JPH01261671A - Synchronous exposure type copying device - Google Patents

Abstract

PURPOSE:To perform correct density controlling by storing the detected density information of originals every original while making the originals one turn so as to count the number of originals prior to synchronous exposure and controlling copying density every original. CONSTITUTION:While the original is moved on a glass plate 10 by a carrying belt 23, a photodiode 37 receives reflection light generated by a scanning exposure optical system 11 and coming from the original. An amplifier 38 converts the output from radio wave to voltage and vice versa, and amplifies the output. Furthermore, the output is A/D converted by an A/D converter 39 and stored in a memory 41 as the density information of the original by the instructions of a CPU 1. Thus, the density information of all the originals is detected and stored in the memory 41 during an counting action. The density information in response to the original is called from the memory 41 and appropriate density instructions based on the density information are sent to a bias control circuit 42, thereby impressing them on a developing device 17. Thus, the developing of an electrophotographic process is performed by the bias voltage, whereby developing can be performed with appropriate density according to the density of the originals.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a so-called synchronous exposure type copying apparatus that exposes a document while moving it in synchronization with a photoreceptor.

(Prior art) There are two types of copying machines that use electrophotographic processes: those that manually set the copy density, and those that automatically detect the density of the original and automatically adjust the density according to the detected density. In either case, the developing bias and the light amount of the exposure lamp are adjusted according to the setting or the detected density to obtain the optimum density.

In the latter type, which automatically detects the density of the original,
Since preliminary exposure for density detection is required before main exposure for copying, there is a problem in that the copying operation takes time.

To solve this problem, we developed a method to detect the original density by using light reflected from the leading edge of the original in the initial stage of exposure scanning when the original placed in a fixed position on the original platen is exposed and scanned. has been proposed (patent application 17530/1982)
No. 9), Isn't there a problem with this original density detection method that it takes time for the copying operation because the density information is detected at the initial stage of exposing the original for copying (corresponding to main exposure)? Since the density of the leading edge of the original, that is, the background of the original, is detected as the original density, it is not the density information of the entire original, so there is a problem that accurate density control according to the original information cannot be performed.

(Objects and Structure of the Invention) The present invention has been made in view of the above points, and it is an object of the present invention to perform accurate density control in a so-called synchronous exposure type copying apparatus that exposes a document while moving it in synchronization with a photoreceptor. To achieve this purpose, the density information of the original is detected and stored for each original while the original is circulated in order to count the number of originals prior to synchronous exposure, and the stored density information is The copy density is controlled for each document based on the following.

(Example) The present invention will be explained below with reference to the drawings.

The copying apparatus to which the present invention is applied is a synchronous exposure type copying apparatus, and therefore the circulation automatic document feeding mechanism (hereinafter referred to as RD
F-tsuki structure) is installed.

An embodiment of the present invention will be described below with reference to FIG.

The copying apparatus has an RDF mechanism 2 disposed on the top of a main body 1 of the copying apparatus, and is configured to copy documents fed one by one by the RDF mechanism 2 using a normal electrophotographic process. Since the general structure and mechanism of the copying apparatus main body 1 and the RDF machine JII 2 are already known, they will be briefly explained. The RDF mechanism 2 is installed on the glass plate lO provided on the top surface of the copying apparatus main body 1, and the RDF mechanism 2
A plurality of M documents G to be copied are placed face up on top of each other in the order of the first page, second page, etc. from the top.

When it is detected that the original G has been placed on the original placing plate 21 and the copy button provided on the operation panel of the copying apparatus body L is pressed, the entire original G is pushed forward (toward the right in the figure). The leading edge of the document is detected.

Copy here! When a document feed signal is output from the IT device 1 at a predetermined timing, the roller 22 rotates and only one document at the lowest position is fed out. The sent original advances along the guide plate 26, its leading edge is detected by the timing sensor R3, and is taken over by the conveyor belt 23 and moves at a predetermined speed over the glass plate 10 of the copying apparatus main body 1. A scanning exposure optical system 11 consisting of a lamp for irradiating an original, a reflecting mirror, etc. is provided below the glass plate 10, and the original is exposed by this scanning exposure optical system 11 while moving. When a document leading edge detection signal from the timing sensor R3 is sent to the copying apparatus main body l, feeding of the transfer paper starts within the copying apparatus main body as will be described later. The exposed original is conveyed, circulated, and placed on top of the remaining originals marked Il and Wl on the original storage plate 21.

Feeding of the second document starts when the trailing edge of the first document is detected by the timing sensor RS.

In the same manner, when the exposure of all the originals by the optical system of the copying device is completed for the third, fourth, etc., it is confirmed that the number of originals is 0, and the feeding of the original for one part of the copy is completed. do.

In synchronization with the above-mentioned operation of the RDF structure 2, the following electrophotographic process is performed within the main body 1 of the copying apparatus.

When an original document passing over the glass plate 10 of the copying apparatus main body 1 at a constant speed synchronized with the rotational speed of the photoreceptor is exposed by the scanning exposure optical system 11, the reflected light from the original document is reflected by the mirror 12, lens 13, . The light is projected onto the photoreceptor 15 via the mirror 14. The surface of the photoreceptor 15 is a band Tl! Since it is uniformly charged by the device 16, an electrostatic latent image is formed when reflected light from the document is projected. The electrostatic latent image is developed into a visible image by the developing device 17, and is transferred onto the transfer paper P fed from either one of the paper feed cassettes 18 and 19 in synchronization with the automatic document feeding operation. transcribed by 30.

The transfer paper on which the visible image has been transferred is separated from the photoreceptor 15 by a separating device 31 and conveyed by a conveyor belt 32.
The sheet is fixed by the fixing device M33, discharged from the fixing device by the sheet discharge roller 34, and discharged onto the sheet discharge tray 35. A cleaning device 36 removes toner remaining on the surface of the photoreceptor 15 after separation of the transfer paper.

Three photodiodes 37 for detecting the density of the original are provided at separate positions to the side of the lens 13, and three photodiodes 37 are provided for detecting the density of the original.
It receives some of the reflected light from the document while passing above it.

The photodiode 37 outputs a current corresponding to the amount of light received as a concentration signal, and this concentration signal is converted into a voltage by an amplifier 38 and then amplified, further A/D converted by an A/D converter 39, and taken into the CPU 39. , is stored in the memory 41 as density information. The CPU 40 receives the output from the two RDF mechanisms and the timing sensor RS, and stores the concentration information in the memory 41.
42 is a C
This is a bias control circuit that supplies the developing device 17 with a developing bias voltage calculated by the PU 40 based on density information.

Next, among the operations of the copying apparatus according to the present invention, the operation according to the present invention will be explained.

Manuscript from RDF machine a2! ! Place a set of documents G on top of each other on the placing plate 21, set the number of copies you want to make on the operation panel of the copying machine body L, and then press the copy button.The copying machine body L begins preparing for the electrophotographic process and prints the RDF. Mechanism 2 starts an operation for counting the number of original sheets. That is, R
The DF mechanism 2 starts feeding the originals in order starting from the lowest one.

When the leading edge of the document is detected by timing sensor RS, C
PU40 enters the operating state. M114 is the conveyor belt 23
While moving over the glass plate lo, the light reflected from the original by the scanning exposure optical system 11 is received by the photodiode 37, the output from the photodiode 37 is amplified by the current-voltage conversion 3 by the amplifier 38, and is further converted into an A/V converter 3. D converter 3
9, the image is A/D converted and stored in the memory 41 as the density information of the document according to a command from the CPU 40. - The circulated manuscript returns to the original LTM board 2nd board 1st upper position.

The density information for the second, third, etc. originals is stored in the memory 41 in exactly the same way, and all the originals go through one cycle.

The density information output as a density signal from the photodiode 37 is the density of image information contained not only in the background of the original but also in the entire surface of the original.

On the other hand, the number of originals is counted and stored based on the output of the timing sensor R3.

In this way, density information is detected for all the originals during the counting operation of the number of originals and is stored in the memory 41.

When the operation of counting the number of originals is completed, synchronous exposure for copying starts, and the originals are fed again starting from the lowest one. During document feeding for this synchronous exposure, when the leading edge of the document is detected by the timing sensor RS,
The CPU 40 reads density information stored in the memory 41 that corresponds to the document, and
An appropriate density command based on the density information is sent to the bias control circuit 42. The bias control circuit 42 applies a bias voltage to the developing device 17 based on a density command from the CPU 40 . The document currently undergoing main exposure is developed in the electrophotographic process using the bias voltage, so that it can be developed at an appropriate density depending on the density of the document.

The same goes for the second, third, etc. originals, and the density information is read out for each original and a bias voltage is applied, thereby allowing each original to be developed at an appropriate density.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of a circuit configuration for automatic density detection and automatic density adjustment in a copying apparatus according to the present invention. Engineering: Copying device body, 2: RDF mechanism, 10...
Glass plate, 11--Scanning exposure optical system, 13--Lens, 17--Developing device, 37--Photodiode, 38--Amplifier 440--CPU, 41--Memory, 42 ...Bias control circuit.

Claims (1)

[Claims] In a synchronous exposure type copying apparatus that circulates the original in order to count the number of originals prior to synchronous exposure, an original density detection means detects density information of the original during one circulation of the original to count the number of originals; The present invention is characterized by being provided with a storage means for storing the original density information detected by the original density detection means for each original, and a density control means for controlling the copy density of each original based on the original density information stored in the storage means. A synchronous exposure type copying machine.