JPS60218639A - Copying machine - Google Patents

Abstract

PURPOSE:To make a density adjustment over a wide range by deriving a frequency distribution on the basis of density information and controlling image formation condition according to the result. CONSTITUTION:A density sensor 18 which detects the density of an original is arranged in the copying machine at the same height with a lens 4. The output of the density sensor 18 is inputted to a density control circuit 21. The impressed voltage to an original light lamp 2 is adjusted by a lamp voltage adjusting circuit 22, etc., to adjust the density of a copy image. The density adjusting circuit 21 consists of an A/D converter 21a which converts the density signal of an original image outputted from the density sensor 18 from analog to digital, nonvolatile memory 21b for storing digital density data, and arithmetic processing part 21c which generates a histogram of the frequency distribution on the basis of the density data and shifts the range of the impressed voltage to the lighting lamp on the basis of the histogram; and the arithmetic processing part 21c is composed of a microcomputer.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Application of M@ The present invention relates to a copying apparatus that allows density adjustment over a wide range regardless of the original density. .

(b) Conventional technology Kameko photo 11! Originals recorded with a copying device such as a photocopier,
There are various types, such as those with a white background like a book, those with a slightly darkened background like a newspaper article, and those called blueprints. Conventional copying machines have adopted a method of manually adjusting the density of these various originals to record easily readable records, but recently, the density of the original is automatically detected before copying, and the detection results are recorded. An apparatus has been developed that automatically adjusts the copy density by adjusting the image forming conditions based on the image forming conditions.

I! which has this kind of automatic density adjustment function! In copying devices, density sensors such as e)) transistors are used to detect the original density, and based on the output of the density sensor, the developing bias pressure, original exposure, light lamp applied voltage, etc. Image forming conditions are being adjusted. - For example, in the case of an exposure lamp voltage adjustment type device, the voltage can be adjusted up and down in 7 steps at 2V intervals depending on the density of the original, centering on 70V. It is set to 70V. This central setting value (70V in the example above) is determined at the design stage, and may be changed by the service person afterwards. However, some users copy many light-textured originals, or copy mainly blue-printed originals. In such cases, the output of the density sensor is often biased towards either side of the standard density, so the adjustment range of the image forming conditions for density adjustment is biased to one side of the center, resulting in a wide range. This makes it impossible to adjust the density sufficiently. That is, to explain using the above example, for users who often print blueprints, the adjustment range of the exposure lamp applied voltage based on the density detection result is often adjusted in a voltage range higher than the normal center setting value of 70V. Therefore, the voltage adjustment range below 70V is not used much, and i! i
l [l! I can't adjust it. As a result, for example, a user who copies many light originals cannot adjust the density of even lighter originals, and a user who mainly copies dark originals such as blueprints cannot adjust the density of even darker originals. be.

(c) Purpose and structure of the invention The present invention has been made in view of the above points, and an object of the present invention is to adjust the density over a wide range regardless of the original density in a copying machine having an automatic density adjustment function. In order to achieve this purpose, the density information of the original is stored, a frequency distribution is determined based on this density information, and image forming conditions are controlled based on this frequency distribution.

2) Examples The present invention will be explained below based on the drawings. ◎ Fig. 1 shows a schematic configuration of a copying apparatus according to the present invention, in which a document G placed on a document table L that reciprocates in the direction of the arrow is illuminated. Irradiate with lamp 2, reflect light from this document G with mirror 3,
The light is focused by the lens 4, reflected by the mirror 5, and projected onto the photoreceptor 6a of the rotating drum 6 rotating in the direction of the arrow. Then, an electrostatic latent image of the image of the document G is formed on the stereoscopic body 6a. Around the rotating drum 6, a charging electrode 7 for uniformly charging the photoreceptor 6a, a developing device 8, a transfer electrode 9, a separation electrode lO, a static elimination electrode 11, and a cleaning device i12 are arranged in order. @
I'm vomiting. The static latent image is developed into a visible image by a developing device 8, and the visible image is transferred from a recording paper P fed by a conveying device 14 from a paper feeding device 13 such as a sumo wrestler to a transfer electrode 9.
Transcribed by. After the transfer, the recording paper PVi is separated from the photoreceptor 6a by the separation electrode 10, conveyed to the fixing device 16 by the conveyance device 15, and discharged there to a sheet discharge tray 17 having fixation streaks.

In the above-mentioned copying machine, the density sensor 18 that detects the density of the original is arranged so that the lenses 4 and #1 are arranged side by side at the same height as shown in FIG. The signal is inputted and output from the density control circuit 19 as a density adjustment signal IJ, which is applied to the lamp voltage adjustment circuit 22 to adjust the voltage applied to the document illumination lamp 2.

As shown in FIG. 2, the density adjustment circuit 21 includes an A/D converter 21a that A/D converts the density signal of the original image output from the density sensor 18, and a non-volatile converter 21a that stores the digital density data obtained as a result. Create a histogram of the frequency distribution based on the sex memo IJ 2 l b and the concentration data,
The arithmetic processing unit 21c shifts the range of the voltage applied to the illumination lamp based on the histogram, that is, changes the width of its vertical change, and the arithmetic processing unit g21c is comprised of a microcomputer.

Next, the density adjustment operation in the present invention will be explained based on FIG.

Prior to the copying operation, if'c, the density of the original G is detected by the density sensor 18 at the same time as the copying operation (F-1
). That is, when the document G is illuminated by the illumination rung 2 while the document table l is moved forward, the reflected light from the document G passes through the mirror 3, the lens 4, and the mirror 5, and is projected onto the photoreceptor 6a. −＋−$ 1 0 1− zeν
04-to 1 〃111 j-Liao Shan ”l a←18
outputs a density signal representing the degree of document information◇
The concentration signal is converted into a digital signal by the A/D converter 21a and then stored as concentration data in the nonvolatile memory 21b (F-2). When a predetermined number of density data is obtained by copying a predetermined number of sheets (for example, 100 sheets) and is stored in the nonvolatile memo IJ2Ib (F-3), the arithmetic processing unit 21c uses this density data to calculate the frequency distribution. Create a histogram (F-4). The method of creating a histogram is already known, and the calculation is performed according to a microcomputer program.

Briefly, the concentration data detected each time is added to a predetermined address in the nonvolatile memory IJ2ib.
! After 100 pieces of data have been taken in, the data contents within each data address are compared and compared with a preset mode to determine the lamp voltage.

The histogram of the frequency distribution thus created has several patterns as shown in FIG. The figure (a) is quite light - when there are many copies of originals (histogram 1) % (
B) is when copying a slightly light original (Histogram 2), (C) is when copying a large number of originals with normal density (Histogram 3), (4IIi is a slightly dark original!
These are the histogram patterns for copying (histogram 4) and (e) copying a fairly dark original (histogram 5).

Next, determine which of histograms 1 to 5 the histogram pattern corresponds to (F-5), and output the lamp voltage corresponding to the determined histogram pattern from the voltage ramp adjustment circuit 22 (F-6). .

Therefore, the central setting value of the applied voltage of the illumination lamp is 70V.
If you prepare a lamp voltage adjustment circuit 22 that can stepwise mvs up to 80V at intervals of 2V vertically and up to 80V, the center of each histogram can be adjusted as shown in the density adjustment table shown in Table 1 below. The set value is shifted above and below 70V, and the adjusted voltage is determined in 7 levels and output.

Table 1 The circle in the table of Table 1 is the center set value of the applied voltage.

For example, considering the case of histogram l, 6
2V is the center setting value of the applied voltage - one step below it #
(sOV), 5 steps above it (64, 66, 68,
70, 72V), and in the case of histogram 4, set 1jX74V as the center setting value, 4 steps below it (66, 68, TO, 72V), and 2 steps above it (lii!). 7 (7s, 78■) ◎Such a shift in the variation range of the applied voltage is performed based on the histogram pattern created by the performance processing unit 21c, and the hood ratio is 0 lamp voltage adjustment circuit 2 in which a shift signal is given to a lamp voltage adjustment and adjustment circuit 22;
2, 7 voltage levels are selected from 11 voltage levels prepared in advance by a shift signal.

7:',,ko:,nini*:'m:s2G,:,t:::
:2; , □ is selected in advance for each copying operation. In Table 1, the voltage applied to the illumination lamp is set to 2V.
The voltage of one of the seven levels is generated, and the lighting lamp 2
to be applied.

However, as shown in the concentration adjustment table shown in Table 2 below, the voltage increase/decrease value is set at t12V12a near the center setting value, and 4V as it moves away from it.
The interval may also be 0 Table 2 If you create a cumulative histogram of the density data of the duplicated original as shown above and shift the density adjustment range based on that pattern, you will be able to copy originals with uneven density. Users with a large number of users can also make fine-grained density adjustments over a wide range.

In the above embodiment, the density data necessary to create a histogram was obtained from the results of 100 copies, but the number of copies can be arbitrarily determined, and the number of copies once determined (for example, In the above example, the density data obtained from more than one copy (100 times) can be stored in non-volatile memory as is, and the data can be used to modify the already created histogram, or to create a new histogram. It's okay.

In addition to the voltage applied to the illumination lamp in the above embodiment, the image forming conditions controlled according to the histogram pattern may be a developing bias voltage or the like.

(E) As described in detail, in the present invention, image density information of a document to be copied is read and stored, a frequency distribution is determined based on this density information, and a frequency distribution is determined based on this frequency distribution. Since the density is adjusted by controlling the image forming conditions, users who often copy originals with uneven density can adjust the density over a wide range, and fine-grained density adjustments can be made for both light and dark originals. .

[Brief explanation of drawings]

1F14 is a diagram showing a schematic configuration of the copying apparatus according to the present invention, FIG. 2 is a block diagram showing an example of the density adjustment circuit of FIG. 1, and FIG. 3 is a diagram showing the density adjustment operation according to the invention. Flow chart showing different histograms of the 41st ffltj frequency distribution? FIG. DESCRIPTION OF SYMBOLS 1... Original table, 2... Illumination lamp, 6a... Photoreceptor, 8... Developing device, 18... Preparation sensor, 21 Density adjustment circuit, 22... Lamp voltage adjustment circuit , 21b
...Non-volatile memory, 21c...Arithmetic processing unit Patent applicant Suzu Konishi Rokuda Shin Kogyo Co., Ltd. Patent attorney
Hiroki Ki

Claims (1)

[Scope of Claims] (Li) Density reading means for automatically reading the density information of the original Mφ to be copied; non-volatile storage means for storing the density information for a predetermined number of originals; A copying apparatus comprising a control means for controlling image forming conditions according to a frequency distribution created based on density and intensity information stored in the means (2) 1ift control semi-control based on a density adjustment table 2. The copying apparatus according to claim 1, wherein the copying apparatus is an automatic density adjustment means for adjusting darkness, and switches the density adjustment table based on the density information.