JPS6026367A - Image controller - Google Patents

Abstract

PURPOSE:To form an excellent copy image easily and efficiently by discriminating the density of a specific area from the front end of an original image according to an original image front end signal, and controlling the image formation. CONSTITUTION:When a signal corresponding to the front end of an original image is impressed from an original front end sensor S, a microcomputer 7 performs interruption processing and discriminates the density of the original surface by original surface reflection signal detection outputs of a photosensor 1, etc., for respective areas obtained by dividing the time from the input of the image front end signal to the development of the front end image by a reference time. A high-voltage transformer 8 is controlled according to the discriminated results to optimize developing processing; and the need for a manual adjustment, etc., is eliminated, and an excellent image corresponding to the density of the original surface is formed easily and efficiently without any miscopying, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic proper image forming apparatus such as a copying machine. The first step in adjusting the transferred image density of conventional copying machines is
The lighting voltage of the original exposure lamp LAi shown in FIG. 2 is changed by adjusting the volume vrt1 in the operating section as shown in the figure, etc., and the lighting voltage of the document exposure lamp LAi shown in FIG. It was common to obtain an II image. However, in this conventional method, there are many cases in which several sheets of transfer paper are wasted before obtaining a proper image, and the number of transfer paper sheets used increases beyond the required number.

The present invention has been made in order to eliminate this type of conventional drawback, and when an original is exposed, the reflected light from the original surface is detected by a photodetector element, or the potential of a photosensitive drum is detected, and the original is detected according to the output level. It determines the density and controls the voltage of the oil, bt bias, or document exposure lamp to obtain an image with an appropriate density.

FIG. 6 shows an embodiment of the present invention. In-mirror lens
An optical sensor DI (in the present invention, a photodiode is installed in front of M to detect the intensity of reflected light from the document glass PC.D is a photosensitive drum, and L is a document exposure lamp.

Figure 4 shows the detection circuit. The detection signal from the photodiode 1 of the PH is amplified by the operational amplifier 2, the gain is adjusted by the operational amplifier 6, and the signal is input to the ADI input of the microcomputer 7 with a built-in AD converter. The microcomputer 7 outputs pulse width modulated pulses from the IB-h boat 01 based on the AD2 person level determined by the input level of the person D1 and the volume 5, and outputs the pulse width modulated pulses from the IB-h boat 01.
By integrating and inputting the pulse width, the output level of the operational amplifier B is output in proportion to the pulse width, and the developing bias DC component of the high voltage transformer 8 is controlled. 9 is a transformer and 2
The next side is full-wave rectified and the operational amplifier 11 performs zero cross point detection. The zero cross pulse is input to the 1NTllll+ terminal of the microcomputer 7, and the resulting signal is
A by the routine program shown in Figure 5 through the 1-include processing.
Reads the Dl input signal and controls the developing bias.

The relationship between each flag (indicated by F()) and the sequence in FIG. 5 is shown in FIG. First, when the copy button is pressed, the main motor starts rotating, and when the pre-rotation for removing static electricity and cleaning the photosensitive drum is completed, the optical system starts moving forward, and the input from the sensor S located on both sides indicates the leading edge of the document (step 1) Start incrementing the P1 counter for the time it takes for the image tip to reach the developing operation Step 2)
Measure the time from when the CA+t& tip is exposed to when the latent image is developed. Note that before the start of development, a bias equal to the preset value FF plus AD2 is applied to prevent toner from adhering to the drum. (Step 0) Sample the doujin D1 repeatedly and add it to the value of L.
When G is set (step 4), the value of L is divided by Pl to calculate the average value of ADl, and fine adjustment volume 5 (sixth
In step 5), the pulse width control value T determined by the value of N is calculated as shown in FIG. 6 of routine a.

Dividing the value of N by 30 in the overhead view is the N value mentioned earlier.
(←W+ A D 2) Cancer Φ converter is 256L
Since it is SB, the minimum is 0 and the maximum is 510, which is 30L8.
This is because if it is divided into B units, it can be divided into 18 parts. Therefore, by controlling the pulse width output to the port 01 in FIG. 4 for each value of N←N÷30, the developing bias DC component can be changed as shown in mqp;4. The developing bias ■ component is -50 to -6 as shown in FIG. 10 depending on the developing bias control voltage VB shown in FIG.
In order to control this VB, the pulse width output from the 01 output port of the microcomputer is controlled.

The control flowcharts are shown in FIGS. 6 and 7. The timer internal interrupt program shown in Figure 7 starts at power-on, and then tl
, lJ included and starts.

After the FG is set during development, the AC zero cross point (INT input signal) is set while the counter P1 mentioned earlier and the bias calculation PG are set as shown in FIG.
The developing bias is switched every time the value of the P2 counter which continues counting matches. and perform control four times.

By the way, since the photosensitive drum is an OPC drum and the primary charge is negative, increasing the developing bias DC component to the negative side tends to decrease the amount of development, resulting in a thin copied image. Therefore, as shown in FIG. 9, as the value of N increases, that is, as the original density becomes thinner, the negative value of the developing bias DC component is decreased and the amount of development is increased to improve thin reproduction. On the other hand, for high-density yiC materials such as newspapers, the developing bias DC component is increased to eliminate the fog in the reproduced image.

As shown in FIG. 11, the volume 5 shown in FIG. This is a means for correcting.

In the present invention, the development bias is controlled by time-dividing the document scanning period based on the time from when the input signal from the document leading edge detection sensor is received until the leading edge image is developed, and calculating sampling data based on the time. However, this method is not limited to this method; for example, the scanning section may be divided based on other suitable predetermined scanning time widths, or the scanning speed of the optical system differs depending on the magnification in the case of copying machines with variable magnification functions. Control such as dividing the scanning section based on a predetermined scanning distance becomes effective. It is also possible to measure the potential on the photosensitive drum immediately after exposure and perform the above-mentioned calculations to control it.

According to the present invention, the reproducibility is good for erudite original images, and copies of dark originals such as newspapers can be obtained without overlapping, and the i! Step 11 by li adjustment (J is omitted, there is no waste of rolled cardboard due to miscopying, and it is efficient! TfCM (iB is actual 1) No.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the operation section of a copying machine, Fig. 2 is a conventional density adjustment circuit diagram, false Fig. 6 is a diagram of the optical system I, Fig. 4 is a circuit diagram realizing the present invention, Fig. 5 7 to 7 are flowcharts of the present invention, FIG. 8 is a sequence timing chart, FIG. 9 is a relationship between calculated values and developing bias, FIG. 10 is a relationship between developing bias control voltage and developing bias, and FIG. FIG. 11 is an E-V characteristic diagram of the drum, in which PH is the 7-point sensor, S is the tip sensor, and D is the photosensitive drum. -498- N = N-30 Pulse width! , 'l Take 100 μT Ku-ζN's Ode 1 Ko JJ Performance J: 5 Ryo) 01 Appearance η Disappearance Transformation Imaginary Bias Ding j'1. ￥F Denkyu 115[VJE-
V vt・1゛E volume 劫seC

Claims (1)

[Scope of Claims] (1) Means for detecting the density of the original, and means for optimally controlling the forming gloss according to the density detection signal, wherein the control means selects a predetermined area from the signal corresponding to the edge of the original. Or an image control device characterized in that it determines the lightness and darkness of a predetermined period of time to determine the optimum area or plurality of periods. /'7.7-''/-'