JP2010197072A - Evaluation chart of image forming device, image forming device, image forming method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaluation chart of an image forming device which facilitates confirmation of deviation, the image forming device, an image forming method, and a program. <P>SOLUTION: The evaluation chart of the image forming device is formed on a sheet by the image forming device, and is acquired by arranging a predetermined number of groups of lines, each of which is composed of a plurality of short lines the same in length in a main scanning direction and arranged being shifted in position one by one by the line width in a sub-scanning direction, and long lines arranged in parallel between a predetermined number of adjoining short lines out of the short lines and longer than the short lines, continuously rectangularly in the sub-scanning direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an evaluation chart of an image forming apparatus, an image forming apparatus, an image forming method, and a program.

  In an image forming apparatus such as a multi-beam optical system or a laser printer having a plurality of beams, the beam pitch, scanning pitch, or scanning interval in the sub-scanning direction is adjusted using image data, an image pattern, or an adjustment pattern. The technique is disclosed in Patent Document 1.

  The invention described in Patent Document 1 is an invention related to an evaluation chart and an image recording apparatus. Specifically, the evaluation chart deflects a plurality of light beams emitted from a light source unit by a deflecting unit on a photosensitive member. FIG. 5 is an evaluation chart of an interlaced scanning type image recording apparatus that scans simultaneously and records an image (different from a television mark or other race), and has n dot lines (n ≧ 2) formed in the main scanning direction. Image evaluation consisting of multiple image patterns formed by combining multiple different light beams in the main scanning direction, consisting of image patterns that repeat in the sub-scanning direction with a period that is an integral multiple of the number of light beams It contains a pattern.

  According to the evaluation chart described in Patent Document 1, it is possible to easily detect the displacement of the beam pitch in the sub-scanning direction in a region where actual image recording is performed with relatively high accuracy.

(Explanation of interlace scanning)
2. Description of the Related Art Conventionally, there is an image forming apparatus provided with a multi-beam exposure unit that simultaneously scans a plurality of light beams on a photoconductor in response to a demand for high-speed image output. In order to obtain high image quality with such an apparatus, it is important to stably maintain the beam pitch of the beam in the sub-scanning direction at the manufacturing stage or in the user's environment.

  In recent years, in particular, in order to further increase the speed and density, what is called interlaced scanning (not interlaced in television) that performs scanning by skipping scanning lines on a multi-beam photoconductor is known. is there. If this method is used, scanning line writing suitable for high-density image formation is possible.

The interlaced scanning optical system will be described.
FIG. 12 is an explanatory diagram of the scanning position on the photosensitive member of the beam for 40 channels.
For example, when the resolution is 4800 dpi and the interval between pixels is about 5.2 μm, scanning S1 at a certain time point and scanning S2 by the next polygon mirror surface will be described.
First, the polygon mirror surface scans 40 beams at a time. The beam is 40 ch, and the 20th channel (ch20) and 21st channel (ch21) in the center are close to each other. The other channels are arranged in a positional relationship such that scanning is performed with a gap of one scanning line.

The position of the intermediate point a between the channel 20 (ch20) and the channel 21 (ch21) is the center of the lens group in the sub-scanning direction and is symmetric in the sub-scanning direction.
When horizontal scanning is performed in such a positional relationship on a certain polygonal surface, the line indicated by S2 in the figure is scanned on the next surface, and the 21 channel (ch21) and 22 channel (ch22) of the S1 line are scanned. The gap is now scanned by one channel (ch1). The same applies to Y, C, and M.
In this way, a writing unit with 4800 dpi resolution is configured.

  As a whole, this is an interlace scanning optical system, and the center 20ch-21ch is close to each other, so that interlace can be performed at a multiple of 8. The ability to process at a multiple of 8 makes it easier to handle even when configuring a circuit for image processing.

In addition, when a VCSEL (Vertical Cavity Surface Emitting Laser) is used as a light source, there is an advantage that the degree of freedom of light source arrangement is high.
Further, the sub-scanning beam interval between 1ch and 40ch is narrower than that of normal interlaced scanning, and the outermost beam is not so far away from the optical axis, so that the sub-scanning beam pitch variation and beam spot diameter variation can be reduced. . Further, there is an advantage that the effective range of the scanning lens can be reduced and the optical element can be miniaturized.

Now, when the optical system described above is used, the sub-scanning pitch is as small as 5.2 μm, so when the adjustment is shifted due to various factors such as a slight deviation of the photoreceptor speed, the location is specified. Or there is a demand for adjustment at the installation location of the device.
In particular, if it can be determined in the user's environment whether or not the sub-scanning pitch adjustment has been made within the correct range, the maintenance person can easily perform maintenance.
In particular, since an apparatus using such an optical system outputs a large amount of printed matter, the life of the apparatus can be extended by increasing the diameter of the photoreceptor.
However, as the diameter of the photoconductor increases, it becomes difficult to suppress variations in diameter, and it becomes difficult to properly match the linear velocity on the surface of the photoconductor.

Therefore, it is necessary to properly match the linear velocity to the beam pitch by some method.
For such applications, Patent Documents 2 and 3 disclose evaluation patterns for easily detecting a change in beam pitch when a multi-beam exposure system is used.
Patent Document 2 discloses a method for generating a pattern on adjacent scanning lines.

However, such a pattern is effective when a non-interlaced multi-beam exposure unit is used, but is not effective when interlaced scanning is performed.
As another method, as disclosed in Patent Document 3, there is a method of detecting a beam pitch using a measuring apparatus.

However, the invention described in Patent Document 3 requires a measuring device and is complicated.
That is, in the case of interlaced scanning, there is a problem that it is not possible to easily detect that the beam pitch has shifted. Therefore, there is a problem that it takes time to pursue the cause when a serviceman or the like copes with a defect in the market.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus evaluation chart, an image forming apparatus, an image forming method, and a program in which deviation can be easily confirmed.

  In order to solve the above problems, the invention described in claim 1 is an evaluation chart of an image forming apparatus formed on a sheet by the image forming apparatus, wherein the length in the main scanning direction is the same and the position is in the sub scanning direction. Are arranged in a line width by a predetermined length in the main scanning direction by a predetermined length and are arranged between the adjacent short lines among the short lines, and are the same length longer than the short lines and parallel to each other. A predetermined number of sets of line groups each including n (n ≠ m) long lines are arranged.

  According to a second aspect of the invention, in the first aspect of the invention, the predetermined number of sets is a number such that a rectangle formed by the line group can be recognized as a rectangle by the naked eye.

  According to a third aspect of the present invention, in the first aspect of the invention, when the length of the long line and the short line in the sub-scanning direction of each of the line groups is less than a predetermined length in the main scanning direction Is used for fine adjustment, and when it is longer than a predetermined length, it is used for coarse adjustment.

  A fourth aspect of the invention is characterized in that, in the invention of any one of the first to third aspects, a marker pattern for position confirmation is arranged between the line groups.

  According to a fifth aspect of the present invention, there is provided an image forming apparatus for forming an image by an electrophotographic method, wherein when the image forming apparatus is evaluated, a plurality of scanning lines on a photosensitive member are arranged in a sub scanning direction by a plurality of light emitting points. The exposure unit that collectively scans a plurality of scanning lines by interlaced scanning and the length of the plurality of scanning lines that are collectively scanned have the same length in the main scanning direction and the position is the line width in the sub-scanning direction, in the main scanning direction. N short lines arranged in a stepwise manner by a predetermined length and n (n ≠ m) pieces of the same length that are arranged between the short lines adjacent to each other and are longer than the short lines and parallel to each other. And an evaluation image data generating means having a pattern in which a predetermined number of sets of line groups composed of long lines are arranged.

  A sixth aspect of the invention is characterized in that, in the fifth aspect of the invention, the n scanning lines are arranged with a plurality of patterns having different numbers in the sub-scanning direction.

  According to a seventh aspect of the invention, in the fifth or sixth aspect of the invention, when data is generated from the evaluation image data generating means, an image is formed in synchronization with the exposure unit.

  According to an eighth aspect of the present invention, in the invention according to any one of the fifth to seventh aspects, a part of the scanning lines to be collectively scanned in the exposure unit scans an odd number of scanning lines, and an even number of scans from the middle. When scanning a line, the pattern is formed only above or below a portion where the odd scan line and the even scan line are switched.

  The invention according to claim 9 is an image forming method for forming an image by an electrophotographic method, and at the time of evaluation of the image forming apparatus, a plurality of scanning lines on the photosensitive member are arranged in a sub scanning direction by a plurality of light emitting points. A plurality of scanning lines are collectively scanned by interlaced scanning, and among the plurality of scanning lines to be collectively scanned, the length in the main scanning direction is the same, and the position is a line width in the sub-scanning direction, and a predetermined length in the main scanning direction. M short lines arranged in a step-wise manner and n (n ≠ m) long lines of the same length that are arranged between adjacent short lines of the short lines and are parallel to each other. An evaluation chart including a pattern in which a configured number of line groups are arranged in a predetermined number is generated.

  According to a tenth aspect of the present invention, there is provided a program for an image forming apparatus for forming an image by an electrophotographic method, wherein the image forming apparatus has a plurality of scanning lines on a photosensitive member by a plurality of light emitting points at the time of evaluation. In the sub-scanning direction, a procedure for collectively scanning a plurality of scanning lines by interlaced scanning, and among the plurality of scanning lines to be collectively scanned, the length in the main scanning direction is the same, and the position is the line width in the sub-scanning direction. N short lines arranged in steps of a predetermined length in the scanning direction and n (n ≠ n) of the same length that are arranged between adjacent short lines of the short lines and are longer than the short lines and parallel to each other. m) A procedure for generating an evaluation chart including a pattern in which a predetermined number of pairs of lines composed of long lines is arranged is executed.

  According to the present invention, an image forming apparatus creates an evaluation chart composed of a large number of alternately arranged patterns, so that even if a slight irradiation position deviation occurs during multi-beam scanning of the image forming apparatus, printing is performed on paper. Since this is reflected in the evaluation chart, visual confirmation can be easily performed.

It is an example of the elements on larger scale of the evaluation chart formed by the image forming device concerning the present invention. 1 is an example of a so-called central sectional view schematically showing the inside of an image forming engine unit of an image forming apparatus of an electrophotographic process. It is a figure which shows an example of an internal structure of the unit 30K of black (K). 1 is an example of a configuration diagram around an exposure system of an image forming apparatus according to an embodiment of the present invention and around a multi-beam writing unit 20. FIG. FIG. 5 is a diagram illustrating an example of a specific hardware configuration of an image processing control unit 113 illustrated in FIG. 4. 5 is an example of a timing chart of the writing unit shown in FIG. (A) is a diagram schematically showing a state where 40 beams are scanned with 6-sided polygons, and (b) is a diagram showing a relationship between a sheet and an image in a normal mode. c) is a diagram showing the relationship between the paper and the evaluation pattern in the test mode. (A) is a diagram schematically showing the beam scanning by the polygon surface described above, and (b) is a diagram showing an area of the patch P _XX formed in the sheet. It is explanatory drawing when the odd-numbered line of the evaluation chart formed with the image forming apparatus which concerns on this invention has shifted | deviated to the subscanning direction. It is a diagram illustrating a pattern arranged in the region of the P ₁₃ in the evaluation chart formed by the image forming apparatus according to the present invention. It is a figure which shows an example of the flow of synchronous switching control. It is explanatory drawing of the scanning position on the photoconductor of the beam for 40 channels. It is a figure which shows the relationship between the exposure amount per area, and a toner adhesion amount.

<Embodiment 1>
(Description of image forming apparatus)
FIG. 2 is an example of a so-called central sectional view schematically showing the inside of the image forming engine unit of the image forming apparatus of the electrophotographic process.
The image forming engine unit 9 includes a multi-beam writing unit unit 20, a photoconductor unit unit 21, an intermediate transfer unit unit 220, a paper feeding unit unit 26, and a fixing unit unit 28. The photosensitive unit 21 includes yellow (Y), cyan (C), magenta (M), and black (K) units 30Y, 30C, 30M, and 30K.

  Reference numerals 23Y, 23M, 23C, and 23K denote rollers, 24 denotes a secondary transfer roller, 25 denotes a sensor, 27 denotes a conveyance belt, and 29 denotes a carrier.

  Here, the black (K) unit 30K will be described, and the other yellow (Y), cyan (C), and magenta (M) units are the same, and the description thereof will be omitted.

  FIG. 4 is an example of a configuration diagram around the exposure system and the periphery of the multi-beam writing unit 20 of the image forming apparatus according to the embodiment of the present invention. Only the portion corresponding to one color is shown. (The folding mirror was omitted.)

  In the writing unit 20, reference numeral 61 denotes a collimator unit as a light source part, which is an integrated semiconductor laser array in which a plurality of laser light sources are arranged in a line and a collimating lens. In this embodiment, a 40-beam (40 ch) VCSEL is employed as the semiconductor laser.

  The emitted laser beam passes through the cylindrical lens 62 and becomes almost parallel light, and is then deflected in the main scanning direction by each mirror surface of the polygon mirror 63 that is driven by a motor (not shown) and rotates at high speed. Each deflected laser beam passes through the fθ lens 64 and the toroidal lens 65 and is condensed on the photoconductor 31 to scan the photoconductor 31 for exposure.

  Exposure scanning is performed by a collimator unit 61 driven by an LD drive circuit 114, a polygon mirror 63, an fθ lens 64, and a toroidal lens 65, and a horizontal synchronization sensor 69 that detects a part of a beam used for exposure, and a phase The synchronization signal generating means 70 feeds back to the image processing control unit 113 to perform accurate scanning. Reference numeral 115 is an operation panel for performing various settings, and 120 is an interface.

In other words, the image forming apparatus can simultaneously perform a plurality of lines of main scanning on the photosensitive member 31 as an image carrier with a plurality of laser beams.
The photoreceptor 31 is rotated in the direction of an arrow 31a in the drawing by a drive motor mechanism. By this rotation, sub-scanning for image formation is performed.

  A horizontal synchronization sensor 69 is provided at a position on the scanning start side out of the image forming area of the photoconductor 31. At the time when the laser beam enters the horizontal synchronization sensor 69, control is performed so that only one specific light source (for example, ch1) of the VCSEL emits light. Thereby, a horizontal synchronizing signal is generated.

(Description of process unit)
As a matter of course as an image forming apparatus, a charger for uniformly charging the surface of the photoconductor 31 and an electrostatic latent image formed on the surface of the photoconductor 31 by scanning the laser beam in the main scanning direction. A developing unit for developing the image with toner, a transfer unit for transferring the developed toner image onto a sheet or the like, a cleaner for removing toner remaining without being transferred to the surface of the photosensitive member 31, and a fixing unit or a sheet There are also transport mechanisms and the like.

FIG. 3 is a diagram illustrating an example of an internal configuration of the black (K) unit 30K.
The photoconductor 31K of the photoconductor unit 30K is driven in the direction of arrow B in the drawing.
The surface of the photoconductor 31K is first uniformly charged by a charger 32K, and then exposed by a laser beam 35K modulated by an image signal.
An electrostatic latent image is formed on the photoreceptor 31K by the laser light 35K. The electrostatic latent image thus formed becomes a toner image by the toner being adhered by the developing device 34K.

  The developing device 34K contains black (K) toner. The black (K) toner image is transferred onto the intermediate transfer belt 22 of the intermediate transfer unit 220 (see FIG. 2) by an electric field generated by the primary transfer roller 23K. The cleaning unit 33K cleans the photoreceptor 31K after the toner image is transferred.

  The toner images are transferred onto the intermediate transfer belt 22 in the same procedure for Y, M, and C.

Next, as shown in FIG. 2, the intermediate transfer belt 22 is driven in the direction of arrow A in the drawing.
The transfer of toner onto the intermediate transfer belt 22 is performed at a timing in accordance with the positions of the respective photoconductors 33Y to 33K, whereby a color toner image having no color misregistration is formed on the intermediate transfer belt 22. .

Next, the paper is conveyed from the paper supply unit 26 at a certain timing, and the color toner image on the intermediate transfer belt 22 is transferred onto the paper by the secondary transfer roller 24.
In this way, a color toner image is formed on the sheet, and the sheet moves on the conveying belt 27 and is conveyed to the fixing unit 28. The toner is thermally fixed on the sheet by the fixing unit 28 and discharged outside the apparatus. Is done.

FIG. 5 is a diagram illustrating an example of a specific hardware configuration of the image processing control unit 113 illustrated in FIG. 4.
The image processing control unit 113 includes an input interface (hereinafter referred to as input I / F) 120, a CPU (Central Processing Unit) 121, a ROM (Read Only Memory) 122, an HDD (Hard Disc Drive) 123, and a RAM (Random Access Memory). ) 124, a memory slot 125, and an output interface (hereinafter referred to as “output I / F”) 126, which are connected to each other via a bus 127.

  The input I / F 120 serves as an interface between the host computer 100 and the image processing control unit 113. Image data from the host computer 100 transmitted by a predetermined transmission method is input to the input I / F 120 and temporarily stored in the RAM 124.

  The RAM 124 serves as a working memory for each process executed under the control of the CPU 121, and serves as a buffer memory for storing image data and flag data described later.

  The CPU 121 is connected to each of the input I / F 120, the hard disk 123, the ROM 122, the RAM 124, and the output I / F 126 via the bus, reads an image processing program stored in the hard disk 123 or the ROM 122, and the CPU 121 reads the image processing program. Execute.

  The image processing program may be stored in advance in the hard disk 123 or the ROM 122. For example, the image processing program is supplied from the outside by a computer-readable recording medium such as the memory card 128, and the image processing program is supplied via the memory slot 125. The data may be stored by being stored in a hard disk 123 provided in the output device.

  Of course, it may be stored by accessing a server or the like that supplies a program via a network means such as the Internet and downloading data.

  Data processed by the image processing control unit 113 is output to the LD drive circuit 114 via the output I / F 126.

Here, the ROM 122 also stores image pattern information for evaluation.
In addition, the image pattern storage method may be stored in the hard disk 123 or may be held in a computer-readable recording medium such as the memory card 128.

(Explanation of adjustment mechanism)
For adjustment of jumping in the sub-scanning direction (adjustment of irradiation position), the jumping position can be adjusted by changing the rotation speed of the photoconductor 31.
Alternatively, when the polygon mirror 63 is used for each color, the jump position can be adjusted by changing the rotation speed of the polygon mirror 63.
In either case, the speed may be adjusted by adjusting a volume controller (for example, a variable resistor) mounted on a photoreceptor motor or a polygon motor board (both not shown), or An adjustment value may be input from the operation panel 115 and a command may be issued from the CPU 121 to change a clock signal that is a reference for rotation of the motor.

(Test mode input)
To enter the adjustment mode, the test pattern printing mode is entered by a predetermined key operation from the operation panel 115. Exiting from the adjustment mode is also performed by a predetermined key operation.

(Explanation of synchronizing images with ch)
(Sub-scan synchronization changes)
Normally, the image is output in synchronization with the leading edge of the sheet in the sub-scanning direction. In the test mode, the signal is further output within the range of the paper in synchronization with the ch1 synchronization signal.

The laser beam timing will be described with reference to FIG.
FIG. 6 is an example of a timing chart of the writing unit shown in FIG.
Sig (a) is a PageSync signal for synchronizing the paper and the image in the sub-scanning direction. Sig (b) is a synchronization signal of ch1. Sig (c) is test image output data.
In the normal image output mode, an image in the sub-scanning direction is formed in synchronization with the PageSync signal. However, in the test mode, after Sig (b) comes after Sig (a), the test image Sig (c) is output.

A practical image will be described with reference to FIGS.
FIG. 7A schematically shows a state in which 40 beams are scanned with 6-sided polygons.
If the polygon mirror is a six-surface mirror and each surface is called 1, 2, 3,..., 6 surfaces, beam scanning is performed sequentially from the first surface. In addition, up to four pages are shown for the sake of space.
FIG. 7B is a diagram illustrating the relationship between the sheet and the image in the normal mode. Normally, since the image is performed in synchronization with the PageSync signal, the image is formed in synchronization with the top of the paper regardless of the beam ch.
FIG. 7C shows the relationship between the paper and the evaluation pattern in the test mode. As shown in the figure, in this case, the evaluation pattern P1 is formed not only on PageSync but also in synchronization with ch1 by any polygonal surface.
That is, for example, the short line in FIG. 1 is simultaneously scanned on the first surface (for example, one surface) of the polygon mirror, and the long line is simultaneously scanned on the next surface (in this case, two surfaces) of the polygon mirror. This is repeated thereafter, and 40 lines per polygon mirror surface advance, so the same thing occurs after 6 surfaces (or 5 surfaces).
Although described as ch1 in the explanation, it is needless to say that it may be synchronized with ch2 or ch40.

(Position in the whole)
This will be described with reference to FIGS. 8 (a) and 8 (b).
FIG. 8A is a diagram schematically showing the beam scanning by the polygon surface described above. FIG. 8B is a diagram illustrating the area of the patch _PXX formed in the sheet. Pattern, each patch P _XX is formed to coincide with the plane of the ch1 and polygons. In the present embodiment, for example, which polygon plane the area of P ₁₁ matches is not controlled.

In this embodiment, only 20ch-21ch are adjacent. When scanning 1ch to 20ch odd scan lines, 21ch to 40ch scan even scan lines.
Thus regions of the P _XX is kept so as to be constituted by 1ch~20ch that are collectively scanned by 21ch~40ch the next polygonal surface which is collectively scanned by polygons surface.
In this way, it is possible to detect a defect with the pattern to be created.
7 and 8, the paper size is assumed to be about A4 horizontal feed, but may be A3 or larger.

(Description of _PXX image data)
Next details of the image data formed by P _11, is described with reference to FIG. 1 (for convenience plotting in the specification, the scale of the vertical and horizontal is quite different.).
FIG. 1 is an example of a partially enlarged explanatory view of an evaluation chart formed by the image forming apparatus according to the present invention.

  The evaluation chart is an evaluation chart of the image forming apparatus formed on the paper by the image forming apparatus, and the length in the main scanning direction is the same, and the position is a line width in the sub scanning direction, and a predetermined length in the main scanning direction. M short lines arranged in a stepwise manner by the length, and n (n ≠ m) long lines that are arranged between adjacent short lines of the short lines and are parallel to each other longer than the short lines. The configured line group is arranged in a predetermined number of sets.

Here, when n = m, it is difficult to detect the deviation.
Moreover, although the short line is arrange | positioned in FIG. 1 at right shoulder downward, this invention is not limited to this, The short line may be arrange | positioned at right shoulder upward.
Further, in FIG. 1, the first, second, fifteenth, and seventeenth short lines in the area of the patch P ₁₁ are not essential parts in the present invention, but are for so-called “foolproof”, and are mechanical of the image forming apparatus. Used for adjustment of the installation position when the setting is greatly deviated (for example, when shock is accidentally applied when replacing the writing unit).

That is, the image data is formed by horizontal lines in even lines and scanning lines whose phases are shifted in the sub-scanning direction. The phase shift in the sub-scanning direction is different for each main scanning block.
For the sake of explanation, horizontal lines in even lines are indicated by lines La as long hatched lines. An odd-numbered line (short line) is indicated by Lb.
In FIG. 1, an ellipse and a hatched ellipse are shown. However, both are actually black line patterns, and the set of patterns following the upper, lower and lower sides in FIG. Repeatedly, a rectangular block of approximately 50 mm length × 70 mm width is formed. The block appears gray in the distance. In the normal state, the central portion of 70 mm in width is the darkest because toner adheres best.

Here, the reason why the toner adheres best at the center will be described with reference to FIG.
FIG. 13 is a diagram illustrating the relationship between the exposure amount per area and the toner adhesion amount.
In the case of an electrophotographic engine, the toner adheres as a result of exposure on the photoreceptor → electrostatic latent image → supply of toner to the electrostatic latent image, but as shown in FIG. In the vicinity of the origin, the toner adhesion amount is small (almost 0), and the toner adhesion amount increases as the exposure amount increases. However, when the exposure amount increases to a certain extent, the toner adhesion amount is saturated. Therefore, the amount of toner adhesion increases because the exposure amount at the center of the pattern of the evaluation chart is large.

In the figure, “160 @ 4800 dpi” means 160 beam scans at 5.2 μm (4800 dpi).
Further, it is divided into several blocks in the main scanning direction, and is designated as B0, B1,..., B6 from the left.

The part B3 is just in the middle, and the odd lines are just between the even lines.
In the portion B2, the Lb line is an odd line, but the phase is shifted in the sub-scanning direction (upward in the drawing). B1 and B0 are further shifted upward. Conversely, B4, B5, and B6 are shifted downward.
Such an image is printed.
When viewed in the sub-scanning direction, there are fewer odd lines than even lines.
At this time, the same exposure energy is given to each of the B0 to B6 blocks, but the width in the sub-scanning direction to which the toner is to be attached is the shortest in the B3 portion.
Therefore, in a normal skipping state, the B3 block is the darkest after toner adhesion, and the density decreases as the distance from B3 increases.

  C1 and C2 are markers indicating the center, and are located at the same main scanning position as B3 so that the area of B3 can be easily understood.

  Here, when the positional relationship between the even-numbered lines and the odd-numbered lines is reversed in the middle, the darkened portion and the lightened portion are reversed. If such a reversal occurs in the adjacent line, it cannot be visually detected.

Next, consider a case where, for example, odd lines are shifted in the sub-scanning direction as shown in FIG.
FIG. 9 is an explanatory diagram when odd lines of the evaluation chart formed by the image forming apparatus according to the present invention are shifted in the sub-scanning direction.
In this case, the B2 block having the shortest length in the sub-scanning direction is the darkest. That is, the darkest part moves to the left and right due to the shift in the sub-scanning direction.
Therefore, the deviation in the sub-scanning direction can be easily checked by printing the pattern as described above in the user's usage environment. Further, it can be seen how much the dark portion is shifted in the sub-scanning direction depending on how many blocks the dark portion has moved to the main scanning.
Although the explanation has been made with the even-numbered line and the odd-numbered line, there is no problem even if each of them is replaced with the odd-numbered line and the even-numbered line.

Here, the reason why the B2 block is darkest will be described.
Considering the energy density of exposure in the sub-scanning direction, the area B2 in FIG. In the area B3 on the right, six exposures are performed in seven regions. Accordingly, when viewed macroscopically, the energy density of B2 is higher and the area of B3 is lower. For this reason, B2 becomes darker due to more toner adhesion.

(Explanation 2 about synchronizing an image with ch)
As already described, in this embodiment, interlaced scanning (not interlaced in television) is performed such that the ch20 and ch21 of the beam are adjacent to each other. Therefore, in the scanning of one polygon surface, the line scanned from the middle is switched from, for example, an odd line to an even line.
Therefore, it is necessary to control the pattern P _XX in synchronism with the ch of the laser beam so as to use only the odd side or only the even side.
As a result, it is possible to detect whether or not the pitch shift between the scanning of the odd lines by a certain polygon surface and the scanning of the even lines by the next polygon surface is correct by the evaluation pattern.

<Embodiment 2>
In FIG. 8, the configuration of the pattern arranged in the region of P ₁₁ is shown in FIG.
P ₂₁ , P ₃₁ ,... Have the same configuration and correspond to the mirror surface of each polygon.
The pattern arranged in the region of the P ₁₃ will be described.
Figure 10 is a diagram for explaining a pattern arranged in the region of the P ₁₃ in the evaluation chart formed by the image forming apparatus according to the present invention.
In the case of FIG. 1, the odd number line n is 1 less than the even number m with respect to the even number line m, but the pattern of FIG. 10 has a smaller number of patterns.
In this case, the portions B3 and B4 are the darkest. As a range of adjustment, if FIG. 1 is fine adjustment, the pattern of FIG. 10 has a coarse adjustment function.

In FIG. 8, n is the same for P ₁₁ and P ₁₂ , but P ₁₃ and P ₁₄ are configured such that n is smaller than P ₁₁ . In this way, since the allowable range of movement of the line is widened, the fine adjustment patch and the coarse adjustment patch are arranged in the sub-scanning direction, and the adjustment becomes easy.

<Embodiment 3>
The pattern can be given not only from the internal ROM and the memory card but also from an externally connected host computer.
In that case, data is supplied from the outside, but it is necessary to switch the synchronization in the sub-scanning direction.
FIG. 11 shows an example of the flow of synchronous switching control.
First, in step S1, a printer control command is input.
In step S2, the command is interpreted, and it is determined whether or not the image data from now on is in the evaluation chart mode.
If it is the evaluation chart mode (step S2 / True), the process proceeds to step S3 so that the beam channel and the image are synchronized, that is, the circuit is controlled so that the timing shown in FIG. (Step S2 / False) Proceeding to step S4, the mode is changed to a mode in which the image is synchronized with the normal paper front end.

<Description of effects>
(1) Since the evaluation chart as shown in FIG. 1 is used in the interlaced scanning exposure system, it is possible to easily know visually whether the interlace is correctly performed.
(2) Since the number of n for m is gradually decreased, information for fine adjustment and coarse adjustment can be provided.
(3) Since an image is formed in synchronization with ch1 of the light emitting point, the evaluation chart functions correctly even when the interlaced scanning line is switched between even and odd.

<Program and storage medium>
The image forming apparatus according to the present invention described above is realized by a program that causes a computer to execute processing. Examples of the computer include general-purpose computers such as personal computers and workstations, but the present invention is not limited to this. Therefore, as an example, a case where the present invention is realized by a program will be described below.

An image forming apparatus program for forming an image by an electrophotographic method,
On the computer,
(A) a procedure in which the image forming apparatus collectively scans a plurality of scanning lines by interlaced scanning in the sub-scanning direction in the sub-scanning direction by the plurality of light emitting points at the time of evaluation;
(B) A main scanning direction line is configured by m even or odd scanning lines adjacent to each other among a plurality of scanning lines to be collectively scanned, and m main scanning direction lines fewer than m are m. Odd-numbered or even-numbered lines in the main scanning direction in the vicinity of the odd-numbered or odd-numbered lines, and the n lines of the lines in the sub-scanning direction are gradually changed in the sub-scanning direction according to the positions in the main-scanning direction. A procedure for generating an evaluation chart consisting of patterns configured to be modified,
The program which performs is mentioned.

Thus, the image forming apparatus according to the present invention can be realized anywhere as long as there is a computer environment capable of executing the program.
Such a program may be stored in a computer-readable storage medium.
Here, examples of the storage medium include a computer-readable storage medium such as a CD-ROM (Compact Disc Read Only Memory), a flexible disk (FD), and a CD-R (CD Recordable), a flash memory, and a RAM (Random). Examples include semiconductor memories such as Access Memory (ROM), Read Only Memory (ROM), and FeRAM (ferroelectric memory), and HDD (Hard Disc Drive).

  The above-described embodiment shows an example of a preferred embodiment of the present invention, and the present invention is not limited thereto, and various modifications can be made without departing from the scope of the invention. is there.

DESCRIPTION OF SYMBOLS 9 Image forming engine part 20 Writing unit part 21 Photoconductor unit part 24 Secondary transfer roller 25 Sensor 26 Paper feed unit part 27 Conveying belt 28 Fixing unit part 29 Carrier 31 Photoconductor 61 Collimator unit 62 Cylindrical lens 63 Polygon mirror 64 f (theta) lens 65 Toroidal lens 69 Horizontal synchronization sensor 70 Phase synchronization signal generating means 113 Image processing control unit 114 LD drive circuit 115 Operation panel 120 Interface 122 ROM

Japanese Patent Laid-Open No. 10-062705 JP 2007-133056 A JP 2007-028509 A

Claims (10)

An image forming apparatus evaluation chart formed on a sheet by an image forming apparatus,
M short lines having the same length in the main scanning direction and positions shifted by a predetermined length in the main scanning direction by a line width in the sub scanning direction, and adjacent short lines among the short lines An image forming apparatus characterized in that a predetermined number of sets of line groups composed of n (n ≠ m) long lines having the same length longer than the short lines and parallel to each other are arranged. Evaluation chart.   2. The evaluation chart for an image forming apparatus according to claim 1, wherein the predetermined number of sets is a number such that a rectangle formed by the line group can be recognized as a rectangle by the naked eye.   When the length in the main scanning direction of the area continuous in the sub-scanning direction of the long line and the short line in each line group is equal to or shorter than a predetermined length, it is used for fine adjustment, and when it is longer than the predetermined length The evaluation chart according to claim 1, wherein is used for rough adjustment.   4. The image forming apparatus evaluation chart according to claim 1, wherein a marker pattern for position confirmation is arranged between the line groups. 5. An image forming apparatus for forming an image by electrophotography,
When evaluating the image forming apparatus, an exposure unit that collectively scans a plurality of scanning lines by interlaced scanning in a sub-scanning direction in a plurality of scanning lines on the photosensitive member by a plurality of light emitting points;
Among the plurality of scanning lines that are collectively scanned, m short lines are arranged with the same length in the main scanning direction and the position shifted by a predetermined length in the main scanning direction by a line width in the sub scanning direction. And a predetermined number of sets of line groups composed of n (n ≠ m) long lines of the same length that are arranged between adjacent short lines of the short lines and are parallel to each other longer than the short lines. And an image data generation means for evaluation comprising a pattern.   6. The image forming apparatus according to claim 5, wherein a plurality of patterns having different numbers in the sub scanning direction are arranged in the n scanning lines.   7. The image forming apparatus according to claim 5, wherein when the data from the evaluation image data generating means is generated, an image is formed in synchronization with the exposure unit.   In the exposure unit, when a part of the scanning lines to be scanned in a batch scans an odd number of scanning lines and scans an even number of scanning lines in the middle, the pattern is a portion where the odd number scanning lines and the even number scanning lines are switched The image forming apparatus according to claim 5, wherein the image forming apparatus is formed only on the upper side or the lower side. An image forming method for forming an image by an electrophotographic method,
At the time of evaluation of the image forming apparatus, a plurality of scanning lines on the photosensitive member are scanned in a sub scanning direction by a plurality of light emitting points, and a plurality of scanning lines are collectively scanned by interlaced scanning.
Among the plurality of scanning lines that are collectively scanned, m short lines are arranged with the same length in the main scanning direction and the position shifted by a predetermined length in the main scanning direction by a line width in the sub scanning direction. And a predetermined number of sets of line groups composed of n (n ≠ m) long lines of the same length that are arranged between adjacent short lines of the short lines and are parallel to each other longer than the short lines. An image forming method characterized by generating an evaluation chart comprising different patterns. An image forming apparatus program for forming an image by an electrophotographic method,
On the computer,
A procedure in which the image forming apparatus scans a plurality of scanning lines on the photosensitive member by a plurality of light emitting points in a sub-scanning direction in a sub-scanning direction at the time of evaluation;
Among the plurality of scanning lines that are collectively scanned, m short lines are arranged with the same length in the main scanning direction and the position shifted by a predetermined length in the main scanning direction by a line width in the sub scanning direction. And a predetermined number of sets of line groups composed of n (n ≠ m) long lines of the same length that are arranged between adjacent short lines of the short lines and are parallel to each other longer than the short lines. A program for causing the generation of an evaluation chart composed of a pattern.

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