JP3675709B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention provides an exposure processing apparatus that scans a document and performs an exposure process for image formation based on image data obtained by the scanning.PlaceIn particular, an exposure processing apparatus that optimizes an exposure data collection area based on a document size, a paper size on which an image is formed, and a copying magnification.PlaceThe present invention relates to an image forming apparatus provided.
[0002]
[Prior art]
The image forming apparatus includes an exposure processing apparatus that performs an exposure process to form a clear image. In the exposure processing apparatus, first, an area for collecting data to be exposed is determined. Then, the determined sampling area is scanned and exposure processing is performed.
[0003]
For example, the image processing apparatus disclosed in Japanese Patent No. 2541937 reads a document by scanning, detects coordinate values of four corners where the document exists, and performs exposure based on the detected coordinate values. Determine the area. And it is comprised so that an exposure process may be performed about the area | region.
[0004]
Also, in the automatic exposure apparatus disclosed in Japanese Patent Laid-Open No. 4-317045, a document size detection sensor for detecting the size of a document is placed on a document holding member, and based on the output from the document size detection sensor, A photometric range is determined, and exposure processing is performed based on data obtained by scanning the determined range.
[0005]
[Problems to be solved by the invention]
However, since the image processing apparatus disclosed in Japanese Patent No. 2541937 detects the coordinate value at which the original exists by reading the original by scanning, it cannot be said that the detection accuracy is sufficient. In other words, after the document is placed on the document table and the document table holding cover is closed and scanned, the color of the document is close to the color of the document table holding cover. It is difficult to detect well. As a result, there is a problem that even an area that does not need to be exposed, that is, an area of the document table holding cover is erroneously detected as an extraction area for exposure, and appropriate exposure processing cannot be performed.
[0006]
Further, the image processing apparatus disclosed in Japanese Patent No. 2541937 and the automatic exposure apparatus disclosed in Japanese Patent Laid-Open No. 4-317045 do not assume the case of enlarging or reducing copying, and paper on which an image is formed. The sampling area for exposure was not determined assuming the size. For this reason, there has been a problem that it is difficult to perform an appropriate exposure process as a result of performing exposure after performing collection even for an area that does not need to be collected. For example, if the document is A4 size, the copy magnification is 144%, and the paper size on which the image is formed is A4, the entire document is sampled even though it is not necessary to collect exposure data for the area where the image is not formed. Was in the area. For this reason, there has been a problem that the exposure processing is performed up to a portion unnecessary for image formation.
[0007]
There is also a problem that the image forming speed decreases as the exposure process becomes complicated.
[0008]
  The present invention has been made in view of such circumstances, and the object of the present invention is to add three sizes, a paper size for image formation and a copy magnification, which have not been considered in the past, in addition to the size of a document. Determine the area from which exposure data is collected as a parameterIn addition, it is possible to achieve exposure processing with higher accuracy by determining the sampling region in the main scanning direction and the sub-scanning direction, and also in the main scanning direction and the sub-scanning direction by simple arithmetic processing. And an exposure processing apparatus capable of accelerating the processing by determining the sampling region for the image, and scanning for the exposure processing (pre-scan) is performed before the scanning for image formation. An image forming apparatus capable of forming images at higher speedIt is to provide.
[0012]
  Another object of the present invention is to perform exposure processing.RunningAn object of the present invention is to provide an image forming apparatus capable of forming an image at a higher speed by making the inspection speed higher than the scanning speed for image formation.
[0013]
[Means for Solving the Problems]
  According to the first inventionImage formationThe deviceArea determination for determining a value obtained by dividing the image forming paper size by the copying magnification as an exposure data collection area when a value obtained by multiplying the original size by the copying magnification is larger than the paper size on which the image is formed Having means,An exposure processing apparatus that scans a document and performs exposure processing for image formation based on image data obtained by scanningImage forming apparatus provided withInFirst scanning means for scanning for exposure data collection based on the exposure data collection area determined by the area determination means; and second scanning means for scanning for image formation based on the document size. The first scanning unit is configured to perform scanning before scanning by the second scanning unit.It is characterized by that.
[0014]
  According to the first inventionImage formationIn the apparatus, the exposure data collection area is determined by using not only the document size but also the paper size on which an image is formed and the set copy magnification as parameters. Can only be collectedFurther, a value obtained by multiplying the paper size of the original document by the copy magnification, that is, the size on which the image is formed is compared with the paper size on which the image is formed. If the multiplied value is larger than the paper size, the paper size is divided by the copying magnification, and the divided size is used as an exposure data collection area. Therefore, the exposure process is performed only for the area where the image is formed on the paper. As a result, high-accuracy exposure processing becomes possible, and furthermore, scanning (second scanning) is performed to read the image data and form an image. Prior to the second scanning, exposure processing is performed on the determined sampling region. A first scan (pre-scan) for performing the above is performed. Since it comprised in this way, the fall of the image formation speed accompanying performing 1st scanning is suppressed.Is possible.
[0015]
  According to the second inventionImage formationThe deviceAn output for calculating the number of output pixels in the main scanning direction and the number of output pixels in the sub scanning direction by multiplying the number of pixels in the main scanning direction and the number of pixels in the sub scanning direction corresponding to the size of the document by the set copy magnification, respectively. The number of pixels calculating means, the number of output pixels in the main scanning (or sub-scanning) direction calculated by the output pixel number calculating means, and the output possible pixels in the main scanning (or sub-scanning) direction corresponding to the paper size on which the image is formed When the comparison unit for comparing the number and the number of output pixels in the main scanning (or sub-scanning) direction is larger than the number of output pixels in the main scanning (or sub-scanning) direction as a result of comparison by the comparison unit And an area determination means for determining, as an exposure data collection area, a value obtained by dividing the number of pixels that can be output in the main scanning (or sub-scanning) direction by the copying magnification, and an image obtained by scanning the document and scanning In an image forming apparatus having an exposure processing apparatus for performing an exposure process for image formation based on a data, a first scan for collecting exposure data is performed based on the exposure data collection area determined by the area determination means. One scanning means and a second scanning means for scanning for image formation based on the size of the document, wherein the first scanning means scans before the scanning by the second scanning means. ConfiguredIt is characterized by that.
[0018]
  SecondInventionImage formationIn the apparatus, first, a copy set in the number of pixels in the main scanning direction (in the case of A4, 4777 pixels at a resolution of 400 dpi) corresponding to the size of the document (in the case of A4, 297 mm in the main scanning direction and 209 mm in the sub scanning direction). The number of output pixels in the main scanning direction is calculated by multiplying the magnification. Similarly, the number of output pixels in the sub-scanning direction is calculated by multiplying the number of pixels in the sub-scanning direction (if A4, 3311 pixels at a resolution of 400 dpi) by the copy magnification. Then, the number of pixels that can be output in the main scanning direction of the paper size on which an image is formed (477 pixels at a resolution of 400 dpi for A3) and the calculated number of output pixels in the main scanning direction are compared. Similarly, the number of pixels that can be output in the sub-scanning direction of the paper size on which an image is formed (if A3, 6622 pixels at a resolution of 400 dpi) is compared with the calculated number of output pixels in the sub-scanning direction.
[0019]
  As a result of comparison, if the number of output pixels in the main scanning direction and the sub-scanning direction is smaller than the number of pixels that can be output, all areas of the document are formed without omission, so the sampling area is the size of the document, that is, the main scanning The number of pixels in the direction and the number of pixels in the sub-scanning direction are used. On the other hand, if the number of output pixels in the main scanning direction is larger than the number of pixels that can be output, in other words, if the entire original image is not formed, main scanning is performed based on the number of pixels that can be output in the main scanning direction and the copy magnification. A direction exposure data collection area is determined. That is, a process of excluding the part where no image is formed from the collection area is performed. Similarly, in the sub-scanning direction, the exposure data collection area is determined by the same method. As described above, since the exposure data collection area is optimized, a more accurate exposure process is possible.Furthermore, since the sampling area is calculated by dividing the number of pixels that can be output in the main scanning direction or sub-scanning direction by the copy magnification, the sampling area necessary for image formation can be determined. Since more accurate exposure processing is possible and the sampling area is determined by simple calculation processing, higher-speed exposure processing is possible, and in addition, image data is read to form an image. A scan (second scan) is performed. Prior to the second scan, a first scan (pre-scan) for performing exposure processing on the determined sampling region is performed. Since it comprised in this way, it becomes possible to suppress the fall of the image formation speed accompanying performing 1st scanning.
[0024]
  Third inventionThe image forming apparatus according toIn any of the above inventions,First scanning meansIsThe second scanning unit is configured to perform scanning at a scanning speed or higher.
[0025]
  According to the third inventionImage forming apparatusIn any of the above inventions,Since there is no problem with the data for optical processing even if the resolution is somewhat lowered, the scanning speed of the first scanning is performed at a higher speed than that of the second scanning. Since it comprised in this way, it becomes possible to suppress the fall of the image formation speed accompanying performing 1st scanning.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
FIG. 1 is a schematic diagram showing the structure of an image forming apparatus 1 according to the present invention. A transparent glass platen 2 is disposed on the upper surface of the image forming apparatus 1, and a scanner unit 3 is disposed below it. The scanner unit 3 includes an exposure lamp 31, a first reflection mirror 32a, a second reflection mirror 32b, a third reflection mirror 32c, a lens 33, and a photoelectric conversion element 34 using a CCD, and the exposure lamp 31 and the first reflection mirror. The image of the original placed on the upper surface of the original table 2 is exposed and scanned by the light emitted from the exposure lamp 31 by reciprocating the surface 32 a in the horizontal direction on the lower surface of the original table 2.
[0027]
On the same plane as the scanner unit 3, size recognition sensors 35, 35,... For detecting the size of the document are disposed at appropriate positions. The size of the original is determined based on the output signal from the size recognition sensor 35 or the original size designated by the user through the operation unit 51 such as an operation panel. In addition, the user can designate the copy magnification and the paper size (output paper size) on which an image is formed from the operation unit 51. Signals relating to the determined document size, copy magnification, and paper size on which an image is formed are output to the exposure processing apparatus 50.
[0028]
The reflected light from the exposure lamp 31 forms an image on the light receiving surface of the photoelectric conversion element 34 via the first to third reflection mirrors 32a to 32c and the lens 33, and the photoelectric conversion element 34 is a signal corresponding to the amount of light received on the light receiving surface. Is output. The signal output from the photoelectric conversion element 34 is digitized by the A / D converter 52 (see FIG. 2) of the exposure processing apparatus 50, and the input document size, copy magnification, and paper size on which an image is formed are converted. Based on this, a sampling area for the exposure process is determined, and a density conversion table 53a (see FIG. 2) of image data obtained for this area is created.
[0029]
Then, after again scanning the exposure lamp 31 and the first reflecting mirror 32a to collect image data, the density is converted with reference to the density conversion table 53a to perform exposure processing. The image data after the exposure processing is output to the optical scanning device 6 after being enlarged or reduced based on the copy magnification.
[0030]
A photosensitive member 4 is supported at the center of the image forming apparatus 1 so as to be rotatable in the direction of the arrow. For example, a charger 5 such as a conductive brush applied to a predetermined voltage can contact the photosensitive member 4. The surface of the photoreceptor 4 is charged to a predetermined voltage by the charger 5. Then, the photoconductor 4 is irradiated with image light modulated based on the image data output from the exposure processing device 50 from the optical scanning device 6 covered with the light-shielding case 70, and is statically applied to the photoconductor 4. An electrostatic latent image is formed. The developing tank 7 supplies a developer to the surface of the photoreceptor 4 and visualizes the electrostatic latent image into a developer image.
[0031]
Prior to the rotation of the photosensitive member 4, the recording paper P in the paper feeding cassette 10 is fed into the paper conveyance path one by one by the rotation of the paper feeding roller 12. The fed recording paper P is conveyed to the registration roller 13 by the conveying roller 12. The recording paper P is stopped in a state where the front end is in contact with the registration roller 13, and rotates at a predetermined timing to guide the recording paper P toward the photoconductor 4. The developer image carried on the photoreceptor 4 is transferred onto the surface of the recording paper P by the transfer device 8, and the transferred recording paper P is heated and pressed while passing through the fixing roller 14. As a result, the developer image is melted and fixed to the lower surface of the recording paper P. The recording paper P to which the developer image is fixed is conveyed by a paper discharge roller 15 and discharged to a multi-stage paper discharge tray 11 (111, 112,... 11n...).
[0032]
  FIG. 2 relates to the present invention.The image forming apparatus 1 includes2 is a block diagram showing a configuration of an exposure processing apparatus 50. FIG. In the figure, reference numeral 51 denotes an operation unit which accepts a document size, a copy magnification, and a paper size on which an image is formed. The received information is temporarily stored in the RAM 54. The copy magnification refers to the ratio of the length of the formed image in the main scanning direction or sub-scanning direction to the length of the document in the main scanning direction or sub-scanning direction. For example, in the case of 121% enlargement copy, the copy magnification in both the main scanning direction and the sub-scanning direction is 1.1. The copying magnification is set based on the document size and the paper size on which an image is formed designated by the user, in addition to the case where the user sets the operation using the operation unit 51. Further, the paper size on which the image is formed is set based on the original size and the set copy magnification, in addition to the case where the user sets it from the operation unit 51. Note that the size of the document may be stored based on a signal output from the size recognition sensor 35. Based on these three parameters, the CPU 55 determines a sampling area necessary for the exposure process by a process described later.
[0033]
Then, the CPU 55 drives the exposure lamp 31 to perform scanning (first scanning), digitizes the electrical signal output from the photoelectric conversion element 34 by the A / D converter 52, and determines the image data for the determined sampling region. Is stored in the storage unit 53 such as a hard disk. Then, the CPU 55 creates a density conversion table 53 a for exposure processing based on the stored image data and stores it in the storage unit 53. The creation process of the density conversion table 53a will be described later.
[0034]
After creating the density conversion table 53 a, the CPU 55 drives the exposure lamp 31 again to perform scanning (second scanning), collects image data, and stores it in the RAM 54. Then, density conversion, that is, exposure processing is performed with reference to the created density conversion table 53a. The image data after the exposure processing is output to the optical scanning device 6 after being enlarged or reduced based on the copy magnification stored in the RAM 54.
[0035]
3 and 4 are flowcharts showing the processing procedure from the start to the end of the copying process. First, the CPU 55 accepts the size of the original, the copy magnification, and the paper size on which the image is formed input from the operation unit 51 (step S31), and stores it in the RAM. Based on these three parameters, a sampling area to be subjected to exposure processing is determined (step S32). The CPU 55 performs scanning for exposure processing (hereinafter referred to as first scanning), captures image data (step S33), and stores it in the storage unit 53.
[0036]
Next, the CPU 55 extracts the image data of the determined sampling area from the image data stored in the storage unit 53, and generates a density histogram for the extracted image data (step S34). FIG. 5 is a histogram of the image data relating to the collection area. In the figure, the horizontal axis represents the density level in 8-bit 256 gradations, and the vertical axis represents the ratio of the number of pixels included in the density level to the number of pixels in the entire collection region. The CPU 55 counts the number of pixels included in the density level according to the density level of each pixel in the collection area, and calculates a ratio to the number of pixels in the entire collection area.
[0037]
A low density threshold and a high density threshold are set in the storage unit 53 in advance. For example, the low concentration threshold is set to 10%, and the high concentration is set to 0.5%. The CPU 55 extracts a density level exceeding the low density threshold. In FIG. 5, density levels “16 to 31” whose ratio exceeds the low density threshold 10% when viewed from the low density level are extracted. Then, a low average value “23.5” that is an average value of density levels exceeding the low density threshold is calculated. On the other hand, similarly for the high density level, density levels “208 to 223” whose ratio exceeds the high density threshold value 0.5% when viewed from the high density level are extracted. Then, a high average value “215.5” that is an average value of density levels exceeding the high density threshold value is calculated.
[0038]
FIG. 6 is a schematic diagram of the density conversion table 53a. In the figure, the horizontal axis indicates the density before conversion, and the vertical axis indicates the density after conversion. As shown in the figure, when the density before conversion is “0” or more and the low average value “23.5” or less, the CPU 55 sets the density after conversion to the lowest “0”. Similarly, when the density before conversion is a high average value “215.5” or more and “256” or less, the density after conversion is set to the highest “256”.
[0039]
Subsequently, the CPU 55 obtains a linear equation connecting these two points based on the coordinate values (low average value, 0) and (high average value, 256), and inputs the concentration before conversion into the obtained equation. To calculate the density after conversion. The above processing is performed for all the densities, and the CPU 55 sequentially stores the converted densities and creates a density conversion table 53a.
[0040]
FIG. 7 is an explanatory diagram showing the data structure of the created density conversion table 53a. The density after conversion with respect to the density before conversion is stored. As described above, since the exposure processing by density conversion is performed, the background is cut to some extent even in the document having the background portion. In addition, since the high density portion is also detected, it is possible to adjust the contrast.
[0041]
After creating the density conversion table 53a as described above (step S35), the CPU 55 performs scanning for image formation (hereinafter referred to as second scanning) again, and executes image data capture (steps S36, A). ). Then, the CPU 55 refers to the density conversion table 53a and performs density conversion, that is, exposure processing (step S41). Then, after enlarging or reducing processing is performed in accordance with the input copy magnification (step S42), the processed image data is output to the optical scanning device 6 (step S43).
[0042]
FIG. 8 and FIG. 9 are flowcharts showing a processing procedure for determining a sampling area for the exposure processing, which is the main part of the present invention. First, the number of pixels in the main scanning direction and the number of pixels in the sub scanning direction corresponding to the size of the document are calculated (step S81). The number of pixels in the main scanning direction is calculated as a value obtained by multiplying the actual length of the document by the resolution. Specifically, the number of pixels in the main scanning direction is 297 mm if the document is A4 size, and if the resolution is 400 dpi (dot per inch), the actual length 297 mm in the main scanning direction is 25. Dividing by .4 mm (length of 1 inch) and multiplying by 400 dpi, the number of pixels in the main scanning direction is calculated as 4,677 pixels.
[0043]
Similarly, the number of pixels in the sub-scanning direction is calculated. If the document is A4 size, the number of pixels in the sub-scanning direction is 3311 pixels. Subsequently, the CPU 55 multiplies the calculated number of pixels in the main scanning direction by the copy magnification to calculate the number of output pixels in the main scanning direction that will be output (step S82). Similarly, the number of output pixels in the sub-scanning direction is calculated by multiplying the number of pixels in the sub-scanning direction by the copy magnification (step S82). Specifically, when the copy magnification is 1.44 times, the number of pixels in the main scanning direction is multiplied by 4,677 pixels and the copy magnification of 1.44 to calculate the number of output pixels in the main scanning direction of 6735 pixels. Similarly, the output pixel number 4768 pixels in the sub-scanning direction is calculated.
[0044]
In addition, the CPU 55 calculates the number of pixels that can be output corresponding to the paper size on which the image is designated designated by the user in each of the main scanning direction and the sub-scanning direction (step S83, B). For example, if the output paper size is A3 (actual length in the main scanning direction is 297 mm, actual length in the sub scanning direction is 418 mm), the number of pixels that can be output in the main scanning direction is 4,677 pixels, which is the same as A4, and can be output in the sub scanning direction. The number of pixels is calculated as 6622 pixels, which is twice A4.
[0045]
Then, the CPU 55 compares whether or not the number of output pixels in the main scanning direction is larger than the number of pixels that can be output in the main scanning direction (step S84). As a result of comparison, if the number of output pixels in the main scanning direction is smaller than the number of pixels that can be output (NO in step S84), the exposure data collection area in the main scanning direction is determined as the number of pixels in the main scanning direction, that is, the size of the document. (Step S85). On the other hand, if the number of output pixels in the main scanning direction is larger than the number of pixels that can be output as a result of the comparison (YES in step S84), the number of pixels that can be output in the main scanning direction is divided by the copying magnification and the divided value is obtained. Is the exposure data collection area in the main scanning direction (step S91). In the specific example described above, the number of output pixels in the main scanning direction is 6735 pixels, and the number of pixels that can be output is 4,677 pixels. Therefore, the enlarged image does not fit on the output paper. Therefore, in order to exclude an area unnecessary for exposure, a value of 3248 pixels obtained by dividing the number of output possible pixels of 4,677 pixels by a copy magnification of 1.44 is determined as a sampling area in the main scanning direction. As a result, unnecessary exposure data on which no image is formed is surely removed, and as a result, the exposure accuracy is greatly improved.
[0046]
Subsequently, a sampling area in the sub-scanning direction is determined. First, it is determined whether or not the number of output pixels in the sub-scanning direction is larger than the number of pixels that can be output (step S92). If the number of pixels that can be output is larger than the number of output pixels in the sub-scanning direction as a result of the comparison (NO in step S92), the sampling region in the sub-scanning direction is determined as the number of pixels in the sub-scanning direction (step S93). In the specific example described above, the number of pixels that can be output in the sub-scanning direction is 6622 pixels, and the number of output pixels is 4768 pixels. Several 3311 pixels are determined as a sampling region in the sub-scanning direction. On the other hand, if the number of output pixels in the sub-scanning direction is larger than the number of pixels that can be output (YES in step S92), the number of pixels that can be output in the sub-scanning direction is divided by the copy magnification, and the divided value is the sub-scanning direction. Is determined as a sampling region (step S94).
[0047]
In the present embodiment, the resolution of the scanner unit 3 is 400 dpi, the frequency at which image data is read so that the scanning speed in the sub-scanning direction is 100 mm / s and the resolution in the main scanning direction and the sub-scanning direction is 400 dpi. However, the scanning speed in the sub-scanning direction may be controlled to be higher than that, for example, 200 mm / s. In this case, if the set frequency is the same value, the image data is read at 400 dpi for main scanning and 200 dpi for sub-scanning. As described above, when the scanning speed is increased during pre-scanning, the amount of image data (number of pixels) obtained decreases, but the influence on the accuracy of the histogram, that is, the influence on the exposure process is small. If the scanning speed is increased, the time required for the exposure process is shortened, and as a result, the image formation can be further accelerated.
[0048]
  In the present embodiment, the case where the exposure processing apparatus is applied to the image forming apparatus has been described.Exposure processing equipmentIs not limited to thisZThe present invention may be applied to other optical devices such as a scanner.
[0049]
【The invention's effect】
  As detailed above, according to the first inventionImage formationIn the apparatus, the exposure data collection area is determined by using not only the document size but also the paper size on which an image is formed and the set copy magnification as parameters. It is possible to perform sampling only for high-precision exposure processing.Also, a value obtained by multiplying the paper size of the original by the copy magnification, that is, a size at which an image is to be formed is compared with a paper size at which the image is formed. If the multiplied value is larger than the paper size, the paper size is divided by the copy magnification, and the divided size is used as an exposure data collection region. As a result, exposure processing with high accuracy is possible. In addition, in the image forming apparatus according to the first invention, scanning (second scanning) is performed to read image data and form an image. Prior to the second scanning, an exposure process is performed on the determined sampling region. A first scan (pre-scan) for performing the above is performed. Since it comprised in this way, it becomes possible to suppress the fall of the image formation speed accompanying performing 1st scanning..
[0051]
  SecondInventionImage formationIn the apparatus, first, a copy set to the number of pixels in the main scanning direction corresponding to the document size (297 mm in the main scanning direction and 209 mm in the sub scanning direction in the case of A4) (4777 pixels in the resolution of 400 dpi in the case of A4). The number of output pixels in the main scanning direction is calculated by multiplying the magnification. Similarly, the number of output pixels in the sub-scanning direction is calculated by multiplying the number of pixels in the sub-scanning direction (if A4, 3311 pixels at a resolution of 400 dpi) by the copy magnification. Then, the number of pixels that can be output in the main scanning direction of the paper size on which an image is formed (477 pixels at a resolution of 400 dpi for A3) and the calculated number of output pixels in the main scanning direction are compared. Similarly, the number of pixels that can be output in the sub-scanning direction of the paper size on which an image is formed (if A3, 6622 pixels at a resolution of 400 dpi) is compared with the calculated number of output pixels in the sub-scanning direction.
[0052]
  As a result of comparison, if the number of output pixels in the main scanning direction and the sub-scanning direction is smaller than the number of pixels that can be output, all areas of the document are formed without omission, so the sampling area is the size of the document, that is, the main scanning The number of pixels in the direction and the number of pixels in the sub-scanning direction are used. On the other hand, if the number of output pixels in the main scanning direction is larger than the number of pixels that can be output, in other words, if the entire original image is not formed, main scanning is performed based on the number of pixels that can be output in the main scanning direction and the copy magnification. A direction exposure data collection area is determined. That is, a process of excluding the part where no image is formed from the collection area is performed. Similarly, in the sub-scanning direction, the exposure data collection area is determined by the same method. As described above, since the exposure data collection area is optimized, a more accurate exposure process is possible.In addition, since the sampling area is calculated by dividing the number of pixels that can be output in the main scanning direction or sub-scanning direction by the copy magnification, the sampling area required for image formation can be determined. The exposure process can be performed with higher accuracy and the sampling area can be determined by a simple calculation process, so that a higher-speed exposure process can be performed. In addition, in the image forming apparatus according to the first invention, scanning (second scanning) is performed to read image data and form an image. Prior to the second scanning, an exposure process is performed on the determined sampling region. A first scan (pre-scan) for performing the above is performed. Since it comprised in this way, it becomes possible to suppress the fall of the image formation speed accompanying performing 1st scanning..
[0055]
  According to the third inventionImage forming apparatusIn any of the above inventionsScan (second scan) to read image data and form imageDo, butSince there is no problem with the data for the exposure process even if the resolution is slightly reduced, the scanning speed of the first scanning is performed at a higher speed than that of the second scanning. Since it comprised in this way, this invention can have the outstanding effect that it becomes possible to suppress the fall of the image formation speed accompanying performing 1st scanning.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the structure of an image forming apparatus according to the present invention.
FIG. 2 relates to the present invention.Provided by image forming apparatusIt is a block diagram which shows the structure of an exposure processing apparatus.
FIG. 3 is a flowchart illustrating a processing procedure from the start to the end of a copy process.
FIG. 4 is a flowchart illustrating a processing procedure from the start to the end of copy processing.
FIG. 5 is a histogram of image data relating to a collection region.
FIG. 6 is a schematic diagram of a density conversion table.
FIG. 7 is an explanatory diagram showing a data structure of a created density conversion table.
FIG. 8 is a flowchart showing a processing procedure for determining a sampling region for exposure processing, which is a main part of the present invention.
FIG. 9 is a flowchart showing a processing procedure for determining a sampling region for exposure processing, which is a main part of the present invention.
[Explanation of symbols]
1 Image forming device
2 Document table
3 Scanner section
50 Exposure processing equipment
51 Operation unit
53a Density conversion table

Claims (3)

Area determination for determining a value obtained by dividing the image forming paper size by the copying magnification as an exposure data collection area when a value obtained by multiplying the original size by the copying magnification is larger than the paper size on which the image is formed An image forming apparatus including an exposure processing apparatus that scans a document and performs exposure processing for image formation based on image data obtained by scanning ;
First scanning means for performing scanning for exposure data collection based on the exposure data collection area determined by the area determination means;
Second scanning means for performing scanning for image formation based on the size of the document;
With
The image forming apparatus according to claim 1, wherein the first scanning unit is configured to perform scanning before scanning by the second scanning unit . An output for calculating the number of output pixels in the main scanning direction and the number of output pixels in the sub scanning direction by multiplying the number of pixels in the main scanning direction and the number of pixels in the sub scanning direction corresponding to the size of the document by the set copy magnification, respectively. Pixel number calculating means;
Comparison in which the number of output pixels in the main scanning (or sub-scanning) direction calculated by the output pixel number calculating means is compared with the number of output pixels in the main scanning (or sub-scanning) direction corresponding to the paper size on which the image is formed. Means,
If the number of output pixels in the main scanning (or sub-scanning) direction is larger than the number of pixels that can be output in the main scanning (or sub-scanning) direction as a result of comparison by the comparison means, the main scanning (or sub-scanning) Area determining means for determining the exposure data collection area by dividing the number of pixels that can be output in the direction by the copy magnification;
In an image forming apparatus provided with an exposure processing apparatus that scans a document and performs exposure processing for image formation based on image data obtained by scanning,
First scanning means for performing scanning for exposure data collection based on the exposure data collection area determined by the area determination means;
Second scanning means for performing scanning for image formation based on the size of the document;
With
The image forming apparatus according to claim 1, wherein the first scanning unit is configured to perform scanning before scanning by the second scanning unit . The image forming apparatus according to claim 1, wherein the first scanning unit is configured to perform scanning at a speed higher than a scanning speed of the second scanning unit .

Images