36, for example, the γ-LUT 25 has all 25 data.
If there are 6 gradations, data for 256 gradations must be set from 16 gradation data of the gradation test pattern. Therefore, in order to improve primary interpolation or accuracy, high-order interpolation and high-order interpolation are performed. It is desirable to make an approximation. On the other hand, if it is determined in step S35 that the relationship between the laser output level and the read density is abnormal, the process proceeds to step S37,
For example, a message such as "Call a serviceman" is displayed on the display 31 of FIG. 2 to prompt the user to call a serviceman, and the process is terminated without setting the γ-LUT 25.

As described above, the γ-LUT 25 in the third embodiment is used.
The setting process of ends. Step S37 of FIG. 6 described above
If the message of the serviceman call is displayed in, there is a high possibility that an apparatus abnormality has occurred. Therefore, after removing the cause of the apparatus abnormality, gradation correction is performed again, that is, the processing is started from step S31. As described above, according to the third embodiment, the same effect as that of the first embodiment can be obtained not only for a single color but also for all colors.

<Fourth Embodiment> In the first to third embodiments described above, the full-color digital copying machine has been described. However, the present invention is not limited to the above example, and a monochrome digital copying machine. Is also effective in.
In the fourth embodiment according to the present invention, an example applied to a monochrome digital copying machine will be described.

FIG. 9 shows a schematic block diagram of a monochrome digital copying machine. The main components are shown in FIG. 1 in the first embodiment.
2 and FIG. 2 are common. Such common configurations are denoted by the same reference numerals as in the first embodiment, and description thereof will be omitted. In the fourth embodiment shown in FIG. 9, since there is no need for multiple transfer because it is monochrome, there is no transfer drum.
This is the main difference from the embodiment shown in FIG.

The method of gradation correction and apparatus abnormality detection in the fourth embodiment is the same as that in the first embodiment. As described above, in the fourth embodiment, the same effect as in the first embodiment can be obtained even in the case of monochrome. First to fourth
Although the laser beam printer has been mainly described in the embodiments, the present invention is not limited to these examples and can be applied to, for example, an inkjet printer or a dot matrix printer.

In the present invention, gradation correction is performed by resetting the gamma look-up table, and various image forming conditions are controlled according to the result of this gradation correction. In addition to the laser light amount and the laser emission time, the potential of the primary charger, the developing bias, and the like can be considered. Other image forming conditions include a distance between an inkjet head and a recording material when applied to an inkjet printer, and a sublimation ink ribbon of a sublimation type head when applied to a dot matrix printer.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0044]

As described above, according to the present invention, when an abnormal portion is found in the density value when the gradation test pattern is read, by notifying that some abnormality has occurred, It is possible to prevent malfunction by not performing gradation correction. Further, by estimating the location where the abnormality has occurred, there is a unique effect that maintenance can be facilitated.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a first embodiment according to the present invention.

FIG. 2 is a block diagram showing a detailed configuration of an image signal processing unit in the present embodiment.

FIG. 3 is a fourth limit chart showing the gradation reproduction characteristics in the present embodiment.

FIG. 4 is a graph of γ in the first and second embodiments according to the present invention.
6 is a flowchart of LUT creation processing.

FIG. 5 is a diagram showing a grayscale test pattern output in the first embodiment according to the present invention.

FIG. 6 is a diagram showing a detailed configuration of a developing device in a second embodiment according to the present invention.

FIG. 7 is a flowchart of a γ-LUT creation process according to the third embodiment of the present invention.

FIG. 8 is a diagram showing a gradation test pattern output in a third embodiment according to the present invention.

FIG. 9 is a diagram showing a schematic configuration of a fourth embodiment according to the present invention.

[Explanation of symbols]

 1 polygon mirror 2 mirror 3 developing device 4 photosensitive drum 5 transfer drum 7 fixing roller pair 21 CCD 102 laser driver 103 semiconductor laser 301 read original 302 original platen glass 303 light source 304 color separation optical system

Claims (3)

[Claims] 1. An image forming means for forming an image, a pattern forming means for forming a specific gradation test pattern, a reading means for reading the gradation test pattern formed by the pattern forming means, and a reading means for reading the gradation test pattern. Storage means for storing the density data of the read gradation test pattern; gradation correction means for correcting the gradation of the image formed by the image forming means based on the density data stored by the storage means; An abnormality determining means for determining whether or not the concentration data stored by the means is abnormal, and a first notifying means for notifying that there is an abnormality in the data when the abnormality determining means determines that the concentration data is abnormal. An image forming apparatus having. 2. The image forming apparatus according to claim 1, wherein the gradation correction by the gradation correction unit is performed by setting a look-up table for performing γ correction. 3. A detection unit that detects at least one image forming parameter when the density determination unit determines that the density data is abnormal, and estimates an abnormal location based on the data detected by the detection unit. The image forming apparatus according to claim 1, further comprising: an abnormal point estimating unit; and a second notifying unit that notifies the abnormal point estimated by the abnormal point estimating unit.