JPH118756A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device capable of minimizing variable power errors to respective variable power rates. SOLUTION: In the case of performing variable power correction, for instance, an original for which the two lines of a length set beforehand, normally the length of 100mm, are drawn one each in a main scanning direction and a sub scanning direction is copied for the three variable power rates (400, 100 and 400%) and variable power rate errors E.40, E.100 and E.400 at the respective variable power rates are found and inputted from an operation part 7. Also, a variable power correction value Δe(ΔE) for the variable power rate M other than the variable power rates of 40, 100 and 400% is calculated in a control part 6 by the linear approximation expression of Δe=(E.100E.40)M/60+(100 E.40-40E.100)/60 if 40%<= the variable power rate<100% and Δe=(E.400-E.100)M /300+(400E.100-100E.400)/300 if 100% <= the variable power rate <400%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a magnification changing function, and more particularly, to an image forming apparatus characterized in correcting a magnification.

[0002]

2. Description of the Related Art Recently, a multifunctional image forming apparatus, for example, a copying machine, has a variable magnification function. This scaling function can be expanded, for example, from B5 to A4, or from B4 to A4.
In addition to the function of reducing the number to 5, it is often set to perform the enlargement or reduction every 1%. In general, zooming is performed by controlling the write clock in the main scanning direction and changing the scanning speed in the sub-scanning direction. Therefore, in such a copying machine, it is considered that a correction function is required if the magnification is required to be accurate. As a device provided with this correction function, for example, a device described in MitaCreage 630 issued in November 1996 and a device described in Japanese Patent Application Laid-Open No. 7-74938 are known.

The former performs correction based on the same magnification (magnification of 100%), and the latter adjusts to satisfy the frequency condition of a write clock for input data, thereby achieving an arbitrary magnification and finer adjustment. It is possible to perform variable magnification.

[0004]

However, in the former technique, since there is only one point when the magnification is equal, the magnification error after the correction cannot be reduced depending on the magnification. Cases arise. In the latter technology,
Although it has a magnification adjustment technology, it is not configured to automatically calculate a correction value from multiple magnification errors. It is necessary to improve the accuracy of each functional unit and to provide an adjustment mechanism, which leads to an increase in cost and a problem of requiring a long adjustment time.

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and an object thereof is to provide an image forming apparatus capable of minimizing a scaling error with respect to each scaling factor.

It is another object of the present invention to provide an image forming apparatus capable of efficiently generating a correction value for reducing a magnification error.

[0007]

In order to achieve the above object, a first means comprises an image forming means for forming an image based on an input image signal, and a changing means for setting a magnification of the formed image. An image forming apparatus comprising: a magnification setting unit; a magnification unit configured to perform magnification based on a set magnification; and a magnification correction unit configured to correct a magnification performed by the magnification unit. The correcting means is configured to detect a magnification error of the output image with respect to a plurality of magnifications, and to set a correction value for the magnification set by the magnification means based on the error.

The second means may be such that the first means includes at least a minimum value or a value near a minimum value and a value near a maximum value or a maximum value of a magnification ratio settable by the magnification means. Multiple magnifications were set.

The third means constitutes a magnification correcting means such that when setting a correction value for each magnification, the correction value is determined by a preset approximate expression using the magnification error.

[0010]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a digital copying machine as an image forming apparatus according to this embodiment. The digital copier includes a scanner 1 for optically reading a document G, a reading processing unit 2 for processing an image signal read by the scanner 1 and converting the image signal into an electric signal, and a predetermined processing for an image signal processed by the reading processing unit 2. Processing unit 3 that performs correction and the like on the image, a writing processing unit 4 that converts a signal processed by the image processing unit 3 into a signal that can be written by a laser, and a writing signal that is output from the writing processing unit 4. Writing unit 5 for performing writing with a laser beam and visualizing the written image, a control unit 6 for controlling these units, and inputting an instruction for an operator to instruct a desired image formation. It is basically composed of an operation unit 7 that performs the operation.

The scanner 1 includes a light source 1-1 for illuminating the original G, first to third mirrors 1-2 to 4 for guiding light reflected on the surface of the original G to the CCD 1-6, and a lens 1--1.
5, and a scanner driving motor 1-7 for scanning the scanner 1 in the sub-scanning direction, and performs reading scanning with the original G placed on the contact glass 1-8.

The read processing unit 2 includes a scanner drive motor control clock signal required for reading and scanning, a timing signal for CCD operation, a timing generation unit for generating timing signals used in the read processing unit 2 and other processing units, and a CCD 1. -6
It is composed of an analog circuit for adjusting the signal level and a sample and hold, an A / D converter, a shading corrector, a controller 6 and a CPU I / F for communication with other units.

The image processing unit 3 performs a scaling process, a filtering process, a gamma correction process, and the like.

The write processing section 4 is composed of a write main scan control section, a write sub-scan control section, an LD power control section, a synchronization detection control section, a polygon motor control section, and a main scan magnification correction section. ing.

The writing mechanism section 5 includes a writing optical system 5-1, a photosensitive member 5-2, a charging device 5-3, a developing device 5-4, and a transfer portion 5-
5, cleaning section 5-6, paper transport section 5-7, fixing section 5
-8, etc.

The control unit 6 includes a CP as a central control unit.
U, a ROM that stores an operation program of the CPU and fixed data, a RAM that functions as a work area of the CPU and stores dynamic data, and an I / O, etc., and controls each unit and the whole. The operation unit 7
The control state of each unit is changed or an operation is performed in accordance with an input signal from the CPU.

The operation unit 7 has the same functions as the operation unit of a conventional copier, and is also capable of inputting a scaling ratio and a scaling correction value.

At the time of scaling, the value of the scaling ratio is input from the operation unit 7, and the value determines the original scanning speed of the scanner 1, the thinning-out by the scaling unit 3, the interpolation, and the contents of the multiple-time interpolation. , Thinning, interpolation, multiple interpolation, that is, scaling in the main scanning direction is performed as follows.

(1) Main Scanning Magnification Operation Magnification processing in the main scanning direction is performed using a cubic function convolution method. Here, for example, the magnification is changed at intervals of 0.5% between 40% and 400% using an interpolation function. The selection of enlargement / reduction is made by the command (kakud
Switch with ai). As for the resampling timing of the image data at the time of scaling, the scaling control data given in advance to the built-in RAM (1K × 4 bits) is read and controlled according to the data. FIG. 2 is a functional block diagram of the scaling unit at this time. In the figure, HI [9: 0] is image input data (actually masked),
The signals are input to the first or second selectors sel1 and sel2. HO [9: 0] is output data (actually processed). Bout [9: 0] is output data to the built-in FIFO, bin1 [9: 0] and bin2 [9: 0] are input data from the built-in FIFO, and are mixed (MIX)
And input from the mixer (MIX) to the second or third selectors sel2 and sel3. Note that the breakdown of the 10-bit image data to be handled is that the upper 8 bits are multi-value data and the lower 2 bits are binary data.

Ram dtrd [2: 0] indicates resampling position data from the internal RAM. Bout, bin
(Bin1 or bin2 selected synthesized signal) has 5K ×
Two 10-bit FIFOs are connected in parallel, and r
En1 and ren2 and wen1 and wen2 are controlled by scaling control data, and a scaling process is realized by toggling two FIFOs. The interpolation processing unit (hokan block) has a second selector se
l2 and ram The signal from dird is input.

(1-1) Processing method at the time of equal magnification FIG. 3 is a timing chart showing processing timing at the time of equal magnification, and FIG. 4 is an explanatory diagram showing a flow of image data at that time.

A command for selecting an enlargement / reduction kakudai =
As “Low”, the data on the A input side is selected by each selector. The input data HI passes through the hokan block via sel2, and is written from sel1 to the FIFO by Bout. Next, the image data written in the FIFO is read out as bin1 or bin2 after a delay timing of one line, and read enable ren1,
Synthesize into bin based on the active state of ren2 and sel
3 and output as HO. At this time, as shown in the timing chart of FIG. 3, since ren and wen are L, the speed conversion is not performed and the same-size operation is performed.

(1-2) Processing Method at the Time of Reduction FIG. 5 is a timing chart showing processing timing at the time of reduction, and FIG. 6 is an explanatory diagram showing the flow of image data at that time.

Selection command for enlargement / reduction kakudai =
As “Low”, the data on the A input side is selected by each selector. The input data HI is sent to the hokan block via sel2, where interpolation is performed. The sampling position for the interpolation is determined by sequentially reading the scaling control data previously written in the built-in RAM. The image data after interpolation is F from sel1 by Bout.
Write to IFO. At this time, Bout outputs data thinned out under the control of wen. The image data written in the FIFO is bin1 or bin2 after one line delay.
And read enable ren1, ren
Under the active state of No. 2, it is combined with bin and output as HO through sel3. At the time of reading, ren =
Under the constant velocity condition of L, the image data from the FIFO is taken in as it is. FIG. 5 shows the timing relationship between clk, wen, and ren at that time.

(1-3) Processing Method at Enlargement FIG. 7 is a timing chart showing processing timing at the time of enlargement, and FIG. 8 is an explanatory diagram showing a flow of image data at that time.

Selection command for enlargement / reduction kakudai =
Each selector selects the data on the B input side as “High”. The input data HI is written to the FIFO by Bout through sel1. At the time of writing, the input data is written as it is to the FIFO under the uniform speed condition of wen = L. FIFO
Is read out as bin1 or bin2 after one line delay timing, and is combined with bin under the active state of the read enable ren1, ren2. At this time, the read timing of the image data is controlled by ren, and the speed conversion is performed. The read data is sent to the hokan block through sel2 and performs an interpolation operation. The sampling position for the interpolation is determined by sequentially reading the scaling control data previously written in the built-in RAM. Then, enlargement processing is performed by changing the sampling position for the data whose reading has been stopped and performing interpolation processing a plurality of times. The interpolated image data is output as HO through sel3. FIG. 7 shows clk and we at that time.
The timing relationship between n and ren is shown.

(2) Magnification control data Magnification control data written in the built-in RAM is as follows.

That is, the built-in RAM has a structure of 1024 × 4 bits, and thinning / duplication control data an (1 bit) for performing speed conversion and resampling position data bn (3) for selecting a coefficient for interpolation calculation. Bit) is stored and used for controlling the scaling operation. Reading and writing of data to the built-in RAM are performed via the CPU. Built-in RAM
Has different meanings in the enlargement mode and the reduction mode.

(2-1) Enlargement mode: "an" is used for overlap control. "An" = "H": The next image data is read from the FIFO.

An = “L”: reading of data from the FIFO is stopped.

(2-2) Reduction mode: "an" is used for thinning control. "An" = "H": Writes image data to the FIFO.

An = “L”: Writing to the FIFO is prohibited.

(2-3) bn is used as resampling position data in any mode. The number of data in the reduction mode is 100, and the number of data at the time of enlargement is a scaling factor (%).

On the other hand, when the original is scaled, the image length on the copy should be the length of the image on the original corresponding to the image multiplied by the scaling ratio. However, due to errors in the original scanning speed, errors in the reading optical system, errors in the writing optical system, errors in the transfer speed of the transfer paper, and expansion and contraction of the transfer paper, there is a change between the input magnification and the actual copy. An error occurs in the magnification. The error is a magnification value, for example, 40 to 4
It changes with a value such as 00%. The error correction, that is, the magnification change correction, is performed by slightly changing the document scanning speed and the writing frequency. The correction in the main scanning direction is performed by changing the writing frequency, and the correction in the sub-scanning direction is performed by changing the document scanning speed.

That is, when the magnification in the main scanning direction is out of order as shown in FIG. 14A, it is necessary to correct the magnification in the main scanning direction to a normal magnification.
As shown in FIG. 14B, the deflection angle of the polygon mirror can be changed by changing the pixel clock (frequency clock) in the writing system, thereby making it possible to correct or correct the magnification. The change of the write frequency is performed by a variable clock generation circuit in the write processing circuit 4. As shown in FIG. 9, the clock generation circuit includes a first crystal oscillator 4-1, a phase comparator 4-2, a low-pass filter 4-3, a VCO 4-4, a frequency divider 4-5, and a second Crystal oscillator 4-6, mixer 4-7, and tuning unit 4-8
And a comparator 4-9.

The first crystal oscillator 4-1 generates a reference frequency signal f0 and inputs it to the phase comparator 4-2. This phase comparator 4-2 has a VCO4 by a frequency divider 4-5.
The frequency f1 (f1 = f2 / n) obtained by dividing the frequency signal f2 output from the -4 by n is also input. The phase comparator 4-2 compares the phases of f0 and f1, and outputs To the low-pass filter 4-3. Low pass furta 4
At -3, a voltage signal from which high-frequency noise components have been cut is output to the VCO 4-4, and the VCO 4-4 generates a signal of frequency f2 from the relationship between the input voltage and the output frequency as shown in FIG.

The f2 signal is also input to a mixer 4-7, where the f2 signal is mixed with a reference frequency signal f3 from a second crystal oscillator 4-6 to produce a frequency signal f4 (f4 =
f3 ± f2). This frequency signal f4 is further input to the tuner 4-8, and the sum signal of f3 and f2 is converted to f5
(= F3 + f2) is input to the + terminal of the comparator 4-9, compared with the ground side, and the clock frequency f5 (f5 = f3
+ N · f0).

At this time, the output f0 of the first crystal oscillator 4-1, the output of the phase comparator 4-2, the low-pass filter 4-
The output timings of the output 3, the output f2 of the VCO 4-4, the output f1 of the frequency divider 4-5, the output f3 of the second crystal oscillator 4-6, and the output f5 of the comparator 4-9 are shown in FIG. As shown.

When the variable clock circuit is configured as described above, the output frequency f5 can be changed by changing the frequency division ratio of the variable clock generation circuit based on the signal from the control unit 6. The scanning speed of the original is changed by changing the rotation speed of the scanner motor 1-7 according to a signal from the control unit.

The magnification correction is to bring the magnification error represented by the magnification error = magnification on the copy−magnification set to near zero. FIG. 13 is a graph showing the relationship between the magnification ratio and the magnification error.

In the case of performing magnification correction, for example, a document having two lines each having a predetermined length, usually 100 mm, drawn in the main scanning direction and the sub-scanning direction, respectively, is used. Copying is performed for each of the four magnifications (40, 100, and 400%), and the magnification error E.E. 40,
E. FIG. 100, E.C. 400 is obtained and input from the operation unit 7. Further, the scaling correction value Δe (ΔE) for the scaling factor M other than the scaling factors of 40, 100, and 400% is as follows: when 40% ≦ the scaling factor <100%, Δe = (E.100−E.40) M / 60+ (100E.40-40E.100) / 60 100% ≦ magnification <100% Δe = (E.400-E.100) M / 300 + (400E.100-100E.400) / 300 It is calculated by the control unit 6 using a linear approximation formula. Here, Δe is rounded off to the second decimal place to become ΔE.
The minimum interval of ΔE is 0.1. The minimum interval of ΔE is limited by the minimum change width of the document scanning speed and the minimum change width of the writing frequency. For example, setting the minimum interval of ΔE to 0.1% is 1/100 of the original scanning speed corresponding to each magnification.
It is assumed that it can be changed at a speed interval of zero. When the writing frequency is not corrected, it is not changed by the scaling factor.
It is assumed that the frequency can be changed at an interval of 1/1000 of the frequency. When ΔE> 0, the original scanning speed is increased by ΔE%, and the writing frequency is decreased by ΔE%. When ΔE <0, the document scanning speed is reduced by ΔE%, and the writing frequency is set to ΔE%
Enlarge.

Returning to FIG. 13, the solid line in FIG. 13 shows the magnification error before correction with respect to the magnification, and the broken line shows the magnification range 40 to 40 based on the magnification error at three magnification points.
This is a linear approximation of the scaling error at 0%. The alternate long and short dash line indicates a case where the correction value is obtained based on a magnification error of 100%. The magnification error after correction using the linear approximation is the difference between the broken and solid lines. 1 point (100% magnification)
The magnification error after the correction based on the correction value in (1) is the difference between the broken line and the solid line. It can be seen from the figure that the former difference is smaller than the latter difference.

In this embodiment, the magnification ratio is 40
The reason for using% and 400% and their magnification errors is that their values are the minimum and maximum values of the variable magnification range, which is advantageous for reducing the magnification error after correction. . The reason why the scaling factor of 100% is used is that the value is usually used frequently.

In this embodiment, three magnifications have been described, but two magnifications may be used. However, in the case of two points, only one approximation formula for scaling correction is required. Further, four or more points may be used, or the approximate expression may be two-dimensional. These are selected according to the magnification error for each magnification of the copying machine.

[0046]

As described above, according to the first aspect of the present invention, the magnification correcting means detects an error in the magnification of the output image with respect to a plurality of magnifications, and based on this error, the magnification is corrected. Since the correction value for the scaling factor set by the means is set, a highly accurate zoomed image can be obtained at the time of scaling.

According to the second aspect of the present invention, the plurality of scaling factors include at least a minimum value or a vicinity of the minimum value and a value near the maximum value or the maximum value of the scaling ratio that can be set by the scaling means. Therefore, the correction values corresponding to the minimum value and the maximum value of the scaling factor are used, so that highly accurate correction can be performed.

According to the third aspect of the present invention, when setting the correction value for each scaling factor, the scaling factor correction means determines the correction value by a preset approximate expression using the scaling factor error. By simply inputting a pair of a magnification and a correction value corresponding to the magnification, it is possible to calculate the correction of each magnification within the magnification range, thereby enabling efficient correction.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a schematic configuration of a digital copying machine according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a circuit configuration of a scaling processing circuit according to the embodiment;

FIG. 3 is a timing chart showing output timings of signals at the same magnification of the variable magnification processing circuit according to the embodiment.

FIG. 4 is an explanatory diagram showing the flow of signals at the same magnification of the scaling processing circuit according to the present embodiment.

FIG. 5 is a timing chart showing signal output timings when the scaling processing circuit according to the present embodiment is reduced.

FIG. 6 is an explanatory diagram showing a signal flow when the scaling processing circuit according to the present embodiment is reduced.

FIG. 7 is a timing chart showing signal output timing when the scaling processing circuit according to the present embodiment is enlarged.

FIG. 8 is an explanatory diagram showing a signal flow when the scaling processing circuit according to the present embodiment is enlarged.

FIG. 9 is a block diagram illustrating a circuit configuration of a variable clock generation circuit according to the present embodiment.

FIG. 10 is a block diagram showing an input / output relationship of a phase comparator of the variable clock generation circuit of FIG. 9;

11 is a diagram illustrating a relationship between an input voltage of a VCO and an output frequency of the variable clock generation circuit of FIG. 9;

FIG. 12 is a timing chart showing clock generation timing of the variable clock generation circuit of FIG. 9;

FIG. 13 is a diagram showing a relationship between a magnification and a magnification error.

FIG. 14 is an explanatory diagram showing the relationship between the deviation of the magnification in the main scanning direction and the pixel clock in the writing system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scanner 2 Read processing part 3 Image processing part 4 Writing processing part 4-1 1st crystal oscillator 4-2 Phase comparator 4-3 Low pass filter 4-4 VCO 4-5 Divider 4-6 2nd Crystal oscillator 4-7 Mixer 4-8 Tuner 4-9 Comparator 5 Writing mechanism 6 Control unit 7 Operation unit

Claims (3)

[Claims] 1. An image forming means for forming an image based on an input image signal, a magnification setting means for setting a magnification of an image to be formed, and a magnification change based on the set magnification. An image forming apparatus comprising: a scaling unit; and a scaling ratio correction unit that corrects a scaling ratio executed by the scaling unit. The scaling ratio correction unit determines an error of a scaling ratio of an output image with respect to a plurality of scaling ratios. An image forming apparatus comprising: detecting an error and setting a correction value for a scaling factor set by the scaling unit based on the error. 2. The method according to claim 1, wherein the plurality of scaling factors include at least a minimum value or a value near a minimum value and a value near a maximum value or a maximum value of a scaling factor that can be set by the scaling means. Item 2. The image forming apparatus according to Item 1. 3. The variable magnification correcting means, when setting a correction value for each variable magnification, determines the correction value by a preset approximate expression using the variable magnification error. The image forming apparatus as described in the above.