JPS606938A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] An image forming device (such as a copying machine, etc.) that forms an image corresponding to a document.
In particular, some electrophotographic copying machines (electrophotographic copying machines) are equipped with an automatic image density adjustment function so that the image density of copies obtained from originals with different densities remains constant. For such automatic image density adjustment, it is necessary to measure the original density.

As a method for measuring the density of the original before automatic image density adjustment, the original is once exposed and scanned as part of the original density measurement process, and the amount of reflected light or the amount of light formed on the photoreceptor is determined by the amount of reflected light. There is a method of measuring the surface potential of a manuscript to measure the paper's originality. Conventionally, the scan interval (and thus the original density measurement interval) of the original exposure scan (hereinafter referred to as "pre-scan") performed in advance for measuring the original density has been constant regardless of the original size, and is generally the same as the minimum copy size. It is decided accordingly. For example, 35
In a copying machine that has copy sizes from A3 to A3, the scanning section of the pre-scan is set to the minimum size of 35, and is constant regardless of the document size. Therefore,
If the document is, for example, A3 size, the density measurement can only be performed in an area corresponding to 85 size in the document, which lowers the reliability of the density measurement. Therefore, with this conventional method, it is not possible to accurately measure the state of document density in all sections of the document, such as maximum density, minimum density, average density, etc., for all document sizes.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and form a highly reliable image by measuring document density over all sections of the document for all document sizes.

In the present invention, optical scanning (pre-scanning) of the original 11b performed for measuring the density of the original before image exposure is performed based on detection signals from the original size detection means and the original exposure scanning system position detection means. The feature is that 100 is performed only in the section where

The original exposure scanning referred to here refers to a moving optical system type in which the original is fixed and optical system members such as lenses and mirrors are moved, an original moving type in which the original is moved relative to the optical system members (fixed), and a combination of these. This includes complex types, etc.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of an electrophotographic copying machine embodying the present invention, in which 1 is a photosensitive drum, 2 is a charger for the photosensitive drum 1, 3 is an original image exposure position, 4 is a developing device, and 5 is a transfer device. The charger is a 6-beam IJ-Jung grade. 7 is a document illumination lamp, 8,9°10.11 is a mirror for transmitting a light image, 12
is an imaging lens.

The document illumination lamp 7 and mirrors 8 and 9 move in a direction parallel to the surface of the document (to the right in the figure) to sequentially illuminate the valleys of the document, and focus the reflected light on position 3 on the photoreceptor drum 1. The darkness of successive parts of the manuscript is then imaged there. That is, the optical system surrounded by the dotted line A in 1 is a moving optical system that performs exposure scanning of the original.

The photosensitive drum 1 rotates in the direction of the arrow, is uniformly charged by a charger 2, is irradiated with a light image from an original at an image exposure position 3, and an electrostatic image is formed on its surface, and then developed. The electrostatic image is developed in the container 4. This developed image is transferred to a transfer material (not shown) by a transfer charger 5, and fixed by a fixing device (not shown) to make a copy. After the transfer, the photoreceptor is cleaned by a cleaning blade 6, and copies are made again in the above cycle. Since the above cycle is well known, detailed explanation will be omitted.

Therefore, prior to making the copy, in order to measure the density of the original, the moving optical system A is moved from the home position (starting point) O and scans the original at a standard exposure amount (i.e., pre-scanning).
An electrostatic image of a document is formed on a photoreceptor tram 1. This electrostatic latent image potential is detected by a potential sensor 13 and a potential measuring circuit 14 disposed close to the photoreceptor drum, and the density of the valley portions of the document is measured as the latent image potential. This potential signal is applied to the arithmetic circuit 1
5, calculate the average, maximum, minimum, etc., or multiple values of the latent image potential, and thereby calculate the average density of the original,
The state of yA inertia concentration such as maximum and minimum is detected. According to this detected amount, the sight control circuit 16 sends a control signal to the lamp regulator 17 so that a copy with an appropriate density can be obtained.
The brightness of the document illumination run shift is adjusted via the lamp regulator 17 so that the document exposure amount becomes appropriate. After this adjustment, the original copy creation process described above begins.

By the way, in order to correctly detect the state of document density as described above, it is necessary to perform the above-mentioned pre-scanning from end to end of the document, so it is necessary to change the scanning section of the pre-scanning in accordance with the document size. In this embodiment, this is done as follows. That is, the original size detection circuit 18 detects the size of the original, and this detection uses input signals such as a cassette signal of transfer paper, a magnification signal of the key of the copying machine, and a cassette signal. 19 is the signal 0 rate for detecting the position of the optical system person, 20, 2] and 22.23 are the document sizes B5 size, A4 size, B4 size, A3 from the home position (starting point) 0 of optical system A in the scanning direction, respectively. The position of the optical system A is detected by the optical system position detection sensor arranged at a distance corresponding to +4. DC controller 24
are the document size signal from the document size detection circuit 18 and the sensors 20 , 21 .

22. Optical system A based on the optical system position signal from 23.
The movement of the optical system A is controlled by sending forward and backward signals to the drive control clutch 25, thereby performing forward scanning only in an area corresponding to the document size.

For example, when the original size is detected to be 35, pre-scanning is performed from the starting point O for an area equivalent to B5, and during this period, the potential of the latent image formed on the photoreceptor drum 1 is measured and calculated to determine the density of the original. When the document size is detected to be A3 size, pre-scanning is performed from the starting point C over an area corresponding to A3 size, and the density is detected over the entire A3 size document. In this way, pre-scanning is performed for a section corresponding to the document size, and the document density is calculated from the measurement of the potential of the latent image of the document. The amount of light 7 is adjusted via the light amount control circuit 16 and the rung regulator F. After this adjustment, the original copying process is started.

In the above embodiment, the document density was measured as a latent image potential, but it is also possible to measure the degree of original distortion based on the amount of light reflected from the document. In addition, the means for detecting the document size is not limited to that of the above embodiment, and for example, an automatic document feeder (ADF) is used.
), it is also possible to detect the document size by providing a document size detection means in the ADF.

FIG. 2 is a flow chart of the operation of the embodiment shown in FIG. First, turn on the power. At this time, the optical system A is at home position (starting point) 0.

After the power is turned on, when the copy start key is turned on, the IfA illumination lamp lights up at the standard light intensity, and then the optical system A begins to move toward the right in FIG. 1 to perform pre-scanning for measuring the original density. The surface potential of the electrostatic latent image corresponding to the original image generated on the surface of the photosensitive drum 1 by the advancement of the optical system A is sequentially measured by the potential sensor 13 and the potential measuring circuit 17 and stored.

When the optical system A completes its advance to a sensor position of the optical system position sensors 20 to 23 that matches the original size detected by the original size detection circuit 8, the optical system A is detected by the optical system position sensor, and the optical system System A is stopped, and the surface potential measurement is completed. Here, the average surface potential is calculated by removing the sum of the surface potentials of each part stored in the calculation circuit 15 according to the document size, and the light amount control circuit is operated according to the average surface potential to obtain an appropriate image density. 16. Adjust the light intensity of run f7 via lamp regirator 17. After completing this lamp light intensity adjustment, optical system A starts moving backwards,
The return to the home position O is detected by the optical system position detection signal plate 19. Thereafter, the optical system A moves forward again to expose the original for copying. Optical system A includes position sensors 20 to 23 corresponding to the document size.
When you reach it with a twist, it reverses and moves backwards, returning to the home position 0-
It will stop when it returns to that point.

In the embodiment described above, the potential sensor 13 reads the potential of the photosensitive drum in a length region corresponding to the document size, but the detection width is independent of the IJF and the size of the paper! The image is read at a constant width of the minimum size (B5 size in this example).

Further, the read signal from the potential sensor 13 is sent to the optical system A.
for a certain period of time from the time when the document exposure start signal is output with the camera placed at home position 0 (the leading edge of the document is exposed, and the corresponding latent image on the photoconductor 1 is within the detection range of the potential sensor 13 in the direction of rotation of the photoconductor. From the time after the first predetermined time required to reach the downstream boundary, from the time when the reversal signal (which one of the microswitches 20, 21, 22, 23) is output, for a certain time is exposed to light and the corresponding latent image on the photoreceptor reaches the upstream boundary in the rotational direction of the photoreceptor within the detection area of the potential sensor 13. It is used as a concentration information signal, and predetermined calculations (averaging, maximum value,
whichever is the minimum value etc.). This allows you to obtain more accurate information and cut down on misinformation.

At this time, useless information due to linear miscellaneous light and information @ of white parts may be input at the leading edge and trailing edge of the document.
Cutting-edge technology for more optimization.

It is desirable to measure the timing of information detection or potential detection so that the information at the last end is not used as the original density information signal.

In any case, the optical system (
Or the original in the case of a copier with a fixed optical system and moving original)
Since the control is performed according to the movement of the sensor, appropriate concentration information can be secured.

In this embodiment, the average surface position is used for the density calculation, but the averaging is performed based on the original detection area (different for each size) depending on the original size.

The above embodiment is based on the same size copying, but if the document scanning distance changes during variable size copying, the image density is determined based on the information corresponding to the document size, so the inverted signal is This is done based on the document size designation signal without using . In addition, the above salary 1. The second predetermined time period is the amount by which the length of the latent image forming area on the photoreceptor changes depending on the magnification (due to changes in photoreceptor moving speed and scan speed).
It is desirable to set it variably. This variable pupil may be, for example, magnification x (predetermined time at same magnification).

As explained above, according to the present invention, the pre-scanning for measuring the original image density in automatic image density adjustment is performed only in an area corresponding to the original size, so that reliability is achieved for all originals of different sizes. Since it is possible to measure the original density with high accuracy, it is possible to improve the performance of automatic image density adjustment.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention. Second
The figure is a flowchart of the embodiment of FIG. 1: /g light drum, 7: M illumination lamp, 13: Potential sensor, 19: Signal grade for optical system position detection, 20.21
, 22, 23: Optical system position detection sensor.

Claims (1)

[Claims] In an image forming apparatus that performs original exposure scanning to measure original density before performing final stroke exposure for image formation, means for detecting the size of an original, means for detecting a scanning position of an original exposure scanning system, and a means for detecting the scanning position of an original exposure scanning system; An image forming apparatus such as an image forming millimeter or a laser printer, characterized in that it has means for exposing and scanning a document only over an area corresponding to the size of the document based on the detection number 1g from the device. It is.