JPS61155863A - Measuring instrument for surface potential - Google Patents

Abstract

PURPOSE:To measure a surface potential accurately without any influence of an offset potential even if it is present by providing a surface potential measuring means and an electric discharging means, a measured value holding means and a correcting means, etc. CONSTITUTION:The surface potentiometer A and the electrostatic discharging means B, the measured value holding means C and a differential arithmetic means D as the correcting means, etc. are provided. When the surface of the potentiometer A is charged electrostatically to the plus polarity, an AC signal is induced across a detection resistance 5 an outputted as a surface potential from an output terminal 6a. In this case, the value of the AC signal induced across the resistance 5 is extremely small, so the device is covered with an external shield except at a part which faces a body alpha to be measured to prevent the influence of the outside and an internal shield 2 protects a measurement system from an internal noise. If the surface potential of the potentiometer A is not measured, the means B performs electrostatic discharging and the electrometer A takes a measurement, which is stored in the means C. the surface potential value is measured again and the means D subtracts the surface potential value stored in the means C. Consequently, the surface potential value including no offset potential is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a surface potential measuring device for measuring the surface potential of an object to be measured, such as a photoreceptor used in, for example, an electronic copying machine.

[Prior art]

In general, photoreceptors that use photoconductive materials and are used in electronic copying machines are susceptible to changes in sensitivity due to changes over time. It is desirable to set the value within ◎ To achieve this, it is necessary to accurately measure the surface potential of the measured object such as a photoreceptor.

Conventionally, surface potentials have been measured by arranging a potential measuring electrode facing the object to be measured and synchronously shielding the electric field generated between the electrodes, which is proportional to the potential difference between the surface of the object to be measured and the measuring electrode. An alternating current signal with a certain amplitude is induced in the measurement electrode,
What is being measured is known. Although this method is said to be capable of relatively high-precision measurement compared to conventionally known methods, even with this method, the measured values still contain error components.
The necessary and sufficient accuracy has not yet been achieved. Most of the error components that cause this decrease in accuracy are error potentials (hereinafter referred to as offset potentials) of the surface potential measurements when the surface charge of the object to be measured is removed, and this offset potential is applied to subsequent measurements. will always be superimposed.

〔the purpose〕

An object of the present invention is to provide a surface potential measuring device that can accurately measure a surface potential without being affected by an offset potential even if the offset potential exists.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

First, a surface potential meter A as a surface potential measuring means of the present invention will be explained based on FIG. In the figure, reference numeral 1 denotes an external shield that forms the outer shell of the surface electrometer and prevents disturbances from the outside, and has an opening 1a formed at a position facing the surface of the object to be measured α, such as the photoreceptor of a copying machine. ing. Reference numeral 2 denotes an internal shield provided inside the external shield 1, which also has an opening 2a formed at a position opposite to the opening 1a of the external shield 1, and a measuring electrode 3 is placed in the opening 2a. is set up. Reference numeral 4 denotes a chopper electrode disposed between the opening 1a of the external shield 1 and the measurement electrode 3, which vibrates synchronously in the direction indicated by the arrow in the figure. Further, this chopper electrode 4 is grounded. 5 is a detection resistor whose one end is grounded and the other end is connected to the measurement electrode 3; 6 is an amplifier that amplifies the voltage appearing across the detection resistor. In the surface potential detection device configured as described above, if the surface of the object to be measured A is now positively charged, an electric field will be generated between the object to be measured A and the measurement electrode 3 through the opening 1a. arise. At this time, since the grounded chopper electrode 4 vibrates periodically, the area of the electric field acting on the measurement electrode 3 also changes periodically. Therefore, since negative charge periodically enters and exits the measuring electrode 3 from the ground via the detection resistor, an alternating current signal is induced at both ends of the detection resistor 5, and after passing through the amplifier 5, it is transmitted to the output terminal 6a and the surface. Output as a potential detection signal ◇ Incidentally, the value of the alternating current signal induced in the detection resistor 5 is extremely small. For example, even if the value of the detection resistor 5 is about 20 MΩ, the induced AC signal when the surface potential of the object to be measured A is several hundred volts is extremely small, only a few volts, and is not susceptible to external influences. easy. For this reason, the object to be measured α
The parts other than those facing the 2 are covered with an external shield to prevent external influences during measurement, and the internal shield 2 protects the measurement system from internal noise.

FIG. 2 is a block diagram showing an embodiment of the present invention using the surface electrometer A described above.

In the figure, B is a static eliminator that removes the electric charge on the surface of the object to be measured α, and C is a static eliminating means that removes the electric charge accumulated on the surface of the object to be measured α, and C is a device that stores the surface potential value of the object to be measured α immediately after static electricity removal, which is measured by the surface electrometer AK. The measured value storage means D is a difference calculation circuit serving as a correction means for outputting the difference between the surface potential value outputted from the surface electrometer A and the surface potential value stored in the storage means GK.

Next, the operation of the surface potential measuring device having the above configuration will be described based on the flowchart of FIG.

explain.

First, in step 1, the device is initialized, and the value stored in the measured value storage means C becomes "0". After this, in step 2, it is determined whether the surface potential of the object to be measured α has been measured using the surface electrometer AK. If the surface potential has not been measured, S first charges the surface of the object to be measured α. The remaining charges are removed by the static eliminating means B (step 3). In step 4, the surface potential value of the measured object α in this state −
That is, the offset potential value Voff is measured using the surface electrometer AK, and this value Voff is stored in the measured value storage means C. Then, after making the determination in step 2 again, in step 5, the surface potential value vrreS of the object to be measured α charged by a predetermined charging means is measured. In step 6, the difference calculation circuit calculates this surface potential value Vme.
The surface potential value Voff stored in the measured value storage means C is subtracted from s. As a result, an accurate surface potential value Vmes' that does not include an offset potential value can be obtained. Then, this value vh1es' is displayed by 7Jλ stored in a predetermined storage means or by a display means. Note that after the above operations are completed, continue to measure the object α.
When measuring the surface potential of , the measurement operation is performed without going through steps 3 and 4.

In addition, although the above embodiment shows a case where the surface potential meter A shown in FIG. 1 is used as the surface potential measuring means, the present invention is not limited to the above embodiment, and it An electrometer may also be used. [Effects] According to the present invention as described above, even if an offset potential exists, the surface potential can be accurately measured without being affected by the offset potential.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a surface electrometer used in an embodiment of the present invention, and FIG. 2 is a block diagram showing an embodiment of the present invention. FIG. 3 is a flowchart showing the operation of the system shown in FIG. A...Surface potential meter 8 as surface potential measuring means
... Static elimination means C ... Measured value storage means D ... Difference calculation means as correction means 1st WJ Fig. 2 y Sude-na 7 Step 07

Claims (1)

[Claims] A surface potential measuring means for measuring the surface potential of the object to be measured, a static eliminator for removing electric charges on the surface of the object to be measured, and a surface potential measuring means for measuring the surface potential of the object to be measured immediately after the static electricity is removed by the surface potential measuring means. Measured value storage means for storing the surface potential value;
A surface potential measuring device comprising: a correction means for correcting a surface potential value outputted from the surface potential measuring means using a surface potential position stored in the storage means.