JP6909192B2 - Image forming method, image forming device, printed matter production method - Google Patents

Description

The present invention relates to an image forming method, an image forming apparatus, and a method for producing a printed matter.

In recent years, in the electrophotographic process for image formation, there is an increasing demand for high image quality and high stability. It is already known that deterioration factors in image formation occur at the latent image stage before development.

In image formation, a technique is disclosed in which the exposure energy per unit pixel is made larger than the exposure energy per unit pixel when writing a solid image when the input image area is smaller than a predetermined value (for example, Patent Document 1). reference.).

In addition, pattern matching is performed by a 1 × 4 pixel detection pattern for the horizontal attention line and the diagonal attention line with a width of 2 pixels, and in addition to the line width correction so as to further increase the brightness of 1 pixel. A technique for performing luminance modulation is disclosed (see, for example, Patent Document 2).

Further, a technique for reducing the potential difference between the high density region and the low density region of the edge portion by increasing the exposure intensity to the low density region of the edge portion is disclosed (see, for example, Patent Document 3).

Furthermore, there is disclosed a technique for correcting the light energy exposed from each light source so as to be uniform by thinning out or adding exposure pixels (see, for example, Patent Document 4).

An object of the present invention is to provide an image forming method capable of forming an image having a latent image MTF (Modulation Transfer Function) resolution.

The present invention is a method of forming an electrostatic latent image corresponding to an image pattern by an exposure step of exposing the surface of an image carrier with light corresponding to an image pattern including an image portion and a non-image portion. parts is composed of a plurality of pixels, each pixel of the image portion, among the pixels constituting the images section, the non-exposed pixels pixels at the boundary between at least a non-image portion, determining the unexposed pixels After performing exception processing to make a part of the pixels to be high-output exposed pixels , at least the pixels adjacent to the non-exposed pixels among the pixels constituting the image portion are the predetermined light required to expose the image portion. A decision is made to make the high-power exposed pixels exposed by light with a light output value higher than the output value, and when the collation pattern is a symmetric two-dimensional array and the image pattern has a part that matches the collation pattern, the collation is performed. determining a pixel of the image portion corresponding to a pixel on the axis of symmetry of the pattern Ru is executed.

According to the present invention, an image having a high latent image MTF resolution can be formed.

It is a central sectional view which shows the embodiment of the image forming apparatus which concerns on this invention. It is a schematic diagram which shows the corotron type charging apparatus of the said image forming apparatus. It is a schematic diagram which shows the scorotron type charging apparatus of the said image forming apparatus. It is a schematic diagram which shows the optical scanning apparatus which comprises the said image forming apparatus. It is a schematic diagram which shows the light source of the said optical scanning apparatus. It is a schematic diagram which shows another embodiment of the light source of the said optical scanning apparatus. It is a block diagram which shows the image processing part of the said image forming apparatus. It is a block diagram which shows the image processing unit included in the image processing unit. It is a block diagram which shows the optical writing output part which the image processing part has. It is a schematic diagram which shows how the image part of the image data is exposed with the predetermined light output value necessary for being exposed. It is a schematic diagram which shows the exposure method performed by the said image formation method. It is a schematic diagram which shows another embodiment of the exposure method performed by the said image formation method. It is a schematic diagram which shows still another embodiment of the exposure method performed by the said image formation method. It is a graph which shows the relationship between a spatial frequency and a latent image MTF due to a difference in an exposure method. These are (a) standard exposure, (b) an exposure method according to the present invention, (c) another embodiment of the exposure method according to the present invention, and (d) yet another embodiment of the exposure method according to the present invention. It is a schematic diagram which shows the exposure pattern when applied to a line pattern. (A) Schematic diagram showing the exposure pattern 400a of FIG. 15 (a), (b) Schematic diagram showing the exposure pattern 400b of FIG. 15 (b), (c) Exposure shown in FIGS. 15 (a) and 15 (b). It is a schematic diagram which superposed the pattern. It is a graph which shows the latent image electric field intensity distribution of the exposure pattern of FIG. It is a schematic diagram which shows the collation pattern used by the said image formation method. It is a schematic diagram which shows how the said image formation method determines an exposure pattern by a collation pattern. It is a schematic diagram which shows how the exposure pattern of another image data is determined by the said collation pattern. It is a flowchart of the exposure method performed by the said image formation method. It is a schematic diagram which shows the state of the embodiment which the said image formation method performs the both ends folding process by the collation pattern. When the double-ended folding process is applied to image data of a line pattern having (a-1) 9 dot width, (a-2) 10 dot width, (a-3) 11 dot width, and (a-4) 12 dot width. It is a schematic diagram which shows the exposure pattern of. (A-1) to (a-4) indicate image data, and (b-1) to (b-4) indicate exposure patterns of (a-1) to (a-4), respectively. It is a schematic diagram which shows the exposure pattern when the said double-end folding process is applied to the image data of the line pattern of 6 dot width. It is a schematic diagram which shows the state which the exception processing was performed on the image data of the line pattern of the said 6 dot width. (A) Image data, (b) Exception handling, and (c) Both ends wrapping processing after exception handling are shown. It is a flowchart of the above-mentioned exception handling. It is a flowchart which performs a data storage process only once and determines an exposure pattern. It is a schematic diagram which shows how the exposure pattern of the image data was determined based on (a) an example of image data, and (b) the flowchart. (A) Another embodiment of a one-dimensional array collation pattern, (b) a two-dimensional array collation pattern, (c) another embodiment of a two-dimensional array collation pattern, and (d) yet another embodiment of a two-dimensional array collation pattern. It is a schematic diagram which shows the form of. It is a flowchart which determines the exposure pattern using the collation pattern of a one-dimensional array and the collation pattern of a two-dimensional array. It is a schematic diagram which shows how the exposure pattern of the said image data was determined based on the flowchart of FIG. (A) A diagram for explaining a 1-dot wrapping process, (b) a diagram for explaining a 2-dot wrapping process, (c) a diagram for explaining a 3-dot wrapping process, and (d) a diagram for explaining a 4-dot wrapping process. (A) It is a figure which shows the state which performs 2 dot wrapping process on the image data of a line pattern of 5 dot width, (b) is a figure which shows how the image data of a line pattern of 3 dot width is performed wrapping process of 1 dot. It is a schematic diagram which shows the flow which performs the 1st to 4th dot folding process. It is a schematic diagram which shows the exposure pattern of the character image by the exposure method of this embodiment. It is a schematic diagram which shows the exposure pattern of the outline character image by the exposure method of this embodiment. It is a central cross-sectional view which shows the example of the electrostatic latent image measuring apparatus. It is sectional drawing of the vacuum chamber apparatus provided in the said image forming apparatus. It is a schematic diagram which shows the relationship between the acceleration voltage and charge. It is a graph which shows the relationship between an acceleration voltage and a charge potential.

Hereinafter, the image forming method and the embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings.

● Image forming device ●
First, the image forming apparatus according to the present invention will be described.

The image forming apparatus according to the present invention is, for example, a laser printer 1000.

In the laser printer 1000 shown in FIG. 1, a charging device 1031, an optical scanning device 1010, a developing device 1130, a transfer device 1033, and a cleaning unit 1035 are arranged around the photoconductor drum 1030 along the rotation direction of the photoconductor drum 1030. They are arranged in the order of.

The charging device 1031 performs a charging process. The optical scanning device 1010 performs an exposure process. The developing apparatus 1130 executes the developing process. Transfer device 1033 executes the transfer process. Cleaning unit 1035 performs an electrophotographic process.

Further, a static elimination unit 1034 is arranged between the transfer device 1033 and the cleaning unit 1035.

The developing device 1130 includes a toner cartridge 1036 and a developing roller 1032 that adheres the toner supplied from the toner cartridge 1036 to the surface of the photoconductor drum 1030 and visualizes the latent image of the photoconductor drum 1030 surface with the toner. ..

The transfer device 1033 transfers the toner image on the surface of the photoconductor drum 1030 to the recording paper 1040 drawn from the paper feed tray 1038 by the paper feed roller 1037. The tip of the recording paper 1040 is positioned by the resist roller 1039, and is conveyed to the fixing device 1041 in synchronization with the toner image on the surface of the photoconductor drum 1030. The recording paper 1040 on which the toner image is fixed by the fixing device 1041 is sent out to the paper ejection tray 1043 by the paper ejection roller 1042.

Further, the laser printer 1000 has a communication control device 1050 and a printer control device 1060.

The communication control device 1050 controls bidirectional communication with a higher-level device (for example, an information processing device such as a personal computer) via a network or the like.

The printer control device 1060 has a CPU (Central Processing Unit) (not shown) and a ROM (Read Only Memory). Further, the printer control device 1060 has a RAM (Random Access Memory) and an A / D (Analog / Digital) converter. The printer control device 1060 comprehensively controls each unit in response to a request from the host device, and sends image information from the host device to the optical scanning device 1010.

The ROM stores a program written in a code that can be deciphered by the CPU and various data used when executing this program.

RAM is a temporary writable memory for CPU work.

The A / D converter converts an analog signal into a digital signal.

The photoconductor drum 1030 is a latent image carrier of a columnar member, and a photosensitive layer is formed on the surface thereof. That is, the surface of the photoconductor drum 1030 is the surface to be scanned. The photoconductor drum 1030 is rotated in the direction of the arrow in FIG. 1 by a drive mechanism (not shown).

The charging device 1031 uniformly charges the surface of the photoconductor drum 1030. For the charging device 1031, for example, a contact-type charging roller that generates less ozone or a corona charger that utilizes corona discharge can be used.

As shown in FIG. 2, the charging device 1031 may be a corotron type charging device.

As shown in FIG. 3, the charging device 1031 may be a scorotron type charging device. Further, the charging device 1031 may be a roller type charging device (not shown).

The components of the laser printer 1000 described above are housed in a predetermined position inside the printer housing 1044.

Returning to FIG. 1, a process for obtaining an output image in an electrophotographic image forming apparatus such as a copier or a laser printer will be described.

The optical scanning device 1010 scans and exposes the surface of the photoconductor drum 1030 charged by the charging device 1031 with a luminous flux modulated based on the image information from the printer control device 1060. The optical scanning apparatus 1010 forms an electrostatic latent image corresponding to image information on the surface of the photoconductor drum 1030.

The electrostatic latent image formed by the optical scanning apparatus 1010 moves in the direction of the developing apparatus 1130 as the photoconductor drum 1030 rotates. The details of the optical scanning device 1010 will be described later.

Toner (developer) is stored in the toner cartridge 1036. Toner is supplied from the toner cartridge 1036 to the developing apparatus 1130.

The developing device 1130 attaches the toner supplied from the toner cartridge 1036 to the latent image formed on the surface of the photoconductor drum 1030 to visualize the electrostatic latent image. The image to which the toner is attached (hereinafter, also referred to as “toner image”) moves in the direction of the transfer device 1033 as the photoconductor drum 1030 rotates.

The recording paper 1040 is stored in the paper feed tray 1038. A paper feed roller 1037 is arranged in the vicinity of the paper feed tray 1038.

The paper feed roller 1037 takes out the recording paper 1040 one by one from the paper feed tray 1038. The recording paper 1040 is sent out from the paper feed tray 1038 toward the gap between the photoconductor drum 1030 and the transfer device 1033 in accordance with the rotation of the photoconductor drum 1030.

A voltage having a polarity opposite to that of the toner is applied to the transfer device 1033 in order to electrically attract the toner on the surface of the photoconductor drum 1030 to the recording paper 1040. By this voltage, the toner image on the surface of the photoconductor drum 1030 is transferred to the recording paper 1040. The recording paper 1040 on which the toner image is transferred is sent to the fixing device 1041.

In the fixing device 1041, heat and pressure are applied to the recording paper 1040, whereby the toner is fixed on the recording paper 1040. Here, the recording paper 1040 on which the toner is fixed is sent to the paper ejection tray 1043 via the paper ejection roller 1042, and is sequentially laminated on the paper ejection tray 1043 to produce a printed matter.

The static elimination unit 1034 eliminates static electricity on the surface of the photoconductor drum 1030.

The cleaning unit 1035 removes the toner (residual toner) remaining on the surface of the photoconductor drum 1030. The surface of the photoconductor drum 1030 from which the residual toner has been removed returns to a position facing the charging device 1031.

In the image forming apparatus according to the present invention, an electrostatic latent image is formed by a charging device, an optical scanning device as an exposure device, a photoconductor, and an image processing unit for converting an image pattern into light output. ..

As described above, in the electrophotographic method, the photoconductor, which is one of the latent image carriers, is uniformly charged in the charging process. Further, in the electrophotographic method, the photoconductor is irradiated with light in the exposure process to partially release the electric charge. By doing so, in the electrophotographic method, an electrostatic latent image can be formed on the photoconductor.

● Configuration of Optical Scanning Device Next, the configuration of the optical scanning device 1010 will be described.

As shown in FIG. 4, the optical scanning device 1010 includes a light source 11, a collimating lens 12, a cylindrical lens 13, a mirror 14, a polygon mirror 15, and a first scanning lens 21. Further, the optical scanning device 1010 includes a second scanning lens 22, a mirror 24, a synchronization detection sensor 26, and a scanning control device (not shown).

The optical scanning device 1010 is assembled at a predetermined position of the optical housing 381 shown in FIG. 38.

In the following description, the direction along the longitudinal direction (rotation axis direction) of the photoconductor drum 1030 is defined as the Y-axis direction of the XYZ three-dimensional Cartesian coordinate system, and the direction along the rotation axis of the polygon mirror 15 is defined as the Z-axis direction. , The direction perpendicular to both the Y-axis and the Z-axis is defined as the X-axis direction.

Further, in the following description, the direction corresponding to the main scanning direction of each optical member is referred to as "main scanning corresponding direction", and the direction corresponding to the sub-scanning direction is referred to as "sub-scanning corresponding direction".

As the light source 11, a semiconductor laser (LD: Laser Diode), a light emitting diode (LED: Light Emitting Diode), or the like can be used.

In FIG. 5, the light source 11A is a semiconductor laser array configured by arranging four semiconductor lasers 11Ak as a multi-beam light source. Further, the light source 11A is arranged perpendicular to the optical axis direction of the collimating lens 12.

In FIG. 6, the light source 11B is, for example, a Vertical Cavity Surface Emitting LASER (VCSEL) having a wavelength of 780 nm and whose light emitting portion is arranged on a plane including the Y-axis direction and the Z-axis direction. ..

Each light emitting unit is arranged so that the distance between the light emitting units becomes equal when all the light emitting units are normally projected onto a virtual line extending in the direction corresponding to the sub-scanning. The "light emitting part interval" means the distance between the centers of the two light emitting parts.

The light source 11B has a plurality of light emitting units. For example, the light source 11B has a total of 12 light emitting units 11B-k, three in the horizontal direction (main scanning direction and Y-axis direction) and four in the vertical direction (sub-scanning direction and Z-axis direction).

When applied to the optical scanning device 1010, the light source 11B can simultaneously scan four vertical scanning lines by scanning one scanning line with three light emitting units arranged in the horizontal direction.

Returning to FIG. 4, the collimating lens 12 is arranged on the optical path of the light emitted from the light source 11 and refracts the light into parallel light or substantially parallel light.

The cylindrical lens 13 focuses the light that has passed through the collimating lens 12 only in the Z-axis direction (sub-scanning direction) in the vicinity of the deflection reflection surface of the polygon mirror 15.

The cylindrical lens 13 forms an image of light 19 emitted from the light source 11 as a long line image in the main scanning direction (Y-axis direction) in the vicinity of the reflecting surface of the polygon mirror 15.

The mirror 14 reflects the light formed through the cylindrical lens 13 toward the polygon mirror 15.

The optical system arranged on the optical path between the light source 11 and the polygon mirror 15 is also called a pre-deflector optical system.

The polygon mirror 15 is a multifaceted mirror that rotates around a rotation axis orthogonal to the longitudinal direction (rotation axis direction) of the photoconductor drum 1030. Each mirror surface of the polygon mirror 15 is a deflection reflection surface.

The polygon mirror 15 rotates at a constant speed at a desired speed when a drive IC (Integrated Circuit) (not shown) gives an appropriate clock to a motor unit (not shown).

When the polygon mirror 15 is rotated at a constant velocity in the direction of the arrow by the motor unit, the plurality of light beams reflected by the deflection reflecting surface become deflection beams and are deflected at an equal angular velocity.

The first scanning lens 21, the second scanning lens 22, the mirror 24, and the synchronization detection sensor 26 constitute the scanning optical system 20. The scanning optical system 20 is arranged on the optical path of the light deflected by the polygon mirror 15.

The first scanning lens 21 is arranged on the optical path of the light deflected by the polygon mirror 15.

The second scanning lens 22 is arranged on the optical path of light through the first scanning lens 21.

The mirror 24 is a long plane mirror, and bends the optical path of light through the second scanning lens 22 in the direction toward the photoconductor drum 1030.

That is, the light deflected by the polygon mirror 15 is applied to the photoconductor drum 1030 via the first scanning lens 21 and the second scanning lens 22, and a light spot is formed on the surface of the photoconductor drum 1030.

The light spot on the surface of the photoconductor drum 1030 moves along the longitudinal direction of the photoconductor drum 1030 as the polygon mirror 15 rotates. The moving direction of the light spot on the surface of the photoconductor drum 1030 is the "main scanning direction", and the rotation direction of the photoconductor drum 1030 is the "secondary scanning direction".

The synchronization detection sensor 26 receives the light from the polygon mirror 15 and outputs a signal (photoelectric conversion signal) according to the amount of the received light to the scanning control device. The output signal of the synchronization detection sensor 26 is also referred to as a “synchronization detection signal”.

The optical scanning apparatus 1010 simultaneously scans a plurality of lines on the scanned surface of the photoconductor drum 1030 by scanning with one deflecting reflection surface of the polygon mirror 15. The buffer memory in the image processing unit 7 that controls the light emission signal of each light emitting unit stores print data for one line corresponding to each light emitting unit.

The print data is read out for each deflection reflective surface of the polygon mirror 15, and the light beam blinks on the scan line on the photoconductor drum 1030 as the latent image carrier in accordance with the print data, and follows the scan line. An electrostatic latent image is formed.

As shown in FIG. 7, the image processing unit 7 includes an image processing unit (IPU: Image Processing Unit) 101, a controller unit 102, a memory unit 103, an optical write output unit 104, and a scanner unit 105. Be prepared.

The controller unit 102 receives the image data from the IPU 101 and performs processing such as rotation, repeat, aggregation, and compression / decompression on the image data. The controller unit 102 outputs the processed image data to the IPU 101 again.

A lookup table for storing various data and calling it as needed is prepared in the memory unit 103.

The optical write / output unit 104 photomodulates the light source 11 according to the lighting data by the control driver, and forms an electrostatic latent image on the photoconductor drum 1030.

The optical write / output unit 104 determines an exposure pattern by time-intensive exposure, which will be described later, based on an input signal from the gradation processing unit 101f, which will be described later. The optical write / output unit 104 forms an electrostatic latent image based on the exposure pattern.

By determining the exposure pattern by the optical writing output unit 104, the exposure pattern can be determined after various image processing described later by the image processing unit 101. That is, an effective exposure pattern can be determined by the time-intensive exposure described later.

The formed electrostatic latent image forms an image on recording paper by the above-mentioned developing device 1130, transfer device 1033, and the like.

The scanner unit 105 reads an image and generates image data such as RGB (Red Green Blue) data based on the image.

As shown in FIG. 8, the image processing unit 101 includes a density conversion unit 101a, a filter unit 101b, a color correction unit 101c, a selector unit 101d, a gradation correction unit 101e, and a gradation processing unit 101f. I have.

The density conversion unit 101a converts the RGB image data from the scanner unit 105 into density data using the lookup table, and outputs the RGB image data to the filter unit 101b.

The filter unit 101b performs image correction processing such as smoothing processing and edge enhancement processing on the density data input from the density conversion unit 101a, and outputs the density data to the color correction unit 101c.

The color correction unit 101c performs color correction (masking) processing on the density data that has undergone image correction processing.

Under the control of the image processing unit 101, the selector unit 101d has any of C (Cyan), M (Magenta), Y (Yellow), and K (Key Plate) with respect to the image data input from the color correction unit 101c. Select. The selector unit 101d outputs the selected C, Y, M, and K data to the gradation correction unit 101e.

The gradation correction unit 101e stores in advance the data of C, M, Y, and K input from the selector unit 101d. The gradation correction unit 101e sets a γ curve that can obtain linear characteristics with respect to the input data.

The gradation processing unit 101f performs gradation processing such as dither processing on the image data input from the gradation correction unit 101e, and outputs a signal to the optical writing output unit 104.

● About the optical write / output unit The optical write / output unit 104 drives and controls a light source. The optical write / output unit 104 is, for example, a control device that drives an LD.

As shown in FIG. 9, the optical write output unit 104 includes a reference clock generation circuit 422, a pixel clock generation circuit 425, a light source modulation data generation circuit 407, a light source selection circuit 414, a write timing signal generation circuit 415, and a synchronization timing signal generation. The circuit 417 is provided.

The arrows in FIG. 9 indicate a typical signal or information flow, and do not represent all the connection relationships of each block.

The reference clock generation circuit 422 generates a high-frequency clock signal that serves as a reference for the entire optical write / output unit 104.

The pixel clock generation circuit 425 mainly includes a PLL (Phase Locked Loop) circuit. The pixel clock generation circuit 425 generates a pixel clock signal based on the synchronization signal s19 and the high frequency clock signal from the reference clock generation circuit 422.

The pixel clock signal has the same frequency as the high frequency clock signal and has the same phase as the synchronization signal s19.

The pixel clock generation circuit 425 can control the writing position for each scan by synchronizing the image data with the pixel clock signal.

The pixel clock signal is supplied to the light source driving unit 410 as one of the driving information, and is also supplied to the light source modulation data generation circuit 407. The pixel clock signal supplied to the light source modulation data generation circuit 407 is supplied to the light source driving unit 410 as a clock signal of the write data s16.

The light source selection circuit 414 is a circuit used when there are a plurality of light sources, and outputs a signal for designating the selected light emitting unit. The output signal s14 of the light source selection circuit 414 is supplied to the light source drive unit 410 as one of the drive information.

● Exposure method ●
Next, the exposure method in the embodiment of the image forming method according to the present invention will be described.

In the image forming method according to the present embodiment, the light output waveform used for latent image formation is a predetermined light output value required to obtain a target image density for an image portion including a line image or a solid image. It is a waveform that exposes the photoconductor for a period of time.

The image portion is a portion composed of a plurality of pixels and for forming an image by adhering toner in an image pattern. The non-image portion is a portion of the image pattern in which toner is not adhered and an image is not formed.

In the following description, the target image density is referred to as "target image density". In the following description, a predetermined light output value required to obtain a target image density is referred to as a “target exposure output value”. A predetermined time for exposing the entire pixel of the image portion with the target exposure output value in order to obtain the target image density is referred to as "target exposure time".

In the following description, an exposure method in which a target exposure output value is used to expose only a target exposure time is referred to as "standard exposure". In the present embodiment, the solid image means an image portion having a larger area than a line image.

In the following description, exposing the photoconductor to an exposure time shorter than the target exposure time with a light output value stronger than the target exposure output value (first light output value) is referred to as "time intensive exposure" (TC (Time Concentration) exposure). Also called.).

As shown in FIG. 10, the exposure method by standard exposure (hereinafter referred to as “exposure method 1”) is a target exposure output value as described above for a 1-pixel (dot) image portion including a line image and a solid image. This is a method of exposing the photoconductor for the target exposure time. Here, the horizontal axis represents time and the vertical axis represents the amount of light. The target exposure output value is 100% light output value, and the target exposure time is 100% duty ratio.

As shown in FIG. 11, the exposure method by TC exposure (hereinafter referred to as “exposure method 2”) in the present embodiment has a duty ratio of 50 with respect to the target exposure time at an optical output value of 200% of the target exposure output value. The photoconductor is exposed at%. Assuming that the width of the image portion is 1, the width of the section to be exposed is 4/8 pixel.

As shown in FIG. 12, the exposure method by TC exposure (hereinafter referred to as “exposure method 3”) in the present embodiment has a duty ratio of 25 with respect to the target exposure time at an optical output value of 400% of the target exposure output value. The photoconductor is exposed at%. Assuming that the width of the image portion is 1, the width of the section to be exposed is 2/8 pixel.

FIG. 13 is a schematic view showing still another embodiment of the image forming method according to the present invention. In this exposure method (hereinafter referred to as "exposure method 4"), the photoconductor is exposed with a light output value of 800% of the target exposure output value and a duty ratio of 12.5% with respect to the target exposure time. Assuming that the width of the image portion is 1, the width of the section to be exposed is 1/8 pixel.

In the exposure methods 2 to 4 described above, the pulse width is narrower than that in the exposure method 1. That is, in the exposure methods 2 to 4, since the latent image formed when exposed with the same amount of light as the exposure method 1 becomes smaller, the amount of light is controlled according to the pulse width so that the integrated light amount at the time of forming the latent image becomes the same. is doing.

That is, in the exposure method by TC exposure, the exposure is performed with a short pulse width and a strong amount of light as compared with the exposure method by standard exposure.

In the above description, in each of the exposure methods 2 to 4, the light output value is set so that the integrated light amount is constant, but the light output value in the image forming method according to the present invention is limited to this. It's not a thing.

FIG. 14 is a graph showing the measurement results of the latent image MTF in the vertical direction when the beam spot diameter used for exposure is 70 μm in the main scanning direction × 90 μm in the sub-scanning direction. The horizontal axis represents the spatial frequency, and the vertical axis represents the latent image MTF. In the exposure methods 2 to 4, the latent image MTF shows a high value up to the high frequency band as compared with the exposure method 1.

The exposure methods 2 to 4 can stably form a latent image having a smaller diameter than the exposure method 1. In particular, among the exposure methods 2 to 4, the exposure method 4 having the shortest pulse width is suitable for stably forming a latent image having a small diameter.

Further, since the exposure methods 2 to 4 perform exposure with a shorter pulse width and a stronger amount of light as compared with the exposure method 1, the latent image resolving power is improved. That is, according to the exposure methods 2 to 4, a latent image having a small diameter can be stably formed as compared with the exposure method 1 used in the conventional image forming method.

The exposure method by TC exposure in the image forming method according to the present invention is superior to the case of exposure by the conventional exposure method with a beam spot diameter of a small diameter when the latent image stability in a high frequency region, that is, a small diameter is emphasized. There is. Here, the optimum beam spot diameter due to the difference in the output image is determined by the latent image MTF at the maximum spatial frequency required for the output image.

The exposure method by TC exposure is characterized in that the width of the latent image electric field vector is narrower than that of other means. That is, it means that the latent image electric field vector is increased and the resolving power is improved.

Further, in the image forming method according to the present invention, unlike the case where the light source is controlled and exposed by power modulation or pulse width modulation, the integrated light amount is equivalent to the case where the exposure is performed at the target exposure output value. Therefore, in the image forming method according to the present invention, the amount of toner adhered and the overall image density are substantially the same as when exposed at the target exposure output value.

As described above, in the case of PM (Pulse Modulation) modulation capable of irradiating a light output value P1 larger than the target exposure output value P0 when forming a solid image density, the ratio TCR of the light output value is TCR =. P1 / P0
Is defined as.

In this case, the exposure method in the present embodiment compresses the width of the vertical line to 1 / TCR and exposes the image with a light output value stronger than the target exposure output value at the time of solid image density. By doing so, according to the exposure method in the present embodiment, it is possible to form an image having a high MTF resolution.

In the exposure method according to the present embodiment, a narrow range of an image portion forming an image in an image pattern is concentratedly exposed with strong light. By doing so, the exposure method according to the present embodiment improves the fidelity of the output image pattern having a small size smaller than the beam diameter size (the influence of the beam diameter size cannot be ignored) and makes the image pattern. It can be adjusted to a desired image density.

That is, according to the exposure method according to the present embodiment, it is possible to form an image in which both the formation of a minute-sized image pattern and the desired image density are compatible.

Further, the exposure method according to the present embodiment can be easily applied to an arbitrary image pattern without performing special processing such as edge detection and character information recognition.

Therefore, according to the exposure method according to the present embodiment, the image pattern can be generated even when the object information cannot be acquired from the computer when the image data is converted into the light source modulation data.

Further, according to the exposure method according to the present embodiment, it is possible to form an image in which a minute-sized image pattern is formed and a desired image density is compatible without making the image data and the light source modulation data correspond to each character. can

Further, the exposure method according to the present embodiment uses PM + PWM modulation which is a combination of PM modulation and PWM (Pulse Width Modulation) modulation. Then, according to the exposure method according to the present embodiment, by using TC exposure in which the maximum light output is intentionally enhanced, the integrated light amount of the image pattern at the time of exposure can be set to the same value as the standard exposure.

Here, according to the exposure method according to the present embodiment, it is possible to enhance the resolving power of the image pattern without changing the image density of the image pattern by forming a deep latent image.

In the exposure method according to the present embodiment, the light output value is set so that one or more pixels (pixel group) in the image portion at the boundary between the image portion and the non-image portion included in the image pattern become unexposed pixels. Set. Here, the non-exposed pixel group in the image portion at the boundary between the image portion and the non-image portion included in the image pattern is referred to as a non-exposure pixel group. Further, in the exposure method according to the present embodiment, the light output value to the pixel group adjacent to the non-exposure pixel group (near the non-exposure pixel group) is added to the light output value to the non-exposure pixel group. Expose with the output value.

That is, the sum of the values obtained by subtracting the predetermined light output value from the light output value of the light exposed to the high-power exposed pixel is obtained by subtracting the light output value of the light exposed to the non-exposed pixel from the predetermined light output value. Equal to the sum of the values.

By doing so, it is possible to form an exposure pattern having a high latent image MTF resolution.

● Example of Forming a Line Image Next, an example of determining an exposure pattern of a line image by the exposure method in the present embodiment will be described. The exposure pattern is a pattern of light output values of exposure for each pixel dot corresponding to image data.

In the following description, the Y-axis direction (main scanning direction) in the drawing is the horizontal direction, and the Z-axis direction (sub-scanning direction) is the vertical direction.

FIG. 15A is an exposure pattern 400a of a line image by standard exposure. The exposure pattern 400a includes an exposure pixel group 411 and a non-exposure pixel group 412. The exposure pixel group 411 is a pixel group to be standard-exposed. The non-exposed pixel group 412 is a pixel group that is not exposed. The exposed pixel group 411 coincides with the image portion of the line image. The non-exposed pixel group 412 coincides with the non-image portion of the line image.

FIG. 15B is an exposure pattern 400b in which one dot at the boundary between the image portion and the non-image portion of the line image is a high-output exposure pixel group 443. Further, FIG. 15C is an exposure pattern 400c in which the two dots at the boundary between the image portion and the non-image portion of the line image are set as the high output exposure pixel group 443. Further, FIG. 15D is an exposure pattern 400d in which 3 dots at the boundary between the image portion and the non-image portion of the line image are set as the high output exposure pixel group 443.

The high-power exposure pixel group 443 is a pixel group for TC exposure at the first light output value.

The exposure patterns 400a to 400d shown in FIGS. 15A to 15D each have a minimum pixel of 4800 dpi and a spatial frequency of 6 c / mm. The exposure patterns 400a, 400b, 400c, and 400d form thick vertical lines (lines in the Z-axis direction) for every 8x8 dots (corresponding to 600 dpi).

That is, the exposure pattern 400a shown in FIG. 15A includes an exposure pixel group 411 and a non-exposure pixel group 412 composed of two vertical lines of 600 dpi. Here, the size of one pixel is about 5 μm.

In the exposure method according to the present embodiment, in the exposure pattern 400b, a plurality of pixel groups (for example, one pixel in the Y-axis direction are arranged in a row in the Z-axis direction) at the boundary between the image portion and the non-image portion 412. The light output value is set so that the image) becomes the non-exposed portion 441.

Then, a pixel group at the boundary between the image portion and the non-image portion (for example, a plurality of pixel groups in which one pixel in the Y-axis direction is arranged in one row in the Z-axis direction) is set as a high-output exposure pixel group 443.

Then, if the variable magnification of the TC exposure with respect to the standard exposure is 2, the high output exposure pixel group 443 is exposed with twice the light output. At this time, since the non-exposed portion 441 is not exposed, the integrated light amount of the entire exposure pattern 400b is the same as that of the exposure pattern 400a.

The number of pixels in the non-exposed pixel group 441 and the high-output exposed pixel group 443 can be set to any number in the main scanning direction or the sub-scanning direction.

The exposure pattern 400c has two pixels each in the Y-axis direction of the non-exposure pixel group 441 and the high-output exposure pixel group 443. Further, the exposure pattern 400d is set so that the widths of the non-exposure pixel group 441 and the high-output exposure pixel group 443 in the Y-axis direction are 3 pixels each.

In FIG. 16, the horizontal axis shows the dots in the Y-axis direction in FIG. 15, and the vertical axis shows the light output value for each dot. The numerical value in the dot indicates a multiple of the optical output value. That is, "0" is an unexposed pixel (light output value is 0), "1" is an exposed pixel, "2" is a high output exposed pixel whose light output value is twice that of an exposed pixel, and "x" is a high output exposed pixel. Indicates any pixel.

As shown in FIG. 16A, the exposure pattern 400a by standard exposure has a multiple of the light output values of all the dots in the Y-axis direction and is exposed with a uniform light output value.

On the other hand, as shown in FIG. 16B, in the exposure pattern 400b by TC exposure, the pixels (boundary pixels) at the boundary between the image portion and the non-image portion are non-exposure pixels, so that the light output of the non-exposure pixels The multiple of the value is 0 (the optical output value is 0). Further, in the exposure pattern 400b, since the pixels at the boundary between the image portion and the non-image portion form the high output exposure pixel group, the multiple of the light output value of the high output exposure pixel group is 2.

As shown in FIG. 16 (c), when the waveform (a) of the light output value by the standard exposure and the waveform (b) of the light output value by the TC exposure are compared, the pixels at both ends of the waveform (a) by the standard exposure are The waveform (b) obtained by TC exposure is a non-exposed pixel.

Then, the light output value of the non-exposed pixel group of the waveform (a) by the standard exposure is added to the light output value of the high output exposed pixel group corresponding to both ends of the waveform (b) by the TC exposure. That is, the high-output exposure pixel group is a process in which the light output value at the end of the image pattern is folded back inward and raised.

FIG. 17 shows a latent image electric field intensity distribution of an image pattern by standard exposure and a latent image electric field intensity distribution of an image pattern by TC exposure in which 2 dots are replaced with a non-exposed pixel group and a high output exposed pixel group.

Comparing the latent image electric field intensity distribution of standard exposure and the latent image electric field intensity distribution of TC exposure, the width of the peak part of the electric field strength is narrower and the slope of the change of the electric field strength is larger in TC exposure (the edge is steep). ) Therefore, it can be seen that a clearer image can be formed.

Here, the process of adding only 1 dot is defined as the 1-dot processing mode, and the process of adding 2 dots is defined as the 2-dot processing mode. Hereinafter, different mode names will be used according to the number of dots to which the optical output value is added to the other dots. The above is an example of the 2-dot processing mode.

● Collation of image data and collation pattern Here, the flow of determining an exposure pattern by TC exposure will be described. The image forming apparatus 1000 determines an exposure pattern by TC exposure (hereinafter, referred to as "TC exposure pattern") by collating a plurality of collation patterns stored in advance in the optical writing output unit 104 with image data.

As shown in FIG. 18, the collation pattern 200 is an array having binary values of 0 or 1 in each pixel. The collation pattern is, for example, a square having 11 pixels in the vertical direction and 11 pixels in the horizontal direction. The pixel in the center of the collation pattern 200 is the attention position 210.

The collation pattern 200 is collated with the image data. The array of the collation pattern 200 is collated with the array of image data, and the same array as the collation pattern 200 is searched for in the image data. When the same array as the collation pattern 200 is detected in the image data, the pixel of the image data corresponding to the attention position 210, that is, the exposure intensity of the pixel of interest is determined.

The number of pixels of the collation pattern 200 is not limited to the above. Further, in FIG. 18, the collation pattern 200 is a two-dimensional array having a plurality of pixels in the vertical and horizontal directions, but it may be a one-dimensional array.

As the number of pixels of the collation pattern 200 increases, various patterns can be extracted, so that the exposure intensity can be determined more accurately. However, as the number of pixels of the collation pattern 200 increases, the number of gates increases and the responsiveness decreases. Therefore, it is preferable to set the matching pattern 200 as appropriate.

FIG. 19 shows how the exposure pattern of TC exposure is determined in the 2-dot processing mode for the pixel of interest 211 of the image data corresponding to the positions of interest 210a to 210d by the collation patterns 201a to 201d.

The collation patterns 201a to 201d are one-dimensional arrays of "01111x" from the left. In addition, "x" indicates that it is an arbitrary value.

The attention position 210a of the collation pattern 201a is the fifth pixel from the left. The attention position 210b of the collation pattern 201b is the fourth pixel from the left. The attention position 210c of the collation pattern 201c is the third pixel from the left. The attention position 210d of the collation pattern 201d is the second pixel from the left.

It is assumed that the image data in FIG. 19 has the same sequence as the collation patterns 201a to 201d.

When the collation pattern 201a is detected, the exposure intensity of the pixel of interest 211a is determined to be "2". When the collation pattern 201b is detected, the exposure intensity of the pixel of interest 211b is determined to be "2".

When the collation pattern 201c is detected, the exposure intensity of the pixel of interest 211c is determined to be "0". When the collation pattern 201d is detected, the exposure intensity of the pixel of interest 211d is determined to be "0".

By collating the collation patterns 201a to 201d with the image data, the TC exposure pattern corresponding to the image data is determined to be "00022x".

This process is also referred to as "left wrapping process" because the left end of the image data is a non-exposed pixel and the end of the exposed pixel by TC exposure is a high-output exposed pixel group adjacent to the non-exposed portion.

FIG. 20 shows a schematic diagram in which the process of determining the exposure pattern as described above is applied to a two-dimensional image. In FIG. 20A, the image data 500a is an image portion that is entirely exposed with a uniform light output value, and the outside of the frame of the image portion is a non-image portion.

FIG. 20B shows the exposure pattern 500b after collating the collation patterns 201a to 201d with the image data 500a. FIG. 20C shows the exposure pattern 500c after collating the collation patterns 201a'to 201d', which are the left-right inverted collation patterns 201a to 201d, with the exposure pattern 500b.

This process is also called "right wrapping process" because the right end of the image data is a non-exposed pixel and the right end of the exposed pixel by TC exposure is a high-output exposed pixel group adjacent to the non-exposed portion.

FIG. 20D shows an exposure pattern 500d after collating the collation patterns 201a to 201d rotated by 90 degrees with the exposure pattern 500c. The rotated collation patterns 201ar to 204dr are, that is, “01111 ×” from the top.

This process is also referred to as "upper folding process" because the upper end of the image data is a non-exposed pixel and the end of the exposed pixel by TC exposure is a high-output exposed pixel group adjacent to the non-exposed portion.

At this time, when the exposure intensity of the pixels of interest 211ar to 211dr is the maximum light output, the exposure intensity of the matching pattern before matching is used as it is. That is, the optical output values of the pixels in the regions 500d-1 and 500d-2 are "2" before the collation of the collation patterns 201ar to 204dr.

Here, assuming that the maximum optical output is "2", the optical output values of the pixels in the regions 500d-1 and the region 500d-2 are "2" even after the collation of the collation patterns 201ar to 204dr.

The exposure pattern 500d has a different shape from the original image data, and has protrusions formed by the regions 500d-1 and the regions 500d-2 at the top and bottom. However, the size of the exposure pattern at the edge is sufficiently smaller than the beam size. Therefore, the image corresponding to the region 500d-1 and the region 500d-2 is not formed.

FIG. 20E shows the exposure pattern 500e after collating the collation patterns 201ar'to 204dr', which are the upside-down collation patterns 201ar to 204dr, with the exposure pattern 500d. Also in this case, when the exposure intensity of the pixels of interest 211ar'to 211dr' is the maximum light output, the exposure intensity of the matching pattern before matching is used as it is.

This process is also referred to as "bottom wrapping process" because the lower end of the image data is a non-exposed pixel and the lower end of the exposed pixel by TC exposure is a high-output exposed pixel group adjacent to the non-exposed portion.

FIG. 21 is a flowchart illustrating the flow of processing of FIG. 20. By collating the original image data (original image) 500a with the collation patterns 201a to 201d, the "left wrapping process" is performed and the exposure pattern 500b is determined (step S11).

The exposure pattern 500b determined by the "left wrapping process" is saved by the process of "data storage 1" (step S12).

By collating the exposure pattern 500b with the collation patterns 201a'to 201d', the "right wrapping process" is performed and the exposure pattern 500c is determined (step S13).

The exposure pattern 500c determined by the "right wrapping process" is saved by the process of "data storage 2" (step S14).

By collating the exposure pattern 500c with the collation patterns 201ar to 201dr, the "upper folding process" is performed, and the exposure pattern 500d is determined (step S15).

The exposure pattern 500d determined by the "upper folding process" is saved by the process of "data storage 3" (step S16).

By collating the exposure pattern 500d with the collation patterns 201ar'to 201dr', the "lower folding process" is performed, and the exposure pattern 500e is determined (step S17).

The exposure pattern 500e determined by the "lower folding process" is saved by the process of "data storage 4" (step S18).

The optical writing output unit 104 forms an electrostatic latent image on the latent image carrier by exposing each pixel with the exposure intensity of the exposure pattern 500e.

In the process of FIG. 21, the wrapping process is performed in the order of left, right, top, and bottom, but it may be performed in a different order.

By processing in this way, an image having a high latent image MTF resolution can be formed. Further, by using the collation pattern, the optical output value can be determined without performing simple operations such as addition processing and multiplication processing on the circuit, so that the processing speed can be increased.

● Both ends wrapping process Next, the "both ends wrapping process" that determines the exposure pattern at the left and right edges, or the top and bottom edges at the same time will be described.

As shown in FIG. 22, the image data is collated with the eight types of collation patterns 201a to 201d and 201a'to 201d' to determine the exposure pattern. After that, data storage processing is performed. That is, in the exposure pattern determination flow described with reference to FIG. 21, the processes of "data storage 1" and "data storage 2" are performed, whereas in the double-ended folding process, the data storage process is performed once.

That is, the number of times of data storage in the double-ended folding process is half the number of times of the determination flow described with reference to FIG.

FIG. 23 is a schematic view in which the both ends folding process is applied to the line pattern. It shows how the wrapping process at both ends is appropriately performed for a line having a line pattern width of 9 dots or more.

When applied to a dot-shaped pattern, it is possible to perform the upper and lower end fold processing in addition to the left and right end fold processing described above. At that time, either the left and right end folding process or the upper and lower end folding process may be performed first.

In the flow described with reference to FIG. 21, the collation patterns 201a'to 201d' when the right wrapping process is performed are collated with the exposure pattern 500b after the left wrapping process. On the other hand, when the left and right ends are folded back, the collation patterns 201a to 201d and 201a'to 201d'are all collated with the image data 500a. Therefore, the right wrapping process can be performed without storing the exposure pattern 500b after the left wrapping process.

From the viewpoint of the processing speed in the image forming apparatus, it is desirable that the exposure pattern determination flow is completed within one clock per pixel. The flow of storing and recalling data multiple times slows down the processing speed of the circuit or requires a huge amount of memory.

According to the double-ended folding process, by simultaneously determining the exposure intensity at both ends, the number of times of data storage can be reduced as compared with the exposure pattern determination flow described with reference to FIGS. 20 and 21.

● Exception handling (1)
Next, exception handling performed before both-end wrapping processing will be described.

FIG. 24 is an exposure pattern 226 when both ends of the image data 225, which is a 6-dot line pattern, are folded back in the 2-dot processing mode.

The integrated value of the light output value when the image data is normally exposed is 600%. On the other hand, the integrated value of the exposure intensity corresponding to the exposure pattern 226 is 400%. In this way, the integral value of the total light output value becomes lower than the integral value of the normal exposure due to the double-ended folding process. Therefore, when the exposure pattern 226 is exposed, the density is low and the image becomes blurred.

Therefore, a pixel that is erroneously turned into a non-exposed pixel in the double-end folding process is converted into a high-output exposed pixel by an exception process. The exception processing is a processing for determining a pixel to be converted into a high-output exposure pixel by collating a collation pattern different from the double-end folding process with the image data, for example.

In the exception processing, the width of the image portion of the image data is less than twice the sum of the number of pixels that convert the exposed pixels into non-exposure and the number of pixels that convert the exposed pixels into high-output exposed pixels in the both-end folding process. It is preferable to perform this when the number of exposed pixels is large.

In the double-end folding process in the 2-dot processing mode, the non-exposed pixels are 2 dots and the high-output exposed pixels are 2 dots, so the sum of the number of pixels is 4 dots. Therefore, when the width of the image portion of the image data is less than 8 dots, exception handling is performed.

FIG. 25A is image data 225, which is a 6-dot line pattern. The collation pattern used in exception handling corresponds to image data 225. That is, the collation pattern used in exception handling is "x01111110x" from the right.

As shown in FIG. 25 (b), the pixel 225a of the second dot from the right in the image portion is determined to be "2", that is, the high output exposure pixel by the exception processing, and the processed pattern 227 is determined.

As shown in FIG. 25 (c), the post-processing pattern 227 is subjected to both end folding processing. At this time, for the pixel whose optical output value is determined by the exception processing, both ends folding processing is not performed. Therefore, the light output value of the pixel 225a remains "2".

The integrated value of the light output value corresponding to the exposure pattern 228 after the both ends folding process is 600%. That is, by performing the exception handling, it is possible to perform the double-ended folding processing without lowering the integrated value of the optical output value.

In the above description, the folding process is performed in one direction, but an exception process may be performed to determine the exposure patterns of the left end and the right end, or the upper end and the lower end at the same time. Exception handling that determines the left and right exposure patterns at the same time is called "left and right exception handling". Exception processing that determines the exposure patterns at the upper and lower ends at the same time is called "upper and lower exception processing".

As shown in FIG. 26, first, left and right exception processing is performed on each pixel of the original image (step S21).

For the pixels whose optical output values have not been determined in the left and right exception processing, the left and right ends are folded back (step S22). After that, data storage processing is performed (step S23).

For the pixel whose optical output value is determined in the left / right exception processing, the data storage processing is performed without performing the left / right both end folding processing (step S23).

Next, upper and lower exception processing is performed on the exposure pattern stored in step S23 (step S24).

For the pixels whose optical output values have not been determined in the upper and lower exception processing, the upper and lower ends are folded back (step S25). After that, data storage processing is performed (step S26).

For the pixel whose optical output value is determined in the upper and lower exception processing, the data storage processing is performed without performing the upper and lower end folding processing (step S26).

By performing exception handling, it is possible to realize high-quality image formation without fading even a narrow image.

● Exception handling (2)
Next, another embodiment of exception handling in the image forming apparatus according to the present invention will be described focusing on a portion different from the above-described embodiment. The present embodiment has been described above in that a one-dimensional array collation pattern is used for left and right wrapping processing and exception handling, and a two-dimensional array collation pattern is used for top and bottom wrapping processing and exception handling. Different from the form.

Exception handling using a two-dimensional array collation pattern is particularly useful in an exposure pattern determination flow in which data storage processing is performed only once.

FIG. 27 shows an exposure pattern determination flow 27 in which the data storage process is performed only once.

First, left and right exception processing is performed for each pixel of the original image (step S31).

For the pixels whose optical output values have not been determined in the left and right exception processing, the left and right ends are folded back (step S32).

Next, upper and lower exception processing is performed on the pixels whose optical output values have not been determined in the left and right both end folding processing (step S33).

The upper and lower ends of the pixel whose optical output value has not been determined in the upper and lower exception processing are folded back at both upper and lower ends (step S34). After that, data storage processing is performed (step S35).

For the pixels whose optical output values have been determined in the left / right exception processing, the left / right both ends folding processing, or the upper / lower exception processing, the data storage processing is performed without performing the subsequent processing (step S35).

Here, the exposure pattern obtained when the determination flow 27 is executed by using the one-dimensional array collation pattern for all the processes will be described.

As shown in FIG. 28A, an image portion that is intricately formed in a corner or a T shape will be described.

A one-dimensional collation pattern as shown in FIG. 29 (a) is used for the upper and lower ends folding process.

FIG. 28 (b) shows an exposure pattern after performing both-end folding processing using a one-dimensional collation pattern in FIG. 28 (a). The pixel group 281 surrounded by a thick frame is a non-exposed pixel. Therefore, the integrated value of the light output value of the entire exposure pattern is 13% lower than the integrated value of the light output value of the normal exposure.

The reason why the integrated value of the optical output value is lowered is that the collation pattern is collated with the image data in the left and right both end folding processing and the upper and lower both end folding processing.

The pixel group 281 does not match the collation pattern in the left and right both ends folding process. Therefore, the light output value after the left and right both ends are folded back is 1. After that, the pixel group 281 is determined to be a non-exposed pixel in the upper and lower end folding back processing.

The correct process is that when exposed pixels are converted to non-exposed pixels, the exposed pixels adjacent to the converted pixel group are converted to high-power exposed pixels, so that the integrated value of the exposure intensity becomes constant before and after the process. ..

When only the upper and lower ends are folded back, the pixel group 281 and the pixel group 282 become non-exposed pixels, and the pixel group 283 is converted into high-output exposed pixels. However, in this example in which the left and right end fold processing is performed before the upper and lower end fold processing, the matching patterns of the pixel group 282 and the pixel group 283 are matched by the left and right end fold processing, and the optical output value is determined. It is a group of pixels.

Therefore, even if the pixel group 281 is set as a non-exposed pixel, the pixel adjacent to the converted pixel group is not converted into a high-output exposed pixel. That is, the pixel group 281 does not need to be converted into non-exposed pixels.

In such a case, by using the collation pattern of the two-dimensional array for the upper and lower end folding processing, it is possible to prevent the adjacent pixels from being unexposed pixels when they are not converted into high-output exposed pixels.

Specifically, the matching pattern of the two-dimensional array is an array of "1" on the left and right of the pixel adjacent to the pixel of interest by the number of pixels in the processing direction of the pixel whose optical output value is determined by folding back both upper and lower ends. It is preferable to use a matching pattern with.

In other words, the matching pattern of the two-dimensional array is a symmetric pattern in which the pixels of interest are arranged on the axis of symmetry. The number of pixels on one side of the two-dimensional array is at least twice the sum of the number of pixels in a continuous row determined for the non-exposed pixels and the high-output exposed pixels.

FIG. 29B shows a collation pattern 291 of a two-dimensional array used for folding back both upper and lower ends when one pixel is a non-exposed pixel and one adjacent pixel is a high-output exposed pixel. Therefore, two rows of "1" arrays are arranged on the left and right of the pixel adjacent to the pixel of interest 291a.

FIG. 29C is a collation pattern 292 used when two pixels are non-exposed pixels and two adjacent pixels are high-output exposed pixels. Therefore, four rows of "1" arrays are arranged on the left and right of the pixel adjacent to the pixel of interest 292a.

FIG. 29 (d) is a collation pattern 293 used when three pixels are non-exposed pixels and adjacent three pixels are high-output exposed pixels. Therefore, six rows of "1" arrays are arranged on the left and right of the pixel adjacent to the pixel of interest 293a.

As shown in FIG. 30, the determination flow 30 uses a one-dimensional array collation pattern in the left and right exception handling and the left and right both ends folding back processing. A two-dimensional array collation pattern is used in the upper and lower exception handling and the upper and lower folding processing.

First, left and right exception processing is performed for each pixel of the original image (step S41).

For the pixels whose optical output values have not been determined in the left and right exception processing, the left and right ends are folded back (step S42).

Next, upper and lower exception processing is performed on the pixels whose optical output values have not been determined in the left and right both end folding processing (step S43).

For the pixels whose optical output values have not been determined in the upper and lower exception processing, the upper and lower ends are folded back (step S44). After that, data storage processing is performed (step S45).

For the pixels whose optical output values are determined in the left / right exception processing, the left / right both ends folding processing, or the upper / lower exception processing, the data storage processing is performed without performing the subsequent processing (step S45).

FIG. 31 is an exposure pattern after executing the determination flow 27 including the upper and lower end folding back processing using the collation pattern 291 with respect to FIG. 28A. It can be seen that the optical output value of the pixel group 281'is determined to be 1.

In this way, by using the one-dimensional array collation pattern for the left and right edge wrapping processing and the one-dimensional array collation pattern for the upper and lower edge wrapping processing, the exposure pattern is correctly determined even for a complicated image. be able to. By this method, it is also possible to make the total amount of light added by high exposure equal to the total amount of light subtracted by exposure.

● Exposure method (2)
Next, another embodiment of the exposure method in the image forming method according to the present invention will be described focusing on the differences from the above-described example of the exposure method.

In the exposure method according to the present embodiment, the number of non-exposed pixels or high-output exposed pixels is determined by the performance of the image forming apparatus, the image area in the image pattern, and the form of the image pattern (black characters, white characters, line types). , The shape of the figure, etc.) may be used properly.

FIG. 32 is a schematic diagram showing an example of addition processing of the optical output values of the exposure pattern. As shown in the figure, in the exposure method according to the present embodiment, 1 to 4 dots of an exposure pattern of an image formed at 4800 dpi are set as non-exposure pixels, and an optical output value is added to other pixels.

FIG. 32A shows an addition example of the 1-dot processing mode. Further, FIG. 32B shows an addition example of the 2-dot processing mode. Further, FIG. 32 (c) shows an addition example of the 3-dot processing mode. Further, FIG. 32 (d) shows an addition example of the 4-dot processing mode.

As shown in FIGS. 32 (a) to 32 (d), it is determined whether or not there are exposed pixels at positions corresponding to the arbitrary number of exposed pixels arranged symmetrically when folded around the virtual axis of symmetry. Match. By adding the light output value to the pixel on the opposite side of the axis of symmetry in this way, the numerical value of the light output value of the pixel on the opposite side becomes "2".

FIG. 33 is a schematic diagram showing another addition process.

FIG. 33A shows the addition processing in the 3-dot processing mode. Further, FIG. 33B shows another addition process in the 3-dot processing mode.

As shown in FIGS. 33 (a) and 33 (b), the exposure method according to the present embodiment is different from the above-described addition process of the optical output values of the symmetrically arranged exposure pixels, and has a virtual axis of symmetry. The addition process can be performed even when there is no exposed pixel at the corresponding position when the image is folded around the center.

That is, in the exposure method according to the present embodiment, when the addition process is performed, if the exposure pixel on the addition side is already a pixel after the addition of the optical output value, the addition process is performed only to the exposure pixels that can be added. It can be performed.

Specifically, as shown in FIGS. 33 (a) and 33 (b), when the wrapping process cannot be performed in the 3-dot processing mode, the wrapping process can be performed in the 2-dot processing mode or the 1-dot processing mode.

As described above, according to the exposure method according to the present embodiment, it is possible to appropriately process the pixels to which the optical output values have been added so as not to add them again.

Further, regarding the wrapping process of the number of pixels smaller than the specified processing mode, the wrapping process of the larger number of pixels may be performed in order. The light source driving unit 410 includes a selector 34 for selecting a processing mode.

As shown in FIG. 34, when the 4-dot processing mode is set, the selector 34 first selects the 4-dot processing mode. The light source driving unit 410 collates with the collation pattern for the 4-dot processing mode. If it matches the collation pattern, the wrapping process in the 4-dot processing mode is performed.

Next, the selector 34 selects the 3-dot processing mode. The light source driving unit 410 collates with the collation pattern for the 3-dot processing mode. If it matches the collation pattern, the wrapping process in the 3-dot processing mode is performed. The same applies to the 2-dot processing mode and the 1-dot processing mode.

In this way, by sequentially processing the wrapping process of the number of pixels smaller than the specified processing mode, a high-quality image can be formed even in the portion where the number of pixels of the image portion is small and the specified wrapping process cannot be performed. Can be done.

In the image forming method according to the present invention, at least two types of image qualities, a first image quality (normal image quality mode) and a second image quality, can be selected. The first image quality is the image quality by standard exposure.

The second image quality is determined by the exposure method according to the embodiment described above, from the first light output value for at least a group of pixels at the boundary with the non-exposed portion among the pixels constituting the pixels of the image portion. Is also the image quality to be exposed with a high light output value.

● Example of Forming a Character Image Next, an example in which the exposure method according to the present embodiment is applied to a character image of a minute size (3 points) will be described.

FIG. 35 is a schematic view showing an exposure pattern of a character image by the exposure method of the present embodiment. FIG. 3A is an exposure pattern of the characters of the “picture” determined in the 2-dot processing mode. FIG. 3B is an exposure pattern at the time of standard exposure.

FIG. 36 is a schematic view showing an exposure pattern of an outline character image by the exposure method of the present embodiment. FIG. 36A is a white exposure pattern of the characters “picture” at the time of standard exposure. Further, FIG. 36B is an exposure pattern determined in the 4-dot processing mode.

The exposure method according to the present embodiment can be applied not only to ordinary colored characters but also to color-reversed characters (outline characters).

According to the exposure method according to the present embodiment, when converting image data to light source modulation data, even if object information cannot be obtained from the information processing device, various characters such as character images, inverted character images, dithers, and line images can be obtained. It is possible to generate an exposure pattern of various images.

The exposure method according to the present embodiment can be further effective by using different exposure pattern processing modes according to the characteristics of the image data.

Generally, in the outline characters shown in FIG. 36, since the periphery is affected by the exposure, the electric field strength of the white background becomes small, and the white background is easily buried in the coloring. Therefore, in the exposure method according to the present embodiment, it is desirable to increase the light output value by time-intensive exposure by setting a large number of pixels in the high-output exposed pixel group and the non-exposed portion.

In the exposure method according to the present embodiment, when a texture or an artifact appears in the dither portion such as a halftone due to interference with other processing, the number of pixels in the high-output exposed pixel group and the non-exposed portion is reduced. May be good. When the number of pixels to be added is 1 dot, that is, the 1-dot processing mode, there is almost no demerit by the exposure method according to the present embodiment, and the effect of reducing the weak electric field can be obtained.

Therefore, in the exposure method according to the present embodiment, when black characters, white characters, and dithers can be identified by the tag information that identifies the type (character or line) of the target to be added to the high-output exposure pixel group. , The number of pixels of the high-output exposed pixel group and the non-exposed portion can be appropriately aligned.

As a specific example, in the case of a normal character or line drawing, a tag is attached in advance to the pixel on the exposure side at the boundary between the image portion and the non-image portion. On the other hand, in the case of inverted characters and inverted line drawings, a tag is attached to the non-exposed side pixel at the boundary between the image portion and the non-image portion, and other dithers and the like are the same as in the case where no dither is attached.

Then, for each tagged image, black characters and black lines are set in a 3-dot processing mode, outline characters and white lines are set in a 4-dot processing mode, dither is set in a 2-dot processing mode, and the like.

The light source modulation data generation circuit 407 described with reference to FIG. 9 detects the boundary pixel between the image portion and the non-image portion of the exposure pattern, and sets the tag to 0 from the tag bit (information that identifies the attribute of the image pattern) of the boundary pixel. Which of 1 is detected.

When the tag bit is 1, the light source modulation data generation circuit 407 determines that it is a black character or a black line, and executes the 3-dot processing mode.

Next, when the tag bit is 0, the light source modulation data generation circuit 407 determines that it is a white character or a white line, and executes the 4-dot processing mode.

If the tag bit is neither 0 nor 1, the light source modulation data generation circuit 407 determines that it is a dither unit and executes the 2-dot processing mode.

As described above, the exposure method according to the present embodiment recognizes whether it is a normal character, an inverted character, or a dither portion based on information provided from the controller side such as an image pattern of a received image or a tag bit of an image. Then, the optimum number of folded pixels is set according to each image.

According to the exposure method according to the present embodiment, since the light output value of TC exposure can be adjusted, it is possible to provide the best image that maximizes the ability of the image forming apparatus.

● Configuration of the electrostatic latent image measuring device Next, the configuration of the electrostatic latent image measuring device capable of confirming the state of the electrostatic latent image formed by the exposure method according to the present embodiment will be described.

The electrostatic latent image measuring device 300 shown in FIG. 37 includes a charged particle irradiation system 400, an optical scanning device 1010, a sample table 401, a detector 402, an LED 403, a control system (not shown), an emission system, and a driving device. It is equipped with a power supply.

The charged particle irradiation system 400 is arranged in the vacuum chamber 340. The charged particle irradiation system 400 includes an electron gun 311, a pull-out electrode 312, an acceleration electrode 313, a condenser lens 314, a beam blanker 315, and a partition plate 316. The charged particle irradiation system 400 has a movable diaphragm 317, a stig meter 318, a scanning lens 319, and an objective lens 320.

In the following description, the optical axis direction of each lens will be the c-axis direction, and the two directions orthogonal to each other in the plane orthogonal to the c-axis direction will be described as the a-axis direction and the b-axis direction.

The electron gun 311 generates an electron beam as a charged particle beam and irradiates the vacuum sample stage portion 384.

The extraction electrode 312 is arranged on the −c side of the electron gun 311 and controls the electron beam generated by the electron gun 311.

The acceleration electrode 313 is arranged on the −c side of the extraction electrode 312 to control the energy of the electron beam.

The condenser lens 314 is arranged on the −c side of the acceleration electrode 313 to focus the electron beam.

The beam blanker 315 is arranged on the −c side of the condenser lens 314 to turn on / off (OFF) the irradiation of the electron beam.

The partition plate 316 is arranged on the −c side of the beam blanker 315 and has an opening in the center.

The movable diaphragm 317 is arranged on the −c side of the partition plate 316, and adjusts the beam diameter of the electron beam that has passed through the opening of the partition plate 316.

The stig meter 318 is arranged on the −c side of the movable diaphragm 317 to correct astigmatism.

The scanning lens 319 is arranged on the −c side of the stig meter 318 and deflects the electron beam through the stig meter 318 in the ab plane.

The objective lens 320 is arranged on the −c side of the scanning lens 319 and converges the electron beam through the scanning lens 319. The electron beam through the objective lens 320 passes through the beam ejection opening 321 and irradiates the surface of the sample 323.

A drive power supply (not shown) is connected to each lens or the like.

The charged particles are particles that are affected by an electric field or a magnetic field. As the beam for irradiating the charged particles, for example, an ion beam may be used instead of the electron beam. In this case, a liquid metal ion gun or the like is used instead of the electron gun.

Sample 323 is a photoconductor and has a conductive support, a charge generation layer (CGL), and a charge transport layer (CTL).

The charge generation layer contains a charge generation material (CGM) and is formed on the + c side surface of the conductive support. The charge transport layer is formed on the + c side surface of the charge generation layer.

When the sample 323 is exposed in a state where the surface (the surface on the + c side) is charged, light is absorbed by the charge generating material of the charge generating layer, and charge carriers having both positive and negative polarities are generated. The carriers are injected by an electric field into the charge transport layer on the one hand and into the conductive support on the other.

The carriers injected into the charge transport layer move to the surface of the charge transport layer by the electric field, combine with the charges on the surface, and disappear. As a result, a charge distribution, that is, an electrostatic latent image is formed on the surface of the sample 323 (the surface on the + c side).

The optical scanning device 1010 includes a light source, a coupling lens, an aperture plate, a cylindrical lens, a polygon mirror, a scanning optical system 393, and the like. The optical scanning device 1010 also has a scanning mechanism (not shown) for scanning light in a direction parallel to the rotation axis of the polygon mirror.

The scanning optical system includes a light source unit, a scanning lens, a light deflector, and the like. The optical deflector is, for example, a polygon scanner 390.

The polygon scanner 390 is provided on a horizontal translation table 392 together with the optical housing 381.

The light emitted from the optical scanning device 1010 irradiates the surface of the sample 323 through the reflection mirror 372, the external light-shielding cylinder 385, the labyrinth portion 386, the light-shielding member 387, the internal light-shielding cylinder 388, and the glass window 368.

The irradiation position of the light emitted from the optical scanning device 1010 on the surface of the sample 323 is along two directions orthogonal to each other on a plane orthogonal to the c-axis direction due to the deflection by the polygon mirror and the deflection by the scanning mechanism. Change.

At this time, the changing direction of the irradiation position due to the deflection of the polygon mirror is the main scanning direction, and the changing direction of the irradiation position due to the deflection of the scanning mechanism is the sub-scanning direction. Here, the a-axis direction is set to be the main scanning direction, and the b-axis direction is set to be the sub-scanning direction.

In this way, the electrostatic latent image measuring device 300 can two-dimensionally scan the surface of the sample 323 with the light emitted from the optical scanning device 1010. That is, the electrostatic latent image measuring device 300 can form a two-dimensional electrostatic latent image on the surface of the sample 323.

As shown in FIG. 38, the optical scanning apparatus 1010 is provided with an incident window at a position 45 degrees with respect to the vertical axis of the vacuum chamber 340 so that a light flux can be incident on the inside of the vacuum chamber 340 from the outside. .. That is, the scanning optical system 393 is arranged outside the vacuum chamber 340.

With this configuration, vibrations and electromagnetic waves generated by the drive motor of the polygon mirror are unlikely to affect the trajectory of the electron beam. That is, it is possible to suppress the influence of vibration and electromagnetic waves from the polygon mirror on the measurement result.

The detector 402 is arranged in the vicinity of the sample 323 and detects secondary electrons from the sample 323.

The LED 403 is arranged in the vicinity of the sample 323 and emits light that illuminates the sample 323. The LED 403 is used to eliminate the charge remaining on the surface of the sample 323 after the measurement.

The optical housing 381 holding the scanning optical system 393 may have the entire scanning optical system 393 covered with a cover 391 to block external light (harmful light) incident on the inside of the vacuum chamber.

In the scanning optical system 393, the scanning lens has an fθ characteristic. That is, when the light polarizing device is rotating at a constant speed, the light beam moves at a substantially constant speed with respect to the image plane. Further, in the scanning optical system, the beam spot diameter can be scanned substantially constant.

In the electrostatic latent image measuring device 300, the scanning optical system is arranged apart from the vacuum chamber. Therefore, the influence of the vibration generated when driving the optical deflector such as the polygon scanner 390 is directly propagated to the vacuum chamber 340 is small.

A vibration isolator such as a damper may be provided between the vibration isolation table 382 holding the scanning optical system 393 and the structure 383. By providing the anti-vibration means, the vibration transmitted to the vacuum champer 340 can be further reduced.

By providing the scanning optical system 393, the electrostatic latent image measuring device 300 can form an arbitrary latent image pattern including a line pattern in the generatrix direction of the photoconductor.

In order to form a latent image pattern at a predetermined position, a synchronous detection sensor 26 that detects a scanning beam from the light deflecting means may be provided.

The shape of the sample 323 may be a flat surface or a curved surface.

By adding the scanning mechanism as described above, it is possible to form an arbitrary latent image pattern including a line pattern in the generatrix direction of the photoconductor.

● Method of electrostatic latent image measurement Next, the method of electrostatic latent image measurement will be explained.

FIG. 39 is a schematic diagram showing the relationship between the acceleration voltage and the charging potential. First, in measuring the electrostatic latent image, the electrostatic latent image measuring device 300 irradiates the sample 323 of the photoconductor with an electron beam.

As the acceleration voltage | Vacc |, which is the voltage applied to the acceleration electrode 313, a voltage higher than the voltage at which the secondary electron emission ratio in the sample 323 is 1 is set. By setting the acceleration voltage in this way, in the sample 323, since the amount of incident electrons exceeds the amount of emitted electrons, electrons are accumulated in the sample 323, causing charge-up. As a result, in the electrostatic latent image measuring device 300, the surface of the sample 323 can be uniformly charged with a negative charge.

As shown in FIG. 39, there is a certain relationship between the acceleration voltage and the charging potential. Therefore, in the electrostatic latent image measuring device 300, by appropriately setting the acceleration voltage and the irradiation time, a charging potential similar to that of the photoconductor drum 1030 in the image forming apparatus 1000 can be formed on the surface of the sample 323. can.

Since the larger the irradiation current is, the target charging potential can be reached in a short time, the irradiation current is set to several nA here.

After that, in the electrostatic latent image measuring device 300, the amount of incident electrons in the sample 323 is increased to 1/100 times to 1/1000 times so that the electrostatic latent image can be observed.

The electrostatic latent image measuring device 300 controls the optical scanning device 500 to two-dimensionally lightly scan the surface of the sample 323 to form an electrostatic latent image on the sample 323. The optical scanning apparatus 500 is adjusted so that a light spot having a desired beam diameter and beam profile is formed on the surface of the sample 323.

The exposure energy required to form the electrostatic latent image is determined by the sensitivity characteristics of the sample, but is usually about ^{2 to 10 mJ / m 2.} For samples with low sensitivity, the required exposure energy may be 10 mJ / m ² or more. The charging potential and the required exposure energy are set according to the photosensitive characteristics of the sample and the process conditions. The exposure conditions of the electrostatic latent image measuring device 300 are the same as the exposure conditions matched to the image forming device 1000.

By calculating the environment of the electrostatic field and the electron orbit in advance and correcting the detection result based on the calculation result, the profile of the electrostatic latent image can be obtained with high accuracy.

As described above, by using the electrostatic latent image measuring device 300, the charge distribution, the surface potential distribution, the electric field strength distribution, and the electric field strength in the direction orthogonal to the sample surface in the electrostatic latent image can be highly accurate. Can be sought.

● Effect ●
As described above, according to the exposure method according to the present embodiment, the following effects can be obtained.

According to the exposure method according to the present embodiment, by performing TC exposure that exposes with a strong light output for a short time, it is possible to obtain the same effect as spatial centralized exposure (reducing the diameter of the beam). According to the exposure method according to the present embodiment, an electrostatic latent image having a narrow area and a depth can be formed, so that a high-resolution image can be formed.

By using the collation pattern, the exposure pattern can be determined without performing simple operations such as addition processing and multiplication processing, and the processing speed can be increased.

By using at least the collation pattern of the two-dimensional array for the vertical folding process, it is possible to process a plurality of pixels at the same time in a minimum of one clock, and the processing speed can be significantly improved.

By performing exception handling before the wrapping processing, it is possible to achieve high image quality even for a narrow image without blurring.

According to the exposure method according to the present embodiment, conditions such as a processing mode can be used properly according to the conditions of the image and the environment.

In the exposure method according to the present embodiment, the exposure pixels are concentrated inside (center portion) of the input image data, and the exposure is performed with a light output value stronger than the standard exposure. As a result, according to the exposure method according to the present embodiment, it is possible to output an image faithful to the target image at a desired image density even if the image pattern is fine.

According to the exposure method according to the present embodiment, TC is applied to various image patterns by increasing the light output value of the exposed portion pixels by using the pixels that are the boundaries between the image portion and the non-image portion as a high-output exposure pixel group. Exposure can be applied.

According to the exposure method according to the present embodiment, when the light output value of the high-power exposure pixel group exceeds a predetermined maximum light output value, the light output value is dispersed and exposed to adjacent image pixels. As a result, according to the exposure method according to the present embodiment, even when the maximum light output value cannot be set high, the image density can be maintained and high image quality can be realized.

In the exposure method according to the present embodiment, the pixels of the image portion at the boundary between the image portion and the non-image portion are converted into the non-exposed pixels, and at the same time, the light output value comparable to the non-exposed pixels is set to the high output exposed pixel group. It is exposed by adding it to the pixels of the image portion adjacent to. By doing so, according to the exposure method according to the present embodiment, TC exposure can be applied to various image data such as a character image, an inverted character image, a dither, and a line image.

According to the exposure method according to the present embodiment, when the light output value of the high-power exposure pixel group exceeds the maximum light output value, the light output value is not added, so that it is not necessary to perform exception processing, which is simple. TC exposure can be applied to various images by various processes.

According to the exposure method according to the present embodiment, when the light output value is added to the high output exposure pixel group, if the high output exposure pixel group has already added the light output value, the addition is possible. Since processing is performed for a large number of pixels, TC exposure can be performed under optimum conditions.

In the exposure method according to the present embodiment, the light source modulation data generation circuit 407 recognizes the state of the image based on the information provided from the controller side such as the image processing circuit or the tag bit, and is optimized according to each image. Set the number of folded pixels. As a result, according to the exposure method according to the present embodiment, it is possible to provide the best image that maximizes the capabilities of the image forming apparatus.

According to the exposure method according to the present embodiment, the weak electric field region is reduced and the dot reproducibility is improved in the region where the image patterns are adjacent to each other and the latent image electric field tends to be small, such as the dither portion. Can be made to.

According to the exposure method according to the present embodiment, since the image quality of the image is improved at the electrostatic latent image stage, it is possible to stably realize high image quality of a minute character image, particularly an inverted character image.

According to the exposure method according to the present embodiment, since it is a simple method, various images can be processed at high speed.

According to the exposure method according to the present embodiment, the integrated light amount of the standard exposure and the TC exposure can be matched by intentionally increasing the maximum light output value by using PM + PWM modulation, so that there is a deep latency. An image can be formed to increase the resolving power.

According to the image forming apparatus according to the present embodiment, it is possible to provide a high-density and high-quality image forming apparatus by developing and visualizing the exposure method according to the present embodiment.

The image forming apparatus according to the present embodiment is particularly suitable for an image forming apparatus equipped with a multi-beam scanning optical system such as a VCSEL.

100 Image processing device 101 Image processing unit 104 Optical writing output unit 300 Electrostatic latent image measuring device 410 Light source driving unit 1000 Laser printer (image forming device)
1010 Optical scanning device (electrostatic latent image forming device)
1030 Photoreceptor drum (image carrier)

Japanese Unexamined Patent Publication No. 2005-193540 Japanese Unexamined Patent Publication No. 2008-153742 Japanese Unexamined Patent Publication No. 2012-15864 JP-A-2007-190787

Claims (8)

A method of forming an electrostatic latent image corresponding to the image pattern by an exposure step of exposing the surface of the image carrier with light corresponding to an image pattern including an image portion and a non-image portion.
The image unit is composed of a plurality of pixels.
At both ends of the image unit, two pixels of the image unit adjacent to the non-image unit are used as non-exposed pixels, and two pixels of the image unit adjacent to the non-exposed pixels are used to expose the image unit. Before performing the wrapping process, the high-power exposed pixels are exposed with light having an output value higher than the required predetermined light output value.
When the number of pixels successive one column of the image area of 6, adjacent to two pixels to be a pixel der Li Kui the high output exposure pixel is determined before Symbol unexposed pixels in the case of executing the loopback Exception processing is performed so that one of the two pixels is the high-output exposure pixel.
The image unit after the exception processing is subjected to the folding process for the pixels whose optical output value is not determined by the exception processing, and the light by the folding process for the pixels whose optical output value is determined by the exception processing. Do not change the output value ,
An image forming method characterized by this. The image forming method according to claim 1, wherein after performing the exception processing, data storage processing is performed on a pixel whose optical output value is determined as a high output pixel by the exception processing. The image forming method according to claim 1 or 2, wherein the determination to obtain a high-output exposed pixel by the folding back processing is performed on a pixel whose optical output value has not been determined as a high-output pixel by the exception processing. Each of the pixels in the image unit is collated with a plurality of collation patterns composed of a plurality of pixels, and a determination to obtain a high output exposure pixel is executed by the exception processing.
The image forming method according to any one of claims 1 to 3. When the collation pattern is a symmetric two-dimensional array and the image pattern has a portion that matches the collation pattern, the exception is made to the pixels of the image portion corresponding to the pixels on the axis of symmetry of the collation pattern. The processing executes the determination of the high output exposure pixel.
The image forming method according to claim 4. The sum of the values obtained by subtracting the predetermined light output value from the light output value of the light exposed to the high-power exposed pixel is the light output value of the light exposed to the non-exposed pixel from the predetermined light output value. Equal to the sum of the subtracted values ,
The image forming method according to any one of claims 1 to 5. An image forming apparatus that forms an electrostatic latent image corresponding to the image pattern by exposing the surface of the image carrier with light corresponding to an image pattern including an image portion and a non-image portion.
The light source that irradiates the light and
A light source drive unit that generates a light source drive current that drives the light source,
An optical system that guides the light emitted from the light source to the image carrier,
Have
The image unit is composed of a plurality of pixels.
The light source driving unit is
At both ends of the image unit, two pixels of the image unit adjacent to the non-image unit are used as non-exposed pixels, and two pixels of the image unit adjacent to the non-exposed pixels are used to expose the image unit. Before performing the wrapping process, the high-power exposed pixels are exposed with light having an output value higher than the required predetermined light output value.
When the number of pixels successive one column of the image area of 6, adjacent to two pixels to be a pixel der Li Kui the high output exposure pixel is determined before Symbol unexposed pixels in the case of executing the loopback Exception processing is performed so that one of the two pixels is the high-output exposure pixel.
The image unit after the exception processing is subjected to the folding process for the pixels whose optical output value is not determined by the exception processing, and the light by the folding process for the pixels whose optical output value is determined by the exception processing. Do not change the output value ,
An image forming apparatus characterized in that. A method for producing a printed matter, which comprises a step of forming an electrostatic latent image corresponding to the image pattern by exposing the surface of the image carrier with light corresponding to an image pattern including an image portion and a non-image portion. ,
At both ends of the image unit, two pixels of the image unit adjacent to the non-image unit are used as non-exposed pixels, and two pixels of the image unit adjacent to the non-exposed pixels are used to expose the image unit. Before performing the folding process to obtain high-power exposed pixels to be exposed with light having an output value higher than the required predetermined light output value.
When the number of pixels successive one column of the image area of 6, adjacent to two pixels to be a pixel der Li Kui the high output exposure pixel is determined before Symbol unexposed pixels in the case of executing the loopback Exception processing is performed so that one of the two pixels is the high-output exposure pixel.
The image unit after the exception processing is subjected to the folding process for the pixels whose optical output value is not determined by the exception processing, and the light by the folding process for the pixels whose optical output value is determined by the exception processing. Do not change the output value ,
A method for producing printed matter, which is characterized by the fact that.

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