JPS60173566A - Copying device - Google Patents

Abstract

PURPOSE:To reproduce a picture without generating a ground fog by deriving exactly a peak level density of a low density side by quantizing it minutely, so that a developing condition can be set by a change of a developing bias voltage value. CONSTITUTION:When an original 1 is being fed, a picture of the original 1 is discriminated by a photoelectric converting element 16 and a signal processing part 17. That is to say, first of all, a light quantity signal is converted to an electric picture signal Se by the photoelectric converting element 16, sampled by a sampling circuit 171, and brought to digital conversion by an A/D converter 172. As for this digitized picture signal Se, in a CPU173, a preparation of a density histogram and a picture discrimination are executed by asking a help of memories 174, 175, and a picture discriminating signal Sb is outputted. A process control part 18 gives a prescribed electrostatic charge current, and from a light source 12a, a light of a prescribed intensity is irradiated to the original 1. In this regard, the developing condition is set by a change of a developing bias voltage value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a copying apparatus that identifies an original image and determines copying conditions.

(Prior Art) As one of this type of copying apparatus, one with the following control algorithm has been considered. That is, a document image is preliminarily scanned, and a density histogram is first created. and,
The lowest density is determined from this density histogram, and the developing bias voltage is determined based on the lowest 81 degree value. However, if the lowest density value is below a certain value, the developing bias voltage is determined based on the 11 degree width of the histogram.

However, in the case of a copying machine using the control algorithm described above, the background density is detected from the lowest density level.
In the case of a blue-printed original with an uneven background of 11 degrees, there is a problem in that background fogging is likely to occur. Further, in the case of the above-mentioned apparatus, there is a problem in that no consideration is given to R1i drawing.

(Object of the Invention) The present invention was made in view of the above-mentioned problems2, and its purpose is to realize a copy HM that can reproduce good images regardless of line drawings and 9-gradation drawings. Sue. (Structure of the Invention) The present invention achieves this object by scanning an original image, photoelectrically converting the image information, muntinating it, creating a density histogram using the quantized data, and calculating at least (ff) from the density histogram. Based on the I11 degree side peak level iar* and the histogram density width, determine the development conditions from these,
It is characterized by a mouth for performing TJ'14 according to the conditions.

(Example)゛.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, and in the figure, 10
(, is the main body of the copying machine α, and 20 is the automatic document feeder part. First, in the main body 10 of the copying machine, 11 is the original 1
Original glass (original platen) on which is set 12
is an exposure optical system that irradiates light from a light source 12a onto the original 1 on the original glass 11, and guides the reflected light to the photosensitive drum 13 via a mirror 12b, a lens 12C, and the like. The photosensitive drum 13 is uniformly charged by the charging electrode 14,
The electrostatic latent image formed on the photosensitive drum 13 by the exposure optical system 12j is developed in the developing sections 1 and 5. Reference numeral 16 denotes a photoelectric conversion element that receives reflected light from the original through a condensing lens (not shown). The photoelectric conversion element 16 may be, for example, a solid-state imaging device such as a COD or photo diode array, or a normal photo sensor. sensor.

A phototransistor is used. In this embodiment, these imaging devices are composed of a large number of elements, each element is arranged in a direction perpendicular to the paper surface of FIG. 1, and main scanning is performed by sequentially reading the output of each element. j. It's turning into a sea urchin. In addition, the sub-scanning is
This is done by feeding the original 1. 17 is a signal processing unit which receives an image signal S photoelectrically converted by the photoelectric conversion element 16;
e, and performs various signal processing for image identification.

The signal processing section 17 and its peripheral circuits [Itsu, 3]
- The diagram is shown in Figure 2. In this FIG. 2, 16 is the above-mentioned photoelectric conversion element that converts an incident light beam signal into an electrical image signal Se, and 171 is a sampling circuit for the image signal Se. The sampling circuit 171 is configured not to perform peak sampling but to perform sampling at equal time intervals, since this makes it easier to grasp the characteristics of the image from a broader perspective. 172 is an A/D converter that converts the analog signal from the sampling circuit 171 into a digital signal. The upper limit 111 of the low-density portion of the original is set at a level of 50 to 80% from the low level side of the input width of the A/D converter 172.
The levels are adjusted so that the output of sampling 171 obtained when scanning 116 (for example, effective reflection [(0,8)) reaches the am histogram. This is to make it possible to detect even the slightest difference in background density at 1:.

173 is a central processing unit (hereinafter referred to as CPU) such as a microprocessor that creates a density histogram based on the output data of the A/D converter 172 and performs image identification from the density histogram; Record data, store it, and transfer the recorded data to CP
Memory (RAM) supplied to LJ 173, 175 is C
A memory (ROM>) stores calculations and other programs for the PU 173.Furthermore, 176 is a reference clock generator that generates pulses that control the light reception time of the photoelectric conversion element 16, and the operation of the sampling circuit 171 and A/D converter 172. It generates a clock signal that determines the timing, a clock signal that determines the calculation of the CPU 173, and the timing of data sending or calling.The image identification in the CPU 173 is based on the peak level density on the low density side of the density histogram (lowest density side). Peak level 11 on the side
and histogram 811 degree width. For example, the third
When a density histogram as shown in the figure is obtained (the horizontal axis of the figure shows the number of levels 0 to 64 corresponding to the effective reflection density), image identification is performed based on the low-density side peak level density d and the histogram density width X. conduct. That is, depending on the value of the low concentration side peak level 1rIJ,d, which fIi! skinny till
After determining whether the image is a dark-colored image, the degree of density distribution of the image can be determined based on the size and width of the histogram density width. Specifically, as shown in Fig. 3, the horizontal axis (effective reflection density) is divided into two density sections ((I), l]T, which are divided by the number of levels 30 in Fig. 3). In addition to determining in which section the low 811α peak level density (1 falls), what value does the histogram m degree width X have (in Figure 3, white to black are 64 When divided into levels, ■ it is wider than the equivalent of 10 levels, or
■We are determining whether it is narrower than the equivalent of level 10. Image identification is performed (described below based on this example). Then, by the combination of (I), (IF>, and ■, ■, an identification signal S11 for determining the development conditions is output.
Each of the sections 171 to 176 described above forms the signal processing section 17.

Incidentally, the shape of the density histogram changes depending on the size of a unit imaging area (area of a reading spot on a document, hereinafter referred to as a spot) by the photoelectric conversion element 16. for example,
In the case of line drawings, the time-series pattern of the light amount signal (effective reflection density) corresponding to the image density obtained when a document image (area to be determined) is scanned with a small-area stub is the most of the low-density signals. This is a pattern in which one or a small number of high-density signals are scattered in each area, and high, medium, or low-density signals are relatively mixed and distributed in both areas.

On the other hand, the time-series pattern of optical confidence @ (effective reflection density) of the image density obtained when the spot area is relatively wide is higher than that of the small-area spot in the case of line drawings due to high temperature changes. However, in the case of inter-story buildings, there is no significant change. Next, the difference in the effective density histogram depending on the size of the spot will be specifically explained. Figures 4 and 5 show the image of the letter m (line wfii) in a certain newspaper.
) and the photographic image area (both between floors) with a spot of 0.11IIl angle (0,0111III12.) and 21+1R, respectively.
This is a histogram obtained by scanning a spot of φ(3,14n11) at equal intervals of 11111 (density 0.1 is used as the density interval). The histogram shown was obtained from the photographic image section (floor 7-7). As is clear from a comparison between the two figures, in the line drawing, the maximum peak of the histogram due to the 2 mm diameter spot is significantly shifted to the lower density side than the maximum peak of the 0.11 square spot. On the other hand, they do not move much between floors. In this situation, the sampling interval is 0.3am, Q, 9w+m, 1.0m.
Since there is almost no difference even if the value is changed to 1.5+am, this is caused by the size of the spot. Further, although the density interval of the histogram can be arbitrarily set, the moving edge of the maximum peak can be observed in the same way. Therefore, choosing the spot area to N is a problem, especially in the case of line drawings, but even if the low density side is finely quantized, the low density peak level Takimaro can be clearly seen. , it is necessary to select a spot area where a steep peak can be obtained. From this point of view, it is preferable to select the spot size to be 0.1 mm2 or more.

A process control section 18 receives the identification signal sb from the signal processing section 17, and sets development conditions based on the identification signal sb. The process controller 18 also performs various other controls such as controlling the feeding operation of the automatic document feeding device 20 and controlling the movement of the reading optical system 12. This control of the development conditions by the process control section 18 is achieved by controlling the development bias voltage. 6th
The figure is indicated by the image identification signal S l+ (I), <
The process control unit 18 depending on the combination of
shows an example of the developing bias voltage Vl selected by . There is. Regarding the table shown in FIG. 6, it is written in the ROM 175, for example, and the CPU
173 to output the above values as set values to the process control unit 18, or a ROM in which the table shown in FIG. 6 is written is separately provided in the process control unit 18, and the C
The PU 173 may output a signal indicating a combination of (:r), (If), ■, and ■. Specification-1
The explanation assumes the latter configuration. □゛Referring to FIG. 1 again, the automatic document feeder 20 includes a paper feed unit 22 that takes in the originals 1 placed on the paper feed unit 21 one by one, and a first A conveyance belt 23 that is sent to the left in the figure, a drive roller 24 and a driven roller 25 that ensure the movement of this conveyance belt 23, and a position where the document 1 taken in by the paper feed section 22 is started to be conveyed by the conveyance belt t-23. In order to send the document 1 to the conveyor belt 23 (the part that wraps around the drive roller 24), the document 1 is pressed by 1]-ru 26 and 27, and a guide [J-ru 28 and 29, the guide roller 28.
Presser rollers 30 and 31 press the conveyor belt 23 toward the original glass 11 side between 29 and 29, a stopper 33 that cooperates with the collar roller 32 to stop the original 1 on the original glass 11 at the proper set position, and discharge after reading. It is comprised of a paper discharge tray 34 on which the original documents 1 are stacked, a sensor 35 for detecting that the original document 1 is set at the proper position on the document glass 11'', and the like.

The operation of the copying apparatus having the above configuration will now be described.

First, when the LRT document 1 is set in the paper feed section 21 and the copy start button (not shown) is activated, the process 1111
181118 returns the reading optical system 12 to the initial position (the leftmost position in FIG. 1, the exposure scanning start position), rotates the paper feed section 22 and the conveyance belt 23 to convey the original 1, and After the document 1 is stopped at an appropriate position at the upper end of the stopper 33 protruding from the upper surface of the glass 11, the rotation of the conveyor belt 23 is also stopped. During this feeding, both images of the original 1 are identified by the photoelectric conversion element 16 and the signal processing section 17. That is, first, the photoelectric conversion element 16 converts the light amount signal into an electrical image signal Se, and the sampling circuit 171 samples this image signal Se. Next, the analog signal Se is converted into a digital signal by the A/D converter 172. This digitized image signal 3e is read by the CPU 173, and the above-mentioned density histogram creation and image identification are performed in the CPLJ 173 with the help of the memories 174 and 175, and the image identification signal sb is J173 = 11- is output. This image identification signal sb is output from the process control unit 1.
8 is input. On the other hand, the camera 1 to the proper position of the original 1
is also performed by the sensor 35, and a signal to that effect is also input to the process control unit 18). , 1-2 are input to the process control unit 18, the process control unit 18 applies a predetermined charging current (surface potential), and causes the light source 12a to irradiate the original 1 with a predetermined intense light ( The reflected light is guided to the photosensitive drum 13 via the mirror 12b, lens 120, etc., and an electrostatic latent image is formed thereon. Then, development is performed while applying a developing bias voltage based on the identification result to the developing section 15, and then the toner image is transferred to a transfer paper (not shown), the transfer paper is separated from the photoreceptor drum 13, and the toner image is transferred to the transfer paper. One copying process is completed through processes such as fixing of the toner image. On the other hand, in parallel with this development, separation, and fixing operation, after the exposure is completed, the process control unit 18 moves the upper end of the stopper 33 onto the document glass 1.
1 and rotates the conveyor belt 23 again to send the copied original 1 to the paper discharge tray 34. Also, 12- At the same time, conveyance of a new original 1 is started and set at an appropriate position on the original glass 11. Thereafter, the same copying operation is repeated, and all the originals 1 placed on the paper feed section 21 are copied.

By the way, FIG. 7 is a diagram showing the relationship between original density and copying 81 degrees when the developing bias voltage is changed, and FIG. 8 is a diagram showing the relationship between surface potential original density and light amount for reference. . The solid line tJ in FIG. 7 shows the characteristics when the amount of light is large, and the broken line shows the characteristics when the amount of light is small. Also, * indicates the case where the developing bias voltage is high, ◯ indicates the case where it is intermediate, and Δ indicates the case where it is low for reference. On the other hand, in Figure 8 (
A solid line and a broken line indicate characteristics under two different settings, where O indicates a large amount of light, . indicates an intermediate amount, and × indicates a small amount. It can be seen from FIG. 7 that the higher the developing bias voltage is, the more the development starts in the high temperature area, and the greater the amount of light, the more noticeable the image skipping in the low density area. Furthermore, from FIG. 8, it can be seen that when the black paper potential is increased, a rapid potential change occurs in the low density area, and this tendency is stronger in areas where the amount of light is large.

According to the above copying apparatus, for example, when the low-density side peak level density d is low and the histogram m width X is narrow, (■)
, ■The developing bias voltage becomes low and low l
lIr# A platform where the I side peak level density d is high and the histogram density width X is wide (■).

In combination (2), the developing bias voltage becomes high, and in other cases, it becomes intermediate. Since this discrimination is performed using the low i1 degree side peak level 1llllud as one discrimination criterion, background fogging can be reliably avoided. In particular, if you select three or more density categories instead of two (I) and (I[), you can increase the number of developing bias voltage levels, so you can avoid background fogging and maintain good density in line areas. In addition, since the histogram 1llll & width X is also used as the discrimination criterion, the reproduction of r8 toning is also of good quality.The division of this histogram density width X can also be 3 or more.

Note that as the histogram density width in the above description, the width cut off at a constant frequency may be used.

Furthermore, although the above description has been made regarding an imaging device in which the photoelectric conversion element 16 does not move during reading for document image identification (the elements of the imaging device are arranged in an array), the present invention is not limited to this. For example, main scanning is performed by running a laser beam over the original 1, and the reflected light from the original 1 is sent to an optical sensor with a single light-receiving surface via a light guiding member such as an optical fiber or a condensing member. It may also be configured to guide the user.

Furthermore, although the above embodiments are related to a copying machine that has an automatic R document feeder, even if it is a general copying machine that does not have this, or even if its type is a movable original platen type, it can be fixed. It is possible to implement even if it is a mold. Also, there is no need to limit the copying process to the conventional Carlson method.

(Effects of the Invention) As explained above, according to the present invention, the peak level concentration on the low concentration side can be determined accurately by fine quantization.
It is possible to accurately identify what level of background density the document has, and therefore the image can be reproduced without causing background fog. Furthermore, since no consideration is given to the space between floors 15 and 15, it is possible to obtain an easy-to-see and high-quality image.

[Brief explanation of drawings]

FIG. 1 shows the main parts of an embodiment of the present invention.
FIG. 2 is a block diagram of the signal processing section in FIG. 1, and FIG. 3 is an explanatory diagram of the low-concentration side peak level concentration and His [gram concentration width, which are the discrimination criteria in the method of the present invention, and the discrimination principle.
4 and 5 are explanatory diagrams of histogram waveforms, FIG. 6 is an explanatory diagram showing a value selection table for 81 degree control,
FIG. 7 is a diagram showing the relationship between original density and copy density, and FIG. 8 is a diagram showing the relationship between original ml and surface potential. 10...Copying device main body 11...Original glass 12.
...Exposure optical system 12a...Light source 13...Photoreceptor drum 14...Charging electrode 15...Developing section 16...
- Photoelectric conversion element 17...Signal processing unit 171...Sampling circuit 172...A/D converter 173...CPU 16-174...Memory (RAM) 175...Memory (ROM) 176 ...Reference clock generation unit 18...Process control unit 20...Automatic document feeder Patent applicant Konishiroku Photo Industry Co., Ltd. Agent Patent attorney Fuji Ijima 1 person - 1 → 1 Torayo Reflection Density Leather 6 Cause 7 Figure 5 Cause 111〉Effective Reflection Density○ 05 10 Haranawa Density-11◆

Claims (3)

[Claims] (1) After scanning the original image and photoelectrically converting the image information, a density histogram is created using the quantized data. , a copying apparatus that determines development conditions from these and performs copying according to the conditions. (2) The development conditions are set by changing the development bias voltage value.
Copying device as described in section. (3) A plurality of the development conditions are prepared, and one of them is selected by balancing the peak level density and the histogram 111 width. Or the copying device according to item 2.