JPH0524923Y2 - - Google Patents

Description

[Detailed description of the invention] <Technical field> This invention uses an optical sensor to receive the reflected light of the light rays emitted from a light source to the document on the document table, and then adjusts the amount of exposure to the photoreceptor according to the detected image density. The present invention relates to a copying machine having an automatic exposure adjustment function that automatically sets the toner density on a photoreceptor to an optimal value.

<Summary of the invention> A copying machine with an automatic exposure adjustment function according to this invention has a scanning optical system on the document table surface in order to prevent deterioration in image quality caused by a delay in the response of the light source output to the detection signal of the sensor. By providing an intermediate density surface over the entire width from the vicinity of the starting position to the leading edge position of the original, and by forming an image of this intermediate density area on the photoreceptor, it is possible to prevent dirt on the peeling nail and copying. A striped white surface that spans the entire width prevents paper from becoming smudged or jammed.

<Prior art and its drawbacks> Copying machines with automatic exposure adjustment function detect only the density of the part of the original that is illuminated by the light beam from the light source, so when copying an original with uneven image density, An appropriate amount of exposure may not be obtained, and an image with poor balance of brightness and darkness may be copied. For this reason, conventional methods have expanded the detection area of the optical sensor, and also slowed down the response of the light source's output to the optical sensor's detection signal, so that the change in the light source's output is gentle when copying originals with uneven density. This was done to prevent the balance between light and dark from worsening. However, in general, a white surface is formed in front of the leading edge of the document on the document table by painting or pasting a film to prevent the shadow part inside the main body from being formed as an image on the surface of the photoreceptor. For this reason, the output of the light source rises slowly due to a delay in response to the detection signal of the optical sensor for the document on the document table, which causes fogging at the leading edge of the paper during image formation, resulting in deterioration of the quality of the copied image.

To overcome this drawback, we set the area in front of the leading edge of the document on the document table as an intermediate density area, and when we start scanning the document, we control the optical system to automatically adjust the exposure so that it can handle both dark and light documents. A copying machine with this function has been proposed. However, in this method, the image in the intermediate density area is formed on the photoreceptor, which may stain the leading edge of the copy paper or the peeling claw.
Sometimes it was the cause of jam.

<Purpose of the invention> In view of the above-mentioned drawbacks of the conventional invention, the purpose of this invention is to improve the rise failure of the output of the light source caused by the delay in response to the detection signal of the optical sensor, to prevent deterioration of image quality, and to Another object of the present invention is to provide a copying machine having an automatic exposure adjustment function that prevents unnecessary images from being formed on a photoreceptor.

<Configuration and Effects of the Invention> The copying machine with the automatic exposure adjustment function of this invention has a continuous intermediate density that spans the entire width from the vicinity of the scanning start position of the optical system light source on the document table surface to the leading edge position of the document. Further, a striped white surface having a width through which the optical system light source passes in a time shorter than its response time is provided over the entire width at the leading edge position of the document.

With the above configuration, according to this invention, the output of the light source can be raised between the time when the optical system starts scanning and the position of the leading edge of the document. Therefore, it is possible to eliminate the failure of the output in the vicinity of the leading edge of the document, and it is possible to prevent deterioration of image quality such as occurrence of fog. In addition, since images of intermediate density are continuously provided over the entire width, reflected light from any position within the document width can be detected as intermediate density. Therefore,
The optical sensor that receives the reflected light from the document can be placed not only near the center of the document, but also at a location away from the center of the document. It can be configured to receive reflected light over a wide range, thereby making it possible to easily and accurately detect the document density.

Further, by providing a striped white portion at the leading edge of the document, an image of an intermediate density portion is not formed on the photoreceptor, and stains and jams on the paper and the peeling nail can be eliminated. Also, even in this case, the width of the stripe is sufficiently narrow that even if the optical sensor detects a change in density, the light source cannot follow this change, so document scanning must be started while maintaining the above-mentioned density control state. This allows for both exposure control and prevention of stains and jams.

<Embodiment> FIG. 1 is a diagram for preliminary explanation of the configuration of a copying machine having an automatic exposure adjustment function, which is an embodiment of this invention, and is a plan view of a document table.

In this embodiment, when performing automatic exposure adjustment, the light source output is changed in accordance with the original image density to adjust the amount of exposure to the photoreceptor. In FIG. 1, an intermediate density surface 2 is provided at the leading end of a document table 1 between a scanning start position 1 of an optical system and a leading end position 3 of a document placed thereon. The optical system consisting of a light source, mirror, and lens is on the document table 1.
Move the bottom surface horizontally in the direction of arrow A. Power is supplied to a motor and a light source (not shown) in this optical system, and the optical system starts moving in the direction of arrow A from a scanning start position 4, and the light beam of the light source scans the document on the document table. The scanning speed of the optical system must be synchronized with the rotation of the photosensitive drum, and is controlled to a constant speed while scanning from the scanning start position 4 to the document leading edge position 3.
In this run-up section, an intermediate density surface 2 is formed which is coated with a paint having an intermediate density in the Macbeth density range of 0.3 to 0.5.

FIG. 2 is a diagram showing the difference in the output change of the light source between the copying machine having the configuration shown in FIG. 1 and the conventional copying machine. In the figure, a solid line 21 shows the change in the output of the light source of the copying machine having the configuration shown in FIG. 1, and a broken line 22 shows the change in the output of the conventional light source.

As shown in FIG. 1, due to the presence of the intermediate density surface 2 formed between the scanning start position 4 and the document leading edge position 3, the optical sensor detects the intermediate density when the optical system starts operating. . As a result, the output of the light source rises immediately from the scanning start position 4, and an output value for an intermediate density is obtained up to the document leading edge position 3. Therefore, even when an original with an image at the leading edge is placed on the original table 1, the amount of variation in the output value is small, and especially when the density of the original is intermediate, the leading edge position of the original changes as shown in the output change 21. Even after passing through 3, the flat state is maintained.

On the other hand, in the conventional device, the output value of the light source exhibits a low value up to the document leading edge position 3 because of the white surface formed between the scanning start position 4 and the document leading edge position 3. After the document is detected at the document leading edge position 3, the output of the light source begins to rise, and as shown by an output change 22, an output value corresponding to the intermediate density cannot be formed until a certain distance after passing the document leading edge position 3. During this time, conventionally, the image would be fogged, but in this embodiment, there is no shortage of the output value of the light source after the document passes the leading edge position, so there is no fogging in the image near the leading edge position of the document.

FIG. 4 is a diagram showing the structure of a document table used in a copying machine having an automatic exposure adjustment function, which is an embodiment of this invention. As shown in the figure, a continuous intermediate density surface 2 is formed over the entire width from the scanning start position 4 of the optical system light source to the document leading edge position 3, and a striped white surface 6 is formed at the document leading edge position 3. is formed over the entire width. Here, the width of the white surface 6 in the scanning direction of the optical system is a width through which the optical light source passes within its response time. Therefore, even if the optical sensor detects a change in density, the light source does not follow this change, and document scanning can be started while maintaining the appropriate density control state.

Generally, an optical sensor receives the reflected light of the light irradiated onto the document from the light source only in a partial detection area in a direction perpendicular to the scanning direction of the optical system. For example, an optical sensor detects the document density in a detection area 5 indicated by two parallel dash-dotted lines with an interval h shown in FIG. In such a case, scan start position 4
Even if the intermediate density surface 12 is formed only in the range surrounded by the document edge position 3 and the document leading edge position 3, it is possible to improve the rise failure of the light source output. However, the document density is not necessarily uniform within one document. However, in general, it is also non-uniform in the width direction. Therefore, in order to accurately detect the density of the original, it is necessary to place the optical sensor not only near the center of the original but also at a location away from the center of the original, or when using a single optical sensor. Even if there is a problem, it is necessary to configure the device so that the reflected light from the document can be received over a wide range.
According to the configuration shown in FIG. 4, since the intermediate density surface is provided over the entire width, reflected light from any position within the document width can be detected as an intermediate density. . Therefore, the optical sensor that receives reflected light from the document can be placed not only near the center of the document, but also at a location away from the center of the document. It can be configured to receive reflected light from a wide range of sources, thereby making it possible to easily and accurately detect the document density.

[Brief explanation of the drawing]

Figure 1 is a plan view providing a preliminary explanation of a document table installed in a copying machine with an automatic exposure adjustment function, which is an embodiment of this invention, and Figure 2 shows the copying machine shown in Figure 1 and a conventional copying machine. Figure 3 is a plan view for a preliminary explanation of a document table installed in a copying machine with an automatic exposure adjustment function, which is an embodiment of this invention, and Figure 4 is a diagram showing changes in the output of the machine's light source. 1 is a plan view of a document table installed in a copying machine having an automatic exposure adjustment function, which is an embodiment of the invention; FIG. 1...Original table, 2...Intermediate density surface, 3...Document leading edge position, 4...Scanning start position.

Claims (1)

[Scope of Claim for Utility Model Registration] A light beam is irradiated from an optical light source to a document on a document table, the reflected light is received by an optical sensor to detect image density, and the amount of light from the light source is controlled according to this image density. In a copying machine that has an automatic exposure adjustment function that automatically sets the toner density on the photoreceptor, there is a continuous intermediate area between the vicinity of the scanning start position of the optical system light source on the document table surface and the leading edge of the document. Automatic exposure adjustment characterized in that a density surface is provided, and a striped white surface having a width through which the optical system light source passes in a time equal to or less than its response time is provided over the entire width at the leading edge position of the document. A copy machine with functions.