JPS62151837A - Image density controller - Google Patents

Abstract

PURPOSE:To obtain a copy having good quality by exposing a photosensitive body secondarily by a secondary exposure lamp by opening and closing shutters in a liquid crystal shutter array provided between a primary exposure lamp and the photosensitive body at every unit with original density image signals read by a photosensor array. CONSTITUTION:Transmitted light from a half-mirror 5 is made incident on the photosensitive body 7 and reflected light is made incident on the photosensor array 8 to decide the density of an original before light reading the original not in parallel to the moving direction of an original platen 1, e.g. in a vertical line direction forms an image on the photosensitive body 7. The density is decide by using a signal sent out of each unit sensor 8a. The photosensitive body 7 is exposed primarily to part of light from the exposure lamp 3 which reads the original, i.e. light passed through the half-mirror 5 to form a latent image and at the same time, secondary exposure is performed by the secondary exposure lamp 14 by opening shutters 12 in the liquid crystal shutter array 12 between the primary exposure lamp 3 and photosensitive body 7 at every unit, with original density information signals read by the photosensor array 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to copying machines. The present invention relates to an image density control 1) device that detects the degree of H and controls the density of a copied image.

BACKGROUND OF THE INVENTION An example of a conventional image density control method (1) will be described below with reference to the drawings.

It is possible to continuously change the exposure amount in a gradual manner according to the density of the original. In this case, the operator visually judges and adjusts the density of the original, so it is the country's destiny to always expose the original properly regardless of the density of the original. Unless the copying is repeated several times; the desired density cannot be obtained. For this reason, attempts have been made to detect the original density using a detection element r.

FIG. 6 shows an example of conventional detection means. Reference numeral 25 denotes a photo sensor, which receives light from a portion of the original image from a mirror 27 attached above the temporary slit 26. This amount of received light is detected as the background density of the original, and the developing
The bias control circuit 28 applies a developing bias pressure to the developing roller 29 to control the density of the copied image. (Japanese Unexamined Patent Publication No. 57-172365) In addition, as a method of controlling the exposure amount 1), when the original B is irradiated with light by the exposure lamp 30, as shown in FIG. Hara 1+'! A photosensor 32 is provided to detect the original density of yB, and a signal obtained from the photosensor 32 is used to control the exposure lamp 30 by a lamp power control circuit 33.
Adjust the exposure ■. (Japanese Unexamined Patent Publication No. 57-201271) By controlling at least one element of the exposure amount, developing bias amount, and charge amount as in the above method, the entire image can always be kept at an appropriate density and sufficient contrast on average. 1
It has been attempted to obtain a copy image that has a high degree of transparency and is free from fog.

Problems to be Solved by the Invention For originals with high background density, the tube current of the exposure lamp is increased and the potential of the photoreceptor is lowered. At this time, the potential of the character part decreases as well as the potential of the background part, resulting in a copy image with a low density in the character part. Therefore, when the charging current is increased, the surface potential of the photoreceptor changes little in areas where the background has a large relative light amount, but changes greatly in the text area where the relative light amount is small, and the potential of the background does not increase. Since the potential of the character portion increases, the copied image has a large difference in contrast between the character portion and the background portion.

This will be specifically explained in detail using figures. As shown in FIG. 3, the original 1 is scanned by the exposure lamp 3 and its accompanying optical system.
5 is read, but is there a document in the traveling direction 2 of the document table 1? When areas 16 and 17 with high seismic intensity coexist, it is possible to obtain a copy image with no unevenness by controlling at least one element of the amount of charge, the amount of exposure, and the amount of developing bias. However, as shown in FIG. 4, in the original 18, the exposure lamp 3 and its accompanying optical system are exposed to the background surface of the original (il) in a line direction that is not parallel to the advancing direction 2 of the table l, for example, in a perpendicular line direction 19. If there are areas with different densities, such as a combination of high-contrast items such as printed matter and low-contrast areas such as newspapers or diazo copies, which have a high background density, This is the case when the concentration is not uniform. For example, when copying a blank paper with newspaper clippings 21 affixed to it, scanning is performed with one fluorescent light or halogen lamp, the photoreceptor is charged with one corona charging wire, and then, for example, Even if the voltage applied to a single developing magnetic brush sleeve is controlled, the reproduced image can be clearly reproduced with fine lines such as letters written on the white part of the notebook, dull blacks, and halftones, but with the help of newspapers. The cutout part is entirely black, and the letters, etc. are developed on a dark background, resulting in an ugly image.

Means for Solving the Problems The present invention solves these problems, and even if there is variation in the density of the background on the line 19 as shown in FIG. Obtain a good skin density,
Even characters written on a dark background can be clearly copied.

In a line direction that is not parallel to the direction of movement of the document table, for example, in a vertical line direction, before the light that has read the document is imaged on the photoreceptor by a fixed lens such as a rod array lens, the distance between the fixed lens and the photoreceptor is An optical path changing member such as a half mirror is provided in between, and the transmitted light is directed to a photoreceptor, and the reflected light is directed to a photosensor array such as a phototransistor to detect the density of the original, thereby determining the density of the original. At this time, the density of the original is identified for each unit area read by the unit sensor using a signal output from each sensor (1), and means is used to control the density of the copied image for each unit area based on the signal. Alternatively, this transmitted light may be made incident on a photosensor array, and the reflected light may be made incident on a photoreceptor.

As a means for controlling the image density, a photoreceptor is primarily exposed to light transmitted through the half mirror out of the light read from the original by an exposure lamp and its optical system, thereby forming a latent image. At the same time, based on the original density information signal read by the photosensor array, the image density control means, such as a liquid crystal shack array, located between the secondary exposure lamp and the photoreceptor is used to control gloss for each unit by the secondary exposure lamp. Open and close to perform secondary exposure. This opening/closing is performed by exposing only the areas with high background density in the area read by each unit sensor.

Effect By using the above-mentioned means, it is possible to identify the difference in density of the document for each unit area in the in/out direction perpendicular to the scanning direction, thereby making it possible to identify the density of the entire document. Even if there are areas on one document that have different background densities, it is possible to control the image density for each area.

EXAMPLE An example of the image density control device of the present invention will be described below.

FIG. 1 shows a structural diagram of an exposure optical scanning system of a copying machine equipped with an image control system. Document mounting table as a detection method
The original document A placed thereon is irradiated with light by a fixed primary exposure lamp 3 and read by moving the mounting table in the direction of the arrow 2. - The light emitted from the next exposure lamp 3 is reflected by the original, enters a fixed lens 4 such as a lot array lens, and then enters a photoreceptor 7 that rotates in the direction of the arrow 6.
primary exposure. Here, an optical path changing member half mirror 5 is inserted between the lot array lens 4 and the photoreceptor 7, the photoreceptor is primarily exposed by transmitted light, and the first reflected light is used as a photo sensor placed at a position where an image is formed. input to array 8. The photosensor array uses A and Z-sensors such as phototransistors and CCDs, and has a serial array structure as shown in 8a of FIG. 2, with an arrangement density of 1 unit sensor/dragon. Although the optical system is fixed here, the document table may be fixed and the optical system may be scanned.

Next, an image density control method will be described. When the photosensor array is irradiated with light, each unit sensor generates an output corresponding to the received light. At this time, the light from the secondary exposure lamp enters the sensor through the half mirror, but since the amount of light is all the same on the line, the amount is subtracted and output as a signal amount.

The document density level information signal from the sensor obtained on line 19 in FIG. 4 is as shown in FIG. The vertical axis shows the signal amount level, and the horizontal axis shows the pitch interval of each unit sensor on the line 19. Signal■ In descending order of level: light background density part 22, dark background density part 23, text part density 2
4 is shown. Processing is performed in which these are taken in digital quantities and the light background density area 22 is set to the t, ow level, and the dark background density area 23 is set to the ligh level. Each unit liquid crystal shutter array 12 is operated by a liquid crystal shutter array control circuit 13. In other words, the shutter of the area processed with It i B )+ level is opened with ON, and the shutter of the processed area is opened with
The shutter of the area processed with the level is closed as leaf F. The secondary exposure is incident on a half mirror, the reflected light is incident on a liquid crystal shutter array, and the photoreceptor is exposed so as to overlap with the secondary exposure. The transmitted light enters the photosensor 8, but since the amount of light is the same on the line, it does not affect the signal amount level.

A liquid crystal shutter array 12 is inserted between the photoreceptor 7 and the half mirror 5, and the photoreceptor 7 is exposed by a secondary exposure lamp 14 by opening and closing the shutter. This makes it possible to control the latent image voltage on the photoreceptor. In other words, the shutter in the thin background density area of the original in Figure 4 is closed and the latent image voltage is not changed, and the shutter in the dark background density area is opened for secondary exposure, and the latent image voltage is changed to change the background density. can be controlled to obtain clear copied images. That is, when the photoreceptor 7 rotating in the direction of the arrow 6 is charged by the charger 1) and the photoreceptor is primarily exposed to light transmitted through the half mirror 5 to form a latent image, the secondary exposure lamp 14 and the liquid crystal shack are A secondary exposure is simultaneously performed by the array 12, and the latent image voltage of a portion with high background density changes here. developer lO
The toner is deposited on the photoreceptor 7 to form a visible image.

The image is transferred to paper by the transfer device 9, and a copy image is obtained through a fixing process.

Effects of the Invention Will one manuscript have different textures due to the present invention? If there is a seismic intensity, it is possible to read the original density product corresponding to the area of density variation in the original density in the '(H?A) range of 1 for each unit even if there is a difference in original density on the line. The background density can be controlled by the image density control means, a copy image with a uniform white background can be formed, and a high-quality copy can be obtained.

, 18 Section Jii Explanation of the Drawings Figure 1 is equipped with the image 7 temperature control device of the present invention? ■A configuration diagram of the copying machine, Figure 2 is a configuration diagram of the photosensor of the same device, Figures 3 and 4 are configuration diagrams showing an example of a manuscript, and Figure 5 is a characteristic diagram showing the level of Shinano from the manuscript. , FIG. 6, and FIG. 7 are configuration diagrams showing an example of a conventional image density control device.

3...- Spray light lamp, 5... Half mirror-17... Angry light body, 8... Photo sensor, 10... Developing device, 12...Liquid crystal shutter array, 13...Control circuit, 1.1
...Secondary exposure lamp.

Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1
10-Developer/2~--1 night shift shift 13-Control circuit/4---Secondary light; R 12Figure 3Figure 65Scanning line directionFigure 6Figure 7

Claims (5)

[Claims] (1) An image density control device for a copying machine, which includes means for detecting the density of the original document for each unit division, and obtaining a signal based on the density level of the original temperature for each unit division, and obtaining the original density level detection signal for each unit division. The apparatus is characterized by comprising means for controlling the density of the copied image for each unit section, and an optical path changing means on the optical path of the reflected light that optically scanned the original is reflected from the original until it forms an image on the photoreceptor. Image density control device. (2) The copy image density control means is provided on an optical path along which the reflected light obtained by optically scanning the original is reflected from the original surface and forms an image on the photoreceptor. The image density control device according to item 1). (3) The image density control device according to claim (1), wherein the copied image density control means is provided between the optical path changing means and the photoreceptor. (4) The image density control device according to claim (1), wherein the copy density control means uses a liquid crystal. (5) The image density control device according to claim (1), characterized in that a secondary light source is provided in association with the image density control means.