JPS616640A - Image processor - Google Patents

Abstract

PURPOSE:To obtain a copy image with proper contrast even from an original with low contrast by setting its copy density on the basis of the difference from the maximum value of original density detected by a reflection density detecting means. CONSTITUTION:When the reflection density of an image area is detected by the photodetecting element group of the relfection density detector 35 for each picture elememt, picture elements with a low reflection factor are obtained after a set of picture elements with a high reflection factor. For example, when the picture element having the maximum reflection factor in the set of picture element having a low reflection factor has a density of 0.07 and the picture element with the minimum reflection factor has a density of 0.5, an input voltage of 65V is applied to an irradiation lamp 25 to determine the potential of a drum according to an E-V characteristic, thereby obtaining a copy image with density determined by the development characteristic. In this case, its original density is equal to the copy density. When the difference between the maximum and minimum of the original density is smaller than a predetermined value, on the other hand, the input voltage to the irradiation lamp 25 is controlled to give artificial contrast to an original 20 with low contrast, and the proper density is set, thereby obtaining a sharp copy image.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an image processing device that detects an image area and image density on a document using the same detection means and controls the copy density within the image area. be.

[Prior art and its problems]

Conventionally, in this type of image processing apparatus, the density of the original is measured using various measurement methods, such as the method of irradiating the original and directly reading the reflected light, and the method of measuring the surface potential of the photoreceptor, and measuring the light intensity of the original irradiation lamp. It is configured to obtain a transferred image with an appropriate density by controlling the lamp voltage, etc., and reads the density of the original evenly and evenly, preventing toner from adhering to other parts of the original and causing fogging. It was controlled like that. For this reason, this kind of control is very effective when the background is slightly foggy and the text is very black, such as in newspapers, but it is not appropriate when the text is thinly drawn on a white background. There were drawbacks such as not being able to obtain a transferred image.

[Purpose of the invention]

The present invention has been made to eliminate the above-mentioned drawbacks, and includes a reflection density detection means by arranging a group of light receiving elements in the main scanning direction.
Image processing that detects the moisture level of the original and sets the copy density based on the difference between the maximum and minimum density of the original to obtain a copy image with appropriate contrast even on originals with unclear contrast. The purpose is to provide equipment.

〔Example〕

FIG. 1 is a schematic sectional view showing an embodiment of an image processing apparatus according to the present invention, FIG. 2 is a control circuit diagram, and FIG. 3 is a front view of a reflection density sensing element.

In FIG. 1, 1 is a drum, 2 is a pre-elimination charger, 3 is a primary charger, and 4 is a charger, which performs corona charge removal on the drum 1. 5 is a copying charger, 6 is a cleaning device,
Consists of a cleaning roller and an elastic blade. 7 is a developing device, and 8 is a pre-exposure lamp, which eliminates static electricity from the drum 1. 9
is a full-surface exposure lamp which forms an electrostatic latent image on the drum 1.

10. Reference numeral 11 is a paper feed roller, and 12 is an upper cassette in which copy paper is stored. 13 is also the lower cassette, 14
15 is a registration roller, 15 is a transport belt, 16 is a fixing roller, 17 is an ejection roller, 18 is a tray, 19 is an original table glass, 20 is an original, 21 is an original pressure plate, and the surface in contact with the original 20 is a mirror surface or has a low reflectance. The parts are coated. 2
2.23 is a standard white plate, 24 is a moving optical system unit, which is composed of an irradiation lamp 25 and a first scanning mirror 26. 27 is a second scanning mirror, and 28 is a position detection piece, which is provided outside the moving optical system unit 24. Reference numeral 29 denotes a switch for detecting the contact state between the original pressure plate 21 and the original platen glass 19, which constitutes the book copy detection means of the present invention. 30°31.32 is a position sensor 1 position detection piece 2
8 is detected. 33 is a slit, 34 is the first scanning mirror 26. A document detection lens 35 forms an image of the reflected light guided by the second scanning mirror 27, and 35 is a reflection density lens in which a group of light-receiving elements such as COD are arranged in a row in the main scanning direction B (perpendicular to the sub-scanning direction A). Document information detection means 1 of the present invention with a detector
Image area detection means.

It constitutes a reflection density detection means, and the document platen glass 19
The document size of the document 20 placed on top, the image area within the M document, the reflection density of the document, the copyable area, and the document position within A are detected. 36 is a projection lens that forms an image of the reflected light guided to the second scanning mirror 27, 37 is a third scanning mirror, 38 is a fourth scanning mirror, and 39 is an optical system drive motor that drives the moving optical system unit 24. . A main motor 40 drives the drum 1. Reference numeral 41 denotes an eraser constituting the eraser means of the present invention, which prevents toner from adhering to the non-image area portion of the drum 1. This eraser 41 is composed of a group of LEDs that emit light corresponding to one pixel of the light receiving element group of the reflection density detector 35. Therefore, this eraser 41
are also arranged in a line in the main scanning direction B.

In the control circuit shown in FIG. 82, 51 is an oscillator that oscillates a clock signal. 52 is a frequency divider, 53 is an amplifier for amplifying the detection signal of the reflection density detector 35, and 54 is an A/D converter, which converts the output of the amplifier 53 into A/D and outputs the digital value to each input port i1 to i4. Output to. 55 is a microprocessor (MP) which receives each sensor output 1 output from the reflection density detector 35 and each timing signal at each input port;
Each control signal is output from each output port. This MP55
is equipped with an internal timer, and also includes copy density setting means, automatic copy magnification adjustment means, eraser control means,
It also serves as a copy magnification setting means. 56 is the MP
RAM randomly accessed by 55, 57
1 to 573 are cassette size input keys constituting the copy paper size detection means of this invention, and the cassette size is determined by MP5.
5 to each input port 19 to i++. 58 is an input key such as a copy start key, numeric keypad, clear key, etc., which outputs a copy start signal and a copy number signal.

Clear signals, etc. are sent to each input port of MP55 from i+3 to i+6.
Enter. 59 is a D/A converter, and the irradiation lamp 25. which the MP55 outputs to each output capo) 013-016. Converts the lamp signal to D/A.

60 is an amplifier that amplifies the lamp signal, and 61 is a lamp regulator (CVR) that controls the voltage of the irradiation lamp 25. A drive driver 62 drives the eraser 41 by receiving the eraser drive control signal outputted from the MP55 to each output port OI-09. 63 is a drive driver, MP
55 for each outgoing capo) 02. The optical system drive motor 39 is driven by the motor drive control signal outputted to t r 022 .

Reference numeral 641 denotes an AND circuit which ANDs the output signal of the frequency divider 52 and the control signal outputted from the MP55 to the output port 012, and inputs a shift pulse signal (S'H) to the reflection density detector 35. 642 is an AND circuit which similarly ANDs the output signal of the frequency divider 52 and the control signal outputted from the MP55 to the output port 011, and inputs the clock signal φ1 to the reflection density detector 35. 651 is an inverter for inverting the signal from the oscillator 51; 652 is an AND circuit;
The frequency divider 52 and the inverter 651 are ANDed, and A/
The Din signal is input to the MP55 (7) input port i5. An inverter 66 inverts the clock signal φ1 of the AND circuit 642, and inputs the clock signal φ2 to the reflection density detector 35.

67 is a clock signal input to the input port i6 of the MP55. Note that the output of the switch 29 is input to the input port 112 of the MP55.

In the reflection density detector 35 in FIG. 3, reference numeral 71 denotes a light receiving element group consisting of light receiving elements (1 to N), which are arranged in a row and divide the reflected light from the entire area in the main scanning direction of the original into parts 1 to N. It receives light and outputs an output voltage (V) corresponding to the reflection density (CD) as shown in FIG.

Next, document exposure and copying operations of the image processing apparatus will be explained with reference to FIGS. 1 and 2.

The surface of the drum 1 is a photoreceptor, and behind the input key 58 is a main motor 4 that is activated when the copy start key is turned on.
0 starts rotation in the direction of the arrow. Due to this rotation, the original 20 placed on the original platen glass 19 (hereinafter, the light-receiving surface of the original platen glass 19 will be referred to as an image area) is slit-exposed by the irradiation lamp 25 integrated in the optical system moving unit 24. The reflected light is transmitted to the first scanning mirror 2.
6 and a second scanning mirror 27. By moving the $1 scanning mirror 26 and the second scanning mirror 27 at a speed of 1:1/2, the original 20 is scanned while the optical path length in front of the projection lens 36 is always kept constant, and the moving optical system The unit 24 is driven by an optical system drive motor 39. At this time, the slit 33. Projection lens 36. Third
Scanning mirror 37. The reflected image passing through the fourth scanning mirror 38 is
A high-contrast electrostatic latent image is formed via the charger 4 on the drum 1, which has already been simultaneously neutralized by the pre-exposure lamp 8 and the pre-discharge charger 2 and further corona-charged by the negative charger 3. The electrostatic latent image formed on the drum 1 is developed by the developing roller of the next developing device 7 and visualized as a toner image, and this toner image is copied onto copy paper. After copying, the drum 1 continues to rotate and is cleaned by the cleaning roller and elastic blade of the cleaning device 6 in preparation for the next image formation.

The copy paper stored in the upper cassette 12 or the lower cassette 13 is conveyed into the machine by paper feed rollers 10 and 11, and the registration roller 14 temporarily stops the copy paper being fed toward the drum 1, so that the leading edge of the copy paper and When the leading edge of the latent image coincides with each other, the copy paper is sent out in the direction of the drum 1 again. Next, while the copy paper passes between the copy charger 5 and the drum 1, the toner image on the drum 1 is copied onto the copy paper. After the copying is completed, the copy paper is separated from the drum 1 and guided to the fixing roller 16 by the conveyor belt 15, where it is pressurized and heated to fix the copied image.
The copy paper is discharged onto the tray 18.

Next, the operation of detecting the document position, document size, and document source degree will be described with reference to the drawings.

After the main switch is turned on, first, the optical system drive motor 39 is driven to correct the light-receiving element group 71-@ which constitutes the reflection density detector 35 and the ripple of the light source, and the position sensor 30 indicates the position of the standard white plate 22. is a position detection piece 28 attached to the outside of the moving optical system unit 24.
The moving optical system unit 24 is moved until it detects.

Next, when the irradiation lamp 25 irradiates the standard white plate 22 that provides a uniform reflection density, the reflected light is transmitted to the first scanning mirror 26. Second scanning mirror 27. The document is fed into a reflection density detector 35 via a document detection lens 34. This reflection density is stored in the RAM 56 as a density correction value. after that,
The optical system drive motor 39 is driven to move the moving optical system unit 24 until the position sensor 31 indicating the position of the leading edge of the image area detects the position detection piece 28. Next, the original pressure plate 2
1 is closed, the irradiation lamp 25 is irradiated onto the image area on the document table glass 19 on which the document 20 is placed, and measurement of the reflection density of the image area is started.

FIG. 5 is a diagram showing the correlation between the original 20 and the eraser 41, and (I) shows that the original 20 is connected to the original platen glass 19 and the original pressure plate 21.
(If) shows the state in which the original 20 is placed on the original platen glass 19,
I[) indicates the relationship between the eraser 41 and the drum 1. In (II) of FIG. 5, A indicates the sub-scanning direction, B indicates the main scanning direction, and the shaded area indicates the image area. In addition, 1-n', ~N, l"m',
-M indicate areas divided corresponding to the light-receiving element group 71 of the reflection density detector 35.

Now, the reflection density detector 35 having a light receiving element group 71 finely divided in the main scanning direction B shown in (II) of FIG. 5 detects the reflection density of the entire image area as the moving optical system unit 24 moves. Then, that value is corrected using the density correction value and stored in the RAM 5B as an image density. That is,
The moving optical system unit 24 is moved in the sub-scanning direction A shown in FIG. The reflection density is detected, and the value is corrected using the density correction value and stored in the RAM 56 as one image density. Therefore, by performing this operation, the reflection density obtained by dividing the entire image area into fine meshes is detected as shown in FIG. From the image density obtained by correcting this reflection density using a density correction value, information on the original size, the image area within the original, and the maximum and minimum excitation density of the original can be obtained. The MP 55 sends out each control signal based on this information.

Note that if the standard white board 23 is installed near the rear end of the image area as shown in FIG. After irradiating and obtaining a density correction value, move the optical system unit 24 from the position of the position sensor 32 indicating the rear end position of the image area to the position of the position sensor 31 in the sub-scanning direction A.
The entire copyable area of the original is divided into meshes as described above, and the reflection density is measured.

Next, the operation of the control circuit of the present invention will be explained with reference to the control circuit diagram in FIG. 2 and the control signal timing chart in FIG. 6.

First, after turning on the main switch, in order to measure the reflection density of the standard white plate 22, the MP55 outputs a motor control signal to drive the optical system drive motor 39 to the port 021.022.
After moving the moving optical system unit 24 until the position sensor 30 detects the position detection piece 28 as described above, the standard white board 22 is irradiated with the irradiation lamp 25.

Then, a shift pulse signal SH shown in FIG. 6 is applied to the reflection density detector 35, and a clock signal φ! which is obtained by frequency-dividing the clock signal CLOCK oscillated by the oscillator 51 by the frequency divider 52 is then applied. It is operated by applying a clock signal φ2 which is an inverted signal of the clock signal φ2. Each of elements 1 to N of the light receiving element group 71 detects the reflected light from the standard white board 22, and the output voltage thereof is amplified by the amplifier 53, and this output signal O8 is converted into a digital value by the A/D converter 54. However, a predetermined count number is sent to the dummy signal (A) as shown in Figure 6.
(hereinafter referred to as dummy processing). Here, dummy processing refers to processing for removing unnecessary signals (dummy signals) from among the signals of l scanning lines output from the reflection density detector 35.

After that, the reflection density is read at the timing specified by the A/D in signal shown in Figure 6, and when it is read 1 to N times as the detection signal (b), the predetermined dummy signal (a) is read. count and perform dummy processing again. Note that the read reflection density data is R
It is stored as a density correction value in the designated area of AM56.

Next, after the MP 55 completes the dummy processing, it turns the irradiation lamp 25 to 0FFL and waits for input of the copy start key among the input keys 58.

Next, when the input of the copy start key is applied to the MP55, the MP55 turns on the optical system drive motor 39 and starts irradiating the irradiation lamp 25, and moves the optical system until the position sensor 31 detects the position detection piece 28. After moving the unit 24, reading of the original image is started. While the moving optical system unit 24 moves in the sub-scanning direction A shown in FIG. 5, the MP55 starts an internal timer to output a shift pulse signal SH to the reflection density detector 35 at predetermined intervals (for example, 10 m5ec). , outputs a shift pulse signal SH every time the internal timer finishes counting. Then, the MP55 starts counting the A/Din signals in order to perform dummy processing together with the output of the shift pulse signal SH, and when a predetermined number of A/Din signals have been counted, it is considered that the dummy processing is completed, and after that, the A/Din signal is Reflection density data 1 to N are sequentially sent to each input port of MP55 at the reading timing specified by the signal! 1~i
4, correction is performed using the density correction value stored in the RAM 56, and the image density data is stored in a designated area of the RAM 56. When the input of the reflection densities from 1 to N is completed, the MP55 inputs a predetermined number of A/Di
Dummy processing similar to the above is performed again until the count of the n signal is completed, and when the tummy processing is completed, the process waits until the count of the internal timer is completed. When the internal timer finishes counting, the shift pulse signal SH is again applied to the reflection density detector 35, the internal timer is restarted, and the same process as described above is repeated.

Repeat this operation in the sub-scanning direction A up to number M.

As shown in FIG. 5, the image density in the image area is obtained from the reflection density detected by the reflection density detector 35, and the original size, original position, and original density are determined from this image density. The drive driver 62 is driven according to the document position, and a signal for controlling the eraser 41 is sent to each output port or
~09 to prevent toner from adhering to non-image areas. In addition, the original density stored in the RAM 56 is compared with a predetermined reference black level value and reference white level value to determine the maximum density and minimum density, and the bias value of the developing device 7 is determined so as to obtain the optimum contrast. control.

Next, control of the eraser 41 based on the reflection density detected by the reflection density detector 35 will be explained with reference to FIGS. 1 and 2.

The eraser 41 is configured to emit light corresponding to each pixel of the light receiving element group 71 of the reflection density detector 35, and is
From the image density stored in M56, a set of pixels, that is, a non-image area, whose reflectance is lower than a predetermined reflectance is obtained. L of the eraser 41 corresponding to this non-image area
The ED emits light according to the copy magnification to prevent toner from adhering to this non-image area.

In addition, the reflectance of pixels on the boundary between the non-image area and the image area is lower than that of a blank original when the original pressure plate 21 is made of a mirror surface, etc., and when developing and copying is performed in this state, the copy paper Toner adheres to the outline of the image. To prevent this, the LED of the eraser 41 corresponding to the pixel on the boundary between the non-image area and the image area is caused to emit light to prevent toner from adhering (edge processing).

Furthermore, a switch 29 provided near the original support table is turned on.
When a signal indicating a non-contact state between the NL original pressure plate 21 and the original platen glass 19 is input to the input port 112 of the MP 55, the MP 55 determines that the original 20 is a book. Therefore, after the reflection density detector 35 detects a document edge, until it detects a white standard higher than a predetermined reflectance, it is determined that the edge is a collection of book edges, and the eraser 41 detects this edge. A control signal is output to each output port O+ to 09 so that the LED corresponding to the set of edges emits light, and the drive driver 62 receives this output and drives, and the LED corresponding to the above-mentioned set of edges emits light. This prevents toner from adhering to the edges where the edges gather.

Further, when the original 20 is a book, a halftone having a reflectance lower than a predetermined reflectance exists in the reflection density detected by the reflection density detector 35 in the center of the original, and the main scanning As a result, the set of halftones is manuscript 2.
If the halftone exists in the edge direction of 0, the MP55 determines that this halftone is due to the fold of the book, and switches each output port 01 to 09 so that the LED corresponding to the position of this halftone in the eraser 41 emits light. A control signal is output to the drive driver 62 that receives this output, and the LED corresponding to the above-mentioned halftone position emits light.

This prevents toner from adhering to the halftone position.

Next, edge control in the image area will be explained.

Note that, hereinafter, the original pressure plate 21 is assumed to have a mirror surface.

As mentioned above, the reflection density of the image area is detected by the reflection density detector 3.
When each pixel is detected by the light receiving element group 71 of 5,
After the set of pixels showing low reflectance, a set of pixels showing high reflectance (original portion) is obtained. The document position and document size can be obtained from the boundary between the set of pixels exhibiting low reflectance and the set of pixels exhibiting high reflectance. In particular, when it is necessary to copy the original 20 on this boundary, when copying is performed using the original size and original position stored in the RA and M 56, the original 20 on the boundary, including the edge of the original, will be toned by the eraser 41. Since adhesion is prevented, it is determined from the reflectance of the pixel next to the pixel on the boundary whether edge processing is necessary. In other words, if characters or the like are printed on the original in the pixel next to the pixel on the boundary, the reflectance will be low. Using this as a criterion, if the reflectance is lower than a predetermined reflectance, the MP55 determines that it is necessary to attach toner to the pixels on the edge of the document, and ), and if the reflectance of the next pixel after the pixel on the boundary is higher than a predetermined reflectance, control is performed to copy at the same size.

Therefore, if there are characters or the like near the boundary, they are reduced, so the characters near the boundary are not affected by image erasure (edge processing) by the LED, that is, the eraser 41.

Next, the control operation for automatic magnification will be explained.

As mentioned above, the reflection density of the image area is detected by the reflection density detector 3.
When each pixel is detected by the light receiving element group 71 of 5,
After a set of pixels exhibiting high reflectance, a set of pixels exhibiting low reflectance is obtained. An image area is obtained from the boundary between the set of pixels exhibiting high reflectance and the set of pixels exhibiting low reflectance. This image area and cassette size oysters-571~
573, and compare the size of the copy paper stored in the upper cassette 12 or lower cassette 13 with the copy paper size of the copy paper obtained by 573, and if the same size copy paper is stored in the upper cassette 12 or lower cassette 13, copy at the same size. conduct. on the other hand,
1 if the above image area and the above copy paper size are different.
The most appropriate reduction or enlargement is selected and the copy is made at a predetermined magnification so that the entire image area is copied onto the copy paper.

Next, the operation of automatic density control will be explained with reference to FIGS. 1, 2, and 7.

FIG. 7 is a characteristic waveform diagram showing the density characteristics, and the first quadrant shows the relationship between the exposure amount (E) and the potential (V) of the drum 1,
The second quadrant is the potential of the drum 1 (V) and the density of the copied image (DC
), the third quadrant shows the relationship between the density of the copied image (DC) and the original density (DO) obtained from the reflection density detected by the reflection density detector 35, and the fourth quadrant shows the relationship between the original density (DC) D.O.
) and the exposure amount (E).

As mentioned above, the reflection density of the image area is detected by the reflection density detector 3.
When each pixel is detected by the light receiving element group 71 of 5,
After a collection of pixels exhibiting high reflectance, pixels exhibiting low reflectance are obtained. Among these images, the one with the highest reflectance (ground color, reference white level) among the images showing low reflectance has a density of 0.
．． 07, and when the minimum reflectance is at a density of 0.5, an input voltage of 65V is applied to the irradiation lamp 25, and the potential of the drum 1 is determined by the E-V characteristic shown in the first quadrant. Development characteristics determined and shown in the second quadrant (7) 10
A copy image with a density determined by a 00Hz, 1000Vp-p curve is obtained.In the above example, an original with a density of 0.07 is developed to a copy density of 0.07, and an original with a density of 0.5 is developed into a copy. Developed to a density of 0.5. In other words, the original density and the copy density are the same. On the other hand, if the difference between the maximum and minimum document densities is smaller than a predetermined value, the copy density is changed as described below.

For example, if the minimum value of the original density before the change was 0.2 and the maximum value was 0.5, it is assumed that the EV characteristic in the first quadrant does not change, and the original density of 0.2 is copied to 0. When changing to .07, the original density is reduced to 0.5 by controlling the input voltage of the irradiation lamp 25 shown in the fourth quadrant to be set to 80V. Further, the development characteristics in the second quadrant are controlled to be set to 1600 Hz and 1800 Vp-p. With this control, if the difference between the maximum and minimum document density values is smaller than a predetermined value, that is, the contrast is artificially added to the document 20 where the contrast is not clear, and an appropriate density is set. Obtain a clear copy image.

Next, the registration roller 14 and eraser 4
1 will be explained with reference to FIGS. 1 and 2.

There is a predetermined document reference position on the document platen glass 19, and when it is determined from the reflection density detected by the reflection density detector 35 that the leading edge of the document deviates from this document reference position, as described above. is the LED of the eraser 41 corresponding to the pixel of the light receiving element group 71 that detected high reflectance.
In addition to emitting light to prevent toner adhesion, the drive timing of the registration rollers 14 is delayed and the registration (
By aligning the leading edge of the copy paper and the leading edge of the image, deviation of the leading edge of the original from the original reference position can be corrected and a proper image can be obtained. In addition, if it is determined from the reflection density detected by the reflection density detector 35 as described above that the leading edge of the original is set at an angle of more than a predetermined parallelism with respect to the original reference position, Stop copying and copy original 20
Displays a request for resetting.

Next, control by the MP55 will be explained with reference to flowcharts shown in FIGS. 8(a), (b), and (c). Note that (1) to (47) represent each step.

When the power of the image processing device is turned on, it starts warming up and determines whether it is the measurement position of the standard white board 221)
, the optical system drive motor 39 is rotated in the reverse direction until the position sensor 30 detects the position detection piece 28 (2). Step (1
), if the standard white plate 22 is at the measurement position, the optical system drive motor 39 is set to 0FFL (3) and the irradiation lamp 25 is set to O.
Do N (4). Next, it waits for the input of the shift pulse signal SH, and when the shift pulse signal SH is input, the A/D
The in signal is counted and dummy processing is performed (5), and then the reflection density of the standard white board 22 is detected and the input of the shift pulse signal SH is waited for again (6).

After inputting the shift pulse signal SH, turn the irradiation lamp 25 to 0F.
FL (7), wait for input of copy start key (8)
). After this, the flow moves to the flow shown in FIG. 8(b), and when there is a copy start input, it is determined whether the moving optical system unit 24 is at the stop position or the standard white board 22 is in the position (8), NO.
If so, the optical system drive motor 39 is rotated in the reverse direction (10). If YES in step (8), the optical system drive motor 39 is rotated forward (11), the moving optical system unit 24 is moved in the sub-scanning direction, and the irradiation lamp 25 is turned on (12). Next, the position sensor 31 determines whether the moving optical system unit 24 has reached the leading edge of the image area (13), and if NO, the system waits until it reaches the leading edge of the image area. Step (
If YES in step 13), initial values regarding the image area and original area are set (step 14), and a reference black level and reference white level of reflection density are further set (step 15). After setting, wait for input of shift pulse signal SH and input A/Din.
The signals are counted (16), and after the counting is completed, the reflection density of the image area in the sub-scanning direction is detected and stored for each light receiving element of the light receiving element group 71 (17). Next, it is determined whether the measurement of the reflection density of the image area has been completed (18). If the determination in step (18) is No, the process returns to step (16) to continue detecting the reflection density of the image area. Also,
If YES, dummy processing similar to step (16) is performed and the irradiation lamp 25 is turned off (19). Next, step (17) is performed using the density correction value stored in step (8).
The reflection density stored in step 2 is corrected (20). Next, the reflection density corrected in step (20) is compared with the reference black level reflection density set in step 2 (15) for each light receiving element (21), and the maximum reflection density is determined and stored in the RAM 56. (22). Next, the reflection density stored in step (1?) is similarly compared with the reference white level reflection density set in step (15) for each light receiving element (23).
, the minimum reflection density is determined and stored in the RAM 56 (24).

After this, the process moves to the flow shown in FIG. 8(C), and then the reflectance of each pixel of the reflection density data stored in step (18) is examined (25), and a set of pixels with a reflectance smaller than 1 is determined. 26) to detect the document size and the image area within the document size, and erase the eraser 4 corresponding to the non-image area.
Set the light emission of LED 1 (27). Next, check whether the reflectance of the next pixel after the pixel on the outline of the original size detected in step (26) is lower than the predetermined reflectance28), and if NO, set the copy magnification to reduction. Step 28), set the light emission of the LED of the eraser 41 according to this magnification (30), then step (22), calculate the maximum density and minimum density in the reflection density data stored in step (24). Calculating the difference 31
), determine whether the difference is smaller than a predetermined concentration difference (3
2). If this judgment is YES, then the distance from the document size outline to the leading edge of the image in the document size is calculated and it is determined whether the distance is smaller than a predetermined distance difference33), and if YES, the cassette size is equal to the document size. Check 34), and if YES, set the bias value of the developing device 7 or the light intensity of the irradiation lamp 25 according to the reflection density stored in step (18) 3B), and start copying (
39), while N in steps (33) and (34)
In the case of O, change the copy magnification35) and set the light emission of the LED of the eraser 41 according to this copy magnification3.
6), proceed to step (38). Also step (32)
If the answer is No, the copying density is set (37), and the light intensity of the irradiation lamp 25 or the bias value of the developing device 7 is set in accordance with this copying density (38).

On the other hand, if YES in step (28), the copy magnification is set to equal magnification (40). Then switch 29- is turned to O.
Please check whether it is in the N state or not (41), and if it is ON (OF
If F, set the LED of the eraser 41 corresponding to the contour point of the document size to emit light 44) and jump to step (31); if YES, set the height from the document size contour point to the edge of the image area in the document size. It is determined whether a set of pixels exhibiting high reflectance exists (42), and if YES, it is further determined whether a set of pixels exhibiting high reflectance exists in the main scanning direction within the document size (43). YES with this decision
In this case, the eraser 41 is set to emit light corresponding to a high reflectance area in the main scanning direction within the original size (47), and the process jumps to step (31). Also, N at step (42).

In this case, a document setting failure is displayed (45). moreover,
If No in step (43), the eraser 41 is set to emit light corresponding to pixels from the document size outline to the tip of the pixel area in the document size (46), and the process jumps to step (31).

〔Effect of the invention〕

As described above, the present invention includes a reflection density detection means that has a group of light receiving elements arranged in the main scanning direction and detects the image area and the density of the original by receiving reflected light from the original; Since it is equipped with an automatic density setting means that sets the copy density based on the difference between the value and the minimum value, the appropriate contrast is always applied even to originals with unclear contrast, resulting in extremely easy-to-read copy images. It has the advantage of being

[Brief explanation of drawings]

FIG. 1 is a sectional view of an image processing device showing an embodiment of the present invention, FIG. 2 is a control circuit diagram, FIG. 3 is a front view of a reflection density sensing element showing an embodiment of the invention, and FIG. The figure is a density characteristic waveform diagram showing the relationship between reflected density and output voltage, Figure 5 is a scan schematic diagram showing division in the scanning direction, Figure 6 is a timing chart of each control signal, and Figure 7 is a density characteristic diagram. The characteristic waveform diagrams in FIGS. 8(a), (b), and (c) are flowcharts showing an example of control. In the figure, 1 is a drum, 2 is a pre-static charger, 3 is a primary charger, 4 is a charger, 5 is a copying charger, 6 is a cleaning device, 7 is a developer, 8 is a pre-exposure lamp, and 9 is a front surface Exposure lamp, 10.11 is paper feed cassette, 12 is upper cassette, 1
3 is a lower force set, 14 is a registration roller, 15 is a conveyance belt, ] 6 is a fixing roller, 17 is an ejection roller, 18 is a tray, 19 is an original table glass, 20 is an original, 21 is an original pressure plate, 22.23 is an original A standard white plate, 24 a moving optical system unit, 25 an irradiation lamp, 26 a first scanning mirror, 27 a second scanning mirror, 28 a position detection piece, 29 a switch,
30, 31. 32 is a position sensor, 33 is a slit, 34
36 is a projection lens, 35 is a reflection density detector, 37 is a third scanning mirror, 38 is a fourth scanning mirror, 39 is an optical system drive motor, 40 is a main motor, 4
] is an eraser, 51 is an oscillator, 52 is a frequency divider, 53.6
0 is an amplifier, 54 is an A/D converter, 55 is a microprocessor, 56 is a RAM, 57 to 573 are cassette size input keys, 158 is an input key, 159 is a D/A converter,
61 is a lamp regulator, 6'2.63 is a drive driver, 641. 642 is an AND circuit, 65+, 652.66 is input, 67 is a clock signal, and 71 is a group of light receiving elements. Figure 3 Figure 5 Figure 8 (a) Figure 8 (b)

Claims (1)

[Claims] An image processing device that irradiates a document placed on a document support table with an irradiation lamp and forms an image of the reflected light on the surface of a photoreceptor, which has a group of light receiving elements arranged in the main scanning direction and detects the light reflected from the document. The apparatus includes a reflection density detection means for detecting an image area and an image density by receiving light, and a copy density setting means for setting a copy density based on the difference between the maximum value and the minimum value of the original density. Characteristic image processing device.