JPS6026366A - image control device - Google Patents

Abstract

PURPOSE:To form efficiently an excellent copy image whose density is controlled by sampling and detecting the light and shade of an original plural time from the front end of an original, judging the light and shade, and performing optimum control. CONSTITUTION:A reflected light detection output of a photodiode 1 for reflected light from the original is inputted to a microcomputer 7 to perform interruption processing. This interruption processing is carried out according to a program based upon the zero-cross signal of an AC power source which is passed through an operational amplifier 11 and a transistor 12, and the light and shade of the original is sampled and detected plural times from the front end of the original to judge the light and shade of the original by the computer 7, optimizing the DC component of a development bias voltage through a high-voltage transformer 8. Consequently, an excellent copy image whose light and shade is controlled according to the original surface is formed efficiently without any miscopying, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic proper image forming bag+i"t for a copying machine, etc. In order to FA-adjust a 6 degree transferred image of a conventional copying machine to an appropriate J11, an operation part as shown in FIG. It was common practice to obtain an appropriate image by adjusting the volume ■1 of the original exposure lamp LIA1 shown in Figure 2. There are many cases in which several sheets of transfer paper are wasted in order to obtain the required amount of transfer paper, resulting in a disadvantage that the amount of transfer paper 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. The density is judged and an appropriate amount of developing bias or voltage control of the original (14 exposure lamps) is performed to obtain a proper density image.

FIG. 3 shows an embodiment of the present invention. In-mirror lens I
An optical sensor DH (in the present invention, a photodiode) is installed in front of M to detect the intensity of reflected light from the document glass PC. In addition, D is a photosensitive drum and L is Hara! 1. 'A 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 one AD of the microcomputer 7 with a built-in AD converter. The microcomputer 7 outputs the AD2 level output boat 01 determined by the ADl input level and volume 5.
outputs a pulse width modulated pulse from , integrates it and inputs it to the operational amplifier 6, outputs the output level of the operational amplifier B in proportion to the pulse width, and outputs the output level of the operational amplifier 8 in proportion to the pulse width.
The developing bias DC component is controlled. Reference numeral 9 denotes a transformer, which rectifies the aftereffects on the secondary side, and performs zero-cross detection using an operational amplifier 11. The zero cross pulse is input to the iN'I"1lll input terminal of the microcomputer 7, and the interrupt processing caused by it causes the routine program shown in FIG.
l11 Read the human power signal and control the developing bias.

The relationship between each of the seven lags (indicated by F'G) 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 detects the leading edge of the document. (Step 1) Start incrementing the P1 counter, which is the time it takes for the image front to reach the development operation.Step 2)
The period from the time when the tip of the mask is exposed to the time when the latent image is developed is measured. 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 surface. (Step 0) Meanwhile A
Dl is sampled repeatedly and added to the value of □ (step 3). When the above time elapses and the FG indicating that development is in progress is set (step 4), the value of L is divided by Pl and the average of ADI is calculated. Calculate i+'j, add it to the input AD2 from the fine adjustment volume 5 (Figure 3), set this value to N, step 5), and set the value of N as shown in Figure 6 of routine a. Calculate the pulse width control value T determined by

In Figure 6, the value of N divided by 60 is 256L.
Since it is 8B, the minimum is 0 and the maximum is 510, which is 50LS.
This is because if it is divided into B units, it can be divided into 18 parts. Therefore, the developing bias DC component can be changed as shown in FIG. 9 by controlling the pulse width output to the port 01 in FIG. 4 for each value of N4-N÷30. The developing bias DC component varies from -50 to -6 as shown in FIG. 10 by 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 FIG. 7 starts when the power is turned on, and then starts when an interrupt occurs due to time-up.

After the FG is set during development, the counter P1 mentioned earlier and P2, which continues counting at the AC zero cross point (INT input signal) while the bias calculation FG is set, as shown in FIG. The development path (,l) is changed every time the counter values match.Therefore, control is performed four times.

By the way, the photosensitive drum is a 01) C drum and the 11 input charge is a negative charge, so if the developing bias ■) C component is increased to the negative side, the current retention value will be slightly reduced to i+, and the copied image will be a thin image. Become. Therefore, as shown in FIG. 9, as the value of N increases, that is, as the density of the original becomes thinner, the negative value of the developing bias DC component is decreased and the amount of development bias is increased. On the other hand, for high-density originals such as newspapers (4V, °h), the developing bias DC component is increased to eliminate the image fog in the ↑M photographs.

As shown in FIG. 11, the volume 5 shown in FIG. 4 controls the developing bias DC component in order to obtain a proper plug image when the EV characteristic of the drum changes from one curve to two curves due to drum deterioration. 31 & is a means for extracting pressure.

In the present invention, the document scanning section is started after input signals from the source 115 and the leading edge detection sensor are received, and then the leading edge IL! Although the development bias is controlled by dividing the time based on the time until the II image is developed and calculating the resulting simbling data, the development bias is not limited to this method. Scanning based on a reference [by dividing the scanning section based on a predetermined scanning distance, etc., because the scanning speed of the optical system becomes 4" depending on the magnification for copying machines with a variable magnification function, etc. It is also possible to measure the potential of the photosensitive drum immediately after exposure and perform the above-mentioned calculation to control it.

According to the present invention, the reproducibility is good for thin original images, and it is possible to obtain copied images for dark originals such as newspapers without overlapping, which eliminates the trouble of adjusting the conventional density adjustment lever, etc., and prevents mistakes in copying. There is no wastage of transfer paper, and an efficient copying function is realized.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the operation section of the i7, Fig. 2 is a conventional seed level adjustment circuit diagram, Fig. 6 is an explanatory diagram of the optical system, Fig. 4 is a circuit diagram realizing the present invention, 5 to 7 are 70-charts of the present invention, FIG. 8 is a sequence timing chart record 1, FIG. 9 is a relationship diagram between calculated values and developing bias, and FIG. 10 is a developing bias control voltage and! Figure 11 is the E-V characteristic diagram of the drum.
)-I is photo sensor, S is photo sensor → 111-) is 1
1i y+, drum. Applicant: Canon Co., Ltd. N-1-#-30 Bano L or wide body 11 bamboo r area T - (N's T thin 1 J tongue large\suru Ik) 01 out η different image bias work F Densho VaLVJE Light quantity Kan Se
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Claims (1)

[Claims] (1) It has a means for detecting the density of the original, and a means for controlling the image forming process based on the density detection signal, and the control means judges the density by sampling the detection means multiple times from a signal corresponding to the image edge of the original. An image control device 6 characterized in that the program is interrupted by a pulse input.