JPH05322759A - Image density correcting device in electrophotographic process - Google Patents

Abstract

PURPOSE:To stabilize the full color and black images of a process control system by providing a sensor having different set angles for the detection angle of the irregular reflected light for a color image and the detection angle of the regular reflected light for a black CONSTITUTION:When the angle theta of a sensor 2 is changed, the angle area reading the regular reflected light quantity A1 A2 from a transfer intermediate 1 is changed to the angle area theta of the reflected light B1 B2 where no regular reflection area can be read. When the color developer stuck quantity is to be detected, the angle theta of the sensor 2 is set to a small angle to detect the color density. When the black developer stuck quantity is to be detected, the angle theta of the sensor 2 is set to a large angle to detect the black density. When the developer stuck quantity on the transfer intermediate of one electrophotographic copying machine is detected, the sensor 2 having a different set angle depending on whether the color to be detected is black or a full color is provided, and both stuck quantities of the black developer and the color developer can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image density correction apparatus in an electrophotographic process, and more particularly to an image density correction apparatus suitable for black and white or full color image density correction.

[0002]

2. Description of the Related Art Conventionally, when correcting a color image density in an electrophotographic process, a belt-shaped film used as a transfer intermediate is made of a black film in which carbon powder or the like is dispersed in a synthetic resin such as polycarbonate. As a means for detecting the amount of adhered color toner on the body, since the intermediate body is black, the amount of diffused reflected light is detected by using an infrared sensor and used in the feedback process. Further, the process control system is operated based on the detected data to stabilize the image quality of the copied image. This process control system means that under the present conditions, an image is created in a copier under certain conditions, the density of the image is detected by, for example, an infrared sensor, and the measured density changes from the initial density value of the process. If there is a difference,
A system for stabilizing the image quality of a copied image by changing various process conditions so as to return to an initial density value,
The applicant has also previously proposed such a color balance adjusting means in Japanese Patent Application No. 3-195411.

[0003]

By the way, the conventional means for detecting the change in the diffused reflection light amount cannot detect the black developer adhesion amount. This is because no matter how the black developer adheres to the black surface of the transfer intermediate, the amount of reflected light does not increase, and therefore it is impossible to detect it. Cannot be used. Therefore, it has been extremely difficult to maintain a stable black image quality during the life of the developer by using the process control system to correct the black image density. Therefore, the object of the present invention is to detect the adhered amount of the black developer on the intermediate as well as the adhered amount of the color developer in an electrophotographic copying apparatus using a transfer intermediate formed of a black film. An object of the present invention is to provide an image density correction device that can be detected on the intermediate and can stabilize a full-color image and a black image by a process control system based on these detected values.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its gist is to form an image on a black transfer intermediate in an electrophotographic process. When reading color or black image density, the detection angle of diffuse reflection light for color image,
An image density correction device in an electrophotographic process, which includes a sensor having a different set angle from the detection angle of specular reflection light for a black image.

[0005]

In the present invention, when the density of an image formed by the electrophotographic process is read, the diffused reflected light of the image is detected when the color developer is used, and the specular reflection thereof is used when the black developer is used. Since a sensor having a set angle with respect to each light is used so that light can be detected, it becomes possible to detect both the black image density and the color image density, and these detected values are fed back to the process control system. This makes it possible to always obtain a stable image in both black and color throughout the life of the developer.

[0006]

The present invention will be described in detail below. First, the relationship between the output value of the sensor for reading the image density on the transfer intermediate and the angle of the sensor will be described. FIG. 1 schematically shows the relationship between the above two. In the figure, reference numeral 1 is a belt-shaped transfer intermediate, and by changing the angle θ of the sensor 2, the transfer intermediate 1 from above is transferred. The angle range in which the specular reflection light amount A ₁ → A ₂ is read (substantially vertical in the figure) changes to the angle range θ of the reflected light B ₁ → B ₂ in which the specular reflection region cannot be read. When using this to detect the amount of adhered color developer, the amount of specularly reflected light from the transfer intermediate 1 should rather be small because there is diffused reflected light from the developer. Therefore, for detection of color density,
The angle of the sensor 2 having a small angle θ (for example, around 60 °) is set.

On the other hand, when detecting the amount of adhered black developer, it is better to receive a large amount of specularly reflected light from the transfer intermediate 1 because there is no diffused reflected light from the developer. That is, when the developer (black) is attached, the transfer intermediate 1
This is used because the reflected light from the (black film) is reduced. Therefore, the angle θ
The angle of the sensor 2 having a large value (nearly right angle) is set. In this way, when detecting the amount of developer attached on the transfer intermediate of one electrophotographic copying machine, by providing a sensor having a different setting angle depending on whether the color to be detected is black or full color. It is possible to detect the adhered amount of both the black developer and the color developer.

Next, an example of a mode of a sensor for embodying the present invention will be described. FIG. 2 shows an example of a photoreflector type sensor 2 incorporated in a copying machine and used for detecting the concentration of the developer as described above. The sensor 2a is attached to the attachment substrate 3 almost vertically. , The sensor 2b mounted on the mounting substrate 3 so as to be inclined at an angle θ is shown. Further, FIG. 3 shows another example of such a mode of the sensor 2, and instead of using only one sensor 2 of the photoreflector type as shown in FIG. 2, a side surface of the sensor 2 is used. Is attached to the rotary shaft 4, one end of the rotary shaft 4 is supported by the end portion of the substrate 3, and the other end is provided with a driving means 5 such as a motor to tilt the sensor 2 to set different angles of black and full color. Can be used as the sensor 2. FIG. 4 shows the sensor 2 of FIG.
FIG. 3 is a diagram schematically showing a usage state of the image forming apparatus, in which the sensor 2 detects the black density in a state perpendicular to the intermediate transfer member 1 and rotates the shaft 4 about the angle θ to obtain the color density. Is to be detected. Examples of the photoreflector used in the above sensor include, for example, RPR-363A type manufactured by Rohm Co., GaAs infrared light emitting diode, silicon planar type phototransistor,
Or its equivalent is suitable.

Next, experimental results for confirming the effects of the present invention will be described. A CX7700 full color copying machine manufactured by Sharp Corp. was used as a copying machine used in the experiment, and the distance between the transfer intermediate and the sensor was kept at 7.5 mm. The photoreflector manufactured by ROHM Co., Ltd. was used as the sensor. Under the above conditions, the angle θ of the sensor 2 with respect to the transfer intermediate 1 is changed variously for magenta for the color developer and for the black developer according to the relationship shown in FIG. FIG. 5 and FIG. 6 are graphs in which various different densities of the created patterns are created, the output voltage value of the sensor with respect to the density is taken for each angle, and these are shown in graphs. Of these, FIG. 5 shows the relationship for magenta, and FIG. 6 shows the relationship for black.

As is apparent from these figures, first, FIG.
As for the relationship with the color density of, when the sensor 2 seen in the case of FIG. 1 is almost perpendicular to the transfer intermediate 1, that is, when θ is close to 90 °, specular reflection is performed on the sensor 2. It can be seen that there is no difference in the output voltage value from the place where the color density is low to the place where the color density is high, and the detection capability is low. On the other hand, when θ is close to 60 °, the amount of specular reflection is small, so it can be seen that the detection capability from the low concentration region to the high concentration region is high. On the other hand, looking at the relationship with the black density of the black developer in FIG. 6, it is the opposite of the case of FIG. 5, and when θ is close to 60 °, diffuse reflection increases, so from the low density area to the high density area. Although the difference in the output voltage value of is generally small and the detection capability is low, when θ is close to 90 °, that is, when the sensor 2 faces the transfer intermediate 1 almost vertically, the specular reflection component is It can be seen that the detection ability from the low concentration region to the high concentration region increased as a result.

In the actual operation, the distance between the sensor 2 and the transfer intermediate 1 may slightly vary. However, even if the variation in output caused by this variation is taken into consideration, the detection capability is low. It is clear from the results shown in FIGS. 5 and 6 that the set angle with the highest output variation with small variations is about 60 ° in the case of color density, and about 90 ° in the case of black density. is there. By using the sensor 2 having different set angles as described above,
The initial value of the color sensor and the initial value of the black sensor are set in advance as the initial value memory of the process control system, and the sensor angle and the respective values are detected depending on whether the color density is detected or the black density is detected. By selecting the initial value, it is possible to operate the process control system to stabilize the image quality of the image in both full color and black.

[0012]

According to the present invention, even in an electrophotographic copying machine using a black transfer intermediate, the amount of black developer attached can be detected on the transfer intermediate, and the amount of color developer attached can be detected. Can also be detected on the transfer intermediate, it is possible to use the process control system for each color based on those detected values, which allows an image density correction device that always supplies a stable full-color image and a black image. It is possible to provide, and the effect is extremely remarkable.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a relationship between a transfer intermediate and a sensor angle.

FIG. 2 is a perspective view showing an example of a mode of a sensor used in the present invention.

FIG. 3 is a perspective view showing another embodiment of the sensor used in the present invention.

FIG. 4 is a schematic diagram showing a usage state of the sensor of FIG.

FIG. 5 is a graph showing the relationship between color image density and sensor output voltage.

FIG. 6 is a graph showing the relationship between black image density and sensor output voltage.

[Explanation of symbols]

 1 Transfer Intermediate 2, 2a, 2b Sensor 3 Mounting Substrate 4 Rotating Shaft 5 Driving Means

Claims (1)

[Claims] 1. In an electrophotographic process, when reading a color or black image density formed on a black transfer intermediate, a detection angle of diffusely reflected light for a color image and a specular reflection for a black image are read. An image density correction device in an electrophotographic process, comprising a sensor having a setting angle different from a detection angle of light.