JPS595859Y2 - Image density control device for electronic copying machine for variable magnification - Google Patents

Description

[Detailed Description of the Invention] The present invention is an image density control device for always maintaining a constant image density of a copy produced by an electronic copying machine for variable magnification, and more specifically, regardless of the variable magnification ratio. It relates to a detection pattern in which the concentration can be detected under the same conditions without any variation over time.

In general, electrophotographic devices such as copying machines have temperature,
It is produced by electrophotographic equipment because it uses a photoreceptor and charging device that have characteristics that are affected by changes in pressure and humidity, and also uses a developer whose development characteristics change depending on the usage time. The image is intensively subjected to the above-described fluctuations in the imaging process members, and its density constantly changes.

For this reason, control means for keeping the image density constant is generally carried out by detecting the density of the image formed on the photoreceptor. Specifically, as shown in FIG. A method is adopted in which the toner image of the detection pattern 5 formed outside the image area 4 is irradiated with light, the sensor 3 detects the amount of reflected light, and the amount of toner replenishment is controlled so that the detection output is constant.

However, such a method requires a charger and a developer that reach the detection pattern 5 outside the image area, and also requires separate installation of an exposure lamp 6 and a shield 7, which makes the device difficult to operate. In addition to unnecessarily complicating and increasing the size, the image forming process conditions for the detection pattern image and the image to be reproduced are different, so even if the image forming process members are controlled based on the density of the detection pattern image, the image It has the disadvantage that the concentration is not always constant.

On the other hand, as for the detection pattern, a solid pattern is generally used that is not affected by the presence or absence of magnification, and its size is larger than the field of view of the sensor.

Therefore, a considerable edge effect appears in such a detection pattern, and this effect is initially strong depending on the surrounding environment and weakens over time.
If the amount of toner replenishment is controlled so that the density at the center of such a detection pattern is constant, there is a problem that the line image density decreases over time.

The present invention aims to eliminate the above-mentioned disadvantages of conventional devices that control image density based on the density of a detection pattern image formed on a photoreceptor, and aims to eliminate the above-mentioned disadvantages of conventional devices that control image density from the density of a detection pattern image formed on a photoreceptor. The purpose of the present invention is to propose a new apparatus that can form an image using the same image forming process as that of the image to be reproduced, and that can also control the line image density to be constant at all times, in particular, by making it independent of magnification.

Hereinafter, the details of the present invention will be explained based on the drawings.

FIG. 2 shows an embodiment of the present invention, in which reference numeral 1 denotes a contact ballast on which a document is placed, one side of which is covered with a mask 2 as is well known.

In addition, the lower edge SH of the contact glass 1 in this figure,
The inner edge Sv of the mask 2 forms a document placement reference line in the X direction and the Y direction, respectively.

A and B are the detection patterns that form the main part of the present invention, and are provided on the contact glass 1 covered by the mask 2 by means such as printing or adhesion, A is the detection pattern for the same magnification, and B is the detection pattern for example A3. A detection pattern for scaling from size to A4 size (for reduction in this embodiment) is shown.

Each detection pattern A provided on one surface of these contact glasses
, B are at the same magnification (lens position Ll) from Fig. 3, and
When changing magnification (in this example, lens position L2 when reducing from A3 size to A4 size), one side of detection pattern A for same magnification is Length l1 and detection pattern B for variable magnification
The relationship between the length l2 of one side and the length l2 is 11:l2=n:1 (n: magnification ratio).

FIG. 5 shows examples of these detection patterns A and B.
Now, if detection pattern A is for A4 size, and detection pattern B is for scaling from A3 size to A4 size, then the ratio of the side lengths of detection patterns A and B is 1. :v2.

In addition, each detection pattern A and B has several parallel lines a in the scanning direction (arrow direction) to prevent edge effects.
A striped pattern is drawn by ......, b..., and the widths W0, W2 and gaps δ1, 62 of each of these lines a... The sensor 3 for detecting the amount of reflected light on the photoreceptor surface has the relationship W1:W2=δ1:62=n:1, respectively, and the detection pattern is always developed into the same shape regardless of whether the magnification is the same or when the magnification is changed. It is designed to detect the concentrations of A and B.

Next, regarding the positions of the detection patterns A and B drawn on one surface of the contact glass, as shown in Fig. 4, which uses an example of center reference to simplify the diagram, these are at the same magnification. The relationship X, : x2=n : l is established between the distances X1 and x2 from the center line so that they are projected at the same position on the photoreceptor surface (distance X from the center line) when changing the magnification. , Depending on the specified copying magnification, for example, when the magnification is equal to the original magnification, the detection pattern A for the same magnification is set, and when the magnification is varied, the detection pattern B for the variable magnification is set to the position of the sensor 3 provided at a predetermined position on the photoreceptor. and the concentration is detected.

In the embodiment described above, when copying at the same magnification, the detection pattern A for the same magnification is scanned before the original image (FIG. 2), reaches the photoreceptor surface via the lens placed at the same magnification position L1, and is further scanned. It is developed and reaches the sensor 3 for detecting the amount of reflected light.

At this time, the detection pattern B for magnification also reaches the photoreceptor surface through the lens placed at the same magnification position L1, but as shown in FIG. Concentrations are never detected.

Sensor 3 detects a striped pattern (fifth pattern) drawn on detection pattern A.
(Figure) is detected and its output is input to a comparator circuit (not shown).

The comparison circuit compares this output with the set value output, controls the amount of toner replenishment based on the output corresponding to the difference, and develops a latent image corresponding to the original image on the photoreceptor at an optimal density.

For example, in the case of variable-magnification copying such as reduction from A3 size to A4 size, the detection pattern B for variable magnification is reduced and imaged on the photoreceptor through the lens at variable-magnification position L2 as shown in FIG. It is further developed and reaches the sensor 3, where the density of the striped pattern is detected.

Incidentally, the detection pattern A for the same magnification appears at the position A' in FIG. 4, and does not have any influence on the sensor 3.

The above has been explained using the examples of full-size copying and only variable-magnification (reduction) copying, but depending on the number of variable magnifications that a variable-magnification copier is capable of, multiple detection patterns corresponding to each variable magnification can be applied to the contact glass. Needless to say, a detection pattern for double copying is shown as C in FIG. 2.

Furthermore, the pattern of the detection pattern is not limited to the above-mentioned striped pattern of parallel lines, but various striped patterns that are not affected by the edge effect can be used as shown in FIG. 6A.

Furthermore, in the above embodiment, it is explained that the amount of toner replenishment is controlled by the output of the sensor 3, but in addition to this, there are other factors that affect the image density, such as the voltage applied to the charger, the bias voltage of the developing electrode, and the light amount of the exposure lamp. It is also possible to control other imaging process means that affect the image quality.

As described above, according to the present invention, since the striped detection pattern is provided in the document scanning area of the document mounting table, this detection pattern is formed on the photoreceptor by the same image forming process as the image to be reproduced. This makes it possible to downsize and simplify the device, and at the same time, it is possible to always match the development state of the detection pattern, which is the basis of image density control, with that of the image. This eliminates the influence of edge effects and maintains line density that does not change over time.

However, multiple detection patterns corresponding to the variable magnification ratio are provided on the document table, and their positions and shapes are adjusted so that the detection patterns corresponding to the specified magnification ratio can be imaged at the same position on the photoreceptor in the same shape. Even though the variable-magnification copying machine is equipped with a striped pattern that is not affected by edge effects, the image density is still low due to the detection pattern scaled at the same magnification ratio as the original image. It has excellent controllable effects.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional device, Fig. 2 is a top view of the device showing an embodiment of the present invention, and Figs. 3 and 4 show the size and position of the detection pattern at the same magnification and at variable magnification. The explanatory diagram, Figure 5, is a diagram showing detection patterns for variable magnification and same magnification, and Figure 6 A,
The mouth is a diagram showing another detection pattern. 1...Contact glass, 2...Mask, 3...Sensor for detecting the amount of reflected light, 4...
...Photoreceptor, 6...Exposure lamp, 7...
...Block body, A, B, C...Detection pattern.

Claims (1)

[Scope of utility model registration request] Based on the density of the detection pattern imaged on the photoreceptor,
In an electronic copying machine equipped with a control device that maintains the density of the image to be reproduced at a constant level, a striped detection pattern corresponding to the magnification ratio is formed within the document scanning area of the document table and in a direction perpendicular to the scanning direction. In addition, in order to ensure that the above-mentioned detection pattern corresponding to the specified magnification ratio is imaged in the same shape at the same position on the photoreceptor when changing the magnification, from the document placement reference line to the detection pattern for the same magnification. Each detection pattern corresponding to the above-mentioned magnification ratio is placed at a position that is the inverse ratio of their magnification ratio based on the distance of An image density control device for an electronic copying machine for variable magnification, characterized in that it has a similar shape.