JPS6010268A - Image processor - Google Patents

Abstract

PURPOSE:To make a titled device adaptive to a partial change in the density of an original and to shorten the time for starting image formation by controlling the value of bias for development with the density values of the original detected in plural regions. CONSTITUTION:When a copying start button is pushed, the 1st mirror 104 and the 2nd and 3rd mirrors 105 scan an original 101 at a speed ratio of 2:1. A means 107 for detecting the quantity of light samples the quantity of light at every 0.1sec and stores successively the same in an RAM via an A/D converter. The bias for development is determined according to the average value of the sampling data between A-C of the original in the stage of developing the position B of the original at the point (b) in a developing device 110. The sampling data between B-D is similarly used in the stage of starting development of the point C and therefore the bias is controlled by the average data before and behind the point to be developed. Good accuracy is thus obtd. and the device is made adaptive with a partial change in the density of the original.

Description

[Detailed description of the invention] The present invention relates to an image forming apparatus such as a copying machine or a fax machine.

In conventional copying machines, in addition to a control device that controls the amount of light emitted from a document illumination light source (hereinafter referred to as a light source) according to the sensitivity of the photosensitive drum, an operator also controls the amount of light emitted by a document illumination light source (hereinafter referred to as a light source) according to the sensitivity of the photosensitive drum. It is common to have a child actor inputting quantities.

In such a semi-automatic (almost manual) mode, selecting the appropriate light emitting time is a very difficult task, and in order to obtain a copy with the appropriate contrast, it is often necessary to try out several copies. I had to waste expensive copy paper.

One way to solve these problems is to detect the density of the original using a photodetector or a surface electrometer on the photosensitive drum, and automatically control the amount of light emitted accordingly. There are also proposals for machines, but there is no evidence that serious consideration has been given to how to respond to the detected document density (i.e., copy density) to meet user demands. In many cases, it is sufficient to make a linear correspondence between detection w, fAP degree and light emission amount.In such automatic n-light copiers, the light emission amount is increased and the light emission amount is increased to detect a high concentration of plagiarism. Normally, the density W is controlled so that the back pressure against the original is reduced, that is, a thick layer with dark spots is copied into the white part, and a white part is copied into the black part, but as mentioned above, the density - If the amount of light emitted was made to correspond linearly, it would not be possible to meet the need for hot copies and whitish copies, and it would not be possible to determine the amount of light emitted by submitting a dark photo of a portion of the original. Oh, it was inaccurate.

It is also possible to detect the density of the entire area of the original, but in that case it would take too much time to set up the appropriate output and start image formation.

Also, there are some cases in which the exposure aperture is adjusted to 11 points in order to make the light on the photosensitive area uniform even if the copying magnification changes, but it is difficult to adjust the aperture in consideration of the original degree and magnification.

SUMMARY OF THE INVENTION It is an object of the invention to obviate the drawbacks of the prior art devices mentioned above.

Another object of the present invention is to provide an image forming apparatus that can obtain appropriate density and contrast for various original densities.

It is also an object of the present invention to provide an image forming apparatus that reproduces dark originals or whitish originals as faithfully as possible.

In addition, the present invention resides in an image forming apparatus that can automatically adjust the density during original exposure for image formation, and also prevents misfires! A is an image forming apparatus that can cope with a partial change in the original density, and the present invention is an image forming apparatus that can start forming an image before the density measurement of the entire original area is completed; The purpose is to form images with appropriate density in response to special processing such as variable magnification image formation.

It is also a copying machine that can form images with high precision and reliability.

To the light.

Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 1 shows a schematic diagram of a copying machine of the present invention. The structure of this copying machine is a known one. During copying, light is emitted from a light source 12 that moves within the document 11, and is reflected from the document 11 on the document table. The light is transmitted to the photosensitive drum 10 ( (rotate in the direction of the arrow). The electrostatic latent image on the drum charged by the charger 14 is cleaned by the cleaner 17 by this exposure, and the drum is charged and exposed again.

In the figure, a light detection means 1a provided near the light R1 and a surface electrometer 1b provided near the photosensitive drum 10 are shown as density detection means according to the present invention. In the present invention, either of the above two methods may be used to detect the degree of # of a document, and both may be used. however.

The light detection means 1aFiW detects the amount of reflected light from the paper 11, and the surface electrometer 1b detects the density of the first nominal by detecting the surface potential of the photosensitive drum 10 after exposure. Before starting image formation, a standard white plate 181 is irradiated with the lamp 12, and the reflected light is measured by the detector 1a or the potential of the reflected light is measured by the potential side 1b. l: Determine whether or not it is in the standard f1 version, and if it is not in the standard value, control the lamp 12 or charger 14 so that it becomes the standard value. The device can thereby be preset in the standard condition. Thereby, appropriate control of the reproduction density after the start of image formation can be achieved to a high sugar Iξ. This standardization process can be carried out after turning on the device 1) and before turning on the image forming start switch (copy key). As a result, the rise time for image formation can be reduced by approximately 1%.

FIG. 2 shows the exposure amount of the copying machine of the present invention: 1! The control system σ) block diagram shows the above-mentioned original density Ji detection means 1 (
1a, 1b) (7) Output #iA/DK 4%
N2 TE digitized and ap via input/output port 3
It is configured to be sent to tr4. The 0PU4 emits light by referring to a data table that is stored in the ROM (read-only memory) 5 and which corresponds to the amount of light emitted, which will be described later, based on the integrated value of the sent density data! ■Determine the data and send it to the input/output boat 3. FIG. 6 shows an example of a circuit for integrating detected values. 1 old is optical or electrical sensor, 1021d operational amplifier, 1a3 level,
This is a switch for resetting the 104-digit integral of the qgm amplifier. Integration time ii Due to A/D converter. Determined by conversion time. This is effective when determining the appropriate iE output by pre-scanning the original, detecting the density of the area, and averaging it. This light emission amount data is converted into analog and digital data by the D/A converter 6 and sent to the light source 12.
It is a configuration that is controlled.

The data of both degrees and luminescence are stored in the ROM 5 as 8-bit information in the form of a constant characteristic curve.

That is, 8 bits or 256. For example, data on the amount of light emitted is stored in each address of the address in 8 bits. Each address corresponds to each data of detected concentration. In other words, a memory address corresponding to the detected integral data is found and the light emission amount data stored at that address is output.

The ROM5 may be a RAM whose data can be changed.

An example of characteristic curve I9 between density and luminescence amount is shown below.

The 0 period of the manuscript is divided into 11 stages from pure black to pure white from 7161 to 1611 (pure black: A I, pure white: A11).
As shown by the solid line in FIG. 3(A), the original density exists.
l, it's going to happen. Below, copy once with a dashed line, yx@
Concentrations are indicated by solid lines. That is, in the case of FIG. 3 (A), the broken line and the solid line overlap. ) The first thing that can be considered is the third method (B ) indicates the finished density of the copy at this time with a broken line. In other words, the original of 161 (pure black) is also 4611 (pure white). All originals will be finished with the same density.

However, from a practical point of view, it makes no sense to finish both the blank manuscript and the old paper with the same density.

In the present invention, as shown in Fig. 3 CD>K, the amount of light emitted is controlled so that copies with the same density cannot be obtained as shown by the broken line for originals of intermediate 4 density near /f66, and the remaining high density copies are Low l on the whites of the eyes? What is necessary is to finish the black eyes by % degree #″i.

However, in the example shown in FIG. 5(C), a completely black original cannot be copied completely black, and a completely white original cannot be copied completely white. Therefore, it is desirable to further draw the KlllllJ image.

Furthermore, since it would be inconvenient if the copy f% rate suddenly changes from one point,
It is ideal that degrees correspond to f4 degrees. Further, an example in which this is corrected according to the sensitivity of the photosensitive drum 10 used is shown in FIG. 3(F).

In order to obtain the copy 8 degrees shown in Figures 6 (A) to (F) of Fujo, press the luminous needle as shown in Figures 4 (A) to (F). It will be +1. In other words, in the present invention, as shown in #'iM4 diagram (,0) to (FC), the original density to light emission is non-linear, and the copy density is 1 at around the intermediate density. ir+% The amount of light emitted is increased for a thinner document, and conversely, the amount of light emitted is controlled to be a little lower for a thinner document.

A non-linear characteristic curve relating document density to luminescence amount as detailed above is stored in FtOM5, and ζt1f
The amount of light emitted is determined by referring to it by CPυ4. This processing procedure t70-chart is as shown in FIG. That is, in step 1h of FIG. 5, the integrated value of the output of the document density detection means 1 using the surface electrometer 1b or the like is output from the input/output port 3 via the A/D converter 2. Low intestine is given to OPU 4. (In step 2, the CJPUF outputs light by comparing the sent concentration data with the address of the density-multi-view characteristic curve digitized and stored in the ROMS. After determining the quantity data, addressing the memory using the density data as address data and outputting the luminescence quantity data, then in step 3 this luminescence quantity data is loaded into the CPH.Then in step 4 this luminescence quantity data is input/output. The light emission 1) of the light source 120 is controlled by, for example, controlling the voltage applied to the lamp 12 in accordance with the light emission amount data sent to the D/A converter 6 via the boat 3 and returned to the analog meter there. It is also possible to control the developing bias voltage of the +Iff device 15.

Figure 7 shows 70- in Figure 5 in more detail, and 810-.
At , the microprocessor CPII senses a predetermined port of I10 boat 3 and obtains sense data a (detected integrated concentration).
is loaded into one of the registers in the CPU, and at 811 R
OM's! , t11 address b to CPU address register)"l,, data C at B12 '[10
Set it on the boat and output the control data.

Next, in another example, a light-receiving element is installed in the optical path of an optical system in which light reflected from an original is focused on a photoreceptor through a lens, and a photoreceptor is placed on a multi-photoreceptor drum by changing the copying magnification. An example will be described in which the discrepancy between the illuminance and the output of the light receiving element is corrected according to the copy magnification, and the developing bias is further controlled according to the corrected data to make the copy density appropriate.

FIG. 8 is similar to FIG. 1.

When the copy start button is pressed, the first mirror 104 and the second
The third mirror 105 starts scanning the original 101 at a speed ratio of 2:1. During scanning, the light amount detection means 107 measures the scene at regular intervals and samples data. A,
B, O, D, and a, b, c, a.

The correspondence between the position of the original and the position where the original image is formed on the drum is shown.

FIG. 2 is a flow diagram showing the procedure for determining the developing bias by averaging and scaling processing after sampling.
1o and 11 are circuit diagrams for achieving this, and FIG. 12 is a flowchart of the above procedure program stored in the program ROM0 of FIG. 10. C in figure 911! PU40
is an OPU with a built-in A/D converter.

FIG. 10 I/'i is an electrical configuration diagram. The sampled data is digitized via Aρ converter and R
The data is sequentially allocated and stored between 9 AM addresses. While the latent image formed on the photoreceptor drum by exposure reaches the level of the developing layer (/l), the data is averaged and the developing bias is controlled according to the data.
In No. 10, point b is being developed, and the developing bias value at this time is set at 0.1 pec every N
Data sampled twice is averaged and determined based on that value. Next, when the development of the 0 point is started, the data (N data) sampled by the light receiver 107 between the document B and D are averaged (see Figure 13), and the DC component of the development point is calculated according to that value. control. In this way, the control of the Do acid component of the developing bias is performed sequentially.

Output correction when magnification differs is based on the averaged value Correction ROM
This is done by multiplying the correction values from .

Sampling is carried out by periodically (for example, 0.1 θec) inputting an interrupt signal to the iNT shown in FIG. 4 to store the sub-ring data in the address space of the RAM.

Reference numerals 115 and 116 in FIG. 11 are similar to the integrating circuit shown in FIG. 6, and 118 and 120 are an integrating circuit and a buffer amplifier, respectively, which constitute the D/A converter 6.

119ti This is a transformer that applies a bias voltage to the developing roller 110.

Figure 12.15 is detailed. When an input pulse causes an interrupt, the input capo) ADi data 0ROtapr
Load register A in y (step 1), set register a indicating the number of samples to +1-t-rule (j, f block 2), sense register HD indicating the RAM address, and load the register in the first atlas of RAM. Store the data of A (step 3).

Since the sample has not been completed N times, the address data in the register HD is advanced by one (step 4-2).
．． Similar sampling and data storage are performed using the pulse after 1 sec.

When the number of samples reaches N, as soon as the sampling of C data 111 is completed, N theta in RAM are added and set in registers A and B (step 4-1).
5). 1/N the added data and load it into register A (
Step 6). f(OM I K Since correction data according to the copy magnification is stored in advance, data at the current magnification is loaded from ROM1 to register B (step 7). Multiply the data in registers A and B to A. Load (step 8).The data in this register A will load the ROM.
2, and load the bias data stored at the corresponding address into register B (step 9).

Transfer the data in register B to boat 0. It is output from and used as a developing bias (step 10). Next, load the register O[N/2, sample the next area (C to D) again (N/2 times), and store the data statement.The V2 converter is newly stored in the RAM by steps 3 to 5. However, in steps 5 and 6, the average value is calculated by calculating the data for N pieces of data, B=D. Therefore, since data from the light receiving element is averaged over the data before and after the data, H(y is good. Note that the light receiving element 1
07 is provided at the rear portion of the zoom lens 106. This zoom lens performs zooming operation by pressing the input key to select magnification. Then, addressing of ROM 1 is performed using the latch data generated by this input key, and old data is obtained. It should be noted that even if the potential cap is provided at a position immediately after the exposure station, the bias splitting frame as described above can be obtained.

With these examples, automatic density control can be performed immediately during image exposure for image formation, and wasted time can be reduced.

In this example, the original image is read by a reader such as a COD, converted into an electric signal, and further converted into a binary video signal. It can also be applied to systems where a latent image is formed or a video signal thereof is transmitted. In that case, the nth degree of the original is also detected by the original image reading means. Determine original density from original read data. Also, one of the image forming conditions to be controlled can be the binarization processing step of the read data, that is, by changing the threshold hold level for binarization according to the judgment value 1ant. I can do it.

[Brief explanation of the drawing]

Fig. 3(A) to (F) are block diagrams showing the control circuit of the copying machine according to the present invention. , a miniature map showing the correspondence between original density 1 and copy density, Figures 4 (A) to (F)
5 is a diagram showing the characteristic of original density to light emission amount of the present invention, FIG. 5 is a flowchart showing the processing procedure 11 of the circuit of FIG. 2, and FIG. Circuit, No. 7 is a detailed flowchart of Fig. 5, Fig. 8 is a sectional view of a copying machine showing another example, Fig. 9 is a flowchart of another example, and No. 10.11.
The figure is a circuit clock diagram of another example, FIG. 12 is a detailed flowchart of FIG. 9, and FIG. 13 is a control explanatory diagram of FIG. 12. In the figure, 1 is a density detection means, 4 is a control means, 12 lamps, and 15 is a developing means. Applicant: Canon Corporation Figure 5 Figure 7 Figure 9 Atsushi Figure 11

Claims (1)

[Scope of Claims] Processing means for image formation, means for detecting original density, and means for controlling image forming conditions of one of the processing means by the output of the detection means, the control means is the original copy #1. g An image processing apparatus characterized in that the detection signals from the detection means obtained by the gA castle are processed and respective control signals are outputted. /