JPS63298170A - Electrostatic latent image detection sensor - Google Patents

Abstract

PURPOSE:To detect a linear electrostatic latent image with high resolutions and a high output, by amplifying a potential generated at both ends of a capacitor to produce an output voltage when a detection electrode detects the electrostatic latent image. CONSTITUTION:An electrostatic latent image detection sensor is equipped with a linear detection electrode 11 and a guard electrode 12 surrounding the perimeter thereof 11. The guard electrode 12 is grounded directly, and the detection electrode 11 through a capacitor 3; thus a potential difference generated at both ends of the capacitor 3 is amplified to produce an output voltage. An electrostatic latent image 6 on an electrostatic recording medium 5 is formed when a test manuscript is copied. The electrostatic recording medium 5 moves in the direction of the arrow. The width of the detection electrode 11 is sufficiently smaller as compared with a peak-to-peak distance L of the electrostatic latent image. Thus, the electrostatic latent image detection sensor provides high resolutions in the direction of moving the electrostatic recording medium 5.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrostatic latent image detection sensor for detecting a linear electrostatic latent image formed on an electrostatic recording medium of a copying machine.

As is well known in the prior art, during the process from when a copying machine reads an original document to creating a copy image, there is a process of forming an electrostatic latent image on an electrostatic recording medium. A line drawing in which white lines and black lines are arranged alternately as shown in FIG. 6 is often used as a test document used when examining the copying performance of a copying machine. In the process of making a copy of this line drawing, an electrostatic latent image is formed on the electrostatic recording medium of the copying machine, corresponding to the line drawing, in which the strength of charge is alternately arranged as shown in FIG. One of the indicators for evaluating the performance of a copying machine is to detect the electrostatic latent image on the electrostatic recording medium. A sensor will be needed.

FIG. 3 shows the principle of an electrostatic latent image detection sensor. While FIG. 2 is a top view of the electrostatic recording medium, FIG.
This is an enlarged cross-sectional view of the area within the circle of the electrostatic recording medium in the figure. In FIG. 3, 1 is a detection electrode, 2 is a guard electrode, 3 is a capacitor, 4 is an amplifier circuit, 5 is an electrostatic recording medium, and 6 is an electrostatic latent image formed on the electrostatic recording medium 5.
7 is a charge induced on the detection electrode 1. Charges 7 are generated on the detection electrode 1 facing the electrostatic recording medium 5 due to the electrostatic latent image on the electrostatic recording medium 5 . As a result, a potential difference occurs between both ends of the capacitor 3, so the amplifier circuit 4 amplifies the potential difference and uses it as the output voltage of the sensor. The guard electrode 2 is provided to block electrical noise from the surroundings that would try to affect the detection electrode 1.

Conventionally, a disk-shaped electrode plate has been adopted as a detection electrode of an electrostatic latent image detection sensor.

The problem that the invention seeks to solve The problems with disc-shaped detection electrodes are described below.

FIG. 4 shows the electrostatic recording medium 5 shown in FIG. 2 by a conventional sensor.
The state of the paper on which the electrostatic latent image is detected and its output voltage are shown.

The symbols 1 to 6 are the same as in FIG. Further, the vertical axis of the graph is the output voltage, and the horizontal axis is the time.

The electrostatic recording medium 5 is arranged so that electrostatic latent images formed alternately corresponding to the white lines and black lines of the original document have a constant charge strength in a direction perpendicular to the direction, that is, in the direction of the arrow in FIG. 4(a). Assume that it is moving at a speed of

In the sensor shown in FIG. 4(a), in order to improve the detection resolution, the diameter of the detection electrode 1 is made sufficiently smaller than the distance between the peaks of adjacent electrostatic latent images. However, since the output voltage of the sensor is proportional to the area of the detection electrode 1, the output voltage of Fig. 4 (al) becomes small as shown in Fig. 4 (bl), making it difficult to detect the electrostatic latent image. .

In order to increase the output voltage, the area of the detection electrode 1 may be increased. Therefore, as shown in FIG. 5 ia+, the detection electrode 1
' is made sufficiently large compared to the distance between the peaks of adjacent electrostatic latent images. The output voltage in this case is shown in Figure 5 (
As shown in bl, since the area of the detection electrode 1' is larger than that of the detection electrode 1 in Fig. 4, the output voltage increases as a whole, but the resolution decreases and the adjacent electrostatic latent image is In terms of identification, there is almost no improvement compared to the case shown in FIG.

Therefore, with a disc-shaped detection electrode, it is difficult to distinguish between adjacent electrostatic latent images regardless of the size of the electrode.

In view of the above problems, the present invention provides an electrostatic latent image detection sensor with high resolution and high output.

Means for Solving the Problems In order to solve the above problems, the present invention provides an electrostatic latent image detection sensor comprising a linear detection electrode and a guard electrode surrounding the detection electrode. is grounded, the detection electrode is grounded via a capacitor, and the potential difference across the capacitor is amplified to produce an output voltage.The positional relationship of the detection electrode with respect to the electrostatic medium is determined by the length of the linear detection electrode. When the shorter one is called the width direction and the longer one is called the length direction, the detection electrode is arranged so that the width direction of the detection electrode is parallel to the moving direction of the electrostatic recording medium.

Effect With the above configuration, high resolution and large output voltage can be obtained in the moving direction of the electrostatic recording medium, so white lines and
It becomes possible to detect an electrostatic latent image formed by a test document in which black lines are arranged alternately.

EXAMPLE Hereinafter, an electrostatic latent image detection sensor according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows how an electrostatic latent image is detected by the electrostatic latent image detection sensor of the present invention and its output voltage.

Figure 1 fat is a top view of the electrostatic recording medium.
12 is a detection electrode, 12 is a guard electrode, 3 is a capacitor, 4 is an amplifier circuit, and 5 is an electrostatic recording medium. It is assumed that the electrostatic latent image 6 on the electrostatic recording medium 5 is formed when the test document shown in FIG. 6 is copied. The electrostatic recording medium 5 is moving in the direction of the arrow. FIG. 1 (bl is a cross-sectional view of the electrostatic recording medium 5 parallel to the moving direction. The detection electrode II has a width that is sufficiently small compared to the distance between the peaks of the electrostatic latent image. Therefore, the electrostatic latent image detection sensor of the present invention has high resolution in the moving direction of the electrostatic recording medium 5.

FIG. 1(C) shows a cross-sectional view of the electrostatic recording medium 5 of FIG. 1(al) perpendicular to the moving direction.
It can be seen that all charges aligned in a direction perpendicular to the moving direction of the electrostatic recording medium 5 are detected.

FIG. 1 (di) shows the output voltage. The output voltage of this sensor has a large difference between the lowest value and the highest crystal value, indicating that it has high resolution and high output.

Effects of the Invention As described above, the present invention includes a linear detection electrode and a guard electrode surrounding the detection electrode, the guard electrode being grounded,
The detection electrode is grounded via a capacitor, and when the detection electrode detects an electrostatic latent image, the potential generated across the capacitor is amplified and used as an output voltage, allowing the linear electrostatic latent image to be detected with high resolution. And it is possible to detect with high output,
Effectively evaluate the performance of copying machines.

[Brief explanation of the drawing]

Figure 1 shows the configuration of the electrostatic latent image detection sensor of the present invention and its output waveform diagram, and Figure 2 shows the electrostatic latent image formed on the electrostatic recording medium when a copying machine copies a test document. Schematic diagram, 3rd
The figure is a principle diagram of an electrostatic latent image detection sensor, and Figures 4 and 5 are configuration diagrams of a conventional electrostatic latent image detection sensor and their output waveform diagrams.
FIG. 6 is a plan view of the test document. 1.1'...Detection electrode, 2.2'...
Guard electrode, 3... Capacitor, 4...
・Amplification circuit, 5... Electrostatic recording medium, 11...
...Detection electrode, 12...Guard electrode. Name of agent: Patent attorney Toshio Nakao Haka1 Meibiki R-4
Ichiga R-ta + 1R-scream

Claims (1)

[Claims] It is equipped with a linear detection electrode and a guard electrode surrounding the detection electrode, the guard electrode is grounded, and the detection electrode is grounded via a capacitor, and the detection electrode detects an electrostatic latent image. An electrostatic latent image detection sensor characterized by amplifying the potential difference generated across a capacitor and using it as an output voltage.