JPS616636A - Image processor - Google Patents

Abstract

PURPOSE:To obtain an invariably sharp copy image by turning on only necessary light emitting elements of an eraser means composed of a light emitting element group arrayed in a main scanning direction and preventing toner from sticking in a no-image area. CONSTITUTION:The eraser 41 turns on in correspondence to respect picture elements of the photodetecting element group 71 of the reflection density detector 53 and a set of picture elements with a reflection factor lower than a predetermined value, i.e. no-image area is obtained on the basis of image density stored in a RAM56. Then, LEDs of the eraser 41 corresponding to the no-image area are turned on according to copy magnification to prevent toner from sticking in the no-image area. Further, picture elements on the border between the no-image area and an image area are lower in reflection factor than a white ground original when an original pressure plate 21 has a specular surface, etc., and when a development copy is taken in this state, toner sticks on the contour of an original. For the purpose, LEDs of the eraser 41 corresponding to the picture elements on said border are turned on to prevent the sticking of toner.

Description

Detailed Description of the Invention [Industrial Field of Application] This invention detects the position, size and density of a document placed on a document support table by using the same group of light receiving elements, and detects non-images on a photosensitive member. The present invention relates to an image processing device that controls toner adhesion on area portions and image area boundaries.

[Prior art and its problems]

Conventionally, this type of image processing apparatus irradiates light onto a document placed at a reference position on a document support table, receives the reflected light,
Furthermore, since toner adhesion was controlled according to the size of copy paper set, toner may adhere to a portion of the copy paper due to misalignment of the original placed in the reference position, making it difficult to obtain clear copied images with good accuracy. There wasn't.

Furthermore, if the original pressing plate or the like is made of white, if dirt adheres to the white portion of the original pressing plate, toner will adhere regardless of the original, resulting in a copied image that is very difficult to see. Furthermore, in devices equipped with a function to detect the document size, if the document pressure plate is mirror-finished or coated with a light-absorbing material, the area other than the image area where the document is placed, that is, the non-image area, may be There is a risk that toner will adhere to the non-image area, and it is very difficult to accurately control the adhesion of toner to the non-image area depending on the document size.

[Purpose of the invention]

This invention was made to solve the above-mentioned problem, and the reflected light from the original is finely divided and received by a reflection density detection means consisting of a group of light receiving elements arranged in the main scanning direction. The density, document position, and document size are detected, and only the required light-emitting elements of the eraser unit, which is composed of a group of light-emitting elements arranged in the main scanning direction corresponding to the light-receiving element group, are emitted to apply toner to non-image areas. It is an object of the present invention to provide an image processing device that prevents the adhesion of particles and can always obtain clear copied images.

〔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, 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). The manuscript information detecting means 2 of the present invention is 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 above, the image area within the document, the reflection density of the document, and the document position within the copyable area 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, 39 is an optical system drive motor,
The moving optical system unit 24 is driven. 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, the erasers 41 are also arranged in a line in the main scanning direction B.

In the control circuit shown in FIG. 2, 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 sends the digital value to each input port 11 to i4. Output to. 55 is a microprocessor (MP) which receives each sensor output 9 and the output of the reflection density detector 35 and each timing signal through 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, 571-
A cassette size input key 573 constitutes copy paper size detection means of the present invention, and inputs the cassette size to each input port 19 to i++ of the MP55. 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 signal etc. to each input capo of MP55) i13 to i+6
Enter. 59 is a D/A converter, which converts the lamp signals to the irradiation lamp 25 outputted by the MP 55 to each of the output boats OL3 to 016 into a D/A converter.

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. Reference numeral 62 denotes a drive driver which receives eraser drive control signals outputted to each of the output ports 01 to 09 by the MP 55 and drives the eraser 41. 63 is a drive dry eight, MP
55 drives the optical system drive motor 39 by receiving the motor drive control signal outputted to each output port Ch+ and 022.

641 is an AND circuit that ANDs the output signal of the frequency divider 52 and the control signal outputted from the MP55 to the output port 012, and outputs the shift pulse signal (SH) to the reflection density detector 3.
Enter 5. 642 is an AND circuit which similarly ANDs the output signal of the frequency divider 52 and the control signal outputted to the output port 0□1 by the MP55, and inputs the clock signal φ1 to the reflection density detector 35. 651 is an inverter that inverts the signal from the oscillator 51; 652 is an AND circuit that connects the frequency divider 52 and the inverter 65. Take the AND with A/
The D in signal is input to the input port i5 of the MP55. 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 i12 of the MP55.

In the reflection density detector 35 shown in FIG. 3, 71 is 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 (D) 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 is a photoreceptor, and the main motor 4 is activated when the copy start key of the input key 58 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 first scanning mirror 26 and the second scanning mirror 27 at a speed of 1:l/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 10.11, and the registration rollers 14 temporarily stop the copy paper being fed in the direction of 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 copying is completed, the copy paper is separated from the drum 1 and guided by a conveyor belt 15 to a fixing roller 16, where it is pressurized and heated to fix the copy image. Next, the copy paper is discharged onto the tray 18 by the discharge roller 17.

Next, the detection operation of the document position, document size, and document density will be explained with reference to the drawings.

After the main switch is turned on, the optical system drive motor 39 is driven to correct variations in characteristics of the light receiving element group 71 constituting the reflection density detector 35 and ripples of the light source, and the position sensor 30 indicating the position of the standard white plate 22 is moved. The moving optical system unit 24 is moved until the position detection piece 28 attached to the outside of the optical system unit 24 is detected.Next, when the irradiation lamp 25 irradiates the standard white plate 22 that can obtain a uniform reflection density, the reflection is detected. The light passes through 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. Thereafter, the optical system drive motor 39 is driven to move the moving optical system unit 24 until the position sensor 31 indicating the image area tip position detects the position detection piece 28. move it. Next, the document platen glass 19 on which the document 20 is placed with the document pressure plate 21 closed.
The upper image area is irradiated with the irradiation lamp 25 and measurement of the reflection density of the image area is started.

FIG. 5 is a diagram showing the correlation between the original 2o and the eraser 41, and (I) shows that the original 20 is connected to the original platen glass 19 and the original pressing plate 20.
(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. Note that l-n', ~N, 1-m', and ~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 FIG. 5 (It) 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 56 as an image density. That is,
The moving optical system unit 24 is moved in the sub-scanning direction A shown in FIG. Detect the reflection density of
The value is corrected using the density correction value and stored in the RAM 56 as an 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. The document size is determined from the image density obtained by correcting this reflection density using the density correction value.
Information on the image area within the document and the maximum and minimum reflection density of the document 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 obtaining the density correction value, the position sensor 3
The movable optical system unit 24 is scanned in the sub-scanning direction A to the position 1, and the reflection density is measured by dividing the entire document copyable area into mesh shapes as described above.

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, the MP55 outputs a motor control signal to drive the optical system drive motor 39 to measure the reflection density of the standard white plate 22.
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 φl obtained by frequency-dividing the clock signal CLOCK oscillated by the oscillator 51 by the frequency divider 52 and a clock signal which is its inverted signal Give φ2 and operate. The reflected light from the standard white plate 22 is transmitted to the light receiving element group 7.
Each element 1 to N of 1 detects the output voltage and sends the output voltage to the amplifier 5.
This output signal O5 is amplified by A/D converter 5.
4 is converted into a digital value, but the predetermined count number is processed as a dummy signal (A) as shown in Figure 6 (hereinafter referred to as dummy processing). This refers to the process of removing unnecessary signals (dummy signals) from among the signals of one scanning line outputted from the 35.

Thereafter, the reflection density is read at the timing specified by the A/Din signal shown in FIG.
When the data is read from 1 to N times, a predetermined dummy signal (a) is counted and dummy processing is performed again. The read reflection density data is stored in the RAM 56.
is stored as a density correction value in the specified area. Then M
After P55 completes the dummy process, turn the irradiation lamp 25 to 0FFL.
,, 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.
An internal timer of the MP55 is started, and a shift pulse signal SH is output every time the internal timer finishes counting. Then, the MP55 starts counting A/Din signals in order to perform dummy processing along 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/D i
Reflection density data numbers 1 to N are sequentially read into each input port 11 to i4 of the MP55 at the read timing specified by the n signal, corrected using the density correction value stored in the RAM 56, and stored in the RAM as image density data.
56 designated areas. And MP55 is 1
When the input of reflection densities up to number N is completed, the predetermined number of A
The same dummy processing as described above is performed again until the counting of the /Din@ number is completed, and when the dummy processing is completed, the process waits until the counting of the internal timer is completed. When the internal timer finishes counting, the shift pulse signal SH is again applied to the 1 reflection intensity detector 35, the internal timer is restarted, and the same process as described above is repeated.

This operation is repeated up to number M in the sub-scanning direction A, and the image density in the image area is obtained from the reflection density detected by the reflection density detector 35 as shown in FIG. , the original density is determined.

The driving driver 62 is driven in accordance with this document position, and a signal for controlling the eraser 41 is output to each output boat 01 to 09 to prevent toner from adhering to the non-image area. 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 To prevent toner from adhering to the contour, the LED of the eraser 41 corresponding to the pixel on the boundary between the non-image area and the image area is emitted 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 ports i and 2 of the MP 55, the MP 55 determines that the original 2o is a book. For this reason, after the 1 reflection intensity detector 35 detects a document edge, it is determined that the edge is a collection of book edges until it detects a white reference higher than a predetermined reflectance. A control signal is output to each output boat OL~09 so that the LED corresponding to the edge set emits light, and the drive driver 62 receives this output and drives, and the LED corresponding to the above edge set part 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 half-tone 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 RAM 56, the eraser 41 prevents toner from adhering to the original 20 on the boundary, including on the edge of the original. Therefore, it is determined whether edge processing is necessary based on the reflectance of the next pixel after the pixel on the boundary. 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 ) to control the reduction and copying.
Furthermore, if the reflectance of the pixel next to 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 change 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,
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 (D
It shows the relationship between 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. The development characteristics determined and shown in the second quadrant x OO
A copy image with a density determined by an OHz, 1000Vp-p curve is obtained.In the above example, an original density of 0.07 is developed to a copy density of 0.07, and an original density of 0.5 is developed to a copy density of 0.07. 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 is smaller than a predetermined value,
That is, contrast is artificially added to the document 20 with unclear contrast, and an appropriate density is set to 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 it was found from the reflection density detected by the reflection source and degree detector 35 as described above that the leading edge of the document was deviated from this document reference position. In this case, the LE of the eraser 41 corresponding to the pixel of the light receiving element group 71 that detected high reflectance
By emitting light D to prevent toner adhesion and by delaying the driving timing of the registration roller 14 and automatically aligning the registration (the leading edge of the copy paper and the leading edge of the image), misalignment of the leading edge of the document from the document reference position is corrected and corrected. You can get a good image. 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 2
Displays a request to reset 0.

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 3o detects the position detection piece 28 (2). Step (
If it is determined in step 1) that the standard white plate 22 is at the measurement position, the optical system drive motor 39 is turned OFF L (3) and the irradiation lamp 2 is turned off.
5 to 0N-i (4). Next, wait for the input of the shift pulse signal SH, and when the shift pulse signal SH is input, count the A/Din signal and perform dummy processing (5)
Thereafter, the reflection density of the standard white board 22 is detected and the input of the shift pulse signal SH is waited 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)
). From this point on, the process moves to the flow shown in FIG. 8(b), and when there is a copy start input, it is determined whether the stopping position of the moving optical system unit 24 is at the position of the standard white board 22 (9), and NO.
If so, the optical system drive motor 39 is rotated in the reverse direction (lO). 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, it is determined by the position sensor 31 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 shift pulse signal SH, input A/Di
n signal is counted 16), and after the counting is completed, the reflection density in the sub-scanning direction of the image area is detected and stored for each light receiving element of the light receiving element group 71 (17), and then the measurement of the reflection density of the image area is completed. (18)

If the judgment in step (18) is NO, step (16)
Return to , and continue detecting the reflection density of the image area. 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 (6).
) and corrects the stored reflection density (20). Next, the reflection density corrected in step (20) is compared with the reference black level reflection density set in step (15) for each light receiving element (21), and the maximum reflection density is determined and stored in the RAM 56 (22). ), then, similarly, the reflection density stored in step (17) is compared with the reflection density of the reference white level 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 (2?). Next, check whether the reflectance of the next pixel after the pixel on the outline of the document size detected in step (26) is lower than the predetermined reflectance28), and if No, set the copy magnification to reduction. 29), and set the light emission of the LED of the eraser 41 according to this magnification (3o). Next, step (22) calculates the density difference between the maximum density and minimum density in the reflection density data stored in step (24).
), 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) 38), and start copying (3).
8), while NO in steps (33) and (34)
In this case, change the copy magnification (35) and set the LED light emission of the eraser 41 according to this copy magnification.
), proceed to step (3 days). Also, if No in step (32), do you want to set the copy density to 3? ), the light intensity of the irradiation lamp 25 or the bias value of the developing device 7 is set according to this copy density (38).

On the other hand, if YES in step (2 days), the copy magnification is set to the same size (40), and then the switch 29 is turned ON.
Please check the status 41), it is OFF instead of ON.
Then, L of the eraser 41 corresponding to the contour point of the document size
Set the ED light emission (44), and jump to step (31). If YES, determine whether there is a set of pixels exhibiting high reflectance from the document size contour point to the edge of the image area in the document size (42). ), if YES, it is further determined whether there is a set of pixels exhibiting high reflectance in the main scanning direction in the document size (43). If this judgment is YES, set the light emission of the eraser 41 corresponding to the high reflectance area in the main scanning direction within the original size (47), and jump to step (31).Also, if the judgment is NO in step (42) Displays a document setting failure (45).Furthermore, if NO in step (43), sets the eraser 41 to emit light corresponding to pixels from the document size outline to the tip of the pixel area in the document size (48), step (48). Jump to 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 density of the original, the position of the original, and the size of the original by receiving reflected light from the original; Eraser means for irradiating light onto the non-image area and image area boundary of the photoreceptor detected by the density detection means prevents toner from adhering to the boundary between the non-image area and the image area, ensuring accurate detection. It has the advantage that clear copied images can be obtained.

[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 the timing chart for each control signal, and Figure 7 is the density characteristic. The characteristic waveform diagrams shown in FIGS. 8(a), 8(b), and 8(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, ] 2 is upper cassette, 1
3 is a lower cassette, 14 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, 22.23 is a standard white board , 24 is a moving optical system unit, 25 is an irradiation lamp, 26 is a first scanning mirror, 27 is a second scanning mirror, 28 is a position detection piece, 29 is 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
1 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, 571 to 573 are cassette size input keys, 158 is an input key, 159 is a D/A converter, 6
1 is a lamp regulator, 62.63 is a drive driver,
641. 642 is an AND circuit, 65□, 652.66 are inverters, 67 is a clock signal, and 71 is a group of light receiving elements. Figure 3 Figure 5 "-1--1--Yu1 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. reflection density detection means that receives light to detect document density, document size, and document position; and eraser means that irradiates light onto the non-image area and image area boundary of the photoreceptor detected by the reflection density detection means. An image processing device comprising: