JPS62210783A - Digital copying machine - Google Patents

Abstract

PURPOSE:To attain the optimum copying regardless of the kinds of original pictures of an object, by operating only a reader before a copying operation, detecting the maximum density value of the original picture, selecting and setting one out of plural number of gamma correction characteristics, and performing an automatic gamma correction fitting for the density of the original picture. CONSTITUTION:A gamma correction circuit 103 changes a gradation characteristics (input gradation data) fitting for the characteristics of a photosensitive body. In an automatic density setting mode, the minimum values are caught by a pre-scanning at a peak hold circuit 120 as the values of the maximum density parts of an original, namely as the values of a red R, a green G, and a blue B. And based on the data, a selection processing for a gamma correction characteristic data is performed. Next, the gamma correction operation characteristic of the gamma correction circuit 103 is selected automatically by the control of a synchronization control circuit 114, then being changed and set. Following that, a regular scanning for a print operation is performed, and the sequence of signal processings including the gamma correction of a set gamma correction characteristics are performed, and print quality with an appropriate print can be obtained.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a digital copying machine, and in particular, although the intention is not limited thereto, an original image is separated into three colors of red, green, and blue by a scanner, and each color component is separated. Obtain the gradation data and record the read gradation data in the recording colors yellow, magenta,
Convert to recording gradation data for each cyan and black,
In a digital color copying machine that converts recorded gradation data into pixel matrix (surface area) recorded information (pattern information) and activates each color recording device to record based on this pattern information to reproduce a color image on a sheet. , relates to an image processing technique that automatically performs appropriate gamma correction in response to an original image of a subject.

■Prior art This type of digital color copying machine reads one original image by color separation, for example red, green, and blue, and makes shading correction on the read information.

Yellow by gamma correction etc. and auxiliary machine generation.

Image information for each recording color component such as cyan, magenta, etc. is obtained, and color-specific recording information is created by performing masking processing, undercolor removal processing, nine-gradation processing, and the like. The obtained color-specific recording information is applied to each color recording device by a light beam scanning device in a recording color category, and is superimposed on the same recording paper to form a color image.

In this process, the original image is read by a reading device, an image signal is obtained, image processing is performed, and the recording device is energized for recording using the obtained recording information. However, depending on the photoreceptor used in the recording device, it has specific gamma characteristics. Therefore, processing is performed to change the gradation by performing gamma correction to change the gradation according to the characteristics.

However, since the original image to be read has specific gamma characteristics, in addition to gamma correction to change the gradation according to the characteristics of the photoreceptor used in the recording device, gamma correction is also performed on the read image signal. In other words, since each type of original image as a subject has its own unique gamma characteristics, in a copying machine that targets several types of subjects, this gamma correction is performed according to the subject. It is preferable.

Therefore, for example, in Japanese Patent Application Laid-Open No. 60-43966,
In an image processing device, it is proposed to store various conversion characteristic curve data for correcting the gamma characteristics specific to the subject as a conversion table in the ROM of the table converter, and to perform gamma correction by switching the characteristic curve to be gamma corrected using a switch. has been done.

This relates to an image processing device, and switching between a plurality of characteristic curves is performed by a switch, which poses a problem when applied to a copying machine. Sunaochi,
Operators who use copying machines are not particularly trained and do not often have special knowledge, so it is difficult for them to make appropriate changes using the changeover switch.

The problem is that it is troublesome.

■Purpose Therefore, the present invention relates to a digital copying machine.

The purpose is to perform gamma correction by automatically changing gamma correction characteristics in accordance with the original image to obtain an optimal copy.

(2) Structure In order to achieve the above object, the present invention provides an image reading means for reading an original image, and a digital conversion means for converting the read image signal into gradation data.

In a digital copying machine equipped with a recording device that projects light corresponding to gradation data onto a photoreceptor to form an electrostatic latent image and develops this electrostatic latent image, an image that has been read and subjected to gamma correction corresponding to gradation data. A gamma correction means that holds multiple sets of information with different correction characteristics, reads a designated set of image information, and generates it corresponding to gradation data, and a density detection means that detects the highest density of the image read by the single image reading means. and instructing the image reading means to read the original image, and designating one set to the gamma correction means, which corresponds in advance to the highest density detected by the density detection means of the original image read by the image reading means. gamma correction characteristic setting means for setting the original image; and recording control for instructing the image reading means to read the original image after the above specification, and instructing the recording device to record the original image based on the image information generated by the gamma correction means. and means.

Here, when the gamma correction characteristic setting means instructs the image reading means to read the original image, the gamma correction characteristic setting means specifies a predetermined set of gamma correction means for the gamma correction means, and the density detection means controls the gamma correction means based on this designation. Detect the highest density of generated image information.

When instructing the image reading means to read the original image, one predetermined set specified to the gamma correction means is a correction characteristic that converts the read gradation data into image information without conversion,
Further, it may be gamma correction characteristic data that changes the gradation according to the characteristics of the photoreceptor used in the recording apparatus.

Furthermore, if the copying machine is a digital color copying machine, the image reading means is an image reading device that separates and reads the original image, and the gamma correction means reads each color component and converts image information in correspondence with gradation data. It happens. The gamma-corrected image information generated by the gamma correction means is
Multiple gamma correction characteristic data for each color component are RO
The density detection means detects the highest density value of the image signal which has been subjected to gamma correction generated in correspondence with the gradation data read by the gamma correction means for each color component.

According to this, in a digital copying machine, for example, a digital color copying machine or a digital monochrome copying machine, in addition to gamma correction for changing the gradation according to the characteristics of the photoreceptor used in a normal recording device, Operate only the reading device prior to operation.

It detects the maximum density value of the original image, selects and sets one of multiple gamma correction characteristics, and automatically changes the gamma correction characteristics according to the density of the original image, so it can be adjusted depending on the type of original image of the subject. Regardless of the situation, the copying machine can always be operated in a state that produces optimal copies.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

FIG. 1 shows an outline of the structure of the mechanism section of an embodiment of the present invention,
Figure 2 shows an overview of the configuration of the electrical equipment section.

First, referring to FIG. 1, an original l is placed on a platen (contact glass) 2, and a fluorescent lamp 31*3 for illuminating the original
2, the reflected light is illuminated by a movable first mirror 41. The light is reflected by the second mirror 42 and the third mirror 43 and passes through the imaging lens 5.

Enters the dichroic prism 6, where the three wavelengths of light, red (R), green (G) and blue (B)
The 0-split light that is split into 0 parts is C0, which is a solid-state image sensor.
D7rt 7g and 7b, respectively. That is, red light goes to C0D7r, green light goes to CC07g.
Also, the blue light enters C0D7b.

The fluorescent lamp 31y32 and the first mirror 41 are connected to the first carriage 8.
The second mirror 42 and the third mirror 43 are mounted on the second carriage 9, and the second carriage 9 moves at a speed of 172 of the first carriage 8.
The optical path length from the X document 1 to the CCD is kept constant, and the first and second carriages scan from right to left when reading an original image. The first carriage 8 is coupled to a carriage drive wire 12 wound around a carriage drive pulley 11 fixed to the shaft of a carriage drive motor 10, and the second
A wire 12 is wound around a movable pulley (not shown) on a carriage 9. As a result, the first carriage 8 and the second carriage move forward (original image reading and scanning) and backward (return) by the forward and reverse rotation of the motor 10, and the second carriage 9 moves 1/2 of the first carriage 8. Move with speed.

When the first carriage 8 is at the home position shown in FIG. 1, the first carriage 8 is detected by a home position sensor 39 which is a reflective photosensor. This detection mode is shown in FIG. 3. When the first carriage 8 is driven to the right during exposure scanning and moves away from the home position, the sensor 39 does not receive light (carriage is not detected), and the first carriage 8 returns to the home position. When the sensor 39 returns to the position, the sensor 39 starts receiving light (carriage detection), and the carriage 8 is stopped when the sensor 39 changes from not receiving light to receiving light. In addition, 4
0 is a carriage guide bar.

Referring now to FIG. 2, CCD 7 r# 7 g
The output of s7b is converted from analog to digital and subjected to the necessary processing in the image processing unit 100 to produce recorded color information of black (BK), yellow (Y), magenta (M) and cyan (C). 2 for each recording activation
It is converted into a digitized signal.

Each of the binary signals is sent to a laser driver 112bk.

112y, 112m and 112c, and each laser driver outputs semiconductor lasers 43bk, 43y, 4
By energizing 3m and 43c, the recording color signal (
A laser beam modulated by a binary signal) is emitted.

Please refer to FIGS. 1 and 4. Each emitted laser beam is reflected by one rotating polygon mirror 13, and is reflected by an f-θ lens 1.
41 and 142, the fourth mirror 15bk, 1
It is reflected by the fifth mirrors 16bk, 16y, 16■ and 16c, and is guided to each gap of each color information recording device arranged in parallel, and is reflected by the photoreceptor belt l of each color information recording device. 8bk,,1
8y, 18m and 18c are imaged and irradiated.

The rotating polygon mirror 13 is fixed to the rotating shaft of a polygon mirror drive motor 41, and the motor rotates at a constant speed to rotate the polygon mirror at a constant speed. Due to the rotation of the polygon mirror, the above-mentioned laser beam is directed to the drive roller 5 of the photoreceptor belt in a direction perpendicular to the moving direction (vertical direction) of the photoreceptor belt, that is, in the width direction.
3bk, 53y.

5311 and 53c are scanned in the direction along the axis.

Details of the laser scanning system are shown in FIG. 4, 43bk.

43y, 43m1 and 43c are semiconductor lasers.

The laser beam reflected by the rotating polygon mirror 13 passes through f-theta lenses 141 and 142, and then reaches the fourth mirror 15, respectively.
bk=L 5yt It is reflected by 15m and 15c, guided to each gap of each color information recording device arranged in parallel, and is reflected by the fifth mirror 16bk, 16ye 16■ and 1
6c, each photoreceptor belt 18bk, 1
8y, 18m and 18c are imaged and irradiated.

A sensor 44 made of a photoelectric conversion element is arranged to receive the laser beam at one end of the laser scanning direction along the width direction of the photoreceptor belt, and this sensor 44 detects each laser beam and separates it from the detection. 1 at the time it changes to detection
Detecting the starting point of line scanning. That is, sensor 44
The laser light detection signal (pulse) is processed as a line synchronization pulse for laser scanning. .

Referring to FIG. 1, each photoreceptor belt 18bk.

'8y*18m and 18c have 4 motors 50bk.

By rotation of 50y, 50m and 50c, gears 5lbk, 51y, 51+i and 51c are fixed to the same motor shaft, and the drive roller 53bk of the photoreceptor belt.

Gear 52 fixed to 53y, 53m and 53c
bk=52yv Driven in a clockwise direction via 52m and 52c. Note that rollers 54bk, 54yt, 54m and 54 located above the photoreceptor belt
c is something that applies tension to the photoreceptor belt.

It is pressed upward by a spring (not shown). The surface of the photoreceptor belt is connected to a charge scorotron 19bk connected to a positive high voltage generator (not shown).

It is uniformly charged by 19yt19■ and 19c. When a laser beam modulated by a recording signal is irradiated onto the uniformly charged surface of the photoreceptor, the charge on the surface of the photoreceptor flows from the photoreceptor belt to the equipment ground of the main body and disappears due to a photoconductive phenomenon. Here, the laser is not turned on in areas where the original density is high, and the laser is turned on in areas where the original density is low.

As a result, photoreceptor belts 18bk, 1sy, 18
The part of the intestine and the surface of 18c that corresponds to the high density part of the 1M manuscript has a potential of +800V, and the part that corresponds to the part of the manuscript with low density has a potential of about +100V. It is formed. Each of these electrostatic latent images is transferred to a black developing unit 20bk.

Yellow developing unit 20y, magenta developing unit 2
0m and cyan developing unit 20c,
Photoreceptor belt 18bk, 18y, 18m and 1
Black and yellow on the surface of 8c respectively.

Forms magenta and cyan toner images.

The toner in the developing unit is negatively charged by stirring, and the developing unit is biased to about +200V by a developing bias generator (not shown), and the toner adheres to the area where the surface potential of the photoreceptor is higher than the developing bias, and is applied to the original. A toner image is formed.

On the other hand, the recording paper 2671 or 2672 stored in the transfer paper cassette 2211222 is fed by the feed operation of the feed roller 231 or 232, and is sent to the transfer belt 25 by the registration roller 24 at a predetermined timing.

Here, a reflective optical sensor 701 #702, which is a paper quality detection device, is provided above the recording paper. The reflective optical sensors 70t and 702 receive the amount of reflected light and detect the paper quality from the difference in the amount of light. From now on, the sensor will not be able to handle normal paper (which has a lot of diffuse reflection) and art paper (which has a lot of specular reflection).
The output is set to be different, and using this optical sensor output, plain paper is automatically sent out for black mode copying in black and white copying mode, and art paper is automatically sent out for color mode copying in color copying mode. It looks like this. Of course,
This control is performed by the control action of a microprocessor system, which will be described later.

Furthermore, when a color mode copy is specified using a color mode/black mode designation switch 302 (described later), if the reflective optical sensors 701 and 702 do not detect art paper, a warning mark 305 on the console panel 300 lights up. It has become.

As the transfer belt 25 moves, the recording paper placed on the transfer belt 25 is transferred to the photoreceptor belts 18bk and 18y.

The black, yellow, magenta and cyan toners are transferred to each of the black, yellow, magenta and cyan toners by the action of the transfer corotron at the bottom of the transfer belt while passing through the photoreceptor belts 18bk, 18y, 18m and 18c sequentially. The images are sequentially transferred onto the recording paper. The recording paper on which the nose has been copied is then sent to a heat fixing unit 36, where the toner is fixed to the recording paper, and the recording paper is discharged to a tray 37. On the other hand, the residual potential on the photoconductor surface after transfer is EL eraser 6
0bk, 60y.

60m and 60c, residual toner is removed by cleaner units 21bk, 21y, 21m and 21c.
will be removed.

A cleaner unit 21bk and a black developing unit 20bk that collect black toner are connected to a toner collection pipe 42.
The black toner collected by the cleaner unit 21bk is collected by the developing unit 20bk. Note that the cleaner unit 21y is caused by reverse transfer of black toner from the recording paper during transfer to the photoreceptor belt 18y.

The yellow, magenta, and cyan toners collected in 21■ and 21c are not collected for reuse because they are mixed with toner from the different color developing device in the preceding stage of those units.

FIG. 5 shows the inside of the toner recovery pipe 42.

Inside the toner recovery pipe 42, a toner recovery auger 4 is installed.
Contains 3. The auger 43 is formed by a coil spring, and the toner collection pipe 4.2 is bent into a channel shape.
It can be freely rotated inside.

The auger 43 is rotationally driven in one direction by a driving means (not shown), and the toner collected in the unit 21bk is transferred to the developing unit 20b by the spiral pump action of the auger 43.
sent to k.

FIG. 9 shows the main parts of the mechanical part of one embodiment of the present invention, centering on the transfer belt part.

Referring to the figure, the recording paper is removed from the photoreceptor belt 18bk.
The transfer belt 25 sent in the direction 8c is moved by the idle roller 2
6. Drive roller 27. It is stretched between the idle roller 28 and the idle roller 3o, and is rotated counterclockwise by the drive roller 27. The drive roller 27 is pivotally connected to the left end of a lever 31 that is pivotally connected to a shaft 32 . A plunger 35 of a black mode setting solenoid (not shown) is pivotally attached to the right end of the lever 31. Plunger 35 and shaft 3
A compression coil spring 34 is disposed between 2,
This spring 34 applies a clockwise rotational force to the lever 31.

When the black mode setting solenoid is not energized (color mode), as shown in FIG. 9, the transfer belt 25 on which the recording paper is placed is the photoreceptor belt 18bk.

18! /, 1811 and 18c are in contact. At this time, art paper is selected as the recording paper feed system.

In this state, when the recording paper is placed on the transfer belt 25 and toner images are formed on all the photoreceptor belts, the toner images of each machine are transferred onto the recording paper as the recording paper moves, forming a color image. (color mode).

When the black mode setting solenoid is energized (black mode),
The lever 31 resists the repulsive force of the compression coil spring 34.
rotates counterclockwise, the drive roller is lowered by 5 mm, and the transfer belt 25 is transferred to the photoreceptor belts 18y*18m and 1
It separates from 8c and remains in contact with the photoreceptor belt 18bk. At this time, plain paper is selected for the paper feed system. In this state, the recording paper on the transfer belt 25 only contacts the photoreceptor belt 18bk, so only the black toner image is transferred to the recording paper (black mode). The photoreceptor belt 18y is placed on top of the recording paper because it does not contact the photoreceptor belts 18c and 18c.

18+m and 18c adhered toner (residual toner) does not stick, and yellow, magenta, cyan, etc. stains do not appear at all. In other words, when copying in black mode, copies similar to those produced by a normal monochrome black copying machine can be obtained.

The console board 300 includes a copy start switch 301. Color mode/black mode designation switch 302 that changes the copy mode (immediately after the power is turned on, the switch key is off and the color mode is set; when the switch is closed for the first time, the switch key lights up and the black mode is set, and the black mode setting solenoid is energized) (When the switch is closed for the second time, the switch key goes out, the color mode is set, and the black mode setting solenoid is de-energized), automatic density setting switch 3
03 (The automatic concentration setting mode is canceled immediately after the power is turned on, the first press of the switch sets the automatic concentration setting mode, and the second press cancels the automatic concentration setting mode), and other It is equipped with input key switches, character displays, and indicator lights.

Next, refer to the time chart shown in FIG.

The operation timing of the main parts of the copying mechanism will be explained. FIG. 6 shows the case where two identical full-color copies are made in the non-automatic density setting mode. Almost at the same timing as the start of exposure scanning of the first carriage 8, the lasers 43bk, 4
Modulation energization is simultaneously started based on the recording signals of 3y, 43m and 43c.

This modulation energization is performed at the same time, and exposure is performed at an irradiation point physically separated by the moving distance of the transfer belt 25 from the transfer point where each recording device is located (Fig. 1), a transfer corotron (transfer charger). 29bk.

29y, 29m and 29c are respectively laser 43
bk, 43y.

They are energized after a delay of a predetermined time (time for the laser irradiation position on the photoreceptor belt to reach the transfer corotron) from the start of the modulated energization of 432 and 43c.

Note that if the automatic density setting mode is set by pressing the automatic density setting switch 303, the 61st! ! ! At I, prescanning is performed as shown by the broken line. In this prescan, only the image reading operation of the image reading device is performed before the copying operation, and at that time, the recording system does not operate and the recording device is not activated for recording. In other words, exposure by carriage scanning is performed. Scan 9 image reading.

Only image processing is performed; no other operations are performed.

See the second [il. The W image processing unit 100 is a C
The three color image signals read by CD7r, 7g and 7b are converted into black (BK) and yellow (Y) necessary for recording.
, magenta (M), and cyan (C) recording signals. Note that the W image processing unit 100 has COD 7 re 7 g and 7 b as described above in the copying machine mode.
However, in graphics mode, three color signals are given from outside the copier to external interface 1.
It is given through 17.

Shading correction circuit 10 of image processing unit 100
1 is color gradation data obtained by A/D converting the output signals of CCDs 7r, 7g, and 7b into 8-pits.

The read color gradation data is created by correcting optical illuminance unevenness y CCD 7 r e 7 g and sensitivity variations of the internal unit elements of 7b.

The multiplexer 102 is a multiplexer that selectively outputs either the output gradation data of the correction circuit 101 or the output gradation data of the interface circuit 117.

A gamma correction circuit (γ correction circuit) 103 that receives the output (color gradation data) of the multiplexer 102 changes the gradation (input gradation data) according to the characteristics of the photoreceptor. The gradation is changed arbitrarily or automatically in the automatic density setting mode, and furthermore, input 8-bit data is changed to output 6-bit data. Since the output is 6 bits, data representing one of 64 gradations will be output.

In this automatic density setting mode, the value of the highest density part of the document, ie, red (R), is set during prescanning.

The smallest green (G) and blue (B) values are captured by the peak hold circuit 120, and based on that data, gamma correction characteristic data selection processing is performed, and gamma correction is performed under control from the synchronization control circuit 114. The gamma correction operating characteristics of the circuit 103 are automatically selected and changed. Next, a main scan for the print operation is performed, and a series of signal processing including gamma correction of the set gamma correction characteristics is performed to obtain appropriate print quality.

The input/output relationship of this gamma correction conversion is shown in FIG. 16, for example.

FIG. 16 exemplifies the relationship of automatic density setting in the automatic density setting mode, and shows the input/output relationship of a plurality of gamma correction characteristic data. The highest density value of the original is detected in a prescan operation before the copying operation, captured by the peak hold circuit 120, and an appropriate gamma correction characteristic is selected and set from this highest density value data. FIG. 16 shows the relationship between the gamma correction circuit input of value data converted to document density and the gamma correction circuit output of value data converted to print density as examples of several types of gamma correction characteristics. . These gamma correction characteristic lines are the characteristic line '401 of gamma characteristic setting when the output of the peak hold circuit during prescan operation is equivalent to 0.7, and the output of the peak hold circuit during prescan operation. is 1.0
A characteristic line 402 for setting the gamma characteristic when the value is equivalent to 1.7, and a characteristic line 403 for setting the gamma characteristic when the output of the peak hold circuit during the pre-scan operation is equivalent to 1.7 are representatively shown. As a typical characteristic line, 3
However, other characteristic curves may be used depending on the type of target document, including the characteristics of the photoreceptor used in the recording system. Each of the data is given as ROM data to a plurality of table converters provided in the correction circuit 103.

FIG. 17 shows an outline of the configuration of the gamma correction circuit 103. The gamma correction circuit 103 has a plurality of gamma correction characteristic data to be selectively set, each as table conversion data, and also as ROM data for each i component. Although FIG. 17 shows only part of the red gamma correction circuit part in some detail, the same applies to other color component systems, and the gamma correction circuits 103R, 103G, and 103B for each color component are shown in detail. The plurality of gamma correction characteristic data to be selected and set are stored in table conversion data 1:L in ROMI, ROM2°ROM3. -, R.O.
I have it in Mn.

In this gamma correction circuit 103, during the pre-scan operation, a microprocessor system 200 (described later) performs selection processing from the highest density value data of the image signal from the peak hold circuit 120, and provides control data from the synchronization control circuit 114. , here one gamma correction conversion ROM is selected by the register and decoder. When a gamma correction conversion ROM is selected, only the selected ROM becomes valid. For example, by receiving the output gradation data from the multiplexer 102 as ROM address data and reading the ROM data, the gamma-corrected output is generated. Gradation data is obtained, the gradation of the image information is changed, and input 8-bit data is converted to output 6-bit data. Red (R), green (G), and blue (B) output from these gamma correction circuits 103
The 6-bit three-color gradation data indicating each gradation is applied to a complementary color generation and black separation circuit 104.

The configuration of the complementary color generation and black separation circuit 104 is shown in 7yA.
Complementary color generation involves converting color reading signals into respective recording color signals, as shown in FIG.

Red (R) gradation data is cyan (C) gradation data.

Green (G) gradation data is converted to magenta (M) gradation data, and blue gradation data (B) is converted to yellow gradation data (Y). The C, M and 7 gradation data are applied as they are to the averaging data compression circuit 105. If all of these gradation data indicate high density, it is sufficient to record black, so the digital comparators 104c and 1
At 04m and 104y, the C, M, and 7th gradation data are compared with the reference value data set by the threshold value setting switch 104gh. digital comparator 104c,
104■ and to4y each compare 8-bit data with each other, and the data (input data) is the 6-bit gradation data plus the upper 2 bits of the L level.
is compared with 8-bit data (reference value data) in which 1 bit of the least significant digit and 3 bits of the upper digit are set to L level, and the 2nd to 4th bits from the lowest order are set as reference value data set by the threshold setting switch IQ4sh. However, if the input data is less than or equal to the reference value data, L is given to the Nant gate 104a, and if it exceeds it, H is given to the Nant gate 104a. The Nant gate outputs L (black) when all the comparators are giving an L signal, and outputs H (white) when any one is giving an H signal, and supplies it to the data selector 110. To explain this in more detail, the gradation data input to the comparator is 6-bit data in hexadecimal notation and ranges from θ to 3FH. When loaded, L represents black and H represents white. Therefore, the MS of 8-bit input data is
The B side 2 bits (Q6, 7) are set to L, and the lower 6 bits (QO
-5) Input the gradation data of C9M and Y, respectively. On the comparison data side, a rotary set of switches 104sh is used so that the comparison level can be set in seven stages. moreover,
Since this is a black level setting, if too many white colors are included in black, halftones (gray) can be recorded as black with higher resolution, but on the other hand, color balance 1 black will occur more often, which is undesirable. The 5th and 6th bits can be set in 7 steps, and since there is no need to set them too precisely, the 1st bit on the LSB side is set to L, and the middle 3rd bit is set to LSB.
The set value from the switch 104sh is input to the bits (Pi-3). now.

When the setting of the switch 104sh is 010, the reference value is 0000010, and when the C, M, and Y data are all below this value, that is, between θ and 3 in decimal, the comparator output is L. The black (BK) output is set to L (black). Here, the setting switch 104sh is set to C,
It is commonly used for comparison judgment of M and Y, but by using 3 sets, it can be set for each color.

By setting the setting range width of each color using the minimum and maximum setting switches, it is also possible to output a specific color in a black pattern with good resolution.

Averaging data compression circuit 105 of image processing unit 100
is 4 bits of gradation data for one image.
×4 image data are averaged and output as 6-bit gradation data. In this example, it is assumed that the input and output images have the same size, and the input data (
The value read from the COD) is A/D converted to 8-bit data, and then converted to 6-bit data by γ correction.
It is exactly 1 bit) data. It is possible to separate densities in a 64WI tone using input 6-bit data, and the dither method and density pattern method are well known for output density reproduction. Generally, an 8×8 matrix is used to express 64 gradations using the density pattern method. Therefore, the density of 8x8 pixels of input data is averaged and the output 8x8 matrix (
It is necessary to correspond to density pattern conversion in the gradation processing circuit 109). Furthermore, this averaging compresses the data amount and processing speed to 1/64, reducing the data capacity for storage and the cost of the hardware unit.

It is possible to make the size of the input reading pixel 8×8 times that of the output, but this is not adopted in this device because, as mentioned above, we do not want to reduce the resolution of black parts (normal characters).

FIG. 8a shows the configuration of the averaging data compression circuit 105,
FIG. 8b shows the operation timing of the circuit 105. What is averaged is 8N elements in the sub-scanning direction (exposure scanning direction of the first carriage 8) x main scanning direction (direction orthogonal to the exposure scanning direction: CCD electrons). (circuit scanning direction) 8 pixel data, a total of 64 pixels.

Also, when averaging 64 pieces of 6-bit data, if you add all the data and then make it 1764, the adder will use 12
Although a bit adder is required, in this embodiment, processing is performed using an 8-bit adder. First, sub-scanning direction 8
To explain pixel addition, the first data is latched in latch 1 and added to the second data in adder 1, and the added value data is latched in latch 2. The third data is latched in latch 1, added to the fourth data in adder 1, further added to the data in latch 2 in adder 2, and the sum of the 4 pixel data (gradation data) is added to the adder 1. Output from 2. This data is latched into latch 3.

Similarly, when the fifth to eighth data are added and output from the adder 2, they are added to the data in the latch 3 by the adder 3, and data for every eight pixels in the sub-scanning direction is output.

Note that the output of adder 1 becomes 7 by adding 6-bit data.
The output of adders 2 and 3 is the addition of 7-bit data, and the processing result of adders 2 and 3 is 8 bits, but the output takes the upper 7 bits and essentially divides the added data by 1/2.
The value is set to 2.

Next, addition in the main scanning direction will be explained. The average value of the 8 pixels output from the adder 3 corresponds to one main scanning line.

It is stored in RAM1 of the memory. The second line is adder 3
When the signal is output from the adder 4, it is added to the contents of the RAM 1 and stored in the RAM 2. By this addition, the first line data+the second line data are stored in the RAM2.

When the third line is output from the adder 3, the adder 4 adds it to the contents of the RAM1 and stores it in the RAM2.

By this addition, 1+2 line data is stored in the RAM2.

When the third line is output from adder 3, adder 4 adds it to the contents of RAM2 and stores it in RAM1. Similarly, RAMI 2 alternately serves as addition data output (reading) and storage, and when the 8th line is output from adder 3, it is added to the contents of RAM 1 by adder 4, and the addition data of line a is output. . Here, adder 4 is also adder 2,
Similarly to 3, by outputting the upper 7 bits of 7-bit data addition, averaged (1/2) data is output. In addition, in this embodiment, the adder is a 0-wire circuit in which two 4-bit binary full adders (74283) are connected in parallel. By changing the number of latches and adders on the sub-scanning side, it is possible to adapt to various matrix sizes. is possible.

Next, the masking processing circuit 106 and the UCR processing circuit 1
07 will be explained. The calculation formula for masking processing is generally as follows: Yi, Mi, Ci: data before masking.

Yo, MO, Co: data after masking.

It can be expressed as

Therefore, in this embodiment, a new coefficient is obtained by using these equations and using the product of both coefficients to calculate the following. The coefficient (a) of the above equation that performs both masking processing and UCR processing simultaneously
lt", etc.) are calculated in advance and substituted into the above calculation formula, and the calculated values (Yo', etc.: UCR processing circuit 107 output) in advance.
It is stored in M.

Therefore, in this embodiment, the masking processing circuit 10
6 and tJCR processing circuit 107 are composed of a set of ROMs, and data at addresses specified by inputs Y, M, and C to masking processing circuit 106 are input to UCR processing circuit 1.
07 is given to the gradation processing circuit 109. By the way, generally speaking.

The masking processing circuit 106 corrects the Y, M, and C signals in accordance with the characteristics of the spectral reflection wavelength of the toner for forming a recorded image, and the UCR processing circuit 107 corrects the color balance in the superimposition of each color toner. It is something to do.

Next, the gradation processing circuit 109 that performs density pattern processing of the image processing unit 100 will be described. This circuit 109 is
, M, and C to generate a pattern corresponding to the density thereof, and is constituted by a ROM.

The 6-bit gradation data can represent density information of 64 gradations. Ideally, if the dot diameter of one dot could be varied in 64 steps, there would be no need to reduce the resolution, but in laser beam electrophotography, the dot diameter modulation is only stable at about 4 steps at most.
Generally, the density pattern method and the combination of the density pattern method and beam modulation are often used.Here, the 0 circuit 109 uses a processing method of 64 gradation expression using an 8 x 8 matrix.
has 64 kinds of 8×8 density patterns per group,
A method is adopted in which 8-bit data in the sub-scanning direction is output based on gradation data and a main-scanning address.

Now, if we assume that the density pattern is 64 patterns (referred to as one group) created based on the binarized data in which the threshold levels are distributed in a spiral shape as shown in Figure 10a, this pattern will be The number of dots to which toner is applied within the 8 x 8 matrix is O, and toner is applied to the number of dots represented by the density data.When the density is 32, toner is applied to the shaded area shown in Figure 10a. . Therefore, data in a certain column is sequentially processed by the processing circuit 109.
, 8-bit data is output in data order from main scanning address 1, and by parallel-to-serial conversion and output, data for one line in the sub-scanning direction is obtained. After outputting this data 8 times in the main scanning direction (8 line processing), input the next data string.0 For example, the main scanning 3 data of data string 20.32.40 is 0011111
0,01111110.11111111. Here we have shown 64 gradation expression using an 8x8 matrix, but as a way to increase the resolution, it is possible to combine it with dot diameter modulation.
Submatrix methods and the like have been proposed. Similar gradation expression can also be achieved by changing the pattern or by outputting from the pattern. Regarding color processing, instead of using the same Y, M, C, and BK density patterns, the pattern generation angle may be changed for each color in order to prevent moiré. Assign to each color.

The recording signals assigned to BK include the dot pattern (binary signal) from the black separation circuit 104 and the OCR processing circuit 10.
It is necessary to synthesize the density pattern (gradation pattern signal) generated from the BK gradation information from 7. Simply put, for black in text areas, toner application based on the binary signal from the black separation circuit 104 has higher resolution than toner application based on density pattern information. However, in gradation image areas such as photographic areas, Conversely, toner application based on density pattern information has higher image reproducibility.

The following method can be considered to synthesize the dot pattern (binary signal) from the black separation circuit 104 and the density pattern (gradation pattern signal) generated from the BK gradation information from the UCR processing circuit 107. That is, (a) simply calculates the logical sum of the two (if at least one is black, toner is applied/recorded); (b) the black to be recorded in the 8×8 matrix is output by the black separation circuit 104; Then, the output of the black separation circuit 104 is assigned to that matrix, and if there is no output, density pattern data is assigned, and (c) the black to be recorded in the 8×8 matrix is output by the black separation circuit 104. Then, the output of the black separation circuit 104 is assigned to that matrix, and the number of "black" output by the black separation circuit 104 is compared with the number of "black" of the density pattern to be assigned to the matrix, and the amount by which the latter exceeds the former is calculated. is randomly assigned to the white part of the matrix.

The 8x8 matrix area is filled with black (
10c), the output of the black separation circuit 104 has a distribution as shown in FIG. 10c.

When the density pattern specified based on the BK output of the UCR processing circuit 107 has the black distribution shown in FIG. 10d, the recording signal shown in FIG. 11a is obtained according to the method (a) above, and According to the method (b), the recording signal shown in FIG. 11b is obtained, and according to the method (c), the recording signal shown in FIG. 11c is obtained.

Method (a) above is simple in terms of hardware, but
As shown in Figure a, the recorded black often increases, and although one of the purposes of this embodiment is to improve the resolution of black characters, the edges of the black image become black and blurred, which is a relatively unfavorable result. . The above method (b) requires 8 data processing steps.
1 black separation circuit in one section as ×8 matrix section
This can be implemented by determining whether or not there is an output "black" of the circuit 104, and if so, allocating the output of the circuit 104 to that category. In other words, it can be realized with relatively simple hardware and logic. Moreover, this method can achieve the purpose of improving the resolution of characters. However, if the image is a half-tone image, the density of black will be 5 dots lower than when a density pattern is assigned.

The above method (c) solves the problems of (a) and (b). However, in reality, although the difference is easily determined, the hardware and logic for randomly assigning the difference to the white area become complex.

As a result of the above considerations, this embodiment adopts the method (b) described above from the viewpoint of improving the resolution of black characters. This method is performed by data selector 110 shown in FIG.

FIG. 12 shows the configuration of the data selector 110.

0 (L: white) for each pixel from the black separation circuit 104.

■ (H: black) data is serial/parallel converter 11
By 0a, every 8 bits are output in parallel and OR gate O
If there is even one black (1) in the 8 bits of RI, "1" is output, and if all of them are black (0), "0" is output. This output is stored in RAM1 for one line, and when the second line is input, the data of the first line stored in RAM1 is ORed and stored in RAM2. In this way, the data for 8 lines are sequentially ORed.

During this time, the parallel-converted O (L: white)) and L (H: black) data for each pixel from the separation circuit 104 are written to the line buffer 110b with a capacity for 8 lines. When this writing is completed, the timing pulse becomes 1, the AND gate AND1 is opened, data is applied to the lid 110c for each line from the line buffer 110b, and the density pattern is applied to the data storage for each line from the processing circuit 109. The data is given to the selector 110c, and the RA
The data of M2 is repeatedly read and the data is sent to the selector 110c.
is applied to the control data input terminal of .

When there is a black output from the black separation circuit 104 in the 8×8 matrix division, the output of the RAM 2 is 1, so the data selector 110c sends the output of the buffer 110b to the laser driver 112b through the OR gate 111 (FIG. 2).
give to k. When no output from the separation circuit is black, density pattern data is given.

The peak detection circuit 115 of the image processing unit 100 is meaningful in the monochromatic black copy mode and the automatic density setting color/monochrome mode, and converts each of the R, G, and B signals into analog signals, and compares the three analog signals. The highest value among these three is output to the binarization circuit 116.

The binarization circuit 116 converts the input signal into black (1: recording).

It is binarized into a signal indicating white (0: non-recording). The binary signal is passed through an OR gate 111 to a laser driver 112.
given to bk.

The peak hold circuit 120 is used for automatic density setting mode in color or monochrome mode. The highest density of image signals R, G, and B of one frame is detected and held.The input is the output from the peak detection circuit 115, and the output of this peak hold circuit 120 is passed to the synchronization control circuit 114.

The synchronization control circuit 114 determines the activation timing of each of the above elements and matches the timing between each element. 200 is a microprocessor system that controls all the elements shown in FIG. 2 described above, that is, controls the copying machine. This processor system 200 controls copying in various modes set on the console, and includes not only the image reading/recording system shown in FIG. 2 but also the photoreceptor power system and the exposure system.

Performs sequence control of the charger system, 11L image system, fixing system, etc.

The copying machine of this embodiment is capable of not only full-color copying but also single-color black copying, and the console 300 is equipped with a switching instruction key switch 302 for switching settings between full-color mode and single-color black mode. This switch 30
The mode settings according to the second operation have already been explained. Here, the operation when the monochromatic black mode is set will be explained.

The image scanning section such as the first carriage operates in the same way as in the full color mode in the monochrome black mode, and the R2O and 8
Three color signals are output from the γ correction circuit 103. Peak detection circuit 1 that did not work in full color mode
15 and the binarization circuit 116 operate, and conversely, the complementary color generation and black separation circuit 104 to the gradation processing circuit 109, which were operating in color mode, as well as the laser driver 112y, cabinet, C, and lasers 43y, m, and c. does not work in monochrome black mode. The operation or non-operation of these circuits is determined by the control operation of the synchronous control circuit 114 based on instructions from the processor system 200. The output of the γ correction circuit 103 is given to the peak detection circuit 115, and the peak detection circuit 115 gives the analog voltage of the highest level among the three voltages to the binarization circuit 116. The binarization circuit 116 has a threshold level set to a predetermined value.
The input is compared with the level, converted into a 1-bit digital signal, and applied to the OR gate 111. This output is given to the laser driver 112bk through the OR gate 111. Laser driver 112bk energizes laser 43bk based on the applied signal. That is, the laser is modulated and controlled based on the signal.

On the other hand, in the recording system, in the monochromatic black mode, the charger corotron '9ye'tC*, the developing unit 20ye, and the CT transfer corotrons 29y, 11, and c stop operating, and the other operations operate in the same manner as in the full-color copy mode.

These operations and non-operations are controlled by their drivers in accordance with instructions from the processor system 200.

FIG. 13 shows an interface between the polygon mirror drive motor 41 and the microprocessor system (200: FIG. 2). The input/output port 201 shown in FIG. 13 is connected to the bus 206 of the system 200. In addition,
In FIG.

44 is one photodetector for line synchronization signal detection. A motor 41 drives the rotating polygon mirror, and is energized by a motor driver 46. 50bk.

50y, 50m and 50c are photoreceptor belts 18bk.

18 y y is a motor that rotationally drives 18 ya and 18c, and the motor drivers 49bk, 49y,
49 theory and 49c.

Also, motor 50bk, 50yt 50m and 50
Seam sensors 55bk, 55y, 55m and 55c (
1 and 13) are provided. Photoreceptor belt drive motor 50bk, 50'J, 50m+ and 50
c is this seam sensor 55bk, 55Vt, s 5
It is rotated for alignment after the copy operation based on feedback signals from m and 55c.

That is, seam sensors 55bk, 55y, 55+m
When motors 50bk, 50y, 50m and 50c detect their joints, the motors 50bk, 50y, 50m and 50c stop rotating and enter a rest state. In addition, photoreceptor belt 18bk,
18y.

Black marks are attached to the inner seams of 18■ and )8c, which are used as seam sensors 55bk and 55y.

55I11 and 55c perform these control operations by detecting changes in the amount of incident light. In addition, there are drivers for energizing each component of the copying machine, processing circuits connected to sensors, etc., which are connected to the input/output port 207 or other input/output ports and coupled to the system 200; has been omitted.

The transfer paper feed roller 231 corresponds to the operation timing of the first carriage 8 in both the full color mode and the single color black mode.
and 232. Developing device 20bk, registration roller 24.
The operation timing of the transfer corotron 29bk and the like is the same.

The fact that the photosensitive drum 18bk for black recording is located at the most upstream position when viewed from the paper feeding side has the advantage that recording device energization control in the monochromatic black mode is simple.

If the black recording device is not located at the most upstream position as in the embodiment but at the most downstream position as in the conventional case, the operation timing of the first carriage 8 will be changed as shown in FIG. Recording paper feed roller 23. The operation timing of the registration roller 24 and the like differs between the full color copy mode and the monochrome black copy mode. In other words, control becomes that much more complicated.

Next, the operation timing of each part based on the control operations of the microprocessor system 200 and the synchronous control circuit 114 will be explained.

First, when the power switch (not shown) is turned on, the device starts a warm-up operation, which increases the temperature of the fixing unit 36, starts rotating the polygon mirror at a constant speed, and returns the carriage 8 to its home position.・Generation of line synchronization clock (1,26KHz), ・Generation of video synchronization clock (8,42MH2), ・Initialization of various counters, etc.The line synchronization clock is generated by the polygon mirror motor driver and COD driver. The former uses this signal as a reference signal for a phase-locked loop (PLL) servo, and the beam sensor 4 which is a feedback signal.
The beam detection signal No. 4 is controlled to have the same frequency as the line synchronization clock and to have a predetermined phase relationship. The latter is used as a main scanning start signal for CCD reading. Note that the signal for synchronizing the start of laser beam main scanning is the detection signal (pulse) of the beam sensor 44.
Use this as it is output commonly for each color.

Note that the frequency of the line synchronization signal and the detection signal of each beam sensor are locked by PLL and are the same, but there may be a slight phase difference, so the scanning reference is not the line synchronization signal but the frequency of each beam sensor. The detection signal is used.

The video synchronization clock has a frequency of one dot (one pixel) and is supplied to the COD driver and laser driver.

Various counters are (1) Reading line counter.

(2) Write line counter.

(3) Read dot counter; and (4) Write dot counter. However, (1) and (2) above are program counters that are substituted by the operation of the CPU 202 of the microprocessor system 200, and (3) and ( Although not shown in the figure, 4) is separately provided on the hardware.

Next, the timing of the print cycle is shown in Figure 14,
Let me explain this.

When the warm-up operation is completed, the printer enters a standby processing operation and becomes ready to print. When the copy start key switch 301 is turned on, the system 200
Due to the operation of the PU 202, the drive motor of the first carriage 8 (Fig. 13) starts rotating and the carriages 8 and 9 (8
172 speed) starts scanning (exposure scanning) to the left. When the carriage 8 is at the home position, the output of the home position sensor 39 is H, and the exposure scan (
Sub-scanning) will start soon after. At the time of switching from H to L, the read line counter is cleared and at the same time, the count is enabled. Note that the time point at which this change from H to L occurs is the position where the leading edge of the document is exposed.

With the line synchronization clock that comes in after the sensor 39 goes low, the read line counter is counted up every pulse. Also, when the line synchronization clock comes in, the reading dot counter is cleared at the rising edge of the clock to enable counting.

Therefore, the first line is read one pixel after the home position sensor 39 becomes L, in synchronization with the video synchronization clock immediately after the first line synchronization clock is input.
9 pixels 2. . . . Pixel 4667 is read sequentially. Note that counting one pixel is performed by a reading dot counter, and the content of the reading line counter at this time is 1.

Similarly, for the second and subsequent lines, the reading line counter is incremented by the next line synchronization clock, the reading dot counter is cleared, and synchronized with the next video synchronization clock, the reading counter is incremented and pixels are read. Let's do it.

In this way, the lines are sequentially read, and when the reading line counter counts up to 6615 lines, the last reading is performed on that line, and the carriage drive motor is reversely energized to return the carriages 8 and 9 to their home positions.

The pixel data read in the above manner is sequentially sent to the image processing unit 100 and subjected to various image processing. The time required to perform this image processing is only two clocks of the line synchronization clock signal.

At least it takes.

Next, in writing, first the write line counter is cleared and counting is enabled in the following manner: When the read line counter is 2, the write counter is cleared and counting is enabled.

These count-ups are performed at the rising edge of the detection signal of the beam sensor 44. Further, the write dot counter is cleared at the rising edge of the detection signal of the beam sensor 44, and counting up is performed by the video synchronization signal.

Writing for each color starts when the content of the reading counter reaches a predetermined value, the writing line counter for each color becomes counting enable, and counting starts with the detection signal of the first beam sensor 44 (content 1). When the write dot counter reaches a predetermined value, the laser driver is driven to perform writing. The dot counter values between 1 and 400 are dummy data, and are 401 to 5077.
(4677 pieces) are writable values. Here is the dummy data.

Beam sensor 44 and photoreceptor belts 18bk, 18y.

This is to adjust the physical distance of 18m and 18c. Also, write data (1 or 0) is captured at the falling point of the video synchronization signal. The writing range in the line direction is when each writing line counter is 1 to 6615 lines.

Now, as shown in FIG. 14, after starting the exposure scan,
Since recording data is obtained from the time of scanning the third line of OD, each recording device starts recording energization in synchronization with the acquisition of data.

In the automatic density setting mode, before the carriage scanning, carriage scanning (prescanning) is performed only to read the maximum density of the document. In this prescan operation, only the W image reading system is operated, and the recording device systems such as the recording system, photoreceptor drive system, exposure system, charger system, developing system, fixing system, etc. are not operated.

Here, an outline of the operation of the control system performed by the microprocessor system 200 will be explained.

Referring to FIGS. 18a and 18b, an outline of the operation of the control system for the entire copying operation will be described, focusing on the prescan operation performed in the automatic density setting mode. These processing operations are carried out by C in the microprocessor system 200.
PU202 is executed by a program stored in ROM204.

The general operation of the entire device is as follows. That is, when the power is turned on, various devices are set to the initial state, the contents of the memory are cleared, and initial values are set in the predetermined memory (step 1; hereinafter, the word "r step" will be omitted in parentheses)0 Next, read the status of various switches, sensors, etc. (2).

Next, a standby process (3) is performed.In the standby process (3), the status of various keys is read, and the number of copies is set and the number of copies is cleared according to the status signals.

Performs control processing such as selection of paper feed system, mode settings, and variable magnification operations. In this period processing, the γ correction characteristic data is set to the initial setting γ correction characteristic data. In the early stages, the characteristics of the original are unknown, so the γ
This is to set it in the correction data. These processes (2) are performed until the copy start switch 301 is turned on (4).

The operations of (3) and (4) are repeated. When the copy start switch 301 is turned on (4), it is determined whether the automatic density setting mode is set (5).

If automatic density setting mode is not set, 1 Carriage scanning for image reading for normal copying operation will not start. 6
), sequence control of copying process (6), (7),
(8) and (9") are continued. That is, as mentioned above, the sequence control of the copying process is to energize the carriage drive motor to rotate forward and start carriage scanning,
Start reading pixels 6).

Subsequently, the read pixel data is subjected to image processing with 2 nits of 10
0 to start the synchronized control of image processing to perform various image processing 7), and then start the control operation of the recording system (8)
The start of the control operation of the recording system is obtained from the third line scanning point after a delay of the time required for image processing in the image processing unit 100 (two clocks of the line synchronization signal clock). A control operation is performed to start recording energization in synchronization with . Start these control operations (6), (7), (8), and then execute other copy sequence control processes (9).
). When the copying sequence control operation for one sheet is completed, it is determined whether or not the set number of copies have been completed (10);
If the set number of copies have not been completed, the sequence control of the copying process in step 6.7.8.9 is repeated. If the set number of copies have been completed, the execution of the copy sequence control process is completed, the process returns to step 2, and the status of various switches, sensors, etc. is read again.
Next, the standby process (3) is performed, and these processes (2),
The operations (3) and (4) will be repeated.

If it is determined in step 5 that the automatic density setting mode is set, the process proceeds to step 13, and before carriage scanning for normal copying operation, ! Carriage scanning (prescanning) is performed only to read the highest density of the document.

Step 13 is similar to step 6 and starts carriage scanning for image reading. In this prescan operation, the carriage drive motor is energized to rotate in the forward direction to start carriage scanning and start reading pixels (13), and then the read pixel data is sent to the image processing unit 100 for various image processing. Starts synchronous control of image processing that performs (
14). In this way, the lines are read one after another, and when the reading line counter counts up to 6615 lines, the last reading is performed on that line, the carriage drive motor is reversely energized, and the carriages 8 and 9 are returned to their home positions. The return to the home position is detected, and the end of the pre-scan carriage scan is detected (15).

In this prescan operation, only the image reading system is operated, and the recording device systems such as the recording system, photoreceptor drive system, exposure system, charger system, @imaging system, fixing system, etc. are not performed. Please note that there is no

When this bliscan operation (11) is completed, the peak hold circuit 120 has detected the maximum density of the original, and the maximum density of the original is detected.

A process (12) for selecting and setting the gamma correction characteristic of the gamma correction circuit 103 is performed, and the process returns to step 6 of the main routine of the normal copying process. In step 6, the carriage scanning for image reading for normal copying operation is started (6), the sequence control of the copying process (6), (
Continue steps 7), (8), and (9).

The process of step 12 for selecting and setting the gamma correction characteristic of the gamma correction circuit 103 will be described with reference to FIG. 18b. By the end of the prescan operation (11) described above, the maximum density of the original has been detected in the peak hold circuit 120, and the gamma correction characteristic of the gamma correction circuit 103 is selected and set based on the detected maximum density value P of the original. In other words, if the maximum concentration value P is less than 0.5 (
20), γ correction characteristic 400 should be selected 30), if the maximum density value P is 0.5 or more but less than 0.7 (21),
The γ correction characteristic 401 is selected (31). In addition, if the maximum concentration value P is 0.7 or more and less than 1.0 (22
), γ correction characteristic 402 should be selected32), maximum density value P
If the value of is 1.0 or more and less than 1.7 (23),
The γ correction characteristic 403 is selected (33). Then, if the value of the highest density value P is 1.7 or more (23) = 404 is selected as the γ correction characteristic (34), and the γ correction characteristic selection process is ended. The γ correction characteristics selected here are:
Although illustrated in FIG. 16, the γ correction characteristics 400 and 404 are not particularly illustrated in FIG. 16.

In this way, Fllll input/disconnection tap 20.21, 22°23
The maximum density value P of the document is determined by the above, and an appropriate γ correction characteristic is selected within the range of the maximum density value P, and the γ correction characteristic setting process is performed in the γ correction circuit.

When the γ correction characteristic selection processing is completed, the process returns to the sequence control processing routine of the normal copying process.

The sequence control processing of the copying process continues.

These control processes are well known to those skilled in the art and do not require detailed explanation.

Next, other embodiments and modifications of the copying machine of the above embodiment will be described. In the above embodiment, in addition to full-color copies, it is possible to make copies of only one color, but this can be done not only in full-color or monochrome black, but also in monochrome copies of other colors and copies of colors less than full color. It is also possible to use a copying machine that makes overlapping copies. An appropriate recording paper feeding system is selected depending on the quality of the recording paper in accordance with each copying mode. An example of a configuration in this case is shown in FIG.

In this case, the transfer belt 25 is replaced by the photoreceptor belt 18.
Four idle rollers 47bk,
47y.

47m and 47c, and solenoids 48bk, 48y, 48m and 48c that drive each idle roller into the contact position. In this case, the solenoid 48bk is used for full color copying.

4831.48- and 48c are all energized and transfer belt 25 contacts the entire photoreceptor belt. solenoid 4
When only 8bk is energized, it becomes a monochrome black copy, and 4
When only 8y is energized, a monochrome yellow copy is produced, when only 48m is energized, a monochrome magenta copy is produced, and when only 48c is energized, a monochrome cyan copy is produced.

Copies of various other combinations of colors may also be set; for example, when solenoids 48yt48m and 48c are energized at the same time, a three-color full-color copy is made. Simultaneous energization of two solenoids results in two-color overlapping copies.

■Effects As described above, according to the present invention, in a digital copying machine,
In addition to gamma correction to improve gradation to match the characteristics of the photoreceptor used in ordinary recording devices, only the reading device is operated prior to copying to determine the maximum density value of the original before copying. The gamma correction characteristic is automatically changed according to the original image based on the density value, and the gamma correction of the read image signal is performed. This allows you to perform optimal copying.

[Brief explanation of drawings]

FIG. 1 is a sectional view mainly showing the structure of the main parts of the mechanism of an embodiment of the present invention, FIG. 2 is a block diagram showing the structure of the main parts of the electrical system, and FIG. FIG. 4 is an exploded perspective view of the exposure scanning system for each recording device shown in FIG. 1, and FIG. 5 is an enlarged perspective view of a part of the carriage 8. FIG. FIG. FIG. 6 is a time chart showing the relationship between original reading scanning timing, recording biasing timing, and transfer biasing timing in the above embodiment. FIG. 7 is a block diagram showing the configuration of the complementary color generation and black separation circuit 104 shown in FIG. 2, FIG. 8a is a block diagram showing the configuration of the averaging data compression circuit 105 shown in FIG. 5 is a time chart showing a data processing sequence of the circuit 105. FIG. FIG. 9 is a side view schematically showing the transfer belt section of the mechanism section shown in FIG. 1. FIG. FIG. 10a is a plan view showing the distribution of threshold level data used in creating the density pattern stored in the gradation processing circuit 109. FIG. 10b is a plan view showing the image distribution of the 8×8 dot matrix area on the original, FIG.
FIG. 0d is a plan view showing the BK density pattern output of the gradation processing circuit 109 developed in a plane. FIG. 11a shows the BK output of circuit 104 and the BK output of circuit 109.
A plan view showing a planar expansion of the logical sum of density pattern outputs,
FIG. 11b is a plan view showing the signal outputted by the data selector 110 when the output of the circuit 104 is black, and FIG. FIG. 3 is a plan view showing a recording signal distribution randomly arranged in a white area. FIG. 12 is a block diagram showing the configuration of data selector 110, and FIG. 13 is a block diagram showing a portion of copying mechanism elements connected to microprocessor system 200. FIG. 14 is a time chart showing the relationship between exposure scanning and recording energization of the copying machine shown in FIG. FIG. 15 is a side view showing an outline of the mechanism of another embodiment of the copying machine. FIG. 16 is a turnout characteristic diagram of the γ correction circuit showing the relationship between automatic density settings in the automatic density setting mode. FIG. 17 is a block diagram showing the general configuration of the gamma correction circuit in slightly more detail. FIG. 18a is a flowchart showing an overview of the operation;
FIG. 18b is a flowchart showing in slightly more detail a part of the γ correction selection process in the flowchart of FIG. 18a. 1: Manuscript 2 Nibraten 31 y32
: Fluorescent lamp 41 to 43: Mirror 5: Variable magnification lens unit 6: Dichroic prism 7r, 7g, 7b: CCD 8: First carriage 9: Second carriage 10: Carriage drive motor 11: Pulley 12: Wire 13: Polygon mirror 141, 142: f-〇 lens 15bk, 15y, 15m, 15c: mirror 16bk
, 16y, 16 ugly, 16c: Mirror 18bk, 18y
, 18m, 18c: Photosensitive trace belt 19bk, 19y,
19m, 19c: Charge Scorotron 20bk,
20y, 20m, 20c: Developing device 21bk
, 21y, 21m, 21c: Cleaner 221.222
: Transfer paper cassette 231.232: Paper feed roller 24 Ni registration roller 25: Transfer belt 26.28
, 30: Idle roller 27: Drive roller 29bk, 29y, 29+s, 29c:
Transfer corotron 31 Nilever 32: Shaft 33: Bin 34: Compression coil spring 35
: Black copy mode setting solenoid plunger 36: Fixing device 37: Tray 39: Home position sensor 40: Carriage guide bar 41: Polygonal mirror drive motor 42; Toner collection pipes 43bk, 43y, 43m, 43c: Laser 44: Beam sensor 46: Motor driver 49bk, 49y, 49m, 49c: Motor driver 50bk, 50y, 50m, 50c:
Photoreceptor belt drive motor 51bk, 51y, 51m, 5
1c: Gear 52bk, 52y, 52m, 52c: Gear 53bk, 53y, 53m, 53c: Photoreceptor belt drive roller 54bk, 54y, 54w+, 54c: Roller 55bk, 55y, 55m, 55c: Seam center, sensor 60bk, 60y, 6 (hs, 60c: E L eraser 701.702: Reflective optical sensor 100: Image processing unit 103: Gamma correction circuit (gamma correction means) 103R:
Red signal gamma correction circuit 103G Nigeleen signal gamma correction circuit 103B Nibble-signal gamma correction circuit 114: Synchronous control circuit 115: 'Peak detection circuit (density detection means) 120:
Peak hold circuit (density detection means) 200: Microprocessor system (gamma correction characteristic setting means, recording control means) 202: Microprocessor (CPU) 203: RAM 204: ROM 2601.260□: First paper feeding system, second Paper feed system 2671
．． 2672: Recording paper 300: Console 301; Copy start key switch 302: Full color/single color black mode switching key switch 3
03: Automatic concentration setting switch 305, 306: Complaint mark voice 5 Figure 15 Figure 16 (Hekabo Hori 夙 term (k value) Foil 18b Figure procedural amendment April 10, 1986 Commissioner of the Japan Patent Office U Ka Michibe Tono 2, Title of the invention Digital copying machine 3, Relationship to the case of the person making the amendment Patent applicant address 1-3-6 Nakamagome, Ota-ku, Tokyo Name
(674) Ricoh Oshahama 1) Hiro 4, Agent 103 Phone: 03-864-6
052 Address: 2-27-6-6 Higashi Nihonbashi, Chuo-ku, Tokyo Contents of amendment (1) "Shuku1" as stated in lines 7 to 8 of page 30 of the specification
bit) data. " is corrected to "The output data to the laser driver is laser on/off (1 bit) data."

Claims (7)

[Claims] (1) An image reading means for reading the original image, a digital conversion means for converting the read image signal into gradation data, and forming an electrostatic latent image by projecting light corresponding to the gradation data onto the photoreceptor;
In a digital copying machine equipped with a recording device that develops this electrostatic latent image, multiple sets of gamma-corrected image information corresponding to read gradation data with different correction characteristics are held, and a designated set of image information is stored. A gamma correction means that generates the data corresponding to the read gradation data; a density detection means that detects the maximum density of the image read by the image reading means; a means for instructing the image reading means to read the original image; gamma correction characteristic setting means for specifying one set to the gamma correction means, which corresponds in advance to the highest density detected by the density detection means of the image; and, after the above specification, reading the original image to the image reading means; A digital copying machine comprising: recording control means for instructing the recording device to record an original image based on image information generated by the gamma correction means; (2) When the gamma correction characteristic setting means instructs the image reading means to read the original image, the gamma correction characteristic setting means specifies a predetermined set of gamma correction means for the gamma correction means; A digital copying machine according to claim 1, wherein a maximum density of generated image information is detected. (3) When instructing the image reading means to read the original image, the predetermined set specified to the gamma correction means is a correction characteristic that converts the read gradation data into image information without converting it. The digital copying machine described in paragraph (2). (4) When instructing the image reading means to read the original image, a predetermined set of gamma correction characteristic data specified to the gamma correction means changes the gradation according to the characteristics of the photoreceptor used in the recording device. Claim No. (2)
Digital copying machine as described in section. (5) The image reading means is an image reading device that separates the original image and reads it, and the gamma correction means generates image information corresponding to read gradation data for each color component. The digital copying machine described in item 1). (6) The digital copy according to claim (5), wherein the gamma-corrected image information generated by the gamma correction means is provided with a plurality of gamma correction characteristic data as ROM data for each color component. Machine. (7) The density detection means detects the highest density value of the gamma-corrected image signal generated in response to the gradation data read by the gamma correction means for each color component. digital copier.