JPH0523535B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an image forming apparatus that forms an image while moving a recording head relative to a recording material.

<Prior Art> Conventionally, when an image signal to be recorded is optically read while relatively scanning a document with a reading sensor, a shading correction process has been performed prior to reading. This shading correction process involves reading a standard white plate, which serves as a reference for white data, before scanning the original, and sampling data for correcting aberrations of the optical system lens and sensitivity variations of each bit of the CCD sensor.

Also, when forming an image by ejecting ink while scanning the recording head relative to the recording material based on the image signal from the reading sensor, a dry ejection process is performed prior to recording. Ta. This idle ejection process is a process performed to ensure stable recording, and is used to prevent uneven ejection at the start of ejection for image formation caused by changes in the viscosity of the ink remaining in the inkjet nozzle. This is an operation to eject and eliminate ink within the inkjet nozzle.

However, if the idle ejection process and the shading correction process are performed sequentially, the time required for preprocessing for performing an image forming operation increases.

<Objective> The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an image forming apparatus that can quickly perform reading and recording operations.

<Embodiment> (Overview of Apparatus Mechanism) FIG. 1 is a perspective view of a digital color image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a configuration diagram schematically showing FIG. 1. The configuration of the present invention will be explained based on FIGS. 1 and 2. An original 20 is placed on the original table glass 1 on a flat surface. The original surface of the original 20 faces the surface of the original platen glass 1, and the original 20
is pressed by the pressure plate 1a. The reading head (hereinafter referred to as reader) 3 that reads the original 20 is a read head,
Green, blue (hereinafter referred to as R, G, B) 3 colors
A reading sensor (hereinafter referred to as a CCD unit) consisting of a CCD array consisting of multiple reading elements in each row.
17 and an exposure lamp 19 are placed thereon, and are coupled to and driven by a main scanning motor 6a by a main scanning wire 8a. The sub-scanning table 5a supports one end of the main-scanning wire 8a, and is connected to and driven by the sub-scanning motor 9a by the sub-scanning wire 10a.

A recording paper 21 is placed on a recording table 2, and a copy image is recorded by a recording head (hereinafter referred to as a printer) 4.
Print 4 is a recording element (hereinafter referred to as a BJ head since a bubble jet head is used in the present invention) for four colors of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and BK). BJ head unit) 18 is placed,
The main scanning wire 8b connects and drives the main scanning motor 6b. The sub-scanning stand 5b supports one end of the main-scanning wire 8b, and is coupled to and driven by the sub-scanning motor 9b by the sub-scanning wire 10b.

When attempting to obtain a copy image in the above configuration, the reader 3 is driven by the main scanning motor 6a via the main scanning wire 8a and reciprocates in the main scanning direction. At this time, the exposure lamp 19 is turned on and the reading sensor 17 reads the document 20 from below and outputs image information as an electrical signal. Based on this electrical signal, the printer 4 is driven by the main scanning motor 6b via the main scanning wire 8b, and prints on the recording paper 21 while reciprocating. At this time, the main scanning directions of the reading head 3 and the recording head 4 are set in opposite directions to each other in this embodiment. Once the copying process in the main scanning direction is completed, the exposure lamp 19
After turning off the light, the reader 3 and printer 4 move in a direction perpendicular to the main scan, that is, in the sub-scan direction, to a position where the next main scan will be performed. At this time, leader 3
is the sub-scanning table 5a supporting the main-scanning wire 8a.
At the same time, it is driven by the sub-scanning motor 9a via the sub-scanning wire 10a, moves to a predetermined position, and stops. Further, the printer 4 is connected to the sub-scanning wire 1 together with the sub-scanning table 5b supporting the main scanning wire 8b.
It is driven by the sub-scanning motor 9b via 0b, moves to a predetermined position, and stops.

(Device control operation...Pre-operation) FIG. 3 is a block diagram of the control circuit of the above-described embodiment, FIG. 4 is a timing chart of the entire sequence, and FIG. 5 is a flowchart of the program. First, an outline of the operation of the apparatus will be explained using FIGS. 4, 5, and 6. Note that the step numbers on the timing chart and flow chart are the same.

Both the sequence controller 23 and the image controller 24 have a microcomputer unit in the center, and perform sequence control of the device, respectively.
The timing of image data formation is programmed, and both microcomputers are connected to line 3.
Data communication is performed via 9. To explain the sequence from the time the power is turned on, the sequence controller 23 performs initial settings of the copying machine in step 1 according to the flowchart shown in FIG. Make a comeback. Next step 3
Then perform the inkjet head recovery operation. The head recovery operation is performed using a porous member, etc. in order to forcefully remove ink stuck to the tip of the inkjet nozzle after the device has stopped operating for a long time, and also to remove a pool of liquid near the tip of the nozzle after the ink ejection operation. This operation is performed by pressing or sliding a highly water-absorbing material against the tip of the head. In terms of sequence, the printer main scanning motor 6b is rotated in the backward direction and stopped by the detection output of the recovery system position sensor 22. Next, a drive mechanism such as a solenoid is turned on to press the porous member against the head, and the porous member is pressed against the nozzle tip for a predetermined period of time. After completion, the printer main scanning motor 7b is rotated in the forward direction and stopped by the detection output of the printer main scanning home position sensor 12.

Next, in step 4, an operation is performed to cap the head in order to prevent a change in the viscosity of the ink at the tip of the nozzle during a pause before the copying operation of the apparatus.
This is accomplished by turning on a drive mechanism such as a solenoid that applies the cap at the home position of the printer. Next, in step 5, the operator waits for input from the operation unit 25, decodes the input data, and sets the copy mode.In step 6, it is determined whether or not it is a copy start command.If it is not a copy start command, step Returning to step 5, if copying is to be started, the process proceeds to step 7, where the cap drive of the head is released in order to start the copying operation. Next, the process advances to step 8, and an idle ejection process is performed on the head prior to the copying operation. The idle ejection process is a process performed to ensure stable recording, and is a process in which copying is paused to prevent uneven ejection at the start of ejection for image formation caused by changes in the viscosity of the ink remaining in the inkjet nozzle. This is an operation for ejecting and discarding ink in the inkjet nozzle according to programmed conditions such as time, internal temperature (temperature sensor not shown), and copying duration. Next, in step 9, the original exposure lamp 19 is turned on and shading correction processing is performed. Shading correction involves reading a standard white plate, which serves as a reference for white data, before scanning the original, and sampling data for correcting aberrations of the optical system lens and variations in sensitivity of each bit of the CCD sensor.

Note that steps 8 and 9 are executed in parallel, as shown in the timing chart of FIG. As a result, the idle ejection process and the shading correction process are performed simultaneously, so that the time required for preprocessing of reading and recording operations can be shortened. Then, wait until both operations are completed before proceeding to the next step.

Next, the process proceeds to step 10, and it is determined whether or not it is immediately after the start of copying. If it is immediately after the start of copying, that is, before the start of the first main scan, the process proceeds to step 11, and if it is the second or subsequent time, the process proceeds to step 12. In step 11, a recovery operation of the head is performed in anticipation of the equipment being stopped for a long time. The recovery operation in this case is the same as that described in step 3. Next, the process advances to step 12 to start main scanning. (Refer to Figure 6 for each signal.) (Device control operation - copying) For main scanning, first, a signal is sent to the motor driver circuit 26a of the reader via line 40 to provide speed data corresponding to the magnification ratio and a rotation start signal in the forward direction of the reader. , and turn on the reader main scanning motor 6a. Next, after a delay time for synchronizing the reader and printer according to the magnification ratio, a rotation start signal in the forward direction of the printer is sent to the motor driver circuit 26b of the printer via line 41 to turn on the printer main scanning motor 6b. The rotation speed of the main scanning motors 6a and 6b of the reader and printer is determined by comparing pulses (FG signals) from rotary encoders 7a and 7b (hereinafter referred to as encoders) for rotation speed detection with rotation speed reference pulses by motor driver circuits 26a and 26b. The rotation speed is locked to a predetermined speed by PLL control, resulting in a constant rotation speed. Further, each encoder pulse is sent to the video data synchronization signal generation circuit 28 and the head data synchronization signal generation circuit 38 via lines 42 and 43.

(Reader side processing) Next, the process advances to step 13 and a copying operation is performed.
The following description will be made with reference to FIGS. 7-e and 7-b. As shown in FIG. 3, the video data synchronization signal generation circuit 28 generates position information in the reader main scanning direction in synchronization with the encoder pulse of the reader main scanning motor 6a, and generates the effective range of video data with a resolution l in the sub-scanning direction. A video line enable signal (hereinafter referred to as VLE) is generated as shown in FIGS. 6-a and 6-b. Furthermore, based on the video data start signal inputted from the CCD drive circuit 29, a video data enable signal (VDE) indicating the effective data width of all pixels of the CCD and synchronized with the encoder pulse is output. At the same time, a CCD start signal is synchronized with the encoder pulse to instruct the CCD drive circuit 29 to read images on the CCDs corresponding to the three colors of blue (B), green (G), and let (R) on the CCD unit 17, respectively. It is supplied through a strain line 57. The analog video signals for the three colors read in the CCD unit 17 are gain-adjusted so that the sensor sensitivities of each color are equal, and then output as digital values with 8-bit depth through the line 44. At this time, the video data start signal indicating the valid data range of all pixels on the CCD is also
It is output from the drive circuit 29. Digital video data of three colors B, G, and R (hereinafter referred to as video data) is input to a reader synchronization circuit 30.

Here, the video synchronization signal generation circuit 58 will be explained. The video synchronization signal generation circuit 28 receives a signal from the reader registration position sensor 15.
PHREGP line 45, VLE signal is line 46
And the value of the VLE signal counted according to the copying magnification from the image controller 24 is shown on line 47.
After the CCD unit passes through the reader registration position for image alignment, the VLE signal is counted to determine the time delay until the CCD unit reaches the leading edge of the document, that is, the reading start position. Further, a signal video enable signal (hereinafter referred to as VE signal) indicating the reading width in the main scanning direction according to the copy size is outputted and inputted to the reader synchronization circuit 30 via line 48.

As shown in FIG. 6-c, the reader synchronization circuit 30 performs a positioning operation in the main scanning direction for reading the same portion of the document on the CCD corresponding to each color of B, G, and R. In other words, CCD compatible with B, G, and R colors
Assuming that the interval between the two images is L1, the image at the position S1 of the document is input to the CCD corresponding to each color with a time lag of L1/V, where the main scanning speed is V. Therefore, the value of R inputted last in time is
B and G until the image of point S1 is input to the CCD.
Video data from CCD is transferred to reader synchronization circuit 3
B, G, and R three-color video data of the image at point S1 are temporarily stored in the buffer memory in 0 and outputted from the reader synchronization circuit 30. Also, VE
After the signal is input, that is, the video data of the original is input, a video data area (VDA) signal indicating the state in which the three color video data of B, G, and R are arranged is output. Note that the vertical direction in FIG. 6-c is the time axis, not the width scanning direction.

The video data subjected to color matching processing by the reader synchronization circuit is then inputted to a scaling buffer memory 31 and subjected to scaling processing.

(Magnification Variation Process) Here, the magnification variation process will be explained using FIG. 7. The scaling process in the main scanning direction is based on the printer's scanning speed.
This is done by keeping V1 constant and changing the reader scanning speed to V1/n. (n is the magnification ratio). This is because the upper limit of the driving frequency of the ink jet head, which is the image forming means of the printer, is lower than the upper limit of the driving frequency of the CCD. Therefore, in order to increase the copying speed when copying at the same size, the maximum inkjet drive frequency is used when copying at the same size. At this time, a variable magnification mode signal is transmitted from the image controller 24 to the video data synchronization signal generation circuit 28 through line 49 in FIG.
The frequency division ratio of the reader's motor encoder pulse is set so that the VLE signal has the same frequency at the same magnification and at variable magnification (Figure 7-a, 7-
b).

That is, as shown in Figure 7-a, when the motor encoder pulse φM is equal in size, it is divided into 1/6 as shown in φM1, and when it is reduced in size by 1/2, it is divided into 1/12 as shown in φM1/2.
When increasing the frequency by 2 times, the frequency is divided by 1/3 as shown in φM2, and when increasing by 3 times, the frequency is divided by 1/2. The motor encode pulse φM is doubled when the frequency is 1/2 of the same frequency, 1/2 when it is doubled, and 1/3 when it is tripled, so φM1, φM2, φM3 ,φM1/2
are actually the same frequency.

Figure 7-b shows the reading position on the manuscript,
It shows the moving distance of the CCD in a certain time t (=VLE section). When reducing the size to 1/2, the distance traveled is twice that of the original size, and when magnifying it to 2 times, the distance is moved 1/2 compared to the original size.

Further, the scaling process in the sub-scanning direction is performed by the scaling buffer memory 31 when each pixel of the RGB video signal sent from the reader synchronization circuit 30 in synchronization with the video clock φ (CLK8) is stored in the scaling buffer memory 31. This is done by controlling the address increment of (Figure 7-c).

This is achieved by inputting the scaling mode signal from the image controller 24 through the line 50 to the memory control circuit 32 and increasing or decreasing the number of clock pulses of the address counter when writing to the scaling buffer memory 31 in accordance with the scaling ratio ( Figure 7-d). As a result, the variable power buffer memory 31
When the double buffer memories 59a and 59b are in write mode (W), the data of the same pixel is written to n addresses when enlarged by n times, and when the data is reduced by 1/n, the data of n pixels is written. 1 pixel in
When the pixel data is written to the address and the read mode is entered, the address is incremented by the video clock φ-CLK8, and interpolation and thinning of the pixel data is achieved. In this embodiment, the motor speed on the reading side is changed, but the motor speed on the recording side may also be changed.

Another function of the variable magnification buffer memory 31 will now be explained using FIG. 7-d. Double buffer memory 59 in variable power buffer memory 31
For a and b, the address increment clock is switched between writing and reading, but this is due to VLE.
Since the signal is generated from the encoder pulses of the reader main scanning motor 6a, if uneven rotation of the motor occurs, the accuracy of the positional information between each main scanning over the entire sub-scanning area will be improved, but the frequency will be uneven.
In order to synchronize with the VLE signal and prevent fluctuations in the CCD accumulation time, the image reading cycle by the CCD is set to 1/2 of the minimum value of the VLE signal cycle.
As follows, shift clock of CCD17 φ−CLK4
is the video clock, and in order to have a frequency more than twice that of φ-CLK8, double buffer memories 59a and 59b are used.
The address clock when writing a same size copy of is
Using shift clock φ-CLK4 of CCD17,
When reading, the video clock φ-CLK8, which is a synchronization signal for pixel data in the reader and printer, is used.
is used.

As described above, in the variable magnification mode, the variable magnification buffer memory 31 and the memory control circuit 32, in addition to interpolating and thinning out pixel data in the sub-scanning direction, keep the CCD accumulation time constant and control the reader main scanning motor 6a. Pixel reading operation is performed in synchronization with the encoder pulse.

(Image Signal Processing) The video data of the three colors B, G, and R, which has been subjected to the above-mentioned scaling processing in the scaling buffer memory 31, is then sent to the image processing circuit 33, where it undergoes the processing shown in the block of FIG. It will be done. First, the video data of the three colors R, G, and B are corrected by the shading correction section 60 based on the data of the standard white board read in step 9. In this example, the CCD exposure amount E
Since the image light is read within the range where the linearity of the optical output voltage V is maintained, the following correction is applied.

Vs=Vsmax/VmaxV However, Vs: Output after shading correction V: Output from CCD Vmax: Output when reading whiteboard Vsmax: Setting output Video data with shading correction added is sent to the next logarithmic conversion section 61 At the same time as input light amount values are converted into ink density values, complementary color conversion is performed, and B, G, and R video data are converted into y, m, and c density data, respectively. The conversion formula is expressed by the following equation, where D is the ink density, Ep is the standard white plate reflected light amount, and E is the image light amount.

D=-logE/Ep The three color density data after conversion is then subjected to black extraction/
It is input to the UCR section 62 and edge extraction section 63.
Black extraction means calculating the amount of black ink to be applied from the density data of the three colors Y, M, and C. this is,
If you try to express black (hereinafter referred to as Bk) with three colors of Y, M, and C ink, it will be difficult to express complete black, and the amount of ink applied will be large, resulting in "bleeding" on the copy paper and excessive paper This is to prevent expansion. or
UCR (undercolor removal) is a method of reducing the amount of ink of each color Y, M, C in relation to the amount of black ink when black ink is used by black extraction. In this example, the following equation is calculated. .

BK={min(Y,M,C)−a ₁ }a ₂ Yout=(Y−a ₃ Bk)a ₄ Mout=(M−a ₅ Bk)a ₆ Cour=(C−a ₇ Bk)a ₈ However, a ₁ to _{a 8} are arbitrary numbers. Edge extraction strengthens the outline of the image by extracting the edges and lines of the image and adding the amount of edges extracted with a specific relationship to the original image data. This is to try. In this embodiment, edges were extracted using a 5×5 convolution mask in the main scanning and sub-scanning directions. In order to remove noise components from the extracted edge amount, a method was used in which low-level detection values were not added to the image data by selecting an arbitrary threshold. Further, the edge extraction section outputs a video data valid signal (hereinafter referred to as a VDV signal) indicating a region where edge extraction using a Laplacian mask is possible during the video enable state. This means that when using a 5x5 Laplacian mask, VD from the third and subsequent VLE signals after the VE signal becomes active.
V. Indicates that a signal is output.

Concentration data YMC after UCR is masking part 6
4 and undergoes masking processing. Masking is a matrix calculation process to correct turbidity when ink is superimposed due to unnecessary absorption of ink, and the following calculations are performed.

Yout Mout Cout=a ₁₁ , a ₁₂ , a ₁₃ a ₂₁ , a ₂₂ , a ₂₃ a ₃₁ , a ₃₂ , a ₃₃ Y MC However, a ₁₁ to a ₃₃ are arbitrary series numbers.

Next, the masked Y, M, C 3 colors and
The Bk density data is input to the output gradation correction circuit 65, where correction is applied to flatten the gradation when expressing a pseudo halftone by the dither method used in the subsequent binarization circuit. The correction formula is shown below.

Yout = {a ₅₁ (Y-a ₅₂ )} ^a ₅₃ Mout = {a ₅₄ (M-a ₅₅ )} ^a ₅₆ Cout = {a ₅₇ (C-a ₅₈ )} ^a ₅₉ However, a ₅₁ to _{a 59} are optional is a series of

Next, the output gradation corrected density data, Y,
M, C, Bk and edge amount ED are input to a binarization unit 66 and subjected to binarization processing.

In this embodiment, the binarization process uses a systematic dither method to uniformly binarize the image data, and then corrects the pixel of interest using edge data ED. In other words, when correction is performed based on the truth table shown in FIG. 8-b, an image with blurred edges due to the systematic dithering method becomes a pseudo-halftone image with enhanced contours.

The video signal processed by the image processing circuit 33 as described above and converted into binary signals of four colors (Y, M, C, Bk) for the inkjet head (hereinafter referred to as density data) is stored in the reader/printer synchronous memory 33. is input through line 51 to

(Processing on the Printer Side) Before explaining the operation of the reader/printer synchronization memory 34, the head data synchronization signal generation circuit 37 will be explained. In the head data synchronization signal generation circuit 37, as shown in FIGS. 6-d and 6-e, the data is synchronized with the encoder pulse of the printer main scanning motor 6b, and is the position information in the reader main scanning direction, and the resolution in the sub-scanning direction is l. The nozzle line enable signal (hereinafter referred to as
NLE) is created. NLE signal is line 52
The signal is sent to the head synchronization signal generation circuit 38 through the head synchronization signal generation circuit 38. A signal from the printer register position sensor 16 is input to the head synchronization signal generation circuit 38 through a line 53, and the signal is inputted to the head synchronization signal generation circuit 38 to determine the registration position.
By counting the time delay until the BJ head unit 18 passes through and reaches the copying position by counting the NLE signal, a signal indicating the copy width in the main scanning direction according to the copy paper size, that is, a nozzle enable signal for each color (hereinafter referred to as NE ) to the reader/printer synchronization memory 34 via line 54.

The reader/printer synchronous memory 34 is connected to the reader main scanning motor 6a and the printer main scanning motor 6.
The density data input from the reader section is output in synchronization with the speed of the printer, that is, in synchronization with the NLE signal. When the VDV signal is input from the image processing circuit 33, only the valid part of the video data is sequentially written in synchronization with the VLE, and the VDV signal is input from the head synchronization signal generation circuit 38.
When the NE signal is input, that is, when there is an inkjet head in the copying area, the density data written in the memory is sequentially read out as head data in synchronization with the NLE. The data of each recording head read from the reader/printer synchronization memory 34 is output to the printer synchronization circuit 35 through line 55.

In the printer synchronization circuit 35, the head data of the four colors Y, M, C, and Bk, which are the color-separated images of _one point of the document S', are simultaneously input via the line 55. Position shifting processing is performed by the distance in the main scanning direction between the heads corresponding to each color.

In other words, as shown in Figure 6-f, Y, M, C, Bk
If the distance between the ink jet heads corresponding to each color is L ₂ , the images of Y, M, C, and Bk color inks at the x point on the document are printed superimposed at the same point in the main scanning direction of the ink jet head. It is sufficient to set the main scanning speed to V and print each color head with a time delay of L ₂ /V. In other words, the M, C, and Bk color head data is temporarily stored in the buffer memory in the printer synchronization circuit 35 up to the Y head position where the image is printed first in the forward direction of main scanning, and then sequentially output from the printer synchronization circuit 35. This is accomplished by inputting the information to the printer head drive circuit 36.
In FIG. 6-f, the vertical direction is the time axis, not the sub-scanning direction.

Further, an NE signal is input to the printer synchronization circuit 35, and the NE signal is a signal indicating the copying area of the Y head.From this NE signal, a head drive enable signal (hereinafter referred to as HDE signal) and line 5
6 to the printer head drive circuit 36. In the printer head drive circuit 36, the NE signal,
A drive signal for the inkjet head in the printer head unit 18 and head data corresponding to each color are output to the printer head unit 18 from the NLE signal, the HDE signal, and the clock φ.

Through the above-described flow, the image of the document is read by the reader 3 and formed into an image by the printer 4.
When the image controller detects the end of the VE signal and NE signal generated from the reader 3 and the printer 4, it determines the end of main scanning one line copying (step 14) and moves to step 15.

(Post-processing) In step 15, the sequence controller 23 first turns off the exposure lamp 19 and turns off the motor driver circuits 26a and 26 of the reader and printer.
Input the motor OFF signal to b, then send the speed data in the reverse direction and the rotation start signal, turn on the motors 6a and 6b, respectively, and start reverse.
It stops at each main scanning home position 11, 12. At the same time, in step 16, the reader sub-scanning stepping motor 9a (hereinafter referred to as reader sub-scanning motor) is fed a predetermined number of pulses corresponding to the copying magnification in a rotation mode in the sub-scanning forward direction to feed the reader for one sub-scanning. Similarly, the printer sub-scanning stepping motor 9b (hereinafter referred to as printer sub-scanning motor) also performs one sub-scanning step. Next, the process proceeds to step 17, where the sub-scanning counter is incremented, and in step 18, it is determined whether or not the sub-scanning counter has advanced by the copy width in the sub-scanning direction.If the count has not advanced, the process returns to step 8, and the main scanning is started. This is repeated until the sub-scanning counter increases. When the sub-scan counter is up, the process moves to step 2, where a predetermined number of pulses are sent to each sub-scan motor of the reader printer in a sub-scan backward rotation mode to return to the home position. Next, proceed to step 3, perform a head recovery operation to clean the inkjet nozzle head after copying is completed, and proceed to step 4, cap the head.
In step 5, the next copy command is input. The above is an overview of the device operation.

(Spatial filtering process) Next, the details of the filtering process will be explained in Sections 9-a to 9-e.
This will be explained using FIGS. 10 and 11. As described above, in this embodiment, edges are extracted using a 5.times.5 convolution mask, and this mask is shown in FIG. 9-a. The mask series is expressed by the following relational expression, and the edge amount ED of the center pixel E can be extracted as a second derivative (Laplacian) together with the polarity.

E-(A+B+C+D+E+F+G+H+I)/
8. Generally speaking, when one scanning direction of an image is considered as a function f(x), the shade change portion or color change portion of the image is as shown in FIG. 9-6A. At this time, the second derivative d ² f/dx ² of f(x) is as shown in Figure 9-b B, and f(x) d/d 2 _f /x ² is as shown in Figure 9-b D. It is known that it has the effect of intensifying changes in images. This effect can be enhanced by using a square mesh Laplacian mask in the main and sub-scanning directions of the image to strengthen the contours in all directions of the image.

In this embodiment, a convolution operation is used as a spatial filtering process, and contour enhancement using a Laplacian mask is shown. If the above-mentioned Laplacian is applied to a scanning method similar to that of this embodiment, a problem as shown in FIG. 10 will occur.
That is, when focusing on the sub-scanning of the N and N+1 lines, the application range of the mask is from the 3rd pixel to the (n-2) pixel, where n is the number of CCD pixels. This is because when attempting to apply a mask to a discontinuous portion of read pixels, if the pixel of interest (center pixel) is placed at the edge of the image, the number of mask data pixels becomes insufficient. In order to solve this problem, the pixel data at the discontinuous part, that is, the trailing edge data of the VLE in the Nth line sub-scanning, can be stored in memory and used as the leading edge data of the VLE in the N+1th line sub-scanning. For example, if an A1 size document is read at a resolution of 16 lines/mm, 26.3KByte (as 8bit/pixel) is calculated from A1 longitudinal width x resolution x number of memory lines.
A counter with 13456 steps is required, and the control circuit is also complicated, which poses problems. Therefore, in the present invention, the following method was implemented in order to solve the above problem. This will be explained using FIG. 11.

Assuming that the number of pixels of the document reading CCD is m, a 5×5 mask is used in this embodiment, so pixels from pixel m-3 at the rear end of the VLE signal of the Nth sub-scanning line to m are sub-scanned. When reading the N+1st line, the lines are overlapped and read twice. In other words, by superimposing pixels 1 to 4, a Laplacian mask can be applied to all pixels to be read, and an image with perfectly enhanced contours can be obtained. Also, at this time, the number of data n to the inkjet head is m-4, which means that the number of recording elements in the head may be smaller than the number of CCD pixels. Furthermore, the feed width in one sub-scanning step of the reader and printer at this time is also m-4. This can be expressed as: n=m-(x-1) where m: number of pixels read by the image sensor; n: element used for recording in the multi-write head; x: number of meshes in one direction of the mask. The above formula is for the case where all the number of pixels read by the image sensor is used, and when not all are used, n≧
It is sufficient if m-(x-1) holds true. Also, in the main scanning direction, if _S6 in FIG. 11 is the edge of the document, the video data area section starts from _S7 . Regarding the trailing edge of the document in main scanning, the video data area section ends two places before the edge of the document. However, reading is performed up to the edge of the document.

(Encoder) Next, regarding the specific configuration of the encoder, Section 7-e
This will be explained based on the diagram. When the reader main scanning motor 6a starts main scanning at step 12 in FIG.
The signal is input to the frequency divider circuit 71 and is frequency-divided to 1/n by the first-stage fixed frequency divider 71a. Here, the effect of the fixed frequency divider 71a will be explained.

FIGS. 12a, b, d, and e schematically show the rising edge of the encoder pulse and the pulse after frequency division. Further, FIGS. 12c, f, and g show waveforms of encoder pulses and frequency-divided pulses measured with an oscilloscope or the like. The period T ₀ of an ideal encoder pulse is constant, and naturally the pulse period T ₁ after frequency division is also constant. However, in an actual system, the period of the encoder pulse has an error of ΔT ₀ with respect to T ₀ due to angular errors caused by the precision of encoder processing, bumps, backlash, processing precision, etc. of the main scanning drive mechanism, and load fluctuations. If this is used as pixel position information as it is, the image in the sub-scanning direction will become erratic. However, by dividing the encoder pulse, the error is averaged, and T ₁ : ΔT ₁ (angular difference in pulse period after division) is
T ₀ : Smaller than ΔT ₀ . In this example, T ₀ = 52 μS, ΔT ₀ = 3.6 μS (6.9%) T ₁ =
625μS, ΔT ₁ = 20μS (3.2%) and error ratio is 1/2
It was as follows.

The motor encoder pulse φM whose error has been reduced by the fixed frequency divider 71a as described above is frequency-divided by the next stage variable frequency dividers 71b to 71e as shown in FIG. 7-a, and is input from the line 49. The AND circuits 72a to 72d and the OR circuit 73 are gated by the variable magnification mode signal, and one of them is selected and output as the frequency division pulse φM4. As a result, even if the displacement of the reader main scanning motor 6a changes in accordance with the copying magnification during variable-magnification copying, a pulse φM4 of a constant period is generated. Therefore, as shown in Fig. 7-b in each variable magnification mode, during reader main scanning, any part S ₁₀
- S ₁₂ , the number of lines to be read changes according to the magnification ratio, and as a result, regardless of the magnification ratio, if the copy paper size is constant, it is possible to read as many lines as the main scanning line of the printer. Double copying is possible. On the other hand, during reader main scanning, when the reader registration position sensor 15 is detected, the D-type flip-flop 61 (hereinafter referred to as D-F/F) and the J/K
-F/F62, 7th-f by NAND circuit 63
Synchronized with the rising edge of video clock 8 as shown in the timing chart in the figure.
signal and CNTφM4ENABLE signal are generated
CNTφM4ENABLE signal is passed through line 81
It is input to AND circuit 64 and to AND circuit 68 through line 84.

At this time, φM4 is input to the A, ND circuit 64 through the line 83, so
Outputs φM4 continuously from the time CNTφM4ENABLE is input, D-E/F65, J/K-
F/F66, AND circuit 69, inverter circuit 6
7, the counter 70 and the AND circuit 68
The VLE signal (VIDEO
LINE ENABLE) and VIDEO LINE HSYNK
A signal (hereinafter referred to as the VLH signal) is generated.
Specifically, when the counter 70 receives CNTφM4ENABLE through the line 84 to the AND circuit 68, the load state of the load terminal of the counter is released and the input of the count preset value from the terminals _D1 to _DN is completed. After that, when the VLH signal is output from the AND circuit 69 for one cycle of CLK8 and the VLE signal is output from the J/K-F/F 66, it is input to the count enable terminal E of the counter 70 through the line 85, and the rising edge of 8 is counted. When it starts and finishes counting the preset value, a ripple clock is output from the terminal RC and the J/K
- It is input to the K terminal of F/F 66, synchronized with 8, and the VLE signal section ends. As described above, the reader registration position sensor 1
5 is detected, the rising edge of φM4 is detected and V.
By counting the section video clock 8 in which the LE signal is preset by the counter 70,
In other words, the number of pixels corresponding to one line of CCD scanning is output.

Here the VLE signal is passed through line 86 to J/K
- Since it is connected to the clear terminal of F/F78 and both J and K terminals, φ-CLK8 is generated in the section where the VLH signal is output. The clock φ before frequency division.
−CLK4 1 period section CCD start signal (hereinafter
CCD STRT signal) is output once from the NOR circuit 80. The signal is input to the CCD drive circuit 29 through the line 57, and the CCD drive circuit 29 reads the data of the CCD unit 17 in synchronization with the signal, and outputs the video data start signal (hereinafter referred to as
DATA STRT) is output and input to the video data synchronization signal generation circuit 28 through line 87.

Here, the signal section is CCD
The effective image area of one line of the CCD corresponding to each color in the unit 17 is shown.

The signal input to the video data synchronization signal generation circuit 28 via the line 87 is transmitted to the inverter circuit 74, D-F/F 75,
The AND circuit 77 converts it into a video data enable signal (VDE signal) and outputs it. Further, the CCDSTRT signal is again output by the DF/F79AND circuit 76 via the NOR circuit 80 for one cycle of CLK4 from the fall of the VDE signal.

In this way, a signal is forcibly output when the rising edge of φM4 is detected, and thereafter it is output at a constant cycle. Moreover, the video signal is read out from the CCD using the video clock φ−.
Since the clock φ-CLK4, which is twice as fast as CLK8, is used, it is possible to read twice during the VDE period, and by sampling the second video data, it is synchronized with φM4 and changes the CCD accumulation time. The image can be read without any interference.

Also, the signal is input to the frequency divider circuit 71 via the line 82 and is input to the internal frequency divider 71a.
- Clear all 71e. This causes φM4 to rise at the same time as the leader registration position sensor 15 is detected.
In other words, the registration position sensor 15 can detect an error of only one pulse of the motor encoder pulse when the motor is moving at the highest speed.

Similarly to the operation of the reader section described above, the head data periodic signal of the printer section is also obtained by frequency-dividing the encoder pulse of the printer main scanning motor 6b from the detection of the printer registration position sensor 16 by the head data synchronization signal generation circuit 37. Reset the frequency pulse and start NLE from the reset pulse.
A signal is created.

Further, the encoder pulses on the printer side are also frequency-divided by the frequency divider circuit in the head data periodic signal generation circuit 37 in the same way as on the reader side, so that errors included in the encoder pulses are reduced. The NLE signal is formed by the frequency-divided pulse, and the BJ head drive circuit 3
6 controls the recording operation of the head.

<Effects> As described above, according to the present invention, the first control means causes the recording head to perform a blank ejection process and causes the reading sensor to perform a shading correction process in response to an instruction to start an image forming operation. Therefore, the time required for preprocessing of reading and recording operations can be shortened. Further, the second control means starts relative scanning of the reading sensor and the recording head to perform an image forming operation after the first control means has completed the dry ejection process and the shading correction process. , deletion of image signals, etc. can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an apparatus according to an embodiment of the present invention, FIG. 2 is a schematic perspective view of an apparatus according to an embodiment of the present invention, FIG. 3 is a block diagram of a control circuit according to an embodiment of the present invention, and FIG. 4 is a sequence diagram. FIG. 5 is a sequence flowchart; FIG. 6-a is a diagram showing the relationship between the reader's document and the reading synchronization signal; FIG.
Figure b is an enlarged view of part A in Figure 6-a, Figure 6-c is an explanatory diagram of the positional shift of the reading CCD of each color, and Figure 6-d
Figure 6-e is a diagram showing the relationship between the copy paper and the recording synchronization signal, Figure 6-f is an explanatory diagram of the misalignment of the recording ink jet heads of each color, and Figure 7-a is the reader main scanning motor. Fig. 7-b is a diagram showing the reading pixel interval in the main scanning direction according to the magnification ratio, and Fig. 7-c is the interpolation timing according to the magnification ratio. , an explanatory diagram of the thinning operation, FIG. 7-d is a detailed circuit diagram of the scaling buffer memory 31 of FIG. 3, FIG. 7-e is a detailed circuit diagram of the video data synchronization signal generation circuit 28 of FIG. 3,
Fig. 7-f is a timing chart of the video data synchronization signal, Fig. 8-a is a detailed circuit diagram of the image processing circuit 33, and Fig. 8-b is an input/output diagram of the edge extraction circuit 63 in Fig. 8-a. A diagram showing the relationship, FIG. 9-a is a diagram showing a convolution mask, and FIG. 9-b is an explanatory diagram of limbal stiffness due to spatial filtering.
Fig. 10 is an explanatory diagram of a scanning system installed in a device similar to the embodiment of the present invention, Fig. 11 is an explanatory diagram of a scanning scheme according to the embodiment of the invention, and Fig. 12 is a time chart of encoder pulses and frequency division pulses. be.

Claims (1)

[Claims] 1. A reading sensor that optically reads an image signal to be recorded while relatively scanning a document, and based on the image signal from this reading sensor,
a recording head that forms an image by discharging ink while scanning it relative to a recording material; and a recording head that performs a blank discharge process in response to an instruction to start an image forming operation; a first control means for causing the first control means to perform a shading correction process; and after the first control means completes the dry ejection process and the shading correction process, starting relative scanning between the reading sensor and the recording head; An image forming apparatus comprising: a second control means for performing an image forming operation.